船用起重机电气改造

本文对工程船起重机的电控系统的现状进行了介绍和分析,针对目前的系统配置和使用过程中存在的问题,提出了采用交流变频电控系统的改造方案,阐述了系统的配置及设备的选型。通过改造,提升了系统操控性和可靠性。     

三电平SVPWM变频调速系统的PSCAD/EMTDC仿真

本文分析了三电平空间矢量脉宽调制的基本原理,应用电磁暂态分析软件PSCAD/EMTDC搭建了基于三电平逆变器的感应电机调速系统模型,实现了电机的矢量控制。仿真结果证明了该方法的有效性。     

基于矢量控制的带式输送机能耗控制方法研究

带式输送机系统是散货码头的重要组成部分,而感应电机作为最重要的驱动组成,其运行效率不高,导致了电力能源的浪费.本文从感应电机转子磁场定向角度出发,建立了一种考虑铁损的感应电机新模型,并提出了最大效率矢量控制策略.通过检测或估计电机的电流信号,使得电机运行于最优效率点,从而提高带式输送机系统的整体效率.最后仿真模拟了该控...     

中控交通综合管理信息系统在高速公路运营管理中的应用

中控交通综合管理信息系统以HIMS为依托,能完成对各种设备,交通事故统计等进行管理,生成对应的报表,系统基于.NET Framework环境,C#语言开发,采用分层架构设计,加入ASP.NET 2.0、Sql Server 2000、AJAX、NHibernate等技术,最终给用户提供简单易懂的管理界面,可以满足高速公路日常运营的无纸化办公管理.     

多气门屋顶型燃烧室发动机动态网格生成方法研究

以具有屋顶型燃烧室的四气门汽油机MV377为例,结合改进的KIVA3V程序,提出了一种适应于该类型燃烧室的分块结构化网格划分策略及相应的动态网格调整方法,并基于该方法所生成的网格完成了汽油机缸内流动过程瞬态数值计算.结果表明用该方法能保证网格生成质量,满足计算精度要求.     

LMS自适应滤波器的FPGA实现

LMS自适应滤波器是一种广泛使用的数字信号处理算法,对其实现有多种方法.通过研究其特性的基础上,提出了在FPGA中使用软处理的嵌入式实现方案,文中对实现方式的优缺点进行了分析,并给出了硬件实现中的有线字长效应进行了详细的分析.     

轻骨料导电混凝土面层的升温与化冰实验研究

采用导电性好的炭黑轻骨料导电混凝土作为混凝土面层的表层,研究了该混凝土面层在模拟低温环境下的升温和化冰与输入电功率的关系.输入电功率较大时,在相同的低温、相同的时间内面层表面温度较高.在路面结冰不超过3 mm且环境温度分别为-10～-5℃,-15～-10℃,20～-15℃时,导电混凝土层基本满足要求的电功率分别应为400,500,600W/m2.炭黑轻骨料导电混凝土在多次通电过程中电阻稳定,因而电功率稳定.     

An efficient threshold key-insulated signature scheme

To tackle the key-exposure problem in signature settings, this paper introduces a new cryptographic primitive named threshold key-insulated signature (TKIS) and proposes a concrete TKIS scheme. For a TKIS system, at least k out of n helpers are needed to update a user’s temporary private key. On the one hand, even if up to k−1 helpers are compromised in addition to the exposure of any of temporary private keys, security of the non-exposed periods is still assured. On the other hand, even if all the n helpers are compromised, we can still ensure the security of all periods as long as none of temporary private keys is exposed. Compared with traditional key-insulated signature (KIS) schemes, the proposed TKIS scheme not only greatly enhances the security of the system, but also provides flexibility and efficiency.     

A selection scheme for optimum number of cooperative secondary users in spectrum sensing

An optimization scheme for choosing the optimum number of secondary users in cooperative spectrum sensing based on the cyclostationary feature detection with Neyman-Pearson criterion is proposed in this paper. The optimal soft combination test statistic for the cooperative spectrum sensing based on cyclostationary feature detection is derived according to the generalized likelihood ratio test and its corresponding detection performance is deduced. A target function, considering two important parameters as the resource use efficiency and the number of samples employed by each cooperative secondary user in the system design, is constructed to obtain the optimum number of cooperative secondary users. It can be found that the selection scheme is to make a tradeoff between the system complexity of the cognitive radio network and the global sensing performance of the cooperative spectrum sensing.     

随机条件下固定公交线路服务频率优化模型

在考虑客流需求波动及车辆运行时间随机变动的情况下,建立了以乘客候车期望和公交车辆利用率总体最优为目标的公交线路服务频率优化模型.利用蒙特卡罗方法随机模拟一条高频线路的公交服务,计算得到了给定线路参数下的最优服务频率.算例表明该模型可用来确定高频服务公交线路的发车时间间隔.