Semi-implicit second order finite volume jet stream computations

Semi-implicit, second order temporal and spatial finite volume computations of the flow in a differentially heated rotating annulus are presented. For the regime considered, three cyclones and anticyclones separated by a relatively fast moving jet of fluid or "jet stream" are predicted. Two second order methods are compared with, first order spatial predictions, and experimental measurements. Velocity vector plots are used to illustrate the predicted flow structure. Computations made using second order central differences are shown to agree best with experimental measurements, and to be stable for integrations over long time periods (> 1000s). No periodic smoothing is required to prevent divergence.

Second-order rate region of constant-composition codes for the multiple-access channel

This paper presents an achievable second-order rate region for the discrete memoryless multiple-access channel. The result is obtained using a random-coding ensemble in which each user's codebook contains codewords of a fixed composition. It is shown that this ensemble performs at least as well as i.i.d. random coding in terms of second-order asymptotics, and an example is given where a strict improvement is observed. © 2013 IEEE.

Effect of metal contact's reflection on the effective coupling coefficient of second-order DFB laser diodes

For a second-order DFB-LD, the presence of a metal contact layer can reduce I-st-order radiation. Part of the reflected power is redistributed into guided modes and results in a variation of the effective coupling coefficient kappa(eff). In this paper, we study the effect of the Au top contact's reflection on the kappa(eff) of 2(nd)-order DFB lasers. (C) 2004 Wiley Periodicals, Inc.

Mode coupling between first- and second-order whispering-gallery modes in coupled microdisks

The mode characteristics for two coupled microdisks are investigated by the finite-difference time-domain technique. In the two coupled micodisks, mode coupling between the same order whispering-gallery modes (WGMs) results in coupled WGMs with split mode wavelengths. The numerical results show that the split mode wavelengths of the coupled first- and second-order WGMs can have a crossing point in some cases, which can induce anticrossing mode coupling between them and greatly reduce the mode Q factor of the coupled first-order WGMs. The time variation of mode field pattern shows the transformation between the coupled first- and second-order WGMs. (C) 2007 Optical Society of America

First and second order Raman scattering spectroscopy of nonpolar a-plane GaN

Nonpolar a-plane [(1120)] GaN samples have been grown on r-plane [(1102)] sapphire substrates by low-pressure metal-organic chemical-vapor deposition. The room-temperature first and second order Raman scattering spectra of nonpolar a-plane GaN have been measured in surface and edge backscattering geometries. All of the phonon modes that the selection rules allow have been observed in the first order Raman spectra. The frequencies and linewidths of the active modes have been analyzed. The second order phonon modes are composed of acoustic overtones, acoustic-optical and optical-optical combination bands, and optical overtones. The corresponding assignments of second order phonon modes have been made. (c) 2007 American Institute of Physics.