Connecting mem-models with classical theories

A family of mem-models, including the mem-dashpots, mem-springs, and most recently, mem-inerters, is emerging as a new and powerful way of capturing complex nonlinear behaviors of materials and systems under various types of dynamic loads involving different frequency, amplitude, and loading histories (e.g., hysteresis). Under the framework of nonlinear state-space representation and hybrid dynamical systems, mem-springs may be formulated to effectively represent an inherent degradation of material state. It is shown in this study, for the first time, how the absement (time integral of strain/displacement), a signature state variable for a mem-spring, can be connected with the damage variable, a key quantity in continuum damage mechanics. The generalized momentum (time integral of stress), on the other hand, is shown to be efficient in modeling strain ratcheting via the concept of mem-dashpot. It is also shown in this study, for the first time, how two formulations of the memcapacitive system models (for mem-springs) are special cases of the Preisach model.

     

Thermophysical properties of o-ring elastomers at pressures to 200 MPA

Abstract

Results on the temperature- and pressure dependence of the specific volume, thermal expansivity and compressibility of elastomeric compounds are reported.     

Impact of coating ageing on susceptibility to high-power damage at fibre bends

For the first time a link is shown between the time to failure, the initial equilibrium temperature and high-power damage coating degradation at failure. A fibre that is sensitive to high-power damage has been observed to have a low equilibrium temperature and a coating that is sensitive to thermal ageing     

Effect of oxygen content on the specific heat and magnetic susceptibility of YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−δ</Subscript>

The specific heat and magnetic susceptibility of a sample of YBa₂Cu₃O_7?δ (YBCO) was measured for 0≤δ≤0.85, 0.8≤T≤120K, and H=0, 3, 5, 7, 9T. The data show the existence of both S=1/2 and S=2 paramagnetic centers, consistent with EPR results. The δ dependences of their concentrations and of other parameters are reported.     

渐入市场的视频家庭 网络技术

消费者正快速采用家庭网络来共享互联网连接、文件和打印机.并且,虽然一些消费者已经用商用5类电缆建立了网络,但更多消费者则采用"不布新线"的技术,如HomePlug电力线网络或Wi-Fi(IEEE802.11)无线局域网,因为这些选择没有电缆安装的昂贵费用.     

The empirical behavior of sampling methods for stochastic programming

We investigate the quality of solutions obtained from sample-average approximations to two-stage stochastic linear programs with recourse. We use a recently developed software tool executing on a computational grid to solve many large instances of these problems, allowing us to obtain high-quality solutions and to verify optimality and near-optimality of the computed solutions in various ways. Research supported by the Mathematical, Information, and Computational Sciences Division subprogram of the Office of Advanced Scientific Computing Research, U.S. Department of Energy, under Contract W-31-109-Eng-38, and by the National Science Foundation under Grant 9726385. Research supported by the Mathematical, Information, and Computational Sciences Division subprogram of the Office of Advanced Scientific Computing Research, U.S. Department of Energy, under Contract W-31-109-Eng-38, and by the National Science Foundation under Grant DMS-0073770. Research supported by the Mathematical, Information, and Computational Sciences Division subprogram of the Office of Advanced Scientific Computing Research, U.S. Department of Energy, under Contract W-31-109-Eng-38, and by the National Science Foundation under Grants 9726385 and 0082065.     

Device processing and characterisation of high temperature silicon carbide Schottky diodes

High temperature silicon carbide diodes with nickel silicide Schottky contacts were fabricated by deposition of titanium-nickel metal film on 4H-SiC epitaxial wafer followed by annealing at 550 °C in vacuum. Room temperature boron implantation have been used to form single zone junction termination extension. 4H-SiC epitaxial structures designed to have theoretical parallel-plain breakdown voltages of 1900 and 3600 V have been used for this research. The diodes revealed soft recoverable avalanche breakdown at voltages of 1450 and 3400 V, respectively, which are about 80% and 95% of theoretical values. I-V characteristics of fabricated 4H-SiC Schottky diodes have been measured at temperatures from room temperature up to 400 °C. The diodes revealed unchangeable barrier heights and ideality factors as well as positive coefficients of breakdown voltage.