U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

QC NBS SPECIAL PUBLICATION 721

100

U57

#721

1987
Cover photo: The scanning

electron microscope with

polarization analysis

(SEMPA) enables researchers to see how the

magnetic ordering off a sur- face Is Influenced by Its physical structure. Such

Information can be used, for

example, to design denser

recording media and lighter,

more efficient motors.

Shown here Is a typical

magnetization Image pro- duced using SEMPA. See

page 5.
CONTENTS

NBS

Research

Reports

Research Update 2

Surface Science: Thin Is In 5 Mapping Micro-structures: A Quest for the 'Smoking Gun' 10

Parallel Processing Research: Turning Supercomputing Promise Into Practice 11

Cancer Prevention Research Examines

Micronutrient Levels in the Body 14

Manufacturing Technology for the Second Industrial Revolution 16 New Values Recommended for the Fundamental Physical Constants 22

Equations and Models Used to Investigate Hotel Fire 24

Atmospheric Contaminants Targets in NBS Version of 'Dating' Game 27

New Publications 30

Conference Calendar 32

U.S. DEPARTMENT OF COMMERCE

Malcolm Baldrige, Secretary

National Bureau of Standards

Ernest Ambler, Director

National Bureau of Standards

Gaithersburg, MD 20899

301/975-2000

National Bureau of Standards

Boulder, CO 80303

303/497-3000

April 1987

NBS Special Publication 721 Prepared by the Public Information Division A903 Administration Building

National Bureau of Standards

Gaithersburg, MD 20899

301/975-2762

Library of Congress

Catalog Card Number:

86-600603

CODEN:XNBSAV

Any mention of commercial products

is for information only; it does not imply recommendation or endorsement

by the National Bureau of Standards

nor does it imply that the products mentioned are necessarily the best

available for the purpose.

1
RESEARCH UPDATE

REE ELECTRON LASER

FACILITY TO BE BUILT

(FEL) facility for research in physics, materials science, and

biomedicine will be constructed at NBS. A

proposal to build the new facility, submitted

jointly by NBS and the Naval Research

Laboratory, has been recommended for funding by the Office of Naval Research

and the Air Force Office of Scientific Research. The two agencies jointly manage

the FEL research program for the Strategic

Defense Initiative Organization, which would

provide $4.9 million to build the facility. The FEL, to be constructed in the accelerator complex at the NBS laboratories in Gaithersburg, Md., will be driven by the Bureau's 185-MeV continuous wave (cw) racetrack microtron currently nearing completion. The microtron, being built in collab- oration with Los Alamos National Laboratory, will be one of the world's most powerful high-current cw accelerators. A free-electron laser is an exotic light source in which the gases, liquids, or

crystals normally used to produce the laser

effect are replaced by bunches of electrons

traveling through a periodically varying

magnetic field. Such lasers are capable of very short, intense bursts of light that can be tuned very finely across a broad range

of frequencies.

The unique properties of the FEL, includ- ing broad wavelength tunability, high peak

and average power, and extremely short pulse lengths, open up a broad range of exciting new research opportunities in such

diverse areas as atomic and molecular

physics, surface science, photochemistry,

biophysics, and biomedicine. Plans for the

facility call for close collaboration with the medical and materials science communities,

including the Uniformed Services University

of the Health Services, the Food and Drug

Administration, the Center for Advanced

Research in Biotechnology, and a number

of universities in the Washington, D.C., metropolitan area.

IOTECHNOLOGY RESEARCH

CENTER UNDER

CONSTRUCTION

Construction is under way for the

nation's first biotechnology

research center involving academia and

government at the federal, state, and local

levels. The one-of-a-kind center, established by The University of Maryland, NBS, and

Montgomery County, Md., will be located

at the county's Shady Grove Life Sciences

Center. Biotechnology companies are ex- pected to join in research at the Center for Advanced Research in Biotechnology

(CARB).

Focusing on protein engineering and ra- tional drug design, CARB now is putting

together multidisciplinary teams of scientists and engineers with state-of-the-art facilities. The organization has been housed at NBS,

where researchers from the Bureau and

The University of Maryland have under- taken several research projects taking ad- vantage of specialized NBS laboratories. When the new CARB building is ready in spring 1988, it is expected to accom- modate 100 researchers. Up to one-third of CARB's research staff will be visiting industrial fellows. Both cooperative and proprietary research will be possible at CARB.

ATTHOUR METER

CALIBRATION FACILITY W

—

IMPROVES ACCURACY

a watthour meter calibration

facility that offers a fivefold improvement in accuracy over the previous Bureau calibration system. The facility, incorporating digital technology, will help ensure the accuracy

of watthour meters used in standards laboratories operated by utilities and meter

manufacturers. These meters are calibrated

at NBS and subsequently used as secondary standards to check the operation of watthour meters such as those found on

customers' houses or businesses. Some

$150 billion per year in electricity is billed to users based on readings from watthour

meters. Domestic meter manufacturers also need accurate products to compete better

in the international marketplace with meter producers from other industrialized nations.

The 5 million new watthour meters manufactured yearly in the United States are ref- erenced to NBS for accuracy. The NBS

facility now enables routine calibrations to be made with a 0.01 percent accuracy.

Previously, typical Bureau calibrations were

in the 0.05 percent accuracy range.

OMPUTER ACCURACY AND

SECURITY IN VOTE-TALLYING

The NBS Institute for Computer

Sciences and Technology recently received $215,000 for a 3-year

project to study the use of computers in vote-tallying. The funding is from the John

and Mary R. Markle Foundation, a private, nonprofit organization in New York. NBS

computer scientist Roy Saltman will review computerized vote-tallying methods currently being used and will evaluate prob- lems that have been encountered. He also

will recommend methods which election administrators can use to assure that computerized vote-tallying systems are accurate and secure. The study should give election

officials a better understanding of the use

of computer technology in vote-tallying and

improved technical tools to assure public

confidence in the reported outcomes. The

project will continue a previous study con- ducted by Saltman for the Office of Federal

Elections, U.S. General Accounting Office, on computerized vote-tallying.

PACE-MADE EDUCATION

TOOL, MEASUREMENT cSTANDARD ON SALE

The first commercial product

made in space is available on a

microscopic slide as an education tool for teachers and students and as a standard

to calibrate microscopes for small particle measurements. Standard Reference

Material (SRM) 1965 contains material pro- duced aboard a National Aeronautics and

Space Administration (NASA) space shuttle using a chemical process developed for NASA by Lehigh University. The standard

is a glass slide with only a few thousand

microspheres permanently sealed in an air chamber on the surface of the slide. The

spheres are arranged in two different groupings on the slide so that students in high schools and colleges can carry out a

2
series of laboratory experiments that are a

part of the new SRM package. SRM 1965,

Microsphere Slide, 10-Micrometer Poly- styrene Spheres, is available for $77 from

the Office of Standard Reference Materials, B31 1 Chemistry Building, NBS, Gaithers- burg, MD 20899, 301/975-OSRM (6776).

EW NVLAP PROGRAM FOR

CONSTRUCTION TESTING NSERVICES

!

: ratory accreditation program

(LAP) for organizations that perform construction testing services on concrete, aggregates, cement, soil, rock, asphalt, and

geotextiles. The program, which was established at the request of industry under the procedures of the National Voluntary Laboratory Accreditation Program (NVLAP), will be particularly useful to laboratories testing construction materials for export. NVLAPaccredited laboratories are recognized as

being equivalent to those of foreign laboratory systems that have international agreements with NBS, and test data

reports issued by one accredited laboratory will be recognized on the same basis by other national accreditation systems.

NBS was requested to establish the new construction testing services pro- gram because many engineering deci- sions are made solely on the basis of laboratory test data. The new program

will help the buyers of private and public

buildings, both here and abroad, to more

easily determine if the products in struc- tures meet specific national building

codes and insurance requirements. For

information on the new construction test- ing services program, contact: Harvey W.

Berger, A531 Administration Building,

NBS, Gaithersburg, MD 20899,

301/975-4016.

n

IRECT OBSERVATION OF

VIBRATIONAL BREAKDOWN

OF MOLECULES

In a unique laser experiment to observe molecules on a picosecond (0.000 000 000 001 s) time scale, NBS chemists have made direct measure- ments of the decomposition of simple,

vibrational^ excited molecules. Vibrational

excitation, as by heating, is a common

method of breaking down weak (van der Waals) molecular bonds, those responsible

for the physical properties of many solids and liquids and for the shape of biomolecules. Even simple molecules have several possible modes of vibration, and the flow of energy from one mode to another occurs

so quickly that previously it has been diffi- cult or impossible to study this process

directly. Using a state-of-the-art laser apparatus

which produces ultra-short light pulses, the NBS team was able to excite selectively two different vibration modes in the nitric oxide dimer (O-N-N-O) and observe the breakdown of isolated molecules—an event

that occurs in less than 1 billionth of a

second. A very important finding that runs counter to intuition (and theory) is that the higher energy excitation is less efficient than

the lower in breaking down the molecule.

ONDESTRUCTIVE METHOD

DETECTS FLAWS IN CERAMIC

POWDERS NAnew ultrasonic method for detecting flaws in compacted

ceramic powders has been developed by

scientists at NBS. It is the first nondestructive evaluation technique to permit ceramic

producers to fully automate the inspection

of compacted powders while the material is in the mold. The system provides pro- ducers with information on the uniformity

and density of materials at almost any

stage of compaction. It will help manufacturers to screen out defective parts before

costly processing takes place.

The ultrasonic sensor method was devel- oped at the Bureau by Johns Hopkins University materials science graduate student

Martin P. Jones and NBS physicist Gerald

V. Blessing. Blessing says, "The ultrasonic system offers producers a way to control the quality of ceramic powders without having to handle the very fragile materials in their green or unfired state. A ceramic part does not have to be removed from its mold

for testing, prior to the firing or sintering stage." The new ultrasonic sensor method

has been developed as a part of the NBS

effort to apply nondestructive evaluation to materials for in-line monitoring and process

control during manufacturing.

OSIMETER PROCESSORS

MUST BE ACCREDITED SAYS

NRC

I

I The Nuclear Regulatory Commission (NRC) has amended regulations to require all NRC-licensed organizations to have their personnel radiation dosimetry device readings performed by a

processor that is accredited by the NBS

National Voluntary Laboratory Accreditation Program (NVLAP). The NVLAP dosimetry program, which provides for periodic eval- uations of dosimeter processors, was established in 1984 at NRC request to improve

the accuracy of measurements on ionizing radiation that may be received by workers. Under the personnel dosimetry program,

accreditation is limited to personnel services

for types or models of dosimeters that doc- ument whole body and skin-dose radiation.

All participating organizations are required

to demonstrate that they are able to pro- cess each dosimeter type in accordance

with ANSI N13.11, Criteria for Testing Per- sonnel Dosimetry Performance. Currently, the NVLAP program has 45 accredited processors with evaluations under way for an additional 13.

3
EW STEAM TURBINE

TECHNOLOGY: LARGE

ENERGY-SAVING POTENTIAL N

—

.

$200 million annually in generating costs by using a new packing ring designed to reduce leakage in steam tur- bines, according to the Department of En- ergy (DOE). The improved ring was

developed by Ronald Brandon of Schenectady, N.Y., with partial funding from a grant by DOE, after NBS reviewed and recom- mended Brandon's proposal to DOE.

Packing rings, located on the turbine drive

shaft of an electric generator, typically become worn from vibration during start-up and shut-down, allowing steam to escape and wasting energy. The new ring reduces wear and allows a tighter seal. It was tested

recently at a power plant in Maryland. NBS

evaluates, free of charge, ideas for energysaving inventions. To date, nearly 400

promising ideas have been recommended

to DOE for possible support.

IRST RESULTS FROM NBS

c BEAMLINE AT NSLS „,„._,

ing the NBS X-24A beamline at the Brookhaven National Synchrotron Light Source (NSLS) confirms that

this facility will be an important national re- source for x-ray spectroscopy. X rays can be tuned through the energy range from 500 to 5000 eV to a bandwidth of 0.2 to 0.5 eV, two to five times better than competing sources, and focused to a 1- by

2-mm spot at the sample chamber. Flux at the sample chamber is 109 to 1013 x rays/second. Current studies of argon, methyl chloride, various freons, and sulfur hexafluoride demonstrate that the instru- mentation is sufficiently precise to separate

x-ray spectral features due to multiple elec- tron effects from those due to specific bond

orbitals, long a stumbling block in such

research.

NATIONAL PROGRAM FOR

RADIATION INSTRUMENT

CALIBRATIONS

NBS and the Health Physics Society (HPS) have begun a national program to accredit laboratories that calibrate instruments used to measure ioniz- ing radiation. Under their agreement, NBS

will continue to be the primary standards

laboratory for these instruments, such as Geiger counters, which are regularly used

in industry to protect radiation workers by

making on-the-spot measurements of radiation levels. HPS will provide a service to accredit secondary- and tertiary-level calibration laboratories using procedures

and technical criteria developed by the society in cooperation with the NBS Office of Radiation Measurements. This program will provide professionals in occupational radiation protection greatly expanded access to the national standards maintained by NBS. HPS says this will result in improved unifor- mity, accuracy, and traceability of ionizing radiation measurements. There are more

than 1 .3 million industrial radiation workers

in the United States who could be affected by the new program. c

EM LINEWIDTH MEASUREMENTS UNDER STUDY

NBS and EDAX International,

Inc., have agreed to a joint re- search program to help devel- op techniques for making precision measurements of the dimensions of integrated

circuit features using the scanning elec- tron microscope (SEM). The dimensions

of integrated-circuit structures are important in their manufacture and must be

carefully controlled. At present, the most

accurate measurements are made on photomasks by optical microscopes, us- ing methods developed at NBS. However

the ability to measure small dimensions of features on actual circuits by optical microscopy is limited by the wavelength

of light and the thickness of the features, so manufacturers look to the SEM to measure feature dimensions below 1 micrometer—the dimensional region of the newest generation of dense integrated

circuits.

EDAX, a manufacturer of SEM peripherals, will supply NBS researchers with equipment and programming support to help develop the new techniques necessary to make precise and accurate

feature-size measurements using SEM's,

and to facilitate comparisons between the custom SEM used by NBS and commercial equipment. Richard Holton of EDAX

International will work as a research associate with the NBS Center for Manufacturing Engineering.

NFRARED SYSTEMS DEVELOPED TO

TEST GALLIUM ARSENIDE WAFERS

Detecting flaws in gallium arsenide (GaAs) semiconductor materials should be easier with two polarized infrared

light systems developed by NBS Semiconductor Electronics Division researchers. Both are nondestructive methods wafer manufacturers can use to screen materials before marketing. One system can examine

an entire wafer, while the other employs a

75- to 600-X microscope to view isolated wafer portions. Both systems allow digital storage of images and the use of false- color graphics to represent wafer characteristics such as variations in the transmitted

infrared intensity, which could indicate

potential problems. GaAs wafer applications

in high-speed electronic and optoelectronic devices are growing rapidly, but production

of the near-perfect GaAs crystals needed

for optimum performance is not as ad- vanced as the older silicon technology.

The two NBS systems can aid in production control by pinpointing wafer flaws and inhomogeneities. Bureau researchers

are using the infrared techniques in- house, but will also assist industries in set- ting up their own systems.

4
Surface Science: Thin is In

uperficial interests? Hardly. Re- searchers who confine their studies

to the surface—the first few atomic

layers of materials— believe the seeds of technological advances in fields as diverse as medicine,

chemical catalysis, nuclear fusion, atmospheric science, materials science, and electronics lie in that curious ultrathin region.

One need only look at advances

in electronics to find striking evi- dence of how technologically fertile the surface is. In the electronics

field, where thin is in and smaller is

better, the ability to engineer the

surfaces of semiconducting silicon chips has resulted in ever faster and more powerful computers. But now scientists and engineers are up against a formidable obstacle, the so-called "micron barrier." The

next truly significant advance in computing power hinges on the

ability of researchers to develop

methods for packing chips with

transistors and other electronic components that are smaller than

the current size limit of 1 micron

(one-millionth of a meter).

"The push is for very small devices, but you can't just scale down the size of the components,"

explains Dr. Robert Celotta, head of the electron physics group in the NBS Center for Radiation Research.

"Inevitably, once you get down to a certain level, things no longer work." Adds Dr. Ted Madey, head of the surface structure and kinetics group in the Center for Chemical

Physics at the Bureau, past

surface-engineering developments

that spawned scores of technoloUsed to view the magnetic microstructure off surfaces, SEMPA (scanning electron microscope with polarization analysis) has a spatial resolution up to 100 times better than the

best optical methods now available. The top two magnetization Images shown here were

obtained by using SEMPA to measure two In-plane components of the polarization In a

Fe-3°/oSI single crystal. At the lower right is an Intensity image showing the surface

topography of the same area. The image at the lower left Is a small region of the Image

at the upper left magnified 50 times.

5
gies have been primarily "guided

by empiricism"—experiments and

observations—and even intuition. But extending these developments

and creating new surface- engineering applications, Madey

and others believe, require fun- damental understanding of the chemical and physical properties of surfaces and interfaces—the thin boundary regions between two substances—and how these properties affect reactions in the critically important regions.

Strictly defined, the surface is the outermost layer—or, at most, the

first few layers—of atoms that lies on top of a solid or liquid. By virtue

of their location, these layers, with a

thickness of a few to tens of angstroms (one angstrom is one ten- thousandth of a micron), are

substantially different from the bulk

of the substance below. "The arrangement of atoms in the surface layer is typically dif- ferent from the bulk solid," explains

Dr. Cedric Powell, chief of the Sur- face Science Division. "The electronic structure of atoms in the surface is also different, so the chemical and physical properties of the surface differ from the cor- responding properties in the bulk." "Most people tend to think there are only three states of mattersolid, gas, and liquid," says Madey,

who has been studying surfaces for more than two decades. "But sur- faces constitute yet another state of matter." To study this complex and

unusual form of matter with the necessary sensitivity, scientists and

engineers have developed an

arsenal of analytical tools. The proliferation of techniques

testifies to the complexities of the research task and the many dif- ferent surface properties to be

measured, including elemental composition, chemical state, atomic arrangement, structural defects, electronic structure, topography, dif- fusion, and surface reaction.

"Ideally, a single technique

would measure a particular property of the surface," Powell explains. The commonly used tech- niques for measuring surface composition, however, differ in sensitivity, specificity, spatial resolution, and ability to identify chemical state. The limitations of these techniques,

such as electrostatic charging of in- sulating specimens and damage to the specimen during analysis, vary as well. Because most scientists need to determine a number of sur- face characteristics, they frequently

combine instruments and tech- niques to obtain the best data for a

given task.

"The arrangement of atoms

in the surface layer is typically different from

the bulk solid."

The rapid growth of surface science and its applications has

led to increased awareness of the need for standards. For example,

ASTM, a voluntary standards or- ganization, has established a committee that is active in this area, and the Versailles Project on Ad- vanced Materials and Standards, a new international group, has

recently formed a surface analysis

working party. NBS scientists are working closely with these and

other standards-writing groups to help improve the accuracy and

reliability of surface science measurements.

For the techniques most widely

used to measure surface composition, Auger-electron spectroscopy

and x-ray photoelectron spectros- copy, researchers in the Surface Science Division are providing

calibration data for the instruments and reference data on materials to make the analyses more accurate. They are also developing reference

materials to allow accurate measurements of composition versus

depth. As part of a joint U.S./Yugoslavia program, researchers developed a Standard Reference Material, SRM

2135, with thin layers of known

thickness, which is sold through the NBS Office of Standard Reference

Materials. Currently, analysts remove surface material by ion sputtering and then measure the in- stantaneous surface composition

versus sputtering time. By using

this SRM, researchers will be able

to convert the sputtering time to a

depth measurement more accurately. In addition, NBS scientists are working with the ASTM Committee

E-42 on Surface Analysis to de- velop reference procedures that will improve the reliability and efficiency

of surface analyses. Powell points out that standards

will enhance the usefulness of the instruments and, in the process, push the field ahead. "Most of the commercial instruments used today

only became available within the past 15 to 20 years," he says. "We're using them in a qualitative fashion, but there is a growing

need for quantitative analyses with improved accuracy."

The biggest boost to the field will come from more detailed under- standing of the composition and

properties of surfaces and inter- faces and from unifying theories

that describe how surface structure influences chemical behavior.

Ejected Ions Reveal

Surface Geometry

One of the basic tenets of chemistry is that structure—shape and

composition—determines function. Two molecules may consist of the same atoms in the same proportions, but if the atoms are arranged

differently, one molecule may react strongly with neighboring sub- stances while the other stands idly by.To get a glimpse of the atomic geometry of solid surfaces, Madey

and his colleagues had to build
their own instrument, a combination

of probes that allows them to deter- mine shape and composition of molecules on surfaces. The novelty

of the instrument is that it provides "a rather direct way to determine

how atoms and molecules are bonded to the surface," Madey

explains.

The method, called electron stim- ulated desorption ion angular distri- bution (ESDIAD), capitalizes on

what had been considered to be a

hazard of the trade—surface damage caused by incident beams

of electrons used as probes. When

the electron beam strikes the sur- face, it imparts some of its energy

to surface molecules, exciting the bonds that hold the molecules

together. If excited sufficiently, the bonds break, the molecules fall apart, and ions are ejected from

the surface of the specimen.

NBS scientists are working closely with these and

other standards-writing

groups to help improve

the accuracy and reliabili- ty of surface science

measurements.

"It turns out that the ions fly off in the direction of the broken bonds,

in highly directed patterns," Madey

says. With the help of an ion detector and a sophisticated computer

system, Madey and his colleagues can determine the original orientation of the molecules on the sur- face. With other equipment on the

device, including a mass spectrometer, the researchers can also determine the number and composition of the ejected ions, and they can make judgments about the motion and internal energy of the ori- ginal bonds.

Put all the information together

and the NBS team has a three- dimensional snapshot of a spec- imen's surface. For example,

Madey has determined that the

position a carbon monoxide molecule assumes on a surface de- pends on its environment. On

nickel and ruthenium, carbon

monoxide stands up, perpendicular

to the surface, but on chromium,

the molecule lies down. And on

palladium, the bond is tilted. Odder still, they have learned

that surface molecules can be

"pushed around" by impurity atoms. For example, a two- dimensional layer of water molecules on a silver surface is badly

disordered. When the surface has a few foreign atoms on it, such as ox- ygen or bromine, the water molecules immediately rearrange to form well-ordered local structures attached to the foreign atoms. Madey and his team have used

ESDIAD to chart the surface land- scape of several noble metal catalysts and to study the structure of surface defects on single-crystal oxides. They also have studied

the bonding of water to the sur- face of silicon, yielding insights

into how the contaminant alters the electronic properties of the semiconductor. Other investiga- tions have focused on the mechanisms of radiation-induced damage to surfaces. Worldwide, researchers at ten

institutions, including five in the United States, have built instru- ments based on the NBS ESDIAD

apparatus. These researchers also are extending the applications of the technique. But are ESDIAD studies, which

probe single-crystal specimens in a high-vacuum environment, relevant

to the surface characteristics of a

Drs. Ted Madey and Allen Johnson use

electron stimulated desorption ion angular

distribution to determine how atoms and

molecules are bonded to the surface.

material exposed to less-than-ideal conditions, such as a metal catalyst

in a chemical reactor or an elec- trode in an electrochemical cell? Madey believes so. "Guided intuition has taken chemists an amazingly long way,"

he says. But analyses of the

detailed information gained with ESDIAD and comparable tech- niques that use photon beams as probes can reveal the fundamental

structural and electronic mechanisms that govern chemical reactions. The insights that evolve from

this understanding will aid efforts to develop computer models of chemical reactions at surfaces. With these models, scientists may be

able to fabricate "designer catalysts," customized mixed-metal compounds that are superior to the

catalysts that nature supplies.

7
With a scanning tunneling microscope, Drs. Robert Dragoset, Daniel Pierce,

Robert Celotta, and Stanley Mielczarek (left to right) study the structure off surfaces and interfaces to determine how changes affect their properties.

New Views of the Atomic

Microstructure of Surfaces

Over in the NBS Center for Radiation Research, there's a scientific in- strument that, as physicist Celotta describes it, "looks like a bird cage

inside a bird cage." But the instru- ment, which stems in part from

pioneering research conducted by

retired NBS scientist Dr. Russell Young during the 1960's, is for scientists, not bird fanciers. With the instrument— a scanning tunneling

microscope (STM)—scientists can

"see" the surface in previously unattainable detail, an atom-by- atom view of the contour of sur- faces and interfaces.

Modeled after the STM built by

the IBM Zurich Research Laboratory, where the first such micro- scope was built, the NBS instru- ment has a vertical resolution of one-tenth of an angstrom—less than the size of an atom—and a

horizontal resolution of 6 angstroms,

according to Celotta. This precision stems from the STM's ability to exploit the wavelike properties of electrons. Celotta explains that the micro- scope gets its name from the pro- pensity of electrons to extend beyond the surface of materials. The ability of electrons to jump be- tween materials that are very close, but not touching, is known as tun- neling. In scanning tunneling

microscopy, a needle-like probe is moved to within far less than a

hair's breadth of the surface of the specimen. When the distance be- tween probe and specimen is less than 10 angstroms, the cloud of a

single electron emanating from the metal tip of the probe intersects with an electron cloud floating above the surface. Applying a volt- age to the probe generates a tun- neling current that flows between

the tip and the surface. As the tip sweeps across the sur- face in a series of parallel lines, a computerized feedback mechanism

maintains the probe at a constant

height above the surface. In effect, the probe traces the atomic topography, which appears as a series of peaks and valleys on a computer

screen. The computerized data can be fashioned into a topographic

map or a three-dimensional rendering. And because the tunneling

current depends on the voltage applied to the electronic structure of the surface, variations in the current

yield details about the electronic behavior of the surface atoms. NBS researchers plan to use the instrument to investigate such

things as the structure of biological

molecules, the growth of single

layers of atoms and molecules on

surfaces, and the structure of finely machined surfaces.

Celotta's group intends to study

"multilayer epitaxial growth," a

technique for growing a crystalline

film on the surface of an underlying

crystal. Although the atomic ar- rangement of the deposited film is assumed to conform with that of the substrate crystal, Celotta suspects that slight deviations arise

at the interface. "There might be defects and

maybe something happens at the

defects," he says. "In the transition region between the crystal layer on

the top and the crystal on the bot8
torn, the lattices could become

stretched or strained." Because of these changes, atoms may be- have in ways that defy current understanding, creating what

Celotta calls a "crack in the

periodic table." Once understood,

the atomic rearrangements would

allow for strategic manipulation of surface properties. Changes

measured on the order of ang- stroms could yield new surface

properties that greatly enhance

the performance of such devices as transistors, lasers, and

magnetic recording materials.

Into the Magnetic Domain

The STM is not the only new addition to the arsenal of research in- struments capable of measuring

the microstructure of surfaces. Another, developed at NBS by

Celotta, Dr. John Unguris, Dr. Daniel Pierce, and Gary Hembree,

brings the magnetic microstructure of surfaces into view. Known

as SEMPA, for scanning electron microscope with polarization analysis, the device has a spatial resolution of 100 angstroms, or up to 100

times better than the best optical methods now available. With it, re- searchers can actually see what is happening on the heads of a tape

recorder, on a floppy disktwo of many types of magnetic

storage media—or on the surface

of a magnet in an electric motor.

First built in 1982, SEMPA

quickly captured the interest of companies that manufacture products with magnetic components, in- cluding General Motors, Kodak,

Control Data, and Westinghouse.

These companies and six others are exploring the possibility of es- tablishing a collaborative research program with the NBS team. Another gauge of interest in the measurement technique is the fact Perkin Elmer, the scientific equip- ment manufacturer, intends to intro- duce a commercial version of SEMPA within the next year or two, according to Celotta.

The key feature of SEMPA is a compact "spin polarization detector" built by the NBS researchers. A cube measuring about 6 centimeters on a side, the detector can

be appended to an ultrahigh vacuum scanning electron micro- scope, where it counts the polar- ized secondary electrons ejected from the surface of a specimen

by the microscope's electron beam probe.

As determined in an important

discovery at NBS by Unguris,

Celotta, Pierce, and Annija Galejs, the spins of the secondary elec- trons are identical to those of the

electrons in the specimen. This find- ing made it possible to develop a means to characterize the local magnetic structure of surfaces. Each atom has a "magnetic moment," the product of its spinning

electrons. In nonmagnetic materials, the magnetic moments of the constituent atoms are randomly

oriented and cancel each other. Magnetic materials, in contrast, contain more electrons spinning in one

direction than they have electrons

with opposite spins, resulting in a

net magnetic field. But ferro- magnetic atoms tend to be "clannish," isolating themselves in separate domains. On the surface

Once understood, the

atomic rearrangements

would allow for strategic

manipulation of surface

properties.

of a material, a domain of atoms

with magnetic moments aligned in one direction may be located next

to a domain of atoms that has a

different preferred orientation of their magnetic moments.

Secondary electrons basically tell the NBS scientists the magnetic

direction of the domain they are

from. For example, if electrons

ejected by the microscope beam at a specific site are polarized—spinning in the same direction—then a measurement of this polarization

gives both the strength and the

direction of the magnetization at that spot. After scanning the entire surface of a specimen, the re- searchers have two computerized

images—one of the topography of the surface and one of its magnetic

microstructure. Because of SEMPA's high resolution, they can

actually "see" inside individual magnetic domains.

From the view that emerges, the researchers can see exactly how

the magnetic ordering of a surface

is influenced by its physical structure. They can determine how, for example, an impurity, a stress, or

"miniaturization" alters the arrange- ment and distribution of surface do- mains. They can also chart changes in the shape and location

of domain walls, the partitions that cordon off domains. According to

Celotta, the shape of the domain

walls is a critical variable in highdensity magnetic recording media

because it influences how many

bits of information can be stored in a given area. The timing of SEMPA's arrival couldn't be better, as demonstrated

by the short span between its de- velopment at NBS and its ap- proaching commercial introduction. As is true for the semiconductor in- dustry, international competition in the magnetics field is intense. The

drive is to develop smaller and better products—denser recording

media and a lighter, more efficient motor, for example. With SEMPA,

researchers have a new tool to guide their efforts.

by Mark Bello Washington, D.C.-area Science Writer
Mapping Microstructures: A Quest for

the 'Smoking Gun'

During the 1960's, a bridge over the Ohio River collapsed. NBS re- searchers eventually determined

that the technological calamity had

its origins in a material defect so

small that it would have evaded detection by the unaided eye. The bridge collapse and the subsequent NBS study preceded

Dr. Dale Newbury's arrival in the NBS Center of Analytical Chemistry,

but he is familiar with the details because they demonstrate the im- portance of the compositional mapping program he directs. "Our interest arises," Newbury

says, "because a large number of physical, biological, and technological processes are controlled by

compositional events that occur on

Dr. Dale Newbury uses com

positional mapping techniques to chart small

changes In the atomic

composition of materials.

a micrometer or submicrometer

basis." Put another way, that statement means big events start as small changes in the atomic composition

of materials. With the tools in the compositional mapping program, Newbury and his colleagues can

chart those changes in intricate

detail, at the level of a micrometer

(one-millionth of a meter) or less. "Strictly speaking, we are not surface scientists," Newbury says. "Our probes take us a microm- eter—a few thousand atomic layers—deep. But the term 'surface'

is a relative one. To many surface

scientists, it may mean a few

atomic layers. To geologists, the surface is a region 50 to 100 miles

thick.'-' The power of the techniques

used in the program is their highspatial resolution. Microanalytical

techniques, some of which were

developed at NBS, allow Newbury

and his colleagues to determine the atoms present at sites 1 micrometer

apart. For example, an electron scan across a human hair—about 70 micrometers across—would

yield 70 different compositional

analyses. While even better spatial resolution is achieved with some of the program's instruments, the micrometer seems to be an especially im- portant unit in nature and in technology. Organelles, the specialized cellular factories that per- form tasks such as assembling

proteins from instructions encoded

in genetic material, for example, are

only a few micrometers in size. In the drive to cram more electronic components on computer chips, the micrometer represents the limit of current chip-manufacturing

technology.

The NBS researchers have now

greatly advanced their methods by

designing computer programs that allow them to determine the number and type of atoms in a given

sample mass. By moving the beam

in a regular pattern (scan) and

repeating the quantitative analysis at many thousands of points, they can develop a complete

"compositional image." The product of years of work, the compositional mapping program does the "number crunching" for the group's primary instrument—a combination of a scanning electron microscope and x-ray microanalyzer.

The compositional maps are actually two pictures in one. Color- enhanced pictures allow viewers to see changes in the concentration and distribution of different types of atoms in a specimen; overlaying

graphs show the actual concentrations that correspond to the

features depicted in the images.

"With the combination of pictures

and numbers you get a much better feel for what's happening in a

material," Newbury says. In effect, the quantitative images provide researchers with what Newbury

calls "the smoking gun"—direct evidence of microstructural changes.

A natural application for the tool

is in the design of new alloys and

advanced composite materials. When researchers change the mixture of atoms in an experimental

material, they will be able to see

the resulting changes in distribution and concentration. They also will be

able to relate these compositional

changes to the macroscopic properties of a material. In addition, the

ability to track microstructural changes will aid efforts to under- stand destructive processes, such

as corrosion, and how slight defects can ultimately lead to structural failures. The potential uses of the NBS

compositional mapping techniques

are not confined to the prov- ince of materials science. As Newbury says, "They can be applied to an incredibly wide variety

of fields." M.B.

10
Parallel Processing Research: Turning

Supercomputing Promise Into Practice

Imost overnight, in the relative time- frame of technology, a new generation of computers is dawning.

Known as parallel or multi- processors, their difference is that they use more than one processor

to simultaneously solve many

pieces of a problem. Their promise

is to make practical the glamorous,

ambitious aspirations of computing

such as artificial intelligence and im- age and speech recognition. But, there are many hurdles to over- come before these aspirations

become reality. The idea behind parallel processing is to get supercomputing speed

for a fraction of the cost. To

achieve this higher performance,

the algorithm—mathematical reci- pes, programming language, and

hardware architecture must be perfectly matched to the application.

The only way to know whether a

particular combination is successful

is through reliable measurements.

But the state of the art in computer performance measurement is poor for computers with one pro- cessor and much worse for multi- processors, says Dr. Stuart Katzke,

of the NBS Institute for Computer

Sciences and Technology.

By developing new techniques

and tools to measure the perfor- mance of these new computer ar- chitectures, researchers at NBS are

evaluating how different configurations of processors solve particular

types of problems. "You can't measure computer

performance in terms of length, or

watts, or joules," explains electronic engineer Robert Carpenter, head of

the parallel processing group at NBS, "and existing measurements

such as 'instructions per second' or

'logical inferences per second' do

not adequately express the perfor- mance of these novel architec- tures." Adds Katzke, "If we know what

to measure and how to measure it then it will be easier to evaluate and compare machines, 'tune' current designs, or improve future designs."

Along the way, the NBS re- searchers will be studying many

aspects of parallel processors. "Before we can develop techniques

to measure their performance, we

have to understand many factors,

"If we know what to

measure and how to

measure it then it will be

easier to evaluate and

compare machines, 'tune'

current designs, or improve future designs."

such as which languages are best, how these machines can be pro- grammed and used, and how dif- ferent architectures work," says

Carpenter.

Serial vs. Parallel

Processing

Conventional computers, sometimes

called serial or Von Neumann, have one processor to perform operations, such as addition, on data. (John Von Neumann is often credited with the general design upon

which most of today's computers

are based.) Even today's fastest

serial computers solve a problem one step at a time, just as they

have since the 1940's.

But one-step-at-a-time computers

are already beginning to approach

speed limits, largely because of basic physical limitations that exist

in today's electronic circuitry. Unlike serial computers, parallel processors use more than one pro- cessor to simultaneously solve many pieces of the problem.

Theoretically, they can comprise two processors connected by a

simple link or tens of thousandseven millions—of processors con- nected by a complex communications network. Von Neumann and others of the time saw the appeal of putting multiple processors to work on a problem. But the high cost and low

reliability of early computer components made the idea impractical even into the early 1970's. The ad- vent of microprocessors, which pro- vide inexpensive, compact, and

reliable processing power on a sin- gle silicon chip, made parallel pro- cessing possible.

Of course, adds Katzke, having

the capability does not mean the technology is well understood.

Bottlenecks

While parallel processors can speed the processing of data, they pose a different set of problems for users, including uneven flow of in- formation and increased likelihood

of communications bottlenecks.

11
Robert Carpenter (rear), head of the NBS parallel pro- cessing group, and computer scientist Gordon Lyon are developing special hardware to help solve problems

such as communications bottlenecks.

In parallel processing, memory

either is shared by many pro- cessors through some common

access network, or each pro- cessor is given its own memory

with the network passing mes- sages and information from pro- cessor to processor. "Both forms need just the right amount of data

flow or some processors will sit idle while others choke on too much data," explains NBS computer scientist Dr. Gordon Lyon.

The NBS team is developing

special hardware to determine

what the computer is doing and

where the problems such as bot- tlenecks are. "Our goal is to de- velop measurement hardware that can be used with a wide range of parallel-processor architectures,

'

'

says Katzke. "The hardware will help find out where the machine is

getting hung up and where it's doing most of the work. With this information, designers and manufacturers can change the architec- ture to become more efficient."

Languages and

Programming

Another key to making these machines run more efficiently is understanding how to program

them. "But," says Katzke, "we

don't have a very good handle on programming parallel processors.

The NBS team is developing special hardware to

determine what the

computer is doing and

where the problems such

as bottlenecks are.

Having more than one processor

drastically changes how you should

instruct a machine via a program- ming language to perform some

task. But we don't fully understand how." He adds, "Programming lan- guages are still oriented to serial or Von Neumann machines. But if a problem is treated sequentially then you are not going to get any in- crease in productivity out of a

parallel machine."

Either the language must provide a way for the programmer to decompose the problem so that it can be executed in parallel, or the compiler has to be smart enough

to recognize the best approach to

partitioning the computational problem, explains Katzke. (A compiler

translates a higher level program- ming language into instructions the machine can understand.)
Benchmarks

While each computer architecture represents a new opportunity for solving problems, according to Katzke it is often difficult to know

which architecture is best for which

application.

To help compare the perfor- mance of machines with different parallel-processing architectures, the NBS scientists are creating, collecting, and evaluating a wide range of

test software known as benchmarks. The benchmarks will repre- sent a variety of applications which

could be run on multiprocessors. Most benchmarks available to- day, such as the Lin pack codes (a package of about 400 Fortran subroutines for solving dense

systems of linear equations), measure performance for only a

particular class of problems and

were not specifically developed with

parallel processing in mind. The NBS collection so far contains a number of programs aimed

at measuring a computer's perfor- mance in areas that include fluid

To help compare the

performance of machines

with different parallel processing architectures, the

NBS scientists are

creating, collecting, and

evaluating a wide range of

test software known as benchmarks.

dynamics, artificial intelligence, image processing, and general

scientific computing.

The NBS researchers will make

the routines available at no charge

over networks such as the Defense

Department's Arpanet* "This

'For information, write or call Robert

Carpenter, B364 Materials Building, NBS,

Gaithersburg, MD 20899, 301/975-5677.

Application

Algorithm

Language

Environment

Operating System

STIMULUS

System

Being

Measured

UJ

(/> zo

Q.(A

LLI DC

Measurement

Hardware

Data

Collection DATA

To achieve the higher performance promised by parallel processors, the

algorithm, programming language, and hardware architecture must be perfectly matched to the application. The only way to know whether a particular combination is successful is through reliable measurements. NBS

researchers are developing new tools and techniques to measure the performance of parallel processors.

should help users decide which

machines might be best for a given

application," says Carpenter,

"because it will offer benchmark

programs characteristic of a variety

of problems."

DARPA

The Defense Advanced Research

Projects Agency—known as DARPA—is interested in the NBS

research for its strategic computing

project. Steven Squires, assistant

director for information science and

technology at DARPA, says the agency's project is taking advantage of the fact that "we can take a

fairly simple technology and create a revolution in computing through

careful engineering."

Squires adds, "These machines

are very hard to characterize. NBS

will be learning what you can measure and developing the technology to do it. By getting NBS

in at the beginning we are planning

for technology transition of this new

generation of computers."

The Best Machine?

"Just as no one car is best for everyone, no single design of a

parallel processor is best for all problems," says Katzke. "We will never come up with a standard for the 'best' parallel processor. But over the next several years, we will be developing ways to measure the performance of these machines, so when someone asks, 'Given my re- quirements, what should I look for?' they may be able to find an

answer."

by Jan Kosko

NBS Public Affairs Specialist

13
Cancer Prevention Research Examines

Micronutrient Levels in the Body

an supplemental doses of certain vitamins and minerals reduce

cancer risks? Researchers from the National Bureau of Standards are helping to answer this question by contributing

to a larger government program

that is examining the cancer

preventive properties of micronutrients. These are compounds such

as vitamins A, C, and E, which

may help prevent some tumors in persons at high risk due to lifestyle or occupational exposure, or in those who have had cancer but now are free of the disease. Sponsored by the Chemoprevention Branch of the National Cancer

Institute (NCI), the larger study re- quires accurate measurements of micronutrient levels in body fluids such as blood serum because

these values will be correlated with the occurrence or recurrence of cancer in populations being studied. Earlier studies have indicated

in many cases that low nutrient levels in the diet or in the body are

related to a higher risk of cancer. The hypothesis now being tested is whether increasing nutrient levels might be related to a lower risk of disease occurrence.

Clinical trials, in which several thousand individuals are taking sup- plements for several years, are test- ing this theory scientifically. About

100,000 volunteers at 50 medical

facilities worldwide are participating

in the studies. At NBS, scientists have established a quality assurance program

to help NCI-sponsored laboratories make reliable analytical measure- ments of the micronutrients. Before any conclusions can be drawn,

participating labs must have comparable data. But preliminary lab

testing has shown a wide variety of results when portions of the same

sample were sent to different laboratories for analysis. So NCI

asked the Bureau to join the project

and lend its chemical measurement

expertise to develop standards that

will improve interlaboratory measurement quality. NBS plans to continue these round robin tests and follow-up consultations until all the labs show

they can make measurements at acceptable levels of accuracy. If a

lab's results are biased, Bureau

researchers will suggest ways to make improvements.

"We may recommend that a lab modify techniques or use an entirely different analytical method,"

says Dr. Willie E. May, who heads

the NBS Organic Analytical

Research Division. "Other times problems might be remedied by

improving equipment calibration procedures."

...study requires accurate

measurements of micronutrient levels in body

fluids.. .because these

values will be correlated

with the occurrence or recurrence of cancer in populations being

studied.

About 20 laboratories are parti- cipating in the NBS portion of the program. These labs are either

directly involved in the project or are striving to improve the quality of their measurements of the micronutrients under study. NCI has stressed the importance

of measurement science. "It

is easy, of course, to know how

much of a compound is being administered," says Dr. Winfred Malone, chief of NCI's Chemoprevention Branch. "But an important factor in a chemoprevention

study is the level of the agent in

body fluids and how much is being

absorbed into tissues. Too little might not be effective, and too much could prove toxic over an ex- tended time period."

The NCI studies are presently focused on the types of cancer that

earlier research has indicated might

be responsive to preventive in- terventions: skin, cervical, colon, mammary, and lung. NCI project leaders hope the study will reveal ways some cancers can be

headed off before they become

what Malone calls "full-blown malig- nancies." At several cancer sites, scientists now can identify "pre- malignant" cells which may be mid- way in the cancer development

process. This is one of several

points where NCI believes tumor chemoprevention may be possible. For example, persons with colonic polyps are often at higher risk of developing cancer. Giving indivi- duals whose polyps have been surgically removed oral supplements

such as beta-carotene or calcium carbonate—two of the chemopreventive agents NCI is studying—might head off subsequent

cancer development. Both of these compounds have shown

preventive promise in human epi- demiological and animal model

studies.

It also may be possible to inter- rupt the transformation of normal

cells to cancer cells through these

interventions with chemopreventive agents. "Even a small delay

in the process of transforming ini- tiated cells (those exposed to car- cinogens) could drastically reduce

cancer incidence," Malone says. Since this promotional phase of cancer induction usually lasts for a number of years, it may be

amenable to cancer prevention by
agents that could block or inter- rupt this second step. While NBS scientists are currently involved in measuring and

examining the cancer prevention

properties of beta-carotene, retinol (vitamin A), ascorbic acid (vitamin

C), alpha-tocopherol (vitamin E), and selenium, NCI has targeted some 500 additional compounds it suspects of possessing chemopreventive qualities for further test- ing. NBS will likely become

involved in developing measure- ment methods for many of these compounds, which include naturally occurring substances found in vegetables such as members of the cabbage and onion families. Additionally, NBS is serving as a

reference laboratory to a concurrent NCI study in which blood samples

of atomic bomb survivors in Hiroshima and Nagasaki who now

have cancer are being measured

for nutrient levels. Under the auspices of NCI's Epidemiology

and Biostatistics Program, the study

is evaluating the effects of ionizing radiation on cancer risk. The program is determining serum levels of beta-carotene,

retinol, alpha-tocopherol, selenium,

and zinc in Japanese donors who

were exposed to various doses of radiation and subsequently devel- oped cancer. This information from NBS will help researchers else- where, who hope to relate amounts

of the various nutrients found in the samples to occurrence of different types of cancer. Comparing NBS analytical

methods with Japanese methods

may help pinpoint potential inac- curacies or measurement biases. Early NBS evaluations have

resulted in the recommendation that one analytical technique be modified for vitamin measurements. NBS

found that the method was subject

to a 40 to 50 percent bias. NBS also is investigating proce- dures for long-term storage of

blood serum samples. If conditions can be established where samples

remain stable over long periods of time, this will open the door to applying the principles of "specimen

banking." That is, samples can be

deposited periodically and kept fro- zen until interest in a particular

sample prompts withdrawal and

analysis. A serum sample, if proven

stable, could be withdrawn from a specimen bank years later and the

resulting analysis would reflect the sample's chemical composition at the time of deposit. This is especially valuable as analytical technol- ogy becomes increasingly sophisti- cated and new possibilities open for detecting different compounds and

smaller concentrations of chemicals more accurately.

by John Henkel NBS Public Affairs Specialist

Chemist Jeanice Brown-Thomas prepares to analyze a blood serum sample for vitamin A,

vitamin E, and beta-carotene using highperformance liquid chromatography. The

research will be used to help determine if these nutrients play a role in preventing cancer.

15
Manufacturing Technology for the

Second Industrial Revolution

Computer scientist Albert Wavering monitors the performance of a robot at the

horizontal machining center In the AMRF.

hen you think of automation, you

probably think of automobile plants, and for good reason. The automobile is perhaps the ultimate symbol

of the Industrial Revolution. Massive

factories turn out millions of cars every year, a feat made possible

by careful measurements and the use of thousands of interchange- able parts. While the innovations of the first Industrial Revolution brought about mass production, small-scale pro- duction remains one of the most

important segments of American in- dustry. Small-scale or small-batch

manufacturing accounts for up to 75 percent of U.S. trade in manufactured goods. Small-scale manufacturing is primarily done by small companies—only one in 10 employs more than 50 people. These

companies need the economies

produced by automation to survive, but they can't use the techniques

of mass production.

The second Industrial Revolution

is for them. And the recently completed Automated Manufacturing

Research Facility (AMRF) at the National Bureau of Standards is at the

frontier of that revolution. The

AMRF has been designed as a

proving ground for the technology

of America's factories in the 21st

century. Research at the facility is helping manufacturers that must

turn out comparatively low numbers

of individual parts. These manufacturers include key suppliers to aerospace, automotive, electronics, and home appliance industries. Although the AMRF looks like a machine shop, it is actually a

unique engineering laboratory

where NBS researchers work with

their colleagues from industry and

universities to learn how modern

computer technology can provide

the small manufacturer with more

efficient techniques and better

quality control. According to NBS

16
researchers, this laboratory was

designed to study standard methods for linking different computerized machines. It also is used

to help manufacturers improve

quality control by experimenting

with efficient and reliable methods

for monitoring the performance of automated machinery.

NBS, as the nation's primary

laboratory for measurement science and engineering, has two principal

goals for its automated manufacturing program: to supply American

industry with a radically new way of making precisely machined parts—

with dimensions that can be refer- enced to national measurement

standards maintained by NBS—and

to encourage the modernization of American manufacturing by providing the technical information necessary to develop standardized

interfaces between various types of equipment.

NBS also is using this facility as a

testbed for research on the next generation of "knowledge-based"

manufacturing systems—automation

systems that incorporate artificial in- telligence capabilities.

Government, Industry,

University Cooperation

The AMRF is one of the largest

cooperative research programs at the Bureau. The Navy's Manufacturing Technology Program is a

major partner in the facility, and the Navy RAMP project, the Air Force

Intelligent Task Automation Project, and other government agencies

also have sponsored specific parts

of the AMRF effort. More than $4.6

million worth of equipment and soft- ware has been loaned or donated

by private companies, part of in- dustry's extensive cooperation in this project. Since 1983, about 35

private companies—large and

small—have contributed to AMRF

research by sponsoring more than 50 of their employees to work at

NBS with Bureau researchers. In addition, a number of universities have contributed to the project by

loaning guest researchers.

Innovative Production of

Precise Parts

Historically, manufacture and measurement have always been two

separate processes. A machinist would cut a part on a milling machine and stop periodically to check dimensions with calipers and

gauges. As manufacturing tech- niques became more and more effi- cient, the measurement portion of the operation consumed an ever- greater percentage of the total work required to produce a part. The development of automated

coordinate-measuring machines

(CMM's) in the 1970's helped

somewhat, but measurement still used up about 50 percent of the

total time required to produce a

precision part.

It would be many times more ef- ficient if the machining process

could be made to produce ac- curate parts without being inter- rupted by the measuring process. Not only would it take less time, but fewer parts would have to be

scrapped for being out of tole- rance. (Some surveys have shown

that in the United States one-third

of the work force in manufacturing

industries is engaged in re- work—correcting out-of-tolerance

parts made by the other twothirds.) NBS research suggests that this problem can be solved by use of today's computer-controlled

machine tools, because the position

of the cutting edge of the tool is known and controlled at all times,

at least in theory, by the computer.

The computer can be programmed

to compensate for known errors in the machine's movement, using sensors that feed back information on the machine's condition. This concept of feedback and

process control is well known in some industries, such as oil refining

and chemical production. In dis- crete parts manufacturing, however,

it will require the development of a

whole new generation of sensors and control systems.

This isn't all just theory. NBS

researchers have already applied some of these ideas to commercial

machine tools and improved their performance in terms of accuracy and control five- to tenfold. Some of

this research already is finding its way into the marketplace in new in- dustrial machine controllers. One important issue to be stud- ied in the AMRF: You can no

longer calibrate a measurement

process that is deeply embedded

in the manufacturing process, one

that depends on the interaction of a

machine tool with its environment

and with one or more computers.

How then do you ensure that the dimensions of the finished parts can be shown to be in agreement

with national standards of measurement?

Importance of

Standardized Interfaces

The automated "factory of the

future" offers American industry an

important weapon in the highly

competitive world marketplace, but even for the largest firms the lack

of agreed-upon standards for "interfacing" complex equipment is a difficult—and costly—problem.

For close to 90 percent of the

small-batch manufacturers—about

100,000 firms—the problem is worse. These are much smaller companies (fewer than 50

employees) without great financial resources. These smaller companies need to be able to buy

automated machinery in stages, one or two machines at a time, and

slowly build up to an integrated

system.
They need the flexibility to buy

from different manufacturers at dif- ferent times with the assurance that the machines they buy will work

together properly without a lot of expensive, custom-designed inter- faces. They need the same flexibility that one can now find when

buying the parts of a home stereo system from several different manufacturers, knowing that they

will all plug together.

These firms also need a system

flexible enough to switch from the production of one part to another

quickly and without expensive

reprogramming. Most of these problems are prob- lems of standardization—standard

procedures, standard protocols, standard interfaces. The challenge

is to develop standards which support current technology and still en- courage equipment manufacturers

to develop new and innovative products. These are problems that NBS is studying in the AMRF.

NBS is not a regulatory agency, and does not set standards, at least

in the legal sense. However, NBS

has a long history of working as a

neutral, third party, providing

technical knowledge and leadership

and encouraging the establishment

of standards. NBS research has become the basis for many stan- dards adopted by private industry on a voluntary basis. Three industrial standards have

already been developed based on NBS automation research. For ex- ample, a standard method for ex- changing graphics data between

otherwise incompatible computeraided design (CAD) systems, devel- oped by a government-industry

coalition led by NBS, was adopted

by the American National Stan- dards Institute (ANSI), a private

voluntary standards organization.

The standard now is supported by

all U.S. CAD vendors which have

at least a 1 percent market share. AMRF research also has led to standards for the characterization of

computerized coordinate measure- ment machines and for a method

of surface texture measurement. Seven other potential standards

are now being considered by

various industrial standards

groups.

Unique Features of the

AMRF

Several things make the AMRF

unique including:

Its location at the National Bureau of Standards. As an open

federal laboratory with no commercial interests, NBS can make

this facility accessible to private firms interested in automation

research—firms that individually could not afford such a complex

research facility. NBS has a long

history of working with private firms and organizations to develop

standards and measurement and

test methods that benefit the entire

industry. The active participation in the AMRF by industry, universities, and other government

agencies. The AMRF has become

a focal point for interactions among all American researchers

in automated manufacturing.

The use of a wide variety of commercially available machine

tools and robots. This is a

direct result of the NBS decision to study the most practical, incremental route to automation for the smallto medium-sized firm; it is an ap- proach that has never been used

before.The flexibility of the system.

One of the goals of the AMRF is to create a facility that is, in the jargon

of the researchers, "data driven"—

the actions of the various machines

and robots should be determined

primarily, or solely, by a computerized description of the part to be manufactured. This stands in contrast to modern "flexible manufacturing" cells which are truly flexible only for a limited "family" of parts for which the machine tools are programmed.

In the AMRF scheme, the pro- grams which actually control the machine tools should not make any

assumptions about the part to be

produced. That information will be

kept in a separate database

system, and control programs will look up the description of the desired part and take the necessary steps to produce it. The pro- duction of a part could then be

changed simply by changing its description in the database, without needing to reprogram the machines.

Sensory interaction. The

AMRF makes use of an unusually

versatile robot control system in which sensory information from, for example, the NBS robot vision system is fed back to the controller

to provide a basis for its decisions. This is important because it enables

the system to react to its environ- ment, eliminating the need for a lot of rigid programming.

The scope of the facility. Re- search at the AMRF covers everything from the preparation of data on a new part to final automated

inspection.

The AMRF Control System

The AMRF has a total of six workstations which include several types

of modern automated machine

tools, such as numerical control mil- ling machines and lathes, auto- mated materials-handling

equipment (to move parts, tools, and raw materials from one workstation to another), and a variety of

industrial robots to tend the machine tools. At the heart of the facility is the AMRF control system—one of the most important innovations. It is flexible and can be adapted easily

to new machines and new technol- ogy, works in the split-second real- time world of factory processes, and is "modular," allowing today's

manual or partially automated fac- tories to evolve into "factories of the
future" incrementally, adding one

or two modules at a time. Several elements of the AMRF

control system are being considered as possible factory automation standards by national and

international standards

organizations.

Among the key features of the

control system are: hierarchical control, the cell control system, and the computer emulation system. The

activities in a manufacturing facility, like those of most complex organizations, fall neatly into a hierarchical framework. NBS pioneered the use

of hierarchical control in the design

of a sophisticated robot control system a decade ago. This work

led to the development of a five- layer, hierarchical control model for an entire factory. Commands go

into the hierarchy at the highest

level, where a complex set of in- structions is initiated. At each lower

level, the instructions are broken down into successively simpler

instructions. The AMRF represents what is probably a unique level of complexity in multilevel control systems.

The modular, hierarchical software developed by NBS for this facility is the most flexible, most advanced

control system ever used in such an application.

The cell control system is the

highest implemented level of the AMRF hierarchy. It receives orders

for parts from an operator terminal, determines the necessary

resources, and then schedules,

coordinates, and monitors the activities of the workstations required

to manufacture the parts. The AMRF hierarchical control system emulator (HCSE) is a tool for testing the effects of new

systems before they are actually linked into the existing factory

system. This testing must confirm

not only that the new system has no internal errors, but also that its

Research engineer Kang Lee at work at the AMRF turning center workstation. Computer control techniques developed at this facility make it possible to operate this machine tool at five to ten times its normal

accuracy.

addition will cause no unexpected

problems in synchronization.

The HCSE provides the pro- grammer with a convenient frame- work for creating modeling programs to take the place of any

element in the AMRF. To the rest of the control system, the computer emulation "looks the same"

as whatever it replaces. So when

research needs dictate, any piece

of equipment or group of machines or subsystem can be

taken out of action and replaced

by the appropriate emulation.

Potentially risky changes to the control system can be tested without endangering expensive equipment.

Versions of the HCSE are already

being used commercially to study new automated manufacturing

facilities.

Data Preparation and

Handling

In a very real sense, the cor- nerstone of the "factory of the

future" will be information. The

hardware of the AMRF—robots, machine tools, and sensors—is very

visible, but the ability to generate,

store, retrieve, and transfer information accurately and on time will be

just as important as any hardware. Such a facility requires a number

of important advances in computer

software, including the development

of standard techniques to "inter- face" different types of computer

systems and software and the de- velopment of standard methods for handling data in an automated

factory.

19
The interface problem in the AMRF is complex. At least nine dif- ferent computer systems are in common use, ranging from large

minicomputer systems to advanced

microcomputers. At least eight dif- ferent computer languages are used throughout the AMRF control system. Special features of the AMRF data-handling system in- clude the use of distributed databases and a specially designed

data communications system.

An equally important task is data

preparation, transforming the cus- tomer's requirements for a parti- cular part into the production

control data needed to manufacture

that part. These tasks include designing the part, determining

what materials and tools are necessary to produce the part, developing the process plans that

detail how the part is to be made,

and generating the programs that

instruct the robots and machine

tools that actually make and inspect the part. Also vital is the ability to

verify these plans—to make sure

that they don't instruct the machines to do something

dangerous or impossible.

A common thread through all of these tasks is the need for stan- dardized methods of handling the

data. At the AMRF, research is under way to determine exactly

what types of data are required by a factory's manufacturing and in- spection systems, and how these data can be generated automatically by the various data

preparation systems in use in the

facility.

Research at the

Workstations

Research projects at the horizontal workstation, focus on basic studies

of generic, real-time control systems, methods of programming

such systems, and the handling of data and materials in an automated

workstation. This workstation

features: a real-time control system,

materials buffer, the automated fix- turing system, tool changing, the

sensory-interactive robot control system, the NBS robot vision system, the Quick-Change robot

wrist, the active pedestal, and the "Watchdog" safety computer.

The vertical machining workstation features an advanced, auto- mated process-planning system tied to its workstation controller, equipVERTICAL WORKSTATION

HORIZONTAL WORKSTATION

This floor diagram shows the arrangement of workstations and equipment In the Bureau's

Automated Manufacturing Research Facility.
ment controller, machining center, robot grippers, pallet system, vise, and the chip removal system.

A major factor in the economics

of automation for the small-batch manufacturer is whether or not the system can be left to run unsupervised for fairly long periods, such

as the overnight shifts. One of the research efforts at the turning workstation has been the study of the sensors and process control systems needed for untended

operation.

The turning workstation includes a malfunction detector—a micro- processor-based device which uses a vibration sensor mounted on the

tool holder in the tuning center to compare the vibration levels to a

"catalog" of acceptable levels for

different machining operations.

Unacceptable levels trigger an error message to the workstation

controller. Research in the cleaning and

deburring workstation focuses on

the investigation of robotic deburring techniques. These techniques

would more closely emulate the

actions taken by a human in deburring a part and would permit a much more specialized treat- ment of a given part than would

the current mass deburring methods.

Gaining this additional flexibility in robotic deburring will require

advances in several areas of robotic control and sensing

systems. A major research topic at

this workstation is the use of CAD

data—the computerized description of the part—to guide the

robot through a trajectory that is sufficiently accurate for deburring

work. Other research topics in- clude: developing remote measurements of the robot's position to enhance its positional ac- curacy; investigating high-speed

feedback control systems using

force sensors; and developing

control methods for coordinating

the cooperative actions of two or more robots.

In the materials-handling workstation researchers study the move- ment of part blanks, raw materials,

tools, and finished parts in and out

of storage and between the other

workstations. One of the key ideas behind the AMRF states that sufficiently good

process control will one day elimi- nate the need for final inspection to assure the accuracy of manufactured parts. The role of inspection

will evolve from simply sort- ing good and bad parts to ulti- mately providing the process control over the most complex sources

of error in part manufacturing.

The inspection workstation repre- sents the first step in developing

this advanced process control

capability for the AMRF. This workstation, which includes CAD-direct

inspection and surface-roughness

measurement, is isolated from the

rest of the shop floor and

temperature-controlled—important

factors in the performance of coordinate-measuring machines.

A Working Research

Laboratory

The AMRF, however, is not a pro- totype of the "factory of the future."

It is extremely unlikely that any actual factory would resemble the AMRF, at least physically. The

AMRF is a laboratory for studying

factory automation. The AMRF is not a demonstration project. Although it does

demonstrate several new and

potentially important techniques for machine control and the integration

of diverse systems, the completed

AMRF is not be a museum piece

but rather a working research

laboratory.

In the coming year, researchers

in the AMRF will concentrate on

aggressively transferring the tech- nology they have learned about, as

well as continuing research on

manufacturing data preparation and

precision manufacturing.

by Michael A. Baum

NBS Public Affairs Specialist

A robot at the AMRF Inspection workstation presents a newly machined part to a device that uses optical

techniques to measure sur- face finish.

21
New Values Recommended for the

Fundamental Physical Constants

hemists, physicists, engineers, and

others in science and technology

have a new, more accurate set of values for the fundamental constants now that work is completed on the 1986 Adjustment of the Fun- damental Physical Constants. These

are the basic quantities used in physics and chemistry worldwide

for scientific investigations.

The 1986 adjusted values are recommended by the Committee on Data for Science and Technol- ogy (CODATA), an interdisciplinary,

scientific committee of the International Council of Scientific Unions

with headquarters in Paris. Dr. David R. Lide, Jr., CODATA presi- dent and director of the Office of Standard Reference Data at the

National Bureau of Standards says, "The new set of adjusted values for the fundamental physical constants

will contribute to improved data in nearly all fields of scientific research." NBS works through CODATA to ensure the international coordination

of scientific information used by

laboratories throughout the world. The 1986 CODATA report, which

gives the new set of recommended

values, is the first revision to the 1973 CODATA report that established the first internationally adopted set of values. The revised version of the fundamental constants takes into account the signifi- cant advances in metrology that have occurred since the 1 973

analysis.

The new set was developed over a 5-year period under CODATA

sponsorship by physicists Dr. E. Richard Cohen at Rockwell International Science Center and Dr. Barry

N. Taylor at NBS. The scientists received guidance on their work

from other members of the

CODATA Task Group on Fundamental Constants that includes

representatives from Canada,

France, Japan, West Germany, the

Soviet Union, and the United Kingdom.

The adjustment includes the new

definition of the meter in terms of the distance traveled by light in a

given time, measurements linking atomic lattice spacings to optical wavelengths that make possible

significant improvement in the determination of the Avogadro constant, and measurements of the

quantization of the electrical con- ductance in certain semiconductor

devices—the quantum Hall ef-

"The new set of adjusted

values for the fundamental physical constants will contribute to improved

data in nearly all fields of

scientific research."

feet—discovered by Nobel laureate Klaus von Klitzing in 1980. While there are changes in all of the 1973 recommended values, the major ones include decreased

values for the Planck constant, the elementary charge, and the elec- tron mass and increased values for the Avogadro constant, the Fara- day constant, and the Josephson

frequency-voltage ratio. Most importantly, throughout the 1 986 set of recommended numerical values, the uncertainties are now typically about 10 times smaller than those

in the 1973 set.

Although the data represent dif- ferent physical quantities, they must be expressed so that coherent comparisons can be made of their uncertainties. As part of their review, Cohen and Taylor ex- amined each originally assigned

uncertainty and modified it, if necessary, to ensure that all uncertainties were expressed consistently

in terms of a variance. Taylor points out that while the 1973 CODATA report provided the

first internationally adopted set of values for the fundamental constants, the recommended values were almost immediately chal- lenged by several new measurements. He says, "Because new

and better data are continually

becoming available, it is always dif- ficult to establish an optimal time for making a change in the recom- mended values of the constants. We finally decided to consider all the data that was available up to January 1, 1986, in this revision." CODATA was established in

1 966 to promote, on a worldwide

basis, the compilation, evaluation, and dissemination of numerical data in all fields of science. Its membership includes 18 nations and 15 international unions. The

member countries include the United States, the Soviet Union,

Japan, China, the major industrialized European nations, and

several developing countries. Copies of the 1986 Adjustment

of the Fundamental Physical Constants, CODATA Bulletin 63, may

be purchased in North America

for $15 prepaid from Pergamon

Press Inc., Maxwell House, Fair- view Park, Elmsford, NY 10523.

Elsewhere, the bulletin may be

obtained from Pergamon Press

Ltd., Headington Hill Hall, Oxford 0X3 OBW, United Kingdom.

by Roger Rensberger

NBS Public Affairs Specialist
Relative Uncertainty

Quantity Symbol Value Units (ppm)

speed of light in vacuum c 299 792 458 ms 1 (exact)

permeability of vacuum 4ttx10- 7 N A

-2 =12.566 370614... 10~ 7 NA-2 (exact)

permittivity of vacuum e 0 I//*., c

2 =8.854187817... lO-^Fm- 1 (exact)

Newtonian constant of gravitation G 6.67259(85) 10 11 m6 kg s -2 128 Planck constant Ln D.0Z0 U < 00(40) 10 Js 0.60

A/27T h 1.054 572 66(63) 10- 34 Js 0.60 elementary charge e 1.602 177 33(49) io- 19 c 0.30 magnetic flux quantum, h/2e $o 2.067 83461(61) 10~ 15 Wb 0.30 Josephson frequency-voltage ratio 2e/h 4.8359767(14) lO^HzV- 1 0.30

electron mass me 9.109 3897(54) 10- 31 kg 0.59 proton mass mp 1.6726231(10) 10" 27 kg 0.59 proton-electron mass ratio rrip/m 1836.152701(37) 0.020

fine-structure constant, fi 0 ce

2/2h a 7.297 35308(33) lO" 3 0.045

inverse fine-structure constant a- 1 137.0359895(61) 0.045 Rydberg constant, me ca 2/2h Roo 10 973 731.534(13) m- 1 0.0012 Avogadro constant NA ,L 6.0221367(36) lO^mol" 1 0.59 Faraday constant, 7VA e F 96 485.309(29) CmoP 1 0.30 molar gas constant R 8.314510(70) Jmol^K-1 8.4 Boltzmann constant, R/N& k 1.380658(12) lO-^JK- 1 8.5 Stefan-Boltzmann constant, a 5.67051(19) 10- 8Wm-2 K- 4 34

(ir 2/Q0)k4

/fi 3c

2

Non-SI units used with SI

electron volt, (e/C) J = {e}J eV 1.602177 33(49) io- 19 j 0.30

(unified) atomic mass unit, u 1.6605402(10) io- 27 kg 0.59

1 u = mu = ^m(12 C)

This table is an abbreviated list of the 1986 recommended values of the fundamental

physical constants, which are based on a least-squares adjustment with 1 7 degrees of

freedom. The digits In parentheses are the one-standard-deviation uncertainty in the

last digits of the given value. Since the uncertainties of many of these entries are cor- related, the full covarlance matrix must be used In evaluating the uncertainties of quantities computed from them.
Equations and Models Used to

Investigate Hotel Fire

The following article is adapted

from a statement made by Dr. Jack

E. Snell*, director of the NBS

Center for Fire Research, before the House Committee on Science,

Space, and Technology, Subcommittee on Science, Research and

Technology, March 5, 1987.

n the late afternoon of the last day

of 1986, a fire of devastating intensity swept through the lower floors

of the Dupont Plaza Hotel in Puerto

Rico, killing 96 people. Other major

hotel fires in just this past decade

include the MGM Grand in Las Vegas which was followed closely

by the Las Vegas Hilton fire, the Westchase Hilton Fire in Dallas, and the Stouffers Inn in New York. The United States continues to post one of the worst fire death records

in the world, and hotels and motels

represent just the tip of the iceberg

of the U.S. fire problem, accounting

for only 1 .3 percent of the total fire deaths according to the National

Fire Protection Association. Hotel fire safety is of concern for a number of important reasons. The public perceives and expects

hotels to be safe. Hotels present a

large number of potential sources

of fire—laundries, kitchens and

storage rooms, restaurants, night clubs, convention centers, shops,

and commercial spaces, as well as occupant rooms. Large concentrations of people are exposed to any

fire incident that may occur in them. Hotels are often the targets

of negligence, carelessness, arson, and, increasingly, terrorist attack.

Finally, hotels are important

because new fire safety practices

"At the request of the governor of the Commonwealth of Puerto Rico. Snell served on

the Commission on Fire Safety, which was

set up to study Puerto Rico's fire safety practices and standards

and technologies introduced in hotels ultimately find their way into homes. Lessons learned about

hotel fire safety can profoundly af- fect the rest of the fire problem. Too many people still think they

are safe in buildings made of non- combustible construction materials.

Fire investigation reports frequently

cite the victim's apparent lack of knowledge of escape routes as a

significant factor in loss of life. We

need to do a better job of communicating fire safety information. While the fire hazards of highly

combustible interior finishes have

been greatly reduced in recent

years, the fire hazards of hotel contents may in fact be even greater now because of the relatively high

energy-release rates of many

modern materials used in them.

Highly combustible contents clearly contributed to the magnitude of

The United States

continues to post one of

the worst fire death

records in the world....

loss in each of these major hotel

fires. Reduction of the hazards of combustible contents remains a major piece of unfinished business

in improving hotel and home fire safety.

It is not always easy or obvious

to tell whether a building is "fire safe." Fire safety depends on many

factors, including, of course, the

vast number of fire scenarios that are possible. What is needed is a means to evaluate a hotel (or any

building) for the many types of fire

it may be subjected to as well as

the likely behavior, and fate of, the occupants. More precise means

are needed for determining the se- quences of events that occur in a

fire.We need to determine what

"would have" happened if various

alternatives, for example, better materials or compartmentation,

early warning, or suppression

systems, had been used. What I am suggesting is that we need

methods to simulate the perfor- mance of a building under

assumed conditions of fire- methods like those routinely used,

for example, by airline pilots to "practice" in-flight emergencies

safely on ground-based computerized simulators. Such realistic simulations are possible because

sufficient knowledge of aeronautical engineering exists to predict aircraft performance and thus produce

realistic software. Until recently there simply wasn't sufficient knowledge about fire to do the same thing. The type of tools NBS is now

working with others in the fire protection community to produce can

provide the bases for powerful new

means to address these needs. For example, these tools can be used

to produce simulators and related materials that will permit people to evaluate how well various combinations of fire protection technol- ogies will work, to enable quantitative evaluation of fire safety

trade-offs, and to stimulate and

guide development of more effective and affordable technologies

for fire protection.

Using Data in Fire

Investigations

NBS staff have used such scientific and engineering tools to study

the Dupont Plaza Hotel fire. Dr. James Quintiere, head of the NBS

Fire Science and Engineering Divi- sion, and Harold Nelson, a senior research engineer, joined the onsite investigation on the fourth day

following the fire. These men,

along with investigators from the United States Fire Administration and a team from the National Fire Protection Association participated
in the investigation directed by the Bureau of Alcohol, Tobacco and

Firearms. Nelson and Quintiere had at their disposal—on pocket and portable,

lap-sized microcomputers—recently

developed fire models and en- gineering equations which they

used to calculate the various stages

of the fire development. This was a

precedent-setting application of these models on the scene of an

active fire investigation.

The investigation reported here focused on the application of scientific and engineering research to im- proving hotel fire safety. The

continuing criminal investigation

prevents discussion of the details of

ignition or other factors that might

affect the criminal investigation.

In the NBS analysis, the Dupont

Plaza Hotel fire was assumed to originate on a large pile of cartons

of new furniture in the south

ballroom (see diagram, arrow 1). The south ballroom is under the balcony and behind a set of re- movable partitions which separated

it from the much larger north ballroom. Smoke began to fill both

the 10-foot-high south ballroom and

flowed into the main 21 -foot-high north ballroom as the fire pro- gressed in the cartons. Ballroom doors leading to the foyer, which

contained the main staircase to the lobby and outside, were open dur- ing this period.

As the smoke filled the

ballrooms, it is estimated to have

emerged into the foyer approximately 5 minutes after the fire started. This, we believe, was the

first general indication of fire to the occupants of the lobby. About 5

minutes later, we estimate flashover** occurred in the south

'Flashover is a phenomenon where fire suddenly spreads from an initial burning object to the whole room after hot gases build up near the ceiling of the room and descend

downward.

DUPONT PLAZA

FIRE GROWTH

Lobby

Guest Floors

3-20

> rp£> Casino

T)

i

Restaurant

Ballroom Foyer

Simplified elevation of the Dupont Plaza Hotel viewed from the north.

ballroom, involving large portions of the combustible floor and wall coverings. The window partitions to the foyer broke, and a large quantity of smoke and flames was

released into the foyer (arrow 2). In roughly 40 seconds, a deep hot smoke front traversed the lobby area (arrow 3) forcing the occupants to flee. During these last few

minutes, people in the casino became aware of the fire, but now

those remaining had their only exits blocked by the dense, black smoke

in the lobby.

Two minutes later, the exposed

wood deck roof of the foyer

became involved in fire, and the extended flames broke the glass

partitions to the casino (arrow 4). This sent a deep front of fuel-rich smoke and flames across the

casino. This front probably ignited most of the combustibles in the casino in the next minute. Occupants were hopelessly trapped.

This is now approximately 12

minutes from the initial development

of the fire. That is all the time we

estimate it took for this tragedy to occur. The conditions leading to the

rapid spread and growth of this fire had little if anything to do with the

allegation that the fire was intentionally set. The outcome resulted from the design, materials, and fire protection devices and systems of the hotel as well as the training, atti- tudes, and perceptions of the hotel occupants and employees at the time of the fire or before.

Evaluating Alternative

Systems

We applied the same equations

and models used to predict the course of this fire to estimate the possible effect alternative fire protection devices or systems may

25
have had. Specifically, we looked at smoke detectors for early warning;

fire sprinkler protection in the

ballrooms, foyer, and casino; and

fire-resistant materials for the parti- tions and the wall and floor coverings in these spaces. The response of a sprinkler de- pends on the particular style of sprinkler head and its location

relative to the fire. Our analysis looked at a range of possibilities. A

modern, quick response sprinkler located directly above the fire would have been expected to go

off about 45 seconds after the car- tons started to bum. At this time, the flame would have only been

about 3 feet tall and there would

have been very little increase in the smoke temperature. If, on the other hand, a traditional sprinkler had

been about 1 0 feet away, probably

the slowest response we should

expect, it would have gone off in about 3 minutes. While this is a

comparatively long time, the

sprinkler would have been activated at just about the time the flames from the fire started to lick the 10-foot-high ceiling. The

smoke layer would have filled down from the ceiling about 2

feet, and its temperature would

have risen to about 265 °F. This would certainly be an uncomfortable place to be but not yet fatal. The hotel had a good water supply, and an operating sprinkler

would have probably extinguish- ed, or at least controlled, this fire. Smoke detectors would have

operated more quickly. If one had

been located directly above the

fire, it would have gone off about

1 5 seconds after the flame got es- tablished on the cartons. At this time that flame would probably

have only been 5 to 6 inches tall.

If a smoke detector had been

located near the far end of the room, say as much as 40 feet

from the point of fire initiation, it would have been another 45 or 50 seconds until the detector operated. Of course, detectors

only send alarms. Their worth de- pends entirely on how people re- spond to them. Many modern building codes

would require that the wall between

the south ballroom and the foyer

have at least a 2-hour fire resis- tance. Had this been present, the

fire would not have broken out into the foyer. There would, of course, have been serious damage inside the ballroom complex and a flow of hot smoke and gas into the kitchen service corridor, but probably little threat to people in the lobby or

casino. Had the partition between the

north and south ballrooms been of a substantial construction, that is, a

fire-rated partition, the time to flashover would have been greatly stretched out. The number of "what if" predictions that could be made is almost as endless as the questions that can be asked. In some instances, we can now make reasonable en- gineering predictions, others would

require extensive testing and ex- perimentation. One example of the

latter would be the contribution of the fabric wall-covering material used in both ballrooms. A series of tests on this material and full-scale tests of the stacked cartons of furni- ture that burned would be needed

to resolve this issue. Summary and

Recommendations

There is no question about it: Technologies exist to make hotels and homes fire safe. The problem

is that fire safety involves trade- offs—trade-offs among cost, function or comfort, and safety. Disasters result when the risks of

fire were not perceived correctly, or these trade-offs weren't assessed

properly, or both. Obviously, it is

difficult to do these things, parti- cularly in the absence of adequate measurement tools. This tragedy, like many before it, demonstrates the fact that most

people have inadequate knowledge

of fire risks and hazards, thus aren't motivated to act appropriately. Most people lack the understanding and the necessary information

to make the properly evaluated

trade-offs among safety, cost, and

function that are required to reduce

fire risks to acceptable levels. Also, this tragedy confirms that available technologies either are too

costly or are perceived as such by

many hotel operators. (For example, the Dupont Plaza is not the

only unsprinklered hotel. It has been estimated by the hotel industry that as many as 95 percent of hotels and motels are not protected

by sprinklers.) The public, state and local governments, and industry can

benefit from further analysis this year of the Dupont Plaza Hotel fire. Much can be learned by examining answers to many "what if" questions and estimating the effect of proposed changes in codes and

practices.

NBS scientists successfully applied their equations and models in the Dupont Plaza fire investigation. This experience suggests that this approach may become a powerful new component of future fire in- vestigations. Specifically, future in- vestigations might include the use

of a multidisciplined on-site in- vestigation team, including fire scientists and engineers; use of computer-based models and en- gineering tools for predicting fire and its consequences; and complementary small- and full-scale tests to verify computer-based fire "re-creations."
Atmospheric Contaminants Targets in

NBS Version of 'Datinq' Game

Chemists Dr. Lloyd Currie (left) and George Klouda

prepare to analyze an atmospheric carbon sample in the Bureau's mini-counter.

eorge Klouda twists a knob and

releases the sample of Las Vegas

air from a bottle. The sample begins a journey

through a maze of tubes, valves, and traps that looks like a tabletop

jungle gym. As the air creeps

through the apparatus, two carbon- based atmospheric contaminants in the sample—methane and carbon

monoxide—are extracted. Klouda and his research chemist

colleagues at the National Bureau

of Standards then convert the ex- tracted components into a solid

...the method allows NBS

researchers to determine

whether contaminant sources are naturally

occurring, manmade, or a combination of the two.

pellet about the size of a dime and

evaluate them with a technique that

is known mainly for its ability to establish the age of archaeological artifacts and geological samples.

Called radiocarbon dating, the method allows NBS researchers to determine whether contaminant

sources are naturally occurring,

manmade, or a combination of the

two.Making these distinctions is im- portant to government bodies like the U.S. Environmental Protection Agency and state environmental

agencies, which identify industrial sources of pollution for regulatory

action. On the other hand, if pollu- tion sources are from nature, the

dating method can prevent industrial firms from being penalized for pollution they did not create. Another example, atmospheric

methane, may be the product of leaking industrial gas. But more

often than not, says Dr. Lloyd

Currie, who heads the NBS at- mospheric chemistry group, nature

is the main source of methane. "We know that biological sources such as swamps, grazing cattle, even termites in the tropics are major methane sources, though motor

vehicles or industry may contribute

significantly," Currie says. "We also know that when nature is responsible, there is little hope of controlling the source." An overbalance of atmospheric

carbon can cause a number of en- vironmental problems. In methane's

27
case, high levels are of concern to environmental agencies because of "greenhouse" properties. That is, the gas absorbs solar radiation- much like a greenhouse absorbs

heat on a sunny day—causing the atmospheric temperature to rise and contributing to a suspected

warming trend in the world's cli- mate. Methane also has been im- plicated as a possible contributor to changes in the ozone layer that protects the Earth from excessive

ultraviolet light. "Levels of methane have been

increasing at an annual rate of about 1 percent over the last decade," Currie says. "This has caused concern in the environmental community, which hopes to de- termine just where the elevated

levels are coming from."

The Dating Technique

The NBS research is aimed at definitively pinpointing sources of methane and other atmospheric

contaminants by determining the

ratio of an unstable radioactive car- bon isotope, carbon-14 (C-14), to stable carbon-12 concentration. This permits scientists to separate

"living" carbon sources (burning

wood or vegetative emissions) from "dead" ones (fossil fuels such as

gasoline).

C-14 is present in the atmo- sphere through the action of cosmic rays, though significant concentrations of the isotope can be

attributed to manmade causes like nuclear weapons testing. It is distri- buted throughout living matter as

the result of carbon dioxide taken

in by plant respiration. While alive, plants or animals exchange C-14

with the environment at an even

pace. However, when an organism

dies, its C-14 level decreases gradually through radioactive decay. C-14 has a half-life of about 5,700

years. That is, at the end of that period of time, only half of the original C-14 concentration will remain.

This "yardstick" works beautifully

for the archaeologist, who can

calculate the age of an artifact by

comparing its C-14 level with that of

living matter. For NBS atmospheric

chemists, the radiocarbon dating

method is used in much the same

way. Fossil fuels such as oil and

coal, because they were last "alive" hundreds of millions of years ago, have no C-14. Their

levels of the isotope have long

since decayed, so researchers can establish their origins because

of this absence. On the other hand, living carbon sources, like burning wood logs or tree emissions, have high C-14 levels, which allow them to be identified.

Tiny Samples Needed

Despite its similarity to archaeological radiocarbon research, the NBS technique differs in the way

samples are analyzed. Archaeologists typically have had the lux- ury of handling large carbon

samples taken from an artifact at hand— 1 to 10 grams (.035 to .35 ounce) is necessary for traditional radiocarbon dating. Atmospheric

scientists are not so lucky. Even

under the most polluted conditions, an air sample only yields about 50 millionths of a gram of carbon per cubic meter of air, which means it could take weeks

to collect enough material for classical analysis methods. "We realized that a special ap- paratus was needed to permit

reliable radiocarbon measurements

of small samples," says Currie, "so we decided to build our own."

Early successes came in the middle 1970's when Currie and his col- leagues fashioned an analytical instrument—known as a mini- counter—from part of a World

War l-vintage cannon barrel the Navy had slated for scrapping. The

6-ton iron barrel, in which the

researchers placed sensitive measuring devices, provided an excellent shield against the natural background radiation that would

have overwhelmed attempts to measure the tiny carbon-14 concentrations. And unlike modern

steel, the World War I barrel did not contain minute amounts of radioactivity from fallout or from radioactive tracers that would interfere with C-14 measurements. (Currie emphasizes the minute amounts of C-14 the researchers examine by

explaining that human beings

naturally contain about "1 million times as much radioactivity" as what NBS is trying to measure.)

While the small counter allowed

the researchers to scale down sample size and gauge C-14 accurately, some specimens were still too

small to be measured reliably by

the NBS device. A more sensitive technique was needed.

...NBS researchers were

able to trace elevated

carbon particle concentrations to the abundance of

residential woodstoves in the cities studied.

By 1978 a method developed at the University of California (Berkeley) a few years earlier, and

improved by the University of Rochester (N.Y.), had attracted the

attention of NBS researchers. Called accelerator mass spectrometry (AMS), the new method offered

1 ,000 times the sensitivity of tradi- tional radiocarbon techniques and a

tenfold improvement over the in- house NBS device. The technique,

however, required samples in the form of solid elemental carbon for analysis. (The mini-counter method

used samples in the form of carbon

dioxide gas.)
Using laboratory techniques,

NBS chemists converted samples

to carbon powder and began successfully using AMS. A later device designed at NBS by Dr. Michael Verkouteren improved sample conversion. His invention takes either gaseous atmospheric samples

(methane or carbon dioxide, for ex- ample) or particle samples (woodstove or automobile exhaust

emissions) and converts them to a

solid carbon pellet which then can

be analyzed by AMS for C-14 concentration. The method results in samples that are smaller and contain less contamination than those produced with previous techniques.

NBS, which has no AMS facility of its own, used the Rochester in- strument until the early 1980's. Bureau researchers now are pri- marily using an AMS device at the

University of Arizona in Tucson. All sample preparation is done at NBS

labs in Gaithersburg, Md.

Real World Results

One recent study using the AMS

technique was a cooperative effort between NBS and the Clark County

Health District in Las Vegas.

Among other things, the two agencies wanted to determine the origin

of elevated carbon monoxide levels detected in the area. Carbon

monoxide, well known as a noxious

compound, also prompts a

chemical reaction that disturbs the

"natural sync" of atmospheric

methane. In effect, this increases methane levels and adds to the greenhouse effect and other methane-related environmental problems.

Our study results pointed to fossil fuel emissions—most likely from

auto exhaust—as the culprit in this case, says Klouda, who coor- dinated the Las Vegas study. (Had

a significant amount of C-14 been

found in the samples, the source

could have been a living one such

as wood burning or tree emissions.)

NBS also has contributed to the Environmental Protection Agency's

Integrated Air Cancer Program.

Part of this project aims to deter- mine the atmospheric concentration

of carbon particles from woodstoves. With support from EPA,

NBS has conducted studies in several cities, including Albuquerque, N.M., and Raleigh, N.C. Using

radiocarbon dating to track the

"living" carbon of burning wood,

NBS researchers were able to trace elevated carbon particle concentrations to the abundance

of residential woodstoves in the

cities studied. The EPA—which can place controls on woodstoves

by requiring scrubbing devices such as catalytic converters—has

accepted the Bureau research as

definitive, Currie says, and now

plans to use the NBS data to validate an analysis method it will use routinely for similar particle measurements. A cooperative study with Norwegian scientists of particle concentrations in Elverum, Nor- way, (which also has many

homeowner woodstoves) yielded conclusions similar to the EPA/NBS study about woodcreated smoke.

What's Next?

Currie says future projects for his group include using the AMS

technique to analyze other carbon- based species in the atmosphere.

NBS scientists already have taken a

step in this direction by examining

C-14 concentrations in polycyclic aromatic hydrocarbons (PAH's),

which are suspected cancer- causing compounds from sources such as automobile exhaust and

combustion of wood and coal. Also high on Currie's projects list

is radiocarbon , research at the ice caps in Greenland and Antarctica. Here, he says, is "an archive of the atmospheric processes of the past

that would allow us to use radiocar- bon dating to produce accurate

Dr. Michael Verkouteren uses his customdesigned apparatus to convert gaseous

samples into solid elemental carbon for

analysis by accelerator mass spectrometry.

data about the state of the environ- ment over history."

In such pristine surroundings, he

adds, where atmospheric pollution

has drifted to the arctic area and

has been trapped by the continual accumulation and compaction of snow, a "time capsule" has formed.

Scientists can examine this and

determine, for example, the history

of ancient fires, or when pollution

caused by the Industrial Revolution

first appeared (because factory emissions are still trapped there), or when automobile exhaust first en- tered the environment (fuel particles are still in the polar ice). "In order to track future pollution trends, we must be able to look at the pollution of the past," Currie

says. "And there are no better places than in the polar region. Here, we can apply what we've

learned through NBS radiocarbon measurements in urban surroundings to a setting where there is no

contamination. For a scientist, this is ideal." J.H.

29
NEW PUBLICATIONS

COOPERATIVE RESEARCH AT NBS

Cooperative Research Opportunities at NBS, Natl. Bur. Stand. (U.S.), NBS Spec.

Pub. 723, 52 pages (December 1986). Order by sending a self-addressed mailing

label to the NBS Office of Research and

Technology Applications, A402 Administration Building, NBS, Gaithersburg, MD

20899. To accomplish its objective of supplying the measurement foundation for industry,

science, and technology, NBS conducts

research in many areas, including ad- vanced ceramics, automated manufacturing, optoelectronics, and biotechnology.

Numerous opportunities exist for scientists and engineers from industrial, professional,

trade, and other organizations to collab- orate in research at NBS on projects of mutual interest. This guide explains a

variety of successes NBS has had in conducting cooperative research with private

companies, universities, and other govern- ment agencies. These programs include research consortia, individual Research

Associate programs, and joint research

centers. In addition, the publication describes specific NBS research projects

that are particularly well suited for collab- orative ventures and outlines ways

cooperative programs can be established.

REPORT ON NBS LARGE-SCALE

SEISMIC PROJECT

Cheok, G.S. and Stone, W.C., Behavior of

1/6-Scale Model Bridge Columns Subjected to Cyclic Inelastic Loading, Natl. Bur. Stand. (U.S.), NBSIR 86-3494, 291 pages (November 1986). Order by stock

no. PB 87-152245 from NTIS, $24.95

prepaid. As part of their studies on how full-scale bridge columns perform during earth- quakes, researchers at NBS constructed and tested six one-sixth scale replicas of the columns. The results will be used to de- termine if the behavior of full-scale columns can be extrapolated from model behavior. The first in a series of reports on the project

is available and gives a detailed description

of the design, fabrication, testing, and eval- uation of the model columns. Included among the findings for small-scale columns

•if)

is that recent California Department of Transportation specifications were sufficient to prevent longitudinal reinforcing bars from

pulling out of the footings for all the specimens. Testing of the first full-scale column was completed in July 1986. A second full- scale column is being fabricated at NBS

and will be tested this year.

SUMMARIES OF 1986 NBS BUILDING

RESEARCH

Wright, R.N., Building Technology Proj- ect Summaries 1986, Natl. Bur. Stand.

(U.S.), NBSIR 86-3490, 67 pages

(November 1986). Order by stock no. PB

87-140216 from NTIS, $13.95 prepaid.

NBS researchers conduct research leading

to safer structures which are more

economical to build and maintain. They de- velop technologies to predict, measure, and test the performance of building

materials, components, systems, and practices. While NBS does not promulgate

building standards or codes, its research is used widely by those in the building industry and government who do have stan- dards and codes responsibilities. This

report summarizes recent research projects

such as conducting studies on using sound

to determine flaws in concrete and studying

the behavior of full-scale bridge columns

during earthquakes. Other areas covered

include computer-integrated construction and building physics and equipment.

ABILITY OF AEC INDUSTRY TO

EXCHANGE CAD DATA

Palmer, M.E., The Current Ability of the

Architecture, Engineering, and Construction Industry to Exchange CAD

Data Sets Digitally, Natl. Bur. Stand.

(U.S.), NBSIR 86-3476, 31 pages (Octo- ber 1986). Order by stock no. PB 87- 134334/AS from NTIS, $11.95 prepaid.

The use of computer-aided (CAD)

systems in the architecture, engineering,

and construction (AEC) industry is in- creasing steadily. But a recent study at NBS confirms that it is difficult and often impossible to transfer data and drawings

from one CAD system to another. Re- searchers found the primary constraint is a lack of dependable and verifiable methods of exchanging data between dif- ferent CAD systems. Intermediate for

mats and translators are available, but, say

the NBS researchers, they are not ade- quate for comprehensive AEC CAD operations. To help resolve the problem, a committee was formed in 1 984 to develop

specifications for exchanging AEC information as part of the Initial Graphics Exchange

Specification (IGES), a national standard

since 1981. The IGES/AEC Committee currently is developing additional exchange

specifications to be incorporated into the

next version of IGES.

CATALOG OF STANDARD

REFERENCE MATERIALS

Seward, R.W., editor, NBS Standard

Reference Materials Catalog 1986-87,

Natl. Bur. Stand. (U.S.), NBS Spec. Pub.

260, 154 pages (June 1986). Order from

the Office of Standard Reference Materials, B311 Chemistry Building, NBS, Gaithers- burg, MD 20899, 301/975-OSRM (6776).

For 80 years, NBS has been providing

scientific, industrial, and commercial users

with carefully characterized materials to assess measurement techniques and to calibrate instruments. This catalog lists more

than 900 Standard Reference Materials (SRM's) available from the Bureau. These

materials are certified by NBS for specific

chemical and physical properties to help

companies and other users to achieve

quality assurance of materials and goods.

The SRM catalog includes a description of each reference material, its certified characterization, and unit size. Ordering

and shipping information also are included.

SOUND WAVES THAT DETECT

FLAWS IN CONCRETE

Sansalone, M. and Carino, N.J., ImpactEcho: A Method for Flaw Detection in Concrete Using Transient Stress Waves,

Natl. Bur Stand. (U.S.), NBSIR 86-3452,

234 pages (September 1986). Order by

stock no. PB 87-1 04444/AS from NTIS, $24.95 prepaid.

NBS researchers have developed a

nondestructive method to detect flaws in concrete. Known as "impact-echo," the technique works on the same principle as

the sonar pings used to locate and deter- mine the depth of a submarine. An impact on the concrete generates sound waves
which are reflected by flaws inside the concrete. A receiver mounted on the surface of the concrete picks up the reflections, or echoes. The location of a flaw is deter- mined by measuring how long it takes to receive the reflected echo. So far, the NBS

researchers have successfully used the technique to find artificial flaws embedded

in a number of different concrete slabs. In addition, they have been able to detect pockets of unconsolidated concrete and

the depth of cracks which are perpendicular to the surface. They also have been

able to distinguish a hollow metal duct from one that is filled with grout. The NBS team

plans to test the technique on other structural elements such as rectangular beams

and round columns.

HVAC PERFORMANCE IN "SMART"

BUILDINGS

Persily, A.K., Specifications for Thermal

and Environmental Evaluations of

Advanced-Technology Office

Buildings, Natl. Bur. Stand. (U.S.), NBSIR 86-3462, 95 pages (November

1986). Order by stock no. PB 87- 134326/AS from NTIS, $13.95 prepaid.

In this report for the General Services Administration, researchers at NBS describe

specifications for evaluating the thermal and environmental performance of advanced-technology buildings. These

buildings, sometimes called "smart"

buildings, have sophisticated controls for heating, ventilation, and air-conditioning

systems. The specifications will help avoid

design, construction, and operation errors which may result in buildings which are

unsuitable for occupants or which have

excessive operating costs. They include ways to measure airtightness and infiltration rates, determine insulation effectiveness, and evaluate indoor pollutant levels. The

report describes various diagnostic tests and the materials and equipment needed.

It also contains work statements which

describe how each test should be conducted, how data should be analyzed, and

how the results should be presented.

Although the specifications were developed

for use on advanced-technology buildings, most of the methods can be used to eval- uate other buildings as well.

SUMMARY OF NBS REACTOR

ACTIVITIES

Shorten, F.J., editor, NBS Reactor: Summary of Activities July 1985

Through June 1986, Natl. Bur. Stand.

(U.S.), NBS Tech. Note 1231, 161 pages

(November 1986). Order by stock no. 003- 003-02787-1 from GPO, $8 prepaid.

The National Bureau of Standards reactor

is a national center for the application of neutron methods to problems of national in- terest. The reactor power, recently in- creased from 10 to 20 MW, combined with 25 experimental facilities ranging from in- tense neutron beams to extensive irradia- tion facilities, make the NBS reactor one of the most versatile high-performance re- search reactors in the country. This report summarizes NBS research and collab- orative programs conducted at the NBS

reactor from July 1985 to June 1986. The

programs described range from the use of neutron beams to study the structure and

dynamics of materials through nuclear physics and neutron standards to sample

irradiations for activation analysis, isotope

production, radiation effects studies, neutron radiography, and nondestructive

evaluation.

OPTICAL FIBER MEASUREMENTS

SYMPOSIUM PROCEEDINGS

Day, G.W. and Franzen, D.L., editors, Technical Digest—Symposium on Optical Fiber Measurements 1986, Natl. Bur. Stand. (U.S.), NBS Spec. Pub. 720, 158 pages (September 1986). Order by

stock no. 003-003-02772-3 from GPO, $8

prepaid.

The 1986 Optical Fiber Measurements

Symposium, sponsored by NBS, brought

together over 300 representatives from 1

7

countries to present 34 papers. This digest

summarizes the 29 contributed papers, which span the full range of measurements

necessary to specify an optical fiber, with a heavy emphasis on dispersion and modefield diameter measurements in single- mode fibers. Also included are abridged

versions of the five invited papers which

summarize the state of the art and look to related and future measurement problems

in the characterization of sources, detectors, specialty fibers, and planar waveguide

devices.

NEW CALIBRATION SERVICES USERS

GUIDE

Uriano, G.A., Garner, E.L., Kirby, R.K., and

Reed, IV. P., editors, NBS Calibration Ser- vices Users Guide 1 986-1 988/Revised,

Natl. Bur. Stand. (U.S.), NBS Spec. Pub.

250, 183 pages (Revised January 1987). Order from the Office of Physical Measure- ment Services, B362 Physics Building,

NBS, Gaithersburg, MD 20899,

301/975-2007.

Calibration services, special test services, and measurement assurance programs

(MAP's) available from NBS are listed in this "users guide." These physical measurement services are designed to help the makers and users of precision measurements achieve the highest possible

levels of measurement quality and productivity. The hundreds of individual services described in this guide are the most ac- curate calibrations of their type available in the United States. These measurements

directly link a customer's precision equip- ment or transfer standards to national measurement standards. The calibrations and special tests include NBS services that check, adjust, and

characterize instruments, devices, and sets

of standards. The MAP's are quality control programs for calibrating a customer's entire measurement system. The following measurement calibration areas are listed in the new guide: dimensional; mechanical; ther- modynamic; optical radiation, ionizing radiation; and electromagnetic. The guide

explains fees, types of services, measure- ment criteria, reports of test results, references to NBS in advertisements, traceability of calibrations, and shipment of equipment.

ORDERING INFORMATION

To order publications from NTIS, send re- quest with payment to; National Technical

Information Service, Springfield, VA 22161.

Publications can be ordered from GPO by

mailing order with payment to: Superinten- dent of Documents, U.S. Government Print- ing Office, Washington, DC 20402.

31
CONFERENCE CALENDAR

4th International Congress on Oxygen

Radicals, University of California at San

Diego, La Jolla, CA

June 27-July 3, 1987

This congress will deal with free-radical pro- cesses and peroxidized products in chemistry, food technology, nutrition, biology, pharmacology, and medicine. The

energetics, kinetics, and mechanisms of simple model systems will be applied to complex biochemical processes and clinical medicine. The meeting will also explore the mechanisms of agents that protect against

free radicals and peroxy products in vitro and in vivo. These agents include antioxi- dants used in materials, food antioxidants, physiological antioxidants, and antioxien- zymes (SOD, glutathione, peroxidase, and

catalases). Sponsored by NBS. Contact: Michael G. Simic, C205 Radiation Physics

Building, NBS, Gaithersburg, MD 20899,

301/975-5558.

MFPG 42: Technology Innovation—Key

to International Competitiveness, NBS,

Gaithersburg, MD

September 15-17, 1987

Principal economic indicators point to in- creased foreign competition in the decades

ahead. Because productivity growth rates

in most major competing nations are higher than in the United States, U.S. government

and industry are focusing attention on the impact of technological change on productivity growth. The 42nd meeting of the Mechanical Failures Prevention Group (MFPG)

will concentrate on technological innovation, especially for small companies, that results

in improved products, processes, and ser- vices. They will also examine the need for establishing the communications and link- ages required between high-technology

companies and the interdisciplinary community of industry, government, and universities. Sessions being organized will highlight materials, fabrication technology, equipment

monitoring, protection of surfaces, mechanics, and machinery. Specific topics

will include polymers, ceramics, robotics, in- strumentation, and nondestructive inspection. Sponsored by NBS and the Office of Naval Research. Contact: T. Robert Shives,

A113 Materials Building, NBS, Gaithers- burg, MD 20899, 301/975-5711.

10th National Computer Security

Conference, Baltimore Convention

Center, Baltimore, MD

September 21-24, 1987

At this year's conference, individuals from government, private industry, and aca- demia will come together in a setting that fosters the sharing of information and the development of valuable relationships. The

theme is "Computer Security—From Princi- ples to Practices." In order to present a

varied program, the conference will be

divided into two tracks of information: technical and general managerial. Attendees may switch between tracks according to

their interests. Sponsored by the National Computer Security Center and NBS. Contacts: Linda Muzik, Attn: C421 , National Computer Security Center, 9800 Savage

Road, Ft. George G. Meade, MD 20755-

6000, 301/859-4506 or Irene Isaac, B266

Technology Building, NBS, Gaithersburg,

MD 20899, 301/975-3360.

11th International Symposium on

Polynuclear Aromatic Hydrocarbons,

NBS, Gaithersburg, MD

September 23-25, 1987

This meeting encourages open discussions between scientists representing government, academia, industry, and research

facilities investigating the chemical properties and biological effects of polynuclear aromatic hydrocarbons (PAH's). It will in- clude presentations on parent PAH's as

well as heteroatomic species and PAH derivatives including amino-, nitro-, and

halogen-substituted compounds. Sponsored

by NBS, the National Institutes of Health, and the Battelle Memorial Institute. Contact:

Dr. Willie E. May, A113 Chemistry Building,

NBS, Gaithersburg, MD 20899,

301/975-3108.

Accuracy in Trace AnalysisAccomplishments, Goals, Challenges,

NBS, Gaithersburg, MD

September 28-October 1, 1987

This symposium will focus on current trends

in quantitative trace analytical chemistry

and will provide perspectives on future challenges. The first day will be devoted to

plenary sessions that will review the history

of quantitative trace analysis, the present

situation from academic and industrial viewpoints, and future directions. Key issues will be highlighted in individual talks. Topics will include the following: biomolecules in trace

analysis, robotics, chemometrics, process

analytical chemistry, expert systems, and

reference materials for the future. The re- mainder of the symposium will consist of

parallel sessions dealing with considerations

of the measurement process; quantitation in environmental, clinical, and nutrient anal- yses; and advances in analytical tech- niques. Sessions directed to the measure- ment process will specifically consider

industrial needs for quality assurance and

efficient sample throughput. Sponsored by NBS. Contact: Harry S. Hertz, A309 Chemistry Building, NBS, Gaithersburg, MD

20899, 301/975-3145.

Tenth Symposium on Thermophysical

Properties—Call For Papers, NBS,

Gaithersburg, MD

June 20-23, 1988

This tenth symposium of the well- established series of conferences on ther- mophysical properties is concerned with

theoretical, experimental, and applied as- pects of thermophysical properties for gases, liquids, and solids. Featured topics

are: properties of new materials; properties

of gaseous and liquid mixtures; new devel- opments in experimental techniques; and

interpretation of experimental data in terms

of new theoretical developments.

Prospective authors are requested to submit their abstracts (200-300 words)

before December 1, 1987, to one of the cochairmen of the symposium: Ared

Cezairliyan, Thermophysics Division, NBS,

Gaithersburg, MD 20899, USA, 30I/975- 5931 or J.V. Sengers, Institute for Physical

Science and Technology, The University of Maryland, College Park, MD 20742, USA,

301/454-41 17. Sponsored by the American

Society of Mechanical Engineers, NBS, and

The University of Maryland.

32
warn

he National Bureau of Standards was established by an act of Congress on March 3, 1901. The Bureau's overall goal

is to strengthen and advance the nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the nation's physical measurement system; (2) scientific and technological services for industry and government; (3) a technical basis for equity in trade; and (4) technical services to promote public safety. The Bureau's technical work is performed by the National Measurement Laboratory, the

National Engineering Laboratory, the Institute for Computer Sciences and Technology, and the Institute for Materials Sci- ence and Engineering.

THE NATIONAL MEASUREMENT

LABORATORY

Provides the national system of physical

and chemical measurement; coordinates

the system with measurement systems of other nations and furnishes essential ser- vices leading to accurate and uniform

physical and chemical measurement

throughout the nation's scientific community, industry, and commerce; provides

advisory and research services to other government agencies; conducts physical

and chemical research; develops, pro- duces, and distributes Standard Refer- ence Materials; and provides calibration services. The laboratory consists of the

following areas:

• Standard Reference Data

• Measurement Services

• Basic Standards

• Radiation Research

• Chemical Physics

• Analytical Chemistry

THE NATIONAL ENGINEERING

LABORATORY

Provides technology and technical ser- vices to the public and private sectors to address national needs and to solve national problems; conducts research in engineering and applied science in support

of these efforts; builds and maintains

competence in the necessary disciplines

required to carry out this research and

technical service; develops engineering

data and measurement capabilities; pro- vides engineering measurement traceability services; develops test methods

and proposes engineering standards and

code changes; develops and proposes new engineering practices; and develops

and improves mechanisms to transfer re- sults of its research to the ultimate user. The laboratory consists of the following centers:

• Applied Mathematics

• Electronics and Electrical Engineering

• Manufacturing Engineering

• Building Technology

• Fire Research

• Chemical Engineering

THE INSTITUTE FOR COMPUTER

SCIENCES AND TECHNOLOGY

Conducts research and provides sci- entific and technical services to aid federal agencies in the selection, acquisition, application, and use of computer

technology to improve effectiveness and

economy in government operations in ac- cordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders,

and other directives; carries out this mission by managing the Federal Information Processing Standards Program, de- veloping federal ADP standards

guidelines? and managing federal participation in ADP voluntary standardization activities; provides scientific and

technological advisory services and assistance to federal agencies; and pro- vides the technical foundation for computer-related policies of the federal government. The institute consists of the

following centers:

• Programming Science and Technology

• Computer Systems Engineering

THE INSTITUTE FOR MATERIALS

SCIENCE AND ENGINEERING

Conducts research and provides measurements, data, standards, reference

materials, quantitative understanding,

and other technical information funda- mental to the processing, structure, properties, and performance of materials; ad- dresses the scientific basis for new

advanced materials technologies; plans

research around cross-country scientific themes such as nondestructive evaluation and phase diagram development; oversees Bureau-wide technical pro- grams in nuclear reactor radiation re- search and nondestructive evaluation; and broadly disseminates generic technical information resulting from its pro- grams. The institute consists of the fol- lowing divisions:

• Nondestructive Evaluation

• Inorganic Materials

• Fracture and Deformation

• Polymers

• Metallurgy

• Reactor Radiation
U.S. DEPARTMENT OF COMMERCE BULK RATE

National Bureau of Standards ~~ POSTAGE & FEES paid

Gaithersburg. MP 20899 NBS

OFFICIAL BUSINESS PERMIT No. G195

Penalty for Private Use, $300