The nonlinear stability of a heavy rigid plate supported by flexible columns

A heavy rigid platform is supported by thin elastic legs. The governing equations for large deformations are formulated and solved numerically by homotopy and quasi-Newton methods. Nonlinear phenomena such as nonuniqueness, catastrophe and hysteresis are found. A global critical load for nonlinear stability is introduced.     

Magnetohydrodynamic flow past a porous rotating disk in a circular magnetic field

This paper studies the effects of a circular magnetic field on the flow of a conducting fluid about a porous rotating disk. Using modern quasi-Newton and globally convergent homotopy methods, numerical solutions are obtained for a wide range of magnetic field strengths, suction and injection velocities and Alfven and disk speeds. Results are presented graphically in terms of three non-dimensional parameters. There is excellent agreement with previous work and asymptotic formulae.     

A Tunneling Model for Afterglow Suppression in CsI:Tl,Sm Scintillation Materials

Combined radioluminescence, afterglow and thermoluminescence experiments on single-crystal samples of co-doped CsI:Tl,Sm suggest that samarium electron traps scavenge electrons from thallium traps and that electrons subsequently released by samarium recombine non-radiatively with trapped holes, thus suppressing afterglow. Experiments on single crystals support the inference that electrons tunnel freely between samarium ions and are trapped preferentially as substitutional Sm⁺ near V_KA(Tl⁺) centers where non-radiative recombination is the rate-limiting step. Afterglow in microcolumnar films of CsI:Tl,Sm is enhanced by inhomogeneities which impede tunneling between samarium ions, but is partly suppressed by annealing.     

Experimental characterization of flow unsteadiness in the centerline plane of an Ahmed body rear slant

This study presents the results of an experimental analysis of the unsteady features of the flow around the rear part of an Ahmed body with rear slant angle of 25°. This analysis focuses on the 3D separated and reattaching zone that develops on the rear slanted surface and provides new information, improving the understanding of the flow unsteadiness. Flow investigations were performed using particle image velocimetry, hot wire anemometry, and unsteady flush-mounted pressure transducers in the plane of symmetry above the rear slanted surface. Spectral analysis and proper orthogonal decomposition of the output signals show the emergence of low frequency unsteadiness and high frequencies activity. Characteristic timescales of both instabilities are provided and the physical effect of the low frequency unsteadiness is related to a flapping motion of the separated shear layer, while the high frequency activity is associated with a large-scale vortex emission. The results focus on the centerline plane of the rear slant and more specifically demonstrate relevant similarities with the unsteady mechanisms of 2D recirculated flow.     

A Re-evaluation of Factors Controlling the Nature of Complementary Hydrogen-Bonded Networks

The energy profiles of hydrogen-bonded heterocyclic aromatics have been decomposed into atomistic energy contributions using the Interacting Quantum Atoms (IQA) method. The resulting energy contributions have been sequenced by the Relative Energy Gradient (REG) approach to determine their influence upon the shape of these energy profiles. The results show inadequacies in Jorgensen's secondary interaction hypothesis (SIH). A novel method of finding a condensed analogy for the interaction between the molecules is presented. The findings of this work further doubt the validity of the SIH, and reinforce previous warnings against its misguided use.     

The ϱ−ππ coupling constant in lattice gauge theory

We present a method for studying hadronic transitions in lattice gauge theory which requires computer time comparable to that required by recent hadron spectrum calculations. This method is applied to a calculation of the decay ?→ππ.     

On the convergence of reflectionless approximations to confining potentials

The construction of reflectionless potentials supporting a prescribed spectrum of Schrödinger bound states is discussed and related to the inverse problem for confining potentials. A simple formula is derived for the Jost solution in a one-dimensional reflection-less potential with N bound states. This leads to compact expressions for the potential and the bound-state wavefunctions in terms of the bound-state energies. For symmetric potentials, N-fold product formulas are obtained for bound-state wavefunctions and their slopes at the origin. Corresponding quantities in a confining potential are given by infinite products. Comparison of the finite-product and infinite-product expressions allows a demonstration of the convergence of the reflectionless results to the confining potential results as N → ∞. Several sum rules satisfied by the reflectionless potential at the origin are applied to numerical studies of convergence.     

Integration, processing and performance of low power thermally tunable CMOS-SOI WDM resonators

Ring waveguide resonating structures with high quality factors represent a key component in silicon photonic links. We demonstrate experimentally and validate numerically spectral tuning with a high efficiency of photonic ring structures when manufactured in a commercial 130?nm SOI CMOS technology with localized removal of back-side substrate using silicon micromachining methods. A comprehensive analysis is reported on the thermal tuning efficiency of tunable ring devices as a function of the ring’s size, type of thermal tuner and amount of back- and front-side post-CMOS micromachining. We further propose a path to maintain a high tuning efficiency of photonic devices with partially or completely removed SOI silicon substrate upon their hybridization to electronic driver chips. Such a platform opens up additional options for increased on-chip system functionality and dense integration in 3-D.