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Interactive FORTRAN Programs for Micro Computers to Calculate the Thermophysical Properties of Twelve Fluids (MIPROPS)
From abstract: The thermophysical and transport properties of selected fluids have been programmed in FORTRAN 77 which is available for micro computers. The input variables are any two of P, p, T (pressure, density, and temperature) in the single phase regions, and either P or T for the saturated liquid or vapor states. The output is pressure, density, temperature, internal energy, enthalpy, entropy, specific heat capacities (Cp and Cv), speed of sound and, in most cases, viscosity, thermal conductivity and dielectric constant.
Date:
May 1986
Creator:
McCarty, Robert D.
Object Type:
Report
System:
The UNT Digital Library
Transparent Metrology of Signal to Noise Ratios of Noisy Band-Limited Digital Signals
From abstract: I propose the use of a template method for quantitative, correct, and transparent measurement of signal power to additive noise power ratios (SNR) of digital signals and systems under full operating conditions. Outer guard chips of digital templates hold intersymbol interference fixed on inner target chips in realizations of the respective template patterns in traffic. The proposed template method needs to be developed and proven as a potentially valuable metrology capability; it can be especially important for real time online performance assessment and monitoring of digital communication systems.
Date:
June 1985
Creator:
Halford, Donald
Object Type:
Report
System:
The UNT Digital Library
Automated Measurement of Frequency Response of Frequency-Modulated Generators Using the Bessel Null Method
From abstract: This paper describes a Bessel null technique to measure the frequency response of a frequency-modulated rf carrier and a program to automate frequency response measurements of signal generators with output frequencies from 0.450 to 2000 MHz. The measurements obtained using this technique are more precise than those obtained by a highly trained technician using a manual system.
Date:
March 1986
Creator:
Major, J. R.; Livingston, E. M. & Adair, Robert T.
Object Type:
Report
System:
The UNT Digital Library
A Statistical Characterization of Electroexplosive Devices Relevant to Electromagnetic Compatibility Assessment
Abstract: Electroexplosive devices (EEDs) are electrically fired explosive initiators used in a wide variety of applications. The nature of most of these applications requires that the devices function with near certainty when required and remain inactive otherwise. Recent concern with pulsed electromagnetic interference (EMI) and nuclear electromagnetic pulse (EMP) made apparent the lack of methodology for assessing EED vulnerability. A new and rigorous approach for characterizing EED firing levels is developed in the context of statistical linear models and is demonstrated in this paper. We combine statistical theory and methodology with thermodynamic modeling to determine the probability that an EED, of a particular type, fires when excited by a pulse of a given width and amplitude. The results can be applied to any type of EED for which the hot-wire explosive binder does not melt below the firing temperature. Included are methods.for assessing model validity and for obtaining probability plots, called "Firing Likelihood Plots". A method of measuring the thermal time constant of an EED is given. This parameter is necessary to evaluate the effect of a train of pulses. These statistical methods are both more general and more efficient than previous methods for EED assessment. The results provide information …
Date:
May 1986
Creator:
Friday, Dennis S. & Adams, John W.
Object Type:
Report
System:
The UNT Digital Library
A Study of Techniques for Measuring the Electromagnetic Shielding Effectiveness of Materials
Abstract: Shielding effectiveness relates to a material's ability to reduce the transmission of propagating fields in order to electromagnetically isolate one region from another. Because a complex material's shielding capability is difficult to predict, it often must be measured. A number of measurement approaches are studied including the use of a shielded room, coaxial transmission line holders, time domain signals, the dual TEM cell, and an apertured TEM cell in a reverberation chamber. In each case, we consider the system's frequency range, test sample requirements, test field type, dynamic range, time required, analytical background, and present data taken on a common set of materials.
Date:
May 1986
Creator:
Wilson, Perry F. & Ma, Mark T.
Object Type:
Report
System:
The UNT Digital Library
Fitness-for-Service Criteria for Assessing the Significance of Fatigue Cracks in Offshore Structure
Abstract: Results of a research program to develop fitness-for-service criteria for assessing the significance of fatigue cracks in offshore structures are presented in five papers. Each paper describes the goals and approaches to a specific task and details the results of the study.
Date:
August 1985
Creator:
Cheng, Yi-Wen
Object Type:
Report
System:
The UNT Digital Library
Site Attenuation
Abstract: Site attenuation is a measure of performance of an open test site used at frequencies below about 1 GHz for antenna calibration and equipment emission and susceptibility testing. These sites typically consist of a large, obstruction-free ground plane and the hemisphere above it. Site attenuation of an ideal site is calculated and compared to data measured using the 30 m by 60 m NBS ground screen.
Date:
November 1985
Creator:
FitzGerrell, R. G.
Object Type:
Report
System:
The UNT Digital Library
Finline Diode Six-Port: Fundamentals and Design Information
Abstract: The preliminary design and testing of a planar circuit six-port with diode detectors is described. The planar circuit medium was chosen to be finline, and all preliminary work was done in WR-42 waveguide (18-26.5 GHz). The finline substrate was alumina, and initially commercial beam-lead diodes were bonded to the finline metalization. The goal is to design an integrated circuit which could be fabricated on one chip (with diode detectors) and used as part of a six port network analyzer in the waveguide bands above 18 GHz. Initial designs proved to b unsatisfactory because of high losses and reflections. Most of the problems have b en solved, and a usable integrated finline circuit is a good possibility for a millimeter wave six-port.
Date:
December 1985
Creator:
Weidman, Manly P.
Object Type:
Report
System:
The UNT Digital Library
Design, Evaluation, and Use of a Reverberation Chamber for Performing Electromagnetic Susceptibility/Vulnerability Measurements
Abstract: This report presents the results of work at the National Bureau of Standards, Boulder, Colorado, to carefully evaluate, document, develop (when necessary), and describe the methodology for performing radiated susceptibility/vulnerability measurements using a reverberation chamber. The report describes the reverberation chamber theory of operation, construction, evaluation, functional operation, and use for performing immunity measurements. It includes an estimate of measurement uncertainties derived empirically from test results and from comparisons with anechoic chamber measurements. Finally, it discusses the limitations and advantages of the measurement technique to assist potential users in determining the applicability for this technique to their electromagnetic compatibility (EMC) measurement needs.
Date:
April 1986
Creator:
Crawford, M. L. & Koepke, Galen H.
Object Type:
Report
System:
The UNT Digital Library
Linear Gain: Standard Antennas Below 1000 MHz
Abstract: Gain and antenna parameters related to input impedance are calculated using a computer program called HVD6. This program uses well documented equations to compute these parameters for gain-standard antennas used in relative-gain or gain-transfer measurements at frequencies below 1000 MHz. The utility of this program is that it calculates gain patterns and input impedances for linear dipoles above perfect or imperfectly conducting plane ground and in free space, and for monopoles on perfectly conducting plane ground. Examples are included to illustrate the use of the program. Uncertainties in the calculated parameters are estimated to be less than those of the measured parameters.
Date:
May 1986
Creator:
FitzGerrell, R. G.
Object Type:
Report
System:
The UNT Digital Library
Electromagnetic Compatibility and Interference Metrology
From abstract: The material included in this report is intended for a short course on electromagnetic compatibility/interference (EMC/EMI) metrology to be offered jointly by the staff of the Fields Characterization Group (723.03) and the Interference Characterization Group (723.04) of the Electromagnetic Fields Division (723). The purpose of this short course is to present a review of some of the radiated EMC/EMI measurement methods, to which the National Bureau of Standards (NBS) at Boulder, Colorado, has made significant contributions during the past two decades.
Date:
July 1986
Creator:
Ma, Mark T. & Kanda, M.
Object Type:
Report
System:
The UNT Digital Library
Refracted-Ray Scanning (Refracted Near-Field Scanning) for Measuring Index Profiles of Optical Fibers
From introduction: The purpose of this Technical Note is to describe refracted-ray scanning in detail, to analyze it as a measurement system, to document a particular system for implementing it, and to show some exemplary results.
Date:
August 1981
Creator:
Young, Matt
Object Type:
Report
System:
The UNT Digital Library
Input Impedance of a Probe Antenna Exciting a TEM Cell
Abstract: The input impedance of a probe antenna exciting a transverse electromagnetic (TEM) transmission line cell is formulated by a variational approach. The formulation also utilizes the results from a previous work on the field distribution inside a TEM cell excited by a vertical electrical Hertzian dipole. The final result of imoedance is shown to consist of two distinct terms, which are respectively contributed by the ordinary rectangular waveguide and the gap perturbation. Numerical results for both the real and imaginary parts of the impedance are given. The resistive part is found to be proportional to the square of the probe length, and the reactive part largely capacitive.
Date:
April 1982
Creator:
Wilson, Perry F.; Chang, David C. & Ma, Mark T.
Object Type:
Report
System:
The UNT Digital Library
Picosecond Time Difference Measurements Utilizing CAMAC-Based ANSI/IEEE-488 Data Acquisition Hardware : Operating Manual IE3, Version 1.0
Abstract: Automated time-difference measurements at the picosecond level have been achieved. The system described combines the best properties of three common methods: the single heterodyne measurement technique, the frequency divider, and the dual-mixer time-difference measurement system. This particular system combines two instrumentation standards, ANSI/IFEE-583 and ANSI/IEEE-488 with new, modular dual-mixer time-difference measurement hardware. The modular, standardized hardware together with the new measurement techniques permit the data acquisition modules to be contained in a standard CAMAC crate. This system, along with an external controller, is capable of measuring eiqht clocks, at the present time, and is expandable to twenty-four clocks with modified software and additional measurement modules. The system noise performance is described by a (rT = 3 x 10^-12 t^-1 for time difference measurements.
Date:
August 1983
Creator:
Glaze, D. J. & Stein, S. R.
Object Type:
Report
System:
The UNT Digital Library
An Electric and Magnetic Field Sensor for Simultaneous Electromagnetic Near-Field Measurements -- Theory
Abstract: This paper describes the theory of a single sensor to perform simultaneous electric and magnetic near-field measurements. The theory indicates that it is possible to obtain the magnetic-loop and electric-dipole currents using a loop terminated with identical loads at diametrically opposite points. The theory also indicates that it is possible to obtain an ideal load impedance for achieving equal electric and magnetic field responses of the loop. Preliminary experiments have been performed using plane waves to verify these results. Key words: electric field, electromagnetic interference, electromagnetic radiation, loop, magnetic field, near fields.
Date:
April 1983
Creator:
Kanda, Motohisa
Object Type:
Report
System:
The UNT Digital Library
The Characteristics of Iris-Fed Millimeterwave Rectangular Microstrip Patch Antennas
From introduction: The fabrication of various iris-fed millimeterwave rectangular microstrip patch antennas is described. A model is proposed to describe the iris-fed antenna. Irises ranging in size from 15 percent of the area of the patch to the fully open waveguide are used to couple energy into the antenna. Resonance of the antenna is observed to be insensitive to the size of the iris for irises up to 115 percent of the size of the patch. A study is also made of th? relationship of coupling to the antenna as a function of position of the iris with respect to the transverse plane of the waveguide, the iris always being centered with respect to the patch. In general, the antenna has a VSWR in the waveguide feed on the order of 5:1 at resonance, except for the fully open waveguide which gives rise to a VSWR of 2.9:1 at resonance. Far-field antenna power patterns are observed to be quite broad with H-plane beamwidths on the order of 1300. Maximum antenna gain is seen to be 4.5 dBi with 3 dBi typical. An initial study is made of the microstrip patch antenna fed from a longitudinal waveguide wall. Results indicate that …
Date:
October 1983
Creator:
Greenlee, D. H.; Kanda, Motohisa & Chang, David C.
Object Type:
Report
System:
The UNT Digital Library
Optical Time-Domain Reflectometer Performance and Calibration Studies
from Introduction: The measurement accuracy of the optical time-domain reflectometer (OTDR) is restricted in some applications by a limited operational dynamic range and by a lack of standardized test procedures. In an effort to better understand these restrictions, we have measured the range of linearity of some avalanche photodiodes used as backscatter detectors. Also, the effect of input launch conditions is examined and a possible standardized OTDR test procedure is proposed. Using these suggestions, we have made comparisons between attenuation values determined by cutback and backscatter methods and found that good agreement is possible. Finally, some methods are described for checking the response. linearity of OTDR systems.
Date:
June 1983
Creator:
Danielson, B. L.
Object Type:
Report
System:
The UNT Digital Library
Reference Flat Pulse Generator
Introduction: A reference step-like pulse generator is described which has been developed at NBS. This generator can be used for accurately characterizing the step response of various kinds of trap ient recording equipment (oscilloscopes, waveform recorders, transient digitizers, etc.). Basic design principles are given as well as complete circuit diagrams and descriptions. An analysis of the output stage of the generator is presented together with the circuit models for developing a time-domain computer simulation program using extended- SCEPTRE. Preliminary specifications indicate that the NBS Reference Flat Pulse Generator provides a negative-going reference transition duration (90 to 10 percent) of 600 ps, *20 percent with baseline perturbations of less than *2 percent for less than 5 ns.
Date:
October 1983
Creator:
Andrews, J. R.; Bell, B. A. & Baldwin, E. E.
Object Type:
Report
System:
The UNT Digital Library
Introduction to STARPAC: the Standards Time Series and Regression Package
From preface: STARPAC documentation is being published as a series of Technical Notes. This Note is the first in the series. It gives an overview of the STARPAC library, defines conventions used in the documentation, provides an example using STARPAC subroutines, and presents general background material. This Note includes information which is essential for using the STARPAC library, and users should be familiar with its contents before attempting to use any STARPAC subroutine.
Date:
October 1983
Creator:
Donaldson, Janet R. & Tryon, Peter V.
Object Type:
Report
System:
The UNT Digital Library
Nonlinear Least Squares Regression Using STARPAC: The Standards Time Series and Regression Package
From preface: This Note documents 16 subroutines for nonlinear least squares regression. Twelve of these compute the least squares estimates, performing either weighted or unweighted analysis with either numerically approximated or user-supplied (analytic) derivatives. The other four are user-callable subroutines for two procedures used within the estimation code: the first selects optimum step sizes for approximating the partial derivatives of the model; and the second checks the validity of a user-supplied derivative subroutine.
Date:
October 1983
Creator:
Donaldson, Janet R. & Tryon, Peter V.
Object Type:
Report
System:
The UNT Digital Library
An Equation of State for Fluid Ethylene
Abstract: A thermodynamic property formulation for ethylene, developed as a part of a joint industry-government project, is presented. The formulation includes an equation of state, vapor pressure equation, and equation for the ideal gas heat capacity. The coefficients were determined by a least squares fit of selected experimental data. Comparisons of property values calculated using the equation of state with measured values are given. The equation of state is not valid in the critical region (pc + 0.3 pc for temperatures of Tc + 0.05 Tc). Errors on the order of 20 percent for derived properties and 10 percent for density may be encountered near the critical point. Tables of the thermodynamic properties of ethylene for the liquid and vapor phases for temperatures from the freezing line to 450 K with pressures to 40 MPa are presented. The equation of state and its derivative and integral functions for calculating thermodynamic properties are included. Estimates of the accuracy of calculated properties are given. A guide for use of computer programs for the calculation of thermodynamic properties of ethylene with listings of subprograms and a sample program to illustrate the use and results of the program are included.
Date:
July 1981
Creator:
McCarty, Robert D. & Jacobsen, Richard T.
Object Type:
Report
System:
The UNT Digital Library
Measurement of Optical Fiber Bandwidth in the Frequency Domain
Abstract: The design, evaluation, and performance of a system for determining the magnitude of the transfer function (hence, the bandwidth) of a multimode optical fiber are presented. The system operates to about 1450 MHz using a tracking generator/spectrum analyzer combination for narrowband detection. It is constructed, almost entirely, from commercially available components. The system is less complex and easier to use than an equivalent time domain system and the measurement precision is comparable. Background information on time and frequency domain specifications, fiber bandwidth limitations, and alternate frequency domain techniques is also presented.
Date:
September 1981
Creator:
Day, G. W.
Object Type:
Report
System:
The UNT Digital Library
Thermophysical Properties of Isobutane from 114 to 700 K at Pressures to 70 MPa
Abstract: Using a modified version of the nonanalytic equation of state, thermophysical properties of isobutane are derived from physical properties data and are tabulated at integral temperatures over the entire range of fluid states from 114 to 700 K along isobars at pressures to 70 MPa. Results include dielectric constants, densities, enthalpies, entropies, equation of state, internal energies, isobars, isochores, isotherms, Joule-Thomson inversion, heats of vaporization, melting line, orthobaric densities, specific heats, sound velocities, vapor pressures, and virial coefficients. In addition to the equation of state, equations are given for vapor pressures, orthobaric vapor and liquid densities, ideal gas properties, second virial coefficients, dielectric constants, heats of vaporization, melting pressures, and orthobaric liquid specific heats, enthalpies, and entropies. Several new sets of data have been used in this correlation; comparisons between experimental and calculated values are given.
Date:
January 1982
Creator:
Goodwin, Robert D. & Haynes, William M.
Object Type:
Report
System:
The UNT Digital Library
Electrical Properties of Materials and Their Measurement at Low Temperatures
Abstract: A review is given of the electrical resistance of materials at cryogenic temperatures. Measurement techniques, the data base, and uses of the data are presented. The emphasis is on metals and alloys of technological importance; a toxic which covers a large range of materials. Similarly, the treatment of theory and of measurement techniques is primarily for the user interested in the more practical aspects of the subject. In every instance, however, references are given which allow the reader to pursue the subject at any level.
Date:
March 1982
Creator:
Fickett, F. R.
Object Type:
Report
System:
The UNT Digital Library