矿山井下低压IT接地系统设计规范探讨

介绍了矿山井下低压IT接地系统第一次接地故障的原理,指出GB 50070—2009《矿山电力设计规范》要求"配电系统相导体和外露可导电部分之间第一次出现阻抗可忽略的故障时,故障电流不应大于5A"的规定是没有实际意义的;通过计算比较IT系统和TN系统单相接地故障时的触电电压和电流,可知在采用IT系统时直接触电的人身触电电流与采用TN系统时基本相同,而在间接触电的情况下IT系统优于TN系统。     

依托网络教学平台 提高课堂教学效果

网络教学作为一种新的辅助教学手段,是目前教学改革主要研究的方向之一。通过对网络教学平台的功能分析,探讨了在网络教学平台上进行教学资源的建设、交流互动教学活动的开展和虚拟实验室的建设,通过应用实践证明,充分利用网络教学平台的优势,能有效地提高课堂教学质量和效率,培养学生的学习能力、实践能力和创新能力。     

An update-based step-wise optimal cache replacement for wireless data access

Many network applications requires access to most up-to-date information. An update event makes the corresponding cached data item obsolete, and cache hits due to obsolete data items become simply useless to those applications. Frequently accessed but infrequently updated data items should get higher preference while caching, and infrequently accessed but frequently updated items should have lower preference. Such items may not be cached at all or should be evicted from the cache to accommodate items with higher preference. In wireless networks, remote data access is typically more expensive than in wired networks. Hence, an efficient caching scheme considers both data access and update patterns can better reduce data transmissions in wireless networks. In this paper, we propose a step-wise optimal update-based replacement policy, called the Update-based Step-wise Optimal (USO) policy, for wireless data networks to optimize transmission cost by increasing effective hit ratio. Our cache replacement policy is based on the idea of giving preference to frequently accessed but infrequently updated data, and is supported by an analytical model with quantitative analysis. We also present results from our extensive simulations. We demonstrate that (1) the analytical model is validated by the simulation results and (2) the proposed scheme outperforms the Least Frequently Used (LFU) scheme in terms of effective hit ratio and communication cost.     

Decoherent dynamics of quantum correlations in qubit–qutrit systems

We study the dynamics of quantum correlations of qubit–qutrit systems under various decoherent channels. It is shown that the multi-local and local decoherent channels bring different influences for the dynamics of quantum correlations measured by negativity, quantum discord and geometric discord, which depend on the initial state parameters and the properties of the decoherent channels. We put emphasis on the phenomena such as entanglement sudden death, sudden transition between classical and quantum decoherence and stable quantum discord and geometric discord.     

A novel method to construct 3D electrodes at the sidewall of microfluidic channel

We report a simple, low-cost and novel method for constructing three-dimensional (3D) microelectrodes in microfluidic system by utilizing low melting point metal alloy. Three-dimensional electrodes have unique properties in application of cell lysis, electro-osmosis, electroporation and dielectrophoresis. The fabrication process involves conventional photolithography and sputtering techniques to fabricate planar electrodes, positioning bismuth (Bi) alloy microspheres at the sidewall of PDMS channel, plasma bonding and low temperature annealing to improve electrical connection between metal microspheres and planar electrodes. Compared to other fabrication methods for 3D electrodes, the presented one does not require rigorous experimental conditions, cumbersome processes and expensive equipments. Numerical analysis on electric field distribution with different electrode configurations was presented to verify the unique field distribution of arc-shaped electrodes. The application of 3D electrode configuration with high-conductive alloy microspheres was confirmed by particle manipulation based on dielectrophoresis. The proposed technique offers alternatives to construct 3D electrodes from 2D electrodes. More importantly, the simplicity of the fabrication process provides easy ways to fabricate electrodes fast with arc-shaped geometry at the sidewall of microchannel.     

一种基于混沌理论的改进否定选择算法

随着网络应用规模的不断扩大,网络安全隐患越来越突出地显现出来,生物免疫系统与木马检测系统在功能上有许多相似之处,具有高度并行性、自治性、动态特征和记忆性等特点。为了能准确、及时地检测出木马入侵,解决检测系统检测正确率低、漏报率高和缺乏检测未知木马等问题,人工免疫原理已被应用到木马检测的研究中。研究了免疫系统的混沌特性,运用混沌理论对否定选择算法进行改进。实验结果显示,该算法能有效提高系统动态学习能力,增强了系统的灵敏性。     

浅析局域网监控与安全

伴随着计算机网络时代的空前繁盛,网络计算机的应用已成为现如今人们生产生活中不可或缺的重要组成部分.同时,人们越来越意识到网络的重要性,通过网络,人们拉近了彼此之间的距离.本来分散在各处的计算机被网络紧紧的联系在了一起.局域网作为网络的组成部分,发挥了不可忽视的作用,而局域网的监控与安全也成为越来越多的人重视的话题.在人们对于信息化生活水平的要求不断提高的同时,对于信息化网络通信的安全性也开始给予了更多的关注,这就必然对于现代的网络安全系统提出了更高的要求.     

基于智能客户端的巡检系统设计与实现

针对健康检查中心医生外出进行健康检查作业时,健康检查系统无法离线使用的问题,本文应用智能客户端技术构建巡检系统。该巡检系统可以在离线状态完成健检系统功能,待系统连线以后,通过调用Web Service访问健康检查中心数据库进行数据上传和下载。对系统进行总体设计,给出体系结构图,并且详细介绍相关技术及实现。