应变Si1-xGex层中p型杂质电离常温和低温特性

本文采用解析的方法计算了应变Si1-xGex层中p型杂质电离度与Ge组分x、温度T以及掺杂浓度N的关系.发现常温时,在同一Ge组分下,随着掺杂浓度的升高,杂质的电离度的先变小,而后又迅速上升到1.在同一掺杂浓度下,轻掺杂时,杂质的电离度随Ge组分的增加先变大,而后几乎不变;重掺杂时,杂质电离能变为0后,杂质电离度为1.低温下,轻掺杂时,载流子低温冻析效应较为明显,杂质的电离度普遍较小,当掺杂浓度大于Mott转换点时,载流子冻析效应不再明显,电离率迅速上升到1.在同一Ge组分下,随着掺杂浓度的升高,杂质的电离度先变小,后变大,而后又迅速上升到1.在同一掺杂浓度下,轻掺杂时,杂质的电离度随Ge组分的增加变大;重掺杂时,杂质电离能变为0后,杂质电离度为1.     

基于爆轰波原理声源定位方法初探

基于弹丸发射时所发出的爆轰波,利用传感器接收时差信息,从而确定声源位置。本文建立了该声源定位反问题的物理和数学模型,并依据该模型寻求适当的数值解法,最后针对延拓-广义逆法声源定位问题进行了演算和简要分析。     

A Modified Szilard Engine: Measurement, Information, and Maxwell's Demon

Using an isolated measurement process, we calculate the effect measurement has on entropy for the multi-cylinder Szilard engine. We find that the system of cylinders possesses an entropy associated with cylinder total energy states, and that it records information transferred at measurement. Contrary to other's results, we find that the apparatus loses entropy due to measurement. The Second Law of Thermodynamics may be preserved if Maxwell's demon gains entropy moving the engine partition.     

Thermal Effects of Microwave Energy in Agricultural Soil Radiation

The thermal treatment by millimeter waves for the soil disinfection can be one possible alternative to chemical treatments. This physical method is based on incrementing the soil temperature and its pathogens irradiating with high frequency electromagnetic waves. So the previous knowledge of the temperature distribution in the irradiated soil is essential for achieving an effective bad microorganism and weed seeds elimination. This report analyse the heating kinetic and spatial distribution of the maximum temperatures reached by the soil. It is presented a mathematic model about how are distributed the reached temperatures in the depth of the irradiated soil. This model concludes that when an orchard soil is irradiated superficially by microwaves, the microwaves have a big attenuation due to the soil dielectric properties and the water located in the pores of the most superficial layer. This fact causes a shield effect blocking the waves penetration in few centimetres. The heating by radiation is reduced to the superficial layer. The heating propagation in the depth is occurred by conduction following the Fourier equations.     

Low sintering temperature MnZn-ferrites for power applications in the frequency region of 400 kHz

In this paper, the effect of cubic zinc metaborate Zn₄O(BO₂)₆ on the sintering of MnZn-ferrites for medium frequency power applications is investigated. Zinc metaborate is synthesized in the laboratory using zinc oxide and boric acid as metal precursors. As observed, when zinc metaborate is added to the MnZn-ferrites at an optimum amount of 0.02 wt%, it significantly enhances densification and therefore allows, for a given density, reduction of the firing temperature by almost 200 °C. MnZn-ferrites exhibiting power losses of 70 mW/cm³ (measured at a frequency of 400 kHz, magnetic field 50 mT and temperature of 90 °C) are synthesized from conventionally milled powders with average particle diameter 0.6 μm, compacted and fired at 1100 °C. Identical experiments conducted under the same conditions on specimens without zinc metaborate additions revealed power losses greater than 300 mW/cm³, because of insufficient densification.     

Estimating tail probabilities of heavy tailed distributions with asymptotically zero relative error

Efficient estimation of tail probabilities involving heavy tailed random variables is amongst the most challenging problems in Monte-Carlo simulation. In the last few years, applied probabilists have achieved considerable success in developing efficient algorithms for some such simple but fundamental tail probabilities. Usually, unbiased importance sampling estimators of such tail probabilities are developed and it is proved that these estimators are asymptotically efficient or even possess the desirable bounded relative error property. In this paper, as an illustration, we consider a simple tail probability involving geometric sums of heavy tailed random variables. This is useful in estimating the probability of large delays in M/G/1 queues. In this setting we develop an unbiased estimator whose relative error decreases to zero asymptotically. The key idea is to decompose the probability of interest into a known dominant component and an unknown small component. Simulation then focuses on estimating the latter ‘residual’ probability. Here we show that the existing conditioning methods or importance sampling methods are not effective in estimating the residual probability while an appropriate combination of the two estimates it with bounded relative error. As a further illustration of the proposed ideas, we apply them to develop an estimator for the probability of large delays in stochastic activity networks that has an asymptotically zero relative error.      

Error estimate for the approximation of nonlinear conservation laws on bounded domains by the finite volume method

In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.

     

Convergence Rate of The Trust Region Method for Nonlinear Equations Under Local Error Bound Condition

In this paper, we present the new trust region method for nonlinear equations with the trust region converging to zero. The new method preserves the global convergence of the traditional trust region methods in which the trust region radius will be larger than a positive constant. We study the convergence rate of the new method under the local error bound condition which is weaker than the nonsingularity. An example given by Y.X. Yuan shows that the convergence rate can not be quadratic. Finally, some numerical results are given. This work is supported by Chinese NSFC grants 10401023 and 10371076, Research Grants for Young Teachers of Shanghai Jiao Tong University, and E-Institute of Computational Sciences of Shanghai Universities. An erratum to this article is available at .     

二分量高温超导机理

用两种电子态,讨论了金属—绝缘相变、反铁磁性—金属相变,以及相分离、正常态—超导态相变、非费米液体行为、高Tc等 关键词： 两种电子态 格林函数 玻色化 高温超导     

椭圆型问题一类广义差分法的L~2模误差估计

1.引 言 广义差分法作为处理偏微分方程的离散技术,能够保持质量,动量,能量等物理量的守恒.广义差分法（有些文献称为box method[3];finite volume element method[4],[5],[6]）利用在对偶剖分体积单元积分原始方程,并将近似解限制于某一有限元空间而得到离散方程.因此,它在局部区域保持了原始方程的物理守恒性和其他重要特性.从而被广泛地应用于数值求解数学物理方程,特别是计算流体力学和热传导问题[11]. 对广义差分法的研究已有许多文献,专著[10]有详细的介绍.早期的工作主要考虑标准的重心对偶剖分.近年来Cai et,al[4],[5],[6],在某些假定下对较一般的对偶剖分给出了能量模误差估计,Huang and Xi[9]去掉了文献[6]中的这些限制.Chou,Li[8]和Li,