等变序列分歧问题关于右等价群的有限决定性

研究在右等价群R(τ)的作用下,等变序列分歧问题f∈ε_(uλ)×(?)(τ)的有限决定性,得到了有限决定性的充分条件和必要条件.     

基于等效静态载荷法的区间参数结构可靠性拓扑优化

研究了用等效静态载荷法,解决动态响应约束下的区间参数结构可靠性拓扑优化问题。对等效静态载荷赋予了新的含义:由等效静态载荷产生的区间静态响应与由动态载荷产生的区间动态响应,其对应的中值与离差均相等。利用泰勒展开计算出区间参数结构动态响应所有可能值组成的集合,再根据集合映射获得包含结构所有不确定信息的等效静态载荷集合,继而建立静态可靠性拓扑优化数学模型。通过集合映射和区间自然扩展,获得静态位移响应区间。基于区间非概率可靠性指标的定义,给出区间非概率可靠性约束的伴随法灵敏度分析算法。采用移动渐近线法完成此优化问题的求解。数值算例验证了模型的正确性和算法的有效性。     

Stochastic response of fractional-order van der Pol oscillator

We studied the response of fractional-order van de Pol oscillator to Gaussian white noise excitation in this letter. An equivalent integral-order nonlinear stochastic system is obtained to replace the given system based on the principle of minimum mean-square error. Through stochastic averaging, an averaged Itô equation is deduced. We obtained the Fokker-Planck-Kolmogorov equation connected to the averaged Itô equation and solved it to yield the approximate stationary response of the system. The analytical solution is confirmed by using Monte Carlo simulation.     

A Partition of the Hypercube into Maximally Nonparallel Hamming Codes

By using the Gold map, we construct a partition of the hypercube into cosets of Hamming codes such that for every two cosets the corresponding Hamming codes are maximally nonparallel, that is, their intersection cardinality is as small as possible to admit nonintersecting cosets.     

Linear recurring sequence subgroups in finite fields

Given a finite field and a linear recurrence relation over it is possible to find, in a fairly “obvious” way, a finite extension of and a subgroup M of the multiplicative group of such that the elements of M may be written, without repetition, so as to form a cyclically closed sequence which obeys the recurrence. Here we investigate this phenomenon for second-order recurrences; the situation in which has prime order and the characteristic polynomial of the relation is irreducible over is described.     

一类新的有限域上的置换多项式

本文研究了有限域上置换多项式的构造问题.利用分段方法构造了F_q²上形如（x^q-x+c）^{（k（q2-1））/（d）+1}+x^q+x的置换多项式,其中1≤k < d且d是q-1的任意因子,推广了已有文献中的某些结果.     

二维海面上舰船目标电磁散射及合成孔径雷达成像技术研究

研究了二维海面上三维金属目标的电磁散射计算以及合成 孔径雷达(SAR)成像技术. 基于物理光学法、几何光学法和射线弹跳法计算了海 面与目标镜面反射及相互耦合作用; 并用等效电流法计算了目标的棱边绕射作用, 该方法考虑了阴影效应,同时为了消除人为截断引起的边缘衍射, 采用锥形入射波入射. 应用蒙特卡罗法生成的Pierson-Moskowitz谱粗糙面模拟实际海洋面, 计算海面上立方体及舰船的双站雷达散射截面, 通过与数值算法的结果相比较, 验证了该算法的正确性. 运用该解析法快速获取不同频率、 不同角度入射波照射下海面与目标的复合后向散射场数组, 结合SAR成像技术, 得到海面上立方体以及不同姿态舰船目标的SAR成像结果. 该研究成果在实际海洋遥感、海面上军事目标的探测与识别 等领域中具有重要的应用价值.     

Hamiltonian replica‐permutation method and its applications to an alanine dipeptide and amyloid‐β(29–42) peptides

We propose the Hamiltonian replica‐permutation method (RPM) (or multidimensional RPM) for molecular dynamics and Monte Carlo simulations, in which parameters in the Hamiltonian are permuted among more than two replicas with the Suwa‐Todo algorithm. We apply the Coulomb RPM, which is one of realization of the Hamiltonian RPM, to an alanine dipeptide and to two amyloid‐β(29–42) molecules. The Hamiltonian RPM realizes more efficient sampling than the Hamiltonian replica‐exchange method. We illustrate the protein misfolding funnel of amyloid‐β(29–42) and reveal its dimerization pathways. © 2013 Wiley Periodicals, Inc.     

Optical and electrical properties of Li2WO4 compound

ABSTRACT

The preparation of the Li₂WO₄ compound was made by the solid–solid method under well-defined conditions of temperature, which has not been dealt with in the bibliography. The previous works have been focused on studying the structure and the conductivity of Li₂WO₄ compound, while our work aims to investigate this compound by X-ray diffractometer, DSC, SEM, impedance spectroscopy, and conductivity analysis. Moreover, the optical properties are also investigated. These measures allow us to confirm that the studied sample crystallizes in the monoclinic structure with the space group (P2/m) and the lattice parameters: a?=?7.49?Å b?=?8.31?Å, c?=?5.92?Å, α=γ=90° and β?=?96.81°. Li₂WO₄ compound presents a compact structure, wherein the presence of some porosity is noticed. The band gap and the Urbagh energies were determined from the optical measurement. The DSC study shows the presence of an endothermic peak at T?=?500?K, indicating the existence of a phase transition. With regards to the electrical properties, the grain and the grain boundary response was modeled by a series combination of two cells, each one of them is composed of a parallel combination of resistance (R) and constant phase element (CPE). The AC conductivity was carried out for a specific range of temperature and frequency, thus allowing the identification of the conductivity mechanism. For the same conditions, the electrical modulus was studied. The theoretical data help us to extract some remarkable results and to confirm the phase transition at T?=?500?K.