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In this paper, heat transfer in a battery pack located in an air duct is studied numerically. Lithium-ion batteries are widely used in electronic devices, and various companies are trying to improve their capacity. One of the problems is their heating during operation. Therefore, in this work, a lithium-ion battery pack in a rectangular case filled with a phase change material (PCM) is numerically investigated. The battery and the PCM enclosure are located in a duct with laminar air flow. This study is performed for Reynolds numbers (Re) of 50 and 250 for one hour. COMSOL Multiphysics software and finite element method are used to solve the governing equations. The results of this study show that as the time increases, the amount of melt PCM around the battery decreases continuously. Re = 250 results in more solid PCM at different times than Re = 50. Also, at Re = 250, the molten PCM is converted to solid PCM in a shorter time. The average temperature of the battery is increased and then decreased over time. In addition, the battery temperature and the trend of increasing the battery temperature decrease with Re. By increasing Re, the temperature of the exhaust air decreases. [ABSTRACT FROM AUTHOR]

As small solid particles are mixed in gas flow in a horizontal pipe, the particles are sometimes long suspended downstream due to dynamic interaction between two phases in turbulent states. Dunes of such particles are naturally formed at the bottom of the pipe in case of heavy flow rate of particles, and the dunes rather help the particles with suspension further downstream. In this study, PTV has been applied for measurement of such particles floating inside a horizontal pipe behind a synthetic dune. Time-resolved PTV analysis of the particle behavior in the section perpendicular to the mainstream has revealed that long-suspended particles keep floating with fountain like convection pattern inside the circular pipe, which consists of ascending flow at the center of the pipe, bouncing flow at the wall, and downwash at the oblique part. The present paper shows their dynamic statistics of the particle behavior for the cross-sectional distributions of concentration, velocity vector, and acceleration vector. [ABSTRACT FROM AUTHOR]

For the design of large dipole switched array antennas, an approximate input impedance model for a dipole in an array environment is extended. The objective of the model is to generate reasonably accurate results in a minimum of time. The extension allows for the application of thick dipoles. The extended approximate model is compared to a three-term dipoledipole coupling model and full-wave analysis results. The extended approximate model gives reasonably accurate results for dipole distances down to 0.20λ for unequal length dipole elements and down to 0.35λ for equal length dipole elements. The three-term model improves the accuracy further at the expense of a more complex model. Both models generate results in times that are orders of magnitude smaller than when a full wave analysis program is being employed. [ABSTRACT FROM PUBLISHER]

Pendry et al have proposed an electromagnetical invisibility cloak based on transformation optic approach [1]. The characteristics of the cloaking material unavoidably require anisotropy or inhomogeneity of the constitutive parameters and present a singularity on the inner boundary. In our paper, we give a deep insight into the linear transformation and try to look for another kind of coordinate transformation to make the structure in favor of practically material layering, meaning that the permittivity and permeability of the medium do not change rapidly. Full-wave simulations of the cylindrical version of this cloaking structure are employed to demonstrate the lower performance degradation of our optimization design than the original linear transformation. In addition, our work also shows that cloaking performance is not especially sensitive to material perturbations. [ABSTRACT FROM PUBLISHER]

The NSLS X28C white-light beamline is being outfitted with a focusing mirror in order to increase, as well as control, the x-ray intensity at the sample position. The new mirror is a 50 mm × 100 mm × 1100 mm single crystal silicon cylindrical 43.1mm radius substrate bendable to a toroid from infinite to 1200 m radius. The unique feature of this mirror system is the dual use of Indalloy 51 as both a mechanism for heat transfer and a buoyant support to negate the effects of gravity. The benefit of the liquid metal support is the ability to correct for minor slope errors that take the form of a parabola. A bobber mechanism is employed to displace the fluid under the mirror +/- 1.5 mm. This allows RMS slope error correction on the order of 2 urad. The unique mounting of the mirror ensures the contributions to slope error from errant mechanical stresses due to machining tolerances are virtually non-existent. After correction, the surface figure error (measured minus ideal) is <= 0.5 urad rms. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Lateral confinement for cylindrical micro-resonator light emitters improves the ratio of the number of the axial resonant modes to the number of the spontaneous emitting lateral modes. We have observed resonator behaviour of cylindrical microstructures as ZnO micro-pillars and glass-rods, whose lateral surfaces were coated with coaxial Bragg reflectors. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]