Infrared absorption and far-infrared diffuse reflection spectra in Pb-doped Bi−Sr−Ca−Cu−O high-temperature superconductor

In this paper we study the room-temperature infrared transmission spectra (400–1600cm^?1) and far-infrared diffuse reflection spectra (50–450cm^?1) in Pb-doped Bi?Sr?Ca?Cu?O (2223) single phase (Tc=107k, sp1), multiphase (Tc=110k, sp2) and nonsuperconducting samples (sp3). The spectral features in superconductor are totally different from those in nonsuperconductor, which show the different crystal structure. The correlation existing between a factor group analysis of the phonons in (2223) and (2212) compounds affords a tentative assignment of ir-active modes in Pb-doped (2223) single phase by comparison with reported data in (2212) materials. The Cu?O stretching E_u vibration (605cm^?1) of CuO₂ layers is the characteristic vibrational mode related perovskitelike crystal structures. Two phonon coupling effect emerges in the infrared transmission spectra in Pb-doped superconductor. The Ca?O vibration A_2u (254cm^?1) might be related to superconductivity of Bi-based family.     

一种联合特征值信息的全极化SAR图像监督分类方法

基于H/平面的分类器对于具有相似散射类型的地物的分类能力很差,为此该文直接使用特征值特征来进行分类。首先提取特征值特征,并使用一种自适应调整高斯分量个数的高斯混合模型对特征值分布进行较为准确地拟合,然后采用朴素贝叶斯分类器进行初步分类。针对可能存在特征值分布较为相近导致错分的问题,计算每两类地物的特征值分布的相似度,将相似度大于给定阈值的类别对组成相似性表,对于这些相似对再用基于Wishart距离的K近邻分类器进行细分。综合分析机载和星载SAR数据上的实验结果,表明这种方法能够克服基于H/的非监督分类方法对于特征值利用的一些不足,且与基于SVM的分类方法效果相当。      

Phosphorus Removal from Silicon by Vacuum Refining and Directional Solidification

Silicon is widely used as a raw material for production of solar cells. As a major impurity in silicon, phosphorus must be removed to 1 × 10^?5 wt.%. In the present study, based on the distribution of phosphorus in a silicon ingot obtained by vacuum refining and directional solidification, the mechanism for removal of phosphorus from silicon is investigated. The results show that the distribution is controlled not only by segregation at the solid–liquid interface but also by evaporation at the gas–liquid interface, showing some deviation from Scheil’s equation. A modified model which considers both segregation and evaporation is used to simulate the distribution, matching quite well with the experimental results. The temperature and solidification rate are two important parameters that affect the overall mass transfer coefficient and the effective segregation coefficient and thus the distribution of phosphorus. A high removal efficiency and a homogeneous distribution can be obtained by adjusting these two parameters.     

多轴越野车辆驱动力分配的优化研究

基于优化设计理论,建立了以车辆动力性为优化目标的多轴越野车辆驱动力分配系数的优化模型.利用MATLAB GUI编制了相应的软件,该软件可对车辆驱动力分配系数进行优化,也可对其车辆动力性进行计算.以某一4×4越野车辆为例,对其驱动力分配系数进行了优化,通过对优化前后车辆动力性能的对比分析,验证了优化模型的精确性及软件的实用性.     

高性能980nm单模半导体激光器

采用经过优化的新型大光腔结构,设计出低发散角的980nm半导体激光器,利用分子束外延系统生长出应变InGaAs量子阱半导体激光器材料,并制作出980nm单模半导体激光器。器件在3μm条宽,750μm腔长时,100mA电流下室温连续输出功率达到70mW以上。激光器的最大斜率效率为0.89W/A.垂直方向远场发散角为28°.器件在250mA工作电流下输出功率达到190mW.器件在70℃温度下仍可以正常工作。     

Stability of Motion for Generalized Birkhoffian Systems

The problem on the stability of motion for a generalized Birkhoffian system was studied. The disturbed equations of motion and their first approximation for the system were established. The criterion of stability of motion for the system was set up by using Liapunov’s first approximation theory. Based on the theory of Noether symmetry,the Liapunov’s function was constructed,and the criterion of stability of motion for the system was also set up by using Liapunov’s direct method. Two examples were given to illustrate the application of the results.     

A New Chaotic Genetic Hybrid Algorithm and Its Applications in Mechanical Optimization Design

A new chaotic genetic hybrid algorithm(CGHA) based on float point coding was put forward in this paper.Firstly,it used chaos optimization to search coarsely and produced a better initial population.Then,a power function carrier was adopted to improve the ergodicity and the sufficiency of the chaos optimization.Secondly,the genetic algorithm(GA) was used to search finely and guaranteed the population's evolution.To avoid the search being trapped in local minimum,a chaos degenerate mutation operator was desig...     

某低空低速飞行器气动特性计算

为研究不同弹头和尾翼形状对飞行器阻力大小和稳定性的影响,用CFD数值模拟方法,采用完全结构化网格,以三维N-S方程为出发方程,采用S-A-方程湍流模型,对6种不同弹头尾翼形状及尾翼片数和厚度的某低空飞行器的气动外形进行数值模拟,并对计算结果进行了比较分析.结果表明,采用卡门曲线的战斗部气动外形和合适尺寸的梯形尾翼对该飞行装置减小阻力和提高静稳定性有利,可为外形优化设计提供依据.     

自适应跳频系统抗部分频带干扰性能分析

由于部分频带干扰对跳频通信系统危害最为严重,而自适应性的引入将大大改善跳频系统的抗干扰能力。文中在常规跳频系统的基础上给出了一种自适应跳频系统,通过介绍自适应跳频系统原理,引入了双态信道模型,分析了在部分频带干扰条件下系统的误码率。在Matlab平台上对文中所给系统的性能进行仿真,并与常规跳频系统进行对比。仿真结果表明该系统能够自适应的去除干扰频点,调整跳频图案,从而使得抗干扰性能得以改善。在阻塞率为0.2时,自适应跳频系统的误码率仅为常规系统的百分之一,能够有效抵抗部分频带干扰的影响。     

EDA工程建模及其管理方法研究

现代电子设计技术面临着集成电路(IC)芯片设计的复杂度不断增大而产品的研发时限不断缩短的挑战。为了提高芯片质量和设计效率,人们将抽象建模的思想应用于芯片设计和管理,提出结合抽象建模技术的芯片设计方法,并且在大规模芯片设计中采用层次化的分组协作。针对当前电子设计自动化(EDA)技术的发展情况,介绍了一种基于统一建模语言(UML)的芯片设计方法及其相关技术,阐述了目前大型EDA工程所采用的层次化分组协作管理方法的原理,分析其优点和不足,并提出了改进方案。