自发电用60kW双频变频发电机的设计和使用

介绍了自发电用60 kW双频变频发电机的结构、工作状态和励磁系统的设计     

宁波轨道交通车载WIFI系统兼容研究

从宁波轨道交通1号线车载Wi Fi全覆盖的实践展开分析,研究Wi Fi覆盖对列车信号系统车地无线通信的影响,优化Wi Fi频段的设置、合理安装车载AP、控制车载AP功率,可消除同频干扰,实现车载Wi Fi覆盖和信号车地无线传输的兼容共存,并确保列车运行的安全。     

Assessment of the effects of highway geometric design features on the frequency of truck involved crashes using bivariate regression

Given the enormous losses to society resulting from large truck involved crashes, a comprehensive understanding of the effects of highway geometric design features on the frequency of truck involved crashes is needed. To better predict the occurrence probabilities of large truck involved crashes and gain direction for policies and countermeasures aimed at reducing the crash frequencies, it is essential to examine truck involved crashes categorized by collision vehicle types, since passenger cars and large trucks differ in dimensions, size, weight, and operating characteristics. A data set that includes a total of 1310 highway segments with 1787 truck involved crashes for a 4-year period, from 2004 to 2007 in Tennessee is employed to examine the effects that geometric design features and other relevant attributes have on the crash frequency. Since truck involved crash counts have many zeros (often 60–90% of all values) with small sample means and two established categories, car-truck and truck-only crashes, are not independent in nature, the zero-inflated negative binomial (ZINB) models are developed under the bivariate regression framework to simultaneously address the above mentioned issues. In addition, the bivariate negative binomial (BNB) and two individual univariate ZINB models are estimated for model validation. Goodness of fit of the investigated models is evaluated using AIC, SBC statistics, the number of identified significant variables, and graphs of observed versus expected crash frequencies. The bivariate ZINB (BZINB) models have been found to have desirable distributional property to describe the relationship between the large truck involved crashes and geometric design features in terms of better goodness of fit, more precise parameter estimates, more identified significant factors, and improved predictive accuracy. The results of BZINB models indicate that the following factors are significantly related to the likelihood of truck involved crash occurrences: large truck annual average daily traffic (AADT), segment length, degree of horizontal curvature, terrain type, land use, median type, lane width, right side shoulder width, lighting condition, rutting depth (RD), and posted speed limits. Apart from that, passenger car AADT, lane number, and indicator for different speed limits are found to have statistical significant effects on the occurrences of car-truck crashes and international roughness index (IRI) is significant for the predictions of truck-only crashes.     

大型医务船生活用水及污水处理系统设计

介绍了变频恒压技术在大型医务船供水系统中的设置、应用及优点,以及生活污水处理系统的设计要点。     

基于数字信号处理实现VOX技术

介绍一种用数字方式实现VOX功能的方法。根据语音信号的特征及短时分析技术,利用语音信号能量和过零率相结合检测方法,可有效进行有声/无声判断。根据所述检测原理和实现方法,进行了不同信噪比条件下的仿真分析。经过实际应用测试,该系统易于实现,实时性好。     

未知参数的舰船辐射噪声线谱Duffing振子检测方法

当被动声呐探测舰船目标时,舰船辐射噪声中的线谱成分是舰船分类识别及航行状态监测的特征参量,通常情况下线谱的频率及数量是未知的。针对现有未知频率的Duffing振子检测方法存在系统结构复杂,判别时间长,需要人为参与等问题,本文构造了变参数单一Duffing振子检测模型,并提出了变频频率切片小波变换的Duffing振子检测方法。该方法通过设置合理的频率灵敏度参数自动地调整系统内置策动力频率值,利用频率切片小波变换提升系统抗噪性能,结合Poincare映射特征函数的系统相态定量判决方法,变频搜索待测信号中的线谱分量。在实测数据的分析处理中,对不同观测时间内的数据进行检测,实现了线谱成分的检测跟踪与频率估计,并根据时间轨迹上的频率识别信息确定存在的稳定线谱成分。数据处理结果表明,该方法能够实现低信噪比下参数未知线谱的检测与频率估计。     

闸楼房无人值守系统的设计与实现

主要介绍闸楼房无人值守系统的设计、实现及运用效果.该系统主要利用射频识别和计算机技术,通过在机车上安装射频IC卡,在车务部门与机务段分界点的闸楼房安装扫描读卡装置,实现机车出入信息的自动识别、采集与处理,并利用现有网络通道,实现铁路局、车务部门和机务段3级网络的信息共享,使各级运输管理人员都能够实时掌握机车出入及运用情况.     

阵列式高射频武器效力仿真分析

针对反舰导弹的运动特性,进行了三维的仿真分析,并研究了反舰导弹的超音速和强机动给目标预测带来不可避免的误差的情况。重点介绍了拦阻射击的概率密度函数公式,通过仿真分析得出结论,在目标预测误差存在而且并不是很小时,拦阻射击比跟踪集火射击在命中率方面有很大的提升。在此基础上,对阵列式高射频武器的结构设计做了初步探讨。     

CKA-C型外锁闭装置动力学特性试验研究

在宁波地铁轨道测试线道岔上,安装了CKA-C型外锁闭装置进行行车试验,采集基本轨、尖轨连接铁、锁闭框、锁钩和锁闭杆的动力学响应数据,通过分析加速度信号的频谱及结构件所承受的应力,评估产品的安全性和可靠性。试验结果表明CKA-C型外锁闭装置能够满足使用需要,且具有较大的安全余量;产品的固有频率也避开了行车的特征频率,不会产生共振。     

88m超规范甲板驳船的结构强度有限元分析

通过充分利用DNV的Sesam软件和MSC.patran以及MSC.Nastran几个软件的优势,对一艘88m超规范甲板驳船进行了横向强度分析,找出船舶在不同工况下所对应的承载规律。并在频域内采用三维线性势流理论的波浪载荷计算方法对甲板驳船进行了波浪载荷直接计算,分析了不同工况先载荷分布的特点,并将计算结果与CCS规范和DNV规范中的结果进行了比较,为合理选取波浪载荷提供依据。