U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

QC NBS SPECIAL PUBUCATION 735

100

U57

No. 735

1987
Cover photo: NBS physicist

Geoffrey Greene acljusts an

x-ray interferometer for

measuring the spacing of

the planes in silicon

crystals—a sort of atomicscale ruler. See article on

page 5.
NBS

Research

Reports

Research Information Center

National Bureau of Standards

Gaithersburg, Marykud 20899

ClCioo

Research Update 2

Back to the Basics 5

Will the Japanese Beat the United States

in Superconductivity? 9

Low-Resistance Contacts Developed for High-Tem peratu re Su perconductivity 12

IGES: Translating Electronic Tongues 13

Lifting System Failure Probable Cause of Fatal Building Collapse 17

Six NBS Projects Win 1987 l-R 100 Awards 20

Matching Processor and Algorithms:

The Challenge of Parallel Computers 23

Process Sensor Measures Internal Temperatures in Extruded Aluminum 25

Life, Death, and Oxygen Radicals 26

New Technique for Evaluating Installation of Home Insulation 30

New Publications 31

Conference Calendar 32

U S DEPARTMENT OF COMMERCE

C. William Verity, 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

December 1987

NBS Special Publication 735

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: 87-619882 CODENXNBSAV

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.

CONTENTS

1
RESEARCH UPDATE

I

ROUND BROKEN FOR COLD

NEUTRON RESEARCH

FACILITY

On November 20, Deputy Secretary of Commerce Clarence J. Brown, NBS Director Ernest Ambler, and

Rep. Connie Morelia (Md.) broke ground at NBS for thie construction of one of the few

cold neutron research facilities in the world. Speaking at the NBS research reactor site

in Gaithersburg, Md., Brown said, "This

country's ability to exploit a variety of emerging technologies will make or break

us economically when the 21st century

arrives. Results of cold neutron studies to be conducted at this facility can help the

United States to turn the potential of these

technologies into commercial successes. We need the very best facilities, like this one, if we are going to beat the competition to markets."

The new $25- million facility will make

cold neutron research easily available to U.S. scientists working in such fields as

materials science, chemistry, and biology.

Cold neutrons are low-temperature,

hence, low-energy, neutrons produced by

specially designed nuclear reactors. Cold

neutron sources have become one of the

most desired tools of modern materials

research because they allow researchers to conduct experiments that would be impractical or even impossible with more

energetic neutron sources. The first experimental stations at the cold neutron facility are expected to be available

late in 1989.

T&T, DEC, AND NBS DEVELOP

TEST METHODS FOR POSIX

^L^k Researchers from AT&T and

^HI^K Digital Equipment Corporation

Ml W (DEC) are working with NBS to develop test methods for the Standard for Portable Operating System Environments,

commonly known as "POSIX" (a trademark

of the Institute of Electrical and Electronics

Engineers [IEEE]). Test methods are needed by manufacturers and users to ensure that the operating system environments being developed conform to the pro- posed POSIX standard. POSIX was

developed by IEEE with participation from

industry and NBS. In addition, NBS is

NBS researcher Peter Huang examines his patented humidity-sensing

device, which effectively senses relative humidity from zero to 100 percent with better accuracy than existing instruments.

developing a Federal Information Pro- cessing Standard (FIPS) based on POSIX.

FIPS are developed by NBS for use by

the federal government.

OVEL HUMIDITY-SENSING

DEVICE DESIGNED

An NBS scientist has received a

patent for the design of a device

that uses organic polymers to sense and measure humidity. Peter H. Huang has been granted patent number

4,681 ,855 for the invention, which is an improvement over existing devices because

of its expected long life, lasting accuracy,

and ability to be used at high temperatures

and humidities. Huang envisions many

potential applications, especially in controlling the drying processes that support

industries such as textiles, paper, chemicals, and food. Meteorological and

electronics applications also are feasible. A major weakness in existing commercial

devices is hysteresis, or the inability of an

instrument to measure abrupt humidity

changes and then return accurately to the

original value. Huang's system significantly

reduces this problem while increasing sensitivity. For information, write or call Peter

H. Huang, 831 2 Physics Building, NBS,

Gaithersburg, MD 20899, 301/975-2621.

EAR TEST APPARATUS

FOR CERAMICS

Existing test methods to measure the friction and

wear of metals are not designed to study the performance of advanced ceramics used in heat engines

and other high-temperature environments

because the material properties of ceramics

are significantly different from steel. At high

temperatures, the low thermal conductivity

and diffusivity of ceramic materials can

generate large temperature gradients in conventional test devices that obscure infor- mation on the friction and wear of advanced ceramics.

NBS has developed a new hightemperature, controlled-atmosphere ceramic wear test facility that features control of temperature to 1500 °C. The facility also permits researchers to study various

gaseous environments as well as the

2
chemical vapor deposition of hightemperature lubricants. For information on

the new ceramic wear test facility, which is available for cooperative programs with

industry, government, and universities, contact: Said Jahanmir, A215 Metrology Building, NBS, Gaithersburg, MD 20899,

301/975-3671.

MPROVEMENT IN SUPERCONDUCTOR CONTACT RESISTANCE

As NBS Research Reports was going

to press, NBS and Westinghouse

researchers reported that they had

lowered high-temperature superconductor

contact resistance to a million times less than indium-solder contacts. This is a 100-

to a 1 , 000-fold improvement over their previous results which are reported on page 12. The newest results are obtained

by annealing the sputter-deposited silver contact pads on the superconductor in ox- ygen at temperatures up to 500 °C for an

hour. (The previously reported technique in- volved temperatures up to 150 °C, but no oxygen annealing.) Where the intermediate

(500 °C) temperatures can be tolerated,

the annealing technique yields resistivities of about 10-8 ohm-cm2 at 76 K for bulk

sintered samples of YBa2Cu307. This

resistivity was measured for current densities of up to 100 A/cm2. The voltage- current characteristic was nonlinear, having

the character of a superconducting proximity effect; at lower current densities, below

30 A/cm2, the resistivity was unmeasurably

low. These results were presented at the

Materials Research Society meeting in Boston, Mass., November 30-December 4,

1 987. (Similar results were observed by a group led by Y. Tzeng at Auburn University

using evaporative deposition and annealing

for 5 hours at 500 °C.) For details, write or

call Jack Ekin, Div. 724.05, NBS, Boulder,

CO 80303, 303/497-5448.

-'V-i^ EDESIGNED CIGARETTES

i JI COULD BE MORE FIRE-SAFE

After testing thousands of com- ^ mercial and experimental ciga- _ wL rettes, NBS researchers have

identified changes in the features of cigarettes that could reduce the lives and property lost each year in cigarette-related

'fires.

Cigarette ignition of soft furnishings, such

as upholstered furniture or mattresses, is by

far the leading cause of fire deaths and

injuries in the United States. The NBS

researchers found that thinner cigarettes

with less tobacco and less porous paper can Significantly reduce the chance of

igniting soft furnishings. They also found

that cigarettes with filter tips were somewhat less likely to ignite furnishings.

The type of tobacco made little difference. Another finding is that low-ignition tendency

does not necessarily lead to higher tar,

nicotine, and carbon monoxide yields as had been thought.

The researchers did not investigate the

toxicity of the cigarette smoke or consumer

acceptance. NBS economists analyzed the

potential economic impacts of developing

low-ignition cigarettes. They looked at the

effects of five hypothetical modifications

which might change the ignition tendency

of cigarettes, including decreased cir- cumference, tobacco density, paper porosity, and chemical additives.

OMPLETION OF FIRST PART

OF DCA GATEWAY PROJECT

NBS researchers have completed the first part of a project

sponsored by the U.S. Defense

Communications Agency (DCA) to build gateways between Defense Department

communication protocols and Open

Systems Interconnections (OSI) networking

protocols. OSI standards make it possible

for different manufacturers' equipment and

systems to communicate with each other

through networks. The gateways will be

used to maintain the agency's operations

during conversion to OS! networks. Working with a guest scientist from IBM, the

NBS researchers developed gateways

and a test system for linking the Defense

electronic mail protocol (Simple Mail Transfer Protocol) to its OSI counterpart

(Message Handling Facility/X.400). The

automated test system is used to deter- mine whether products comply with the

gateway specifications. Specifications are

still being developed for a second

gateway to connect the military's File Transfer Protocol and OSI's File Transfer,

Access, and Management Protocol. When completed, these specifications

and testing procedures will be available

to computer and communications ven- dors as well as to test service organizations for use in developing gateway

products that link Defense and OSI

protocols.

EW METHOD FOR

PREDICTING THE HAZARDS

OF FIRE

NBS researchers are issuing for

trial use a unique, computerized

method of predicting the hazards of fire. Known as HAZARD I, this prototype

system for the first time takes into account

the complex combination of physics,

chemistry, fluid mechanics, heat transfer,

biology, toxicology, and human behavior

that influences the outcome of a residential

fire.HAZARD I will be distributed to a limited number of fire and building professionals

who agree to evaluate it and provide comments to assist in the development of future improved versions of the method. Tools like HAZARD I are designed to complement

existing codes and standards by enabling new materials and technology to be eval- uated safely and quickly.

AB ACCREDITATION

PROGRAM FOR ASBESTOS IN SCHOOLS

A laboratory accreditation pro- gram for organizations that per- form tests of asbestos in schools has been

established by NBS under the National

Voluntary Laboratory Accreditation Program

(NVLAP) to meet the requirements of the

Asbestos Hazard Emergency Response

Act of 1986. This law requires the

Environmental Protection Agency (EPA) to develop a program for the inspection,

management, and abatement of asbestos

in the nation's schools.

Under the law, NBS will accredit laboratories to perform analysis for asbestos content in samples of bulk insulation and

building materials, and to analyze airborne

particulates collected during school inspections and asbestos abatement projects. For

information on the new asbestos program,

contact Harvey W. Berger, A531 Administration Building, NBS, Gaithersburg, MD

20899, 301/975-4016,

3
AT&T

SCIENTIST TO STUDY

THIN-FILM POLYMERS AT

NBS

AT&T Bell Laboratories is sponsoring a researcher under

the Bureau's Research Associate Pro- gram to study the behavior of polyimide

polymers at NBS. The research will be

done using the NBS spectrofluorimeter to make fluorescence measurements on the

structural properties of thin-film materials. Polyimides are important materials for use

in electronics and other high-technology

applications because of their thermal stability and suitability for photoresists.

The NBS Research Associate Program

provides an opportunity for people from

industry and other organizations to conduct cooperative research at the Bureau on programs of mutual interest, with

salaries paid by the sponsor.

ONSORTIUM TO INVESTIGATE

EMI PROTECTION

NBS and the Building Industry

Consulting Service International have created a consortium of organizations interested in curbing the

potentially damaging effects of conducted

electromagnetic interference (EMI). These

rapid surges, caused by sources such as

lightning, transformer cycling, and relay

switching, can severely damage computers

and other equipment. The consortium is concentrating on improvements in the per- formance and cost-effectiveness of surge

protection devices and is emphasizing fac- tors such as long-term stability and realistic voltage rating selection of these devices.

The group also is measuring the propagation of EMI surges in the wiring systems of actual buildings to complement or confirm

NBS EMI experiments under controlled laboratory conditions. Consortium members

are at an advantage because they will have

up-to-date information on the research as it develops, and participating organizations . are providing direction on the scope of the

project. Currently, eight organizations are

talking part in the consortium. Others are welcome to join and can get more information by contacting Francois D. Martzloff,

B162 Metrology Building, NBS,

Gaithersburg, MD 20899, 301/975-2409.

(NBS laboratories in Boulder, Colo., are

concurrently researching "radiated" EMI,

which is prompted by sources like walkietalkies, citizens band radios, and radar.)

NDUSTRY AND NBS

CERAMICS EFFORT

ADVANCED

NBS has agreed to cooperate with the

W Ceramics Advanced Manufacturing

Development and Engineering Center,

Inc. (CAMDEC) to develop measurement

technology, systems, and procedures for the processing of advanced ceramics. The

establishment of CAMDEC, a not-for-profit

Tennessee corporation, is the outgrowth of recommendations made by advanced

ceramic leaders at a workshop held at NBS, July 10-11, 1985, on the "Future of the U.S. Advanced Ceramics Industry."

CAMDEC has as its mission the creation of a national center for developing the pro- cessing and manufacturing technology

required to commercialize advanced structural ceramics. Under the agreement, NBS

will provide technical advice to CAMDEC,

participate in non-proprietary research and

development projects, and conduct

cooperative tests at NBS and CAMDEC

facilities. For information on the cooperative

program, contact Stephen Hsu, A257

Materials Building, NBS, Gaithersburg, MD

20899, 301/975-6119.

C VERSION OF NBS/EPA/MSDC

MASS SPECTRAL DATABASE

A major international resource of more than 44,000 analytical mass spectra is now available for use on personal computers (PC's). The PC

version was prepared from the

NBS/EPA/MSDC Mass Spectral Database

that is in use worldwide in a computermagnetic tape format and as a six-volume,

7,000-page reference. The collection of evaluated electron ionization mass spectra of organic and inorganic substances was originally put together by the

Environmental Protection Agency (EPA)

and the National Institutes of Health. It is now maintained by NBS, EPA, and the

Mass Spectrometry Data Centre (MSDC)

in the United Kingdom. The PC database

is contained on 13 high-density floppy

disks that can be stored on a hard disk

of any AT-class or XT-class PC. Rapid

searches can be made for the spectra of specific chemical name, formula, molecular weight, or Chemical Abstracts Registry Number, as well as for spectra with pre-selected characteristics such as peaks at certain masses. The PC version

of the NBS/EPA/MSDC Mass Spectral

Database is available for $750. For infor- mation, or to obtain a license agreement,

contact: Office of Standard Reference

Data, A320 Physics Building, NBS,

Gaithersburg, MD 20899, 301/975-2208.

LECTROMAGNETICS LAB

ACCREDITATION PROGRAM

EXPANDED

The electromagnetics laboratory

accreditation program, managed

by NBS under the National Voluntary Laboratory Accreditation Program (NVLAP), has

been expanded to meet requests from participating laboratories, manufacturers, and

the U.S. Naval Air Systems Command. Test methods have been added to help laboratories improve the quality of their testing

services on products that must meet Federal Communications Commission (FCC)

approval and to assure the quality and per- formance of electronic devices used in mili- tary weapons systems.

The expanded program includes test methods for radio frequency devices such

as receivers (FCC Part 15); industrial, scientific, and medical devices (FCC Part 1 8); radio transmitters (FCC Part 90); and a mili- tary standard (MIL STD 462) to measure

electromagnetic interference characteristics. The electromagnetics program was initially

limited to test methods for computing

devices (FCC Part 1 5J) and for telephone

equipment compatibility (FCC Part 68).

Laboratories interested in accreditation

for any of the test methods offered under

the expanded electromagnetics program,

or for information on NVLAP, should contact: Harvey W. Berger, A531 Administration Building, NBS, Gaithersburg, MD

20899, 301/975-4016.

4
Back to the Basics

The needs of modem

science and industry drive

the basic standards

research at the Nationai

Bureau of Standards to

extremes: extremes of

temperature, size,

pressure, and above all,

accuracy.

hermometers have more uses in hospitals than simply checking

patients' fevers. Roughly half of all

clinical laboratory tests are sensitive

to temperature—in some cases

requiring accuracies of five- hundredths of a degree in temperature measurement.

Makers of refrigerators, inte- grated circuits, and nuclear waste

casks all share a common concern. They don't want their products to

leak.Some of the most important

advances in early clock design were developed to meet the needs

of sailors—celestial navigation

depends on time. Today, the needs

of ships at sea still drive the time

business, but they've gotten more

demanding. With sophisticated electronic navigation systems an error

of about three-thousandths of a second could put a ship (or plane) a kilometer off course.

All of these users of measure- ments and millions more throughout

American industry and commerce owe something to the basic stan- dards research done at the

National Bureau of Standards.

It is here, for example, that the

U.S. standard for mass, a small

cylinder of platinum-iridium alloy, is kept in a safe in a temperaturecontrolled room.

Here, too, are the researchers,

laboratories, and equipment behind

national and international measure- ments of time, temperature,

pressure, length, and the basic

units of electricity.

Maintaining measurement stan- dards, however, is only a part of the basic standards activities at

NBS. The goal of Bureau re- searchers working in this area is to push against the current limits of physical measurement, to provide

the underpinnings of theory and

experiment for science and industry

The goal of Bureau

researchers... is to push

against the current limits

of physical measurement,

to provide the underpinnings of theory and

experiment for science

and industry....

which demand ever-better levels of accuracy and precision. For example. . ,

In the Dungeon

"We call this 'the dungeon',"

James Schooley explains,

somewhat unnecessarily. He is hauling up on a heavy trap door

set in the floor of a basement

laboratory. A short steel ladder

leads below to a small chamber

crammed with air-conditioning

equipment and another trap door,

leading to a still-lower chamber.

Down here in a small insulated

cubicle, two floors below ground

level, is the heart of the NBS gas

thermometer. An assemblage of pressure fittings, wires, pipes, and

various nondescript mechanisms,

the gas thermometer looks some- how anachronistic, and it is. It is the

perfection of 19th century technol- ogy, but for its particular task, it probably has no equal anywhere in the world. The gas thermometer is the basis of the international temperature scale. We use the concept of "temperature" every day, and in some

fields—clinical chemistry, scientific research, and chemical process

control, for example—accurate

NBS physicist James Schooley prepares to place a gauge

block to preset the manometer system of the NBS gas

thermometer, the most accurate instrument of its type in

the world.
temperature measurement is vital. But just what is temperature?

For most people, temperature is a number produced by a ther- mometer. There are many different ways to make thermometers, so some system is needed to make

them all consistent. As a matter of convenience, thermometers are

calibrated against the so-called

"International Practical Temperature

Scale of 1968" (iPTS-68). IPTS-68

is basically a list of reproducible

physical phenomena, and an

agreed-on set of "temperatures" for each phenomenon:

Boiling point of oxygen—

-182.962 °C

Boiling point of water—

100 °C

Melting point of zinc—

419.58 °C

Melting point of gold—

1064.43 °C

and so forth. The IPTS-68 provides

"fixed points" to nail down the

temperature scale and give the

scientist something handy for cali- brating thermometers.

Part of the Bureau's work is to provide scientists and engineers

with convenient access to IPTS-68.

A series of NBS Standard

Reference Materials (SRM's) have

been developed to put IPTS fixed points in convenient form. Other

SRM's provide additional fixed points that have been certified by

NBS in terms of the IPTS, such as

the clinical temperature standards,

gallium, rubidium, and succinonitriie, which were selected because

they have melting points near

important reference temperatures

for clinical chemistry tests. IPTS-68 is only a convenience,

however. "True" temperature is a phenomenon of thermodynamics,

and it is best defined by the gas

law, which says that for a given

amount of a gas, the pressure

and volume of the gas are directly related to its temperature. In principle, that sounds simple enough;

in practice, the accurate measure- ment of "thermodynamic temperature" is such a finicky, painstaking

business that it is only occasionally attempted.

"Temperature measurements

can be made very poorly unless

you are careful," explains

Schooley. "We now know that IPTS-68 has an error of a half a degree (Celsius) in some ranges. The gas thermometer is still the

best way to measure thermodynamic temperature, but it's very

difficult to use. We worked

extremely hard to get the melting

point of aluminum to within 10

millidegrees."

Schooley is wrapping up an NBS

effort to re-evaluate the practical

temperature scale in terms of ther- modynamic temperature that began

almost 30 years ago when his pre- decessor, Leslie Guildner, began

work on an improved, hightemperature gas thermometer. That

instrument, cossetted and corrected

for every conceivable source of

error, has pushed the technology of gas thermometry about as far as it

The NBS data.. .will

become a major factor in

the planned 1990 revision

of the International Practical Temperature Scale.

can go. It is probably the last of its kind in the world, according to NBS

officials, because other national laboratories have dropped their efforts in anticipation of the NBS

results. Guildner and his colleague

Robert Edsinger helped establish,

for instance, that the assignment of 273.15 kelvins to the ice-point of water (IPTS-68) was in error. It should be 273.22.

Who needs such accuracy? "For one example," says Schooley, "the

physicists and chemists who

measure properties of materials

such as thermal expansion or heat

capacity. Someone doing precise

calorimetry finds it very sensitive to imperfections in the temperature

scale." The NBS data, which should be

ready soon, will become a major

factor in the planned 1990 revision

of the International Practical Temperature Scale.

Standard Leaks...

have nothing to do with the evening news. The rate at which a gas

leaks from one volume to another

has become a matter of much

industrial interest in the last couple

of decades.

"There is a wide variety of products in our society whose perform- ance or lifetime depends on their

ability to retain or exclude gas,"

explains Charles Tilford, who

oversees leak and vacuum stan- dards. "Refrigerators, which have

to retain coolants, integrated cir- cuits—they're sensitive to moisture, vacuum systems of all kinds, auto- mobile shock absorbers, nuclear

weapons, and the casks used to ship nuclear wastes, these are all tested on a routine basis for leaks. "Even soup cans. You can esti- mate the leak rate in food cans

equivalent to the minimum size hole a microorganism can get through."

Measuring a leak may not sound

too difficult, but these are very slow

leaks. A typical industrial range, says Tilford, may be about from

10-9 to lO-''^ moles (a measure of the number of molecules) per second. In more familiar terms, if you had a 1 -liter container with an

absolute vacuum, at those rates you could fill it to atmospheric

pressure in (approximately) 1 to 10,000 years. The most common way to measure such leaks is to put

helium gas on one side of the

vessel and a mass spectrometer

tuned to helium on the other side. If
any helium leaks through, the mass

spectrometer detects it. The problem comes in trying to calibrate such a system. "You use a 'standard' leak," says Tilford, "which is typically a glass thimble

surrounded by a reservoir of helium

which diffuses through the glass at a 'constant' rate. This gives you a known rate for calibrating your mass spectrometer."

In theory. In practice, heliumpermeation leaks, although easy to make and use, are difficult to use

accurately. For one thing, says

Tilford, they are very sensitive to temperature. They are also difficult to calibrate. "Since we began our

special test service for standard

leaks," says Tilford, "we've had

companies sending leaks for cali- bration that were leaking at about

half their specified rate. We've

heard stories that when you go to lower leak rates you can find errors

of a factor of ten." Leak-sensitive products are

tested for maximum acceptable

leak rates, so a 50-percent error in your standard translates to real money. Fifty percent low and you

are rejecting or reworking units that are actually acceptable; 50

percent high and you are shipping units that can come back

and haunt you with warranty

repairs or product liability claims.

Until a year ago, the problem was exacerbated by the fact that the United States had no national

standards for leak rate. Tilford and

his colleagues Charles Ehrlich and

Richard Hyland devised a calibration system based on the high- vacuum standards maintained by

NBS. With support from Sandia

National Laboratories, a nuclear

research facility with an active in- terest in leak standards, they have

developed a calibration service for standard leaks and have launched

NBS physicists Richard Hyland (left) and Charles Ehrlich

discuss a typical "reference leak" to be calculated on the

NBS primary leak standard.

the first of a projected series of workshops in the use of leak

standards.

"Right now we're working in what we think is the most widely

used range, and with the most

widely used type of leaks," says

Tilford, "We want to broaden that range in both directions, faster and

slower leaks."

"It's been a process of developing primary standards, understanding how the transfer standards—the

helium-glass permeation leaks—behave, and making the calibrations

useful to people through

mechanisms like workshops, We

also need to understand how people operate standard leaks. We've

done a lot of work on this because

operating procedures can have even more of an effect on your final measurements than the calibration

of your standard."

The Smallest "Yardstick"

Some NBS researchers ask questions of less immediacy. Questions

that arise from basic physics or that may affect the measurement

systems of tomorrow.

How do you measure the almost

unimaginably small? Where do you

find a ruler that will mark off the

distance between atoms?

For almost two decades, a handful of Bureau researchers have

been refining the answer to those

questions. Their tools are x rays,

lasers, nuclear reactors, and small,

perfect blocks of silicon crystal.

In an intricate experiment, x rays are passed through an "inter- ferometer" carved out of a single

block of silicon, and the shifting

peaks of intensity as the crystal is moved, measured by a visible or

optical laser interferometer, mark

out the distance between adjacent

planes of atoms in the silicon. The distances involved beggar

the imagination. Two planes of atoms in a near-perfect silicon crystal are separated by about 1 .9 angstroms: about 0.000 000 007 5

of an inch. What's more, the experimenters estimate their accuracy at about 1 part in 10,000,000.

The work involved is so hair- raisingly delicate—even the fact that

7
the solid crystal will expand ever so

slightly when moved from room

pressure to a vacuum chamber for measurement is a source of error—that you can count the

number of labs in this business,

worldwide, on one hand.

Why? "The motivation is to find a way to get from measurements in the optical wavelength region which

form the international standard for length measurement to the scale of X rays and gamma rays," says

Ernest Kessler, Jr. Division chief Richard Deslattes, Albert Henins,

Geoffrey Greene, and Kessler make

up the silicon-crystal lattice-spacing team.

Their closest competitor and col- laborator is the PhysikalischTechnische Bundesanhalt (PTB) in West Germany. NBS and PTB

NBS physicist Albert Henins iiolds carefully cut silicon crystals used to precisely measure silicon-crystal lattice

spacings.

have interchanged silicon samples

and measured the difference between the two samples.

When all the measurements are complete, the silicon block

becomes an atomic-scale ruler, the

spacing of its atomic planes known

precisely. It can then be used in other experiments: to make direct measurements of the wavelength of X or gamma rays, for example. The

gamma ray measurements are done at the special reactor facility of the Institut-Laue Langevin in France (ILL). The NBS group ran into a stumbling block several years ago when

unexpected instrument errors were

discovered which badly flawed the

first series of silicon crystal

measurements: By "badly" we

mean about 2 parts in 1 million—still quite outstanding by

anyone's standard. Since then the

apparatus has been completely

redesigned and reassembled, and

a new set of values, due to be

published within the year, will report

silicon-crystal lattice spacings at unmatched levels of accuracy.

The goals are scientific. Measured silicon crystals are the

measurement link to the scale of gamma-ray wavelengths, important

values for both theoretical and

experimental physicists. Ultimately,

this work provides a link between

the standards for length and mass,

according to Kessler. "When you go high enough in gamma-ray energy, you can make

accurate equivalent mass and

energy measurements," he says. "At about 5 million electron volts,

in principle, you can unify the

scales of mass and wavelength at the 1 part in 1 million level. In fact, the current best known value for the mass of the neutron comes

out of our work at ILL." Work by the Bureau's time and

frequency group made it possible,

4 years ago, to link the scales for time and length. At the frontiers of

basic standards, the units of measurement seem to converge.

Pushing the State of the

Art

This article only touches upon a

small fraction of the basic stan- dards research under way at the

National Bureau of Standards.

Nothing has been said about the

work which ensures that all U.S.

electrical measurements are referenced to NBS standards. Or

the fact that the Bureau's work in pressure and vacuum standards is used in such critical areas as

assuring the accuracy of airplane

altimeters. Or that time is kept for the United

States by an NBS clock, and

Bureau researchers in the NBS

Boulder, Colo., laboratories are at work on ever-better systems not only for keeping time, but for passing it on to others. NBS researchers

in Colorado at the Joint Institute for Laboratory Astrophysics contribute

to fields as fundamental as gravity

research and as practical as streetlight design.

"It is important to pay proper

attention to basic measurements,"

observes Helmut Hellwig, acting

director of the NBS National

Measurement Laboratory.

"Measurement plays an increasingly important role in all our industrial and commercial activities; it is particularly important to the quality

of products and services offered by

our high-technology industries. "Much of our scientific, technological, and industrial development

over the last few decades has been

driven by measurement. Better, more accurate, state-of-the-art measurements have driven both

practical and theoretical physics,

chemistry, and industry, and have

resulted in new knowledge, and

ultimately, new and improved products and processes."

by Michael A. Baum

NBS Public Affairs Specialist
Will the Japanese Beat the

United States in Superconductivity?

Adapted from remarks of NBS

Director Ernest Ambler at the conference "Assessing tlie Commercial

Realities of New Higti Temperature

Superconductors," November 16, 1987, San Francisco, Calif

find it botln fascinating and reveal- ing that as soon as the first reports

of laboratory successes with higher

temperature superconductivity were

announced, the news media began

zeroing in on the question of whether or not the Japanese or others will beat us to the punch in capitalizing on this astonishing

scientific advance. That is both

good news and bad news.

For the first time, we are paying

close attention to what the competition is planning when it comes to exploiting new research results: That is good news. On the other hand an excessive

amount of attention paid to how the

Japanese are doing in superconductivity can distract us from solv- ing our own problems, which have

implications far beyond superconductivity: That is bad news.

"Will the Japanese beat the

United States in superconductivity?"

Actually, I think we may be asking

ourselves the wrong question, or too narrow a question. The more

important question is whether or not the Japanese or others will beat us

in exploiting a whole range of new

and emerging technologies.

Although the commercial potential

of these technologies is mostly in the future, many are closer at hand

and better commercial bets right now than superconductivity.

Let me assert that the Japanese

are attempting to dominate world

markets in all of them. Among

these technologies are: Photonics, which includes

applications of optical fibers,

optoelectronics, and solid-state lasers to communications, computers, and information technology;

Advanced materials, including

biomaterials, ceramics, composites,

and now, superconducting materials; and

Automated manufacturing,

especially the higher-level applications of robots, flexible manufacturing systems, and the broader

scheme of computer-integrated

manufacturing.

The United States is not unaware

of the Japanese intentions and has

been completely familiar with their

very successful strategies and tactics for many years. So why are we

so slow in revitalizing our own

strategies? What is standing in the

way of U.S. success?

Economic Barriers

Earlier this year, I headed up a Commerce Department group

which examined the economic

potential of important emerging

technologies. It soon became clear

to us that, while there should be no

complacency, scientific research,

technical ideas, and inventiveness are not our major problems when it comes to competing.

The most serious problems fac- ing the United States are largely

The more important question is whetlier or not the

Japanese or others will

beat us in exploiting a

whole range of new and

emerging technologies.

non-technical barriers. There are the so-called "macroeconomic"

barriers, which are related to high

costs of capital funds, antitrust regulations, and so forth. But I think some "microeconomic" barriers are equally

important when it comes to emerging technologies. These microeconomic barriers are structural and behavioral problems, and

therefore, they are potentially the

most intractable.

If you want to worry about U.S. competitiveness in superconductivity-based products, or any

other high-technology products for

that matter, in my opinion these are

the things you should really be having nightmares about.

Here, we are talking about inadeRecent advances in high-temperature superconductors

have sparlced an internationai race to produce the first

product using these new materials.

9
quate long-range strategic planning

by U.S. firms and/or a failure to execute long-range strategic plans

in the face of short-term and unex- pected difficulties. This is often because of excessive importance

attached to short-range financial statements and concomitant managerial incentives. The fact of the matter is that in the United States, as compared to Japan, our corporate leaders are judged and rewarded for short-term

performance. They are not rewarded for the long haul. Recent activities in mergers,

leveraged buy-outs, and hostile takeovers make these pressures even stronger, and their implications for long-range R&D invest- ments are ominous.

Product vs. Process

Technology

We also have to face up to other

problems relating to corporate

strategies. We have a poor mix of engineering improvements in this country, with too much focus on

product technology and not enough attention on process

technology. This makes it difficult

for companies to adapt to rapid

advances in technology because

they may become too locked into a particular product.

The Japanese have shown us

the value of taking the larger view.

They focus not just on the better product, but on a better way to make the product so that quality

and reliability can be built into the

product and so that technological

changes can be readily incor- porated to gain maximum per- formance at minimum cost.

Integration and

Cooperation

This points to a broader, more

basic problem that has plagued

U.S. industry: We have not been

properly integrating research, development, manufacturing, and

marketing functions.

It is vital to have effective communication among these functions

within the corporate environment in order to move new technologies

rapidly to the marketplace. The

length of time from research to marketing—the technological life cycle—has been compressed

substantially, and the Japanese

have shown that they understand

that also. Better integration of these functions is probably one of the best

We have not been properly integrating research,

development, manufacturing, and marketing

functions.

ways to achieve greater productivity

in our high-technology manufacturing enterprises.

These microeconomic barriers are people-oriented and managerial

in nature, and, therefore, they fall squarely on the backs of the

private sector. But we all must help.

I have mentioned the need for greater cooperation among cor- porate R&D, manufacturing, and

marketing functions. Likewise, the

lack of cooperation and integration

among institutions is formidable.

That is due in part, I think, to the

fact that all of us, but especially

corporate managers, are trained to compete rather than to cooperate.

We are fighting in global markets

where the scale of efforts demand

we use all available resources. We

are seeing some major improvements in this regard, with the for- mation of dozens of research

consortia and changes in the ways

in which federal laboratories, for instance, can work directly with

companies and grant very

favorable patent rights.

I have given much attention to these barriers to emerging technologies because I am convinced that they must be recognized and

addressed both bluntly and quickly

if the United States is to be commercially competitive when the next century dawns.

Superconductivity

Competition

Now, where are we specifically in terms of commercializing hightemperature superconductivity?

My own opinion is that some of the structural and behavioral barriers have been addressed

somewhat better in superconductivity than in other emerging or soon-to-emerge technologies. For one thing, there is a sense of urgency for a change, which is promising. We certainly can't be

accused as a nation of being complacent about the Japanese

challenge in this field. We have seen a dramatic

buildup in research capabilities.

Japan is not alone in assembling

corporate research efforts of 50 or more people to work on this exploding field, and cooperation

between institutions is pretty good.

The United States is probably about on a par with the Japanese at this point.

The obvious gap today is that everyone—Americans and JapanMaking products Is a

private sector job. There

Is no substitute for action

by Industry.

ese alike— lacks the necessary

theoretical understanding of hightemperature superconductivity. The

result is that current research on

both sides is somewhat empirical.

If, in fact, a U.S. strength over

the past several decades has been

our broad and deep basic science
At a federally sponsored conference, President Reagan

announced an 11 -point initiative to ensure U.S. readiness in

commercializing superconductivity advances. Here Reagan

discusses high-temperature superconductors with NBS

scientist Stephen Freiman amd Secretary of State Shultz.

capability, we can be optimistic

about the odds that we will advance the basic theory of superconductivity faster than the

Japanese, or the Europeans, for that matter. But we have learned the hard

way that leads in basic knowledge

are all too fleeting, and we can't be

complacent. That's especially

important considering the substantial Japanese efforts in electronics

and advanced ceramics that position them so well for possible hightemperature superconducting

applications.

So what do we have to do?

We need to focus on achieving comparative advantages in applied R&D, for both product and

process development. This includes

designing in quality and manufacturability during applied R&D.

We need to work on process

control and quality assurance tech- niques. This would have been

especially true in the ceramics area even without the discovery of hightemperature superconductors.

We need to adopt longer

range marketing strategies which

emphasize global market share

over short-term profits.

We need to better integrate

the research, development,

manufacturing, and marketing

strategies for superconducting

products.

We need to compress the

length of time between product concept and marketing.

We need to think broadly

about targeting entire systems that

will utilize high-temperature superconductivity principles. As with sili- con, you won't make a lot of money on the raw materials—it's the integrated circuits that pay off.

Government Role

The federal government has an

important part to play. Government can provide support,

through R&D, through procure- ment especially in the defense

area, through fair and decisive

actions to provide a good

business environment, to help

industry turn the technological

promise of superconductivity into commercial success. But government has never been

successful in showing industry how

to do its job, and there is absolutely no reason to think that will change

in the future, or that superconductivity is different in this regard from

other areas of technology.

Making products is a private sector job. There is no substitute for action by industry. And I mean

action on its own behalf and not

just in response to government

requirements.

So, where does that leave us?

Nothing is inevitable about the

competition in superconductivity.

No good reasons exist for us not to beat the Japanese and the Euro- peans in superconductivity. But we must translate today's sense of urgency into actions. We

must be willing to make fundamental changes in corporate and

government strategies if we are to overcome the structural and

behavioral barriers blocking the

commercial prospects for this and

other technologies. If we don't I think we will do well in the sprint to commercialize superconductivity

and end up losing the longer race. We must learn from rather than

repeaf the mistakes of the past if we are to make sure the first— but

not just the first— high-temperature

superconducting products carry a "Made in the USA" label.
Low-Resistance Contacts Developed for

High -Temperature Superconductivity

igh contact resistance has been a

nnajor obstacle to eventual commercial applications of the new highcritical-temperature ceramic

superconductors. Work by Jack W.

Ekin of the NBS Electromagnetic

Technology Division, Boulder,

Colo., and Armand J. Panson and

Betty A. Blakenship of the Westinghouse Research and Development

Center, Pittsburgh, Pa., has pro- duced a new method for making

low-resistance electrical contacts on

these superconductors.

The new method, announced

September 18, 1987, reduces the contact resistivity several thousand

times below that previously

achieved with conventional

contacts.

*

Resistance at electrical contacts causes heating in any device, but it

is particularly fatal in superconductors. Even modest heating can

raise the temperature of the super- conductor enough to weaken or destroy the property of superconductivity.

The high resistance that usually occurs where external leads are attached to ceramic superconductors is an obstacle to both measurements and practical applications of the newly developed

high-critical-temperature superconductors. Future superconducting

magnet and circuit board applications will require resistivities of less than 10 to 100 micro-ohm-cm^, but contact heating caused by high

resistance presently limits measure- ments of critical current in bulk

samples at low temperatures and

low fields. The new contacts have a surface

resistance of about 1 0 micro-ohmcm2 at 76 kelvins (liquid nitrogen

temperature), when tested on the new yttrium-barium-copper-oxide

(YBa2Cu307) superconductor. This

resistance is 1,000 to 100,000

'As NBS Research Reports was going to press, the researchers announced further ad- vances in this work. See page 3 for update.

Low-resistance contacts

(white squares at ends of

superconducting black bar) are being readied for lowtemperature testing.

times lower than that exhibited by

indium solder, silver paint, or silver epoxy contacts. The contact pro- cess IS carried out at temperatures

below 200 °C and therefore affords good control and avoids possible

degradation of the underlying

superconductor from excessive dif- fusion of the contact material which can occur at high temperatures.

The method also allows post-firing

shaping and processing steps

before contacts are applied.

The researchers developed the new method after noticing a correlation between the ages of many

superconductor samples and their contact resistivities. They reasoned

that, if age were a factor, reducing

the time the surface was exposed

to air should improve the contacts. Further testing indicated that signifi- cant surface deterioration occurred

in a matter of seconds.

The new method involves three

steps, which work together to pro- duce low contact resistivity. Minimizing the air exposure time minimizes

the degradation of the superconductor surface that occurs before

making the contacts. Sputter etch- ing the surface removes the

degraded layer, and depositing a

thin layer of a noble metal—silver and gold were used—protects the

surface and minimizes further degradation of the superconductor

surface. The exposure of the surface can be minimized, or preferably

eliminated, by reducing the time

between the final firing and the pro- cessing of the contact pad, and more importantly, by keeping the

superconductor in an atmosphere

devoid of moisture, carbon dioxide,

and other gases that interact with it. Pure dry oxygen or inert gases

such as argon may serve as protection. Variations of this general

method, such as glow-discharge

cleaning followed by evaporative

deposition of the noble metal, may

yield good results, too. Other contact materials were

tried, but silver proved much better than indium and somewhat better than pure gold. Moreover, silver does not degrade the bulk super- conductor as much as copper does on reheating. The contacts showed

The new method...

reduces the contact

resistivity several thousand times below that

previously achieved with

conventional contacts.

consistently low resistivity and were

stable when exposed to air for more than 4 months.

Further details of the new

method will be published in a

forthcoming issue of Applied

Physics Letters. Preprints may

be obtained from Jack Ekin, Div. 724.05, NBS, Boulder. CO 80303;

ask for the "Low Resistivity Contact" paper.

by Collier Smith

NBS Public Affairs Specialist
IGES: Translating Electronic Tongues

IGES is the product of an NBSguided voluntary organization tliat goes by the same acronym and

currently has more than 600

members who represent some 250

companies and agencies. The 8- year-old cooperative effort, born out

of industry-wide frustration over the

communication impasse between

computers, has been so successful

that it has fostered an even more

ambitious standardization scheme,

the Product Data Exchange Specification (PDES). PDES, which probably won't be ready for commercial

application until the early 1990's,

will allow for swapping not only

geometric data, but every single

detail about a part—everything that a computer-operated machine will need to make the part.

If experience with IGES is any

gauge, PDES will be well received.

In 1981, less than 2 years after a

national meeting of CAD/CAM

users and vendors voiced the need

for a "translation format," the first

According to IGES chairman Bradford Smitli, storing data in

an almost universally accepted format—IGES—assures

that digitized product models will always be available.

he proliferation of computer

systems has the potential to erect a modern-day Tower of Babel, a confusion of electronic "tongues" that can add cost and complexity to most computer-aided tasks, from

word processing to design and

manufacturing. But unlike the biblical tower that was toppled by a communications

failure, today's predicament lends

itself to solution. For users and

manufacturers of computer-aided

design and manufacturing

(CAD/CAM) systems, the most

widely accepted answer is the Initial Graphics Exchange Specification,

better known as IGES. The specification provides a "neutral file" for storing the geometric information

and drawings typical of the

CAD/CAM systems used by parts

manufacturers of all types and

architectural and construction firms. The file serves as an intermediary,

facilitating the transfer of data between incompatible systems.

version of IGES was issued and

adopted by the American National

Standards Institute as a major portion of its standard for the "digital

representation for communication of product definition data." The evolution from idea to usable specification proceeded at what can

rightfully be described as a breakneck pace in the deliberative arena

of industrial standards.

Widespread Use

The rapid turnaround and acceptance of IGES testify both to the

need for the specification and to the value of a cooperative response

to an industry-wide problem. Philip

Kennicott of the General Electric Co., Walter Braithwaite of the Boeing Co., and Roger Nagel, formerly

of NBS now with Lehigh University, are credited with leading and coordinating the effort. Several government agencies, including three

branches of the military, were also

heavily involved. In fact, the Air Force Computer-Integrated

Manufacturing Program is a major

sponsor of the IGES organization.

Today, virtually all U.S. -made

CAD/CAM systems are compatible

with IGES, a matter of adding a

post-processor for converting data

to the neutral format and a pre- processor for translating IGES data

into the receiving system's native format. Among users, IGES, soon

to be issued in its fourth version,

has "worked its way into the nooks

and crannies of many manufacturing businesses," says William

Burkett, senior engineer at the

McDonnell Aircraft Co. in St. Louis,

Mo.

In effect, the specification is a

"superset" of modeling entities that accommodates the large, yet highly

specialized and highly secretive

CAD/CAM field, says the Bureau's

Bradford Smith, IGES chairman.

"You cannot decree," he explains,

"a particular brand of CAD/CAM

13
system for all the units in your

business enterprise because there

is no one system that will solve all needs. Each CAD system has its own niche in the market—the stuff

that it does really well. The trouble

is the units have to do business

Among users, IGES...has

"worked its way into tlie

nooks and crannies of

many manufacturing

businesses."

with each other. I think the data

exchange of product models will always be with us." An alternative to the neutral-file approach for exchanging models

is to use direct converters, pro- grams that translate data from one

system into the format used by

another. This alternative quickly

becomes unwieldy and prohibitively expensive, as the number

of converters required for data

exchanges grows geometrically

with the number of CAD/CAM

systems. To link four systems, for example, eight direct converters

are needed; introducing a fifth system requires eight additional converters. Four systems that exchange data through IGES also use eight translators—a pre- processor and post-processor on

each machine. But for each

subsequent addition to the

CAD/CAM network, only two additional translators are needed.

According to Kennicott, an infor- mation scientist at GE's corporate

research and development center

in Schenectady, N.Y., heavy

reliance on direct converters eventually imposes penalties. "It's not the expense as much as it is the

delay," he says. "It can take 6

months to a year" to develop one

converter. And because the typical

CAD/CAM system is updated about

twice a year, the task of keeping

converters current may be

constant. "IGES," says Smith, "has been

popular as a means of exchanging

part models between CAD

systems" within the same company

and between those of different

firms, such as contractors and subcontractors. Ultimately, the specification may prove even more

valuable as a tool for archiving

product models developed on out- dated systems.

"The CAD market is very competitive and quite volatile," Smith

explains. "What do you do if you

have the system of a vendor who

has gone out of business? It might

be useful for a couple of years, but

it will become obsolete relatively soon. You can't just throw out the

old system and get a new one. What about the hundreds of thousands of staff hours of CAD ter- minal time that you've put in on

that system? What about your

entire corporate database of product data models that's on that system?"

Smith says that a growing

number of companies will discover

that IGES is the answer to this quandary. Storing data in an almost

universally accepted format assures

that digitized product models will always be accessible, regardless of the vagaries of the CAD/CAM

market.

Keeping Pace

IGES, however, must be responsive

to the almost continuous improvement of CAD/CAM technology,

which explains why four versions of the specification have been devel- oped since 1980 and why a fifth

will be issued in the next year.

While limited initially to handling

geometric data in the wire-frame

format typical of blueprints, each

succeeding version of IGES

extended capabilities for two- and

three-dimensional representations of geometric entities, including sur- faces; for finite-element modeling,

which is necessary for design analysis; and for annotating dimensions,

tolerances, and other product data. Although compatible with earlier versions, IGES 4.0 will offer constructive solid geometry, one of two

popular methods for solids modeling. The next release will include

the other method, known as boundary representation.

Before it is released, a new IGES

version is subjected to painstaking

review within the organization.

Drafted and redrafted, each new

feature, extension, and application are scrutinized, debated, and dem-

...some of the liarshest

critics may reside within

the organization itself, but

their ideas and suggestions foster improvements

that are incorporated into

future IGES versions.

onstrated by technical committees

before the entire membership votes on their acceptance. "We have

been very particular in what we

do," Smith says, "and very responsible, I think." As a result, IGES

"has a good following among vendors." In fact, two CAD/CAM ven- dors were so confident in the

organization's work that they added

the IGES solid geometry feature to

their systems after it was approved

in balloting, but well before it was

officially released in the soon-to-be

published fourth version.
An advantage of the IGES format is that users do not need

special translators for each different piece of equipment

used. Rather, they are only required to have a translator to

and from the IGES format. These translators, called preand post-processors, are generally available from equipment vendors.

The Criticisms

IGES does have its detractors who

complain that data exchanges take

too long, the neutral file is too large, or transfers occasionally result in errors. Some of the criticisms are

valid. Smith and other members of the IGES organization acknowledge. In fact, some of the harshest

critics may reside within the

organization itself, but their ideas

and suggestions foster improvements that are incorporated into future IGES versions. In response

to complaints that the neutral file consumes too much computer

memory, for example, the third ver- sion includes an optional technique

for reducing the file size by twothirds. Data transfer from one CAD/CAM

system to another "can take any- where from seconds to hours, and

it varies from computer to computer," Smith says. But even if it takes

hours, an exchange through IGES

is a much faster alternative "than

sitting a CAD operator down and

regenerating everything," he says. While some transfers are

flawless, others result in lost infor- mation, a problem, according to Smith, that usually does not orig- inate with IGES. Two systems, for example, may not share a con- cept—say, a spline curve. If the

target system is not programmed

to handle a spline curve, it may

choose to represent this geometrical information as a series of lines that approximate the curve,

or it may jettison it altogether,

leaving a blank spot on the

screen. "You have to recognize and

work within certain constraints,"

explains Charles L. Stoddard,

CAD/CAM requirements analyst at Pratt-Whitney in West Palm Beach,

Fla. Stoddard says he routinely

exchanges data between systems

"that don't even think alike." These transfers, however, are more complicated, requiring foresight and close coordination.

"I spend a lot of time working

with people in the exchange of data between systems," he says. "You still have to be able to communicate effectively. If you do

that, then the data become

usable." Stoddard admits to occasional frustrations with IGES, but he

and his colleagues regularly use

the tool. At Pratt-Whitney, which

has several different CAD/CAM

systems, IGES is used almost

hourly for in-house transfers of data

and for exchanges of parts models

between facilities, Stoddard says. Smith acknowledges that some

exchanges are demanding in their rigor and that errors can arise. "But," he asks, "if you transfer 90

percent of the information, isn't it easier to regenerate the missing 10

percent than it is to regenerate the

entire product model?"

Sometimes errors originate in the

software of the pre- and postprocessors that the vendors have

added to their systems. Simply put,

the problem is that some vendors

have been less than thorough in implementing the specification,

despite their claims to the contrary.

The IGES organization is developing a test for evaluating the completeness and accuracy of translators. The Society of Auto- motive Engineers plans to use the

test in a voluntary validation pro- gram it will offer CAD/CAM

vendors.

IGES users range from big firms,

such as Pratt-Whitney, General

Motors, Boeing, and McDonnell Aircraft, to small subcontracting "job"

shops. The Department of Defense

(DOD) also IS a major proponent of IGES, and it is taking measures to
assure greater use of the specification by contractors. "DOD has gone on record that they want to procure all weapons

data packages in digital form,"

Smith explains. "That includes all documents—text and illustrations,

all drawings, and all three- dimensional product models. By

1990, they want to be doing

business digitally." As a step in that

direction, DOD will soon issue a

specification (Military Standard

1840) requiring that IGES be used

for technical illustrations, twoAs envisioned, PDES will

be used to produce a

"computer-sensible

description of products."

dimensional drawings, and printed

circuit boards.

Standard for the Future

Meanwhile, the Product Data

Exchange Specification is beginning

to take shape. As envisioned,

PDES will be used to produce a

"computer-sensible description of products," explains Kennicott. To

some extent, this can already be

done with IGES, but the general consensus within the organization is that a much more comprehensive

and exacting specification is needed, he says. PDES will be a unifying thread in

efforts to develop a truly computerintegrated manufacturing environment, linking "islands of

automation" that now act independently rather than in concert. As

McDonnell Aircraft's Burkett sees it, the specification could foster inte- gration to the point that buying

CAD/CAM systems and other auto- mated equipment would be much

like purchasing components for a

stereo system—just as audiophiles

assemble stereo systems with speakers, amplifiers, and other

components from a variety of suppliers. Freed of compatibility constraints, manufacturers could focus on the price and performance of each equipment piece.

Obviously, PDES will not only be

used to transfer graphic representations of parts, but also a wide

range of non-geometric data, such

as manufacturing features, toler- ance specifications, properties of materials, and surface finish specifications. Smith says the specification will "support the entire productdesign and -manufacturing life cycle. So, PDES will have data ele- ments that far surpass those in IGES."

Experience with IGES is the

springboard for PDES, but the new

specification will be entirely different

in its construction, guided by the

database-design principles of computer science and by the tenets of information modeling. As a result, Smith says, PDES, despite its greater sophistication and complexity, should be "much simpler and

easier to implement" than IGES.

The PDES effort also will borrow

heavily from the U.S. Air Force's Product Definition Data Interface

project, carried out by McDonnell

Aircraft Co. Tailored primarily to the needs of the aircraft industry,

the ongoing project has devel- oped and demonstrated the hard- ware and software to transfer parts data all the way from the

design and engineering phases to the applications programs of the

manufacturing phase.

Development of PDES parallels

the International Standards

Organization's efforts to establish a worldwide Standard for the

Exchange of Product Model Data

(STEP). If all goes according to plan, the first version of PDES,

which already is in review, will be

presented in 1988 as the official U.S. proposal for the international standard.

Smith anticipates that the

earliest users of PDES will be very

sophisticated high-technology

companies, those involved in extending the applications, for example, of robotics, computeraided vision, and artificial intelli-

...the specification [PDES]

will "support the entire

product-design and

-manufacturing life cycle.

So, PDES will have data

elements that far surpass

those in IGES."

gence. For other parts designers

and manufacturers, IGES, which

will continue to be refined and

enhanced, will satisfy most needs

for transferring data files. But as technology advances. Smith predicts, the ranks of PDES users will begin to swell.

by Mark Bello Washington, D.C.-area Science Writer
Lifting System Failure Probable

Cause of Fatal Building Collapse

t approximately 1:30 p.m. on April

23, 1987, the L'Ambiance Plaza, an apartment building under construction in Bridgeport, Conn., col- lapsed, killing 28 construction

workers. This was the largest loss

of life in a U.S. construction acci- dent since 51 workers were killed

in the collapse of a reinforced concrete cooling tower under construction at Willow Island, W. Va., in 1978.

On April 24, the U.S. Occupational Safety and Health Administration (OSHA) asked the National

Bureau of Standards to investigate

and determine the most probable

technical cause of the collapse. A

The building was being constructed using the lift-slab tech- nique. The floor and roof slabs were cast one on top of the other on the ground. The slabs then were raised, most in packages of three, by a lifting assembly consist- ing of a hydraulic jack, threaded

jack rods, and attachments.

At the time of the collapse, a package of three slabs for floors 9,

1 0, and 1 1 of the west tower was

being put into place and temporary

wedges were being installed under

the 9th floor slab. The NBS

investigators determined that the

failure of a key component of the

system for lifting concrete floor

The failure of a key component of the system for lifting

concrete floor slabs was the most probable cause of the

L'Ambiance Plaza building collapse on April 23, 1987.

team of engineers from the NBS

Center for Building Technology

arrived at the site of the collapse

that same day to begin the

investigation.

slabs was the most probable cause

for the building's collapse.

Specifically, the collapse most

probably began when a jack rod

supporting three concrete floor slabs slipped out of a u-shaped

opening in a steel bracket. The

bracket, or lifting angle, was part of a steel collar, known as a shearhead. Shearheads were placed

around individual steel columns on

the two-tower complex. Concrete

floor slabs were cast around the

shearheads.

NBS researchers pinpointed the

location where the jacking system

used to lift the slabs into final position most likely failed. They con- cluded that the load placed on a

jack at one of two columns caused

parts of the shearhead on the 9th

floor slab to deform, allowing a jack

rod and nut to kick out from the

shearhead. This caused the three

floor slabs to fall, resulting in the

collapse of the entire west tower

and then the east tower. This failure mechanism was duplicated in NBS

laboratory tests. "Our investigation of this tragedy, as well as earlier failures, points out the need to pay more attention to the structural integrity of buildings

during the construction process,"

said Charles Culver, chief of the

Structures Division in the NBS

Center for Building Technology.

Culver, who led the NBS

investigation, said "Special care must be given so that structures can withstand the load experienced

during construction, and so that the

failure of a single component, like a

lifting system, does not bring down

the entire structure through a pro- gressive collapse, as was the case

with L'Ambiance Plaza."

The researchers investigated a

variety of possible causes of failure, but concluded that only the lifting system failure played a significant

role in initiating the collapse. The

possible causes of the initial failure which were considered and ruled out included the quality of materials

used in the structure, the use of a

horizontal jack to plumb the structure, inadequate resistance to lateral movement due to the lack of guy

wires and improper placement of supporting shear walls, earth pressure against a basement wall, and foundation settling.

17
NBS researchers arrived at and

confirmed their conclusions with laboratory tests of the debris, computer analyses, on-site investigations, an extensive review of project

documents, and interviews with eyewitnesses.

In addition to a series of computer analyses, laboratory tests were conducted to evaluate the

properties of materials like the steel and concrete used in the construction. Compression tests were con- ducted on concrete cores. Tensile

tests, metallographic and chemical

analyses, hardness tests, and frac- ture analyses were conducted on

the steel columns and welds. Tensile tests also were conducted on

the post-tensioning tendons used

to give the concrete slabs added

strength.

Other tests were carried out on

individual components and

assemblies of the lifting system.

Tensile tests were carried out on

the jack rods and attachments.

Load tests were conducted on the

shearhead-column assembly and

the lifting assembly (jack, jack

rods and attachments, and shearhead) to see how they performed.

A team of NBS researchers was

involved in the $375,000

investigation, some full-time, some

as needed. The work was done

m

'Our investigation of this

tragedy, as well as earlier

failures, points out the

need to pay more attention to the structural

integrity of buildings during the construction

process."

primarily by seven researchers in the NBS Center for Building

Technology, and was directed by

Culver, a civil engineer. Re- searchers in two other areas of NBS, the Fracture and Deformation

Division and the Inorganic Analytical Research Division, also assisted in the investigation.

NBS, which has no regulatory

authority, carried out the investigation for OSHA specifically to deter- mine the cause of the collapse. The

NBS researchers did not evaluate

the overall design of the structure, nor was it NBS' role to assess

responsibility for the collapse.

NBS investigation results are dis- tributed widely to help designers,

builders, and regulatory officials improve construction safety. The

314-page report. Investigation of

L'Ambiance Plaza Building Collapse

in Bridgeport, Connecticut (NBSIR

88-3640), that NBS prepared for OSHA is available from the National

Technical Information Service,

Springfield, VA 22161, for $30.95

prepaid. Order by title and PB

#88-112438.

The NBS report on the investigation was released at an OSHA

press briefing on October 22. A 22- minute videotape of Culver explaining the NBS findings can be

purchased, in either Beta or VHS

format, for $30 from the Public

Information Division, A903 Administration Building, NBS, Gaithersburg,

MD 20899, 301/975-2758. Make

checks payable to the National

Bureau of Standards; an information package is included.

by Jan Kosko

NBS Public Affairs Specialist

The L'Ambiance Plaza building collapse most probably

began when a jack rod supporting three concrete floor

slabs slipped out of a u- shaped opening in a steel

bracket called a lifting angle

(right). The lifting angle was

part of a steel collar known

as a shearhead (center).

Shearheads were placed

around individual steel columns and concrete floor

slabs were cast around the

shearheads. The drawing on

the far right shows the complete lifting system.

Threaded -

jack rod

Shearhead arm channel ^

Utting angle

Lifting nut

_ Steel column
NBS Structural Failure Investigations

As a federal science and engineering research laboratory, tlie National Bureau of Standards

has a long history of investigating structural failures. The investigations focus on determining

the most probable technical causes of the failure. Since NBS

has no regulatory authority and

does not promulgate building

standards or codes, it is often viewed as a neutral "third party"

which can conduct independent

investigations. Through its Center for Building Technology,

NBS develops the tools and

technology to test and improve

the performance of structures.

Typically, NBS researchers

conduct an extensive field investigation at the site of the building

failure to determine conditions

before and after the failure. Documents such as drawings, specifications, and inspection reports are reviewed to gain information

about the structure as it was

designed. Extensive laboratory

tests on materials are conducted

to determine physical properties.

NBS may fabricate mockups or

replicas of parts of the structure and test these also. In addition

to laboratory tests, NBS

researchers can use computers

to model a structure and anal- yze and predict its structural performance.

The NBS laboratories are

extensively equipped; some of the facilities are one-of-a-kind. For example, NBS has several

types of universal testing

machines which can apply

forces in several directions for structural components up to 60-

feet tall. Other facilities include

materials research laboratories

for characterizing materials, and

a high-performance computer

graphics laboratory.

Requests for assistance in a

structural investigation can come

from other federal agencies,

such as the Occupational Safety

and Health Administration, state

and local governments, or other

organizations. Also, NBS may

initiate an investigation of a significant failure after consulting

with local authorities. Investigations that NBS has

conducted include the collapse

of walkways in the Hyatt

Regency hotel in Kansas City,

Mo., and construction failure of a reinforced concrete cooling

tower at Willow Island, W. Va. In addition, NBS investigated the

structural soundness of the U.S. Embassy office building under

construction in Moscow.

The results of these investigations are made public and help ensure that those involved in the

building process understand the

most probable causes of these

accidents. Under a grant from

NBS, The University of Maryland

is developing a computerized

database containing case

histories of structural failures in the United States.
Six NBS Projects Win 1987

l-R 100 Awards

nnovations in semiconductors, sen- sors and measurement techniques

for quality control, and chemistry were among the six projects from

the National Bureau of Standards to be given l-R 100 awards this year.

l-R 1 00 awards are given

annually by Research & Development magazine to honor the "100

most significant" new technical

products of the preceding year. Presentations were made

September 17, 1987, in Chicago,

bringing to 57 the number of l-R 100 awards NBS has received

since first entering the competition

in 1973.

Descriptions of the award-winning

projects follow.

Crystal Axis Detection

Sidney Weiser. formerly of the NBS

Center for Manufacturing Engineering, now retired, earned an l-R 100

award for the invention of an auto- mated laser scanner that deter- mines the orientation of the crystal

axis in single-crystal semiconductor

materials. The proper alignment of crystal axes IS an important element in the

manufacture of semiconductor

devices, which are fabricated on

thin "wafers" sliced from a single

crystal of silicon or other material. Weiser's crystal axis laser scanner was developed for a particularly difficult case: the crystals of cadmium

telluride which are the heart of mer- cad telluride infrared detectors. Previous methods of determining

the major axis of cadmium telluride crystals required the use of x-ray

diffraction techniques, which work

only on wafers and require from 5

to 20 minutes per observation. A

more recent technique depends on

the reflection of laser light from the

crystal surface which has been

selectively etched to highlight the

crystal planes. Very low signal-tonoise ratios make this technique difficult to use. Weiser's instrument uses a

significant modification of the laser scattering approach and a computerized pattern recognition

algorithm to make the same measurement in less than a second—so

fast that the machine can easily

prepare maps of multi-crystalline areas. The instrument works with both single wafers and the original

crystal boule from which the wafers

are cut.

Sidney Weiser developed a

crystal axis laser scanner

that determines the orientation of the crystal axis in

single-crystal semiconductor materials.

Weiser's device will be manufactured commercially by Exotech

Incorporated of Gaithersburg, Md.,

and is expected to cost from

$25,000 to $85,000, depending on

features.

Surface Roughness

IVIeasurement

Four NBS researchers shared an

l-R 100 award for their development of an automated technique

using thermography to measure the

roughness of surfaces and find defects. The procedure is faster and more versatile than current methods.

Being able to measure surface

profiles and detect defects is important for quality control in industries such as electronics, automotive,

ceramics, and construction. The

NBS technique should be adaptable to in-line inspection since the

measurements are made quickly,

without touching the surface, and

the instrumentation requires little calibration.

In the NBS method, the material

to be inspected is heated slightly
Gerald Blessing, with Martin

Jones, designed a teclinique

for evaluating ceramic

powders during production.

and the resulting emissions are detected by an infrared thermographic camera. Using a

microcomputer-based image pro- cessor, the thermographic image

can be converted to an equivalent

topographic map of the surface. Accompanying software mathematically describes surface

roughness and isolates defects. The technique was developed

initially to measure very rough sur- faces, such as steel which has

been blasted with an abrasive like sand. But the NBS researchers are

confident it also can measure the

roughness of much finer surfaces.

In addition, they have used it to

find defects, such as rust spots

under paint on metal surfaces. Mary E. McKnight, Jonathan W.

Martin, and Edward J. Embree of the NBS Center for Building

Technology and Dale P. Bentz, now with the W.R. Grace Corporation, developed the technique.

Ceramic Quality Sensor

Martin P. Jones, formerly of NBS,

and Gerald V. Blessing of the

NBS Center for Manufacturing

Engineering won an l-R 100

award for the development of a new ultrasonic method for monitoring the quality of ceramic

powders during compaction. The

sensor is the first nondestructive

evaluation technique that permits

ceramic producers to fully auto- mate the inspection of compacted

powders while the material is in the mold.

The sensor system uses piezoelectric transducers to generate

ultrasonic wave pulses that travel through a mold and into a sample. The resulting ultrasonic

echoes are recorded as they

reflect back and forth through the

material until the pulses die out. The sensor, which is sensitive to porosity, moisture, and chemical

content, offers producers a way to control the quality of ceramic

powders at almost any stage of

compaction without having to handle the very fragile materials in

their green or unfired state. The in-situ ceramic quality sensor was developed at NBS as part of the Bureau's effort to apply nondestructive evaluation techniques to measure the properties and

characteristics of materials for in-line monitoring and process control during manufacture. Jones, who now

works for Alcoa Laboratories, Alcoa

Center, Pa., developed the sensor

with Blessing while he was a Johns

Hopkins University graduate stu- dent at NBS.

Pipe Porosity Sensor

An industry-government team was

given an l-R 100 award for the

development of another ultrasonic sensor technique that will enable

steel producers to quickly detect

flaws in hot metal and more

accurately crop unsound material

before it is run through the complete production cycle.

The sensor, which has the potential for saving the U.S. steel industry

millions of dollars annually, was

developed under a cooperative

agreement between NBS and the

American Iron and Steel Institute

(AISI) and evaluated and tested at

Argonne National Laboratory. It is based on an ultrasonic system

developed for AISI by the Magnaflux Corporation of Chicago.

The Magnaflux system uses contact rollers that require heavy

pressures (1 0,000-20,000 pounds

per square inch) to transmit highfrequency sound waves into hot

steel.

Melvin Linzer (left) and Haydn Wadley were part of an

industry-government team that developed a sensor for

detecting flaws in hot steel.
Top. Honored for their digital composition

mapping system were (from left) David

Bright, Ryna Marinenko, Dale Newbury, and

Robert Myklebust.

Bottom. H.M. (Skip) Kingston and Lois Jassie

designed a microwave system for dissolving

chemical samples in closed containers.

Melvin Linzer of NBS modified

this system by placing a powder

flux—which melts at high temperatures—in front of the rollers. This

eliminates the need for heavy wheel

pressures to couple ultrasound

pulses into and out of hot steel blooms, billets, and slabs. The

award-winning technique uses a

piezoelectric transducer that is isolated from the hot steel surface

by a buffer rod. The powder flux is used as a liquid couplant to pro- vide excellent acoustic contact between the rod and the hot steel surface. The other members of the

research team include Haydn N.G.

Wadley, NBS Metallurgy Division; Lev Spevak, Magnaflux Corporation; David S. Kupperman, Argonne

National Laboratory; and C. David

Rogers, United States Steel, USX

Corporation, and AISI program

manager at NBS.

Digital Compositional

Mapping

A team of eight researchers from

NBS and the National Institutes of Health (NIH) was honored for the

introduction of a system that uses

digital computer technology

coupled with electron beam instru- ments to "map" the distribution of chemical elements on the surfaces

of a variety of samples.

The key advantage to the system

is that it can create compositional

images which display both the type

and number of atoms at sample

sites 1 micrometer or finer in dimension. That is, besides giving

qualitative information on which ele- ments are distributed in the sample,

the system also provides a complete quantitative analysis at every

1 -micrometer-wide point. The

researchers can view these dual

functions through a color-enhanced

video image of the sample. Other

devices on the market are limited in

their ability to provide a complete

quantitative analysis.

The system has many applications, including characterization of

microstructures in various materials

and the linking of disease to chemical imbalances in the body.

The digital compositional mapping system was developed by

Ryna B. Marinenko, Dale E. Newbury, Robert C. Myklebust,

and David S. Bright of the NBS

Center for Analytical Chemistry and

Charles E. Fiori, Richard D. Leapman, Carol R. Swyt, and Keith

E. Gorlen of NIH.

Microwave Dissolution

H.M. (Skip) Kingston of the NBS

Center for Analytical Chemistry and

Lois B. Jassie, Michael J. Collins,

and Ronald J. Goetchius of CEM

Corporation, a North Carolina

manufacturer of research

microwave equipment, shared an

l-R 100 award for their design of a

system that uses microwaves to rapidly dissolve chemical samples

in closed vessels. Sample dissolution is the first step in most

instrumental elemental analysis.

The new system is an improvement over traditional dissolution techniques. It is rapid, safe, and

contaminant-free, factors essential to reliable chemical analyses. By

combining the microwave tech- nique's ability to directly couple

energy and heat materials quickly

with the superior dissolving properties of closed containers under

pressure, the NBS/CEM team has

designed a method for decomposing samples that takes less than 15 minutes. Older hot plate

methods using open-vented

beakers typically require dissolv- ing times of anywhere from 4

hours to 4 days, depending on

the complexity of the sample.

Kingston and Jassie are editing a book for the American Chemical

Society that will allow industrial chemists to predict conditions and

safely tailor their own microwave

devices for desired results.

22
Matching Processor and Algorithms:

The Challenge of Parallel Computers

arallel processors are the new stars on the horizon of computing. With a handful of thousands of separate

calculating engines (processors)

linked together, these new computer architectures promise to replace single processors as the

workhorses for number-crunching

scientists and engineers. Unfortunately, mathematicians and computer scientists are just beginning to understand how best to program

these new machines.

Francis Sullivan, director of the

Center for Applied Mathematics

(CAM) at the National Bureau of Standards, hopes to clear away

We are going to take a broad look at scientific

applications and try to build a taxonomy of

problem types says Francis Sullivan, director of

the NBS Center for Applied Mathematics.

some of the mists now shrouding

the programming of parallel pro- cessor computers.* He and his col- leagues are particularly interested in computational methods, termed

algorithms, used to solve numerical

problems. An algorithm is a set of logical directions for calculating an

answer, much as a recipe is a set

of directions for cooking. The

'This work is in collaboration with the work

reported earlier in NBS Research Reports

(April 1987).

researchers' goal is to run scientific calculations faster by matching an

algorithm to a computer's design.

Today, the major tool scientists and engineers use to tackle complex numerical problems is the

supercomputer, the crowning glory

of electrical engineering's ability to pack circuits more and more closely. The supercomputer's compact,

but extremely powerful, processor

performs hundreds of millions of calculations per second—one

calculation at a time. This speed

lets these machines obtain answers once thought beyond reach.

A problem that would take weeks

or months to solve on a personal

computer can be solved in minutes

or hours on a supercomputer.

Chemists use these machines to calculate the behavior of molecules

from the laws of quantum

mechanics; meteorologists depend

on supercomputers to simulate the

atmosphere for accurate, long-term

weather forecasts; engineers

designing aircraft simulate the air- flow around a wing or fuselage with a precision previously obtained only

in a wind tunnel. "The existence of supercomputers has broadened everybody's

horizons," says Sullivan. But, their

relatively high cost puts supercomputers beyond the means of most

researchers and companies. In addition, computer engineers are approaching the limits that the laws

of physics impose on the speed of an individual processor. "The next step has to be a radical change in computer architecture, coupled with a lot more thought about how one

writes programs," explains Sullivan. These costs and limitations are

driving scientists and engineers to investigate parallel, or multi- processor, computers as less expensive substitutes for supercomputers.

Traditional, single-processor computers execute only one instruction

at a time. In contrast, parallel

machines can perform several—or even thousands—of actions at the same time, depending on the

number of processors.

This gives even machines with

relatively simple individual pro- cessors much of the power of a supercomputer at a fraction of the

cost. Parallel computers can cost $100,000 or less and are capable

of performing 400 million calculations per second, while a traditional computer, which can do a billion calculations per second, can cost as much as $15 million. "The parallel computers are

here," Sullivan observes. "They are

not toys. There are hundreds of

parallel computers now installed and used for scientific applications." In fact, the fastest computers

currently available are parallel

supercomputers with, usually, four

or eight very powerful processors.

Unlike the single-processor

machines, parallel computers come

in a wide variety of architectures.

Some designs have many pro- cessors sharing a common

memory; other designs give each

processor its own local memory,

with no shared memory.

In a single-processor computer one instruction is brought from

memory and executed, then the

next, and so on. A multiprocessor

computer, in contrast, can perform

many operations at the same time,

letting each processor work on a

separate part of a problem. Or it can perform the same instruction simultaneously on more than one

piece of data, running its pro- cessors in lockstep.

The computer science community is just beginning to match

problems in engineering, physics,

or chemistry to the parallel computer architecture able to solve

them the fastest. Funded by the

U.S. Department of Energy and the

Office of Naval Research, the

National Research Council last year

issued a report, entitled An Agenda

for Improved Evaluation of Supercomputer Performance, emphasizing the importance of this effort.

23
"One thing that the report says is that we don't really know how to evaluate the perfornnance of super- computers and parallel computers,"

Sullivan says. "It's about time we

began to think very seriously about

how to do that."

Historically, computer perform- ance has been measured in terms

of the speed of simple computational operations of the central pro- cessing unit, a measure not adequate for multiprocessor

architectures. Another widely used

approach is to take a "typical"

calculation—a benchmark—and run

it on a variety of machines.

This approach is limited, since

information is gathered on only one

class of problem, and it may not be

representative of other types of computations. What is needed is a method that predicts which

architecture will allow the most effi- cient solution of a given problem.

"There is a fundamental dif- ference between knowing that an

application [program] computes on

a system for a certain length of time and knowing that the time is well-used," the National Research

Council report says. Determining

which type of parallel computer will run a scientific problem most effi- ciently is the task undertaken by

Sullivan and his associates in the

Center for Applied Mathematics, in collaboration with researchers in the

NBS Institute for Computer

Sciences and Technology (ICST).

Working with them are scientists at the University of Colorado and The

University of Maryland.

In this project, which is also sponsored by the U.S. Department

of Energy, the researchers will use

standard programming languages

(FORTRAN and C) adapted to run on parallel computers. Their first step towards their goal is to classify

scientific problems and the algorithms used to solve them. One can

group problems by their discipline area (chemistry) and problem type

(molecular dynamics), but Sullivan

considers this approach

inadequate.

"What I think is important in look- ing at problems is trying to understand what the essential problem

is—how the data move around and

what it takes to perform the calculation," he says. "So part of what we

are going to try to do is to take a broad look at scientific applications

and try to build a taxonomy of problem types—not by discipline area, but by what the core calculation is.

"It turns out that, if you look at it the right way, you can take areas

that seem to be completely dif- ferent, like fluid dynamics and

elementary particle theory, and

from the point of view of the kind of algorithm you are working with and

the kind of data flow that goes on, they are the same problem."

Once they have built this tax- onomy of problem types, Sullivan and his colleagues plan to identify

and extract the fundamental portion

of the algorithm, the kernel process. They are in a good position to do

that because of their involvement

with the entire spectrum of computational mathematics.

If the researchers are able to

identify six or seven classes of problems and extract the kernel processes, what will they do with them? An obvious idea is to run these fundamental calculations on

all possible parallel machines, as benchmarks. Measuring the speed

of the algorithm is not enough.

Instead, Sullivan hopes to understand what happens when each of these kernel processes is executed

in different parallel computers.

He considers it important to establish whether any perform- ance limitations are related to the

algorithm itself, the manner in which

information is passed between

memory and the processors (the

communications protocol), or the

machine's hardware. Another

group of NBS researchers,

headed by Robert Carpenter in ICST, has developed hardware to

gather information on fundamental

events in the hardware of parallel

computers. Sullivan's group will contribute to the development of

test routines for this equipment.

Using instrumented sharedmemory and local-memory parallel

machines, the researchers plan to observe basic machine events

during execution of the algorithms. A software technique,

code profiling, will provide them

with additional information. Unlike a benchmark, which tells you how

long it took to run the program, a code profile tells where in the pro- gram you are spending your time. "When you actually run a profiler on something, you find out that some little piece of code you hardly ever think about is where you are spending all your time," Sullivan notes. "You need to go in and

work on that piece of the

program."

From this information, the re- searchers expect to determine the

operations dominating each kernel process. Guidelines based on this data will help computational scientists select the proper machine to run a particular algorithm or choose

the best way to implement a specific algorithm on a particular parallel

computer.

Rarely is there only one algorithm

suitable for solving a scientific problem, so the mathematical method

can generally be tailored to the

available computer.

"The problems people are facing are not how to integrate differential equations. We know something

about that by now," Sullivan says. "The problem is: What is a reason- able way to organize this data so

that I can get my algorithm to work

efficiently? We hope to be able to answer that question."

by David I. Lewin

Washington, D.C.-area Science Writer
Process Sensor Measures Internal

Temperatures in Extruded Aluminum

process control sensor that rapidly measures the internal tennperatures

of extruded aluminum as it comes

out of a die has been developed

by the National Bureau of Stan- dards and the Extruded Products

Division of the Aluminum Association. With improved temperature

control at the extrusion press, manufacturers will be able to increase the production speed of extruded materials, prevent surface

cracking, and improve product

yield.

The sensor was produced under a cooperative research program,

established in 1986, between the

Bureau and the aluminum industry

group to develop a process control sensor for the manufacture of

NBS scientist Arnold Kahn (left) and

research associate IMichael IViester discuss

their process control sensor, designed to

be used in the production of extruded

aluminum products.

extruded aluminum products. Of

the more than 16.1 billion pounds

of aluminum projected for shipment

in 1987 by U.S. manufacturers,

nearly one-fifth of the production will be extruded shapes, bars, pipe,

and rods. The new process control sensor was designed by Michael L. Mester, an Aluminum Associationsponsored researcher at the

Bureau, and NBS scientists Arnold

H. Kahn and Haydn N. G. Wadley.

It has been tested by researchers

at the Cressona Aluminum Company, Cressona, Pa., where its online performance at an extrusion

press in a working mill repeated

successful laboratory measurements. The scientists were assisted

in the Cressona tests by Richard M.

Harris, vice president for manufacturing, and a team of production

engineers.

The new sensor can measure the

body temperatures of extruded

aluminum at 500 °C to a depth of one-half the thickness of the

material with an accuracy of 5 °C.

Based on an electromagnetic

concept, the sensor generates

eddy currents in hot aluminum as it

is extruded from a die. (Eddy cur- rents are electrical currents induced

in a metal by changing magnetic

fields.) By measuring the properties

of eddy currents in metal, it is possible to determine temperature.

With the new sensor, electro- magnetic signals from the extruded

material are recorded by a computer and rapidly processed to show temperatures for on-line pro- cess control. According to Wadley, NBS head

of the project, the process control device is the first non-contact method to accurately measure the

body temperatures of extruded hot

metals. Mester points out that the sensor has potential in the production of non-magnetic steels, copper, and

metal alloys. It could be used in other manufacturing processes

such as the rolling and drawing of metals. Kahn explains that the automated

system also is designed to measure

the dimensions of extruded

materials as they come out of the

press. This additional capability

could be used to provide information on die wear during extrusion runs and for other dimensional sensor needs such as in hot isostatic

pressing.

The testing of the prototype sensor on an extrusion press completes the first part of the

multi-phase program between NBS

and the Aluminum Association.

Robert I. Werner, chairman of the

Aluminum Association's Extruded

Products Division Research Task

Group, says, "We are pleased with

the successful Cressona tests. The

sensor was developed on time,

within budget, and it withstood the

rigorous demands of a working mill environment."

Werner says that the next step

by the task group will be to offer the sensor design to instrument

builders for development into a pro-

'duction system.

John C. Bard, president of the

Aluminum Association, says, "The

program between NBS and our group is an example of how industry and government can work

together to improve our nation's

industrial competitiveness. This new

process control sensor will offer producers improved quality control throughout the entire manufacturing

process and eliminate 'guesswork'

in several critical areas." The program between NBS and

the Aluminum Association is one of many such cooperative undertakings with industry at the Bureau.

In the metals area, a similar agreement between NBS and the

American Iron and Steel Institute has produced a prototype ultra- sonic sensor for detecting flaws in hot steel billets, and has made

possible another ultrasonic sensor

technique for reading internal temperature profiles in metals. The Aluminum Association,

headquartered in Washington,

D.C., IS a national organization of 87 aluminum producers and

fabricators of materials and products for industry, construction, and

consumers.

by Roger Rensberger

NBS Public Affairs Specialist

25
Life, Death, and Oxygen Radicals

At the 4th International

Congress on Oxygen

Radicals, scientists from

around the world considered the delicate balancing act of life in a cor- rosive environment.

number of science fiction authiors have speculated that inquiring

aliens might well write the Earth off

after a cursory inspection because

of its corrosive, lethal atmosphere.

We usually think of oxygen as

beneficial, necessary to life. It is also a killer. Last June more then 400 re- searchers gathered from all around

the world in La Jolla, Calif., to dis- cuss the paradoxical, dark aspect

of oxygen chemistry at the 4th

International Congress on Oxygen

Radicals (ICOR), organized by the

National Bureau of Standards.

Other sponsors of the congress were the National Heart, Lung and

Blood Institute; the International Life Sciences Institute; the National

Cancer institute; the American

Industrial Health Council; and the

Institute for Research on Aging.

Seventeen major corporations and

industrial associations also contri- buted funds.

The meeting's arcane title belied

the universality of its topics, for the

chemistry of oxygen radicals is now

believed by many researchers to play a crucial role in a host of generally undesirable processes,

including food spoilage, aging, cancer, arthritis, atherosclerosis,

various eye and lung disorders,

tissue damage following strokes or heart attacks, and a growing list of other afflictions. Oxygen radicals also play a role

in several beneficial things, such as

the action of some antibacterial drugs.

Oxygen radicals are highly reactive chemical groups derived from

oxygen. They are produced in a

variety of ways including chemical

and biochemical reactions and by

radiation. They are generally pres- ent for only a fraction of a second

before they react with some other

molecule.

Michael Simic of the NBS Center

for Radiation Research chaired the

congress. He explains that the

interest in oxygen radical processes

in biochemistry is a comparatively

recent phenomenon.

"In the 1950's and 1960's there was a lot of interest in food

...the chemistry of oxygen

radicals is now believed

by many researchers to

play a crucial role in a

host of generally undesirable processes, including food spoilage, aging,

cancer, arthritis,

atherosclerosis, various

eye and lung disorders....

systems. Things that are kept refrigerated, by and large, spoil

chemically. Food chemists were

interested in enzyme reactions that generated free oxygen radicals,

which then lead to the reactions

that cause rancidity and spoilage,"

he says. The role of oxygen radicals in biochemistry was largely unconsidered until the late 1960's when

researchers Joseph McCord and

Irwin Fridovich of Duke University

demonstrated the existence of a

naturally occurring enzyme,

superoxide dismutase (SOD) which seems to have no purpose other

than to convert the simple oxygen

radical superoxide to the more

stable forms of hydrogen peroxide

and molecular oxygen. The

existence of SOD's suggested that the superoxide radical, at least, is so prevalent in biochemical systems

that enzymes have evolved to deal

with it. "In the 1980's, things accel- erated tremendously," says Simic.

Biologists who were coming up

with more and more evidence for the role of oxygen radicals in living

systems hooked up with chemists

who had long experience in handling these species. Radiation

chemists, for example, contributed

their experience in the behavior of the extremely important hydroxyl

radical (formed by the dissociation

of water).

Indeed, one of the main reasons

for the four ICOR meetings held

since 1977 has been to bring

together researchers from normally

widely separated disciplines to exchange notes. The June meeting

included physicists, chemists, biologists, and physicians, as well as

specialists in food chemistry, clinical chemistry, and pharmacology. "It is a very fertile time for these combined conferences." Simic adds.

The last two decades of research

have revealed a still-incomplete pic- ture of oxygen radicals intimately

involved in a host of biochemical

processes, both good and bad.

"When you talk about free

radicals in biological systems, you

have to come to grips with a couple of things," observes Ajit Singh

of Atomic Energy of Canada, Ltd., who organized the first ICOR.

"First, in biological systems, free radicals are usually under control. The body knows how to deal with them, and they are doing a job for the body. When we overload the

body's systems, for example by

radiation, we may overwhelm the

body's ability to deal with free

radicals."
"Life is a tightrope act," agrees

colleague William Lands of the

University of Illinois, known for his work on oils in the human diet. "There is a delicate balance in the

response to stimuli." A principal goal of the re- searchers who gathered in La Jolla

is to understand the role that oxygen radicals play in this balance, and what happens when

things go awry. Some samples:

Lands is studying the importance of balancing the kinds of fats

in the diet. By far the most com- mon fats in the American diet are

so-called "n-6 fatty acids," found in almost all vegetable oils, including

corn, soybean, and safflower, and

in the flesh of animals fed those

grains. Although important to the

body's mechanism of cell messenger molecules, says Lands, an

excessive imbalance of these oils, and their biological products, has

been implicated in a rogues' gallery

of diseases ranging from headaches, menstrual cramps, and

hypertension through heart disease,

stroke, coronary thrombosis, and

cancer. Many of these effects apparently can be mitigated, according to Lands, by diminishing the use of n-6-type oils and increasing the

intake of n-3-type oils found in green, leafy vegetables and, in particular, seafood. Too much of the

latter, however, seems to interfere with the useful aspects of n-6 fats, leading to such things as hemorrhagic stroke. A paper presented by Kelvin

Davies and Susan McKenna from

the University of Southern California

offers an explanation of the

mechanism by which "neutrophils"

in the blood attack and destroy

invading bacteria. According to

their theory, the neutrophils initiate a

rapid chain of reactions, beginning

NBS radiation chemists iViichaei Simic (left) and David

Bergtoid and guest scientist Ambier Thompson of The

University of iUiaryiand, Baltimore County (foreground) use

a spectrofluorimeter to analyze the products of oxygenrelated free-radical reactions.

with the conversion of molecular

oxygen to superoxide radicals and

ending with the production of hypochlorous acid—common laun- dry bleach. This "bleach" then

attacks the DNA and RNA synthesis mechanisms in the bacteria,

destroying its ability to reproduce.

This allows the neutrophils to dis- mantle it at leisure. A growing body of evidence,

much of it discussed at this meeting, implicates uncontrolled

free radicals in a variety of dis- eases, including the two major

killers in Western nations: atherosclerosis and cancer. Although still somewhat controversial, an increasing number of researchers believe that many of the basic effects of aging are due

to the gradual accumulation of the

products of reactions of oxygen

radicals with cell components.

Vitamins E and C are increasingly seen to be important in protecting cells from the harmful effects

of oxygen radicals. Vitamin E, embedded in the cell's membranes, sacrifices itself to break an

otherwise cell-lethal chain reaction

initiated by oxygen radicals. Vitamin

C, found in fluids outside the cell,

27
NBS research chemist Stephen Stein (right) and guest

scientist IMahendra Suryan of West Virginia University with

the apparatus used to measure chemical bond strengths

in models for antioxidants such as vitamin E. Bond

strengths are important in understanding the kinetics of

these molecules. Their work is supported by the Gas

Research institute.

sacrifices itself to repair the

damaged vitamin E. Gregory Bulkley and his col- leagues from Johns Hopkins

University presented what may be

the first direct evidence in a living

system of the action of oxygen

radicals in damaging organs that have been deprived of blood and

then resupplied. This phenomenon,

called "ischemia" (blood deprivation) and "reperfusion" (resupply),

has received much attention

recently because it seems to be one of the primary ways in which

the brain, heart, and other organs

are damaged after strokes, heart

attacks, surgery, or other events

that temporarily halt blood supply.

Oxygen-free radicals have been the

chief suspects in the process, and

the Johns Hopkins team reports

the detection of the extremely low

levels of light that are generated

by free radical reactions, called chemiluminescence, in intact, living

organs at reperfusion. Drugs that

limit the action of the radicals in these cases may dramatically

improve the chances of stroke vic- tims to achieve full recovery. Hyperbaric oxygen chambers,

which involve breathing almost

pure oxygen under pressure, are seen by some researchers as

needlessly risky save in the treat- ment of certain conditions such as gas gangrene or stroke. Elevated

levels of oxygen at high pressures

bring on convulsions and death in lab animals, according to University

of New South Wales researcher

Dana Jamieson, with oxygen

radical-mediated processes in both

the lungs and brain vying to bring on death. "If you think of oxygen

as a drug," observes Jamieson, "it has a very low therapeutic ratio. It would be difficult or impossible to get it approved by the FDA."

Although NBS is not known for biomedical research. Bureau

researchers contributed to several

different sessions of the congress.

Typically, NBS research concentrates on obtaining basic chemical

data and developing measurement

techniques.

Steven Stein of the NBS Center

for Chemical Physics, for example,

presented basic research results on

the thermochemistry and kinetics of the important class of phenoxyl

radicals—hydrogen-oxygen radicals which include a benzene group.

"We've done a long series of studies to be able to predict the bond

strengths in phenols on the basis of

their structure," explains Stein. "Typical phenols and their radicals are quite important in biosystems,

such as vitamin E, which prevents

the oxidation of cell membranes.

Ultimately you'd like to be able to

predict, for example, the antioxidant

activity of a compound based on its structure."

28
Ambler Thompson, an NBS

guest researcher from The University of Maryland, chaired an ICOR

session on his specialty—chemiTypically, NBS research

concentrates on obtaining

basic chemical data and

developing measurement

techniques.

luminescence, the study of chemical and biochemical reactions

that produce light. Chemiluminescence is an emerging technique with great potential

for creating tailored chemical

systems that can monitor directly

oxygen radical reactions in living

systems by the light they produce.

Bulkley and his colleagues at Johns

Hopkins used chemiluminescence

in their study of oxygen radical reactions during reperfusion.

"Given modern photon-counting

methods, v\/hich are capable of detecting photon-emitting chemical

species at a level of 1 in a trillion, chemiluminescence can be an

extremely sensitive, noninvasive

analytical technique—theoretically more sensitive than radioisotopes,"

says Thompson.

The combination of specialists

from a wide variety of disciplines

and an array of sophisticated and

often rare experimental facilities makes NBS an excellent place to do the basic research required by a multidisciplinary field like oxygen

radical biochemistry, according to Simic.

"Our pulse radiolysis facility is a good example," he notes. "Pulse

radiolysis allows you to generate

specific free radicals, in high

concentrations, and follow their reactions with very high time

resolution." "Food oxidation takes several

weeks. Pulse radiolysis compresses

that to less than 1 microsecond,

with the reaction products formed

in milliseconds. You can get infor- mation you can't get by any other

method. There are only four other

places in the United States where

you could do this." Slobodan Jovanovic, an NBS

guest researcher from the Boris

Kidric Institute of Nuclear Sciences

in Yugoslavia, has been working

with Simic to measure redox potentials for a variety of compounds of interest to the congress—data that

relates to the ability of the com- pound to participate in a given

chemical reaction. "In order to make useful models

of an antioxidant for a given

system, you first need to know

what kind of species are causing

trouble, and second what mode of reaction would those species preferentially follow," notes Jovanovic.

"This is very basic research, but it helps put theories on a sound

scientific basis. What we are doing

now may help in the development

of antioxidants for food and

plastics, and it also has application

to certain biochemical studies in, say, cancer research or nutrition." "Of paramount importance,"

says Simic, "is the fact that all these life processes are in a very

complicated system of equilibrium

and balance. We have to consider

the mechanisms of these processes

in order to make major steps for- ward. By mechanisms we mean

thermodynamics—what reactions

are possible, kinetics—how fast do

they occur, and what products are generated—measurement at the

molecular level. "Our understanding of basic

oxygen radical chemistry is fairly good, although some more work is needed, but what is really missing

is the effect of parameters in living

systems on the balance of free

radicals. How many years is it since

the beginnings of radiation biology?

We still don't understand the

oxygen effect—with oxygen present

the killing of cells is greatly potentiated, by factors of two to four. "We don't understand these

phenomena because coupling between the biological system and the

simplest level of understanding

"What we are doing now

may help in the development of antioxidants for

food and plastics, and it also has application to

certain biochemical

studies in, say, cancer

research or nutrition."

doesn't exist. We don't yet have

the proper mechanisms to study

free radicals in living systems.

"This is where we come in. Once

you understand the great importance of studying mechanisms, you

need to detect, measure, and stan- dardize the species involved. That

is what we do here at NBS." M.A.B.
New Technique for Evaluating

Installation of Home Insulation

BS researchers are completing test- ing of a new measurement tech- nique, based on acoustics, that shows considerable promise for quality control in the manufacture of insulation and could also be the

basis for efficient, low-cost tools for evaluating loose-fill attic insulation

after it is installed.

Loose-fill thermal insulation is a

light, fluffy material—typically

fiberglass, mineral fiber (rock wool), or treated cellulose—which is installed in attics, crawl spaces, or

walls by blowing or pouring the

fiber into the space to be insulated. Measurement difficulties in assessing loose-fill insulation have raised concerns about problems with quality control and consumer protection.

The effectiveness of home insulation is measured in terms of its ther- mal resistance, or "R-value."

Directly measuring the R-value by

classical thermal techniques

typically requires several hours in the laboratory and several days

under field conditions. The uncertainty of R-value measurements

made under field conditions also may be quite large. For these

reasons, it has been customary to measure a quantity—the coverage

in pounds per square foot—that is related to the R-value of installed insulation rather than to measure

the R-value directly. For a given insulation product,

the R-value depends upon the

thickness and the density of the

insulation after it is installed. At

present, the only practical field method for determining the

coverage of loose-fill insulation involves measuring its thickness at multiple locations in the attic, taking core samples at each of these loca- tions using a tool resembling a

giant cookie cutter, removing the

insulation samples in plastic bags,

weighing them, calculating the density, and then replacing the

samples.

Researchers in the NBS Center

for Manufacturing Engineering—funded by the Mineral Insulation Manufacturers Association, the

U.S. Department of Energy, and

NBS—have developed a fiighspeed method for indirectly measuring either the coverage or the R- value of certain types of loose-fill insulation by passing sound waves

through a sample of material and

measuring the sound insertion loss

...the principles could be

applied to field instrumentation for characterizing

insulation installed in

attics....

(i.e., the decrease in sound level) caused by the insulation at various

frequencies.

In the laboratory system devel- oped by the acoustic measure- ments group at NBS, pulses of sound containing energy in the fre- quency range of 2.5 to 25 kilohertz are projected through a sample of insulating material. The samples of insulation are contained in individ- ual baskets which have acoustically

transparent bottoms and are sup- ported inside a specially designed

test chamber.

The sound insertion loss of loosefill insulations has been found, for a

given insulating material, to correlate quite well with the coverage

(mass per unit area) of the material,

particularly for fiberglass materials. Predicting coverage of rock wool

insulation is somewhat problematic.

according to researchers, because

of the presence of fused material. When comparing results obtained

for the R-values of a variety of samples of insulation using the

extremely accurate 1 -meter guarded hot-plate designed

and built in the NBS Center for Building Technology with results obtained for the sound insertion loss of the same samples, good

correlation was found between the

results of the two methods.

Researchers say that a version of the laboratory apparatus used at NBS could be useful to insulation manufacturers for quality control. The acoustic test apparatus collects and analyzes data in a few minutes

and yields results that would re- quire several hours to obtain using

thermal measurement procedures.

Moreover, they say, the principles could be applied to field instrumentation for characterizing

insulation installed in attics by using

acoustic probes either suspended

over the insulation, or inserted into the insulation through holes bored

in the ceiling. NBS researchers,

Gerald V. Blessing and Daniel R. Flynn, have been granted a patent

for various design concepts for a

field instrument utilizing tfiese ideas. The NBS results have been pre- sented to ASTM Committee C16 on

Thermal Insulation, which is interested in the acoustic technique as a possible ASTM test method. In addition, ASTM has agreed to coor- dinate an effort to raise the funds

needed to develop a practical field instrument based on acoustic

measurements of installed loose-fill

insulation. M.A.B.
NEW PUBLICATIONS

DUPONT PLAZA HOTEL FIRE

Nelson, H.E., An Engineering Analysis of

the Early Stages of Fire Development—The Fire at the Dupont Plaza

Hotel and Casino, December 31, 1986,

Natl. Bur. Stand. (U.S.), NBSIR 87-3560,

113 pages (April 1987). Order by stock no. PB 87-201828 from NTIS, $18.95 ($37.50

foreign) prepaid.

On December 31, 1986, a fire in the

Dupont Plaza Hotel in San Juan, Puerto

Rico, killed 98 people. As part of the

federal team investigating the fire, scientists and engineers from the NBS Center for

Fire Research used tools developed

through a decade of research to calculate

the course of the fire. The results showed

that once set, the fire spread from the

ballroom through the first two floors of the

hotel killing most of the victims in 10 to 15

minutes. Had this fire growth analysis been

done to test the building design, say the

researchers, it would have shown that the

glass partitions separating the ballroom

from the hotel lobby were insufficient to

resist this fire. Also it would have shown

that both of the exits from the casino,

where most of the victims died, could be

quickly blocked by the fire. The NBS

researchers also calculated what would

have happened if sprinklers or smoke

detectors had been present. The NBS

investigation represents a new approach to

fire analysis, say the researchers, and

demonstrates how these tools can be used

to both investigate and prevent fires.

MEASURING FAULTS IN PARALLEL

PROCESSORS

Roberts, J.W., Mink, A., and Carpenter,

R.J., On the Measurement of FaultTolerant Parallel Processors, Natl. Bur

Stand. (U.S.), NBSIR 87-3568, 49 pages

(May 1987). Order by stock no. PB 87-

208328/AS from NTIS, $11.95 prepaid.

In a recent study for the Defense

Advanced Research Projects Agency, NBS

researchers investigated a number of measurement techniques that can be used

to detect and recover from hardware faults

in parallel processors. "Fault-tolerance" is particularly important in computer systems

used, for example, to solve large problems

such as weather forecasting and to control

aircraft and spacecraft. The researchers

looked at ways to detect transmission and

data storage errors and faults in pro- cessors, controllers, computer components,

and input/output systems.

NBS MEASUREMENT SERVICE FOR

NEUTRON PERSONNEL DOSIMETERS

Schwartz, R.B., NBS Measurement Services: Neutron Personnel Dosimetry,

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

250-12, 44 pages (July 1987). Order by

stock no. 003-003-02811-8 from GPO,

$2.50 prepaid.

The calibration and related measurement

services of NBS are intended to assist the

makers and users of precision measuring

instruments in achieving the highest possi- ble levels of accuracy, quality, and productivity. NBS offers over 300 different calibration, special test, and measurement

assurance services. These services allow

customers to directly link their measurement

systems to measurement systems and stan- dards maintained by NBS. This supplemental guide provides a detailed description of the important features of this specific cali- bration service. It describes the preparation

and calibration of neutron dosimeters and

remmeters with californium neutron

sources, both "bare" and moderated. Corrections for scatter, room-return, anisotropic neutron emission, and deviation from the

inverse square law are discussed with specific examples given.

MOTOR FUEL QUALITY

Brickenkamp, C.S., editor. Uniform Laws

and Regulations, Natl. Bur. Stand. (U.S.), NBS Hdbk. 130-1988, 192 pages

(September 1987). Order by stock no. 003-

003-02814-2 from GPO, $10 prepaid.

The latest edition of this NBS handbook

contains two new recommendations for motor fuels that were adopted by the

National Conference on Weights and

Measures (NCWM) at the 72nd annual

meeting. Both the "Uniform Motor Fuel

Inspection Law," and the "Uniform Regulation for Motor Fuel," require registration of motor fuel and certification that meets

ASTM standards. The law would establish a motor fuel quality testing capability by

any state that adopts it. The handbook also contains recommendations for other uni- form laws and regulations. There is a basic

weights and measures law that establishes

standards, authorities, and duties of the

states for legal metrology, and a weighmaster law. The regulations include

packaging and labeling, method of sale of commodities, unit pricing, registration of servicepersons and service agencies for commercial weighing and measuring

devices, open dating, and a regulation for national type evaluation.

MASS FLOW METERING STANDARDS

Oppermann, H.V., editor, Specifications,

Tolerances, and Other Technical

Requirements for Weighing and Measuring Devices, Natl Bur Stand. (U.S.), NBS

Hdbk. 44—1988, 301 pages (September

1987). Order by stock no. 003-003-02820-7

from GPO, $15 prepaid.

The producers and distributors of fuels, lubricants, and petrochemicals will be

interested in the changes made to the

codes for "Liquid Measuring Devices" and

"Liquid Petroleum Gas (LPG) and Anhydrous Ammonia Liquid Measuring Devices"

added to this NBS handbook. The National

Conference on Weights and Measures

(NCWM) adopted the standards at its 72nd

annual meeting to recognize the use of mass flow metering systems. Mass flow

metering systems that are affected by

changes in the density of the product

being measured must incorporate an auto- matic means to determine product density

and correct for changes in density while

the product is being measured. The toler- ances for mass flow meters are consistent

with those for other meters used in the same application.

ORDERING INFORMATION

To order publications from NTIS, send

request with payment to: National Technical

Information Service, Springfield, VA 22161.

Publications can be ordered from GPO by

mailing the order with payment to Superintendent of Documents, U.S. Government

Printing Office, Washington, DC 20402.

31
CONFERENCE CALENDAR

Fourth International Symposium on Resonance Ionization Spectroscopy and

Its Applications, NBS, Gaithersburg, MD

April 11-15, 1988

The RIS-88 symposium is a major forum for the presentation of results of multidis- ciplinary research involving resonance

ionization phenomena and related laser applications. The program will consist of posters, contributed and invited papers, and plenary lectures on the following

topics: photophysics and spectroscopy; resonance ionization mass spectrometry

(RIMS); molecular resonance ionization spectroscopy; noble gas atom counting;

analysis of materials and surfaces; medical

and environmental applications; optical sources; atom reservoirs and sampling;

physics applications, including elementary

particles and nuclear processes; and

chemical applications, including diffusion,

reactions rates, and clustering. Sponsored

by NBS, this symposium is organized by

an International Advisory Group through an

appointed program committee and is coor- dinated by the Institute of Resonance

Ionization Spectroscopy of the University of Tennessee. Contact: Thomas B. Lucatorto,

A243 Physics Building, NBS, Gaithersburg,

MD 20899, 301/975-3734.

4th International Conference on

Metrology and Properties of Engineering Surfaces, NBS, Gaithersburg, IVID

April 13-15, 1988

Metrology and properties of engineering

surfaces have continued to assume great

importance to both the practicing engineer

and the researcher. In recent years, industry has gained increased awareness of the

importance of surface preparation tech- niques. This international conference is the

fourth in a series of meetings, held every 3

years since 1976, on metrology and properties of engineering surfaces. The main

topics to be discussed at this meeting will be: the application of new surface tech- niques in industry; the development of new

tactile instruments; the development of new

techniques for the optical measurement of engineering surfaces; the compilation and

analysis of data for specific manufacturing

processes; and the relationships between

surface generation and practical perform- ance. Sponsored by NBS, Coventry

Polytechnic, and Whitestone Business Communications. Contact: K.J. Stout, Coventry

Polytechnic, Department of Manufacturing

Systems, Priory Street, Coventry CV1 5FB,

England, 0203 24166, ext. 278; or Theodore V. Vorburger, A117 Metrology

Building, NBS, Gaithersburg, MD 20899,

301/975-3493.

Microstructure and IVIacromolecular

Research with Cold Neutrons, NBS,

Gaithersburg, MD

April 21-22, 1988 (NOTE DATE CHANGE)

A major expansion of the neutron scattering

facilities at the NBS 20-megawatt research

reactor is now under way. The Cold Neutron Research Facility (CNRF), scheduled

for completion in 1989, will provide cold neutron beams for many new types of experimental facilities including several with specialized capabilities for the study of structure and dynamics of materials. The CNRF is intended to be a national

facility serving a broad-based community of researchers in materials science, physics,

chemistry, and biology. In an effort to inform and involve this community at an

early stage while conceptual and detailed

planning for instrumentation for the facility is progressing, NBS is hosting a series of workshops, each of which will deal with a

major area of cold neutron research. This

workshop will focus on the scientific opportunities in the study of submicron structures

in materials, including macromolecular

structures in polymers and biomaterials,

which arise from experimental techniques

that take special advantage of cold neutrons. Sponsored by NBS. Contact: Kathy

Stang, A345 Physics Building, NBS,

Gaithersburg, MD 20899, 301/975-4513.

Twenty-Seventh Annual Technical

Symposium of the Washington, D.C.,

Chapter of the Association for

Computing Machinery—Productivity:

Progress, Prospects and Payoff, NBS,

Gaithersburg, MD

June 9, 1988

Productivity is a key issue in the information industry. Information technology must

provide the means to maintain and

enhance productivity. This symposium will explore the theoretical and practical

issues in developing and applying

technology in an information-based society. How productive are we? How pro- ductive can we become? What are the

inhibitors and facilitators? Sponsored by

the Washington, D.C., Chapter Association for Computing Machinery and NBS.

Contact: Wilma Osborne, B266 Technology Building, NBS, Gaithersburg, MD

20899, 301/975-3339.

Tenth Symposium on Thermophysical

Properties, NBS, Gaithersburg, MD

June 20-23, 1988

This symposium is concerned with

theoretical, experimental, and applied

aspects of thermophysical properties for gases, liquids, and solids. Topics to be

included in the symposium are; thermodynamic properties; transport properties;

optical and thermal radiative properties;

interface properties; and data correlation. Special topics will be; properties of new

materials; properties of gaseous and liquid

mixtures; new developments in experimental techniques; and interpretation of experimental data in terms of new theoreti- cal developments. Sponsored by the American Society of Mechanical Engineers,

NBS, and The University of Maryland. Contact: Ared Cezairliyan, Room 124 Hazards

Building, NBS, Gaithersburg, MD 20899,

301/975-5931 or J.V. Sengers, Institute for Physical Science and Technology,

The University of Maryland, College

Park, MD 20742, 301/454-4117.

32 U,S. GOVERNMENT PRINTING OFFICE: 1988 - 201-597 - 814/72502
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

sen/ices 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, developing federal ADP standards

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

technological advisory sen/ices and as- sistance to federal agencies; and pro- vides the technical foundation for

computer-related policies of the federal

government. The institute consists of the

following divisions: • Information Systems Engineering

• Systems and Software Technology

• Computer Security

• System and Network Architecture

• Advgnce Systems

THE INSTITUTE FOR MATERIALS

SCIENCE AND ENGINEERING

Conducts research and provides measurements, data, standards, reference

materials, quantitative understanding,

and other technical information fundamental to the processing, structure, properties, and performance of materials; addresses 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

l^atiofial'Bui^u WS!anMras'"TM

Gaithersburg, MD 20899

OFFICIAL BUSINESS

BULK RATE

POSTAGE& FEES PAID NBS

PERMIT No. GI95