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A Unique Institution: The National Bureau of Standards, 1950-1969 (Contents)
No full textA Unique Institution: The National Bureau of Standards, 1950-1969 (SP925) by Elio Passaglia chronicles the expansion of National Bureau of Standards (NBS) to Boulder, Colo., and the relocation of the main site from downtown Washington, DC to Gaithersburg, Md. The NBS encountered tremendous challenges during this period. When faced with extreme outside pressure, its technical integrity remained intact
Near infrared 45 degrees/0 degrees reflectance factor of pressed polytetrafluoroethylene (PTFE) powder
No full textPressed polytetrafluoroethylene (PTFE) powder is commonly used as a reflectance standard for bidirectional and hemispherical geometries. The wavelength dependence of the reflectance factor of PTFE is presented for the near-infrared spectral region (800 nm to 1600 nm) for the 45 degrees/0 degrees geometry, as well as in the visible spectral region (380 Nm to 800 nm) for comparison with previously published results
Manufacturer's CORBA Interface Testing Toolkit: Overview
No full textThe Manufacturer's CORBA Interface Testing Toolkit (MCITT) is a software package that supports testing of CORBA components and interfaces. It simplifies the testing of complex distributed systems by producing "dummy components" from Interface Testing Language and Component Interaction Specifications and by automating some error-prone programming tasks. It also provides special commands to support conformance, performance, and stress testing
Trilateral intercomparison of photometric units maintained at NIST (USA), NPL (UK), and PTB (Germany)
No full textA trilateral intercomparison of photometric units between NIST (USA), NPL (UK), and PTB (Germany) has been conducted to update the knowledge of the relationship between the photometric units disseminated in the three countries. The luminous intensity unit (cd), the luminous responsivity scale (A/lx), and the luminous flux unit (lm) maintained at each laboratory were compared by circulating transfer standard lamps and photometers. The results showed that the relative luminous intensity values, with respect to the average, measured by NIST, NPL, and PTB were 1.0014, 1.0021, and 0.9966; the relative inverse values of the luminous responsivity (corresponding to illuminance) were 1.0023, 1.0011, and 0.9965; the relative luminous flux values were 0.9994, 1.0034, and 0.9972, respectively. The results agreed within the stated uncertainties of the units maintained at the three laboratories
ELECTRONIC COMMERCE OF COMPONENT INFORMATION WORKSHOP, Gaithersburg, MD, July 15-17, 1998
No full textOn the diffraction limit for lensless imaging
No full textThe diffraction limit for lensless imaging, defined as the sharpest possible point image obtainable with a pinhole aperture, is analyzed and compared to the corresponding limit for imaging with lenses by means of theoretical considerations and numerical computations using the Fresnel-Lommel diffraction theory for circular apertures. The numerical result (u = pi) obtained for the best configuration parameter u which defines the optical setup is consistent with the quarter-wave criterion, and is the same as the value reported in a classical paper by Petzval but smaller than the Value (u =1.8 pi) found by Lord Rayleigh. The smallest discernible detail (pixel) in a composite image is defined by an expression found by Rayleigh on applying the half-wave criterion and is shown to be consistent with the Sparrow criterion of resolution. The numerical values of other measures of image size are reported and compared to equivalent parameters of the Fraunhofer-Airy profile that governs imaging with lenses
Performance verification of impact machines for testing plastics
No full textValid comparison of impact test energies reported by various organizations and over time depends on consistent performance of impact test machines. This paper investigates the influence of various specimen and test parameters on impact energies in the 1 J to 2 J range for both Charpy V-notch and Izod procedures, leading toward the identification of a suitable material for use in a program to verify machine performance. We investigated the influences on the absorbed energy of machine design, rest material, specimen cross sectional area, and machine energy range. For comparison to published round robin data on common plastics, this study used some common metallic alloys, including those used in the international verification program for metals impact machines and in informal calibration pro-grams of tensile machines. The alloys that were evaluated include AISI type 4340 steel, and five aluminum alloys: 2014-T6, 2024-T351, 2219-T87, 6061-T6, and 7075-T6. We found that certain metallic alloys have coefficients of variation comparable to those of the best plastics that are reported in the literature. Also, we found that the differences in absorbed energy between two designs of machines are smaller than the differences that can be attributed to the specimens alone
