加强计量信息化建设,提高企业计量管理水平

网络化的计量管理信息系统在技术上的实用性和维护性上面都有其可靠性,对计量管理工作采用信息化管理可以真正实现完全意义上的信息共享,使我们管理的计量装置、计量器具准确可靠的运行。     

嵌入式系统芯片的软硬件协同仿真环境设计

针对嵌入式系统芯片SoC开发验证阶段的需求,介绍了一种通用的SoC软硬件协同仿真平台。软件仿真由C／C＋＋和汇编语言编写,硬件仿真基于VMM验证方法学所搭建,SoC设计代码由RTL代码编写而成。将SoC设计代码中的ARM由DSM模型替代,通过VCS编译器将软硬件协同起来进行信息交互,实现一种速度快、真实性高、调试方便的...     

Optimal replacement policy for a two-dissimilar-component cold standby system with different repair actions

In this paper, a cold standby repairable system consisting of two dissimilar components and one repairman is studied. When failures occur, the repair of both component 1 and component 2 are not ‘as good as new’. The consecutive operating times of component 1 after repair constitute a decreasing geometric process, while the repair times of component 1 are independent and identically distributed. For component 2, its failure is rectified by minimal repair, and the repair time is negligible. Component 1 has priority in use when both components are good. The replacement policy N is based on the failure number of component 1. Under policy N, we derive the explicit expression of the long-run average cost rate C(N) as well as the average number of repairs of component 2 before the system replaced. The optimal replacement policy N*, which minimises the long-run average cost rate C(N), is obtained theoretically. If the failure rate r(t) of component 2 is increasing, the existence and uniqueness of the optimal policy N* is also proved. Finally, a numerical example is given to validate the developed theoretical model. Some sensitivity analyses are provided to show the influence of some parameters, such as the costs for replacement and repair, and the parameters of the lifetime and repair time distributions of both components, to the optimal replacement policy N* and corresponding average cost rate C(N*).     

基于SWOT分析的我国第三方物流发展研究

第三方物流是现代物流的发展方向,这种物流模式在我国起步比较晚。我国第三方物流在理论研究和实践方面都落后于发达国家,发展中还存在着诸多方面的问题。本文通过SWOT分析对我国第三方物流发展现状进行了探讨,并提出了推进我国第三方物流发展的对策。     

Heterogeneous acid catalytic esterification by porous polyoxometalate-tantalum pentoxide nanocomposites

Polyoxometalates (POMs) are useful catalysts in both redox and acid catalysis reactions since its catalytic features can be controlled at a molecular level. We investigated POM (POM = H₃PW₁₂O₄₀) on tantalum pentoxide (Ta₂O₅) via hydrolysis of tantalum pentachloride (TaCl₅) in the presence of POM using the sol-gel method for acid catalytic reaction. All obtained amorphous materials have been characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), Fourier transform infrared (FT-IR) spectra, Raman scattering spectroscopy, ³¹P magic-angle spinning (MAS) NMR, field emission scanning electron microscopy (FESEM), and nitrogen adsorption/desorption analysis, in order to confirm the structure integrity of the Keggin unit in as-prepared composites and investigate the morphology and surface textural property of the composites. Catalytic activity of the catalysts has been evaluated for esterification of acetic acid with ethanol as a model reaction with different catalytic reaction parameters such as POM loading, reaction time, catalyst dose, molar ratio of the reactants, etc. The conversion of ethanol reached 87.4 % and the turnover frequency (TOF) was 2.9×10³.Meanwhile, it is easy to separate and recover POM/Ta₂O₅ from the reaction system.     

An interpolation model to accelerate the frequency-domain response calculation of grounding systems using the method of moments

The transient characteristics of grounding systems are essential for their designs and related electromagnetic-compatibility problems in power systems. Although the method of moments (MoM) is a popular way to analyze the characteristics of grounding systems, it is time-consuming. In this paper, a two-stage method is presented to construct fitted models of the frequency-domain responses of grounding systems to accelerate the calculations of the MoM. In the first stage, the adaptive model-based parameter estimation is used to adaptively choose the most valuable frequency sampling points to construct the initial fitted functions, and then the fitted functions are adjusted in the second stage by comparing the fitted results with those computed by the first principle model at some points. The validation was achieved by a comparison of the numerical results and those obtained by inverse fast Fourier transformation.     

石墨炉原子吸收测定化探样品中痕量金的研究

采用以王水分解样品,泡沫塑料富集,硫脲解脱,石墨炉原子吸收分光光度计测定微量金。研究了测定时干燥温度和时间的选择,原子化温度和时间的选择,灰化温度和时间的选择,以及王水体积分数对吸附效果等条件对测定结果的影响。该方法检出限为0.2×10-9,经国家一级分析标准样品验证,结果与标准值相符。     

光传送网的未来发展探讨

文章从网络结构与拓扑两个方面，重点对下一代光传送网进行了探讨，具体介绍了新兴的光传送网——自动交换光网络(ASON)结构及其关键协议，并从运营商和设备商两个不同角度，较为深入地探讨了现有网络向ASON过渡时所采用的策略。