由感应电压引起的电压异常原因分析与处理措施

针对外高桥三厂启动调试过程中导致断路器无法合闸的高感应电压现象,基于电磁暂态程序(EMTP)建立了外高桥三厂的感应电压分析模型,研究了外高桥三厂在各种工况下的桥引线感应电压,并提出了调度操作中应注意的问题和解决措施.     

Performance of Polymer Modified Asphalt Bridge Expansion Joints in Low-Temperature Regions

Conventional asphalt bridge expansion joints used in low-temperature regions generally show cracking within the first 2?years. To improve the low-temperature performance of these joints, the commercial MEIJIA asphalt binder commonly used in bridge expansion joint construction was modified with two polymers: thermoplastic rubber and rubber. The goal is to find an optimum combination of polymers, binders, and aggregates to improve the performance of asphalt expansion joints in low-temperature regions. The polymer modified binders and mixtures were evaluated for their low-temperature properties using ductility, penetration, indirect tension, and bending tests. The study indicates that performance of these joints at low temperature can be enhanced significantly with the right combinations of polymers, binders, and aggregates. Four expansion joints made with the polymer modified asphalt mixtures were installed on two bridges in a cold region. A construction procedure was also developed to install these joints properly to minimize low-temperature cracking along the interface between the joint and bridge deck. After 7?years of service, the four joints show good performance without any visible cracking or rutting.     

Analysis and improvement of an authentication protocol for the multi-server architecture

Cryptanalysis of Li et al.'s authentication protocol shows that it is vulnerable to masquerade attack, session key disclosure attack and forge smart card attack. To overcome these security flaws, an improved protocol is presented. This protocol proves secure against some possible attacks. Besides, the improved scheme maintains the features of identity anonymity, concise registration, simple operation, and so on.     

基于关键点信息的鲁棒参考水印算法

鲁棒参考水印(RRW)算法是基于小波多分辨分析的用于静态图像的数字水印算法,在分析了RRW算法在图像小波分解系数的平均值较小时的缺陷的基础上,根据人眼视觉原理,提出了利用水印的关键点信息来改进RRW算法的思想.与常规RRW算法不同,算法使用关键点信息,在对小波系数进行特征量化时,对关键点取较小的Q值,对非关键点取较大的Q值.在水印检测中,对关键点和非关键点赋予不同的权值,并深入分析了该方法的正向错误概率和负向错误概率的计算公式.实验结果表明,改进算法不但其性能优于原算法,而且还在一定程度上缓解了水印的不可见性和健壮性之间的矛盾.     

Uncertainty analysis and robust control of fuel delivery systems considering nitrogen crossover phenomenon

In this paper, the fuel delivery subsystem (FDS) with hydrogen recirculation and anode bleeding is applied in proton exchange membrane fuel cell (PEMFC) system, which is utilized to supply hydrogen to the anode of stack and recirculate fuel back to the supply line. As the diffusion of nitrogen from cathode to anode is inevitable in a real PEMFC during long-term operation. To prevent system performance decline due to nitrogen accumulation. Therefore, this paper firstly develops a control-oriented nonlinear dynamic FDS model involving gas diffusion. Additionally, the FDS is very sensitive to operating environment, uncontrolled operation conditions may cause stack degradation. Specifically, a method based on Monte Carlo simulation is proposed to identify the key parameter boundaries. Then the gas distribution in FDS due to nitrogen crossover is analyzed in detail. After this, a hybrid robust methodology based on sliding mode algorithm is also proposed to maintain adequate hydrogen pressure supply, suitable hydrogen and nitrogen content in the system in presence of nitrogen crossover and renewed uncertainties. Finally, the performance of the presented controller is compared with nonlinear PID (NPID) control and nonlinear multi-input-multi-output (NMIMO) control through a hardware-in-the-loop test bench. Experimental results show that the hybrid controller is accurate and suitable for control purpose, the nitrogen content is restricted to the given range and the variation of output voltage is limited to the desired boundaries, the feasibility and effectiveness are validated.     

Simulation and experiment of heat and mass transfer in a proton exchange membrane electrolysis cell

A full-scale, two-phase, single-channel model of proton exchange membrane electrolysis cell is established. The electrochemical model and the thermal model are coupled to explore the mass transfer of the channel, catalytic layer and diffusion layer, and the heat transfer of the entire electrolysis cell. Two different calculation models are compared, and it is found that the calculation results of the model with bipolar plates are closer to the actual values. Simultaneously, effective water and thermal management strategies are proposed: The temperature of the electrolysis cell can be reduced effectively by supplying water to the cathode side. The Counter-flow mode has a lower temperature than the Co-flow mode, but the temperature gradient in the Counter-flow mode is greater. Reducing the channel depth and increasing the channel width can improve the water transmission in the electrolysis cell and reduce the temperature of the electrolysis cell, but a larger channel width will increase the electrical loss. Therefore, the selection of appropriate channel size is of great significance to the long-term stable operation of the electrolysis cell.     

面向大批量定制的计算机辅助制造系统研究

为了满足大批量定制企业快速响应客户个性化的需求,将大批量定制相似性原理、重用性原理和整体性用于计算机辅助制造系统中,提出了面向大批量定制企业计算机辅助制造的基本特征和体系架构.在该体系架构中,利用基于相似性原理的主模型和事物特性表技术来实现数控程序快速成型;用产品数据管理实现加工信息的统一管理和高度重用;利用产品数据管理和分布式数控的集成来实现对车间加工的任务分配、管理和快速加工;对其中的关键技术进行了研究,提出了相应的解决方案,并成功地运用于企业生产.     

变风量空调系统应用研究

对变风量系统的工作原理、系统特点、适用场合均作了详细地阐述。对系统设计中各主要方面诸如负荷计算、风量取值、风口选型以及系统在冬夏运行调节时的风机控制方式,系统运行模式作了一定的探讨并提出了自己的见解。     

Windows内核恶意代码分析与检测技术研究

Windows内核恶意代码是指能够通过改变Windows执行流程或者改变内核审计和簿记系统所依赖的数据结构等手段以达到隐藏自身，实现恶意功能的程序或程序集，对操作系统安全造成很大的危害。对近年来基于NT内核的微软Windows操作系统下恶意代码主要的隐藏实现技术（包括对进程函数、注册表函数、SSDT等的HOOK行为）进行了深入分析研究，提出了一些具有实用价值的恶意代码检测技术方案。实践表明文中提出的恶意代码分析检测技术在实际中具有积极的指导意义。     

节能减排背景下电力需求分析预测研究

在充分了解国家及华东地区节能减排政策的基础上,结合华东地区工业化进程情况及经济发展现实,分析了华东地区在节能减排背景下电力需求变化呈现出的新特点.通过对常用中长期电力需求预测方法在节能减排背景下的适用性分析,对其中弹性系数法、相关分析法以及模糊预测方法等进行了深入探讨,同时为了验证所提出预测方法的可用性,对华东地区"十二五"期间的电力需求情况进行了预测和分析,并对节能减排背景下华东地区未来的用电结构进行了展望.