Journal of Research of the National Institute of Standards …Volume 102, Number 4, July–August...

Volume 102, Number 4, July–August 1997Journal of Research of the National Institute of Standards and Technology

General DevelopmentsInquiries about News Briefs, where no contact personis identified, should be referred to the Managing Editor,Journal of Research, National Institute of Standardsand Technology, Building 820, Room 126, Gaithersburg,MD 20899-0001; telephone: 301/975-3572.

ENERGY-RELATED INVENTIONS PROGRAMMAKES RECOMMENDATIONSDuring February and March 1997, the NIST Office ofTechnology Innovation recommended three innovativetechnologies forcommercialization to its Department ofEnergy partner under the Energy-Related InventionsProgram. They include: Laser Ultrasonic FurnaceTube Coke Monitor—a laser-based instrument for mea-suring the thickness of coke deposits in a tubular indus-trial furnace while the furnace is in use; The AnaerobicPump—a new process and hardware design for theanaerobic digestion of organic wastes to producemethane-carbon dioxide (biogas) mixtures; CompositeElectrodes for Advanced Electrochemical Applica-tions—a composite electrode for the electrochemicalindustry using a highly conductive ceramic coating forboth the anodes and cathodes.

U.S.-BRAZIL STANDARDS IN TRADEWORKSHOP, APRIL 7-18, 1997NIST sponsored a Standards in Trade Workshop April7-18, 1997, for 20 standards and conformity assessmentofficials from the government and private sector ofBrazil. This successful workshop helped to establish theNIST Regional Standards Attache´, who is stationed withthe Commercial Section of the U.S. Embassy in BuenosAires, Argentina, as an important and knowledgeabletechnical resource for South American countries; inparticular, the attache´ serves to facilitate the flow ofinformation on standards and conformity assessmentpractices between the United States and Brazil.

News Briefs

The workshop familiarized U.S. and Brazilian par-ticipants with each other’s technology andpractices instandardization, conformity assessment, metrology,and measurement systems. Experts from NIST, theAmerican National Standards Institute (ANSI), andother key government and private-sector organizations,as well as Brazilian participants, provided briefings thatillustrated similarities and differences between the twostandards and conformity assessment systems as well asthe roles of the private and governmental sectors in eachsystem. Activities included visits to NIST laboratories,the Department of Commerce, the U.S. Chamber ofCommerce, and the American Society for Testing andMaterials (ASTM). Working receptions were hosted byANSI, the National Fire Protection Association, and theEmbassy of Brazil. Discussions throughout the work-shop focused on the importance of continued trust andmutual confidence to enhance trade.

Brazilian participants proposed next steps for futureshared projects, such as research exchanges, the estab-lishment of a Standards Reference Materials Programwithin Brazil, and a similar Standards in Trade work-shop to be hosted by Brazil. It was acknowledged thatNAFTA and Mercosul are important building blocks forthe formation of the Free Trade Area of the Americas,and that the professional relationships establishedduring the workshop will greatly enhance follow-up andfuture collaboration.

VXIbus-BASED VOR TEST SYSTEMDEVELOPEDA VXIbus-based test set has been developed by NISTscientists that is designed to test VHF omnidirectionalranging (VOR) receivers used in aircraft navigation.VOR transmitters propagate waveforms that consist of a10 kHz subcarrier, which is frequency- and amplitude-modulated by two 30 Hz signals. VOR receivers de-modulate these signals and measure the phase anglebetween the 30 Hz signals to determine the angle fromtrue north to the transmitter. The term “VXIbus” refers

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to Institute for Electrical and Electronics EngineersStandard 1155-1992, a specification for describing thebackplane interconnection and communications proto-col of standard-sized modules, contained in a set ofstandard-sized enclosures, or crates, for housing andpowering the modules.

The new VOR test set, based on another test systemoriginally developed by a team of NIST scientistsemploys a VXIbus-controlled arbitrary waveformgenerator and an analog-to-digital converter to synthe-size and to sample VOR waveforms, respectively. Con-trol and signal analysis software was developed in agraphical programming language (LabVIEW) thatsimplifies the human interface to the VXIbus instru-ments. The system was developed to support the largeinventory of VOR receivers still in use by the Army andto assess the state of VXIbus instrumentation as possiblereplacements for stand-alone instruments in the Armycalibration laboratories and mobile vans.

This new test set also will be used to augment theNIST phase angle calibration services for testing com-mercial VOR receivers. NIST expects that next year thiscapability will replace the VOR calibration services pre-viously offered at NIST Boulder.

ON-WAFER NOISE TEMPERATUREMEASUREMENT METHODOLOGY RESPONDSTO INDUSTRY NEEDSNIST scientists have developed the theoretical formalismand experimental methods for performing accuratenoise-temperature measurements on wafer in responseto industry needs. Noise temperature is a measure ofthe noise power available from a given source.

Characterization of the noise properties at microwavefrequencies of microelectronic devices fabricated onwafer is an essential ingredient in the design and testingof components which are used in virtually all modernelectronic systems, including those used in communica-tions, home entertainment, radar, and test and measure-ment. Methods and even commercial systems exist forthe noise measurements of most interest on wafer. Thereis a continuing need to improve and extend all suchmethods, but NIST has identified some of the morepressing needs to be in the areas of accuracy assess-ment, traceability, and general quality assurance. Thecurrent work constitutes a first step in responding tothese needs.

The formalism and measurement methods wereverified in a series of tests to measure known noisetemperatures on wafer at frequencies around 8 GHz.With known off-wafer noise sources, several differentconfigurations were used to obtain different, known,on-wafer noise temperatures. The noise temperaturesproduced on wafer ranged from about 160 K to about7600 K. These were then measured, and the results werecompared to predictions. Good agreement was found,with a worst-case disagreement of 2.6 %. An uncer-tainty analysis of the measurements resulted in a relativestandard uncertainty (one standard deviation estimate)of 1.1 % or less for most values of noise temperature.The tests also confirm the group’s ability to produceknown noise temperatures on wafer. The work isreported in NIST Technical Note 1390, which presentsthe theoretical formulation and describes the design,methods, and results of the tests performed to verifyNIST’s ability to measure on-wafer noisetemperature.

NIST-SANDIA COLLABORATIONESTABLISHED TO PURSUE SINGLE-CRYSTALCD ARTIFACTFourteen companies have joined a new NIST consor-tium intended ultimately to provide industry with a newclass of artifacts for critical-dimension (CD) measure-ments, based on collaborative work at NIST and SandiaNational Laboratories. Feature linewidth on these arti-facts can be measured using all known techniques in-cluding electrical probing, transmitted optical mi-croscopy, scanning electron microscopy (SEM),transmission electron microscopy, and scanned-probemicroscopy. The line features of the artifacts, fabricatedat Sandia of single-crystal (110) or (100) silicon, haveplanar sidewalls, either vertical with respect to the planeof the substrate or having a known slope angle of ap-proximately 578, respectively.

The intense interest in this development lies in theanticipation that the fabrication methodology will leadto a critical-dimension artifact standard from NIST,traceable to the meter, having deep-submicrometerfeature widths. At present, companies rely on variousmethods for CD measurement, with scanning-electronmicroscopy being dominant. Many companies havedeveloped internal methods for standardizing themeasurements of one or more specific procedures.

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These measurements are not calibrated, in the sense thatthey are not traceable to the meter; further, there isgenerally little correlation among the results of variousmeasurement methods. An additional factor is thatedge-determination issues for CDs at or below the180 nm level are likely to cause industry to seek toolsother than the SEM for primary CD measurement.

Through the establishment of the colloaboration,NIST and Sandia are responding to the need for amanufacturable structure having known geometricproperties, specifically, narrow lines of rectangular orotherwise known cross section, having sidewallsdefined by the method. Difficulties encountered inearlier attempts to fabricate by conventional methods a“universal” artifact are reduced greatly becauseambiguities in the width of the line have beeneliminated. The work also is expected to lead toimprovements in other electrical test structures widelyused in industry, including those developed at NIST.

NIST WORK UNDERLIES IEEE GUIDE FORMEASUREMENT OF QUASI-STATICMAGNETIC AND ELECTRIC FIELDSThe Institute of Electrical and Electronics Engineers(IEEE) has published Standard 644-1996, “IEEE Guidefor the Measurement of Quasi-Static Magnetic and Elec-tric Fields.” This action represents the culminationof work begun at NIST 2 years ago in collaboration withthe ELF (Extremely Low Frequency) Field Measure-ments Working Group, a component of Subcommittee 1of IEEE Standards Coordinating Committee 28. Thefirst draft and subsequent revisions were prepared atNIST on behalf of the working group. The guide isintended to aid groups and individuals interested in de-veloping magnetic and/or electric field measurementprotocols by describing different magnetic and electricfield measurement methods that can accomplishspecific measurement goals. A single measurementapproach is not identified because the measurementstrategies and instrumentation requirements will differdepending on the measurement environment of interestand the goals of a measurement program. For example,the measurement protocols and instrumentation forcharacterizing electric and magnetic fields from powerlines will differ significantly from those for characteriz-ing fields from electrical appliances such as hair dryersand shavers.

A companion document for this Guide is IEEEStandard 1308-1994, “Recommended Practice forInstrumentation: Specifications for Magnetic FluxDensity and Electric Field Strength Meters-10 Hz to3 kHz,” which describes the types of available instru-mentation used for measuring quasi-static magnetic andelectric fields, their principles of operation, definitionsof terminology,calibration procedures, and sources ofmeasurement uncertainty. Frequent reference is made inthe Guide to IEEE Standard 1308. Drafts of IEEEStandard 1308 also were prepared at NIST, in collabora-tion with the AC Fields Working Group in the IEEEPower Engineering Society.

IEEE PES RECOGNIZES DEVELOPMENT OFHIGH-VOLTAGE TESTING STANDARDINCORPORATING NIST CONTRIBUTIONSThe Institute of Electrical and Electronics Engineers(IEEE) Power Engineering Society (PES) has namedthe High Voltage Test Techniques (HVTT) Subcommit-tee to receive its 1997 Working Group RecognitionAward for the publication of the revision to IEEEStandard 4, “Standard Techniques for High Voltage Test-ing.” The PES recognizes its working groups with twoawards given annually: one for the best technical reportand the other for the best standard or guide. NIST hasprovided significant technical support to the develop-ment of this revision of Standard 4, particularly in thesections covering the measurement of impulse highvoltages. A convolution technique developed at NISThas been incorporated into Standard 4 as one of the testsfor qualifying high-voltage impulse dividers. Thistechnique checks the temporal response of dividers witha low-voltage step pulse to determine if they aresuitable for measuring impulses having microsecondrisetimes. The digitized response is mathematically con-volved with an analytic waveform of the type to bemeasured. A comparison of the resultant waveform tothe analytic input waveform then shows if the dividerintroduces significant measurement errors.

The latest revision of Standard 4 is the seventhedition of a document that has existed as a separatestandard since 1928. (Historical note: The subject ofhigh-voltage measurements was addressed in theearliest Standardization Report of the Institute ofElectrical and Electronics Engineers (AIEE) in 1889.)The seventh edition incorporates major changes from

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the sixth, including new tests such as the convolutiontest described above. In addition to the PES WorkingGroup Recognition Award, HVTT’s development of thenew edition was recognized in 1996 by the IEEE PowerSystems Instrumentation and Measurement (PSIM)Committee for “producing the best standard of theprevious three years.”

HEXAPOD MACHINE TOOLSHexapod machine tools have a number of potential ad-vantages over conventional machine tools. These includehigh stiffness, low weight, low effective inertia of themoving components, and mechanical simplicity. Disad-vantages include complex workplace, a small orienta-tion range, and, unless measures are taken, low struc-tural damping. a NIST researcher has completed a seriesof experiments to assess the errors of the prototypehexapod milling machine located at NIST. His resultsindicate that the Hexapod errors differ from those ofconventional machine tools. Since each strut only real-izes a distance, its roll, pitch, yaw and straightness errorsare not important. However, new errors are introduced.These errors stem from the positions of the platform andbase joints, the accuracy of these joints, and the averagelength of the struts.

In an unloaded state, the geometric errors are deter-mined by 35 constant parameters and 18 functions.Errors in the relative strut length can be measuredindividually. The significant constant error parameterswere estimated simultaneously by using conventionalperformance evaluation metrology. However,there is nostraightforward relationship between the results of suchtests and the parametric errors. More optimizederror assessment procedures are needed, including thosefocused on subsets of the error parameters.

The data also indicate a need for closed-loopthermally invariant metrology that addresses the lengthof the total strut, low-friction high-stiffness joints, and ahigher structural damping.

HEXAPOD USER GROUP MEETINGThe National Advanced Manufacturing Testbed(NAMT) hexapod project team hosted a meeting ofthe Hexapod User Group on March 26, 1997, at NIST.The Hexapod User Group is an informal organizationof machine tool builders who are building Stewart

platform-based hexapod machines, government and uni-versity engineers who are conducting hexapodmachine research, and machine tool users who arefollowing the development of these machines with aneye toward adopting the technology for use intheir pro-duction operations. More than 40 people attended themeeting, with approximately equal representation fromeach of these three categories. This was the secondmeeting of the group; the first was held at MIT inAugust 1996.

The goals of the meeting were to:

• provide a forum for discussion of hexapodmachine tool research issues;

• obtain a status update on the different hexapodresearch and development efforts in progress; and

• serve as a catalyst for identifying potential collab-orative projects and leveraging opportunities.

The meeting featured 10 presentations on topics suchas the state of commercial machine development, hexa-pod calibration, error modeling and assessment,workspace analysis and approaches to modeling andsimulation, and control algorithm development. Several“focus areas” such as hexapod metrology, applications,machining test parts, and art-to-part approaches alsowere discussed. One machine tool maker presentedtest results indicating impressive progress towardobtaining performance competitive with conventionalserial/Cartesian machines. NIST scientists sharedthermal characterization data recorded on theoctahedral hexapod machine at NIST; reported consid-erable success in improving the performance of the ma-chine through calibration; demonstrated the NIST octa-hedral hexapod machine; and showed hexapodmodeling, simulation, and control system capabilitiesbeing developed as part of the NAMT.

The meeting provided representatives of machine toolusers with an opportunity to discover the current statusof the technology—“a font of information” in the wordsof one industry attendee, as well as to express views onthe direction of hexapod technology development. Twoparticipants announced future meetings of interest: aspecial panel session on hexapod machines at the ASMEInternational Mechanical Engineering Congress andExhibition to be held Nov. 19-21, 1997 in Dallas, TX;and a first meeting of the newly formed EuropeanHexapod User Group to be held in Nottingham,England, this fall.

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ATDNET DEMONSTRATION OF NAMTThe National Advanced Manufacturing Technology(NAMT) program successfully conducted its first exper-iment on ATDnet, a Washington-Area, high-speedAsynchronous Transfer Mode (ATM) network connect-ing several government agencies. NAMT participated inan ATDnet capabilities demonstration at the recentFOSE conference in Washington DC. Live, full-motionvideo was sent from several NAMT project sites atNIST, to the Federal Office Systems Expo (FOSE) con-ference, through the ATDnet. FOSE attendees also wereable to manipulate the pan/tilt/zoom cameras, at NIST,from a workstation at FOSE. The importance of thisexperiment was to show how ATM networks can beused to transport simultaneously data, voice, andfull-motion video across a wide geographic area.

SIMULATING THE SPATIAL EVOLUTION OFCHEMICAL REACTIONS AT BIOMOLECULARSURFACESMolecular recognition in biology and in bioanalyticalapplications involves complex molecular shapes, reac-tive surfaces, and diffusion processes. Diffusion limitedreactions involving macromolecules can be described byBrownian motion and the Smoluchowski kinetics modelthat requires the computation of the electrostatic capac-itance of an irregularly shaped object to describe thebimolecular chemical reaction rate of small moleculeswith complex macromolecules.

An algorithm for calculating these rates recently hasbeen developed at NIST. This algorithm uses a smalllibrary of exact Green’s functions for the Laplaceequation to eliminate the need to explicitly constructthose portions of a diffusing particle’s trajectory thatare not near an absorbing surface. This computationalprocedure virtually eliminates systematic sources oferror in the calculation of capacitance; therefore, itconsiderably simplifies the construction of computersimulations of these types of problems. This treatment isespecially efficient when the reactive objects havehighly irregular shapes and, as such, will be anextremely important tool for modeling reactions involv-ing biological macromolecules. A model based on thisalgorithm can address questions such as how the densityof reactive sites at a surface influences the total reactiv-ity of the surface. For example, a spherical surfacecontaining totally reactive disc-shaped sites that occupy20 % of the total surface area is predicted to be asreactive as another surface covered with 100 % suchsites. The model also allows accurate predictions of howthe geometry of the reactive sites and their relative loca-tions influence the overall surface reactivity.Continued development of the model will permit

detailed predictions concerning the evolution of sizeand shape of self-organizing groups of molecules atreactive surfaces.

ELLIPSOMETRY OF PROTEIN ADSORPTIONON METALSEllipsometry is a well-established optical method formeasuring the extent and kinetics of organic moleculeadsorption on metal surfaces. Interpretation of the ellip-sometric measurements to acquire parameters of theadsorbed phase such as its thickness and its complexindex of refraction requires an accurate optical model ofthe interface. This interface is commonly described interms of three phases—bulk metal/adsorbate film/solution. The ellipsometric contributions in a stratifiedmedia are additive. NIST scientists have shown thatprotein film properties for ellipsometry measurementsof a ferredoxin adsorbing on gold are poorly repre-sented by the three phase model over the range of400 nm to 750 nm (spectroellipsometry). The problemis due to the model’s failure to account for the interfa-cial charge redistribution which makes the protein filmlook “gold-like” in the three phase model. A quantita-tive method that accounts for the influence of the metalsurface on the optical properties of the adsorbingprotein film has been developed. Simultaneousmeasurements of electrode impedance and in situspectroscopic ellipsometry allow the parameters of themodel to be specified. This leads to the elucidation ofthe complex index of refraction spectrum for theadsorbed protein that is free of the influence of thesubstrate’s optical properties. This index of refractioncan be used for calculating protein surface concentra-tion as a function of adsorption time, which is of practi-cal value to biomaterials research and manufacture.The results of this study will appear in the journalLangmuir.

NEW MICROCONTAMINATION MODEL FORCHEMICAL VAPOR DEPOSITION REACTORSContamination via small gas-phase generated particles,i.e., microcontaminants, is a major problem afflictingsemiconductor processing in chemical vapor deposition(CVD) reactors. Researchers at NIST have developed anew model for analyzing this problem in the commonlyused rotating disk CVD reactor. This model utilizes aflow/chemistry/aerosol formulation to predict thelocations where particles form as well as the subsequentevolution and transport of these particles. Of particularconcern is the rate at which the largest of themicro-contaminants, i.e., the “killer” particles, impactthe fabricated material and thus render it defective. The

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model generates performance maps, which indicateboth material growth rate and contamination rate asfunctions of reactor operating parameters. A set ofparameters then can be selected, which results in anoptimal growth rate without excessive contamination. Aplanned series of experiments at NIST will be used tovalidate the predictions of this unique new tool for en-hancing the productivity of the semiconductorfabrication process.

NEW STEAM TABLES IN SOFTWARE FORMNIST scientists in cooperation with the American Soci-ety of Mechanical Engineers, have produced a new soft-ware program for the calculation of the thermophysicalproperties of water. The program is distributed byNIST’s Standard Reference Data Program as StandardReference Database 10: NIST/ASME Steam Properties.

Engineers long have used steam tables in the powerindustry for the design of chemical plants and refineriesand in many other applications. Accurate water proper-ties also are needed for solution chemistry and otherresearch. Standards for water properties are set by theInternational Association for the Properties of Water andSteam (IAPWS). IAPWS recently adopted a new formu-lation for the thermodynamic properties of water. Thenew NIST software implements this formulation, alongwith other present and proposed IAPWS standards fortransport properties, surface tension, the dielectric con-stant, and fluid/solid phase boundaries. Calculationsmay be performed along saturation boundaries, alongconstant-property paths such as isotherms, and at speci-fied states of two independent variables. The user canspecify which properties to display and the units inwhich to enter and display data. Additional features ofthe software include on-line help, plotting capability,and the ability to copy and paste data to and from otherapplications.

A key feature of the new NIST program is that theunderlying calculations are modular, via well-docu-mented interface routines. This makes it easy for othersto integrate the calculations into their own programs.NIST recently concluded an agreement with a privatecompany, to allow the company to integrate NIST’scalculational routines in their widely used chemicalprocess simulation software.

PREVIOUSLY UNKNOWN SOURCE OF ERRORIN CHEMICAL ANALYSIS IDENTIFIED ANDCORRECTEDResearch conducted at NIST has identified a previouslyunrecognized source of error in chemical analysisperformed using glow discharge optical emissionspectrometry (GDOES). GDOES has been used for

many years in industrial labs for the elemental analysisof materials directly in the solid state. Although thetechnique has been applied traditionally to the analysisof electrically conductive materials, such as metals andalloys, its applicability recently has been extended toelectrically nonconductive materials, such as ceramics,glasses and polymers as well as to the depth-resolvedanalysis of films and coatings.

Despite the broad applicability and long-time use ofthe technique, the optical systems used to measure emis-sion from the glow discharge device have in some re-spects remained in a state of developmental infancy.Specifically, emission from the device is usually trans-ferred to the spectrometer via a single lens, whichimages the discharge onto the entrance slit. Thesuitability of this simple-minded approach for applica-tion in analytical GDOES has met with little, if any,scrutiny.

In a recent paper, it was reported that materialremoved from the sample surface during analysis did notmix thoroughly in the gas phase in their glowdischarge device. This suggests that the use of a singlelens to image the discharge onto the entrance slit mayinduce analytical error when the sample is chemicallyheterogeneous. During the NIST studies, the behavior ofGDOES with samples known to be chemicallyheterogeneous was evaluated in order to investigate thispossibility. Two samples were used. The first was asynthetic sample consisting of a brass surface with a1 mm diameter implanted steel plug. Since this sampleis not realistic in terms of its severity of heterogeneity,a second sample also was employed. This sample was abrass disc that had been rejected previously as astandard reference material, owing to a small Pbheterogeneity.

Studies with both samples indicated the presence ofoptically induced analytical error. The error demon-strated for the synthetic sample was about 35 %,indicating that the error can be large. In two trials, theerror associated with the more realistic sample wasbetween 1 % and 2 %. This magnitude of error is ofconcern in quantitative GDOES analyses.

Elimination of the optically induced error wasattempted with the use of an alternative optical transfermethod. This method, which essentially averages overthe entire volume of the glow discharge, utilizes twolenses to transfer emission from the discharge device tothe entrance slit. The alternative approach successfullyeliminated the error for both the synthetic and “real-world” samples, while maintaining analytical sensitivityand low limits of detection. These results suggest thatthe two-lens system should be employed routinely inanalytical GDOES. This work recently waspublished in Appl. Spectrosc. 50(2), 245 (1996).

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NIST SCIENTISTS HOLD WORKSHOP ONNIST-NIH DESKTOP SPECTRUM ANALYZERNIST research staff members hosted 26 scientists andengineers from industry, university, national laborato-ries, and other U.S. government laboratories at a specialworkshop on the NIST-NIH Desktop SpectrumAnalyzer (DTSA) March 26-28, 1997. More than 200scientists have attended these workshops since their in-ception. DTSA is a comprehensive x-ray spectrometrysoftware engine developed by NIST and NIHscientists for application to electron beam instrumenta-tion, including the scanning electron microscope, theelectron probe x-ray microanalyzer, and the analyticalelectron microscope. DTSA is capable of spectralcollection, peak deconvolution from spectral overlapsand background, qualitative analysis, quantitativeanalysis through detailed matrix corrections, andspectrum modeling from first principles at all stages ofgeneration, propagation, and detection. Incorporatedinto DTSA is a complete database of x-ray information,which forms the basis for the advanced mathematicalprocedures for peak deconvolution. DTSA is capable ofprocessing spectra measured with the semiconductorenergy dispersive x-ray spectrometer, the wavelengthdispersive (crystal diffractometer) spectrometer, and thenew NIST microcalorimeter energy dispersive x-rayspectrometer.

NEW X-RAY DATABASES AVAILABLEONLINEInformation developed for use by those working inx-ray diffraction and related fields has been convertedinto a World Wide Web (WWW) database and is nowavailable online: the Theoretical Form Factor,Attenuation, and Scattering Tabulation for Z = 1–92from E = 1–10 eV to E = 0.4–1.0 MeV(FFAST). Thesedata have been available previously in printed andmagnetic media formats, but the WWW databasepresents the information on demand in both graphicaland tabular form.

Information is provided for each atom at each ofmany energies. It includes the total attenuation coeffi-cient, the photoelectric cross section, the sum of thecoherent and incoherent scattering, and self-consistentvalues of the atomic scattering factorsf1 and f2. TheWWW user of this database is given significant controlover the information that is viewed. Those using a webbrowser with a frames feature can have both tabular andgraphical information delivered on the same screen.(Browsers not supporting frames receive the sameinformation sequentially.)

The FFAST database may be accessed on the WWWat the URL: http://physics.nist.gov/PhysRefData/FFast/Text/cover.html. A complete set of the databasescurrently provided by the Physics Laboratory’sOffice of Electronic Commerce in Scientific andEngineering Data may be accessed at the URL:http://physics.nist.gov/PhysRefData/contents.html.

SENSITIVE DIAGNOSTICS OF INFRAREDFILTERSNarrow-band infrared filters are devices that are trans-parent only over a small range of infrared wavelengths.They are used in applications such as two-color opticalpyrometers (to remotely measure the temperature of hotobjects), filter radiometers (such as those used tocalibrate multispectral imagers), and military guidanceand infrared seeker systems. Small “leakage” bands onthe order of 10–5 to 10–4 in transmittance are oftenpresent in these filters in the wavelength regions wherethey are nominally opaque. This leakage can be ofcritical importance in some applications where aninfrared sensor must be very well shielded from un-wanted radiation.

NIST has developed the capability to measure theout-of-band rejection of narrow-band infrared trans-mittance filters down to a transmittance level of 10–6,over a wavelength range from 2mm to 20mm, attemperatures from 10 K to 300 K. To allow the out-of-band transmittance to be measured with high sensitivity,the measurements are performed using a Fourier trans-form infrared spectrometer and a set of high- and low-pass optical filters to block the main band trans-mittance of the filters under test.

NEW 2.5 METER PHOTOMETRICINTEGRATING SPHEREA new 2.5 m integrating sphere has been installed atNIST to improve flux measurement standards for a vari-ety of lamp types, such as incandescent, fluorescent,and discharge. This new sphere will be used for theNIST realization of the SI unit of luminous flux, thelumen, and for improving photometric calibrationservices using a new detector-based measurementmethod.

The lumen is a measure of the total light from a lamp,in all directions, as evaluated using the human eyeresponse. It is the radiometric quantity of most interestfor lamp manufacturers and others in the lighting indus-try. The large sphere reduces the uncertainties associ-ated with the geometrical size and shape of the testlamps and with the stability of ambient temperature forfluorescent lamps.

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NIST recently developed a new method for realizingthe lumen using an integrating sphere rather than thetraditional goniophotometer. The new 2.5 m sphere willbe equipped with additional optical instrumentation toallow a world’s first: the detector-based calibration ofluminous flux. The new method will result in a shortercalibration chain and reduced uncertainties in luminousflux calibrations.

MEDICAL IMAGING WITH POLARIZED 3HeStarting in 1992, researchers at NIST have been devel-oping an ability to produce large quantities of polarized3He gas. In ordinary helium gas, the nuclear spins of theatoms point in random directions; however, in apolarized sample, the nuclear spins are made to pointpreferentially in a given direction.

The initial reason for developing this competencewas to produce a neutron polarizer based on preferentialtransmission of one spin state of an unpolarized neutronbeam through the polarized gas. However, recent eventshave shown that this technology has another, previouslyunexpected application: magnetic resonance imaging(MRI) for medical diagnosis. While ordinary MRItechniques rely on the proton spin in water molecules,researchers have found that it is possible to obtain MRIpictures by using polarized3He or 129Xe gas as acontrast agent. For example, if a patient inhales one ofthese inert gases, the lungs can be imaged. (Normallylung tissue cannot be imaged with MRI because of itslow density and low water content.)

Researchers at NIST are collaborating withresearchers at the Metabolic Magnetic Research andComputing Center at the University of Pennsylvania todevelop polarized3He MRI. In this collaboration, NISTproduces the cells filled with gas and shares its exper-tise in how to produce highly polarized gases usingoptical pumping. The Pennsylvania collaboratorscontribute their knowledge in MRI techniques and theMRI apparatus. The project recently passed a signifi-cant milestone by producing a high-resolution image ofa set of human lungs using this process. Work continuesto improve the technology and develop techniquesuseful for clinical applications.

NIST FINDINGS LEAD TO HIGHERPRODUCTIVITY IN CERAMIC GRINDINGMechanical components made of advanced ceramicsfrequently offer significant advantages over other mate-rials in terms of improved wear resistance, resistance tocorrosion, and capability to operate at elevated temper-atures. High manufacturing costs, however, have

impeded the extensive use of these materials. By someestimates 50 % to 80 % of the cost is associated withmachining. Grinding with diamond grit wheels is thepredominant method used for shaping and final finish-ing. Because of potential surface and sub-surfacedamage in the form of microcracks and a resultingincreased risk for part failure, the grinding process isgenerally carried out at low material removal rates.

In conjunction with the NIST Ceramic MachiningConsortium, the effect on strength for a range of differ-ent grinding conditions has been obtained for threetypes of silicon nitride ceramics. Utilizing an experi-mental design that was prepared by NIST scientists, theoptimum conditions were determined for grinding theceramics at high material removal rates. The results ofthis study have shown that a high specific material re-moval rate does not necessarily lead to an increased lossin strength. By utilizing the data obtained in this study,it is anticipated that increased efficiency and reducedceramic manufacturing costs can be achieved.

NIST ELECTRONIC PACKAGING PAPERRECEIVES AWARDA recent award-winning paper describes work from theNIST program on microelectronic packaging thataddresses an important technical challenge facing themicroelectronics industry: how to measure reliably therelevant properties of exceedingly thin polymer filmsand highly filled polymers materials. Industry needsthese measurements to enhance the robustness ofmulticomponent material interfaces and to improve theresistance of plastic assemblies to effects of moisture. Asuite of advanced measurement techniques that includesneutron and x-ray reflectivity together with solid statenuclear magnetic resonance spectroscopy (NMR) wereused in the NIST work to determine quantitatively thedistribution of water and hygroscopic expansion ofextremely thin polymer films. The neutron and x-rayreflectivity techniques also measure directly the coeffi-cient of thermal expansion of thin polymer films andneutron techniques yielded information about theconcentration profile of water near an interface. NMRmeasurements of water uptake in a commercial epoxymolding compound revealed that liquid-like waterdoes not accumulate in the mold compound underhigh-humidity storage conditions and hence is not acontributor to “popcorning,” which can occur duringsolder reflow. However, liquid-like water doesaccumulate during aggressive accelerated conditioningleading to a mold compound, which is not representativeof that found in an electronic package subjected to highstorage humidities.

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AUTOMOTIVE METAL FORMING PROGRAMSheet metal forming, always an important element ofautomobile manufacture, has become critical now thatthe industry is attempting to switch to high strengthsteels and aluminum alloys to reduce vehicle weight andhence to improve fuel economy. The behavior of thesematerials during stamping is significantly different fromthat of the currently used mild steels, and the major U.S.automobile companies and their suppliers are, therefore,focusing attention on the efficient forming of these newmaterials. NIST has been involved in this activitythrough collaboration in ongoing external projects.

Finite-element modeling (FEM) is at the core ofmodern automotive metal forming operations. It hasreplaced the earlier, more empirical approach, butconsiderable trial and error is still required, largelybecause of a lack of suitable materials data and becauseof shortcomings in the models themselves. In theformer case, many different forming tests are employedby industry, but none provide data of the type requiredfor FEM. A major component of the NIST effort is thedevelopment of a relatively small number of standardtests to provide the necessary data. The major short-coming of existing finite-element models is that they arelimited by poor basic understanding of the mechanicalproperty changes that occur during forming operations.The second part of the NIST program is designed tosignificantly increase fundamental understandingthrough the use of of sophisticated new measurementtechniques developed by NIST scientists.

NIST has consolidated its overall program and alsoadded an important new element, namely informationtransfer between NIST and remote forming facilities. Aprototypical forming operation, located at the Univer-sity of Michigan, will be data-linked to computers atNIST performing modeling using an improved finite-element code developed in collaboration witha private corporation. An instrumented plane straintensile test will be developed at NIST, which willgenerate appropriate data for entry into the processmodel and for transfer to the forming facility. Three-dimensional shapes of the prototypical parts will bemeasured on-line using techniques developed by NIST,and these shapes will be compared with those predictedby FEM.

NEUTRON GUIDE NETWORK COMPLETEDAT THE COLD NEUTRON RESEARCHFACILITYThe installation of the new supermirror cold neutronguide network, which delivers beams to the ColdNeutron Research Facility (CNRF) at the NIST Centerfor Neutron Research, is essentially completed, thus

providing U.S. science and technologywith the benefitsof the world’s largest area of cold neutron beams.Constructed of highly polished glass with reflective,metallic coatings, neutron guides transport long-wave-length neutrons over long distances in a manneranalogous to light transport by fiber optic cables: allneutrons with an angular divergence less than the criti-cal angle for total reflection for the guide surface arereflected back into the guide cavity. Using technologydeveloped and tested with the help of NIST scientists,the CNRF neutron guides use58Ni coated mirrors, orNiCTi multilayer coatings called supermirrors, toincrease the critical reflection angle and thus providealmost twice the usable neutron flux of naturalNi-coated mirrors. Eight guide tubes made from theseneutron mirrors transport neutrons from the new liquidhydrogen moderator over distances of nearly 70 m to 15state-of-the-art cold neutron spectrometers in the NISTCNRF. The guides are carefully aligned by NISTtechnicians with an accuracy better than 20'' over theirentire length and then sealed and evacuated to minimizetransport losses.

Already the only facility of its kind in the UnitedStates, the completed guide network will have thelargest total area of cold neutron guide available any-where in the world. The size and intensity of the beamsgreatly enhance measurement capabilities using coldneutrons for many applications in materials research,chemistry, physics, and biology. NISToperates the coldneutron spectrometers in the CNRF Guide Hall as anational user facility providing unique measurementcapabilities to the entire U.S. scientific community.

1997 AWARD FOR EXCELLENCE INTECHNOLOGY TRANSFER PRESENTATIONTwo mechanical engineers at NIST have received a1997 Award for Excellence in Technology Transfer fromthe Federal Laboratory Consortium (FLC). The awardrecognizes the engineers’ work to develop, patent, andtransfer to the public technology forusing a solar photo-voltaic modules to electrically heat stored water viamultiple in-tank resistive elements and a system controlmodule. The system maintains the annual conversionefficiency of the energy generating system at approxi-mately 95 % of the theoretical maximum and avoids theneed for expensive auxiliary equipment such a batterystorage system, special direct current (dc) appliances, adc to ac power inverter, load matching electronics, and/or a two-way utility electrical energy meter. Ascompared to solar water heating systems that arecurrently in use, the photovoltaic system is much morereliable, is expected to have a longer operating life, iswell suited for all regions of the country, and is more

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adaptive to a dual-use function. The technology isbeingtransferred by three instrumented field demonstrationsites, conference and small group presentations, journalpapers, press releases, magazine articles, regional televi-sion, and web pages, the sum of which have led tonumerous inquiries and the mailing of more than 500information packages to interested parties.

The Federal Laboratory Consortium represents over500 federal laboratories that contribute to the missionsof 14 Federal agencies. Each year, nominations for theExcellence in Technology Transfer Awards are selectedby a committee composed of members from industry,state and local government, academia, and federallaboratories. The NIST engineers, who were among30 winners for 1997, were presented a commemorativeplaque and medallion during a banquet at FLC’sApril 14-17 National Technology Transfer Conference.

INNOVATIVE ANTENNA CALIBRATIONALGORITHM AND SOFTWAREAn algorithm and corresponding software have beendeveloped at NIST for the processing of antennameasurements corrupted by probe position errors. Themethod exploits position information available duringthe measurement procedure to compute far fields asaccurately as when no position errors are present, at acomputational cost, which is acceptable even forelectrically very large antennas.

The interpretation of near-field antenna measure-ments, which requires transformation to the far field, istypically accomplished with the fast Fourier transform(FFT). When the measurement positions deviate froman ideal rectangular grid, however, the FFT is notapplicable without modification. The new algorithmemploys a combination of a recently developed,unequally spaced FFT, interpolation, and the conjugategradient method to accurately transform to the far fieldat a cost proportional toN log N, whereN is the numberof measurements (typically between 10 000 and1 000 000).

The method will be used for measurements at higherfrequencies and those taken on mobile platforms, wheretight tolerances are difficult to maintain. The software isavailable to antenna measurement laboratories ingovernment and industry and will support the futuredeployment of communications satellites operating nearthe terahertz band.

NIST INSTRUMENTAL IN DEVELOPINGSTANDARD FOR THE EXCHANGE OFFORENSIC INFORMATIONNIST’s successful collaborations with industry and withthe law enforcement community resulted in the develop-ment of a specification, which supplements a previousstandard, for the exchange of forensic information. Con-sensus on the specification was achieved through a can-vass that NIST conducted under its accreditation by theAmerican National Standards Institute (ANSI) as asponsor of standards for information interchange. NISTalso sponsored workshops where participants reachedagreements on technical details. The ANSI Board ofStandards Review recently approved the Data Format forthe Interchange of Fingerprint, Facial and SMT Infor-mation (ANSI/NIST-ITL 1a-1997) as an AmericanNational Standard. This work is also a component of theframework that NIST has been discussing with theOffice of Law Enforcement Standards to support digitalrepresentation and exchange of cartridge and bulletimagery data gathered at a crime scene.

ADVANCED SCHOOL FOR METROLOGY:EVALUATION OF UNCERTAINTY INMEASUREMENTThe National Institute for Metrology, Standardizationand Industrial Quality (INMETRO); the CAPESFoundation; the National Research Council of Brazil;and the Brazilian Society of Metrology jointlysponsored a metrology conference in Brazil recently atwhich NIST scientists spoke on “Evaluation of Uncer-tainty in Scientific Measurement,” presented a paper on“Design and Analysis of Mixture Experiments,” and leda roundtable discussion of the “Impact of Metrology inInternational Development.” They also moderated ses-sions on practical applications of metrology. Theconfer-ence attracted 120 people, including speakers from ninenations.

NIST SEEKS TO DEVELOP AN ADVANCEDENCRYPTION STANDARD (AES)NIST is seeking a strong cryptoalgorithm that could beused by both the public and private sectors in protectingsensitive unclassified information for the next 20 to 30years. Other NIST goals for the AES include analgorithm that would support standard codebook modes

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of encryption, one that is significantly more efficientthan triple Data Encryption Standard (DES3), one witha variable key size so that security could be increasedwhen needed, and a selection process that is fair andopen.

A Federal Registernotice of Jan. 2, 1997 announcedNIST’s intent to develop an AES and proposed mini-mum acceptability requirements and evaluation factors.Draft submission requirements for candidate algorithmswere also announced. A call for comments produced 33comments for discussion at an April 15 workshop,which NIST hosted on developing an AES. About 80participants from industry, government, and academiaattended the workshop, including representatives fromCanada, the United Kingdom, Belgium, and Japan. Thediscussion focused on the draft minimum acceptabilityrequirements, evaluation factors, submission require-ments, intellectual property issues, and the selectionprocess.

NIST intends to issue a public call for submission ofcandidate algorithms. After the call period closes, NISTwill make all submissions available for public reviewand analysis. Through a series of open workshops andpublic review periods, NIST will select the bestalgorithm for the AES based on its ability to provide therequired level of security first, then on cost and flexi-bility considerations. For more information, visit theWeb site at http://csrc.nist.gov/encryption.

CONSORTIUM TO PROTOTYPE THEVIRTUAL WAYNIST has launched a new consortium that aims to in-crease prototyping capabilities and cut the time requiredto introduce new parts and products. The goal of NISTmanufacturing researchers and their prospective part-ners is to develop the basis for virtual machine tools andinspection machines that behave just like their factoryfloor counterparts. “This project will help bridge indus-try’s communication gap between design and manufac-turing,” says a member of the senior technical staff inproducibility engineering at a consortium partner.

By means of NIST’s recently opened NationalAdvanced Manufacturing Testbed—a distributedresearch facility built on a state-of-the-art computingand communications infrastructure—the partners willdevelop software tools to accurately predict machineperformance and, therefore, whether new parts can bemachined to as-designed specifications. Examples ofsuch tools include computer models that representactual machine behavior, mathematical representationsof part geometry, virtual machining and inspection al-gorithms, standardized data formats, and remotelyaccessible performance-data repositories.

For information on the Consortium for Machine ToolPerformance Models and Machine Data Repository,contact Automated Production Technology Division,B108 Sound Building, NIST, Gaithersburg, MD 20899-0001, (301) 975-6600, .

PUBLICATION FEATURES TESTS FORCOMPUTER ACCURACYIf a wristwatch isn’t keeping proper time or athermometer is off by a couple of degrees, you can tellby comparing the errant device to one that’s more accu-rate. But making sure computer programs are up to paris a little trickier.

That is why NIST is working on tests for software andother information technology products and systems.Such research, which encourages companies to developquality products, is among the highlights of the newpublication,Information Technology Laboratory Techni-cal Accomplishments 1996.

As a resource that highlights the technical research,industry collaborations and standards-related work ofthe Information TechnologyLaboratory, this publicationtouches on issues emerging from today’s informationrevolution. It covers such topics as human-machineinterface technologies,software diagnostics and perfor-mance, tests for new standards, computational scienceand computer security.

NIST’s information technology research con-centrates on developing tests and test methodsfor information technologies that are still in the earlystages of development.

The information in this publication is available on theWorld Wide Web at . For aprinted copy, send a self-addressed mailing label toElizabeth Lennon, A216 Technology Building,NIST, Gaithersburg, MD 20899-0001, or e-mailyour address as it would appear on a mailing label to.

BROCHURE HELPS U.S. FIRMS OBTAINCE MARKThe “CE” mark is now mandatory for a wide range ofproducts sold in the European Union. It indicates that aproduct conforms to EU safety, health and environmen-tal legal mandates. The European Commission calls it “apassport” that allows manufacturers to trade industrialproducts freely within its internal market. Unfortu-nately, many U.S. manufacturers view the process ofsecuring a CE mark as difficult and timeconsuming.

A new brochure “CE Alert,” prepared by NIST, endsthe confusion surrounding the CE requirement and

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makes it easier for American businesses to secure themark. The brochure gives solid recommendations formanufacturers to follow and then works through anexample. It also lists sources of information that canprovide assistance throughout the process.

Copies of the brochure may be obtained by sending aself-addressed mailing label to the National Center forStandards and Certification Information, Building 820,Room 164, NIST, Gaithersburg, MD 20899-0001.Copies also may be requested by phone:(301) 975-4040, fax: (301) 926-1559, or e-mail:.

MSTQ SYSTEMS IN 70 NATIONS PROFILEDFor the first time officials in industry and governmenthave a single source for obtaining important informationon the national metrology, standards, testing, and qualityinstitutions (MSTQ) in more than 70 countries. NISTSpecial Publication 912,Profiles of National Standards-Related Activities, provides users with concise informa-tion on the MSTQ systems of the world’s majoreconomies and many less-developed countries.

The new directory was prepared for the NISTOffice of Standards Services, which serves as thenational focal point for information on domestic andinternational standards and certification programs. ANIST spokesperson notes that in today’s global econ-omy, U.S. industry and government agencies must beaware not only of a foreign nation’s standards but alsohave information on the availability and the authority forrelated activities such as metrologyservices, conformityassessment activities and institutions, and accreditationbodies.

The new directory is a single resource for obtainingthe names and addresses of a country’s metrology centerand legal metrologyagency; its primary standards andquality organizations; government and private-sectoraccreditors of calibration and testing laboratories;product certifiers, quality and environmental manage-ment system registrars; information sources and manyother aspects of the country’s industrial infrastructure.

Included in each nation’s profile are: basic data on itseconomy and trade, its MSTQ framework, responsibleagencies and institutions, and key contacts and informa-tion sources. The directory is expected to be a usefulreference for all organizations involved in standards andconformity assessment-related activities in the globalmarketplace.

Copies of SP 912 are available from the Superinten-dent of Documents, U.S. Government Printing Office,Washington, DC 20402, (202) 512-1800. Order bystock no. 003-003-03462-2.

REPORT EXAMINES FIRE PROTECTION FORHIGH-CEILING SPACESA new report by a team of fire prevention professionalsfrom NIST, the Naval Facilities EngineeringCommand, and private industry should prove useful tothose designing, installing or retrofitting smoke detec-tors, automatic sprinklers and other fire protection sys-tems into high-ceiling structures, such as aircrafthangars, warehouses and hotel atriums.

The team’s report, Analysis of High-Bay Hangar Fa-cilities for Fire Detection Sensitivity and Placement(NIST Technical Note 1423), looks at placement spac-ings for ceiling heat detectors, describes methods toimprove the effectiveness of projected beam or opticalsmoke detectors, and compares various sprinklersystems. The researchers gathered data from 33 full-scale fire tests conducted in high-bay aircraft hangarslocated at naval air stations in Hawaii and Iceland.The fires, ranging from 0.09 m2 to 20.9 m2 in area, werestudied in the hangars under varying conditions (includ-ing air flow, ambient temperature, fuel type and closed/open doors). Each fire yielded data on 200 separatemeasurement points.

As a result of these tests, the researchers gained in-sight into heat and smoke behavior in high-ceiling struc-tures, the response time of fire detection and sprinklersystems, the ignition flash points of new jet fuels, therole of ceiling architecture on detector and sprinklerresponse, and the ability of computer models to predictfires.

NIST Technical Note 1423 is available from the Su-perintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402, (202) 512-1800. Orderby stock number 003-003-03446-1. The report, a nine-minute video “Aircraft Hangar Fires: Fire ProtectionImprovements” and a CD titled “U.S. Navy High-BayHangar Tests” are available as a set from Joseph E. Gott,Naval Facilities Engineering Command, 299 StovallStreet, Code 150, Alexandria, VA 22332-2300,.

IMPROVED WATTHOUR CALIBRATIONSSAVE TIME, MONEYIn response to its industry customers’ needs, NIST nowoffers a new calibration service for watthour meters thatprovides faster turnaround time and reduced cost.Automation of a commercial calibrator and automateddata collection/analysis software makes the improvedservice possible. What permits the full automation ofthe watthour meter calibration process is that only thethree most requested test points (power factors of unity,0.5 lag and 0.5 lead at set conditions of 120 V, 5 A and

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60 Hz) are offered. The results: turnaround time cut toless than 2 weeks—approximately one-fourth of thetime for standard watthour meter calibrations and thecost lowered to $650—a greater than three times reduc-tion in the fee.

The new service was developed after a quality effortby NIST identified repeated customer requests for theseimprovements.

For more information, contact James K. Olthoff,B344 Metrology Building, NIST, Gaithers-burg, MD 20899-0001, fax: (301) 948-5796,..

A GUIDE TO THE CONFORMITYASSESSMENT MAZEHow can you be assured that the product you purchasewill perform as expected? Conformity assessmentprocedures provide a means of ensuring that products,services or systems produced or operated in the UnitedStates do so. A new report by NIST, The ABC’s of theU.S. Conformity Assessment System (NISTIR 6014),provides an overview of this nation’s conformityassessment system for a better understanding of itsimpact on the marketplace.

The report describes the various steps in a conformityassessment system and the interrelationship betweenthose steps. Included is discussion of standardization,inspection, testing, laboratory accreditation, and certifi-cation. In addition, management system assessment andregistration (such as ISO 9000 and 14000 standards) arecovered.

A printed copy of NISTIR 6014 may be requested bysending a self-addressed mailing label to Maureen A.Breitenberg, Building. 820, Room 282, NIST,Gaithersburg, Md. 20899-0001, fax: (301) 963-2871,. The publication alsocan be obtained from the World Wide Web as an AdobeAcrobat file at . Multiple copies soon will be available fromthe National Technical Information Service,Springfield, VA 22161, (703) 487-4650, fax: (703) 321-8547, .

NOVEMBER MEETING TO SPOTLIGHTSECONDARY LABSThe role of secondary laboratories in ionizing radiationmeasurements and standards will be the focus of thesixth annual meeting of the Council on IonizingRadiation Measurements and Standards to be held atNIST headquarters in Gaithersburg, MD, Nov. 12-14,1997. Secondary laboratories have been part of thenetwork that maintains measurement standards in

ionizing radiation for more than two decades and areserving as a model for other U.S. calibration systems.

The technical program of the 1997 CIRMS meetingwill cover medical applications, public and environ-mental radiation protection, occupational radiationprotection, and radiation effects. CIRMS serves as aforum for discussing ionizing radiation measurementsand standards issues, for identifying new needs of theuser communities and for disseminating information onstandards. CIRMS brings together representatives fromacademic, industrial and government agencies involvedin nearly every aspect of ionizing radiation.

The registration fee is $150. For registration informa-tion, contact Lori Phillips at B116 AdministrationBuilding, NIST, Gaithersburg, MD 20899-0001,( 3 0 1 ) 9 7 5 - 4 5 1 3 , f a x : ( 3 0 1 ) 9 4 8 - 2 0 6 7 ,. For technical information,contact Bert Coursey, C229 Radiation PhysicsBuilding, NIST, Gaithersburg, MD 20899-0001,( 3 0 1 ) 9 7 5 - 5 5 8 4 , f a x : ( 3 0 1 ) 8 6 9 - 7 6 8 2 ,.

DON’T LET SALTS, MINERALS IN STEAMGET YOU BOILING!It has been known for more than 50 years that deposi-tions of solids—such as salts and minerals—fromexpanding steam can be a significant problem in theelectrical power industry. In steam turbines, the impuri-ties impair turbine efficiency by causing corrosion orconstriction of passages. However, the same deposits(which have been only minor concerns for steamturbines) may be major headaches for the high-efficiency combustion turbines currently under devel-opment. The newer systems use steam from a steamturbine cycle to cool parts of a combustion turbine.Even small amounts of salts and minerals in thepassages could lead to overheating and part failure.

To assist the power industry, NIST recently under-took a project to collect and, if possible, correlate allavailable data for the solubility in steam of variouscompounds. These compounds include sodiumchloride, sodium hydroxide, sodium sulfate, sodiumphosphate, iron oxides, copper oxides and silicondioxide. The correlations will be helpful in developingsteam purity recommendations for the conditionsencountered in the advanced turbines.

The temperature range considered was from 2008Cto 9008C (with 3008C to 6408C as the range ofprimary interest). Pressures considered were from1 mPa to 6 mPa (with 2 mPa to 4 mPa as the range ofprimary interest). The data collected are contained inEvaluation and Correlation of Steam Solubility Datafor Salts and Minerals of Interest in the Power Industry(NIST Technical Note 1387).

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NIST TN 1387 may be ordered for $7 from theSuperintendent of Documents, U.S. Government Print-ing Office, Washington, DC 20402-9325. Order bystock number 003-003-03470-3.

REPORT DETAILS WORKSHOP ONAMMONIA/WATER MIXTURESCan ammonia/water working fluids be used to replacesteam in the design of some electrical power plants? Yes,but it is vitally important to know first the thermophys-ical properties of these mixtures. That was theconclusion of the Workshop on ThermophysicalProperties of Ammonia/Water Mixtures held at NIST inBoulder, CO, in June 1996. The report from that work-shop is now available.

Included is NIST’s work investigating properties inthe temperature range from 280 K to 450 K with amaximum pressure of 3.5 mPa and with ammonia molfraction compositions in the range 0.8 to 1.0 for geother-mal applications. The project involves theevaluation of literature data, experimental measure-ments, and the development of models for the thermody-namic and transport properties over these ranges.ndustry interest, as learned from the workshop, is forproperties up to 895 K at pressures to 22 mPa, and forthe complete range of compositions.

Industry and government representatives at the work-shop agreed to work together to investigate funding op-tions, maintain communication among themselves, andto meet again, as appropriate, to reassess the status ofproperties work on the ammonia/water binarymixtures.

A copy of theReport of the Workshop on Thermo-physical Properties of Ammonia/Water Mixtures(NISTIR 5059) is available for $38 from the NationalTechnical Information Service, Springfield, VA 22161,(703) 487-4650, . Order byPB 97-167522.

APPROVAL/RECOGNITION OFACCREDITATION BODIESThe NIST Accreditation Body Evaluation Program(ABEP) is responsible for approving (recognizing)qualified domestic and foreign accreditation bodies thatwish to engage in the accreditation of fastener testinglaboratories under the Fastener Quality Act. The ABEPhas been operating this program since publication of thefinal implementing regulations in September 1996. Todate, three accreditation bodies have applied forapproval/recognition. Their evaluations have beencompleted and the results presented to an “ABEPPanel,” consisting of members from within and outside

NIST. The accreditation bodies approved by the ABEPPanel as of April 23, 1997, are: American Associationfor Laboratory Accreditation, National Aerospace andDefense Contractors, and United Kingdom Accredita-tion Service.

Effective April 23, 1997, and in accordance with theFastener Quality Act, these organizations have beenauthorized to engage in the accreditation of laboratoriesthat test fasteners and raw materials used in fastenermanufacturing under the act. To be sold in the UnitedStates, all covered fasteners must be tested in an accred-ited laboratory after May 28, 1998.

ENERGY-RELATED INVENTIONS PROGRAMMAKES RECOMMENDATIONSDuring the month of April, the NIST Office of Technol-ogy Innovation recommended three innovativetechnologies for commercialization to its Department ofEnergy partner under the Energy-Related InventionsProgram.

High Throughput Manufacturing of High-EfficiencySolar Cells—a continuous vacuum process designed toreplace conventional vacuum batch processes for manu-facturing high efficiency CdTe solar cells for generatingelectricity; Novel Method and Apparatus for EjectingParticulates from the Primary High Temperature InletFlow Path of a Coal Fired Turbine Generator—a devicefor removing, by centrifugal force, solid particulatematter from the high temperature exit stream of a coalgasifier; The Road Patcher—an assembly of hydrauliccomponents designed to be installed easily on a conven-tional dump truck.

SPECIAL NIST MEASUREMENTS AIDMANUFACTURER OF SUPERCONDUCTINGMAGNETIC ENERGY STORAGE SYSTEMSA series of electromechanical tests has been performedon a new aluminum stabilized coil structure by NISTscientists. The measurements were carried out at liquid-helium temperature in a 4 Tmagnetic field on a set ofcomposite rings designed to simulate new magnetsbeing constructed for superconducting magnetic energystorage (SMES) using high-purity (99.995 %)aluminum and a high-strength aluminum alloy(6061-T6). The rings were designed to simulate themechanical and electrical characteristics of thealuminum stabilizer system designed for the AnchorageMunicipal Light & Power SMES magnet by a privatecompany. The conductor system is based on a conven-tional copper-stabilized niobium-titanium super-conducting cable; however, for additional stability, thecable is encased in a high-purity aluminum jacket.

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Stability in this sense refers to the provision of an alter-native electrical conducting path and mechanicalconstraint should the superconductor revert to normalstate. The increased stability is necessary because of themagnet’s high energy-storage capacity, 1800 MJ. Ahigh-strength aluminum-alloy overwrap is added to theconductor for structural support. Aluminum wasselected instead of copper as the primary stabilizermaterial to reduce the magnet’s size, mass, and costwhile actually increasing its stability. The team adaptedthe division’s unique superconducting composite ringmeasurement system to simulate operating conditionswithin the SMES magnet and, specifically, to test theeffect of mechanical fatigue and magnetic field on thecomposite’s resistivity (the conductor will be subjectedto fatigue as the magnetic field is cycled in response tothe power system’s requirements).

The test results showed that the actual stabilizerdegradation is much lower than predicted by a simpli-fied analytical model. Ultimately, the private companyand the expanding power utility industry will use thesedata to optimize the stabilizer design, substantiallyreducing the required quantity and cost of materials.

NIST REPORT OUTLINING MEASUREMENTCHALLENGES FOR DEREGULATED U.S.ELECTRIC-POWER INDUSTRY DRAWSINTEREST, PRAISEA recently issued report, identifies the measurementchallenges to be faced by the rapidly deregulating elec-tric power industry and is drawing intense interest fromindustry and praise for its conception and implementa-tion. The report was developed by NIST scientists inconsultation with experts in industry, other governmentagencies, and universities.

Measurement Support for the U.S. Electric-Power In-dustry in the Era of Deregulation (NISTIR 6007)describes the changes taking place in the industry, trans-lates those changes into key technical needs that indus-try must address, and describes the measurement capa-bility required for a successful response. The technicalneeds of the electric-power industry are described inresponse to the principal driving forces of the electric-power industry: (1) efficiency, reliability, and stabilityof the power system; (2) equity in trade, and interna-tional competitiveness; (3) global warming and healtheffects; and (4) power quality. The study identifies themost critical long- and short-term measurement needsthat require NIST’s assistance, with focus on electricalmeasurements for the transmission and distribution ofelectric power. Finally, the document distinguishes be-tween the measurement needs that NIST is currentlyable to address and those that remain to be addressed.

The U.S. electric-power industry is being deregulatedto promote competition in providing electricity at lowercost and with greater responsiveness to customers’needs. This is a dramatic change for a huge industry thathas annual electricity sales of $208 billion (1995),employs 441 000 people (1995), and impacts the lives ofevery U.S. company and citizen. As a result of deregu-lation, more companies are likely to enter the businessof providing electricity; both newcomers and existingproviders will be seeking a competitive edge. Their indi-vidual success, and the collective benefits realized forthe nation as a result of competition, will be highlydependent on their ability to adopt and exploit modernand emerging technologies.Exploiting these technolo-gies effectively will require new measurement capabil-ity. NIST staff have looked into the future and produceda study that identifies the measurement capabilityrequired.

CALCULATIONS OF MAGNETIC FIELDMEASUREMENT ERROR DISTRIBUTIONSEXPLAIN WHY INSTRUMENTS MAY DIFFERIN READINGS BY MORE THAN 30 %NIST scientists recently have calculated the probabilitydistributions for the errors when three-axis and single-axis magnetic field meters are used to measure a dipolefield, taken as a reasonable approximation of the fieldsproduced by many appliances. The calculated resultsprovide an explanation of why two identical three-axismagnetic field meters used to make measurements at thesame point in space near an electrical appliance in thehighly nonuniform field produced by the appliance canyield values that differ by more than 30 %. In each case,the distributions are found to be asymmetric. However,with knowledge of the 68 % and 95 % confidence inter-vals, determined as part of the computations, estimatesof uncertainty can be assigned to measurementsperformed in fields having large gradients. The resultsof the calculations, presented in a tabulated format, alsoallow selections to be made of probe size whichare consistent with total permitted measurement uncer-tainties.

The concern in the mid 1970s regarding healtheffects from exposure to electric and magnetic fields inthe vicinity of power lines has shifted in recent years tohealth effect concerns from exposure to powerfrequency magnetic fields in residences, the work place,and in transportation systems. The magnetic fields inthese environments can be highly nonuniform, particu-larly near electrical equipment such as motors, trans-formers, and heating elements. Because magnetic fieldmeasurements are frequently made with field metersemploying circular coil probes, the measured field

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values are actually averages over the cross sectional areaof the probe. Since the measurement location is nor-mally taken to be the center of the probe, differencesbetween the average field and the central field can beregarded as a source of measurement error. Previously,calculations have been performed at NIST to determinethe maximum error that could occur when magneticfield meters with single-axis and three-axis coil probeswere used to measure the magnetic flux densityproduced by a small loop of alternating current, i.e., amagnetic dipole.

NIST RESPONDS TO INDUSTRY REQUESTSFOR MICROWAVE-FREQUENCY MATERIALMEASUREMENTSNIST scientists responded to a number of industryrequests for special measurements of the dielectricand magnetic properties of specimen materials atmicrowave frequencies. In one instance, a companywanted the information to enable them to choseabsorber material for a radiofrequency anechoicchamber. This company supplied specimens of 13 dif-ferent magnetic materials for characterization over thefrequency range of 30 MHz to 2 GHz by means of a14 mm-diameter coaxial transmission/reflectionapparatus. These specimens also were measured with aNIST-developed permeameter to confirm the resultsfrom the coaxial measurements over the frequencyrange of 30 MHz to 100 MHz. In a second example, thecompany requested measurements of the complexpermittivity of a glass dielectric material over thefrequency range 8.2 GHz to 12.4 GHz (X-Band). Awaveguide transmission/reflection method was em-ployed. In a third instance, three companies requested atotal of 75 measurements on various substrate materialsover a frequency range of 1 GHz to 10 GHz. NISTscientists carried out these measurements using thesplit-post resonator technique specifically developed toprovide industry with accurate and expedient measure-ments of printed wiring board and substrate materials.

ASSEMBLY LEVEL TOLERANCINGWORKSHOPThe Assembly Level Tolerancing: Standards andImplementation Issues workshop, was held April 24-25,1997, at NIST. The workshop provided an excellentforum to: (1) identify and develop system level toleranc-ing standards and technology; (2) provide an open forumfor CAD/CAT vendors and manufacturing industry toidentify the gaps in the current available technology andto find some suitable solutions and alternatives;and (3) provide a roadmap that will aid in directing

future research, development, and support to bringabout rapid development and technology transfer.

The workshop was well attended and included repre-sentation from industry end users, standards community,academia, computer aided design, and tolerancingsoftware vendors. Topics discussed included tolerancetheory and standards, representation and implementa-tion, tolerance analysis, industrial applications andbenchmarks, STEP implementation and advanced toler-ancing methodologies (statistical and knowledge-based).The workshop proceedings will be made availableas a NIST IR. Details of the workshop can be found athttp://www.nist.gov/mel/div826/event/workshop/assembly/workshop.htm.

QUANTUM ENZYMOLOGY SUGGESTS ROUTETO NEW ANTIBIOTIC DEVELOPMENTAs part of a broad, long-range effort involving proteinengineering and rational drug design, NIST and Univer-sity of Maryland scientists collaborating at the Centerfor Advanced Research in Biotechnology haveused newab initio quantum mechanical techniques combinedwith high-resolution structural information from proteinx-ray crystallography to propose a novel, microscopicchemical mechanism for the hydrolysis ofb-lactamantibiotics byStaphylococcus aureusPC1b-lactamase.The therapeutic effectiveness of the penicillins and thecephalosporins has been reduced significantly by theemergence of resistant strains of bacteria that containnew enzymes able to break down these compoundsbefore they can carry out their designed role. Thelimited, qualitative mechanistic information for thisclass of enzymes has been an obstacle to the develop-ment of next-generation penicillins and cephalosporins.This alternative mechanism suggests that the properstructural framework for substrate binding and orienta-tion during catalysis plays a larger role in catalysis thanpreviously appreciated. These insights provide newguidance to the pharma-ceutical industry in the develop-ment of non-b-lactam antibiotics to kill bacteria.

NEW METHODS FOR DNA DIAGNOSTICSResearchers at NIST are developing improved methodsfor DNA mutation detection using capillary elec-trophoresis (CE). Analysis of DNA by single strandconformational polymorphism (SSCP) provides anefficient means of screening these mutations before thecostly and time-consuming task of sequencing is begun.SSCP is a method used to detect single-base changes(mutations) in DNA that introduce conformationalchanges in the polymer. The finding that theseCE-SSCP measurements have specific temperature

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dependencies provides the basis for developing thistechnique as an improved method for genetic profiling.For example, in the p53 system under study at NIST,specific mutations may be identified by CE-SSCP.(Mutations in the p53 gene are highly correlated tomany forms of cancer.)

This work is being done in collaboration with aprivate company. Preliminary results were presented atthe HUGO Meeting on Mutation Detection, May 29,1997, in Brno, Czech Republic. Complementing thesestudies, computerized RNAfolding analyses are beingperformed to predict which mutations are detectable bySSCP. In collaboration with scientists at a privatecompany and the Laboratory of Experimental andComputational Biology of the National CancerInstitute, preliminary findings have resulted in molecu-lar models of SSCP that are predictive. This informationis being used in the design of measurement conditionsand standards for SSCP.

UNDECOMPOSED HYDROGEN PEROXIDEACCELERATES REACTION RATES INSUPERCRITICAL WATER OXIDATIONREACTORSRecent experiments reveal the advantages of usinghydrogen peroxide (H2O2) instead of oxygen (O2) as anoxidant in supercritical water oxidation (SCWO) flowreactors. The results obtained, resolve a long-standinginconsistency in the literature, establish some opera-tional benefits, and provide insight into the mechanismof SCWO reactions.

Industrial SCWO systems effectively treat organicwastes by taking advantage of the high mutual solubilityof organics and oxidants above the critical point of water(647 K, 22 MPa). Oxidation reactions typically achievea high level of completion and generate benign effluentproducts (e.g., carbon dioxide and water). However,inconsistencies have been reported in the extent of reac-tion where H2O2 has been used. In some studies, H2O2behaves identically with O2, while in others it acceler-ates oxidation, and yet in others, it leads to large scatterin the data.

At NIST, experiments with H2O2 oxidant are com-pared with tests where O2 is substituted (i.e., generatedvia peroxide thermolysis). The results show that carefuldecomposition of H2O2 is the key. If H2O2 is quantita-tively thermolyzed to O2, then mixed with the waste,literature results with O2 are reproduced. For reactionswith undecomposed H2O2, accelerated rates areobserved with ~260 % decrease in activation energy vs.O2. For varying levels of decomposition, a range ofreaction rates are observed. Thus, NIST researchers canreproduce the spectrum of literature data with H2O2 and

attribute the variable behavior observed to incompletedecomposition to O2. The researchers also have demon-strated that H2O2 is more thermally stable under super-critical conditions than previously thought, which isreasonable since decomposition to O2 is thermo-dynamically suppressed at elevated pressures. Theaccelerated reaction rates with H2O2 can offer substan-tial process advantages over pure O2 by allowingreactions to be conducted at lower temperatures(DT ≈ 50 K to 150 K) which reduces energy andmaterial costs. Further, because the effective activationenergies with H2O2 are substantially lower, reactionsare less sensitive to temperature excursions resulting inmore robust operation. Finally, the results suggest thatthe OH radical is important in SCWO reactions, andthat data from previous studies using H2O2 must beinterpreted carefully.

NIST MEASUREMENTS SUPPORT MOREACCURATE 190Pt HALF-LIFEDETERMINATIONA method developed recently at NIST for the determi-nation of the platinum group elements (PGEs) in auto-mobile catalysts has been applied to the analysis ofunique geologic and meteoritic samples. Scientists atNIST have collaborated with a team from the Univer-sity of Maryland and Colorado State University to studyosmium and platinum in a set of 250 million year oldrocks from Noril’sk, Siberia. This study resulted in asignificantly more accurate determination of the half-life of 190Pt. The two elements are linked by the radio-genic system based on the alpha decay of190Pt to186Osand previous investigations were difficult because190Ptis rare in nature. In addition, it has an extremely longhalf life, previously poorly defined as (6506 46)billion years (95 % confidence limit) based on reportedliterature data ranging from 470 billion to 690 billionyears.

The University of Maryland-Colorado State Univer-sity team has expertise for high-precision isotopicmeasurements of osmium, but they did not have thecomparable capability for platinum measurements.190Ptin the Noril’sk rocks was determined at NIST using theisotope dilution inductively coupled plasma mass spec-trometry method developed earlier for the determina-t i on o f PGEs in used au tomob i l e ca ta l ys tmaterials. These measurements allowed the first preciseisochron to be demonstrated for the Pt-Os isotopicsystem. The ratio of the natural concentrations ofosmium and platinum plotted versus the amount of190Ptdaughter product (186 Os) would normally be used todetermine the age of rocks. However, in this experi-ment, rocks of well-known age were used to determine

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the 190Pt decay constant as 1.54310–12 per year with anuncertainty of about 1 %, which translates to a190Pt halflife of 449 billion years. In addition, the University ofMaryland-Colorado State University team also hasshown that these precise Pt and Os measurements can beused to probe interactions between the Earth’s core andmantle and promises to be very useful in studying otherfundamental geochemical processes.

NEW INVENTION AIDS SEMICONDUCTORMANUFACTURINGOptical scattering is used in the semiconductor industryto measure microroughness and to detect particulatecontaminants and subsurface defects on silicon wafers.As the feature sizes in modern integrated circuitscontinue to shrink, ever stricter demands are being madeon instruments to detect smaller and smallercontaminant particles. One important issue that limitsthe sensitivity of such instruments is that light scatteringdue to the silicon wafer microroughness can obscure oroverwhelm the scattering due to particles. This problemis widely recognized. The Semiconductor IndustryAssociation roadmap declares that detection of particleswith diameters less than 0.1mm is a potential “showstopper.”

Researchers at NIST have pursued an ingenioussolution to this problem. By developing a noveltechnique, bidirectional ellipsometry, they found thatthe light scattered by microroughness has a characteris-tic, well-defined polarization for each scatteringdirection. Other scattering sources, such as particlecontaminants and subsurface defects, scatter withdifferent characteristic polarizations. The discovery ofpolarization signatures enabled the design of a micro-roughness-blind hemispherical optical scatter measur-ing instrument. A patent application has been filed onthis invention, which addresses the issue of measuringnanoscale particles on silicon wafers; however, it is ex-pected that bidirectional ellipsometry also will be apowerful technique for identifying and characterizingdefects in optical components, data storage materials,and film coatings.

TWENTY-FIFTH ANNIVERSARY CORMCONFERENCEThe Council for Optical Radiation Measurements(CORM) is an industry organization that works withNIST to identify industry needs and to deploy new NISTservices in its area of expertise. Founded in 1972,CORM has grown to represent about 150 companies intheir search for a consensus on pressing problems andnational needs in optical radiation measurement.

In recent years, CORM has held an annual meeting toconduct business and to hold workshops in specificareas of common concern. This year’s annual meetingwas held at NIST April 28-May 1, 1997, and focused onrecent advances in optical remote sensing, reflectanceand transmittance metrology, andinfrared metrology.The program featured invited presentations by expertsin government, academia, and industry.

WORKSHOP ON NEEDS FOR COLOR ANDAPPEARANCE STANDARDSIn conjunction with the CORM annual meeting, NISTparticipated in a workshop on April 28, 1997, to allowindustry to comment on their needs for measurementstandards in the fields of color and appearance. ThisCORM-organized workshop provided the attendees theopportunity to help define and prioritize ongoing NISTwork. A previous workshop last year was sponsored byNIST to help researchers better understand industrialneeds for color and appearance measurements and stan-dards. Subsequently, NIST work was begun to advancethe science and capability of appearance measurements.

The NIST objective is to develop measurementservices and Standard Reference Materials for appear-ance attributes such as color, gloss, translucency, luster,sheen, texture, orange peel, distinctness of image, andcontrast. These standards are most important to thepaint, coating, and textile industries, and to the myriadof other industries that make consumer goods wherespecific color and appearance are quality attributes.This workshop helped to establish the desired physicalproperties and ranges of measurement quantities forthese reference materials.

WORKSHOP ON RETROREFLECTANCEMEASUREMENTSAlso in conjunction with the CORM annual meeting,NIST held a workshop on May 1, 1997, to allow indus-try to comment on their needs for measurementstandards in the field of retroreflectance. Retroreflectantmaterials are used widely and, in many cases required,to increase the visibility and conspicuity of people,vehicles, signs, and safety markings on the nation’shighways and in transportation industries to reducedeaths and injuries.

Currently, there are no national measurementstandards for retroreflective materials, and the work-shop participants conveyed the need to have NISTprovide such standards. The suggestions provided at thisworkshop will be used to formulate the NIST effort forretroreflective measurements.

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SHORT COURSE IN RADIATIONTHERMOMETRYOn May 6-8, 1997, NIST and the ASTM CommitteeE20.02 on Radiation Thermometry inaugurated a newShort Course on Temperature Measurement byRadiation Thermometry. It was designed by expertsfrom NIST and a professor at Purdue University andeditor of Theory and Practice of Radiation Thermome-try. It was conducted in the new radiometric facilitylocated in Building 245: FARCAL, the Facility forAdvanced Radiometric Calibrations.

The course consistsed of lectures that cover thefundamentals of radiometry and temperature measure-ments. They were complemented with hands-on,skill-building, problem-solving laboratory experiments.During these exercises, the participants learn ASTMvol

Journal of Research of the National Institute of Standards …Volume 102, Number 4, July–August...

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Transcript of Journal of Research of the National Institute of Standards …Volume 102, Number 4, July–August...