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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]

Abstract: Extremization of a weak form for the continuum energy conservation principle differential equation naturally implements fluid convection, radiation and flux Robin boundary conditions associated with unsteady heat transfer. Combining a spatial semi-discretization via finite element trial space basis functions with time-accurate integration for computing. Closure for grey body radiation is a newly derived radiosity formulation generating piecewise discontinuous solutions, while that for natural-forced-mixed convection heat transfer is extracted from the literature. Algorithm performance, mathematically predicted by asymptotic convergence theory, is subsequently validated with data obtained in 24h diurnal field experiments for 1/8’’ and 1’’ thick aluminum plates. [Copyright &y& Elsevier]

The (3 + 1) -dimensional Einstein-Gauss-Bonnet theory of gravity which breaks the Lorentz invariance in a theoretically consistent and observationally viable way has been recently suggested by Aoki, Gorji and Mukohyama [5]. Here we calculate grey-body factor for Dirac, electromagnetic and gravitational fields and estimate the intensity of Hawking radiation and lifetime for asymptotically flat black holes in this theory. Positive coupling constant leads to much smaller evaporation rate and longer life-time of a black hole, while the negative one enhances Hawking radiation. The grey-body factors for electromagnetic and Dirac fields are smaller for larger values of the coupling constant. [ABSTRACT FROM AUTHOR]

We have carried out high-resolution observations with the Atacama Large Millimeter/Submillimeter Array (ALMA) of continuum emission from the Orion Kleinmann–Low (KL) region. We identify 11 compact sources at ALMA band 6 (245 GHz) and band 7 (339 GHz), including the Hot Core, Compact Ridge, SMA1, IRc4, IRc7, and a radio source I (Source I). A spectral energy distribution (SED) of each source is determined by using previous 3 mm continuum emission data. Physical properties such as size, mass, hydrogen number density, and column density are discussed based on the dust graybody SED. Among 11 identified sources, Source I, a massive protostar candidate, is a dominant energy source in Orion KL. We extensively investigate its SED from centimeter to submillimeter wavelengths. The SED of Source I can be fitted with a single power-law index of 1.97, suggesting an optically thick emission. We employ the H− free–free emission as an opacity source of this optically thick emission. The temperature, density, and mass of the circumstellar disk associated with Source I are constrained by the SED of H− free–free emission. Still, the fitting result shows a significant deviation from the observed flux densities. Combined with the thermal dust graybody SED to explain excess emission at higher frequency, a smaller power-law index of 1.60 for the H− free–free emission is obtained in the SED fitting. The power-law index smaller than two would suggest a compact source size or a clumpy structure unresolved with the present study. Future higher resolution observations with ALMA are essential to reveal more detailed spatial structure and physical properties of Source I. [ABSTRACT FROM AUTHOR]