正交各向异性弹性层/功能梯度压电半空间结构中Love波的传播

研究了功能梯度压电半空间上覆盖一层正交各向异性弹性层结构中Love波的传播特性.覆盖层与基底的界面连接方式分别考虑了理想接触和非理想接触2种模式,功能梯度压电半空间的材料性能沿垂直于界面方向以指数函数形式变化.基于推导的频散方程,结合数值算例分析了材料性能梯度变化、正交各向异性材料的切割角度和非理想界面的连接程度对相速度的影响,其结果对功能梯度压电材料的覆层结构在声波器件中的应用具有重要的参考价值.     

柴油机供油系统中压力波信号的小波分析

通过压力传感器、放大器、A/D卡和计算机对柴油机供油系统中泵端和嘴端压力波信号进行了采集 ,然后用小波分析法对其时频特性进行了研究。研究结果表明 :通过小波变换 ,可将柴油机供油系统中压力波信号的各个频带成份清晰地显示出来 ,并可以看出泵端和嘴端压力波在小波分析后的差别     

Cu(111)表面能及功函数的第一性原理计算

应用基于局域密度泛函理论的第一原理赝势法,计算了铜体材料的结合能及晶格常数的理论值,并由此计算了Cu(111)面的表面能及功函数。计算所得到结果与实验数据吻合较好。     

生物用无镍奥氏体不锈钢的塑性变形以及对耐腐蚀性能的影响

对无镍奥氏体不锈钢经塑性变形后自由表面微观形态变化以及对耐腐蚀性能的影响进行了观察分析.结果表明:随着压缩应变量的增加,各晶粒变形不均匀性加剧,试样表面形成的褶皱增大,原本平整的表面逐渐变成粗糙表面,茶碱对试样无腐蚀作用,而生理盐水对变形试样起应力腐蚀作用.     

Upper pycnocline turbulence in the northern South China Sea

The first regional mapping of the averaged turbulent kinetic energy dissipation rate <εp> in the upper pycnocline of the northern South China Sea is presented and discussed.At φ=20°N and to the north of this latitude,<εp> appears to be more than two times larger than that to the south of 20°N.It is suggested that this asymmetry is associated with the predominant northwestward propagation and dissipation of the internal waves originated in the Luzon Strait area.An approximately linear relationship between <εp> and the available potential energy of the waves P IW,suggests a characteristic time of the P IW dissipation of about 6 h.     

消除岩石动态实验曲线振荡的有效途径

就岩石动态应力－应变－应变率曲线测定中存在的严重振荡问题进行了讨论，提出了消除这一振荡的有效途径：改传统的矩形波加载为半周期正弦波加载。并就实现半周期正弦波加载的冲头结构进行了研究。     

非线性不规则波二阶分离模型

基于二阶波势流理论,建立了一个非线性不规则波浪二阶分离模型．通过求解频域内一、二阶成分之间的传递函数,建立起二阶项求解关系式,将二阶项变换到与一阶项同一个傅里叶频域空间,采用Newton-Raphson迭代方法分别求解出目标波浪中一阶、二阶和频与二阶差频．利用所建立模型分别对规则波和二阶非线性不规则波进行了数值验证,并对波浪非线性的影响进行了分析,典型数值计算结果表明模型是有效的．     

一种新型的频率选择反射表面

本文对一种新型的频率选择反射表面进行了理论研究。这种新型的反射表面是由一无限大理想导体平板后加载二维周期性腔体阵列所组成,它比导体平板上开有二维周期性孔阵有更好的反射选择特性。文中对平面波入射到二维周期性矩形腔阵列加载导电屏的反射特性进行了计算,给出了主模反射系数随频率腔长等参量变化的关系曲线。     

多级自组织映射用于心电信号QRS波群聚类

提出了一种利用多级自组织映射(MSOM)网络进行心电QRS波群聚类的算法。此方法将归一化的两导联心电数据作为第一层自组织映射网络的输入,其输出作为第二层自组织映射的输入,最后得到聚类结果。网络迭代学习过程采用了特殊的设计,能根据不同类别自适应调整学习参数,从而提高了自组织映射的聚类能力。使用MIT-BIH数据库数据的聚类结果表明,这种方法非常适合心电QRS波群的聚类,对室性早搏(PVC)真阳性检出率达到99.1%,且聚类效率比ART-2网络方法、匹配方法有明显优势。     

It ain't necessarily so: Gravitational waves and energy transport

I review and critically examine the four textbook arguments commonly taken to establish that gravitational waves (GWs) carry energy-momentum: 1. the increase in kinetic energy that a GW confers on a ring of test particles, 3.Bondi/Feynman's Sticky Bead Argument of a GW heating up a detector, 3. nonlinearities within perturbation theory, construed as the gravity's contribution to its own source, and 4. the Noether Theorems, linking symmetries and conserved quantities. As it stands, each argument is found to be either contentious, or incomplete in that it presupposes substantive assumptions which the standard exposition glosses over. I finally investigate the standard interpretation of binary systems, according to which orbital decay is explained by the system's energy being dissipated via GW energy-momentum transport. I contend that for the textbook treatment of binary systems an alternative interpretation, drawing only on the general-relativistic equations of motions and the Einstein Equations, is available. It's argued to be even preferable to the standard interpretation. Thereby an inference to the best explanation for GW energy-momentum is blocked. I conclude that a defence of the claim that GWs carry energy can't rest on the standard arguments.