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.

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.

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.

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.

Review of the progress in research, instrumentation, and service activities of the Spectrochemical Analysis Section from July 1970 to June 1971.

Graphical presentation of K-factors for eight isotherms, published data on the solid-vapor region, and a bibliography of approximately 450 references.

The need for thermodynamic functions of para hydrogen, especially in compressed liquid and dense fluid states, prompts the tabulation of these provisional properties, computed by approximate methods utilizing the new PVT data of these reports. Computation and preparation of the tables is discussed under the following: Approximate Computational Methods; Correlation Methods; Discussion of Errors; and Tables of Functions.

Description of 15 specific systems employing search-type selection principles.

Parameters determined by a least-squares method for the reduced Simon equation and for a new, empirical melting equation.

Summarizes progress to date on the formulation and numerical integration of systems of equations modeling general two-phase flows in a pipe.

Formulas, computer program, and illustrations for a great circle path at ionospheric heights.

Description of a computer program for searching chemical information on magnetic tape.

Modification of an earlier program to remove restrictions in calculating the short or long great circle path.

Graphical presentation of he three-phase region at and near the triple point of parahydrogen.

Design and performance of a new near-zone electric field-strength meter.

Integrated tables of pressure, volume, and temperature for the saturated liquid, from the triple point to the critical point, for oxygen, nitrogen, argon, and parahydrogen.

Technique for varying the coupling of power from far-infrared gas lasers and the design and construction of these lasers.

Tables and graphs constructed for electron probe x-ray spectrometers equipped with crystal changers and calibrated for LiF crystals in angstroms.

Design of a flashlamp-pumped dye laser capable of emitting light pulses 500 ns wide with a risetime of 300 ns.

Permanence and colorimetric properties of signal glass.

Descriptions of the principal changes in the calorimeter and bolometer unit from the WR28 models of a microwave serving as National Bureau of Standards standard for power measurements in the frequency range 50 to 75 GHz.

This paper presents the details to implement a WR15 attentuation and reflection coefficient magnitude measurement system.

The survey covers PVT, thermodynamic, thermal, transport, electrical radiative and mechanical properties.

Report issued by the U.S. National Bureau of Standards discussing the construction of large electromagnetic cells. As stated in the introduction, "this instruction provides information and procedures necessary to fabricate a large transverse electromagnetic (TEM) cell to be used for experimental "electromagnetic interference" (EMI) evaluation studies" (p. 1). This report includes illustrations, and photographs.