杂质对Nb2GeC性质影响的第一性原理研究

为进一步研究Nb₂GeC在辐照环境中的稳定性, 本文研究了O, H和He杂质在Nb₂GeC中的稳定情况. 所有杂质的研究都是从替代和间隙两个方面来进行的, 计算得到了替代和间隙的形成能, 存在替代和间隙时Nb₂GeC的晶格常数, 以及单胞体积, 并且与完美的晶胞进行了比较. 此外, 通过电荷密度分布和Mulliken 布居, 分析了O, H, He杂质对Nb₂GeC 的电子性质的影响.     

Raman investigation of chemical reaction product in thermal‐treated SiCf/C/Mo/Ti6Al4V composite

SiC fiber‐reinforced titanium matrix composite (TMC) is an interesting material for aerospace industry because of its excellent properties. Characterization of their interfacial reaction product is principal to further optimization of the TMCs. Here we report application of Raman spectroscopy to identify reaction products and their microstructural details in thermal‐treated SiC_f/C/Mo/Ti6Al4V composite. Meanwhile TEM is performed to help explain phenomena in Raman result. Raman line scanning along interface indicates thickness of two sublayers (Ti₅Si₃(C_x) layer next to SiC fiber and TiC_x layer next to matrix). The main Raman result of phase distribution is confirmed by TEM. While a 300‐nm Ti₃SiC₂ layer whose Raman features are similar with nearby Ti₅Si₃(C_x) layer is also detected. Raman peakshift in Ti₅Si₃(C_x) layer possibly results from residual stress or/and microstructural evolution caused by carbon solution. No evidence indicates Mo participation of interfacial reactions. However, Mo diffusion changes phase distribution of matrix alloy and affects interfacial reaction indirectly. Meanwhile, TEM and Raman results indicate that particles are TiC_x and defective Ti₃AlC₂. Raman features of Ti₃AlC₂ particles differ from that of bulk material, which is attributed to defects. Although Ti₃AlC₂ formation mechanism is ambiguous, it possibly relates to TiC_x formation nearby. Copyright © 2014 John Wiley & Sons, Ltd.     

普朗克和能量子概念--纪念能量子概念诞生100周年

本简述了普朗克生平经历，回顾他提出了能量子概念这一伟大发现过程，分析他科学研究的方法及其“悲剧”，以此来纪念这位伟大的、正直的物理学家，以期对今后科研工作有借鉴意义。     

虚拟仿真技术在物理实验中的应用

利用3D MAX建模工具进行三维建模,用GL Studio做面板仿真,并在Vega和VC 中进行驱动和集成,来完成对物理实验的仿真,同时本文对虚拟仿真在物理实验中的前途和重要性进行了说明,并对产品的开发也做出了简要的介绍。     

一类时变MAX序列样本均值的极限分布

本文讨论来自一类时变MAX序列的一段样本(X_1,X_2,…,X_N)的联合特征函数的表示形式,并在一些简单的限制条件下给出样本均值N_~β(_N-E_N)渐近退化分布或正态分布的结论。     

MAX+PLUSⅡ9.23软件及其在EDA实验教学中的应用

介绍了学生版MAX+PLUSⅡ9.23软件的功能,并通过举例来说明其主要特点,论述其在EAD实验教学中的广阔应用.     

基于VHDL语言的全功能计数控制装置的设计

利用VHDL语言在PLD器件上设计全功能计数控制装置，使其实现计量、显示长度并根据预置数输出控制信号的功能。设计体现了VHDL语言的规范、高效，编程灵活、容易升级的特点。系统程序采用Ahera公司的MAX plusⅡ软件设计，下载至FLEX10K系列芯片。     

Structural parameters, electronic structures, elastic stiffness and thermal properties of M2PC (M=V, Nb, Ta)

Using pseudo-potential plane-wave method based on the density functional theory in conjunction with the generalized gradient approximation, structural parameters, electronic structures, elastic stiffness and thermal properties of M₂PC, with M=V, Nb, Ta, were studied. The optimized zero pressure geometrical parameters are in good agreement with the available results. Pressure effect, up to 20 GPa, on the lattice parameters was investigated. Electronic properties are studied throughout the calculation of densities of states and band structures. The elastic constants and their pressure dependence were predicted using the static finite strain technique. We performed numerical estimations of the bulk modulus, shear modulus, Young's modulus, Poisson's ratio and average sound velocity for ideal polycrystalline M₂PC aggregates in framework of the Voigt-Reuss-Hill approximation. We estimated the Debye temperature and the theoretical minimum thermal conductivity of M₂PC.     

基于VRML的计算机组装虚拟实验的研究与实现

在计算机组装教学过程中,教学条件不足和硬件更新迅速等问题影响了教学的效果,采用虚拟现实技术对计算机组装课程中所需的硬件和实验过程进行仿真,可以很好地解决这些问题.开发了基于VRML的计算机组装虚拟实验系统;描述了实现虚拟实验的各种关键技术,包括虚拟场景的构建、虚拟部件的动态组合、虚拟实验场景交互等.将该虚拟实验系统用于实际教学中可达到预期的教学效果.     

基于FPGA数字钟的设计与实现

伴随着集成电路(IC)技术的发展,电子设计自动化(EDA)逐渐成为重要的设计手段,经广泛应用于模拟与数字电路系统等许多领域.本设计给出了多功能数字钟自顶向下(TOP)的设计思想和实现方案,采用结构描述风格,依据功能将系统分为五个模块组成:分频模块:控制模块、计数器模块、闹铃模块、显示模块,并用Verilog HDL实现各个功能模块,图形输入法生成顶层模块.最后在EDA工具MAX PLUS II下进行仿真,验证数字钟FPGA设计的正确性和实用性.