Transient Green’s Tensor for a Layered Solid Half-Space With Different Interface Conditions

Pulsed ultrasonic techniques can be and have been used to examine the interface conditions of a bonded structure. To provide a theoretical basis for such testing techniques we model the structure as a layer on top of a half-space, both of different elastic properties, with various interface bonding conditions. The exact dynamic Green’s tensor for such a structure is explicitly derived from the three-dimensional equations of motion. The final solution is a series. Each term of the series corresponds to a successive arrival of a “generalized ray” and each is a definite line integral along a fixed path which can be easily computed numerically. Willis’ method is used in the derivation. A new scheme of automatic generation of the arrivals and ray paths using combinatorial analysis, along with the summation of the corresponding products of reflection coefficients is presented. A FORTRAN code is developed for computation of the Green’s tensor when both the source and the detector are located on the top surface. The Green’s tensor is then used to simulate displacements due to pulsed ultrasonic point sources of known time waveform. Results show that the interface bonding conditions have a great influence on the transient displacements. For example, when the interface bonding conditions vary, some of the first few head waves and regular reflected rays change polarities and amplitudes. This phenomenon can be used to infer the quality of the interface bond of materials in ultrasonic nondestructive evaluation. In addition the results are useful in the study of acoustic microscopy probes, coatings, and geo-exploration.     

An Implementation of Bouchouev's Method for a Short Time Calibration of Option Pricing Models

We analyse the Bouchouev integral equation for the deterministic volatility function in the Black–Scholes option pricing model. We areable to reduce Bouchouev's original triple integral equation to a single integral equation and describe its numerical solution. Moreover we show empirically that the most complex term in the equation may often be safely ignored for the purposes of numerical calculations. We present a selection of numerical examples indicating the range of time values for which we would expect the equation to be valid.     

浅谈2000版IS09000族质量管理体系标准的结构与特点

结合对2000年版ISO9000族质量管理体系标准的理解和分析,对标准的结构和特点进行了探讨。     

工矿供电系统谐波治理新方法研究

针对现有无源滤波器滤波效果较差,易出现谐振过电压、谐波放大等现象的问题,提出一种基于基波谐振原理的谐波治理新方法。该方法在电网与无源滤波器之间的三相线路中分别串联一组由电感和电容组成的基波谐振电路,迫使谐波电流最大限度地流入无源滤波器,从而大幅提升滤波器的效率。实验结果表明,增加基波谐振电路后,电流畸变率从10.6%下降为0.942%,滤波效果更佳。     

用简化的Goertzel来实现正弦基波与谐波

通过对Goertzel算法的优化和运用查表法处理来加快其运算速度。在硬件电路的基础上,用C语言完成了实际应用的算法程序。采用Atmel公司51系列外接晶振时钟频率可高达24MHz的单片机AT89C2051-24SU,运算后输出了一定频率的正弦基波及其多次谐波组成的波形。     

基于锁相放大器原理的基波无功检测方法研究

无功补偿控制系统需要快速、准确地检测出系统基波无功功率以及功率因数等参数,用以控制无功补偿设备输出系统所需的基波无功功率。针对现有检测方法受电网以及无功补偿设备本身产生的谐波影响而造成计算结果准确度降低、计算速度慢等问题,基于锁相放大器原理,提出一种适用于无功控制系统的快速、准确的基波无功功率以及功率因数检测方法;在Matlab上进行了仿真分析,对比了含有多种谐波时,不同信噪比下各参数的最大误差,并搭建了实验平台,以Fluke-435-II电能质量分析仪验证该方法的准确性;经仿真和实验表明,该方法可以在含有谐波时准确、快速地检测出系统的基波无功功率及功率因数,为无功补偿系统的无功检测提供了理论依据和实用方法。     

煤气化联合循环发电示范状况和煤气化工艺对比

煤炭气化已被确认为制取管道煤气或合成气的技术。经多方研究已被工业化规模生产和煤气化联合循环发电所证实。本文评述了煤的基本性质对气化效率的影响，煤气化联合循环发电示范厂现状和各种选定用于煤气化联合循环发电的第二代煤气化方法的对比。本文最后阐述了煤气化联合循环发电用于改造高能耗的以煤、油和天然气为燃料的中小规模电厂的现实性。     

大学计算机基础课程基于分级的专题教学方案探索

大学计算机基础课在高校越来越受到重视,结合目前计算机基础教学的现实情况和分级教学的不足,提出了基于分级的专题教学方案。此教学方案在分级的基础上,增设了"应用技能提高"的专题教学和实践教学,以达到提高学生计算机应用能力的目的。此方案有利于保留分级教学的优势,改进其不足;有利于因材施教、提高学生的学习兴趣、发挥教师特长。但是在实施过程中还存在若干问题需要我们进一步研究。     

计算机公共课教学现状及对策研究

通过问卷调查和计算机统计软件,科学分析了现状差异。根据各专业学生对计算机课程的兴趣、计算机基础和各专业对计算机公共课程的要求的差异,针对性采取了教学改革对策:针对不同学科制定不同的教学计划与内容;开发课程教学网站,使课堂教学与网络教学紧密结合;对不同层次的学生分层管理;由"以教师为主"向"学生自主学习"教学模式的转变,收到较好的教学效果。     

一类带谱参数的奇异Sturm-Liouville算子特征的渐近分析工

研究了一类具有转换条件且在一个边界条件中带谱参数的奇异Sturm—Liouville问题．将上述问题的基本解的渐近分析,转化为考虑定义在适当的Hilbert空间H中的一个线性算子A的基本解的渐近分析,同时推导出该奇异的Sturm-Liouville算子A的基本解的渐近式．