滤波电路电容器联接方法对滤波效果影响的分析

文章对滤波电路电容器的联接方法进行分析,得出联接方法对谐波效果有很大影响的结论。尤其是零序谐波,采用角型连接的电容器,没有滤波作用。目前大部分厂商采用角型连接电容器串接14．5％电抗器滤除3次谐波,其实作用甚微。提出了解决方法和需注意事项。     

嵌入式可信平台构建技术研究

为了解决嵌入式终端缺乏完整性度量和应用软件任意执行的问题,在研究可信计算技术、嵌入式可信密码模块和服务模块的基础上,通过引入星形链可信传递模型和软件签名验证机制,设计了在内核空间软件签名验证的实现方案,构建了针对嵌入式设备的可信平台体系结构。该嵌入式可信平台可保证终端的完整性和应用软件的可信启动,可防止恶意代码的破坏,有效提高了嵌入式终端设备的安全性和可信性。     

A novel initiating system for ring‐opening polymerization of ε‐caprolactone: Synthesis of triarm star‐shaped poly(ε‐caprolactone)

The rare earth compound, scandium trifluoromethanesulfonate [Sc(OTf)₃], has been used as a water‐tolerant catalyst for the synthesis of star‐shaped poly(ε‐caprolactone)s (SPCLs) with trimethylol propane as trifunctional initiator in solvent at 40°C. Triarm SPCLs have been successfully prepared. The molar mass of SPCLs were determined by end‐group ¹H NMR analyses, which could be well controlled by the molar ratio of the monomer to the initiator, and were independent of the amount of Sc(OTf)₃ used. Differential scanning calorimetry analyses suggested that the maximal melting point, the cold crystallization temperature, and the degree of crystallinities of SPCLs increased with the increasing of the molar mass and were lower than the linear poly(ε‐caprolactone) (LPCL) with similar molar mass. Furthermore, polarized optical microscopy indicated that LPCL showed fast crystallization rate and good spherulitic morphology with apparent Maltese cross pattern, whereas SPCLs exhibit much lower crystallization rate and poor spherulitic morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of star‐shaped poly(ε‐caprolactone)‐b‐poly(L‐lactide) copolymers: From star architectures to crystalline morphologies

Hexa‐armed star‐shaped poly(ε‐caprolactone)‐block‐poly(L ‐lactide) (6sPCL‐b‐PLLA) with dipentaerythritol core were synthesized by a two‐step ring‐opening polymerization. GPC and ¹H NMR data demonstrate that the polymerization courses are under control. The molecular weight of 6sPCLs and 6sPCL‐b‐PLLAs increases with increasing molar ratio of monomer to initiator, and the molecular weight distribution is in the range of 1.03–1.10. The investigation of the melting and crystallization demonstrated that the values of crystallization temperature (T_c), melting temperature (T_m), and the degree of crystallinity (X_c) of PLLA blocks are increased with the chain length increase of PLLA in the 6sPCL‐b‐PLLA copolymers. On the contrary, the crystallization of PCL blocks dominates when the chain length of PLLA is too short. According to the results of polarized optical micrographs, both the spherulitic growth rate (G) and the spherulitic morphology are affected by the macromolecular architecture and the length of the block chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

星等能量检测系统设计

空间目标场景模拟器是在实验室环境下进行星等探测能力评价和定标的设备,该系统的关键是对弱星等的标定要求很高,最高检测星等为16等星。本文设计了基于光电倍增管的单光子计数器作为模拟星的能量检测设备,给出了光电倍增管的选择方法及其分压器的设计原理,最后通过实验验证了该单光子计数器的测量精度能够满足定标的要求。     

高可用性企业数据交换平台的设计与实现

为了使企业中构建在不同平台上的众多应用系统能够进行安全、可靠的信息交换,基于企业应用集成（EAI）的理念,提出了一种独立于原有系统、具有星型拓扑结构的高可用性企业数据交换平台解决方案。该平台采用通信层、服务层及适配层三层架构应用模型。对构成平台的这三个层次进行深入研究,说明设计实现的方法。此外,为保证平台的高可用性提出了以内存镜像为基础的双机热备算法。该平台的实现不仅能为企业中各应用系统提供高可用的数据交换,而且还可对数据交换的过程进行集中监控和管理,大大提高了数据交换的可管理性与可扩展性。     

深空测控系统跟踪接收机射电星校相的可行性分析

在深空测控系统的实际应用中,由于其天线口径大等原因,面临着角跟踪系统和差通道相位一致性需要在无塔条件下校准的关键技术难题.基于利用射电星校相的解决思路,首先通过分析确定了设计实现方案,并针对射电星信号的特点,结合具体的设计实现对其进行了理论分析,最后给出了实验验证结果.实验证明了射电星校相的可行性,这将对深空测控系统的应用具有非常重要的指导意义.     

三相星型六状态无刷直流电动机传动系统仿真研究

针对无刷直流电动机,运用三相星型六状态的控制方式,建立无刷直流电动机的数学模型,分析其电子控制的运行状态,最后利用MATLAB/simulink搭建了三相星型六状态无刷直流电动机的仿真模型,并进行仿真。仿真结果表明,系统性能良好,为无刷直流电动机的应用提供依据。     

基于IEC 61850-9-2的变电站通信网络仿真

以太网的通信能力是支撑基于IEC 61850标准的数字化变电站正常运行的重要因素。文中围绕全站统一环形网和星形网,采用仿真软件OPNET对变电站的各种典型数据流建模,采样值采用IEC 61850-9-2协议,考虑星形和环形2种网络结构、网络带宽、过程层网络传输采样值、环网断线故障、文件传输对采样值与跳闸报文的影响等因素,制定了多套仿真实验方案,针对一个实际的中型变电站进行了对比仿真实验与分析,为数字化变电站系统的构建提供一定的参考。     

八角茴香及其提取物莽草酸的研究进展

由于中国传统香料八角茴香因含有抗禽流感病毒的重要成分,使其具有了重要的药用价值,综述了国内外关于八角茴香的化学成分、药理作用方面的研究进展,以及八角茴香的重要成分莽草酸的分离提取及药理方面的内容,为进一步开发和利用八角茴香提供了参考依据.