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NASA-HBCU

Space Science and Engineering

Research Forum

Proceedings

March 22 - 23, 1989

Alabama A&M University

Huntsville, Alabama

FOUNDED NORHAL

Editors: Yvonne D. Sanders

Yvonne B. Freeman

M.C. George
Typesetting and printing of this publication was performed by the University of Alabama in Huntsville

Reproduction Services. Body text typeface is 11 point Dutch.
PREFACE

The role of science and scientific research in universities is well recognized by the public, university

administrators, faculty and students. The National Aeronautics and Space Administration (NASA) has been and

continues to be a leading supporter of research at universities. To enhance research at Historically Black Colleges

and Universities (HBCUs) NASA has embarked upon a special program through its Office of Equal Opportunity

that is designed to build greater research and training linkages among HBCUs and NASA centers. The program

brings together active scientists and students who are pursuing research in broad areas and subjects of interest to

NASA. It encourages collaboration by providing an opportunity for researchers to develop personal contacts with

NASA and other universities and discuss the details in a structured, yet informal and relaxed atmosphere. It is

hoped that these interactions will lead to long term collaborative research and a strengthening of research programs

at HBCUs.

The success of the effort is being evidenced by increased participation of HBCU faculty in NASA-HBCU

Space Science and Engineering Research Forums. The first and second NASA HBCU Research Forums held at

Atlanta University have amply justified the validity of continuing such efforts. The 1989 forum, third in the series,

was hosted by Alabama A&M University in Huntsville, Alabama March 22-23. The excellent participation

exceeded previous forums with 338 registered participants representing 38 colleges and universities plus 207 high

school students representing 27 regional high schools.

The organizing committee is pleased to publish the proceedings of the 1989 forum. There were many

outstanding and significant contributions, keynote addresses, plenary papers, invited papers and contributed

papers (both oral and poster) that formed the framework of this forum. The papers presented in this document

cover a wide range of research topics from plant science to space science and related academic areas. Outreach

activities being supported by NASA with the intention of replication in other educational institutions are also

included.

These proceedings are not intended to replace publication of new and complete research results in those

technical journals that cover the field. Rather, the brief accounts of research summarized here are intended to

provide sufficient description (aided by a listing of key references) to enable the reader to understand the basis of

what has been accomplished and where to find more detailed information. In some instances historical perspectives

and thoughts on future directives are also presented.

The organizing committee expresses its appreciation to all the participants, the various NASA field centers

and other academic and NASA administrators for their continued support. Special thanks goes out to Anesia

Holland, Administrative Assistant, and the many Alabama A&M University, Marshall Space Flight Center, and

NASA Code "U" coordinators; their efforts were essential for the success of the forum.

The Editors:

Yvonne Sanders, Project Coordinator

Alabama A&M University

Yvonne B. Freeman, Project Manager j

NASA Headquarters

M. C. George, Project Director

Alabama A&M University
NASA-HBCU SPACE SCIENCE AND ENGINEERING

RESEARCH FORUM

Program Agenda

Tuesday / March 21, 1989

6:00 PM-- RECEPTION

Hilicrest

The President's Home

Alabama A&M University

8:00 PM-- STUDENT RESEARCHER PRE-CONFERENCE

PRESENTATION CLINIC

E/more Heahh Science Complex

R6om 5

Dr. Mildred Wyatt

Goddard Space Flight Center

Wednesday, March 22, 1989

8:00 AM-- REGISTRATION

3:00 PM Elmore Health Science Complex Lobby

8:00 AM-- CONTINENTAL BREAKFAST

8:,30 AM Elmore Health Science Complex Lobby

GENERAL SESSION

E/more Health Science Complex Gymnasium

8:,30 AM OPENING REMARKS AND INTRODUCTION OF

GUESTS

Dr. Carl Harris Marburg

President, Alabama A&M University, Presiding

8:40 AM WELCOME

The Honorable Steve Hettinger

Mayor of 11untsville, Alabama

8:45 AM-- INTRODUCTION OF NASA ASSOCIATE

DEPUTY ADMINISTRATOR

Mr. James R. Thompson

Director, Marshall Space Flight Center

KEYNOTE ADDRESS

Dr. Noel W. Hinners

Associate Deputy Administrator, NASA

INTRODUCTION OF GUEST LECTURER

Dr. M. C. George

Forum Coordinator, AIabama A&M University

GUEST LECTURER

A T&T Bell Laboratories

"Free Electron Laser Program"

Dr. Earl Shaw

AT&T Bell Laboratories

"SCIENTIST OF TOMORROW"

Program Component

Dr. Rather Brown

Director, Minority Access to Research Careers

tMARC], Alabama A&M University

BREAK

8:50 AM

9:20 AM

9:25 AM

9:45 AM

9:50 AM

10:00 AM-- CONCURRENT SESSIONS I, II, III

12:00 AM--

2:00 PM--

1:45 PM--

4:00 PM

4:00 PM--

6:00 PM

LUNCH

Elmore Health Science Complex Gymnasium

Mr. J. Albert Diggs

Director, Equal Opportunity Program Office

Kennedy Space Center, Presiding

INTRODUCTION OF LUNCHEON SPEAKER

Dr. Yvonne B. Freeman

Manager, Minority University Program, NASA

Headquarters

SPEAKER

Dr. Ivan Van Sertima

Author-Professor, Rutgers University

NEW FRONTIER OPPORTUNITIES

Elmore Health Science Complex. Room 5.

Alabama A&M University

Mr. James R. Thompson

Director, Marshall Space Flight Center, Presiding

Dr. Lew Allen

Director, Jet Propulsion Laboratory

The JPL Historically Black College and University

Initiative

Dr. C. Richard Chappell

Chief Scientist, Marshall Space Flight Center

NASA/University JOint VEnture to Enhance Space

Science and Expand University Space Activities

Dr. Edward Fort,

Chancellor, North Carolina A&T State University

Dr. Samuel Massenberg

Langley Research Center, University Affairs Officer

Mr. Sal Majied, BDM Corporation

Space Technology Development and Utilization

Program

Mr. Kyle O. Fairchild

Technology and Commercial Programs Division

New Initiatives Office, Johnson Space Center

Technology Challenges of the Future

CONCURRENT SESSIONS IV, V, VI, VII

SCIENTIST OF TOMORROW PROGRAM

Space and Rocket Center, 1 TranquiIity Base,

Huntsville, AL

Dr. Rather Brown

Director, Minority Access to Research Careers

(MARC], Alabama A&M University, Presiding

"YOUTH CHALLENGE"

Mr. Homer McCall, Jr.

Senior Class President, Huntsville High School,

Huntsville, Alabama

KEYNOTE ADDRESS

Dr, Mae C. Jemison

NASA Astronaut
6:00PM

7:00 PM

Thursday,

8:00 AM8:30 AM

TOUR

Space and Rocket Center

HOSPITALITY HOUR

The Space and Rocket Center Lobby

BANQUET

Space and Rocket Center

Mr. James Rice

Equal Opportunity Officer, Marshall Space Flight

Center, Presiding

RECOGNITION OF SPECIAL GUESTS

Dr. Oscar Montgomery

Director, Office of Government Relations, Alabama

A&M University

PRAYER

Dr. Phillip Redrick

Director, Institutional Advancement, Alabama A&M

University

DINNER

INTRODUCTION OF SPEAKER

Mr. Lewin Warren

Deputy Assistant Administrator for Equal

Opportunity Programs, NASA Headquarters

SPEAKER

Mr. Isaac Gillam

Senior Vice President, OAO Corporation

APPRECIATION

Dr. Bessie Jones

Dean, School of Arts and Sciences,

Alabama A&M University

ADJOURNMENT

March 23, 1989

CONTINENTAL BREAKFAST

Elmore Health Science Complex Lobby

GENERAL SESSION

Elmore Health Science Complex Gymnasium

8:30 AM-- NASA FELLOWSHIP/TRAINING PROGRAMS

9:45 AM THE NATIONAL SPACE GRANT COLLEGE AND

FELLOWSHIP PROGRAM

Ms. Sherri McGee

Education Specialist, Educational Affairs, NASA

Headquarters

GRADUATE STUDENT RESEARCHER PROGRAM

Dr. Samuel Massenberg

University Affairs Officer, Langley Research Center

MINORITY GRADUATE PROGRAM

NASA/USKA UNIVERSITY ADVANCED SPACE

DESIGN PROGRAM --

"MARS SURFACED-BASED FACTORY"

Dr. John Fuller

Professor, Prairie View A&M University

SPACE LIFE SCIENCES TRAINING PROGRAM

Dr. Kenneth Redda

Program Coordinator, Florida A&M University

9:45 AM-- BREAK

10:00 AM-- CONCURRENT SESSIONS VIII, IX, X

12:00 AM

12:00 AM--

1:30 PM

1:45 PM--

3:45 PM

4:00 PM--

5:00 PM

LUNCH

Prentice Hail Banquet Room

Dr. Joseph D. Atklnson, Jr.

Equal Opportunity Officer, Johnson Space Center,

presiding

SPEAKER

Dr. Julian Earls

Chief, Health Safety and Security Division, Lewis

Research Center

CONCURRENT SESSIONS XI, XlI, XlR

POSTER PRESENTATIONS

TOUR OF RESEARCH LABORATORIES

ALABAMA A&M UNIVERSITY

CONCURRENT SESSIONS

SESSION I

Wednesday / March 22

10:00 AM-- Elmore Health Science Complex, Lecture Room

12:00 noon

PRESIDING:

Dr. Yvonne B, Freeman

NASA Headquarters

RESEARCH AND TRAINING PROGRAMS

10:130 AM-- "Women in Science and Engineering Scholars

Program." Institution: Spelman College, Project

Director: Dr. Etta Falconer, Technical Monitor: Ms.

Betty White IHQ-UI]

10:20 AM "UDC Saturday Academy - Engineering, Mathematics

and Computer Sciences for Academically Talented

Students." Institution: University of the District of

Columbia, Project Director: Dr. Winson R. Coleman,

Technical Monitor: Dr. Yvonne Freeman [HQ-U].

10:40 AM "Project LEAP Engineering Bridge Pros_am," and

"Project PRESERVE Institutional Engineering

Program." Institution: Xavier University of New

Orleans, Project Director: Mr. G. Baker and Dr:

Carole Morning, Technical Monitor: Dr. Yvonne

Freeman IHQ-U}.

11:00 AM "Lincoln University Aerospace and Engineering

(LASERJ Program." Institution: Lincoln University,

Project Director: Dr. Willie Williams, Tee/mica/

Monitor: Dillard Menchan {GSFC).

11:20 AM "Summer Intern Program fog Disabled Students in

Technical Fields." Institution: Gallaudet University,

Project Director: Anne Nissen, Technical Monitor:

Ms. Lynda Sampson {HQ-UI}.

11:40 AM "Massachusetts Pro-Engineering Mass PEP Program

[or Minority Students." Institution: Wentworth

Institute of Technology, Project Director:

Dr. Anthony Maddox, Technical Monitor: Ms. Betty

White {HQ-UI].

SESSION lI

Wednesday / March 22

10:00 AM-- Elmore Health Science Complex, Room 6

12:00 NOON
PRESIDING:

Dr.JohnHail

Milligan Science Research Institute, Atlanta

University Center, Inc.

SPACE PROCESSING AND UTILIZATION

10:00 AM

10:20 AM

10:40 AM

11:00 AM

11:20 AM

11:40 AM

"Optically Controlled Millimeter Wave Devices",

Institution: Howard University, Principal Investigator: Dr. Raj Chowdhary, Technical Monitor." Dr.

A S. Burgess [GSFC].

"A Study on Growth and Characterization of

Ternary ZnxCdl-xTe Single Crystals." Institution:

Fisk University, Principal Investigator: Dr. Enrique

Silberman, Co-lnvestigators: Dr. A Burger, Dr. D.

Henderson, Dr. S. Morgan and Dr. T. Springer,

Technical Monitor." Dr. S. L. Lehoczky [MSFC}.

"Solution Growth of TGS Crystals on International

Microgravity Laboratory IIML-11." Institution"

Alabama A&M University, Principal Investigator:

Dr. R. B. Lal, Co-Investigators: Dr. lames Trolinger,

Dr. William Wilcox, Dr. A. K. Batra, Student

Researcher: Li Yang, Technical Monitor: Mr.

Rudolph Ruff [MSFC).

"Electrode Erosion in Low Power Constricted Arcjet

Thrusters." Institution: Tuskegee University,

Principal Investigator." Dr. Pradosh K. Ray, Student

Researcher: A Ghosh, Technical Monitor: Francis M.

Curran ILeRCJ

"A Study of Spatial Data Management and Analysis

System." Institution: lackson State University,

Principal In('estigator: Dr. Robert Leflore,

Technical Monitor: R. A. Galle ISSC].

"Progress on a Proton Transport Program."

Institution: Hampton University, Principal

Investigator: Dr. Warren Buck, Student Researcher:

Duc Ngo, Technical Monitor: Larry Townsend

/LaRCl.

SESSION m

Wednesday / March 22

10:00 AM-- Elmore Health Science Complex, Room 7

12:00 NOON

PRESIDING:

Dr, Walter Watson

Alabama A&M University

PHYSICAL SCIENCES

10_00 AM

10:20 AM

10:40 AM

"Structures o| Cyano-Biphenyl Liquid Crystals."

Institution: Howard University, Principal

Investigator: Dr. Tung Tsang, Student Researcher:

YC. Chu, Technical Monitor: Dr. L. Yin [GSFC].

"Polarographic Study o| Cadmium 5-Hydroxy-2-

IHydroxy Methyll-4H-Pytan-4-one Complex."

Institution: Texas Southern University, Principal

Investigator. Dr. Ray F. Wilson, Student Researcher:

Robert C. Daniels, Technical Monitor: Dr. Donald L.

Henninger [ISC]

"Densitometric Analysis o| Commercial 35mm

Films." Institution: Morgan State University,

Principal Investigator: Dr. Ernest C. Hammond, Jr.,

Student Researcher: Christopher M. Ruffin, III,

Technical Monitor: Mr. Gerald R. Baker {GSFCI

11:00 AM

11:20 AM

11:40 AM

"Studies of Superconducting Materials with Muon

Spin Rotation." Institution: Virginia State

University, Principal Investigator: Dr. Carey E.

Stronach, Student Researcher: Michael R. Davis,

Technical Monitor." Dr. lohn W. Wilson [LaRC)

"Non.Linear Polarizabilities of Substituted PlConjugated Systems." Institution: Milligan Science

Research Institute of Atlanta University Center,

Inc., Principal Investigators." Dr. R. E Stickel, Sr.,

and Dr. BH. Cardelino, Technical Monitor: T. L.

Randall [MSFC}

"Ellipsometric Measurement of Liquid Film

Thickness."lnstitution: Alabama A&M University,

Principal Investigator: Dr. Ki loon Chang,

Technical Monitor. Dr. Donald O. Frazier [MSFC}

SESSION IV

Wednesday / March 22

1:45 PM--

3:45 PM

Elmore Health Science Complex, Lecture Room

PRESIDING:

Ms. Amanda Harris

Marshall Space Flight Center

SPACE SCIENCE

1:45 PM

2:05 PM

2:25 PM

2:45 PM

3:05 PM

3:25 PM

"Optically Controlled Solid State Devices", Institution: Howard University, Principal Investigator:

Dr. Raj Chowdhary, Student Researcher: Mr. Trevor

Correia, Technical Monitor: Dr. A. S Burgess [GSFCJ

"Evaluation of On-Board Hydrogen Storage Methods

for Hypersonic Vehicles." Institution." Hampton

University, Principal Investigator: Dr. A Akyurtlu,

Co-Investigators: |. F. Akyurtlu, A. A. Adeyiga,

Student Researcher: Samara Perdue [LaRC).

"Mossbauer Spectroscopy and Scanning Electron

Microscopy of the Murchison Meteorite."

Institution: Morgan State University

Principal Investigator: Dr. Ernest C Hammond, It.

and Dr. Frederick Oliver, Student Researcher: Mr.

Christopher L. Brown, Technical Monitor: Mr.

Gerald R. Baker [GSFC].

"The Effect of the Orbital Environment in llaO

Spectroscopy Film." Institution: Morgan State

University, Principal Investigator: Dr. Ernest C.

Hammond, It., Technical Monitor: Mr. Gerald R.

Baker [GSFC).

"Characterization of Non-Linear Quantum Well

Transmission Line Structures using a Photo Cathode

Electron Microscope." Institution: Howard

University, PrmcipaI Investigator: Dr Michael

Spencer, Graduate Student Researcher: Craig Scott,

Technical Monitor: Andre Burgess IGSFCI.

"Relativistic Nucleus-Nucleus Collisions and Dense

Nuclear Matter Formation." Institution: Alabama

A&M University, Principal Investigator. Dr. Stephen

McGuire, Technical Monitor: Thomas A Parnell

{MSFCJ.

SESSION V

Wednesday / March 22

1:45 AM-- Elmore Health Science Complex, Room 6

3:45 PM
PRESIDING:

Mr.Leonard Fisher

Lawrence Livermore National Laboratory

SPACE TECHNOLOGY: MEASUREMENTS, TECHNIQUES,

MATERIALS

1:45 PM

2:05 PM

2:25 PM

2:45 PM

3:05 PM

3:25 PM

"Low Energy Sputtering of Cobalt by Cesium Ions."

Institution: Tuskegee University, Principal

Investigator: Dr. Pradosh K. Ray, Student

Researcher: A. Handoo, Technical Monitor: Robert

T. Bechtel (MSFCJ.

"Parameters of Tensile Strength, Elongation, and

Tenacity of 70ram IIaO Spectroscopic Film."

Institution: Morgan State University, Principal

Investigators: Dr. Ernest C. Hammond, Jr. and Kevin

Peters, Technical Monitor: Mr. Gerald Baker

[GSFC].

"Influence of Temperature on the Permeation

Properties of Protective Clothing." Institution:

Tuskegee University, Principal Investigator: Dr

Nadar Vadat, Student Researcher: Michael Bush

IKSC}

"The Preparation and Study of Titanium, Zirconium,

and Hafnium Complexes." Institution: Texas

Southern University, Principal Investigator: Dr

Bobby Wilson, Technical Monitor: Dr. David S.

McKay (JSC).

"The Effect of Grinding on the Fatigue Life of

Ti-SAi-2.SSn Under Wet and Dry Conditions."

Institution: Tuskegee University, Principal

Investigator: Dr. Shaik Jeelani, Student Researcher:

Pardha Rangaswamy, Technical Monitor: Mr Paul

Munafo {MSFCI.

"A Scanning Elecron Microscopic Study of Crystals

of (2,4-Dintrobenzyl) Pyridine." Institution:

Morgan State University, Principal Investigator:

Dr Ernest C. Hammond, Jr. Student Researcher:

Jacqueline Ware, Technical Monitor: Mr. Gerald

Baker (GSFC).

SESSION VI

Wednesday / March 22

1:45 AM--

4:05 PM

Elmore Health Science Complex, Room 7

PRESIDING:

Mr. Carrington H. Stewart, P.E.

Johnson Space Center

TECHNOLOGY: LASERS, SYSTEMS ENGINEERING,

DIFFUSION

1:45 PM

2:05 PM

2:25 PM

"Atmospheric Effects on Coherent Laser Systems."

Institution: Alabama A&M University, Principal

Investigator: Dr. S. R. Murty, Technical Monitor:

Mr. James W. Bilbro (MSFC)

"Analysis of Thermal Lansing in Pumping Laser

Rods." Institution: Hampton University, Principal

Investigator: Dr. Usamah Falrukh, Student Researcher: Mr. Vincent Brackett, Technical Monitor: Dr.

Phillip Brockman (LaRCI.

"A Dynamic Systems Engineering Methodology

Research Study." Institution: Howard University,

2:45 PM

3:05 PM

3:25 PM

3:45 PM

Principal Investigators: Dr. Tepper Gill and Dr.

Arthur Paul, Technical Monitor: A Goodson [GSFC}

"Engineering Management for Large Scale Systems."

Institution: Howard University, Principal Investigators: Dr. Tepper Gill and Dr. Arthur Paul,

Technical Monitor: A. Goodson [GSFC].

"Systems Engineering in A Dynamic Environment."

Intitution: Howard University, Principal Investigator: Dr Arthur Paul, Technical Monitor: A.

Goodson {GSFC)

"Development of Flashlamp-pumped Q-switched

Ho:Tm:Cr:YAG Lasers for Mid-lnhared Lidar

Application." Institution: Hampton University,

Principal Investigator: Dr. Donald A. Whitney and

Dr Kyong H Kim, Technical Monitor: Robert V.

Hess {LaRCJ.

"XeCI Laser Pumped Iodine Laser Using t-C4F91."

Institution: Hampton University, Principal Investigators: Dr. Kwang S. Han and Dr IH. Hwang,

Technical Monitor: Mr. Robert Coston (LaRC).

SESSION VII

Wednesday/March 22

1:45 PM--

4:05 PM

Elmore Health Science Complex, Room 8

PRESIDING:

Mr. Arthur Henderson

Marshall Space Flight Center

SPACE SCIENCE

1:45 PM

2:05 PM

2:25 PM

2:45 PM

3:05 PM

3:25 PM

"Center for Spatial Data Research Applications: New

Facilities and New Paradigms." Institution: ]ackson

State University, Principal Investigator: Dr. Bruce

E Davis, Technical Monitor: Rick Galle [SSC].

"An Analysis of the Moon's Surface Using Reflected

Illumination from the Earth During a Waning

Crescent Lunar Phase." Institution: Morgan State

University, Principal Investigator: Dr. Ernest C.

Hammond, Jr., Student Researcher: Ms. Brenda [.

Queen, Technical Monitor: Mr. Gerald R. Baker

IGSFCI.

"Laboratory Studies of Acetylene Photochemistry

Related to Titan's Atmosphere." Institution:

Howard University, Principal Investigators: Dr.

Hideo Okabe and Dr. Joshua B. Halpern, Technical

Monitor: J T. Bergstralh [HQ-EL]

"A 10-Watt CW Photodissociation Laser with IODO

Perfluoro-Tert-Butane." Institution: Hampton

University, Principal Investigators: Dr. Demetrius D.

Venable and Bagher M. Tabibi, Technical Monitor."

Willard Meador, Jr. (LaRCJ.

"Vibrational Excitation of Nz by Electrons: Application and Development of the PDE Method." Institution: Florida A&M University, Principal Investigator:

Dr. Charles A Weatherford, Go.Investigators: Dr.

Roy Tucker and Gregory Odom, Technical Monitor:

Aaron Temkin (GSFC].

"Rapid Characterization of High Tc Superconductors

- D.C. Magnetic Susceptibility." Institution: Howard

University, Principal Investigator: Dr. Arthur N.

Thorpe, Student Researcher: Mr. Quoc A. Nguyen,

Technical Monitor: Dr Sidney Alterescu (GSFC).
4:45 PM "Photometric and Spectroscopic Study of Chromospherically Active Stars." Institution: Tennessee

State University, Principal Investigator: Dr. Michael

R. Busby, Student Researcher: Mathias Teke, Technical Monitor: John M Davis {MSFC}.

SESSION VIII

Thursday / March 23

10:00 AM--

12:00 NOON

Elmore Health Science Complex, Room 6

PRESIDING:

Dr. Datyush Ha

Alabama A&M University

SPACE TECHNOLOGY: MATHEMATICAL MODELING

10:00 AM Mathematical Models for Film Sensitivity Measurement." Institution." Morgan State University, Pnncipal Investigator: DL Ernest C. Hammond, Jr., CoInvestigators: Dr. Stephen Gerwirtz and Osborne

Parchment, Technical Monitor: Mr. Gerald R. Baker

IGSFC]-

10:20 AM "Finite Difference Models of Differential Equations

and Related Topics." Institution: Atlanta University,

Principal Investigator: Dr. Ronald E. Mickens,

Technical Monitor: Dr. John Shoosmith [LaRC).

10:40 AM "Kaon-Nucleus Scattering Calculations." Institution. Hampton University, Principal Investigator."

Dr. Warren Buck, Graduate Student Researcher:

B. Hong, Technical Monitor: E C. Owens [HQ-XE}.

I 1:00 AM "Implementation of an Algorithm for Cylindrical

Object Identification Using Range Data." Institution:

Spetman College, Principal Investigators: Dr. Sylvia

Bozeman and Dr. Benjamin Martin, Technical

Monitor: Michael Goode [LaRCI.

11:20 AM "Image Databases: Problems and Perspectives."

Institution: Jackson State University, Principal

Investigator: Dr. Naidu Gudivada, Technical

Monitor: Dr. Richard Gal]e {SSC}.

11:40 AM "Design o| Parallel Graphic Application Algorithms." Institution." Hampton University, Principal

Investigator: Dr. Reginald L. Walker, Technical

Monitor: Donald Lansing {LaRC}.

SESSION IX

Thursday / March 23

10:00 AM-- Elmore Health Science Complex, Room 7

12:00 NOON

PRESIDING:

Ms, Hazelyn Patterson

Marshall Space Flight Center

SPACE LIFE SCIENCES

10:O0 AM

10:20 AM

"Nitrogen Transformation and Gaseous N. Emissions

in a Pasture Ecosystems." Institution: Prairie View

A&M University, Principal Investigator." Dr. E.

Brains, Technical Monitors: Dr. G. Hutchinson

[ARS/USDA] and Dr. G. Livingston {ARC].

"Sweet Potato Production in Soilless Culture for

Controlled Ecological Life Support." Institution:

Tuskegee University, Principal Investigator: Dr. E. R.

Martinez, Co-Investigators: Dr. C. K Bonsi, D. G

Mortley, P. A. Loretan, C. R. Ogbuehi, C. Morris,

and W. A. Hill, Technical Monitors: William M.

Knott, lIl and Ralph Prince {KSC).

10:40 AM "Influence of the Nutrient Solution Application

Protocol on Growth and Yield of Hydroponically

Grown 'Georgia Jet' Sweet Potatoes." Institution:

Tuskegee University, Principal Investigators: Dr.

C. R Ogbuehi, W. A Hill, P. A. Loretan, C. K. Bosi,

C. E. Morris, P. K. Biswas, D. G. Mortley, Technical Monitors: William M. Knott, III and Ralph Prince

[KSCI.

11:00 AM "Manipulating Cyanobacteria for Potential CELSS

Diet." Institution: Alabama A&M University, Principal Investigator." Dr. Mahasin Tadros, Student

Researchers: B. Joseph, P. Mbuthia and W. Smith,

Technical Monitor: Dr. Robert MacElroy IARC}

l 1:20 AM "International Food Patterns for Space Station

Foods." Institution: Texas Southern University, Principal Investigator: Dr. Selina Ahmed, Student Researchers: Ms. Amanda Cox and Ms. Pauline V.

Cornish, Technical Monitor: Dr. Charles T. Bourland

(lSCl

11:40 AM "X-Ray Sensitivity of Diploid Skin Fibroblasts from

Patients with Fanconi Anemia," Institution: Alabama A&M University, Principal Investigator: Dr_

Ranjini Kale, Technical Monitor: Mr. Bob Schneider

(MSFCI.

SESSION X

Thursday / March 23

10:00 AM-- Elmore Health Science Complex Lecture Room

12:00 NOON

PRESIDING:

Ms. Audrey Robinson

Marshall Space Flight Center

SPACE SCIENCE

10:00 AM

10:20 AM

10:40 AM

11:00 AM

11:20 AM

"Dynamic Analysis of Large Space Structures."

Institution: Howard University, Principal Investigator: Dr. Taft Broome, Technical Monitors: Mr. S.

Woodard (LaRC).

"Evaluation and Characterization of Superconducting

Materials lot Space Applications - D.C. Magnetization." Institution." Howard University, Principal

Investigator: Dr. Arthur N. Thorpe, Student Researcher: Mr. David Davis, Technical Monitor: Dr.

Sidney Alterescu [GSFCt.

"Coefficient of Linear Expansion of Laser Materials."

Institution: Virginia State University, Principal

Investigator: Dr. George Henderson, Student Researchers: Anthony Helm, D'Anthony Woods, and

Francine Davis, Technical Monitors: Dr. Marry

Buoncristinani and Dr. Philip Brockman [LaRCh.

"Computer Simulation o| Radiation Damage in

Gallium Arsenide." Institution: Virginia State University, Principal Investigators: Mr. John J. Stith and

Dr. James C. Davenport, Technical Monitor: Dr.

John Wilson [LaRC).

"Surface Roughness of Flat and Curved Optical

Surfaces", Institution: Alabama A&M University,

Principal Investigators: Dr. P. Venkateswarlu, Dr.

B. R. Reddi, Technical Monitor: Dr. I. L. Randall

IMSFC)
SESSION XI

Thursday / March 23

h45 PM-- Elmore Health Science Complex, Room 6

3:05 PM

PRESIDING:

Mr. Johnnie Clark

Marshall Space Flight Center

SPACE TECHNOLOGY I

1:45 PM

2:05 PM

2:25 PM

2:45 PM

"Effects o| Ionizing Radiation on VLSI Electronic

Devices." Institution: Hampton University, Principal Investigator: Dr. Demetrius Venable, Technical

Monitor: E G. Stassinopoulos (GSFC].

"Relativistic Nucleon-Nucleus and AntinucleonNucleus Interactions." Institution: Hampton

University, Principal Investigator: Dr. Warren Buck,

Student Researcher: Khin Maung, Technical

Monitor: I. W. Wilson ILaRCI.

"Optimal Planar Slewing of the Flexible Orbiting

SCOLE." Institution: Howard University, Principal

Investigator: Dr. P. M. Bainum, Co-Investigator:

Feiyue Li, Technical Monitors: John W. Young and

Larry W. Taylor (LaRC).

"Forced Convection and Flow Boiling With and

Without Enhancement Devices for Top-Sided-Heated

Horizontal Channels." Institution: Prairie View

A&M University, Principal Investigators: Mr. Jerry

C. Turknett and Dr. Ronald D Boyd, Technical

Monitor: Mr. Richard Parish {ISCI.

SESSION XII

Thursday / March 23

1:45 PM-- Elmore Health Science Complex, Room 7

3:05 PM

PRESIDING:

Dr. Shaik Jeelani

Tuskegee University

SPACE TECHNOLOGY II

1:45 PM

2:05 PM

2:25 PM

2:45 PM

"Application of the Schwinger Variational Principle

to Electron-Hydrogen Atom Scattering: Investigation

of Pseudo-Resonances." Institution: Florida A&M

University, Principal Investigator: Charles Weatherford, Co-Investigators: Roy Tucker and Gregory

Odom, Technical Monitor: W. M. Hun {GSFC I.

"Study of Non Linear Properties of Organic Materials: Phase Conjugation by Degenerate Four Wave

Mixing in Disodium Fluoresein Solution in Methanol." Institution: Alabama A&M University, Principal Investigators: P. Venkateswarlu, P. Chandra

Sekhar and M.C. George, Student Researcher: H.

Abdeldayem, Technical Monitor: Dr. Joseph Randall

[MSFCI.

"An Evaluation of the lnter[acial Bond Properties

Between Carbon Phenolic and Glass Phenolic

Composites." Institution; Tuskegee University,

Principal Investigator: Dr. Shaik Jeelani, Technical

Monitor: Mr. Raymond Clinton [MSFC).

"A Study of Microstmctural Characteristics and

Differential Themal Analysis of Ni-based Superalloys." Institution: Alabama A&M University, Prin3:05 PM

cipal Investigators: Dr. R. B. Lal and Dr. M. D. Aggarwal, Student Researcher: Mr. Samuel Oyekenu,

Technical Monitor: Richard Parr [MSFC}.

"Nozzle Materials Investigation." Institution: Alabama A&M University, Principal Investigator: Dr.

James Thompson, Student Researcher: Janet Daniel,

Technical Monitor: Mr. John Austin [MSFC).

SESSION XIII

Thursday / March 23

1:45 PM-- Elmore Health Science Complex Lecture Room

3:45 PM

PRESIDING:

Dr. Mildred Wyatt

Goddard Space Flight Center

SPACE TECHNOLOGY m

1:45 PM

2:05 PM

2:25 PM

2:45 PM

3:05 PM

3:25 PM

"Servo Motor-Linked Articulated Versatile End E|-

lector ISLAVE2_ - Large Robotic Hand." Institution:

Central State University, Principal Investigator: Dr.

William A. Grissom, TechnicaI Monitors: Dr. Edwin

P. Kan [JPL). Mr. James Aliberti IKSC}.

"Joint Conjugates for Robotic Assembly o| Large

Truss Structures in Space: A Second Generation."

Institution: Jackson State University, Principal Investigator: Mr. William Brewer, Technical Monitors:

Mr. Marvin Rhodes and Ralph Will [LaRC}.

"Subcooled Ereon-11 Flow Boiling in Top-Heated

Finned Coolant Channels With and Without a

Twisted Tape." Institution: Prairie View A&M University, Principal Investigator: Mr. Alvin Smith and

Dr. Ronald D. Boyd, Technical Monitor: Mr. Richard

C. Parish (JSC).

"Growth and Characterization o[ Crystals for IR

Detectors and Second Harmonic Generation Devices." Institution: Alabama A&M University, Principal Investigators: Dr. A. K Batra, Dr. R. B. Lal, and

Dr. M. S. Rao, Student Researchers: Sandeep Bhatia

and Kunar P. Chundum, Technical Monitor: Dr.

William Wilcox [Center for Commercialization of

Space].

"Automated Assembly in Space." Institution: Bowie

State University, Principal Investigator: Dr. Sandanand Srivastava, Technical Monitor: Mr. Gary Jones

(GSFC).

"Excimer Laser Interaction with Dentin of the

Human Tooth." Institution. Morgan State University, Principal Investigator: Dr. Ernest C. Hammond,

Jr., Student Researcher: Ruth Gilliam, Technical

Monitor: Mr. Gerald baker [GSFC].

SCIENTISTS OF TOMORROW PROGRAM

Wednesday / March 22, 1989

Elmore Health Science Complex

Alabama AeOM University

SCHEDULE OF EVENTS

PRESIDING

Dr. Rather Brown, Director
8:00 AM

8:30 AM

10:30 AM

10:40 AM

11:15 AM

12:00

NOON

1:00 PM

1:45 PM

2:10 PM

2:30 PM

3:40 PM

4:00 PM

4:15 PM

4:20 PM

5:00 PM

REGISTRATION AND CONTINENTAL BREAKFAST

Elmore Health Science Lobby

GENERAL SESSION OF THE NASA-HBCU SPACE

SCIENCE AND ENGINEERING RESEARCH FORUM

Elmore Health Science Gymnasium

BREAK

VISIT BOOTH DISPLAYS

Elmore Health Science Lobby

TOUR OF ALABAMA A&M UNIVERSITY'S

SCIENCE DEPARTMENTS

1. Biology 6. Computer Science

2. Chemistry 7. Natural Resources

3. Mathematics 8. Food and Animal Science

4. Physics 9. Soil Science

5. Civil and Mechanical Engineering

10. Military Science

LUNCH

AAMU Students Cafeteria

ADMISSIONS AND FINANCIAL AID WORKSHOP

Carter Hall Auditorium

Mr. James Heyward, Director

Office of Admissions, AAMU

Mr. P. N. Lanier, Director

Office of Financial Aid, AAMU

DEPART FOR SPACE AND ROCKET CENTER

FILM "THE DREAM IS ALIVE"

Museum Theater

TOUR SPACE AND ROCKET MUSEUM

REFRESHMENTS

"YOUTH CHALLENGE"

Afuseum Auditorium

Mr. Homer McCall, Jr.

Sr. Class President, Huntsville High School

INTRODUCTION OF SPEAKER

Ms. Yvonne Sanders

Program Coordinator, AAMU

SPEAKER

Astronaut Mac C. Jemison, MD

STUDENTS DEPART FOR HOME.

POSTER PRESENTATIONS

1. "Genetic Effects of Heavy Ions," Institution: Alabama A&M

University, Principal Investigator: Dr. Purushottam Kale,

Technical Monitor: Dr. Stuart Nachtwey {ISC].

2. "Teacher Training and Improvement in Science: The Alabama

A&M Science Improvement Project," Institution: Alabama A&M

University, Principal Investigator: Dr. Saundra Y. McGuire,

Technical Monitor: Mr. James Rice (MSFC).

3. "Synthesis of 3-[Bromoacetamido)-propylamine Hydrochloride

as Sulphydryl Reagent for Myosin Subfragment," Institution,"

Miles College, PrincJpal Investigator." Dr. Prasanta Sharma.

4. "Effects of Radiation and Space Flight on Testicular Morphology in Rats and Mice," Institution: Tuskegee University,

Principal Investigator: Carol S. Williams and Walter J. Sapp,

Technical Monitor: Dr. Delbert E. Philpott (ARC].
CONTENTS

Preface ................................................... iii

Program ................................................... v

Presentations ............................................... 1

I. Life Science

A Comparative Study of Seminiferous Tubular Epithelium from Rats Flown on

Cosmos 1887 and SL3 .......................................... 1

W.J. Sapp, D.E. Phiipott, C.S. Williams, K. Kato, J. Stevenson, and L.V. Serova

Effect of Biweekly Shoot Tip Harvests on the Growth and Yield of "Georgia Jet" Sweet Potato

Grown Hydroponically .......................................... 9

C.R. Ogbuehi, P.A. Loretan, C.IC Bonsi, W.A. Hill, C.E. Morris, P.IC Biswas, and D.G. Mortley

Effect of Channel Size on Sweet Potato Storage Root Enlargement in the Tuskegee University

Hydroponic Nutrient Film System ................................... 15

C.E. Morris, E. Martinez, C.K. Bonsi, D.G. Mortley, W.A. Hill, C.R. Ogbuehi, and P.A. Loretan

Excimer Laser Interaction with Dentin of the ltuman Tooth .................... 20

E.C. Hammond, Jr., R. L. Gilliam, and G.R. Baker

International Food Patterns for Space Food ............................. 26

S. Ahmed,/L Cox, P.V. Cornish, and C.T. Bourland

In Vitro Regeneration of _dtsfJ]lLA]baL ................................. 33

N.A. Edney, M.A. Rizvi, and N.F. Rizvi

Manipulating Cyanobacteria: Spirulina for Potential CELSS Diet ................ 40

M.G. Tadros, W. Smith, P. Mbuthia, and B. Joseph

Seasonal Nitrous Oxide Flux from Intensively Managed Pasture in Humid

Subtropical Ecosystems ......................................... 45

E.A. Brams, W.H. Anthony, G.L. Hutchinson, and G.P. Livingston

X-Ray Sensitivity of Diploid Skin Fibroblasts From Patients with Fanconi's Anemia ..... 46

R. Kale
II. Mathematical Modeling, Image Processing,

Pattern Recognition, and Algorithms

Construction of Stable Explicit Finite-Difference Schemes for Schr6dinger Type

Differential Equations .......................................... 47_)_3

R. Mickens and J. Shoosmith

Image Databases: Problems and Perspectives ............................. 53

V. N. Gudivada

Implementation of an Algorithm for Cylindrical Object Identification

Using Range Data ............................................. 61

S.T. Bozeman and B.J. Martin

Mathematical Models for Film Sensitivity Measurements ..................... 69

E. Hammond, Jr., S. Gewirtz, and O. Parchment

Prediction of Pseudo-Resonance Positions in the Schwinger Variational Principle ....... 77

C.A. Weatherford, R. Tucker, and G. Odom

III. Microgravity Processing, Space Utilization and Application

Growth and Characterization of Crystals for IR Detectors and Second Ilarmonic

Generation Devices ............................................ 84

R.B. Lal, A. Batra, M.S. Rao, S.S. Bhatia, ICP. Chunduru, R. Paulson, and T.K. Mookherji

Jackson State University's Center for Spatial Data Research and Applications:

New Facilities and New Paradigms ................................... 90

B.E. Davis and G. Elliot

Solution Growth of Triglycine Sulfate (TGS) Crystals on International Microgravity

Laboratory (IML-I) ........................................... 96

R.B. Lal, A.K. Batra, L. Yang, W.R. Wilcox, and J.D. Trolinger

Study of Spatial Data Management and Analysis Systems .................... 101

C. Christopher and R. Galle

IV. Physical Science and Chemistry

Analysis of Cured Carbon-Phenolic Decomposition Products to Investigate the Thermal

Decomposition of Nozzle Materials ................................. 108_ /

J. M. Thompson and J.D. Daniel

3-(Bromoacetamido)-Propylamine Hydrochlortde: A Novel Sullhydryl Reagent and

Its Future Potential in the Confignrationai Study of SI-Myosin ................. 127_2 _

P. Sharma and H.C. Cheung
EilipsometricMeasurementof Liquid Film Thickness ...................... 134

K.J. Chang and D.O. Frazier

Formation and Study of Titanium, Zirconium and Hafnium Complexes ............ 141

B. Wilson, S. Sarin, L. Smith, and M. Wilson

Kaon-Nucleus Scattering ....................................... 146-

B. Hong, W.W. Buck, ICM. Maung, J.W. Wilson, and LW. Townsend

Phase Conjugation by Degenerate Four Wave Mixing in Disodium Fluorescein

Solution in Methanol .......................................... 162 -

? jH. Abdeldayem, P. Chandra-Sekhar, P. Venkateswarlu, and M.C. George

Polarographic Study of Cadmium

5-Hydroxy-2-(Hydroxy Methyl)-4H-Pyran-4-One Complex .................... 171

R.F. Wilson and R.C. Daniels

Purification, Growth and Characterization of ZnxCAi.xSe Crystals ............... 188.

E. Silberman, A. Burger, W. Chert, D.O. Henderson, S.H. Morgan, J.M. Springer, and Y. Yao "

Scanning Electron Microscopy Study of the Macro-Crystalline Structure of

2-(2,4-Dinitrobenzyl) Pyridine .................................... 195-.

J. Ware, E. Hammond, Jr., and G.R. Baker

Structures of Cyano-Biphenyl Liquid Crystals ........................... 205 .....

Y.C. Chu, T. Tsang, E. Rahimzadeh, and L. Yin

Studies of Superconducting Materials with Muon Spin Rotation ................ 211

M.R. Davis, C.E. Stronach, W.J. Kossler, H.E. Schone, X.H. Yu, Y.J Uemura,

B.J. Sternlieb, J.R. Kempton, J. Oostens, and W.F. Lankford

10-Watt CW Photodissociation Laser with IODO Perfluoro-Tert-Butane ........... 218_c>'-_

B. Tabibi and D.D. Venable

UV Photochemistry of C2N2 ...................................... 231

J. B. Halpern and S.A. Barts

V. Research and Training Programs

Encouraging the Pursuit of Advanced Degrees in Science and Engineering:

Top-Down and Bottom-Up Methodologies .............................. 240

A.B. Maddox, R.P. Smith-Maddox, and B.E. Penick

Jet Propulsion Laboratory's Initiative on ltistorically Black Colleges and Universities

L. Allen, P. Forte, and M.H. Leipold

• . . 247

Lincoln Advanced Science and Engineering Reinforcement (LASER) Program ........ 254

W.E. Williams
Model Summer Program for Handicapped College Students ................... 262 _.

A.B. Nissen

Successful Intervention Program for High Ability Minority Students .............. 266

W.R. Coleman

Women In Science and Engineering CWlSE) Scholars Program ................. 270

E.Z. Falconer and L.A. Guy - rVI. Space Science: Astronomy, Planetary Science,

Asteroids, Moon, etc.

An Analysis of the Moon's Surface using Reflected Illumination From the Earth

During a Waning Crescent Lunar Phase ............................... 276

E.C. Hammond, Jr., M. Linton-Petza, and G.R. Baker

Densitometric Analysis of llaO Film Flown Aboard the Space Shuttle

Transportation System STS #3, 7 and 8 ............................... 283

E.C. Hammond, Jr.

M6ssbauer Spectroscopy and Scanning Electron Microscopy of

the Murchison Meteorite ....................................... 294_

C.L. Brown, F.W. Oliver, E.C. Hammond, Jr., and G.R. Baker _-_ z/ 6

Solving the BM Camelopardalis Puzzle ............................... 298

M. Teke, M.R. Busby, D.S. Hall, and John Davis

VII. Space Technology: Engineering, Structures and

Systems for Application in Space

Aerosol Speckle Effects on Atmospheric Pulsed Lidar Backscattering Signals ......... 304

S.R. Murty

Automated Assembly in Space .................................... 313

S. Srivastava, S.N. Dwivedi, T.T. Soon, R. Bandi, S. Banerjee, and C. Hughes

Electrode Erosion in Low Power Arcjet Thrusters .................. ........ 323

A. Ghosh and P. Ray

Evaluation of On Board llydrogen Storage Methods for Hypersonic Vehicles ......... 329

A. Akyurtlu, J.F. Akyurtlu, A.A. Adeyiga, S. Perdue, and G.B. Northam

Joint Conjugates for Robotic Assembly of Large Truss Structures in Space: •

A Second Generation .......................................... 336

W.V. Brewer
MarsSurfaceBasedFactory:PhaseII - TaskiC - ComputerControl of a

Water Treatment System to Support a Space Colony on Mars .................. 343 7 =

J. Fuller, W, Ali, and D. Willis

Servomotor-Linked Articulated Versatile End Effector (SLAVE z) ................ 349

m.J. Ajayi-Majebi, W.A. Grissom, B. Wingard, and D. Walker _ "

VIII. Space Technology: Physics of Materials and

Systems for Space Applications

Computer Simulation of Radiation Damage in Gallium Arsenide ................ 356

J.J. Stith, J. C. Davenport, and R.L. Copeland

Forced Convection and Flow Boiling With and Without Enhancement Devices for

Top-Side-lleated llorizontai Channels ............................... 363 _-_

R.D Boyd, Sr. and J. C. Turknett

Progress in Proton Transport Code Development: Microelectronic Application ........ 371 _rc.: i

D.M. Ngo, W.W Buck, T.N. Fogarty, and J.W. Wilson /

Study of Microstructural Characteristics and Differential Thermal Analysis of

Ni-based Superalloys .......................................... 382_

M.D. Aggarwal, R.B. Lal, S.A. Oyekenu, R. Parr, and S. Gentz

Subcooled Freon-ll Flow Boiling in Top-Heated Finned Coolant Channels With and

Without a Twisted Tape ........................................ 39Q

A. Smith and R. Boyd, Sr.

XeCl Laser Pumped Iodine Laser Using t-C4F91 .......................... 398

H. Hwang and ICS. Han

IX. Technology: Materials, Techniques, Measurements

Characterization of Quantum Well Structures Using a Photocathode

Electron Microscope .......................................... 405

M.G. Spencer and C.J. Scott

Densitometric Analysis of Commercial 35mm Film ........................ 409

E.C. Hammond, Jr., C. Ruffin, III, and G.R. Baker

Development of Hashlamp-Pumped Q-Switched Ho:Tm:Cv.YAG Lasers for

Mid-Infrared Lidar Application ................................... 422

Y.S. Choi, I_H. Kim, D.A_ Whitney, R.V. Hess, N.P. Barnes, C.H. Bair, and P. Brockman

Effect of Grinding on the Fatigue Life of Titanium Alloy (SAI-2.SSn) Under Dry and

Wet Conditions ............................................. 428

P. Rangaswamy, H. Terutu'ng, and S. Jeelani _: _'_::
Engineering Management of Large Scale Systems ......................... 443_;._

S. Sanders, T.L. Gill, and A.S. Paul

Evaluation of the lnterfacial Bond Properties Between Carbon Phenolic and Glass

Phenolic Composites .......................................... 450_,_)_

K. Jordan, R. Clinton, and S. Jeelani

Low Energy Sputtering of Cobalt by Cesium Ions ......................... 471 .;\_

A. Handoo and P. Ray

Parameters of Tensile Strength, Elongation, and Tenacity of 70mm llaO

Spectroscopic Film ........................................... 479 _

E. Hammond, Jr., K.A. Peters, and G.R. Baker

Surface Roughness of Flat and Curved Optical Surfaces ..................... 482 i,_

M.C. George, B.R. Reddy, H. Jagannath, M. Perera, and P. Venkateswarlu

Suggested Criteria for Evaluating Systems Engineering Methodologies ............ 489 ,,¢

A. Gates, A. Paul, and T. Gill

List of Participants ........................................... 494

Authors Index .............................................. 516
w

N91-28064

A COMPARATIVE STUDY OF SEMINIFEROUS TUBULAR EPITHELIUM

FROM RATS FLOWN ON COSMOS 1887 AND SL3

Walter J. Sapp, Carol S. Williams, and K. Kato,

Department of Biology

Tuskegee University

Tuskegee, AL

._.?_,._ f,?-.--

and

Delbert E. Philpott and J. Stevenson

NASA - Ames Research Center

Moffet Field, CA

and

L.V. Serova

Institute for Biomedical Problems

Moscow, USSR

ABSTRACT

Space flight, with its unique environmental constraints such as immobilization, decreased and

increased pressures, and radiation, is known to affect testicular morphology and spermatogenesis.

Among the several biological experiments and animals on board COSMOS 1887 Biosputnik flight were

10 rats, from which wehave collected testicular tissue. Average weights of flight testes were 6.4% below

that of the vivarium control when normalized for weight loss / 100 grams body weight. Counts of surviving

spermatogonia per tubule cross section indicated an average of 39 spermatogonia for flight animals, 40

for synchronous controls and 44 for the vivarium controls. Serum testosterone was significantly

decreased when compared to basal controls but the decrease was not significant when compared in

vivarium and synchronous control groups. The significant decrease in spermatogonia and the decrease

in serum testosterone are similar to that in animals flown on Space Lab 3 (Challenger Shuttle).
A COMPARATIVE STUDY OF SEMINIFEROUS TUBULAR EPITHELIUM

FROM RATS FLOWN ON COSMOS 1887 AND SL3

Introduction

The testes have been shown to be affected by space flight, immobilization, irradiation and

increased gravity. Fedorova (1) reported an increase of 30 to 70% atypical spermatozoa consisting of

tail curling and absence of a tail. These abnormalities decreased to the high normal range of 30% by 75

days postflight. Rat testes from SL-3 showed a 7.5% decrease in Stage 6 spermatogonia and a weight

loss of 7.1% when compared to controls (2). In earlier studies of rats flown aboard COSMOS 690 (3)

and COSMOS 605 (4) no specific changes in the testes, directly attributed to flight, were reported.

Immobilization, applied for a short or long period, is considered a form of physiological stress, and

induces a decrease in plasma testosterone levels (5-7). While most reports indicate no change in the

morphology of differentiating germ cells as a result of immobilization (8), a "striking" arrest of

spermatogenesis in a primate has been reported (9). The sensitivity of the testes to radiation is well

known and well studied. The details of spermatogonial effects of irradiation in mice, rats and primates

have been the subject of studies utilizing X-irradiation and gamma irradiation (10-13). Alpen and

Powers-Risius (14) have quantitated HZE irradiation effects using testes weight loss. Philpott et

a1.(15-19) have reported the results of cosmic (HZE) type irradiation on spermatogonial cell counts

using an assay method that concentrates on cell numbers in spermatogonial Stage 6 (12) and which

provides a means of detecting cell population changes at doses of less than 0.5 rads (17). This sensitive

response makes the testes a possible candidate as a biological dosimeter.

Summary of Flight and Recovery

The following is from the "Summary of the COSMOS 1887 flight and specimen collection" as

compiled by Dr. R.E. Grindeland, NASA:

The COSMOS 1887 Biosputnik flight was launched September 29, 1987 and landed October 12,

1987 after a flight of 12.5 days. Inflight, 10 male SPF rats of Czechoslovakian origin (Institute of

Endocrinology, Brattislava, Czechoslovakia) were housed in a single cage which had 10 nozzles for

delivery of a paste diet and 10 lixits for water. Fourteen-gram boluses of food (total 55g/day/rat) were

provided ad libitum. The air pressure in the cage was 760 mm Hg, the humidity averaged 58%, and the

ambient temperature was 22°C - 23°C. Lights were on from 0800-2400 and off from 2400-0800 hours.

Light intensity was 4-8 lumens at the cage floor. The Biosputnik had an orbital inclination of 62.8

degrees; the apogee and perigee were 406 and 224 kilometers, respectively.

Due to difficulties during reentry, the Biosputnik landed in Siberia rather than the designated site

where the recovery/dissection team was located. The calculated landing force was less than 4 g. At the

landing site there were about 15 cm of snow and the outside temperature varied from -5°C to -20°C.

The Biosputnik was located in 3 hours and a rescue team placed a heated tent (23°C) around the vehicle.

The following morning, 20 hours after landing, the animals were placed in transport cages and carried

by bus (3 hours), airplane (6.5 hours), and van (0.5 hour) to the designated recovery/dissection site.

Rats were sacrificed the next morning. Due to the recovery delays, rats had been without food for 42

hours. While the biosateilite was on the ground, the ventilation system continued to work so the animals

2
received an adequate air supply. The temperature of the rat cage was not recorded after landing, but

calculations indicate that the temperature fell slowly and did not go below + 12°C. When examined

upon removal from the flight cage, the rats were somewhat dirty but apparently healthy and free from

injury. During the airplane trip back from the landing site the animals "appeared exhausted" - much

like the rats after the Space Lab 3 flight.

Methods

For each of the five animals in each group (flight, synchronous control and vivarium control) testes

were removed, weighed, immediately slit open and immersed in cold Triple Fix (20). The specimens

were kept at 4°C, shipped to Ames Research Center and refrigerated until time for processing. Samples

were treated with 1% osmium tetroxide for 1 hour, dehydrated in ascending concentrations of acetone,

infiltrated with Epon-Araldite and polymerized at 60°C for 48 hours. Six blocks were produced from

each testis. Two-micron cross sections were cut on a Porter-Blum ultramicrotome and mounted on glass

slides. The sections were stained with 1% toluidine blue in 1% borax. Alternate sections containing

maturation Stage 6 (12) were scored for surviving spermatogonia.

Results

The average weight difference of the COSMOS flown rat testes is 6.4% as compared to vivarium

controls when normalized for weight/100 grams. There is no difference in testis weight when flight

animals and synchronous control animals are compared.

Counts of surviving spermatogonia (Table 1) per tubule cross section indicate an average of 38.79

spermatogonia for flight animals, 40.20 for synchronous controls and 43.75 for vivarium controls. The

decreases of spermatogonia in flight tissues are significant when compared to synchronous control

(P<0.02, 1 tail; P<0.05, 2 tail) and vivarium control (P<0.0002, 1 tail; P<0.005, 2 tail). Rats flown on

SL-3 experienced a similar decrease in number of spermatogonia (2). Preliminary counts of Sertoli cells

per tube cross section indicate no significant difference (P>0.05) when vivarium control animals are

compared to either synchronous controls or to flight animals. This consistency in Sertoli cell numbers

per tubule cross section demonstrates their stability under the adverse conditions of space flight and

indicates that the minor volumetric changes in tubular epithelium due to spermatogonial cell loss do

not affect the relative numbers per tubule of cross section. Spermatogonial cell loss can be quantitated

per number of Sertoli cells or per tubule cross section. Changes in spermatogonial cell populations are

indicative of actual cell loss and are not significantly influenced by volumetric changes in the tubules

(Figure la, lb, lc).

Discussion

While it is general knowledge that the testes are very sensitive to certain environmental factors

including stress and irradiation, not all reports agree on the extent and nature of morphologic changes

in the seminiferous epithelia (8). Most reports indicate that stress decreases testosterone levels (5-7)

but does not cause any morphological changes in seminiferous tubules (8). Interestingly, in human

3
beings,stressmaycauseeitheran increase or decrease in serum testosterone depending upon whether

the stress is perceived as a threat to dominance/control (increased testosterone) or a loss of control

(decreased testosterone) (7). On the other hand, irradiation, depending on the dosage, can result in

the depletion of all spermatogonial cells except a few of the stem cells (17,13), but testosterone levels

do not seem to be affected in the serum or intratesticular tissue by irradiation (21). Grindeland et al.

(22) measured the serum testosterone in the COSMOS 1887 animals and reported lower hormone

levels when flight animals were compared to vivarium and synchronous controls.

Previous space flight investigations prior to SL-3 have not reported changes in seminiferous

epithelium while simulated conditions, at least in some investigators' labs, result in changes (4). Data

obtained from rats flown on COSMOS 1887 indicated significantly reduced numbers of spermatogonia

when compared to both synchronous control animals (4% decrease) and vivarium control animals (11%

decrease) and were generally similar to results obtained from rats flown on SL-3 (2,23). Our assay

procedure provided excellent quality specimens, sections thin enough to provide morphological differentiation of each spermatogonial cell class, and precise quantitation.

Data indicte a significant difference in spermatogonial population when the two control groups

are compared. This difference may be caused by stresses encountered under simulated space flight

conditions, or to as yet unexplained responses. A similar decrease in spermatogonia was seen in rats

subjected to suspension in a simulated SL-3 flight (Table 1). We postulate that the decrease (4%) in

spermatogonia observed in rats actually flown on COSMOS 1887 when compared to the synchronous

controls is due to space flight conditions not adequately duplicated on the ground based synchronous

experiment. One possible factor is radiation. Dosimetry reports from COSMOS 1887 indicate a dose

factor of 0.313 rad at the dosimeter location within the space craft. Dosimeters were not located near

the animals; therefore, the exact dosage received in that area is not known. Low radiation levels do not

produce gross changes in morphology; however, spermatogonia near the first meiotic division are

reduced in number. This is not unexpected and many investigations, including our own, substantiate

these results (17). We have shown with X-rays and with HZE particles the extreme sensitivity and

predictable response of the testicular epithelium to irradiation. The loss of cells not accounted for except

by space travel could have resulted from radiation, especially since any particles penetrating the space

craft would have been galactic and of similar energy to Iron. Our previous experiments indicate that

irradiation with HZE particles of Iron at 0.5 rad level caused significant decreases in spermatogonia in

mice (19) and these changes could be detected down to the 0.1 rad level (Unpublished).

Previous work in our laboratory led us to conclude that the testicular seminiferous epithelium is

a good model for radiation sensitivity studies since it is composed of cellular populations which vary in

individual radiosensitivities, indicated by the multiple slopes seen in spermatogonial survival curves (17).

These characteristics of testicular epithelium provide an accurate means for biological dosimetric

assessment of radiation exposure. Data collected from this flight (COSMOS 1887) as well as from the

earlier SL-3 flight indicate that the biological effects of space flight are multifaceted. Impact on the

morphophysiology of the testes through a number of different pathways, i.e., decreases in serum

testosterone and testes weight loss, is observed in the animals described in this report. Stress related

gonadal dysfunction and possible galactic radiation exposure, possibly along with other factors, apparently contribute to the significant decrease in spermatogonial cell numbers observed in rats flown in

space. Various changes in the environment can alter testicular integrity. The site of action of these

various environmental impacts and the mechanisms by which they interfere with both spermatogenesis

and steroidogenesis need further investigation. These important investigations should be repeated with

longer flights and a shorter time span between recovery and specimen preparation. When it becomes

possible, fixation in flight will remove any doubt about the effect recovery may have.

4
Acknowledgments

This work was supported in part by the NASA/Ames Research Center Cooperative Agreement

#NCC2-12 and #NC2-455 (to W.J.S.). Ultrastructural Facility support was provided by

NIH/DRR/RCMI grant #G12RR03059-01AI.

Note: The work presented here also appears as a publication in the FASEB Journal.

References

1. Fedorova, N.L, Kosmichesda Biol Med., 1967, 1, 28. Space Biol. Med. 1, 28.

2. Philpott, D.E.; Sapp, W.; Williams, C.; Fast, T.; Stevenson, J.; Black, S., Proc. EMSA.,

1986, 44, 248.

3. Plakhuta-Plakutina, G.I., Aviat. Space Environ. Mcd., 1977, 48, 12.

4. Portugalov, V.V.; Savina, E.A.; Kaplansky, A.S.; Yakovleva, V.I.; Plakhuta-Plakutina,

G.I.; Pankova, A.S.; Katunyan, P.I.; Shubich, M.G.; Buvalio, S.A., Aviat Space Environ.

Med., 1976, 47, 813.

5. Carpenet, G.; Tache, Y.; Forest, M.G.; Haour, G.; Saez, J.M.; Bernier, M.; Ducharme,

J.R.; Collu, R., Endocrinology, 1981, 109, 1254.

6. Armario, A.; Castellanos, J.M., Physiol. Behav., 1984, 32, 517.

7. Collu, R.; Gibb, W.; Ducharme, J.R., J. Endocrinol. Invest., 1984, 7, 529.

8. McGrady, A.V.; Chakraborty, J., Arch. Androl., 1983, 10, 95.

9. Zemjanis, R.; Gondos, B.; Adey, W.R.; Crockett, A.T.IC, Fertil. Steril., 1970, 21,335.

10. Oakberg, E.F.; Clark, E., J. Cell. Comp. Physiol., 1961, 58 (Suppl 1), 173.

11. Hugon, J.; Borgers, V.M., Anat. Rec., 1966, 155, 15.

12. Huckins, C., Anat. Rec., 1978, 190, 905.

13. VanAlphen, M.M.A.; VanDeKant, H.J.G.; DeRooij, D.G., Radiat. Res., 1988, 113,473.

14. Alpen, E.L.; Powers-Risius, P., Radiat. Res., 1981, 88, 132.

15. Philpott, D.E.; Sapp, W.; Williams, C.; Stevenson, J.; Black, S., Proc. EMSA., 1981, 39,

542.

16. Philpott, D.E.; Sapp, W.; Williams, C.; Stevenson, J.; Corbett, R.; Black, S., Proc. EMSA.,

1983, 41,674.

5
17. Philpott,D.E.;Sapp,W.;Williams,C.; Stevenson, J.; Corbett, R.; Black, S., Scanning

Electron Microsc., 1983, III, 1345.

18. Philpott, D.E.; Sapp, W.; Williams, C.; Stevenson, J.; Black, S.; Corbett, R., The

Physiologist., 1985, 28(6)suppl, s211.

19. Philpott, D.E.; Sapp, W.; Williams, C.; Stevenson, J.; Black, S.; Corbett, R., Prec. EMSA.,

1985, 43, 652.

20. Philpott, D.E., Corbett, R.; Turnbill, C.; Black, S.; Dayhoff, D.; McGourty, J.; Lee, R.;

Harrison, G.; Sovick, L. Aviat. Space Environ. Med., 1980, 51,556.

21. Cunningham, G.R.; Huckins, C., Radiat. Res., 1978, 76, 331.

22. Grindeland, R.; Popova, I.; Vasquez, M., FASEB J., 1989, Submitted for publication.

23. Sapp, W.J.; Philpott, D.E.; Williams, C.S.; Kato, K.; Stevenson, J.; Serova, L.V., Prec.

EMSA., 1988, 46, 276.

6
TABLE 1. TOTAL SURVIVING SPERMATOGONIA PER STAGE 6

SEMINIFEROUS TUBULE PROFILE a

Treatment

Group Data

Individual Mean + S.E.M. c SL-3 d

Animals b

SL-3 e

Simulation

Flight

Synchronous

Vivarium

37.90 ± 0.15

38.77 + 0.12

39.36 ± 0.15

39.08 + 0.12

38.83 + 0.13

40.44 + 0.10

41.13 + 0.15

39.08 + 0.19

40.00 + 0.12

40.35 + 0.12

43.15 ± 0.17

44.36 ± 0.13

43.58 + 0.16

43.55 + 0.20

44.12 + 0.17

38.79 + 0.06**

40.20 + 0.06*

43.75 ± 0.07

39.75 ± 0.14

N/A

42.71 ± 0.17

26.82 + 0.27

N/A

44.24 + 0.27

a Tubules identified according to Huckins (Anat. Rec. 190:905, 1978).

Cross section only.

b 200 tubules scored per animal; mean + standard error.

c 5 animals per treatment; total = 1000 tubules scored.

d SL-3 data shown here for comparison (See Philpott et al., EMSA 44:248, 1986).

Mean + standard error, 200 tubules scored.

e Rat tail suspension; 50 tubules scored; mean + standard error

* Significantly different from vivarium control, P<0.001

** Significantly different from vivarium control, P<0.0005

7
ORIGINAL PAGE

_,LACK AND Wi-i.I.TEPHOTOGRAPH

Figure legend

Figure 1. Representative sections of seminiferous tubules: (a) Vivarium control;

(b) Synchronous control; (c) Flight animals. Arrows indicate spermatogonia.

Magnification = 300x.

8
N91-28065

EFFECT OF BIWEEKLY SHOOT TIP HARVESTS ON THE

GROWTH AND YIELD OF "GEORGIA JEW SWEET POTATO

GROWN HYDROPONICALLY

C.R. Ogbuehi*, P.A. Loretan, C.K. Bonsi, W.A. Hill

C.E. Morris, P.K. Biswas and D.G. Mortley

G.W. Carver Agricultural Experiment Station

Tuskegee University

Tuskegee, AL

ABSTRACT

Sweet potato shoot tips have been shown to be a nutritious green vegetable. This study was

conducted to determine the effect of biweekly shoot tip harvests on the growth and yield of "Georgia

Jet" sweet potato grown in the greenhouse using the nutrient film technique (NIT). The nutrient

solution consisted of a modified half Hoagland solution. Biweekly shoot tip harvests, beginning 42 days

after planting, provided substantial amounts of vegetable greens and did not affect the fresh and dry

foliage weights or the storage root number and fresh and dry storage root weights at final harvest. The

rates of anion and cation uptake were not affected by tip harvests.

*Author presenting paper. Contribution No. PS014 of the George Washington Carver Agricultural Experimental Station, School of Agriculture and Home Economics, Tuskegee University. This

research was supported by funds from the National Aeronautics and Space Administration (Grant No.

NAG10-0024) and USDA/CSRS (Grant No. ALX-SP-1). We wish to thank Mr. Ralph Prince and Dr.

William M. Knott III of the NASA/John F. Kennedy Space Center for technical assistance.
EFFECT OF BIWEEKLY SHOOT TIP HARVESTS ON THE

GROWTH AND YIELD OF "GEORGIA JET" SWEET POTATO

GROWN HYDROPONICALLY

Introduction

In a number of countries where sweet potato is a staple, the shoot tips (top 10 cm) are eaten as

vegetable greens. Villareal et al. (1979) reported that in Southeast Asian countries yields of sweet potato

shoot tips consumed as vegetables varied from 10 to 16 t/ha while marketable roots for those cultivars

studied as possible dual vegetable crops varied from 1 to 16 t/ha. In West Africa, Liberians consume

sweet potato tips on a daily basis (As-Saqui, 1982). Pace et al. (1985a,b) reported that sweet potato

green tips are as nutritious in Ca and Fe as are other leafy vegetables such as spinach, mustard, turnip

and collard greens and can be similarly prepared. They suggested that sweet potato tips have potential

as a new food in the U.S.

Because of its value as a dual vegetable in that both shoot tips and storage roots can be eaten,

sweet potatoes have been selected by the National Aeronautics and Space Administration as a potential

food source for space missions. Investigations are underway to determine the optimum conditions for

production of sweet potatoes in Controlled Ecological Life Support Systems (CELSS). One aspect of

this research is to study the effect of periodic harvesting of sweet potato shoot tips on the growth of the

plant and its storage root yield.

Dahniya (1980) investigated the effect of leaf harvests and topping on the foliage and root yields

of sweet potato. He showed that topping shoot tips resulted in 34 to 42% less shoot yield than did cutting

plants at the base of each shoot. Storage root yield was less severely reduced when shoot tips were

topped than when vines were cut at the base. Total shoot yield was unaffected when tips were harvested

at 2-, 3-, or 4-week intervals.

Bartolini (1981) reported that shoot topping increased storage root yield of sweet potatoes

significantly when done between one and two months after planting. Shoot topping beyond two months

or continuous topping was detrimental to storage root production. Gonzales et al. (1977) studied the

effect of topping and fertilization on yield of sweet potatoes and found that topping reduced storage

root yields. The highest storage root yield was obtained from the no topping treatment; successively

lower yields were obtained by topping at 3-week intervals and topping at biweekly intervals. In a related

study, Hopkinson (1986) investigated the effect of shoot tip harvests of sweet potato at 45, 60 and 75

days after planting. He found that removal of 15 cm from the terminal ends of sweet potato vines at

these dates did not significantly reduce storage root yields.

In an open hydroponic system study employing sand as the aggregate, Pace et al. (1988) showed

that the dry matter and nutrient content of sweet potato green tips and roots harvested on different

dates differed according to cultivar. Loretan et al. (1988) and Hill et al. (1988) also reported that the

nutritive quality of storage roots and foliage of hydroponically grown sweet potatoes were similar to

field grown sweet potatoes and suggested the crop has high potential for CELSS. However, Hill et al.

(1988) reported that there was a higher shoot/storage root ratio, as measured by the harvest index, for

sweet potato plants grown using the nutrient film technique (NFT) as compared to those grown using

an aggregate. Depending on the cultivar, foliage growth in NFT can be prolific; this can be an advantage

for CELSS in that the shoot tips can be cut and used as vegetable greens and the total biomass produced

10
can be increased. However, too much foliage growth could be a disadvantage because of limited space

in the biomass production chamber (BPC) (Prince et al., 1986).

The objective of this study was to evaluate the effect of biweekly cutting of shoot tips on sweet

potato plants grown in an NFT system.

Materials and Methods

Experiments on the effect of harvesting foliage shoot tips were carried out with plants grown in

the Tuskegee University NFT system. Three channels, each with its own reservoir, were used with the

first and third channels holding four plants each. Shoot tips (10 cm) from plants in the first channel

were harvested starting at 42 days after planting and thereafter on a biweekly basis until the end of the

experiment (Treatment A). The plants in the third channel were the control and were left intact until

harvested at 120 days (Treatment C). The middle channel with no plants was used to monitor water loss

due to evaporation for the other treatments.

A modified half Hoagland solution (30.4 liters) was used as the nutrient solution in each tank. The

solution pH values were maintained at 6.0 by addition of either NaOH or H2SO4 (Bakker, 1986) while

the temperature, salinity and electrical conductivity were recorded at regular intervals. Nutrient solution

was pumped to all the channels by a small submersible pump (Teel Model IP680A, 1/200 HP) in the

reservoir and the flow rate was maintained at 16 ml s 1. Solutions were changed at 2-week intervals and

were topped with deionized water if the volume was reduced to 8 liters prior to the 2-week interval.

Samples of nutrient solutions from treatments A and C were taken at the time of solution preparation

and prior to the solution change and analyzed for CI, NO3, H2 PO4 and SO4 with a Dionex Ion

Chromatograph model 40001. NH4, K, Mg, and Ca cations were also analyzed in addition to the anions.

Abaxil stomatal conductance (cm s-1) was also measured for five days between 1200 and 1400 h

CST. The measurement was made on the third uppermost, fully expanded and unshaded leaf of each

plant using a LI-1600 Steady State Porometer (LI-Cor, Inc., Lincoln, NE). If the third leaf was found

damaged, measurement was made on the fourth or fifth leaf. The transpiration rate of each plant (ug 2.1

cm" s" ) was also recorded for five days. All five measurements were done during the last quarter of the

plant's growth ( 90-100 days after planting).

Each shoot tip harvest of a plant was weighed fresh and again following drying at 70°C for 48 h.

At the end of the experiment, all foliage was cut at the base, weighed fresh and dried for 48 h at 70°C

and reweighed. The fibrous root mat thickness was measured before it was dried and weighed. Storage

roots were counted and weighed fresh. A 25 gram sample of the roots from each plant was taken and

dried at 70°C for 48 h in order to find percentage dry matter and storage dry root weight. The amount

of solution taken up by the plants in each treatment was calculated by subtracting the volume of water

that evaporated out of the middle unplanted channel from the volume of nutrient solution in each of

the treatments. The experiment was repeated once. Results of the two experiments were pooled.

11
Results and Discussion

The biweekly anion (CI, NO3, H2PO4 and SO4) uptake patterns for both the biweekly harvest and

the control treatments were similar and followed the same trend. Uptake of NO3 and H2PO4 for each

2-week period generally increased up to 8 weeks after planting before reaching a relatively steady state

uptake rate. Uptake of SO4 and Cl each increased up to the fourth and sixth week respectively, and

subsequently oscillated up and down in value through the 18th week. More Cl and NO3 were taken up

than with the other anions. These results agree with the study by Kirkby (1969) who showed that C! and

NO3 were taken up more rapidly than SO4. Anion uptake increased with increased plant root formation.

The overall uptake patterns of the anions are in agreement with those of Schwartzkopf (1987) using a

modified half-Hoagland solution in which lettuce was grown.

The cation (NH4, K, Mg and Ca) uptake pattern as measured on a biweekly basis for both

treatments also followed the same trend. K, Mg, and Ca uptake tended to be higher for the control

plants than for plants in which the foliage was harvested. The uptake for these three cations oscillated

from the sixth week to the eighteenth week. The nutrient uptakes were in general agreement with the

findings of Mengel and Kirkby (1983) that the rate of uptake of each anion and cation specie was

dependent on the magnitude of each ionic specie in the nutrient solution.

Both the mean stomatal conductance and the mean transpiration rate for control plants were

higher than for those plants with biweekly foliage harvests. The comparative stomatal conductance

values were 1.26 cm s 2 for Treatment C and 1.00 cm s 2 for Treatment A. The mean transpiration rates

were 8.54 and 7.98 ug cm2s 1 for treatments C and A respectively. For both treatments the results are

within the range of those measured for sweet potatoes grown under ambient and elevated levels of

carbon dioxide in open top chambers (Biswas et al., 1985). The higher values obtained for the control,

Treatment C, may have caused the higher use of nutrient solution by these plants (170.3 L) compared

to Treatment A plants (126.0 L). Since the water loss due to evaporation was taken into account, these

figures represent net uptake values. Water as well as light have been reported as two factors that have

the greatest influence on stomatal resistance in plants (Turner, 1974).

There were no differences in sweet potato yield components (Tables 1 and 2) for sweet potatoes

between Treatment A and Treatment C. However, storage root yields tended to be higher for the

control, i.e., fresh storage root weight of 482.5 g/plant as compared to 423.5 g/plant for Treatment A.

Likewise, if biweekly foliage harvests were not included in the totals, the total foliage yield tended

to be higher for the control, e.g., fresh weight of 396.8 g/plant as opposed to 329.5 g/plant for Treatment

A. However, if the biweekly shoot tip yields were included, the total foliage fresh weight of 433.0 g/plant

in Treatment A tended to be higher than the 396.8 g/plant for the control.

Although these yield components were lower than those reported by Hill et al. (1988) for "Georgia

Jet" sweet potatoes grown in NFI', the conclusions drawn that there were no differences between

treatments were the same as those found by Hopkinson (1986). In field studies with sweet potatoes he

found that topping treatments did not significantly affect fresh or dry storage root yield. However, the

results are contrary to those reported by Gonzales et al. (1977) for field grown sweet potatoes which

showed that topping reduced the storage root yields of sweet potato when shoot tips were harvested

on a biweekly basis.

12
Table 1. Effect of biweekly topping on storage root yield components*

of "Georgia Jet" sweet potato grown in NFT.

Treatment Storage Root

No. Fresh Wt. Dry Wt. Dry Matter

(g) (g) (%)

A (Biweekly topping) 5.1 423.5 77.7 18.0

C (Control) 6.1 482.5 81.7 16.9

LSD (5%) NS NS NS NS

*Mean of eight plants.

The results of these experiments show that harvesting "Georgia Jet" sweet potato shoot tips on a

biweekly basis in an NFT system for use as a green vegetable will not affect storage root yield. "Georgia

Jet" sweet potato has the potential for serving as a dual purpose food -- a green vegetable and a fresh

storage root -- for long-term manned space missions. Further research on the relationship of shoot

topping frequency on storage root yields of selected sweet potato cultivars is needed for CELSS.

Table 2. Effect of biweekly topping on fibrous roots* and foliage* of

"Georgia Jet" sweet potato plants grown in NFT.

Treatment Fibrous Roots Foliage

Dry Wt. Fresh Wt. Dry Wt.

(g) (g) (g)

A (Biweekly topping) 8.8 329.5 (433.0)* * 55.0 (65.9)* *

C (Control) 7.9 396.8 62.1

LSD (5%) NS NS NS

*Mean of eight plants

**Total foliage weight + shoot tips.

13
References

As-Saqui, M.A., Proc. 1st Intl. Syrup., AVRDC, Shanhuan, Tianan, Taiwan, 1982, 59.

Baker, E.M.V., Proc. 7th Ann. Conf. Hydroponics. 1986. Concord, CA.

Bartolini, P.U., Proc. 1st Intl. Symp., AVRDC, Shanhuan, Tianan, Taiwan, 1982, 209.

Biswas, P.K.; Hilcman, D.R.; Allen, J.R.; Bhattacharya, N.C.; Lu, J.¥.; Pace, R.D.; Rogers,

H.H.; Coleman, ICB.; Eatman, J.F.; Ghosh, P.P.; Mbikayi, N.; McCrimmon, J.N.; Mcncfcc,

A., Rcp. 022, U.S. DOE, Carbon Dioxide Rcs. Div. Off. of Energy Rcs., Wash., D.C., 1985,

70.

Dahniya, M.T., Proc. 1st Tricn. Root Crop Symp., Int. Soc. Trop. Root Crops - African Branch,

137.

Gonzalcs, F.R.; Cadiz, I.G.; Gugawan, M.S., Phillipinc J. Crop Sci., 1977, 2, 97.

Hill, W.A.; Lorctan, P.A.; Bonsi, C.K., Morris, C.E.; Lu, J.Y.; Ogbuchi, C.R., Comm. on Space

Rcs. (COSPAR) XXVII Plenary Mtg., Espoo, Finland, 18-29 July 1988.

Hopkimon, S.R.A., M.S. Thesis, 1986, Tuskegce U., Tmkegce, AL.

Kirkby, E.A., British Ecol. Soc. Syrup. 1969, 9, 212.

Lorctan, P.A.; Morris, C.E.; Bomi, C.K.; Hill, W.A.; Pace, R.D.; Lu, J.Y., Biswas, P.K., 7th Int.

Cong. on Soilless Culture, Flevohof, Netherlands, May 13-21, 1988.

Mcngcl, K.; Kirkby, E.A., 4th F_I. Intl. Potash Inst., Bern, Switzerland, 1987, 143.

Pace, R.D.; Dull, G.G.; Phills, B.R., J. Food Sci. 1985, 5, 537.

Pace, R.D.; Sibiya, T.E.; Phills, B.R.; Dull, G.G., J. Food Sci. 1985, 5, 940.

Pace, R.D.; Bomi, C.K.; Lu, J.Y.; Loretan, P.A., Hill, W.A.; Morris, C.E., I-IortSci. 1988, 23 (5),

828.

Prince, R.P.; Knott HI, W.M.; Hilding, S.E.; Mack, T.L., 33rd Ann. Mtg., Amer. Astro. Soc.

Prcpfint AAS-86-338, San Diego, CA, 1986.

Schwartzkopf, S.H., Adv. Space Rcs. 1987, 7(4), 89.

Turner, N.C., Plant Physio. 1974, 53, 360.

Villareal, R.L; Tsou, S.C.S.; Lin, S.K.; Chiu, S.C., Exp. Agric., 1978, 15, 117.

14
N91:28066

EFFECT OF CHANNEL SIZE ON SWEET POTATO STORAGE ROOT

ENLARGEMENT IN THE TUSKEGEE UNIVERSITY

HYDROPONIC NUTRIENT FILM SYSTEM

C.E. Morris, E. Martinez*, C.IC Bonsi, D.G. Mortley,

W.A. Hill, C.R. Ogbuehi, and P.A. Loretan

$3 -5/

G.W. Carver Agricultural Experiment Station

Tuskegee University

Tuskegee, AL

ABSTRACT

The potential of the sweet potato as a food source for future long-term manned space missions is

being evaluated for the National Aeronautics and Space Administration's (NASA) Controlled Ecological Life Support Systems (CELSS) program. Sweet potatoes have been successfully grown in a specially

designed Tuskegee University nutrient film technique (TU NFT) system. This hydroponic system has

yielded storage roots as high as 1790 g/plant fresh weight. In order to determine the effect of channel

size on the y/eld of sweet potatoes, the width and depth of the growing channels were varied in two

separate experiments. Widths were studied using the rectangular TU NFT channels with widths of 15

cm (6 in), 30 cm (12 in) and 45 crn (18 in). Channel depths of 5 cm (2 in), 10 cm (4 in) and 15 cm (6 in)

were studied using a standard NASA fan-shaped Biomass Production Chamber (BPC) channel. A

comparison of preliminary results indicated that, except for storage root number, the growth and yield

of sweet potatoes were not affected by channel width. Storage root yield was affected by channel depth

although storage root number and foliage growth were not. Both experiments are being repeated.

* Graduate student presenting paper. Contribution No. PS015 of the George Washington Carver

Agricultural Experiment Station, Tuskegee University. This research was supported by funds from the

U.S. National Aeronautics and Space Administration (Grant No. NAG10-0024) and USDA/CSRS

(Grant No. ALX-SP-1). We wish to thank Mr. Ralph Prince and Dr. William M. Knott HI of the

NASA/John F. Kennedy Space Center for technical assistance.

15
EFFECT OF CHANNEL SIZE ON SWEET POTATO STORAGE ROOT

ENLARGEMENT IN THE TUSKEGEE UNIVERSITY

HYDROPONIC NUTRIENT FILM SYSTEM

Introduction

Research on the growth and yield of food crops in a controlled environment is currently being

conducted by NASA through its Controlled Ecological Life Support Systems (CELSS) program for

future applications on space missions. The sweet potato is one of eight crops initially selected by NASA

to be used for the CELSS program (Wheeler and Tibbitts, 1984). Studies in progress at Tuskegee

University are being directed toward growing sweet potatoes hydroponically to evaluate sweet potato

production potential for CELSS and to better understand the physiology of storage root enlargement.

For several years, sweet potatoes have been grown in a specially designed Tuskegee University

nutrient film technique (TU NFT) system (Loretan et al., 1988b). This system uses growth channels

measuring 15 cm (6 in) deep x 15 cm wide x 1.2 m (48 in) long, and a storage root yield as high as 1790

g/plant (Hill et al., 1988) has been obtained. Sweet potatoes grown hydroponically in sand and perlite

in different size pots showed no significant effect from pot size (Loretan et al., 1988a). However, the

storage root yield tended to increase with increased pot size.

The objectives of the present studies are to evaluate the effect of various channel widths and

depths on the yield of "Georgia Jet" sweet potatoes grown in the TU NFT system.

Materials and Methods

Experiment I

Four vine cuttings (15 cm) of the "Georgia Jet" sweet potato cultivar were planted into each of

three TU NFT channels. The experiment used channels of standard depth and length (15 cm [6 in] and

1.2 m [48 in], respectively)with treatments of varying widths: (a) the standard- 15 cm [6 in]; (b) 30 cm

[12 in] and (c) 45 cm [18 in]. A separate reservoir (30.4 liter capacity) for the nutrient solution was used

for each treatment. A modified half-Hoagland nutrient solution was delivered to the plants in each

channel at a flow rate of 1 liter/min. The nutrient solution was changed every 14 days or was topped

with deionized water if the volume fell to 8 liters or less before the biweekly changeover date. Nutrient

solution pH was kept at 5.5 to 6.0 and solution temperature, salinity and electrical conductivity were

frequently measured. The ambient temperature within the greenhouse varied between 22 ° and 35°C,

depending on weather conditions. The daytime irradiance level ranged from 200 - 2000 umol m'2s t.

Supplemental cool white fluorescent (CWF) lighting was used on cloudy days. Carbon dioxide was at

ambient level.

Experiment lI

In a second experiment, "Georgia Jet" sweet potato vine cuttings (15 cm) were planted into three

NASA fan-shaped channels (Prince et al., 1985). These channels have an overall length of 83 cm with

16
amaximumwidthof 42 cm at one end and a minimum width of 18 cm at the other. Three channel depth

levels were used: (a) 5 cm (2 in)---standard for the Biomass Production Chamber, (b) 10 cm (4 in) and

(c) 15 cm (6 in) (equivalent to the TU NFT channel depth). Methodology and growing conditions were

similar to those listed in experiment I.

As the foliage grew in both experiments, the vines were trained to vertical strings dropping 1 m

from above each channel. Plants were harvested 120 days after planting and storage root number and

fresh weight as well as foliage fresh weights were taken. A 25 g sample of fresh storage root from each

plant was dried in a 70°C oven for 48 h to provide percentage dry matter and storage root dry weight.

Foliage and fibrous roots were dried in an oven at 70°C for 48 h and weighed to obtain dry weights.

Results and Discussion

The effects of three channel widths on the growth of "Georgia Jet" sweet potato are shown in

Table 1. There was no effect of channel width on fresh or dryweight of foliage or storage roots. However,

channel width influenced storage root number, with the 45 cm wide channel producing a significantly

higher storage root number than either the 30 or 15 cm wide channels. The 45 cm channel width also

tended to produce higher fresh storage root weight than the other two. Observations on the location

of root enlargement within the channel showed that it took place more to the center of the channel

except in the 15 cm channel where the roots made contact with the side walls. No storage roots were

observed to have contacted the side wails in either the 30 cm or the 45 cm wide channels. Enlargement

of the storage roots started at approximately the same distance (5 to 10 cm) from the plant stem in each

treatment.

Table 1.

The effects of channel width on growth of "Georgia Jet" sweet

potato plants* in a greenhouse using NFI'.

Channel Storage Roots Foliage Fibrous Roots

Width

No. Fr. Wt. Dry Wt. Fr. Wt. Dry Wt. Dry Wt.

(era) (g) (g) (g) (g) (g)

45

30

15

4.8A 356.9A 79.8A

3.0B 303.0A 68.5A

2.513 306.1A 65.5A

364.8A 60.0A

319.6A 48.0A

349.9A 46.3A

10.0

8.0

7.3

* Mean of four plants - means in the same column with the same letter are not significantly

different using Duncan's Multiple Range Test at the 5% level.

17
The effects of channel depth on the growth of "Georgia Jet" sweet potato are shown in Table 2.

The effect on storage roots was inconclusive. The number of roots tended to increase with channel

depth, but there were no significant differences among channels. However, the largest fresh storage

root weight (659.1 g per plant) was produced in the channel with the least depth (5 era)---significantly

higher than the 317.5 g per plant produced in the 10 cm channel. It was also higher than the 553.7 g per

plant produced in the 15 cm channel depth although not significantly different. One storage root (815.7

g) in the 5 cm channel depth accounted for most of the yield in that channel. The dry storage root

weights followed the same trend as the fresh weight. Even though the magnitude of the foliage weight,

both fresh and dry, was in the same proportion as the storage roots, there were no significant differences

among these treatments. The dry fibrous root weight also followed this trend. Thus there is no clear

effect of channel depth. This may be due to an incidence of stem rot in some of the treatments. This

experiment along with the experiment on channel width is presently being repeated so that the effect

of channel size on the growth of "Georgia Jet" sweet potato may be clarified.

Table 2.

The effects of channel depth on growth of "Georgia Jet" sweet

potato plants* in a greenhouse using NTT.

i

Channel Storage Roots Foliage Fibrous Roots

Width

No. Fr. Wt. Dry Wt. Ft. Wt. Dry Wt. Dry Wt.

(cm) (g) (g) (g) (g) (g)

15 5.5A 553.7AB 91.0AB 561.0A 73.9A 10.5

10 3.0A 317.5B 51.1B 324.0A 50.3A 10.0

5 2.5A 659.LA 109.2A 616.0A 89.3A 13.0

* Mean of four plants - means in the same column with the same letter are not significantly

different using Duncan's Multiple Range Test at the 5% level.

18
References

Hill, W.A.; Loretan, P.A.; Bonsi, C.IC; Morris, C.E.; Lu, J.Y.; Ogbuehi, C.R., Comm. on Space

Res. (COSPAR) XXVII Plenary Mtg., Espoo, Finland, 18-29 July, 1988.

Loretan, P.A.; Hill, W.A.; Bonsi, C.K.; Morris, C.E., HortSci. 1988, 23 (5), 828.

Loretan, P.A.; Morris, C.E.; Bonsi, C.K.; Hill, W.A.; Pace, R.D.; Lu, J.Y.; Biswas, P.K., Proc.

7th Intl. Cong. on Soilless Culture, Flevohof, Netherlands, May 13-21, 1988.

Prince, R.P.; Knott, W.M. III; Hilding, S.E.; Mack, T.L., 33rd Ann. Mtg., Amer. Astro. Soc.

AAS Preprint AAS-86-338, San Diego, CA, 1986.

Wheeler, R.M.; Tibbitts, T.W., NASA Contractor Report 177323.20pp.

19

w

N91-28

EXCIMER LASER INTERACrION WITH DENTIN _ _, _ g

OF THE HUMAN TOOTH

F-4

Introduction

It is well known that light _ by _ em_ion of _ is represented by the

acronym laser. This project had its beginning in the quantum electronics department of the IBM Thomas

J. Watson Research Center in Yorktowne Heights, New York. Using a excimer laser, whose frequency

is in the deep ultra-violet region of the spectrum, produced many unusual conical structures within the

dentin of the inner part of the human tooth.

Structure of Tooth

The structure of the tooth consists of the crown, neck, pulp cavity and root. The crown is the part

of the tooth that is covered by enamel and projects beyond the gum line. The neck is the narrow area

of the tooth, and the pulp cavity is that area which contains a soft vascular and sensitive organ called

dental pulp. The root of the tooth is the area which is the embedded part of the tooth.

Description

Examination of the structures of the enamel reveals the following characteristics. It is the hardest,

most compact part of the tooth which forms a thin layer over an exposed crown. It consists of a collection

of small hexagonal rods and columns which lie parallel to each other. Dark lines mark the mode of

formation of the rods (Fig. 3). The enamel's chemical composition consists of 96.5% earthy matter

(phosphate with the carbonate of calcium, with traces of fluoride of calcium and phosphorous magnesium) and 3.5% animal matter.

The composition of dentin differs from that of enamel in that dentin is the calcareous part of the

tooth beneath the enamel which forms the greater mass of the tooth and also covers the exposed part

of the crown. Microscopic examination shows that dentin consists of a number of minute wavy branches

called dentinal tubuli which are embedded in a dense homogeneous substance known as the intertubular

tissue. Dentin is composed of 28% animal matter and 72% earthy matter. The cortical substance,

cementum, a thin layer on the root of the tooth extends from the termination of the enamel to the apex

of the root. This cortical substance chemical compound resembles bone in that it contains lacunae and

canaliculi.

'+',+, ,mo.m,u.,mm

21

PRBCEDING PAGE BLANK NOT FILMED
Method and Results

The dentin of various molar teeth were exposed to 1300 pulses to 4000 pulses using an excimer

laser. The results indicate some very unique structures occurring within the dentin. The interaction of

the laser light seemed to form unusual conical structures within the dentin. Using false color (when all

of the gray levels have the same value, the computer will pick a particular color and the next value up

or down will show as a different color) permits the eye to see detail that would not normally be visible

under normal perceivable gray levels.

Conclusion

By varying the frequency of the laser one can disperse the energy and cause more bleeding in laser

surgery, but not destroy the cells associated with the incision. Therefore, the healing process will virtually

be without scarfing. Whereas, using the infrared laser the blood loss would be less, but the healing

process would tend to be longer because cells are being destroyed due to the cauterization effect of the

laser. The question is, are these structures produced as an interaction with the laser or are they an

intrinsic part of the structure? We are still studying the effects of the laser interaction upon dentin, and

in using the EM we will be able to understand more clearly the interaction of the excimer laser upon

the tooth dentin and other various biological tissue.

The Effects of Laser Interaction upon Dentin

Figure 1 Figure 2

22

ORIGINAL PAGE IS

OF POOR QUALITY
The Effects of Laser Interaction upon Dentin

Figure 3 Figure 4

Figure 5 Figure 6

ORIGINAL PAGE IS

OF POOR QUALrT¥

23
The Effects of Laser Interaction upon Dentin

Figure 7

Figure 8

Iai:_ ._ I_____,• _'°_ "_ '" _ '

llh:..._-J,:__'_\ :_,,'_' _ .'S _ ' "." "_"

Figure 9

Figure 10

24 ORIGINAE PAGE

BLACK AND WHITE PHOTOGRAPH
The Effects of Laser Interaction upon Dentin

|_,, ".. , ,.._,J : . /.'_r_I

r,",Y__.J,_,_'_l_ .-__. 4_._1

Figure 11 Figure 12

ORIGINAl_ PAGE

BLAC_ AND V/NiT[ P.' '._T_,'q_,_PN

25
f

N91-28068 |

INTERNATIONAL FOOD PATrERNS FOR SPACE FOOD

Selina Ahmed

Department of Home Economics

Texas Southern University

Student Researchers:

Amanda Cox

Pauline V. Cornish

Technical Monitor:

Charles T. Bourland (JSC)

Introduction

The food pattern of a given group of people originates from the availability of foods in the country

where they live (11). Food patterns are interwoven with the culture of the people, and are the response

of individuals or groups to social and cultural pressures in selecting, consuming, and using portions of

the available food supply (7,8). Food patterns are based on edible materials a culture considers to be

food, as well as on the type of food production and service in a country (10).

A country's food patterns are molded by its agricultural resources, technical progress, buying

power, and cultural patterns. In trying to understand the food habits of a people, one needs to learn

about the country from which they come (9). The quest for space exploration is shared by cosmonauts

and astronauts from American, Asian, and European countries (6). Thus, space exploration has not

only become international, but also a multicultural affair. It is, therefore, necessary that scientists

involved in space research investigate the multicultural backgrounds of cosmonauts and astronauts in

order to learn more about food patterns of representative countries. This type of research is important

in order to understand the cosmonauts' and astronauts' food habits, so appropriate menus can be

developed to better serve the space explorers.

In 1982, Soviet scientist V.P. Bychkov, researched the diet of crews in Salyut-6 Orbital Space

Station. He confirmed that conventional and familiar foods such as fresh fruits and vegetables have

positive psychological effects as they alleviate the monotony of the processed, unconventional food

common on long duration missions (5). Food consumption and psychological wellness are significantly

improved by familiarity (4). Familiar foods normally enhance morale (1).

Based on the above studies, it is important to have knowledge of the food patterns of space

explorers to ensure psychological well being and enhance morale. Therefore, the intent of this research

is to investigate the integration of international food patterns in space nutrition programs. It is

26
speculatedthat nutritionally balanced, cross-cultural diets can be provided to meet the needs of space

explorers from various cultural and ethnic backgrounds.

Statement of the Problem

The purpose of this research effort is (a) to obtain basic data on ethnic foods by studying dietary

patterns and multicultural foods, and (b) to determine nutritional status of multicultural space explorers

by evaluating dietary, clinical, biochemical, and socioeconomic factors.

Objectives

1. To study food patterns of selected countries' ethnic groups and cross-cultural aspects of

foods' suitability for space explorers.

2. To identify appropriate foods for selected ethnic groups in terms of preparation needs,

nutritional benefits, preservation, and packaging requirements.

3. To evaluate and analyze selected food items recommended for space nutrition programs.

4. To integrate selected foods into an international space food system.

Justification of the Study

The study will play a significant role in providing nutritional research for space explorers of

different ethnic backgrounds. It will provide scientific background information by bringing together

cross-cultural dietary and nutritional information from different ethnic groups. Results of this study will

also help the health care personnel including physicians, dietitians, and nutritionists to better understand and assist patients from other cultures during illness. Also, the results will provide data which will

help in the development of future food plans for long duration flights involving manned exploration to

Mars and lunar base colonies.

Methodology

A literature review will determine ethnic food patterns for international crew members. Foods

vary in their nutrient composition. Some have high nutrient density in relation to energy. Even ethnic

foods which are familiar may not, by themselves, be nutritionally sufficient; therefore, a nutritional

analysis of multicultural foods will also be conducted. The study will be conducted in four tasks (Table

1).

27
0 I"-- *"*

N

28
In task one the identification of the countries and determination of their typical dietary practices

will be evaluated. Foods which provide cross-cultural satisfaction will be studied. The study will also

determine food handling characteristics such as shelf life, packaging, preparation, preservation, and the

nutrient content of foods from different ethnic origins.

Task two will include food preparation (in flight) and sensory evaluation by Research Guidance

Panels (a mechanism to measure the acceptance of food products by using organoleptic testing).

Task I

Identification of the countries and determination of their typical dietary practices will be one of

the parts of task one. Task one will also identify the foods which provide cross-cultural satisfaction and

can be recommended for astronauts of different ethnic backgrounds. In order to identify food for the

space food and nutrition programs, the following food handling characteristics will be considered.

A. Shelf Life Determination

Shelf life is the study of the keeping quality of food. The process involves keeping food at various

desirable temperatures for different lengths of time. The maximum shelf life study will last up to 90 days

for the following temperatures:

-20 degrees F frozen

40 degrees F refrigerated

70 degrees F ambient

After each shelf life study, the foods will go through acceptability tests by sensory evaluation. Food

will also be tested for chemical and microbiological safety parameters. Nutritional analysis will also be

considered.

B. Packaging

Packaging possibilities for the foods will be reviewed for compatibility with the Space Food Service

Systems (3).

C. Preparation

Processing requirements for in-flight meal preparation will be used as a criterion in the identification of suitable foods for the space food programs.

29
D. Preservation

Differenttechniquesto preserve the quality of food and retain nutritional values will be considered. Freezing, freeze drying, pre-eooking, dehydrating, etc., are all preservation methods to be

evaluated in developing a menu for space food service systems for astronauts of different ethnic origin.

E. Nutritional Analysis

In order to determine the suitability of food for the space food programs, nutrition analysis is

essential. It can help when planning the daily menus for the astronauts. Comparison of each complete

menu with recommended dietary allowances is also necessary.

Task II

Preparation of food items passing task one tests will be examined in task two. Task two will consist

of the following steps:

A. Preparation (In-Flight)

Food preparation prior to eating, e.g., cutting, peeling, adding water, chilling, and heating are the

various methods of in-flight preparation to be reviewed to help select the appropriate food for the space

food programs. (2)

B. Sensory Evaluation

Sensory evaluation of the foods will be conducted by technical taste panels.

Task III

The experimental foods which pass the sensory evaluation will be selected for final studies of shelf

life and packaging. Foods will be packaged in appropriate containers and placed in controlled storage

and evaluated at predetermined intervals.

30
Task IV

The ultimate goal of this study is to select suitable foods for astronauts from different ethnic

backgrounds. The scientific data derived will be integrated to advance knowledge of space nutrition

programs for future endeavors.

Discussion:

Based on the Johnson Space Center's selection of astronauts, the researcher selected the

countries to be studied. Presently, the countries that have been selected are European countries:

Sweden, West Germany, Italy, Poland, and the USSR; and Asian countries: India, Bangladesh, Pakistan,

Japan, Philippines, and Thailand. The foods for these countries have also been selected.

In April 1989, ground base studies of the quality characteristics of food patterns will start.

Progression of the study as indicated by the schematic diagram of methodology will be completed

systematically.

Summary

The purpose of the research effort is to (a) obtain basic data on ethnic foods by studying dietary

patterns and multicultural foods, and (b) to determine the nutritional status of multicultural space

explorers by evaluating dietary, clinical, biochemical and socioeconomic factors.

The study will be conducted in four tasks which include identification of the countries and

determination of their typical dietary practices. The study will also identify the foods which provide

cross-cultural satisfaction and can be recommended for astronauts of different ethnic backgrounds. In

order to identify foods for the space food and nutrition programs, the following food handling

characteristics will be considered: shelf life determination, packaging, preparation, preservation, and

nutritional analysis. Menu recommendations from the selected foods will also be developed.

References

1. Ahmed, S., Comparison of Soviet and U.S. Space Food and Nutrition Programs. NASA/JSC,

NGT44-001-800, August, 1988.

2. Bourland, C.T., Heating Food in Space. Memo, 1985.

3. Bourland, C.T., Fohey, M.F., Rapp, R.M., and Sauer, R.L., Space Shuttle Food Processing

and Packaging. Journal of Food Protection, 44:313-319, 1981.

4. Bourland, C.T., Fohey, M.F., Kloeris, V.L., and Rapp, R.M., Designing a Food System for

Space Station Freedom. Food Technology. Feb. 78-81, 1989.

31
5. Bychkov, V.P., Ushakov, A.S., Kalandarov, S., Markaryan, M.V., Sedova, Y.E.A., Sivuk,

A.K., and Khokhlova, O.S., Diet of Crews in Salyut-6 Orbital Station. USSR Report: Space

Biology and Aerospace Medicine, Vol. 16, No. 2, pp. 11-15, 1982.

6. Gazenko, O.C., Man in Space: An Overview. Aviation, Space and Environmental Medicine.

Dec. 53-55, 1983.

7. Krause, M.V., Mahan, L.K., Food, Nutrition and Diet Therapy, Seventh Edition, W.B.

Saunders Company, pp. 334-335, 1984.

8. Lewis, J.S.; Glaspy, M.FE., Food Habits and Nutrient Intakes of Filipino Women in Los

Angeles. J.Am. Diet.A. 67:122, 1975.

9. Lowenberg, M.E., Todhunter, E.N., Wilson, E.D., Savage, J.R., and Lubawski, J.L.: Food

and Man, 2nd Edition, NY, John Wiley & Sons, p. 120, 1974.

10. Mitchell, H.S., Ryanbergen, H.J., Anderson, L., Dibble, M.V., Nutrition in Health and

Disease, Sixteenth ed. J.B. Lippincott, Inc., 1976.

11. Robinson, C.H., Lawler, M.R. Normal and Therapeutic Nutrition, Sixteenth Edition.

Macmillan Publishing Co., Inc., pp. 284-286, 1982.

12. Tobias, A.L., Thompson, P.J., Issues in Nutrition for the 1980's, Wordsworth Health

Sciences Division, Monterrey, California, 1980.

32
N91-28069

IN VITRO REGENERATION OF BASELLA ALBA L.

Norris Allen Edney, Muhammad A. Rizvi

and Narjis F. Rizvi

Department of Biological Sciences

Alcorn State University

Lorman, Mississippi

t

ABSTRACT

BA_cJlaAtlha_L. is a tropical vine used as a vegetable in some Asian and African countries. It has

potential as a non-traditional crop for small family farms. A short day plant, it blooms during fall,

provided the temperatures are mild. In the southeastern United States, the short days of fall are

associated with sub-freezing temperatures, and plants are killed before blooming. In this study attempts

were made to regenerate the plant using tissue culture techniques. Several trials were conducted with

different media, hormones and explants. It was found that nodal segments on Gamborg medium

regenerated shoots. Interaction studies of auxins and cytokinins indicated that its endogenous auxin

content might be high because callus proliferated in almost all treatments and roots initiated even when

the medium was not supplemented with an auxin.

33
IN VITRO REGENERATION OF BASELLA ALBA L.

Introduction

In recent years an increasing interest has been expressed in non-traditional crops that show

promise for small American family farms (Tiwari et. al., 1988). _ could be a promising new

vegetable crop for small farms because it is pest and disease resistant, it has a high nutritive value, and

its yield is 8 times higher than regular spinach (Yamaguchi, 1983).

]$a&cJla__aLL. is a tropical vine (Bailey, 1951). It is used as a vegetable in some countries of

Southeast Asia (Yamaguchi, 1983 and Tiwari et. al., 1988). Basella leaves and stems taste like spinach;

therefore, it is known as "Malabar Spinach" in English (Yamaguchi, 1983). In India and Bangladesh it

is known as "Poi Sag" (Tiwari et. al., 1988). In China it is called "Lok Kwa" (Yamaguchi, 1983).

_. blooms during the short days of fall provided the temperatures are mild at nights.

In Mississippi and all other parts of the southeastern United States short days are associated with

sub-freezing temperatures at night. Therefore, _ vines die before flowering.

Plant tissue culture techniques have been valuable in alleviating such problems through vegetative

propagation of plants (Evans et. al. 1983). Plant regeneration _ is the key to practical application

for most purposes using tissue culture techniques (Tomes, 1985).

Regeneration of any member of B_t_Lla.alEaL. has not been reported with the use of tissue culture

techniques. Therefore, the purpose of this study was to investigate regeneration of lia_E_alt.L, in

vitro.

Materials and Methods

This study was conducted in three phases. The objective of phase I was to compare the performance of the three most used plant tissue culture media: Murashige & Skoog (MS), Anderson (AND)

and Gamborg B5 (GB5) on callus proliferation, and root and shoot initiation on five explants: petiole,

stem, meristem, leaf and node. Explant used were 0.5 cm 3 in size or segments of stem, leaf, petiole,

meristem and node. All of the explants were put in Murashige and Skoog (MS), Anderson (AND) and

Gamborg B5 (GB5) media after surface sterilization. Explants were sterilized as described by Thorpe

(1981). MS medium had 100, 0.5, 0.5, 0.1, 2.0 and 80.0 mg/i of myo-inositol, nicotinic acid, pyrodoxine

HCI, thymine HCI, glycine and adenine sulfate (Hartman and Kester, 1983). AND medium was

supplemented with 4 mg/1 thiamine HCI, 100 mg/l myo-inositol and 80 mg/l adenine sulfate (Hartman

and Kester, 1983). GB5 medium had 10.0, 1.0, 100.0 and 80.0 mg/1 of thiamine HCI, nicotinic acid,

pyridoxine HCI, myo-inositol and adenine sulfate respectively in addition to basal inorganic salts

(Hartman and Kester, 1983). Growth regulators for callus proliferation, shoot and root initiation trials

were 0.1, 0.2, 0.4, 0.8 and 1.6 mg/l of napthaleneacetic acid (NAA) as auxin and 0.1, 0.2, 0.4, 0.8 and 1.6

mg/l of benzyl adenine (BA) as cytokinin. In every trial, one set without growth regulators was used as

control. The pH of the media were adjusted to 5.7 before autoclaving. All three culture media had 30

g/l sucrose and 7 g/l agar (Thorpe, 1983). Media were autoclaved at 121°C for 20 minutes. The culture

environment was maintained at 25°C and illuminated with cool white fluorescent lamps at 40 u

34
Einsteins/m2/secfor 16hoursperday.After 3weeksthecultureswereevaluatedbydeterminingthe

sizeof callusesandtotalnumberof shootsgreaterthan5mminlengthproducedperexplant.

Theobjectiveof thephaseII experimentswasto evaluatethe interactions of napthalenenacetic

acid (NAA) and benzyi adenenine (BA) on callus proliferation and initiation of roots and shoots from

explants selected earlier in phase I. It was 6 x 6 diallel experiment (Sondahl et. al., 1981). Dilution of

NAA and BA were 0, 0.1, 0.2, 0.4, 0.8 and 1.6 ppm. Each treatment had 5 replications.

Mature vines were used as source of explants. The explants used were 3 - 5 mm segments of nodes.

The explants were surface sterilized with 20% chlorox for 5 minutes and washed with distilled water 5

times. (Thorpe, 1981). Standard Gamborg B-5 medium was used as a source of nutrition for explant

growth. It was supplemented with 3% sugar and 0.8% agar. After addition of NAA and BA, the pH of

the medium was adjusted to 5.7 - 5.8 by NaOH and/or HCI solution. The medium was sterilized and

autoclaved at 121°C at 15 lbs. PSI for 15 minutes.

Results and Discussion

Five explants: leaf, stem, meristem, petiole and nodal segments, and three media: MS, AND and

GB-5 were used in phase I experiments. It was found that all explants initiated calluses but shoot

initiation was restricted to a few combinations. Leaf explants on all three media showed signs of cell

growth and cell elongation but did not produce a well defined callus. Stem, meristem and petiole

initiated calluses on all three media are under investigation. Nodes produced calluses and proliferated

shoots on GB5 and AND media but not on MS medium. In primary cultures shoot'initiation occured

only with the use of GB5 and AND media. Leaf, stem, meristem and petiole when used on shooting

medium initiated calluses. The failure of leaf, stem, meristem and petiole explants to produce shoots

on any of the media was not unprecedented. Endogenous hormones play a very significant role in the

outcome of exogenous hormones on shoot proliferation (Band and Lineveger, 1986). Because of poor

shooting responses on MS and AND media, further studies were made on GB5 medium only.

In the interaction trials it was found that the effective dilutions of NAA and BA for initiation of

shoots ranged in between 0 - 1.6 ppm (Table 1).

35
Table1:

Effectof NAA andBAin GB5mediumon shoot regeneration

from nodes of lta,_lit_a_,., after two weeks of inoculation.

BA NAA Percent of culture

mg/1 mg/1 with shoots

0 - 0.1 0 - 0.1 9.3

0.8 - 1.6 0 - 0.1 89.4

0.2-0.8 0.2-0.8 5.7

In the second experiment of interaction of NAA and BA it was found that calluses were observed

in all of the treatments (Table 2).

Table 2:

Interaction of NAA and BA on callus formation.

BA in ppm NAA in ppm

0 0 0.8 1.6

0.1 1.2" 2.0 2.0

0.2

0.4

0.8

1.6

1.7

1.6

1.6

0.1

0.6

0.8

1.2

1.2

1.2

0.2 0.4

1.3 2.0

1.3 2.0

1.8 2.0

1.8 2.0

1.8 2.0

2.0

2.0

* x explant size

36
ShootsinitiatedonlywhenNAA wasin the range Of 0 to 0.1 ppm. Higher concentrations of NAA

inhibited shoot formation (Table 3).

Table 3:

Interaction of NAA and BA on shoot formation.

BA in ppm

0.1

0.2

0.4

0.8

1.6

0.1

2 •

NAb. in ppm

0

3

0.2 0.4 0.8 1.6

* number of shoots/treatment

NAA favored root formation. Absence of BA was not critical for root formation. In some

treatments, root initiation was found even in high concentrations of BA, but such incidence was rare

(Table 4).

In phase H it was found that the favorable ratios for rooting and shooting were 0.1 - 0.2 ppm of

BA/0.8 - 1.6 ppm of NAA, and 0.8 - 1.6 ppm of BA/0.1 - 0.2 ppm of NAA respectively. Media with the

same ratios were used in phase III of this experiment. It was found that calluses did not respond to these

treatments. Further studies are suggested to be conducted with the use of other hormones.

37
Table4:

Interactionof NAA and BA on root formation.

BA in ppm

0

0.1

0.2

0.4

0.8

1.6

NAA in ppm

0 0.1

2111

0.2 0.4

6

6

0.8

6

8

8

* number of roots/treatment

1.6

6

8

8

Literature Cited

1. Bailey, L. H. (1951). Manual of Cultivated Plants. Macmillan Co., New York. p. 367.

2. Brand, Mark H. and R. Daniel Linebeger (1986). In Vitro Propagation of Halesia Carolina

L. and the Influence of Explantation Timing on Initial Shoot Proliferation. Plant, Cell,

Tissue and Organ Culture: Mar. Nuj. Publisher, Netherlands.

3. Evans, D., W. Sharp, P. Ammirato and Y. Yamada (1983) Handbook of Plant Cell Culture.

Macmillan & Co., New York p. 126.

4. Hartman, Hudson T., and Dale E. Kester (1983). Plant Propagation, Prentice Hall Inc.,

Englewood Cliffs, New Jersey.

5. Thorpe, Trever A. (1981). Plant Tissue Culture. Academic Press., Orlando, FL.

6. Tiwari, S. C., P. E. Igbokwe and J. B. Collins (1988) Malabar Spinach (__dl2a_L.)

MAFES Information Sheet 1321, Miss. State University, MS 29762.

38
o

o

t

Tomes, Dwight T. (1985). Opportunities and Limitations of Genotypic Influence on

Establishment of Plant Regeneration from Callus and Cell Cultures of Crop Species in

Biotechnology in Plant Science. Eds: Zaitlin, Day and Hollaender. Academic Press.

London.

Sondahl, M. R., L. C Monaco, and W. R. Sharp (1981). In Vitro Method Applied to

Coffee in Plant Tissue Culture. Ed. Thorpe. Academic Press, Orlando, FL. p. 325.

Yamaguchi, M. (1983). Other Succulent Vegetables. World Vegetables: Principles,

Production and Nutritive Values. AVI Publication Co., Westport, CT., p. 267-368.

39
N91-28070

MANIPULATING CYANOBACTERIA: _ FOR

POTENTIAL CELSS DIET

Mahasin G. Tadros, Woodrow Smith, Peter Mbuthia and Beverly Joseph

Department of Biology

Alabama A&M University

Normal, AL

ABSTRACT

r,.la,as a bioregenerative photosynthetic and an edible alga for spacecraft crew in a CELSS,

was characterized for the biomass yield in batch cultures, under various environmental conditions. The

partitioning of the assimalitory products (proteins, carbohydrates, lipids) were manipulated by varying

the environmental growth conditions. Our experiments with Soirulina have demonstrated that under

"stress" conditions (i.e. high light 160 uE m "2s "1,temperature 38°C, nitrogen or phosphate limitation;

0.1 M sodium chloride) carbohydrates increased at the expense of proteins. In other experiments, where

the growth media were sufficient in nutrients and incubated under optimum growth conditions, the total

proteins were increased up to almost 70% of the organic weight. In other words, the nutritional quality

of the algal could be manipulated by growth conditions. These results support the feasibility of

considering _ as a subsystem in CELSS because of the ease with which its nutrient content can

be manipulated.

40
MANIPULATING CYANOBACTERIA: FOR

POTENTIAL CELSS DIET

Introduction

Pursuit of our national goals in space exploration will eventually require man's long-duration

tenancy of celestial vehicles and planetary bases. Requirements for life support could be met through

expenditure of stored supplies and by regeneration and reuse of the waste products of human

metabolism. The logistics necessary for regeneration for extended space missions are well documented

(1). The primary source of all man's food and organic raw materials is solar energy. Conventional food

sources consist of higher plants and animals. Unconventional food sources for human consumption are

photosynthetic algae and bacteria and non-photosynthetic bacteria, yeast and fungi. Conventional food

sources are highly palatable, but require a long time to produce. Algae, on the other hand, grow rapidly;

their metabolism can be controlled; they produce a high ratio of edible to nonedible biomass; and their

gas-exchange characteristics are compatible with human requirements. The biological components of

Controlled Ecological Life Support System (CELSS) will serve as subsystems for the revitalization of

air for the long term space flight.

Cyanobacteria single cell protein (SCP) has been used as a food source in various parts of the

world (e.g. Mexico, China and Africa) since ancient times; in fact, dried cyanobacteria and

cyanobacterial tablets are now sold in health food stores in Japan, North America and Europe because

they are recognized for their nutritional value. The nutritional quality of all cyanobacteria which have

been tested appears to be very high. The protein of S. maxima is easily digestible and approximately

65% of the protein is assimilable.

In order to evaluate the potential of Spirulina for a CELSS diet, it is essential to have background

information on the environmental tolerance of the species. The purpose of this project was to evaluate

the chemical composition of Spirulina under different growth conditions in batch cultures. This paper

presents the results of one year's work.

Materials and Methods

Spirulina maxima (UTEX LB 2342) was cultured in Zarrouk medium (3). For mass culturing, algal

cells were grown in bottles. Cultures were illuminated continuously by placing them in front of a bank

of two cool white fluorescent lamps (40W). Light irradiation, measured at the surface of the culture

bottles, was 80 uE m "2 sa. The cultures were grown in a water bath kept at 29-30°C by the use of a

heater-thermostat combination. Cultures were grown under different conditions. Cells were collected

after five days growth and analyzed for total proteins, carbohydrates and lipids.

41
Results and Discussion

Physiological Characterization of Cultures, under Stress Conditions: The results of analysis were

expressed on the basis of organic weight (Ash Free Dry Weight: AFDW) and arerepresented in Table

1.

Light Irradiance and Temperature: Increasing the light irradiance to 120 uE m "2s"1,led to an increase

in the total carbohydrate content and a decrease in protein content: S. Maxima 19.58%, 29.06%.

Increasing the temperature of culture incubation to 38°C influenced the composition of the strain in a

similar manner to the light irradiation experiment: S. m_ma, 45.28%, 18.75%, for protein and

carbohydrates, respectively. The culture produced a low percentage of lipids when grown in high

temperature experiments. Nutrient Limitation: Media limited in nitrate-N and phosphate-P favored

the accumulation of carbohydrate rather than protein. Nitrate and phosphate limited cultures: S.

maxima had 37.52%, 35.21% carbohydrate and 21.56%, 41.25% protein. When the cultures were

transferred to media limited in nitrogen and phosphate, cultures changed in color from blue to

yellow-green. N-limited cultures of _ nidulam (7), and P-limited cultures of Oscillatoria

agar_0_ (8), showed elevated levels of polysaccharide storage. Sodium Chloride: As Zarrouk (3) media

were enriched with 0.1M and 0.5M NaCI, the carbohydrate content of the cells increased, when

compared to that of the control (Zarrouk: 0.01M NaCI), to 26.24%, 36.73% in S. maxima. On the other

hand, the total protein decreased respectively to 52.62%, 45.64% in S. maxima. The lipid percentages

showed little increase when compared to those of the complete media (control). Bicarbonate: When

bicarbonate concentration of Zarrouk media was reduced to one quarter (4.g/L), the culture showed

much difference in the chemical composition as compared with the control media except their yield was

somewhat below the control. The carbohydrates increased to 38.53% when 0.03% CO2 in air was used

for aeration and to 40.23% when 1% CO2 air was used for aeration.

It can be concluded that through manipulating environmental conditions of the algal growth, one

can modify the photosynthetic products. Thus, Spirulina can be, through manipulating growth factors,

used as palatable diet compared to higher plants.

Acknowledgment

This work was supported by NASA/Ames Research Center Cooperation Agreement #NCC2-501.

42
References

1. MacElroy, R.D., Bredt, J. CELSS, NASA CP-2378, 1985, 1.

2. Fogg, G.E. Ann. Bot., 1956, 20 265.

3. Zarrouk, C. Thesis, University of Paris (France), 1966.

4. Faucher, O., Coupal, B. Ledny, A. Can. J. Microbiol. 1979, 25, 752.

5. Goldman, J.C., Graham, S., J. Appl. Environ. Microbiol., 1981, 41, 60.

6. Lang, D.S., Brown, E.S., Appl. Environ. Microbiol., 1981, 42, 1002.

7. Lehman, M., Wober, G., Archin. Microbiol., 1976, 3, 93.

8. Riegman, R., Rutgers, M., Mur, L.R., Archin. Microbiol., 1985, 142, 66.

43
Table 1. Molecular Composition of _ maxima

Growth

Conditions

% Organic Wt. (AFT)W)

Protein Carbohydrate Lipids

*Sufficient

Nutrients 69.75 11.5 4.68

High Light

(160uEm-2.s-1) 29.06 19.58 3.56

High Temperature

(38°C) 45.28 18.75 3.75

N-limited 21.56 37.52 4.68

P-limited 41.25 35.21 5.20

Sodium Chloride

O.1M

52.62 26.25 4.68

0.1M 45.64 36.73 7.52

Bicarbonate

(nAg/L)

(0.03% co2) 45.67 38.53 6.22

(1% CO2) 43.52 40.23 6.53

*Experimental conditions were:

temperature 30°C; light irradiance 80uEm'2sa;

air flow rate 300 ml/min.;

The values shown are averages of four independent determinations.

44
N91-28071 °

SEASONAL NITROUS OXIDE FLUX FROM AN INTENSIVELY

MANAGED PASTURE IN A HUMID SUBTROPICAL ECOSYSTEM

E. A. Brams and W. H. Anthony

Cooperative Agricultural Research Center

Prairie View A&M University

Prairie View, Texas

G.L. Hutchinson

Agricultural Research Service, U.S. Department of Agriculture

Northern Plains Area

Fort Collins, Colorado

G.P. Livingston

Ecosystems Science & Technology Branch

National Aeronautics & Space Administration (NASA)

Ames Research Center

Moffett Field, California

ABSTRACT

Nitrous oxide (N20) flux from vented chambers was measured over intensively and minimally

managed bermuda grass _-'ynodon dactylon hay meadows in a humid, subtropical ecosystem (S.Texas)

for several calendar years during scheduled sampling protocol following harvest, fertilization and

rainfall events _,hile measuring diel N20 emissions once during each of 5 - seasonal day growth cycles

which divided each calendar year. Soil pools of nitrite NO2", nitrate NO3" and ammonia (NH3) were

measured in soil samples taken at 2 and 10 cm depths during each emission collection to determine

transformations of the nitrogen pools coupled with N20 emissions. The highest diel N20 emission occur

midday in the Spring cycle, measuring 9.0 g N/ha/d only for several weeks, while emissions dropped to

< 1.0 g N/ha/day during hot, dry and colder months. Intensively managed meadows (4 fertilizations and

harvests per year, respectively, plus integrated pest management procedures) induced higher seasonal

N20 emissions than minimal treatment (one fertilization and harvest, respectively, per year), averaging

2.75 and 5.97 g N ha/day, respectively. Nitrous oxide emission data as responses to soil parameters

(temperature and moisture) and environmental parameters (air temperatures, relative humidity, wind

velocity and direction and rainfall) were also measured where air temperature, soil moisture and

fertilization were the most powerful factors driving the N20 flux.

45
_-,5 2.._

: sor2

X-RAY SENSITIVITY OF DIPLOID SKIN FIBROBLASTS

FROM PATIENTS WITH FANCONI'S ANEMIA

Ranjini Kale

Biology Department

Alabama A&M University

Normal, AL

ABSTRACT

Experiments have been performed on Fanconi's anemia and normal human fibroblast cell lines

growing in culture in an attempt to correlate cell cycle kinetics with genomic damage and determine

their bearing on the mechanism of chromosome aberration induction. FA fibroblasts showed a significantly increased susceptibility to chromosomal breakage by x rays in the G2 phase of the cell cycle. No

such response was observed in fibroblasts irradiated in the GO phase. The observed increases in

achromatic lesions and in chromatid deletions in FA cells as compared with normal cells appear to

indicate that FA cells are deficient in strand break repair and also possibly in base damage excision

repair. Experiments are now in progress to further elucidate the mechanisms involved.

46
N91-28073

CONSTRUCTION OF STABLE EXPLICIT FINITE-DIFFERENCE

SCHEMES FOR SCHRODINGER TYPE DIFFERENTIAL EQUATIONS

Ronald E. Mickens

Departments of Mathematics and Physics

Clark-Atlanta University

Atlanta, Georgia

Technical Monitor

John Shoosmith

Langley Research Center

ABSTRACT

A family of conditionally stable, forward Euler finite-difference equations can be constructed for

the simplest equation of SchrSdinger type, namely tu = iuxr. Generalization of this result to physically

realistic SchrSdinger type equations is presented.

47
CONSTRUCTION OF STABLE EXPLICIT FINITE-DIFFERENCE

SCHEMES FOR SCHRODINGER TYPE DIFFERENTIAL EQUATIONS

Introduction

Discrete finite-difference models of differential equations have been a traditional and popular

technique for obtaining numerical solutions of both ordinary and partial differential equations [1,2].

An essential component of this procedure is the replacement of the derivative by its discrete analogue

based on the definition of the derivative as a limit process; that is

_-dx = Lim x(t +h)h- x(t) , (1)

h-*O

and

dx Xk+l --Xk

• " _ h ' (2)

where Xkis an approximation to x(t,) with tk = hk. However, more general definitions of the derivative

can be defined. As an example consider

dx x(t +h) - x(t)

_i- = Lira (3) h--O ¢(h) '

where ¢(h) has the property

_(h) = h +0(h2). (4)

Note that for this case the discrete replacement for the derivative is

dx Xk+l -- xk

-di- _ ¢(h) ' (5)

which, in general, differs from Eq. (2) for finite values of the step-size h.

The major implication of the above remarks is that new discrete models of differential equations

can be constructed based on Eq. (3). These models have the potential for providing solutions that arise

when the conventional discrete derivation of Eq. (2) is used.

As an illustration, consider the differential equation

dx

= i2x, x(t0) = x0, 2 = real parameter, (6)

with solution

48
x(t) -- xo exp [ i2 (t - to) ]. (7)

Application of conventional procedures [1] gives, for example, the finite-difference scheme

Xk+1 - _ _ iX_. (8) h

In contrast, consider the following exact scheme [3]

Xk+l -- xk

¢(h) = fix,, xo = given, (9)

where

e/_h - 1

¢(h) = t_ (10)

An easy and direct calculation [4] shows that for Eqs. (6) and (8), we have for their solutions

x(tk) # x_, while for F__xlS.(6) and (9), x(tk) = Xkfor all step-sizes h. A/so, from Eq. (10), we obtain

¢(h) =h +_h 2 +0(h3). (11)

Consider the simplest SchrSdinger-type equation

ut = iux_. (12)

Conventional finite-differences, using a forward Euler replacement for the time-derivative, give a

scheme that is unconditionally unstable [5]. We now show how conditionally stable schemes can be

constructed.

To proceed, based on the discussion presented earlier, we construct the following finite-difference

scheme

u_ +1- u_ Urn+l-- 2U_ + _-1

_l(At,,].) -" ¢2 (Ax,2) (13)

where the "denominator functions" have the properties

_pl(At,2) =At + i2(At) 2 + 0[(At) 3] (14a)

¢2 (Ax, t) = (/_[)2 + 0[(_tX)3] (14b)

and 2, for the moment, is an unspecified parameter. Defining R(At, Ax, _.) as

i_j(At, 2)

R = _p2(Ax, ;t) = RI(At, Ax, 2) + iR2 (At, Ax, 2) (I5)

we can rewrite Eq. (13) in the form

49
u_n+1 = Ruin+1 + (1-2R) u_ + Ru_.

The substitution of a typical Fourier mode

= C(n) exp [ ko(Ax)m], (17)

into Eq. (16) and requiring the C(n) be bounded allows the determination of the stability properties.

(This concept of stability is called "practical stability" [5,6].) A straight-forward calculation shows that

Eq. (16) is stable if the following condition is satisfied.

(R1 - )2 + (R2)2 _< _"1 (181

This relation has the interesting geometric interpretation: In the (R1,R2) plane, Eq. (16) is stable for

points on and inside the circle of radius 0.25 centered at (0.25, 0). We will refer to the inequality of Eq.

(18) as the circle condition.

For a given application, the following procedure is to be followed:

a) Select denominator functions with the properties given in Eqs. (14) and calculate R in Eq. (15).

b) Choose a point (R1, R2) consistent with the circle condition of Eq. (18).

c) Determine RI(At, Ax, 2) and R2(At, Ax, 3.) from Eq. (15) and set them equal, respectively to

R1 and R2, i.e.,

RI(At, Ax, 2) = R1, R2(At, AX, 3.) = R2. (19)

d) Select a value for the space-step, Ax, and solve the two relations of Eq. (19) for At and 3. in

terms of Ax. Doing this gives

At = fffAx), 3. = f2(Ax). (20)

Thus, the selection of the point (R1, R2), satisfying the circle condition and the relations of Eq. (20),

defines completely the finite-difference scheme of Eq. (16).

As an example, consider the following denominator functions

¢1 = At + i2(At) 2, ¢2 = (AX) 2, (21)

with

_. 1 + i (22)

= ----TThe following results are easily obtained

50
_[(_.__] = 1-i (23) At = , 2 = 4 , _1 -4""

and

Notethateverythingcanbeexpressed in terms of Ax, the space step-size; its value can be selected as

desired.

A second, nontrivial example is the nonlinear SchrSdinger equation

tit = iuxr + [ul2u. (25)

A finite-difference scheme that embodies the work of this paper and also uses the nonlocal modeling

of the nonlinear term [3] is

u_n+l-u_-_1 i[ u'qn+l - 2u_ ]_ + u_-I

+ ]. U_+l + U_-I

2

. =

u_ +1, (26)

where the star (*) denotes complex conjugation, and the denominator functions _pl(At,2) and

,p2(Ax, 2) satisfy the conditions of Eqs. (14). Note that Eq. (20) is an explicit finite-difference scheme.

In summary, we have presented a new procedure to construct explicit finite-difference schemes

for SchrSdinger type partial differential equations. In general, we expect these schemes to be conditionally stable. This paper summarizes research that has already been published in Physics Review A,

June 1989 and in the "Proceedings of the 2nd IMAC Conference on Computational Acoustics."

References

1. M.K. Jain, Numerical Solution of Differential Equations, Halstead Press, New York, 1984.

2. A.R. Mitchell, Computational Methods in Partial Differential Equations, Wiley,

New York, 1969.

3. R.E. Mickens, Mathematical modeling of differential equations by difference equations,

in ComputationalAcoustics, Vol. 1, D. Lee, R.L Sternberg and M.H. Schultz, eds.,

North-Holland, Amsterdam, 1988.

4. R.E. Mickens, Difference Equations, Van Nostrand Reinhold, New York, 1987.

51
o

.

T.F. Chan, D. Lee and L. Shen, Stable explicit schemes for equations for the SchrSdinger

type, Siam Journal of Numerical Analysis, 23 (1986), 274-281.

R.D. Richtmyer and K.W. Morton, Difference Methods for lnitial-Value Problems,

Interscience, New York, 1967.

52
N91:2S074

IMAGE DATABASES: PROBLEMS AND PERSPECTIVES

V. Naidu Gudivada

Jackson State University

Department of Computer Science

Jackson, MS

?J

ABSTRACT

With the increasing number of computer graphics, image processing, and pattern recognition

applications, economical storage, efficient representation and manipulation, and powerful and flexible

query languages for retrieval of image data are of paramount importance. This paper examines these

and related issues pertinent to image databases.

53
IMAGE DATABASES: PROBLEMS AND PERSPECTIVES

1. Introduction

With the rapid advances in the Image Processing/Pattern Recognition and Computer Graphics

fields, Image Database (IDB) systems have recently attracted the attention of many researchers. The

recent special issue of IEEE Transactions on Software Engineering (IEEE 88) attests to this fact. Even

though there has been considerable research activity on issues such as image compression, hierarchical

data structures for storing complex images, and various similarity measures for efficient retrieval of the

images with partial specifications, but not until recently has serious thought been given to integrating

these results and techniques into a unified framework for efficient storage, processing, and retrieval of

complex images. Many of these techniques were used in several applications to varying degrees such as

Desktop Publishing/Office Automation, Cartographic and Mapping Applications, Interactive Computer-aided Design (CAD), Geographic Information Systems (GIS), Spatial Database Management

Systems (SDMS), Message Management Systems(MMS), and Remote Sensing (RS) ofearth resources.

This paper examines some issues and techniques for designing image databases and provides a

survey of some existing systems. The outline for the remainder of the paper is as follows. Section two

provides a historical perspective and sets the terminology. Various existing design paradigms for image

databases are examined in section three. Future outlook and conclusions are given in section four.

2. Historical Perspective and Terminology

The disadvantages of traditional file processing were recognized early in the seventies. Several

database management systems (DBMS) were proposed and implemented in the later years for efficient

storage, retrieval, and management of alphanumeric data. Enormous amounts of storage are required

for storing images/pictures. A sharp decline in hardware prices coupled with advances in processor

speeds and mass storage devices paved the way for integration of image data with alphanumeric data

in several application areas. These systems capable of managing both alphanumeric and image data

came to be known, depending on the application area and the extent to which facilities are provided by

the system for managing image data, as Pictorial Database Systems (PDBS)(Chan 81) (Yang 87),

Integrated Database Management Systems (IDMS)(Tang 81), Image Database (IDB) systems (Tamu

84), Geographic Data Processing (GDP) Systems (Nagy 79), and Geographic Information Systems

(GIS)(Fran 88). Parker (Park 88) lists many other terms used synonymously with GIS. Some of these

systems are not functionally distinct in the sense that some complement each other and some are

supersets of others. This nomenclature problem is not uncommon for a broad and rapidly evolving

discipline such as the one under discussion.

There are two basic approaches to the processing of pictorial data (Tamu 84). The first one is

image processing/pattern recognition and emphasizes analysis, transformation, and recognition to yield

other images or a symbolic description of the images. The second approach is computer graphics which

synthesizes images from given descriptions. For computer graphics, data structures are of paramount

consideration, whereas for image processing/pattern recognition, processing is of primary consideration. In other words, these two approaches vastly differ in the processing methods involved and data

structures employed. Therefore, image database design concepts also differ. Graphic oriented pictorial

databases are suitable for applications such as CAD/CAM which involve pictorial data of great

complexity. Modeling, 3D object representations, and complex data structures/formats are of primary

54
concern. Image processing oriented pictorial databases are suitable for applications based on

LANDSAT imagery. The primary concern here is for efficient storage techniques and use of pattern

recognition techniques for retrieval. Pictorial databases refer to both graphic oriented and image

processing oriented databases. Tamura and Yokoya (Tamu 84) refer to these database systems as image

databases and so does this author.

Tamura (Tamu 80) classifies image database systems into five types. Type one refers to a large

collection of images systematically collected and made available to several users. Remote sensing data

centers databases fall into this category and require no explicit image database management system.

Type two refers to databases for retrieval of secondary information such as date of acquisition, quality,

altitude, etc. A conventional DBMS can be used for this type for storage and retrieval of secondary

information which is inherently alphanumeric. Type three systems are characterized by the existence

of a management system for imagery and map data for spatially-oriented processing. Type four systems

store structural information describing pictures or scenes. Type five systems constitute a set of library

images which are intended to be used as benchmarks for evaluating and comparing new algorithms.

This classification is mentioned for historical interest and has no relevance for classifying today's

systems.

Vector format and raster format are the two principal formats used for storing images. Applications

such as cartography, topography, and spatial analysis or GIS use vector format. Spatial data are

represented by using point, line or segment, and polygon data types. Applications using LANDSAT

imagery use only point data type. Also, the output produced by many modern image capturing devices

is inherently in raster format. Since raster format stores images as a collection of points along with their

attributes, this leads to enormous storage requirements. However, several image compression techniques for compressing raster image data are reported in the literature (Yang 87) (Barn 88). Of course,

compression techniques consume computational time for encoding and decoding of images. In addition

to the vector and raster formats, there are several other formats (Chan 81).

3. Design Paradigms

Image data models, image data types, image data structures, mechanisms for describing image

features, storage/compression techniques, and a flexible query language are integral parts of an image

database system. A system to integrate and coordinate the functionalities of these components is an

image database management system. In the following sections, each of the component structures is

examined in detail.

3.1 Image Data Models

A data model for image databases should provide a uniform framework for handling both

alphanumeric and image data. The associated management system is expected to store, retrieve, and

process a large number of pictures of great complexity. There exists three main data models for

managing alphanumeric data, namely, hierarchical, network, and relational models. It may seem natural

to extend the concepts and techniques of conventional DBMS to bear with image database systems.

This approach has two main disadvantages (Econ 83). Since conventional DBMS are geared to handle

structured alphanumeric data, the resulting image databases are inefficient and cumbersome with

unnatural query languages. Secondly, these query languages are very complex because they emphasize

low-level descriptions of images.

Design characteristics of an image database depend on the intended functionality, types of images,

and the extent of data abstraction and image data structures. An archival system for LANDSAT imagery

55
is more concerned about efficiency of storage and retrieval than the processing methods and data

structures. On the other hand, a system for map database applications focuses on efficient data structure

design, ease of update, coloring, and overlays rather than storage requirements. Some applications may

impose significant data abstraction. For these applications, image features are completely symbolized

and the symbolic information, not the original images, is stored and managed. On the other extreme,

are the cases where the images are stored without compression and the management system simply

maintains pointers to these locations. Between these two extremes are a number of other possibilities.

There are three basic approaches to image database design. The first approach is to simply extend

the conventional database by adding images as a standard data type and extending the query language.

ADM (Aggregate Data Manager) (Taka 80) is an example of this kind. Its architecture is based on a

relational database management system, System-R. System-R's query language, SEQUEL is suitably

modified to handle image data. A second approach is to add database capabilities to an existing image

processing system. EIDES (ETL Image Database for Experimental Studies) (Tamu 80) and MIDAS

(Multi-sensor Image Databases System) (McKe 77) are two examples of this approach. In addition to

these two, there are several approaches from application fields such as geographic data processing,

medical imaging, remote sensing, and fingerprint analysis (Tamu 84).

In general, a relational data model is widely used in experimental image database systems because

of its mathematical simplicity. GRAIN(Graphics-oriented Relational Algebra Interpreter) and

REDI(Relational Database System for Images) are two examples of early implementations (Tamu 84).

Unfortunately, relational model has several shortcomings for modeling pictorial data (Moha 88). A

relational model is inherently suitable for representing one-dimensional data in the tabular form but

pictorial data is two-dimensional. Hierarchical structured data cannot be easily represented using a

relational model. Many tables are required for representing hierarchy links. It is not possible to explicitly

specify semantic information about relationships. Since most of the semantic information is distributed

over several hierarchy link relations, meaning has to be guessed by the user before performing any

operation.

3.2 Data Types, Data Structures, and Storage Techniques

Spatial data are inherently multi-dimensional (Oren 88). Also, notions of spatial data tend to vary

from one application to another.

Geographic applications require two-dimensional data, geological applications require three-dimensional data, and some solid modeling applications require four-dimensional data. Spatial operations

and representations are highly application dependent. And for this reason, many models that are

implemented are application specific including query languages (Jose 88).

Image data can be viewed as a matrix of gray levels or two dimensional signals in raster format. In

vector format, image data is encoded by simple data structures such as points, line segments, and

polygons or regions. Quadtrees, Octtrees, and Pyramid representations are some data structures

proposed for storage efficiency (Tamu 84). Cheng and others (Chen 88) recently proposed a method

for compressing binary digital images using irreducible covers of maximal rectangles. Barnesley and

Sloan (Barn 88) describe a method for compressing images based on fractal encoding. Only iterated

function system (IFS) codes are stored rather than the original images. This approach seems promising

for automatic image analysis because the combinatorial search space for feature extraction is dramatically reduced.

56
Orenstein and Manola (Oren 88) proposed a new approach to extend the database system

functionality for spatial data modeling and query processing. Extensibility is built into their object-oriented data model, PROBE, thereby making the model flexible enough to be adapted to a different

number of applications. They also show how their system can be used for spatial data modeling and

querying for image database applications. Economopoulos and Lochovsky (Econ 83) have designed

and implemented an image data model which represents images in terms of high-level semantic

descriptions rather than a pixel-oriented description. This system is a component of a larger prototype

system, Message Management System (MMS), intended for intelligent communication and processing

of messages.

Joseph and Cardenas (Jose 88) describe the requirements for a generalized pictorial database

management system (PDBMS) to provide data heterogeneity transparency over pictorial and non-pictorial data. The data manipulation capabilities that are expected of a generalized PDBMS are classified

into six categories such as image manipulation operations, pattern recognition operations, spatial or

geometric operations, function operations, user defined functions and programming language interface,

and input/output operations. The proposed architecture has two database management system components, one to manage the pictorial data, called PICDMS, and the other to manage conventional data,

referred to as non-pictorial database management system. Similarly, the query language has two

components to manipulate and access pictorial and non-pictorial data. A notable thing about this system

is that it allows a user to define his own pictorial data types in addition to the point, line, and region

data types provided as standard pictorial data types.

3.3 Image Retrieval and Query Languages

There are three levels of retrieval: retrieval by an identifier, retrieval by conditional statements,

and similarity retrieval by a given sample. Retrieval by an identifier corresponds to physical retrieval of

an image corresponding to the given identifier. Retrieval by conditional statement is based on the image

features. Image features can be precomputed or computed dynamically.

Many query languages implemented up to 1980 have been summarized (Chan 81). The majority

of the query languages developed till today are command-oriented languages. Some query languages

are newly designed with emphasis on registration, editing, and display of images. Other query languages

are simple extensions of data manipulation languages for image file management.

Chang and Fu[Chan80] developed Query-by-Pictorial-Example (QPE), a query language for a

relational database system for images (REDI). Image processing and pattern recognition techniques

are used to extract structures and features from images. These extracted features are integrated and

used in query processing. Original image data is retrieved and processed only when the feature data are

insufficient and/or imprecise to process a query. The graphical interface for querying is similar to the

well known relational query language, Query-By-Example (QBE).

PICQUERY (Jose 88) is a pictorial query processing language for PICDMS (mentioned above).

PICQUERY has an open-ended design to interface with other robust PICDMS also. PICQUERY

provides a fundamental shell on which user defined operations for pictorial data may be built. PSQL,

a query language for the manipulation of pictorial databases, allows pictorial domains to be represented

in their analog form (Rous 88). The associated database can perform direct spatial search and

computation by using efficient data structures, R- and R + trees.

The most desirable feature of a query language for image database applications is the ability to

retrieve images from a large image database based on a partial description of the image content. Rabitti

57
and Stancher proposed a formalism based on fuzzy set theory for this task. There are four stages

involved: element recognition, segmentation object recognition, added information definition, and

image clustering. During the element recognition stage, the system tries to match the image elements

with the terminal symbols of an adapted grammar. Fuzzy formalism helps when the system is unable to

find an exact match with the stored representations (all possible elements the system is likely to

encounter are stored to start with). More than one match is assigned with different certainty factors.

Objects correspond to nonterminal symbols of the adopted grammar, and applying the production

rules of the grammar recursively, objects are identified starting with the image elements. During the

added information definition stage, a user can add more information to the object description. The

image interpretation obtained is compared with all the given class descriptions during the last stage.

The class assignment is made on the basis of distance measures.

A model based on object-oriented knowledge representation for spatial information has been

reported as flexible enough to capture any type of information one wishes to represent about a given

pictorial world (Moha 88). The visual user interface for map information retrieval has been reported

in (Tana 88). The system is designed to reduce the semantic gap between the user's view and the system

function.

4. Future Outlook and Conclusions

Image database systems started as application specific systems and are gradually evolving toward

more general-purpose systems. The advances are in two specific directions based on the two basic

approaches for processing of pictorial data. For the approach based on computer graphics, commercial

systems such as ARC/INFO are already available and provide a uniform framework for GIS applications.

Even though ERDAS is a general-purpose commercial image processing system, it is far from ideal.

Substantial research into proposing and demonstrating a unified framework for image database

management systems is required. This framework is expected to provide a pictorial data model that truly

provides data independence and captures all the implicit semantic information in the pictorial data.

This framework is also expected to provide flexible query languages for the partial specification of

queries based either on precise or imprecise image description or the image itself (specified in the

format). Advances in this area will have a profound impact on providing intelligent graphical user

interfaces for applications.

Acknowledgments

The author gratefully acknowledges the support received from NASA and DOEIDE-FG05-

86ER75274]. The author is also thankful to Mr. Rick Galle, Stennis Space Center, and Dean Leflore

and Professor Lupton at Jackson State University for their continued encouragement.

References

(Barn 88) Barnsley, M.F.; Sloan, A.D., A Better Way to Compress Images, BYTE, 1988,

January, 215-223.

(Chan 80) Chang, N,; Fu, K.S., Query-by-Pictorial Example, IEEE Transactions on Software

Engineering, 1980, November, 519-524.

58
(Chan 81) Chang, S., Pictorial Information Systems: Guest Editor's Introduction, Computer,

1981, November, 10-11.

(Chan 81a) Chang, N.S.; Fu, K.S., Picture Query Languages for Pictorial Data-Base Systems,

Computer, 1981, November, 23-33.

(Chen 88) Cheng, Y.; Iyengar, S.S.; Kashyap, R.L., A New Method of Image Compression

Using Irreducible Covers of Maximal Rectangles in [IEEE88].

(Econ 83) Economopoules, P.; Lochovsky, F.H., A System for Managing Image Data,

Proceedings of IFIP Congress, 1983.

(Fran 88) Frank, A., Requirements for a Database Management System for a GIS,

Photogrammetric Engineering and Remote Sensing, 1988, November, 1557-1564.

(IEEE 88) IEEE Transactions on Software Engineering Special Issue on Image Databases,

1988, May.

(Jose 88) Joseph, T.; Cardenas, A.F., PICQUERY: A High Level Query Language for Pictorial

Database Management in IIEEE88].

(McKe 77) McKeown Jr., D.M.; Reddy, D.R., A Hierarchical Symbolic Representation for an

Image Database, Proceedings of 1977 IEEE Workshop on Picture Data Description and

Management, 1977, 40-44.

(Nagy 79) Nagy, G.; Wagle, S., Geographic Data Processing, Computing Surveys, 1979, June,

139-181.

(Oren 88) Orenstein, J.A.; Manola, F., PROBE Spatial Data Modeling and Query Processing

in an Image Database Application, IEEE Transactions on Software Engineering, 1988, May,

611-629.

(Park 88) Parker, D.H. The Unique Qualities of a Geographic Information System: A

Commentary, Photogrammetric Engineering and Remote Sensing Special GIS Issue, 1988, November, 1547-1549.

(Rous 88) Roussopoulos, N.; Faloutsos, C.; Sellis, T., An Efficient Pictorial Database System

for PSQL in [IEEE88]

(Taka 80) Takao, S.; Itoh, S.; Iisaka, J., An Image-oriented Database System, Database

Technique for Pictorial Applications, A. Blaser, Ed., Springer-verlag, 1980, 527-538.

(Tamu 80) Tamura, H., Image Database Management for Pattern Information Processing

Studies, Pictorial Information Systems, S.K. Chang and K.S. Fu, Eds., Springer-Verlag 1980,

198-227.

(Tamu 84) Tamura, H.; Yokoya, N., Image Database Systems: A Survey, Pattern Recognition,

1984, 17, 29-43.

59
(Tana 88) Tanaka, M.; Ichikawa, T., A Visual User Interface for Map Information Retrieval

Based on Semantic Significance in [IEEE88].

(Moha 88) Mohan, L; Kashyap, R.L, An Object-oriented Knowledge Representation for

Spatial Information in [IEEE88].

(Tang 81) Tang, G., A Management System for an Integrated Database of Pictures and

Alphanumeric Data, Computer Graphics and Image Processing, 1981, 16, 270-286.

CYang 87) Yanguang, W., The Research of Digital Picture Storage Methods for Picture

Database, 38th Congress of the International Astronautical Federation, Brighton, UK, 1987,

October, 1-23.

6O
N91-2S()75

IMPLEMENTATION OF AN ALGORITHM FOR CYLINDRICAL OBJECT

IDE_CATION USING RANGE DATA

Sylvia T. Bozeman and Benjamin J. Martin

Department of Mathematics

Spelman College

Atlanta, Georgia

ABSTRACT

This research addresses one of the problems in 3-D object identification and localization. In

robotic and navigation applications the vision system must be able to distinguish cylindrical or spherical

objects as well as those of other geometric shapes. An algorithm has been developed to identify

cylindrical objects in an image when range data is used. The algorithm incorporates the Hough transform

for line detection using edge points which emerge from a Sobel mask. Slices of the data are examined

to locate arcs of circles using the normal equations of an over-determined linear system. Current efforts

are devoted to testing the computer implementation of the algorithm. Refinements are expected to

continue in order to accommodate cylinders in various positions. A technique is sought which is robust

in the presence of noise and partial occlusions.

61
IMPLEMENTATION OF AN ALGORITHM FOR CYLINDRICAL OBJECT

IDENTIFICATION USING RANGE DATA

Introduction

Among the various tasks assigned to the National Aeronautics and Space Administration is the

investigation of space related automation and robotics. NASA has chosen to use the telerobotic system

configuration as the basis for progressively studying and implementing spaceborne automation.

Telerobotic systems consist of a human, a robot, a human-robot interface capability, sensors, and the

accompanying computational tools. By basing research on this system structure, NASA can progressively evolve its automation capability from teleoperator, where the human is directly involved in every

operation of the machine, to near autonomy, where man is only involved as a monitor of the machine's

activity.

In designing automated robotic activity, it is necessary to be able to automatically (i.e., without

human involvement) recognize objects, their positions, and their orientations in order to be able to

grasp and manipulate them. Thus the ability to take the data from the scanning rangers and determine

the composition of the image scanned and the locations of the various components is needed. Even as

work progresses on the development of faster and more accurate scanners, considerable research is

underway on methods for using range data in object detections and recognition. (See reference list of

Faugeras and Herbert, 1986.)

In the problem of 3-D recognition and localization of objects that are rigid, a major consideration

is the method of representing objects. After considerable investigation Faugeras and Herbert (1986)

concluded that representation should be in terms of linear primitives, such as points, lines, and planes,

although these may be derived from consideration of curved patches at intermediate stages.

The technique here employed for detecting cylinders is based on the use of external descriptors.

In the case of the cylinder it is noted that in one direction the boundary should appear as straight lines.

In a direction orthogonal to the first the data should fit the equation of a circle (or an ellipse in the

more general case). Information on the boundary in the third orthogonal direction is not used.

The approach used in this project has been to develop the algorithm while testing it on ideal data

for a right circular cylinder with the axis of the cylinder parallel to the y-axis. This condition is later

relaxed to allow the introduction of an angle a that indicates the angle between the cylinder's axis and

the y-axis; thus freedom of rotation in one direction is allowed. The ultimate goal is to refine the

algorithm so that it is robust in noisy environments. The algorithm should also yield a high rate of

accuracy when the cylinders have partial occlusions.

In approaching this problem the spirit of a comment attributed to A. Guzman is followed: "If you

recognize a foot you know where (in the picture) to look for a leg..." Hence the procedure for locating

cylinders in a picture has been to look first for parallel lines; then the algorithm can check for a cylinder

between the lines. Therefore, the first major part of the programming project consisted of identifying

edgepoints in the image and extracting lines from those edgepoints. Both tasks have been the subject

ofconsiderable research over the past 20 years. The basic methods employed in this part of the algorithm

are then somewhat classical in nature.

62
Locating Edgepoints and Lines

The first step is to locate the pixels that are the edgepoints. At each pixel in the image a 3x3 mask

centered at (i, j) is used to determine the variation on distance from the sensor in both the vertical and

the horizontal directions. Note that i represents the row, j the column, and P(i, j) the range data at the

pixel location (i, j). This mask is known as a basic Sobel edge detector where

igrad = 2(P(i-l,j)-P(i+l,j)) + P(i-l,j+l)-P(i+l,j+l) + P(i-l,j-1)-P(i+l,j-1)

jgrad = 2(P(i,j+l)-P(i,j-1)) + P(i-l,j+l)-P(i-l,j-1) + P(i+l,j+l)-P(i+i,j-1)

estimate the variations in the vertical and horizontal directions, respectively, at (i,j). Using these two

quantities in a vector G=(jgrad, igrad) to approximate the gradient vector at (i,j), both the magnitude

and direction of the greatest variation at (i,j) can be obtained. If the magnitude of the gradient,

k = ((igrad) 2 + (jgrad) 2 )_,

is above some predetermined threshold value, T, then it is assumed that there is an edgepoint at (i,j).

T may vary and can be selected interactively prior to runs. Using a threshold of 100 it was found that

certain edgepoints around the top of the cylinder were not detected even with ideal data.

In searching for lines among the edgepoints, the gradient directional information may or may not

be used. Using gradient information, the edge angle at (i,j) is found as g = arctan(igrad,jgrad).

J. Kittler [1983] has given considerable attention to the performance of the Sobel edge detector

in terms of the accuracy of its magnitude and angle. He proved that the basic Sobel edge detector

described above will correctly detect the true angle of the edge direction at the boundary between the

object and the background in the interval 0 _<g_<arctan(_). He predicts an error of approximately 2 ° in

direction for larger angles and an accurate magnitude onlywhen the edge is vertical or horizontal. Davis

[1987] points out that this technique loses accuracy when the edges of the objects are fuzzy.

In attempting to extract lines from among the edgepoints the Hough transform has been shown

to be an effective technique. It is especially attractive in this environment because of its robust

performance in noisy environments. Although it can be employed with or without the gradient

information, we chose to use the gradient information in order to reduce the number of lines associated

with each pixel and thereby reduce the storage requirements.

This technique for detecting collinear points dates back to 1962 with a patent issued to P.V.C.

Hough. The technique is based on the fact that a line through a point (x,y) can be completely

characterized by its angle (from the positive x-axis) and the length of the normal from the origin to the

line. The line can be expressed using the equation

XiCO_0 +yisin0 =r. (1)

63
This approach to finding lines is based on the fact that if enough pairs ( xi ,yi ) appear in the image which

give rise to the same (r, 0) pair then these points may well represent a line in the image (if they can be

shown to be contiguous). Thus a "voting" system is established and a two-dimensional accumulator array

is created to count the votes. When gradient information is not used the angle 0 is allowed to vary

independently over a 18(1° range (using small increments) and each point ( xi, yi )) can produce a value

of r for each value of 0. If r lies within the limits specified by the physical dimensions of the image, the

number of votes at location (r,0) is incremented by one. When gradient information is used at each

point, the only value of (r,0) incremented for that point is the one where 0 corresponds to the gradient

at the point, and r is calculated using (1).

In the latter case Gorman and Clowes [1976] recommended the creation of "contributing point

lists" to keep track of the points whose votes account for the value in a particular cell of the accumulator

array. The data structure chosen here to accomplish this tracking was a second array, matching the

accumulator array, which consisted of pointers, each pointing to the list of pairs contributing to the

value at (r,0). Once the accumulator array is filled (i.e. once the selected portion of the image has been

processed) the list would contain all points found to be on or near the line specified by the parameters

(r,0).

This method works well to find the line containing line segments in the image but has two

shortcomings. (1) It does not give any indication as to whether the points found are contiguous. (2) It

does not give the location of line segments on the lines found. The difficulty resulting from the latter

is somewhat diminished by employing the contributing point lists.

Isolating Edges and Cross-Sections of a Cylinder

Attention is now turned to analyzing the data in the parameterized space of (r,0). Since finding

consecutive pairs of parallel lines is of interest, peaks in the data taken from a cross-section of the space

are sought. For a fixed value of 0, consecutive values rl and r2 are sought in which the accumulation of

"votes" for a line at (ri,0) exceeds some predetermined value M. The value M may be selected

interactively and should depend on (1) the required length of a line in order to be considered

meaningful, and (2) the size of the image (or subimage) being processed.

In an image of size 256x256 pixels a value of M=20 was used. The two problems that arise with

this (as with any) choice of M are that (1) cylinders of less than 20 pixels in height go undetected, and

(2) if less than 20 pixels are visible along the edge of the cylinder due to occlusion by other objects in

the image, then the necessary matching pair of edges will not be found. If peaks appear in the

parameterized data at (rl,0) and (r2,0) but for no other value of r, rl<r<r2, then a cylinder is sought

between the corresponding parallel lines 11and 12.

Labeling in 3-D

Since a right circular cylinder in standard position (i.e., having its axis parallel to the y-axis) has

uniform cross sections whose boundaries are all circles of the same radius, the goal is to isolate a cross

section of the image between the two parallel lines. The points along the visible portion of the cross

64
section will be tested to determine if they lie on an arc of a circle---a circle which in 3-D lies perpendicular

to the plane of the image.

It is only now that the labeling of the points in the image of the 3-D space becomes important.

Prior to this point in the discussion, consideration of the projection of 3-D objects onto the image plane

has been sufficient. If an xy-coordinate system is superimposed onto the image, so that the origin of the

system lies in the lower left corner of the image (at a background point), then each pixel location (i,j)

also can be referenced as (x,y), where x=j and y=256 - i. (Figure 1.)

If a third coordinate axis z which is orthogonal to the xy image plane is added then the distance

from a point R, located on an object in the scene, to the plane of the sensor can be measured along z.

(Figure 1.) The grey level of each pixel in the image represents the range data and indicates the relative

distance of the object from the sensormlighter areas (higher grey levels) being closer. Thus if z=0 at

R then the point R is as far as possible from the sensor. Let R be a given point on an object in the scene

which appears at location (i,j) in the 2-D image. Suppose that the plane of the sensor is at a distance S

from the reference background point at the origin of the coordinate system. If k is the 3-D distance at

point R from the object to the sensor, then the z-coordinate of R is z=S-k. Thus, the point R can be

positioned relative to the xyz-coordinate system since its x and y coordinates are the x and y coordinates

of (i,j) (Figure 2).

V=256-1

×=J

(o.o,o)

Figure 1.

Z

Pl QP2

the plane of the sensor

Figure 2.

65
Analyzing a "Slice" of the Data

In locating data which might lie on the arc of a circle between the two parallel lines 11and/2 already

found, a point is chosen from each of the two lines which lies on a single slice of the data. Thus we seek

two points pl and p2 that are endpoints of a line segment perpendicular to 11and/2, so that pl lies on

11and p2 lies on/2. For the cylinder in a standard position such points have the same i (or y) value. Thus

we need only return to the lists of contributing points corresponding to the (r,0) values giving rise to

the two lines and locate two points with the same y coordinate. (The search is made easier by ordering

points as the lists are created.) In the more general case, the angle of inclination of the parallel lines

can be used to determine the relationship between the y values of the two corresponding points sought.

In order to determine whether pl and p2 are the endpoints of the arc of a circle in 3-D space we

test the range data at these two points and points in between (on the same orthogonal slice). Denote

by D this set of points. If we confine ourselves for a moment to the case of the cylinder in standard

position, it is no longer necessary to consider the y direction for points on the slice. Thus each point in

the image can be considered as having only x and z components (Figure 2). In this case

D ={(x,yo, z) I XI<X<X2' where pl = (xl,yo,z0, p2 = (x2,yo, z2)}

In this two-dimensional subspace the equation of a circle (whose center has y-componenty0) determined

uniquely by any three points in D is sought. However, if the points of D approximate an arc all of its

points must lie on, or near, the circle determined.

If we suppress the constant component, then for any point (Xi,Zi) in D,

(Xi --Xc) 2 + (Zi --Zc) 2 ----- r2 (1)

if the point lies on the circle with center (xc,yo,Zc) and radius r. By equating two such equations using

points (xi,zi) and (xj,zj) we can eliminate r and get the equation

2Xc (Xi -- Xj) + 2zc (zi - zj) = _ + zi2 - _ - z_,

a linear equation in the two unknowns xc and Zc.

Selecting m points (Xi,Zi) , i= 1,...,m, from D, m-1 equations in 2 unknowns can be formed as

2x,:(xi -Xm) +2zc(zi -Zm) =x 2 +z 2 -x2m -z 2,i=l,...m-1- (2)

This system of m-1 equations in 2 unknowns can be written as a matrix equation Ay=b, where A is the

(m-1)x2 matrix

A

Xl --Xm Z1 -- Zm X2 -- Xm Z2 -- Zm

_ 2 • •

Xm-I -- Xm Zm-I -- Zm

66
yT = (Xc,Zc), and bT = (x{ + z{ - x2m - z2 ,..., X2m-1 + z_-i - x2m- z2). If the rank of A is 2 then

the least squares problem

Ay=b

has a unique solution _ that is determined by solving the normal equations

(3)

ATAy = AXb. (4)

The unique solution to (4) (if it exists) is _ = (ATA) -1 A T b and is simple to obtain since ATA is a 2x2

matrix.

Finally, r can be obtained using (1) and any one of the m points, although an average of the values

of r found with several points is preferred.

In order to determine the accuracy of this technique the sum of the deviations, in the z direction,

from the circle at each point is computed.

m

Thus e = E(zi -zpi) where zpi - zc + Round ((r 2 - (xi - xc)2 )_ ). Ire is small then the points

i=l

of D lie on a circle with radius r and center (Xc,yo,z¢). The size of e which is acceptable is expected to

depend on r or m.

The above algorithm should be repeated to locate several circles between the two parallel lines

11and 12,all having approximately the same radius and having their centers on a single line (the proposed

axis of the cylinder) before concluding that a cylinder has actually been detected and localized.

Further analysis is needed to determine a priori error bounds for the solution of (4) because of

the ill-conditioned problem that often results from forming the normal equations.

Given that this algorithm was tested on ideal data (rather than the noisy data from an actual sensor)

the next step in this research effort is to test the robustness of the algorithm in the presence of noise.

Future effort will also involve implementing this algorithm in the case when the cylinder is not in

standard position but has a nonzero angle of inclination between its axis and the y-axis. The current

algorithm represents a step toward an autonomous system for detection and localization of cylindrical

objects in images created using range data.

67
References

Ballard, D.H., Pattern Recognition, 1981, 13(2), pp 111-122.

Davis, E.R., Pattern Recognition Letters, 1987, 6, pp 1-7.

Faugeras, O.D.; Herbert, M., The International Journal of Robotics Research, 1986, 5(3),

pp 27-52.

Gonzalez, Rafael C.; Wintz, Paul, Digital Image Processing, 1987, 2nd ed., Reading, Mass:

Addison-Wesley, pp 331-349.

Gorman, Frank and M.B. Clowes, IEEE Transactions on Computers, 1976, 25(4), pp 449-456.

Kittler, J., Image and Vision Computing, 1983, 1(1), pp 37-42.

68
.a

N9 1-28 6

MATHEMATICAL MODELS FOR _/'_- ,._._-

FILM SENSITIVITY MEASUREMENTS

Ernest Hammond, Jr.

Department of Physics

Stephen Gewirtz and Osborne Parchment

Department of Mathematics

Morgan State University

Baltimore, MD

and

Gerald R. Baker

Technical Monitor

Laboratory of Astronomy and Solar Physics

Goddard Space Flight Center

ABSTRACT

The quality of the pictorial record developed from photographic material depends on the composition of the material, the procedures used in its exposure and processing_as well asthe nature of the

physical/and temporal environment extant during the creation of the record. By holding many of the

variables fixed, this paper examines_the effect of two environmental parameters, namely temperature

and aging, i,on the characteristic curve of a given film. Polynomial and exponential functions are

evaluated, as empirical formulas for the characteristic curve, and the sensitivity of derived coefficients

to the selected parameters is assessed.

/

69
MATHEMATICAL MODELS FOR

FILM SENSITIVITY MEASUREMENTS

I. Data Description and Rationale for Data Analysis

In a variety of applications of scientific photography, there is an unavoidable time lapse between

film exposure and film processing. During this time, the exposed film may be subject to varying levels

of ambient temperature. Such is the case, for example, when films of experiments are exposed at various

times during a space mission and developed at the end of the mission. A similar scenario occurs when

films are exposed at distant experimental sites and returned by common carrier to a central location for

processing. In such cases the extent to which the photographic record may be affected by the aging

and/or the temperature is an important consideration. The data used in this analysis was developed to

assess the effect of these physical parameters on one type of common film. A description of the method

used follows.

Film of the type selected was exposed for a f'LXedtime using a light sensitivity wedge of thirty gray

levels. Following exposure, the film was aged for a selected number of days at a selected temperature

and then developed. The density for each gray level in the wedge was measured using a densimeter to

produce data similar to that shown in Table I. For this analysis, aging periods were assigned in multiples

of three days to a maximum of twenty days and the incubation temperatures were eleven and forty

degrees. The development procedure was identical for all the films used in this phase of the project.

The actual film used to generate the density readings used in this report was KODAK IIaO.

The density readings accurate to two decimal places, as shown, are dependable for the method as

outlined. No attempt is made to correct for differences in storage times between film manufacture and

film exposure. However, the supplier maintained manufacturing and shipping practices designed to

minimize the effects of this factor [1].

II. Selection, Implementation and Testing of Empirical Models

The earliest researchers in the science of photography realized that a functional relationship exists

between photographic densities and the exposures which produce them. F. Hurter and V. Driffield [2]

originated the method of plotting density against the common logarithm of exposure to obtain

empirically the characteristic curves (Figure I) so central to the theory of sensitometry. Researchers in

population biology may also notice a strong similarity to the logistic growth curve.

Despite many attempts to describe this curve globally by a single mathematical formula, no

satisfactory functional relationship has so far been commonly accepted as theoretically based and

empirically accurate. Consequently, this study uses regression analysis on a selection of curves to

represent the experimental data and presents the root mean square error resulting from each choice.

7O

L _ JJ
WEDGE

NUMBER

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

DENSITY

(15 day_, ll°C)

0.22

0.23

0.24

0.25

0.27

0.30

0.35

0.39

0.46

0.53

0.62

0.72

DENSITY

(15 days, 40°C)

0.31

0.31

0.32

0.34

0.38

0.41

0.51

0.57

0.66

0.73

0.82

0.91

0.78

0.90

1.03

1.13

1.25

1.35

1.47

1.60

1.68

1.75

1.82

1.88

1.93

1.99

2.03

2.07

2.11

2.14

1.00

1.10

1.19

1.26

1.35

1.43

136

1.64

1.69

1.74

1.78

1.82

1.91

1.94

1.97

2.00

2.03

2.04

TABLE I

Density Values for KODAK IIaO Film Aged 15 Days at 11, 40 Degrees Celcius.

A. Polynomial Fit by Regression Analysis

Although characteristic curves exhibit segments which appear to be approximately linear, the

graph of density versus the logarithm of admissable exposures is obviously not globally a straight line.

Thus an attempt to model these curves by polynomials requires them to be at least quadratic. In fact,

the presence of at least one inflexion point suggests that cubits are the minimum needed if a reasonably

accurate fit is to be assured. Consequently, this analysis begins with the selection of the most general

cubic polynomial as a possible regression curve and proceeds to test higher degree functions until there

is no perceptible change in the root mean square error computed.

The regression method for fitting a polynomial

PN (X) = Co + C1 X + C2 X 2 +... CN X N

71
to thedata set (XK, YK) k = 0...N, involves finding the coefficients CK so that the expression for the

least square error

LSE = (YK - PN (XK))2

or for the root mean square error

RMSE = (LSE/N)

is minimum. This is a standard procedure in numerical or statistical analysis. The procedure results in

a set of M+I simultaneous, linear equations for the unknown coefficients. Using the Gauss-Jordan

method [5] for solving such equations, the unknown coefficients which determine the best fitting

polynomial are determined. The algorithms to do this were coded in Pascal and the code may be obtained

by writing to the authors. Figure II shows the experimental data together with cubic and quintic

regression curves.

DS

u

t.D

Z

ILl

+0 0

GAMMA = TAN 8

/

1 2 3 4 5

LOG E

6

FIGURE I: Typical Characteristic Curve

Film Density vs. Log of Exposure.

72
CUBIC APPROXIMATION - --_

jQUINTIC APP

i I !

LOG E

FIGURE II. Two Polynomial Approximation Curves.

2.2

Z0

1.8

1.4

T_

-1.0

0.8

0.6

o-

/

I I I

1-G 2S0 3.0 : 4.0

Exponential

Data

FIGURE III. Exponential Regression Fit to Data.

73
Film Density Data Approximated by Selected Polynomials

B. Exponential Fit by Regression Analysis

The polynomial curves derived in the preceding section produce a very good fit with the experimental sensiometric data. However, the simplest of the models considered requires the determination

of four unknown coefficients. A useful question to consider is the existence of other curves capable of

producing an acceptable fit with fewer adjustable constants. The general nature of the characteristic

curves suggests that the rate of change of density y with respect to the logarithm of exposure x should

have the form

* dy/dx = y(a-by)

where a and b are unknown constants. Viewing this as a differential equation for y in terms of x, we

could impose the initial condition:

y(0) = the fog density of the film.

Solving the resulting initial value problem using methods outlined for example in [6], yields the general

solution:

** y = a/[b +(ahy(O) -b)exp(-ax)].

The problem is to determine the constants a, b from the experimental data. It will be helpful to

note two relevant properties of the solutions of equation *.

Property I: For large values of x, the values ofy approach the ratio a/b.

Property II: Any solution has a flexpoint at the value y =a/(2b) and the rate of change at this flexpoint

is a'/(4b).

The first is obvious from the solution formula **; the second can be derived by the substitution of

a/(2b) for y in the right hand side of *. A reasonable assumption is that they approximated the linear

portion of the characteristic curve. Using this assumption together with Property I & II gives:

a2/(4b) = slope of linear regression line

a/b = maximum density of exposed film

Consequently, the values for the constants a and b are determined by the data. Figure III compares

the experimental data with the exponential regression curve derived as described above.

74
C. Comparision of the Models

Analysis of the approximation data shows a very good agreement of the experimental data with

cubic polynomials. Although there is evident improvement resulting from the use of quintic regression

curves, the changes are not significant enough to warrant the significant amount of additional computation required. Futhermore, extending mathematical approximations to accuracies beyond the error

tolerance of the measuring instruments is not generally a useful exercise.

The results obtained by exponential regression show a considerably higher error when compared

to the polynomial regression figures. When tempered by the fact that this method needs the determination of only two arbitrary constants compared to four and six respectively in the polynomial cases

considered, the evaluation of the exponential model improves somewhat. The geometric properties of

the exponential regression curve suggest better agreement for longer exposure time.

III. Conclusions and Questions for Further Study

If the commitment has been made to model the data by polynomial regression, it is clear from the

study that the quintic polynomial regression provides a better fit than the same procedure applied to

cubic ones. However, the increase in accuracy is not dramatic enough to justify the additional complexity

and computation time required for the higher degree. Cubic splines, although not used in this analysis,

are likely to provide an even better fit, but are not global polynomials although they belong locally to

this class of functions. Lagrange polynomials are not practical for this model because of the high degree

required to fit the data and the consequent increase in computation time.

Choosing the model by exponential regression has some theoretical appeal. However, the errors

generated are an order of magnitude higher when compared to the cubic polynomial fit.

For fixed temperature, the coefficients of the respective regression curves used remained stable

as functions of aging. On the contrary, for a fixed age there was significant variation in the respective

coefficients as functions of temperature. Because the data was available only for three distinct

temperatures, this variation is not enough to support a claim of instability of the coefficients as functions

of temperature. Additional analysis with more closely spaced temperature readings would be necessary

to support such a claim.

75
IV. References

1. Eastman Kodak Company, "Plates and Films for Scientific Photography", First Edition.

2. T.H. James & C.E.IC Mees, The Theory. of the Photo p_raphic Process, Third Edition,

Macmillan Company.

3. P.W. Purdom & C.A. Brown, The Analysis of Algorithms. Holt, Rhinehart and Winston.

4. R.L Burden, J.D. Faires, Numerical Analysis, Third Edition, Prindle, Weber & Schmidt.

5. R.P. Yantis & R.J. Painter, Elementary. Matrix Algebra with Applications, Second Edition,

60, Prindle, Weber & Schmidt.

6. M.R. Spiegel, Applied Differential Equatiom, Third Edition, 35, Prentice-Hall.

!

76
N91-2S077

THE PREDICTION OF PSEUDO-RESONANCE POSITIONS IN

THE SCHWINGER VARIATIONAL PRINCIPLE

Charles A. Weatherford

Roy Tucker, and Gregory Odom

Department of Physics

Florida A & M University

Tallahassee, FL

ABSTRACT

The Schwinger Variational Principle is applied to s-wave electron-hydrogen atom scattering. We

show computationally, that, consistent with a recent paper by B. Apagyi, P. Levay, and K. Ladan);i_-

there are pseudo-resonances at the static exchange level of approximation, but not at the static level.

We employed !he T-matrixas well as the K-matrix version of the Schwinger Principle, with a real Slater

basis, and obtained the sa_(e results in both. We are able to identify the origin of the pseudo-resonances %x__ . .

as resulting from singularities in the separable potential that is ef_ctively employed in the Lippman- _ cL:_'_, _

Schwinger equation from which the Schwinger Variational Principle can be derived. The determ!nation

of the pseudo-resonance p_ameters from the separable potential is computationally inexpensive and

may be used to predict the pseudo-resonance parameters for the scattering calculations so that they

may be avoided, i

/I,_

-,_,c_ _-:_ _-_L

77
THE PREDICTION OF PSEUDO-RESONANCE POSITIONS IN

THE SCHWINGER VARIATIONAL PRINCIPLE

Rationale

The present work is a computational study of electron scattering from atomic hydrogen in its

ground electronic state. We are studying this system using the Schwinger Variational Principle (SVP).

This system has been studied many times before at a very high level of accuracy. 1 It is not our intent

to study e- + H just for the cross section data that result, but rather to study this system as a model

system to explore some of the subtle aspects of the SVP. We are primarily interested in electron-molecule collisions where L 2 basis set methods, such as the SVP, have shown the greatest utility, especially

for processes such as electronic excitation and dissociative recombination.

However, there are a number of problems that are encountered in using the SVP. In particular,

two recent papers 2,3 have shown that, contrary to the prevalent belief 4, the SVP does encounter

pseudo-resonances, even in the simple s-wave e- + H system, so long as the exchange effect is included.

Indeed, it is necessary to have an energy dependent potential in order to see these pseudo-resonances.

At the static level, the pseudo-resonances are not encountered in the SVP, in contrast to the Kohn

Variational Principle 5 (KVP) where they are encountered even at the static level.

This fact apparently led many researchers 4,6 to conclude that the SVP did not suffer from the

occurrence of pseudo-resonances. The argument that was used to explain the assumed non-occurrence

of pseudo-resonances in the SVP is based on the paper of Adhikari and Sloan 7 who show that the

derivation of the SVP, from the Lippman-Schwinger equation by taking the variations of the wavefunction and deleting second order terms, is equivalent to approximating the exact potential in the

Lippman-Schwinger equation, by the projection of the exact potential onto an L" basis set, thus

producing a finite rank separable approximation to the exact potential. It was then argued that the SVP

implementation was equivalent to solving the Lippman-Schwinger equation exactly for a certain

separable potential, and since the solution was exact, no spurious resonances would occur in the

solution. This, as it turned out, was true, but a somewhat subtle flaw in the argument leads to

pseudo-resonances anyway. We shall presently elaborate.

These false resonances are non-physical. This is especially troubling since resonance processes

have turned out to be the predominant mechanism by which molecules are excited and by which

molecules dissociate upon scattering by electrons. It is, therefore, extremely important to distinguish

the real resonances from the pseudo resonances.

Thus, in order to study the origin and characteristics of these resonances, it is fortuitous to

encounter them in so simple a system as s-wave e- + H, at the static exchange level _ (static + exchange

potential). We therefore decided not only to repeat the calculation of Ref. 2, but also to perform the

calculation using the T-matrix approach, as well as the K-matrix approach, in contrast to the authors of

Ref. 2 and 3. In doing so, several interesting aspects of the use of the SVP were studied and the origin

of the pseudo resonances was explained.

78
Sketch Of The Theory

The theory for the K-matrix version of the calculation is given rather completely in Ref. 1. We

shall just limit our description of the theory to certain fundamental points that are useful to define the

differences in our work from Ref. 1 and to facilitate the explanation of our conclusions. We are solving

the time-independent ShrSdinger equation, for electron-H atom scattering, which, in atomic units, is

/-P¥( _, _) = EW(_, _) (1)

where H is the Hamiltonian operator given by

12 12 1 1 + 1

H = -_Vl - _V2 _ r2 ler - r_l (2)

and where W is the system wavefunction. We then employ the basic idea of the close-coupling method

which is to expand the total wavefunction W in target states. 2.s We then obtain, in standard fashion of

the close-coupling method, the following static exchange equation for the continuum orbital F

(V 2 +k2)F(F ") = U(F_)F(F _) + (-1)sQ_ IF) (3)

where k is the projectile momentum, U is the static potential, and _°is the exchange kernel. The symbol

s is 0 for singlet scattering and 1 for triplet scattering. F of Eq. (3) is required to satisfy the standard

time-independent scattering boundary conditions 5 of incoming plane waves and outgoing spherical

waves.

We then expand the continuum orbital in partial waves according to

F(F _) = 2fl (r)Y_t (O,tp). (4)

l,m

We just keep the I = 0 term in Eq. (4); hence, we are considering only s-wave scattering. Thus the model

is simple but realistic. Then, the partial s-wave continuum orbital f, satisfies the K-matrix boundary

conditions given by

lim f(r) = A (tOGO)(kr) + B (h')G(2)(kr)

r...._ 0o

where the K-matrix is given by

K = tan(h) = B(tO/A (h').

The T-matrix boundary conditions are given by

lim f(r) = A(T)G0)(kr) + B(T)/-/(+)(kr)

¥ --_oo

where theT-matrixisgivenby

(5)

(6)

(7)

79
T = eUsin(,_)= #_/a(n. (8)

The G 0) and G (2) are related to the spherical Bes_l functions by

G(1)(]O ") = ]o'j0 (]o') (9)

and

G(2)(kr)= -/a'n0(kr) (I0)

where j0istheI= 0 regularBesselfunctionand noistheI= 0 irregularsphericalBesselfunction.Also,

H (+)isthe Hankel functionof the firstkind givenby

H(+)(kr) = G(1)(kr)+ iG(2)(kr). (11)

The staticexchange differentialequationfors-wave scatteringisthen changed intoan integral

equation,instandardfashion,which iscalledthe Lippman-Schwinger equation,and isgivenby

:(r)= w(1)(r) -

(-1)s_? _dy [w(1)(r<)w(2)(r>)]r,v _dr VS(y:c)f(x) (12)

where the w functions are related to the Gs by

wO)(r)= G(1)(kr)

wO)(r)=G(2)(kr)+/_G0)(kr) (13)

where fl=0 fortheK-matrixcaseand fl=i fortheT-matrixcase.In Eq. (12),V" isthe sum of thestatic

and exchange potentialso that

V'fy:) = U(x)a(x-y) + (-lf _(W) (14)

Then, we have 2

D = -_(w(1)lV'l:) (15)

where D iseitherthe K- orT-matrixdepending on the form ofw 2 inEqs. (12)and (13).

Then we expand f ina Slaterbasisset

_n(,_:)=/'-_e-°" (16)

accordingto

8O
f(a,r) = E Cn _n (a,r) (17)

n

We then proceed in a standard fashion which may be taken from Ref. 6 or 7 or from many other

places. We then obtain the following set of working equations:

where

and

D = -];8_M--18 (18)

Cm -" (w(1)lV$ Item) (19)

M,,m = (Sin]V a - V s _"V s ]$n) (20)

In F_xI.(21),_'isthe reduced Grecn'sfunctionoperator.Itsform can be inferredby rewritingEq.

(12) in Dirac notation

If) = lw0))+_'VsIf)

and comparing Eq. (21) and (12).

(21)

Results and Conclusions

The Mof Eq. (18) can be written as

M = MR +flMl (22)

where fl =0 if we are using the K-matrix form and fl =i if we are using the T-matrix form. One of the

surprising results of the present work is that MI is explicitly singular and cannot be inverted. This does

not mean that M is singular, since we can use the following results. If, in general,

and

then

and

M_A +iB (23)

M-q_C+/D__ (23)

_c =[d +B,4- B (24)

81
D_= -CBA (25)

However, if B is singular, then, as the size of the matrices increases, the accuracy with which

M --1 can be compu-i'ed decreases until the inverse is no longer accurate. In fact, for any matrix size, the

inverse is somewhat corrupted. The accuracy of the inverse computation can be tested by constructing

the unit matrix. Also, the results can be compared with the K-matrix result where there is no Mr. The

agreement between the phaseshifts decreases as the basis set size increases. On a 64 bit word length

computer, however, the agreement was still eight significant figures for a 15x15 matrix. We would like

to note that we attempted to alleviate this problem by using an orthogonalized basis set instead of the

Cs of Eq. (16). This improved the agreement between the K-matrix and the T-matrix phaseshifts by one

to two significant figures, but did not alleviate the problem. The conclusion to be drawn from these

results seems to be that there is no point in using the T-matrix form if real basis functions are to be used.

Pseudo-resonances are encountered, just as in Ref. 2, for both the K-matrix and T-matrix forms.

A surprising result, however, was that _Ma is not singular until the energy is very near the pseudo-resonance energy. You have to be right on top of the pseudo-resonance energy before you lose the ability

to compute _1. This is quite different from our experience with the Kohn anomalies, s The explanation for this and for the existence of the pseudo-resonances can be understood by considering the

argument given above in the Rationale for the supposed non-existence of the pseudo-resonances in

the SVP. The finite rank potential that is substituted into the Lippman-Schwinger equation is given by

where

I_ Iv" (26)

A-' = Iv' ) (27)

If V s is energy independent (static potential), then V 'ep is well behaved. If V sis energy dependent,

then there are going to be energies where A_does not exist. In other words, the phase shift that we are

computing is indeed the exact phase shift for the separable potential V sep.The problem is, the separable

potential is non-physical at energies where A does not exist.

We have now investigated the energy dependence of_A to see if the energies where pseudo-resonances occur are related in an identifiable way to the energies where the separable potential does not

exist. The central result of this paper is the finding that they are exactly the same energies. Thus, we

can predict the energy positions of the pseudo-resonances before we run the scattering calculation, and

thus avoid the troublesome energies. This ability is aided by the fact that the pseudo-resonances are

very narrow and become more narrow as the basis set size increases.

Acknowledgments

This work was supported by NASA Grant NCC 2-492 and by a grant of computer time from the

Florida State University Supercomputer Computations Research Institute.

82
References

1. Callaway, J., Phys. Rep. 1978, 45, 89.

2. Apagyi, B.; Levay, P.; and Ladanyi, K., Phys. Rev. A, 1988, 37, 4577.

3. Ladanyi, K.; Levay, P.; and Apagyi, B., Phys Rev. A, 1988, 38, 3365.

4. Rescigno, T; McKoy, V.; and Schneider, B., editors, Electron - Molecule and

Photon - Molecule Collisions, Plenum, 1979, page 103.

5. Nesbet, R.K., Variational Methods in Electron - Atom Scattering Theory, Plenum, 1980.

6. Watson, D.IC, and McKoy, V., Phys. Rev. A., 1979, 20, 1474.

7. Adhikari, S.K., and Sloan, I.H., Nucl. Phys. A, 1975, 241,429.

8. Weatherford, C.A., Int. J. Quant. Chem. S, 1982, 16, 277.

83
.Ng -2SOrs

GROWTH AND CHARACTERIZATION OF CRYSTALS FOR IR

DETECTORS AND SECOND HARMONIC GENERATION DEVICES*

Ravi B. Lal, Ashok Batra, M.S. Rao, S.S. Bhatia** and K.P. Chunduru**

Department of Physics

Alabama A&M University

Huntsville, AL

and

Ron Paulson

EDO Corporation/Barnes Engineering Division

Shelton, CT

and

Tripty K. Mookherji

Teledyne Brown Engineering

Huntsville, AL

ABSTRACT

Two types of materials, L-Arginine Phosphate (LAP) and doped Triglycine Sulfate (TGS), are

examined for their growth characteristics and relevant properties for second harmonic generation and

¢r2_detector applications respectively.

* Work supported by Center for Commercial Crystal Growth in Space, Potsdam, N.Y., a NASA

Sponsored Center for Commercial Development of Space (CCDS) - Clarkson University.

** Graduate Students.

84
GROWTH AND CHARACTERIZATION OF CRYSTALS FOR IR

DETECTORS AND SECOND HARMONIC GENERATION DEVICES

A. L-Arginine Phosphate Crystals

Introduction

LAP is considered to be a potential new material for efficient second harmonic generation for an

Nd:YAG laser. It is phase matchable with conversion efficiency between 3 to 4 times that of potassium

dihydrogen phosphates (KDP). It has a high damage threshold (about 50 times of KDP) and a high

figure of merit (40 times of KDP). Being a fairly new material, little data are available in the literature

on growth parameters under which optical quality crystal can be grown from solution. In this section,

characteristics of LAP solution and growth kinetics of LAP crystals grown under different conditions

are described. The preliminary results of second harmonic conversion efficiency of LAP Crystals in

comparison with KDP are also discussed.

f

Experimental Procedures and Results

The compound L-arginine phosphate, which is not commercially available, was synthesized in the

laboratory. L-arginine and phosphoric acid were mixed in stoichiometric ratio and dissolved in deionized

water. The mixture was stirred and heated to dissolve homogeneously. The chemical reaction can be

presented as C6 H14 N4 02 + H3 PO4 -_ C6 H16 N4 03 •H3 PO4. The solution was kept at room

temperature for evaporation. The self nucleated crystallites of LAP compound were formed and were

removed from solution and dried. In order to find that the compound was in fact LAP, a powder sample

was prepared and packed into a thin cell formed by two glass slides. The sample was illuminated with a

1064nm Nd:YAG laser and the second harmonic output from the sample which was green in color, was

observed (corresponding to 532 nm wave length). This confirmed the formation of an L-arginine

phosphate compound. Since no data were available about the solubility of LAP in water, it was

determined at various temperatures. The details of the method are described elsewhere (1). The

solubility data for LAP compound are presented in Table I.

Table I

Data for Solubility of LAP in Water

Temperature Solubility

S.No. (°C) (gin/100 gm of Water)

1 28.0 13.93

2 35.0 20.04

3 40.0 25.66

4 45.0 32.32

5 50.0 40.02

85
The index of refraction of a solution is a sensitive indicator of the concentration. The measuremerits of the refractive index of LAP solution were made using an Abbe refractometer with a

temperature controlled sample stage, and white light. Fig. 1. shows the index of refraction of the

saturated solution as a function of temperature. The growth of crystals from the solution depends on

various parameters: temperature of growth, degree of supersaturation, character of solution and

hydrodynamic conditions. In the present work, in order to find the optimum conditions under which

optical quality crystals can be grown, character of solution (pH) and hydrodynamics conditions were

varied, keeping other conditions constant. The crystals were grown using temperature lowering techniques in a modified crystallizer (1,2). It was found that the morphology and optical quality of the LAP

crystal changes with the pH of the solution. The optical quality crystals with prismatic morphology were

grown from solution with optimum pH. At the optimum value of the pH of the solution, it was found

that rotating the seeds between 17-26 rpm does not affect significantly the morphology and optical

quality of the crystals. Single crystals of LAP, cut and polished, were placed in an Nd:YAG laser beam

(1064nm) and the second harmonic was recorded at 532.2nm. The conversion efficiency of LAP samples

was comparable with that of KDP. The lower value may be due to small thickness and bad polish. Further

work to understand the growth mechanism and optical studies are in progress. The most important task,

reducing growth time and increasing the growth rate in the desired direction, is also in progress.

1,3840

1,3760

Z 1,3680 O

W

0

× 1,3600

W

z

1,3520

TSA T = 50"C

TSAT = 45"C

TSA T =40'C

TSA T = 35"C

1,34.40 I

25 30 35 40 4.5 50 55 60

TSAT - 28"C

I I I I I I 1

TEMPERATURE "C

Figure 1. Index of Refraction Versus Temperature for LAP Solution.

86
B. Triglycine Sulfate Crystals

Introduction

TGS is a well known ferroelectric material and is widely used for i.r. detection at room temperature

in scientific, medical, and commercial applications. It is the most sensitive material among available

pyroelectric materials. However, it has a strong tendency ofdepoling (Te = 49 ° C) due to temperature

and mechanical shocks, causing degradation of the detector performance. In order to improve the

pyroelectric properties and check depoling, various dopants have been tried. In this section, growth and

characteristics of doped TGS crystals are described. The results are compared with a pure TGS crystal.

Experimental Procedure and Results

Triglycine sulfate crystals were grown using the reciprocating crystallizer designed and fabricated

in the workshop of the Physics Department (2,3). The seed crystals with the desired amount of dopants

were grown by slow evaporation. The detail of the method of growing crystals, growth kinetics and

characterization techniques for electrical and detector properties are described elsewhere (3,4). The

detectors were fabricated and tested at EDO Corporation / Barnes Engn. Div., Shelton, CT. The results

of measurement for material characteristics are presented in Table II. It can be inferred from the table

that the figure of merit of TGS crystals doped with L-alanine and simultaneously doped with L-alanine

and cesium is higher than that of the pure TGS crystal. Moreover, L-AL+Cs doped TGS crystals are

relatively harder and easier for sample handling and processing. The detector characteristics of doped

TGS crystals are presented in Table III. It is shown that Detectivity (D*) of L-alanine doped crystals is

higher than for other crystals investigated. It is probably the best value reported so far in the literature.

The amount of dopant and conditions of growth chosen resulted in uniform incorporation of L-alanine

in the crystal, as can be seen from the values of D* obtained for five detectors fabricated on one chip.

Conclusion

The present studies demonstrate that large optical quality LAP crystals can be grown by a solution

cooling technique in a reciprocating crystallizer. However, studies to understand the role of the

character of the solution (pH and dopants) on the crystal growth and optical quality of LAP crystals are

required.

From the work on TGS crystals, it can be concluded that L-alanine and Cs+L-alanine doped

crystals are attractive for pyroelectric infrared detector applications.

Acknowledgments

The authors would like to thank Lloyd Sharp and Keith Land for technical assistance, P. Chandra

Sekhar for helping in optical studies, and R.S. Adhav of Quantum Technology, Inc. for supplying the

KDP crystals.

87
TABLE II

MATERIAL PARAMETERS OF TGS CRYSTALS

CRYSTAL

TEMP°C

PYROELECTRIC DIELECTRIC FIGURE OF MERIT

COEFFICIENT, p CONSTANT ]p/e'(nc/cm 2 °C0

(nc/cm 2 °C) e'

30 35 40 45 30 35 40 45 30 35 40 45

TGS 53 70 98 170 48 64 106 250 1.1 1.09 0.92 0.68

TGS + C¢ 37.2 53 84 150 61 76 115 350 0.61 0.7 0.73 0.42

TGS + Cs 43 64 85 155 67 84 120 300 0.64 0.76 0.70 0.52

TGS +LA

TGS + Cs + LA

38

55

44 80 172 30 37 48 62 1.2 1.48 1.6 2.7

134 200 315 38 41 54 69 1.44 3.26 3.7 4.5

TABLE HI

DETECTOR CHARACTERISTICS

SAMPLE

NO. 1 fiGS)

NO. 2 (TGS +

L-ALANINE)

NO. 3 (TGS + Ca

+ L-ALANINE)

CELL NO.

20930

20944

20752

20885

20963

20803

2O941

2O986

2O924

2O98O

RESPONSIVITY Cv/w)

1000 K/BLACKBODY

15Hz 90Hz

1 x 103 160

1 x 103 160

lxl03 160

1 x 103 160

950 160

1 x 103 160

1 x 103 160

1 x 103 150

850 130

890 140

NOISE (nV/Hz) D* (1000K, f,1) xl0 s

15 Hz

7.7

12.0

11.0

11.8

12.0

13.5

12.3

15Hz 90Hz

260 8O

170.5 56

190 65

167 60

190 66

175 60

167 54

560 140

280 92.5

760 170.5

3.35

6.25

2.20

90Hz

4.0

5.5

5.0

5.3

5.2

5.6

5.7

2.05

3.0

1.6

88
References

1. Bhatia, S., M.S. Thesis, AL A&M University, AL; 1988.

2. Aggarwal, M.D.; Lal, R.B., Rev. Sci. Inst. 772, 54(6), 1983.

3. Banan, M. M.S. Thesis, AL A&M University, AL; 1986.

4. Lal, R.B.; Aggasrwal, M.D.; Batra, A.IC; Kroes, R.L., Final Technical Report, NAS8-

32945, 1987.

89
N91-28079

JACKSON STATE UNIVERSITY'S

CENTER FOR SPATIAL DATA RESEARCH AND APPLICATIONS:

NEW FACILITIES AND NEW PARADIGMS

Bruce E. Davis

Gregory Elliot

Jackson State University

Jackson, MS

ABSTRACT

Jackson State University recently established the Center for Spatial Data Research and Applications, a Geographical Information Systems (GIS) and remote sensing laboratory. Taking advantage of

new technologies and new directions in the spatial (geographic) sciences, JSU is building a Center of

Excellence in Spatial Data Management. New opportunities for research, applications, and employment are emerging. GIS requires fundamental shifts and new demands in traditional computer science

and geographic training. The Center is not merely another computer lab but is one setting the pace in

a new applied frontier. GIS and its associated technologies are discussed.

The Center's facilities are described. An ARC/INFO GIS runs on a Vax mainframe, with numerous

workstations. Image processing packages include ELAS, LIPS, VICAR, and ERDAS. A host of

hardware and software peripherals are used in support. Numerous projects are underway, such as the

construction of a Gulf of Mexico environmental data base, development of AI in image processing, a

land use dynamics study of metropolitan Jackson, and others. A new academic interdisciplinary program

in Spatial Data Management is under development, combining courses in Geography and Computer

Science. The broad range of JSU's GIS and remote sensing activities is addressed. The impacts on

changing paradigms in the university setting and in the professional world conclude the discussion.

90
THE JACKSON STATE UNIVERSITY CENTER FOR

SPATIAL DATA RESEARCH AND APPLICATIONS:

NEW FACILITIES AND NEW PARADIGMS

We are in an era of rapid technological change and few fields have seen such dynamic evolution

as computer technology. Many disciplines are benefiting from the remarkable advances that are

emerging, but the spatial (geographic) sciences seem to be profiting extraordinarily well. In particular,

the new specialty of GIS (Geographical Information Systems) is experiencing an international growth

of over thirty-five percent per year, which opens the door for new directions in research and applications

and new markets for employment. Because of GIS, novel operational and philosophic paradigms are

being introduced into numerous disciplines. Jackson State University (JSU) has embraced GIS technology and is developing a unique center of excellence in spatial data analysis and applications. This

paper presents Jackson State's efforts and plans. A brief explanation of GIS and associated technologies

is given, followed by discussion of JSU's GIS infrastructure and activities. Intrinsic in the presentation

are the changes in educational, research, and applications directions that are arising from these

technological advances. In particular, we emphasize the dynamic paradigms that are sure to have

long-reaching influence in the profession. (Note: herein GIS refers to the broad range of computer

spatial techniques and technologies rather than to a specific package of mapping routines.)

GIS and Remote Sensing

GIS is a computerized methodology for collection, organization, analysis, and display of geographic

data. Far more than simple computer mapping it provides sophisticated techniques for manipulating

geographic data. First, GIS is a spatial data base, an ideal inventory structure from which diverse forms

of information can be stored and extracted. Any type of data that can be located ("georeferenced") can

be used, e.g., maps, imagery, census information, etc. From there data can be extracted in "raw" form

for direct readout or combined with other data sets to produce new information.

More important is the analytical capability of GIS, especially considering the graphics functions

for mapping. Data from various scales and formats of maps can be combined (overlaid) to assess

relationships previously impossible to determine. Buffer zones of select size can be built around features

for proximity analysis. Many other "tricks" are available for manipulating data either graphically or

within the data base. Each generation of data forms a new base from which to perform analysis.

Remote sensing imagery (photographic or digital) from aircraft or satellites forms an important

data resource for GIS. Unlike traditional airphoto depositories where imagery is stored on rolls of film

in canisters for occasional visual inspection, modern remote sensing techniques convert landscape

scenes to digital format. Once in the computer, a plethora of processing procedures is available for

extracting new information not perceivable in the original imagery.

Satellite data, for example, are obtained in several distinct bands or channels of the electromagnetic spectrum, each channel providing unique views of a scene. Digital manipulations can be applied

to each band to derive a variety of data. When composited in different combinations, synergetic

renditions can result. Many versions of the original imagery are obtainable.

91
GISalsohasadvantagesfor mapproduction,e.g.,ease, rapidity, and flexibility. Traditional pen

and ink methods of cartography are too limiting in terms of time and design agility. For example, map

size reproduction can be changed quickly and easily, typically via a simple computer instruction.

Segments of the digital coverage can be separated and mapped. Also, the range of data to be used is

selectable, from the full set (maximum discrimination) to a more simple (generalized) classification.

Efficient and flexible productivity is a primary characteristic of GIS.

Other advantages are apparent. Statistical reports can be produced automatically, describing the

quantitative and qualitative nature of each viewed feature. Map storage no longer needs physical

equipment such as large cabinets or racks. Data can be shared over long distances rapidly, easily, and

cost effectively. In effect, GIS offers highly efficient and flexible methods and technologies to innovate

the spatial data world.

Jackson State University

Jackson State is developing a Center of Excellence in Spatial Data Management to take advantage

of the many research and market opportunities afforded by GIS technology. JSU is particularly

well-suited to such innovation because of several advantages: (1) Having considerable computation

power, major GIS and remote sensing packages can be facilitated without additional expensive

investment. (2) With a large computer science (CS) faculty, a substantial human resource base exists.

(3) Having the largest computer science enrollment of any HBCU, an excellent student resource base

and a foundation to establish an academic program are in place. This is particularly true given the

extraordinary enthusiasm exhibited by students thus far.

(4) A relative vacuum exists in the state and region concerning GIS, thus giving an unparalleled

opportunity to the institution having prescience. (5) Probably the most important factor has been the

presence of an administration, from the top down, with remarkable foresight, ambition, vision, competence, and cooperation in emplacing a new direction in the university setting. Therefore, ISU is building

a substantial and exceptional program in the new spatial technologies from which it can become a

prominent and pace-setting leader.

Central to the center of excellence concept is JSU's new Center for Spatial Data Research and

Applications (CSDRA). The CSDRA (also referred to as the Center) is a GIS and remote sensing lab

providing the setting for research, educational, and professional out-reach efforts in the spatial sciences.

Described below are its facilities and equipment, major research efforts, academic developments,

professional activities, and plans.

Facilities, Equipment and Staff: Housed in the new science building, the CSDRA contains most

of the GIS and remote sensing equipment. The nucleus of the GIS infrastructure is a Vax cluster

ARC/INFO, the premier international system. It uses a powerful mapping graphics package integrated

with a relational database program. Three Tektronix workstations serve as the primary interfaces, but

numerous other graphics terminals are used as secondary workstations. Micro-based ERDAS is also

used.

Image processing software consists of NASA's ELAS and LIPS, Jet Propulsion Laboratory's

VICAR, and ERDAS, all functionally linked to ARCflNFO for direct feed of imagery to a mapping

base. A 40" Calcomp color electrostatic plotter and two Tektronix color inkjet plotters serve as the

primary hardcopy devices. Mapping data entry is performed on a large digitizing tablet and with an

92
Eikonixscanningdigitizer.A hostof peripheralequipmentsupportsoperations,e.g.,microcomputers,

film recorder,etc.

CSDRAstaffconsistsof aprincipalinvestigator,Centerdirector,labmanager,a project manager,

five CS faculty, three systems technicians, and several clerical personnel. Twelve research assistants and

four workstudy staff form the student help. The academic program (to be discussed) will be supported

by two new faculty, one in computer science and the other in geography. Adjuncts from local GIS and

remote sensing operation agencies serve as program associates.

Projects: Two major funded research projects, begun in late 1987, formed the initial and primary

efforts of the Center. The Department of Interior's Minerals Management Service (MMS) initiated a

project to develop GIS in its operations, to build a Gulf of Mexico environmental database, and to assist

in various research and applications tasks. MMS is responsible for off-shore mineral leases and mineral

extraction activities, so its basic duties are ideally suited to GIS methodologies.

The first task was to construct a lease block data base to serve as the base map and data for

subsequent informational needs. Over 30,000 blocks are distributed in the Gulf and each has unique

identifiers that must be quickly recalled and used either graphically or in the relational data base. GIS's

ability to relate to either graphics or tabular data is a critical asset for MMS needs. Other MMS tasks

include mapping of Alaska off-shore blocks and data, mapping of coral reefs and offshore structures,

digitizing of shallow geology, and data base preparation to support oil spill accidents off Florida.

The National Aeronautics and Space Administration (NASA) has aimed primarily at image

processing (IP) but is also interested in using remote sensing in support of GIS. One of the major

projects is the inventory and analysis of metro Jackson, Mississippi urban dynamics--land use, demographic factors, quality of life, environmental impacts, and application of artificial intelligence (AI) and

expert systems to identification of undeveloped lands. Remote sensing from NASA aircraft will cover

the city with large and medium scale color infrared photography and digital scanner data. Imagery is

the principal data source but associated contemporary and historic information is employed for

comprehensive coverage.

Other NASA assignments consist of a variety of data conversion and programming tasks, publication of a nation-wide remote sensing facilities survey, assistance in development of an academic program

and associated specialized training, construction of a publication data base to support numerous GIS

and remote sensing needs, and provision of overall guidance in the establishment of the center of

excellence. Other smaller projects are under consideration (see Plans below).

Academic Programs: One of the major new paradigms to emerge from GIS is the development

of a truly interdisciplinary methodology in the spatial sciences. A new (Fall, 1990) interdisciplinary

academic graduate and undergraduate program in Spatial Data Management (tentative title) is under

development. The undergraduate program consists of courses in both the departments of Computer

Science (Science and Technology Division) and Urban Affairs/Geography (Liberal Arts Division),

forming a concentration in both disciplines. A graduate concentration in CS will be part of the

information science direction. Courses in GIS, remote sensing, spatial analysis, and traditional applications and systems are used. Projects, theses, and an intern option provide practical experience. One

thesis has been completed and two are underway. The JSU spatial data program is distinctive in the

American university system in that it integrates two traditionally segregated departments Geography

and CS. Unique in HBCUs, JSU's GIS-based academic program is approached only by a very small

number of higher education institutions. New directions and new educational paradigms are being

93
established. Both geographers and computer specialists must redefine their approaches to the management and analysis of spatial data, but the potential rewards can be tremendous.

Professional Activities: CSDRA personnel have been instrumental in instituting a state-wide

alliance of GIS and spatial data users--the Mississippi GIS Association. It provides a linkage among

academic, public, and private users of GIS or geographic data. A newsletter is to be published and

several activities for community out-reach are planned, including surveys of systems and relevant data

bases in the region. A coastal branch was begun recently and other divisions are under discussion.

Presentations and publications on several themes have been produced. Fundamentals of marine

GIS were established. Future directions of GIS and associated fields, particularly the contributions of

computer science advances, have been presented. A national survey of remote sensing has been

published. Numerous papers have been given and several publications are in process.

Plans: Two other major projects are pending (summer initiation planned): economic mineral

mapping of northeast Mississippi and institution of a county GIS operation. Additional small formal

and informal research and applications activities are under discussion. For example, GIS is a perfect

mechanism for design and creation of thematic atlases and a quality of life atlas for the state has been

proposed.

Jackson State's GIS program has only begun and it is difficult to predict the specific directions that

will be taken. The themes mentioned will continue to be important but other interests may be pursued.

As expertise and capabilities build, one desirable direction is the application of GIS to Third World

development, particularly Africa. Preliminary contacts with relevant agencies have begun, e.g., the

United Nations Environmental Program's Global Resource Information Database (GRID).

Enhancement of the academic program has high priority. As the initial strategy develops, more

depth will be added in terms of courses and faculty. New disciplines will be included. Equally important

will be increased opportunities for student hands-on experience, either in the Center or in additional

internship locations. Because GIS is a practical application, we feel that it is essential that properly

trained graduates have functional credentials.

Purpose

As a progressive institution, JSU is interested in cutting-edge advances in many disciplines, but

GIS is perhaps one of the most exciting and productive new fields to emerge from technologic progress.

To embrace the GIS field is a logical and forward step in institutional evolution. To date, only a few

schools offer training beyond an introductory course and broad, strong programs like the one at JSU

are largely absent on the academic scene. However, the strengths, potential, and market for GIS is not

a secret, for it has become entrenched in several disciplines in the last few years; it is only a matter of

short time before analytical computer mapping becomes a standard curriculum item. By taking a lead

at this relatively early stage, JSU stands to become broadly noted, not only among HBCUs, but on the

national scene as well. That purpose alone suffices as relevant support for contemporary development

of GIS at Jackson State.

The market potential for GIS-educated personnel is tremendous, especially given the very high

growth rate of the field and shortage of qualified personnel. It takes little to become marketable today

(usually a little experience or a course in GIS), hut enhanced training (dedicated program with

94
specialized directions) will ensure high promise of professional success for graduating seniors or

masters. This is specifically valid for minorities, who are vastly underrepresented in the field. Thus,

marketability is a major purpose for initiating a center of excellence.

One of the primary reasons that GIS and its related fields are doing so well is that more and more

types of data are becoming "spatialized", i.e., tagged to location. Once the locational attribute has been

identified, GIS can apply its many capabilities to produce information heretofore unavailable. There is

little wonder that sales of GIS software and hardware are increasing internationally at over thirty-five

percent per year. This is another substantial support for JSU's activities.

Paradigms

As used here, "paradigm" denotes a model of thinking or acting, a philosophic or practical basis

for operating in a prescribed manner, or a fundamental logic or motivation for development of values

and social or professional behavior. Paradigms guide, often tell, how to proceed and what to expect.

However, paradigms change--society evolves and ideas go through "life cycles", from birth and infancy

through maturity to old age and eventually, death. Scientific paradigms are especially sensitive to

technologic and social changes and may have relatively brief lives. Paradigms in computer science have

rather particularly short life expectancies.

GIS is much more than a technologic advance; it is establishing new ways of doing new things with

spatial data. New paradigms in scientific and social training, analysis, and applications are under

construction. Disciplines and professions are undergoing radical transformations; change is inevitable.

For example, as JSU's Geography program plans for reinvigoration of its techniques courses in

preparation for the spatial data management concentration, a detailed budget must be furnished. The

"shopping list" of cartographic supplies does not include drafting equipment, press-on lettering, or any

of the paraphernalia commonly found in traditional mapping labs. We plan to begin at the digital level

and build from there. The rationalization (i.e., new paradigm) is that the professional world is much

more interested in modern training than in old style techniques.

Another paradigm under development is that no longer can a single discipline provide the

necessary breadth that is demanded by employers today. The market is best for those who have both

technical skills and a broad understanding of what to do with the new techniques. The most viable GIS

training involves both operations and applications. We have accepted that premise and are designing

programs to a .c¢.ommodate the CS major and the applications disciplines. There can be pockets of

resistance in interdisciplinary or trans-divisional programs (the new paradigm), but the vision that is

making JSU a leader in the field recognizes the necessity of different paths for different destinations.

Despite reluctance to overstate, it is difficult to exaggerate the potential that exists in this new

approach to the use of geographic information. Jackson State University is at the forefront of initiating

and instituting important new paradigms not only in the educational universe, but in the applications

world. As an HBCU, JSU is responsible for an added dimension of substantiating the role and mission

of minorities. The wealth of possibilities, the richness of potential, and the inevitability of new horizons

are apparent; JSU intends to be at the front, providing avenues for all. Clearly, we are at an age of new

paradigms.

95
v

N91-28080

SOLUTION GROWTH OF TRIGLYCINE SULFATE (TGS) CRYSTALS ON

THE INTERNATIONAL MICROGRAVrI'Y LABORATORY (IML-1)*

R.B. Lal, A.K. Batra, and Li Yang**

Department of Physics

Alabama A&M University

Huntsville, Alabama

and

W.R. Wilcox

Clarkston University

Potsdam, New York

and

J.D. Trolinger

MetroLaser

Irvine, California

ABSTRACT

An experiment has be-Eh planned for the International Microgravity Laboratory (IML-1) to be

launched around February, 1991. Crystals of triglycine sulfate (TGS) will be grown by low temperature

solution crystal growth technique using a muitiuser facility called Fluid Experiment System (FES). A

special cooled sting technique of solution crystal growth will be used where heat is extracted form the

seed crystal through a semi-insulating sting, thereby creating the desired supersaturation near the

growing crystal. Also, a holocamera will be used to provide tomography of the three dimensional flow

field and particle image dispacement velocimetry to monitor the convective flows.

* Work supported by NASA contract NAS8-36634.

** Graduate Student

96
SOLUTION GROWTH OF TRIGLYCINE SULFATE (TGS) CRYSTALS ON

THE INTERNATIONAL MICROGRAVITY LABORATORY (IML-1)

Introduction

In the Spacelab-3 flight flown in 1985, the Fluid Experiment System (FES) was used to conduct

crystal growth experiments to help in the understanding of the solution growth of crystals in a

micro-gravity environment. This paper describes the reflight of the FES on the IML-1 mission to be

flown on Spacelab mission in early 1991, with different objectives and a refined optical system. The

objectives of the experiment are 1) to grow crystals of TGS using a modified version of the Fluid

Experiment System (FES), 2) to study the holographic interferometry tomography of the fluid in three

dimensions, and 3) to study the fluid motion due to g-jitter by measuring the fluid velocity using simple

multiple exposure holography of tracer particles and to study the influence of g-jitter on the growth

rate of TGS crystals.

Importance of TGS

Triglycine Sulfate (TGS) is a good model material for solution crystal growth. TGS crystals can be

grown at considerably low temperatures like 30-45 ° C, TGS solution is transparent and so holographic

techniques can be used to study the fluid properties, considerable ground based work has been

completed, and it is easy to handle. Apart from this, TGS has technological importance for pyroelectric

infrared detectors which require no cooling as compared to quantum detectors. The present devices

have detectivities (D*) from 5 x 108- 1 x lO'_cm HzlrZ/watt. This is about an order of magnitude away

from the theoretical value for a pyroelectric bolometer operating at room temperature. This difference

is expected to be due to the dielectric loss in the material.

Growth of Crystals Using FES and Cooled Sting Technique

During the IML-1 mission TGS crystals will be grown from an aqueous solution using a specially

developed technique of cooled sting 2. Many crystals of TGS have been grown in the laboratory using

the cooled sting technique and the growth rate is monitored using a three axes movement

telemicroscope. During the IML-1 mission, two experimental runs are planned where the saturation

temperature of the TGS solution will be around 45°C. In the first experiment a polyhedral seed with

(010) orientation will be used; in the second experiment a similar seed with (001) orientation will be

used.

In the absence of convection, crystal growth from solution will rapidly become slower as the

adjacent solution layer is depleted in solute, unless the growth in temperature is lowered to compensate.

However, if the temperature is lowered too fast, the growth rate will reach a level where sovent

inclusions are formed. To accomplish a uniform growth rate, the temperature is lowered at a programmed rate. This can be done by programming down the walls of the growth cell. However, in reduced

convection or in the absence of convection, only change of temperature of the walls would require a

97
long time to inwards towards the crystal. On the other hand, controlling the temperature of the sting

in intimate contact with the crystal should allow the growth rate to be held constant. Details of this have

been given earlier 3. Details of the flight growth cell are given in fig. 1.

Planned Crystal Growth Runs on IML-1 Mission

The first crystal growth run will be for a period of about 1 day. During this run, the fluid flow in

three dimensions will be studied. To achieve this, TGS solution will be seeded with small particles that

can be imaged by holography to show the direction and velocity of fluid movements. The present plans

include the use of polystyrene microballons added to the fluid as tracer particles. In this run a seed

crystal of TGS with (010) orientation will be used. The data from the first run will be used to grow a

high quality single crystal during the second run that will last several days. No tracer particles will be

used during this run, because they would contaminate the crystal by forming inclusions and other defects.

A three dimensional view of the crystal and flow field can be recorded by applying holographic optical

elements to the crystal growth cell. Tomography is made possible by passing light through the FES

windows at three different angles. Studies have shown that this will be sufficient to extract three

dimensional density data from the field of the type anticipated. Details of the optical holography system

are published elsewhere 4.

On the IML-1 mission, the accelerations that cause convection and disturb crystal growth will be

carefully monitored. In addition to an internal FES accelerometer that measures accelerations above

5 Hz, the Space Acceleration Monitoring System (SAMS) has two accelerometers located near the FES

crystal growth cell and one more mounted in the Spacelab aisles. This special set of accelerometers

measures low-frequency (0 to 5 Hz) vibrations that are harmful to crystal growth experiments.

Analysis of the Crystals

Considerable ground-based data have been generated for TGS crystals grown by a similar

technique. After the mission the grown crystal will be returned to our laboratory for extensive analysis

of their structure and electrical and other physical properties, including their infrared detection

characteristics. The space-grown crystals will be compared with crystals grown by commercial companies. The detector characteristics of the ground crystals and later for the flight crystals will be measured

at EDO/Barnes Engineering Division, Shelton, Connecticut.

Acknowledgments

The authors would like to thank The National Aeronautics and Space Administration, Office of

Microgravity Science and Applications for the support of this work through a contract. Thanks are also

due to Rudy Ruff, William Witherow, David Mclntosh, Todd Macleod, and David Johnston of

NASA/Marshall Space Flight Center for their continued support during the preparation of this

experiment.

98
References

1. Yoo, Hak-Do, Wilcox, W.R., Lal, R.B., and Trolinger, J.D.J. Crystal Growth, 1988, 92, 101.

2. Lal, R.B., Aggarwal, M.D., Kroes, R.L., and Wilcox, W.R., Phys. Status. Sol(a). 1983, 80,

547.

3. Liu, L.C., Wilcox, W.R., Kroes, R.L, and Lal, R.B., in Material Processing in the Reduced

Gravity Environment of Space, Ed G. Rindone (North-Holland, Amsterdam, 1982) p. 389.

4. Trolinger, J.D., Tan, Hung., and Lal, R.B., International Congress on Applications of

Lasers and Electro-Optics (ICALEO), San Diego, CA, Nov 9, 1987.

99
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100
N91- 8 81

A STUDY OF SPATIAL DATA MANAGEMENT

AND

ANALYSIS SYSTEMS

Clyde Christopher

Jackson State University

Jackson, Mississippi

and

Richard Galle

Stennis Space Center

NSTL, Mississippi

ABSTRACT

The Earth Resources Laboratory of NASA's Stennis Space Center is a center of space related

technology for earth observations. It has assumed the task, in a joint effort with Jackson State University,

to reach out to the science community and acquire information pertaining to characteristics of spatially

oriented data processing.

101
A STUDY OF SPATIAL DATA MANAGEMENT

AND

ANALYSIS SYSTEMS

1. Introduction

During the past 15 years much computer software has been developed for handling spatial data.

A number of centers have been set up for processing spatial data, all with different configurations. Some

studies have been conducted to collect and disseminate data on software in this area. Scientists at the

Earth Resources Laboratory (ERL) were interested in knowing the software and hardware characteristics in such centers. Additionally, they wanted to know with what centers those who are actively

engaged in spatial data processing are communicating. This information is to be shared with scientists

in those centers so that all will be fully aware of the state-of-the-art software and hardware for spatial

data processing.

2. Methodology

The desired information was collected by means of a survey. The survey instrument was designed

by Christopher and Gaile with approval from proper authorities. Part I asked for background information including names of adminnistrators, primary mission, list of principal application areas, and a list

of representative projects currently supported at that facility.

Part II requested data processing methodology. First, it asked for a listing of hardware devices

devoted to spatial data processing including the host computer, display devices, digitizers, disk drives,

tape drives, plotters, etc. Next, it asked for a list of software packages currently supported by the facility,

including compilers, GIS systems, statistical packages, data base management systems, etc. Finally, it

asked with what other facility they were linked and what communication package is being used.

Part III is a request for data characteristics. The survey asks what types of data are used (Landsat,

TM, AVHRR, Soils Maps, etc.), what are the sources, how is it input for processing, what is its internal

format (Raster, Vector, Etc.), and what CAD related capabilities are available for editing the data sets.

Part IV asked for data analysis characteristics. It specifically asked what types of data processing

(statistical, analytical, expert system decision making, polygon declaration, model structuring) supports

the applications at that installation. Also, it asks whether there is merging or overlaying of data and

what steps are taken in the processing life cycle.

Part V, the concluding section, asked for representative research which has been undertaken at

the facility in the area of spatial data processing and, also, the research objectives which are needed.

The survey was first mailed under a cover letter dated July 10, 1987. A second copy was mailed to

those facilities that had not responded by September 8, 1987. The survey was mailed to 349 different

installations. Completed forms were received from 115 installations. A survey instrument worded so

that all answers could be given by checking the correct item probably would have yielded a higher

number of responses. However, that type of instrument would not have yielded as much detailed

information as the one used.

102
Thedata will be used to build a data base with appropriate query language so that local users will

have access to it. Hopefully, problems in communication will be solved, providing access to this data on

a nationwide basis.

3. Results

A. Background Information. The survey was sent to basically three types of organizations: 1)

government agencies, 2) private industry, and 3) educational institutions. In addition to supplying names

of key contact personnel at the installation this section of the survey provided us with a statement of

the primary mission of the installation and a list of ongoing projects. The government and industrial

organizations said they were involved in research in remote sensing and in analyzing terrain and giving

technical advice on use of land and water resources. The educational institutions are involved in training

students in the use of remote sensing as well as research in that area.

No two installations listed the same project. Typical projects were: "Land use of 13 county region

of Tennessee", "Training in forestry and wetlands remote sensing techniques", and "produce 7 1/2 foot

wetland maps of the United States". Some indicated that project titles are not available to the public.

The principal application area is an important response in this section. These ranged from "land

use classification" to "geological engineering". However, the most frequent responses were "remote

sensing", "image processing", "GIS", or some combination of these.

B. Data Processing Methodology. Computer systems used to process spatial data range from

microcomputers to mainframes. The most frequently listed microcomputers are the IBM PC-AT and

APPLE II PC. In the minicomputer class the VAX 11/780 is most used. In the largest class an Amdahl

V7/V8 was listed by one installation. The Prime 9650 was listed by several installations_

TABLE 1. Host Computer(s)

Model

Microvax II

Apple IIe

Amdahl (5860/V7/V8)

Harris (1000, 500, 800)

VAX (8200, 11/730, 11/750,

11/780, 11/785)

Hewlett-Packard 9000

IBM PC (ATXT)

SUN

PDP 11/70

Concurrent (Perkin Elmer)

Prime (400, 550, 750, 465, 9755,

9650, 2655, 2275, 6350, 250, 9955)

Data General

Gould 32/27

IBM (3013, 3081, 3084, 4361, 4381)

Zenith 248

MASSCOMP 5600

AT&T (3B5, 3B2)

Number of Installations

15

2

3

3

36

2

12

3

8

5

32

4

5

11

3

5

3

103
TABLE 2. Operating Systems

Softw_e

RIPS

VMS

VOS 6.1

UNIX

PRIMOS

MVS

RT-11

MS -DOS

MPX

RSX-11M

OS-32

VM/CMS

VORTEX

AOS

ULTRIX

Nmnberoflnstallations

1

39

2

11

30

7

3

6

4

2

5

3

2

2

I

TABLE 3. Digitizers

Model

GTCO

Hitachi

CALCOMP 9100

Altek

Goegraphics

Summagraphics

Perkin Elmer (concurrent)

Talos

NUMONICS

Intergraph

Tektronix

Number of Installations

15

4

32

23

5

6

1

5

3

2

7

TABLE 4. Display Devices

Model

Tektronix

Comtal

De Anza

ADAGE

Visual 500

CALCOMP

Lexidata

Hewlett-Packard

lntergraph

ERDAS

Hitachi

Number of Installations

58

11

3

2

8

2

6

3

2

3

3

104
The type of compilers available depends upon the model of computer and the memory size. Some

installations list Fortran, only. Pascal and C are also frequently listed. Many installations listed all three

of the above languages, but Fortran was listed most frequently. Other languages used inclined Lisp,

Prolog, BASIC, SCAN, COBOL, MODULA2, Ada, and PL/1.

Among the image processing and GIS systems listed, ELAS and ARC/INFO were most frequent.

Others in the order of occurrance were RIPS., ORSER, GRASS, ERDAS, MOSS, SYNERCOM, and

ODYSSEY.

TABLE 5. Image Processing Software

Model Number of Installations

ELAS 30

RIPS 6

COS 3

ARC/INFO 45

GRASS 6

ERDAS 22

MOSS 10

SYNERCOM 2

ORSO 2

ATLAS 2

Intergraph 2

EROS 2

Some installations indicated that their processing involves statistical analyses and they named the

statistical package that is available on their system. SAS, SPSS, GLIM, BMPD, MINITAB, OSIRIS,

NAG, VECTOR, MATH 77, SSPLIB, IMSL and Microstat were among the packages named.

Database management systems were as varied as statistical packages. However, some who responded did not name a DBMS. One installation stated that it has as in-house information storage and

retrieval system. The usual response was one or more of the familiar ststems such as Datatrieve, INFO,

PC INF, RBASE, Dbase III, ORACLE, BASELINE, CDOS, SMARTSTAR, SPIRES, or INGRES.

TABLE 6. Data Base Management Systems

DBASE II or III

Datatrieve

INFO

SMARTSTAR

ORACLE

BASELINE

RBASE

Prime-INFORMATION

SPIRES

OPS-83

CDOS

INGRES

Number of Installations

2O

5

36

1

7

1

5

4

1

1

1

4

105
Somelarge installations at government sponsored organizations indicated that they are connected

with state or regional offices through some type of communication link. In general, the educational

institutions have local networks. This was the case with several other installations as well, but there

were those who indicated that they have no networking.

C. Data Characteristics. Landsat, TM and MSS data are the most used data in the installations

that responded. However, a great variety of data types are used. AVHRR, Soils Maps, SPOT, and GOES

were frequently named in the survey. Most installations named several types. Some other types listed

were land use maps, USGS topographic maps, ACZCS, census, transportation networks, streams and

rivers, watershed and aerial photos. The primary sources of data were EROS, NASA, USGS, SPOT

Image Corporations, and virtually all map sources.

TABLE 7. Data Types

Number of Installations

LANDSAT (MSS AND TM) 72

AVHRR 24

Soils Maps 41

Land Use Maps 12

Census 10

SPOT 21

GOES 6

SIR-B 2

USGS Topographic Maps 18

As a rule digitizers and magnetic tapes are used to input data for processing. Floppy disks were

frequently listed as input media. Video cameras, optical disks, and keyboards were each listed by at least

two installations.

TABLE 8. Data Input Scheme

IaRut.htgd_ lq_aber of Installations

Digitizer 84

Magnetic Tape 86

Magnetic Disk 21

Optical Disk 3

Keyboard 9

Scanning 6

Digital Camera 6

The internal format for data was given as raster or vector or both. CAD related capabilities at

various installations include scroll, zoom, draw, density slice, classification, cut, paste, and paint.

106
TABLE 9. Input Format

Number of lnstallatiQns

Raster 86

Vector 72

Gridded 4

D. Data Analysis Characteristics. In answer to the question on analysis of data during processing,

we found that a majority of installations do a statistical analysis. Several installations use the data in

decision making for expert systems. A few installations are doing polygon declarations. A small number

indicated that they are merging data sets and at least one installation is overlaying data. Some

installations were cooperative in sharing with us the steps in the processing life cycle, not an easy task.

E. Conclusion. In this section some installations listed some research efforts that are ongoing in

special areas. A non-conclusive list of these follows:

1) Incorporation of the SOI-5 soil interpretation records into ARC/INFO

2) Incorporate spatial data (GIS) into a decision support system

3) GRASS G&D functions

4) Link between S and GRASS

5) Hydrologic modeling, flood damage analysis

6) Image texure recognition

7) Geometric rectification, image animation

8) Map display techniques

9) Digital image processing-both spectral and spatial analysis

(Notes. The researchers acknowledge assistance in this project from the following: Pauline Frances,

Systems Analyst; Jeanette Lewis, Laboratory Coordinator; Andrew Ward, Kimberly Wallace, Rickey

Myers, Jody B Hasten, and Shelton James, students; Jackson State University.)

107
N91 -28082 ,

ANALYSIS OF CURED CARBON-PHENOLIC DECOMPOSITION

PRODUCTS TO INVESTIGATE THE THERMAL DECOMPOSITION OF

NOZZLE MATERIALS

James M. Thompson and Janice D. Daniel

Department of Chemistry

Alabama Agricultural and Mechanical University

Huntsville, Alabama

ABSTRACT

This paper describes the development of a mass spectrometer/thermal analyzer/computer

(MS/TA/Computer) system capable of providing simultaneous thermogravimetry (TG), differential

thermal analysis (DTA), derivative thermogravimetry (DTG) and evolved gas detection and analysis

(EGD and EGA) under both atmospheric and high pressure condition_.The combined sys!,,emhas been _-_

used to study the thermal decomposition of the nozzle material that/cOnstitutes the "throat of the solid

rocket boosters (SRB). /,,

/

' .

108
ANALYSIS OF CURED CARBON-PHENOLIC DECOMPOSITION

PRODUCTS TO INVESTIGATE THE THERMAL DECOMPOSITION OF

NOZZLE MATERIALS

Introduction

Since the development of the first themrobalance by Honda in 1915, thermal analysis has become

an important instrumental method in understanding the behavior of non-metallic materials. The method

is especially important in understanding the properties of polymeric materials. For instance, the

procedure has been used in determining the flexibility, impact strength, resistance to wear, oxidative

stability, amount of additive, and cure time of polymeric materials. Thermal analysis also plays an

important role in solving production and quality control problems and it has become an indispensable

tool in thermal studies of strategic materials.

The workers in this laboratory have developed an MS/TA/Computer system which has been used

to study the thermal decomposition of the nozzle material that constitutes the "throat" of the solid

rocket boosters (1-5). This material consists of a carbon cloth impregnated with a modified phenolic

resin in which certain additives have been added. The uncured prepreg material is built up in layers to

form the throat of the solid rocket booster and then cured in place. Thermal stability of this cured

material is most important in materials evaluation and in component failure analysis.

Prior to beginning this work, several workers had reported the coupling of a mass spectrometer

with a thermoanalyzer (6-16). Relying on this information, a Balzers QMG-511 quadrupole mass

spectrometer has been successfully coupled with a Mettler thermoanalyzer (TA-2). In addition, the

mass spectrometer has been interfaced with a microcomputer. This has resulted in a versatile instrument

system whereby mass spectral data on decomposition gases may be rapidly acquired and processed under

programmed conditions. Data from the mass filter and other units of the spectrometer may be digitally

transferred to the computer whereupon mass spectral data are generated and displayed on the CRT

and/or produced as hard copies. The combined system is also capable of providing simultaneous TG,

DTA, DTG as well as partial pressure changes when studies are carried out under vacuum conditions.

While commercial thermoanalyzers are capable of providing valuable thermal information, these

instruments are usually incapable of providing information on the identity of decomposition products.

Obviously, such information represents an important complement to the traditional thermal data and

is often useful in expanding our understanding of the thermal behavior of materials.

The Mass Spectrometer/Computer Interface

The mass spectrometer/computer interface has been achieved using the Teknivent Microtrace"

system (Teknivent Corp.). This turnkey system consists of a dual card interface-controller and the

software necessary to control, acquire and process data from the QMG-511 quadropole mass spectrometer. The interface card plugs into the BF-511 buffer of the mass spectrometer, while the controller

card plugs into an IBM-AT (or one of the compatible systems). The MS/TA Computer system, which

is schematically shown in figure 1, is capable of continuous or disjointed spectrum scanning up to 1023

109
atomicmassunits (amu).All data are presented in real time on a color or monochrome CRT.

Multitasking features allow simultaneous data acquisition and processing. The system is also capable

of functioning as the front panel of the console unit allowing the operator to set and adjust twenty one

(21) parameters of the mass spectrometer from the keyboard of the computer. Other features include

keyboard control of all tuning parameters, the ability to monitor up to 28 selected ions simultaneously,

top acquisition speeds of up to lO00/amu/sec, subtraction of background gases, scaling, translation and

normalization of data. The capability to search a mass spectra data base is an optional feature.

I MASS SP_CTIqOM_TER]

JTHERMAL ANALYZER_

/U_ACE

II _ b,_lll AI,_LVSI[ I_

II

Figure 1. A Schematic Diagram of the Combined MS/"FA/Computer System.

Through joint efforts with the Teknivent Corporation, low cost modifications have been made to

the software and electronic interface of the Microtrace TM unit so that thermal data may also be obtained

from the Mettler TA-2 thermoanalyzer. As a result of these modifications, the combined MS/TA/Computer system is able to acquire, monitor and process (in real time) TG, DTA, DTG, temperature and

partial pressure data simultaneously with mass spectral data. By implementing these modifications, the

need to re-plot weight loss vs. temperature curves has been eliminated; thermal data among different

nozzle material samples may now be compared at the computer; weight loss curves may be superimposed

upon mass chromatograms and hard copies of all data generated. Thermal data may also be monitored

by the strip chart recorder of the TA-2 unit.

Again, through joint efforts with Teknivent, a second IBM-AT compatible microcomputer has

been outfitted with a remote processing unit. Thus, data collected using the dedicated computer may

now be transferred to the remote unit and processed. Overall, these modifications have increased

production and facilitated data interpretation. The installation of the Teknivent Microtrace TM unit has

vastly enhanced the capability of the MS/TA system to acquire and process mass spectrometric data on

decomposition gases.

The MS-TA-computer system has also been modified to allow partial pressure curves to be

generated as part of the data provided by the thermal analyzer. This modification becomes significant

when thermal decompositions are conducted under vacuum conditions.

110
Another major enhancement to the MS/TA/Computer system includes the addition of a second

mass analyzer which occupies a permanent position in the chamber of the thermobalance (figure 2).

Prior to installing this second unit, it was necessary to transfer the mass analyzer from the vacuum

chamber of the mass spectrometer to the chamber of the thermobalance when evolved gas studies were

desired under high vacuum conditions. This cumbersome procedure often required a retuning of the

resonance frequency generator, a procedure which was awkward and time consuming. With the second

analyzer in place, evolved gas studies can now be undertaken under both atmospheric and high vacuum

conditions at any pressure between with only a transfer of cables.

Figure 2. A Schematic Diagram of the Thermobalance of the Mettler Thermoanalyzer Showing the

Second Mass Analyzer in the Vacuum Chamber.

Determination of the Accuracy and Reliability of the MS/TA/Computer System

The decomposition of CAC204 • H20 has been studied by several workers (17-27) and its thermal

decomposition profile is well known. Consequently, it was decided to use this material to determine the

reliability and accuracy of the mass spectrometer unit of the combined system. In determining the

accuracy and reliability of the unit, a sample of CaC204 •H20 was placed in a 0.45 ml platinum crucible,

and in a second identical crucible was placed an A1203 reference standard. Both materials were placed

on the DTA sample holder and the sample and reference heated between 25 - 1000°C by the middle

range temperature furnace. As the decomposition gases evolved, theywere pulled into the chamber of

the mass spectrometer through a heated capillary tube (figures 1 and 2). During the entire heating

period, evolved gases between amu 1-55 were monitored using the computer/Teknivent system.

111
104-

90"

60-

70"

60"

50

40"

30'

20'

%0"

0

\

m/e 44

1

250 500 750 I000 1250 1500

Scan Numbers

Figure 3. The Overlaid Mass Chromatograms for m/z 18 and 44 from the Thermal Decomposition of

CaC204-H20 under Atmospheric Conditions (Note: the CO formed in the Second Decomposition

Step Reacts with 02 in the Air to form CO2; thus, CO is Not Observed).

Based on the overlaid mass chromatograms shown in figure 3, three gas evolutions were observed

as shown below. The first evolution consisted of water, followed by CO (which reacts with 02 to produce

CO2). The last decomposition produced CO2.

CaC204"H20 ---> CAC204 + H20

CAC204 --> CaCO3 + CO

CaCO3 --> CO2 + CaO

The nature of the gases, their order of evolution, and the temperatures corresponding to each

evolution were consistent with repeated values, thus confirming the accuracy and reliability of the

system.

The Thermal Decomposition of Nozzle Material (FLX-D) Under Atmospheric Pressure

Between 25 - 1000°C

A 106.55 mg powdered sample of nozzle material (called FLX-D) was placed in a 0.45 ml platinum

crucible and positioned on the thermocouple crucible holder. The crucible holder is designed so that

the "hot junction" of the thermocouple is in direct contact with the bottom of the crucible. The furnace

was mounted over the sample and both sample and reference heated between 25 - 1000°C at a linear

temperature rate of 8°C/min. The chamber of the mass spectrometer was monitored under computer

control for fragment ions between 5-200 mass units. The thermal decomposition was conducted using

112
a non-discriminating gas inlet valve (figure 4) and a special dual side arm quartz furnace (figures 1 and

2). The non-discriminating inlet valve is a two stage pressure reduction gas inlet valve that allows the

evolved gases to enter the chamber of the mass spectrometer without changing the ratio of the gaseous

components or the chamber pressure. One end of a heated (200°C) one meter stainless steel capillary

tube (with a diameter of 0.15 nm) was attached to the side-arm of the furnace and the other end to the

non-discriminating gas inlet valve. The decomposition gases were swept out of the furnace by a stream

of dry air which traveled through the thermobalance up the inner tube and to the side arm of the furnace

(figure 2). Once the gases reached the side arm of the furnace, they were pulled through the heated

stainless steel tube by a rotary vane pump attached to the non-discriminating valve. From the stainless

steel capillary, the gases entered the non-discriminating valve and moved into the vacuum chamber of

the mass spectrometer. In the chamber, the gases were ionized by electron impact and the positive ions

accelerated into the quadropole filter where they were separated and detected in normal fashion.

d

/

a high vacuum connection e laminar flow regulator

b frit (;)oral filter) (throttle)

c heating jacket f capillary

d gas inlet g rotary vane pump

I

g

Figure 4. Schematic Diagram of the Non-Discriminating Gas Inlet System (Balzers High Vacuum

Systems).

Discussion

Soon after heating, the nozzle material sample underwent a small weight loss which was attributed

to cither surface or occluded watcr as indicated by the bar chart in figure 5, the replotted TG curve in

figure 6 and the overlaid mass chromatograms in figure 7. The water loss reached its maximum intensity

near 375°C. Also, near 375°C, CO2 was observed and its presence was evident for the remaining of the

heating cycle (figure 7). No other evolved gases were observed.

113
The Thermal Decomposition of FLX-D

i00._/ i_ _ I I ! I I I I I I I I 1 I I I I I 1 I 1 I I I I I i

I I|UndcrAtm°sl 9hericC°nditi°ns'25"10000C I II II

80 i

i

i

60

40

i

0 /'7 _ r'-_ ¢"

25 40 100 150 250 300 350 400 4S0 SO0 550 600 700 800 g00 g40

Temperature °C

Figure 5. Bar Chart Showing the Thermal Decomposition of FLX-D Under Atmospheric Conditions

Between 25 - 1000°C.

t/i

Itl

O

,,d

ii

.-e

100

80

60

40

2O

The Decomposition of FLX-D

0 20O 400 6OO 8O0

Temperature *C

1000

Figure 6. Replotted TG Curve, Showing the Thermal Decomposition of FLX-D Under Atmospheric

Conditions Between 25 - 1000°C.

114
50_ .................................................

456 }_'III_, _TI_H,gRIC COHDITIOHS

4_35, _/e 18 / I-'% 25-10_8,EC. C

155 I 161 C t ._" --L

".'r_-;_-'_:_-_-.-_ ?. , .... , .... , .... , .... , .... , ..... . . .

8 58 188 1,58 288 250 388 358 400 450

Figure 7. The Overlaid Mass Chromatograms for m/z 18 and 44 from the Thermal Decomposition of

the FLX-D Nozzle Material Between 25 - 1000°C Under Atmospheric Conditions.

Evolved Gas Studies Between 35 -300°C Under High Vacuum Conditions.

The study of evolved gases under high vacuum conditions was conducted using the MS/TA/Computer system shown in figure 1; however detection of the decomposition gases was carried out using the

mass analyzer which had been installed in the chamber of the thermobalance (figure 2).

Each of the seven nozzle material samples which were the object of this study was reduced to

powder form, weighed and placed in a platinum crucible. An A1203 reference material was placed in an

identical crucible and both sample and reference were placed on the DTA thermocouple. Sample size

was kept to a specific weight level so as to maintain a pressure at the mass analyzer of no higher than

10.4 torr. Beyond this pressure, the proportionality between ion current and sample concentration is

no longer valid. The standard middle temperature range furnace was sealed over the sample and

reference and both the furnace chamber and chamber containing the mass analyzer were evacuated to

approximately 1 - 5 x 10.6 torr using a pumping system consisting of both rotary and diffusion pump.

Once the approximate vacuum had been reached, the sample and reference were heated between 25 -

1000°C at a linear rate of 5°C/min. Just prior to heating the sample, the mass spectrometer was placed

under computer control to receive the mass spectrometric data output. The furnace pressure, temperature, DTA, TG, and DTG were monitored using the strip chart recorder located on the control unit

of the thermoanalyzer, while the decomposition gases were monitored at the CRT. Evolved gas studies

were carried out under programmed control between 10-200 amu using the Teknivent Microtrace"

system. During data acquisition the total ion current (TIC) curve and ion masses at m/z 18, 28, 32, and

44 were selected for direct monitoring.

Discussion

As indicated by figure 8 and Table 1, all seven samples of nozzle material underwent small weight

losses between 25°C and approximately 300°C, under both atmospheric and high vacuum conditions.

These initial weight losses were relatively small, ranging between 3.1 and 4.5% of the total weight of

115
the sample (Table 1). Under high vacuum conditions, major decompositions of the nozzle material

occurred near 350°C and near 300°C under atmospheric conditions.

Of the seven samples, FLX-D was arbitrarily selected for evolved gas studies between 25 - 300°C.

On heating, the sample lost approximately 3.1% of its original weight as shown by the replotted TG

curve in Figure 9. This weight loss did not include a 0.02% weight loss which was observed during pump

down.

o

18-

17.

16

15

14

13

12

11

I0

9

8

7

6

5

4

3

2

I

0

25.00

.¢

200.00

f

F

400.00 600.00 80000 100000

+COM.M 0 FLX-E _ COM-T x FLX-D _7 FLX-R o GOLD

Figure 8. A Series of TG Curves Showing the Small Weight Loss of Different Nozzle Material Samples

Between 25 - 1000°C When Thermally Decomposed Under High Vacuum Conditions.

Table 1. Percent Weight Loss of Several Samples of the Nozzle Materials When Thermally Decomposed Between 25°C and 300°C Under High Vacuum Conditions.

Sample Temperature of First Weight Loss (°C) % Weight Loss

COM-M (35-40)- 240 3.9

FLX-R 40-180°C 4.0

FLX-E (30-40)- 190 4.2

GOLD 35 -200b 4.1

COM-T (35-40)- 150 3.1

COM-A 30-190 4.5

116
4

3

i 2

I

0

Thermal Decomposition of FLX-D (25-280°C)

0 100 200 300

Temperature

Figure 9. The Replotted TG Curve for the Thermal Decomposition of FLX-D Under High Vacuum

Conditions Between 25 - 1000°C.

An Analysis of the Evolved Gases Resulting From the Decomposition of FLX-D Nozzle Material Between 25 - 300°C Under High Vacuum Conditions

The Total Ion Current -FLX-D

The total ion current (figure 10) was uneventful, revealing a slight but continuous increase in total

ion abundance between the 25 - 300°C heating cycle.

TIC

Lilt

LI|

lU

lee

|l

TO,

411 ̧

30

II

to

|

J

i it is ie is i0 is ie i_ _'o ._5 t'o

Time (minutes)

Figure 10. The Total Ion Current for the Thermal Decomposition of FLX-D Nozzle Material Between

25 - 300°C Under High Vacuum Conditions.

117
Mass 18

Based on a comparison of figures 11-14, the chromatogram corresponding to mass 18 revealed the

largest overall increase in ion abundance, suggesting that the major weight loss of the FLX-D nozzle

material during the 25 - 300°C heating cycle was due to water. The abundance of the m/z 18 ion over

the heating range was sufficiently high that it partially influenced the overall shape of the TIC curve

(compare figures 10 and 11). The suggestion that water constitutes the major weight loss of the FLX-D

sample between 25 - 300°C was also supported by an analysis of the mass spectral histograms.

,_/z 10

"_1_

45_

41_,la

3_J

zm_i

xot,_!

A

O

_'e 11 lrl._-D 2S - 3N delr_es Centilrde

........ i .... n- ., * - m ..... a . i

Time (minutes)

Figure 11. The Mass Chromatogram of m/z 18 (H20 +) Obtained from the Thermal Decomposition of

the FLX-D Nozzle Material Between 25 - 300°C Under High Vacuum Conditions.

Mass 28

The m/z 28 mass chromatogram (figure 12) revealed only a slight increase in overall abundance

between 25 - 300°C. However, near 150°C, the abundance of the ion began to increase and reached a

maximum near the 300°C temperature limit. Based on separate studies which are not reported here,

the mass 28 ion appears to have resulted, at least in part, from the fragmentation of isopropyl alcohol

(5). This contention is based on observations that the m/z 28 ion and certain other fragments were

common to both the evolved gases of the FLX-D sample and to the mass spectrum of isopropyl alcohol.

These fragment ions appeared at m/z 27, 29, 31, 41, 42, 43, 44 and 45 (base peak in the mass spectrum

of isopropyl alcohol). In addition, the shapes of the mass chromatograms corresponding to these ions

revealed a distinct commonalty, suggesting that they probably resulted from the fragmentation of a

common parent ion which may very well have been isopropyl alcohol. Still, the relative abundance of

the mass 28 fragment (as indicated by the counts on the vertical y-axis) suggests that more than one

mass 28 fragment may be implicated. Structural possibilities for the m/z 28 ion include CO +, H2C =

CH2, and N2 +.

118
n/zn

LUe

te_

see

?ee

ceQ

See

4o8

3_

28_

• Ilass O_ttasrm }'or II/l 2tl 23-3M 11,5. ¢*ntlsrtJe

rts-i f 290°C

Time (minutes)

Figure 12. The Mass Chromatogram for m/z 28 Obtained from the Thermal Decomposition of the

FLX-D Nozzle Material Between 25 - 300°C Under High Vacuum Conditions.

Mass 32

The mass 32 chromatogram (which is believed to be 02 +) is shown in figure 13. Among the ions

shown by the chromatograms in figures 11-14, this ion revealed the lowest increase in overall abundance

over the 25 - 300°C heating range, suggesting the production of only a relatively small amount of 02.

ot/z 32

327-

300

275-

250

225-

200

175.

150

125.

lO0

75-

50

25-

O

8

14_SSCIII_OIMT_N _ _ 32 25-300 DEC. C

FLX-D

_m,

150°C

I

280°C

I

5 1t5 15 28 25 30 35 40 45 50 55 GO

Time (minutes)

Figure 13. The Mass Chromatogram for m/z 32 (02 +) Obtained from the Thermal Decomposition of

the FLX-D Nozzle Material Between 25 - 300°C Under High Vacuum Conditions.

119
Mass44

The chromatogram represented by mass 44 (figure 14) was almost devoid of ion activity until about

125°C. Between 125 and 170°C, a relatively sharp increase in abundance was observed. Near 170°C,

the overall abundance of the ion decreased just slightly, followed by a relatively sharp increase which

continued for the duration of the heating period. The presence of the mass 44 ion is consistent with the

fragmentation of isopropyl alcohol and may represent, at least in part, lhe following "isopropyl"

fragment or some modification thereof.

[ ]

CH3--C--H

II

0

m/z 44

Fragment ions detected at m/z 15 (CH3 +) and m/z 45 (shown below) also offer support to the

argument that isopropyl alcohol is implicated in the thermal decomposition of the nozzle material. It

should also be mentioned that the most abundant fragment ion in the mass spectrum ofisopropyl alcohol

is m/z 45.

H

--- 6m R

m/z 4.5

As mentioned, other ions corresponding to the fragmentation of isopropyl alcohol were observed

in the decomposition gases of FLX-D. These ions were located at m/z 19, 27, 29, 30, 38, 42, 43. A

conclusive identification of the structure of the m/z 44 fragment must await a studyofthe nozzle material

using TG/FrlR.

2'19(_C I_,SS _311tl31q_TO¢1_l_F011_ 44 - I_X-D

n/z 44 [

2G_

24_

Z2_"

2_

18B"

126- 170°C

4_

20

0 $ 10 15 20 25 30 35 48 45 50 55 GO

Figure 14. The Mass Chromatogram of m/z 44 Obtained from the Thermal Decomposition of the

FLX-D Nozzle Material Between 25 - 300°C Under High Vacuum Conditions.

120
An Analysis of the Evolved Gases Resulting From the Decomposition of FLX-D Nozzle Material Between 300 - 1000°C Under High Vacuum Conditions

After obtaining evolved gas data on the FLX-D sample between 25 - 300°C, the same sample was

heated between 300 - 1000°C (without cooling) and evolved gas data acquired and processed under

computer control as previously described. The sample was scanned 1488 times between a mass range

of 10-3000 amu at a rate of 5,478 seconds per scan, making a total heating time of approximately 140

minutes. During data acquisition, the TIC curve (Figure 15) and mass chromatograms corresponding

to masses 18, 28, 32 and 44 were again monitored (figures 16-19).

The Total Ion Current

As expected, the total ion current (figure 15) obtained for the 300- 1000°C run was totally different

from what was observed for the 25 - 300°C run (compare figures 10 and 15). In addition, the maximum

number of counts were larger for the 300 - 1000°C run, suggesting, as expected, that decomposition at

the higher temperature range was more pronounced. For the 300 - 1000°C run the TIC curve (figure

15) revealed two levels of high ion abundance near 450 and 590°C. Beyond 590°C, there was a decrease

in ion abundance, reaching a minim,m near 850°C. Between 850 - 1000°C, the ion current was almost

level.

gill

2G0

Zs,_

22O

2_

120

8O

G_

4_

20

ll

I

18 20 30 _ 5B G8 78 98 50 1/_ 118 /28 latl TIIQ'

Time (minutes)

Figure 15. The Total Ion Current (TIC) for the Thermal Decomposition of FLX-D Under High

Vacuum Conditions Between 300 - 1000°C.

Mass 18

The mass 18 fragment which is believed to be due to H20 ÷ was so abundant during the

decomposition that it caused the mass chromatogram to go off scale near 450°C and reappear near

650°C (Figure 16). Based on the mass 18 chromatogram, it appears that water is also the major

decomposition product between 300 - 1000°C, just as it was for the 25 - 300°C study. Thus, water appears

to be the major overall decomposition product.

121
_z ill

¢14ii

_,lel

5o0(

4_D_

40_

3'_M

3000

|_00,

ll/e ii !11-1 11 - IN illlntl Cltltilrdll

leee

2_

ii Ii li ,4 fl li il (i fl-iii-iil-iie-fil

'l'irneCrninutr.sl

b

Figure 16. The m/z 18 Mass Chromatogram for the Thermal Decomposition of the FLX-D Nozzle

Material Between (a) 25 - 300°C and (b) 300 - 1000°C Under High Vacuum Conditions.

It is believed that an amine curing agent is involved in the fabrication of the nozzle material, thus

the mass 18 fragment may also include fragments attributed to NH4 +

Again, the mass 28 chromatogram (figure 17) is believed to be related, at least inpart, to the

fragmentation of isopropyl alcohol. Structural possibilities include N2 +, and CH2 = CH2 +with CO +

and/or CH2 = CH2 +, probably resulting from the decomposition of isopropyl alcohol. The abundance

of this ion peaked near 595°C, followed by a fairly sharp drop.

Again, the overall abundance of the mass 32 ion (figure 18) was much smaller than for m/z 18, 28

or 44, reaching a maximum between 435 to 575°C

The mass 44 chromatogram (figure 19) revealed a number of peaks and valleys indicating changes

in the relative abundance of the ion during the 300 - 1000°C heating cycle. The increase in abundance

continued beyond the 300°C temperature limit of the first study, reaching a maximum near 435°C.

Other Fragment Ions Observed for the Thermal Decomposition of FLX-D Between 300 -

1000°C Under High Vacuum Conditions

Recognizing the versatility of the Teknivent Microtrace TM data collecting system, it was decided

to recall from the acquired data, the mass chromatograms of all major fragments observed between the

10-300 amu limits. This resulted in a total of 114 fragment ions of varying relative abundances. Efforts

to identify a number of these fragments have been reported elsewhere (5). Because of space limitations,

discussion is prohibited in this paper.

122
_tr 7n

I_aM _Mfq.I_ Dr_ CI)_|aAI)F

?_Vl

Cmvl

4_

3_

Z_

xm_ 785"JC

Ig .....

_o ze 3* _ _* c, _e te le z_ x_ _e ,_e

Time (minutes)

Figure 17. The m/z 28 Mass Chromatogram for the Thermal Decomposition of FLX-D Under High

Vacuum Conditions Between (a) 25 - 300°C and (b) 300- 1000°C.

Time (minutes)

Figure 18. The m/z 32 Mass Chromatogram for the Thermal Decomposition of FLX-D Under High

Vacuum Conditions Between 300 - 1000°C.

123

ORIGINAL PAGE IS

OF POOR QUALITY
w'¢ 44

Zl)

I(0

34_

zze

2t_

tie

!(o

14o

tao

ee

4a

:0

ii

IJ

e,_t 4.4

LZ8_*

m

II,m

ten

toll

5ao

lee

11,15

it

N_$ O(_J,_fC_L41e Ir_ _ 44 - rlLJl-lt I

I

l$-)m IF.C. O_lrf_li(

mrs ormmt_ r_ _ 44 It.x-; Q_)"t.

Time (minutes)

Figure 19. The m/z 44 Mass Chromatogram for the Thermal Decomposition of FLX-D Under High

Vacuum Conditions Between (a) 25 - 300°C and (b) 300 - 1000°C.

Conclusions

The MS/FA/_mputer system as presently configured has been shown to be a useful and reliable

instrument for understanding the thermal decomposition of the nozzle material of the solid rocket

booster as well as other non-metallic materials. However, as with any instrument system there are certain

inherent limitations, most of which relate to the inability of the present system to make distinctions

among different structures of identical masses. The problem becomes even more acute as efforts are

made to make structural assignment to fragments of high molecular masses. FTIR/TG data would

provide functional group analysis and would aid in the resolution of these structural problems.

The ideal systcm for studying evolved gas would be a combined TG/MS/FTIR system which has

not yet been developed (28). A rough schematic of such a system is shown in figure 20.

124
Purge

Adjustable valve; ca 1-5 %

to MS, rest to FTIR

TGA

Air, Nitogen ..... t

Heated transter line

e.g. PVC

Porous Membrane, e.g. PVC

Figure 20. Rough Schematic of a Potential TG/MS/FTIR System (re-drawn from ref. 28).

Literature Cited

1. Thompson, J.M., Laboratory Automation of a Quadropole Mass Spectrometer, Faculty

Fellowship Program, NASA Contractor Report No. 170942, December, 1983.

2. Thompson, J.M., A Computer Controlled Mass Spectrometer System for Investigating the

Decomposition of Non-Metallic Materials, Faculty Research Program, NASA Contractor

Report No. NASA CR-171317, January, 1984.

3. Thompson, J.M., A Thermoanalytical-Mass Spectrometer Investigation of the Nozzle

Material That Constitutes the Throat of the Solid Rocket Boosters, First Annual

Contractor Report No. NAS 8-36299.

4. Thompson, J.M., Nozzle Materials Investigation, Second Annual Contractor Report, NAS

8-36299, June, 1988.

5. Thompson, J.M., Evolvcd Gases and Thermal Profiles-A Comparative Study of Nozzle

Material, Third Annual Contractor Report, NASAS-36299, January, 1989.

6. Zitomer, F., Anal. Chem., 40, 1091 (1968).

7. Wilson, D.E., and F.M., Thermal Analysis, R.F. Schwenker and P.D. Garn, Editors,

Academic, new York 1969, Vol. 1, p. 295.

8. Gibson, E.K., and S.M. Johnson, Themochem. Acta., 4, 49 (1972).

9. Chang, T.L., and T.E. Mead, Anal Chem., 43, 534 (1971).

10. Mettler Thermal Techniques, Series T-107.

125
11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

Langer, H.G., R.S. Gohlke, and D.H. Smith, Anal. Chim. Acta., 32, 405 (1965).

Wiedemann, H.G., Thermal Analysis, R.F. Schwenker and P.D. Garn, Editors,

Academic, New York 1969, Vol. 1, p. 229.

Wendlandth, W.W., and T. M. Southern, Anal. Chim. Acta., 32, 405 (1965).

Redfern, J.P., B.L. Treherne, M.L. Aspimal, and W.A. Wolstenolme, 17th Conference

of Mass Spectrometry and Allied Topics, Dallas, Texas, May 1969.

Gaulin, C.A., F. Wachi, and T.H. Johnson, Thermal Analysis, R.F. Schwenker and P.D.

Garn, Editors, Academic, New York, 1969, Voi. 2, p. 1453.

Dunner, W. and H. Eppler, Advanced Coupling Systems for Thermoanalyzers With

Quadropole Mass Spectrometers, the 4th International Congress on Thermal Analysis

(ICTA), Budapest, July 1974.

Angeloni, F.M., Differential Thermal Analysis Studies on the Mechanism of the Thermal

and Oxidative Decomposition of Calcium Oxalate, Ph.D. Dissertation, The University of

Akron, 1976, Dissertation Abstracts International, Vol. 37/05-B.

Chang, J., A Study of the Decomposition of Calcium Oxalate, Ph.D. Dissertation,

The Pennsylvania State University, 1965, Dissertation Abstracts International, Vol. 26/08.

Freeman, E.S., Non-Isothermal Reaction Kinetics: The Dehydration of Calcium Oxalate

Monohydrate and Thermal Decompositions of Calcium Carbonate on the Solid State,

Ph.D. Dissertation, Rutgers University, 1961, Dissertation Abstracts International,

Vol., 22/01.

Szekely, T., Varhegyi, F. Till, P. Szabo and E. Jakab, Kinetic Reaction of the Thermal

Decomposition of Calcium Oxalate and Calcium Carbonate, J. Anal. Appl. Pyrolysis.,

11, p. 71-81, (1987).

Ninan, K.N., Thermal Decomposition Kinetics: Effects of Sample Mass on the Thermal

Decomposition Kinetics of Calcium Oxalate monohydrate, Thermochim Acta, 74, No. 1-3,

p. 143-50.

Ninan, K.N., and C.G.R. Nair, Thermochim Acta, 30, no. 1-2 (1979).

Nair, C.G.R., and K.N. Ninan, Thermochim Acta, 23, No. 1, p. 161-9 (1978).

Gurrier, S., G. Siracusa and R. Cali, J. Therm. Anal., 6, no. 3, p. 293-8 (1974).

Dollimore, D., T.E. Jones and P. Spooner, J. Chem SOc., 17, p 2809-12 (1970).

Nerad, 1., S.Vitkova and I. Prokks, J. Therm. Anal., 33, No. 1, p. 291-5 (1988).

Gadalla, A.M., Thermochim. Acta, 74, No. 1-3, p. 255-72 (1984)

Prime, R.B., NATAS NOTES, Vol. 19, No. 4, p. 48 (Winter 1987-88).

126
N91-28083

3-( BROMOACETAMIDO ) - PROPYLAMINE HYDROCHLORIDE:

A NOVEL SULFHYDRYL REAGENT AND ITS FUTURE POTENTIAL IN

THE CONFIGURATIONAL STUDY OF S1-MYOSIN

Prasanta Sharma

Miles College

Birmingham, AL

and

Herbert C. Cheung

Department of Biochemistry

University of Alabama at Birmingham

Birmingham, AL

ABSTRACT

Configurational study of S1-Myosin is an important step towards understanding force generation

in muscle contraction. Previously reported NMR studies nave oeen corrooorateo by us. We have

synthesized a novel compound, 3-( Bromoacetamido ) - Propylamine Hydrochloride, and its potential

as a sulfhydryl reagent provides an indirect but elegant approach towards future structural elucidation

of S 1-Myosin. Our preliminary investigation has shown that this compound, BAAP, reacted with $1 in

the absence of MgADP and the modified enzyme had a 2-fold increase in Ca-ATPase activity and no

detectable K-EDTA ATPase activity. Reaction of BAAP with $1 in the presence of MgADP resulted

in a modified enzyme which retained a Ca-ATPase activity that was about 60% of unmodified $1 and

had essentially zero K-EDTA ATPase activity. Suifhydryl titration indicated that about 1.5 and 3.5 -SH

groups per $1 molecule were blocked by BAAP in the absence and presence of MgADP, respectively.

When coupled to a carboxyl group of EDTA, the resulting reagent could become a useful -SH reagent

in which chelated paramagnetic or luminescent lanthanide ions can be exploited to probe $1 conformation.

127
3-( BROMOACETAMIDO ) - PROPYLAMINE HYDROCHLORIDE:

A NOVEL SULFHYDRYL REAGENT AND ITS FUTURE POTENTIAL IN

THE CONFIGURATIONAL STUDY OF S1-MYOSIN

Introduction

Myosin Subfragment 1 is the globular head of myosin and contains two sets of functional sites that

are essential for force generation in muscle contraction. These are the two actin-binding sites and the

single nucleotide-binding site at which ATP is hydrolyzed. One current model of contraction 1proposes

that force generation results from structural changes occurring in the S1 region of myosin while myosin

is still attached to actin. Considerable attention has been paid to the structure of S1 in intact myosin or

myofibriis as well as isolated S1 and structural changes that occur in S1 resulting from interaction with

actin and nucleotides.

Among the various tools used in the study of proteins, NMR has been used successfully for proteins

of molecular weights less than 20K. For larger macromolecules, however, the spectra are accompanied

by broad, poorly-resolved overlapping NMR signals. Nevertheless, recent high-resolution NMR has

provided valuable information on structural changes that proteins undergo under varied conditions. 2

Within the context of structural studies of S1 in solution, in the present work 1H NMR spectra

were observed both with and without the addition of chemical denaturants. The spectra were then set

against a computer-simulated random-coil spectrum 3 (Fig.l) and the derived assignments compared

against previously published results 4. The present NMR data seem to be in general agreement with

those previously reported.

S1 contains two reactive thiols (SH1 and SH2) located at Cys 707 and Cys 697 of the heavy chain

5

which are readily alkylated by a number of sulfhydryl reagents. The chemically-modified protein

provides a model in which structural information can be obtained. Modification of one -SH group (SH1)

of $1 typically activates the Ca-ATPase by a factor of 2-3 and suppresses the K-EDTA ATPase activityL

When both SHt and SH2 are blocked, both types of ATPase activity are abolished 7. Early studies

indicated that the tWO -SH groups can be crossiinked or chelated by several bifunctional alkylating

agents s suggesting considerable flexibility of the polypeptide backbone between Cys 697 and Cys 707.

The equilibrium separation between SH1 and SH2 was determined by measuring the extent of fluorescence resonance energy transfer between probes covalently attached to the two thiols 9. The measured

distance was found to be sensitive to MgADP. Other workers have also investigated $1 conformation

by using several extrinsic fluorescent probes 1°.

A different approach to 11theuse of fluorescent probes for distance measurements was provided

by Mears and coworkers , who synthesized para-substituted derivatives of 1-phenyl

ethylenedinitrilotetraacetic acids in which the substituents are NO2, NH2, N2 +, HNCOCH 2Br, etc.

Once attached to a protein, the tetraacetate groups can be exploited to chelate cation possessing

suitable spectroscopic or radioactive properties for structural studies of the host protein. In particular,

lanthanide ions can be used for this purpose. In preliminary studies we were unable to selectively modify

SH1 of subfragment 1 and to obtain the desired degree of ATPase activation. This lack of success led

us to synthesize an aliphatic EDTA analog with sulfhydryl reactivity. In this report we describe the

synthesis of a precursor of such an analog, 3-(Bromoacetamido)-propylamine hydrochloride, and its

reaction with SH1 and SH2 of S1.

128
Figure 1C.

Computer simulated NMR

spectra.

I,

_t

,7, _

v A.--_

.#

_. . .?

._ -j,.m

i. * . • g _+ 1

3 CA, . i

i

i 'tij

Figure lB.

S1/Phosphate Buffer (2H20) -

denatured with 8M urea.

Figure 1A.

S1/Phosphated Buffer (2H20) -

native.

I .

v

÷

;, ftl

i

7.'0 " 5_.0 " 3'.0

''t, " I%

[

1

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t

t

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1_.0 in pla-n

129 ORIGINAL PAGE IS

OF POOR QUALITY
Experimental

Synthesis of BAAP.

An indirect method for synthesis of bromoacetamidoalkylamines has been reported 12. Though

direct monoacylation of diamines has proved to be difficult _3,in our present work we have obtained the

product, the reaction being carried out at a relatively low temperature. To 2.5 mL of 1,3 diaminopropane

(0.03 tool), in a small volume of dry chloroform, was added dropwise 2.47 mL bromoacetylchloride (0.03

mol) while stirring in an atmosphere of nitrogen. The reaction was carried out in the presence of dry

ice/acetone. The sticky white precipitate that formed was separated and extracte d overnight with

chloroform under ice-cold conditions. On evaporating to dryness, the chloroform extract yielded a white

crystalline solid ( m.p. 113-115°C ). TLC tests with ninhydrin and 4-(4-Nitrobenzyl) pyridine established

the purity of the product. 1H NMR profile corresponded to four methylene resonances (4.1-1.7 ppm)

and a downfield component (7.1 ppm) resulting from the exchange of the amide proton.

Microanalysis data ( Table 1 ) correspond to the empirical formula CsH12BrC1ON2 (FW 231.6).

The molar extinction coefficient of a sample of BAAP in dimethyl sulfoxide was determined ( E277 =

4.4 x 103 ).

Table 1. Microanalysis of BAAP.

Calculated

Microanalysis

%C

25.93

26.03

%H

5.22

5.11

%N

12.10

11.96

% Halogen

49.81

50.16

Protein Preparation.

Myosin was obtained from rabbit skeletal muscle by a method described by Flamig and

Cusanovich 14. The procedure involved extraction of freshly-ground back and leg muscles with a

phosphate buffer, pH 7.5 containing 0.3 M KCI for 1 hr. The precipitate was dissolved in 0.5 M KCI

and subsequently reprecipitated. Subfragment 1 was obtained by digestion of myosin with a-chymotrypsin, followed by purification on a DEAE-celluiose ( DE-52 ) column 15.The S1 concentration was

estimated from a molecular weight of 115,000 and an extinction coefficient of Ezs0 _% = 7.5 cm 1 16

Reaction of S1 with BAAP.

S1 was labeled at SH1 with a 1.5-fold molar excess of BAAP in a buffer containing 60 mM KC! and

50 mM Tris at pH 7.8 ( Buffer A ). Prior to labeling, the protein solution (130 pM) was dialyzed in

Buffer A in the presence of 1 mM DTr. Any residual DTlr was subsequently removed by extensive

dialysis with Buffer A. Appropriate quantities of 5 mM BAAP ( dissolved in Buffer A ) were added to

S1 followed by incubation in the dark under ice-cold conditions for 18-20 hr. Any unreacted probe was

subsequently removed by exhaustive dialysis in Buffer A. The percentage of protein sites labeled was

calculated by measuring the absorbance of a sample of labeled protein at 280 nm and subtracting the

optical density 17 derived for an equivalent concentration of protein at this wavelength. The Lowry

method was used to determine protein concentration in labeled S1 to avoid optical interference from

the label.

130
ForSH2modification,SHl-modifiedS1wasincubatedwitha 4- and 50-fold molar excess of BAAP

(3 mM) and MgADP, respectively, under ice-cold conditions in the dark for 38-40 hr. Ca and K-EDTA

ATPase activities were determined by measuring the release of inorganic phosphate using a modification of the Fiske-Subbarow method as previously described s. The thiol content was determined using

Ellman's method TM.$1 (0.1 mL of 30-50/zM) was added to 2.6 mL of a freshly-prepared urea solution

( 9.0 M Urea, 10 mM EDTA, 50 mM Tris, 0.1 M KCI, pH 8.0 ) and the absorbance was measured at

412 nm. After approximately 15 minutes 0.3 mL of freshly-prepared DTNB ( 1 mM DTNB, 0.1 M KCI,

10 mM phosphate, pH 7.0 ) was added and the absorbance at 412 nm was followed until there was no

further increase in absorbance. A molar extinction coefficient of 13600 at 412 nm was used for DTNB.

NMR

Sample buffer containing 50 mM KCI, 12 mM phosphate, 1 mM NaN3 in 2H 20 at p 2H 7.0 was

passed through a column packed with chelex. $1 in sample buffer was next dialyzed against 330 mM

EDTA in buffer followed up by dial_is against several changes of buffer at 4°C. Denatured samples

were prepared by adding 8M Urea (2H). The _H NMR spectra were obtained on a Bruker WH-400

spectrometer operating in the FF mode. A typical sample consisted of 0.4 ml $1 (90/_M) in the presence

of TSP, an internal standard. The H2HO resonance was saturated with a homonuclear decoupling phase.

All spectra were recorded at 4°C.

The 1H NMR spectra of BAAP in CDCI3 were recorded in a Nicolet -300-W.B. FF NMR

spectrometer.

Results and Discussion

The relative ATPase activities of native and modified S 1 and their sulfhydryl content are reported

in Table 2. Modification of the SH1 site was evidenced by a two-fold increase in Ca-ATPase while the

corresponding K-EDTA ATPase activity was completely abolished. Comparison of the data on the third

row of Table 2 indicated that the second site (SH2) was labeled.

Table 2. Comparison of relative ATPase activities between native and modified S1

and the corresponding loss in the number of free sulfhydryl groups.

Sample

1. Sl-unmod

2. $1-(1) BAAP

3. $1-(1,2) BAAP

Relative ATPase activities (a)

Ca(%) (b)

100

207

61

K-EDTA(%) (c)

100

0

4

Loss of -SH Groups per

mole of $1 (a)

1.48

3.43

(a) The data are obtained by averaging over two samples.

(b), (c) 100% Ca-ATPase and K-EDTA ATPase activities correspond to 1.07 and 2.68

moles Pi rag-1 rain-1, respectively.

131
Overall,preliminarybiochemicaltestsindicate that BAAP is a monofunctional SH-coupling

reagent. It has a relatively short span (10.80 _ 0.03 _)19 and appears reasonably specific for myosin SH1

and SH2. It should be possible to link BAAP via its terminal amino group to a carboxyl group of EDTA.

Such a compound should still possess sulfhydryl reactivity and is expected to chelate paramagnetic or

luminescent lanthanide ions such as Tb (III). The chelated cation provides a spectroscopic signal that

may be useful for elucidating the structural properties of the protein by luminescence or NMR methods.

Acknowledgement

This work was supported in part by AR31239 from the U.S. National Institute of Health.

References

1. Huxley, H.E. and Kress, M., J. Muscle Res. Cell Motil., 1985, 6, 153.

2. Jardetzky, O. and Roberts, G.C.K., NMR in Molecular Biology, 1981, Academic Press,

New York.

3. McDonald, C.C. and Phillips, W.D., J. Am. Chem. Soc., 1969, 91, 1513.

4. Prince, P.; Trayer, H.R.; Hen_, G.D.; Trayer, I.P.; Dalgarno, D.C.; Levine, B.A.;

Cary, P.D. and Truner, C., Eur. J. Biochem., 1981, 121,213.

5. Cheung, H.C.; Gonsoulin, F. and Garland, F., J. Biol.Chem., 1983, 258, 5775.

6. Sekine, T. and Kielley, W.W., Biochim. Biophys. Acta, 1964, 81,336.

7. Yamaguchi, M. and Sekine, T., J. Biochem., 1966, 59, 24.

8. Burke, M. and Reisler, E., Biochemistry, 1977, 16, 5559

9. Cheung, H.C.; Gonsoulin, F. and Garland, F., Biochim. Biophys. Acta, 1985, 832, 52.

10. Dalbey, R.E.; Weiel, J. and Yount, R.G., Biochemistry, 1983, 22, 4696.

11. Stryer, L.; Thomas, D.D. and Mears, C.F., Ann. Rev. Biophys. Bioeng., 1982, 11,203.

12. Lawson, W.B.; Leafer, M.D.; Tewes, A. and Rao, G.J.S., Hoppe- Seylors Z. Physiol.

Chem., 1968, 349, 251.

13. Moore, T.S.; Boyle, M. and Thorn, V.M., J. Chem. Soc., 1929, 132, 39.

14. Flamig, D.P. and Cusanovich, M.A., Biochemistry,1981, 20, 6760.

15. Weeds, A.G. and Taylor, R.S., Nature (London), 1975, 257, 54.

132
16. Wagner,P.D.andWeeds,A.G.,J.Mol. Biol.,1977,109,455.

17. Lowry,O.H.;Rosebrough,N.J.;Farr,A.L. andRandall,R.J.,J.Biol.Chem.,1951,

193,265.

18. Elman,G.L.,Arch.Biochem.Biophys.,1959,82,1970.

19. ThisvaluewascomputedfrominteratomicdistancestakenfromtheCRCHandbook

of ChemistryandPhysics,58thEdition,1977-78.

Abbreviations:S1,chymotrypticsubfragment-1of myosin;BAAP, [3-(Bromoacetamido)-Propylaminehydrochloride];DTT, dithiothreitol; DTNB, 5,5'-dithiobis(2-nitrobenzoicacid);TSP,[3-

(Trimethylsilyl)propionicacid,Na salt);SI-(1) BAAP, subfragment-1modifiedwith BAAP atSH1;

S1-(1,2)BAAP,subfragment-1modifiedwithBAAPatSH1andSH2.

133
N91-28084

ELLIPSOMETRIC MEASUREMENT OF LIQUID FILM THICKNESS

K.J. Chang

Department of Chemistry

Alabama A&M University

Huntsville, AL

and

D.O. Frazier

Marshall Space Flight Center, NASA

Huntsville, AL

ABSTRACT

The immediate objective of this research is to measure liquid film thickness from the two

equilibrium phases of a monotectic system in order to estimate the film pressure of each phase. Thus

liquid film thicknesses on the inside walls of the prism cell above the liquid level have been measured

ellipsometrically for the monotectic system of succinonitrile and water. The thickness varies with

temperature and composition of each phase.

6<_n_le

The preliminary results from both layers at 60t_a of incidence show dearly uniform thickness

from about 21Wto 23'_C. The thickness increases with temperature but near 30 C the film appears foggy

and scatters the laser beam. As the temperature of the cell is raised beyond room temperature it becomes

increasingly difficult to equalize the temperature inside and outside the cell. But the fogging may also

be an indication that solution, not pure water, is adsorbed onto the substrate.

Nevertheless, our preliminary results suggest that ellipsometric measurement is feasible and

necessary to measure more accurately and rapidly the film thickness and to improve thermal control of

the prism walls.

134
ELLIPSOMETRIC MEASUREMENT OF LIQUID FILM THICKNESS

Introduction

Considerable interest in monotectic systems within NASA and in materials science in general

during the last decade or so is evidenced b)_the large number of publications on this subject. A few of

them are listed in the reference section. 1'''3'4 Succinonitrile is a transparent organic compound and

freezes like metals with small entropies of melting. 5

The monotectic system of succinonitrile-water has been subjected to considerable investigations

not only due to its transparency but also due to a convenient temperature range to work with for its

solution and solidification. Its upper consolution temperature of near 56°C and monotectic temperature

of close to 19°C make the system 2 nearly ideal for various experiments.

In our current investigation attempts have been made to estimate the thickness of liquid films

formed on the inner wall of a prism cell from each of the two separate layers: water-rich and

succinonitrile-rich layers of the monotectic system. Several other monotectic systems including

succinonitrilc-cthanol, succinonitrile-glyceroi and succinonitrile-phenanthrene will be subjected to

similar investigations. The reason for this study is to assess Cahn's critical wetting theory 6 in a

quantitative manner by determining solid-liquid interfacial tension input to Young's equation

7LzS =7L_S + YLtLz COS 0

where 0 is the contact angle and y is the interfacial energy corresponding to the interface denoted by

the subscript pair. The liquid film from these solutions may be formed by condensation of the vapor or

by van der Waals adsorption of the liquid along the wall. Thus, it becomes necessary to estimate partial

pressures of each component for each solution equilibrated at different temperatures. This task is

pursued by Frazier and coworkers 7 at the Marshall Space Flight Center.

Experiment

Since ellipsomctric measurement of film thickness requires refractive indices of medium, liquid

and substrate, it is absolutely imperative that these values be available or estimated accurately at the

particular wavelength, in our case, 632.8 nm of He-Ne laser. Unfortunately these quantities are not

available and therefore must be estimated with some degree of accuracy at various temperatures.

Refractive indices are very sensitive to temperature s and composition of the liquid. Therefore,

index measurements were made using two different devices, a prism spectrometer and the ellipsometer

with He-Ne laser. There was some variance between the two apparatuses, as shown in Table 1, which

may be due to thermal sensitivity of the prism spectrometer. The table was not completed for all the

listed temperatures due to the lack of temperature control device for the prism spectrometer. Thermal

control stability on the solution in the prism cell was ___0.1°C, although it was difficult to achieve this

stability on the prism wall at temperatures other than ambient temperature. This was the case because

circulation of the bath water around the wall on which film thicknesses were measured would not be

permitted since it would obstruct the measurement.

135
Table1.Indicesof Refraction for Succinonitrile-rich Phase

Prism

T°C Ellipsometer Spectrometer

18.9 1.42114

19.2

19.6

19.9 1.41871

21.0

22.0

24.0 1.41990

24.6

25.5

26.0 1.42003

28.0 1.41416

29.0 1.41135

30.0 1.41096

31.0 1.41036

1.42017

1.41945

1.41763

1.41661

For the ellipsometric work, prism cells of three different angles of incidence were specifically

designed for refractive index and thickness measurements. As stated earlier, the inner wall temperature

of the prism could not be controlled as accurately as the solution temperature in the cell. Refractive

indices of water from the literature 8 are compared with those estimated ellipsometrically in our

experiment in Table 2. The agreement between the two is excellent near room temperature. In this

measurement the refractive index of the cell prism glass was assumed constant over the temperature

range.

Table 2. Indices of Refraction for Water

T°C Ellipsometer Ref. 8* Deviation %

16.0 1.32880 1.33245 0.3

18.0 1.32977 1.33229 0.2

22.0 1.33197 1.33194 0.002

25.0 1.33119 1.33165 0.03

29.0 1.33099 1.33121 0.02

40.0 1.32970 1.32977 0.005

*Temperature was rounded to 3 digits for this table.

136
The manuallyoperatedellipsometer(leasedfrom the Marshall Space Flight Center) has been

used very extensively, but is very time-consuming and tedious. A temperature shift during a long reading

period was entirely possible unless the room and the water jacket were at the same ambient temperature.

Preliminary Result

Liquid film thickness and refractive indices are presented in Figs. I and 2 for the monotectic system

of succinonitrile and water (SN-water) at the 60 ° incident angle. Both water-rich and succinonitrile-rich

(SN-rich) phases show variation of thickness with temperature. Variations are small between 21 ° and

23°C. At higher temperatures, film thickness increases, while at lower temperatures thickness decreases.

The two layers gave rise to the same thickness near the monotectic temperature. Formation of foggy

film as the cell temperature was raised beyond room temperature may indicate precipitation of the

conjugate phase within the adsorbed film itself if indeed the film composition is similar to the liquid

solution composition, rendering the film quite foggy. The fogging is one of the most consistent problems

that should be dealt with. Similar results were obtained with the cells of different glass and angles of

incidence.

In calculation of thickness, experimental values of index of refraction for the solution phases

obtained in this lab were used. No literature data are available for the solution. Measurements were

usually made on a large drop of the phase placed at the floor corner away from the prism wall to minimize

capillary migration of the liquid along the wall. Condensation of the vapor onto the wall is the main

mechanism of film formation when the wall is not in contact with the sample solution. This allows use

of the Gibbs adsorption equation to determine film pressure of liquid films formed from adsorbed phase.

The variation of the index with temperature for both conjugate phases of each succinonitrile-water

solution is as anticipated because at higher temperatures there will be more homogeneous mixing

between the two components. This trend was shown by both the hollow-prism spectrometer and the

ellipsometer. Thus, the succinonitrile-rich phase has a decreasing index as the temperature is raised. In

fact, the graph of indices, Fig. 1, is a combination of two separate data from the prism spectrometer and

ellipsomcter. The result is rather remarkable for the two entirely different instruments. On the other

hand, the index of the water-rich phase varies very little with temperature near 23 ° to 25°C but slowly

decreases again above this temperature range. Under nearly identical conditions, variance between the

two spectrometers is usually less than 0.1%, still a remarkable agreement.

A preliminary calculation of film pressure was also attempted by utilizing the estimated film

thickness and partial pressure data 7 for the two components, succinonitrile and water, obtained

elsewhere. The result was obviously too large when the specific surface was replaced by the total inner

walls (24 cm 2) of the sample cell. Since for the flat surface of prism glass specific area has not been

defined, some new parameters need to be defined and estimated for the Gibbs adsorption equation to

calculatc film pressure. One parameter under considcration in our laboratory is the quantity defined as

the total empty volume of the cell divided by the total inner surface area of the available space.

Conclusion

Much work remains to be done including more precise control of the sample cell and accurate

measurement of film thickness with a fully automated ellipsometer system. This system requires a new

design of prism cells so that the difficulty of observing liquid film formation on the vertical wall can be

eliminated. The liquid film itself on the cell ceiling will be less dependent on any capillary adsorption

of liquid. Partial pressures and composition of each component vapor phase should also be estimated.

137
Acknowledgements

We gratefully acknowledge the funding support of the National Aeronautics and Space Administration for this work and for their loaning of the ellipsometer.

References

1. Ang, C.Y.; Lacy, L.L.; NASA TMX-64956, 1975; Giles, S.H.; Markworth, m.J.; NASA

TM-78125, Nov., 1977; Kaukler, W.; Frazier, D.O.; Facemire, B.; NASA TM-82581,

April, 1984.

2. Smith, J.E.; Frazier, D.O.; Kaukler, W.; Scripta Metali. 1984, 18, 677.

3. Frazier, D.O.; Facemire, B.; Fanning, U.S.; Acta Metall., 1986, 34, 63.

4. Rai, U.S.; Sing, O.; Sing, N.; Can. J. Chem., 1987, 65, 2639.

5. Jackson, K.A.; Hunt, J.D.; Acta. Metall., 1965, 13, 1212.

6. Cahn, J.W.; J. Chem. Phys., 1977, 66, 3667.

7. Frazier, D.O.; Coworkers; Private Communications, Marshall Space Flight Center,

Alabama 35812.

8. Stanley, E.M.; J. Chem. Eng. Data, 1971, 16, 454.

138
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A

THE FORMATION AND STUDY OF TITANIUM,

ZIRCONIUM AND HAFNIUM COMPLEXES

N91-28085

Bobby Wilson, Sam Sarin, Laverne Smith and Melanie Wilson

Department of Chemistry

Texas Southern University

3100 Cleburne

Houston, Texas

ABSTRACT

Research involves the preparation and characterization of a series of Ti, Zr, Hf, TiO, and HfO,

complexes using the poly(pyrazolyl)_orates as ligands. The study will provide increased understanding

of the decomposition of these coordination compounds which may lead to the production of molecular

oxygen on the moon from lunar materials such as ilmenite and rutile. These model compounds are

investigated under reducing conditions of molecular hydrogen by use of a high temperature/pressure

stainless steel autoclave reactor and by thermogravimetric analysis.

141
Introduction

Currently, there is considerable interest in the United States in producing molecular oxygen from

lunar ores to be used as fuel and in life support systems for space travel. Ilmenite (FeTiO3) and rutile

(TiO2) are both abundant on the moon. Reduction of these ores to produce the pure metal and

molecular oxygen is most desirable. Even though several technically different approaches are reported

in the literature, none is acceptable for use on the moon.

A survey of the literature on research concerning the use of ilmenite and rutile in the generation

of O2 and Ti brings us to the following conclusions: (1) There is evidence of a lack of research in the

above stated direction because of the focus of many industrial firms is the extraction and use of pure

TiO2 and Ti in other processes with no attention being given to the recyclability and energy efficiency

of oxygen production(l). However, on the positive side, a variety of these processes do appear to be

adaptable to lunar processing, with the modification of these chemical processes. The real bonus of

lunar processing is the inert atmosphere, which is very conducive for the production of ultra pure

titanium. Because of the considerable amount of energy and time wasted in the earth processes to effect

high temperature vacuum annealing of titanium, reduction in a lunar environment becomes even more

attractive (2). For example, the Plasma Reduction Process which occurs at 25000 to 35000 K with

hydrogen is clean when there are no leaks from the environment (3). The reactions may be written as

follows:

TiO2 + 2H2 .... > Ti + 2H20

2HzO .... > 2H2 + 02

One solution to the improvement of the TiO2 reduction is the development of appropriate catalysts

that will enhance a lunar process. These catalysts must be chemically stable, or be converted into species

which are stable under the conditions required to reduce TiO2 or FeTiO3 to Fe, Ti and O2 which may

be quite severe. The primary purpose of this research is to prepare and characterize a series of Ti, Zr,

Hf, TiO and HfO complexes using the poly(pyrazolyl) borates as ligands.

The poly(pyrazolyl)borates, anions of the general structure (HnB (Pz)4-n) -, (where n =0,1 or 2)

can be made to function as a bidentate ligand, a tridentate ligand of C3_ symmetry analogous to the

cyclopentadienide anions, and even as a tetradentate (bis-bidentate) ligand with appropriate control

substituents (see Scheme 1 (4-7)). The formation of transition metal complexes with these ligands allows

for the option of varying the form (group attachment) of the ligand that is used in the preparation of

the coordination complex. The aim is to determine the importance of altering the molecular weight and

size of the poly(pyrazolyl)borate and to correlate the chelate effect on complex formation. The

decomposition temperature of the enclosed metal complex should have a profound effect upon the

metallurgical aspects of the lunar material. Thermogravimetric analyses are currently under study on

selected samples under an inert atmosphere in an effort to correlate decomposition temperature with

speciation.

z

142
SCHEME I

a.; ÷

I HN--N

\,/ /.-.,",.-.. /

180" I HI_

1

_".N / N--_\

220* I HPZ

Experimental Details

Since the compounds synthesized during this study were sensitive to air and moisture, all syntheses

and subsequent handling of the compounds were conducted under vacuum or in an inert atmosphere.

Samples and solutions were prepared in a nitrogen-filled glove box.

Materials

Titanium tetrabromide and titanium tetraiodide (97%), obtained from Alfa Inorganic Products,

were used as received. Potassium borohydride (98%) and pyrazole, which were obtained from Fisher

Scientific, were also used as received. Analytical grade methylene chloride was purchased from Fisher

Scientific Company and dried by refluxing for 24 hours over calcium hydride.

Preparation

Ligand - the following reaction gives rise to potassium

K(H2B(Pz)2):

KBH4 + 2HPz .... > K(H2B(Pz)2) + 2H2

dihydrobis(pyrazolyl)borate,

143
The potassium dihydrobis(pyrazolyl)borate was prepared by mixing potassium borohydride (45 g,

1 mole) with pyrazole (272 g, 4 moles) in a one-liter round bottom flask equipped with a magnetic stirrer,

thermometer and vent line. The pyrazole was carefully melted by means of an oil bath at 90°C. When

the contents of the flask were sufficiently molten to allow magnetic stirring, the mixture was stirred and

heated to 120°C. Potassium borohydride dissolved slowly with the evolution of hydrogen. After 24

hours, only a few small particles of KBH4 were still floating in the melt. These particles were removed

mechanically. The melt was poured into 500 ml of toluene, stirred Until it cooled to room temperature,

and filtered. The filter cake was washed three times with 150 ml portions of hot toluene and then air

dried, yielding 140 g of white solid with a melting point of range of 171 - 172°C (8).

Metal Complexes

Preliminary results are consistent with the following reactions on preparation of the titanium

complexes:

TiX4 + 2K[H2B(Pz)z] .... > TiX2[H2B(Pz)2]2 + 2KX

TiX4 + 4K[HzB(Pz)2] .... > Ti[HzB(Pz)2]4 + 4K

(where X = Br and I)

Results and Discussion

Compounds of early transition metals in oxidation state IV are extremely sensitive to oxygen and/or

moisture. Therefore, it is essential that all manipulations of these complexes be effected under inert

conditions. Since these compounds require special working conditions, relatively few have been

prepared and fully characterized. We feel that the poly(pyrazolyi)borate anions with their good

chelating abilities and uni-negative property afford an excellent opportunity to increase our knowledge

in this area of inorganic chemistry. It is known that the choice of ligands influences the stereochemistry

of the metal ions. Small donors decrease the steric repulsions and tend to favor the higher coordination

numbers. Large donors tend to favor lower coordination because of the increase in steric repulsions.

This series of ligands allows us to test both trends without changing the donor atoms or charge on the

ligand. It is also known that the ionic radii increase from titanium(IV) to hafnium(IV) (8,9). These

complexes will be investigated under inert conditions by use of nuclear magnetic resonance, vibrational

spectra, and x-ray powder diffraction and GC/Mass Spectrometry. It is aimed to elucidate the structure

and to ascertain the mode of bonding in the products obtained by the reactions of the metal halides and

oxyhalides with potassium dihydrobis(pyrazolyl)borate, potassium hydrotris(pyrazolyl)borate, and potassium tetrakis(pyrazolyl)borate.

144
References

1. Vilk, W.; Stotler, H.H., Journal of Metals, 1970, 22, 50.

2. Chase, J.D.; Skrivan, J.F., AIChE Symposium Series, 1979, 75, 38.

3. McLaughlin, W.J., "Plasma Reduction of Titanium Dioxide," U.S. Patent 3,429,691, 1969.

4. Asslani, S.S.; Rahbornochi, R.; Wilson, B., Inorg. Chem. Lett., 15, 59 (1959)

5. Trofimenko, S., J. Amer. Chem. Soc., 1966, 88, 1842.

6. Trofimenko, S., J. Amer. Chem. Soc., 1967, 890, 3270.

7. Trofimcnko, S. Chem. Rev., 1972, 72, 497.

8. Calderon, J.L.; Cotton, F.A.,; Shaver, A., J. Organometal. Chem., 1972, 37, 127.

9. Bagnell, K.W.; Edwards, J.; Preez, J.G.H.; Warren, T.F., J. Chem Soc. (Dalton), 1975, 140.

145
N9 1 - 28 086

KAON - NUCLEUS SCATrERING

Byungsik Hong, Warren W. Buck and Khin M. Maung

Department of Physics

Hampton University

Hampton, Virginia

Technical Monitors

John W. Wilson and L.W. Townsend

NASA Langley Research Center

Hampton, Virginia

ABSTRACT

Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models,

are used withi_ t-matrix that is taken from the scattering experiments to find a simple optical potential.

The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown.

The eikonal approximation was chosen as our solution method to estimate the total and absorptive

cross sections for the kaon-nucleus scattering.

.=

146

r

r

z
KAON - NUCLEUS SCATI'ERING

For the scattering of the high energy incoming particle, particulary a meson, by a nucleus, it is

expected that the situation can be considered in terms of its scattering by the constituent nucleons of

the nucleus individually. This means the many body problem may be reduced to a collection of the two

body interactions.

One of the successful scattering frameworks is the multiple scattering theory. A simple picture of

the scattering of elementary particles by a nucleus is to view the scattering in terms of the projectile

interactions with each single constituent of the nucleus (single scattering). There may be other terms

contributing to the scattering such as the projectile interacting with two consecutive constituents

(double scattering). Similarly there are contributions from three, four, and more successive scatterings.

The formalisms using this picture are called multiple scattering theories) '2'3 It is clear from this

description that the scattering from a nucleus is determined from the amplitude for the scattering of

the projectile from a single target constituent, i.e., a two body scattering amplitude:

A general multiple scattering theory for scattering between two nuclei (neglecting three body

interaction) has previously been developed by Wilson. 4"sThe reaction for the hcavy ion projectile which

is the previous application of Wilson's theory was well developed by Wilson et al.U And the application

to the antiproton, antideuteron and antinuclei was also done by Buck et al. 7 giving good agreement with

the available experimental data.

A successful feature of multiple scattering theories manifests itself when combined with the optical

model. This allows the optical potential for elementary particle scattering from a nucleus to be

determined from more fundamental quantities such as the two body scattering amplitude and the target

number density function.

W(R) = A f d3r'pA(r ') t (e,r' - R) (1)

where R is the distance between the origin and projectile particle, r' is the separation between the origin

and the considered target constituent, A is the target mass number, e is the kaon-nucleon kinetic energy

in the center of the mass frame, ,o,4 is the target number density, and t is the energy dependent

kaon-proton transition amplitude obtained from scattering experiments. The origin was taken at the

center of the mass of the target nucleus. In the eikonal context, the scattering amplitude for the

kaon-nucleus scattering is given by

f (k,O) = _-[ d2be i q" b [eix (2)

where

1 _2t:_y__ W(b,z)dz (3) x(b'k) = 2k _-2 0o

147
istheeikonalscattering phase shift function, b is the impact parameter, and/_ is the reduced mass of

the K-nucleus system. Using the above scattering amplitude and the optical theorem, we can obtain the

total and absorption cross section expressed as follows:

Ototal= 2f d2b [1 - eImxC*'_)cos(Rex (b_) ] (4)

and

aabsorption = f d2b [1 - e -2tmx (b_) ]. (5) .-

The number densitypA of nuclear matter can be extracted from the corresponding charge density pc

by assuming 7

pc(r) = f pN(r')pA (r +r')d3r ' (6)

wherepc is the nuclear charge distribution, pN is the nucleon charge distribution, and pA is the nuclear

single particle density, pN was taken to be the usual Gaussian function

3 ) 3/2 3/2

pN (r) = ( _ exp ( -_ ) (7)

with the nucleon root-mean-square charge radius set equal to the proton value of 0.87fm 12.

For nuclei with A <20 we used an harmonic well form ofpc as

pc (r) = po [1 + y (_)2]exp (-a_2 -) (8)

with the charge distribution parameters y and a listed in Table I. Substituting Eq.(7) and Eq. (8) into

Eq.(6), we get

P°a---_3[1 +33, _3ya 2 +ya2r 2- pA (r) = 8s3 2 8s 2 16s4 I exp (- ) (9)

where

S2 a 2 r2N (10)

=4 6"

For target nuclei with A ->20 we choose a Woods-Saxon form of charge distribution

pc (r) = po [1 + exp (L__) 1-1 (11)

where the parameters R and c are given by

148
and

n = to5 (12)

tc (13)

c=_-_

and r0_sis the radius at half-density with tc representing the skin thickness. Values for R and tc are also

shown in table I. If we substitute Eqs. (7) and (11) into Eq. (6), we'll see the nuclear single particle

density that is also of Woods-Saxon form with the same R, but different normalization coefficient, p0,

and surface thickness. The latter is given (in fm) by

U = [5.08rN In (_)]-1 (14)

and

fl = exp (2.54 _ ). (15)

We choose the kaon-nucleon scattering amplitude to be the function of momentum transfer q as

k (i + a)e -Bq2/2 (16) f (q) = -_ or

where k is the wave number of the kaon-nucleon system, ar is the kaon-nucleon total cross section, a

is the ratio of the real to imaginary part of the forward elastic scattering, and B is the slope parameter.

Then the t-matrix in the coordinate space is

/eh 1

t(r) = -W 2"_7_aT(i + (27rB)3/2 (17)

where e is the total kinetic energy in the c.m. frame and/_' is the reduced mass of the colliding particles.

We compared our scattering amplitude, Eq. (16), with the experimental data of the K+p differential

cross section taken from Ref.13 and show the results in Figs. 1 and 2. In the case of the kaon-nucleus

scattering, the comparison to our calculation utilizing eikonal scattering amplitude, Eq. (2), with the

experimental data 9 for C 12are displayed in Figs. 3 and 4. The optical potentials coming from the above

informations for K + and K- projectiles and C 12target are shown in Figs. 5 and 6.

The total cross sections of the K ±- proton system may be fitted by the following form:

or = ob( ob)+ Z' (ePb) (18)

i

where PLKabis the corresponding kaon laboratory momentum in GeV/c and the unit of a is mb. The

typical form ofgi (Pt_Kb) is that

149
mi (19)

gi (pLKab) = [(Pn, - b)2]2 ni +1

where PRi is the resonance momentum of the ith peak and mi and ni are the constants which have to be

determined from the data.

Eq. (18) actually corresponds to the superpostion of Breit-Wigner formulae where Ob (/Or'_b) is a

non-resonant background. Our fitting constants in the resonance energy range are displayed in table

II. The background functions are fitted by

ab (PtgaKb) = 23.2e -°°°3e_'x (20)

for K- p scattering and

1

C,b(/OKab) = 16.8 (21)

for K + p scattering. When I_Kab is less than 0.7 GeV/c in K- p scattering, we used the following function:

aT = 172.38e -2'°( re_ + 0.1) (22)

In the more high energy region, the empirical formulae for Kp system are given by

Or = 20.18 + __24"63 (23)

when p_ab > 20GeV/c in K- p system and

aT = 16.8 0.22 (24)

when PLrab > 5GeV/c in K + p system.

The fitting formulae which we used for K -_ - Nsystems are Eq. (25) through (28).

For K-- n scattering,

aT =-1033.0 + 1060.0PLK ab-°'°3 + 28.01npLK ab (25)

when tCK°b > 2.5GeV/c and

or = 23.91 + 17.0e -( fete' - 1°)2/°12 (26)

when PLK_b< 2.5GeV/c. And for K + n scattering,

or = 18.4 + 175.0pLKab-7"a5+ 0.21n2t_Kab -- 0.751niCKab (27)

150

=_.

[-

=

i
when PLKab >--2.5GeV/c and

oT = a (18.0 + 3.0e -(xfl_ - 1"2)2/°"°8) (28)

when I_rab < 2.5 GeV/c. The constant a is equal to 1 when PtgaKb>--1.2GeV/c and 0.94 when

t_K ab < 1.2GeV/c.

We determined the fitting formulae of slope parameter, B, in the range of

0.1 _< [ t I -< 0-4(GeV/c) 2. The resultant formulae are shown below.

B = 7.3 (29)

for K- p scattering and

B = -24.3 + 7.01n (s + 50.0) (30)

forK + p interaction. The square of the momentum transfer t (GeV/c)2,, and the invariant mass squared,

s(GeV/c2), are two convenient Mandelstam variables.

Our parameterized formulae, a, for K- p and K + p scattering, respectively, are as follows.

a = - 0.32 sin{ PLrab -- 0.2)} (31)

1.0 + 0.9/_r ab'

for K- p scattering and

a = - 1.86e-(_b _ 0.1)2/0.41 --0.44 (32)

for K ÷ p interaction where e_ab is the kaon laboratory monentum in GeV/c.

The total and absorptive cross sections for K +- -AI z7 scattering using the harmonic well and

Woods-Saxon single particle densities are shown in Figs. 7 and 8. Although we cannot evaluate the exact

error due to the scaricty of experimental data, we expect that our calculation reasonably represents the

situation, because of the good agreement between our calculation and the experimental data of other

quantities such as the differential cross sections of kaon-proton and kaon-nucleus scattering.

In case ofK + p scattering our scattering amplitude was quite reasonable. Moreover, the calculation

of the differential cross section gave us more accurate result as the energy of projectile went higher.

For K _ -C 12scattering the differential cross sections are estimated lower than the experimental results.

It may be natural because we used a very simplified, non-relativistic optical potential. At the very forward

angle the experiments show us the differential cross sections rise very rapidly, but the calculations

converge smaller values. This comes from the fact that we have neglected the contribution of Coulomb

interaction which is the long range interaction in the optical potential.

The total and absorptive cross sections for K- - nucleus scattering were bigger than those of K+

- nucleus scattering. This, of course, indicates that K- meson interacts with nucleons stronger than

K+ meson. According to the quark model, K+ resonant peak requires the formation of five-quark

151
objects which have never been found, but the K- N interactions are so strong that the cross sections

are roughly comparable to those of nucleon-nucleon scattering.

K + -nucleus total cross section shows almost perfect linear dependence of A and K- - nucleus

total cross section also represents linearity of A at high energies, but exhibits a little complexity at low

energies. Other things that we can give attention to are that the absorptive cross section ofK + - nucleus

scattering depends on A °s2 linearly, but K- - nucleus absorptive cross section does not show fairly good

linear dependence of A °82 as in the case of total cross section at relatively low energies. The linear

dependence of A °82 of absorptive cross section tells us that the nucleus is not perfectly black to the

kaon projectile.

The results of this work will be used in the hadron transport computer code at NASA Langley

Research Center (Ref. 18).

References

1. Watson, K.M., Phys. Rev. 1953, 89, 575

2. Frank, R.M.; Gammel, J.L.; Watson, K.M., Phys. Rev. 1956, 101,891

3. Watson, K.M., Phys. Rev. 1957, 105, 1388

4. Wilson, J.W., A Dissertation for Ph.D, 1975

5. Wilson, J.W.; Phys. Lett. B 1974, 52, 149

6. Wilson, J.W.; Townsend, L.W., Can. J. Phys. 1981, 59, 1569

7. Buck, W.W.; Norbury, J.W.; Townsend, L.W.; Wilson, J.W., Phys. Rev. C 1986, 33, 234

8. Aguilar-Benitez, M. etal., "Particle Properties Data Booklet", North-Holland, Amsterdam,

April 1986

9. Marlow, D.; Varnes, P.D.; Colella, N.J.; Dytman, S.A.; Eisenstein, R.A.; Grace, R.;

Takeutchi, F.; Wharton, W.R.; Bart, S.; Hancock, D.; Hackenberg, R.; Hungerford, E.;

Mayes, W.; Pinsky, L.; Williams, T.; Chrien, R.; Palevsky, H.; Sutter, R., Phys. Rev. C

1982, 25, 2619

10. Siegel, P.B.; Kaufmann, W.B.; Gibbs, W.R., Phys. Rev. C 1984, 30, 1256

11. Goldberger, M.L.; Watson, K.M., "Collision Theory", John Wiley & Sons, New York,

1964

12. Borkowski, F.; Simon' G.G.; Walther, V.H.; Wendling, R.D., Z. Phys. A 1975, 275, 29

13. Price, LeRoy R.; Barash-Schmidt, Naomi; Benary, Odette: Bland, Roger W.; Rosenfeid,

Arther H.; Wohl, Charles G., "A Compilation of K+N Reactions , Lawrence

Radiation Laboratory, University of California, Berkley, California, UCRL-20000

K+N, Sept. 1969

152

=

__=
14.

15.

16.

17.

18.

Giacomeli, G., "Total Cross Section Measurement", Pergamon Press, Ltd, New York,

1970

Baldini, A.; Flaminio, V.; Moorehead, W.G.; Morrison, D.R.O., Landolt-BSrnstein

New Series 1/12a and 1/12b, "Total Cross-Sections for Reactions of High Energy

Particles", Springer Berlin Heidelberg, 1988

Perl, Martin L., "High Energy Hadron Physics", John Wiley & Sons, Inc., 1974

Lusiguoli, M.; Restignoli, M.; Violini, G.; Snow, G.A., Nuovo Cimento 1966, 45,A792

Wilson, J.W.; Townsend, L.W.; Chun, S.Y.; Lamkin, S.L.; Ganapol, B.D.; Hong, B.S.;

Buck W.W.; Khan, F.; Cucinotta, F.A.; Nealy, J.E., "BRYNTRN; A baryon transport

model", NASA TP-2887, Feb. 1989.

Table I.

Nuclear charge distribution parameters from electron scattering data taken from Ref. 8.

Nucleus Distribution y or tc (fm) a or R (fm)

H 2 0 1.71

He 4 HW 0 1.33

Li 7 HW 0.327 1.77

Be 9 HW 0.611 1.791

B 11 HW 0.811 1.69

C12 HWHW 1.247 1.649

N14 HW 1.291 1.729

016 HW 1.544 1.833

Ne 2° WS 2.517 2.74

A127 WS 2.504 3.05

Ar 4o WS 2.693 3.47

Fe56 WS 2.611 3.971

Cu64 WS 2.504 3.05

Br80 WS 2.306 4.604

AglO8 WS 2.354 5.139 WS

Ba138 WS 2.621 5.618

Pb 2°8 2.416 6.624

153
Table II.

Kaon-nucleon total cross section parameters

i Pg. (GeV/c) mi (rob) ni (GeV/c)

ICp

1 0.8 11.

2 1.05 27.

3 1.60 9.

4 2.30 4.

5 3.50 4.30

0.21

0.2

0.35

1.

2.

K+p 1 0.80 -4. 0.40

2 1.30 2.50 1.

q_

2.0

1.5

1.0

0.5

0.0

I''-'' I '' ' ' I ' ' ' ' I

I I i I

1 0.8 0.6 0.4 0.2 0

COSOc.m.

Figure 1. Differential cross section of K+p scattering at 503 MeV

154

|

|
0

>

aD

b

t°e I ' ' I ' I .... -

I I I I I I i I I J I I I I

i0 1

- -r"

tO o

i0-i

10-2

10-3 , J , , J.. , , , , i

0 0.5 1 1.5 2

t (GeV/c)2

Figure 2. Differential cross section of K+p scattering at 6324.9 MeV

155
3

I0 2

101

i0 0

i0--i

10-2

10-3

10-4

Figure 3. Differential cross section of K+C 12 scattering at 800 MeV/c

i

i

156

=

=
"E"

3

103

102

tO 1

100

10-1

10-2

10-3

10-4

0 10 20 30 40

8 C. i"D.

50

Figure 4. Differential cross section of K-C 12scattering at 800 MeV/c

157

•..._ )
OJ

v

v

v

[..,

3O

2O

10

0

-10

-2O

-30

0

t ! I t I I I

m

1 2 3 4 5

r(tm)

i I L I

Figure 5. Optical potential for K+C 12 at 800 MeV/c

158
>

0)

v

g.,

I

:>

o.)

E

40

20 --

0 -

-20

L

-40 --

-60 --

-80 i

0

I 1 I

I I I

I '''' I ''' ' I'' ' ' I

I I I I

I,,,, I,, ,, I,,,, I,,,

1 2 3 4

r(tm)

t _

5

Figure 6. Optical potential for K "C12at 800 MeV/c

159
400

30O

20O

i00

0

[ [ i l I I .! "I ! L ! Z.l I ! ! I I • ! 1 I I

102 103 10 4

k(+) Lab energy(MeV)

Figure 7. Total (solid) and absorptive (dashed) cross sections for K+A127

E

160
600

400

200

0

I I { | I I I | I I I I I I I ] • I I I I I ]

10 2 10 3 10 4

k(-) e rgy( V)

Figure 8. Total (solid) and absorptive (dashed) cross sections for K _l127

161
N9 1 - 28 087

PHASE CONJUGATION BY DEGENERATE FOUR WAVE MIXING IN

DISODIUM FLUORESCEIN SOLUTION IN METHANOL*

H. Abdeldayem, P. Chandra Sekhar, P. Venkateswarlu and M.C. Geroge

Department of Physics

Alabama A&M University

Normal, Alabama

ABSTRACT

Organic dyes are known to show resonant type of nofi_l'inear optical properties, including phase

conjugation. In b_" present work, disodium fluorescein in methanol is used as an organic nofirlinear

medium for degenerate four wave mixing at 532 nm to see the intensity dependence of the phase

conjugate signal at different concentrations of the solution. It is observed that the maximum reflectivity

of the signal occurs in a concentration range of 5 x 10.3 g/cm 3 to 1.2 x 10 .2 g/cm 3. It is also observed that

the intensity of the signal drops suddenly to less than half of its maximum outside the concentration

range mentioned above.

An investigation of the phase conjugate signal intensity by changing the delay time between probe

signal and the forward pump signal is also examined.

Briefly discussed is the possibility of population grating in dye liquids as a source of enhancing the

third order susceptibility besides the other techniques mentioned in reference*.

The experiment is done by beam splitting the second harmonic (532 nm) of Nd:YAG laser,

Q-switched at 20-pulses/sec. (pulse width _Sns and -7200 mJ per pulse).

l'

L

Z

=

*Supported by NASA Grant No. 2-356-14-3300-390.

162

=

E
PHASE CONJUGATION BY DEGENERATE FOUR WAVE MIXING IN

DISODIUM FLUORESCEIN SOLUTION IN METHANOL

Introduction

Phase conjugation by degenerate four wave mixing (DFWM) has shown considerable promise as

a technique of generating high fidelity phase conjugate signals. The only difficulty which limits its use

is its low efficiency. Because of that, a great deal of research work is concentrated on finding the proper

and most efficient nonlinear media with the highest possible third order susceptibilities to improve the

efficiency.

In an earlier experiment 6, Caro and Gower obtained a DFWM signal which decreased and

vanished if the path difference was greater than the coherence length, showing that their signal was

purely due to DFWM. On the other hand, Basov et. als obtained stimulated Brillouin Scattering from

two pump beams even with a path difference much larger than the coherence length of the laser. Seeded

.... . • • 9

Bnlloum Scattering has also resulted m phase conjugahon of two incoherent beams.

Recently, considerable interest has been generated in the study of organic dye solutions as efficient

nonlinear media. A class of highly efficient organic dyes with a wide and flexible range of operating

conditions has become known.

The purpose of our experiment is to pick up an organic dye as a nonlinear medium for our DFWM

experiments to investigate the possible mechanisms which are responsible for phase conjugation.

Disodium fluorescein was chosen among several other organic dyes as a candidate for our experiment

based on the idea that it showed a relatively strong phase conjugate signal, using a frequency doubled

Nd:YAG laser (532nm), Q-switched at 20 pulses/sec (pulse width -8 ns and -200 mJ/pulse), although

its absorption spectrum in ethanol shows only a small tail beyond 525 nm.

Mechanisms for DFWM:

When mutually coherent laser beams interfere in an absorbing medium, the interference pattern

heats the medium nonuniformly. The nonuniform heating causes density variations in the medium,

consequently an index of refraction grating, which Bragg scatters a read beam into the conjugate wave

signal, is formed.

It is believed I that in the initial few picoseconds after the energy has been deposited, the medium

has not yet had time to expand, the density is thus constant and any index change is due to the intrinsic

variation in the index of refraction with temperature at constant density. Subsequently, sound waves

produced by the nonuniform heating propagate across the medium and begin the expansion process.

Finally, the sound waves damp out and the usual thermally induced grating _ becomes dominant.

Besides the thermal grating mechanism, there are other possible mechanisms which are also

responsible for producing nonlinear susceptibility like saturable absorption 3 and the optical Kerr

effect 4.

163
In addition to these different mechanisms, one may also examine the energy level structure of a

typical dye molecule, shown in Fig. 15, where the first excited singlet state is generally higher than the

lowest triplet state. Since dye molecules are large, the vibrational and rotational levels in any electronic

state are too numerous and too closely spaced, and the spread of these levels is large. Further, the

excited singlet states are not well separated from one another. All the dye molecules in the excited states

relax quickly by nonradiative interactions to the lowest singlet state $1. This is the only state which has

been observed to fluoresce and has, in most of the cases, lifetimes of the order of a few nanoseconds.

The upper singlet states are not known to fluoresce and they relax to the $1 state in times of the order

of picoseconds. There are two other competing processes for relaxation of the molecules from $1 in

addition to the spontaneous emission to the ground state. Although singlet to triplet state transitions

are generally forbidden, relaxation to triplet levels is still possible. The triplet state T1 has a lifetime of

a few microseconds which is large compared to the life time of the $1 state.

The possible excitation to the triplet state TI, which is of a relatively longer lifetime, may result in

a population grating which should be considered as an extra mechanism which will contribute to the

third order nonlinearity and Bragg scattering of the phase conjugate signal.

Experiment

The experimental set up is as shown in Fig. 2 in which the frequency doubled Q-switched Nd:YAG

laser (532 nm) is split to obtain -20% as a probe beam A3 and the rest as two equally intense and

counter propagating pump beams A1 and A2. The phase conjugate signal is seen as a beam counter

propagating to A3, the intensity of which is first observed at different concentrations of the disodium

fluorescein in methanol in a I cm thick cuvette. The experimental results obtained are as expected (Fig.

3). At relatively low concentrations the number of the dye molecules are not enough to form a strong

grating to reflect the signal. As the concentration increases to the optimum one, -7 x 10.3 g/cm 3 in this

specific case, the grating is good enough to reflect a relatively powerful phase conjugate signal. At higher

concentrations up to 20 x 10.3 g/cm 3 the curve shows a weaker phase conjugate signal.

The decay in the phase conjugate signal at high concentration can be attributed to two factors:

(1) The fluorescence quenching where the fluorescence emitted by some molecules are absorbed by

others in the medium. This contributes to heating the medium quickly. The rise in temperature inhibits

the formation of the grating and hence the medium becomes less efficient. (2) The heat increase in the

cell causes the medium to boil. The hydrodynamic motion of the liquid tends to wash out the grating

and reduces its efficiency.

The dependence of the phase conjugate signal on the delay time between the probe and the

forward pump is shown in Fig. 4. Since the phase conjugate signal is thought to be due mainly to the

grating which is formed by the interference pattern of the two coherent beams, A1 and A3, one expects

that if the path difference between the beams is larger than the coherence length of the laser, which is

-1 cm (0.03 ns delay time), the signal should vanish. Surprisingly, the phase conjugate signal is detected

even for a path difference of more than 360 cm (12.0 ns delay time) (Fig. 5). This result is probably

attributable to the presence of stimulated scattering. Similar results are obtained for the same sample

in a smaller cell of I mm thickness. Preliminary experiments with a single beam show that stimulated

back-scattering signals can be obtained from pure ethanol, acetone and methanol. Experiments on

stimulated scattering in dye solutions are now in progress to clarify this situation.

164

L

F
In summary, we discussed a population grating as a mechanism for the index grating in liquids,

along with the previously mentioned ones. In addition, our experimental results show that the phase

conjugate signal through DFWM could be superimposed on a signal due to stimulated scattering.

Acknowledgments

The authors wish to thank NASA for a grant and a fellowship (Grant No. 2-356-14-3300-390).

References

1. R.C. Dcsai, M.D. Lcvenson and J.A. Barker, Phys. Rev. A27, No. 4, P.1968 (1983)

2. G. Martin and R.W. Hellwarth, Appl. Phys. Lett., Vol. 34, p.371 (1979).

3. R.L. Abrams and R.C. Lind, Opt. Lett., Vol. 2, P. 94 (1978); Opt. Lett. Vol. 3, p. 205

(1978).

4. D.M. Bloom and G.C. Bjorklund, Appl. Phys. Lctt. Vol. 31, p. 592 (1977)

5. P. Venkateswarlu, M.C. George, H. Jagannath, Y.V. Rao, G. Chakrapani and A.

Miahnahri, A report on Optical Studies in Laser Dyes, submitted to Ballistic Missile

Defense Systems Command, Huntsville, Alabama 35807, from Alabama A&M University,

Physics Department, October, 1985.

6. R.G. Caro and M.C. Gower, Appl. Phys. Lett. 39 (11) December 1981.

7. R.G. Caro and M.C. Gower, IEEE J. of Quantum Electronics, Vol. QE-18, No. 9,

September, 1982.

8. N.G. Basov, I.G. Zubarev, A.B. Mironov and A. Yu Okulov, Soy. Phys. JETP 52(5). P. 847,

November, 1980.

9. T.R. Loree, D.E. Watkins, T.M. Johnson, N.A. Kurnit, and R.A. Fisher, Opt. Lett., Vol. 12,

No. 3, P. 178, March, 1987.

165
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N91-28088

POLAROGRAPHIC STUDY OF CADMIUM

5-(Hydroxy-2- (Hydroxymethyl)-4H-Pyran-4-one COMPLEX

Ray F. Wilson and Robert C. Daniels

Department of Chemistry

Texas Southern University

Houston, Texas

ABSTRACT

A polarographic study _as _e_n _rrle_[out on the products formed m the interaction of cadmium(II) with 5-Hydroxy--_-(Hydroxymethyl)_'_4H-Pyran-4-one, using varying conditions of pH, supporting electrolyte, and concentration. Measurements using the differential pulse method show that

cadmium(II) exhibits a molar combining ratio of complexing agents to cation ranging from 1 to 1 to 3

to 1 depending on the pH and the supporting electrolyte employed.

171
POLAROGRAPHIC STUDY OF CADMIUM

5-(Hydroxy-2- (Hydroxymethyl)-4H-Pyran-4-one COMPLEX

Introduction

Polarography has been applied variously to the quantitative determination of cadmium in different

supporting electrolytes (1). The presence of relatively high concentrations and toxicity of cadmium in

process wastewaters which contain phenolic type compounds resulting from coal gasification and

liquefaction (1,2) gives rise to a need to study further the coordination chemistry of this metal. Further,

the study of the polarography of cadmium could add to the understanding and ascertainment of this

element as a possible trace metal in selecte._l lunar like materials. A polarographic study of the

interaction of selected organic complexing agents should add to the understanding of cadmium solution

chemistry.

This study was undertaken to investigate the formation constants and determine the stoichiometry

in a solution of the interaction of cadmium(II) with 5-Hydroxy-2-(Hydroxymethyl)-4H-Pyran-4-one,

commonly called kojic acid. The polarographic data obtained using the differential pulse method

revealed that the cadmium(II) exhibits complexes ranging from 1 to 1 to 3 to 1 molar ratio of complexing

agent to cadmium. The formation constants for the cadmium complexes are supporting electrolyte and

pH dependent.

At sufficiently negative potentials, simple and complex ions of cadmium are reduced at the

dropping mercury electrode and dissolve in the mercury to produce an amalgam on the surface of the

mercury drop. For a reversible electrode reaction involving complex metal ions, Kolthoff and Lingane

(3) have shown that the half-wave potentials of metal ions are generally shifted to more negative values

by complex ion formation. Further, these authors (3) have derived the relationship for calculating both

the formation constant and the coordination number for metal complexes based on this negative shift

as a function of the concentration of the complexing agent employed. Thus, according to Kolthoff and

Lingane (3) reactions

M n+ + ze = M (n-z)+

and

M n+ + xR -y = MRx (n-xy)

give

-0.0591 logKf -0.0591x log CR (1) E_° - Ev_® = z z

where M *+, M (n-Z)+, R -y, MRx (n-,_,), Ev_0, E_., and Kf, respectively represent the metal ion in oxidation state one, metal ion in state two, complexing agent, metal complex (where x is the coordination

number of the metal ion), halfwave potential for the complex, half-wave potential for the simple metal

ion, and the formation constant for the complex.

172

F

Z

=
Theory of Phenolic Differential Polarography

Phenolic type compounds are generally strong complexing reagents because in the ionized form

they have three pairs of electrons and a negative charge. Further, the stability of metal phenol complex

ions is changed markedly by adjusting the pH of the solution. According to the law of mass equilibrium

the ionization of phenol type compounds in aqueous media may be represented as follows:

RHi = Ri-+ iH + (2)

and correspondingly, phenolic metal complex ion formation can be written in the following manner:

M n+ + xRHi = [MRxl C.-ix)+ + ixH + (3)

The formation constant expression for the above reaction is

Kf = ([MRx] (n-ix)*) (H+)ix (4)

(M n+) (RHi) x

For a reversible reduction, at the dropping mercury electrode, to the metallic amalgam state of a

complex ion of a metal that is soluble in mercury, one may represent the reaction as follows:

[MRx] (n-ix)+ = Mn++ xR i- (5)

Mn++ Hg + ze = M(Hg) (6)

[MRs] C"-ix)++ Hg + ze = xRi-+ M(Hg) (7)

where equation 7 is the sum of equations 5 and 6.

Assuming the activities of mercury and the amalgam to be constant or unified and that molar

concentrations may be employed in place of activities in dilute solutions within a moderate concentration range, one may reasonably propose that for phenolic complex ion solutions at constant temperature

Evz = f(lnCR, pH) (8)

where CR and CH are the molar concentrations of the complexing agent and hydrogen ion respectively.

Thus within the range of experimental data

( OEv2 _dCR + (OEv_ dpn

dEv2 = _01n-i-ff_RJpn _o--p--ff]INCR" (9)

Kolthoff and Lingane (3) have shown previously that the effect of complexing agents on the halfwave potential at the dropping mercury electrode is generally to make the half-wave potential more

negative. Similarly, based on equations 5 and 6, respectively, the reduction of the simple metal ions and

the corresponding complex phenol metal ion at the dropping mercury electrode, one may express the

simultaneous effect of complexing agent and pH on the half-wave potential as follows:

173
Evz"= F__ 0.0591 log (IMRx] (n-i_)÷) (10)

z (Ri-)x

Ev_' = E_ 0.0591 log (M n+) (11)

Z

Ev,z° - Evz' = F__ - F_ 0.0591 log ([MR,,_ ("-ix)*) (12)

Z (Ri-)x (M.+)

where the subscripts c and s refer to the complex and simple metal ions, respectively, and the superscript

o refers to the standard potential of each reaction. The substitution of the molar concentration ratio

of the complexing agent ion from equation 4 or 4a into equation 11 gives

Ev_c - Evz' = F_ff - F__ 0.0591 log Kr (RHi) _ (13)

z (H+)ix (Ri-)x "

upon combining the F_ -F__ and the -0.0591 logKr terms in equation 13, one obtains equation 1:.

E_ °- E_'=-0.0591 log Kf-0.059I log (RHi) x (14)

z z (R i-) (H+)i_

where

E1/z c - Et,'z' = -0.0591 log Kf -0.0591 xlog (RHi) -0.0591ix log 1 (15)

z z (R i-) z (H +)

Evz ° - Evz' - -0.0591 log Kf -0.0591 xlog _ -0.0591ix pH (16)

Z z (R i-) z

Based on the above equation both pH and concentration of the complexing agent will cause the

half-wave potential, E_ _,of phenolic complexes to shift to more negative potentials. Moreover, it should

be noted that neither the concentration of the metal complex nor the simple metal ion is a factor in

equation 15; thus Evz c is not a function of these ions. However, equation 4 shows that the ratio of the

concentration of complex to simple ion

[MR"l("-ix)+ = Kr (RHi)_

(M n+) (H+) ix

(4a)

is proportional to the ratio of complexing agent to hydrogen ion. Thus Ev_c is an implicit function of

the above ratio and not the concentration of the complex or simple metal ions. If the stability of the

phenolic complex ion is a function of pH, then, based on equation 15, as the pH of a series of solutions

containing a fixed amount of complexing agent approaches an upper limiting value, the Ev2 of the

solution should approach a limit of maximum half-wave potential E_cm. Similarly, as the pH of the

series approaches a lower limit, the Ev2 of the solutions should approach a limit of minimum half-wave

potential, Ev_sm), the Ev2 of the simple metal ion. At any constant pH, the magnitude of the quantity

E_(cm) - Evz(sm) essentially corresponds implicity to the relative amounts of the complex and simple

174
metalionsinthesolution. The molar concentrations of complex ions and simple ions should be equal

at OE_/0pH 2 = 0.

Firstly, the above discussion and theory show that the complexing agent and the pH simultaneously

cause the half-wave potentials of phenolic complex ions to shift to more negative potentials, and,

secondly, that differential polarographic study of the complex ion chemistry of these ions requires

carefully controlled conditions of pH in excess, complexing agent concentration. A third consequence

of the aforementioned theory is that a plot of Evzc - E_s or E_c vs. pH should give a graph with

asymptotic lower and upper limits, a plot of d(AEv_)/dpH vs. pH should give a parabolic plot, and a plot

of d2(AEvz)/dpH 2 vs. pH should give a graph with both a positive and a negative area.

In order to test the aforementioned theory, a cadmium complex in our laboratory was selected for

study.

Experimental

Apparatus and Reagents. All polarographic measurements were obtained at 25°C employing a

Sargent-Welch Voltammetric Analyzer Model 7000 Microprocessor. All data were collected using the

differential pulse method (2) over the range -0.300 to -0.900 volt using a scan rate of 0.002 volt per

second, a drop time of one second, and an excitation energy of 0.02 volt. All solutions were purged with

N2 for 10 minutes.

Standard solutions of cadmium(II) chloride in water were prepared from EM Science atomic

absorption standards traceable to National Bureau of Standards. All other reagents employed in this

study were reagent grade chemicals.

The effect of complex formation on the polarographic wave of the cadmium(II) complex was

determined as follows: To a series of 50 mlvolumetric flaskswere added the desired volumes of standard

cadmium(lI) solution, the volume supporting the electrolyte required to give optimum buffer concentration, and varying concentrations of the chelating agent, and the solutions were diluted to volume

with water. Na2 B4 O7 supporting electrolyte was employed, and dilute aqueous NaOH or HNO3 was

added drop wise prior to dilution to obtain the final desired pH. These solutions show reproducible

differential pulse peaks (used in place of half-wave potentials) within the region of -0.300 to -0.900

volts.

The kojic acid was purified as follows: The chelating agent was recrystallized after being dissolved

in boiling ethanol mixed with finely divided charcoal. This solution was filtered while hot and allowed

to recrystallize in a refrigerator at about 5°C. After discarding the alcohol, the chelating agent was dried

and stored in a dessicator. The white crystallized solid gave a sharp melting point at 153°C.

Discussion

Differential pulse polarographic measurements obtained in these studies show that cadmium(H)

reacts with excess chelating agent to form a 1 to 1, 2 to 1 and 3 to 1 cadmium to reagent products. The

ionic strength and the activity coefficients of the reducible complex and the complexing agent were

175
assumed to be constant over the concentration range studied. Thus on rearranging, equation 16

becomes

• Z

log Ke = --xlogCR/Ck- -- ix pH _ (Ev_ - E_) (17)

and on differentiation, equation 18 is obtained since Evz= for the simple metal ion is a constant.

AE_ Alog CR/C_t- -0.0591ix

Ap--I:i- + 0.0591 x ApH = z

(18)

at constant CR/CkAE_ _ -0.0591ix

ApH z

(19)

and at constant pH, equation 16 becomes equation 1

z

logKf = xlog CR + 0.0591 (Ev_ -E_)

which was used to calculate the formation constant for the cadmium(II) complexes. Since Evz mfor the

simple metal ion is a constant, knowing that cadmium(II) is reduced to cadmium metal at the dropping

mercury electrode (4) corresponding to a two electron reduction, one can calculate x the molar

combining ratio of complexing agent to the central metal ions for varying conditions of pH supporting

electrolyte, etc.

Graphical and tabular data are shown in Figures 1 through 5 and Tables 1 through 9 for the

systematic study of several cadmium(II) kojic acid complex ions. These results indicate that the

composition and stabilities of the cadmium complex ions formed in these interactions, in the presence

of excess chelating agent, depend on optimum conditions of pH and the nature of the supporting

electrolyte. Figure 1 shows that all of the cadmium complex ions studied are reversibly reduced at the

dropping mercury electrode. Graphical representations (Figure 2) and the data in Tables 1, 2, and 3

indicate that the stability and molar combining ratio of kojic acid to cadmium in ammonium hydroxideammonium chloride supporting electrolyte decreases as the pH increases. At pH = 8.38, the molar

combining ratio of kojic acid to cadmium is 2 to 1. At pH >_-9.88, the molar ratio is 1 to 1.

In an attempt to obtain some understanding of the separate ligand ion effect in the aforementioned

interactions, sodium borate was selected as a non-competing supportingelectrolyte. The data in Tables

4, 5, 6, and 7 and Figure 3, employing sodium borate as a non-complexing supporting electrolyte, show

that the molar-combining ratio of kojic acid to cadmium is 2 to 1 and does not depend on the pH of the

solution in the pH range 9.8 to 10.8. The composite of these data, Tables 1 through 7, suggest that the

ammonia molecule and/or the hydroxide ion may compete with kojic acid when relatively large

concentrations of the three are present in the same solution. Data for the effect of pH at constant

complex ion concentrations in borate medium are shown in Table 9 and Figure 5 as predicted.

The complexing effect of ammonium hydroxide on cadmium(II) in sodium borate supporting

electrolyte is shown in Table 8 and Figure 4. Based on the magnitude of the formation constants in the

two support-electrolytes, in the absence of knowing the exponential order of the mass law equations,

176
the cadmium ammine complex appears to be less stable than the cadmium kojic acid complex. The

proposed cadmium ammonium hydroxide interaction in sodium borate supporting electrolyte is

Cd +2 + 3NH4OH = [Cd(NH3) 3 (OH)] + + H + + 2H20

which indicates that cadmium exhibits a coordination number of 4 and a combining ratio of 3 to 1 of

ammonium hydroxide to cadmium. Further, assuming kojic acid to be a bidentate ligand, one would

expect kojic acid to cadmium interaction to give a combining ratio of 2 to 1 corresponding to a

coordination number of 4. At a pH _<8.38, in ammonium hydroxide-ammonium chloride buffer, the

combining ratio of kojic acid to cadmium is 2 to 1. In the interval 8.38_<pH-<9.88, non-whole number

combining ratios are obtained which suggest a mixture of complex species, resulting from competing

complexation between kojic acid and ammine and/or hydroxide. At a pH-<9.88, a combining ratio of 1

to 1 of kojic acid is obtained which suggests that the composition of the complex becomes constant.

Acknowledgment

The authors wish to express their sincere thanks to the United States National Aeronautics and

Space Administration and the U.S. Department of Energy for grants which supported this study.

References

1. Drummond, C.J., Noceti, R.P., et. al., _, 40, 26-32 (1985).

2. Drummond, C.J., Noceti, R.P., et. al., _, 1, 73-78 (1982).

3. Kolthoff, I.M. and Lingane, J.J., "Polarography," 1, 2nd., Interscience Publishers,

N.Y., (1952), pp. 189-234.

4. Rubinson, K.A., "Chemical Analysis," Little, Brown, Con., (1987), p. 413.

5. Meites, L., "Polarographic Techniques," Interscience Publishers, N.Y. (1967), p. 268.

6. Kolthoff, I.M. and Lingane, J.J., "Polarography," 2, (1952) p. 475-511.

177
TABLE 1

Cadmium(ll)

Micromolar

Kojic Acid

Millimolar

Diffusion Half-Wave Formation

Current E_, Volts Constant

Nanometers

89 O 34

89 0.79 34

89 1.74 33

89 3.16 35

89 5.01 34

89 iO.00 34

89 25.00 34

89 54.95 34

-0.623

-0.610 5.74 x 105

-0.630 5.72 x 105

-0.645 5.57 x 105

-0.657 5.66 x 105

-0.674 5.36 x 105

-0.698 5.52 x 105

-0.717 5.07 x 105

Supporting Electrolyte:

Coordination Number:

0.08 M NH3/NH4CI Avg. Kf

2 pH: 8.38

= 5.52 × 105 -+ 0.24

TABLE 2

Cadmium(ll)

Micromolar

Kojic Acid Diffusion Half-Wave Formation

Millimolar Current

E,, Volts Constant

Nanometers

89 0 34 -0.666

89 0.79 35 -0.670

89 1.74 34 -0.679

89 3.!6 34 -0.687

89 5.01 34 -0.693

89 I0.00 33 -0.702

89 25.00 34 -0.714

89 54.95 34 -0.724

Supporting Electrolyte: 0.2 M NH3/NH4CI Kf = 1.67 x 103 +

Coordination Number: l pH: 9.88

I •74 x 103

I 58 x 103

i 62 x 103

i 66 x 103

1 66 x 103

1 70 x 103

1 70 x 103

0.05

178
TABLE 3

Cadmium(ll) Kojic Acid Diffusion Half-Wave Formation

Micromolar Millimolar Current E_, Volts Constant

Nanometers

89 O 34 -0.704

89 0.79 34 -0.688 3.63 x

89 1.74 33 -0.698 3.63 x

89 3.16 34 -0.706 3.70 x

89 5.01 34 -0.712 3.72 x

89 i0.OO 34 -0.721 3.77 x

89 25.00 34 -0.733 3.80 x

89 54.95 34 -0.743 3.82 x

102

102

IO 2

102

102

102

102

Supporting Electrolyte: O.4M NH 3 - NH4CI Kf = 3.72 x 10 -2 _ 0.006

Coordination Number: 1 pH: 10.15

TABLE 4

Cadmium(ll) Kojic Acid Diffusion Half-Wave Formation

Micromolar Millimolar Current EL, Volts Constant

Nanometers

89 O 34 -0.527

89 5.01 33 -0.572 1.33 x 106

89 13.80 33 -0.598 1.34 x 106

89 20.40 34 -0.607 1.27 x 106

89 50.10 35 -0.630 1.23 x 106

89 IOO.OO 34 -0.647 1.17 x 106

89 199.50 34 -0.665 1.20 x 106

Supporting Electrolyte: 0.04 M Na2B407 Avg. Kf = 1.25 × 106 _ 0.07

Coordination Number: 2 pH: 7.00

179
TABLE 5

Cadmium(ll) Kojic Acid Diffusion Half-Wave

Micromolar Millimolar Current E1⁄2, Volts

Nanometers

Formation

Constant

89 0 34 -0.

89 5.01 34 -0.

89 13.80 34 -O.

89 20.40 35 -0.

89 50.10 34 -0.

89 i00.00 34 -O.

89 199.50 34 -0.

535

614

640

650

673

691

7O8

•90 x 107

.90 x 107

•90 x 107

•90 x 107

•94 x 107

.84 x 107

Supporting Electrolyte: 0.04

Coordination Number: 2

M Na2B407

pH:

Avg.

8.00

Kf =

1.90 x 107 -+ 0.03

TABLE 6

Cadmium(ll)

Mi cr omo far

Kojic Acid

Millimolar

Diffusion

Current

Nanometers

Half-Wave

E1⁄2, Volts

Formation

Constant

89 0

89 5.01

89 13.80

89 20.40

89 50.I0

89 i00.00

89 199.50

34

34

33

35

34

34

34

-O. 558

-0. 632

-O.658

-0.669

-O. 6 92

-0.7 iO

-0. 727

I.28

1.29

1.39

1.39

1.42

1.34

x 107

x 107

x 107

x 107

x 107

7

x I0

Supporting Electrolyte: 0.04

Coordination Number: 2

M Na2B407 Avg. Kf

pH: 9. OO

= 1.35 x 107 + 0 O6

180
TABLE 7

Cadmium(ll) Kojic Acid Diffusion Half-Wave Formation

Micromolar Millimolar Current E_, Volts Constant

Nanometers

89 0 33 --0.574

89 5.01 34 -0.633 3.98 × 106

89 13.80 34 -0.658 3.69 x 106

89 20.40 35 -0.669 3.98 × 106

89 50.10 34 -0.692 3.98 x 106

89 100.00 33 -0.710 4.08 x 106

89 199.50 34 -0.727 3.86 x 106

Supporting Electrolyte: 0.04 M Na2BaO 7 Avg. Kf = 3.93 x 106 Z O.15

Coordination Number: 2 pH: I0.00

TABLE 8

Cadmium(ll) Ammonium Diffusion Half-Wave Formation

Micromolar Hydroxide Current E1⁄2, Volts Constant

Millimolar Nanometers

89 O 34 -0.544

89 30.00 34 -0.572 3.23 x 105

89 50.00 34 -0.591 3.11 x 105

89 iOO.00 34 -O.618 3.22 x 105

89 150.00 34 -0.634 3.24 x 105

89 200.00 34 -0.645 3.34 x 105

89 251.19 34 -0.654 3.38 x 105

Supporting Electrolyte: 0.04 M Na2B407 Kf = 3.25 x 105 + 0.096

Coordination Number: 3 pH: 9.8 to 10.8

181
TABLE 9

Cadmium(ll)

Micromolar

Koj ic Acid

Mi ii imolar

Na2B407

Millimolar

FH Diffusion

Current

Nanometer

Half-Wave

E1⁄2, Volts

89

89

89

89

89

89

89

89

89

89

89

89

89

89

89

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

13.7

30.0

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Reversibility Plots:

A m pH - 8.00 - O.04m Na2B204 + 89urn Cd(II) + 13.8m Mol Kojic Acid

B m pH - 10.15 - O.0_m Na2B204 + 89urn Cd(II} + lOOm Mol NH4OH

C m pH - 8.38 - O.08m NH3/NH4CI + 89urn Cd(II) + 13.8m .Mol Kojic Acid

Figure 1

183
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Log CR

Effects of Complexing Agent Concentration on the Half-Wave Potential

of Cadmium in 0.4M NH3-NH4CI at (a) pH-8,38; (b) pH-9.SB; (c) pH-IO.15

Figure 2

184
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Effects of Comple'_xing Agent Concentration on the Half-Wave

Potential of Cadmium in 0.04 M Na2B/,O 7 at (a) pH-7; (b) pH-8;

(c) pH-9 and pH-lO

Figure 3

185
m

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Effects of Complexing Agent Concentration on the Hal f-Wave

Potential of Cd(II) in 0.I0 M NH40H

Figure 4

186

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Figure 5

187
N91-28089

PURIFICATION, GROWTH AND CHARACTERIZATION

OF ZnxCdl-xSe CRYSTALS

E. Silberman, A. Burger, W. Chen, D. O. Henderson,

S. H. Morgan, J. M. Springer and Y. Yao

Physics Department

Fisk University

Nashville, TN

ABSTRACW

We report here on.the purification of starting materials which were used in growth of Z_Cdj._e_

(x=0.2) single crystals usin _the traveling solution method (TSM_ Up to 13 cm long single crystals and

as grown resistivities of_ ff2ohm.cm could be achieved. Infra_t and Raman spectra of Z_.2Cdg.8_e

are also presented and dis( ussed. /

!

:, >, tO ,z)

188

E

-i
PURIFICATION, GROWI'H AND CHARACTERIZATION

OF ZnxCdl-xSe CRYSTALS

Introduction

The existence of the ZnxCdl.xSe single crystal system was demonstrated as early as 1951 (1) and

its potential for optoelectronic applications is due to the possibility of obtaining variable energy gaps

from 1.74 to 2.67 eV. The materials are interesting as phosphors for color TV applications (2) and, more

recently, the lasing properties of ZnxCdl.xSe single crystals, for x--0.33, were reported (3).

Growth of medium resistivity crystals of ZnxCdl.,,Se has been demonstrated in the past using the

temperature gradient solution zoning (TGSZ) method (4). Following this development, ZnxCdl.,,Se

has been proposed (5) as an alternate material to CASe for room temperature nuclear radiation

detection because replacement of Cd by Zn in the crystal lattice results in an increased energy band

gap and a higher resistivity material, which is a prerequisite for such an application. Crystal growth using

the traveling solution method (TSM) was sucessfully applied to the growth of tellurides (6,7), resulting

in low contamination and good crystalline perfection. It was therefore interesting to determine the

possibilities of this method in the case of selenides, which involve higher growth temperature and

pressure.

In this paper we present the steps completed in our research program, which include: the

purification of raw materials; the crystal growth using the traveling solution method (TSM), which, to

the best of our knowledge, is the first attempt to use this technique for the growth of selenide crystals;

and the characterization of the as-grown crystals by electric measurements and by Raman and infrared

spectroscopy.

Experimental

a)Purification. CASe commercial reagents (Alfa, 99.999% purity on a metal basis, and General

Electric, electronic grade) were subjected to repeated vacuum sublimations at 700 and 1000°C. Unlike

CA and Zn, Se is not commercially available in high enough purity and therefore we used Se of 99.999%

purity (Johnson Matthey) which was further purified in a laboratory built zone refiner.

b)Crystal growth. Up to 40 g of raw material composed of Zn and Cd having 99.9999% purity

(Cominco), in the desired composition, together with a stoichiometric amount of Se of 99.999% purit_

(Johnson Matthey) were loaded in a quartz reaction ampule. The ampule was vacuum sealed at 10"

torr, mounted in a laboratory designed and built rocking furnace, and then the temperature was

increased slowly (100°C/day) up to 900°C. After two weeks the reaction was completed and the charge

was used as starting material, together with 10% additional Se, in the crystal growth experiment. The

crystal growth ampule had an internal diameter of i cm and was 26 cm long. The crystal growth system

included a three zone furnace mounted on a vertical translational stage. The middle zone was narrow,

(approx. 5 cm) with the highest temperature slowly (IO°C/min) increasing to 1I70°(2, while the upper

and lower zones were kept at 970°C. The ampule was static and the furnace was moved upwards at 0.5

to 2 cm/day.

189
c)Characterization. Samples were prepared by cleaving the crystal along the a or c planes, followed

by grinding and polishing to the desired thickness. Lapping and etching were performed in a solution

containing 10% bromine in methanol. Electric contacts were applied using aquadag paint or by vacuum

evaporation of Au. A SPEX Model 1403 Double Spectrometer and a Coherent Model Innova 90 Ar

laser (514.5 nm, 800 mW) were used to record the Raman spectra. The Fourier transform infrared

spectra were reca_rded in the 400- 4000 cm "1range using a Bomem DA.3 FT-IR spectrometer.

Results and Discussion

The diffuse reflectance infrared Fourier transform (DRIFT) spectra of the raw material, CdSe

powder purchased from two different vendors, have shown the presence of peaks which can be assigned

to the sulphate group. The reaction of CdSO4 with H2Se is one common way to synthesize CdSe, and

the presence of an unreacted residue of CdSO4 could be the explanation for these impurity bands.

DRIFT spectra of repeated vacuum sublimed powders showed that the SO4 2 bands disappeared, due

probably to thermal decomposition. However, the method was probably not sufficiently efficient in

removing the sulphur impurity. CdSe crystals grown using this purification method have shown a new

band appearing at 540 cm "1, which was attributed to sulphur impurity induced modes (8). We have

therefore used the synthesis from Zn, Cd and Se elements as preparation of the starting material for

crystal growth using TSM. Up to 13 cm long single crystals could be grown using the above technique.

Fig. 1 shows an infrared transmittance spectrum obtained from a 0.5 mm thick sample. The absence of

any major band around 540 cm 1 proves that synthesis from elements results in ZnxCdl._Se crystals

having less S impurity. We did not observe a broad band, such as the one seen in the 500 to 1200 cm-1

region in Bridgman grown CdSe (8), which was attributed to infrared absorption by free carriers in nonstoichiometric (Cd-rich), low resistivity crystals. The I-V curve of an as-grown Zn0_Cd0.sSe sample is

shown in Fig. 2. From the slope of the graph we can calculate a resistivity of 6X10 ohm.cm, which is

the highest reported for this class of ternary compounds (4).

The vibrational properties of ZnxCdl.rSe were studied using Raman scattering and the spectra are

shown in Fig. 3. The general features agree with a previous study (9) where crystals were in the x=0.4

to 1 composition range. From Valakh et al. (9) spectra and from our spectra it can be concluded that

ZnxCdl.xSe belongs to the one-mode type of crystals in which the frequency of the LO-phonon changes

continuously versus crystal composition.

More work is under way to calibrate these LO frequencies against actual composition as determined by chemical analysis, which will enable us to use Raman measurements for determinations of

Zn/Cd molar ratio distributions along the crystalline boule.

L

Acknowledgment

The research was sponsored by NASA, Grant no. NAG8-113.

190

z=
References

1. S. Forgue, R. Goodrich and A. Cope, RCA Rev., 1951, 12, 335.

2. W. Lehmann, J. Electrochem. Soc. 1966, 113, 449.

3. J. Khurgin, B.J. Fitzpatrick and W. Seemungal, J. Appl. Phys. 1987, 61(4), 1606.

4. A. Burger and M. Roth, J. of Cryst. Growth, 1984, 70, 7.

5. A. Burger and M. Roth, I.E.E.E. Trans. Nucl. Sci., 1985, 32, 556.

6. R. Triboulet and Y. Marfaing, J. Electrochem. Sot., 1973, 120/9, 1260.

7. R. Triboulet and G. Didier, J. Cryst. Growth, 1975, 28, 29.

8. A. Burger, D. Henderson, S. Morgan and E. Silberman, to be published.

9. M. Ya. Valakh, M. P. Lisitsa, G. S. Pekar, G. N. Polysskii, V. I. Sidoprenko, and A. M.

Yaremko, Phys. Stat. Sol. (b), 1982, 113, 635.

191
0

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10 100

Voltage (V)

Figure 2.

The I-V curve of an as-grown Zn0.2Cd0.sSe sample, 0.15 cm thick, 0.06 cm 2 contact area.

193
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Raman scattering spectra for CdSe, Zno.2Cdo.sSe and ZnSe single crystals.

194

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m_
N91 0

A SCANNING ELECTRON MICROSCOPY STUDY OF THE

MACRO-CRYSTALLINE STRUCTURE OF

2- (2,4-DINITROBENZYL) PYRIDINE r_0

Jacqueline Ware and Ernest Hammond,Jr.

Morgan State University

Baltimore, MD

and

Gerald R. Baker

Technical Monitor

Laboratory of Astronomy and Solar Physics

Goddard Space Flight Center

ABSTRACT

The compound, 2-(2,4-dinitrobenzyl) pyridine, was synthesized in the laboratory; an introductory

level electron microscopy study of the macro-crystalline structure was conducted using the scanning

electron microscope (SEM). The structure of these crystals was compared with the macro-structure of

the crystal of 2-(2,4-dinitrobenzyl) pyridinium bromide, the hydrobromic salt of the compound which

was also synthesized in the laboratory. A scanning electron microscopy crystal study was combined with

a study of the principle of the electron microscope.

195
A SCANNING ELECTRON MICROSCOPY STUDY OF THE

MACRO-CRYSTALLINE STRUCTURE OF

2- (2,4-DINITROBENZYL) PYRIDINE

Theory of Color Change

Sandy colored crystals of the 2-(2,4-dinitrobenzyl) pyridine have the unusual property of turning

a deep blue color when exposed to sunlight. The deep blue color can then revert again to sandy color

when kept in the dark. This color change from sandy to deep blue takes only a few minutes; however,

the color change from deep blue back to sandy takes about one day in the dark. Observations show that

the interconversions are reversible an unlimited number of times. The phenomenon is explained by the

formation of a tautomeric form by the action of light.

In the presence of light the sandy colored dinitro compound rearranges to the deep blue colored

acid-nitro tautomer. In doing so, the sandy colored compound undergoes intramolecular hydrogen

bonding. A proton (H+) is transferred from the methyl group to the oxygen of the nitro group. This

results in extended conjugation of multiple bonds in the blue tautomer (shown in the encircled group).

This chromophore is responsible for producing the color in the blue tautomer.

Visible ultraviolet spectroscopy, providing information of conjugation, confirms that the blue

tautomer has a greater degree of conjugation. Maximum absorption of radiation is expected to take

place at a longer wavelength for the compound with the greater number ofconjugated multiple bonds.

Maximum absorption occurs at a wavelength of 248 nm for the sandy compound and 567 for the blue

compound.

Superiority of the Electron Microscope Over the Light Microscope

The macro-crystalline structures of the photochromic compound, 2-(2,4-dinitrobenzyl) pyridine

and its salt, 2-(2,4-dinitrobenzyl) pyridinium bromide, were studied using the scanning electron microscope (SEM). The SEM along with a high speed-camera was used to magnify, photograph, study, and

compare the small details of the macro-structure of the crystals. It is the overwhelming superiority of

the electron microscope that allows the observation of minute details, such as the inner structure of

tiny crystals (note micrograph 3.8), which exceeds the scope of the light microscope.

The principle of this 20th century invention reveals its high degree of superiority over the light

microscope. With the optical microscope, it is the wave length of light that places an ultimate limit to

the resolution or the smallest distance between two points at the object that can be seen separately

through a microscope. The overwhelming superiority of the electron microscope is due to the fact that

the wavelength of the electron can be many thousand times smaller than the wavelength of light.

Whenever the size of an object in front of a wave is about the same size as the wavelength of the

wave, the wave will bend or diffract around it. To project the outline of an object on a screen, one must

use a wave whose wavelength is very small compared with the object. Visible light has a wavelength of

about 0.5 x 10-6m so it is hard to see the outline of a body whose diameter is about 0.5 x 10-6m. The

196
electron can have a wavelength of 10-1°m so the outline of an atom whose diameter is 10-1°m is barely

perceptible for this wavelength. Electrons will form a sharp shadow of viruses having a diameter of

about 10-6m, while visible light will diffract around them. A small wavelength gives the most accurate

measurement of a body's position. The behavior of electrons in this manner is an example of the

wave-particle duality set forth by Louis de Broglie in 1924.

The more powerful lens microscope can magnify an object only about 2,000 times its own diameter.

An electron microscope magnifies about 200,000 times, or 100 times as much as an ordinary microscope.

This image can also be photographed and magnified to approximately 800,000 times the original

diameter, or 400 times as much as a regular microscope magnifies. The electron microscope has a

theoretical resolution of about 3A which is about the distance between atoms in solids. The scanning

tunneling electron microscope can attain an amazing vertical resolution of about 0.1A. At the same

time, the great depth of focus, which is about 300 times that of a light microscope, endows images of

objects with a life-like, three dimensional quality. This is lacking in the light microscopes of the same

magnification. Operation at the ultimate peak of performance requires a well-experienced microscopist.

Principle of Electron Microscopes

Electrons are strongly scattered by all forms of matter including air. Therefore, the electron

microscope must be evacuated to about 10-4mm Hg (10-7atmospheric pressure). The lenses cannot

be material in nature. They are electric or magnetic fields, which are symmetrical about the axis of the

instrument. The source of electrons is housed in the electron gun which shoots beams of electrons

toward the object. The electron source relies on high temperatures to enable a fraction of the free

electrons in the cathode material to overcome the barrier of the work function and leave. In effect, the

electrons are "boiled out" of the cathode material. The electron source is an incandescent, hairpinshaped filament of tungsten (W) or lanthanum hexaboride (LAB6), surrounded by electrodes which

accelerate and collect the electrons in a narrow, intense beam. The electron gun can operate at voltages

of 1-100kV.

Highly accelerated beams of electrons from the electron gun are focused by the electron lens into

a tiny spot. The electric or magnetic field, or a combination thereof, which comprises the lens, acts upon

an electron beam in a manner analogous to that in which an optical lens acts upon a light beam.

The condenser and objective or probe-forming electron lenses serve to demagnify the image of

the crossover, the narrowest cross section of the beam from the electron gun. The condenser lens

determines the beam current, and the probe-forming lens determines the final spot size of the electron

beam which impinges upon the sample. The electron beam is focused by the electromagnetic field of

the magnetic lens as the electrons travel down the column or bore of the lens.

In the axially symmetrical condenser lens, solenoid windings of copper wire are used to induce a

magnetic field (when traversed by electric current). The solenoid windings are surrounded by an iron

mantle, except for a gap in the iron core representing the distance between the north and south pole

pieces of the lens. The magnetic strength of the lens is stronger by the presence of the iron core than

in its absence. At the gap, the concentrated magnetic field forms the electron lens having a focal length

of one eighth to about one sixteenth of an inch, which is inversely proportional to the strength of the

lens. The lens height is 10-15 cm in a 30 Kv SEM. The strength (or intensity of the magnetic field) of

the magnetic lens in the gap is proportional to the flow of current through the lens, as well as the number

of turns in the solenoid winding.

197
Productionof a minimumelectronspotsizebeginswith the reductionof the electronbeamat

crossover(50umfor atungstenhairpin)to agreatlyreducedscale.An electronimageof thecrossover

passesthroughthecondenserlens,andit isfocusedto asmallerintermediatediameter.Thedistance

theelectronsarefocusedisvariedbychangingthestrengthof thecondenserlenssystem.If thecurrent

isincreased,thenthestrengthof the lensincreases,andthedemagnificationincreases(the focused

spotgetssmaller).Also,thedivergenceof theelectronrayfromthe focusedspotwill increase.Less

beamcurrentwill enterthefinalprobe-forminglens,toobtainaminimumprobesizewhichimproves

resolution.Thecondenserlenscanbefocusedto allowmostof theelectronbeamto passthroughthe

apertureof the objectivelens,to obtainmaximumbeamcurrentandsignal.Consequently,onecan

decidebetweenmaximumbeamandcurrentsignal,or losecurrentbut haveminimumprobesizefor

optimumresolution.

In the scanning electron microscope a fine electron beam is focused on a thick specimen and the

pattern of the reflected electrons is displayed on a television-like image tube. A mechanical stage allows

scanning of the object. The image can be photographed on regular photographic film. However, the

problems and complexities of high-voltage electron microscopes limit their application.

Scanning Electron Microscopy Crystal Study

Sample preparation for observation in the electron microscope involved mounting the sample on

a specimen stub with silver paint, and coating the crystal sample with a thin film of conducting material

of gold-palladium by the process called sputter coating. This was done to eliminate or reduce the electric

charge which can build up in a non-conducting sample when scanned by a high-energy electron beam.

The coating provides a conducting path and should help eliminate the problems associated with

charging.

The electron micrographs show the expected variations in crystal shapes, sizes, and lengths for

crystals not grown in a controlled environment. Micrograph 1.1, for example, shows crystals of various

shapes and sizes at low magnification.

The samples were coated by the process of sputter coating. By this process, an energetic ion or

neutral atom of argon gas accelerates towards and strikes the surface of the negatively biased gold-palladium target and imparts momentum to the atoms. Some of the atoms of the target may receive enough

energy in the collision to break bonds with neighboring atoms and be carried away from the solid, if the

velocity imparted to them is sufficient. Electrons are ejected from the negatively charged target,

discharging a glow normally associated with sputter coating. As the electron accelerates towards the

positive anode, under the influence of an applied voltage, it may collide with a gas molecule, leaving

behind an ion and an extra free electron. The positive ions then accelerate towards the negatively biased

gold-palladium target where they cause sputtering as the atoms lying near the surface of the target are

ejected in this collision and sputtered onto the sample as a thin film deposit of gold-palladium.

Micrograph 1.1 shows one of the advantages of sputter coating. The target atoms, after collision,

are traveling in all directions as they sputter coat on the surface of the sample. In this way, the target

atoms are able to "go around corners" and achieve a complete coating without the need of rotating or

tilting the sample. An artistic pile-up of crystals can be adequately coated by sputter coating.

Some _sadvantages of sputter coating can be seen in micrographs 3.4 and 3.8. These include

thermal damage due to heat of radiation from the target and electron bombardment of the sample.

198
Anotherpotentialproblemissurfaceetching. It is attributed to either stray bombarding gas ions, or

metal particles hitting the surface with sufficient force to erode it away. In micrograph 3.2 the crystal

in the center contains many small holes sometimes found in sputter coated samples. At a magnification

of about 2,000, micrograph 3.8 shows surface erosion and sample destruction at a pitted area. It is not

known for certain whether the very small holes found in sputter coated samples, examined at high

resolution, are the result of surface etching or just thermal damage. Thermal damage, when it occurs,

is manifested as melting, pitting, and in extreme cases, complete destruction of the sample. But this is

thought to be mainly due to the sample being subjected to inordinately high power fluxes.

Thermal damage can also be caused by excessive heating in the electron microscope, which results

in specimen or sample movement and instability to breakdown and destruction. It is manisfested as

blisters, cracks, and holes in and on the surface of the sample.

Micrograph 3.9 exhibits beam damage by the appearance of blisters on the surface of the crystal

specimen. The blistering effect is only obtained, or at least seen, under higher magnifications of about

2,000 or greater. A vertical fracture near the lower center of micrograph 3.9 may be due to be am damage.

Hair-like fibers extend from one side of the fracture to the other as the crystal breaks and melts under

the heat of the electron beam, resulting in sample breakdown and destruction. Problems of thermal

damage can be reduced by working at lower beam currents. Sample heating from the probe current in

the picoampere range is expected not to be a problem for samples in the SEM. An alternative is to coat

with a thin film of copper, aluminum, silver, or gold.

Crystals of the protonated compound (hydrobromic salt of the photochromic compound), 2-(2,4-

dinitrobenzyl) pyridinium bromide, can be seen in micrograph 4.13. In comparison, the gold-palladium

coated sample of salt crystals appear to be wider and flatter than the crystals of the unprotonated

photochromic compound. The width of the long, wide, diagonal crystal in the lower right of micrograph

4.13 is 53 microns. Holes in the crystals of the salt compound are smooth and precise. Inner layers are

not found in the holes of the salt crystals, as can be found in the unprotonated photochromic compound

from which they were prepared. Additionally, the salt crystals do not exhibit properties of photochromism.

An interesting outcome of the study is the detection of inner layers in the macro-crystalline

structure of the photochromic compound, 2-(2,4-dinitrobenzyl) pyridine. A very interesting layering

effect is seen in the crystal on the right side of micrograph 1.4. The long horizontal crystal on the right,

in micrograph 3.2, is similarly layered. However, the former appears to have more inner layers as

compared to the hollow appearance of the latter. Micrograph 2.11 is that of an uncoated crystal sample,

and exhibits a great deal of charging. Nevertheless, thermal damage has exposed many inner layers of

the crystal. These layers are calculated to be less than 1.7 microns in thickness.

The relationship of the inner layers to the color change for these photochromic crystals remains

to be determined. Additional study may reveal a relationship between layering phenomenon and the

color change, along with the action of light, by which the compound is able to undergo intramolecular

hydrogen bonding, allowing it to rearrange to the deep blue tautomeric form. Layers of 2-(2,4-

dinitrobenzyl) pyridine as thin as 0.015 mm have been crystallized between fused silica plates. 2 Layers

of crystalline films reduced to 0.004 - 0.008 inches thick can be investigated by transmission microscopy

for the study of structure and structural defects.

Lastly, several potential areas of usefulness of the photochromic compound, 2-(2,4-dinitrobenzyl)

pyridine, exist in the deformation of dye laser pulses, 4 in the photographic screen stencil printing

process, 1 and in information storage. 3

199
Acknowledgments

The contributions of Professor Ernest Hammonds and Dr. Roosevelt Shaw to this project are

gratefully acknowledged.

References

1. Brynko, C., et. al., "Photographic Screen Stencil Printing Process", Chemical Abstracts,

10th Collective Index, 93: 177283r.

2. Clark, W.C., et. al., "Phototropic Properties of 2-(2,4-dinitrobenzyl) Pyridine",

Chemical Abstracts, 6th Collectine Index. (1957-61), 51-55.

3. Cowan, D.O., and Drisko, R.L., Elements of Organic Photochemistry..

4. Garness, J.I, et. al., "Apparatus for deformation of dye laser pulses...",

Chemical Abstracts, 10th Collective Index, 91:11997IC

200
ORIGINAL PAGE

Bt.ACK AND WHITE PHOTO_I_AP_4

Micrograph 1.1

Micrograph 1.4

201
ORIGINAL PAGE

BLACK AND WHITE PHOTOGRAPH

Micrograph 2.11

Micrograph 3.2

202
ORfG!NAL PAGE

BLACK AND WHITE PHOTOGRAPH

Micrograph 3.4

Micrograph 3.8

203
ORIGINAL PAGE

BLACK AND WHITE PHOTOGRAPH

Micrograph 3.9

=

L

=

Micrograph 4.13

204 lg
N91-28091

STRUCTURES OF CYANO-BIPHENYL LIQUID CRYSTALS

Yuan-Chao Chu, Tung Tsang and E. Rahimzadeh

Department of Physics and Astronomy

Howard University

Washington D.C.

s e-Tc 

and

L. Yin

Technical Monitor

NASA Goddard Space Flight Center

Greenbelt, Maryland

ABSTRACT

The structures of p-alkyl-p'-cyano-bicyclohexanes, C.H2n+I(C6Hlo)(C6H,o)CN (n-CCH), and

p-alkyl-p'-cyano-biphenyls, CnH2n+ffC6H4)(C6H4)CN (n-CBP), have been studied. It is convenient

to use an x-ray image intensification device to search for symmetric x-ray diffraction patterns. Despite

the similarities in molecular structures of these compounds, very different crystal structures have been

found. For the smectic phase of 2CCH, the structure is close to rhombohedral with threefold symmetry.

In contrast, the structure is close to hexagonal close-packed with two molecules per unit cell for 4CCH.

Since intermolecular forces may be quite weak for these liquid crystals systems, it appears that crystal

structures can change considerably when the alkyl chain length is slightly altered. Different structures

have also been found in the crystalline phases of n-CBP for n=6 to 9. For n=7 to 9, the structures are

close to monclinic. The structures are reminiscent of the smectic-A liquid crystal structures with the

linear molecules slightly tilted away from the c-axis. In contrast, the structure is quite different for n =6

with the molecules nearly perpendicular to the c-axis.

2O5
STRUCTURES OF CYANO-BIPHENYL LIQUID CRYSTALS

p-alkyl-p'-cyano-bicyclohexane (n-CCH), R(C6H10)(C6Hlo)CN, and p-alkyl-p'-biphenyl (n-CBP),

R(C6H4)(C6H4)CN, are new classes of liquid cystals 1'2, where C6I-I4 is the phenyl ring, C6H10 is the

saturated cyclohexane ring, R may be any alkyl (C_H2,+1) group, and n is the number of carbon atoms

in the alkyl chain. These molecules have long rod-like shapes. Extensive investigations have already

been reported for the structures of a variety of these liquid crystals. For the CBP systems, there are

stronger interactions between the molecules due to the double bonds in the phenyl rings. The smectic-A

structures are commonly observed for these compounds with n =8,10,12 where the CBP molecules are

tilted with respect to the smectic layers) The ratio between the smectic layer spacing and the molecular

length is about 1.4. In contrast, the molecular interactions are relatively weak for the CCH systems. The

smectic phase structures are apparently unstable for 7CCH and higher members. For lower values of

n, great varieties of structures have been observed for the smectic phases. 4

Because of the important roles of both the alkyl chain lengths (n) and the ring systems, we have

studied the structures of these systems in our present work. Because of the weak intermolecular forces,

the crystallization processes are rather slow. We are able to obtain single-domained samples in capillary

tubes by slow cooling from the less-ordered phase at higher temperature. Nevertheless, the spatial

orientation of the domain inside the capillary depends on the direction of the initial nucleation and is

therefore rather arbitrary. With the sample mounted on a goniometer, we have found it convenient to

use an x-ray image intensification device to search for symmetric diffraction patterns visually while the

goniometer is rotated.

The x-ray image intensification device was developed by Yin and collaborators at NASA Goddard

Space Flight Center. s'6 The diffracted x-rays are converted into visible light images by a rare-earth

phosphor as shown in Fig. 1. The visible light is then coupled via fiber optics to a microchannel-plate

photon photon elec_n els_:'vn

to electron ohO_on

gain gain •

conver_ion _nversion

! .....

i

t t t

Soingillator_ Photoctghode Output ?hosphor

?iheP] optics Microchannel _iber _optlcs

plate

visible

li_t

Figure 1. X-ray image intensification system.

2O6
image intensifier whic intensifies the visible light signal with a luminous gain of -105. Because of the

high luminous gain, the intensified visible light output can be viewed directly, photographed, or coupled

to other video devices. The transmission Laue spots on the output screen can be easily viewed in subdued

room light while the sample is being rotated. Hence this is a convenient technique to study the liquid

crystals whose molecular alignments inside the capillaries are not known.

The X-rays are produced by a copper anode tube with a nickel filter, usually operating at 22kV

and 500 watts. After collimation, the X-ray beam is directed onto the liquid crystal sample which is

placed in a thin-walled capillary tube installed on a two-axis goniometer. The goniometer is enclosed

in a container so that the sample may be heated or cooled in an air stream with controlled temperature.

The X-ray image intensification device, which is small and compact, is placed in the forward scattering

direction about 4 cm from the sample. The diffraction pattern displayed on the output screen may be

recorded by a Polaroid camera. The calibration is accomplished by placing standard lead grids (with

circular and with rectangualr grid patterns) over the scintillation screen. The angular resolution is about

0.03 °. It should be noted that the diffraction spots can come from both the characteristic CuKa radiation

(wave length of 1.54_,) and the white radiations with shorter wave lengths from the copper anode. The

former spots tend to have higher intensities. These two types of spots may be more clearly distinguished

by lowering the X-ray tube voltage. There would be much larger reductions in the intensities of white

radiation spots as compared to the CuKa radiation spots. Because of the low crystalline orders and large

molecular fluctuations in liquid crystals, diffraction spots are observable only in the forward scattering

direction within a few degrees of the incident X-ray direction. It is, therefore, necessary to measure

several diffraction patterns for various goniometer orientations and then express the scattering vectors

of these different orientations in terms of a common set of unit vectors arbitrarily f'Lxedin the crystal.

For the smectic phase of 4CCH, we have used the X-ray image intensification device to search for

symmetric diffraction patterns. These patterns are shown on the left side of Fig. 2. Patterns of sixfold

symmetry are shown in (a) and (b). Changing the goniometer angles resulted in patterns with twofold

symmetry as shown in (c) and (d) where the incident X-ray direction is perpendicular to the c-axis with

sixfold symmetry. These results indicate a hexagonal close-packed structure for the smectic phase of

4CCH with c=31_, and a=b=5.7_. The packings of the molecules are sketched on the right side of

Fig. 2. The unit cell parameters a and b are nearly the same as the molecular diameter. The parameter

c is slightly less than twice the molecular length ( - 17_).

It is surprising to find that the smectic phase structure of 2CCH is quite different from 4CCH

despite the similarities in their molecular structures. Again, we have used the X-ray image intensification

device to search for symmetric diffraction patterns. A diffraction pattern with threefold symmetry is

sketched in Fig. 3(a). The incident X-ray direction is coincident with the direction of the threefold axis.

At other goniometer angles, the diffraction patterns shown in Figs. 3(b), (c) and (d) have been observed.

The incident X-ray directions for these patterns are tilted about 16° from the threefold axis and are

distributed symmetrically about the threefold axis. These results indicate that the smectic phase

structure of 2CCH is close to rhombohedral with a = b =c = 12.5_and the common angle of 28 ° between

pairs of these units' cell vectors. These vectors are 17° away from the threefold axis direction.

These experiments indicate that the liquid crystal structures can change considerably even when

their molecular structures are only slightly altered. This may be a consequence of the weak intermolecular forces in these systems. The effects of the alkyl chain length n may also be important.

Different structures have also been found for the crystalline phases of n-CBP for n=6 to 9. For

8CBP, several typical diffraction patterns are shown in Fig. 4. After some searching with the X-ray image

intensification device, a clean symmetric pattern of four spots has been found as shown in Fig. 4(a) (the

207
shaded circle is the beam stop). This pattern demonstrates the monoclinic symmetry of the lattice. When

the X-ray beam is more than 3° away from the monoclinic e-axis, the diffraction spots are usually

observed in pairs only, as shown in Figs. 4(b), (c) and (d). These results indicate that the crystalline

phase structure of 8CBP is close to monoclinic with a=b=5.5_ c=37°_ a=fl=90 ° and ),=99 °. There

are two molecules per unit cell. The unit cell parameters a and b are comparable to the molecular

diameter. The parameter c is slightly less than twice the molecular length - 215 This structure is similar

to the hexagonal close-packed structure except that the angle y is 99 ° instead of the standard value of

120 ° . Similar structures have been found for 9CBP (a=b=4.9_ e=27°_y=l10 o) and

7CBP(a=7_, b=6X, c=30_, y= 133°). These structures are reminiscent of the smectic-A liquid crystal

structures with molecules tilted slightly away from the c-axis. In contrast, the structure is quite different

for 6CBP with a = 19_ b=9_ c=6_ )'= 148 °. The molecules are nearly perpendicular to the c-axis. Our

experimental results have demonstrated that the crystal structures can change considerably when the

alkyl chain length n is altered.

d

d

C

(a)

(c)

cF [,

a t

(b)

'4"/

(d)

Figure 2. Left: Sketch of diffraction patterns of smectic phase of 4CCH.

(a)(b) X-ray beam along the sixfold c-axis., (c)(d) X-ray beam

perpendicular to sixfold axis.

Right: Sketch of the molecular packing (c-axis in the perpendicular direction).

208
&

D

.[ •

eb

Ca)

-h

• •

f

(b)

(d)

J

ok

I •

Figure 3. Diffraction patterns of smectic phase of 2CCH from CuKa X-rays.

(a) X-ray beam along threefold axis; (b)(c)(d) X-ray beams 16° away

from the threefold axis and 120 ° apart azimuthally.

A

C

8

®

D

Figure 4. Diffraction patterns of the crystalline phase of 8CBP from CuKa X-rays.

(a) incident X-ray along monoclinic c-axis, (b)(c)(d) incident X-rays 3 °, 16 °,

14° away from c-axis.

209
The partial financial support by the National Aeronautical and Space Administration grant

NAG-5-156 is gratefully acknowledged. We thank Dr. L. Yin of NASA Goddard Space Flight Center

(Greenbelt, Maryland) for many useful discussions.

References

1. L. Pohl, R. Eidenschink, J. Krause and D. Erdmann, Phys. Letters A60, 421 (1977).

2. L. Pohl, R. Eidenschink, J. Krause and G. Webe, Phys. Letters A65, 169 (1978)

3. G.J. Brownsey and A.J. Leadbetter, J. Physique Lettres 42, L135 (1985).

4. A.J. Leadbetter, J.C. Frost, J.P. Gaughan, G.W. Gray and ,A. Mosley, J. Physique 40,

375 (1979).

5. L. Yin, J.I. Trombka and S.M. Seltzer, Nuclear Instrum. and Methods 158, 175 (1979);

172, 471 (1980).

6. D.Y. Chung, T. Tsang, L. Yin and J.R. Anderson, Rev. Sci. Instrum. 52, 1112 (1981).

210
 91-28099_

STUDIES OF SUPERCONDUCTING MATERIALS

WITH MUON SPIN ROTATION <_-

M.R. Davis and C.E. Stronach

Physics Department

Virginia State University

Petersburg, VA

W.J. Kossler, H.E. Schone, and X.H. Yu

Physics Department

College of William and Mary

Williamsburg, VA

Y.J. Uemura and B.J. Sternlieb

Physics Department

Columbia University

New York, NY

J.R. Kempton

TRIUMF

4004 Wesbrook Mall

Vancouver, BC

Canada

J. Oostens

Physics Department

University of Cincinnati

Cincinnati, OH

and

W.F. Lankford

Physics Department

George Mason University

Fairfax, VA

211
STUDIES OF SUPERCONDUCTING MATERIALS

WITH MUON SPIN ROTATION

ABSTRACT

The muon spin rotation/relaxation technique has been found to be an exceptionally effective

means of measuring the magnetic properties of superconductors, including the new high temperature

superconductor materials, at the microscopic level. The technique directly measures the magnetic

penetration depth (type II SC's) and detects the presence of magnetic ordering (antiferromagnetism

or spin-glass ordering has been observed in some HTSC's and in many closely related compounds).

Extensive studies of HTSC materials have been conducted by the Virginia State University - College

of William and Mary - Columbia University collaboration at Brookhaven National Laboratory and

TRIUMF (Vancouver). A survey of LaSrCuO, YBaCaCuO systems shows an essentially linear relationship between the transition temperature Tc and the relaxation rate o. This appears to be a

manifestation of the proportionality between Tc and the Fermi energy, which suggests a high energy

scale for the SC coupling, and which is not consistent with the weak coupling of phonon-mediated SC.

Studies of LaCuO and YBaCuO "parent" compounds show clear evidence of antiferromagnetism.

YBa2Cu3-xCOxO7 shows the simultaneous presence of spin-glass magnetic ordering and superconductivity. The three-dimensional SC, (Ba,K)BiO3, unlike the layered CuO-based compounds, shows no

suggestion of magnetic ordering. Experimental techniques and theoretical implications will be discussed.

212
STUDIES OF SUPERCONDUCTING MATERIALS

WITH MUON SPIN ROTATION

The Muon Spin Rotation Technique

The use of the positive muon as a probe of condensed matter was first suggested by Garwin,

Lederman and Weinrich in their 1957 paper describing their experimental observation of parity

violation in muon production and decay. ' The positive muon is one of a number of light positive ions

which have been used to probe condensed matter. These include the positron (e+), hole (h+), muon

(p+), pion (:r+), proton (p+), deuteron (d +) and triton (t+). The muon is the least easily produced of

all these particles, but the details of its behavior in condensed matter are far more easily discerned than

for any other particles. This is because of subtleties in the nature of the weak interaction. Because of

the parity violation inherent in the/z + production,

:t + _/z + + v/,,

muons resulting from pion decay are 100% polarized in the center-of-mass frame. Consequently, by

appropriate momentum selection (with magnets) one can obtain a nearly 100% polarized muon beam

regardless (within reasonable limits) of the momentum of the source pions.

In like manner the muon decays into a positron through the weak interaction,

/z + _ e + +re +_,.

The positrons are emitted asymmetrically with respect to the muon spin, and with considerable kinetic

energy (average: 35 MeV).

Data are taken with an apparatus such as the one our group uses at the Alternating Gradient

Synchrotron of Brookhaven National Laboratory (Figure 1). Signals in scintillators 1,2 and M5 with no

signals in F6 indicate that a muon has stopped in the sample, which is in a thin-walled container (usually

a cryostat). Signals in A4 and A3 (or in F7 and FS) indicate the emission of a positron in the backward

(or forward) direction. The muon signal starts a clock, a positron signal stops it, and two histograms

(backward and forward) are accumulated. A pair of magnet coils provides an external transverse field.

The muons precess at a rate directly proportional to the magnetic field they sense, and this precession

signal decays at a rate which depends upon the variance in the magnetic field observed by all the muons

in the ensemble.

The data are fit to a function of the general form:

N(t) =No e -t/r [1 +A Gx(t) cos(tot +_)] +B,

where r = 2.2 microseconds (mean muon lifetime), A is the e ÷ anisotropy, Gx(t) is the depolarization

function, to is the precession rate, ¢ is a geometrical phase angle, and B is random background. A,

Gx(t) and to are usually the quantities of physical interest.

213
Figure 1.

Muon Spin Rotation Apparatus at the AGS Brookhaven National Laboratory.

MuSR Studies of HTSC Materials

The high-temperature copper-oxide-based superconductors discovered since the initial breakthrough on LaSrCuO by Bednorz and Mtiller, 2which have transition temperatures ranging from about

40K up to about 125K, are some form of type II superconductors. Type II's have a surface-to-volume

energy relation which favors the intrusion of external applied magnetic fields in flux quanta which

generally take on a uniform triangular geometry. This produces a variation in the internal magnetic field

sensed by microscopic probes implanted into the material, such as/z +. This variation produces a

depolarization of the muon spin precession, as in Figure 2, which shows the experimental asymmetry

we obtained in YBa2fu307, both above and below its transition temperature. From the depolarization

rate observed in the superconducting state, the magnetic penetration depth can be calculated. By

combining the values from/_SR with more conventional measurements, the superconducting charge

carrier density and the effective mass of the carriers (m*/mc) may also be determined.

The variation in the magnetic field in a type II sample is given by

B (x) = Bo exp (--X/;tL)

Our data show that, to a good approximation, the depolarization rate a is proportional to To. Relating

this to the penetration depth gives

a a ,_2 a nJm* a To.

This suggests that the carrier density ns plays a major role in determining To. Furthermore, this relation

appears to be inconsistent with standard Bardeen-Cooper-Schrieffer (BCS) theory, and suggests a high

energy scale for the coupling mechanism. 4 Such a high energy scale is found in models based on a large

transfer integral between the oxygen and neighboring Cu atoms, s and is also expected in the resonating-valence-bond picture. 6

214
0.15

0.10

0.05

<_ -0.05

- 0.10

-O.I 51

YBo2CusO 7 Hext = I kG

- T=IO0 K

i '

I I I !

0.15

O.IO

n- 0.05

FU

:_ 0

>-

o_ -0.05

<

-0.I0

-0.I5_

T=70 K

• ! I I I

) 0.5 1.0 L5 2.0

TIME (/l, sec)

Figure 2. Asymmetry in normal (top) and superconducting (bottom) YBazCu307.

Magnetic Ordering in HTSC Materials

Muon spin rotation also serves as an exceptionally effective probe of magnetic ordering in

materials at the microscopic level, and we have utilized this aspect of/aSR to observe magnetic ordering

in materials very closely related to HTSC materials. A prime example of this is our study of

LaCuO4-y, which is "parent" to the HTSC LaSrCuO. Figure 3 shows our data taken with zero external

field on LaSrCuO (top) and La2CuO4-y (Bottom). No oscillations are present in the top case, but they

are clearly observed in the lower plot. This indicates the presence of antiferromagnetism with a moment

per Cu atom of about 0.5 Bohr magneton. 7 A similar experiment done at TRIUMF on oxygen-depleted

YBa2Cu307-y shows similar antiferromagnetic ordering in that material, n These results suggest a close

relationship between superconductivity and magnetic ordering in the new CuO-based HTSC materials,

which is opposite to all experiences with conventional superconductors (heavy-fermion materials which

have superconducting phases show close relations between SC and magnetism in some cases also).

215
n_

W

0.15

0.10

0.05

0 o

(LOL85Sro.15) Cu 0 4

*T=50K

_'_,_,?_. o 13 K

• "o¢._,

-

I I o !

2 4 6

TIME (#sec)

Q04

>. o.o21

oc

uJ 0

_E

_E

>- -Q02

O3

<

-0.04 -

O

n

La 2 Cu 04. _y

I

O.5

TIME

T= 5OK"

I 1

1.0 1.5

(_sec}

Figure 3. Zero-field asymmetry in LaSrCuO and LaCuO4.y.

FM is observed in the lower spectrum.

A study of YBaCuO doped with Co, YBa2Cu3-xCoxO7, shows simultaneous SC and magnetic

ordering, in this case the spin-glass variety in which magnetic moments are frozen into random but static

orientations. For x = 0.1, for example, the depolarization rate begins to rise at about 40K, indicating

the onset of SC, while the initial polarization begins to decrease at about 30K, indicating the onset of

spin-glass ordering. Figure 4 shows how the SC transition temperature Tc and the magnetic ordering

transition temperature Tm vary with Co concentration. There is a clear overlap of SC and spin glass

ordering. We suspect that this does not violate the Meissner effect because the two effects are probably

occurring in microscopically distinct regions of the sample, such as alternating planes.

In light of the magnetic ordering present in materials closely related to the essentially two-dimensional CuO perovskite HTSC's, we studied three-dimensional perovskite superconductors which do not

contain Cu, (Ba,K) BiO3. These showed no evidence for magnetic ordering, 9 which suggests that these

materials are probably not likely candidates for record-setting values of Tc.

216
f_

TransitionTemperatures

A

0._

Cobalt x

LEGEND

,,r

0 T_

0.50

Figure 4.

Transition temperatures as functions of Co concentration in YBazCu3.xCoxO7.

Acknowledgments

This work was supported in part by NASA grant NAG-I-416, NSF grant DMR-8503223, and US

DOE contract 76-A002-CH00016. Our colleagues at TRIUMF are supported by the National Science

and Engineering Research Council of Canada. Special thanks to R.S. Cary for assistance in producing

this document.

References

1. Garwin, R.L.; Lederman, L.M.; Weinrich, M., Phys. Rev. 1957, 105, 1415.

2. Bednorz, J.G.; Mtiller, K.A., Z. Physik 1986, B64, 189.

3. Kossler, W.J.; Kempton, J.R.; Yu, X.H.; Schone, H.E.; Uemura, Y.J.; Moodenbaugh, A.R.;

Suenaga, M.; Stronach, C.E., Phys. Rev. 1987, B35, 7133.

4. Uemura, Y.J.; Emery, V.J.; Moodenbaugh, A.R.; Suenaga, M.; Johnston, D.C., Jacobson,

A.J.; Lewandowski, J.T.; Brewer, J.H.; Kiefl, R.F.; Kreitzman, S.R.; Luke, G.M.; Riseman,

T.; Stronach, C.E.; Kossler, W.J.; Kempton, J.R.; Yu, X.H.; Opie, D.; Schone, H.E., Phys.

Rev. 1988, B38, 909.

5. Emery, V.J., Phys. Rev. Lett. 1987, 58, 2794.

6. Anderson, P.W., et al., Phys. Rev. Lett. 1987, 58, 2790

7. Uemura, Y.J.; Kossler, W.J.; Yu, X.H.; Kempton, J.R.; Schone, H.E., Opie, D.; Stronach,

C.E.; Johnston, D.C.; Alvarez, M.S.; Goshorn, D.P., Phys. Rev. Lett. 1987, 59, 1045.

8. Brewer, J.H.; et al., Phys. Rev. Lett. 1988, 60, 1073.

9. Uemura, Y.J.; et al., Nature 1988, 355, 151.

217
N91-28098 !

A 10-WATr CW PHOTODISSOCIATION LASER WITH

IODO PERFLUORO-TERT-BUTANE

Bagher Tabibi and Demetrius D. Venable

Department of Physics

Hampton University

Hampton, VA

ABSTRACT

t-C4 F91 has been successfully tested as a lasant in a solar-simulator-pumped laser system and

produced a 14-W CW output. The pump-to-laser efficiency was determined to be three times that of

the commonly used n-C3 F7 I.

218
A 10-WAT]" CW PHOTODISSOCIATION LASER WITH

IODO PERFLUORO-TERT-BUTANE \

Introduction

NASA has been investigating the feasibility of direct solar-pumped laser systems for power

bcaming in space.[1] Among the various gas, liquid and solid laser systems being proposed as candidates

for solar-pumped lasers,[2-4] the iodine photodissociation gas laser has demonstrated its potential for

space application.[5-8]

Of immediate attention is the determination of system requirements and the choice of lasants to

improve the system efficiency. The development of an efficient iodine laser depends on the availability

of a suitable iodide which has favorable laser kinetics, chemical reversibility, and solar energy utilization.

Among the various alkyliodide lasants comparatively tested in a long-pulse system, perfluoro-tert-butyl

iodide, t-Ca F9 I, was found to be the best.[9] However, the operating conditions for the laser medium

in a continuously pumped and continuous-flow iodine laser differ considerably from those in the pulsed

rcgime. [10] Therefore, this experiment reports the results of CW laser performance from t-C4 F9 I.

Perfluoro-n-propyl iodide, n-C3 F71 is used for comparison in this study because of its universal

usc in photodissociation iodine lasers.

Solar-Pumped Iodine Laser

Successful excitation of an iodine laser by a solar-simulator was first reported in 1980 [5]. The

active media for such lasers are CF3 I, or C3 F7 I, and are generally described by the formula RI, where

R stands for the radical CF3, C3 FT, C4 Fg, or C6 F13. The absorption bands of these iodides are in the

UV part of the solar spectrum (250-300 nm). Resulting photodissociation produces excited I ° atoms

with the reaction

RI + hvs o R + I ° (52Pv,).

Lasing occurs because of the atomic transitions

I ° (52Pv2) o I(52py2) + hvL,

where

"_L w C

VL -- 1.315,um.

The quantum yield of the excited iodine atoms, I°, the most important quantity in the laser kinetics, was

measured to be near unity for most alkyliodides.[10] (See Table 2.)

219
Fourotherprocesseswhichoccurfollowingthephotodissociationarealsoimportantandmustbc

considered: the collisional deactivation of I°, by the parent molecule RI according to

I* + RI --(Q1) -_ I + RI; therecombinationprocessof R +I* --(K1)--> RI; the dimcrization R +R --(1<3)---,R2; and formation of molecular iodine I +I + M_I2 +M or

I" +I +M --,12+M. Thesereactionsaretheimportantlossmechanismsfor theiodinelasersystem.

t-C4 F9 1 Laser

Perfluoro-tert-butyl iodide, t-C4 F9 I, is attractive for direct solar-pumped laser medium bccausc

of two important properties. First, the photodissociation absorption peak is centered at 288 nm which

is red-shifted by 15 nm from the 275 nm absorption center of n-(73 F71 (see Fig. 2). This red-shift and

the broader half-width (see Table 1) increase the solar spectrum utilization and result in a higher

photodissociation rate. The photodissociation rate of the solar-pumped iodine laser can be calculated

from[11]

if

whcre h is Planck's constant; c is light velocity, tris absorption cross-section, S;_is solar spectral irradiance

and ;t is wavelength. A calculation using the data for air mass zero (AMO) solar spectral irradiance [12]

provides y(n-C3 F7 I) = 0.83 × 10-3 s-I and y(t-C4 F9 I) =2 x 10 -3 s-1 which is 2.4 times higher

for t-C4 F9 1 when compared with n-C3 F7 I.[11] The photodissociation rate was calculated for

t-(74 F9 1 in comparison with that for CF3 I.[11] The second advantage for this gas is the absence of

extremely small contributed reactions which lead to the direct loss of radicals.[13] Particularly, recombination reaction of radicals R between each other, observed for the other iodides, are strongly inhibited

for t-C4 F9I.[13-15] Other kinetic rate coefficients were found to be similar to those for the

n-C3 F71 molecules.[14] (See Table 2.) Therefore, the photodissociation of t-C4 F91 by solar radiation could lead to a stationary concentration of the radicals, I atoms, and 12 molecules.

Experiment

The present experiment used the laser system of reference 6 which used the iodide, n-C3 F7 I, so

that comparative evaluation to the t-C4 F9 1could be made directly. Figure 1 shows a schematic of the

experiment. A Vortek Industrial model 107 arc lamp [6] with a 0.2-m-long arc length was used as the

solar-simulator. The lamp was capable of electrical input powers up to 150 kW. However, only 75 kW

was used in this experiment. Considering the -45% conversion efficiency, as claimed by Vortek

Industry, a maximum of -34 kW of visible and near-infrared radiant power could be achieved.

The arc lamp and the laser tube were optically coupled on the conjugate focal lines of a

water-cooled elliptical cylindrical reflector of polished aluminum. The suprasil laser tube had a 20-mm

ID and 0.45 m length. The gain medium was shadowed by the side plates of the reflector. The total

pumping power used in this experiment was - 13 kW.[6] Equivalent pumping power density was 994

solar constants (1 solar constant equals 1.35 kW/m 2) on the surface of the laser tube. The pumping

power density was varied by adjusting the arc current. The emission spectrum of the Vortek solar

simulator was similar to the air mass zero solar spectrum and is given in reference 6.

22O
The laser cavity consisted of a 70% output mirror and a maximum reflectivity rear mirror. The

cavity length was 0.9 m, and a pyroelectric power meter was used to monitor the laser power output.

The lasant supply is shown in Figure 1. The flow of t-C4 F91 vapor was longitudinal and

maintained by a pressure differential between the heated evaporator and the liquid nitrogen cooled

condenser containing iodide. To obtain sufficient flow rates of t-C4 F9 I, the evaporator had to be

heated because the vapor pressure of t-C4 F9 1 was only 76 Torr at room temperature which is about

5 times lower than that of n-C3 F71 (350 Torr).

The photoabsorption of t-C4 F9 1 was accurately measured by spectrophotometry and is comparcd to that of n-C3 F7 | in Figure 2. Photoabsorption, vapor pressure, and heat capacity parameters

for t-C4 F9 1 and n-C3 F71 are summarized in Table 1. Note that the high heat capacity of t-(24 F9 I

is advantageous for maintaining reduced lasant temperatures with high power, cw operation.

Results

CW lascr opcration from t-C4 F9 I, unlike the n-C3 F7 I, requires some technical efforts leading

to high purity of the iodide and a large surface area of evaporator to achieve sufficient flow rate and

corresponding pressurc in the laser tube. t-C4 F9 1 is solid at room temperature and melts at 60°C. The

maximum vapor pressure of t-C4 F9 1 obtainable with flow from a room temperature evaporator was

only a fcw Torr and fell down to zero within a few seconds because of insufficient compensation of

evaporation cooling in the reservoir. In order to increase the flow, the pressure was increased by heating

the rescrvoir and the laser tube to 45°C. The vapor pressure of t-C4 F91 increased to 30 Torr but fell

to l0 Torr and Iowcr within one minute. Thus, the period of CW output from t-C4 F9 Iwas limited to

a fcw seconds in this experiment by the limitation of the amount of iodide and its evaporational cooling.

Figure 3 shows a typical oscillogram of the CW power output of t-C4 F9 1 (lower trace). The upper

tracc is the pressure of t-C4 F9 1 inside the laser tube during a lasing period of - 20 s. To recycle back

Io the initial pressure, it was necessary to shut down the flow of iodide by the controllable valve (see

Figure 1) for almost 3 minutes to compensate for insufficient thermal dissipation of the evaporational

cooling in the reservoir. A maximum power output of - 14 W CW was achieved for -20 s with a flow

rate and a vapor pressure of 2700 SCCM and - 19 Torr, respectively.

To compare the CW output of t-C4 F9 1 to that of n-C3 F7 1 another set of experiments was

pcrformed for both iodides under the same operational conditions of flow rate, flow velocity, and

pressure. The results of the tests for the two iodides pumped by different simulator arc currents are

shown in Figure 4. The flow rate and the vapor pressure of n -Ca F71 were constant at 900 SCCM and

6 Torr, respectively, throughout the tests, but those of t-C4 F9 1 unavoidably decreased from 1200 to

700 SCCM and from 9 to 5 Torr, respectively. The measurements were made from low to high arc

currents. In spite of the reduced flow rate of the t-(24 F9 I, more than a three-fold increase in the power

output was measured.

221
CWLaser from the Mixture oft-C4 F9 1 and n-C6 FI3 1

To maintain the flow and pressure of t-C4 F91 throughout the lasing period we attempted to mix

it with n-C6 F131 which is liquid at room temperature and has much lower vapor pressure than

t-C4 F91 (see Table 1). We dissolved equal amounts of t-C4 F91 in n-C6 FI3 1 until it reached

saturation. The idea was to speed the heat conduction by stirring the liquid mixture.

The absorption band of the mixture of equal amounts of each iodide was measured by the OMA

spectral analyzer (see Table I). The mixture had a 285 nm absorption peak and 85 Torr vapor pressure

at room temperature. This mixture was used for the CW laser. The conditions of the experiment were

kept the same as for the pure t-C4 F9 I. A typical oscillogram of CW output from the mixture of

t-C4 F91 + n-C6 F131 (1:1) is shown in Figure 5 (lower trace). The upper trace is the pressure of the

mixture inside the laser tube during the lasing period of 4.6 minutes. Evidently, the lasing period for

the mixture increased considerably in comparison to that for pure t-C4 F9 I. A maximum power output

of 11.5 Wwas achieved with a pressure of 25 Torr and a flow rate of - 4300 SCCM. The results of these

tests indicate some usefulness of the mixing of t-C4 F9 1 in n-C6 F13 1 to maintain the flow rate and

the pressure during the longer lasing time period but the mixture is less efficient than pure t-C4 F9 I.

It is important to note that the power output of this mixture after treatment with

Na2 $2 O5 + Ag, which acts as an 12 absorbing agent, decreased by half from the power output of the

first run. The treatment period was about one week. The power output of the third run of the mixture

which was chemically treated for a longer period of about one month still decreased. The measurement

of the absorption band of the used mixture demonstrated an absorption peak of 275 nm indicating the

presence of iodides other than t-C4 F9 1 in the medium.

Conclusion

The iodide t-C4 F9 1 was successfully tested in a solar-simulator-pumped CW laser. Its efficiency

(pump-to-laser) was measured to be three times that of the commonly used iodide n-Ca F7 I.

t-C4 F91 also demonstrated a higher chemical reversibility than that of n-C3 F7 I. However, some

technical efforts are required for obtaining and maintaining high flow rates and pressures throughout

the CW laser operation.

222
References

[1] R.J. DeYoung, G.D. Walberg, E.J. Conway, and L.W. Jones, "A NASA High-Power

Space-Based Laser Research and Applications Program", NASA Langley Research

Center, NASA-SP-464, Langley AFB, VA (1983).

[2] A.L. Golger and I.I. Kliniovski, "Lasers Pumped by Solar Radiation (review)", Sov.

J. Quantum Electron, vol. 14, No. 2, pp 164-179 (1984).

[3] R.T. Schneider, V.H. Kurzweg, J.D. Cox, and N.H. Weinstein, "Research on Solar

Pumped Liquid Lasers", Univ. Florida, Gainsville, FL., rep. No. NAG-l-135 (1983).

[4] M. Weksler and J. Shwartz, "Solar-Pumped Solid-State Lasers", IEEE J. of Quantum

Electron, Vol 24, No. 6, pp 1222-1228 (1988).

[5] J.H. Lee, Willard R. Weaver, Appl. Phys. Lett. 39, (1981) 137.

[6] J.H. Lee, M.H. Lee, and W.R. Weaver, Proceeding of the International Conference

on Lasers '86, (1986) 150.

[7] J.H. Lee, B.M. Tabibi, D.H. Humes, and W.R. Weaver, "High-Power, Continuously

Solar-Pumped and Q-Switched Iodine Laser", AlP Conf. Proc. 172, Advances in Laser

Science III (1988) 109.

[8] R.J. DeYoung, G.H. Walker, M.D. Williams, G.L. Schuster, and E.J. Conway, IECEC,

Philadelphia, PA., August 10-14, 1987, Paper 879038.

[9] B.M. Taibibi, J.H. Lee and W.R. Weaver, "Performance on Perfluoro-alkyl Iodides in

a Long Gain-Length Laser", Bull. Am. Phys. SOc. 31 (1986) 1756.

[10] T.L. Andreeva, G.N. Birch, I.I. Sobelman, V.N. Sorokin, and I,I, Struck, "continuously

Pumped Continuous-Flow Iodine Laser", Sov. J. of Quantum Electron, 4, (1977) 2150.

[11] V. Yu Zaleskii, Kvantovaya Elektron. (Moscow) 10, 1097 (1983).

[12] J.R. Carter, H.Y. Tada, "Solar Cell Radiation Handbook", Jet Propulsion Lab., CIT,

Pasadena, California, (1973) 2-2.

[13] T.L. Andreeva, G.N. Birch, I.I. Sobelman, V.N. Sorokin, and I.I. Struck, Sov. J.

Quantum Electron 7, (1977) 1230.

[14] L.S. Ershov, V. Zaleskii, V.I. Sokolov, Sov. J.Q., 8, (1978) 494.

[15] J.H. Lee, J.W. Wilson, T. Enderson, W.R. Weaver, D.H. Humes, and B.M. Tabibi,

Optics Comm. 53, 356 (1985).

223
AppendixA: HumanResources

Graduatestudentscontinueto betrainedinthisareaof research at the University. To date, five

students have completed theses and four students are enrolled. Eight of the nine MS students are

American citizens and seven of the nine are considered members of an underrepresented minority in

physics. Table A1 lists students and thesis titles.

GRADUATE STUDENT TRAINEES

STUDENT _IESIS TITLE DATE

Gill Lee A Parametric Study of the Threshold Pump Power of a '84

(NASA-GRTP) Direct Solar Simulator Pumped C3FTI Laser

Kenneth Preston A Study of Selected Dyes for Enhancement of Lasing Using

the Converter Technique

'86

Julie Williams Solar Simulator Pumped Waveguide Amplifier for Dye

Laser

'87

Won Yi UV Dye Lasers Pumped by Hypocycloidal Pinch Plasmas '87

Todd Pilot Solar Simulator Waveguide Dye Amplifier Under a Long

Excitation Pulse

'88

Lamarr Brown Nd:YAG and Nd:Cr:GSGG as Candidates for Solar

Simulator Pumped Solid State Laser

'89

Vincent Jones Comparison of t-C4F9I and C3F7I for Direct Solar Pumping

Abdulaziz Gambo ???

Clarence Wells ???

(US Military)

Note: 8 of the 9 MS students are American citizens.

7 of the 9 MS students are considered underrepresented minorities in physics.

224
Table1. Characteristic Parameters of Iodides.

Absorption

Temperature Cv Cp

Iodide Peak. X[nm] AX[nm]

[tort] [J/MoleOK] [J/moleOK]

Absorption Cross

Section, O'ma x [ 10" 19c m 2]

Room

Vapor Pressure

t-C4Fgl 288 50

0.05 76

n-C3F71 273 42

0.1 350

n-C6F131 272 42

I-C4F91 + 285 - -

n-C6F131

4.8 +

181

6.6 +

146

6.0 + 0.5

189

154

~16

85

Table 2. Kinetic Parameters for Iodides.

Paramctcr

Quantum Yicld

K2, cm 3 / s

K3, cm 3 / s

QI, cm 3 / s

t-C4FgI

0.88

6.0 x 10 "12

_--0

2.9 x 1016

n-C3F7I

0.98

8.0 x 1012

2.0 x 10 12

3.0 x 10 "17

225
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wo 0 I. x 'NOI1:3:3SSOI90 NOII,:II::IOSEIV 6l.-

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-k

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I ! ! ! !

200 250 300

ARC CURRENT, A

Figure 4. CW power output vs. the arc current.

229
M 'i:13MOd .LRdJ.RO

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230
THE UV PHOTOCHEMISTRY OF C2 N2

<=>2. <U /

Joshua B. Halpern and Samuel A. Barts

Department of Chemistry

Howard University

Washington, DC

ABSTRACT

The absorption, emission and photodissociation yield spectra of C2 N2 have been measured in the

220 and 210 nm region near the 4o1and 101401bands of the A1Z- _ XIZ + system. The emission spectrum

showed very few lines which appeared in the absorption spectrum. Moreover the emission had 660 ns

lifctime and, at 210 nm a very large electronic emission quenching rate. We used laser induced

fluorescence to measure the relative yield of CN radicals as a function of photolysis wavelength. This

spectrum seemed to follow the absorption spectrum below the dissociation threshold. Energy in the

CN fragments appeared to be statistically distributed.

231
THE UV PHOTOCHEMISTRY OF C2 N2

Introduction

Cyanogen is a photochemically important molecule found in the atmosphere of Titan, and perhaps

in other astronomical systems. We have discovered that this molecule has a strong and distinctive

emission spectrum that can be used for remote detection.

Cyanogen is also an extremely simple tetra-atomic system in which predissociation can be studied.

Potential energy surfaces have been calculated for all of the excited states which means that models of

dissociation dynamics can be tested in detail.

Experimental

The apparatus was similar to that described in Reference [1]. C2 N2 from Matheson was purified

by freeze-thaw cycling. The gas flow from a 3 liter reservoir was controlled by a Granville-Phillips fine

metering valve and introduced into the cell through a hypodermic needle. The pressure was monitored

by a MKS Model 200 capacitance manometer of a cold cathode gauge.

The excitation source was a Spectra Physics PDL-2 dye laser pumped by a DCR-11 Nd-YAG

system. Light from the dye laser was frequency doubled in a KDP crystal and Raman shifted in about

10 atmospheres of hydrogen gas. For this experiment third and fourth anti-Stokes shifted beams were

used. Since the doubled light is 100% polarized, all of the Raman shifted beams will be fully polarized.

The intensity of the dye laser beam ranged between 25 and 60/_J depending on the dye gain curve and

dye used. The energy contained in each pulse of the photolysis beam ranged from a few to perhaps a

hundred microjoules.

Emission from C2 N2 was detected directly through an unfiltered 11 stage EMR VUV photomultiplier. The signal was integrated by a PAR Model 160 boxcar analyzer.

CN fragments were detected by laser-induced fluorescence (LIF) excited by Molectron DL-II dye

laser pumped by UV400 Nitrogen laser. The roughly 200,uJ beam was expanded, attenuated by neutral

density glass filters and passed through a thin film glass polarizer to eliminate any elliptical character.

Care was taken that the LIF signal was unsaturated. The electric vector of this dye laser beam was

parallel to that of the photolysis laser. The overlapping laser beams passed through the experimental

cell in opposite directions. The LIF signal was monitored about 100/_s after the photolysis pulse. This

delay eliminates the effect of any changes in the nascent CN distribution as the photolysis wavelength

was changed. The nitrogen pumped dye laser was tuned to resonance with the R(7) line of the CN

B2y. + _- X2y + violet system. LIFwas monitored by an EM19558 photomultiplier tube looking through

a 388 nm bandpass filter. The photomultiplier was placed perpendicular to the plane of the laser beams

and the electric vector of the photolyzing light. The fluorescence signal was integrated in one channel

of a PAR Model 162 boxcar analyzer. The intensity of the dye laser beam was measured by picking off

a reflection and sending it into a photodiode.

The experiments were controlled by an IBM PCXXT microcomputer based data acquisition system

constructed in our laboratory. The firing of the lasers and the dye laser scanning was controlled by the

microcomputer.

232
Absorptionspectra were measured directly on a Cary 2390 UV-VIS-NIR spectrophotometer or

by measuring the far UV light intensity before and after the cell using scintillators to convert the light

[requency into regions that can be detected by two Si photodiodes.

Results

Figure 1 shows an absorption spectra measured on the Cary 2390 spectrophotometer between 200

and 230 nm. The lower half of the diagram shows the difference between spectra measured at 20 and

70°C when the cell was heated by water from a thermostated bath. This identifies lines that originate

in excited vibrational states and aids in the assignment of the vibrational bands. Figure 2 shows an

absorption spectrum taken in the 220 nm region with a higher resolution instrument [2].

1.0

0.0

Cyanogen Absorption Spectrum

,o,to ___,.._.y-0.05000 Hot Band Difference48,000 Speclrum "Hot" 46,000BandsI I -_1

FREQUENCY cm-1

Figure 1

233
1

4 o

4 0 A 4 2 __

i I i I I

222 22O

WAVELENGTH (nm)

Figure 2

Figure 3 shows the spectrum of total emission following laser excitation in the 220 nm region.

Attempts to detect CN fragments from photodissociation were unsuccessful although we were able to

detect fragments if we used the much weaker 200 nm fourth anti-Stokes beam. This confirms the bond

energy measurements of Eres and McDonald [3] which predicted that the dissociation threshold would

be 212.76 nm. The emission spectrum does not match the absorption spectrum in all detail. The ratio

of intensities between the 401 and 412 bands is somewhat different from that seen in absorption as is the

shape of the bands. The emission lifetime obtained at the peak of the 401 band is 660 ns. Figure 4 shows

the fluorescence spectrum obtained when the dye laser is fixed on the Q bandhead of the 401 line.

Z

O

O3

O9

iil

....!

<

IO

I--

ABSORPTION

_]t_j_ ] 3x lO-19 cm

_i_,_l,r,,_ o

, I , , I , , , , I .....

219.0 219.5 220.0 220.5

WAVELENGTH (nm)

Figure 3

234
60

¢--

w

I17

v

I11

O

Z

ILl

O

09

ILl

O

__J

Lt_

15 -

10 -

5 -

0

210

I I I

0 1

ln401 I

0 1

1o4 I I

1°3°4, ,

I 4U,_UA |

1

I I

I I I

I I

I I

1 L | I 1 I .,

230 250 270 290

Figure 4

Figure 5 shows the absorption spectrum measured between 206.4 and 211 nm. Figure 6 shows the

yield of CN fragments in the same region. The relative yield of CN was measured as a function of

photolysis wavelength by (LIF). The photolysis yield generally follows the absorption spectrum as would

be expected in any predissociation. Figure 7 shows the emission spectrum measured in the same region.

Only a few peaks are observed. Note that the signal from the 10'40 ] band extends far above the top of

the scale. The insert in Figure 7 shows the ..... band attenuated by a factor of 50. Structure can be

seen on the red side of the emission at higher gain. We have measured the lifetimes of the emission

excited in this band as a function of pressure. A Stern-Volmer plot of the measured decay rates is shown

in Figure 8.

28

2O

10 -

0

206

I .... I

208

I

210 22

Figure 5

235
28

u

2O

nt"

_..i

.<

Z

(-9 lO

u_

.J

Z

0 0

206 208 210 212

WAVELENGTH (nm)

Figure 6

28

2O

i

1G0

206 2O8 210

WAVELENGTH (nm)

22

Figure 7

236
8

7

•" 6

5

ILl

4

m

I---- 3

LI.I

!1

--i 2

0

_, 1 l.J_h_. , I i I I I , 1 I

0 20 40 60 80 100 120 140 160 180

CYANOGEN PRESSURE mtorr

Figure 8

Figure 9 shows the fragment yield spectrum between 200 and 202 nm corresponding to excitation

of the 102401transition. The right hand half of Figure 10 shows the emission spectrum in the 1024o1region

as compared to that from the 401 region. There is a factor of several thousand difference in the intensities

of the emissions.

Cyanogen Fragment Yield

UF" eR RI_

m

m

"W I

kS

14 i

L3

t +N

ID

g

T

|

. it i

Figure 9

237
3rd Anti-Stokes 4th Anti-Stokes

30

¢-

._o

03

03

.iE

ILl

>

nc

i_

1

40

1000 X Gain

Scan 1 Scan 2 Scan 3 Scan 4 Scan 5

Figure 10

Discussion

Figure 11 is a linear correlation diagram from Reference 4. These observations can be qualitatively

explained with the following model: C2 N2 is excited from the ground X_E + state into the AlE - state.

At excitation energies below the dissociation limit the molecule simply fluoresces and returns to the

ground state. This is shown conclusively by the fluorescence spectrum as explained in Reference 1.

After excitation above the dissociation limit there is a competition between fluorescence, dissociation

(where energetically possible) and crossing over to a lower triplet system. Emission can also occur from

this triplet system back down to the ground state. The correlation diagram indicates that the A15: - state

cannot directly dissociate to ground state CN fragments in the linear configuration. While this restriction

would be relaxed in a bent configuration it is also possible that dissociation occurs through a crossing

to the a3 Zu + system which correlates with ground state fragments. The barrier in the linear configuration can be avoided if the molecule bends.

Future experiments will attempt to elucidate this mechanism and add quantitative detail to this

qualitative model. Experiments to be done include measurement of the fluorescence spectra below the

dissociation limit. This will allow us to elucidate the mechanism of dissociation. Second, we will compare

the intensity of emission with that from known pressures of NO, allowing us to calculate quantum yields

for all processes. This will allow us to map the state density of the emitting triplet state and provide a

clock for measuring photodissociation rates.

238
9-

8-

gg

4

t'\

! _'=_-"')L/__/ _x2='-x2="

C2N a - 2 CN

Figure 11

ORIGINAL PAGE IS

OF POOR QUALI'W

Conclusion

The study of cyanogen C2 N2 photolysis has produced several important results. First, significant

emission was observed from C2 N2 following excitation to both bound and unbound states. This emission

has not previously been reported. If, as has been suggested, cyanogen is a minor constituent of

astronomical objects the intensity of this emission would be the measure of the cyanogen concentration.

Second, we made initial measurements of the competition between emission and dissociation.

Acknowledgments

Parts of this work were supported by NASA under Grant NAG-5071 and a grant of money from

the Howard University Research Development program. S.A. Barts was supported by a Danforth

Foundation Fellowship.

1. J.A. Russell, I.A. McCiaren, W.M.Jackson and J.B. Halpern, J. Phys. Chem., 91 (1987)

3248.

2. Taken with the assistance of Dr. Alan Laufer at NIST.

3. D. Eres, M. Gurnick and J.D. McDonald, J. Chem. Phys., 81 (1984) 5552.

4. Dateo, C.; Thesis, University of California, Berkeley, 1987.

239
N91-28095

ENCOURAGING THE PURSUIT OF ADVANCED DEGREES

IN SCIENCE AND ENGINEERING:

TOP-DOWN AND BO'ITOM-UP METHODOLOGIES

Anthony B. Maddox

Massachusetts Pre-Engineering Program and

Brandeis University Computer Science Department

Ren_ie P. Smith-Maddox

Massachusetts Pre-Engineering Program and

Brandeis University Heller Graduate School

Benson E. Penick

Benson Penick & Associates

ABSTRACT

This paper describes the MassPEP/NASA Graduate Research Development Program (GRDP) 1

whose objective is to encourage Black Americans, Mexican Americans, American Indians, Puerto

Ricans, and Pacific Islanders to pursue graduate degrees in science and engineering. GRDP employs a

top-down or goal-driven methodology through five modules which focus on research, graduate school

climate, technical writing, standardized examinations, and electronic networking. These modules are

designed to develop and reinforce some of the skills necessary to seriously consider the goal of

completing a graduate education.

GRDP is a community-based program which seeks to recruit twenty participants from a pool of

Boston-area undergraduates enrolled in engineering and science curriculums and recent graduates with

engineering and science degrees. The program emphasizes that with sufficient information, its participants can overcome most of the barriers perceived as preventing them from obtaining graduate

science and engineering degrees.

Our experience has shown that our top-down modules maybe complemented by a more bottom-up

or event-driven methodology. This approach considers events in the academic and professional experiences of participants in order to develop the personal and leadership skills necessary for graduate

school and similar endeavors.

1The MassPEP/NASA GRDP is supported by the National Aeronautics and Space Administration (NASA)

Office of Equal Opportunity Programs under Training Grant NGT 224)05-900 and administered by the Massachusetts Pre-Engineering Program (MassPEP). We gratefully acknowledge GRDP staff and participants for their

comments and perspectives.

240
ENCOURAGING THE PURSUIT OF ADVANCED DEGREES

IN SCIENCE AND ENGINEERING:

TOP-DOWN AND BOTTOM-UP METHODOLOGIES

Introduction

As the United States becomes more technology-based, there is a corresponding growth in the

demand for technically-trained people. Some recent demographic projections indicate that approximately 0.75 million technical positions may go unfilled at the beginning of the 21st century. Many of

these positions will require research-oriented master's and doctoral degrees, which are increasingly

being awarded to individuals who are not citizens of the United States. One way to increase our national

resource of technical people is to encourage Americans from racial and ethnic populations who are

underrepresented in technical disciplines to pursue engineering and science degrees and careers.

For the past 10 years, the Massachusetts Pre-Engineering Program (MassPEP) has been successfully encouraging Boston and Cambridge middle and high school students from these populations to

study engineering and science. Recently, more than 80 percent of MassPEP participants have attended

college, many selecting technical majors. Since the Fall of 1986, MassPEP and the National Aeronautics

and Space Administration (NASA) have collaborated on the Graduate Research Development Program (GRDP). The goal of GRDP is to encourage Black Americans, Mexican Americans, American

Indians, Puerto Ricans, and Pacific Islanders (hereafter referred to as our target population) to pursue

research-oriented graduate degrees in engineering and science.

Top-Down Program Design

GRDP employs a top-down or goal-driven methodology through five modules which focus on

research, the graduate school process, technical writing, standardized examinations, and electronic

networking. These modules are designed to develop and reinforce some of the skills necessary to

seriously consider the goal of completing a graduate education. GRDP modules were also designed to

disseminate information needed when applying to and completing graduate programs in a wide range

of technical disciplines.

The modular activities of the GRDP curriculum were generated directly from the program

objectives, which are the subgoals of the program. They were designed to achieve the objectives over

a twelve-week period with four-hour meetings scheduled on Saturday of each week. To accommodate

scheduling disparities, GRDP does not emphasize the structure of regular meeting attendance, but

instead, places an emphasis on effective time management within the constraints of other commitments.

The objective of the RESEARCH module is to expose each participant to the process of

developing a technical research proposal. Each participant generates a 5-10 page proposal including

abstract and bibliography in an area of interest. An oral presentation is given in an open forum which

may include representatives from academia, industry, and government as well as GRDP staff and

participants. Generally, undergraduate research opportunities are seized by upperclassmen who have

241
developedrelations with faculty or have exhibited exceptional academic ability. Factors such as social

isolation and academic performance can prevent our target population from developing these necessary

faculty relationships thus curbing an interest in research. GRDP offers an opportunity to explore a

technical research topic of interest.

The SEMINAR module's objective is to help each participant develop perspectives on various

research opportunities and apply for research internships, admission to graduate research programs,

and financial support. Pursuit of a research-oriented experience is illustrated as a planned sequence of

activities guided by a thorough investigation of technical interests and objectives. Attention is given to

specific strategies, heuristics, and personal development issues. The module's agenda is supported by a

booklet published by GRDP entitled Graduate School in Science and Engineering: iT PAYS TO GO

and discussions with invited speakers. Participants are asked to submit applications to at least two

research internship or graduate programs and financial aid sources. All application fees are reimbursed

by GRDP.

Success in graduate school involves: (1) academic performance, (2) understanding departmental

agendas and procedures, and (3) successfully interacting with colleagues and faculty. GRDP participants learn about the explicit and implicit details of applying to and being successful in graduate

programs. There are opportunities for participants to discuss and examine various aspects of the

graduate school process. Topics include: matching one's skills with particular academic institutions, the

application process, financial support, tenured versus non-tenured advisors, oral versus written qualifying and comprehensive examinations, etc.

Thc objective of the COMMUNICATION module is to provide each participant with practice and

experience with communicating written and oral technical information and opportunities to discuss

technical issues. Occasionally the module's format includes class discussions pertaining to racial and

ethnic issues which can affect graduate students. The result is a completed research proposal and an

oral presentation with visual aids. Some undergraduate engineering and science curriculums do not

include many courses on writing, though written communication is an essential part of an engineering

or science career. GRDP gives its participants the opportunity to develop the writing skills which are

necessary for graduate school applications, research reports and papers, etc.

The Graduate Record Examination (GRE) module's objective is to reinforce each participant's

skill in taking the GRE. Practice GRE General Tests are administered by GRDP while each participant

is offered the option of taking an Educational Testing Service (ETS) administered GRE General or

Subject Test. Participants are responsible for completing two examinations and the verbal, quantitative,

and analytical sections of past examinations as in-class assignments. There are also opportunities to

freely discuss individual or group concerns about the GRE. All GRE registration fees are reimbursed

by GRDP. The rationale is that if practice improves GRE scores, the chances of being accepted into

graduate school also improve.

The objective of the COMPUTER module is to reinforce the use of computers as an essential

means to support research and as an effective means to maintain professional networks for each

participant. Participants have the opportunity to use electronic bulletin boards and mail to reinforce

networking. The major concern of GRDP participants is that the program will interfere with their

academic or work schedules. Computer-based communications allow staff and participants to interact

when personal contact is not possible. This "electronic mentoring" also helps participants and staff

become more familiar with the use of computers, terminals, and modems.

242
Participants

GRDP is a community-based program which seeks to recruit twenty participants from a pool of

Boston-area undergraduates enrolled in engineering and science curriculums and recent graduates with

engineering and science degrees. We have found that recent graduates, those who have received their

degrees within the past five years, have been the most consistent participants in GRDP. Two possible

reasons are that: (1) their employment schedules do not interfere with GRDP activity as much as the

academic schedules of undergraduates and (2) their experience has shown them the value of an

advanced degree.

Admission

Recent graduates are accepted for admission if they have a bachelor's or master's degree in

engineering or science. Undergraduates (excluding freshmen) are admitted as long as they meet the

minimum academic requirements for their academic institution. One of the strongest messages sent by

the program was that there is no reason not to consider a graduate degree in engineering or science.

GRDP is committed to showing its participants how they could use a variety of strategies for overcoming

many apprehensions based on their academic or personal histories. Though GRDP maintains that

standardized examination scores and other factors such as research experience may strengthen an

average undergraduate record, we acknowledge that there are few substitutes for above average

academic performance.

Benefits

In addition to paying graduate school application and GRE fees, GRDP provides the use of a

modem and personal computer or terminal for networking. This has proven to be helpful to participants

who access computers regularly in their work or studies. A $200 stipend is also awarded to participants

who complete two GRE examinations, give an oral presentation on their written research proposal,

and submit two research internship or graduate school applications. For partial completion of program

activity, a pro-rated amount is awarded based on accomplishments within each module.

GRDP participants who apply to a graduate school or a research laboratory are reminded that

visiting an institution or facility may enhance an applicant's chances of being offered a desired

opportunity. To underscore this point, GRDP reimburses or advances travel expenses to visit a research

laboratory or graduate school before or after being offered a position, respectively. These travel grants

are limited and the GRDP staff helps participants plan to maximize the travel resources allotted to

them. GRDP establishes contact with an administrator, professor, scientist, engineer, or student who

may assist the participant in assessing opportunities at the institution or facility. A one-page trip

summary of the visit is a responsibility of the participant. Travel is arranged so that academic commitments may be maintained.

GRDP participants who are juniors and accept an internship at a research facility are eligible for

GRDP research internship support. On an individual basis, GRDP attempts to provide the difference

between a research internship salary and a non-research salary, up to a designated maximum. Brief

progress reports or research papers are required to receive the grant throughout the summer.

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Staff

The Boston metropolitan area has provided GRDP with a diverse staff. Each staff member is or

has been a graduate student, most in technical disciplines, and has a part-time association with GRDP.

For staff which are currently graduate students, GRDP has the secondary benefit of providing them

with support for their graduate education. In the three-year history of GRDP, two staff members have

been awarded NASA fellowships.

GRDP staff members have had a variety of experiences. Some have had experience in industry.

Others were born outside of the United States (Jamaica, Guyana, Japan, Panama). We have had single

parents as well as married couples with adult or pre-school children. GDRP thus provides participants

with social as well as professional role-models.

GRDP's Competition

Encouraging the target populations to pursue degrees requiring technical and quantitative skills

has been difficult but generally successful. It appears that as a result of attrition at the undergraduate

level, a relatively small number of individuals from the target populations receive undergraduate

degrees in engineering and science. It is from this small pool that candidates for graduate-level degrees

are generally selected.

This pool is also the recruiting source for business and industry. Individuals with undergraduate

science and engineering degrees command high salaries from employers seeking people with state-ofthe-art skills for various technical positions. Annualsalary offers approachingthe middle $30,000 range

are not uncommon. Large starting salaries deter many from continuing on to graduate school. Unlike

professional fields such as medicine, law, or dentistry, engineering practice generally does not require

an advanced degree or licensure. Though professional registration for engineers is often encouraged,

many laws allow employers to assume the legal responsibilities for engineering practice. Consequently

there is less incentive to attend graduate school.

Bottom-Up Methodologies

Our experience has shown that our top-down modules may be complemented by a bottom-up or

event-driven methodology. This approach considers events in the academic and professional experiences of participants as a means to guide the development of the personal and leadership skills necessary

for graduate school and similar endeavors. We have learned that it is important for GRDP to understand

more about each individual participant. To help accomplish this, each staff member serves as a mentor

to a participant. Each mentor decides when and how much information to share with other staff about

their participant. We often find that similar issues and problems surface in different modules and we

become better equipped to deal with them when they are discussed in an open manner.

Our conclusion is that the best strategy for encouraging our target population to consider graduate

school is to foster individual interaction with them. It is important for us to understand many of the

issues that cause participants to investigate or reject graduate school. These issues include family and

244
employmentpressures,self-esteemandconfidenceproblems,research interests, indecisiveness, academic burnout, etc.

Results

From the approximately 50 people who have participated in GRDP, five have applied to graduate

programs. Two have successfully been admitted to graduate school. One individual is employed with a

master's degree, and is pursuing her doctorate part-time. She is also the instructor for the program's

GRE module. The other participated in GRDP since her junior year and is enrolled full-time in a

master's degree program with fellowship support. Two of the remaining three applicants are awaiting

decisions on admission and financial aid. One individual was unsuccessful in gaining admission for

graduate study. We believe that this was mainly due to her not actively seeking admission for graduate

study until the second semester of her senior year. Four of the five were females of Black and/or Hispanic

origin who had majored in engineering. The remaining individual was a Black male who majored in

engineering technology.

We do not base the success of GRDP solely on the numbers of individuals who attend graduate

school. We believe that for undergraduates to include GRDP in their weekly activities is significant.

Since GRDP offers no direct benefit to academic pursuits, and offers a modest stipend, participation

is an indicator of interest in graduate school. We have had several undergraduates who could not

accommodate GRDP in earlier program years, return to GRDP seeking admission.

Quite often we have been told by our participants that GRDP serves as means for social

interaction. They felt that GRDP was a comfortable environment where issues could be discussed

candidly and straightforward answers and comments could be expected. We were not surprised that our

recent graduates would share this perspective. There is limited support provided for our target

population by employers. We did not expect this response from undergraduates who were associated

with academic, professional, and social support organizations internal and external to their academic

institutions. Apparently the existence of sophisticated social avenues for undergraduates does not

reduce the need for programs similar to GRDP.

Future Issues

There are several important issues which will be explored in future program years. First, it is not

easy to identify how GRDP has had an effect on its participants; for example, whether GRDP supports

existing intentions or promotes non-existing aspirations to pursue graduate degrees. Knowing the

difference could lead to program designs which allow a program's resources to be used more efficiently

and effectively.

Second, profiles need to be established to detect common characteristics of those who attend

graduate school and those who do not. We believe that specific identification of factors beyond

employment and salaries which cause selection of employment over graduate study would be helpful in

deciding how to suggest graduate study earlier in a student's academic career. For example, we need to

discover why: (1) fewer males in the target population appear to be applying to graduate school and (2)

fewer females apply to technical graduate schools.

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Third, an effort is needed to expand the scope of such programs to include more disciplines which

are underrepresented by racial and ethnic populations. Many of the details illustrated in this paper may

apply for various types of graduate programs. Techniques and strategies which are generally applicable

will be very useful for attracting students to graduate programs.

Summary

From our experiences with GRDP, we have summarized some of the important aspects of the

program:

1. Program setting. Programs such as GRDP benefit from being housed in academic settings. In

large metropolitan areas such as Boston, where there are several academic institutions, a communitybased program has the opportunity to attract a diverse undergraduate student population. It also attracts

recent graduates from nearby business and industry. University environments also allow recent graduates to become reacclimated to academic surroundings. Commitments from administrative personnel

for meeting space, laboratory tours, computer resources, etc., are easier to secure.

2. Diverse participants. One of the most receptive audiences for the message of graduate school

is the recent graduate, These individuals have the advantage of having experience as a way to measure

the importance of a graduate degree. Recent graduates may also be able to influence undergraduates

through associations developed within the program. First-year graduate students who continue to

require mentoring and skill development should also be invited to participate in programs such as

GRDP.

3. Mentorlng. Mentoring relationships are essential for success in structured and competitive

environments. The lack of role models at the graduate level in science and engineering departments

often does not allow undergraduates to have the exposure they need. The same can be true in industry

where there may not be scientists and engineers who are visible to younger employees. Therefore, the

selection of a staff which includes role models who have had experience in graduate school has been

critical. The fact that the staffhas had experience in both industry and academia has been a plus to the

program.

4. Admissions. A rolling admissions policy has been essential to the success of the program. Our

efforts to structure the program around self-initiative as opposed to a schedule was not only necessary,

but provides the participant with a first-hand opportunity to learn to manage the resources necessary

to complete the graduate school process. Our admission procedure has increased the workload on staff

members, but it has allowed us to attract and retain individuals as soon as they discover the program

and its benefits.

5. Information. GRDP attempts to maintain an environment where a participant may match his

or her level of preparation, skills, and commitment with his or her desire to attend and complete

graduate school. The program provides a forum for asking questions about graduate school and the

politics of the graduate school process while allowing the participant to simulate different aspects of

the graduate school process. There is a constant flow of information in the form of articles, books and

presentations which are available to anyone, including non-GRDP participants.

246
JPL INITIATIVE N 9 1 - 2

ON U RSm S

qL. Allen, P. Forte and M. H. Leipold

Jet Propulsion Laboratory

I. Background

Executive Order # 12320 of September 15, 1981, established a program designed to significantly

increase the participation of historically black colleges and universities (HBCUs) in Federal programs.

Because of its geographical remoteness and position as a contractor operated center, JPL had not

participated in grant and training programs with the HBCUs. In recognition of our responsibility to the

national commitment on behalf of the historically black colleges and universities, this paper describes

an initiative with effective, achievable guidelines and early progress for a better and more productive

interaction between JPL and the HBCUs.

While responding to the Federal mandate, the JPL initiative contributes to our University research

base and our ability to recruit capable engineers and scientists. The historically black colleges and

universities are staffed with motivated, competent and experienced scientists and engineers and

graduate students. They have performed excellent research for other NASA centers. It is in the interest

of JPL to tap this capability in meeting our research needs. Therefore, key elements of this initiative

provide efficient mechanisms to allow for the granting of research funds to enable consulting, fellowships, academic part time, and summer employment for faculty and graduate students and to provide a

means for JPL employees to attend these schools. This will provide the opportunity for students to

learn, about both technology and JPL.

II. Program Content

Numerous areas of interaction with the historically black colleges and universities have been

identified and are being implemented. They have two broad objectives, research interactions and

faculty/student interactions. Plans and progress to date for each specific area are summarized below.

1. Research Grants

The fundamental mechanism for promoting research at the HBCUs is through a grant. Although

JPL is barred from directly issuing grants due to our contractor status, a mechanism has been established

to allow NASA to issue grants in our behalf. If funding for a grant is available entirely at NASA

Headquarters, the grant is issued directly by NASA with JPL named as the technical monitor. If JPL

wishes to release funds to use on a grant, JPL returns those funds to NASA and NASA similarly issues

a grant and names JPL as technical monitor.

The responsibility for providing grant money and identifying research areas is with the Technical

Divisions at JPL in concert with JPL's program offices. Through informal discussion and announcements of opportunity, appropriate HBCUs are apprised of the need for work. In making JPL research

247
interestsknowntoHBCUs,emphasisisplacedonindividual-to-individual interfacing.Contactsamong

technical personnel and visits between institutions are encouraged. The HBCUs will respond with

unsolicited proposals to accomplish the work, as germane to their academic needs and focus. We also

submit to NASA a correct, exciting, and timely description of the Laboratory and its needs for inclusion

in the NASA Initiative with Historically Black Colleges and Universities.

Review criteria have been pre-established and are included in information to prospective applicants to ensure that they have a prior understanding of the bases for evaluating their proposals. They

include technical and programmatic relevance to JPL's objectives, scientific or engineering merit,

qualifications of the investigator, qualifications of the investigator's institution, and overall cost. After

review, the proposals, evaluations, and evaluation summaries are returned for further action - either a

request to the Grants Program Analysis Officer, NASA Code U, for a grant award or a letter declining

the proposal.

Funds are provided from one or more of the following four possible sources; 1) Redirection of

JPL funds through the appropriate NASA headquarters program office to Code U, 2) Transfer of

uncommitted NASA Headquarters program office funds to Code U, 3) Matching or enabling funds

provided by NASA Headquarters EEO, Minority University Program, Code U, or 4) Other NASA

program offices, centers or other government agencies. Upon receipt of the proposal and summary,

Code U first obtains NASA program office concurrence that the proposed project is appropriate.

Technical and administrative monitoring of the grant is the responsibility of JPL.

For each grant, there is a task manager who is responsible for coordinating all technical administrative and monitoring activities with the appropriate program office. Semi-annual and annual technical

status reports are required of the grantee to assist in monitoring the grantee's progress.

At present, slightly over 20 proposals and white papers have been received and reviewed. Of these,

six have been selected for funding and their status ranges from under negotiation to funding in place.

Most of the the remaining proposals are still under consideration, frequently in a continued effort to

develop necessary funding.

2. Technical Clinics

Claremont College in Claremont, California has, for many years, operated a Mathematics Clinic

and an Engineering Clinic for JPL. These clinics were established to give undergraduate and graduate

students experience with "real-world" problems in math. To make use of the clinic, an organization

(company, government agency, etc.) contracts with a clinic to perform research on a particular problem.

The clinic utilizes undergraduates under the guidance of a professor to seek the solution to the problem.

This provides an excellent educational experience for students while making low cost talent available

to the contracting organization. Further, it allows the student and contracting organization to better

know each other.

While these clinics are sponsored by JPL, they are available to the rest of NASA and to industry.

It is in JPL's interest to maintain close contact with the clinic through a guidance committee in order

to assure a close interaction between JPL and the school's faculty and staff.

It is our intent to encourage the establishment of clinics at the HBCUs as appropriate to the

school's area of interest. JPL's role is to sponsor the establishment of the clinic through the use of

research grants as well as the sponsoring of actual clinic problems. We envision clinics in spectroscopy,

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remotesensing, materials, and computer science. At present, no specific working relationships have

been identified.

3. Equipment Loan

An existing NASA program makes unused JPL equipment available to colleges and universities

in support of their research programs. Most elements of the transfer of equipment to support a grant

at an HBCU by JPL are covered under existing procedures. In addition to this provision for loans,

equipment which has been transferred to a school in support of a grant may frequently be abandoned

in place at the conclusion of a research grant. The existence of a Memorandum of Understanding

between JPL and a specific HBCU normally contains a statement advocating equipment transfer as a

goal. This may also serve as a mechanism for transfer of equipment. In addition to assisting JPL and

HBCUs in the administrative aspects of a transfer, this inititive may be able to assist in the financial

aspects of transfer costs and instructions on equipment operation to the HBCU staff. As part of this

initiative, a group at JPL working with data visualization problems has begun the transfer of film readers

and software for Video Imaging Communication and Retrieval to Jackson State University. This

capability at Jackson State is expected to result in continued joint efforts between the two groups.

4. Facilities Use

An existing NASA program allows colleges and universities to use JPL facilities on a non-interference basis for the enhancement of their research programs. Again, the JPL Initiative provides a

mechanism for specific attention to the needs of HBCUs.

5. Personnel Loan Program

Another potential interaction is a personnel loan program whereby JPL employees are sponsored

as visiting faculty at an HBCU. This employee spends one to two years at the candidate school

performing teaching and research duties. Ideally, a research grant accompanies the employee to allow

JPL sponsored research to be accomplished by a JPL employee and his/her students. The approval and

awarding process for these grants follows the procedures outlined earlier.

The HBCU would normally provide support for the teaching/research activities including supplies

and course expenses, equipment (leasing only), transportation expenses (related to University work),

student assistant wages, and applicable university burden costs. A Memorandum of Understanding

(MOU) between the JPL employee and the cognizant JPL organization detailing the terms is normally

required.

At present, Dr. Kofi Apenyo from JPL is on loan to the Dolphus E. Milligan Research Institute

of the Atlanta University Center. He will be teaching and doing research on database query systems for

about 2 years.

6. Cooperative Education

Utilizing a highly successful existing program, undergraduate students are invited to take part in

co-op programs. This program provides practical experience for students and develops a bonding

between those students and JPL. Cooperative education programs are now in place between JPL and

several schools. These programs will be extended to other schools as appropriate.

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TheCooperativeEducationProgramisdesignedto giveundergraduatestudentsanopportunity

to preparefor acareerwith on-the-jobtrainingasasupplementto classroominstruction.Periodsof

classroom-related, fullypaidemploymentalternatewith periodsof full-timestudy.In addition,work

experienceissupplementedbyweeklymeetingsof Co-opstudentsincludinginformationon projects

in progressat the Lab and toursof variousLab facilities,aswell ascareerandskill-development

programs.Theselatterlearningexperiencesservebothto broadenthestudent'stechnicalbaseaswell

asprovideanunderstandingof operatingproceduresatJPL.

In order for a student to be eligible for the JPL Cooperative Education program he/she must be

enrolled in a Cooperative Education Program at a college or university with whom JPL has a signed

Co-op agreement, be in good academic standing, have at least a 3.0 grade-point average on a 4.0 scale,

and meet the regular JPL employment criteria. Work assignments are normally designed so that they

may be completed during a six month time period and include scientific, technical, or administrative

assignments. The difficulty and responsibility of the task depends on the position, experience, and

interest. In addition, students are given the opportunity to learn new technical fields and organizational

procedures.

Included are salary and a weekly housing allowance for eligible students. Limited funds may be

available to support the hiring of minorities and women and every effort is made to ensure that a majority

of the Co-op employees are females and/or minorities. All school expenses are the responsibility of the

student.

JPL has had a small number of students from HBCU's as co-op students each year from the 4

HBCUs involved. These numbers are expected to increase as this initiative becomes fully effective.

7. Summer Employment

An existing summer employment program has provided a rich work experience for hundreds of

students. Unlike the co-op program, this effort is not specifically tied to a course of instruction and is

available to graduate students and faculty. It provides learning opportunities for participants as well as

direct benefit to JPL for work conducted. Because the HBCU schools are outside of California, special

provision for travel and housing expenses is made to make the program more attractive. The existing

summer program budget is augmented by Minority Office funds to assure that HBCU hiring goals are

realistically met. The intent is to enhance and increase the capabilities of minority scientists in JPL's

hiring pool. This assists in the recruitment of college graduates as regular Laboratory employees. Not

infrequently, summer faculty positions have been filled by professors in science, engineering, and

business administration from universities where JPL frequently recruits.

College-level students are preferred, particularly those majoring in science, engineering and

business administration. Student summer employees must have plans to return to school in the fall.

Candidates from schools where the Laboratory regularly recruits are given preference. The minimum

hiring age is sixteen. Salaries are based on a set salary structure in accordance with the student's

academic standing at the beginning of summer.

Here as with the co-op program, the number of students involved is expected to increase as

knowledge of our program is disseminated throughout the HBCU's.

25O
8.FacultyResidentProgram

A Faculty Exchange Program to employ faculty on leave or sabbatical for 6 months to one-year

periods has been established. This provides an excellent opportunity for HBCU faculty to learn about

us and for us to establish long-term ties to HBCUs.

This program is designed to further the interaction with HBCUs in the employment of faculty

members in Laboratory research or project activities while in residence at JPL. Selected faculty

members spend one or more academic units (quarter or semester) at the Laboratory working in an area

of their choice and expertise, as part of an existing JPL team/group. This arrangement is renewable for

up to two years.

Interested faculty members submit curriculum vitae to the Manager of Historically Black Colleges

and Universities Initiative, together with a brief description of the activity they would like to be

associated with as well as an endorsement from their dean or department head. JPL then circulates the

applicant's material to potentially interested Laboratory organizations. Pre-established contacts between faculty and JPL staff greatly enhance successful selection. JPL positions are open to any bona

fide faculty member for whom an appropriate position can be identified. Faculty interactions with an

HBCU are also facilitated through existing programs such as the NASA Summer Faculty Fellowship.

This program is NASA- wide and JPL is involved. It invites engineering and science educators who have

interests in common with a professional peer at JPL to spend ten weeks during the summer on research

here.

At present, no faculty have been placed at JPL under this Initiative.

9. Minority Fellowship Program

The Minority Fellowship Program is instituted as a JPL Affirmative Action Program to 1) provide

JPL under-represented minority employees with an attractive opportunity to acquire an undergraduate

or graduate college degree, 2) provide an employment incentive to attract newly graduated minority

scientists, engineers, and administrative personnel, and 3) improve our level of interaction with HBCUs

through direct contact between JPL employees and HBCU staff.

To meet these goals, the Minority Fellowship Program provides a full fellowship to deserving

candidates. This includes full tuition and salary and benefits during full-time study at an HBCU.

Fellowships are awarded for a maximum of five years. To assure that the employee has high career

potential at JPL, that there is a reasonable chance that he will pursue a long-term career at the

Laboratory and that he has a reasonable chance of successfully completing a degree program, the

following conditions for candidacy apply:

1) The employee must pursue a course of instruction in a technical or administrative discipline

that is appropriate for employment at JPL;

2) The employee must have at least 2 years of experience at JPL;

3) The

4) The

5) The

6) The

employee must have completed at least 2 years of college;

employee must have exhibited a high potential for a successful career at JPL;

employee must demonstrate financial need; and

employee must be willing to agree to 3 years work at JPL after completing his degree.

Appointments are made by a committee established by the assistant laboratory director. This

committee administers, coordinates and monitors the program. Fellows must make consistent, appro251
priateand significant progress toward their degree objective, and progress is regularly reviewed. If a

Fellow's progress is deemed to be below reasonable expectations in terms of attendance, grades, etc.,

appropriate remedial action is recommended.

Award of a fellowship is contingent upon the candidate being accepted by the proposed college

or university within six months following selection. Acceptance prior to application for the program is

preferred and enhances the applicant's chance for a fellowship.

The first group of applicants is being reviewed at this time for inclusion under this element of the

initiative. The number is expected to be small, only 2 to 4, because of the limited funds available to

support this part of the initiative.

10. Operation Pipeline

The intent of this activity is to outline a long-range development program to increase interest of

local minorities in the math and science fields, leading to eventual graduation from an HBCU in a field

related to the work of the Laboratory. JPL has participated in a very successful program with Elliot

Middle School in Pasadena, California. In an extension to that program, we are pursuing a "pipeline"

program that monitors and helps the progress of gifted students identified at Elliot and other schools

as they progress toward college. Besides enrichment programs and summer or part-time employment

at JPL, students are eligible for scholarships made available by HBCUs to fund their study at an HBCU.

In most cases, this element does not introduce new activities, but serves as a continuous thread tying

the various existing activities together and applying them to individual students.

Major program goals are to (1) develop student interest in math and science, 2) provide training

for minorities who exhibit potential for success in the fields of science and math, 3) provide some

financial support for needy and deserving minority students, and 4) provide a pool of talented minorities

at JPL who have both experience and supporting education.

As an addition to the existing JPL Outreach Program to improve science teaching at the grade

school level in our local area, a joint effort involving the University of the District of Columbia is under

negotiation.

III. Technical Interchange Workshop

As part of the Initiative, JPL sponsors an Annual Technical Interchange Workshop involving the

HBCUs taking part in the JPL program. Held at JPL, the Workshop primarily focuses upon the research

grants and clinics. As appropriate, Workshop sessions also review and discuss progress in faculty and

student interaction programs. It is the intent of JPL that the Workshop also be available as a forum to

discuss the challenges of HBCUs as they work toward a strengthened competitive status in taking part

in NASA and JPL work. The purpose of this conference is to:

1. Encourage annual interaction between faculty at historically black colleges and universities

(HBCUs) and JPL personnel involved in sponsored research;

2. Familiarize JPL personnel with HBCU research capabilities; and

3. Further develop NASA supported HBCU research.

The conference also provides a forum to discuss, evaluate, and recommend appropriate changes

in JPL/HBCU research interactions.

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Theinitial conference occurred in May 1988. JPL personnel involved in this orientation included

personnel from sections where research interests exist; contract management staff; recruitment staff,

and other appropriate laboratory individuals. The second is planned for June 13 and 14, 1989. A number

of additional schools are expected to take part this year.

IV. Supporting Organization

A division-level manager in the Technical Divisions serves as manager of the JPL HBCU initiative.

This position is presently filled by Dr. Martin H. Leipold who acts as advocate to the technical divisions

and program offices, provides information for and assures correct reporting to NASA, and monitors

the performance of the varied activities. He is assisted by an Initiative Administrator, Mr. Paul Forte,

who is responsible for generating required reports and coordinating initiative activities with managers

from the Administrative Divisions.

The office of the Director at JPL has appointed a Steering Committee to review the actions taken

or to be taken in the HBCU program and to provide guidance in the proper operation and functioning

of the program at JPL and NASA. This committee reports on the activities being conducted as a part

of the total HBCU Program. It is presently chaired by Dr. A. Zygielbaum.

The Initiative Manager and Administrator generate and distribute an annual plan showing

important dates covering the mechanics of the initiative and establishing goals for participation by

Laboratory organizations.

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N91-28

LINCOLN ADVANCED SCIENCE AND

ENGINEERING REINFORCEMENT

(LASER) PROGRAM

Dr. Willie E. Williams, Director

Physics Department

Lincoln University

Lincoln University, Pa

097. .

ABSTRACT

Lincoln University, under the Lincoln Advanced Science and Engineering Reinforcement

(LASER) Program, has identified and successfully recruited over 100 students for majors in technical

fields. To date over 70% of these students have completed or will complete technical degrees in

engineering, physics, chemistry, and computer science. Of those completing the undergraduate degree,

over 40% have gone on to graduate and professional schools.

This success is attributable to well-planned approaches to student recruitment, training, personal

motivation, retention, and program staff. Very closely coupled to the above factors is a focus designed

to achieve excellence in program services and student performance.

Future contributions by the LASER Program to the pool of technical minority graduates will have

a significant impact. This is already evident from the success of the students that began the first year of

the program. With program plans to refine many of the already successful techniques, follow-on

activities are expected to make even greater contributions to the availability of technically trained

minorities. For example, undergraduate research exposure, broadened summer and co-op work experiences will be enhanced.

This program is supported in part by the Office of Naval Research, National Aeronautics and

Space Administration, and the Department of Education under grant #N00014-83-G-0082, Grant

#NGT-90020, and Grant #P120BS0021, respectively.

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LINCOLN ADVANCED SCIENCE AND

ENGINEERING REINFORCEMENT

(LASER) PROGRAM

Introduction

LASER is a program sponsored by the National Aeronautics and Space Administration (NASA),

Office of Naval Research (ONR), and the Department of Education (DOE) to explicitly encourage

minority students to pursue engineering and science studies. The program was established in 1980 by

NASA and Lincoln University as a joint effort to increase the number of students entering careers in

engineering. Since then, the program has been expanded to include Physics, Mathematics, Computer

Science and Chemistry majors. Lincoln was chosen as the site for the program because of its long history

of providing students with the preparation skills needed to succeed in science and engineering careers.

The program consists of summer and academic year components in an overall effort to prepare talented

students for a course of study leading to a B.S. degree in Chemistry, Physics, Biology, Mathematics, or

Computer Science or a dual degree: a bachelor of science in engineering and a bachelor of arts in liberal

arts. Students are annually recruited nationwide to fill the twenty slots available.

The summer program provides the opportunity for participating students to begin their early

course of study in an environment that has support services for success. Class sizes are small to provide

the opportunity for students to work closely with instructors. In addition, special math, writing, and

reading labs are maintained to provide additional help as needed. Each student is assigned a faculty

advisor and counselor to offer academic and career guidance.

The program also provides the opportunity to work and interact with engineers and scientists. In

subsequent summers, NASA, ONR, and other agencies provide employment with an opportunity to

gain first hand knowledge of the careers in science and engineering.

LASER participants receive financial support to cover the cost of normal college expenses such

as room and board as well as tuition for the summer program. In addition, the student receives a stipend

to help cover his or her personal expenses.

The remainder of the paper provides a detailed discussion of the program components and review

of the program's successes.

Philosophy

The LASER Program is a quest for excellence! In these times of diminishing quality and

expectations, the LASER Program still stands for excellence and the best one can be. Like its acronym,

the LASER Program is a very narrowly focused project aimed at producing an excellent and outstanding

group of young men and women for careers in science and engineering. It is no accident that the

expectations are so high. Each student is hand-picked based on high school performance, academic

potential, natural ability, drive and motivation. Each student selected becomes a member of a select

group that will make a major contribution to the world of engineering and related fields. From the very

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outset the founders of the LASER Program designed a concept of excellence in every aspect of the

program and conveyed it to the students accepted into the program.

Students are expected to achieve their highest potential. No second rate work or efforts are

tolerated. Everyone must strive to be the very best he or she can as a student, as a person, as a human

being. Nothing less than each student's individual best effort is ever accepted. The student's foremost

concern must be achieving good grades in all course work. A "C" grade is not satisfactory, only "A" and

"B" are grades worthy of a LASER student.

Students serve as role models of excellence in math and science and throughout the entire

university. The LASER student is with few exceptions the best in all his or her classes and extra-curricular activities. He or she is a leader, setting goals and standards to be met by all.

Achievement and success in the LASER Program represent the collective efforts of LASER

students, parents, staff, the Director and other university officials, all striving for excellence. In fact,

excellence in LASER can only come as a result of this collective effort. The achievement of excellence

is the single most important goal that runs throughout the LASER Program. All activities, tasks and

specific objectives are set up to help achieve this excellence.

Program Objectives

Objective 1: To seek out and identify future minority scientists and engineers to meet the future

requirements of our technical society.

The hallmark of LASER over the years has been an ability to understand the needs of students

and, through the application of special aid and support, money, and technical skill, devise means to

assist these young men and women to become successful. However, if one does not have an understanding of the student needs, no amount of money or technical skill will result in successful students.

A good understanding of the student requirements does not just happen. It takes hard work and

a thorough understanding of the students themselves. One must deal actively and prudently with the

environment that the students come from, as well as the environment that students find themselves in

while attending the program. One must insure that the student involvement with the local environment

is controlled and does not become counter productive for overall program goals.

Objective 2: To help LASER students achieve success by providing opportunities for advancement

based on their academic performance, recognizing their individual achievements, and insuring the

personal satisfaction that comes from a sense of accomplishment in their work.

One can take pride in the students and people in the LASER Program, their performance, and

their attitude toward their jobs and toward the program. The LASER Program has been built around

these individuals, the personal dignity of each, and the recognition of personal achievements.

The general policies and attitudes of the staff toward students and the people that work with them

are more important than any specific person. Staff and student relationships will be good only if people

have faith in the motives and integrity of their supervisors and the program management. On the other

hand, relations will be poor if they do not.

256
Administrative Overview

Organization

The LASER Program is organized into four major efforts. The first of these involves the

identification, recruitment, and training of minority students for careers in science and engineering.

The second and equally important component of these efforts is the student reinforcement and

retention activities. After careful analysis,the focus here is to provide the all important support system

each student requires to be successful. This represents the bulk of the effort to date. The third

component is the introduction of research and development experiences as well as exposure to national

facilities like NASA, Fermi Lab, Stanford Accelerator Lab, Bell Labs, etc.The final component of the

program tries to address the required facilities and equipment needed to maintain current, and when

possible state-of-the-art, experience and exposure to emerging science and engineering concepts.

ORGANIZATION CHART

LASER

i PROGRAM OFFICE

ADVISORY

COMMITTEE

RECRUITMENT J

EFFORT

• SL.'?*4MEIR PROGI_t.M

• 2 YR mAgiC ACADEMIC PROGg.A.M

• 2.J _'R. SCIL'NCE & ENG. MAJOR

RETENTION

EFFORT

• WORK EXPERIENCE

• C OL'Nb'ELLNG

• MATH • OTHER

• F'EELD TRIPS

• MONITORING SYSTEM

RESEARCH

EFFORT

• DEVELOP FACULTY R.Eb"E.A_CFI

• DEVELOP UND1L"RGRADUATI[ R.ES.

• PROM OTE GRADUATI_ SC"HOOL

REVITALIZATION

EFFORT

• LMPROVE EQUnPMENT & LA.BS

• IMPROVEFACUL'I't" EXCI_LLENCE

• UPGRADE STAFTSKILI.,$

• E_PM_' FACILIT'IES

257
Participants

Students are recruited nationwide for the program. However, major efforts are concentrated

within a radius of about 150 miles beyond the campus. Such areas as Baltimore, Philadelphia, New York,

and Washington are target cities. The number of participants sought range form 12 up to 20, depending

on the amount of available funding during a given year. The number 12 is regarded as the minimum

number to be cost effective. Table 1 below summarizes the results for the past several years.

TABLE 1

MALE

m

FEMALE

TOTAL:

1981-82

Group I

#

12

20

1982-83

Group II

#

13

14

1983-84

Group III

#

1984-85

Group IV

#

12

19

1985-86

Group V

#

I0

16

1986-87

Group VI

#

5

3

8

1987-88

Group VII

#

15

1988-89

Group Villi

#

14

TOTAL

#

71

44

115

Recruitment

The multi-approach is used in recruiting students for the program. The approach utilizes science

faculty, admission personnel, high school counselors, science and math teachers, alumni and the media.

Extensive use is also made of mailings to alumni, high schools, and other groups. During the Fall

term, letters and materials are sent to all known alumni on the East Coast. The mailing describes the

program and requests their support in identifying potential candidates. During the same time high

school science and math teachers are also mailed similar materials seeking their help in recommending

students for the program.

Limited media exposure is provided for the program on a few local radio stations and in several

newspapers. Occasionally, the program is able to receive TV coverage on one of the local community

service programs.

258
Participant Selection

Each potential participant is required to complete both a program and university application,

provide three (3) letters of recommendation, a high school transcript, and SAT scores.

Upon receipt of the LASER application and materials, the student is invited for an on-campus

interview. The main purpose of the interview is to allow for a close review and evaluation of the student's

abilities, academic potential, strengths and weaknesses. A team of 3 to 5 people spend from 45 to 90

minutes talking with each student. From the interview each student is rated on six items that are

considered important to the student's success in the program.

Following the interview, students are required to complete the math placement test. This is an

ETS test designed to evaluate the student's skills in algebra and pre-calculus. Based on their performance, students are placed in one of several math courses: algebra, pre-calculus or calculus. Normally,

only those students testing into calculus are considered for the program. However, the final decision

on selection is made by the director only after careful review of all the information available on a given

student. Generally, with the exception of math background, no single item is the sole basis for selection.

Faculty and Staff

The pertinent program staff consists of a director, secretary, and an advisory committee. In

addition, one or more assistants to the director, counselors, parents, course instructors, student tutors,

and resident advisors are utilized during the course of the program.

Curriculum

The curriculum for this program is based on very specific requirements needed to complete

technical programs in science and engineering. Most of these requirements have been worked out with

participating science departments and engineering schools. The actual courses are in our science and

pre-engineering curriculum.

The academic phase of the initial year of the program begins in the summer. During this period,

students complete first year pre-engineering requirements in mathematics (calculus) and physics, as

well as a survey course in engineering sciences taught by the project director and other engineers and

scientists. At the conclusion of this summer trimester, students have earned approximately 18 credit

hours. These students continue their studies in the fall.

Student Outcomes

The overall goal of the LASER program is to improve students' interest in and ability to pursue

a technically-oriented education that leads to a career (or at least a degree) in engineering or a related

science field. Thus, the entire program has been designed and implemented to achieve that end. The

significant accomplishments of the project are summarized under the headings listed below and in Table 2.

259
Undergraduate Degrees Awarded

The most significant results of this project is the number of technical graduates. The program has

had 34 students complete degree programs. Of this total, over 70% completed degrees in one of several

technical areas. Expected graduates for the 1988-89 academic year will include 8 physics majors, 8

chemistry majors, and 1 electrical engineer.

TABLE 2

LASER PARTICIPANTS STATUS (RETENTION/TRANSFERS/GRADUA_ON)

Number of Students Retained

With Years Since Entry

Year # 1 2 [ 3 4 ] 5 6 Trans ] Eng._ Tech Non Grad

1981-82 20 20 17 9 6 1 0 6 5 14 3 5

(110%) (85%) (45%) (3o%) (5%) (3o%) (25%) (7o%) (15%) (25%)

1982-83 14 10 5 5 4 1 0 5 4 8 1 2

(71%) (36%) (36%) (29%) (7%) (36%) (29%) (57%) (7%) (14%)

[1983--84 9 9 8 6 4 3 0 1 1 7 0 0

(100%) (89%) (67%) (44%) (33%) (11%) (11%) (78%)

1984-85 19 18 18 18 10 5 3 2 14 0 6

(95%) (95%) (95%) (53%) (26%) (16%) (11%) (74%) (32%)

1985-86 16 16 14 11 8 6 4 5 1 0

(100%) (88%) (69%) (50%) (30%) (25%) (31%) (6%)

1986-87 8 8 8 7

(100%) (100%) (88%)

1987-88 17 16 16

(94%) (94%)

1988-89 15 14

(93%)

Tram represents the # of students that have transfered. Eng represents the # of students

that are Engineering graduates or persisting. Tech represents the # of students that are

Technical graduates or persisting. Non represents the # of students that are Non-technical

graduates or persisting. Grad represents the # of students that are in graduate school.

26O
TheLASERconceptissuccessfullyaddingto the number of minorities completing undergraduate

degrees in science and engineering. By the close of the 1988-89 academic year, the program expects to

have graduated 13 B.S. engineers; 28 B.S. physicists; 6 B.S. chemists and 8 M.S. level scientists and

engineers.

Graduate and Professional Programs

Equally impressive has been the project's success in encouraging students to seek advanced

degrees in a wide variety of areas. A total of 14 students have enrolled in some type of advanced studies.

Of this total, 80% are completing degrees in one of several technical areas that include engineering,

physics, and chemistry, or non-technical areas such as psychology.

During 1988, three (3) students were selected as recipients of national fellowships from the Office

of Naval Research and Oakridge Associates. Yvette Bell and Octavia Blount received ONR Fellowships

that year, while Lori Thomas and Yvette Bell received Oakridge Fellowships.

Participants

The program has over 40 participants this academic year. Ten (10) of these participants are

currently completing degrees at other colleges. Eight (8) of the ten students are pursuing degrees in

engineering. In addition to the above students, a large number of students will be completing their

studies at Lincoln. Over 80% of the students are pursuing technical degree programs.

261
N91-28098. |

A MODEL SUMMER PROGRAM FOR HANDICAPPED

COLLEGE STUDENTS

Anne B. Nissen

Gailaudet University

Washington, D.C.

During the summer of 1988, the Goddard Space Flight Center was the site of a new NASA project

called "A Model Summer Program for Handicapped College Students." Directed by Gallaudet University, the project's aim was to identify eight severely physically disabled college students -- four from

Gallaudet University and four from local historically black colleges and universities (HBCUs) E

majoring in technical fields and to assign them technical projects related to aerospace which they would

complete under the guidance of mentors who were full time employees of Goddard.

Gallaudet University is unique. It was founded in 1864 by an Act of Congress under President

Abraham Lincoln and became the only liberal arts college in the world for the deaf. Located in northeast

Washington, D.C., Gallaudet isjust a twenty minute drive from Goddard. Virtually all its undergraduates

are deaf or hard of hearing. A large percentage have additional disabilities including visual and mobility

impairments. While at Gallaudet, deaf students are not handicapped, for virtually all the staffand faculty

use sign language. Also commonplace to make collegiate life more accessible are TDDs (Telecommunication Devices for the Deaf), flashing lights (to complement hells and sirens), and captioned movies

and television. Gallaudet is the only university in the world to have a deaf president.

Even as Galluadet provides a non-handicapping environment, so too can the workplace create an

environment for disabled people that is enabling, comfortable, and accommodating. Towards this end,

the model summer program at Goddard was established.

The greatest challenge of the project was locating students who met the project's four criteria for

participation. This task tended to he difficult because offices offering services to handicapped students

are not well established at the majority of HBCU's contacted. Students were required to:

1. he enrolled at Gallaudet or an HBCU;

2. be making progress toward a BA/KS degree in a technical or scientific field;

3. have a respectable grade point average; and

4. have a severe disability.

262
Thepoolfor eligibleapplicants is exceedingly small. Few severely disabled minority young people

are enrolled at four-year colleges. Furthermore, persons with disabilities do not traditionally select

majors in scientific and engineering fields. The reasons for this situation are many:

1. While growing up, frequently the focus by the family and social services was on coping with

the child's disability. Little thought was given to preparing the child for a career.

2. In many high schools, disabled students were waived from the science requirement due to

inaccessibility to the lab, and real or imaginary dangers perceived by parents, teachers, and

administrators.

3. There were few role models in the scientific or technical fields for the disabled student.

These combined factors severely limit the number of candidates for the program. We expect that

the pool of candidates will grow as students are encouraged to explore the possibility of a future in a

technical or scientific field while they are still in elementary school. Furthermore, the laws now require

that all students receive an equal access to education.

Other factors complicate the placement of students in the work environment. Many disabled

students have had little, if any, prior work experience and are reluctant to seek a work experience: issues

of transportation, communication or accessibility often may seem overwhelming.

On the other hand, many organizations hesitate to consider severely disabled candidates because

the organizations themselves feel uncomfortable and do not understand the abilities of these people

who are different from the typical applicant.

Thus, with these issues in mind, Goddard Space Flight Center and Gallaudet University designed

a model ten week program which provided:

1. support, resources, and training to supervisors and co-workers through workshops and

individual assistance;

2. accessible housing at Gallaudet and accessible transportation for the students;

3. a mentor from Goddard for each student;

4. bi-weekly sign language classes for all interested Goddard employees;

5. an actual technical project for each student to work on;

6. on-site seminars on various technical topics for all participating students;

7. sign language interpreters for all training seminars;

8. a full-time coordinator who arranged the seminars, taught the sign language classes,

handled the logistical issues, and met with the students as a group each week to evaluate

and examine their experiences.

Was the program a success? Although we were unable to fill all four slots designated for the HBCU

students because of the aforementioned reasons, seven students participated: five were from Gallaudet,

263
one was from the University of the District of Columbia, and one was from Bowie State College in

Bowie, Maryland. Five of the seven had GPAs of 3.0 or higher. All were severely handicapped and

majored in math and/or computer science.

The participants were almost unanimous in stating they received much more than they had

expected. They were especially surprised at how challenging the tasks were for which they were

responsible. Most did not expect to be treated so professionally: One participant stated "For the first

time I was able to work on projects with other professionals...l learned so much!"

Almost all the participants responding listed improvement in their technical skills and an increase

in self confidence as their primary growth areas. Other areas of growth listed included improvements

in human relationship skills and the ability to handle responsibility. One participant summed it up best:

"I felt positive about myself...I learned so much that my brain almost exploded." Another student said

"I felt so good and proud to work for NASA."

As for the supervisors' reactions to the students:

* Six of the seven supervisors involved in the project want to be included in the coming

year's project.

* Five of the seven participating students would "definitely" be hired if a position became

available.

Other positive outcomes of the program:

* Three of the seven students are still working at NASA, one as a stay-in-school, and the

other two are enrolled in Goddard's co-op program.

Twenty-three employees studied sign language so that they are able to communicate

more effectively with their summer co-worker and other permanent deaf employees.

One of the participants made a presentation about her NASA experience to a group of

about 200 Gallaudet freshmen who were considering a major in the Computer Science,

Physics, Engineering, or Math fields. At that presentation the freshmen were also given

information about the various ways they might be considered for employment at a

NASA facility.

Three Gallaudet participants made presentations about their experiences at a meeting

of 50 Co-op interns.

The success of this project and examples of student participants' accomplishments have

been used by Gallaudet faculty in advising other Gallaudet students about career

opportunities and skill requirements.

A group of 15 deaf high school students participating in a Young Scholars Program at

Gallaudet toured Goddard Space Flight Center and visited the deaf college students at

their worksites.

264
Summing up the first year's program, the project was a threefold success:

* Disabled students received important technical work experience.

* Goddard was sensitized and exposed to the abilities of physically-challenged persons and

became more aware of a new pool of talent.

* Younger students, high school and entering freshmen or sophomores, were encouraged

by older students' positive experiences related to the technical opportunities offered by

NASA.

According to almost all participants, the model program was a success. It will be repeated during

the summer of 1989 at Goddard.

265
¢y,

N91 "28099

A SUCCESSFUL INTERVENTION PROGRAM FOR

HIGH ABILITY MINORITY STUDENTS

Winson R. Coleman

Director - Science and Engineering Center

College of Physical Science, Engineering and Technology

University of District of Columbia

Washington, D.C.

Among professional occupations in the United States, non-Asian minorities are least represented

in science and engineering fields. Minorities represented at least 20% of the total population, but less

than 2% of the doctoral degrees in science and engineering are awarded to non-Asian minorities. If we

trace the process that produces Black, Hispanic, and Native American scientists and engineers back

one step further, we continue to find underrepresentation. Within the college-age population, blacks

make up 14%, Hispanics constitute 6.4% and Native Americans constitute 0.6%. However, only 5% of

the full-time college students majoring in engineering are Black, only 4.5% are Hispanic, and only 0.4%

are Native American (Engineering and Manpower Commission 1987). The Bureau of Labor Statistics

predicts that over the next decade, civilian employment of scientists and engineers has the potential to

grow by 40%. Further, projections for the year 2000 indicate that 100,000 fewer B.S. and B.A. degrees

will be awarded than were awarded in 1984 (Devarics 1987). The latter projection takes into consideration the overall declining proportion of all 18-year old college students. Within this shrinking pool of

18-year old potential college students will be an increasing proportion of Blacks and Hispanics. in order

to Change the educational patterns for minority youth, we must take an intense look at the factors that

affect the science and mathematics performance of minorities. Further, we must examine and document,

with the intent of replicating, the work of programs that are successful at producing minority scientists

and engineers. The fundamental concern at this time appears to be the quality of precollege experience

because research has shown that lack of precollege preparation is the single most important cause of

underrepresentation of minorities in science and engineering careers. For many years, intervention

programs have attempted to improve the quality of the minority precollege experience by latter year

intervention in grades eleven and twelve. Later efforts, such as this one, have concentrated on earlier

years. The vast majority of these programs have operated with little or no emphasis placed on the formal

evaluation of their efforts. Casual evaluations (e.g., George 1987; Wellington 1984), however, have

shown that many of the students involved in such programs have gone on to pursue studies in

quantitative fields. That intervention programs are effective is widely accepted but not rigorously

documented. The mechanisms these programs have developed need to be identified and their potential

for broader use evaluated. The ultimate goal of such studies would be to provide the different

educational communities with a set of proven cost-effective state-of-the-art mechanisms designed to

increase participation and success of minority students in science and mathematics-related courses. One

such intervention program is the Saturday Academy program for high ability minority students in the

Washington, D.C. area. The purpose of this study is to provide a description of the Saturday Academy

with the intent of making it available to personnel who are considering the development of similar

projects and to examine the effect of participation in the program on high school graduation rates,

college enrollment and choice of quantitative major.

266
Description of the Saturday Academy Program

Located on the campus of the University of the District of Columbia the program operated in

1987-88 on a direct cost budget of $68,063, funded primarily by the National Aeronautics and Space

Administration (NASA), and serviced 282 students (approximately $242 per student). Participants are

students who have been identified as academically talented, primarily seventh, eighth, and ninth graders

from the metropolitan Washington, D.C. area. To be selected for this program, first students must have

an overall B-average or better. Second, the students must be recommended by their math/science

teacher or counselor. Third, students must have a parent or guardian willing to attend two Saturday

sessions and an orientation session. Finally, the student must agree to the program's mandatory

attendance requirements - more than one unexcused absence results in dismissal from the program.

The Saturday Academy is designed to provide enrichment experiences for academically talented

minority youth without cost to them. These experiences are in creative mathematics, electrical engineering, and computer science. The program has been in existence since September 1982.

Electrical Engineering Component

The engineering component is designed to introduce the participants to the world of electrical

engineering in an organized scientific manner. For the most part this is accomplished by first introducing

basic theory of electricity in terms of current and voltage and the instruments that measure these

quantities. Secondly, the various components used in electrical construction are introduced through

theory and observation. Students are also given specific instruction in soldering, reading schematic

diagrams, and in identifying components such as resistors, diodes, capacitors, integrated circuits and

transistors. They then go on to construct light generators, sound generators and/or transistor radios and

robots.

Computer Science Component

The computer science component is designed to help program participants become computer

literate. Most participants do not have access to personal computers at home and have limited access

at their regular schools. Instruction begins with teaching the present limitations of the computer and

its internal structure. Participants learn to program in BASIC; they access the university's Vax 8650,

Vax 11-780 or IBM 4341 with a modem or by direct link. IBM PC's are also available to participants.

More advanced students are instructed in PASCAL.

Mathematics Component

This component provides students with abstract and semi-abstract experiences in what the

program calls non-numerical mathematics. The end result of such experiences is designed to be the

student's acquisition of application, analysis, and synthesis skills. All students work with group tables

and the construction of mathematical systems. They learn operations in bases other than base 10,

3-dimensional explorations, and basic set theory. Advanced students study trigonometric and geometric

concepts.

267
Evaluation

In an attempt to evaluate the Saturday Academy Program, all persons involved were given an

opportunity to give input. Parents (or guardians) of the current participants, participants, and program

teachers were asked to complete questionnaires. Administrative personnel were interviewed and

project reports were examined. Results of these surveys and interviews will be made available during

the actual presentation. Also included in the evaluation were alumni of the Saturday Academy Program.

Eighth and ninth grade participants in the 1982 program and ninth grade participants in the 1983

program formed the experimental population. There were 180 students in the population. Of the 180

students, 69 students were still living at the same address and/or still had the same telephone number

as when they were participants in the program or were accessible through other accessible participants.

The experimental group was made up of these 69 Saturday Academy alumni. Telephone contact was

made with the homes of each of the 69. If the former participants were not available, information was

obtained from parents or guardians; information was not accepted from siblings or others. Questions,

read from a prepared survey form, were asked about high school graduation, enrollment in college and

choice of college major. One hundred and thirty four students were in the control population. All control

population students were ninth graders in 1983. They were identified as having the same profile as the

Saturday Academy participants with regard to performance in high school course work and recommendations of teachers and/or counselors. No parental participation was required of the control group; this

factor may have an effect which limits the generalizability of this study. Of the 134 control population

students, 50 (37%) were still living at the same address and/or still had the same telephone number as

they had in 1983 or were accessible through other accessible control group students. The control group

was made up of these 50. Control group students were contacted by telephone in the same fashion as

were the experimental group members. A tally was kept on the number of each students in each group

completing high school, enrolling in college and choosing a quantitative major. The results are given

below.

The program had a significant effect on the three variables; the effect was, however, more

pronounced for males than for females.

Experimental Group vs. Control Group

VARIABLES EXPERIMENTAL CONTROL DIFFERENCE

P1 P2 P1 - P2

kigh school graduation .99 .76 .23

college enrollment .91 .46 .45

quantitative major .45 .20 .25

268
Discussion

Several common themes emerged in the evaluation by the various groups: the effectiveness of

hands-on activities, the necessity for improvement in some aspects of instruction, the desirability of

including career information and field trips. Parents mentioned that more black males should be

recruited, a particularly crucial factor given the success of the program with males. The study of the

alumni of the program shows that it was successful in improving high school graduation rates, college

enrollment rates, and the rate of selection of a quantitative major. The program had substantially greater

effect on male participants than on female participants. Moreover, substantially more than half of the

participants were female. This highlights a feature that distinguishes the participants of this program

from the white participants of most science and mathematics programs in the United States, where

generally females are underrepresented. Colleges and universities sometimes see intervention programs as recruitment devices. Thus it is of interest to note that of the students in this study (experimental

and control), thirteen chose to attend the University of District of Columbia. Nine of these 13 were

Saturday Academy alumni. The results of this investigation serve to document the success which this

intervention program has enjoyed with respect to encouraging non-Asian minority students to prepare

themselves for quantitative careers. It is not possible to point to an intervention program that can trace

its successful influence through the participants' sophomore year in college. Further research, however,

is needed to track these same students through their college graduation and into graduate school and/or

careers. Such studies would then determine the proportion of intervention programs students that i)

graduate from college; ii) graduate with a quantitative degree; iii) complete a graduate degree; iv)

complete a graduate degree in a quantitative field; and v) enter a career field requiring quantitative

expertise. In-depth interviews with alumni who chose quantitative majors should inquire as to whether

they found some part of the Saturday Academy program particularly helpful. Longitudinal studies of

later alumni are also needed; the program should encourage all alumni to continue their contact

throughout their college studies.

Research is also needed with controls for the parental involvement factor. Other influential

variables to be studied include the students' academic performance and socio-economic factors.

References

Dervarics, Charles. "White House Urges More Minority Participation in Math and Science",

Black Issues in Higher Education, 1987, 4, 5.

Engineering Manpower Commission, Engineering Manpower Bulletin: Minorities in

Engineering, Washington, DC.: American Association of Engineering Societies, 1987.

Hayden, Linda, The Impact of an Intervention Program for High Ability Minority Students.

American University, 1988.

George, Y., Chu-Clewell, B., and Watkins, N. "Lessons for HBCUs from Precollege

Mathematics and Science Programs." Paper presented at the U.S. Dept. of Education White

House Initiative on Historically Black Colleges and Universities, Washington, D.C., 1987.

Wellington, R.G. "Subsequent Academic and Career Development of Participants in Selected

NSF Student Science Training (Pre-college) Programs," 1974, DDJ-74-09447.34/10A: 6478.

269
N91 "28 1 O0

THE WOMEN IN SCIENCE AND ENGINEERING SCHOLARS PROGRAM

Etta Z. Falconer and Loft A. Guy

Spelman College

Atlanta, Georgia

ABSTRACT

The Women in Science and Engineering Scholars Program provides scientifically talented women

students, including those from groups underrepresented in the scientific and technical work force, with

the opportunity to pursue undergraduate studies in science and engineering in the highly motivating

and supportive environment of Spelman College. It also exposes students to research training at NASA

Centers during the summer. The program provides an opportunity for students to increase their

knowledge of career opportunities at NASA and to strengthen their motivation through exposure to

NASA women scientists and engineers as role models. An extensive counseling and academic support

component to maximize academic performance supplements the instructional and research components. The program is designed to increase the number of women scientists and engineers with graduate

degrees, particularly those with an interest in a career with NASA.

270
THE WOMEN IN SCIENCE AND ENGINEERING SCHOLARS PROGRAM

The Women in Science and Engineering Scholars Program was initiated in 1987 as a cooperative

effort between Spelman College and NASA. The program provides scientifically talented women from

groups underrepresented in the scientific and technical work force with the opportunity to pursue

undergraduate studies in science and engineering in the highly motivating and supportive environment

of Spelman College.

The goal of the Women in Science and Engineering Scholars Program or the WISE Scholars

Program is to increase the number of women, including minority women, entering scientific and

technical careers. The specific objectives are:

1. To identify high ability women students from underreprcsented groups and to provide the

students with an opportunity to pursue undergraduate study in engineering and science.

2. To enable high ability women college students to maintain academic excellence in scientific

and technical studies.

3. To motivate and encourage students to pursue scientific and engineering careers.

4. To provide research training for selected students both in the undergraduate setting and at

NASA Centers.

5. To motivate and prepare students to earn graduate degrees in science and engineering.

Scholars are actively recruited and are selected by a competitive process. Preference is given to

students residing close to NASA Centers. Selection criteria include high potential and achievement in

science and mathematics as measured by college entrance examinations and the high school record, and

an interest in pursuing a career in science or engineering. Scholars are selected by a committee of

Spelman faculty and staff, the NASA Center Equal Opportunity Officers, and the NASA Agency wide

Fcdcral Women's Program Manager.

Currently, there are 13 sophomore and 15 freshman Scholars. Each Scholar has a sponsoring

NASA Center. The Equal Opportunity Officers and the Federal Women's Program Managers at NASA

installations have a primary role in the development of the students. The NASA Centers and the number

of students sponsored are given below.

271
NASACENTERSAND WISESCHOLARS

Ames Research Center

Goddard Space Flight Center

Jet Propulsion Laboratory

Johnson Space Center

Kennedy Space Center

Langley Research Center

Lewis Research Center

Marshall Space Flight Center

Stennis Space Center

3

4

2

4

3

4

4

2

2

TOTAL 28

Scholars pursue majors in electrical or aerospace engineering through the Dual Degree Engineering Program, physics, mathematics, or another scientific or engineering major related to the mission of

NASA and the work of the sponsoring NASA Center. In the Dual Degree Engineering Program a

student spends three years at Spelman and two at Georgia Tech, Rochester Institute of Technology,

Boston University, or Auburn University, earning degrees from both Spelman and the engineering

institution.

A three-day Orientation Conference was held prior to the beginning of the Fall semester for the

Freshman WISE Scholars, parents, NASA officers, Spelman administrators and faculty and program

supporters. The objectives of the conference were to provide a detailed explanation of the program,

including the role of NASA, and to make certain that student and parents understand their responsibilities and the various support mechanisms available to help students meet program requirements. The

conference was valuable in providing an opportunity for the Scholars to become acquainted with NASA

officers and the WISE program staff. It was particularly effective in creating a bonding of the Scholars

which has been instrumental in their academic success.

The Academic Year

The students take a strong sequence of science and mathematics courses leading to a major in

science or engineering. The following courses are required of every Scholar.

Honors Analysis I, II (Calculus of One Variable)

Analysis 111 (Calculus of Several Variables)

General Chemistry I, II

Mechanics and Heat

Electricity and Magnetism

FORTRAN or Pascal

Honors English I, II

Independent Study/Research

272
FreshmanScholarstakeascheduleof challenging courses, including Honors Mathematics, Honors

English, and chemistry. Engineering majors also take Introduction to Engineering and Engineering

Graphics. Honors Mathematics is offered on three levels and students are assigned mathematics courses

based on placement examination scores. Honors Mathematics provides an introduction to research

methods through the requirement of at least one paper or project reflecting independent work, library

research, and oral and/or written presentation. Freshmen also enroll in a special Study Skills and Critical

Thinking Seminar. Additional courses from the required general studies complete the schedule.

Sophomore Scholars take Mechanics and Heat, and Electricity and Magnetism, along with

appropriate mathematics courses. General studies and major courses such as Computer Systems, Linear

Algebra, or Organic Chemistry complete the schedule.

Academic Support and Counseling Component

The director serves as academic advisor during the first two crucial years and maintains close

contact with instructors of Scholars in order to take necessary intervention action to assure student

success. Early identification of potential problems in science and mathematics courses is made by

requesting student progress reports during the semester from their instructors.

Tutorials are an important part of the Academic Support Program. Tutors are provided for

students in mathematics, chemistry, physics, and computer science. Tutors are graduate students or

upper-level undergraduates of exceptional ability and achievement. The graduate tutor in mathematics

conducts a group session for freshmen who are taking Honors Quantitative Reasoning I, Honors

Quantitative Reasoning II, or Honors Analysis I. The session is designed to develop the ability of the

students to work in small, productive groups. The tutor moves from one group to another offering

assistance as needed. The graduate student is also available at other hours to provide individual tutoring.

In chemistry, a graduate tutor conducts a required group tutorial session for two hours. Difficult

but basic topics are emphasized by the tutor, and questions are taken from the group. The tutor is also

available for individual tutoring. In physics, an undergraduate senior provides individual or small group

tutoring. Students are encouraged to attend tutorial sessions as a means of enhancing learning.

Individual tutoring is provided in computer science.

All freshman and most sophomore Scholars live in the same dormitory, the Living Learning

Center. A special graduate residential assistant is available to provide counseling and to give assistance

during the evenings, nights and weekends. Students also attend group meetings with the director during

the year for the purpose of assessing progress, determining problem areas, and providing support. Each

freshman Scholar has a sophomore Scholar who serves as her Big Sister. The students are matched by

major and the Big Sister provides advice, support and friendship.

Freshmen attend a seminar in Study Skills and Critical Thinking. The non-credit course meets

once a week for a semester and covers topics such as study and test-taking skills, time management, and

techniques for studying the sciences. The seminar is taught by a college counselor and guest lecturers.

Each semester a woman scientist or engineer from NASA spends two days on campus as the NASA

Lecturer. She gives several talks and conducts an informal session for the WISE Scholars. Through the

visit a strong statement is made that women can achieve in science and engineering.

273
Research Experiences

Scholars engage in a lO-week research experience at the sponsoring NASA Center each summer.

Each student is required to submit a paper upon return to Spelman and to give a presentation of her

work. The following presentations were given this semester:

Inertial Reference Package

Detector Array

Computer Research at Stennis

Fuel-Rich Catalyst Combustion

Model for Research of LCG

Investigation of Space Adaptation Syndrome

Computer-Aided Design for Large Advanced Space Systems

The Attitude Heads by Display Prototype

Controlling Indoor Pollution

Zirconium Ignition Test

Thermal Cycling Effects on Crack Densities in the Space Station

The following report by WISE Scholar Lori Ann Guy is representative of the summer research

component of the program.

Computer-Aided Design for Large Advanced Space Systems

The Large Advanced Space Systems Computer-Aided Design and Analysis Program (LASS) has

the capability of modeling intricate structures that are too complex to be built by most existing

computer-aided design software packages. Last summer under the direction of Melvin Ferebee, Jr. of

NASA Langley Research Center, I developed expertise in the use of LASS and created a model of a

space platform in order to validate the program.

LASS includes several antenna synthesizer programs and corresponding databases for each

configuration. The configurations are: a box-ring, a box truss, a hoop and column, a radial rib, a

tetrahedral truss, and a default database. Each database contains the information necessary to create

an antenna or model. Once a configuration has been specified, the appropriate synthesizer must be

activated. The synthesizer is the part of the program that creates the antenna that will be used for

analysis. The size and design of the antenna must be specified after the synthesizer is activated.

Following the selection of the desired antenna for the model of the space station, the execution

of the corresponding synthesizer resulted in an output of a model file, a database file, and a set of mass

properties. Next, a translator program which writes a universal file of the structure was executed. It

contained all of the structure, geometry, and data sets pertaining to the model. It was necessary to specify

whether the antenna would be added to an existing model during the writing of an universal file.

The universal file creates a permanent group of the individual models which is useful in allowing

the user to manipulate all of the nodes of the antenna as a whole structure. While writing the universal

file, the user has the ability to translate and/or rotate the model.

274
Modificationsof thephysicalstructureandanalysis of the physical and material properties were

made to the various models of the space station by using other programs. An internal program translated

the modifications into a NASTRAN output file, which in turn had to be translated into a format suitable

for use in the LASS program. Then the General Truss Synthesizer (GTS) was used to make final changes

in the model and to review its components. GTS has two input categories - a listing of the values for

the structural model in addition to those of a tetrahedral truss, and a second category which may require

additional changes in order to identify antennas other than a tetrahedral truss. GTS writes the elements

and nodes of the model to a file which contains the structural and geometric data of the elements in the

model. Finally GTS outputs information about synthesizers including the number of nodes and elements

contained in the model, the types of elements (beams, cables, or rods), and data on physical and material

properties.

Following the viewing of the GTS output for the models of the Space Station, the Thermal Analysis

program was executed. This program specified the orbit and material properties of the model and then

computed temperatures and heat rates. This data was also translated into an analysis data set in a

universal file that could be read into another program.

Several antennas were designed and analyzed as trial cases in order to validate the program before

the actual modeling of the space platform. LASS is an excellent tool for modeling large and intricate

structures and with modifications, will become an essential tool in the design process of space craft.

Outcomes

An early evaluation based on the outcomes of the first year indicates that the program is successful.

Thirteen of the original 15 Scholars are still in the program. The average GPA of the returning students

was 3.3.

Fourteen Scholars made the honor roll at least one semester last year and 11 made the honor roll

for both semesters. Two students were among the 15 Dual Degree Engineering students of all levels

from the Atlanta University Center institutions who received outstanding student awards at the Annual

Awards Banquet. Seven students received honor pins at the affair.

The WISE Scholars Program has given a high visibility to NASA on the campus. It has created a

core of high potential minority women students who share common interests and goals in science and

engineering. There is a sense of enthusiasm and confidence in the Scholars which has had a positive

effect on other science and engineering students. The Scholars are already interested in pursuing

graduate degrees and are determined to succeed.

275
P

367_fS

N9 -2s s61

AN ANALYSIS OF THE MOON'S SURFACE USING REFLECTED

ILLUMINATION FROM THE EARTH DURING A WANING

CRESCENT LUNAR PHASE

Ernest C. Hammond, Jr., and Maggie Linton-Petza

Department of Physics

Morgan State University

Baltimore, MD

and

Gerald R. Baker

Technical Monitor

Laboratory of Astronomy and Solar Physics

Goddard Space Flight Center

ABSTRACT

There have been many articles written concerning the lunar after-glow, the spectacular reflection

from the moon's surface, and the possible observation of luminescence on the dark side of the moon.

The researcher, using a 600 mm cassegrain telescope lens and Kodak 400 ASA T-Max film, photographed the crescent moon whose dark side was clearly visible by the reflected light from the earth. The

film was digitized to a Perkin-Elmer 1010M microdensitometer for enhancement and enlargement. The

resulting pictures indicate a completely different land pattern formation than observed during a full

moon. There is an attempt to analyze the observed structures and to compare them to the pictures

observed during the normal full moon. There are boundaries on the digitized dark section of the moon

that can be identified with structures seen during the normal full moon. But, these variations do change

considerably under enhancement.

276
AN ANALYSIS OF THE MOON'S SURFACE USING REFLECTED

ILLUMINATION FROM THE EARTH DURING A WANING

CRESCENT LUNAR PHASE

Introduction

There have been many articles written about the lunar afterglow, the spectacular reflection from

the moon's surface and the possible observation of luminescence on the dark side of the moon. Using

a 600 mm Cassegrain telescope lens and Kodak 400-ASA T-Max film, we have photographed the

crescent moon, whose dark side was clearly visible by the reflected light from the earth. The film was

then digitized to a Perkin-Elmer 1010-M microdensitometer for enhancement and enlargement.

Method

We began with an actual negative taken with a 600 mm Cassegrain telescopic lens. The resulting

image was then digitized using the microdensitometer. This project of photographing the major

luminary next to the sun has given us an opportunity to test both hard and software in digitizing

photographic films (Figure I).

Figure I.

Results

OI_I(_INA[ PAGE

BLACK AND WHITE PHOTOORAPH

After digitizing using the microdensitometer, an outline of cratering was produced along with the

flat plain areas. The light part represents the flat plains, with minimal cratering (Figure II).

277
FigureII.

i i , i

Figure III represents pseudo or false coloring of the moon. Every color represents a different gray

level value. One should note, in particular, that the limb around the moon seems to be brighter than

most of the interior. It is also noteworthy, that with pseudo coloring, there are structures within the

maras or seas that are invisible in the black and white enhanced views (Figure III).

Figure III.

Changing the pseudo color pixel values again will produce dramatic changes within the so-called

"lunar seas". Given value determination, we suspect that all blue or red values can tell us something

about the mineral content of the surface, if we could know the reflectivity of certain minerals.

278

ORIGINAL PAGE

BL_,CK AND WHITE F'h'OTOGR'AP_
Photographs of some of the lunar rocks that the astronauts brought back from the moon, should help

identify mineral Contents on various parts of the moon (Figure IV).

Figure IV.

Further study of this technique, with an appropriate telescopic instrument, will permit us to review

the moon's surface in a way that would be very beneficial and enlighting, and would provide a substantial

amount of information about the local cratering areas (Figure V).

Figure V.

Figure VI represents the zoom capability of looking at the center of the moon, representing an

area of 20-square miles. The dark areas represent craters and the flat areas represent plains (Figure

VI).

ORIGINAL PAGE

BLACK AND WHITE P_OTt"),,'_R_PH

279
FigureVI.

Whenone applies false color to this magnified view of the surface, one can clearly see cratering

and other structures associated with the same values, along with even greater changes ,_ithin the

interface between the plain and cratering area. The resolution is bad primarily due to the grain size of

the film (Figure VII).

Figure VII.

Looking at the moon illuminated by earth shine, the dark area represents the reflected light from

the sun and the grayish area represents the reflected light from the earth. Let us consider the

enhancement on the slide as the earth's reflected light illuminating the moon (Figure VIII).

ORIGINAL PAGE

BLACK AND WHITE PHOTOGiiIAV_

28O
Figure VIII.

A computer zoom of the interface between the waning crescent and the dark side of the moon produces

the image seen in Figure IX. One can see cratering, as well as a glow along the limb of the moon. The

craters appear as small blobs along the interface between the sunlit part of the moon during this waning

crescent.

Figure IX.

O_C_tt'_AL PAGE'

BLACK AND WHITE PHOTOGRAPt.:I

281
Figure X is a view of the entire moon with its dark side partially illuminated by the light reflected

off the earth's surface and atmosphere. Note that the pattern observed is considerably different from

those patterns observed when the full disk of the moon was shown. Notice also the ridges and lines that

run throughout the surface of the moon, which the eye perceives very differently than when the moon

is full (Figure X).

Figure X.

By using false color, one can clearly show patterns and structures which are not seen during the

full moon. Also, lens problems within the Cassegrain lens give us some optical flaring effects. However,

one of the more interesting aspects is that we can use this technique of pseudo coloring to show lines

equal in light intensity.

Conclusion

Careful evaluation of the slides reveals cratering from the same value of the moon. Increased

intensity of light on the surface opposite the sun is also noted at the upper limb of the moon. But even

more important, the entire pattern on the dark side of the moon is totally different from the pattern

observed when the moon is full. We want to continue to explore the pattern differentials, to see if there

is any potential to identify mineral content based on the reflected light from the earth and sun.

282

ORtGTNAL PAGE

BLAC_ AND WHITE PHOTOGRAPN
N91-28 1()2

A DENSITOMETRIC ANALYSIS OF HaO FILM FLOWN ABOARD THE

SPACE SHUTTLE TRANSPORTATION SYSTEM STS #3, 7 AND 8

Ernest C. Hammond, Jr.

Morgan State University

Baltimore, Maryland

ABSTRACT

Since the United States of America is moving into an age of reusable space vehicles, both electronic

and photographic materials will continue to be an integral part of the recording techniques available.

Film as a scientifically viable recording technique in astronomy is well documented. There is a real need

to expose various types of films to the Shuttle environment. Thus, the purpose of this study is to look

at the subtle densitometric changes of canisters of IIaO film that were placed aboard the Space Shuttle

#3 (STS-3).

283
A DENSITOMETRIC ANALYSIS OF IlaO FILM FLOWN ABOARD THE

SPACE SHUTI'LE TRANSPORTATION SYSTEM STS #3, 7 AND 8

Introduction

Since the first major use in Skylab in 1974, scientists have used over 400 rolls of photographic film

in the space environment to obtain sensitometric data. The present research team prepared 3 canisters

of IIaO film along with packets of color film from the National Geographic Society, which were then

placed on the Space Shuttle #3 (STS-3). The ultimate goal was to obtain reasonably accurate data

concerning the background fogging effects on IIaO film as it relates to the total environmental

experience. This includes: the ground based packing and loading of the film from Goddard Space _ight

Center to Cape Kennedy; the effects of solar winds, humidity, and cosmic rays; the Van Allen Belt

radiation exposure, various thermal effects, reentry and off-loading of the film during take-off, and 8

day, 3 hour 15 minute orbits. The development and analysis of the returned film constitute the basis of

this report. The objective of this experiment was to examine the total densitometric change caused by

all of the above factors.

The Laboratory for Solar Physics and Astronomy, Goddard Space Flight Center, has been using

large quantities of IIaO film in its rocket and space shuttle flights. Next year, during the Ultra Violet

Image Telescopic Experiment, the UIT is launching a payload which will be using 70 millimeter IIaO

film. Thus, it was a requirement for the laboratory to quantitatively determine the aging effects

associated with the sensitometric images on film.

IIaO film for this experiment (Figures 2 & 3) was obtained from the same roll of Kodak film Mfg.

date 5-76-A5J. The film was loaded into specially prepared aluminum anodized packages that would fit

aboard the Space Shuttle's Getaway Special Container. One roll of film was cut from the same stock

and maintained as the control. The control film was maintained at a temperature of 22 degrees

Centigrade at Goddard Space Flight Center. After the mission, the three rolls oflIaO film were shipped

back to the Small Payload Section of the Laboratory for Astronomy and Solar Physics. One film and

the control film were developed as Set I, while the other IIaO sample film was developed as Set II.

Using a MacBeth Densit0meter, measurements were obtained form the film every 2 centimeters,

developing 3 columns of data. Significant differences were found when samples were compared with

the control. Sample A and Sample B had a 5.26% increase in density or fogging background, while the

film developed shortly after its arrival at Goddard Space Flight Center displayed a 3.8% increase in the

density or the fogging background.

An analysis of the data for each sample film aboard the Space Shuttle (Figures 5, 6, & 7) indicates

variation in intensity with respect to the fogging levels as a function of position on the film. There is a

tendency of more random variation toward one end of the film, but the actual orientation in the Space

Shuttle is unknown. A possible theory is that the high energy cosmic rays had penetrated the aluminum

film cartridges aboard the Space Shuttle causing certain secondary reactions that produce variations

towards one end of the film due to the wrapping procedure used in placement of the film in the canister.

Other theories suggest thermal effects cause density variations. It is known that aluminum containers

tend to innately fog various UV films along with the wrapping geometry of the film within the canister.

284
Densitometric Response of llaO Film Flown on STS-7

Three canisters of 35mm IIaO film were flown on STS-7 in a getaway special canister in cooperation with NASA's Plasma Physics Branch and the Naval Research's Solar Astronomy Branch. The

results indicate a high degree of thermal aging during the space shuttle mission.

The future requirements for film used aboard the space lab and on the UIT (Ultra Violet Imaging

Telescope) will include the following. Some ultraviolet films may have to be exposed directly to the

particular vacuum of space at those altitudes, thus giving rise to concern of metallic outgasing of

chemicals that may do permanent damage to the film's emulsion. The IIaO film being used on the UIT

will not be exposed directly to space, but may be exposed to ionospheric fields associated with a low

orbiting space shuttle. The major factor that can cause fogging is thermal exposure.

Experimental Set-Up

Using a sensitometer, a continuous roll of IIaO film was exposed for ten seconds using a General

Electric Lamp 328 at 195 ma + 3 ma with a 10 - 18 hour calibration burn in time. The film was placed

in three 35 mm canisters, sealed in air and attached to the getaway special canister containing other

special ultraviolet films. The film was loaded in the canister approximately 22 days before the launch of

the Space Shuttle Columbia.

Discussion

During the loading or pre-flight launch, post-flight analysis (Figure 8) indicates that the IIaO film

had been exposed to some type of thermal aging effects. The exact nature of these effects was not

apparent as we examine the temperature profiles for STS-7. But there is a concern that the rapid

increase in temperature from approximately -15 °C to a temperature of +22 °C in an hour and a half

after touchdown of the shuttle could explain the exaggerated thermal aging effects. There is another

real concern which is associated with the fact that the shuttle landed on the West Coast, and the

automatic temperature cut-off control was turned off approximately three days before the shuttle

arrived at Cape Kennedy where the getaway special canister containing the film was unloaded.

Analysis of terrestrial thermal and aging effects produced similar curves as observed in this

experiment, but the slopes of the individual curves tended to vary dramatically. In conclusion, there

were observed densitometric changes in comparing the control films and the flight film, though both

had been developed at the same time as the flight film received from STS-7.

Experimental Set Up for STS-8

This research team was able to use one of the canisters to place four rolls of llaO film of STS-8,

one roll of IIIford G5 nuclear emulsion, and one roll of a new batch of llaO. The Naval Research

Laboratory setup was using a very sensitive ultraviolet film to study the effects of space on the ultraviolet

emulsions. The shuttle orbit was low enough to expect some minimum cosmic ray damage to the film

as well as tracks on the nuclear emulsion film. The Getaway Special was aligned in the bay of the shuttle

with bay portals pointed to the earth for cooling purposes as shown in figure 9.

The temperature profiles for STS-7 and STS-8 were very similar, going from a temperature of

approximately 23 degrees centigrade before launch to a temperature of -22 degrees centigrade during

the flight. This increased the density of the wedges. The major differences between STS-7 and STS-8

285
occurredbecauseSTS-7hadtolandin California where the automatic temperature control devices and

appropriate air conditioning units for the shuttle cargo were not present. Once the shuttle had landed,

one can measure the dirunal temperature variations (Figure 8). Terrestrial experiments have shown

that less dense wedges produce densitometric increases as the temperature increases (Figure 12) over

a number of days. The diagram shows the effects of the first 3 step wedges including the aging effect of

the background at 32 degrees. The lowering of the temperature decreases the slope of the family curves

for each of the darker step wedges. Figures 11 & 14 (aging effects) show the slope variation at 21 degrees

and at 32 degrees over a 90-day period.

A most interesting effect occurs at the darker patterns. They tend to drop in density, while the

lighter patterns tend to increase in density. Furthermore, the IIaO film seems to perform nonlinearly

for temperature values above 67 or 68 degrees (Figure 13). The least dense step wedges tend to show

dramatic increases in density above 68 degrees Centigrade while the darker wedges show a reduction

of temperature above 70 degrees. The slopes of these films are increased further when the ambient

temperatures seem to increase.

A brief examination of the aging effects will assist us in understanding the observed effects on the

film caused by exposure to the space environment of the shuttle (Figure 14). We used a microdensitometer to contrast and compare the terrestrial film as well as the shuttle flight film (Figure 15). Using

this technique we were able to calculate the signal to noise ratio for flight as well as for control film. On

board STS-8 the signal to noise ratio increased while the control film decreased. The signal to noise

ratio computed for STS-7 shows that at higher exposure the signal to noise ratio is less than for the

flight films (Figure 16). But at lower exposures the control and flight film seem to have larger signal to

noise ratios (Figure 17). This difference may be caused by additional thermal activity within the canister

as shown in Figure 17 and the lack of appropriate air conditioning equipment at the California landing

site.

Signals to Noise Ratio of Aging Film

Analysis of the signals to noise ratio for IIaO film aged 8, 9, 21, 17, and 71 days indicates that a

certain amount of aging reduces the signal to noise ratio over the short term, but will increase the signal

to noise ratio over long periods of time (Figure 18).

An examination of the interaction of protons of varying dosages and energies indicates that the

very light wedges are very sensitive to proton interaction with the emulsion while the very dark patterns

tend to be less sensitive to very high MEV protons (Figure 19). MEV vs. dosage figures were obtained

by using the Harvard University Cyclotron.

Using the Harvard University Cyclotron, we bombarded the IIaO film with alpha particles, (Figure

18) searching for parallel interactions in the space shuttle due to cosmic rays as from the cyclotron. We

bombarded the IIaO film using the alpha particles at 47 MEV, 79 MEV and 153 MEV for the 6.8 rad

dosage. We expected to see similar results when we examined the films from the shuttle. But we did not

see such effect (Figure 19). There is a difference in the front part of the curve, but the toe and the

shoulders did not seem to respond; as a result we do not think that there was any dramatic cosmic ray

activity (Figure 20A).

286
Microdensitometric Analysis

When comparing similar step wedges that have been aged from 3 to 71 days, one can immediately

see an increase in granularity. However, this is not consistent for all step wedges as it is for the middle

wedges. The denser the wedges, the more one observes the converse of less granularity. Furthermore,

as aging occurs, granular definition between step wedges seems to decrease, while other step wedges

under densitometric aging will produce a heavier granularity indicative of increased grain structure.

Microdensitometric Comparison of Control Vs. Flight Film

The control film of STS-8 for step wedges 3 has larger grain structure than the flight film. Similarly

on STS-8 strip 4, a new batch of IIaO film indicates a slight increase of granularity toward the darker

wedges (Figure 24). Conversely, the least dense step wedge controls are heavier than the traces for the

flight film (Figure 25). Microdensitometric traces of step 4 and strip 4 tend to illustrate very small

changes. Finally, traces from STS-8 again show greater granularity for the flight film than for terrestrial

controls (Figure 27).

A new approach to the examination of the IIaO film emulsion is the use of the scanning electron

microscope to investigate surface grains and their structure. Varying the voltage of the probe electrons,

we are able to examine grain structure under the surface of the emulsion at the proper accelerating

voltage of the electrons. All the IIaO films were coated with gold palladium using standard sputtering

techniques.

Using about 1,000X Magnification (Figure 27), it became very evident that the energy of the

electrons within the scanning electron microscope striking the emulsion is very crucial in terms of the

viewing of the grain structure. What we want to do in the future is to look at the aged film and see

exactly how these grains change (Figure 28).

We found that a workingvoltage for SEM ISI SS 40somewhere between 2 kilovolts and 10 kilovolts

is sufficient to produce clear images without flaring. The flaring of the image from the SEM produces

a 4-8% increase in the total area of the grain under investigation from direct measurements of the

micrograph.

But as the energy of the electrons increases, one notices that there is a flare effect, each grain

spreading out brightly (Figure 29). Then one begins to see some of the grains beneath the surface of

the emulsion. So using this scanning electron technique, we can examine some of the grains just below

the surface if the charging voltage is appropriate.

We also attempted to look at the wedges under the electron microscope. The extreme left

represents the least dense, and the extreme right represents the most dense. (Figures 33, 34, 35 & 36

A&B). Of course, as the density increases, the size of these grains seems to decrease. Using this

technique, one can measure with ease and acquire some statistical understanding (Figure 38).

Qualitative analysis techniques of energy dispersion reveal a very large silver peak along with traces

of copper sodium and sulfur and argon peaks as shown in Figure 38. These trace element peaks are

associated with the elements used in the development process and other materials in the emulsion.

287
Reciprocity Failure of llaO Film

Reciprocity failure was examined for IIaO spectroscopic film. The failure was examined over two

ranges of time from one second to thirty-one seconds and one minute to 180 minutes. The variation of

illuminance was obtained by using thirty neutral density filters. A standard sensitometric device

imprinted the wedge pattern on the film as exposure time was changed. Our results indicate reciprocity

failure occurring for higher density patterns within the first minute. Multiple failure occurs at 13, 30,

80, and 180 minutes.

Materials and Methods

Twenty-seven wedge patterns were placed on IIaO spectroscopic film in total darkness using a

light sensitometer with a 24 hour burn in time for the bulb. Each film section was exposed to the light

sources for a specific period of time. Time intervals were the following: 1-30 seconds and 1-11, 15, 19,

22.5, 25, 27, 30, 35, 40, 45, 58, 90, 125, and 180 minutes respectively.

±

The film was then developed using Kodak D-19 developer, rapid f'txer, hypo-ciearing agent and

photo-flo solutions. The following development procedure was used for each film section: In absolute

darkness, and a water bath at a temperature of20c + 1.5c, one section of film was placed in Kodak D-19

developer and gently agitated for four minutesusing a specific soak and agitating pattern. It was washed

in water for 30 seconds, shaken, then placed in Kodak rapid fixer solution, using the exact same pattern

of agitation and soaking, and gently agitated for four minutes. It was then removed, rinsed in water for

30 seconds, washed in water for one minute, then hung to dry. After developing, the optical densities

of the wedge patterns were read using a MacBeth Densitometer.

Results

An examination of the reciprocity failure for the 1 to 30 second exposure periods (i.e., a separate

wedge pattern that was exposed to an amount of light from 1 to 30 seconds sequentially) reveals that

for two separate batches of film whose histories of use were different, there is some reciprocity failure

occurring at the darker wedge patterns. While an examination of the very light patterns further shows

the trend of reciprocity failure at the 30th and 31st seconds, it should be noted that the very darkest

patterns have a marked decrease in reciprocity failure around the 30 second interval, with other

variations occurring at 10, 15 and 19 seconds consistently with each variation of the pattern.

An examination shows that reciprocity failure minimum points occur at 13 minutes, 20 minutes,

30 minutes, and 90 minutes, with a less defined failure at +80 minutes. The middle density wedges

indicate the same reciprocity failure points occurring at the same time. The darkest wedges show

remarkable stability for the first 10 minutes exposure, but dramatic failures occur at 11 and 20 minutes.

Very dramatic reductions occur at 30 minutes.

Conclusion

For exposure times of 30 to 31 seconds, darker wedges experience failure more than light wedge

patterns. This indicates that the lighter wedges are less sensitive to Reciprocity Failure at short exposure

times. As the exposure time increases, there appear to be some migration of grains in the darker wedges;

especially the last three columns which gave an appearance that a double exposure had occurred. There

is also an increased darkening of the film with increased exposure times. Fogging of the film is prevalent

at 30, 45, 58, 90, and 180 minutes, again with increased exposure times. An examination of the reciprocity

288
failurefrom 1 to 180minutescompletelydemonstrates the following: (a) The reciprocity failure

minimum points are at 13 minutes, 20 minutes, 30 minutes, and 90 minutes, whereas, less defined failure

occurs at 11 minutes. The light and middle density wedges showed this result. Darker wedges (b) show

remarkable stability for the first 10 minutes of exposure, but reductions occured at 11 minutes, 20

minutes, and dramatic reductions at 30 minutes.

Summary

The results of these studies have implications for the utilization of the IIaO spectroscopic film on

future shuttle and space lab missions. These responses to standard photonic energy sources will have

immediate applications in a terrestrial or extraterrestrial environment with associated digital imaging

equipment.

The author is indebted to Gerry Baker and AI Stober of the Small Payloads Section of the

Laboratory for Solar Physics and Astronomy for their hours of discussion and support. Special thanks

to Dr. Dan Klingsmith of the interactive Astronomical Data Analysis Facility, also of the Goddard Space

Flight Center, Greenbelt, Maryland for his patient assistance during the imaging processing of these

films. Very special thanks to Kevin Peters, Sean Gunther, Lisa Cunningham, and Deborah Wright for

their careful assistance during the development process.

289
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N9 1 - 28 1 03 I

MOSSBAUER SPECTROSCOPY AND SCANNING ELECTRON

MICROSCOPY OF THE MURCHISON METEORITE

Christopher L. Brown, Frederick W. Oliver, and Ernest C. Hammond, Jr.

Morgan State University

Baltimore, Maryland

and

Gerald R. Baker

Technical Monitor

Laboratory of Astronomy and Solar Physics

Goddard Space Flight Center

ABSTRACT

Stones from heaven, better known as meteorites, provide a wealth of information about the solar

system's formation, since they have similar building blocks as the Earth's crust but have been virtually

unaltered since their formation. Some stony meteorites contain minerals and silicate inclusions, called

chondrules, in the matrix. Utilizing MSssbauer spectroscopy, we identified minerals in the Murchison

meteorite, a carbonaceous chondritic meteorite, by the gamma ray resonance lines observed. Absorption patterns of the spectra were found due to the minerals olivine and phyllosilicate. We used a scanning

electron microscope to describe the structure of the chondrules in the Murchison meteorite. The

chondrules were found to be deformed due to weathering of themeteorite. Diameters varied in size

from 0.2 to 0.5 ram. Further enhancement of the microscopic imagery using a digital image processor

was used to describe the physical characteristics of the inclusions.

294
MOSSBAUER SPECTROSCOPY AND SCANNING ELECTRON

MICROSCOPY OF THE MURCHISON METEORITE

Introduction

Today we know most meteorites are extremely primitive remnants of the formation of the solar

system 4.6 billion years ago. They provide a valuable record of that event. In order to distinguish between

meteorites in terms of physical and chemical composition, scientists have divided meteorites into three

broad classes. They are iron meteorites, stony meteorites, and stony-iron meteorites. Furthermore,

these meteorites contain minerals and metallic components.

The Murchison meteorite fell in Australia in 1969. The Murchison is a rare type of meteorite called

a carbonaceous chondritc. The carbonaceous chondrites are of interest because complex organic

chemicals, including amino acids, have been found in them and it is possible that they may hold clues

to the process by which life originated on Earth. Carbonaceous chondrites are also the least altered

samples wc have of the material which formed our solar system.

Utilizing MSssbauer spectroscopy, we may study the iron composition in carbonaceous meteorites

without altering the sample by chemical analysis. By comparing the M/Sssbauer spectra with those of

known terrestrial minerals, one can identify the iron minerals present in the sample and indicate the

state of the iron. 13 We used this technique to identify iron-containing minerals in the Murchison

meteorite.

Scanning electron microscopy may be used to derive information about the nature of stony

meteorites. A scanning electron microscope was used to describe the shape, composition, crystal

structure, and physical characteristics of the Murchison meteorite. Using electron microscopy in

combination with digital image processing methods, the structural organization of the meteorite was

determined.

Theory

The general principle of the MSssbauer effect is based on the nuclear gamma ray resonance. The

effect is a method of attaining recoil-free emission and resonant absorption of nuclear gamma rays by

placing the gamma ray source in a solid crystal lattice. An absorption spectrum is obtained when gamma

rays from this crystalline source are transmitted through an absorber and measured as a function of

velocity of the source. As a consequence, it is possible to detect the very small line shifts and splitting

which result from the presence of magnetic and electric fields surrounding the absorbing nucleus. The

splitting of the spectra are due to magnetic (Zeeman) splitting and quadrupole splitting. 4 It is also

possible to measure a parameter called the isomer shift, which is just the difference in the source, S,

and absorber, A, transition energies. The quadruple splitting is the velocity difference between double

peaks. The isomer shift, quadrupole splitting, and magnetic splitting of the iron (Fe) have been

calculated for many minerals. In order to identifywhich minerals are present in a sample, measurements

are made of the isomer shift, quadrupole splitting, and magnetic splitting and comparison is made with

spectra of known minerals. Ferromagnetic compounds are distinguished by six line patterns and

paramagnetic compounds have one or two line patterns. 5

295
Thescanningelectronmicroscope is a multi-lens system. The versatility of the scanning electron

microscope for the study of solids is derived in large measure from the rich variety of interactions which

the beam electrons undergo in the sample. The primary beam enters the sample and undergoes elastic

scattering: 30 percent emerges from the surface of the sample as backscattered electrons and secondary

electrons. The microscopist uses this information to determine other information about the nature of

the sample - shape, diameter, composition, and physical characteristics of the material. 6

Experimental Procedures

The techniques employed in sample preparation are those of standard MSssbauer spectroscopy

and electron microscopy. For the MSssbauer spectrometer measurements, a 42.3 mg sample of the

Murchison meteorite was pulverized into a fine powder. Sample preparation included using epoxy to

shape the sample into a disk. The sample was placed in a chamber and the test run at room temperature.

An Fe foil standard was also run at room temperature. The MSssbauer effect in Fe was used to

determine the iron minerals pr_ent in the Murchison. A Canberra multi-channel analyzer was used to

store and analyze the data. A MSssbauer computer program using least square analysis Was usi_d to

calculate the peaks of the spectra. The data were fitted to Lorentzian lines.

To determine the structure and composition of the Murchison, the SX-30 scanning electron

microscope (SEM) was used. A 13 mg sample of the meteorite was cut into small chips. The sample was

sputter-coated with gold-palladium, mounted on a stage, placed in a chamber, and the SEM focused

for optimum image sharpness. The Murchison meteorite is a unique type of meteorite known as a

carbonaceous chondrite, consisting of chondrules within a matrix. The SEM was used to examine these

chondrules' shape, size and diameter. Further enhancement of the SEM images, using a digital image

processor was used to describe the silicate inclusions. Two high resolution monitors were used to display

the digitized images by way of a computer program.

Data Analysis

MSssbauer Results

In the MSssbauer spectrum of the Murchison meteorite, the predominant absorption lines are of

two non-magnetic patterns. The lines may be identified by comparison with reference spectra of iron

compounds expected to be present in stony meteorites. The two most intense lines of the Murchison

spectrum were found to correspond to the 2-lined patterns of the minerals olivine,(Mg,Fe)2 SIO4, and

a phyllosilicate. There was evidence of ferromagnetic materials; however, they were not very pronounced. The magnitude of the isomer shift was found to be +.87 +_0.01 mm/s for the olivine. The

quadrupole splitting for the olivine was found to be 3.20 +_0.01 mm/s.

SEM Results

The stony meteorites are composed of a silicate material similar to the Earth's crustal rocks and

are difficult to distinguish from ordinary rocks. When the Murchison was examined under the SEM, it

296
wasfound to contain chondrules embedded in a black crust. However, in the Murchison meteorite very

few of the chondrules were found to be really spherical; most appeared to be sintered together and/or

plastically deformed. The chondrules in the Murchison were found not to have a uniform composition.

Instead, they could possibly be composed of different minerals packed together. Structural examination

of an individual chondrule at a magnification of 11.6 kx showed layers on the surface. The chondrules

may be composed of minerals, other than olivine and phyllosilicates, densely packed together. The

chondrules in the Murchison matrix have diameters in the range of 0.2 to 0.5 mm.

Conclusion

M6ssbauer spectroscopy and scanning electron microscopy are analytical methods that have been

successfully applied to the analysis of meteorites. The M6ssbauer effect has been investigated as a

method to identify iron in stony meteorites without altering the meteorite chemically. Computer analysis

of the gamma ray resonance lines indicates the iron minerals present to be predominantly olivine,

(Mg,Fe)2 SIO4, and phyllisilicates. The relative abundances of minerals are nearly the same as in the

Earth. The MSssbauer spectrum showed magnetic components; however, they were not very pronounced.

The SEM study showed that some of the chondrules in the matrix are spherical and deformed.

Although they appear to be clustered together, their diameters range from 0.2 mm to 0.5 mm. Based

on the classification of Wiik 7, our results indicate the Murchison to be type II carbonaceous chondrite

and definitely of primitive material since chondrules are typical of primitive meteorites.

References

.

.

Herr, W. and Skerra, B. "MSssbauer Spectroscopy Applied to the Classification of Stone

Meteorites," Meteorite Research (P.M. Millman ed. Symposium, Vienna, (1968),

pp.108-118.

Sprenkel±Segal, E.L. ed. "MSssbauer Analysis of Iron in Stone Meteorite" Geochimica

et Cosmochimica, (1964), Vol. 28, pp. 1913-1931.

3. Oliver, F.W. and Isuk, E., "M5ssbauer Study of the Allende Meteorite" Meteoritics,

(1984), Vol. 19, pp. 26-26.

4. Beiser, A., Concepts of Modern Physics. Columbus, Ohio, Bell and Howell CO., 1985,

pp. 189-210.

5. May, Leopold, ed. An Introduction to M'6ssbauer Spectroscopy, New York, Plenum Press,

1979.

6. Goldstein, J.I., Scanning Electron Microscopy and X-Ray Microanalysis. New York,

Plenum Press, 1981.

7. Wiik, H.B., Gechim. Cosmochim. Acta. (1956), Vol. 9, p. 279.

297
N91-28 104 t

.5/_// -?a.

9..

SOLVING THE BM CAMELOPARDALIS PUZZLE

Mathias Teke

Department of Mechanical Engineering

Tennessee State University

Nashville, Tennessee

Michael R. Busby

Center of Excellence in Information Systems

Tennessee State University

Nashville, Tennessee

Douglas S. Hall

Dyer Observatory

Vanderbilt University

Nashville, Tennessee

John Davis

Technical Monitor

NASA/Marshall Space Flight Center

ABSTRACT

BM Camelopardalis (= 12 Cam) is a chromospherically active binary star with a relatively large

orbital eccentricity. Systems with large eccentricities usually rotate pseudosynchronously. However, BM

Cam has been a puzzle since its Observed rotation rate is virtually equal to its orbital period indicating

synchronization. All available photometry data for BM Cam have been collected and analyzed. Two

models of a modulated ellipticity effect are proposed, one based on equilibrium tidal deformation of

the primary star and the other on a dynamical tidal effect. When the starspot variability is removed from

the data, the dynamical tidal model was the better approximation to the real physical situation. The

anaiysis indicates that BM Cam is not rotating pseudosynchrnously but is rotating in virtual synchronism

after all.

298
SOLVING THE BM CAMELOPARDALIS PUZZLE

BM Camelopardalis (= 12 Cam) is an SB1 in which a K1 giant orbits its unseen companion star

in an eccentric 80-day orbit. The K1 giant shows strong emission in its H and K lines of Ca II, so it is

chromospherically active (Abt, Dukes, and Weaver 1969). The photometric variability, produced by

longitudinally concentrated starspot regions, was discovered by Eaton et al. (1980). Hall and Osborn

(1986) analyzed the photometric variability and found two periodicities, 0.3% faster than and 1.0%

slower than the 800.174469 orbital period, presumably caused by two starspot regions at different

latitudes. Hall (1986) calculated that, if the K1 giant is rotating pseudo-synchronously, the photometric

period should be 450. 2 ___2 °. 5. He noted that it was a disturbing coincidence to have the observed

rotation rate virtually equal to the orbital period. If the rotation is not pseudosynchronous, then any

period faster than or slower than 45 days would be possible, with no reason for 80 days to be preferred.

This is the BM Cam puzzle.

To solve this puzzle we collected all available photometry. The 1979 and 1980 photometry

discussed by Eaton et al. (1980) was not published but was available in our files. Fernandes (1983)

published some 1983 photometry. We had in our files photometry from the years 1980 through 1985,

obtained by 15 different observers and sent to us for analysis. Photometry obtained between 1983 and

1987 by the 10-inch automatic telescope in Arizona will be published by Boyd, Genet, Busby, Hall, and

Strassmeier (1989). The preliminary analyses by Nelson et al. (1987) and by Strassmeier, Hall, Boyd and

Genet (1989) were based on subsets of these data. We also had access to 1988 photometry obtained by

the Vanderbiit 16-inch automatic telescope on Mt. Hopkins (Hall 1988). The analysis in this paper is

restricted to the V-band data, which was the most extensive. All telescopes except that of Fernandes

used the same comparison star, HR 1688. To compensate, we added --0M995 to his differential

magnitudes.

One source of photometric variability which should be exactly in phase with the orbital period is

the ellipticity effect (Morris 1985). That, however, should produce two maxima and two minima during

each orbital cycle and thus show up in a periodogram at P = 40 days. A periodogram of the entire data

set showed the most power around 80 days, very little around 40 days.

In the discussion which follows m = magnitude, e = orbital eccentricity, w = angle of periastron

measured from the ascending node of the spectroscopic primary in the direction of its orbital motion,

M = mean anomaly, v = true anomaly, a = orbital semi-major axis, d = distance between star centers,

and R = stellar radius.

Then it occurred to us that the ellipticity effect should be modulated by the varying star-to-star

separation in this eccentric orbit. The giant star should experience greater tidal deformation at

periastron and less at apastron. This should be a strong effect because it depends on the cube of the

ratio R/d (Russell and Merrill 1952). Ifw is near 90 ° or 270 °, then the light curve should show a maxima

of equal height but minima of unequal depth. Abt, Dukes, and Weaver had found w = 72 °. 5, not far

from 90 °, so we formed the tentative hypothesis that this modulated eilipticity effect could explain at

least one of the strong 80-day periodicities.

To quantify this hypothesis, we considered two versions. The first assumes that the long axis of the

tidally distorted star always points towards the other star and that the effect on the light curve, in

magnitude units, is proportional to (R/d) 3. This would correspond to the theory of equilibrium tides.

The second assumes that the long axis of the tidally distorted star rotates uniformly in time, i.e., directly

299
proportionalto the meananomaly,andthat the effecton the light curvevariesuniformlyin time

betweenthetwoextremes,i.e.,betweenthemaximumeffectat d = a(1-e)andtheminimumeffectat

d = a(1+e).Thiswouldcorrespondto thetheoryof dynamicaltides.Bothversionshavethesamecos

24' dependence, where ¢ is the angle between the line of sight and the long axis of the tidally elongated

star. Thus, in both versions, the ellipticity effect vanishes at ¢ = 45 °, 135 °, 215 °, and 225 °.

For the first version, the change in magnitude produced by the ellipticity effect is given by

Am = k (d/a) -3 cos26b, (1)

where ¢ =v + w - 90° and the usual equations of the two-body problem can be used to compute d

and v as functions of time.

For the second version, the change in magnitude produced by ellipticity is given by

Am = k (a +/5 cos M) cos2_, (2)

where now _ = M + w -90 °. In this equation

a = 1/2 (fp + f_) (3)

,,8 = t/2 (fp - fa) (4)

and

fp = (1 -e) -3 (5)

= (1 + e) -3 (6)

Note that, in this second version, there is no need to compute v or d as functions of time.

In both versions the coefficient k would correspond approximately to the coefficient A2 as defined

by Russell and Merrill (1952). In the case of a circular orbit, where d = a in equation (1) or e = 0 in

equation (2), one would get k = A2.

To try this hypothesis on BM Cam we proceeded by iteration. The observed magnitudes were

plotted modulo; the known orbital period and means were taken in bins 0.02 phase units wide. There

was considerable dispersion within each bin, of course, because of the other variability present in the

system with supposedly different periodicities. We were encouraged that the resulting mean light curve

had roughly the expected shape: two nearly equal maxima and two quite unequal minima. Then this

mean light curve was subtracted from the observed magnitudes and the residuals examined.

The residuals showed something we recognized as variability produced by starspots. Within each

observing season there was a roughly sinusoidal variation with a period similar to but significantly

different from the orbital period. That period was about 82 d.5 up through 1984.5 and about 81 d.0 after

that, with a half-cycle phase shift also around 1984.5. The amplitude of this roughly sinusoidai variation

changed dramatically: up to a maximum of 0 .ryll5 at 1981.3, down to a minimum of 0._3 at 1984.0, up

to another maximum of 0.M15 at 1985.6, and possibly decreasing thereafter. In addition, the average

light level changed significantly from year to year, covering a range of 0 ._06.

300
The next step of the iteration was to find analytical expressions to approximate this starspot

variability. An assumed sinusoid required as its parameters the mean light level, the epoch of light

minimum, the period, and the amplitude. Additionally, we allowed the mean light level to increase or

decrease linearly with time.

The starspot variability was then removed from the original observed magnitudes with these

analytical expressions. These residuals, which we presume contain only the ellipticity effect, were then

fit in turn with equations (1) and with equation (2). Both fits yielded P, k, e, and w. The period P enters

as a parameter when we convert Julian date into mean anomaly.

Results with equation (2) were superior, in the sense that the sum of the squares of the residuals

reached a much smaller minimum. We take this as indication that the theory in the second version is a

better approximation to the real physical situation. The parameters are presented in Table I with their

formal standard errors and compared to the corresponding elements of the Abt, Dukes, and Weaver

(1969) solution to the spectroscopic orbit.

Table I

Derived Elements

element photometric spectroscopic

P(orb.) 79 d.93 80 d. 174469

___. 05 +_.. 000003

e 0.25 0.35

__+. 03 --- . 02

W 95°0 72°.5

+5.0 --+3.0

k 0.u018

___. 002

The difference between the two determinations of the orbital period amounts to 5 standard errors

and thus poses an apparent conflict. The spectroscopic determination was supposedly uncertain by only

__.0 d.00003, but we can show that it could be significantly in error. The solution of Abt, Dukes, and

Weaver (1969) was based on 13 radial velocities obtained in 1966, 1967, and 1968 plus three radial

velocities obtained long before, in 1916 and 1917. That long 50-year baseline gave them their high

301
precisionbutdependedcriticallyon proper phasing. The three old velocities fell coincidentally at very

nearly the same phase and had about the same velocity, namely Vr = -8.km/sec. If one places them on

the falling slope of the radial velocity curve rather than the rising slope, one could have gotten orbital

period of 80 a.04 or 80 e.79. The first of these would differ from our photometric determination by only

2 standard errors.

The difference between the two determinations ofw amounts to 3 standard errors and thus poses

another apparent conflict. There is, however, an easy explanation for this discrepancy, namely apsidal

motion. The 22 °. 5 increase in w between 1967 and 1984 would correspond to an apsidal motion period

of 272 years. Theory shows that the rate of apsidal motion is proportional to the fifth power of the ratio

R/a. Since that ratio must be large in any binary with an observable ellipticity effect, it is expected that

apsidal motion in BM Cam would be relatively rapid, i.e., measurable within a few decades.

The period of the photometric variation produced by the starspots is a measure of the rotation

period of the K1 giant. The fact that it differs only a few percent from the orbital period indicates that

BM Cam is not rotating pseudosynchronously but is rotating in virtual synchronism after all. From this

we might conclude that the theory of pseudosynchronism does not apply when dynamical tides

phase-locked with the orbital period are more important than the equilibrium tides.

This investigation is not quite finished. We need to improve the analytical representation of the

starspot variability by allowing the amplitude of the assumed sinusoidal variation to increase or decrease

linearly with time within each season. We need to repeat the iterative process a few more iterations,

and we need to compute the theoretically expected apsidal motion period, which will require a

determination or estimate of the orbital inclination and the mass ratio, neither of which is known directly

for a single-lined spectroscopic binary nor for a non-eclipsing ellipsoidal variable.

Acknowledgments

The Vanderbiit 16-inch telescope was obtained with NSF research grant AST 84-14594 and the

analysis in this paper was supported by NASA research grant NAG 8-111.

References

Abt, H.A., Dukes, R.J., and Weaver, W.B. 1969, Ap. J. 157, 717.

Boyd, L.J., Genet, R.M., Busby, M.R., Hall, D.S., and Strassmeier, K.G. 1989, Ap. J.

Suppl., in preparation.

Eaton, J.A., Hall, D.S., Henry, G.W., Landis, H.J., McFaul, T.G., and Renner, T.R.

1980, I.B.V.S. No. 1902.

Fernandes, M. 1983, B.A.V. Rundbrief32, 119.

Hall, D.S. 1986, Ap. J. 309, I_.83.

3O2
Hall, D.S. 1988, in Automatic Small Telescopes, edited by D.S. Hayes and R.M, Genet

(Mesa: Fairborn Press), in press.

Hall, D.S. and Osborn, S.A.G. 1986, in Cool Stars, Stellar Systems, and the Sun, edited by

M. Zeilik and D.M. Gibson (Berlin: Springer-Verlag), p.84.

Morris, S.L. 1985, Ap. J. 295, 143.

Nelson, E.R., Boyd, L.J., Genet, R.M., Hall, D.S. 1987 in Cool Stars, Stellar Systems,

and the Sun, edited by J.L. Linsky and R.E. Stencel (Berlin: Springer-Verlag), p. 497.

Russell, H.N. and Merrill, J.E. 1952, Contrb. Princeton Univ. Obsv. No. 26, chapter IV.

Strassmeier, ICG., Hall, D.S., Boyd, L.J., Genet, R.M. 1989, Ap. J. Suppl. 69, 141.

3O3
N9 1- 28 1 05

AEROSOL SPECKLE EFFECTS ON ATMOSPHERIC PULSED LIDAR

BACKSCATI'ERED SIGNALS

S.R. Murty

Alabama A&M University

School of Engineering and Technology

Normal, Alabama

The effects of refractive turbulence along the path on the aerosol speckle field propagation and

on the decorrelation time are studied for coherent pulsed lidar systems.

Introduction

Lidar systems using atmospheric aerosols as targets exhibit return signal amplitude and power

fluctuations which indicate speckle effects. 1,2 The speckle effects are manifested statistically as

Rayleigh-distributed amplitude and exponentially distributed power of the backscattered signals. The

signals from the various scatterers which make up the target combine to form a speckle pattern at any

point along the backscattered beam. The speckle size is -_ 2 Z/b,where z is the range from the target, 2

is the wavelength, and b is the radius of the illuminating beam on the diffuse target. Therefore, as the

beam size on the diffuse target increases, the speckle size at the receiver decreases. Since the field across

a speckle pattern is produced by the addition of a number of signals of random phase, the speckle pattern

changes as each particle moves, thereby generating spatial and temporal changes in intensity. The

particles move primarily due to atmospheric turbulence, and the changes in the speckle pattern are

caused by the velocity turbulence in the illuminated region of the atmosphere which contributes to the

backscattered signal at the receiver. For a pulsed laser, the backscatter region of the atmosphere is

ctp/2 around the range point where tp is the pulse duration and c is the speed of light.

In addition to producing signal intensity fluctuations, aerosol-generated speckle causes a

decorrelation of the backscattered signals, as the aerosols are free to move about relative to each other

along the beam axis and transverse to it. The resulting decorrelation time determines the temporal

window of the return signal from which the power spectrum can be calculated to obtain wind speed.

A laser beam experiences fluctuations in intensity and a reduction in coherence due to propagation

in the refractive turbulence of the atmosphere between the telescope range point as shown in Fig. 1.

Consequently the received signal characteristics are affected by a combination of refractive turbulence

and speckle effects. The objective of this paper is to examine the effects of refractive turbulence along

the path on the aerosol speckle field propagation and of the decorrelation time.

3O4
ChurnsideandYura3havedevelopedthe basic theoretical formulation of the spatiotemporal

correlation function for the aerosol return-signal field. Ancellet and Menzies 4 presented results of

measurement using a pulsed TEA CO2 laser and found a decorrelation time of 2-2.5 p s over a 1.3-km

range. Laser pulses shorter than - 150ps are broadened due to atmospheric turbulence, but the pulse

spreading and wander in turbulence decrease as the pulse becomes longer, s,6 In this work, the pulse is

represented as a Fourier integral, and we make use of the two-frequency mutual coherence function

to study propagation of the aerosol speckle field.

x"

AI/'IOSPffERIC 80rING AEROS_ TARGET

LASER T_ASSMI TTER T_8OLENCE

Fig. 1. Sketch of pulsed lidar propagating through atmospheric

turbulence using moving aerosols as a target.

Analysis

The transmitter and receiver are assumed to be colocated having a common telescope aperture

diameter d. The laser transmitter is assumed to be pulsed with a pulse duration tp and a transmitted

power Pr (t) at time t. The complex field of the pulse propagating in the turbulent medium at any range

point z is given by

UI ( z,pct ) = f __**A(to)ut (p,k,t) exp(itot)d to, (1)

where A (to) is the Fourier spectral amplitude, ut is the monochromatic field amplitude at a distance z

from the transmitter, p is a 2-D transverse vector in the aerosol target plane, and k is the optical wave

number. Using the paraxial approximation and the extended Huygens-Fresnel principle, "ut can be

expressed as

u/(p,k,t) = k exp(ikz)2_izf d2rur(r't-z)

×exp [_(p-r)2+lp(r,p,k,t)]. (2)

In Eq. (2), r is a transverse vector in the transmitter plane, _p(r, pfl¢,t) is the sum of the logamplitude and

phase perturbation experienced by a spherical wave propagating from r to p through the atmospheric

turbulence, and ur represents the field amplitude at the transmitter given by

UT (r,t)= k _ra2 J exp - _-£ +

(3)

where a is the beam radius at exp(-2) intensity, and f is the geometric focus of the telescope.

3O5
Thecomplexfield Ut (z,p,t) is assumed to be backscattered at range z by an atmospheric aerosol

present in the illuminated volume. The scattered pulse propagates back to the receiver through

atmospheric turbulence, and its field is given by

Us (q,t) = f ** A(co)us (qJc,t) exp(icot)dco,

OD

where the monochromatic wave field us (q,k,t) is given by 9

(4)

us(q,k,t) = s (z) z ut p,k,t- )

In Eq. (5), q is a transverse vector in the receiver plane and S(k) is the monochromatic backscatter

coefficient of the aerosol.

The pulse is assumed to have a center carrier angular frequency co0 and optical wavenumber k0

and is narrowband. It is convenient to write Eq. (4) as

Us (q,t) = exp[i(coot - k0z)l f __ dcoA(co + too)

0o

xus (q, co + coo,t) exp(/tot). (6)

During a small time interval of < 1 ms, the aerosol position is assumed to change due to a radial

velocity vz, a transverse velocity Vr to a new position given by the following relations:

zT = z(t + r) + z(t) +Vz r; :-

pr =p(t+r) =p(t) +VTr.

The backscattered field at time t + r, is given by

Us (q,t + r) = exp[ico0(t + _r -z,/_)]f** A(co + coo)

oo

X Us (q, co + coo,t + r)

x exp[/co(t + r - z./_ ) dco, (7)

and the monochromatic wave field at time and t + r is given by

". 306
us (q,c_,t + r )

= kSexp(2/kzO2_riz2f dr2ur(r,t +r---_-)

× exp[_ (i_- r) 2 ,+ (q -1_) 2]

+W(r,l_Jc,t +6r) +W(l_,q,kd + r). (8)

The cross-product of the received fields at time t and t + r is given by

(ql,t)_ (q2,t+ r) : f_ d0)If: d0)_V4e(0)I) Us

x us (ql,0)l,t)Ae (0)2) u; (q2,t02, t + r)

x exp [i (0)1 - 0)2) t ], (9)

whereAe (0)) = A (0) + 0)o).

Equation (9) will be ensemble-averaged over the propagation path for refractive turbulence and

over the illuminated volume for velocity turbulence to obtain the pulse spatiotemporal correlation

function. This process is represented by double angular brackets, and the correlation function of the

received optical fields is given by

<<Us(ql,t)Lr_s(q2,t+r)>>=f: do)if: d0)2Ae(0)x)A;(0)2)

OO

xF(qbq2,0) l,0)2)

× exp[i (0)1 - 0)2) t], (10)

where F(ql,q2,o)1,0)2) = <._u, (ql,0)l,t)us (q2,0)2, t +r) >::,isa two-frequency mutual coherence function. The determination of the effects of aerosol speckle, refractive turbulence, and pulse shape are

now dependent on the evaluation of the function F.

Ensemble Averaging

Following Churnside and Yura 3 for the averaging over velocity turbulence, the aerosol velocities

are assumed Gaussian-distributed within the inertial subrange, and we obtain the expected value of the

mutual coherence function as

(11)

XUs (ql,0)l,t) Us (q2,0)2 t +r)

×P (Vz )P (VT )/V.

307 "
In Eq. (11), V is the illuminated volume, and the probability density functions of the velocity

components are given by

P(Vz) -- 1 exp [--(vz -- _z)2/20 2 ], V"2V_

P (VT) = -- 1 exp [ -- (V T - "VT)2/_ ],

where Vz, V'r and tr 2z, tr _-are the means and variances of the wind components along the z axis

and transverse to it.

The ensemble average over path turbulence is given by

o) * .klk2S(o)l)S(co2) exp[2/(kl -k2)z

( Us (ql, 1,t) Us (q2,o92,t + r) ) = (2_Z2) 2

-2ik2vzr] f f d2r_d2r2ur (r_,t --_)

/k2 VTr) 2

--_- (q2 -- p - ]

xH(ql,q2,rl,r2_l_2),

where H is the fourth-order mutual coherence function given by

H =(exp[1F (p,rl_l,t) +tIJ (P,qlJq,t) + tI/* (p+VTr, r2_:2,t + r)

(12)

+qJ*(p +VT r, q2,k2,t + r) ). (13)

The change in the aerosol position has very little effect on the refractive turbulence encountered

along the path for small r and will be neglected in evaluating the mutual coherence function, which can

be written as s

+D14 +D23 +D34 -D24 +D34)

(14)

= D(lri - ry l) is the two-frequency wave structure function of a point source

H = exp [--(1/2)(912 -D13

+2Cxn + 2Cx34 ].

In Eq. (14) D 0

given by lo

3O8
D(p) = 2(.o/,oo) v3 -2A22/fl 2 ,

p0 = (0.545k0C 2 z) -_,

Q-z = 0.39koC2 L_z, Ale =lkl -kzl/ko, (15)

where L0 is the outer scale of turbulence, c is the speed of light, and Cn2 is the turbulence structure

constant assumed uniform along the path.C_j = Cx ( Iri - rj I) is the two-frequency covariance of the

logamplitude of a point source given by

= O'132_2klkjz C2 _o dt ,f uu -_ Jo

x sin u2t (1 -t )z (16)

The integrations of Eq. (12) are lengthy and cannot be performed in closed form. We present the

approximate results in this work for the simplified case of a collimated beam and negligible transverse

velocity component and consider points along the beam axis. It is also assumed that A12 << 1, and we

make use of a quadratic approximation for the structure function. With these simplications, the

integrations of Eq. (12) can be carried out, and the result is

2S2F2

( Us (o,o)l,t) Us (O,o)2,t +r) ) = a2z2(1 +F 2 +2a2/p20 )Tt

x exp{/(cox - toe) Td - (o)1 - o)2)2/f2 2

where F = ko ae/2z is the Fresnel number of the source, Td si the time delay given by

F ( 1 +a2/p_ v/)

Td (18)

_-00 1 + F 2 + 2a2/p2| '

309
the coherence bandwidth is given by

_"_-2 ._ 0.39C 2 Lo_ Z/C 2, (19)

and Lo is the outer scale of the turbulence, and c is the speed of light. It may be noted that the

pulse broadening is inversely proportional to the coherence bandwidth. We will now carr_ out integrations indicated in Eq. (11) over the velocity spectrum and sensing volume V and replace S" N/Vby the

aerosol backscatter coefficient fl, where N is the total number of aerosols within the volume V. The

result is

 ,ooo, o,:y5

x exp [i (0)1 --0)2) Td --(0)1 --0)2) 2/(`]2

+2/(kl - k2) z - 2/k 2 _z Gz 1[:" - 2_z k_2 121 dz. (20)

The integrations over (,01 and to2 are carried out for a Gaussian pulse with frequency spectrum

given by

A(¢o) =(2_o2_ )-vz exp[(0) -0)0)2/202,,, ],

where o_ is the bandwidth of the pulse. The variables are changed using 2w'0 = 0)x + 0)2,

t_ =0)1 --0)2.

The spatiotemporal correlation function is calculated for a Gaussian transmitted power distribution given by

Pr(t) = _tp exp(-t2/_ ),

where E is the total energy in the pulse, and the pulse width is related to bandwidth as

te =v'-'2-0,7,k The integration over z is performed designating arbitrarily the time of peak power by t =

0, and the result is

310
<<Us (o,t)U_ (o,t +r) >> - cflE Q re

+ +

X 1 :o3 

1 +6F 2 + 2aZ/p_ exp

-T (32 + 2_ a_ r/c

X Irate2 r2/4+(Ta+Tz 3/c) 2] + 3 2

-i(o_o3 + 2koPzr)], (22)

where 32 = 0,7,2 + 4Q -2 and z0 is the range. Equation (22) is the main result of this paper, which

exhibits the effects of refractive path turbulence on pulse spreading and aerosol speckle. The first term

in the exponential gives the decorrelation effect due to velocity turbulence along the beam of the axis;

the second and third terms give the effect of refractive turbulence and velocity turbulence on pulse

broadening and its contribution to the decorrelation of aerosol scattered signals.

Discussion

The spatiotemporal correlation function obtained by Churnside and Yura 3 has been extended to

include the spectral effect of pulsed signals and refractive turbulence along the propagation path. An

approximate result for a collimated beam along the beam axis is presented in Eq. (22) for the combined

effects assuming a quadratic approximation for the structure functions. These approximations permit

us to bring out explicitly the effect of time delay Ta and coherence bandwidth f2 on the correlation

function.

We consider a long path wind-measuring pulsed lidar having a pulse duration of 100 ns operating

at 9.1 _m wavelength. The path length is assumed as loo km through a turbulent atmosphere with

Cn2 = 6.4 x 10-15 m-Z'3 corresponding to a clear day in the lower atmosphere with an outer scale length

L0 =100m and az =1 m/s.The beam radius at exp(-2) intensity is taken as 1 m, which gives the Fresnel

number of the source as F = 3.45. The transverse coherence length for this path isp0 = 0.0465m.

The coherence bandwidth f_ and the time delay Td corresponding to these parameters are

f2=4.1 xl011 rad/sand Td = 1.65 x 10-14s.Using these values, we obtaino, o =l.4x101° rad/sand

re = 70.9 ns. These time scales are shorter than the correlation time of the order of lps corresponding

to moderate turbulence-induced aerosol dephasing, and the effect of pulse broadening is negligible for

this case. When the correlation time due to aerosol dephasing approaches the nanosecond range, pulse

broadening effects need to be considered.

This work is supported by NASA grant NSG 8037. It is a pleasure to acknowledge the discussions

with James W. Bilbro of NASA Marshall Space Flight Center.

311
References

1. R.M. Hardesty, R.J. Keeler, M.J. Post, and R.A. Richter, "Characteristics of Coherent

Lidar Returns from Calibration Targets and Aerosols," Appl. Opt. 20, 3763 (1981).

2. P.H. Fiamant, R.T. Menzies, and M.J. Kavayaa, "Evidence for Speckle Effects on Pulsed

CO2 Lidar Signal Returns form Remote Targets," Appl. Opt. 2.3, 1412 (1984).

3. H. Churnside and H.T. Yura, "Speckle Statistics of Atmospherically Backscattered Laser

Lights," Appl. Opt. 22, 2559 (1983).

4. G.M. Anceilet and R.T. Menzies, "Atmospheric Correlation Time Measurements and

Effects on Coherent Doppler Lidar," J. Opt. Soc. Am. A 4, 367 (1987).

5. C.H. Liu and K.C. Yeh, "Pulse Spreading and Wandering in Random Media," Rad. Sci, 14,

925, (1979).

6. I. Sreeivasiah, A. Ishimaru, and T.S. Hong, "Two Frequency Mutual Coherence Function

and Pulse Propagation in a Random Medium: An Analytic Solution to the Plane Wave

Case," Rad. Sci. 11,775 (1976).

7. R.F. Lutomirski and H.T. Yura, "Propagation of a Finite Optical Beam in an

Inhomogeneous Medium," Appl. Opt. 10, 1652 (1971).

.

.

10.

H.M. Lee, J.F. Holmes, and J.R. Kerr, "Statistics of Speckle Propagation Through the

Turbulent Atmosphere," J. Opt. Soc. Am. 66, 1164 (1976).

H.T. Yura, "Mutual Coherence Function of a Finite Cross-Section Optical Beam

Propagating in a Turbulent Medium," Appl. Opt. 11, 1399 (1972).

R.L. Fante, "Electromagnetic Beam Propagation in Turbulent Media: An Update," Proc.

IEEE 68, 1424 (1980).

11. A. Ishimaru, "Temporal Frequency Spectra of Multifrequency Waves in Turbulent

Atmosphere," IEEE Trans. Antennas Propag. AP-20, 10 (1972).

312
AUTOMATED ASSEMBLY IN SPACE

S. Srivastava, Professor

Bowie State University

N91 .8 1

/

Suren N. Dwivedi, Professor

West Virginia University

Gary Jones, Manager

Goddard Space Flight Center

Greenbelt, MD

Toh Teck Soon, Reddy Bandi, Soumen Banerjee, and Cecilia Hughes

Student Assistants

Bowie State University

Bowie, MD

ABSTRACT

The installation of robots and their use for assembly in space will create an exciting and promising

future for the U.S. Space Program. The concept of assembly in space is very complicated and error

prone and it is not possible unless the various parts and modules are suitably designed for automation.

This paper develops certain guidelines for part designing and for an easy precision assembly. Major

design problems associated with automated assembly are considered and solutions to resolve these

problems are evaluated in the guidelines format. Methods for gripping and methods for part feeding

are developed with regard to the absence of gravity in space. The guidelines for part orientation,

adjustments, compliances and various assembly construction are discussed. Design modifications of

various fasteners and fastening methods are also investigated.

In phase 2, a smart menu driven user friendly software will be developed containing all these

guidelines and rules. Finally, this software will be implemented and its performance will be evaluated.

Some examples will be considered and tested using the guidelines and/or software.

313
AUTOMATED ASSEMBLY IN SPACE

Introduction

In the coming years, the first permanently manned space station, which will perform such tasks as

collection of data from distant stars, repairing satellites and manufacturing of extremely pure pharmacological products, will be launched. The space robots will be designed in such a way that they would

assemble the space station itself, perform satellite repairing and testing, and various extra vehicular

activities (EVA) under the control commands given from the earth station. Almost total reliance upon

space robots in the space station will free astronauts for accomplishing more significant tasks including

taking advantage of unforeseen opportunities, solving unexpected problems, occasionally saving a

mission, supervising machines and acquiring, integrating and interpreting multisensory data.

The concept of assembly in space seems quite complicated, unproductive and error prone unless

various parts and modules are suitably designed for automation from the beginning.

This paper basically focuses on the development of such guidelines and rules for the design of

products that will be assembled in space. The parts once designed with these considerations will be

easily assembled by simple telerobots, programmed robots or manually, without any error and in shorter

time. It will also reduce the need for complicated grippers and end-effectors to monitor the assembly

process.

In addition, these proposed modifications that are incorporated into the design of a part facilitate

easy handling, omit orientational ambiguities and require simple assembly steps by robots. What is more

important about these guidelines is their applicability under the prevailing condition of zero gravity in

space.

Development of Guidelines and Rules

1. Design for Part Handling and Gripping

The gripping of the components to be assembled is the most difficult part of assembly by robots

in space. If the components are not gripped properly, they can become projected missiles and damage

vital equipment as well as the spacecraft and the astronauts. While designing the products and the

grippers, care should be taken so that when the components are moved, their movements are secure,

verifiable and failsafe.

For higher productivity in assembly by robots in space, the design of the general purpose gripper

is a critical factor. The design emphasis and functional requirement of grippers used in industries and

space are different in some respects. The object escaped from the end-effector would take off with a

velocity in an arbitrary direction determined by the robot motion, transforming it into a potentially

harmful projectile. The grip provide by the end-effector has necessarily got to be failsafe. This

requirement translates into considerations such as positive grasp (see Fig. 1), low friction grasping

surfaces, sensory verification, zero back-drivability, and extreme gripper strength. Furthermore, the

issue of compliance in space robotic gripping should be considered. Compliance has to be incorporated

either in the object, f'Lxture, gripper, or the arm. In the majority of the cases vacuum suction and magnetic

pick will be used for part handling (see Fig. 2).

314
Rubber Fr Lc t/.on

S,=rface

Side View

Robot CcJpper

FLngecs ._

Bearing Surfaces

Side Vlew

Top View

(A.) [.d.srrial Crll,pet

(F_ Lcr.Lona]. (;rail,)

Top View

(B.) Space Cr|ppor

(l_aN I r Lye (;r a._p)

Figure 1

_itlicult to g,ip preferred

=at_e, flat, smooth too surface lot vacuum

Figure 2

Inner hole for spearing

2. Design for Part Feeding and Orientation

There are several key concerns when considering design for proper part feeding and orientating.

Parts coming to the assembly station are usually bulk components. They are fed along a suitable

conveyor-media (a conveyor box) and will be latched between two fixed ends in the space ship, and thus

avoiding the parts swimming in space.

315
First, part dimensions should be designed to facilitate automation. It is very difficult to automatically orient parts that have dimensions that differ by only a small amount. The obvious alternative is to

make these parts' dimensions either identical or their differences more pronounced.

Second, a part should be designed so that symmetry is the priority. It will be a lot easier for a robot

to handle a symmetrical part than an asymmetrical part (see Fig. 3). Sometimes asymmetry also makes

part orientation easier (see Fig. 4).

Designs should be created so that they do not conflict. This includes avoiding such feeding

problems as tangling, nesting, shingling, wedging and jamming. Springs must have closed end loops.

Tangling problems are reduced by eliminating protrusions or closing off holes that are unnecessary on

the parts (see Fig.5). Parts that travel on a conveyor should be thick enough so that they do not have a

tendency to shingle, or start stacking on one another. Additional care should be taken with angles so

that the parts do not tend to wedge with each other (Fig.6).

_udl IO Or NI_I

O

Figure 3

_etla'rKI

Fltl

Figure 4

316
OF POOR qUALmf

o;¢rdcu.,t to film]

Open _as

Prqlhfff_

0

Figure 5

Pvofm_r_

L_

Figure 6

317
3. Design for Part Fastener

Fastening is one of the most time consuming operations in the assembly. This can be alleviated by

using integral fasteners and building the fasteners right into the product, and using snaps and latches

built in to fasten parts quickly, without the necessity of extra fastening parts. If screws were to be used

in fastening, using the screw with built-in washers, and reducing the screws in number and variety in any

component would help. (see Fig.7).

The methods of assembly including mechanical fastening, staging, kiting, and soldering techniques.

Devices for feeding and orienting should all be evaluated in order to reduce time of assembly/disassembly.

Figure 7

4. Design for Minimum Number of Parts

Economizing on the number of parts either by redesigning or elimination can produce dramatic

results for assembly in space. This can only happen if a concentrated effort is made to design equipment

which require a minimum number of parts. Fewer parts are advantageous to the assembly cycle, assembly

costs, system costs, material costs, and warehousing costs; and in many cases provide a higher quality

product (Fig.8).

318
0_ _ - ?; :,.

_l +_ _ '_L_':"

OF pGG_ _'+ .......

Pr_Ikl lld l--m_++ d++illl l_r u+m+ml.l)

i_.,,, _

Figure 8

5. Design for Modular Assembly

A strictly structural approach should be taken for assembly of equipment. Designing a product in

modules is advantageous. Subassemblies may be built in different areas. Modules may be tested and

repaired before final assembly. Model variations can be accomplished at the subsystem level. This system

will also make it easier for servicing the part. In addition, assemblies can take place from any direction

but must be in optimal sequence (Fig. 9).

6. Design for Minimum Part Variations

When product variation is low, commonality of parts is high. However, if follow on products

maintain a family resemblance, the assembly of the product will be greatly simplified, and cost

effectiveness and quality for assembly in space will naturally follow(Fig. 10).

319
Figure 9

di|licutl lot ,,lulom,llion pteletred

Figure 10

Benefits of Guidelines and Rules

The direct benefits of the space assembly products include: Facilitating automatic assembly with

ease, reduction or elimination of the need for expensive electronics normally required for precise

positioning, allowing relaxed positioning tolerance, reduction in downtime of assembly equipment by

reducing wedging, jamming and damaging of parts, increased productivity with humans functioning as

managers rather than as operators, increased responsiveness to innovation since the automated station

will become more flexible and adaptable, lower cost of operations with highly automated systems which

will run at peak efficiency, uniform quality control, greater autonomy with machine intelligence to

support monitoring and Control of station systems, thereby lessening reliance on ground support,

320
improvedreliability,theabilityto performwithrobotsandteleoperatorstaskswhichareunsuitableto

humansalone,for instance,theassemblyof largestructures,andareducedneedto exposehumansto

hazardousconditionsexistinginspace.

Conclusion

In conclusion, it can be said that assembly by robots in space will be a very interesting research

area. It will help in establishment of a station in outer space to assemble and launch satellites and

spacecraft automatically. The space station will also be capable of testing, servicing, refueling and

recovering a space shuttle or satellite by teleoperation from the ground. Automated assembly in space

stations can also be used for various material processing and manufacturing. The key feature of

manufacturing in space is the extended period of weightlessness that is permitted in its low gravity

environment. Thus, these guidelines will be helpful in automizing the tasks of the space industry by

properly designing various containers, etc., suitable for robotic handling.

References

.

*

.

Mahalingam, S., Sharifi, M., Dwivedi,S.N. and Vranish, J., "Special Challenges of Robotic

Gripping in Space", Pro. IEEE Comp. Soc. 20th Southeastern Conf. on Systems Theory,

pp. 581-586, March 1988.

Vranish, J.M., "A Quick Change Gripper for Robots", Robot Grippers, Springer Verlag,

pp. 277-298, 1986.

Robert-Bunch, W. and Vranish, J.M., "Split Rail Parallel Gripper", RILSME Robots 9

Conf, June 1985.

.

.

Salisbury, J.K., "Teleoperator Hand Design Issues", Proc. IEEE Int. Conf. on Robotics

and Automation, pp. 1924-1928, 1987.

Tournassoud, P., Lozano-Perez, T. and Mazer, E., "Regrasping", Proc. IEEE Int. Conf.

on Robotics and Automation, pp. 1355-1360, 1986.

6. Craig, J.J. and Raibert, M., "A Systematic Method for Hybrid Position/Force Control of

a Manipulator", Proc. IEEE Comp. Software Applications Conference, 1979.

7. Cutcosky, M.R., "Robotic Grasping and Fine Manipulation", Kluwer Publishers, 1985.

8. Van der Loos, H. F. M., "Design of a Three-fingered Robotic Gripper", The Industrial

Robot, International Fluidic Services, Bedford, England, Vol. 5, No. 4, pp. 179-183, Dec.

1978.

9. Chen, F. Y., "Gripping Mechanism for Industrial Robots - An Overview", Mechanism

and Machine Theory, Vol. 17, No. 5, pp. 299-311, 1982.

10. Analysis of Large Space Structure Assembly, Essex Corporation. Huntsville, Alabama.

321
11.

12.

Preliminary Program Plan for the Space Station Flight Telerobotic Servicer Program,

Prepared by Goddard Space Fight Center for the Office of NASA Headquarters,

Washington, D.C., p. 6, 1987.

Nevins, J.L., "Exploratory Research in Industrial Modular Assembly", R-800, Charles

Starks Draper Laboratory, Inc; March 1974.

7

322
 91:es ov

ELECTRODE EROSION IN LOW POWER ARC JET THRUSTERS*

A. Ghosh and P. Ray

School of Engineering and Architecture

Tuskegee University, AL

f

ABSTRACT

Low power arcjet thrusters (0.5 to 3kW) are currently being considered for North-South station

keeping of geosynchronous communications satellites. The erosion mechanisms of cathodes in these

thrusters are not well understood. The experimental set-up to produce a steady state electric arc in a

gas flow is described and some preliminary theoretical results on cathode erosion are presented.

*Work supported by NASA Grant NAG3-726

323
ELECTRODE EROSION IN LOW POWER ARC JET THRUSTERS

Introduction

The power available for auxiliary propulsion on communications satellites currently ranges from

0.5 to 3kW. Low-power arcjet thrusters are being developed for North-South station keeping of these

satellites. These devices convert electrical energy to thermal energy by heat transfer from an arc

discharge to a propellant gas and subsequently from thermal energy to directed kinetic energy by

expanding the gas through a nozzle. Arcjet thrusters offer more than 50 percent increase in specific

impulse over state-of-the-art auxiliary propulsion [1]. Significant mass savings can thus be achieved for

these spacecrafts using auxiliary propulsion.

Extensive work has been done in the last few years in understanding the interaction between

various parameters of the low-power constricted arcjet thrusters [2-4]. This has resulted in significant

advances in the performance of these devices. A 1000-hr life test (500 cycles of 2-hr duration) at a

specific impulse of about 450 sec and about 1.2kW power level was recently successfully completed [5].

It was observed from this test that a burn-in period spanning over several cycles existed before a

stable and consistent thruster operation was obtained. The burn-in period was characterized by voltage

excursions, some of which were rapid While others were step changes. A rapid increase in steady state

arc voltage was observed during the burn-in period, indicating rapid cathode tip recession.

To maintain the arc, the cathode emits electrons through an extremely complex process which

makes it one of the key components in the arcjet thruster. One result of an arc discharge is the loss of

cathode material ejected in the form of vapor jets at high velocities. The arc termination at the cathode

is characterized by the formation of molten areas called spots, which can be highly mobile. It is presumed

that the voltage fluctuations observed during the burn-in period are caused by the motion of the arc

spot at the cathode tip. The objective of this research is to understand the mechanisms of cathode

erosion in the low-power constricted arcjet thrusters by using both experimental techniques and

theoretical analysis.

Experimental Setup

An experimental assembly to generate an open dc arc has been fabricated. The arc is established

in an argon environment at or below one atmosphere pressure. Initial studies have been made to gain

an understanding of the arc ignition and maintenance processes and to get preliminary information on

electrode erosion. A schematic drawing of the experimental system is shown in Fig. 1.

The cathodes used are 3.2 mm diameter, 2 percent thoriated tungsten rods ground to a 30 ° half

angle tip. For preliminary arc characteristic studies and mass loss information, the anode inserts used

are finely polished bolt heads made of various materials such as low carbon steel, aluminum, brass and

titanium. Cathode and anode holders are designed in a way so that the electrode inserts can be replaced

quickly.

324
Thecathode is put inside a brass electrode holder and held in place by a brass screw clamp. The

brass electrode holder is made to thread into the copper cooling jacket. The cathode tip would typically

extend about 2 cm from the brass holder.

The anodes are threaded directly into the copper cooling jacket. The inlet and outlet connections

to the cooling water jackets are fitted with thermocouples to monitor temperatures of water circulated

through the electrode assemblies.

The distance between the cathode and the anode can be set precisely by the use of a micrometer

head. The rotation of the micrometer spindle is translated into a linear motion of the cathode assembly,

thereby adjusting the gap width to the desired value. The gap width generally ranges from 1 to 5 ram.

A current-controlled, voltage-regulated dc power source (Sorenson Power Supply) with a maximum capacity of 18 A at 600 V is used to provide the power. Initial testing has been done in the range

of 5 to 15 A arc current.

The test chamber which contains the arc is a pyrex cross. To start the arc ignition process, vacuum

is first obtained by the use of a roughing pump. Argon is then forced into the pyrex test chamber to

increase the pressure to the desired level.

The arc is started at about 200 V by separating the electrode contacts. After the arc is initiated,

the voltage across the arc drops to approximately 40 V. For the ballast resistance, a set of I kW, 1 ohm

resistors are used. The resistors could easily be added to or removed from the system. It was found that

a combination producing 2 ohm of resistance provided adequate stability to the arc.

The measured voltage-current characteristics confirm the observed trend that the arc voltage

decreases as the current increases. The arc voltage also tends to increase as the distance between the

electrodes increases. The mass loss is observed to range from 1 to 40/t g/C depending on the material

and the arc power level.

Theoretical Analysis

A preliminary theoretical parametric study of the cathode processes of a low-current electric arc

was done. The independent parameters were the cathode fall potential, work function of the electrode

material, atomic mass of the electrode material and thermal conductivity. The dependent variables were

the electron current density, the ion current density at cathode spot, the ratio of ion current to total

current, the electric field in the cathode fall region and the temperature of the cathode spot.

The cathode temperature was found to be related to the cathode spot radius, a, the heat flux, Q,

and the thermal conductivity, K. It is given by the relationship:

Tc = a.Q/IC (1)

The heat flux was related to ion current density, Ji; cathode fall potential, Uc, and work function,

,¢,by

Q =Ji. (Uc - _p). (2)

325
a

Defining v

a

Hence,

T¢

The cathode spot radius can be written as a function of arc current, I, and arc density, J.

= (I/_ j)v2. (3)

= Ji/J, one gets

= (I v/_r Ji) _ . (4)

= (I v Ji) v2 . (Uc - _)/( 1_ K). (5)

The erosion of the cathode can be calculated by assuming that the ion bombardment raises the

temperature of the cathode spot beyond the melting point of the cathode material. The cathode mass

removal rate, m, is given by

m = v (Uc - ,p)/[(L + C_ (Ts - Tr) +C_ (To - "Is)] (6)

where L is the latent heat of fusion of the cahtode material, Cs and Ci are the specific heats of cathode

in solid and liquid state respectively, Tr is the room temperature and "Is is the melting point of the

cathode material.

Discussion

An experimental assembly to generate an open arc in an argon environment has been fabricated

and is operating satisfactorily. In the next phase of this research, we plan to incorporate an arcjet thruster

into this assembly and study the cathode spots through the use of optical spectroscopy, high speed

photographic techniques and scanning electron microscopy.

From the theoretical analysis it was found that the ion current density plays a crucial role in

determinin_ the cathode spot temperature and cathode spot size. For an ion current density ranging

from 1 x 113"A/m 2 to 1 x 101° A/m 2, the cathode spot temperature varies between 2000°K to 600(f'IC

The cathode spot size varies between 4_m to 15Qum for the given range of ion current density. The rate

of cathode erosion is dependent on the cathode spot temperature as well as on the melting point of the

cathode material. The erosion rates are in the range of tens of micrograms per coulomb and these values

correspond well to the erosion rates that have been observed with electric arcs.

References

1. Stone, J.R., "Recent Advances in Low Thrust Propulsion Technology", Paper No. AIAA88-3283. (1988).

2. Hardy, T.L.; Curran, F.M., "Low Power dc Arcjet Operation with Hydrogen/Nitrogen/

Ammonia Mixtures", Paper No. AIAA-87-1948. (1987).

326
3. Haag,T.W.;Curran,F.M.,"Arcjet StartingReliability:A MultistartTestonHydrogen/

NitrogenMixtures",PaperNo.AIAA-87-1061,(1987).

4. Curran,F.M.;Haag,T.W.,"Arcjet ComponentConditionsThroughaMultistartTest",

PaperNo.AIAA-87-1060,(1987).

5. Curran,F.M.;Haag,T.W.,"An ExtendedLife andPerformanceTestof aLowPower

Arcjet", PaperNo.AIAA-88-3106,(1988).

327
Argon Tank

Ca t hod e

\

To Vacuum

Pump

Pyrex Cross

Anode

Q

Voltmeter

D° C°

Power

Supply

Cooling

Water

+

( Ammete

_Varlable Resistance

1 - 5 Ohm

600V, 18A

Figure 1. Schematic drawing of the arc discharge experimental system.

328
N91-28108

EVALUATION OF ON-BOARD HYDROGEN STORAGE METHODS

FOR HYPERSONIC VEHICLES

A. Akyurtlu, J.F. Akyurtlu, A.A. Adeyiga, and S. Perdue

Department of Engineering

Hampton University

Hampton, Virginia

and

"3

G.B. Northam

NASA/Langley Research Center

Hampton, Virginia

ABSTRACT

Hydrogen is the foremost candidate as a fuel for use in high speed transport. Since any aircraft

moving at hypersonic speeds must have a very slender body, means of decreasing the storage volume

requirements below that for liquid hydrogen are needed. The total performance of the hypersonic plane

needs to be considered for the evaluation of candidate fuel and storage systems.

To accomplish this, a simple model for the performance of a hypersonic plane follows. To allow

for the use of different engines and fuels during different phases of flight, the total trajectory is divided

into three phases: subsonic-supersonic, hypersonic and rocket propulsion phase. The fuel fraction for

the first phase is found by a simple energy balance using an average thrust to drag ratio for this phase.

The hypersonic flight phase is investigated in more detail by taking small altitude increments and

calculating the thrust, drag, fuel fraction and the effective specific impulse of each increment. This

approach allowed the use of flight profiles other than the constant dynamic pressure flight. The effect

of fuel volume on drag, structural mass and tankage mass was introduced through simplified equations

involving the characteristic dimension of the plane. The propellant requirement for the last phase is

found by employing the basic rocket equations.

The candidate fuel systems such as the cryogenic fuel combinations and solid and liquid endothermic hydrogen generators are first screened thermodynamically with respect to their energy densities

and cooling capacities and then evaluated using the above model.

329

f _ /_-
EVALUATION OF ON-BOARD HYDROGEN STORAGE METHODS

FOR HYPERSONIC VEHICLES

Introduction

Hydrogen is the foremost candidate as a fuel for use in high-speed transport. The National

Aerospace Plane program has been recently initiated by NASA and the Department of Defense (DOD)

for developing hypersonic/trans-atmospheric vehicles for takeoff from conventional airport runways to

orbit, or for rapid, long-distance, intercontinental aerospace transportation. For this purpose, airbreathing hydrogen-fueled supersonic combustion ramjet (scramjet) engines are being developed for

speeds of Mach 5 to 25.

The main difficulty encountered in the use of hydrogen as a high-speed aircraft fuel is the space

requirement for its on-board storage. If hydrogen is stored as a liquid, it requires about four times the

volume to produce the same amount of energy as conventional fuels. This is especially important for

supersonic and hypersonic aircraft which need to have slender designs.

The main aim of the present study is to identify and evaluate the storage media capable of

increasing the hydrogen storage density (mass of hydrogen stored per unit storage volume) to a level

higher than that of liquid hydrogen (approximately 70 kg/m 3 of hydrogen).

Evaluation Criteria

During hypersonic flight, besides providing propulsion, the fuel has to contribute to structural and

engine cooling. In addition, combustibles other than hydrogen in the storage system may serve as rocket

fuel in space flight or may be burntto provide power for the aircraft subsystems. Therefore, the hydrogen

storage density, and the heats of combustion of hydrogen and other combustibles in the storage system

are important parameters for the evaluation of possible storage systems.

It should be realized that for any improvement in hydrogen storage density a certain penalty has

to be paid in terms of increased gross lift-off mass, decreased specific impulse, or increased cost and

complexity of tankage, fuel feed systems and technology development. These effects depend on, among

others, the flight trajectory, whether the plane will be designed as a launch vehicle or as a hypersonic

transport plan e, the structural design of the plane, the types of engines to be used, and the switchover

Mach numbers for the engines. Only the first two of these effects are considered in the present

evaluation. To account for them, differences in the effective specific impulses and the payload capacities

are taken to be the additional evaluation criteria.

Since actual design and flight data for the National Aerospace Plane (NASP) do not exist, a need

for a mathematical model for the purpose of evaluating the effective specific impulses and payload

capacities, especially in the hypersonic range, was strongly felt.

As a result, in order to provide a tool for the comparison of different fuel storage systems, a very

simplified model was written for the SSTO flight of the NASP.

330
Sincethemainaim is not to obtain a quantitative description of the performance of a hypersonic

vehicle but only to compare the performances of two vehicles with different fuel storage systems, no

attempt was made to evaluate various structural and flight parameters. Instead, these were left as

adjustable parameters. Initially, only the hypersonic segment of the flight trajectory was considered 0).

Simplifying assumptions such as isentropic compression, constant pressure combustion and

isentropic expansion to ambient pressure were used in the evaluation of the engine performance. At

this step, engine geometry was assumed not to change with the type of fuel or storage system.

Thrust-to-drag ratio for a baseline liquid hydrogen plane was left as an adjustable parameter. The

required fuel fraction was calculated using the simplified analysis of Jones and Donaldson (2).

The thrust structure mass, thermal protection mass, fuel tankage mass, engine mass and drag for

the vehicle were expressed in terms of a characteristic dimension which was iteratively calculated from

the specified mean thrust to drag ratio. Conditions at the combustion chamber exit were obtained by

interfacing with the NASA/Lewis Chemical Equilibrium Program CEC. Isentropic frozen expansion to

ambient pressure was assumed after complete, constant pressure combustion.

Preliminary Results

Percent changes in the payload capacity and the effective specific impulse with respect to the

cryogenic LH2 vehicle were computed to aid in the comparison of different fuel systems. The results

indicated that if liquid methane is used as fuel, it would result in a 22% less payload capacity and 10%

lower effective specific impulse. But, if a mixture of 83% hydrogen and 17% by mass methane is used,

the corresponding reductions in payload capacity and effective specific impulse were 3% and 0.7%,

respectively. A sample endothermic fuel, cyclohexane, was also tested. If only the hydrogen extracted

from cyclohexane is used as fuel negative payloads are obtained. On the other hand, the effective specific

impulse increased by 7% due to decreased drag. This indicated that unless the benzene obtained after

the extraction of hydrogen from cyciohexane is used as fuel for a later stage of flight, it will not be

possible to use cyclohexane as a hydrogen storage medium.

Modified Model

The preliminary results indicated that in order to be able to evaluate complex fuel systems the

model should be modified to enable the use of different fuels for different stages of flight. Furthermore,

there is a strong indication that the air-breathing propulsion will not be sustained up to orbital velocities

and the last stage of flight will be rocket propelled.

The outcome of the considerations is the second generation model. Its information flow diagram

is shown in Appendix A.

In this model the total SSTO flight is considered in three stages: (1) subsonic-supersonic AB

propulsion; (2) hypersonic AB propulsion; and (3) rocket propulsion. The hypersonic AB phase is

further divided into small segments for which a different dynamic pressure and climb angle can be

specified. Thus, for this phase a specified flight profile can be approximated.

331
For the subsonic-supersonic AB propulsion phase, an average thrust-to-drag ratio is specified and

the initial to final mass ratio for this phase is calculated using Jones and Donaldson's analysis.

A more detailed analysis is performed for the hypersonic AB propulsion phase in order to obtain

an effective specific impulse profile. At the engine inlet, isentropic compression is assumed. Chemical

equilibrium conditions for a complete, constant pressure combustion is obtained by calling relevant

subroutines of the NASA/Lewis Chemical Equilibrium program (CEC). Exit velocities are then

calculated assuming isentropic, frozen expansion to ambient pressure. Engine inlet size is fixed by

specifying an initial thrust-to-drag ratio for hypersonic flight and assumed not to change. The thrust

structure mass and the engine mass is taken to be proportional to the gross lift-off mass of the vehicle.

Thermal protection mass and the mass of propellant tanks are expressed in terms of a characteristic

dimension of the vehicle following Dorrington's approach. O) Equipment mass is assumed to be

independent of flight and vehicle characteristics. Total drag is assumed to depend on the square of the

characteristic dimension which is in turn a function of the total propellant volume. The mass ratio for

each segment is calculated using a modified version of Jones and Donaldson's analysis (2), and therefore

requires information on thrust-to-drag ratio. For this reason, the characteristic length is found by an

iterative procedure in which the propellant volume is estimated; characteristic length, drag and total

propellant mass is calculated and a new propellant volume is obtained.

During the rocket phase extending up to orbital velocity, it is assumed that the specific impulse is

constant at 455 seconds and any variation is accommodated in the velocity losses.

Conclusion

A modified computer model is obtained to evaluate relative performances of hypersonic vehicles

with different fuel systems.

The candidate fuel systems such as the cryogenic fuel combinations, gelled fuels, and solid and

liquid endothermic hydrogen generators were screened thermodynamically with respect to their energy

densities and cooling capacities. Some sample results are presented in Appendix A. These systems will

be evaluated using the new computer model with respect to their relative payload capacities and

effective specific impulses with the possibility of integration of air-breathing and rocket phase propellants. The critical issue is the availability of data on the NASP and the various propulsion systems,

especially on the new integrated engines in various stages of development. For example, cryogenic fuels

may start the air-breathing propulsion with LACE engines (or its derivatives) while endothermic

hydrogen generators will probably employ engines with some type of turbine propulsion. Also, combustion of certain fuels in some engine types may not be technically feasible. Integration of the cooling

duty to propulsion requirements should be the topic of further study.

332
Bibliography

I° Akyurtlu, A.; Akyurtlu, J.F.; Adeyiga, A.A.: "Evaluation of On-Board Storage Methods for

High Speed Aircraft," First Annual Report on the project NAG-I-767 submitted to NASA

Langley Research Center, January 29, 1988.

2. Jones, R.A. and Donaldson, C. duP: Aerospace America 25(8), 32-34, 1987.

3. Dorrington, G.E.: "Optimum Combined-Cycle Propulsion Systems for Earth-to-Orbit

Transportation," paper presented at Joint Propulsion Conference, Boston, July 11-13, 1988.

Nomenclature

AFR

AFRH

AIN

AINH

C

CR

DV

DZ

E2,E1

EP

ERP

F

FD

FDH

FH

FT

FTH

IEFF

IEFFH

IFH

IFS

ISR

L

M

MA

MCI

MD

ME

MF

MFH

MFT

MPF

MPH

MR

Air flow rate for the vehicle with candidate fuel system

Air flow rate for LH2 vehicle

Engine inlet area for the vehicle with candidate fuel system

Engine inlet area for LH2 vehicle

Drag coefficient for the planes (a function of TETA only)

Air inlet compression ratio

Velocity increment for rocket propulsion phase

Altitude increment

Final and initial total energies for a flight segment defined by E = V2/2 + gZ

Propulsion efficiency

Error criterion for the convergence of propellant volume calculations

Air to fuel mass ratio for the vehicle with the candidate fuel

Drag for the vehicle with the candidate fuel system

Drag for the LH2 vehicle

Air to fuel mass ratio for the LH2 vehicle

Thrust of the vehicle with the candidate fuel system

Thrust of the LH2 vehicle

Effective specific impulse for the vehicle with the candidate fuel system

Effective specific impulse for the LH2 vehicle

Fuel specific impulse for the LH2 vehicle

Fuel specific impulse for the vehicle with the candidate fuel system

Specific impulse for the rocket propulsion phase

Characteristic length of the vehicle

Mach number

Switchover Mach numbers

Mach number at the combustion chamber inlet

Dry mass of the vehicle

Engine mass

Vehicle mass with the candidate fuel system

LH2 vehicle mass

Thrust structure mass

Payload mass of the vehicle with candidate fuel system

Payload mass of the LH2 vehicle

Final to initial mass ratio of the vehicle with the candidate fuel system, for a

specific flight segment

333
MRH

MRR

MSS

MTNK

MTOT

MTPS

P

PCI

O

QF

RHO

RHOF

RHOF1

T

TCI

TDR

TDRM

TETA

V

VE

VORB

VPF

VPFAB

VPH

VPRO

Z

Final to initial mass ratio of the LH2 vehicle for a specific flight segment

Final to initial mass ratio for rocket propulsion phase

Equipment mass

Propellant tank mass

Gross lift-off mass

Thermal protection mass

Pressure

Combustion chamber pressure

Dynamic pressure

Heat of combustion of propellant

Density

Density of the candidate fuel for hypersonic AB propulsion

Density of the fuel for subsonic-supersonic AB propulsion

Temperature

Temperature at combustion chamber inlet

Thrust to drag ratio

Mean thrust to drag ratio

Climb angle

Velocity

Exit velocity

Orbital velocity

Propellant volume for the vehicle with the candidate fuel system

Propellant volume for AB propulsion

Propellant volume for the LH2 vehicle

Rocket phase oxidant volume

Altitude

334
r! I__

[i

w •

ORIGINAL PAGE IS

OF POOR QUALITY

335
N91-28 109 !

END-EFFECFOR . JOINT CONJUGATES FOR ROBOTIC ASSEMBLY

OF LARGE TRUSS STRUCTURES IN SPACE:

A SECOND GENERATION

William V. Brewer

School of Science and Technology

Jackson State University

Jackson, MS

in association with

Langley Research Center

Hampton, VA

ABSTRACT

Attachment of strut to node can be accomplished with a variety of mechanisms: references

[1,2,3,4]. All require extensive standoff elements (called scars) added to the nodes. These increase

packaging volume for the nodes by as much as 300%. First generation designs also tend to be either

heavy or expensive due to complex parts. This investigation focuses on screw thread mechanisms as the

simplest and most easily manufactured of alternatives. Torque and rotational motion must be transmitted across the strut to end-effector interface accomplishing the joining process and establishing a

specified preload. Four drive mechanisms are considered: worm, helical, bevel, and differential gears.

All are developed with the following criteria in mind.

1. Preload: 250 to 500 lbs.

2. Envelopes: 1.0" strut; 2.5" node (reduce violation of specified diameters to a minimum)

3. Cost Reduction: reduce part complexity, diversity and count; increase "off the shelf" part

fraction

4. Feedback mechanisms: incorporate in strut design

336
END-EFFECTOR - JOINT CONJUGATES FOR ROBOTIC ASSEMBLY OF

LARGE TRUSS STRUCTURES IN SPACE:

A SECOND GENERATION

Introduction

Current designs, a first generation intended for robotic assembly, have given priority to the ease

and certainty of the assembly process under less than ideal conditions with a minimum of sensory

feedback. As a consequence they are either heavy or expensive and all exhibit a relatively low packaging

density. Low packaging density is caused by extensive "scars" applied to the node, increasing its envelope

diameter by as much as 150%. Strut envelopes are violated to a lesser extent with diameters increased

by 25% or more. This smaller percentage is still a significant problem owing to a much higher fraction

of the packaged volume represented by struts. As structures in space become larger, packaging density

becomes an important consideration.

Objectives

Develop end-effector - joint conjugates that do not violate the envelopes of a 2.5" diameter

node or a 1.0" diameter strut.

Reduce cost by:

increasing the fraction of "off the shelf" parts;

reducing part complexity, diversity and count.

Incorporate feedback mechanisms as an integral part of the overall scheme.

Discussion

Attachment of strut to node can be accomplished with a variety of mechanisms: references [1, 2,

3, 4]. All require extensive scars or standoffelements added to the node. These permit compliance when

a strut must be fitted between nodes whose separation distance is ei't_er greater or smaller than the

length. Two methods that do not require standoffs are the screw thread and conical wedge (concrete

anchor) [5]. They allow the node separation distance to be too great, but depend on distortion of the

truss in the case when the distance is too small. The present effort is designed around the screwthread

as the simplest and most easily manufactured of all alternatives.

Torque and rotational motion must be transmitted across the strut to end-effector interface

accomplishing the joining process and establishing the requisite 250 to 500 lb. preload. Four drive

mechanisms were considered: worm gear, helical gear, bevel gear and differential gear. A strut-end

design based on the differential gear was developed because it is the most compatible with the drive

mechanism used on a first generation end-effector currently under fabrication. Torque capacities of

available differential gears that would fit within the 1" envelope could not overcome friction in the

screw-threads generated by the requisite 250 lb. preload. Helical gears provide a much better basics for

achieving the objectives of a 2nd generation based on screwthread assembly. Part complexity, count

and cost are all reduced. Attaching a left-hand helical gear to the bolt shaft so that it "travels" with the

bolt has an additional advantage: axial thrust will always assist in driving the bolt in the desired direction.

337
The traveling helical assembly ( Fig. 1 ) was integrated into a strut-end design ( Fig. 2 ) that incorporates

features which assist in the assembly process.

Capture of the node by a robotically manipulated strut-end can be assisted by active feedback

mechanisms, parts of which are embedded in the strut-end ( Fig. 3 ) or by passive spring loading devices

( Fig. 4 ) without feedback. Active feedback is interfaced with the end-effector by means of a probe

inserted thru a slot in the strut envelope and into a receptacle drilled in a non-rotating axial "traveler".

This probe can assist in axial translation of the bolt as well as in reading its location and the axial force

applied to it.

References

[ 1 ] Gralewski, M., "Development of Joint Connector Model and Associated End Effector

Concept for Automated Assembly of Large Space Truss Structures", Contract No. NASI17536, Doc. No. 36230-114, Astro Aerospace, Carpenteria, CA 93013-2993, 2/29/88

[ 2 ] Final Report, "... same as title above ...", Response to AS&M

RFP 18235-39-092887, Honeybee Robotics, New York, NY 10002, 1988

[ 3 ] Everman, M. R.,"Final Report on the ASMI End Effector", AECR88336/429, Able

Engineering Company, Goleta CA 93116-0588, 3/11/88

[ 4 ] Stout, D. A., "Joint Connector Concept", D-300-01-001, Jewett Automation, 2/8/88

[ 5 ] Wesselski, C. J.,"Space Station Lock Joint", Div/Off ES22, Johnson Space Center,

Houston, TX

338
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342
N9 1 - 28

MARS SURFACE BASED FACTORY:

COMPUTER CONTROL OF A WATER TREATMENT

SYSTEM TO SUPPORT A SPACE COLONY ON MARS

PHASE H - TASK 1C

Dr. John Fuller, Warsame Ali, and Danette Willis

Department of Electrical Engineering

Prairie View A&M University

Prairie View, Texas

ABSTRACT

In a continued effort to design a surface based factory on Mars for the production of oxygen and

water, the Design Group at Prairie View A&M University made a preliminary study of the surface and

atmospheric composition on Mars and determined the mass densities of the various gases in the Martian

atmosphere. Based on the initial studies, the design group determined oxygen and water to be the two

products that could be produced economically under the Martian conditions.

Studies were also made on present production techniques to obtain water and oxygen. Analyses

were made to evaluate the current methods of production that were adaptable to the Martian

conditions. The detailed report (Phase 1- Mars Surface-Based Factory: A Preliminary Design) was

contained in an Interim Report submitted to NASA/USRA in August of 1986.

Even though the initial effort was the production of oxygen and water, we found it necessary to

produce some diluted gases that can be mixed with the oxygen produced to constitute "breathable" air.

In Phase II - Task 1A, The Prairie View A&M University team completed the conceptual design

of a breathable air manufacturing system, a means of drilling for underground water, and storage of

water for future use. The design objective of the team for the 1987-88 academic year (Phase II-Task

1B), was the conceptual design of an integrated system for the supply of quality water for biological

consumption, farming, residential and industrial use. The design has also been completed.

Phase II - Task 1C is the present (1988-89) task for the Prairie View Design Team. This is a

continuation of the previous task.

The continuation of this effort is the investigation into the extraction of water from beneath the

surface and an alternative method of extraction from ice formations on the surface of Mars if they are

accessible.

In addition to investigation of water extraction, a system for computer control of extraction and

treatment will be developed with emphasis on fully automated control with robotic repair and maintenance. It is expected that oxygen and water producing plants on Mars will be limited in the amount of

human control that will be available to man large and/or isolated plants. Therefore, it is imperative that

computers be integrated into plant operation with the capability to maintain life support systems and

analyze and replace defective parts or systems with no human interface.

343
MARS SURFACE BASED FACTORY: PHASE lI - TASK 1C

COMPUTER CONTROL OF A WATER TREATMENT

SYSTEM TO SUPPORT A SPACE COLONY ON MARS

Introduction

The Design Group at Prairie View A&M University is designing a computer control system for a

water treatment plant to support a colony on Mars. The system is being developed with emphasis on

fully automated control, robotic repair and maintenance. It is expected that the water producing plant

on Mars will be limited in the amount of human control that will be available to man the plant.

Therefore, it is imperative that computers be integrated into plant operation with the capability to

maintain the water system and analyze and replace defective parts or systems with no or limited human

interface.

Methods to extract water from beneath the surface of Mars are also being investigated. It is

believed that water exists on Mars in polar ice deposits and in permafrost layers (ground ice). There is

also evidence that water exists underneath the permafrost zon e . The Prairie View Design Team is

investigating ways of extracting and treating the water for human consumption and protein production.

To carry out the described task, teams were formed to investigate problems, and design necessary

equipment and implementation procedures for the four areas of drilling for water, plant control,

computer interface and maintenance. Figure ! shows the structure of the design team as developed for

the 1988-89 academic year. The project will be completed in the summer of 1989. As this project

continues, the focus will shift to the production of proteins for human consumption.

I

I DRILLING

• Roe= Brlce

Jerltlnds Mo|ley

PROJECT

ADVISOR

Dr, John Fuller

I I

I PLANT

CONTROL

•O&nellll Willie

Ketch Colemen

Cr Itl_ Mlrtln

Lyndan Shelby

COMPUTER

CONTROL

*Ulrlcs Kelley

Eric Renrro

Oregory Orllflth

I

j MAINTENANCE

*All Will' ilim i

Oeclr DI'¢I I

Tim H littleo_l

• a*eee keeeer

Figure 1

344
Drilling for Water

The success or failure of any attempt to colonize the planet Mars will largely depend on the

availability of the most important life sustainer, water. Not only is water important for life but also any

meaningful self-sustained technological advancement on Mars will be based on water as a process fluid.

It is therefore imperative that every attempt be made to locate an adequate supply of water on Mars.

Mars is presently too cold to support oceans or any form of stable liquid water on its surface. The

mean ambient temperature is -25 degrees Celsius. It is believed that there are ice deposits or permafrost

beneath the surface of Mars. The thickness of the zone containing ground ice is about 10 to 30 cm.

More water may exist underneath the permafrost zone.

In order to assess the amount of water on the planet other than by mere estimation, some form of

drilling must be done.

The study of the composition of the Martian soil is very important in determining its drillability.

A survey of the Martian soil has been conducted through the exploration by the Viking Landers. The

soil is composed of different elements such as silicon, iron, phosphorus, calcium, aluminum, thallium,

and sulfur. The debris analyzed by the Viking Landers showed silicon oxides in abundance of approximately 45 percent by weight.

One other important factor to consider in the design of the drilling unit is the drilling rate. The

drilling rate is a function of several variables, the most important of which are the rock drillability, the

weight on the bit and the extent of cleaning the hole. The effect of the weight on the bit is of great

importance to our design since the gravity on Mars is substantially less than that on Earth.

The drilling process will involve boring a hole by using a rotating bit to which a downward force is

applied. The bit is supported and rotated by a hollow stem composed of high-quality steel, through

which a drilling fluid is circulated. The fluid leaves the stem at the bit, thereby cooling and lubricating

the cutting structure. By flowing across the cutting surface, the drilling fluid drags cuttings from the hole

stem annulus. This process will form the basis for the design of the drilling unit.

Plant Control and Computer Control

The integrated water treatment plant consists of several processes, such as a suspended solids

removal unit, ultrafiltration unit, and reverse osmosis unit, which have parameters that need to be

monitored or controlled. These parameters include flow rate, temperature, pressure, and conductivity.

Therefore, devices such as sensors, transmitters, and control valves must be employed.

To facilitate the need of automated control, a personal computer would be used to maintain and

run the entire water system. The electronic sensors, transmitters, and control valves along with analog

to digital and digital to analog converters will communicate with the personal computer.

Through the use of one or more microprocessors, RS232 serial cables and/or fiber optics along

with analog to digital converters, the above devices will be integrated with each other.

The purpose of the A/D and D/A converters will be to interpret the analog signals being sent from

the sensors and convert them to digital signals to be analyzed by the computer. If an adjustment needs

" 345
to bemadewithina process, the computer will send a signal to a valve (actuator) to make the proper

adjustment. The microprocessors that are being investigated are the Intel 8086, Motorola 68000 and

the Z80.

Maintenance

The initial habitation of Mars will require machining and maintenance for space applications.

Machining and maintenance on Mars is complicated due to the following factors: the absence of

atmosphere, light is not diffused or scattered, the natural space environment consists of intensive light

and dark periods, small number of persons, and the lack of machining parts. The factory communication

network system will consist of an industrial microcomputer cell control, computer interface units, a

robotic controller, vision, and a computer numerical control machine (CNC lathe).

Robotics for space applications have been proposed for increased productivity, improved reliability, increased flexibility, higher safety and for the performance of automating time consuming tasks. If

a malfunction takes place within the system, it takes almost twenty minutes to receive a signal from

Earth. This signal instructs the machine on how to recover from the fault. So, it is necessary to have an

emergency plan that can start automatically right after the shutdown of the plant.

Vision/sensing is projected to include the fusion of multi-sensors ranging from microwave to

optical with multi-mode capability to include measuring capability for position, attitude, recognition

and motion parameters. [1]

The objective of using a CAD/CAM system on a CNC lathe machine is to produce machine parts

on Mars, and it is planned to modernize the computer numerical control (CNC) lathe by developing a

software system on a personal computer. The CADCAM system is able to take all the data from design

programs and convert the information to numerical control (NC) programs which are used on the CNC

lathe.

The design programs are written in Basic language on a personal computer. The CAD/CAM

software system is developed in Fortran language. By using software packages the need of punched

tape for the CNC lathe and blueprints of the design drawings are eliminated. As a result, the complete

automation from design to manufacturing for the CNC lathe is achieved. The sample design program

is shown in Figure 2, the sample of a manufactured work piece is shown in figure 3, its horizontal tool

path cutting is shown in Figure 4, and its NC program is shown in Figure 5.

The computer graphics method using basic language to generate CNC program offers the

following advantages:

1. It is safer. A problem, such as the cutting tool colliding with the chuck of an engine lathe, would

provide a genuine hazard to a user trying out a CNC program. With the CAD/CAM program, the

problem is eliminated.

2. It is economical. Besides saving all of the scrap work that would have been produced in the actual

situation, CAD/CAM program allows the limited machine tools to be utilized.

3. It is psychologically more satisfying. The major advantage of using this CAD/CAM system is to

generate a CNC program.

=

346
Recommendations for Future Research

The following are recommended areas for future development:

1. Develop the CAD/CAM software package of the CNC lathe for threading operation.

2. Comprehending all errors and malfunctions that can take place between the personal

computer and the CNC lathe.

3. Testing the system by a set of design programs to produce mechanical parts.

4. Design a plant prototype with simulation of all system parameters.

5. Study the Martian moon, Phobos, as an alternate source of water.

6. Raise fish on the planet Mars for life support.

References

1. Kumar, Krishen; "Space Robotic Vision System Technology." International Conference

and Exhibit, Houston, Tx. October i6-21, 1988.

2. Ali, Warsame; "Development of a CAD/CAM System on An EMCO-5 CNC Lathe",

Master Thesis at Prairie View A&M University, December 1986.

3. EMCO-5 CNC Lathe Manual, 1986.

4. Haberle, Robert; "The Climate of Mars."

1(| r f_ [ P_ 0 f I r*.'*r3 ===============================

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348
N91 : 2

SERVOMOTOR-LINKED ARTICULATED

VERSATILE END EFFECTOR (SLAVE 2)

Abayomi J. Ajayi-Majebi, William A. Grissom,

Brian Wingard and Derrick Walker

Manufacturing Engineering Department

Central State University

Wilberforce, Ohio

ABSTRACT

A strategy is presented for the design and construction of a large master/slave-controlled, five-finger robotic hand. Each of the five fingers will possess four independent axes each driven by a brushless

DC servomotor and, thus, four degrees-of-freedom. It is proposed that commercially available components be utilized as much as possible to fabricate a working laboratory model of the device with an

anticipated overall length of approximately three feet (0.9 m). The fingers are to be designed to

accommodate proximity, tactile, or force/torque sensors imbedded in their structure. In order to provide

for the simultaneous control of the twenty independent hand joints, a multilevel master/slave control

strategy is proposed in which the operator wears a specially instrumented glove which produces control

signals corresponding to the finger configurations and which is capable of conveying sensor feedback

signals to the operator. Two dexterous hand master devices are currently commercially available for

this application with both undergoing continuing development. A third approach to be investigated for

the master control mode is the use of real-time image processing of a specially patterned master glove

to provide the respective control signals for positioning the multiple finger joints.

349
SERVOMOTOR-LINKED ARTICULATED

VERSATILE END EFFECTOR (SLAVE 2)

Design Objectives

Development is underway to design and construct a large, five-finger, anthropomorphic, master/slave-controlled, robotic hand. The envisioned device would be larger and more powerful than the

human hand while possessing sufficient dexterity to closely mimic the fingering and grasping configurations of its human counterpart. Control signals would be generated by a master glove worn by the

operator. The device has been assigned the acronym, SLAVE 2 for, "Servomotor-Linked Articulated

Versatile End Effector," reflecting the planned master/slave control mode and the use of an individual

electric servomotor to drive each joint.

Anticipated commercial applications include handling of hazardous wastes, munitions, or large

radioactive or chemically contaminated object s. Fire fighting, construction, demolition, disaster cleanup, and rescue operations might provide additional applications for a large, dexterous end effector

operated remotely under master/slave control.

A rapid prototype R&D strategy utilizin_ off-the-shelf components wherever possible is being

employed for the development of the SLAVE" laboratory prototype. A key goal of the strategy is to

minimize development time and costs b_yeliminating long lead times for design and construction of

individual components. Thus, commercial availability of components, including the electric servomotors

and power transmission mechanisms to drive the individual finger joints, will dictate size, weight, payload

and finger length of the hand assembly. Based upon this consideration and current design est!mates, it

is anticipated that the initial working laboratory model will be approximately four-times human size

with an overall hand length of approximately three feet (0.9 m) and an individual fingertip clamping

force of 10-12 pounds (44 - 53 N). It is expected that the finger will have a typical length of about 18

inches (46 cm) and weigh approximately 15 pounds (6.8 kg). Initial estimates indicate that a frequency

response of 0.5 Hz can be achieved.

Proposed Robotic Hand Design

Mechanical Configuration

A mechanical hand configuration possessing four fingers and a thumb is contemplated. Each of

these five members will have four joints or degrees-of-freedom. More specifically, for each finger/thumb

member three joints would provide flexion and extension (and possibly hyperextension) and a fourth

joint would allow abduction and adduction. This would give the hand a total of twenty degrees of

freedom and provide sufficient dexterity to closely replicate the gripping and fingering actions of a

human hand.

The goal of the first year of the development effort currently underway is to develop a working

laboratory prototype of a single four degree-of-freedom finger. Initial emphasis has been placed upon

the selection of the most desirable mechanical configuration for the compound knuckle joint which

must provide for both flexion/extension and abduction/adduction angular motions. In arriving at a

35O
prototype design a number of different mechanical configurations were considered before selecting the

arrangement shown in the sketch of Figure 1. This configuration features coincident flexion/extension

and ab/adduction axes and provides for the drive motors for these two axes to be mounted on the

stationary palm rather than on the moving finger.

Figure 1 - Compound Axis Knuckle Joint Configuration

Drive Component Selection

The selection of the drive components to power the finger joints was governed by a desire to

achieve optimum performance and compactness while utilizing commercially available components to

the greatest extent possible. Thus, an attempt was made to balance the load capacity of the servomotors,

gear reducers, and right angle drive units. In this regard, when evaluated on the basis of torque

capacity-to-density (weight and compactness), the right angle drive units surprisingly proved to be the

limiting factor in achieving greater payloads.

Servomotors

Each of the twenty joints is to be directly driven by an independent brushless DC servomotor and

integrated speed reducing mechanism. Although practical brushless DC servomotors are a relatively

recent development triggered by advances in solid state electronics and permanent magnet technology,

units are now available from a number of major manufacturers. The selection of 24 volt DC brushless

motors from the Inland Motor Division of Ko!lmorgen Corporation was based upon high torque-todensity ratios and the convenient operating voltage range. The brushless DC type of servomotor

duplicates the external performance of a conventional DC motor without utilizing a commutator or

brushes. This is possible because solid-state electronic switching replaces the conventional brush

commutation switching process. A second major difference is that the wound member, or armature,

reverses its role and relative position from rotor (rotating member) and inner component in the

conventional DC motor, to stator (stationary member) and outer component in the brushless motor.

351
These two differences lead to a number of significant advantages from the brushless DC motor with

respect to performance, safety and reliability [1,2]:

1. No brushes to wear out: increased reliability,

reduced maintenance requirements.

2. No commutator bars to oxidize: ability to sit idle

for years without loss of performance.

3. Absence of brush arcing: safer in the presence of

fumes, dust, paint spray, etc.

4. Speeds up to 80,000 RPM are practical.

5. Less radio-frequency interference.

6. Easier cooling of windings with fins or cooling jacket:

extended operating range.

7. Smaller diameter, more compact.

8. Reduced inertia: increased acceleration

and improved control.

Power Transmission

Electric motors characteristically produce relatively low torque in the low speeds range. This is

true as well for brushless DC motors, and preliminary calculations indicate that torque multiplication

(or speed reduction) rates of about 100:1 will be required to achieve the desired robotic hand strength.

To meet this requirement, the patented harmonic drive gearing device available from the Harmonic

Drive Division of the Emhart Machinery Group, Wakefield, MA, has been identified.

The unique design of the harmonic drive with three simple concentric components yields the

following advantages for robotics gear reduction applications:

1. Exceptionally high torque and power capability

in a small package.

2. Essentially zero backlash.

3. Efficiencies as high as 90%.

4. Ratios as high as 320:1 in a single reduction with

much higher ratios achieved by compound stages.

5. Concentric input and output shafts.

6. No radial loads since torque is generated by a pure

couple; this simplifies the supporting structure

requirements.

7. Resists back driving, providing a measure of braking.

Drawbacks of the harmonic drive are that it is relatively compliant exhibiting a soft windup

characteristic in the low torque region, and that it produces a small, sinusoidal positional error on the

output. This error varies inversely with the pitch diameter at a predominant frequency of twice the input

speed. Additionally, an amplitude modulation typically occurs twice per output revolution.

A detailed explanation of the operating principles is given in the "Harmonic Drive Designers

Handbook" [3] along with load and accuracy ratings, operating life expectancies and installation and

servicing guidelines.

352
In view of the need to maintain a slender aspect ratio in the design of the finger configuration, it

is necessary to utilize a right angle drive mechanism to provide torque about an axis perpendicular to

the axis of the servomotor-harmonic drive assembly. For this purpose spiral bevel gears manufactured

by the Arrow Gear Company of Downers Grove, Illinois, were selected. This type of gearing features

efficient and smooth operation and relatively high strength.

Electronic Programmable Controllers

With the many degrees of freedom required for dexterous robot hands, the problem of control

and demand on computing escalates. The simplest approach is to use a local control loop for each joint.

However, for precise motion control, a coordinated motion for all joints is essential for an efficient

design.

For master-slave operation, where the coordination is achieved by the action of a human in the

loop, the coupling between the fingers is neglected. Currently, a number of high performance servomotor controllers are commercially available. These controllers are designed to be programmable and

installed in personal computers.

The Galil DMC/600 series Advanced Motion Controller has been selected to fulfill this role in the

finger prototype development. The DMC/600 is a fully programmable servo motion controller contained on an IBM PC compatible card. It controls the motion of up to three DC motors with incremental

encoder feedback. Modes of motion include independent or vector positioning, contouring, jogging

and homing. A FIFO buffer allows fast pipelining of instructions. The DMC/600 contains a digital filter

with an integral gain term for eliminating position error at stop. Several error handling features are

available including automatic shut-off for excessive position error, limit switch inputs, emergency stop

inputs and programmable torque limits.

Dexterous Hand Masters

The proposed master/slave control mode calls for the operator to wear a specially instrumented

dexterous hand master. This device must produce control signals capable of directing the servomotor

actuators of the robotic slave hand into correspondence with the respective positions of the human

operator's hand joints. Plans call for consideration of three different dexterous hand masters to carry

out this control function. Two such devices, the A. D. Little "Sarcos Dexterous Hand Master" and the

VPL Research "DataGlove" are currently commercially available though both are undergoing continuing development. Their application will be discussed briefly in the following paragraphs together with

a third approach utilizing real-time image processing of a special optically patterned master glove.

Arthur D. Little, Inc. of Cambridge, Massachusetts [4,12] offers a Sarcos Dexterous Hand Master.

The device utilizes mechanical linkage assemblies secured to the individual finger digits by means of

flexible ring-like bands. Built-in hall effect potentiometers translate the various linkage motions into

electrical signals which can be correlated to the individual finger joint movements.

VPL Research of Redwood City, California markets the DataGlove [5-7], an ingenious glove-like

dexterous hand master that senses hand gesture position and orientation in real time. The device utilizes

fiber-optic cables sandwiched between a stretchable inner glove and a cloth outer glove. Each joint

353
motionto be detected requires a separate fiber-optic cable laid in a parallel path running across the

joint and looping back so that both free ends are anchored in an interface board mounted near the wrist.

At one end of the cable is a light emitting diode source and at the other a phototransistor. The segments

of the cable which rest over the joint are specially treated so that the light escapes when the joint is

flexed. The greater the degree of bending, the greater is the loss of transmitted light. This effect can be

detected by the phototransistor and calibrated to provide angular measurements with a resolution of

one degree. A data acquisition rate of 60 times per second is used.

A third method suggested for the master control mode is the use of a master glove imprinted with

a special color-coded optical pattern. In this approach, the respective control signals for positioning the

multiple finger joints would be extracted from the glove image. Potentially, the patterned glove could

be lighter, better fitting, less cumbersome, and less expensive than either the A. D. Little Sarcos

Dexterous Hand Master or VPL DataGlove. The authors are not aware of any commercially available

devices of this nature or any researchers who have applied this approach to date.

Acknowledgments

Funding is being provided by NASA Grant No. NAGW 1336, Jet Propulsion Laboratory Contract

No. 958292, and an Ohio Board of Regents Research Challenge grant. Mr. James Aliberti of Kennedy

Space Center and Dr. Edwin P. Kan of Jet Propulsion Laboratory are serving as technical monitors.

The NASA support was achieved through the efforts of Dr. Yvonne B. Freeman of NASA Headquarters.

References

1. McCormick, Malcolm, "A Primer On: Brushless DC Motors," MECHANICAL

ENGINEERING, New York, NY, Vol. 110, No. 2, February 1988, pp. 52-57.

2. TORQUE MOTOR ENGINEERING HANDBOOK, Clifton Precision, Litton

Systems, Inc., Clifton Heights, PA, 1986, Section 3.

3. HARMONIC DRIVE DESIGNER'S HANDBOOK, Harmonic Drive Division,

Emhart Machinery Group, Wakefield, MA, 1986.

4. "A. D. Little/Sarcos Dexterous Hand Master," product brochure, Arthur D. Little, Inc.,

Cambridge, MA, 1988

5. "VPL Research DataGlove Model 2 System," product brochure, VPL Research Inc.,

Redwood City, CA, 1987.

6. Foley, J. D., "Interfaces for Advanced Computing," SCIENTIFIC AMERICAN, New

York, NY, Vol. 257, No. 4, October 1987, pp. 127-135.

7. Fisher, S. S., "Telepresence Master Glove Controller for Dexterous Robotic

End-Effectors," INTELLIGENT ROBOTS AND COMPUTER VISION - FIFTH

354
.

.

10.

11.

12.

IN A SERIES, Proceedings of SPIE-The International Society for Optical Engineering,

Vol. 726, Cambridge, Massachusetts, 28-31 October 1986.

Abd-Allah, M. A., "Eigenimage Filtering of Medical Images Using Multispectral Image

Sequences," Ph.D. dissertation, University of Toledo, June 1986.

Windham, J. P., Abd-Allah, M. A., et al., "Eigenimage Filtering in MR Imaging,"

JOURNAL OF COMPUTER ASSISTED TOMOGRAPHY, Vol. 12, No. 1,

January/February, 1988, pp. 1-9.

Davis, V. L., "Computer Hardware and Software for Robotic Control: The Kennedy

Space Center (KSC) Robotics Applications Development Laboratory (RADL)," 1987

Goddard Conference on Space Applications of Artificial Intelligence (AI) and Robotics,

May 14, 1987.

Grissom, W. A.; Abd-Allah, M. A.; White, C. L., "Concept for a Large Master/SlaveControlled Robotic Hand," PROCEEDINGS OF THE SECOND ANNUAL WORKSHOP ON SPACE OPERATIONS AUTOMATION AND ROBOTICS (SOAR), July

1988, pp. 353-359.

Marcus, B. A.; Churchill, P. J., "Sensing Human Hand Motions for Controlling Dexterous

Robots," PROCEEDINGS OF THE SECOND ANNUAL WORKSHOP ON SPACE

OPERATIONS AUTOMATION AND ROBOTICS (SOAR), July 1988, pp. 481-485.

355
N91-28112

COMPUTER SIMULATION OF RADIATION DAMAGE

IN GALLIUM ARSENIDE

John J. Stith, James C. Davenport, and Randolph L. Copeland

Department of Physics

Virginia State University

Petersburg, Virginia

ABSTRACT

A version of the binary-collision s_mulation code MARLOWE has been used to study the spatial

characteristics of radiation damage in proton and electron irradiated gallium arsenide. Comparisons

made with experimental results have proved to be encouraging.

356
COMPUTER SIMULATION OF RADIATION DAMAGE

IN GALLIUM ARSENIDE

The main objective of this research is to study radiation damage and annealing in gallium arsenide

through the use of computer simulation.

Electronic devices manufactured from semiconductors are vital to the space program. These

devices must be capable of surviving and operating in an environment where various types of radiation

are present. In order to design the devices for maximum tolerance to the radiation encountered in the

space environment, the damaging effects of the radiation on the semiconductor must be studied.

Extensive laboratory testing and/or computer simulations of the effects of the specific radiation on the

semiconductor are required. The present study was done with computer simulation.

Gallium arsenide has received considerable attention over the past few years due to its potential

usefulness in high-power space-energy systems where high operating temperature is a limiting factor

for other semiconductors. However, space radiation may be a limiting factor unless sufficient shielding

is provided to keep damage levels within acceptable limits.

In order to determine design parameters for a specific space environment, a fundamental understanding of specific radiation interaction with the semiconductor is required.

On impinging upon the semiconductor, radiation produces a variety of defects. The defects which

are of the most interest to researchers include interstitials, vacancies, vacancy clusters, and improper

replacements for binary crystals such as gallium arsenide. There are at least three classes of electrically

active defects that are produced in gallium arsenide, and they are the following." (1) those that do not

anneal (including improper replacements, some distant interstitial-vacancy pairs, and some vacancy

clusters), (2) those that anneal at relative low temperatures, and (3) those that anneal at high

temperatures.

In space, simultaneous radiation exposure and annealing might result in very limited degradation

because the duration of radiation exposure is many mean-annealing-times. A terrestrial experiment to

verify this would be inconclusive since the usual duration of radiation exposure will be less than the

required annealing time. A laboratory experiment which properly simulates the effect of simultaneous

irradiation and annealing in space would be costly and difficult. Computer simulation provides a

convenient technique for studying atomic scattering in crystals. It is particularly useful at moderate

energies where crystal effects may be pronounced, but where clear distinction between random and

aligned processes is difficult.

A theoretical understanding of the effects of displacements in semiconductors caused by radiation

requires a detailed analysis of the dependence of the number of point defects and their spatial

distribution on the energy of the primary recoil atom.

The binary-collision simulation code MARLOWE has been modified to run on NASA LaRC

computer system and used to simulate radiation damage produced in a gallium arsenide crystal when it

is irradiated with electrons and protons. Primary recoil atoms possessing energies corresponding to the

average energy transfer between a 1-Mev electron and a gallium or arsenic atom, and primary recoil

atoms possessing energies corresponding to the average energy transfer between a 100-Kev proton and

357
a gallium or arsenic atom were used to start the displacement cascades in the crystal. The 1-Mev electron

is used in the equivalent fluence testing of devices and the 100-Key proton has been shown through

theory and experiment to be most effective in damaging the .5 and .8 micron junction gallium arsenide

solar cells. 2'3

The results from the computer simulations yielded information on the spatial distribution of the

defect pairs (close pairs, near pairs and distant pairs), as well as details on possible clusters of defects,

such as multiple vacancies.

Analysis of vacancy-interstitial pairs was made. The graphs in figures I and2 show the distribution

of the separations of the pairs for the 20 and 90 eV recoil energies, respectively. The distributions

include close, near, and distant pairs. When the distributions on the two graphs are compared, it is clear

that there is a greater number of interstitial-vacancy pairs for the higher-energy cascades than for the

lower-energy cascades. Figures 3 and 4 are included to show the relative positions of the interstitials

and the vacancies produced in the crystal. Close, near and distant pairs are displayed. In figures 5 and

6 the close pairs are not included since it is a good possibility that the vacancies and interstitials that

form the close pairs will combine (self-anneal). Figures 7 and 8 only display the distant pairs which may

still exist after annealing of the crystal which stimulates the near pairs to combine. When a proper pair

combines, two defects are eliminated, but when an improper pair combines, two defects are reduced to

one defect which is different from either of the two original defects. The distant pairs will most likely

remain as stable defects within the crystal even through the annealing process. There is a sizeable

difference between the number of distant pairs for the high-energy primary recoil atoms. This is in good

agreement with the experimental results that demonstrated a high degree of difficulty in annealing

proton radiation damage as compared with annealing electron radiation damage in gallium arsenide.

References

1. Robinson, M.T. and Torrens, I.M.; Phy. Rev. B, 1974, 9(12), 5008.

2. Stith, J.J. and Wilson, J.W.; Proc. of the Eighteenth IEEE Photovoltaic Specialists Conf.,

1985, 1716.

3. Wilson, J.W., Walker, G.H., and Outlaw, R.A.; IEEE Electron Devices, 1984, Vol. 31,421.

4. Benedek, R.; J. Appl. Phys., 1981, 52(9), 5557.

358
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ORIGINAL PAGE IS

OF POOR QUALITY
N91:-28 113

FORCED CONVECTION AND FLOW BOILING WITH AND WITHOUT

ENHANCEMENT DEVICES FOR TOP-SIDE-HEATED

HORIZONTAL CHANNELS

Ronald D. Boyd, Sr., and Jerry C. Turknett

Department of Mechanical Engineering

Prairie View A&M University

P.O. Box 397

Prairie View, TX

/

ABSTRACT

A three-year research program has been launched to study the effect of enhancement devices on

flow boiling heat transfer in coolant channels, which are heated either from the top side or uniformly.

Although the study will include other orientations and working fluids in subsequent years, the first years

will involve studies of the variations in the local (axial and circumferential) and mean heat transfer

coefficients in horizontal, top-heated coolant channels with smooth walls and internal heat transfer

enhancement devices. Initially, the working fluid will be freon-11. The objectives of the fiscal year's

work are to: (1) examine the variations in both the mean and local (axial and circumferential) heat

transfer coefficients for a circular coolant channel with either smooth walls or with both a twisted tape

and spiral finned walls, (2) examine the effect of channel diameter (and the length-to-diameter aspect

ratio) variations for the smooth wall channel, and (3) develop an improved data reduction analysis.

The case of the top-heated, horizontal flow channel with smooth wall (1.37 cm inside diameter,

and 122 cm heated length) has been completed. The data have been reduced using a preliminary analysis

based on the heated hydraulic diameter. Preliminary examination of the local heat transfer coefficient

variations indicates that there are significant axial and circumferential variations. However, it appears

that the circumferential variation is more significant than the axial ones. In some cases, the circumferential variations were as much as a factor of ten. The axial variations rarely exceeded a factor of three.

Integrated averaged heat transfer coefficients will be obtained after the improved data reduction model

has been implemented.

363
h

h**

qc

qR

r

Tf

Tm

Tsat

T**

Z, Zi

7,

Nomenclature

Local heat transfer coefficient, W / m2 °C

Mean heat transfer coefficient due to natural convection between the test section

and the ambient, W / m 2 °C

Heat loss from the test section due to convection, W

Heat loss from the test section due to radiation, W

Radial coordinate for the data reduction model, m

Bulk temperature of the flowing fluid, °C

Local measured outside wall temperature of the test section, °C

Saturation temperature (316 K at 0.19 MPa for freon-11), °C

Ambient temperature, °C

Axial coordinate for heated portion of the test section; in Figures 3a through 3d,

Zi represents Zi, where Z_ = 20.32 (i-1), cm

Greek Letters

Circumferential coordinate; see Figure la for the datum.

In figures 3a through 3d, _pis also referred to as "Phi."

Half of a full rotation of 180°; in Figures 3a through 3d, ar is also referred to as "Pi."

364
FORCED CONVECTION AND FLOW BOILING WITH AND WITHOUT

ENHANCEMENT DEVICES FOR TOP-SIDE-HEATED

HORIZONTAL CHANNELS

Introduction

Space commercialization will require efficient heat transfer systems. The future success of many

efforts will be based on our understanding of the behavior of two-phase flow boiling in both the space

(zero-g or reduced-g) and earth environments. This three-year program is intended to focus on the

following fundamental characteristics (e.g., nonuniform heat flux distribution, Marangoni effects, and

single and double enhancement devices) of experimental flow boiling heat transfer and pressure drop

in the earth environment [1].

The objectives of the first year's efforts are to: (1) examine the variations in both the mean and

local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either

smooth walls or with both a twisted tape and spiral finned walls, (2) examine the effect of channel

diameter (length-to-diameter ratio) variations for the smooth wall channel, and (3) develop an improved

data reduction analysis.

In this paper, we report on forced convection and flow boiling of freon-11 in a smooth-wall

horizontal coolant channel (1.37 cm inside diameter and 122.0 cm heated length) heated from the top

side. The inlet freon temperature was 24°C, the exit pressure was 0.19 MPa absolute, and the mass

velocity was 0.28 Mg / m2s.

Experimental Investigation

The reader is referred to references 1 and 2 for detailed descriptions of the experimental flow

loop, procedures, and data acquisition. Figure I a is a schematic of the cross section of the heated portion

of the test section [which is preceded by an upstream unheated portion for flow development]. The

measured wall temperatures are used along with the data reduction analysis to determine the unknown

heat transfer coefficient, h. Recently, a data reduction technique based on the heated hydraulic

diameter [2] (see Figure lb) was used to reduce the experimental data. This approach will result in, at

most, a qualitative indication of the local distribution of h. Work is proceeding on more viable data

reduction approaches; e.g., finite difference for local h and analytical for mean h.

In applying either model, knowledge of the fluid's bulk temperature must be used. An iteration

scheme is used to compute the inside wall temperature, Tw, of the flow channel. The fluid's temperature

is chosen based on the magnitude of the inside wall temperature relative to the wall temperature

required to cause the onset to nucleate boiling Tot, re. If Tw is greater than Tor,rB, the fluid temperature

is set equal to the saturation temperature. However, if the above condition is not satisfied, the fluid

temperature is computed from the energy equation, using the measured inlet fluid temperature and the

measured net thermal energy transfer to the fluid.

365
h_

Domain "C"

Domain "B" _ I

Epoxy

Domain "A"_ i

Rock Woo! Insulation

Uniform Heat

Flux

=

Thermocouples

(4 locations)

(on epoxy pads)

Rock Woo!

Insulation

I

Freon-11

Copper

Figure 1:

(a)

Plnne of Symmetry

(a) Cross section of the heated

portion of the test section.

(b) Control volume of heated

hydraulic diameter model.

366
Results

The results are presented for the case of forced convection and flow boiling with freon-11 flowing

in a horizontal channel with smooth walls.

The variation in the heat transfer coefficient is more pronounced in the circumferential direction

than the axial direction. The heat transfer coefficients for the single-phase and hypocritical regions are

shown in Figure 2. The fully developed nucleated boiling region does not appear in the figure but occurs

somewhere in a narrow range between ,p = 7_/4 and _r/4 (see Figure la for the datum for _p). The

heat transfer coefficient in this narrow region is expected to be greater than any of those shown.

The last two highest points on each of the curves show an increase in the heat transfer coefficient.

For 7, =3:t/2 and 7_r/4, the increase is due to the onset of nucleate boiling which we see results in

more than a fifty percent increase in h. For these two locations we see that there is only a secondary

variation in h with _p.

Both axial and circumferential variations in h are found to be significant. Comparisons of Figures

3a (_p = _r/2), 3b (¢, = _/4), 3c (,p = 7_/4) and 3d (,p = 3at/2) reveal the complex nature of the

variations. The variation in the local heat transfer coefficient increases from the bottom (_ = 3:t/2)

to the top (,p = _r/2) of the test section at all axial locations. As noted earlier, the variation between

7_/4 and 3._/2 is small even at the locations where incipient nucleate boiling occurs

(h = 1400 W/m2K). It is interesting to compare the magnitude of h !_r the three regimes: (1)

single-phase (800 W/m2K), (2) incipient nucleate boiling (1400 W/m K) and (3) film boiling

(10 to 100 W/m2K).

11 /f

I V _> ./2

3 I * ./4

0

0 200 400 _ BOO

Power(W)

Figure 2: Heat transfer coefficient versus power generation and

circumferential location at Z = Z4 = 61.96 cm (center

of the test section) for top-side-heated smooth tubes

for: 0.19 Mpa exit pressure, 0.281 Mg/m2s mass velocity,

1.22 m heated length.

367
• _ 4> Zl= O.00m

: / * Z2_ 20.:12¢m

' _ _ Z:Im 40.Mc_n

Amel_ aee- _ Q Z4= 44.Nr.m

:1 / I I \ '¢' Zl. O.oom : _ _ _ zs. et.ncm

-- _ | l ll.__k \ • ZA= eO,Nm

-t/r I//_\\ \ ,_ a. 01_..

1/ m N,_,\ \ • Zlal_l.dlOm 101"

0 I ......... I ......... i ......... t ......... I .........

0 *No _ _ m m Q NO _ _ NO

poww(w) Power(w)

0 "

n

4

n 4

2

7nl4 3nl2

! -

-I I * Z_ 44JI4om I I .e Z3,, _l.e4em

-I I o z4. m.N_,, _I ! 0 Z4. ,e.N_,

"t I _' zs. o1.,.,,a,, •4 I _' Z_Iu 11.3e elm

I I • ZIImlOl.eOem "11 • YemlOl"eO em

1' " °'"" 1' " z,.,.,,..

O--_rT1 r [ r _ I r_r_rTTT T T _ ' ' ' '" I ' ' ' ' ' .... I ...... '''I O/ ......... I ...... '''I ......... ! ......... ! ......... I

0 NO 410 10e NO NmO O _ 4410 em io0

PoNt (w) Power(w)

Figure 3: Heat transfer coefficient versus power and axial location at Phi = Pi/2

(top), Pi/4, 7Pi/4, and 3Pi/2 (bottom) for top-side heated smooth tubes at

2

0.19 MPa and 0.281 Mg/m s. Channel diameter = 1.27cm, heated length =

1.22m.

368 ORIGINAL

OF POOR

PAGE IS

QUALrW
If one takes time to study the relative positions of the curves and use the reduced wall temperature,

some of the character of the flow is revealed (e.g., see Figure 3a). In particular, notice from Figure 3a

that: (1) h at Zs and Za are almost identical at between 380 and 640 W, (2) h at Z6 is much higher

than all values of h at other locations, and (3) in some cases curves are crossing one another. These

observations may imply a slug type of flow. For example, at Z6 the unusually large value of the heat

transfer coefficient could be due to local cooling (slug flow). Contrasting the above description, Figure

3b (_0 = _r/4) shows that between Z2 and Zs the heat transfer coefficient decreases in the downstream

direction. This is consistent with the previous observations made. That is, at _p = _r/4 the film boiling

regime predominates.

Conclusions

Local (axial and circumferential) measurements of the outside wall temperature have been made

for horizontal freon-11 flow (0.19 MPa exit pressure and 24°C inlet temperature) through a 1.37 cm

inside diameter coolant channel with smooth walls and heated from the top side. A preliminary data

reduction model was used to relate the measured wall temperatures to the local heat transfer coefficient.

Although the local temperature measurements are quantitative, the preliminary data reduction model

results in what may be only qualitative local heat transfer measurements. Work is proceeding to evaluate

and improve, if necessary, the existing data reduction model.

The preliminary heat transfer data indicate that there are significant axial and circumferential

variations in the local heat transfer coefficient. However, it appears that the circumferential variation

is more significant than the axial ones. The single phase heat transfer coefficient (near 900 W/m2K) is

increased by more than 50% at the onset of nucleate boiling. For the test performed, the circumferential

heat transfer coefficient varied from the hypocritical to the single phase heat transfer regimes. This

resulted in some cases in a factor of ten increase in the local heat transfer coefficient. The axial variations

rarely exceeded a factor of three.

369
Acknowledgments

The authors would like to acknowledge Richard Parish, Dr. Joseph Atkinson, Dr. Y. Freeman,

and Richard Kennedy for their support and assistance. The authors would also like to thank other NASA

personnel, both at headquarters and JSC, for their support.

References

. Boyd, R.D, "Flow Boiling with and without Enhancement Devices for Horizontal,

Top-Heated, Coolant Channels for Cold Plate Coolant Channel Design Applications,

Preliminary Report," Department of Mechanical Engineering, Prairie View A&M

University, Prairie View, TX, Submitted to NASA (JSC), Contract no. 9-16899

(Task-5), December, 1986.

. Turknett, J.C, "Forced Convection Flow Boiling with and _th0ut Enhancement Devices

for Top-Side-Heated Horizontal Channels," MS Thesis, Department of Mechanical

Engineering, Prairie View A&M University, Prairie View, TX (to be published).

_i

370
N91-28114

PROGRESS IN PROTON TRANSPORT CODE DEVELOPMENT:

MICROELECTRONIC APPLICATION

Duc M. Ngo, W.W. Buck, and T.N. Fogarty

Physics Department

Hampton University

Hampton, VA

72---

,_)c,, d 32---

and

J.W. Wilson

NASA, Langley Research Center

Hampton, VA

ABSTRACT

The process of target nucleus fragmentation by energetic protons is examined and their effects on

microelectronic devices considered. A formalism for target fragment transport is presented with future

applications to microelectronic effects discussed.

371
PROGRESS IN PROTON TRANSPORT CODE DEVELOPMENT:

MICROELECTRONIC APPLICATION

Introduction

Since the early suggestion that some spacecraft anomalies may result from the passage of the

galactic ions through microelectric circuits (ref. 1), it has now been well established as a fact. Although

the direct ionization of protons appear as unlikely candidates, their nuclear reaction products are

suspected as a source of Single Event Upset (SEU) phenomena (ref. 2-4). As a result a number of

fundamental experimental and theoretical studies were undertaken to better understand the phenomena. McNulty and coworkers examined the energy deposition of proton reaction products in Si using

surface barrier detectors of various thickness from 2.5 to 200/zm (ref. 5). They also developed a Monte

Carlo code for theoretical evaluation of energy deposition from such products (ref. 5,6). Comparisons

of McNulty's work with the well established MECC7 developed by Bertini and coworkers at Oak Ridge

National Laboratory showed some differences in predicted reaction products and even greater differences in energy spectral contributions (ref. 7). An evaluation of Si reaction products was likewise made

by Petersen (ref. 4), and although no direct comparison was made to McNulty's experiments, an estimate

of SEU rates in the trapped proton environment was made.

Following these fundamental studies came more detailed application to devise specific questions.

Bradford evolved an energy deposition formalism (ref. 8) using the cross sections of Hamm et. al. (ref.

7). The McNulty Group applied the Monte Carlo model to DRAM devices with reasonable success and

discussed the implications of heavy ion SEU phenomena on proton induced SEU events through

secondary reaction processes (ref. 9). The fundamental consideration is the evaluation of the energy

deposited within the sensitive volume (depletion region) of the device in question due to a passing

proton. The ionization of the proton itself makes only a small contribution to the critical charge. Nuclear

reaction events usually produce several reaction products (usually a heavy fragment and several lighter

particles although a few heavy fragments may be produced simultaneously on some occasions) and all

of the resultant products can make important contributions to the energy deposited. Such nuclear event

products are of course correlated in both time and space.

There are three distinct approaches to a fundamental description of the energy deposition events.

McNulty and coworkers have developed a Monte Carlo code in which multiparticle events are

calculated explicitly including spatial and specific event (temporal) correlation effects. Although this is

the most straightforward way of treating the full detail, it is a complex computational task. A second

class of methods begins with the volumetric source of collision events and calculates the SEU probability

using the cord length distribution (ref. 8,10). Although in principle the correlation effects could be so

incorporated, they appear to be ignored in both of the cited references. A third approach, in which LET

distributions and cord length distributions are used, seems most appropriate for external sources (ref.

11,12). It would seem that this last approach applies if the LET distribution from external sources is

constant over the sensitive volume but its applicability to volumetric sources is questionable. At the

very least this approach ignores correlation effects.

In an earlier work we examined nuclear data bases for biological systems (ref. 13). In that work

we found that the MECC7 results underestimated by nearly a factor of two the cross section for multiple

charged ion products. In a more detail analysis, we found the Silberberg-Tsao fragmentation parameters

to be superior to the MECC7 results (ref. 14). The primary differences appear for the lighter of the

372
multiplechargedfragments.Furthercomparisonwithexperimentsof AI targets show all three Monte

Carlo nuclear models (OMNI, VEGAS as well as MECC7) to underestimate production cross sections

for products lighter than fluorine in proton induced reaction. Although these intranuclear cascade

models are capable of representing multiparticle correlation, the inherent inaccuracies in predicting

cross sections is a serious limitation. In the present paper we examine the implication of the nuclear

recoil effects on electronic devices and begin the development of a formalism for application to specific

device parameters.

Microelectronie Upsets

An electronic device is sensitive to the sudden introduction of charge into active elements of its

circuits. The amount of such charge which is sufficient to change state in a logic circuit is called the

critical charge. There is a rough relationship between the critical charge Qc and the device feature size

L (ref. 11) as shown in Fig. 1. This relationship is approximately

Qc = 0.0156L 2 (1)

where Qc has units pC and L has units/t m. Upsets in a device are then dependent on the charge produced

compared to the critical charge.

The charge released AQ in a material due to the passage of an energetic ion is related to the kinetic

energy lost AE during the passage given by

AE

AQ = _ (2)

where AQ has units pC and AE has units MeV.

dEThe energy lost by an ion in passing through a region is related to its stopping power

(---_- = Sz(E,)) in the medium. The distance traveled before coming to rest is

t_E dE,

Rz(E) = ,J0 _zz(E,)" (3)

If an ion is known to come to rest in distance x then its energy is found through the inverse of the

relation (3) as

E = Rz I (x) (4)

and we note that equation (4) is used to calculate energy loss. The energy loss by an ion of charge Z

and energy E in passing through a device with collection length L will have its energy reduced by

AE = E - Rz 1 [Rz(E) -Lc] (5)

and

373
Lc = Wepi + Wn (6)

where Wepi is the epi thickness and Wn is the depletion width.

We note in passing that AE does not depend on the particle isotope (i.e., ion mass). The range

energy relations described elsewhere (ref. 14) are utilized. As a practical matter to reduce numerical

error inherent to numerical interpolation, we use

AE = Rz I [Rz(E)] - Rz I [Rz(E) -Lc] (7)

in place of equation (5). Note the result of equation (5) depends on the global error (fixed at 1 percent)

of the code while equation (7) depends only on the local relative error (quite small). The charge

introduced is given by equation (2) and (7). An example of a particular collection length of 2pm is shown

in Fig. 2 for each ion type. We assume a simplified geometry in which the channel length and width and

the collection length are take as equal to the feature size. We take the critical energy as the upper and

lower limit of the range of energy for which

AQ(E)->Qc (8)

which depends on the feature size L. The ion mass for each A is taken as the natural mass. The critical

energies are shown in Fig. 3. Also shown in Fig. 3 are the average recoil energy from the fragmentation

16 28 of O and Si produced by collision with a high energy proton (ref. 14).

It is doubtful that any of the fragments are produced in the 4_um and larger devices (note that we

have used simplified geometries). Also, the lighter fragments of Li, He, and H are not suspected for

SEU events, at least in this simple geometry. Also note that Fig. 3 is applicable to cosmic ray ions.

Nuclear Fragmentation Cross Section

Although nuclear fragmentation has been under study for nearly 50 years, the absolute cross

sections still stir some controversy. The experimental problem is that the reaction products could be

directly observed only in recent years and even now only in rather sophisticated experiments. Rudstam

studied the systematics of nuclear fragmentation and supposed the fragment isotopes to be distributed

in a bell-shaped distribution about the nuclear stability line (ref. 15). Silberberg et al. continued the

Rudstam parametric approach and added many correction factors as new experimental evidence

became available (ref. 12).

Concurrently, Monte Carlo simulation of the Serber model (reL 16) coupled with final decay

through compound nuclear models showed some success (ref. 7, 17). Even so, Monte Carlo simulations

show little success in predicting fragments whose mass is small compared to the original target nuclear

mass (ref. 13,18). Of the various models for nucleon induced fragmentation in 28Si, probably that of

Silberberg et al. (ref. 12) is currently most reliable. The main limitation of their model is that only

inclusive cross sections are predicted and particle correlations will undoubtedly prove important in

predicting SEU.

27

Measurements of Al fragmentation in proton beams have been made by Kwaitkowski (ref. 18).

These experiments are compared in Fig. 4 to the Monte Carlo results of OMNI, VEGAS, and MECCT.

374
Also shown are the results of Silberberg et al. Generally the Silberberg et al. results appear to be within

a factor of 2 of the experiments and this is the only model which predicts significant contributions in

the important range below 74 = 6.

The spectrum of average recoil energy is calculated using the Silberberg - Tsao cross sections and

compared with the spectrum according to Bertini cross sections in Fig. 5. The Bertini cross section is a

serious underestimate above 8 MeV and greatly overestimates below 3 MeV. Experimental evidence

indicates that even the Silberberg-Tsao values are too small above 6 MeV (ref. 18).

Nuclear Recoil Transport

The transport of the recoil fragments is described by the following

[Q. V -_E Sz (E)]_z (x,Q,E) = _z (Q,E) (9)

where _z (x,Q,E) is the ion flux and Cz(Q,E) is the ion source density assumed to be uniformly distributed

through the media. The solution to equation (9) is to be found in the closed region bounded by the

surface F subject to the boundary condition

4z(r,Q,E) = Fz(Q,E) for n. Q <1 (10)

where n is the outward directed normal. The solution as found using the method of characteristic (ref.

19) is:

_z (x,Q,E) = _SzfEb) _z (F, t2,Et,) + Sz(E) 1 _E _z (Q,E,)dE, (11)

where F is taken as the point on the boundary by projecting x along -Q and

Et, =Rz 1 [Rz(E) + b] (12)

where

b = n. (x - r). (13)

Using equation (11), we may evaluate the spectrum of particles leaving the region which can be related

to the spectrum of energy deposited in the media. Such a task will be completed in the near future.

375
References

1. D. Binder, et al., IEEE Nucl. Sci. Trans., 1975, NS-25, 2675-2680.

2. R.C. Wyatt, P.J. McNulty, P. Toumbas, P.L. Rothwell, and R.C. Filz, IEEE Nucl. Sci.

Tram., 1979. NS-26, 4905 - 4910.

3. C.S. Guenzer, R.G. Allen, et al., IEEE Nucl. Trans., 1980 NS-27, 1485-1489.

4. E.L Petersen, IEEE Nucl. Sci. Trans., 1980, NS-27, 1485-1489.

5. P.J. McNulty, G.E. Farrell, R.C. Wyatt, P.L. Rothwell, R.C. Filz, and J.N. Blanford, IEEE

Nucl. Sci. Trans., 1980, NS-27, 1516-1520.

6. P.J. McNulty, G.E. Farrell, and W.P. Tucker, IEEE Nucl. Sci. Trans., 1981, NS-28,

4007-4012.

7. R.N. Hamm, M.L. Rustgi, H.A. Wright, and J.E. Turner, IEEE Nucl. Sci. Trans., 1981,

NS-28, 4004-4006.

8. J.N. Bradford, IEEE Nucl. Sci. Trans., 1982, Ns-29, 2085-2089.

9. J.M. Bisgrave, J.E. Lynch, P.J. McNulty, W.G. Abdel-Kader, V. Kletnicks, W.A.

Kolasinski, IEEE Nuci. Sci. Trans., 1986, NS-33, 1571-1576.

10. K.W. Fernald and S.E. Kerns, IEEE Nucl. Sci. Trans., 1988, Ns-35, 981-986.

11. E.L. Petersen, P. Shapiro, J.H. Adams, and E.A. Burke, IEEE Nucl. Sci. Trans., 1982,

2055-2063.

12. R. Silberberg, C.H. Tsao, and J. Letaw, D. Reidel Publ. Co., 1976, 49-81.

13. J.W. Wilson, S. Y. Chun, W.W. Buck, and L.W. Townsend, Health Physics, 1988, 55,

817-819.

14. J.W. Wilson, L.W. Townsend, S.Y. Chun, S.L. Lamkin, et al., 1988, NASA TP 2887.

15. C. Rudstam, Zeitschrift fur Naturforschung, 1966, 21a, 1027-1041.

16. R. Serber, Phys. Rev., 1947, 72, 1114-1115.

17. H.W. Bertini, Phys. Rev. 1969, 188, 1711-1730.

18. K. Kwaitkowski, et al., Phys. Rev. Lett., 1983, 21, 1648-1651.

19. J.W. Wilson and S.L. Lamlin, Nucl. Sci. Eng., 1975, 57, 292 - 299.

376
CRITICAL CHARGE FOR SINGLE EVENT UPSETS

loo

,o!

- I

Q. r"

- I

a0.31 !'

I00

• NMI3S

• • CI, IO S-3UL.'<

'_ x C},IQ S-S<35

x • I=L

' \x

%

• \

dh

10 1

FEATURE SIZE Z (]jm)

0.1

Figure 1

Critical charge Qc as a function of feature size.

377
8

O.

C3

laJ

I,,.-..

l..J

LLI

..l

d

0

l.J

LLI

(.3

r,-

7"

(..J

_ARO_ COLLEC_D WZTH L_=2_ON

I@-3

,,,,,I ..... ,,l! , .,;..!,;! I I I I III!

ION ENERGY CMEV3

Figure 2

Charge collected as a function of ion energy.

378
Critlcal Energy, MeV amu -I

o

=3

0

=3-

11)

o

,°

o

0

O

o

!

I i I w I

9,0 o

| ........

II •

O QO

__,,

, _..

0

3

N"

3

Figure 3

Critical energy as a function of ion charge for several

feature sizes.

379
+C]

I1tI

I()O ,-rr l_r tV-l-V-l-v-I-v'rv'l-t-rrlrv'1-1-' _-Vl i.

60

t,O

........ MECC1

VEGAS

.... OMNI

• Sllberberg-Tsao

• Kwailkowskl el al.

°

,v;,i

_,_.,.u_,..t_,..t _'"J,.t.'l_,_, .L.L.,_

4 [I 12 16

A

2(]

_l_k LL.I.,_o_t_l

2O 2./, 20

Figure 4

Fragmentation of 27A1according to four models and the

experiments of Kwaitkowski et al.

380
o

ILl

v

010 -

O0[l

0(14

000 i ! T

0 _ 4 It # 10

_L _. Berlinl

---- Silherberg-Tsao

Eo(MeV)

Figure 5

Spectrum of average recoil energy for the Bertini and

the Silberberg-Tsao models.

381
¢'N. "¢"" N91-28115 '

A STUDY OF MICROSTRUCTURAL CHARACTERISTICS AND

DIFFERENTIAL THERMAL ANALYSIS OF Ni-BASED SUPERALLOYS*

M.D. Aggarwal, R.B. Lal and S.A. Oyekenu

Department of Physics

Alabama A&M University

Normal, AL

and

Richard Parr and Stephen Gentz

Materials Laboratory, NASA/MSFC

Marshall Space Flight Center, AL

ABSTRACT

The objective of this work is to correlate the mechanical properties of the Ni-based superalloy

MAR-M246(Hf) used in the space shuttle main engine, with its structural characteristics by systematic

study of optical photomicrographs and differential thermal analysis. In this paper, we have developed

a method of predicting the liquidus and solidus temperature of various nickel based superalloys viz.,

MAR-M247, Waspaioy, Udimet-41, polycrystalline and single crystals of CMSX-2 and CMSX-3 and

compared with the experimental DTA curves using Perkin-Elmer DTA 1700. The method of predicting

these temperatures is based on the additive effect of the components dissolved in nickel. The results

have been compared with the experimental values.

* Work supported under NASA Grant NAG8-076

382
A STUDY OF MICROSTRUCTURAL CHARACTERISTICS AND

DIFFERENTIAL THERMAL ANALYSIS OF Ni-BASED SUPERALLOYS

Introduction

The purpose of this investigation is to study the microstructural characteristics of Ni-based

superalloy MAR-M246(Hf) which is used in manufacturing the components of the space shuttle main

engine. These superalloys are heat treated prior to their use. The heat treatment should be optimum

to get the best performance. To find out the optimum heat treatment, the techniques of differential

thermal analysis and optical photomicrographs are being utilized. Ni-based superalloys can be considered as "chemical stew" containing as many as 14 different elements) Nickel serves as an ideal base for

such alloys because of its high melting point, 1453°C, adequate corrosion resistance and ability to

dissolve a number of other metallic elements which serve to strengthen it. The various elements go into

the solid solution to provide different effects: Molybdenum, tantalum, and Tungsten go in to the alloy

for strength; chromium, aluminum and tungsten add to oxidation resistance and y' phase.

Differential thermal analysis (DTA) is a technique which continues to aid in defining the phase

changes that occur in superalloys and is undoubtedly of considerable value to the metallurgist studying

these complex systems. The effect of changes in major elements are easily determined. The DTA

technique has proved to be a valuable technique for the superalloy metallurgist to study liquidus-solidus

data, carbide precipitation reactions, y' solvus temperatures and incipient melting temperatures. 2

The width of the solidification range is an important casting parameter and has the controlling

effect in the process of directional solidification. In a simple system, the equilibrium value of this quantity

can be determined from the equilibrium diagram, but in more complicated systems like these, superalloys containing 12 to 14 elements, only approximate estimates can be obtained. In the present paper,

we discuss a method of predicting the solidus and liquidus temperatures based on the additive effects

of the components dissolved in nickel and the results are compared with the experimental results

obtained from the DTA curves for various Ni-based superalloys such as MAR-M246(Hf), MAR-M247,

Waspaloy, Udimet-41, polycrystalline and single crystals of CMSX-2 and CMSX-3.

Prediction of Solidification Range

For highly diluted systems as in Ni-based superalloys, Hayes and Chipman 3 gave a relation for the

change of the melting point AT of the parent metal M after adding a small amount of component B:

AT=(1 -ko,e ) NL,B (TM ) 2/AHM (I)

where k0,n is the equilibrium distribution coefficient of component B in the parent metal M, AHM is the

heat of melting, TM is the melting point of metal M (K), Nt._ is the molar fraction of component B

dissolved in the liquid phase of metal M, and R is the constant (8.314 JK -1 tool -1 ).

The equilibrium distribution coefficient k0_ is defined as T = constant by the relationship

383
ko_ = Ns_ /NL_ (2)

where Ns,a is the molar fraction of component B in the solid solution based on metal M.

For highly diluted solutions, the liquidus and solidus curves can be replaced by straight lines (Fig. 1)

and the solidification range of the solution M-B, denoted by IB = TL_ --Ts,B, can be expressed by the

relationship

In = (1 -ko,B ) AT/ko;_ = (1 -k0,a )2 TM 2 R Nt._ /ko_ AHM. (3)

_7

\

kO.B =

NL.B

\

Ns.B Nt.e -- N 8

Fig. 1 Equilibrium diagram

If the metal is represented by nickel, Eq. (3) can be written in the form

IB = 832.3 (1 -ko,e )2 cB /ko_ M8 (4)

where cB is the concentration of component B in weight percent, MB is the molecular mass of component

B, and/8 is in degree Celsius. If we assume the mutual independence of the effect of the components

on the change of the melting point of parent metal M, the equilibrium solidification range I can be

written as

Differential Thermal Analysis

In the differential thermal analysis (DTA) method, a reference sample and the sample under test

are heated at a certain rate in a specific temperature range. The reference should exhibit no transformations within the temperature range of interest. The temperature of the sample and reference are

monitored separately and the thermocouples measuring the temperature are connected in opposite

polarity to measure the temperature differential (AT = Tsample - Tref_r,',,ce). AT is amplified and then

fed to Thermal Analysis Data Station (Perkin Elmer DTA 1700) which displays a plot of ATversus T

for any sample. A schematic diagram of the DTA apparatus is shown in Fig. 2. Silver (melting point :

384
961C) andnickel(meltingpoint : 1455C) areusedto calibrate the instrument reasonably near our

temperatures of interest. Sample holders/crucibles are 6 mm 3 cups made up of high density high purity

alumina. Thermograms are stored in the computer's memory as well as displayed on the monitor which

can be stored on floppy disks for later analysis. DTA curves of the various nickel based superalloys viz.,

MAR-M246(Hf), MAR-M247, Waspaloy, Udimet-41, polycrystalline and single crystals of CMSX-2

and CMSX-3 are compared with the calculated values using Eq. (5) neglecting the mutual interaction

of the components.

Results and Discussion

Fig. 3 shows a typical DTA curve from which the values of solidus and liquidus can be determined.

The onset for Ni-based superalloy UD-41 is 1293.8 C which represents the solidus and the minimum

which represents the liquidus is at 1345.3 C. The solidification range is thus determined to be 52.5 C.

Table 1 lists the values ofcB, k0_ and the solidification range of this alloy using Eq. (4). Table 2 lists the

solidification range as obtained from DTA measurements and calculated using Eq. (5) for the other

superalloys. The values for UD-41 are in better agreement than for the other superalloys. Further

analysis of the data is in progress and will be reported elsewhere.

Acknowledgments

The authors wish to thank Mr. Richard J. Quigg, Vice-President of Cannon-Muskegon Corporation for providing us polycrystalline samples of CMSX-2 and CMSX-3. Thanks are due to Mr. Gregory

Bell of Howmet Corporation for providing single crystal samples of CMSX-2 and CMSX-3. We also

thank Mr. Sam O. Mancuso of Special Metals Corporation for providing us with samples of MAR-M247,

UD-41 and Waspaloy. Thanks are also due to Dr. Bill Bhat, NASA/MSFC for useful discussion during

the progress of this work.

References

1. Sims, C.T.; Stoloff, N.S. and Hagel, W.C., Eds. Superalloys (John Wiley, New York, 1987).

2. Wendlandt, W.W., Thermal Analysis (John Wiley, New York, 1986).

3. Hayes, A. and Chipman, J., Trans. AIME, 1939, 135, 85.

385
o<_

Ld

N LLI

v

z c_

-J 0

T

rr"

i,i

8-_

0 o _E

n-" Z

c) 0

®

I

1

t_

7

t-- ]

i f

l 0._,

I !

I_. J

n,"

u.J

H" u_

<1 -5

rl

"5:

UJ

._1

W

I-- t.W _

o:: "_ _

00 Z o

._j o

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o") w

or) j

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0

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oo

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387
TABLE 1

Ni-based Superalloy UD-41

Element Ca k0,b Mb Solidification

range

C 0.08 0.22 12.01 15.33

Mn 0.10 0.72 54.94 0.16

Si 0.10 0.36 28.08 3.37

Cr 18.70 0.82 51.99 11.83

Ni Bal 1.00 58.70

Co 10.80 1.03 58.93 0.14

Mo 9.80 0.89 95.94 1.16

Ti 3.21 0.73 47.90 5.57

Al 1.59 0.87 26.98 0.95

Zr 0.07 0.09 91.22 6.20

P 0 0.01 30.97 8.85

Cu 0.01 0.82 63.55 0.01

Ta 0.01 0.74 180.95 0.00

Total I 53.58

From DTA Curve

TS = 1293.8 C

TL = 1345.3 C

Diff. = 52.5 C

388
TABLE 2

Comparison of Experimental and Calculated Values of the Solidification Range.

Ni-based Superalloys Solidification Range

Experimental

(DTA)

Calculated

(Eq.5)

UD-41

Waspaloy

CMSX-2

(Polycrystal.)

CMSX-3

(Polycrystal.)

CMSX-2

(single crystal)

CMSX-3

(single crystal)

MAR-M246(Hf)

52.5 C

40.3 C

33.4 C

39.8 C

32.9 C

36.2 C

44.4 C

53.58 C

52.49 C

26.07 C

26.315 C

25.97 C

25.95 C

56.31 C

389
N91-28116

SUBCOOLED FREON-11 FLOW BOILING IN TOP-HEArD FINNED

COOLANT CHANNELS WITH AND WITHOUT A TWISTED TAPE

\

Alvin Smith and Ronald D. Boyd, Sr.

Department Of Mechanical Engineering

P.O. Box 397

Prairie View A&M University

Prairie View, Texas

ABSTRACT

An experimental study has been conducted in top-heated finned horizontal tubes to study the

effect of enhancement devices on flow boiling heat transfer in coolant channels.The objectives of the

present work are to: (1) examine the variations in both the mean and local (axia|and circumferential)

heat transfer coefficients for circular coolant channels with spiral finned walls and/or spiral fins with a

twisted tape, and (2) improve the data reduction technique of a previous investigator. The working fluid

is freon- 11 with an inlet temperature of 22.2°C (approximately 21oC subcooling). The coolant channel's

exit pressure and mass velocity are 0.19 M Pa (absolute) and 0.21 Mg/m2s, respectively. Two tube

configurations were examined; i.e., tubes had either 6.52 (small pitch) or 4.0 (large pitch) fins/cm of the

circumferential length (26 and 16 fins, respectively). The large pitch fins were also examined with a

twisted tape insert. The inside nominal diameter of the copper channels at the root of the fins was 1.0

cm.

The results show that by adding enhancement devices, boiling occurs almost simultaneously at all

axial locations. The case of spiral fins with large pitch resulted in larger mean (circumferentially

averaged) heat transfer coefficients, hm, at all axial locations. Finally, when a twisted tape is added to

the tube with the large-pitched fins, the power required for the onset of boiling is reduced at all axial

and circumferential locations.

39O
SUBCOOLED FREON-11 FLOW BOILING IN TOP-HEATED FINNED

COOLANT CHANNELS WITH AND WITHOUT A TWISTED TAPE

Nomenclature

ac

As

CHF

D

Dh

G,

tt

hm

H

K

L

Cross sectional _rea, m 2

Surface area, rn

Critical heat flux, W/m 2

Tube diameter, cm

Heated hydraulic diameter, m

Mass velocity, kg/m2s

Local heat transfer coefficient, W/m2°C

Mean heat transfer coefficient, W/m2°C

fin height

Thermal conductivity, W/m K

Heated length of test section, m

N Number of fins per test section

p Static exit pressure, M Pa

q Heat flux W/m 2

r Radial coordiante for data reduction model, m

R Tube radius, cm

Tf Bulk temperature of the flowing fluid, °C

Tm Local measured outside wall temp. of the tube, °C

Ts Local inside wall temp. of the tube, °C

Tsat Saturation temperature, °C

T_ Ambient temperature, °C

Z Axial coordinate for heated portin of test section, cm

Greek Letters

p Density, kg/m3; _ Circumferential coordinate; n Half of a full rotation or 180 °(bottom of test section)

Introduction

Subcooled flow boiling (locally boiling fluid whose mean temperature is below its saturation

temperature while flowing over a surface exposed to a high heat flux) has the greatest potential of

accommodating high heat fluxes [1]. In space, the active cooling of cold plates, turbine blades, fusion

reactor components, chemical reactor components, electronic components, refrigeration systems components, and other systems necessary for the successful commercialization of space will require an

efficient heat transfer system. Therefore, the need to understand the behavior of two-phase flow boiling

in both the space (zero-g or reduced-g) and earth environments is essential to thermal designers,

especially where pumping power requirements must be optimized. Since thermal designers are forced

on occasion to use data from uniform heat flux applications for non-uniform heat flux applications, it

is important to assess the effect of the non-uniformity on the local and mean heat transfer.

Ideal heat transfer is achieved when the sum of the component thermal resistances is reduced to

a minimum. However, flow dynamics through plain tubes rarely provides the ideal conditions needed,

because the stationary fluid layer at the tube wall leads to the buildup of a slow moving laminar boundary

layer caused by frictional drag forces. This results in heat transfer being principally controlled by fluid

conductivity and the thickness of this layer.

Research related to enhanced surfaces for heat transfer has increased in recent years [2]. The

immediate benefit from recent research has led to increasing efficiency of heat exchanges and to the

development of the spirally fluted tube [3]. Fins (sometimes called extended surfaces) are often used

to increase heat transfer rates to fluids in cases where low heat transfer coefficients exist. If the wall

temperature is sufficiently high to cause film boiling and all other resistances are small, fins will cause

an increase in the heat transfer rates in a boiling situation [4]. Examples include cooling of nuclear fuel

391
rods, cooling of electrical equipment such as radio-power tubes, and some evaporators. Devices for the

establishment of fluid swirl are often used to increase heat transfer in tube flows. The increase in

pressure drop, however, is less than the increase in heat transfer in many cases. Twisted tape inserts

have been studied by Hong and Bergles [5], who found that in laminar flow, heat transfer could be

increased by a factor of as much as 9 whereas pressure drop increased by a factor of less than 4 over

empty tube values. In turbulent flow, twisted tape inserts can improve heat transfer by a factor of 2 over

empty tube values, but the pressure drop is increased by several orders of magnitude. Brown Fintube

Company reported in its literature that increases in heat transfer rate of up to 300 percent have been

achieved in viscous fluids with nominal increases in pressure drop with the addition of twisted tapes.

Experimental Investigation

The flow loop (Figure 1) is a closed system designed to control the working fluid (freon-11) and

reservoir temperatures, pressures, heating capabilities, and overall system stability. The reader is

referred to references 6-8 for detailed descriptions of the experimental flow loop, procedures, and data

acquisition.

The loop was designed to study both saturated and subcooled flow boiling, although only subcooled

flow boiling was considered here. By allowing both saturated and subcooled flow regimes, the heat

rejection can be either isothermal or at a slightly variable axial temperature. The latter case (subcooled

flow boiling) will result in enhanced heat rejection capability (above the saturated case) to the extent

that the given application will allow a variable axial temperature.

Referring to Figure 1, the reader should be made aware of the possible circulation patterns of the

working fluid that can be accomplished by opening and closing various valves within the loop. However,

for the tests performed within this investigation, only reservoir #1 was utilized.

,.,, "",_Q.,,.,=.'(3 ,,,. I

-2- i

---U ...... . 11 "g"/

--_--_----_,_,,,_ II ......................... _-.T,_,--_S----7. I I."_','. .... _- t-------

I_I ,, I_.__I I --...... _ ,

I-'I ......... , l........I.... _L_..t_ I :':'=.._"--,.-_

,III_.V¢ I I _eul _111,_. I

I"_Z"l =:.... :u_---I ,'=_:=:,-, ,..L-. I }

................. *-i IltlTt, I I ¥lhlq Ill%roll

--, .... I -- -a;,-- •"L._ I I,..... I

"_" T ,.. _ ,,_,-,- A .,-.,. I__ I

Figure 1. Ereon-11 flow loop for both subcooled and saturated flow boiling experiments.

392

ORIGINAL PAGE IS

OF POOR qUALm'
The measured outside wall temperatures of the test sections were used to calculate the unknown

heat transfer coefficient, h. This was achieved through a data reduction technique developed by

Turknett and Boyd [7], based on the heated hydraulic diameter, Dh. This approach will result in, at most,

a qualitative indication of the local (axial and circumferential) distribution of h. A piece-wise linear

profile method was used to evaluate the mean (circumferentially averaged) distribution of hm. A finite

difference technique (although not used for the present work) was developed to evaluate the local h

[8].

Results

The results are presented for the case of subcooled freon-ll boiling in top-heated horizontal

channels with internal fins and/or twisted tape inserts.

Figure 2 shows the circumferential variations in the heat transfer coefficient at the axial location

Z4 (center of the heated portion of the test section). It is evident that the variations in heat transfer

coefficients in the circumferential location are increased by adding more enhancement devices. The

s_al fin with large pitch shows no variations in the single phase region located at the bottom

(--4 and zr) of the tube, and minor variations at the top (0 and _) of the tube in the film boiling region.

Adding a twisted tape (spiral fin large pitch tape) decreased variations in heat transfer coefficients in

3:r

the film boiling region (0 and _), but increased the variations in the single phase region (-4 and :r).

The spiral fin small pitch shows the largest variation of h in the single phase region (_- and :r) and only

_r

a minor variation in the film boiling region (0 and 7).

The axial variation of h as a function of power for the three (3) cases is presented in Figure 3. The

axial locations Zt and Z7 are excluded due to end losses and the effect of axial conduction. At

circumferential location 0 (top of the tube), the onset of boiling appears to occur more uniformly along

•

the length of the channels than at circumferential location -_. At circumferential locatmn _-, the spiral

fin large pitch (3a.2) provides higher heat transfer coefficients than any case presented• By adding a

twisted tape to the large pitch tube, the power required for the onset of nucleate boiling was reduced

at all axial and circumferential locations, but the average heat transfer coefficients were reduced

:r (Figure 3c.2), provided a

(Figure 3b.2). The spiral fin small pitch tube at circumferential location _-

more uniform onset of boiling in the axial direction than the tubes with large pitch or large pitch with

a twisted tape insert. However, at circumferential location 0, the tube with twisted tape had a more

uniform onset of nucleate boiling. The average axial heat transfer coefficients at circumferential

location 0 (top of the tube) were higher for the case of the tube with a small pitch than the other cases

(spiral fin large pitch and spiral fin large pitch with tape), but were found considerably lower at

zt

circumferential location _- for the same cases.

Figure 4 is a plot of the mean (circumferentially averaged) heat transfer coefficient hm, as a

function of power. The averaged h (i.e., hm) appears to be consistently higher for the case of the spiral

fin large pitch (4a) than the cases with a tape (4b) and small pitch (4c). In some cases, the addition of

the tape to the spiral fin large pitch reduced the average heat transfer coefficients in the axial direction.

However, adding a twisted tape or reducing the pitch of the fins caused boiling to occur more uniformly

over the length of the test section. Heat transfer coefficients literally remained unchanged in the spiral

pitch tube (4c) in the axial direction when compared with Figure 3.

393
Z00000 -

150000.

E •

_. lctmoo L

/-

D

0

ZOO00

l"-,Og<

%

s0oo:

/

t

SPf_ FIN LM_CI_ PITCH (N1011)

SYUEOL C_'CUU_[_.4L _'nO_

,° _/4

IM/4 1 -

1-l

i-

'_- f:; rr _ ;':7 f', c, ,:, ". 7-_'f _ _ , _ , , ._ , . , I ' '' ' ' , . ,% _ ........ • ] 0

+00 600 _lO0 1000

Power (W)

F,:,.;, ,',;'_,';_. ,......,_ ...._. ........

Powor (W)

_7 .... .,-'_.'T _ , ,-, ,-. , , . .', ," ..... ; ..... 't.,.; ......... ,

200 400 8(:X) _ l

Power(W)

q" = CONSTANT

¢ = TT INSULt.TED

Figure 2. Heat transfer coefficient versus power at axial location Z = Z4 (center of

heated section of the test section) for top-heated finned tubes at 0.19 MPa and 0.210

Mg/m2s. Channel diameter = 1.27 cm, Heated length = 1.22 m.

394 ORIGINAL PAGE IS

OF POOR QUALITY
/

SFIPAL f_ft V,F'C[ PIICI(fP_q-(:]/4) I

S'_4BOL5 AXIAL LOCATt_(HI"O f 1B)

,," j

S_JRAt. FIN LARCE PITCH c PNI_ O_ _ _ _ Z032 ¢m

SYMBOL AXIAL I_OCATqONS i Z" _ 40_4 cm

• Z_ _ 2032 ¢_ A Z5 _ 8i_2B c_

_ Z_ _ 40 64 ¢rn 1_ • Z6 _ 101_60 ¢_

& Z4 _ 60,96 ¢m __

• Z5 _ BI 28 ¢_ __

Q Z6 - 101 60 cm "E

o z7 . 121,_2 cm _.

o ............................................. o

-t

A S'(k_r_oLS AX_4L LocArlc_sI'II I 127D)

: _- 20ooo32 ,,,, cm

• Z3 40 84 cm

SPIP_L tin L_PCE Pli'CII (PH_.Pl/4) 0 Z4 60g_* cm

• _t I_ SYU_OLS AXIAl. LOCATIOHS(HlOI1B) . ZS BI 2fi cm

LV ' . z,- oooo. -- . z, ,o,.,o..

• _T" : Z052 Cr_ _ o 77 121 _12

li_ \ O. Z.t - 6_96 cm "'I_

o Z8 - iOl 60 cm

........._ ........_........._........._........;_ ' ........._........_........._........_. .......

Pow,r 01') Power (_1

(3b. I) (3b .2)

llil FIN SMALL pITCH (PHI- 0)

l I |_ _ gY)dE)c*mq _X_q. LOCAI'IONS(HI)I_,A) J l - , I 4

m _ _ _pIRI.(. FIH _!IAL PIrC_q_PHI-_/" )

• _)- _ _ :_

i Z5 B1 Z0 c _' . 406_ c_

_- a _ - .... ou cm "_ L_ Z4 - 60 6

= .= "1 l-_ o Z6 _ Iv_vu cm

- _._=_

........i'd......... _........ _' ......... _' ......._ •_,_m_. ...._......... ,_........ ,_........ ,_.......1._.

Power (W) Pcn,m I_)

(3c. 1) (3c.2)

Figure 3. Axial variations of h versus power at circumferential locations 0 and _- for

spiral fin large pitch (3a), spiral fin large pitch with tape (3b), and spiral fin small pitch

(3c)

ORIGINAL PAGE IS

OF POOR QUALFiY

395
4OO

_E

.......*

I,JE,it4 Dl_'_fEnJ't?.GtlS _NlOI I-A)

SPI_.L fin L.4.r..a_ 4oTrCH

S'YklEOL_ AX1AL L.Cr._'rIc,(,_

• Zl - 0.00 cm r_ k . ,.,. _.:__,

\\ •• o.o ,o 7.5 J el.Z4 ,=m

• Ze _ 1011_0..,,,,n

(a)

_0 eO0 ZlO0 1000

Power (IV')

_,_ _A ,,, Z3 - 4oe4 =m

(b)

o ,, .... ,,,i,,,, ..... i,,, ..... ,i,,,,,,,,,, ......... ,

200 400 BOO 800 ;

Power (W)

"'E "

zooI _I\ "_. , z_ - a_.za

(¢)

Pc_wer (W}

Figure 4. Mean heat transfer coefficient versus power for spiral fin large pitch (4a),

spiral fin large pitch with tape (4b), and spiral fin small pitch (4c).

396 ORIGINAL PA_E I$

OF PO01_ Q_JAL/rY
Acknowledgments

Support for this study was provided by Sandia National Laboratories and NASA (JSC). The

authors would like to thank the personnel at these facilities for their support.

References

° Boyd, R.D., "Subcooled Flow Boiling Experiments Using Small Diameter UniformlyHeated Tubes," ASME, 86-HT-23, AIAA/ASME 3th Joint Thermophysics and Heat

Transfer Conference, Boston, Mass., June, 1986.

. Bergles, A.E., and Webb, R.L., "A Guide to the Literature on Convective Heat Transfer

Augmentation," Advances in Enhanced Heat Transfer - 1985, ASME Publication, HTDVol. 43, 1985, pp. 81-89.

. Panchal, C.B., et al., "A Spirally Fluted Tube Heat Exchanger as a Condenser and

Evaporator," Proc. 4th Miami Intl. Symp. on Multi-Phase Transport and Particulate

Phenomena, Dec. 1986.

4. Burmeister, L.C., Convective Iteat Transfer, John Wiley & Sons, New York, 1983,

pp. 615-616.

. Hong, S.W. and Bergles, A.E., "Augmentation of Laminar Flow Heat Transfer in Tubes by

Means of Twisted-Tape Inserts," Journal of Heat Transfer, Trans. ASME, Vol. 98, May,

1976, pp. 251-256.

° Boyd, R.D., "Flow Boiling With and Without Enhancement Devices for Horizontal, TopHeated Coolant Channels for Cold Plate Design Applications, Preliminary Report,"

Department of Mechanical Engineering, Prairie View A&M University, Prairie View, TX.,

Submitted to NASA(JSC), Contract No. 9-16899 (Task-5), December, 1986.

. Boyd, R.D. and Turknett, J.C., "Forced Convection and Flow Boiling With and Without

Enhancement Devices for Top-Side-Heated Horizontal Channels," Department of

Mechanical Engineering, Prairie View A&M University, Prairie View, TX., (presented

at these proceedings).

. Smith, A., "Subcooled Freon-11 Flow Boiling Heat Transfer With and Without

Enhancement Devices for Top-Heated Horizontal Tubes," MS Thesis, Department of

Mechanical Engineering, Prairie View A&M University, Prairie View, TX.,

(to be published).

397
[

XeCI LASER PUMPED IODINE LASER USING t-C4F9|

In H. Hwang and Kwang S. Han

Department of Physics

Hampton University

Hampton, VA

ABSTRACT

An iodine photodissociation laser using t-C4FgI as the active material was pumped by an XeCI

laser. An iodine laser output energy of 3 mJ with pulse duration of 25 nswas obtained when the pumping

pulse energy was 80 mJ, the iodide pressure was 70 torr, and the reflectance of the output mirror was

85%. The high pumping efficiency and low threshold pump power achieved in this experiment are

attributable to the high absorption cross section at the pump laser wavelength (308 nm) of the iodide

used.

398
XeC! LASER PUMPED IODINE LASER USING t-C4F9I

I. Introduction

Since the atomic iodine photodissociation laser was discovered by Kasper and Pimentel in 1964

[1], numerous research efforts have been concentrated on this laser to increase the power level needed

for laser fusion [2,3]. The fusion-experiment-oriented iodine laser is constructed in a master-oscillatorpower-amplifier (MOPA) architecture [4].

The iodine laser is also being considered as a direct solar pumped laser for space applications such

as the laser propulsion for an orbital transfer vehicle. The first solar simulator pumped iodine laser was

reported in 1981 by Lee, et. al. [5]. This laser was operated in quasi-continuous-wave mode. After this

report, various iodine compounds were tested and evaluated as candidates for direct solar pumped laser

materials [6,7,8].

Although many space applications are best served by a continuous wave (CW) laser, a continuously

pulsed laser also has good applicability in space, especially for laser propulsion. Ifweak pumping (such

as solar radiation pumping) of laser materials exists, use of a MOPA system is essential for obtaining

high peak power when the laser material has a long upper-state lifetime like an iodine atom. In previous

research, the feasibility of the oscillator-amplifier scheme was proposed and tested for the solar pumped

iodine laser [7.9].

In order to be incorporated in the MOPA system, the iodine laser oscillator must generate

temporally smooth and short pulses. In the fusion-oriented-iodine-laser-experiment the short pulse is

provided by mode-locking of the flashlamp-pumped oscillator. However, the repetition rate of the

flashlamp-pumped oscillator is usually very low (<5Hz), and the mode-locking devices are generally

complicated. An excimer laser pumped iodine laser oscillator was demonstrated by Fill et. al. [10]. In

their experiment, a 500-mJ excimer laser was used for the pumping of the iodine laser, and a temporally

smooth laser pulse with duration from 2.6 ns to 12 ns was obtained by using i-C3F7I as the laser material.

In this report, a XeCI laser pumped iodine laser using t-C4F9I is described. This laser oscillator

has much a higher efficiency and a lower threshold pump power than the system using i-C3F7I. The laser

output energy dependence on the gas-filled pressure and on the reflectance of the output mirrors are

measured for both longitudinal and transverse pumping.

II. XeCI Excimer Laser

A laboratory built XeCI laser was used for the pumping of the iodine laser in this experiment. The

electrical circuit of the XeCI laser is shown in Fig. 1. A pyrex tube with an I.D. of 0.1 m and a length of

0.66 m was used as the laser chamber. The two brass electrodes were rounded in order not to develop

an arc discharge in the discharge volume. The width of the electrodes was 20 mm, and the length was

about 0.45 m. The separation between the two electrodes was 20 mm. Seventeen pairs of arc arrays

were located beside the electrodes so that the discharge volume could be preionized uniformly. The

optimized gas composition was HCI: Xe: Ar: He = 0.2% : 5.9% : 19.5% : 74.4% at a total pressure of

2 atm. The addition of argon gas improved the discharge uniformity at the higher operating voltage.

399
When the XeCI laser was operated at the charging voltage of 25 kV, the output energy was 80 mJ per

pulse. If the charging voltage was increased, the output energy also increased, but an arc discharge

developed between the electrodes. Thus, operation above 25 kV was not pursued. A typical laser pulse

is shown in Fig. 2. The half width (FWHM) of the XeCI laser pulse was about 25 nsec, and no significant

variation of the laser pulse was found for prolonged operation.

high voltage 500K 300K

_ prelonlzer

pulse 1250pF I "r_ ] I "_::_;_C/500pFx 17

- -- 300K 300K

Figure 1

Electrical circuit diagram of the XeCI excimer laser.

"0

E

0

Q

(

V

50ns/div.

Figure 2

A typical pulse shape of the XeCI laser output.

4OO
III. Iodine Laser Experiment

The iodide used in this experiment was t-C4FgI (perfluoro-tertiary-butyl iodide). This material was

chosen mainly due to the absorption cross section at the wavelength of XeCI laser light (308 nm). The

• • - * 2

pubhshed data show that the absorption cross section of t-C4FgI at 308 nm Is about 3.6 x 10 -10 cm [7].

Also, t-C4FgI has shown good chemical reversibility in a flashlamp-pumped system [6,7], and thus the

iodine molecule buildup in the laser cell is minimized. The main disadvantage of this iodide is the low

vapor pressure (--85 torr) at room temperature. The other chemical kinetic properties are nearly the

same or better than other commonly used perfiuoralkyl iodides in the flashlamp-pumped experiment

[7]. The quantum yield of excited atomic iodine in the UV photodissociation is nearly unity [11].

A quartz cuvette with a square cross section of 1 cm 2 and length of 50 mm was used as the iodine

laser cell. The windows of the laser cell were nearly perpendicular to the optic axis of the laser cell.

Both longitudinal and transverse pumping of the iodine laser were employed.

When the iodine laser was pumped longitudinally, a dichroic mirror was used to introduce the

XeCI laser light into the iodine laser cell. The dichroic mirror transmitted about 80% of the XeCI laser

light and fully reflected the iodine laser light. The XeCI laser light was directed through the dichroic

mirror and was focused into the center of the laser cell by a quartz spherical lens of focal length 0.2 m.

When the iodine laser was pumped transversely, a quartz cylindrical lens of focal length 0.3 m was used

to focus the XeCI laser light into the iodine laser cell.

The output energy dependence on the gas filled pressure at different output mirror reflectances

is shown in Figs. 3 and 4. As shown in Fig. 3, there is an optimum iodide pressure for each output mirror

reflectance for the longitudinal pumping. However, for the transverse pumping, the laser output energy

increases monotonically with the t-C4F9I pressure as shown in Fig. 4 The results in Figs. 3 and 4 were

taken when the laser was operated at 2-Hz repetition rate. When the pulse repetition rate was increased

to 5 Hz, the laser output energy per pulse was reduced slightly (.-_10%) due to the reduction of the

XeCI laser pumped energy.

A typical laser output is shown in Fig. 5. The half width (FWHM) of the pulse is about 25 nsec.

The iodine laser onset is delayed from the XeCI pump laser and occurs at the end of the pump pulse.

The pulse shape is nearly the same for both pumping geometries.

IV. Discussion

In this experiment, a XeCI laser pumped iodine laser was developed and tested by using t-C4F9I

as the laser material. This lasant t-C4F9I has a larger absorption cross section at the XeCI laser line

compared with other iodides used in the laser experiment, such as i-C3FTI. The larger absorption cross

section allows the high utilization of pumping energy in short gain length and low pressure operation

of the iodine laser. The low-pressure operation of the iodine laser is suitable for single longitudinal

mode output because of the reduced pressure broadening of the gain profile. The single-longitudinal

mode operation of the laser oscillator is necessary to obtain a temporally smooth pulse.

The iodine laser described in this report was operated up to 5 Hz, which was limited by the power

supply of the XeCI laser. Further increase of the repetition rate can be made by scaling up the pump

laser system. The iodine laser was operated in a sealed-off mode. There was no significant reduction of

the laser output energy after a few hundred pumpings with a single fill t-C4FgI in the laser cell. There

401
was also no noticeable change in the t-C4F9I gas after a few hundred pumpings and no deposits on the

wall of the laser cell (contrary to the report of Ref. 10 where t-C3FTI was used). This may be attributable

to the superior chemical reversibility of the iodide used.

@

eILl

¢

O

---in R=85%

++=:2

;o =;o _o 4'o......5'o 60 7'o 8'o

presgure(torr)

Figure 3 - Iodine output energy dependence on the gas

fill pressure in the laser cell at each output mirror

reflectance. The iodine laser was pumped longitudinally

with the XeCI laser of pulse energy 80 mJ.

om

"O

>

E

O

O

! I

1 /"" '" ,_ ....... XeCI laser

t

/t

,;a._ ;-.-..- -- iodine laser

50ns/div.

Figure 4 -Iodine laser output energy dependence on the

gas fill pressure when the iodine laser was pumped

transversely. The pumping energy from the XeCI laser

was fixed to 80 mJ.

402
A

E

v

"1

r_

e,L

tw

-n

e-L

u

-1

O

+R=85% /

_b 2'o 3'o 4'o s'o _o r'o a'o

pressure(tort)

Figure 5 - A typical iodine laser pulse shape which is

compared with the pumping pulse. (a) XeCI pump laser

pulse. (b) Iodine laser output pulse.

V. Conclusion

An iodine laser oscillator pumped by an XeCI laser was developed using t-C4FgI as the laser

material, and a 3 mJ laser output energy was obtained with only 80 mJ pumping energy. Compared with

previous results, the pumping energy was dramatically reduced in this experiment, The pumping

efficiency (i.e., the ratio of the iodine laser energy and the XeCI laser energy) was 3.75%. This

experiment also demonstrated a repetitive operation of the iodine laser oscillator with a stable output.

Since the threshold pumping energy (20 mJ) is low for t-C4F9I, a moderate size XeCI laser may suffice

for the pumping of the high-repetition-rate laser oscillator required for solar pumped master-oscillator

power-amplifier systems.

Acknowledgments

This work is supported by NASA grant NAG1-441.

References

1. J.V.V. Kasper and G.C. Pimentel, AppI. Phys. Lett. 5, 231 (1964).

2. G. Brederlow, E. Fill and K.J. Witte, "High-Power Iodine Laser," Springer-Verlag, New

York, N.Y. (1983).

4O3
3. S.B. Kormer, Izvesteriya Akademii Nauk SSSR. Seriya Fizicheskaya 44, 2002 (1980).

4. K.J. Witte, Czech. J. Phys. B34, 790 (1984).

5. J.H. Lee and W.R. Weaver, Appl. Phys. Lett. 3.,9_,137 (1981).

6. J.H. lee, J.W. Wilson, T. Anderson, D.H. Hume, W.R. Weaver and B.M. Tabibi, Optics

Comm. ,5.3.,367 (9185).

7. B.M. Tabibi, M.H. Lee, J.H. Lee and W.R. Weaver, Proceedings of International

Conference on Lasers' 86, pp 144-149 (1986).

8. R.J. Deyoung, IEEE. J. Quant. Electron. OE-22, 1019 (1986).

9. I.H. Hwang, J.H. Lee and M.H. Lee, Optics Comm. 58, 47 (1986).

10. E. Fill, W. Skrlac and K.J.K. Witte, Optics Comm. 37, 123 (1981).

11. A.B. Alekseev, A.M. Pravilov, I.I. Didorov and V.A. Skorohodov, Soy. J. Quantum

Electron. 17, 1539 (1987).

404
w

N91-28118

CHARACTERIZATION OF QUANTUM WELL STRUCTURES USING A

PHOTOCATHODE ELECTRON MICROSCOPE

M.G. Spencer

Department of Electrical Engineering

Howard University

Washington, D.C.

C.J. Scott

Naval Research Laboratory

Introduction

Present day integrated circuits pose a challenge to conventional electronic and mechanical test

methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to

facilitate electrical contact to circuits and devices being tested. In addition, microwave operating

frequencies require careful attention to distributed effects when considering the electrical signal paths

within and external to the device under test. In this paper an alternative testing approach which

combines the best of electrical and optical time domain testing will be presented, namely photocathode

electron microscope quantitative voltage contrast (PEMQVC).

Comparison of Test Methods

High speed electrical characterization of microstructures using a stroboscopic quantitative voltage

contrast electron beam probe has advantages over mechanical and optical methods. For comparison

the photocathode electron microscope and other time domain test methods are listed in table 1.[1]. It

can be seen that the PEMQVC offers superior spatial and temporal resolution at the expense of voltage

accuracy. Electro-optic probing eliminates some of the spatial transition problems which can introduce

considerable error in high frequency mechanical probe measurements. Alternatively, when characterizing micron scale structures, electron beam testing has the following advantages over the electro-optical

method: 1) the spatial resolution of the electron beam is limited to the minimum primary gaussian

electron beam current waist (typically _ 80A) as compared to the diffraction limited beam waist of

monochromatic light (typically _ lum), 2) the sampling media is not limited to materials with intrinsic

birefringence such as GaAs and LiTaO3 so that silicon, InP and other materials with low electroptic

figures of merit can be tested, and 3) the necessity of gold coating and polishing the backside of the test

sample is eliminated.

4O5
PEMQVC Components

A standard SEM is modified by: 1)replacing the conventional thermionic electron gun with a

photo-excited electron gun, 2) enhancing the SE detector electrostatic environment to measure the

energy spectrum of the scattered ,secondary electrons, and 3) providing feed-throughs for electrical

signals. Schematic diagrams of a conventional SEM and the photocathode electron microscope are

shown in Figure 1. The instrument can be usedin a dual mode for either conventional SEM work or

time domain characterization if the SEM conversion is done properly. A circuit can be examined for

visual defects and then exercised at speed functionality evaluation. There are three different test modes

the photocathode electron microscope can operate in: 1) static voltage contrast, 2) quantitative voltage

contrast, and 3) stroboscopic voltage contrast.The first mode gives a qualitative indication of voltage

levels on the sample. The second mode gives a quantitative voltage for the sample but no time domain

information. The third mode gives both voltage and time quantitatively.

The photostated provides a pi_nd electron source by photoemission of electrons using a

frequency quadrupled Nd Yag (1.06 ram) laser source. A KDP crystal is used for the first frequency

doubling stage and a BBO crystal is used for the second frequency doubling stage. BBO is an efficient

second harmonic generation medium for the 532/266 nm doubling process. The emission surface is a

200A thick Au layer on a polished 40 mm A1302 substrate. The photo cathode is held at the primary

electron acceleration potential (- 1KV).

A Feuerbaum [2] or planar type detection scheme is used to quantize the SE spectral shift (Fig.

2). This type of analyzer simplifies the electrostatic field pattern analysis for detector refinement for

achieving higher measured signal resolution. The retarding potential sets the lower limit of integration

for the photomultiplier tube (PMT). The nonlinear photomultiplier tube (PMT) "S curve" currents are

linearized using a computer controlled feedback loop to establish the required retarding potential to

maintain a preset PMT output current. The retarding potential is equal to the sample potential.

Temporal delay is implemented on the optical bench with a right angle prism on a sliding optical rail.

Summary

The electron beam testing apparatus will provide direct experimental verification for numerical

simulations and a means of contactless probing of devices and interconnects at spatial and temporal

resolutions not achievable by any other means. When the flexibility and high spatial resolution of the

electron beam technique is combined with the inherent high speed capabilities of optical pulse

generation, this contactless probing method may prove to be an essential tool in any integrated circuit

research and development facility.

References

[1] G. Chiu, J. Halbout, and P. May, J. Vac. Sci. Technol. 6,1814 (1988)

[2] H.P. Feuerbaum, SEM/I, pp. 285-296, (1979)

4O6
tF

Superconductive 20ps

Analog 25ps

E-Beam Strobe lOOps

E-Beam Photo 5ps

E/O Sampling 5ps

VF

luV/,rl 

7uV/h z

3mV/,[_

3mv//,/'E_

x Jitter

lOOum 5ps

100um lOps

O.lum 10ps

O.lum 5ps

3um 5ps

Table 1.

Time domain measurement comparison.

m_m

%

llectron Gun

Aperture

Condenser Lens

Scan Coils

Objective Lens

8E Detector

a)

I.oo_,..--'- . =-=_-=f2_..

I TOo| / _32nm/ , LrL_L r..q,, L:::.%_

TRIQGER FOR ELLrCTRICAL_

WAVIEFORM ON OUT

CATHOOI[

I

i

!

I

r

ANOD(

CONOENSER

tENSES

UPPER

i-_1" I I 0ETECTOR

J_-LENS I J--___L.._\ 1 LOWER

_lcRoscoPE BOO'/'

b)

Figure 1.

Schematic diagrams of

a) a conventional SEM and

b) a photocathode electron microscope.

407
E-beam

I It

I I

I I

I I

] I

I I

m

I

,, _ Detector

I I L_

I I vo

[ I

I I

OV VG

I,_ED =I_Emax

50eV

f

eVG

N (E + eV, p) dE

Figure 2.

A Feuerbaum type SE detector.

408
 91-28119

A

A DENSITOMETRIC ANALYSIS OF COMMERCIAL 35mm FILMS

Ernest C. Hammond, Jr. and Christopher Ruffin, III

Morgan State University

Baltimore, MD

and

Gerald R. Baker

Technical Monitor

Laboratory of Astronomy and Solar Physics

Goddard Space Flight Center

ABSTRACT

IIaO films have been subjected to various sensitometric tests. They have included thermal and

aging effects and reciprocity failure studies. In order to compare the special IIaO film with popular

brands of 35mm films and their possible use in astrophotography, the following brands: Agfa, Fuji and

Kodak print and slide formats, as well as black and white and color formats, were subjected to

sensitometric, as well as densitometric analysis. A scanning electron microscope was also used to analyze

grain structure size, and shape a function of both speed and brand. Preliminary analysis of the grain

structure using an ISI-SS40 scanning electron microscope indicates that the grain sizes for darker

densities are much larger than the grain size for lighter densities. We will analyze the scanning electron

microscope findings of the various grains versus densities as well as enhancement of the grains, using

the IP-8500 Digital Image Processor.

y -

409
A DENSITOMETRIC ANALYSIS OF COMMERCIAL 35mm FILMS

lntorduction

As the United States reestablishes its space exploration program, accurate reproduction by

electronic and photographic recordingkt_finiques will remain an integral part of these studies. The use

of film as a recording medium in astronomy is well documented. In hopes of establishinganother method

of calibration, and to determine whether or not commercial films can be used in astrophotography, films

of color, black & white, print and slide formats were subj_ted to various tests. We wish to make it

perfectly clear that this paper is analyzing films after development, and the results are not to be

misinterpreted as proof of a particular film's superiority over another brand.

Experimental Procedure

The films were exposed on a densitometer which contained thirty neutral density wedges of

differing values. These wedges simulate thirty different exposure times. Once the rolls were processed,

by the same commercial lab, a densitometer was used to obtain the gray levels of the wedges. These

levels were recorded and then plotted for each film. The iightest and darkest wedges of each sample

were then placed in our ISI-ss40 scanning electron microscope. (The terms light and dark refer to the

translucence of the film.) Photographs were made of each wedge at two different energy levels to analyze

both the surface and the grains of each wedge. At 10 kv, the electrons lack the energy to fully penetrate

the emulsion of the film, thereby showing the grains, peaks and valleys of the surface. When the energy

is increased to 30 kv, the surface effects are lost and the grains are seen as they react to the secondary

electrons. The Polaroids were then digitized using our Gould IP-8500 digital image processor. The

enhanced and false color images were then studied. Grain counts and sizes were made and plotted for

a visual comparison. The results of these tests follow.

Light Surfaces

For Plus X, (Fig. 1.3R) hereinafter referred to as Px5062, the boundaries of the larger conglomerates of grains and their depth or proximity to the surface is assumed by their focal clarity. This

ambiguity may be overcome by placing the image in false color. Pcmake is one of the methods used to

do this. Through experimentation and carefully choosing contrasting and complementary colors, the

background grains, emulsion, and grain boundaries can be enhanced or diminished (Figs. 6.1 & 6.2).

While looking at the Tri-X, Tx5063 (Fig. 1.4R), one is immediately able to see that there are fewer

but larger grains present on this surface. The pcmake version gave the illusion of depth for a 3-D effect

and had great resolution, but still did not fully isolate the foreground. The pseudocolor image lacked

resolution, but did a better job of separating the foreground and background of the emulsion (Figs. 6.5

& 6.6).

The T-Max 400, TmyS053, had a surface unlike any of the previous samples. Fewer and smaller

grains with a few conglomerates appear to be the composition of this film. The pseudocolor version

410
showed three fairly distinct regional densities. Other samples tended to have more uniform dispersion

of the density.

Fuji Pr.III, referred to simply as Fuji, has a surface that is more like the Tmy5053 than any other.

The pcmake and pseudocolor versions again show a more regional grouping of grain densities than in

previous samples.

Dark Surfaces

It is immediately apparent that on the surface, the dark wedge has many more grains. This is both

characteristic and to be expected. The dark wedges have far more grains, and thus allow less light to

pass through. Fig. 1.3L is of Px5062, and the pcmake version gives a 3-D effect, while the pseudocolor

mode decreases the background (Figs. 6.3 & 6.4).

Fig. 1.4L is of the surface of the dark Tx-5063 wedge. More spaces or holes are present than in

the Px5062, but again the film has more grains than its light counterpart. However, this time the ix:make

version has done a better job of separating the background from the higher level grains.

The Tmy5053 surface is interesting because it seems to have a couple of separate levels; one with

loose grains suspended in space, and the other more of a surface like the lighter wedges.

The final surface to be analyzed here is that of Fuji. This surface has very few loose grains, and

has a more uniform density. A change in density occurs near the edge of the sample.

Light Grains

The energy of the electrons was increased to 30 kv so that they would have the energy necessary

to penetrate the emulsions of the film. There are fewer but larger grains than were previously seen. By

placing the image in pcmake false color, the boundaries of the grains become more distinguishable.

Figure 5.1R is of Px5062 and set next to its dark counterpart for a contrast. The large but relatively

fewer grains are clearly evident in this side by side comparison.

The number of grains present in Tx5063 (Fig. 5.2R) was still further reduced. An increase in the

size of the grains is noticeable, especially in the pseudocolor version of the sample, where the boundaries

of the grains are readily discernible.

The grains of Tmy5053 (Fig. 5.3L) appear to be twice as large as those of Tx5063. The pcmake

version highlights the few grains closest to the surface of the emulsion.

The light Fuji (Fig. 5.4R) film grains in the equalized version were an unresolved blob. The pcmake

version turns the image into a well defined image of the grains. Similarly, the pseudocolor view makes

boundary and size analysis possible.

411
Dark Grains

The last samples to be analyzed by electron microscopy are the dark wedge grains. Px5062 (Fig.

5.1L) had a far greater number of grains that were considerably smaller. The large number of grains

would make boundary identification and size distinction very difficult if not for the false coloring

techniques.

The dark wedge grains of Tx5063 (Fig. 5.2L) revealed the difference that choosing different colors

can make in analysis. This first ix:make version decreased the background, and defined the boundaries

better than the second version which tended to only moderately decrease the background.

Tmy5053 (Fig. 5.3R) showed a considerable grouping_ _ of grains towards the bottom center of the

wedge. The pseudocolor image supports the pcmake analysis.

Fuji (Fig. 5.4L) had a fairly uniform clustering of grains throughout the wedge. The pseudocolor

image better defines the grain boundaries than does pcmake, which, however, had a better resolution.

Graphs of the Gray Levels

The gray levels of the films were plotted against each other by color format (Figs. 1.1 & 1.2). In

analyzing the graphs of the films, Fuji, Pan-X, Plus-X, and T-Max have relatively the same optical

densities. As the exposure increases, their optical densities vary significantly. Based upon this, one can

assume that a fairly reasonable amount of quality control is present. The films that vary from the

beginning have a significantly different ASA. The same situation is true for the color format. The curious

difference is that the highest ASA film in black & white has the highest optical density, while the

opposite is true in the color format. Research is being conducted to find the reason for this behavior.

The Grain Chart

The average and number of grains in a 9 cm 2 area were calculated and recorded on the chart (Fig.

2). An approximation of the shape of the grains was made. The grains were categorized by translucence.

The chart should require no explanation.

Bar Graphs

The average area of the grains of the light and dark wedges were graphed together as were the

number of grains in a 9 cm 2 area. A possibly significant but definitely interesting trend was found (Figs.

3 & 4). In each case of either a light or dark wedge the highest value peak has as its counterpart not the

lowest, but the next to the lowest peak of the opposite wedge.

412
Figure 1.1

Figure 1.2

ORIC_INAIL PAGE

IBI._CK AND _,.A'a_ITE r.._ ,-,--m,',oA_L_

413 ORIGINAL PAGE I$

OF POOR QUALITY
ORIGINAl..: PAGE

BLACK AND WHITE PHOTOGRAPN

L Figure 1.3 R

L Figure 1.4 R

414
Film Type

Px 5062

Tx 5063

Tmy 5053

Fuji

# grains/9 cm*cm T_ r,

80+

50

50

40

Average Area _=

2,200

9,070

5,050

7,370

Shape

pebble

elongated

pebble

irregular

Dark Grains

Film Type

Px 5062

Tx 5063

Tmy 5053

Fuji

# gralng9 cm*cm

12

11

13

17

Average Area _,_

7,980

11,280

21,260

12,230

Shape

pebble

elongated

pebble

irregular

Light Grains

Figure 2

415
416

°m

r_

E

[-

t'_

ORIGINAL PAGE IS

OF POOR QUALn_'
iii

ill

III

ill

It L

Ill

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tu_ 6 u_ su!ezO #

417
ORIGINAL PAGE

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L Figure 5.1 R

- - " i 27_; i - -

L Figure 5.2 R

418
ORIGINAL PA(I'E

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L Figure 5.3 R

L Figure 5.4 R

419
Figure6.1

O_;TG!NAL" PAGE

BLACK AND WHITE PHOTOGRAPI..;

Figure 6.2

Figure 6.3

Figure 6.5

420

Figure 6.4

Figure 6.6
Conclusion

Because of the triple layer of emulsion, the color films were set aside until the black and white

films were understood. The densitometric analysis is a viable method of calibration and comparison.

Insofar as the use of commercial films in astro-photography is concerned, one has but to consult the

density plot and choose a film based on the anticipated lighting.

Acknowledgments

The author is indebted to Gerry Baker and AI Stober of the Small Payloads Section of the

laboratory for Solar Physics and Astronomy of the Goddard Space Flight Center, Greenbelt, Maryland

for their support. I would also like to thank the following students: Dana Dunsen, Theresa Williams,

and Michael Blake for their assistance with this project. A special thanks to Ernest C. Hammond, Jr.,

for without your discussions and support, this project would not have been completed.

421
DEVELOPMENT OF FLASHLAMP-PUMPED Q-SWITCHED

Ho:Tm:Cr:YAG LASERS FOR MID-INFRARED LIDAR APPLICATION

38 Young S. Choi, Kyong H. Kim, and Donald A. Whitney

Department of Physics

Hampton University

Hampton, Virginia

Robert V. Hess, Norman P. Barnes, Clayton H. Bair, and Philip Brockman

NASA Langley Research Center

Hampton, Virginia / : _

i

ABSTRACT

j • _

A flashlamp-pumped 2.1/zm Ho:Tm:Cr:YAG laser has been studied for both normal mode and

Q-switched operations under a wide variety of experimental conditions in order to optimize performance. Laser output energy, slope efficiency, threshold and pulselength were determined as a function

of operating temperature, output mirror reflectivity, input electrical energy and Q-switch opening time.

The measured normal-mode laser thresholds of a Ho 3+ (0.45 atomic %) :Tin 3+ (2.5 at. %) :Cr3-+ (0.8

at. %) : YAG crystal ranged from 26 to 50 J between 12&and 200° Kelvin with slope efficiencies up

to 0.36% with a 60% reflective output mirror. Under Q-switched operatic_)n the slope efficien_ was

90% of the normal-mode result. \

422
DEVELOPMENT OF FLASHLAMP-PUMPED Q-SWITCHED

Ho:Tm:Cr:YAG LASERS FOR MID-INFRARED LIDAR APPLICATION

= =

Introduction

S,

\

-\

Development _f solid state lasers with Ho 3 +, Tm _ + and(or) Er 3+ doped crystals has been pursued

by NASA for eye-safe mid-infrared LIDAR (light detection and ranging) application. As a part of the

project we have been working on evaluation of Ho 3+ :Tin 3 +:Cr 3 + :YAG crystals for normal-mode and

Q-switched 2.1/_m laser operations in order to determine an optimum Tm concentration under

flashlamp pumping conditions.

Lasing properties of the Ho 3+ in the mid-infrared region have been studied by many research

groups since the early 1960's. l"s However, the technology of those lasers is still premature for lidar

..... 3+

apphcatlon. In order to overcome the inefficiency related to narrow absorption bands of the Ho ,

Tm 3+ and Er 3+, the erbium has been replaced by chromium. The improvement in flashlamp-pumped

Ho 3+ laser efficiency has been demonstrated recently by several research groups6'7by utilizing the broad

absorption spectrum of Cr 3+ which covers the flashlamp's emission spectrum. Efficient energy transfer

to the Tm 3+ and then the Ho 3+ occurs subsequently. It is known that high Tm 3+ concentration and

low Ho 3 + concentration are preferred to achieve a quantum efficiency approaching two and to avoid

large reabsorption losses. 6 However, determination of the optimum Tm 3+ concentration required to

ensure efficient energy transfer from Cr 3+ to Tm 3+ and from Tm 3÷ to Ho 3+ has not been made in the

Ho:Tm:Cr:YAG crystal. This paper will present the results obtained so far with one out of the three

Ho:Tm:Cr:YAG crystals with three different Tm 3+ concentrations with similar Cr 3+ and Ho 3+

concentrations.., f: := = : _=_ J

Quantum Processes in Ho 3 +, Tm 3 + and Cr 3 + -Ions

The energy levels of the Cr 3 +, Tm 3+ and Ho 3+-ions and the energy transfer mechanisms among

the ions in a YAG crystal are illustrated in Fig. 1. The use of Cr 3 + for flashlamp pumping is based on

its broad absorption spectrum provided by the transitions from the ground 4A2 state to the u_per 4T1

and "I"2 states. Subsequently, efficient near resonant energy transfer to the 3H4 state of the Tm 3 occurs.

Fig. 2 shows the absorption spectrum of the Ho 3+ (0.45 atomic %) :Tm 3÷ (2.5 at. %) :Cr 3+ (nominally

1.5 at. %) :YAG crystal. The chromium concentration of 1.5 atomic % stated byvendor turns out to be

0.8 atomic % based on absorption measurement. The two broad bands in the visible region correspond

to the chromium absorption while the other sharp peaks correspond to the absorption by the holmium

and thulium ions. Armagan, et al.'s work (Ref. 8) showed that the energy transfer processes are more

effective in crystals with low Cr 3+ and high Tm 3+ concentrations.

For high Tm concentrations, the transition from the 3I-I4manifold to the 3F4 manifold induces the

cross relaxation process which provides two Tm ions in the 3F4 manifold from a single Tm ion in the 3I-I4

manifold. As a result, the quantum efficien_cy approaches two. Then, the near resonant energy transfer

process from the 31=4manifold of Tm to the 517manifold of rio provides an efficient pumping mechanism

of the Ho-ions. In order to operate the 2.1 ktm Ho laser efficiently at room temperature, the Ho 3+

concentration must be low. The increase of the Ho 3+ concentration increases the ground state

population of sis of Ho manifold which causes high resonant reabsorption losses for the sI7(Ho) -518(Ho)

423
laser transition. However, as the temperature goes down, the upper levels of the lower laser manifold

of the Ho 3 + become thermally unpopulated. By decreasing the temperature and the population density

of the lower laser levels, the efficiency of the laser performance increases. Since the upper laser level

lifetime of the Ho 3+ is longer than 5 ms when at room temperature, efficient storage time for the

Q-switched operation is possible. A high holmium ion concentration may be effective for high Qswitched laser output since the population in the 517 manifold can be increased.

18-

_, .

u 9£

z

0

: !

0-

300 z_0 S00 _00 ?00 r_00

WAVELEtJGTH {nm}

900

Figure 1. Energy transfer processes in a

Ho:Tm:Cr:YAG crystal.

Figure 2. Absorption spectrum of the

Ho:Tm:Cr:YAG crystal

(0.45% Ho, 2.5% Tm, 0.8% Cr).

Experimental Methods

The experimental configuration used in this _research is shown in Fig. 3. The temperature of the

laser rod was varied from 120°1( to room temperature by circulating cold nitrogen gas around the rod.

The flashlamp was cooled by circulating deionized water. The flashlamp and laser rod were placed in a

pumping cavity made of highly reflective aluminum. This cavity was 76.2 mm long and had an elliptical

cross section with major and minor axes of 152.4 mm and 149.1 mm, respectively. The detailed cavity

design was reported elsewhere. 9 In order to achieve thermal isolation, the entire pumping cavity was

placed in a vacuum system. Good thermal isolation Was necessary since the cooling capacity Of liquid

nitrogen vapor w_ limited. A 450 torr Xefiashlamp with 4 mm bore diameterand 76.2 mm arc length

was used and surrounded by a uranium doped flow tube water jacket to reduce possible solarization

effects. The size of the Ho: Tin: Cr: YAG laser rod used was 4 mm in diameter and 55 mm in length.

Since the Ho: TM: Cr: YAG has a long upper laser level lifetime, the pulse forming network (PFN)

for the flashlamp was designed for long pulse operations. With a 146.5 _f capacitor and a 184 pH

inductor critically damped pulses of 300_s FWHM pulse length were obtained. At the input voltage of

905 volts required for a critically damped pulse, the electrical input energy was 60 J. A highly reflective

mirror at 2.1 pm with a 10m radius of curvature was attached to one end of the vacuum box as a window,

and an antireflection coated quartz fiat was place on the other side of the vacuum box. Flat mirrors with

various reflectivities were used as output couplers. The total resonator length was 88 cm. In Q-switched

operations a lithium niobate crystal (LiNbO3) with dimensions of 9 mmx 9 mm x 25 mm and a ZnSe

polarizer of 2.17 mm thickness were used as a Q-switch. The hold-off voltage for the Q-switch crystal

was 1.62 kV. The Q-switch trigger signal could be delayed from 0 to several ms with respect to the trigger

for the flashlamp.

424
Thelaseroutputenergy and pulse shape were measured with a pyroelectric energy meter and with

a liquid N2 cooled HgCdTe detector, respectively. The bandwidth of the HgCdTe detector was 10 MHz.

t

NrrJ_CG_ Nrr_'33_

.=)

El00'

1-

80'

O

u.] 40 ̧

O

O

.3 2o

nO

Z

60% MIRROR y = 3.16(x.31.93) /

I• 80%MIRROR y = 2.50(x-23.35)

• 95% MIRROR y = 1,05(x-19.37) ,2,'_/

10 20 30 40 50 60 70

ELECTRICAL INPUT ENERGY (J)

Figure 3. Schematic diagram for the

experimental setup.

Figure 4. Normal-mode laser output

energy of the Ho:Tm:Cr:YAG

crystal as a function of electrical

input energy at 150 K.

Results

Fig. 4 shows the normal-mode laser output energies of the Ho(0.45%) :Tm(2.5%) :Cr(0.8%)

•YAG crystal measured as a function of the electrical energy stored in the capacitor for various output

mirror reflectivities at the operating temperature of 150°K. As expected, the slope efficiency and

threshold energy increase with the decreasing mirror reflectivity. The measured normal-mode laser

output energies as a function of operating temperature at various electrical input energies with a 60%

reflectivity mirror are shown in Fig. 5. The decrease of the laser output energy with the increasing

temperature clearly indicates the effect due to thermal population in the lower laser level. Figs. 6 and

7 show the dependence of the laser threshold and slope efficiency, respectively, on the operating

temperature at various mirror reflec_tivities. The highest slope efficiency, 0.36 %, was obtained with a

60% mirror at 120 K, while the lowest extrapolated threshold electrical input energy of 14.8 J was

achieved at 120 K with a 90% mirror. The low slope efficiency may be attributed to several causes. The

laser crystal diameter is relatively small compared to the mode diameter of about 2.8 mm. The Cr 3÷ and

Tm 3+ concentrations in the crystal are low. The laser rod is short compared to the flashlamp and

produces poor optical coupling between the flashlamp and the laser rod. Low cavity reflectivity which

was less than 80% at 633 nm also causes poor optical coupling.

The measured Q-switched and normal-mode laser outputs are plotted in Fig. 8 as a function of

the electrical input energy stored in the capacitor at various temperatures. The output mirror used in

this comparative measurement had a 60% reflectivity and the normal-mode operation was done with

the Q-switch crystal and ZnSE polarizer in the resonator. The Q-switched laser output and slope

efficiency are only slightly lower and the threshold is slightly higher than those of normal mode

operation. The observed slope efficiencies are 0.123% for normal-mode and 0.111% for Q-switched

operation at the operating temperature of 130°K. The Q-switched slope efficiency of the Ho:Tm:Cr"

YAG crystal corresponds to approximately 90% of the normal-mode slope efficiency. The measured

wavelength of the Ho:Tm:Cr-YAG laser with a spectrometer was about 2.095/_m.

425
g_40,

_120'

_100'

_ 80'

_ 60'

W

a 40

0

20

<

6

o 100

o Ein-60J

o * Ein-55J

o • Ein.50J

• o • Ein.45J

• . o + Ein-40J

• o + Ein-35J

o • Eino30J

• • o [] Ein=25J

& • I= • • 0

.f 41,

41, • • • • []

• 4" <. & • I • _ 0

n • L _, ._ .; .: n

120 140 160 180 200 220

OPERATING TEMPERATURE (K)

240

A 6O

W

z

W

40'

Z

-- 30'

O

20'

100 I_0

o 60%MIRROR / /_

i / /--/

_io 2io 2+0

.M_ERA+URE(_

Figure 5. Normal-mode laser output energy

as a function of the operating

temperature with a 60%

reflectivity output mirror.

Figure 6. Threshold input electrical energy

as a function of the operating

temperature with various output

mirror reflectivities.

0.4 t

_'0.31

io2t

_0.1

in

0,0

100

o o

o

o _ MIRROR

• 80=/,MIRROR

O O • 95% MIRROR

o & 98% MIRROR

o o

• o

A & & & & "_" & _ & & & A &

,;o 1_o 2_o

TEMPERATUREtm

260

4O

@

g

3o

m'

[tl

Z

ILl

o

E

_ t0'

2O

rn 130K/Normal y=l+23(x-29.20) //

• 130K/Q-sw y-1.ll(x-30.02) / / / /1

A 150 K,'No,'mal y. 1.24(x-3r.86) .,J:;( / / / I

• 1som+'o-=, y. us(x-3s7o) / / / / I

O 170K/No*'mal y-l.0g(x-45.11) ../.,_ .,,,_/

.,+o.+yy

.... g/.. .. _,..-+ .,.,/+_

30 40 50 60 70

ELECTRICAL INPUT ENERGY (J)

Figure 7. Slope efficiencyas a function of

temperature with various mirror

reflectivities.

Figure 8. Normal-mode and Q-switched

laser output energies as a function

of the input energy with a 60%

reflective mirror.

426
Conclusion

A Ho:Tm:Cr:YAG laser with concentrations of 0.45 at. % Ho, 2.5 at. % Tm and 0.8 at. % Cr has

been studied for both normal mode and Q-switched 2.1/_m laser operation under flashlamp pumping

at various operating temperatures, various output mirror reflectivities, and various input energies.

Continuing work on the evaluation of the other two crystals with different Tm3+-ion concentrations is

in progress and will provide an optimum Tm concentration in the Ho:Tm:Cr'YAG crystal.

Acknowledgments

This work was supported by NASA under grant number NAG-I-877. We acknowledge that Mark

E. Storm and Coherent Technology provided the laser crystals and Lewis G. Burney, Donald Gettemy,

Edward A. Moldin, and Keith E. Murray provided the technical support during the course of this

research work. We also appreciate valuable discussion with Dr. Alfred M. Buoncristiani.

References

1. Johnson, L.F., Boyd, G.D., Nassau, K., Proc. IRE, 1962, 50, 87.

2. Chicklis, E.P., Naiman, C.S., Folweileer, R.C., Gabbe, D.R., Jenssen, H.P., Linz, A. Appl.

Phys. Lett. 1971, 19(4), 119.

3. Barnes, N.P., Gettemy, D.J., IEEE J. Quantum Electron., 1981, QE-17(7), 1303.

4. Lotem, H., Kalisky, Y., Kagan, J., Sagie, D., IEEE J. Quantum Electron., 1988, 24(6), 119.

5. Duczunski, E.W., Huber, G., Appl. Phys. Lett., 1986, 48(23), 1562.

6. Mitzscherlich, P., Tunable Solid-State Lasers II (Edited by Budfor et al.), Springer-Verlag,

New York, 1986, p. 282.

7. Scherbakov, I.A., Tunable Solid-State Laser_ II (Edited by Budgor et al.), Springer-Verlag,

New York, 1986, p. 293.

8. Armagan, G., Di Bartolo,., Buoncristiani, A.M., "Spectroscopic Investigation of the Cr to

Tm Energy Transfer in Yttrium Aluminum Garnet Crystals," to be published. (1989).

9. Gettemy, D.J., Barnes, N.P., Griggs, E., Rev. Sci. Instrum. 1980, 51(9), 1194.

427
N91.-28121 '

EFFECT OF GRINDING ON THE FATIGUE LIFE OF TITANIUM ALLOY

( 5 AI - 2.5 Sn) UNDER DRY AND WET CONDITIONS*

Partha Rangaswamy, Hendra Terutung, and Shaik Jeelani

Materials Research Laboratory

School of Engineering and Architecture

Tuskegee University, AL

ABSTRACT

The principal factors in the performance of aerospace materials are strength-to-weight ratio,

fatigue life, fracture toughness, survivability and, of course, reliability. Machining processes and, in

particular, grinding under adverse conditions have been found to cause damage to surface integrity and

affect the residual stress distribution in the surface and subsurface region. These effects have a direct

bearing on the fatigue life.

In this investigation the effects of grinding conditions on the fatigue life of Titanium 5 AI-2.5Sn

were studied. This alloy is used in ground form in the manufacturing of some critical components in the

space shuttle's main engine. It is essential that materials for such applications be properly characterized

for use in severe service conditions.

Flat sub-size specimens 0.1 inch thick were ground on a surface grinding machine equipped with

a variable speed motor at speeds of 2000-6000 rpm using SiC wheels of grit sizes 60 and 120. The grinding

parameters used in this investigation were chosen from a separate study. The ground specimens were

then fatigued at a selected stress and the resulting lives were compared with that of the virgin material.

The surfaces of the specimens were examined under a scanning electron microscope, and the roughness

and hardness were measured using a standard profilometer and microhardness tester, respectively.

The fatigue life of the ground specimens was found to decrease with the increase in speed for both

dry and wet conditions. For both grit sizes, the fatigue life was lower than that of the virgin material for

the dry condition. The fatigue life of specimens ground under wet conditions showed a significant

increase at the wheel speed of 2000 rpm for both the grit sizes and thereafter decreased with increase

in speed to below that of the virgin material. The results of the investigation are explained using

profilometry, microhardness measurements and scanning electron microscopic examination.

* Work supported by NASA Grant NAG8-068

428
EFFECT OF GRINDING ON THE FATIGUE LIFE OF TITANIUM ALLOY

( 5 AI - 2.5 Sn) UNDER DRY AND WET CONDITIONS

Introduction

Titanium alloys are extensively used in aerospace applications because they meet the design and

service requirements. It is observed that during manufacturing the consistent preservation of their

inherent strength is difficult to achieve. Catastrophic failures have resulted from damage to the surface

integrity by machining during manufacturing. Therefore, manufacturing procedures are required to be

specified to avoid damage to thc surface and the sub-surface, and, if possible, to specify processing which

will enhance part performance. This makes it imperative for the design engineer to possess complete

information about the surface characteristics of a component and the mechanical properties of the bulk

material before the component is designed so that manufacturing procedures could be suggested to

withstand service conditions such as fatigue, creep and stress corrosion cracking [1-3]. Previous

investigations have shown that in the machining of mctals a damaged surfaced region is produced that

is diffcrent from the bulk of the material [4-7]. Changes in material surface properties can, in turn,

influcnce mechanical properties of which fatigue life and stress corrosion resistance are usually of the

most concern [8-11].

Of the various material removal processes studied to date, grinding causes the most impact on

material properties [12,13]. Grinding is an abrasive machining process (more precisely termed micromachining process) and it differs from machining in that grinding speeds are much faster, depth of cut

smaller and there is very little quantitative information on the geometry of individual grits at the

periphery of grinding whecis. Studies on surface alterations due to grinding have revealed that the extent

of deformed layer depends on the size of the grit as well as its rake angle, grinding speed and depth of

cut [14]. Studies carried out on grinding of titanium and titanium alloys (Ti-6AI-4V) have also revealed

that a large scale rcdeposition of metal on the surface accounts for poor surface finish at high speeds

using silicon carbidc (SIC) and aluminum oxide(Al203) grinding wheels [15]. Also, the high temperatures developed at the whcel-work interface due to the vast range of process parameters involving rapid

rates of material removal have led to lowering the level of surface integrity and producing extremely

complex pattern of residual stress distribution [8,12]. These factors have a detrimental effect on the

fatigue strength and the fatigue life of the components.

The objective of this research was to investigate the effects of grinding on the fatigue life of

Ti-5AI-2.5Sn at room temperature under dry and wet conditions. There are no data available at the test

range considered in this work to showwhat effect, if any, grinding has on the fatigue life of a Ti-5A1-2.5Sn

alloy at various grinding speeds and for various grit sizes.

429
Experimental Work:

A) Specimen Preparation

The Ti-5Al-2.5Sn alloy used in this investigation is an alpha type alloy and is the most widely used

commercial alloy in this group. It exhibits excellent fracture toughness and corrosive resistance and is

widely used for structural and cryogenics applications. Mechanical properties and chemical composition

of the material are give in Tables 1 and 2, respectively.

The sub-sized specimen and the loading grips used in this investigation to hold it were selected

from the work done earlier by Jeelani et al [17]. The specimen was designed with 0.1 inch gauge section

width and 1.0 inch gauge section length. The specimen thickness was 0.1 inch. These specimens were

made as per the specification shown in Figure 1, on a numerically controlled machining center. These

specimens were made out of a 2-inch Iongflat plate, 0.75 inch wide _iiad 0_i25 inch in thickness.

After the specimens were fabricated, they were annealed by heating and holding at 1400 ° for 60

minutes and at 1600 ° for 10 minutes and then cooling in air. Stress relieving was performed by soaking

the specimens for 1 hour at 1000°E However, it should be noted that Ti-5AI-2.5Sn cannot be hardened

by heat treatment. It is used only in annealed condition [18].

The oxidized layer and the too!marks and other surface irregularities were removed by wet

grinding/polishing using silicon carbide emery papers of sizes ranging from 60 to 4000 grits per square

inch.

B) Grinding Tests

The grinding of all the specimens was carried on a precision surface grinding machine, (BOYARSCHULTZ 1A618 Hydraulic Surface Grinder), equipped with a 2 hp variable speed motor (0-6000

rpm) powered by Volkmann Drives 2 HP Adjustable drive unit which converts the fixed input AC

frequency to the motor to a variable frequency range, thus changing the usually fixed motor speed to

variable speed.

Grinding was carried out with silicon carbide (39C60H8VK and 39C12018VK) wheels. The wheels

were of 6 inch diameter and 1/2 inch width received in dressed condition (coarse dressing). Grinding

wheel speeds of 2000 - 4000 - 6000 rpm were used and a table speed of 40 rpm. All grinding tests were

made in a single pass. Table 3 shows a summary of the grinding conditions used in this investigation.

These conditions are based on the recommendations of the METCUT [12].

C) Fatigue Testing

For testing the virgin and the ground specimens a direct tension-compression fatigue testing

machine (Fatigue Dynamics Model DS-6000 HLM) which is equipped with a hydraulic load maintainer

was used. It adjusts the preload continuously to preset value without affecting the cyclical load. The

cyclical load can be adjusted manually up to 6000 pound force. The test frequency of the machine ranges

from 600 to 2200 cycles/minute. A load cell is provided to read tensile or compressive load on the

specimen, directly. The load cell is connected to the strain indicator which is calibrated to read the load

on the specimen. A stress ratio of R = 0 was used in this investigation. Throughout the test, the cycle

speed was maintained constant at 200 cycles per minute. Tests were performed at room temperature.

430
D) Surface Examination

Small pieces approximately 0.25 X 0.25 inch were cut from all virgin and ground specimens. The

pieces were cleaned in an aqueous methanol solution, and were then air dried. The ground surfaces

were examined by a scanning electron microscope over a wide range of magnification.

A Bendix profilometer group 7L equipped with a Sheffield Profilometer, Model QED-6, Digital

amplifier, Sheffield Profilometer type VEG Gated Pilator and type LK tracer with Ft skidmount was

used to measure the roughness of the surfaces produced. A tracer stroke of 0.5 inch was used with a

selected cut-off of 0.0125 inch. The roughness measurements were made on the specimens in the

direction parallel to the work-tool motion. Surface roughness measurements of the parent metal

specimens as well as those of the ground specimens were taken.

Microhardness measurements using Buhler Micromet II Digital Microhardness tester were made

on the ground surfaces produced at all wheel peripheral speeds. At least five measurements were made

on each specimen and the average taken for comparison.

Results and Discussion

Figure 2 shows the S-N diagram generated by using 30 polished specimens of Ti-5AI-2.5Sn alloy.

Approximately five specimens were tested at each stress level and the fatigue life data were obtained

at five stress levels. A software called Grapher especially used for producing two-dimensional graphs

was used to produce the S-N curve. Point REF in the diagram, which corresponds to a stress of 100,000

psi and the fatigue life of 125,000 cycles was used as a reference for comparison of the lives of the

specimens ground under various conditions used in this investigation.

Figure 3 shows the effect of the type and speed of the grinding wheel and the presence or absence

of the cutting fluid on the fatigue life of the specimens. Each data point on the graph represents an

average of five tests. For the specimens ground with wheels of both grit sizes (60 and 120) the fatigue

life decreases with an increase in the speed. This trend is consistent with the data published in previous

studies [8,19,20]. The fatigue life of the specimens ground under dry conditions was lower than that of

the virgin specimens. Dry grinding is also termed abusive grinding, which has been shown to cause severe

damage to the surface integrity and affect the residual distribution at the surface, lowering the fatigue

strength, therefore resulting in lowered fatigue life. Published data have indicated that dry grinding

generally produces tensile stress near to the surface under conditions far from low stress condition

[7,21,22].

Figure 4 shows the variation in the surface roughness due to a change in the type and speed of the

grinding wheel and the presence or absence of the cutting fluid. It can be seen that for all the grinding

conditions used in this investigation the surface roughness is higher than that of the virgin material, and

increases as the grinding speed is increased. The presence of cutting fluid in the grinding region has

decreased the surface roughness, but the change does not appear to be significant. The graph shows

that the surface roughness changes due to a change in the grit size of the grinding wheel, but the change

is not significant enough to establish a trend.

Figure 5 shows the variation in the microhardness due to a change in the type and speed of the

grinding wheel and the presence or absence of the cutting fluid. For all the grinding conditions used in

this investigation it can be seen that the microhardness values show a decrease in hardness with an

431
increase in grinding speed. The presence of cutting fluid slightly increases the hardness values of the

specimens ground under wet conditions as compared with the specimens ground dry. At the low grinding

speed of 2000 fpm the hardness of the specimens ground under wet conditions is higher than that of

specimens ground dry. This trend is consistent up to 4000 fpm but thereafter it is observed that with an

increase in the grinding speed the specimens ground with the wheel of grit size 120 for both the dry and

wet conditions show slightly higher hardness values than those of the specimens ground with the wheel

of 60 grit size. Here again, the graph shows that the microhardness changes due to a change in the grit

size of the grinding wheel, but again, the change is not significant enough to establish a trend.

The scanning electron micrographs of the surfaces produced under both dry and wet conditions

showed that the surfaces consisted of microcracks and tears showing plowing of the metal by the abrasive

action of the grit, evidence of large scale plastic deformation, redeposition and cavities. The texture

showed grooves of non-uniform width and spacing for all the grinding speeds [23].

Figures 6a and 6b show scanning electron photomicrographs of the surfaces produced when

ground under dry conditions with the wheel of 60 grit size at the lowest and highest grinding speed in

the range tested. These photomicrographs reveal a drastic change in texture ranging from long straight

grooves parallel to the wheel-work direction to short discontinuous grooves which vary in width and

depth with an increase in the grinding speed. This also explains the high roughness values obtained with

increase in speed. It was also observed that at a speed of 6000 rpm the ground surfaces revealed cracks

and microcracks for both the grit sizes. The cracking occurs because of the generation of heat during

the transfer of metal (redeposition) back onto the ground surface at high speeds and subsequent rapid

cooling. These cracks and microcracks could be one of the reasons for the decrease in fatigue life of

the specimens ground under dry conditions at higher speeds. The effects of rubbing, plowing and cutting,

characteristic of the grinding process, were present for all three speeds [12].

Figures 7a and 7b show scanning electron photomicrographs of the surfaces produced when

ground under wet conditions with the wheel of 60 grit size at the lowest and highest grinding speed in

the range tested. The texture was well defined at the low grinding speed of 2000 fpm indicating that

considerably lesser amounts of redeposition on the surface had taken place. Also, the micrographs

revealed that the extent of severity of damage caused to the surface was considerably less than the

surface ground under dry conditions. But at the speed of 6000 rpm, the surface did reveal cracks

transverse to the direction of grinding similar to that of the surfaces ground under dry conditions which

had resulted in a considerable decrease in fatigue life. This shows that the presence of cutting fluid,

which appreciably reduced the wheel-workpiece temperature and also aided in removing the grinding

chips, thereby minimizing redeposition, had virtually no effect in preventing damage to the surface in

the form of cracks as a result of increase in process intensity caused by an increase in grinding speed.

Studies have shown that grinding carried out at low speeds in the presence of a lubricant results

in producing residual stresses which are compressive in nature in the surface and sub-surface region

[12]. For the titanium alloy used in this investigation, there are no data reported yet concerning the

nature of the residual stresses in the surface and subsurface due to grinding.

The surface roughness measurements also show that the roughness increases with an increase in

the grinding speed, an observation which is supported by the SEM photomicrographs as shown in

Figures 6 and 7. It is to be noted as mentioned earlier that this particular alloy cannot be hardened and

therefore the high temperatures reached due to heat generated at the work-wheel interface anneal the

workpiece, thereby softening the workpiece at the surface and the sub-surface region. This is one of

the reasons for the microhardness measurement showing a decrease with an increase in the grinding

432
speed. Also, visual examination of the surface of the specimens ground under dry condition at high

speeds showed evidence of burnt marks.

Conclusion

From the results of the investigation of the effect of grinding conditions on the fatigue life of

Titanium 5AL-2.5Sn, the following conclusions may be drawn:

. The results of the study indicated that fatigue life of the specimens decreased

considerably with an increase in the speed. The fatigue life of the specimens ground

under dry conditions was lower than that of the virgin specimens for the speed range

tested. The fatigue life of the specimens ground with cutting fluid was higher than

that of the virgin specimens in the range of 2000 - 4000 rpm.

. The results of surface roughness measurements over the entire speed range of the

ground specimens showed an increase in roughness with an increase in the speed.

The roughness values of the specimens ground under dry and wet conditions were

higher than those of the virgin specimens. The roughness of the specimens ground

under dry conditions was higher than that of the specimens ground under wet

conditions at all speeds and for both grit sizes.

. The microhardness measurements for both the grit sizes and for both the dry and wet

conditions used in this investigation showed a decreasing trend in hardness for all the

speeds.

4. The grit sizes of the grinding wheel selected for this study showed no significant effect

on the fatigue life.

References

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steel, 6242-titanium alloy, and red brass". M.S. Thesis, Tuskegee Institute, 1979.

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433
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processes", Technical Paper MRR76-12, Society of Manufacturing Engineers, Dearbon,

MI, 1976.

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of 2024-T351 aluminium alloy", In J Fatigue 6 No 3 (1984) pp 169-172.

11. Jeelani, S. and Collins, M.R. "Effect of electric discharge machining on the fatigue life of

Inconel 718", in J Fatigue 10 no 2 (1988) pp 121-125.

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Materials Science and Engineering, 21 (1975) pp 261-271.

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(Ti-6AI-4V)", Wear., 104, 1985 pp 323-335.

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No 3 (1986) pp 159-164.

17. D.O.D. Aerospace Structural Metals Handbook, Vol. 4, Code 3706, pp 1-13.

18. Kahles, J.F., Field, M., Eylon, D. and Froes, F.H. "Machining of Titanium alloys", Journal

of Metals, 1985 pp 27-35.

19. Imamn M.A. and Gilmore, D.M. "Fatigue and microstructural properties of quenched

Ti-6AI-4V", Met. Trans. (A) 14A, 1983 pp233.

20. Leverant, G.R., Langer, B.S., Yuen, A. and Hopkins, S.W. "Surface residual stresses,

surface topography and the fatigue behavior of Ti-6AI-4V", Met. Trans. (A) 10A 1979

pp 251-257.

434
21. Takemato,T., Jimg,K.L.,Tsakalakos,T., Weissmann, S. and Dramer, I.R. "The

importance of surface layer on fatigue behavior on a Ti-6AI-4V alloy." Met. Trans. (A)

14A 1983 pp 127-132.

22. Rangaswamy, Partha., "Effect of grinding on the fatigue life of Ti-SAI-2.SSn under

unlubricated conditions", M.S. Thesis, Tuskegee Institute, 1989.

23. Terutung, Hendra., "Effect of grinding on the fatigue life of Ti-5AI-2.5Sn under

lubricated conditions", M.S. Thesis, Tuskegee Institute, 1989.

Acknowledgments

The authors gratefully acknowledge the support of NASA- Marshall Space Flight Center through

Grant NAG8-068 for this study.

435
TABLE 1. MECHANICAL AND PHYSICAL PROPERTIES OF TITANIUM 5AL 2.5 SN

Ultimate Tensile Stength

Yield Strength (0.2 % offset)

Hardness (Rockwell C)

Elongation in 2 in.

Reduction of Area

Impact, Charpy V

Rupture Stress

Modulus of Elasticity, tension

Modulus of Elasticity, torsion

Density

Melting Range

Sp. Elec. Resis.

Specific Heat

Mean Coeff. of Ther. Exp.,/oF

120 Ksi

115 Ksi

36 Rc

10 %

25 %

19 Ft.lb

108 Ksi

16 Mpsi

6.5 Mpsi

0.162 lb/cu in.

2822-3000 oF

157 10-6Ohm-cm

0.125 (Btu/IboF)

5.2 X 10-6

TABLE 2. CHEMICAL COMPOSITION

Element Percent (weight)

AI 4.0 - 6.0

C 0.15

H 0.003 - 0.020

Fe 0.5

Mn 0.3

N 0.07

O 0.2

Sn 2.0 - 3.0

Ti Balance

TABLE 3. SUMMARY OF GRINDING CONDITIONS

Wheel Type

Wheel Speed(fpm)

Table Speed(flSm)

Down Feed per pass(inch/pass)

CnroSs Feed(inch/pass)

eel t.,lassmcatlon

39C60H8VK. 39C 12018VK

2000, 4000, 6000

50

0.0005 (16 passes,)*

0.0004 t z passes)

0.0002 ( 6 passes)**

0.05

Soft grade ( H, I)

pen _tructure (8)

Grain _ize t oo, 12)

"All Grinding done in Single Pass

"'Wheel Dressed before Final Pass ( Coarse dressing done to maintain sharpness)

436
30" 30"

0.75

all

i [ I

dimensions in

--4- --- 0.1

i

m

1

_ 1

- j

0.2125

inches

Figure 1. Fatigue specimen.

437
0

m,-i

M

m

120

100

80

60

40

l0 s

S-N curve

ar'enf metal

itanlum Allo Y

(5 AI and 2.5 Sn)

I I I Iml[I I i i Illll I I I I Illll I

l0 ' 10 = 10 '

Number of Cycles

REF

I I I I lilt I I

10 7

Figure 2. S/N Diagram for Titanium alloy virgin material.

438
O

300

H

="

4)

¢J

¢J

lO0

0

0

FATIGUE LIFE COMPARISON

0--- --0-- --0

; 0 ;

,o.,.° ,. to.o ,o • • •

DRY GROUND 60

WET GROUND 60

DRY GROUND 120

WET GROUND 120

VIRGIN

Selected stress level = I00,000 psi

i I I I [ i I i I [ I I I I [ I I i

2000 4000 6000

IrheeI speed (ft/min)

1

8000

Figure 3. Fatigue life vs wheel speed: virgin material and ground specimens.

439
4O

O

¢130

Io

0

0

Ild

_10

0 I

0

SURFACE ROUGHNESS COMPARISON

0-- --0-- ---0

A A A

v v •

DRY GROUND 6O

WET GROUND 60

DRY GROUND 120

WET GROUND 120

VIRGIN

...O

i , i I l i i , I i i i i I i J i

2000 4000 6000

Wheel speed (ft/min)

1

8000

Figure 4. Surface roughness vs wheel speed: virgin material and ground specimens.

440

f
VICKERS HARDNESS COMPARISON

o---¢----o DRY GROUND 60

I000- -" : : WET GROUND 60

0----¢-- -0 DRY GROUND 120

_, : : WET GROUND 120

" •................ VIRGIN

800

600 .................

% l,d

400

200

0 l , , i I ' i i , I i i i , I i

0 2000 4000 6000

Wheel speed (ft/min)

i ! 1

8000

Figure 5. Vickers hardness vs wheel speed: virgin material and ground specimens.

441
Figure 6. Scanning electron micrographs of surfaces ground under dry condition:

(a) magnification X150, grinding speed 2000 feet/minute.

(b) magnification X150, grinding speed 6000 feet/minute.

Figure 7. Scanning electron micrographs of surfaces ground under wet condition:

(a) magnification X150, grinding speed 2000 feet/minute.

(b) magnification X150, grinding speed 6000 feet/minute.

442

ORIGiN._L PAGE IS

OF PO0_ QI!_I.LIT Y
N91-28122

ENGINEERING MANAGEMENT OF LARGE SCALE SYSTEMS

Serita Sanders, Tepper L. Gill, and Arthur S. Paul

Department of Electrical Engineering

and

Department of Systems & Computer Science

Howard University

Washington, D.C.

Introduction

The organization of high technology and engineering problem solving, has given rise to an

emerging concept. Reasoning principles for integrating traditional engineering problem solving with

systems theory, management sciences, behavioral decision theory, and planning and design approaches

can be incorporated into a methodological approach to solving problems with a long range perspective.

Long range planning has a great potential to improve productivity by using a systematic and

organized approach. Thus, efficiency and cost effectiveness are the driving forces in promoting the

organization of engineering problems. : .....

This paper broadly covers aspects of systems engineering that provide an understanding of

management of large scale systems. Due to the focus and application of research, other significant

factors (e.g. human behavior, decision making, etc.) were not emphasized but were considered.

i 7 _ i i

Systems Engineering Concepts

A. Definition and Objective of Systems Engineering

A system is a combination of parts or elements to form a unitary whole. Systems engineering is a

management of technology. This is accomplished by the following activities: (1) Transforming an

operational need into a description of systems performance parameters and a systems configuration

through the use of a process of definition, synthesis, analysis, design, test, and evaluation; (2) Integrating

related technical parameters and ensuring compatibility of all physical, functional, and program

interfaces in a manner that optimizes the total system definition and design; and (3) Integrating

reliability, maintainability, safety, survivability, human, and other such factors into the total engineering

effort to meet cost, schedule, and technical performance objectives.

443
A uniform systems engineering process is required to manage projects because:

1. The science and technology required to design and produce a completely integrated and

coherent system exceeds any one person's capability to master;

2. There is a need for a communication vehicle for specialists with dissimilar technical

knowledge, skills, and interests to contribute to an integrated system design

and development process; and

3. Systems engineering, to be effective, must provide the process for making many

technical and management decisions progressively as the need occurs in system design

and development.

B. System Life Cycle

A life cycle is used to develop a system. It begins with the initial identification of a need and extends

through planning, research, design, production or construction, evaluation, consumer use, field support,

and an ultimate product phase out (illustrated in figure 1).

Challenges of Large Scale Systems

A. Large product organization

Large scale systems require combined inputs of specialists representing a wide variety of engineering disciplines. These engineers must be able to communicate with one another as well as be conversant

with such interface areas as purchasing, accounting, personnel management, and to some extent legal

requirements. Technological and economic feasibility are no longer the main determinants for the

engineer.

Large scale systems usually require fluctuating the manpower loading, and depending on the

functions to be performed on the project, applying a phase-by-phase development process implementation.

Subcontracting is a major factor associated with large projects. The development of large scale

systems can involve extensive contracting and subcontracting.

B. Technological growth and change

Technological growth occurs continuously and is stimulated by an attempt to respond to some

unmet current need and/or to perform on-going activities in a more effective and efficient manner. In

addition, these changes are being stimulated by social changes, political objectives and ecological

factors.

444

z
Figure 1

A life cycle is used to integrat e various support mechanisms

that ultimately bring a system into existence.

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Identification

of Need

System

Planning

Function

System

Research

Function

System

Design

Function

Production

and/or

Construction

Function

System

Evaluation

Function

System

Use and

Logistic Support

Function

"Wants or desires" for systems (because

of obvious deficiencies/problems or

made evident through basic research

results_.

Marketing analysis; feasibility study;

advanced system planning (system

selection, specifications and plans,

acquisition plan research/design/

production, evaluation plan, system

use and logistic support plan);

planning review; proposal.

Basic research: applied research

("need" oriented): research methods:

results of research: evolution from

basic research to system design and

development.

Design requirements; conceptual design;

preliminary system design: detailed

design: design support; engineering

model/prototype development: transition

from design to production.

Production and/or construction

requirements; industrial engineering

and operations analysis (plant

engineering, manufacturing engineering,

methods engineering, production control):

quality control: production operations.

Evaluation requirements; categories

of test and evaluation: test preparation

phase Iplanning, resource requirements,

etc_; formal test and evaluation: data

collection, analysis, reporting, and

corrective action: retesting.

System distribution and operational

use: elements of logistics and life

cycle maintenance support: system

evaluation; modifications, product

phase-out: material disposal, reclamation,

and. or recycling.

445
Systems Engineering Management

Systems engineering management (SEM) provides the necessary overview functions to ensure

that all required engineering disciplines and related specialties are properly integrated (Figure 2). These

functions include planning, organizing and staffing, monitoring, and controlling which are used to

design, develop and produce a system that will meet the stated need in an effective manner. The result

is a system that has the proper mix of resource hardware, software, facilities, personnel, and data. The

underlying objective is to produce a system at the right location, at the right time, with a minimum

expenditure of resources.

A. Planning

Planning is a process for developing and formulating a course of action to be taken in the future.

The systems engineering management plan includes the appropriate planning information for the

project as an entity. All projects should include a single top level document of this type to provide

successful project guidance.

B. Organizing and Staffing

The first step in organizing the project is to determine the governing activities. Grouping these

identified activities in terms of a functional oriented structure of some type (e.g. unit, group, department, or division) establishes organization. Staffing the structure with appropriate personnel skills to

perform the designated activities in a coordinated manner is the next step.

C. Monitoring

Figure 3 is a basic milestone chart that gives the status of the project at a glance. It includes

scheduled, actual and anticipated completion dates. This allows for careful scrutiny of the project status.

D. Directing and Controlling

Directing program implementation consists of day-to-day managerial functions and the identification of responsibilities to ensure that project objective(s) are met. Project control is the sustaining of

on-going management activity that will guide, monitor, and evaluate project accomplishment by the

stated objective(s).

446
Systems Engineering Management

Reliability

program plan

ity

program plan

Program 1

requirements

I

Program J

management

plan (PMP)

Integrated

test plan

Manufacturing

program plan

factors

program plan

SYSTEM

ENGINEERING

MANAGEMENT

PLAN

Quality

assurance

program

plan

Safety

engineering

plan

Functional "

plan(s) design Sgra.ted" _ Other plans

! logistic I

supp_

Supplier

program plan(sl

Figure 2.

Program Plan Relationships

This figure depicts the relationship between the PMP and governing activity,

all of which need systems engineering management for preparation.

447
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448

C_

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_J

.__
Summary

Considering the following questions when implementing systems engineering practices will ensure

a well managed system of any magnitude.

1. Have systems engineering tasks been identified?

2. Have the responsibilities for systems engineering functions been established?

3. Has a systems management plan been developed?

4. Have detailed program plans been developed for reliability and maintainability?

5. Has a corrective action procedure been established to handle proposed system changes?

6. Have conceptual system equipment and critical design reviews been scheduled?

References

1. Blanchard, B.S. and Fabrycky, W.J. Systems Engineering and Analysis. (Englewood Cliffs,

New Jersey: Prentice-Hall), 1981.

2. Churchman, C. West, The Systems Approach, (New York: Dell Publishing Co., Inc.) 1968.

3. Hall, Arthur D., A Methodolo_ for Systems Engineering, (New York: Van Nostrand

Reinhold Company), 1962.

. Mission Operations and Data Systems Directorate System Management Policy., (Greenbelt,

Maryland: NASA Goddard Space Flight Center), 1986.

5. Nadler, Gerald, "Systems Methodology and Design", (IEEE, Vol. 15, No. 6) November/

December 1985.

o Sage, Andrew P., Methodology for Large Scale Systems, (New York: McGraw-Hill Book

Company), 1977.

449
N91-' 8 123 &,

AN EVALUATION OF THE INTERFACIAL BOND PROPERTIES

BETWEEN CARBON PHENOLIC AND GLASS PHENOLIC COMPOSITES*

¢ Kelvin Jordan

Hughes Aircraft Company

Tucson, Arizona

Raymond Clinton

NASA - Marshall Space Flight Center

Huntsville, Alabama

Shaik Jeelani

Materials Research Laboratory

Tuskegee University, Tuskegee, Alabama

ABSTRACT

The effects of moisture and surface finish on the mechanical and physical properties of the

interfacial bond between the carbon/phenolic (C/P) and glass/phenolic (G/P) composite materials are

presented in this paper.

Four flat panel laminates were fabricated using the C/P and G/P materials. Of the four laminates,

one panel was fabricated in which the C/P and G/P materials were cured simultaneously. It was identified

as the cocure. The remaining laminates were processed with an initial simultaneous cure of the three

C/P billets. Two surface finishes, one on each half, were applied to the top surface. Prior to the

application and cure of the G/P material to the machined surface of the three C/P panels, each was

subjected to the specific environmental conditioning. Types of conditioning included: (a) nominal

fabrication environment, (b) a prescribed drying cycle, and (c) a total immersion in water at 160°F.

Physical property tests were performed on specimens removed from the C/P materials of each

laminate for determination of the specific gravity, residual volatiles and resin content. Comparison of

results with shuttle solid rocket motor (SRM) nozzle material specifications verified that the materials

used in fabricating the laminates met acceptance criteria and were representative of SRM nozzle

materials.

Mechanical property tests were performed at room temperature on specimens removed from the

G/P, the C/P and the interface between the two materials for each laminate. The double-notched shear

strength test was used to determine the ultimate interlaminar shear strength. Results indicate no

appreciable difference in the C/P material of the four laminates with the exception of the cocure

laminate, where a 20 percent reduction in the strength was observed. The most significant effect

occurred in the bondline specimens. The failure mode was shifted from the C/P material to the interface

and the ultimate strength was significantly reduced in the wet material. No appreciable variation was

noted between the surface finishes in the wet laminate.

*Work supported by NASA Grant

450
AN EVALUATION OF THE INTERFACIAL BOND PROPERTIES

BETWEEN CARBON PHENOLIC AND GLASS PHENOLIC COMPOSITES

Introduction

The Space Shuttle's solid rocket motor (SRM) nozzle is constructed from carbon/phenolic (C/P)

and glass/phenolic (G/P) composite material. The C/P is used as the outer or ablative material of the

nozzle ring and it is backed by a thin G/P insulator. These composite rings are adhesively bonded to a

structural metal housing, forming the nozzle. Anomalies in performance of the ablative material during

flight and static testing have stimulated research to examine the effects of moisture, cure cycles and

surface finish on the integrity of the interfacial bond between G/P and the C/P rings.

It is well recognized and reported that the high performance composites absorb moisture from

their surrounding environments, especially under warm and humid conditions [1-6]. In epoxy-based

composites, absorbed moisture has been shown to affect the matrix and the interface dominated

properties of the composite. Degradation is evident in the interlaminar shear strength and ultimate

strength specifically, as well as other mechanical properties [1-11]. In contrast to the fairly large

literature base for the epoxy-based composites, the phenolic-based composites have essentially remained unstudied with respect to the effect of moisture.

The objective of this research was to assess the integrity of the interfacial bond between the C/P

and the G/P material as a function of the moisture/volatile content present in the C/P material prior to

the bonding of the G/P material. Another variable, the effect of surface finish applied to the bonding

surface of the C/P prior to the bonding of the G/P material, was also investigated.

Materials

Materials were obtained from the Wasatch Division of Morton Thiokol Incorporated (MTI) for

use in nozzle material development research. MTI purchased the materials in the form of 48-inch width

preimpregnated (prepreg) broadgoods from the Fiberite Corporation. The C/P and G/P materials are

designated by Fiberite as MX-4926 and MXB-6001, respectively. The constituent materials of the

MX-4926 prepreg were Polycarbon CSA, an eight-harness satin rayon-based carbon fabric, Borden's

SC1008 phenolic resin system and Fiberite 1148 carbon black filler. The constituent materials of the

MXB-6001 were United Merchant 184 weave S-glass fabric and Borden's SC1008 phenolic resin system.

A series of physical property tests were conducted on the prepreg materials to ensure conformity

with MTI material acceptance specifications, STW5-2651F and STW5-3279A from the G/P and C/P

materials, respectively [12,13]. The critical properties measured to assess the quality of the materials

were the resin content, filler content, volatile content, resin flow, sodium content and cloth content.

A summary of the prepreg acceptance test results may be found elsewhere [14]. All prepreg

physical properties met the acceptance criteria stated in MTI specifications. Based on the compliance

of all the prepreg physical properties with the specification limits, the materials were accepted for use

in the program.

451
Carbon-phenolic and glass-phenolic 10 inch (fill) by 12 inch (warp) plies were arranged in stacks

which when cured yielded an inch thick laminate. The C/P and G/P stacks contained 84 and 40 plies

respectively with the J-type 30 gage thermocouples place at the designated plies to monitor temperatures during debulking and subsequent curing.

The C/P and G/P stacks were individually debulked in a tetrahedron press to 86 percent of their

cured density simulating the nominal debulk obtained during the tape wrapping of the materials during

the processing of SRM nozzle components.

3. Fabrication of Glass-Phenolic and Carbon-Phenolic Test Articles:

a) Lay-up and Cure of Carbon-Phenolic Laminates:

Three C/P laminates were assembled using the six debulked stacks CP-1 thru CP-6 (figure 1) as

follows: (a) Panel A consisted of stacks CP-1 and CP-2, (b) Panel B consisted of stacks CP-3 and CP-4,

and (c) Panel C consisted of stacks CP-5 and CP-6. The three panels were assembled and bagged on a

trilateralcure tool. The hydroclave trilateral tool was designed to simultaneously cure three fiat panel

laminates with cured thickness of 2.5 inches each. The laminates were cured according to the hydroclave

cure cycle designed by MTI [15].

After the cure, the laminates were nondestructively examined using X-rays to ensure the quality

of each. No low density indications or delaminations were observed in any of the laminates.

b) Surface Preparation:

For investigation of the interfacial properties, precise and reproducible duplications of the surface

finishes are critical to the creditability and validity of the results. Surface finishes of 125 and 250

microinches were precisely duplicated to match the finishes produced at MTI. The 250 microinch

surface finish (maximum upper limit) is applied by MTI to cured C/P surfaces of SRM nozzle

components, prior to over-wrap of the G/P insulator.

c) Conditioning:

The panels were subjected to prescribed environmental conditioning detailed in the following

sections.

Panel A. Panel A (also identified as the as-received panel) was the control. This laminate was fabricated

according to nominal processing conditions and environments. In this manner, it represented the typical

state of the SRM C/P material prior to the overwrap and curing of the G/P insulator.

Panel B. Many authors have noted that microcracking was induced in polymeric materials when the =

material was subjected to extreme thermal gradients [2,8,11,16]. This damage to the material was =

irreversible and resulted in degradation of the ultimate interlaminar shear strength and ultimate tensile

strength. Such damage can be unintentionally created in materials during conditioning if sufficient

precautions are not observed.

452
In the phenolic-based composites, there are additional concerns relating to potential effects on

the properties by changing the state of cure when these materials are subjected to extreme thermal

gradients.

A research program was initiated at Southern Research Institute (SRI) [17] to determine an

effective and nondamaging drying process for C/P materials, which provided accelerated weight loss

without altering the cured state or microcracking in one-half inch cube samples.

Panel B (also identified as the dry panel) was subjected to a modified SRI drying cycle which

included corrections for size and shape of the laminates. The drying cycle was designed to yield drying

of the bonding surface to a depth of 0.50 inches into the thickness of the laminate. The cycle was as

follows:

a. Dessicate for 66 days,

b. Dry at 100 o F and 0.1 Torr vacuum for 11 days,

c. Dry at 140 o F and 0.1 Torr vacuum for 6 days,

d. Dry at 160 o F and 0.1 Torr vacuum for 13 days.

Panel C (also identified as the wet panel) was subjected to controlled moisture conditioning. It

was originally placed into an environmental chamber maintained at 160 °F and 95% relative humidity

(RH). After 47 days in the chamber, the panel was relocated and submerged in water at 160 °F with the

machined surface placed upward in a pan. This was done to accelerate the absorption process.

Percent weight gain versus time data were plotted as shown in Figure 2. The conditioning resulted

in a 0.96 percent weight gain.

d) Lay-up and Cure of Glass/Phenolic to Carbon/Phenolic Laminates:

Lay-up and cure of the G/P immediately followed the conditioning of the C/P laminates. Prior to

the lay-up of the G/P debulked stacks, the stacks GP-1 thru GP-3 (Figure 3) were machined to equal

the dimensions of their respective C_ laminates. The lay-up and bagging sequences for cure may be

found in reference [14]. The composite laminates were machined and test sections removed.

e) Lay-up and Cure of Cocure Laminate:

A COCURE laminate was fabricated using the debulked C/P stacks CP-7 and CP-8 and the

debulked G/P stack GP-4. The laminate was assembled and cured according to the autoclave cure cycle

presented in [18]. The cured laminate was machined and test sections removed.

Experimental Testing and Examination

a) Physical Property Tests:

A series of physical property test were conducted on the C/P and G/P materials of each cured

laminate to ensure the quality of the materials after curing. The tests were performed according to the

procedures contained in the MTI cured material acceptance specification STW5-2845D, which con453
sistedof residual volatile content, specific gravity and resin content [19]. The MTI specifications require

that resin content tests be performed using the tested residual volatile specimens. The same test

geometry was used for each of the above three tests. The specimen geometry/s shown in Figure 4.

b) Optical Photomicroseopy:

Optical photomicroscopy examinations were conducted on specimens taken from the C/P, G/P

and at the interfaces of each laminate. The objectives were to : (a) observe material for possible

microstructural damage; (b) characterize the appearance of the microstructure of the C/P and G/P

materials; and (c) characterize the appearance of the different interfaces between the C/P and G/P

laminates. A typical final machined specimen is presented in Figure 5. Prior to the examination, each

specimen was mounted in epoxy and then polished. Photomicrographs were taken of each specimen at

several magnifications.

c) lnterlaminar Shear Strength Test:

Matrix/interface dominated properties are considered to be among the most critical to solid rocket

motor nozzles and the critical failure mode for phenolics was determined to be delamination [20].

Observations made in the past after static and flight tests, which support delamination as being the

critical failure mode, include ply-lift in the virgin C/P material and separation of the insulating (G/P)

material from the ablative (C/P) material The critical properties for prediction of the margin of safety

for delamination at the G/P and C/P interface are interlaminar shear and across-ply tension. In this

program, the property selected for evaluation of surface finish and moisture effects on the interface

between the C/P and G/P materials was interlaminar shear strength. A double-notched shear specimen

was used for the determination of the ultimate interlaminar shear strength at room temperature (70°10

for the C/P, G/P and at the interface between these materials.

The basic cutting plans for the specimen removal may be found elsewhere [14]. Specimens were

first excised as blanks, then machined to the specified dimensions shown in the schematic presented in

Figure 6. The gage section was maintained at 0.375 inches (fill) by 0.300 inches (warp) by 0.050 inches

(A/P), allowing four plies to be isolated in the gage section for the C/P specimens and two plies in the

gage section for the G/P specimens. The number of plies isolated in the gage section was determined

by dividing the A/P dimension of the gage section by the cured ply thickness of each material. For the

interface specimens, approximately 2 plies of C/P and 1 ply of G/P were isolated in the gage section

with the bondline centered in the gage section. The specimens were loaded in axial compression to

provide pure shear at the gage section. Each specimen was loaded at a rate of 10,000 pounds per minute

[21]. The load versus time plot obtained from the Instron for each specimen was transformed into a

stress versus time plot by dividing load values by the shear (gage) area. The data obtained from the

linear stress versus time plot were used to determine the ultimate interlaminar shear strength.

Results and Discussion

a) Physical Property Tests:

A summary of the physical property test results is presented in Table 1. Based on the compliance

of all the physical property test results with the specification requirements, the C/P and G/P materials

of the four laminates were accepted as representative nozzle materials.

454
b) Photomicroscopy:

Examination of the photomicroscopy specimens at a magnification of 1000 revealed no evidence

of microstructural damage such as microcracks, voids or delaminations in any of the materials. The shape

of the fibers and presence of fillers in the matrix materials were used in characterizing the appearance

of the materials. The C/P fibers exhibited the typical non-uniform erenulated cross-section, while the

G/P fibers exhibited uniform circular cross-sections. The matrix material of the C/P material revealed

the presence of the carbon-black filler; no fillers were present in the G/P matrix material. The

carbon-black filler appears in the photomicrograph as the light spots in the matrix material.

The different C/P to G/P interfaces were also characterized based upon their appearances. Three

different interfaces were observed: (a) 125 microinch; (b) 250 microinch; and (c) the cocure interface.

Surface finish is defined as the mean distance _een peak and valley measured in microinches.

Observed from the examination was that the distance from peak to valley for the 125 microinch finish

was half that of the 250 microinch interface. The appearance of the cocure interface was unmachined

with evidence of the carbon-black filler migration across the interface. The migration was attributed to

the cocuring of both the G/P and C/P materials.

c) Interlaminar Shear Strength:

The results of the interlaminar shear strength tests are summarized and presented in Table 2 for

the four laminates. Analysis of the data yielded the following results:

(a) There were no appreciable differences in the ultimate strength observed for the G/P material

among the four laminates.

(b) There was no significant difference in the ultimate strength of the C/P material of the 3

laminates which received the hydroclave cure. There was, however, a 20 percent reduction in ultimate

strength in the C/P material of the cocure laminate. The reduction in the C/P material of the cocure

when compared with the strengths of the 3 other laminates was attributed to the differences in the

pressures of the autoclave and hydroclave cure cycles. The cocure laminate was cured using the

autoclave cure cycle where the maximum pressure obtained was 240 psig, while the hydroclave cured

laminates experienced maximum pressure of 1050 psig.

(c) The results from the evaluation of the interfacial bond strength showed for the cocure, dry and

as-received laminates, that the ultimate strength of the interface was at least as high as that of the C/P

material of each laminate, because failure occurred in the C/P material at the gage section. The most

significant effect occurred in the interface specimens of the wet laminate, where the failure mode was

shifted from the C/P (observed for the as-received, dry and cocure interface specimens) to the interface

and the ultimate strength was significantly reduced. The effect of moisture at the interface is believed

to have masked any potential variations in surface finish, and to have caused the shift in failure mode.

(d) There was no appreciable difference between the 125 and 250 microinch surface finishes for

the wet laminate. A test [22] was performed to determine if there was any difference in the values of

the ultimate strength for the two interfaces of thewet laminate. It was found that the individual specimen

results for the 125 surface finish were within the bounds of the 95 percent confidence interval of the

250 surface finish results. The results obtained from the test showed that there was no significant

difference in the ultimate strengths of the two populations.

455
The test results (mean value) for the C/P material of the as-received laminate were compared

against the mean values of the existing MX-4926 C/P material databases [20,23] to assessthe reliability

of the results obtained in the program. The mean value for the ultimate strength obtained from the

existing databases with curing and test parameters identical to those of this program, clearly indicates

that the results are in agreement with those of previous programs.

(d) SEM Examination:

The double-notched shear specimens were visually examined after testing to determine the mode

of failure. Of the specimens tested, only two distinguished modes were observed. These were across

laminar and interlaminar failure.

Examination of the fracture surfaces by the conventional technique of optical microscopy rendered accurate observations impractical and therefore the scanning electron micrcyseopy was required.

Scanning electron microscopy (SEM) examination was performed using a Cambridge 250 ink2 scanning

electron microscope. The fractured surfaces were etched with gold prior to their examination.

Interlaminar failure (presented in Figure 7) was characterized by a fracture surface exhibiting one

or more of the following features: (a) large areas of exposed denuded fibers, (b) thin cracks between

the fibers and matrix, and (c) clear imprints in the matrix where fibers were removed. This type of failure

was characteristic of the interface specimens of the wet laminate and the glass phenolic material of all

laminates.

Across-laminar failure (presented in Figure 8) was characterized by a fracture surface exhibiting

similar features on interlaminar failure with the addition of some extensive fiber breakage across

individual plies of material. This type of failure was common to all carbon phenolic material and the

bondline specimens of the dry, as-received and the cocure laminates. From analysis of fracture surfaces

of failed DNS C/P specimens by SRI, it was found that the predominate mode of failure was interlaminar

although the presence of across-laminar failure was observed [21].

Conclusions

The following conclusions were based upon the test results presented in the previous section.

(1) Moisture substantially degrades the integrity of the interfacial bond between C/P and G/P

materials.

(2) The apparent effect of autoclave curing of the C/P material reduces the ultimate interlaminar

shear strength of the C/P material by nearly 20% as compared to the hydroclave curing of the C/P

material.

(3) The variation in applied surface finishes had no appreciable effect on the ultimate interlaminar

shear strength of the interface in the wet laminate. The variation in the applied surface finishes on the

remaining three laminates was not conclusively determined due to the failure having occurred in the

C/P material of the gage section for the interface specimens.

456
References

1. Curtis, P.T., "Residual Strains and the Effects in Fiber Reinforced Laminates", Technical

Report 80045, (April 1980)

o Desai, R., Whitesinde, J.B., "Effects of Moisture in Epoxy Resins and Composites",

Advanced Composite Materials Environmental Effects, ASTM STP 658, J.R. Vinson, ed.,

ASTM, pp. 2-20, (1978)

, Hertz, J., "Moisture Effects on the High Temperature Strength of Fiber-Reinforced

Composites", Convair Aerospace Division of General Dynamics, National SAMPE

Technology Conference, (October 1972)

4. Powell, J.H., and Zigrang, D.J., "Moisture Absorption and Desorption Characteristics of

Three Graphite-Epoxy Systems", SAMPE Journal, 13:4, (1977)

5. Shen, C.H., and Springer, G.S., "Moisture Absorption and Desorption of Composite

Materials", Journal of Composite Materials, 10: 1-20, (1976)

6. Springer, G.S., "Moisture Absorption in Fiber-Resin Composites", Developments in

Reinforced Plastics Chapter 3: 60, (1982)

o Browning, C.E.,"The Mechanics of Elevated Temperature Property Losses in High

Performance Structural EPOxy Resin Matrix Materials After Exposure to High Humidity

Environments", Polymer Engineering and Science, 18:31, (1978)

. Mazor, A., Broutman, L.J., and Erkstein, B.H., "Effects of Long Term Water Exposure on

Properties of Carbon and Graphite Fiber Reinforced Epoxies", Journal of Material Science,

15:751-754, (1980)

9. Morgan, R.J., O'Neal, J.E., and Fanter, D.L, "The Effects of Moisture on the Physical and

Mechanical Integrity of Epoxies", Polymer Engineering and Science, 18:31, (1978)

10. Scola, D.A., "A Study to Determine the Mechanisms of S-Glass/Epoxy Resin Composite

Degradation Due to Moisture and Solvent Environments", Society of Plastics Industry 30th

Annual Technology Conference, Reinforced Plastics Composites Institute, (February 1975)

11. Young, H.L and Greener, W.L., "High Temperature Strength Degradation of Composites

During Aging in Ambient Atmosphere", Hercules Incorporated, (May 1972)

12. Morton Thiokol Incorporated, "Glass Cloth Phenolic Preimpregnated Specification",

STWS-2651F, (May 1987)

13. Morton Thiokol Incorporated, "Glass Cloth Phenolic Preimpregnated Specification",

STW5-3279A, (May 1987)

14. Morton Thiokol Incorporated, "Aft Inlet Ring Manufacturing Plan", C.P.I. Number I-IP30L,

(October 1984)

457
15.

16.

McKague, L, "Environmental Synergism and Simulation in Resin Matrix Composites",

Advanced Composite Materials-Environmental Effects, ASTM-STP 658, J.R. Vinson, ed.,

p. 193, (1978)

Stokes, E., "Moisture Diffusion in Carbon Phenolic Composites", Southern Research

Institute, JANNAF Conference, (October 1987)

17.

18.

19.

Morton Thiokol Incorporated, "Aft Exit Cone, Second Wrap Manufacturing Plan", C.P.I.

Number HP43w, (November 1986)

Morton Thiokol Incorporated, "SRM Nozzle Tag End Testing Specification", STW5-2845D,

(September 1988)

Canfield, A.R., Mathis, J.R., Starett, H.S., and Koenig, J.R., "Materials Property Definition

and Generation for Carbon-Carbon and Carbon-Phenolic Materials", AIAA/ASME/

ASEE/SAE 23rd Joint Propulsion Conference, (June 29 - July 2, 1987)

20. Stokes, E., "Personal Communication", Southern Research Institute, (August 1988)

21.

22.

Freeman, D. Pisani, and Purves, R. "Statistics", W.W. Norton and Company Publishers, New

York, (1978)

Neighbors, B., "MX-4926 and FM-5055 Carbon-Phenolics", SORI EAS-86-340-5694-3-I-F,

(April 1986)

Acknowledgments

The authors gratefully acknowledge the support from NASA - Marshall Space Flight Center

through grant NGT - 50130 for this study.

458
TABLE 1: SUMMARY OF THE PHYSICAL PROPERTY TEST RESULTS

Panel Status Material

Residual Resin Specific

Volatiles Content gravity

As - received

Dry

Wet

Cocure * *

* C/P 2.9 30.9 1.5

** C/P 2.6 30.8 1.5

** G/P 1.1 22.2 2.1

* C/P 2.9 31.1 1.5

** C/P 2.7 30.7 1.5

** G/P 1.1 22.1 2.1

* C/P 2.9 31.1 1.5

** C/P 2.8 29.5 1.5

** G/P 1.1 22.6 2.1

C/P 2.8 32.4 1.5

G/P 1.2 23.6 2.1

S*

Proceeding C - P cure and prior to conditioning

- Proceeding the G - P cure

459
TABLE 2: SUMMARY OF INTERLAMINAR SHEAR TEST RESULTS

Panel Glass - phenolic Carbon - phenolic

(Psi) (Psi)

(125 S.F.)

Interface

Cocure 3650 2988 3374 CP *

(5.71) (2.93) (3.71)

As - received 3650 3672 3838 CP

(2.58) (3.49) (3.49)

Dry 4226 3790 3734 CP

(5.89) (4.96) (3.38)

(250 S. F.)

Interface

3840 CP

(2.38)

3726 CP

(6.79)

Wet 3832 4008 1843 BL

(3.01) (12.22) (4.44)

2038 BL

(7.00)

( ) - coefficient of variation

* - Surface finish not applicable

CP - Failed in carbon - phenolic

BL - Bondline failure

460
12.0 WARP

()

CARBON PHENOLIC

MATERI_

)

4 3 2 1 GP- 8

4 3 2 1 GP- ?

4 3 2 1 GP- 6

4 3 2 t GP- 5

4 3 2 1 GP- 4

4 3 2 1 GP- 3

4 3 2 1 GP- 2

4 3 2 I GP- 1

3'

NOTES:

i. CUT 3 FOOT SWATCHES AT THE BEGINNING AND AFTER EVERY 168

PLIES UNTIL 504 PLIES ARE CUT.

2. CUT 504 [10 IN BY 12 IN (WARP)] PLIES OF C/P MATERIAL MAKE 6

STACKS (84 PLIES PER STACK), BY STACKING THE FIRST 4 PLIES,

SMOOTH SIDE UP, IN STACK CP - 1, THE NEXT 4 IN STACK CP - 2, ETC.

UNTIL EACH STACK CONTAINS 84 PLIES.

Figure 1. Cutting and stacking plan for carbon phenolic material (Roll 1B).

461
1.1

1.0

0.9

0.7

EC3

0.6

Z 0.5

r_

0.4

0.3

0.2

O.I

L

/

/

0.0 1

0 1 z 3 4

TIME (hours) X 1000

Figure 2. Percent weight gain for wet panel.

462
()

GLASS PHENOLIC )

MATERI_

8 ? 8 5

8 ? e 5

8 7 8 5

8 ? 8 5

4 3 2 1

4 3 2 1

4 3 2 1

4 3 2 1

GP- 4

GP- 3

GP- 2

GP- 1

GP- 4

GP- 3

GPGP- 1

3' _ SWATCH

NOTES:

1. CUT 160 10 IN BY 12 IN (WARP) PLIES.

2. MAKE 4 STACKS BY STACKING THE FIRST 4 PLIES IN STACK GP - 1, THE

NEXT 4 IN GP - 2, ETC., UNTIL EACH STACK CONTAINS 40 PLIES.

Figure 3. Cutting and stacking plan for glass phenolic material (Roll 1).

463
// f0.50

0.50

Figure 4. Specimen geometry of specific gravity,

residual volatile, and resin content tests.

r

r

k

464
FILL _

0.25

.50

Figure 5. Specimen geometry for photomicroscopy evaluation.

465
0.3?5 --4"

q,

O.250 -j

<------WARP DIRECTION ------>

1.250

d 0.050

0.125

TI' F.o_o It "-"

TOL_ *.005

FINAL MACHINED SPECIMEN

ALL D/i_,NSIOI_ IN MHES

Figure 6. Specimen geometry for DNS test.

466
ORIGINAL PAGE

BLACK AND WHITE PHOTOGRAPH

Figure 7a. SEM photomicrograph at 15X of fracture

surface depicting interlaminar failure.

Figure 7b. SEM photomicrograph at 200X of fracture

surface depicting interlaminar failure.

467
ORIGINAL PAGE

BLACK AND WHITE PHOTOGRAPH

Figure 7c. SEM photomicrograph at 200X of fracture

surface depicting interlaminar failure.

468

Z
ORIGINAL PAGE

BIJ-_CK AND WHITE PHOTOGRAPH

Figure 8a. SEM photomicrograph at 15X of fracture

surface depicting across-laminar failure.

Figure 8b. SEM photomicrograph at 200X of fracture

surface depicting across-laminar failure.

469

F
ORIGINA£ PAGE

BLACK AND WHITE PHOTOC-,RAF_

Figure 8c. SEM photomicrograph at 200X of fracture

surface depicting across-laminar failure.

470
N91-28124

LOW ENERGY SPUTI'ERING OF COBALT BY CESIUM IONS*

A. Handoo and P. Ray

School of Engineering and Architecture

Tuskegee University

Tuskegee, AL

?

ABSTRACT

An experimental facility to investigate low energy (_:500 eV) sputtering of metal surfaces with

ions produced by an ion gun is described. Results are reported on the sputteringyield of cobalt by cesium

ions in the 100 to 500 eV energy range at a pressure of] x_10"6Torr. The target was electroplated on a

copper substrate. The sputtered atoms were collected_oF a cobalt foil surrounding the target. 57C.o was

used as a tracer to determine the sputtering yield. =-

/

/

*Work supported by NASA Grant NAG8-020

471
LOW ENERGY SPUTTERING OF COBALT BY CESIUM IONS

1. Introduction

- Electron bombardment ion engines are required to have operational lifetimes of up to 15,000

hours at 2 A beam current for Su_fui completion Of many proposed space missions [1]. From the

mission profile life tests, it was observed that the major life-limiting mechanism is the formation of flakes

of sputtered material which might be of sufficient size to cause electrical shorts or arcing in the discharge

chamber [2]. The internal surfaces of the discharge chamber where the erosion is most severe are

subjected to bombardment by ions having energies less than 100 eV, assuming that up to triply charged

ions exist in the plasma potential of 32 V within the discharge chamber where the ions are generated.

However, the data on yields from low energy sputtering aresparse and there are uncertainties due to

difficulty in detecting the extremely low sputtering yields [3-5]. In view of the scarcity of sputtering yield

data at low energies, a systematic experimental study is being undertaken using a radioactive tracer

technique. In the present study cesium ions having well-defined ion energies impinge on a cobalt target

mixed with a small amount of cobalt-57. Cobalt is chosen as the target material for initial studies because

its tracer, cobalt-57, has a relatively long half-life of 270 days and decays predominantly by emitting

low-energy (122 KeV) gamma rays. Since the total sputtering yield at low incident ion energies is

expected to be very small even after a prolonged exposure, the radioactive tracer technique appears to

be quite useful. The sputtering yield data reported are taken at a pressure of 1 x 106 Torr with energy

of the cesium ions varying from 100 to 500 eV.

2. Experimental Design and Procedure

The vacuum chamber is 10 cm in diameter, 22.5 cm long and has six ports. The ion gun enters from

the left through a 150 mm CF port. The target assembly is introduced from the right port by a linear

motion feedthrough which is connected to the vacuum chamber through a 150 mm CF adapting nipple.

The ionization gauge is mounted on another 70 mm CFport. A viewport is attached through a 115 mm

port on the top and there is also a provision to introduce a SIMS probe through an auxiliary 70 mm CF

port which is at a 45° angle.

a) Vacuum system:

Before any successful sputtering can be undertaken, the surface should be made as free of adsorbed

layers of gases as possible. This can be achieved by baking and maintaining a very high vacuum in the

system. A turbomolecular pump of 170 Is1 pumping speed is used to maintain the vacuum. All the

flanges used in the chamber are metal gaskets sealed to have minimal outgassing and diffusion rates. A

hot cathode ionization gauge with its digital readout controller is used to monitor the pressure level

inside the vacuum chamber.

b) Ion Gun:

It is desirable that the ion beam impinges on the target in a small area with a high current density.

However, space charge in the ion beam represents the fundamental limit on the ion current density.

Hence, the lower the kinetic energy of the beam, the lower is the maximum current density that can be

472

E
generated. The ion gun used in the present setup is procured from Kimball Physics Inc. and is capable

of producing low-energy ion beam at well defined energies for both Cesium and noble gases. This will

enable us to cross check the sputtering yield data using a variety of ions.

c) Target and collector assembly:

The target and collector assembly is shown in Fig. 1. At the end of the linear motion feedthrough

is the holding rod with a tapped hole at the end. The target is cobalt (99.9% and 0.1% 57Co) electroplated

on the tip of a 4.8 mm diameter copper specimen. The edge of the copper specimen on which the cobalt

is electroplated is at an angle of 45 °, so the surface of the target is elliptical in shape with an area of

25.8 mm 2. The surface density of cobalt is approximately 50 _g / cm 2, which resulted in an activity of the

target of 110_Ci. The other end of the specimen, which is threaded, is attached to the holding rod. The

copper specimen is completely surrounded by a 19 mm diameter hollow cylinder, the inside of which is

lined with a 0.05 mm thick cobalt foil. The distance between the target and the ion gun was optimized

for maximum sputtering yield after conducting several initial runs under similar experimental conditions.

The operating distance was found to be about 19 mm (Fig. 2).

The vacuum chamber is pumped down to a pressure of 1 x 10 .6 Torr. The ions are extracted and

accelerated to the desired energy by setting corresponding grid voltages. The beam current is then

measured with a Faraday cup which is pneumatically operated to intercept the beam. The ion beam

impinges on the target at a 45 ° angle. The target is exposed to the ion beam for a period ranging from

5 to 20 minutes depending on the beam energy level. The experiments were run for beam energies of

100, 200, 300, 400 and 500 eV for both focused and unfocused ion beams. The focused ion beam

diameter is about 1 mm whereas the unfocused beam diameter is about 3 mm. The ion beam current

ranged from 0.45 microampere at 100 eV to 1.15 microampere at 500 eV. After bombarding the target

with cesium ions, the cobalt foil is removed from the vacuum chamber and taken to a multichannel

analyzer for counting the gamma rays emitted by the disintegrating 57Co atoms deposited on the foil.

The analyzer is set so that only photoelectric peak is counted. A standard 57Co source of 0.115 _Ci is

used to determine the efficiency of the counter. The amount of radioactive atoms in the sputtered

material is then a measure of the total sputtering yield.

3. Sputtering Yield Measurement

Let N be the number of total atoms counted under the photoelectric peak in time t¢. Then the

total number of radioactive atoms NR on the cobalt foil is given by

NR = N / (tc 2r/)

where 2 is the disintegration constant of 57Co and r/the efficiency of the counter. The percentage of

radioactive atoms on the target, ),, decreases with time and is determined by

-2T

)' = )'o e

where ?o is the percentage of radioactive atoms on the target at the time of electroplating, and T is the

elapsed time between electroplating the sample and the day the data were taken. Assuming that all the

sputtered atoms are deposited on cobalt foil, the sputtering yield S is given by

473

T
s = (NRq)/ (r I tO

where q is the charge of an ion, I the ion beam current and t. the beam exposure time of the target.

4. Results and Discussion

The sputtering yields of cobalt by cesium ions at 100, 200, 300, 400, and 500 eV are presented in

Fig. 3 for both focused and unfocused ion _ams. For _mpa_n, the sputtering yield of cobalt by

mercury ions reported by Wehner is also presented, although the experiments were performed under

different conditions [3]. The sputtering yield values obtained by Wehner are 2 to 5 times higher than

those obtained from our experiments with focused beams.

The discrepancy in the sputtering yield values can be traced to the vacuum chamber pressure and

the ion current densities at which these data were taken. Wehner's experiments were performed with

the target immersed in a low-pressure mercury plasma discharge at about I x 10.6 Tort and 5 mA/cm 2

ion current density. The highest current density obtained in our experiments was 0.15 mA/cm 2. At 0.15

mA/cm 2 a surface atom of the target receives about 30 impacts per minute form the incident ions

whereas the residual gas molecules at 1 x 10.6 Torr will impinge about 10 times on the surface atoms

during the same period [6]. Thus, the surface of the target will have an appreciable amount of adsorbed

gases which inhibit the sputtering process significantly.

The effect of ion current density on the sputtering yield can be clearly seen in Table 1, where the

ratios of the sputtering yields for the focused and the unfocused beams at various ion energies are listed.

At all ion energies the sputtering yields of unfocused beams are lower by factors of 10 to 14. The focused

and ihe _f/x:S.tsed ion beam densities differ by ai_ut t[ie same vaquesl It is obvious that a very high

vacuum is requlredt0 minimize the effect of the residua| gas on thesputterlng yields at low ion current

densities. In view of this, our vacuum system is being upgraded to a pressure of 10 -8Torr. Currently, we

are in the process of obtaining data for sputtering yield of cobalt bombarded by low energy argon ions.

The amounts of material sputtered at ion energies down to 50 eV are within the detection limits

using the 110,uCi target. A higher activity target would enable us to measure sputtering yields below

100 eV.

Table 1.

Ratio of the Sputtering Yields for the Focused and the Unfocused Ion Beams.

ION ENERGY

(eV)

RATIO

100

200

300

400

500

10.4

10.0

13.7

11.9

11.1

474
References

1. Austin, R.E., "Solar Electric Propulsion Systems (SEPS), Tomorrow's Propulsion System

Today", Paper no. AIAA-79-2045, Oct. 1979.

2. Bechtel, R.T.; Trump, G.E.; James, E.J., "Results of the Mission Profile Life Test", Paper

No. AIAA-82-1905, Nov. 1982, 22.

3. Wehner, G.K., Phys. Rev., 1956, 102, 690.

4. Laegreid, N.; Wehner, G.K., J. Appl. Phys., 1961, 32, 365.

5. Rosenberg, D.; Wehner, G.K., J. Appl. Phys., 1962, 33, 1842.

6. Chopra, ICL., Thin Film Phenomena (McGraw-Hill, New York, 1969).

475
tOom

a

0

t_

._.1

m

rE

O

E

I.u

C_

E

z

476
I .00 -

0.80

i

0.60

131

"E 13

_ 0.40

oz.<

br)_

0.20

0.00

15

w = I I I

2O

Distonce of the torget

from the gun (mm)

25

Figure 2. Variation of sputtering yield with distance.

477
0

10 _

10 _

.2°

ID

-o" -2

10_

10 _

O3

10

o o o_

o o />/-

o

/ A FOCUSED BEAM

o WEHNER (Hg ions)

0

I I I I I

1O0 200 300 400 500

Ion Energy, eV

Figure 3. Sputtering yield of cobalt by cesium ions at various ion energies.

478
N91-28125

PARAMETERS OF TENSILE STRENGTH, ELONGATION,

AND TENACITY OF 70mm HaO SPECTROSCOPIC FILM

Ernest C. Hammond, Jr. and Kevin A. Peters

Morgan State University

., 6 .-26

and

Gerald R. Baker

Technical Monitor

Laboratory of Astronomy and Solar Physics

Goddard Space Flight Center

ABSTRACT

70mm IIaO spectroscopic film was tested to determine its tensile strength, elongation, and

breaking strength, using an Instron (strength & compression) 4201 Test Instrument. These data

provides information leading to the upper and lower limits of the above parameters for 70mm IIaO

spectroscopic film. This film will be developed by a commercial developing machine after the Ultraviolet

Telescope Space Shuttle Mission returns to the earth in the early 1990's; thus it is necessary to

understand these force parameters.

Several test strips of approximately 200 mm in length were used. The results indicate that when a

stress load of 100 kg was applied, the film elongated approximately 1.06 mm and the breaking strength

was 19.45 kilograms.

.z

479
PARAMETERS OF TENSILE STRENGTH, ELONGATION,

_D TENACITY OF 70ram HaO SPE_OSCOPic FILM

Introduction

IIaO spectroscopic film is a special ultraviolet sensitive film which will be used on the ultraviolet

imaging telescope to be launched by the space shuttle in the early 1990's. Quality control of this film is

an important ingredient in understanding the various parameters that the film will undergo in space

and the extraterrestrial environment.

NASA uses a large commercial developing machine to develop its 70mm IIaO spectroscopic film.

During the process, the film is exposed to various forces that could cause possible stress or strain on

the film. The purpose of this research is to study the parameters of elongation (strain), tenacity strength

(breaking point), and tensile strength (load strength) of 70mm IIaO spectroscopic film.

Materials and Methods

Five samples of developed and five samples of undeveloped 70ram IIaO spectroscopic film were

cut to a gage length of 5 inches for testing purposes. An Instron 4200 strength and compression

instrument was used to test the properties of elongation and tenacity of the film. Each sample was

exposed to a maximum load range of 500 kg for stretching purposes. The film was put in a 2-inch grip

on the instrument and streched to its breaking point. Elongation curves for each sample were made

using a graphic recorder connected to the Instron instrument for further analysis.

Results

From the analysis of the elongation curves, the undeveloped film shows greater strength than do

the developed film samples. The undeveloped film appears to begin stretching at a load range of 50 kg

and continues stretching until it reaches a breaking point at approximately 86 kg. The undeveloped film

appears to elongate a total of 2 inches during the experiment. The developed film appears to stretch at

approximately 30 kg and continues stretching until it reaches a breaking point of approximately 75 kg.

The developed film appears to elongate a total of 1.5 inches during the experiment.

Discussion

The adhesive properties of the undeveloped film appear to give the film added strength as

compared with the developed samples. These results are demonstrated by the differences in the

breaking points of the undeveloped film versus the developed film samples. The tension associated with

the developing machine is needed in order to complete this study. This information will be obtained

when the machine is set up again at Goddard's Laboratory of Solar Physics. Most of the concern for

stretcthing of film is with the science of astrometry where very crude and sensitive measurements are

needed relative to distances and positions of stars. If film stretches in the machine by any significant

amount, it could distort images and sensitive measurements that are made by researchers in astrometry.

480
I.l.I

O

._J

HI

1.12

IZI

I.I.I

fr-

,<

O

00

-r

I- w

I.I.I

13_

O

.,_I

I.I.I

I.I.I

a

z

z_

48!
D

N91- S S {

SURFACE ROUGHNESS OF FLAT AND CURVED

OPTICAL SURFACES

M. C. George, B. R. Reddy, H. Jagannath,

M. Perera, and P. Venkateswarlu

Department of Physics

Alabama A&M University

Normal, Alabama

ABSTRACT

A profilometer has been fabricated based on optical heterodyne detection technique. The vertical

height sensitivity of the technique has been improved to much better than 10X rms. The surface

roughness of several coated and uncoated samples has been measured. A typical surface profile and

surface characterization plots are also shown.

482
SURFACE ROUGHNESS OF FLAT AND CURVED

OPTICAL SURFACES

Introduction

Surface roughness measurement has several applications. Even a few _oughness will cause

scattered light in optical systems. Smooth surfaces are required in a wide variety of instruments. For

example, the outputs of the high power lasers are limited by the surface roughness of mirrors and

windows. Similarly, the information storage capacity of magnetic media is limited by the roughness of

the surface. Roughness reduces the resolving power of optics and distorts images. The performance of

certain thin film components in electronic industries is affected by the roughness on the film surface.

X-ray astronomical telescopes require smooth curved surfaces. To improve the surface quality, super

sensitive detection methods are required. Wide ranging measurement techniques are developed based

on interferometry, electron microscopy, X-rays, ellipsometry, light scattering, and using mechanical

stylus, etc. Though there are several techniques t'_ available for measurement and evaluation of the

surfaces, no single technique is fully adequate. Also, the technique used should be nondestructive and

highly sensitive. So, we fabricated an optical heterodyne profilometer 3 and its current sensitivity is much

better than 10g rms. It is a noncontact and nondestructive technique. The instrument can be operated

even by unskilled personnel for routine measurements.

Principle

The principle 4 behind the technique is simple and elegant. Briefly, in this experiment, a laser beam

is split into two parts and focused at two different points on the surface under investigation, and then

the phase variation of the reflected beams is measured, which directly relates to the height difference

between the two points. A brief description of its theoretical background is given elsewhere 4.

Experimental

Ablock diagram of the experimental setup is shown in Fig. 1. The experiment uses a lmW Zeeman

split (Aw = 1.5 MHz) He Ne laser (HP 5501A) whose frequencies are collinear but orthogonally

polarized. The laser output is passed through a spatial filter/telescope combination to reduce the spatial

noise and the beam size to - 0.5 mm. The laser beam is split into two parts of unequal intensities, but

both parts contain the two Zeeman components. One part is detected by a receiver (I-IP 10780B) whose

output is hereafter called reference signal and the other part is directed vertically upwards to the surface

mounted on an airbearing rotary table (Dover Instruments). Before falling on the sample, the beam

passes through a wollaston prism and on exit the two frequencies are spatially separated and then

focused at two different points on the surface of the sample. The beam path is arranged such that one

of them falls at the axis of rotation of the table and the other is separated from it by only a fraction of

a millimeter. The reflected beams are recombined by the wollaston prism and then directed to another

identical receiver (HP 10780B) whose output is hereafter called measurement signal. Whenever two

different frequency signals fall on a detector its output is an average de current proportional to the

483
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Figure 1. Block Diagram of the Experimental Set Up.

484

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SurFace Profile

_7. RMS 72. P-V

Date: may 3 89 Sample no. i

Figure 2. Surface Profile of a GaAs Wafer.

485
intensityplusanrf signal at the beat frequency (Aw). The dc part is elemented by a preamplifier built

into the reciever (HP 10780B). The outputs of the two receivers are rf signals at 1.5 MHz (Aw), but the

phase of the measurement signal varies due to roughness. The two rf outputs are given to the two inputs

of a phasemeter (HP 3575A) whose output is an analog signal and its amplitude is proportional to the

phase difference between the two inputs (10 mV/degree). The analog output of the phasemeter is

interfaced with an IBM-AT computer using a 14 bit-A/D converter (Keithley series 500). A dc motor

is attached to the table and its motion is controlled by a DMC 100 controller (Copley controls), and a

two channel incremental encoder (Teledyne Gurley) provides feedback from the motor to the controller. There is one general program in BASIC that triggers DMC 100 for table rotation and initiates

Keithley module for online data acquisition. The sample/table is rotated at the rate of one revolution

per two minutes and data are acquired at the rate of 128 samples per revolution or an integral multiple

of it. During table motion one of the spots is stationary and the other encounters different points in a

circular path and so the measured signals are plotted in circular format.

Results and Discussion

The measured phase difference A¢ and the surface height variation or roughness

AH (AH _ --A-_-)are related by A¢ _- --_ Az where Az is the extra pathiength traveled by one of the

beams due to roughness. A typical surface profile of a GaAs wafer is shown in Fig. 2. The rms values of

the roughness and peak-to-valley (P-V) values are calculated for eight different segments and the entire

profile and are printed in the same figure. A number of functions are used to characterize the surfaces

like autocovariance, spectral density, height and slope distribution functions. Autocovariance function

refers to the distribution of correlation lengths, which are separations between similar topographic

features. The spectral density function describes the angular distribution of the scattered light. Classical

scattering theories were based on the assumption that the autocovariance and height distribution

functions are gaussian which may not be true for every surface. All these functions have been calculated

using the formulas given in reference 4 and are plotted in Fig. 3. Obviously, the autocovariance function

deviates from gaussian distribution.

Sensitivity

Sensitivity of the technique is determined from the relation A¢ _-_-AH. Roughness

(AH) _- 15 will cause a phase change of -0.1 ° which is the resolution of the phasemeter. A severe

limitation to the sensitivity is set by improper alignmentof the optical beams. Some of the important

criteria to be fulfilled are (1) one of the spots has to fall at the axis of rotation, (2) the surface normal

has to be parallel to the axis of rotation and (3) the contact area between the table top and the sample

are to be free from dust. When all these criteria are fulfilled the sensitivity of the instrument will be

improved to the theoretical limit - lg, because the noise from other sources is insignificant.

This work was supported by NASA-Grant No. NAG8-029.

Z

486
References

1. Bennett, J. M., Appl. Opt. 1976, 15, 2705.

2. Lindsey, IC; Penfold, A. B., Opt. Engg. 1976, 15, 220.

3. George, M. C.; Jagannath, H.; Reddy, B. R.; Perera, G. M.; Venkateswarlu, P., Opt. Fab.

and Test. (OSA) 1988, Tech. Dig. Ser., 13, 61.

4. Sommargren, G. E., Appl. Opt. 1981, 20, 610.

487
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488
SUGGESTED CRITERIA FOR EVALUATING SYSTEMS

ENGINEERING METHODOLOGIES -_,_ _-3 f

Audrey Gates, Arthur Paul, and Tepper Gill,

Department of Systems and Computer Science

and

Department of Electrical Engineering

Howard University

Washington, D.C.

ABSTRACT

Systems engineering is the application of mathematical and scientific principles to practical ends

in the life-cycle of a system. A methodology for systems engineering is a carefully developed, relatively

complex procedure or process for applying these mathematical and scientific principles. There are many

systems engineering methodologies [or possibly many versions of a few methodologies] currently in use

in government and industry. These methodologies are usually tailored to meet the needs of a particular

organization. It has been observed, however, that many technical and non-technical problems arise

when inadequate systems engineering methodologies are applied by organizations to their systems

development projects. This paper discusses various criteria for evaluating systems engineering methodologies. Such criteria are developed to assist methodology-users in identifying and selecting methodologies that best fit the needs of the organization.

489
SUGGESTED CRITERIA FOR EVALUATING SYSTEMS

ENGINEERING METHODOLOGIES

Introduction

This paper is one of several results of a Dynamic Systems Engineering Methodology Research

Study being conducted at Howard University under a grant from NASA. The study is sponsored by the

Networks Division of the Mission Operations and Data Systems Directorate (MO&DSD) at Goddard

Space Flight Center. The objective of the study is to examine systems engineering methodologies in

light of changing environments and changing needs. The results of this investigation are to be used to

identify and validate new methodologies with potential applications to NASA's systems life-cycle

processes.

The study is divided into two phases. Phase One is a study of NASA's projects, its organization,

resources, and environment to identify factors that affect the successful application of systems engineering methodologies. Phase Two involves evaluating existing methodologies, tools, and techniques

with potential application to NASA's systems project.

The criteria for evaluating systems engineering methodologies were developed based on the

findings in Phase One. These criteria are to be used as a guide and weighing scale for evaluating existing

systems engineering methodologies in Phase Two of the project, and in making recommendations to

NASA.

Purpose of a Systems Engineering Methodology

Systems engineering as described by Blanchard is a process employed in the evolution of system's

development from the time when a need is identified through production and/or construction to the

ultimate deployment of that system[l, p. 11]. The series of steps involved in this process is a systems

engineering methodology. A methodology is primarily used to improve the effectiveness of the overall

system. It provides a means to increase reliability, decrease downtime, maintain cost effectiveness, and

avoid redundant and wasted efforts. Furthermore, it provides a means of checking, cross checking, and

quality control.

A systems engineering methodology is almost vital for large-scale projects because the su_ of

such projects depends upon a strong systems approach to integrate diverse elements into a harmonious

whole[2, p. 2]. It is also vital to proper project management. The steps of a systems engineering

methodology are generally presented in the context of a system life-cycle. A life-cycle is a logical

evolutionary flow of what has to be done for the duration of the project.

490

't
Participants in the SystemsEngineeringProcess

There are two basic participants involved in the systems engineering processwthe problem

originator and problem solver. The problem originator is the individual who has a problem that needs

to be solved. Typically, the problem originator is referred to as the client, decision-maker, manager,

sponsor, or problem owner[3]. The problem solver is responsible for providing the problem originator

with a solution to his problem. This role is likely to be filled by a person called a consultant, analyst, or

designer. The problem solver is also the methodology-user for (s)he is the one who uses the set of

procedures, which may or may not be formally defined, to create an environment whereby a solution

can be brought about[3]. Therefore, it is essential that the user identifies what tasks must be carried out

to obtain the desired results. These tasks and the persons responsible for completing each task must be

clearly defined in the organization's methodology.

Suggested Criteria for Evaluating Systems Engineering Methodologies

The criteria that were developed to evaluate a systems engineering methodology fall within five

major categories: Structure, Flexibility, Accountability, Documentation, and Special Considerations of

User (in this case NASA). Structure addresses the composition of the system life cycle process and its

ability to accommodate simple to large-scale systems. Flexibility refers to the methodology's ability to

adapt to change. The third area of interest is accountability. Accountability addresses the ability of the

systems engineering methodology to ensure that proper procedures are being applied as intended and

that appropriate procedures are being kept. Documentation refers to how well the methodology is

written; the level of detail, clarity and ease with which it can be followed. Lastly, because all methodologies are tailored to meet an organization's particular needs, it is necessary to examine the factors that

are of critical concern to that organization (in this case NASA). The criteria that were developed for

each category are as follows:

. Structure

• Does the methodology address activities that are likely to involve engineering work such as

design, construction, installation, and operation?

• Is it structured to handle large-scale or complex systems (interacting components to achieve

defined objectives)?

• Is it structured to handle at least one component that is extensively hardware?

• Is the methodology partitioned into clearly defined and logical phases, processes, activities,

or tasks that can be used as a basis for resource allocation and events such as the start or

completion of phases that can be used as milestones or decision points?

491
2. Flexibility

.

Does the methodology accommodate systems of varying size, nature

(such as utility/public sector, military, consumer products), and complexity?

Does the methodology address ways of handling new information, feedback,

or unforeseen circumstances (such as new requirements)?

Does the methodology allow for acquisition through a variety of approaches

(procurement, development, etc.)?

• Does the methodology allow maximum flexibility with time-allocation (scheduling)

of resources?

• Does the methodology address ways Of identifying and selecting the best human

and material resources to assign or allocate to its various phases?

Accountability

Does the methodology specify the documentation that is appropriate at different

points during its application?

Does the methodology provide for communication and information exchange to

ensure that all participants are aware of significant project decisions and have the

most up-to-date information on the projeci status and activities?

Does the methodology specify an auditing or tracking procedure to ensure that it

has been applied as intended?

Does the methodology suggest a management structure to ensure that it is applied

as intended?

• Does the methodology identify its intended users, class of systems, and scope of its

intended applications?

• Does the methodology provide ways of addressing critical considerations such as

national security, risk (environmental, evolving technologies), human safety, etc.?

. Documentation

• Is the methodology written clearly, precisely, completely, and at a level of detail

that is appropriate for its intended users? Is it a good road map?

492

S
5. Special Considerations of NASA

• Is the methodology fairly independent of organizational structure?

• Does the methodology allow for the retention of key personnel throughout the life-cycle?

• Does the methodology provide for the incorporation of requirements identified during

the system analysis, design, or subsequent phases?

• Does the methodology provide tools and techniques for predicting or projecting future

requirements, through the planning horizon?

• Does the methodology suggest strategies and techniques for designing and developing

systems in the absence of specific requirements?

• Does the methodology provide tools and techniques (including graphics and prototyping)

for communicating among individuals and various organizations or organizational units

working on major systems projects?

• Does the methodology provide tools and techniques for redesigning and making major

modifications to extend the useful life of a system in operation?

Summary

As mentioned, these criteria will be used in Phase Two of the project to evaluate other agencies'

and authors' systems engineering methodologies with potential applications to NASA. They will serve

as a guide and weighing mechanism for justifying our recommendation to NASA/GOddard.

References

1. Blanchard, Benjamin S. Engineering Organization and Management. Prentice-Hall, Inc.,

New Jersey. 1976.

2. Davidson, Frank Paul. Macro-Engineering and the Future: Management Perspective.

Westview Press. 1982.

3. Keys, Paul. "A Methodology for Methodology Choice." Department of Management

Systems and Sciences, University of Hull, U.K. 1987 pp. 65-76.

493
1989 NASA-HBCU SPACE SCIENCE AND ENG EERING

RESEARCH FORUM

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494
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Department of Systems and Computer Science

Howard University

Washington, DC 20059

202-636-6585

Mr. Isaac Gillam

Senior Vice President

OAO Corporation

110 South Arroyo Blvd.

Pasadena, CA 91105

818-354-8049

*Ms. Ruth Gilliam

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

*Mr. Victor A. Glasgow

Howard University

Washington, DC 20059

Ms. Sherryl Goffer

Director, University Relations

Alabama A&M University

Normal, AL 35762

205-851-5230

*Mr. Marquer Griffin

Jackson State University

1400 J. R. Lynch St.

Jackson, MS 39217

601-968-2144

Dr. William A. Grissom

Manufacturing Engineering Department

Central State University

Wilberforce, OH 45384

513-376-6435

Dr. Naidu Gudivada

Department of Computer Science

Jackson State University

Jackson, MS 39217

601-968-2105

Dr. M. Gunasekaran

Dept. of Biology

Fisk University

Nashville, TN 37203

615-329-8555

*Ms. Loft Ann Guy

Spelman College

P.O. Box 929

350 Spelman Lane

Atlanta, GA 30314

*Mr. Bobby Hall

Jackson State University

433 Cally #A8

Jackson, MS 39217

Ms. Gloria G. Hall

EO Officer

Ames Research Center

Equal Opportunity Programs Office

Mail Stop 241-7

Moffet Field, CA 94035

415-694-5626

Dr. John Hall

Milligan Science Research Institute

Atlanta University Center

440 Westview Dr., SW

Atlanta, GA 30310

404-523-5150

50O
Ms. Oceola S. Hall

Director, Discrimination Complaints Division

NASA HO - Code UC

Office of Equal Opportunity Programs

400 Maryland Avenue, SW

Washington, DC 20546

202-453-2180

Dr. Joshua B. Halpern

Chemistry Department

Howard University

Washington, DC 20059

202-636-6895

Prof. Ernest C. Hammond, Jr.

Dept. of Physics

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

Dr. Kwang S. Hart

Department of Physics

Hampton University

Hampton, VA 23668

804-727-5277

*Mr. A. Handoo

Mechanical Engineering Department

Tuskegee University

Tuskegee, AL 36088

205-727-8918

Mr. A. Haquiz

Mechanical Engineering Department

Tuskegee University

Tuskegee, AL 36088

205-727-8918

Ms. Amanda Harris

NASA/MSFC

Marshall Space Flight Center, Al

205-544-7381

35812

Dr. Leonard A. Harris

Chief Engineer for Aeronautics

and Space Technology

NASA HO - Office of Aeronautics

and Space Technology

Code R

600 Independence Avenue, SW

Washington, DC 20546

202-453-2727

Dr. William H. Harris

President

Texas Southern University

Houston, TX 77004

713-527-7036

Dr. Linda Hayden

University of the District of Columbia

Washington, DC 20008

202-28"2-7550

*Mr. Anthony Helm

Virginia State University

P.O. Box 42

Petersburg, VA 23803

804-520-6152

Mr. Arthur Henderson

NASA/MSFC

Marshall Space Flight Center, AL

205-544-2577

35812

Dr. D. Henderson

Physics Department

Fisk University

P.O. Box 15

Nashville, TN 37208

615-329-8555

Dr. George W. Henderson

Virginia State University

Box 42

Petersburg, VA 23803

804-520-6152

The Honorable Steve Hettinger

Mayor of Huntsville

Office of the Mayor

P.O. Box 308

Huntsville, AL 35804

205-532-7304

Dr. Walter A. Hill

G.W. Carver Experiment Station

Tuskegee University

Tuskegee, AL 36088

205-727-8315

Dr. Noel W. Hinners

Associate Deputy Administrator

National Aeronautics and Space Administration

400 Maryland Avenue, NW

Washington, DC 20546

202-453-I024

501
*Mr. Richard A. Hogg

Florida A&M University

Tallahassee, FL 32307

Mr. Carl Holden, Jr.

NASA/MSFC

Marshall Space Flight Center, AL

205-544-3837

Mr. Quintanny Holifield

Biology Department

Alabama A&M University

Normal, AL 35762

205-851-5329

Dr. Lawrence R. Holland

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Mr. Paul F. Holloway

Deputy Director

Langley Research Center

Mail Stop 103A

Hampton, VA 23665

804-864-1000

*Mr. Byungsik Hong

Dept. of Physics

Hampton University

Hampton, VA 23668

Mr. J. D. Horne

Director, Executive Staff

Marshall Space Flight Center

DX01

Marshall Space Flight Center, AL

205-544-1913

Dr. In Heon Hwang

Hampton University

Hampton, VA 23668

804-727-5320

*Mr. Mahdi lbrahim

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

35758

35812

*Mr. John S. Idasetima

Dept. of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Dr. Daryush na

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

*Mr. Weldon Jackson

Morehouse College

830 Wcstview Dr.

Atlanta, GA 30314

Dr. Shaik Jeelani

Chemistry Department

Tuskegee University

Tuskegee, AL 36088

205-727-8833

Dr. Mae C. Jemison

NASA Astronaut

NASA Johnson Space Center

Houston, TX 77058

713-483-2629

*Mr. Hemanta Jena

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Dr. Harriett G. Jenkins

Assistant Administrator for

Equal Opportunity Programs

NASA Headquarters

Office of Equal Opportunity Programs

400 Maryland Avenue, SW

Washington, DC 20546

202-453-2167

Dr. Joseph R. Jenkins

School of Engineering and Technology

Alabama A&M University

Normal, AL 35762

205-851-5581

*Mr. David Johns

Manufacturing Engineering Department

Central State University

Wilberforce, OH 45384

513-376-6435

5O2

t
Ms. Jewel Joiner

Coordinator, Sponsored Programs

Alabama A&M University

Normal, ALL 35762

205-851-5677

Dr. Bessie Jones

Dean, School of Arts and Sciences

Alabama A&M University

Normal, AL 35762

205-851-5300

Dr. Jeanette Jones

Dept. of Biology

Alabama A&M University

Normal, AL 35762

205-851-5329

Mr. Kevin Jordan

School of Engineering and Architecture

Tuskegee University

Tuskegee, AL 36088

205-727-8970

*Mr. B. Joseph

Department of Biology

Alabama A&M University

Normal, AL 35762

205-851-5329

Dr. Purushottam Kale

Department of Biology

Alabama A&M University

Normal, AL 35762

205-851-5329

Dr. Ranjini Kale

Department of Biology

Alabama A&M University

P.O. Box 610

Normal, AL 35762

205-851-5329

*Mr. Mohammad Kalin

E.E.T. Department

Alabama A&M University

Normal, AL 35762

205-851-5581

Mr. Sher S. Kannar

Miles College

P.O. Box 3800

Birmingham, AL 35208

205-923-2771

503

Mr. Richard J. Keegan, Jr.

Executive Assistant to the

Associate Deputy Administrator

National Aeronautics and Space Administration

400 Maryland Avenue, NW

Washington, DC 20546

202-453-1024

Dr. Kyong H. Kim

Physics Department

Hampton University

Hampton, VA 23668

804-727-5320

Dr. Carl H. Kirksey

Department of Mathematics/Computer Science

Bowie State University

Bowie, MD 20715-9465

301-464-3000

*Ms. Yvonne Knight

Chemistry Department

Tuskegee University

Tuskegee, AL 36088

205-727-8833

Dr. R. B. Lal

Department of Physics

Alabama A&M University

P.O. Box 71

Normal, AL 35762

205-851-5306

*Mr. Carlos Lara

Alabama A&M University

Normal, AL 35762

Mr. Robert F. Lawrence

Chief, Office of Equal Opportunity Programs

NASA Lewis Research Center

21000 Brookpark Road

MS 500-311

Cleveland, OH 44135

216-433-2323

Dr. Robert Leflore

ARCC

Jackson State University

P.O. Box 18769

Jackson, MS 39217

601-968-2332
Dr. Martin H. Leipold

Manager of HBCU Programs

Jet Propulsion Laboratory

4800 Oak Grove Drive

Pasadena, CA 91109

818-354-3931

*Ms. Janice Lewis

Alabama A&M University

Normal, AL 35762

Dr. Feiyue Li

Howard University

Washington, DC 20059

202-636-6100

Dr. G. S. Liaw

Civil Engineering Department

Alabama A&M University

Normal, AL 35762

205-851-5581

Dr. Phil Loretan

GWC Agricultural Expt. Station

Farm Mechanization Bldg., Room 100

Tuskegee University

Tuskegee, AL 36088

205-727-8315

Dr. Steven Lukefahr

Food Science and Animal Industries

Alabama A&M University

P.O. Box 264

Normal, AL 35762

205-851-5445

Mr. W. I. Bill Lupton

Jackson State University

1400 J. R. Lynch St.

Jackson, MS 39217

601-968-2121

*Mr. Gratian Macharaga

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Dr. Anthony B. Maddox

MassPep, Inc.

P.O. Box 1081

Waltham, MA 02254

617-647-0042

Ms. Renee Smith-Maddox

MassPep, Inc.

P.O. Box 1081

Waltham,MA O2254

617-647-0042

Dr. Abayomi J. Ajayi-Majebi

Manufacturing Engineering Department

Central State University

Wilberforce, OH 45384

513-376-6435

Mr. Sal Majied

Manager, Advanced Information Systems

The BDM Corporation

7915 Jones Branch Drive

McLean, VA 22102

703-848-5000

Dr. Carl Harris Marbury

President

Alabama A&M University

Normal, AL 35762

205-851-5230

Dr. Benjamin Martin

Spelman College

350 Spelman Lane

Atlanta, GA 30314

404-681-3643

*Mr. Mark Martin

Department of Mechanical Engineering

Prairie View A&M University

Prairie View, TX 77446

409-857-4023

*Mr. Edwin Martinez

GWC Agricultural Experimental Station

Tuskegee University

Tuskegee, AL 36088

205-727-8124

Dr. Samuel E. Massenberg

Head, University Affairs Office

NASA Langley Research Center

MS 105A

Hampton, VA 23665

804-865-2188

*Mr. Khin Maung Maung

Department of Physics

Hampton University

Hampton, VA 23668

804-727-5277

5O4
Mr. M.Mayo

Mr. P. Mbuthia

Biology Department

Alabama A&M University

Normal, AL 35762

205-851-5329

Dr. Caldwell McCoy, Jr.

Deputy Director

Communications and Information Systems Division

NASA Headquarters

600 Independence Avenue, SW

Washington, DC 20546

202-453-1495

Dr. Frank B. McDonald

Associate Director/Chief Scientist

Goddard Space Flight Center

Code 100 - Bldg. 8/Room 650

Greenbelt, MD 20785

301-286-8936

Ms. Sherri McGee

NASA Headquarters

University Programs Branch

Educational Affairs Division

Code XEU

Washington, DC 20546

202-453-8344

Ms. Cherryi McGhee

Manufacturing Engineering Department

Central State University

Wilberforce, OH 45384

513-376-6435

Dr. Saundra Y. McGuire

Department of Chemistry

Cornell University

P.O. Box 354

Ithaca, NY 14850

607-255-6121

Dr. Stephen S. McGuire

Cornell University

5151 Upson Hall

Ithaca, NY 14853

607-255-7425

Dr. Negash Medhin

Department of Mathematics

Clark-Atlanta University

Atlanta, GA 30314

404-681-0251

Mr. Dillard Menchan

Equal Opportunity Programs Manager

NASA/Goddard Space Flight Center

Equal Opportunity Programs Office

Greenbelt Road

Greenbelt, MD 20771

202-82.4-2698

*Mr. Alan Miahnari

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

*Ms. Monique Michaux

Texas Southern University

3100 Cleburne Avenue

Houston, TX 77004

713-527-7003

Dr. Ronald E. Mickens

Clark-Atlanta University

P.O. Box 306

Atlanta, GA 30314

404-653-8662

*Ms. Marjorie Miller

Fisk University

1000 17th Avenue N.

Nashville, TN 37208

615-329-8555

Mr. Mehdi Moghbel

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Mr. Peter M. Molton

Battelle K2-12

Pacific Northwest Laboratories

P.O. Box 999

Richland, WA 99352

Dr. DeLester Monk, Jr.

Howard University

2300 6th Street, NW

Washington, DC 20059

202-636-6100

5O5
Dr. Francis J. Montegani

Chief, Office of University Affairs

NASA Lewis Research Center

MS 3-7

21000 Brookpark Road

Cleveland, OH 44135

216-433-2956

Dr. Oscar Montgomery

Director, Office of Government Relations

Alabama A&M University

Normal,AL 35762

205-851-5675

Dr. S. Morgan

Physics Department

Fisk University

P.O. Box 15

Nashville, TN 37208

615-329-8555

Dr. Carole Morning

Project PRESERVE

Xavier University of New Orleans

7325 Palmetto Street

New Orleans, LA 70125

504-486-7411

Dr. Carlton Morris

GWC Agricultural Expt. Station

Tuskegee University

Tuskegee, AL 36088

205-727-8315

Mr. Desmond Mortley

204 Farm Mech. Building

Tuskegee University

Tuskegee, AL 36088

205-727-8315

Dr. S. R. Murty

Alabama A&M University

P.O. Box 47

Normal, AL 35762

205-851-5581

*Mr. Due M. Ngo

Department of Physics

Hampton University

Hampton, VA 23668

804-727-5277

*Mr. Quoc A. Nguyen

Howard University

Washington, DC 20059

Ms. Anne Nissen

Gallaudet University

Experimental Programs Off Campus

Kendall Green

800 Florida University, NE

Washington, DC 20002

202-651-5000

Dr. James Nixon

City College of New York

140th Street& Convent Avenue

New York, NY 10031

Mr. Gregory Odom

Physics Department

Florida A&M University

Tallahassee, FL 32307

904-599-3470

Dr. Cyriacus Ogbuhei

GWC Agricultural Experimental Station

Tuskegee University

Tuskegce, AL 36088

205-727-8315

Dr. Hideo Okabe

Chemistry Department

Howard University

Washington, DC 20059

202-656-6100

Dr. Frederick Ofiver

Morgan State University

Cold Spring Ln.& Hillen Rd.

Baltimore, MD 21239

301-444-3333

*Mr. Ronald C. Oliver

5415 Oakwood Rd.

Huntsville, AL 35896

*Mr. Sawandi Olugbala

1130 Cleary St.

Jackson, MS 39217

*Mr. Chi Onuoha

Plant and Soil Science

Alabama A&M University

Normal, AL 35762

205-851-5785

506

=
*Mr. Albert Osei

3887 Oakwood Avenue

Huntsville, AL 35816

*Mr. Samuel A. Oyekenu

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Dr. Sunil IC Pancholy

Research Director

Florida A&M University

Tallahassee, FL 32307

904-599-3225

*Mr. Osborne C. Parchment

Morgan State University

P.O. Box 2178

Wheaton, MD 20902

301-444-3405

Mr. Keith S. Parker

UCLA

1103 Ueberroth Building

405 Hilgard Avenue

Los Angeles, CA 90024

Dr. Larry D. Parks

National Aeronautics and Space Administration

Science and Technology Department

Code HA41

Stermis Space Center, MS 39529

601-688-2211

Dr. Arthur S. Paul

Department of Systems and Computer Science

Howard University

Washington, DC 20059

202-636-6595

Ms. Hazelyn Patterson

NASA/MSFC

Marshall Space Flight Center, AL

205-544-2583

35812

*Mr. Ronald B. Paulus

1705 Laverne Dr.

Huntsville, AL 35816

*Mr. Stephen D. Pearson

Dept. of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Mr. Benjamin Penn

Space Science Lab

NASA/MSFC

Marshall Space Flight Center, AL

2O5-544-7809

35812

*Ms. Samara Perdue

Queen Street Dorm - Rm. 254

Hampton University

Hampton, VA 23668

804-727-5589

*Mr. Gerard M. Perera

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

*Mr. Cortes L. Perry

P.O. Box 4325

Huntsville, AL 35815

Mr. Wayne D. Perry

Prairie View A&M University

P.O. Box 2415

Prairie View, TX 77446

409-857-4510

Mr. Burnett W. Peters, Jr.

Equal Opportunity Programs Manager

Langley Research Center

Hampton, VA 23665

804-865-3487

*Mr. Kevin Peters

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

*Ms. Maggie Linton-Petza

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

Dr. Delbert Phiipott

Ames Research Center

Mail Stop 239-14

Moffett Field, CA 94035

415-965-5000

507
Dr. Ralph P. Prince

NASA MD-RES

J. F. Kennedy Research Center, FL

305-853-5153

32899

Dr. O. P. Purl

Clark-Atlanta University

240 J. P. Brawley Dr., SW

Atlanta, GA 30314

404-681-3080

*Ms. Brenda J. Queen

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

Dr. Joseph L. Randall

NASA/MSFC

EB 31

Marshall Space Flight Center, AL

205-544-3282

35812

*Mr. Partha Rangaswamy

School of Engineering and Architecture

Tuskegee University

P.O. Box 959

Tuskegee, AL 36088

205-727-8355

Dr. Sistla M. Rao

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5306

Mr. S. C. Subba Rao

Lincoln University

Lincoh University, PA

215-932-8300

19352

Dr. Pradosh K. Ray

Mechanical Engineering Department

Tuskegee University

Tuskegee, AL 36088

205-727-8918

Mr. William Raymond

Lawrence Livermore National Laboratory

Livermore, CA 94551-0610

415-423-0192

Dr. Anugu S. Reddy

Selma University

1501 Lapsley St.

Selma, AL 36701

205-872-2533

Dr. Bandi Jagannadha Reddy

Bowie State University

Bowie, MD 20715

301-464-3000

Dr. Phillip Redrick

Director, Institutional Advancement

Alabama A&M University

Normal, AL 35762

205-851-5755

Dr. Robert Reiss

Department of Mechanical Engineering

Howard University

Washington, DC 20059

202-636-6608

Dr. Howard Renfro

Special Assistant to the Director

NASA/Johnson Space Center

Houston, TX 77586

713-483-3111

*Ms. Margaret Reynolds

Jackson State University

Jackson, MS 39217

601-968-2121

Mr. James Rice

Equal Opportunity Officer

NASA/MSFC - CE01

Marshall Space Flight Center, AL

205-544-4927

35812

*Mr. Muhammad Rizvi

Alcorn State University

Lorman, MS 39096

601-87"/-2251

Ms. Audrey Robinson

NASA/MSFC

Marshall Space Flight Center, AL

205-544-2732

35812

Mr. GilbertRochon

Remote Sensing UGIS Lab

Dillard University

New Orleans, LA 70122

504-283-8822

508
Dr. Decatur B. Rogers, Dean

School of Engineering and Technology

Tennessee State University

3500 John Merritt Blvd.

Nashville, TN 37209-1561

615-320-3550

*Ms. Zelma Rozier

Jackson State University

Jackson, MS 39217

601-968-2121

Mr. Jesse R. Rubalcaba

Manager,Jet Propulsion Laboratory

Affirmative Action Program Office

4800 Oak Grove Dr. - MS 114-121

Pasadena, CA 91109

818-354-6400

Dr. Rudolph C. Ruff

NASA//vlFSC

JA 63

Marshall Space Flight Center, AL

205-544-1990

35812

*Mr. Christopher M. Ruffin

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

Mr. David Rupert

DOE/Oak Ridge National Laboratory

P.O. Box 2008

Oak Ridge, TN 40402

615-574-0762

Mr. Joseph L. Russell

Aicorn State University

Lorman, MS 39096

601-877-2251

Dr. Elias G. Abu-Saba

Department of Architecture and Engineering

North Carolina A&T State University

McNair Building, Room 455

Greensboro, NC 27411

919-334-7940

Dr. M. Sambandham

Mathematics Department

Morehouse College

Atlanta, GA 30314

404-681o2800

*Ms. Serita Sanders

Dept. of Electrical Engineering

Howard University

Washington, DC 20059

292-636-6585

Ms. Yvonne D. Sanders

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5311

Mr. Walter J. Sapp

Dept. of Biology

Tuskegee University

Tuskegee, AL 36088

205-727-8822

*Mr. Craig Scott

School of Engineering

Material Science Center

Howard University

Washington, DC 20059

202-636-6618

Dr. Jennie Sethna

Director, Dual Degree Engineering and

Computer Science Program

Wilberforce University

226 Walker Center,

Wilberforce, OH 45384

513-376-2911

Mr. Rony Shahidair

Tennessee State University

3500 John Merritt Blvd.

Nashville, TN 37209

615-320-3432

Dr. Prasanta Sharma

Natural Science Division

Miles College

P.O. Box 3800

Birmingham, AL 35208

205-923-2771

Dr. Earl D. Shaw

AT&T Bell Laboratories

Room 1E330

600 Mountain Avenue

Murray Hill, NJ 07974

201-582-5403

509
Ms. Angela Shields

NASA/MSFC

Marshall Space Flight Center, AL

205-544-2793

35812

Dr. John Shoosmith

NASA Langley Research Center

Hampton University

Hampton, VA 23668

804-864-1000

Mr. Roya Siddiqi

Tennessee State University

Nashville, TN 37209

615-320-3432

Dr. E. Silberman

Physics Department

Fisk University

P.O. Box 15

Nashville, TN 37208

615-329-8620

*Mr. Alvin Smith

Department of Mechanical Engineering

Prairie View A&M University

Prairie View, TX 77446

409-857-4023

Mr. Jim Smith

Consultant, NASA Headquarters

1000 Rivermist Ct.

Brinklow, MI 20862

*Ms. Laverne Smith

Texas Southern University

3100 Cleburne Avenue

Houston, TX 77004

713-527-7004

*Ms. Sharonda D. Smith

Tennessee State University

Hale Hall

P.O. Box 309

Nashville, TN 37209

615-320-3432

*Mr. Woodrow Smith

Alabama A&M University

Normal, AL 35762

Dr. Michael Spencer

School of Engineering

Material Science Center

Howard University

Washington, DC 20059

202-636-6618

Mr. John Springer

F'tsk University

Nashville, 'IN 37208

615-329-8621

Dr. T. Springer

Physics Department

Fisk Unive_ity

P.O. Box 15

Nashville, TN 37208

615-329-8621

Dr. Shobha Sriharan

Division of Natural Sciences

Selma University

1501 Lapsley Street

Selma, AL 36701

205-872-2533

Dr. T. P. Sriharan

Division of Natural Sciences

Selma University

1501 Lapsley Street

Selma, AL 36701

205-872-2533

Dr. Sandanand Srivastava

Bowie State University

Bowie, MD 20715

301-464-3000

Dr. Mary Stanley

Department of English and Foreign Language

Alabama A&M University

Normal, AL 35762

205-851-5381

Dr. Arthur W. Stelson

Atlanta University Center

440 Westview Dr., SW

Atlanta, GA 30310

404-523-5153

Mr. Carrington H. Stewart, P.E.

NASA Johnson Space Center

Houston, TX 77058

713-483-3111

510

z
Dr. Robert E. Stickel, Jr.

D. E. Milligan Science Research Institute

Atlanta University Center, Inc.

440 Westview Dr., SW

Atlanta, GA 30310

404-523-5148

*Mr. Narvaez Stinson

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5305

Dr. John J. Stith

Dept. of Physics

Virginia State University

P.O. Box 42

Petersburg, VA 23803

804-520-6152

Ms. Sheree D. Stovall

NASA Headquarters (Code DU)

400 Maryland Ave., SW

Washington, DC 20546

202-953-2180

Dr. Carey E. Stronach

Virginia State University

P.O. Box 358

Petersburg, VA 23803

804-520-6153

Mr. Avaine Strong

Denmark Tech.

Denmark, SC

Dr. Ellis E. Sykes

Albany State College

504 College Drive

Albany, GA 31705

912-430-4604

Dr. Bagher M. Tabibi

Department of Physics

Hampton University

Hampton, VA 23668

804-727-5277

Dr. Mahasin Tadros

Department of Biology

Alabama A&M University

P.O. Box 13

Normal, AL 35762

205-851-5329

Dr. Shawky Tadros

Department of Chemistry

Alabama A&M University

Normal, AL 35762

205-851-5350

*Mr. Mathias Teke

Tennessee State University

330 10th Avenue North

Nashville, TN 37203-3401

615-320-3432

Dr. Hendra Terutung

School of Engineering and Architecture

Tuskegee University

Tuskegee, AL 36088

205-72%8355

Dr. Sidney Tetenbanm

Department of Electrical Engineering

Tennessee State University

3500 John A. Merritt Blvd.

Nashville, TN 37209-1561

615-646-1952

Dr. James M. Thompson

Chemistry Department

Alabama A&M University

Normal, AL 35762

205-851-5350

Mr. James R. Thompson

Director, NASA/MSFC

Marshall Space Flight Center, AL 35812

205-544-1910

Dr. Arthur N. Thorpe

Howard University

Washington, DC 20059

202-636-6244

Mr. E. R. Tossie

Florida A&M University

Tallahassee, FL 32307

Dr. Tung Tsang

Department of Physics and Astronomy

Howard University

Washington, DC 20059

202-636-6244

511
*Mr. Roy Tucker

Physics Department

Florida A&M University

P.O. Box 981

Tallahassee, FL 32307

904-599-3470

*Mr. Jerry C. Turknett, Jr.

888 Hunting Horn Way

Evans, GA 30809

*Ms. Patricla N. Ubaike

Alabama A&M University

Normal, AL 35762

Mr. Nader Vahdat

Chemical Engineering Department

Tuskegee University

Tuskegee, AL 36088

205-727-8978

Ms. Jacqueline Van Sertima

347 Felton Avenue

Highland Park, NJ 08904

201-932-4023

Dr. Ivan Van Sertima

347 Felton Avenue

Highland Park, NJ 08904

201-932-4023

Mr. Bill Vardaman

Center for Space and Advanced Technology

500 Boulevard, South

Huntsville, AL 35801

Dr. Demetrius D. Venable

Department of Physics

Hampton University

Hampton, VA 23668

804-727-5277

Dr. P. Venkateswarlu

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5305

Dr. M. Ludus Walker, Jr.

Office of the Dean

School of Engineering

Howard University

2300-6th Street, N-W

Washington, DC 20059

2O2-636-6555

Dr. Reginald L. Walker

Department of Computer Science

Hampton University

Hampton, VA 23668

804-727-5552

Mr. Robert Walker

NASA/MSFC

Marshall Space Flight Center, AL

205-544-4927

35812

Mr. Scotty Walker

Biology Department

Alabama A&M University

Normal, AL 35762

205-851-5329

Dr. Jae-Ching Wang

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5305

*Ms. Jacqueline Ware

Morgan State University

Cold Spring Ln. & Hillen Rd.

Baltimore, MD 21239

301-444-3405

Mr. Lewin S. Warren

Deputy Assistant Director

NASA Headquarters, Equal Opportunity Programs

400 Maryland Avenue, SW

Washington, DC 20546

202-453-2171

Prof. Nazir A. Warsi

Department of Mathematical and Computer Sciences

Clark-Atlanta University

223 James P. Brawley Dr.

Atlanta, GA 30314-4391

404-523-5150

Ms. Jamesina Watson

Staff Assistant

Space Life Sciences Training Program

Florida A&M University

Tallahassee, FL 32307

904-599-3636

Dr. Walter C. Watson

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5305

512
Dr. Charles A. Weatherford

Physics Department

Florida A&M University

P.O. Box 981

Tallahassee, FL 32307

904-599-3470

Mr. Charles Weaver

Assistant Operator

Florida A&M University

Tallahassee, FL 32307

904-59%3636

Mr. Paul J. Weitz

Deputy Director

NASA Johnson Space Center

Houston, TX 77586

713-483-3111

Mr. W. Ida Westbrook

Chemistry Department

Alabama A&M University

Normal, AL 35762

205-851-5350

*Mr. Stacey White

Jackson State University

Jackson, MS 39217

Dr. Donald A. Whitney

Physics Department

Hampton University

Hampton, VA 23668

804-727-5277

Dr. Alton Williams

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5305

Dr. Carol S. Williams

Department of Biology

Tuskegee University

Tuskegee, AL 36088

205-727-8822

Dr. Willie Williams

Physics Department

Lincoln University

Lincoln University, PA

215-932-8107

19352

513

*Ms. Danette Willis

Electrical Engineering Department

Prairie View A&M University

Prairie View, "IX 77445

409-857-3923

Dr. Leonard Wilmer

Chairman, Division of Natural Sciences

Southern University-Shreveport

3050 Martin Luther King, Jr. Dr.

Shreveport, LA 71107

318-674-3300

Dr. Bobby Wilson

Texas Southern University

3100 Cleburne

Houston, TX 77004

713-527-7004

*Ms. Melanie Wilson

Texas Southern University

3100 Cleburne Avenue

Houston, TX 77004

713-527-7004

Dr. Ray F. Wilson

Texas Southern University

3100 Cleburne St.

Houston, TX 77004

713-527-7004

*Mr. Brian Wingard

Manufacturing Engineering Department

Central State University

Wilberforce, OH 45384

513-376-6435

*Mr. D'Anthony Woods

Virginia State University

P.O. Box 358

Petersburg, VA 23803

804-520-6153

Dr. Mildred Wyatt

NASAIGoddard Space Flight Center

Equal Opportunity Programs Office

Greenbelt Road

Greenbelt, MD 20771

301-286-7913
Dr. Varona L. Wynn

Mathematics/Computer Science

Clark- Atlanta University

P.O. Box 155

240 James P. Brawley Dr.

Atlanta, GA 30314

404-523-5150

*Mr. Li Yang

Department of Physics

Alabama A&M University

Normal, AL 35762

205-851-5305

Dr. GilYanow

Jet Propulsion Laboratory

4800 Oak Grove Drive

Pasadena, CA 91109

818-354-7546

Dr. Art Zygielbaum

Jet Propulsion Laboratory

4800 Oak Grove Drive

Pasadena, CA 91109

818-354-7546

i

*Student

514
515
AUTHORS INDEX

Abdeldayem, H., P. Venkateswarlu, P. Chandra Sekhar, and M. C. George. "Phase

Conjugation by Degenerate Four Wave Mixing in Disodium Fluorescein Solution

in Methanol": Alabama A&M University ............................. 162

Aggarwal, M. D., R. B. Lai, Samuel Oyekenu, Richard Parr, and Stephen Gentz.

"A Study of Microsctructural Characteristics and Differential Thermal Analysis

of Ni-Based Superalloys": Alabama A&M University ...................... 382

Ahmed, Selina, Amanda Cox, and Pauline V. Cornish. "International Food Patterns

for Space Station Foods": Texas Southern University ....................... 26

Ajayi-Majebi, A., W. A. Grissom, B. Wingard, and, D. Walker. "servo Motor-Linked

Articulated Versatile End Effector (SLAVE 2) : Central State University .......... 349

Akyurtlu, A., J. F. Akyurtlu, A. A. Adeytga, and Samara Perdue. "Evaluation of On-Board

Hydrogen Storage Methods for Hypersonic Vehicles": Hampton University ......... 329

Allen, Lew, Paul Forte, and M.tt. Leipoid. "JPL Initiative on Historically Black Colleges and

Universities": Jet Propulsion Laboratory, California Institute of Technology ........ 247

lloyd, Ronald D., and Jerry C. Turknett. "Forced Convection and Flow Boiling With and

Without Enhancement Devices for Top-Sided-Heated Horizontal Channels": Prairie

View A&M University ........................................ 363

Bozeman, Sylvia, and Benjamin Martin. "Implementation of an Algorithm for Cylindrical

Object Identification Using Range Data": Spelman College ................... 61

Brains, E.A., W.H. Anthony, G.L. ttutchinson, and G.P. Livingston. "Seasonal Nitrous

Oxide Flux from an Intensively Managed Pasture in a Humid Subtropical Ecosystem":

Prairie View A&M University ...................... .............. 45

Brewer, William. "Joint Conjugates for Robotic Assembly of Large Truss Structures in Space:

A Second Generation": Jackson State University ........................ 336

Brown, Christopher L, Frederick Oliver, and Ernest C. Hammond, Jr. "M6ssbauer

Spectroscopy and Scanning Electron Microscopy of the Murchison Meteorite": Morgan

State University ........................................... 294

Chang, Ki Joon. "Ellipsometric Measurement of Liquid Film Thickness": Alabama A&M

University ............................................... 134

Choi, Young S., Donald Whitney, Kyong H. Kim, Robert Hess, Norman Barnes, Clayton

Bair, and Philip Brockman. "Development of Flashlamp-pumped Q-Switched

Ho:Tm:Cr:YAG Lasers for Mid-Infrared Lidar Application": Hampton University ..... 422

516

PRECEDING PAGE BLANK NOT FILMED

=
Christopher, Clyde, and Richard Galle. "A Study of Spatial Data Management and Analysis

Systems": Jackson State University ................................ 101

Chu, Y. C., Tung Tsang, and E. Rahimzadeh. "Structures of Cyano-Biphenyl Liquid Crystals":

Howard University .......................................... 205

Coleman, Winson R. "A Successful Intervention Program for High Ability Minority Students":

University of the District of Columbia ............................... 266

Davis, Bruce E., and Gregory Elliot "Jackson State University's Center for Spatial Data

Research Applications: New Facilities and New Paradigms": Jackson State University .... 90

Davis, Michael R., Carey E. Stronach, W. J. Kossler, H. E. Schone, X. H. Yu, Y. J. Uemura, B.J.

Sternlieb, J.R. Kempton, J. Oostens, and W. F. Lankford. "Studies of Superconducting

Materials with Muon Spin Rotation": Virginia State University ................ 211

Edney, Allen Norris, Muhammad Rizvl, and Narjis Rizvi. "In Vitro Regeneration of Basella

Alba L": Alcorn State University .................................. 33

Falconer, Etta, and Lori Guy. "Women in Science and Engineering Scholars Program":

Spelman College ........................................... 270

Fuller, John, Warsame Ali, and Danette Willis. "Mars Surface Based Factory: Phase II -

Task 1C - Computer Control of a Water Treatment System to Support A Space Colony

on Mars": Prairie View A&M University ............................. 343

Gates, Audrey, Tepper Gill, and Arthur Paul. "Suggested Criteria for Evaluating Systems

Engineering Methodologies": Howard University ........................ 489

George, M.C., B. R. Reddi, II. Jagannath, M. Perera, and P. Venkateswarlu. "Surface

Roughness of Flat and Curved Optical Surfaces": Alabama A&M University ........ 482

Ghosh, A., and Pradosh K. Ray. "Electrode Erosion in Low Power Arcjet Thrusters":

Tuskegee University ......................................... 323

Gudivada, V. Naidu. "Image Databases: Problems and Perspectives": Jackson State

University ................................................ 53

ltalpern, Joshua, and Samuel Barts. "The UV Photochemistry of C2N2": Howard

University. .............................................. 231

llammond, Ernest C. "A Densitometric Analysis of IIaO Film Flown Aboard the Space

Shuttle Transportation System STS #3, 7 and 8": Morgan State University ......... 283

Hammond, Ernest C., Stephen Gerwirtz, and Osborne Parchment. "Mathematical Models

for Film Sensitivity Measurement": Morgan State University ................... 69

Hammond, Ernest C., and Ruth Gilllam. "Excimer Laser Interaction with Dentin of the

Human Tooth": Morgan State University .............................. 20

517
Hammond, Ernest C., and Maggie Linton-Petza. "An Analysis of the Moon's Surface Using

Reflected Illumination from the Earth During a Waning Crescent Lunar Phase": Morgan

State University ........................................... 276

Hammond, Ernest C., and Kevtn Peters. "Parameters of Tensile Strength, Elongation and

Tenacity of 70ram IIaO Spectroscopic Film": Morgan State University ............ 479

Hammond, Ernest C., and Christopher M. Ruflla, III. "Densitometric Analysis of Commercial

35mm Films": Morgan State University .............................. 409

Handoo, A., and P. Ray. "Low Energy Sputtering of Cobalt by Cesium Ions": Tuskegee

Univeristy ............................................... 471

Hong, B., and Warren Buck "Kaon-Nucleus Scattering": Hampton University ......... 146

Hwang, I. H., and Kwang S. Hart. "XeCI Laser Pumped Iodine Laser Using t-C4F9 I": Hampton

University ............................................... 398

Jeelanl, Shaik, Kelvin Jordan, and Raymond Clinton. "An Evaluation of the Interfacial Bond

Properties Between Carbon Phenolic and Glass Phenolic Composites": Tuskegee

University ............................................... 450

Kale, Ranjlnl. "X-Ray Sensitivity of Diploid Skin Fibroblasts from Patients with Fanconi's

Anemia": Alabama A&M University ................................ 46

Lal, R. B., A. K. Batra, M. S. Rao, Sandeep Bhatia, and Kunar P. Chundurn. "Growth and

Characterization of Crystals for IR Detectors and Second Harmonic Generation Devices":

Alabama A&M University ...................................... 84

Lal, R. B., William Wilcox, A. K. Batra, and Li Yaag. "Solution Growth of TGS Crystals on

International Microgravity Laboratory (IML-1)": Alabama A&M University ......... 96

Maddox, Anthony, and R_nee Maddox. "Encouraging the Pursuit of Advanced Degrees in

Science and Engineering: Top Down and Bottom-Up Methodologies": Wentworth

Institute of Technology ....................................... 240

Martinez, E. R., C. IL Bonsi, D. G. Mortley, P. A. Loretan, C. R. Ogbuehi, C. Morris, and

W. A. Hill. "Effect of Channel Size on Sweet Potato Storage Root Enlargement in the

Tuskegee University Hydroponic Nutrient Film System": Tuskegee University. ....... 15

Mickens, Ronald E. "Construction of Stable Explicit Finite-Difference Schemes for

Schrrdinger Type Differential Equations": Clark-Atlanta University .............. 47

Murty, S. R. "Aerosol Speckle Effect on Atmospheric Pulsed Lidar Backscattered Signals":

Alabama A&M University ..................................... 304

Nlssen, Ann. "A Model Summer Program for Handicapped College Students": Gallaudet

University ............................................... 262

518
Ngo, Due, and Warren Buck. "Progress in Proton Transport Code Development:

Microelectronic Application": Hampton University. ...................... 371

Ogbueht, C. R., W. A. Hill, P. A. Loretan, C. K. Bonsi, C. E. Morris, P. K. Biswas, and D. G.

Mortley. "Effect of Biweekly Shoot Tip Harvests on the Growth and Yield of

"Georgia Jet" Sweet Potatoes Grown Hydroponically": Tuskegee University ......... 9

Rangaswamy, Pardha, Shaik Jeelani, and Hendra Terutung. "The Effect of Grinding

on the Fatigue Life of Titanium Alloy Under Wet and Dry Conditions": Tuskegee

University ............................................... 428

Sanders, Serita, Tepper Gill, and Arthur Paul. "Engineering Management of Large

Scale Systems": Howard University ................................ 443

Sapp, Walter J., Carol S. Williams, D. Philpot, K. Kato, J. Stevenson, and L.V. Serova. "A

Comparative Study of Seminiferous Tubular Epithelium From Rats Flown on Cosmos

1887 and SL3": Tuskegee University ................................ 1

Sharma, Prasanta, and Herbert Cheung. "3-(Bromoacetamido)-propylamine Hydrochloride:

a Novel Sulphydryl Reagent and Its Future Potential in the Configurational Study of

S1-Myosin': Miles College ..................................... 127

Silberman, Enrique, A. Burger, D. ltenderson, S. Morgan, T. Springer, and Y. Yao.

"Purification, Growth and Characterization of ZnxCdl.xSe Crystals": Fisk University .... 188

Smith, Alvin, and Ronald D. Boyd. "Subcooled Freon-11 Flow Boiling in Top - Heated Finned

Coolant Channels With and Without a Twisted Tape": Prairie View A&M University. . . 390

Spencer, Michael, and Craig Scott. "Characterization of Quantum Well Structures using a

Photo Cathode Electron Microscope": Howard University ................... 405

Srivastava, Sandanand, and Suren N. Dwivedi. "Automated Assembly in Space": Bowie State

University ............................................... 313

Stith, John J., James C. Davenport, and Randolph Copeland. "Computer Simulation of

Radiation Damage in Gallium Arsenide": Virginia State University .............. 356

Tabibi, Bagher M., and Demetrius D. Tenable. "A 10-Watt CW Photodissociation Laser with

IODO Perfluoro-Tert-Butane": Hampton University ...................... 218

Tadros, Mahasin, B. Joseph, P. Mbuthia, and W. Smith. "Manipulating Cyanobacteria for

Potential CELSS Diet": Alabama A&M University ........................ 40

Teke, Mathlas, and Michael R. Busby. "Solving the BM Camelopardalis Puzzle": Tennessee

State University ........................................... 298

Thompson, James, and Janlce D. Daniel. "Analysis of Cured Carbon-Phenolic Decomposition

Products to Investigate the Thermal Decomposition of Nozzle Materials": Alabama A&M

University ............................................... 108

519
Ware, Jacqueline, and Ernest C. Hammond. "A Scanning Electron Microscopy Study of

Macro-Crystalline Structure of 2-(2,4-Dinitrobenzyl) Pyridine": Morgan State

University ...............................................

195

Weatherford, Charles A., Roy Tucker, and Gregory Odom. "Prediction of Pseudo-Resonance

Positions in the Schwinger Variational Principle": Florida A&M University .......... 77

Williams, Willie. "Lincoln Advanced Science and Engineering Reinforcement (LASER)

Program": Lincoln University .................................... 254

Wilson, Bobby, S. Savin, L. Smith, and M. Wilson. "The Formation and Study of Titanium,

Zirconium, and Hafnium Complexes": Texas Southern University ............... 141

Wilson, Ray F., and Robert C. Daniels. "Polarographic Study of Cadmium 5- Hydroxy-2-

(Hydroxy Methyl)-4H-Pyran-4-One Complex": Texas Southern University .......... 171

520