球形传声器阵列脉冲响应测量的非线性失真分析

在球形传声器阵列的脉冲响应测量中,其几何结构对入射声波产生散射作用,使各传声器检拾信号中声源非线性失真的谐波比例发生变化.文中选取以最大长度序列以及正弦对数扫频为激励声源的两种脉冲响应测量方法,通过仿真和实际测量评估非线性失真对其测量结果的影响.仿真和测量结果表明,由于声波在球面散射的作用,谐波成分将随入射声波角度而产生变化;声源谐波失真阵列背对声源的传声器对输出影响较小,而面对声源的传声器对输出影响较大;总体上最大长度序列测量法对声源的非线性失真更为敏感,对数扫频方法更适于球形传声器阵列的脉冲响应测量.     

复杂机械系统时变不确定性设计方法

考虑机械系统参数随时间的演化,基于连续时间模型和伊藤引理,推导建立了多参数复杂机械系统时变不确定性计算模型,将系统整体时变不确定性由其漂移函数和波动函数表达,系统漂移函数和波动函数则由底层时变参数的漂移率和波动率决定,从而解析了机械系统时变不确定性设计的原理。与传统方法相比,该多参数复杂机械系统时变不确定性设计方法既可以针对各零件(或子系统)进行时变不确定性设计,也可以建立统一的系统状态方程,针对复杂机械系统进行不确定性设计,并且算得的系统可靠度是动态的,可以预测未来任意时刻的可靠度,从而为系统的未来发展趋势提供先期预警,为设备维护提供指导。通过具体算例,说明了该设计方法的应用。该设计方法具有普适性,可以推广应用于城市公交系统、城市给排水系统、燃气系统、核电系统等的时变不确定性设计和可靠性分析。     

Haemagglutinin mutations responsible for the binding of H5N1 influenza A viruses to human-type receptors

H5N1 influenza A viruses have spread to numerous countries in Asia, Europe and Africa, infecting not only large numbers of poultry, but also an increasing number of humans, often with lethal effects. Human and avian influenza A viruses differ in their recognition of host cell receptors: the former preferentially recognize receptors with saccharides terminating in sialic acid-alpha2,6-galactose (SAalpha2,6Gal), whereas the latter prefer those ending in SAalpha2,3Gal (refs 3-6). A conversion from SAalpha2,3Gal to SAalpha2,6Gal recognition is thought to be one of the changes that must occur before avian influenza viruses can replicate efficiently in humans and acquire the potential to cause a pandemic. By identifying mutations in the receptor-binding haemagglutinin (HA) molecule that would enable avian H5N1 viruses to recognize human-type host cell receptors, it may be possible to predict (and thus to increase preparedness for) the emergence of pandemic viruses. Here we show that some H5N1 viruses isolated from humans can bind to both human and avian receptors, in contrast to those isolated from chickens and ducks, which recognize the avian receptors exclusively. Mutations at positions 182 and 192 independently convert the HAs of H5N1 viruses known to recognize the avian receptor to ones that recognize the human receptor. Analysis of the crystal structure of the HA from an H5N1 virus used in our genetic experiments shows that the locations of these amino acids in the HA molecule are compatible with an effect on receptor binding. The amino acid changes that we identify might serve as molecular markers for assessing the pandemic potential of H5N1 field isolates.     

风电场计算机监控系统设计

随着国家可持续发展能源战略的实施,风电场的数量和规模都将快速增长。针对当前风电场计算机监控系统在适应性、开放性、扩展性等方面的不足,提出了一套遵循IEC61850"三层两网"模型,以光纤以太网为基础,采用分层分布、双网双服务器冗余架构的风电场计算机监控系统设计方案。详细阐述了该方案的总体结构、组网方案、控制节点的软硬件设计等。同时,对监控系统软件的架构以及基于组态软件的系统实现进行了分析和设计。     

基于现场总线的电力企业生产过程实时监控系统

本文在湛江电厂生产过程实时监控系统设计的基础上，介绍了作为控制系统最新发展潮流的现场总线技术。并在应用需要调研的基础上，给出了湛江电厂的生产过程实时监控系统设计方案。     

硬件描述语言在专用集成电路设计中的应用

介绍了硬件描述语言ＶＨＤＬ的特点，讨论了ＶＨＤＬ语言与计算机高级语言的区别及寄存器ＰＴＬ描述方式的限制，阐述了在可编程ＡＳＩＣ设计吵降低目标器件硬件资源占用率的技巧及方法。     

单峰符号序列的一些性质及单峰函数中的周期轨道

本文给出了单峰函数符号序列即由字母R.L.C组成的一类序列的一些性质,推广了Collet和Eckmann的文章中的某些结论,证明了关于单峰函数的点的旅程的一些命题,并对作者的另一篇文章中的一个主要定理作了进一步的讨论。     

The character of <Emphasis Type="Italic">EBNA1</Emphasis> gene variation in Cantonese and its association with nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is closely associated with nasopharyngeal carcinoma (NPC), which occurs with highest incidence in Guangdong. However, EBV is ubiquitous and remains a life-long asymptomatic infection in the peripheral B lymphocytes of healthy carriers; thus it is supposed that there is a substrain of EBV with carcinogenesis potential in NPC high incidence area.     

硅基一维纳米半导体材料的制备及光电性能

硅基一维纳米半导体材料是新型的硅基光电子材料，在硅基光电集成和纳电子领域有重要的应用前景．主要论述了硅基一维纳米半导体材料(纳米硅线、纳米ZnO线)的制备，着重一维纳米材料的阵列化制备，讨论了其生长机理，研究了硅基一维纳米半导体材料的的光学、电学等物理性能．     

可缩多面体是绝对收缩核

在文献［１］（ＰｒｏｃＡｍｅｒ．Ｍａｔｈ．Ｓｏｃ．１９８３，８８：３３３～３３７）中我们证明了每一个可折叠多面体均可内射度量化。借助于这一结果，本文证明了每一个可缩多面体均是个绝对收缩核。