Evaluation of a standard test method for total hemispherical emittance of surfaces from 293K to 1673K

Emittance tests were made on samples of Rene' 41, Haynes 188, and Inconel 625 superalloy metals in an evaluation of a standard test method for determining total hemispherical emittances of surfaces from 293 K to 1673 K. The intent of this evaluation was to address any problems encountered, check repeatability of measured emittances, and gain experience in use of the test procedure. Five test specimens were fabricated to prescribe test dimensions and surfaces cleaned of oil and residue. Three of these specimens were without oxidized surfaces and two with oxidized surfaces. The oxidized specimens were Rene' 41 and Haynes 188. The tests were conducted in a vacuum where the samples were resistance-heated to various temperature levels ranging from 503 K to 1293 K. The calculated results for emittance, in the worst case, were repeatable to a maximum spread to + or - 4% from the mean of five sets of plotted data for each specimen

Approximation Techniques for Planar Periodic Structures

The rigorous calculation of electromagnetic properties of periodic meshes using moment methods requires considerable algebraic work and computer resources. In this paper, a number of easy to use approximation techniques for analyzing thin structures with square, rectangular, and circular holes are presented. Formulas for the effective impedante of these meshes are described which can easily take into account oblique incidence and the presence of a dielectric substrate. In addition, techniques for analyzing more complex-shaped apertures such as a cross are discussed. These methods are more accurate than existing approximation techniques and can be applied to a wide range of situations that could not be handled before

A brazing process for Cb-1Cr heat receiver tubes Final report

Zirconium-based alloy brazing of internal fins of Cb-1Zr foil to Cb-1Zr heat receiver tube

Evaluation tests of platinum resistance thermometers for a cryogenic wind tunnel application

Thirty-one commercially designed platinum resistance thermometers were evaluated for applicability to stagnation temperature measurements between -190 C and +65 C in the Langley Research Center's National Transonic Facility. Evaluation tests included X-ray shadowgraphs, calibrations before and after aging, and time constant measurements. Two wire-wound low thermal mass probes of a conventional design were chosen as most suitable for this cryogenic wind tunnel application

Income Inequality in U.S. Metropolitan Areas: Which Areas Have the Greatest Inequality and Why?

In recent years, much focus has been placed on the high and growing level of income inequality in the United States. This composition begins to fill a void in the existing literature by examining specific urban areas that have particularly high levels of inequality and the characteristics that factor into inequality. In this paper, I construct a qualitative model for a particularly unequal metropolitan area. I then apply the model to a set of U.S. metros that are among the most unequal in the country and share a particular set of characteristics consistent with the model

The dyadic green's function for an infinite moving medium

Derivation of dyadic Green function for electromagnetic field in moving medium using Minkowski theory and method of Fourier analysi

Common Factors in Unplanned Cesarean Section

Obstetrical delivery by cesarean section is a prevalent form of delivery. Whether clinically indicated or by maternal request, cesarean delivery rates in the United States have risen to account for over a third of all deliveries. Cesarean section procedures are often clinically indicated and occur because of fetal factors, but they can also be elected by maternal request. The aims of this study are to analyze the frequency of the factors in the study questions that are associated with unplanned cesarean section procedures and to compare the frequency of these factors per cesarean section with the time of day the cesarean section procedure occurred. Based on the results of this study, there is no correlation between the discussed constant factors and the time of day, meaning the presence or absence of any factor will not accurately predict the time the cesarean section will occur. In this sample, the most frequent constants were as follows: Caucasian females, gravida one para one, full term pregnancy, spontaneous labor type ,no augmentation, fetal indications, and between the times of 1200-1359 and 2200-2359. In summary, the information learned in the frequencies will help to further identify patients at increased risk for unplanned cesarean sections

Elf: computer automation and error correction for a microwave network analyzer

A microwave measurement system has been developed that combines a personal computer (PC) and an conventional vector network analyzer to yield a full complex-error-corrected automatic network analyzer. The system consists of a Hewlett-Packard HP 8410C network analyzer, an HP 8350B sweep oscillator, and an IBM PC. A program called Elf runs on the PC, performing calibration and measurement algorithms and providing a flexible, menu-oriented user interface. The system, when calibrated, achieves a worst-case measurement error vector of magnitude ≤ 0.02 for transmission and reflection coefficient measurements over the 2-12.4-GHz frequency range and has a measurement speed of three frequency points/s. Elf provides an inexpensive method for upgrading the HP 8410 to achieve the high accuracy of an automatic network analyzer