NUMERICAL STUDY ON THE EFFECTS OF SMALL-AMPLITUDE INITIAL PERTURBATIONS ON RM INSTABILITY

采用Navier-Stokes 方程对入射激波及其反射激波连续诱导小振幅扰动界面的Richtmyer-Meshkov 不稳定性增长过程进行了二维数值模拟,分析了单模和随机多模两种不同初始形态的界面上钉结构和泡结构在反射激波作用前后的发展特性. 研究结果发现：单模扰动的初始界面形态对反射激波前、后界面的扰动增长都有影响,反射激波前的界面形态信息可以通过钉和泡结构之间的反转传递到反射激波过后. 扰动界面上钉结构的发展速度控制了界面混合区总体的发展速度,反射激波前界面上发展成具有完整冠部形态的钉,在反射激波后会反转成复杂的泡结构,此泡结构对反射激波后钉的发展不利. 随机多模界面显示了与单模界面类似的发展规律,但随机多模界面上的复杂泡结构分布的不对称性使得其对钉结构增长的拖曳效应相对要弱,这导致了相似扰动波长下多模随机界面的扰动发展相对单模界面扰动发展要快.     

基于AT91RM9200短消息监控系统的设计与实现

介绍了GSM无线模块在嵌入式系统的应用,系统采用基于ARM9核的AT91RM9200微处理器,GSM无线模块采用华为MG323无线模块,在嵌入式Linux系统下,通过ARM与MG323进行控制通信,实现了短消息模块的软件功能。该系统支持PDU短信模式及中文短信。     

DAC7714在嵌入式激光跟踪仪中的应用

在某型激光跟踪仪的设计中,通过实时控制俯仰、方位两路电机,实现目标的快速、平稳跟踪。使用AT91RM9200处理器,扩展12位DA转换器DAC7714,完成2路直流电机的控制。阐述了在嵌入式Linux环境下该芯片驱动程序开发过程,说明了该驱动程序与测试程序及内核的之间关系。通过驱动程序、测试程序代码的讲解,归纳出嵌入式驱动程序开发的共性及具体开发流程,为嵌入式开发打下基础。     

求解阵列天线自适应滤波问题的一种调比随机逼近算法

提出了求解阵列天线自适应滤波问题的一种调比随机逼近算法.每一步迭代中,算法选取调比的带噪负梯度方向作为新的迭代方向.相比已有的其他随机逼近算法,这个算法不需要调整稳定性常数,在一定程度上解决了稳定性常数选取难的问题.数值仿真实验表明,算法优于已有的滤波算法,且比经典Robbins-Monro （RM）算法具有更好的稳定性.     

逻辑函数RM展开式和CRM展开式的转换

讨论了逻辑函数在与-异或和或-符合代数系统中的RM展开式和CRM展开式.根据异或和符合运算的性质详细讨论了逻辑函数bj系数和dj系数间的关系,并提出了两者的矩阵转换法,举例说明了转换过程.该方法揭示了bj系数和dj系数的内在联系,具有较好的实用性.     

Challenges in preparing water-matrix reference materials for PAHs and pesticides: examples from SWIFT-WFD proficiency-testing schemes

In accordance with Article 8 of the European Union (EU) Water Framework Directive (WFD), EU Member States are required to establish monitoring programs for the quality of the surface water and the groundwater within each river-basin district. As such data are the basis for regulatory decisions and measures required to achieve WFD environmental objectives, appropriate analytical quality-assurance and quality-control tools have to be implemented by the monitoring laboratories. In this respect, reference materials (RMs) play a key role. Within the framework of the SWIFT-WFD project (Screening methods for Water data InFormation in support of the WFD), several approaches to the preparation of matrix RMs for the analysis of polycyclic aromatic hydrocarbons and pesticides in water have been used in wide-scale proficiency-testing (PT) schemes. We present the different strategies employed in preparing water-matrix RMs for organic analytes. By reviewing the results from the SWIFT-WFD PT schemes, we reflect on the applicability and the suitability of the different approaches.     

计算机网络三维安全模型

文章分析了网络安全问题的解决途径，提出了网络安全分区，分层和分级管理的原理，并在此基础上，给出了一种实用的计算机网络安全三维模型，为网络安全设计提供了系统化的指导。     

Investigation of structural and optical properties of nanoporous GaN film

The structural and optical characteristics of porous GaN prepared by Pt-assisted electroless etching under different etching durations are reported. The porous GaN samples were investigated by scanning electron microscopy (SEM), high-resolution X-ray diffraction (HR-XRD), photoluminescence (PL) and Raman scattering. SEM images indicated that the density of the pores increased with the etching duration; however, the etching duration has no significant effect on the size and shape of the pores. XRD measurements showed that the (0 0 0 2) diffraction plane peak width of porous samples was slightly broader than the as-grown sample, and it increased with the etching duration. PL measurements revealed that the near band edge peak of all the porous samples were red-shifted; however, the porosity-induced PL intensity enhancement was only observed in the porous samples; apart from that, two additional strain-induced structural defect-related PL peaks observed in as-grown sample were absent in porous samples. Raman spectra showed that the shift of E₂ (high) to lower frequency was only found in samples with high density of pores. On the contrary, the absence of two forbidden TO modes in the as-grown sample was observed in some of porous samples.     

Premiere编辑RM/RMVB格式视频的一种方法

Premiere不能导入RM/RMVB格式视频素材,使很多编辑工作者深感遗憾。利用Premiere的插件和系统软件的方法,可解决RM/RMVB格式流媒体视频在Premiere中进行的编辑问题,同时,使视频质量劣化程度较小。