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The greybody factor of massless, uncharged scalar fields is studied in the background of cylindrically symmetric spacetimes, in the low-energy approximation. We discuss two cases. In the first case we derive analytical expression for the absorption probability when the spacetime is kinetically coupled with the Einstein tensor. In the second case we do the analysis in the absence of the coupling constant. For this purpose we analyze the wave equation which is obtained from Klein-Gordon equation. The radial part of the wave equation is solved in the form of the hypergeometric function in the near horizon region, whereas in the far region the solution is of the form of Bessel's function. Finally, considering continuity of the wave function we smoothly match the two solutions in the low-energy approximation to get the formula for the absorption probability. [ABSTRACT FROM AUTHOR]

Clinching joint quality and functionality may have undesirable features because of the choice of the forming process parameters. In fact, there are different factors controlling the mechanical connection strength such as the tools' geometry and the joint final shape. This paper presents the implementation of the Taguchi-based Grey optimization of the mechanical clinching with fixed dies for dissimilar materials (Aluminum alloy 7075 and Mild Steel) to derive the optimal process parameters combination that leads to a high strength connection subjected to multiple characteristics, namely, the bottom thickness, the interlock length, and the neck thickness of the joint. LS-DYNA explicit and implicit finite element (FE) software was used to simulate the process in order to evaluate the joint strength by loading the sheets vertically. Taguchi's L27 orthogonal array design and the notion of signal-to-noise (S/N) ratio were utilized to obtain the objective function. Analysis of variance (ANOVA) showed the importance of factors on overall output. The output of the study provided the optimal geometrical parameters of the punch, die, and blank holder. Indeed, the die groove height, die diameter, punch diameter, punch corner radius, and clearance between punch and blank holder were found to be the most influential parameters on the bottom and neck thicknesses. In addition, the output indicated that when bottom thickness or neck thickness increased, the interlock decreased. [ABSTRACT FROM AUTHOR]

Calibration of infrared radiation thermometers at non-unity emissivity settings is a poorly solved problem for establishment of traceability to meet user needs, for instruments with both fixed and variable emissivity setting functions. A variable-temperature gray-body radiator having a constant value of emissivity independent of both wavelength and temperature can be a perfect tool for the calibration purpose. In this paper, two types of high-transmittance optical neutral density filters, one utilizing a rotating-sector optical chopper, and another of a wire-mesh type, are shown to perform well with a precise transmittance between 90 % and 100 % in the wide infrared wavelength range. These optical filters in combination with a blackbody cavity traceable to ITS-90 can realize reliable gray-body radiation. These methods are applied successfully to several models of infrared thermometers operated in the emissivity correction mode. [ABSTRACT FROM AUTHOR]