Serial/Series Title
States
Decade
Month
Language
526 Matching Results
Results open in a new window/tab.
Shielded Balanced and Coaxial Transmission Lines: Parametric Measurements and Instrumentation Relevant to Signal Waveform Transmission in Digital Service
Abstract: A method is presented for determining the impulse and step responses of a shielded cable using time domain terminal measurements and a physically based mathematical model for the transmission line properties of the cable. The method requires a computer controlled time domain measurement system and was implemented using the NBS Automatic Pulse Measurement System (APMS). Data are also developed for the frequency domain complex propagation function (attenuation and its related minimum-phase shift). The method is applied to 12 shielded paired-conductor (balanced) cables and 5 coaxial cables. Time domain responses are presented for three nominal cable lengths, 60 m (200 ft), 150 m (500 ft), and 300 m (1000 ft). The time domain responses are applied to the estimation of bit error rate increases due to the insertion of the cables into a digital signaling system employing a balanced polar NRZ waveform. Also discussed is the application of the time domain responses to time domain reflectometry techniques for cable acceptance tests and field-site testing of installed cables.
Date:
June 1981
Creator:
Gans, William L. & Nahman, N. S.
Object Type:
Report
System:
The UNT Digital Library
The Characterization of Optical Fiber Waveguides: A Bibliography with Abstracts, 1970-1980
Abstract: This bibliography contains approximately 450 citations of papers concerning the characterization of optical fiber waveguides. Papers from scientific journals, trade journals and conferences are included along with book chapters. The citations of organized by parameter measured and measurement method. Where published abstracts are available they are included.
Date:
June 1981
Creator:
Day, G. W.
Object Type:
Report
System:
The UNT Digital Library
WR 10 Millimeter Wave Microcalorimeter
Abstract: A microcalorimeter has been built in WR 10 waveguide, 75-110 GHz, to serve as a power standard at the National Bureau of Standards (NBS). Included here is an evaluation of the errors in using the microcalorimeter for the measurement of effective efficiency of bolometer mounts. The error analysis shows a systematic uncertainty of +/- .83 percent and a random uncertainty of .37 percent.
Date:
June 1981
Creator:
Weidman, Manly P. & Hudson, Paul A.
Object Type:
Report
System:
The UNT Digital Library
A Review of Supercritical Fluid Extraction
Forward: The purpose of this report is to summarize the results obtained from a brief investigation of supercritical fluid extraction principles and applications. This study was one portion of a project funded by the U.S. Department of Energy, Office of Fossil Energy, contract nuriber DE-AI01076PR06010, in response to a preliminary proposal submitted by the authors. This report sometimes uses company trade naries to identify processes and patent holders. This usage implies no endorsement by HBS. Note also that some figures reproduced from other sources do not conform with NBS policy concerning SI units.
Date:
December 1983
Creator:
Ely, James F. & Baker, Jolene K.
Object Type:
Report
System:
The UNT Digital Library
An Error Analysis for the Use of Presently Available Lunar Radio Flux Data in Broadbeam Antenna-System Measurements
From introduction: Simple, precise expressions for lunar diameter, average brightness temperature, flux density, and shape factor are presented. An analysis of the relationship between these parameters and corresponding errors are included. For broadbeam (HPBW>d) antennas, results show that flux density and shape factor can be determined with errors less than 13 percent and 0.4 percent respectively at frequencies below 10 GHz. Extension of the analysis to higher frequencies is indicated.
Date:
February 1984
Creator:
Daywitt, William C.
Object Type:
Report
System:
The UNT Digital Library
A Coaxial Noise Standard for the 1 GHz to 12.4 GHz Frequency Range
From introduction: This note describes the design and construction of a coaxial thermal noise standard. The standard is designed to operate at the boiling point of liquid nitrogen with a noise temperature accurate to t 1 K in the frequency range from 1 GHz to 12.4 GHz.
Date:
1984
Creator:
Daywitt, William C.
Object Type:
Report
System:
The UNT Digital Library
Tests of Commercial Densimeters for LNG Service
Abstract: Densimeters for liquefied natural gas (LNG) from four manufacturers were tested in liquid methane and an LNG-like mixture of methane, propane, and nitrogen in the density reference system (DRS). The calibration and performance of one type tested for the first time are reported. The stability of the calibrations and performances of three densimeters of a type previously tested have been examined and are also reported here.
Date:
June 1982
Creator:
Siegwarth, J. D. & LaBrecque, J. F.
Object Type:
Report
System:
The UNT Digital Library
Beam-Profile Measurement of Laser Pulses Using a Spatial Filter to Sample the Hermite Modes of a String of Pulses
Abstract: As a first step in the development of a beam-profile measuring instrument for laser sources that is capable of determining the distribution of low-order (less than 25) Hermitian modes in a series of laser pulses, I designed and evaluated the three key parts of such an instrument. First, there is the telescope system which allows the incident laser beam to be phase, beamwidth, and beam center matched to the optical spatial filter. Second, there is a brief error analysis of the structure of the mismatch function between the beam out of the telescope and that expected by the filter. Finally, there is the detailed analysis and design of the computer-generated spatial filter that will cause the incident-laser beam to be cross correlated with the low-order Hermite modes and will create an array of light spots in the detector (Fourier transform) plane each of which can be uniquely related to a particular Hermite mode of the original laser pulse. The principal conclusion is that the Hermite mode analysis can be done with better than 99 percent separation between modes, provided the phase between modes is uncorrelated from pulse to pulse when the filter has been fabricated with a two-level, gray-scale …
Date:
September 1982
Creator:
Johnson, Eric Gunnar, Jr.
Object Type:
Report
System:
The UNT Digital Library
A System for Measuring Energy and Peak Power of Low-Level 1.064 [mu]m Laser Pulses
From introduction: For the first time, transfer standards have been developed for measuring 1.064 Pm laser pulses of duration about 10-100 ns, peak irradiance of about 10-8-10-4 W/cm2, and fluences of about 10-16-10-11 J/cm2 . These energy and power measurement devices use PIN and APD silicon detectors, respectively, and can be used as stable transfer standards with total uncertainties (random errors computed at the 95 percent confidence level) of 10 to 15 percent. The system for calibrating these transfer standards is also described and consists of a cw Nd:YAG laser beam acousto-optically modulated to provide low-level laser pulses of known peak power and energy. A detailed evaluation of systematic and random errors is also shown.
Date:
October 1982
Creator:
Sanders, A. A. & Rasmussen, A. L.
Object Type:
Report
System:
The UNT Digital Library
A Method to Quantify the Radiation Characteristics of an Unknown Interference Source
From introduction: A new method for determining the radiation characteristics of leakage from electronic equipment for interference studies is described in this report. Basically, an unintentional leakage source is considered to be electrically small, and may be characterized by three equivalent orthogonal electric dipole moments and three equivalent orthogonal magnetic dipole moments. When an unknown source object is placed at the center of a transverse electromagnetic (TEM) cell, its radiated energy couples into the fundamental transmission mode and propagates toward the two output ports of the TEM cell. With a hybrid junction inserted into a loop connecting the cell output ports, one is able to measure the sum and difference powers and the relative phase between the sum and difference outputs. Systematic measurements of these powers and phases at six different source object positions, based on a well-developed theory, are sufficient to determine the amplitudes and phases of the unknown component dipole moments, from which the detailed free-space radiation pattern of the unknown source and the total radiated power can be determined. Results of simulated theoretical examples and an experiment using a spherical dipole radiator are given to illustrate the theory and measurement procedure.
Date:
October 1982
Creator:
Ma, Mark T. & Koepke, Galen H.
Object Type:
Report
System:
The UNT Digital Library
Phase Equilibria: an Informal Symposium
From introduction: The accurate prediction of phase equilibria plays an important. role in the chemical process industries. A grief overview of final phase equilibria predictive techniques is presented with special emphasis on methods in current use in industry. Areas were better fundamental understanding will lead to improved models are discussed whenever possible.
Date:
January 1983
Creator:
Eaton, B. E.; Ely, James F.; Hanley, H. J. M.; McCarty, Robert D. & Rainwater, James C.
Object Type:
Report
System:
The UNT Digital Library
Excitation of a TEM Cell by a Vertical Electric Hertzian Dipole
From abstract: The excitation of a transverse electromagnetic (TEM) cell by a vertical electric Hertzian dipole is analyzed where the gap between the septum and side wall is assumed to be small. Approximate expressions for the field distribution and characteristic impedance are derived. These expressions are numerically evaluated for some typical geometries, and good agreement with previously published results is shown. The formation also allows a vertical offset for the septum position, thus offering more flexibility of increasing the size of the test area to accommodate larger pieces of test equipment.
Date:
March 1981
Creator:
Wilson, Perry F.; Chang, David C. & Ma, Mark T.
Object Type:
Report
System:
The UNT Digital Library
Cryogenic Fluids Density Reference System: Provisional Accuracy Statement (1980)
Abstract: The improved Density Reference System, the reference densimeter, and the method of determining sample density are described. The uncertainty of the density reference system is + 0.055%. The contribution from the estimated systema -ic error in density was + 0.022%. The estimated uncertainty caused by random error is three times the standard deviation of 0.011% and is based on sixty-three measurements of the densities of saturated liquid methane. The total density uncertainty is taken to be the sum of the systematic and random errors. This applies to the density range of 400 to 480 kg/m at pressures from 0.8 to 4 bar absolute and temperatures between 109 and 128 K. This accuracy statement is expected to apply over ranges of at least 400 to 1000 kg/m3 in density, 77 to 300 K in temperature, and 0.8 to 7 bar in pressure though the accuracy over these ranges has not been verified.
Date:
April 1981
Creator:
Siegwarth, J. D. & LaBrecque, J. F.
Object Type:
Report
System:
The UNT Digital Library
Design and Error Analysis for the WR10 Thermal Noise Standard
From introduction: This note describes the design and error analysis of a WR10 thermal noise power standard. The standard is designed to operate at the boiling point of liquid nitrogen with a noise temperature accurate to plus or minus 1 K.
Date:
December 1983
Creator:
Daywitt, William C.
Object Type:
Report
System:
The UNT Digital Library
Theory of Near-Field Phased Arrays for Electromagnetic Susceptibility Testing
From introduction: The feasibility of using a near-field array for electromagnetic susceptibility testing is studied. The basic objective is to control the element weightings such that a plane wave is generated within the test volume. The basic theory is developed for arbitrary array geometries, and numerical results are obtained for finite planar arrays. A general near-field array synthesis technique is developed, and the technique minimizes the mean square error in the test volume while constraining the array excitations. The constraint prevents large excitations and is useful in minimizing the fields outside the test volume. The basic idea looks promising, but some practical considerations, such as bandwidth and angular scanning limitations, require further theoretical and experimental investigation.
Date:
February 1984
Creator:
Hill, D. A.
Object Type:
Report
System:
The UNT Digital Library
Electromagnetic-Acoustic-Transducer/Synthetic-Aperture System for Thick-Weld Inspection
Abstract: This report describes a system based on electromagnetic-acoustic transducers (EMATs) as an approach to automated nondestructive evaluation of thick weldments (>25 mm). Good signal-to-noise ratios, often a problem with EMATs, were possibTe through careful design of the transducers and associated electronic circuits and the use of signal averaging. At 454 kHz, the transducers produce shear-horizontal waves of approximately 7-mm wavelength in steel. The long wavelength permits determination of through-thickness flaw depth from the amplitudes of scattered ultrasonic waves. A minicomputer controlled transducer positioning and acquired the digitized ultrasonic waveforms for synthetic aperture processing. The synthetic aperture technique further improved signal quality and yielded flaw localization through the weld thickness. Measurements on artificial flaws demonstrated a detectability threshold of 0.5 mm (through thickness) and sizing ability up to 2.5 mm, in agreement with theoretical predictions. Details include the design of the transducers and electronics, as well as the mechanical positioner, signal processing algorithms, and complete computer program listing.
Date:
1984
Creator:
Fortunko, C. M.; Schramm, R. E.; Moulder, J. C. & McColskey, J. D.
Object Type:
Report
System:
The UNT Digital Library
Small Aperture Analysis of the Dual TEM Cell and an Investigation of Test Object Scattering in a Single TEM Cell
Introduction: Small aperture theory is used to investigate the dual TEM cell. Analyzing coupling through an empty versus a loaded aperture leads to a model of dual TEM cell shielding effectiveness measurements. Small obstacle scattering yields results for both the field perturbation and the change in a cell's transmission line characteristics due to the presence of a test object in a TEM cell. In each case, theoretical values are compared to experimental data.
Date:
1984
Creator:
Wilson, Perry F. & Ma, Mark T.
Object Type:
Report
System:
The UNT Digital Library
VOR Calibration Services
from Introduction: The National Bureau of Standards has designed, constructed, and evaluated a standard for the support of very-high-frequency omnidirectional range (VOR) air navigation aids. The standard consists of two instruments: (1) a digital waveform signal generator for the composite VOR audio waveform, and (2) a standard phasemeter based on time series analysis of this waveform. Experimental results, a statistical analysis of them, and the principal software listings are included.
Date:
April 1985
Creator:
Larsen, Neil T.; Vecchia, Dominic F. & Sugar, George R.
Object Type:
Report
System:
The UNT Digital Library
European Footwear Sizes
Description of the differences in European shoe sizes in comparison to American shoe sizes.
Date:
1948
Creator:
Hobbs, Robert B.
Object Type:
Report
System:
The UNT Digital Library
The Fundamental Basis for the Standardization of Electrical Instruments and Meters
Description of the standards used by the electrical power industry for the measurement of the electrical quantities.
Date:
May 7, 1948
Creator:
Silsbee, Francis B.
Object Type:
Report
System:
The UNT Digital Library
Safety for the Household
Introduction: The purpose of this circular is (a) to emphasize the seriousness of certain risks to life and property frequently occurring in or about the home, (b) to give simple methods of care and caution against such hazards, and (c) to stimulate interest in public measures directed toward safety for household and community.
Date:
January 12, 1948
Creator:
Owen, S. J.
Object Type:
Report
System:
The UNT Digital Library
Map of Standard Time Zones of the United States and Adjacent Parts of Canada and Mexico as of January 1, 1948
Map of the United States and surrounding areas with time zones marked and labeled in red. Bodies of water are marked, with depth marked by hatchures, as well as state lines and major cities..
Date:
January 1, 1948
Creator:
Geological Survey (U.S.)
Object Type:
Map
System:
The UNT Digital Library
Nomograms for Obtaining the Compound Composition of Hydrated Limes from the Oxide Analysis
Report with two nomograms presented for rapidly obtaining the compound composition of hydrated limes from the oxide analysis. The general nomogram can be applied to any commercial hydrated lime and gives values accurate to within 0.3 percent while the special nomogram is applicable only to regularly hydrated and highly hydrated dolomitic limes and is accurate to within 0.1 percent.
Date:
December 30, 1949
Creator:
Levin, Ernest M.
Object Type:
Report
System:
The UNT Digital Library
Charts of Compressibility Factors and Charts Showing Quantities Delivered by Commercial Cylinders for Hydrogen, Nitrogen, and Oxygen
Two charts are given for each of the gases hydrogen, nitrogen, and oxygen. The first gives directly the number of standard cubic feet of the gas which a cylinder will deliver. The second chart gives values of the compressibility factor and of the density.
Date:
November 17, 1948
Creator:
Hoge, Harold J.; Meyers, Cyril H. & McCoskey, Robert E.
Object Type:
Report
System:
The UNT Digital Library