完全信息下可修M/M/1排队系统的均衡分析

研究可修M/M/1排队系统的均衡策略.顾客到达系统后可以观察到系统的队长和服务台的状态（工作或处于修理状态）,根据这些系统状态、排队等待费用及完成服务后的回报报酬等信息,顾客将决定是否加入到系统中.本文在修理时间服从k阶Erlang分布的假设下得到了顾客选择进入排队系统的均衡阈值.     

发展中的滴状冷凝强化换热研究

根据"八*五"、"九*五"滴状冷凝课题研究情况,介绍BFe30-1-1管表面实现滴状冷凝换热的工艺及其换热试验结果,并简介BFe30-1-1管表面滴状冷凝换热实现机理.     

Road traffic conditions in Kenya: Exploring the policies and traffic cultures from unstructured user-generated data using NLP

Road traffic accidents (RTA) are a prevalent cause of fatality with African countries having the highest fatality index (25–34 per quota). The World Health Organization estimates Kenya's fatality rate due to RTA at 28 per quota. From literature, the country's fatality and injuries have increased by 26% and 46.5%, respectively, since the year 2015. The country is faced with incomplete RTA data capturing, hindering effective planning and policy adjustments to curb the menace. In this paper, we scrapped user-generated data (Twitter) and national transport and safety authority's (NTSA) reports to shed light on traffic safety, practices, and cultures in the country. To this end, we gathered 1,000,000 tweets and 8000 speeding entries between 2015 and 2021 and performed natural language processing (NLP) and quantitative study of the data. We applied NLP and n-gram search of keywords to categorize data into 8 topics: traffic, public service vehicle (PSVs), policing, accident, infrastructure, recklessness, robbery, and corruption. From the data, policing, which touches on all police and law-enforcement-related activity was found to be highly correlated with PSVs, recklessness, accidents, traffic congestion, robbery, infrastructure, and corruption with indices of r(76) = 0.92, 0. 91, 0.87, 0.82, 0.81, 0.76, and 0.70, respectively with p < 0.001. The topic modeling confirmed the identified topics to be the latent discussion issues affecting the public. From the study, PSVs, policing and traffic flow were isolated as key issues that ought to be addressed immediately. The research recommended the integration of driver monitoring systems to strengthen policing. The research, which utilized unstructured data, points to the utility of data mining which would greatly benefit traffic research, particularly African-based studies, that suffer from data inadequacy.     

航空货运多航段多阶段模型

在航空货运运力分配中需要解决两个问题:一是选择哪条航段来运输货物,二是在满足货物运输的前提下,选择哪个时期运输货物.本文使用数学规划方法建立了航空货运多航段多阶段模型,以解决航空货运运力分配中的两个问题.通过实例数值仿真,证明了该模型的有效性,并揭示了飞机的承载能力、航段的收益水平和货物的利润水平对舱位分配策略影响较大.     

《中国舰船研究》2019年第1期目录

[1]CFD数值模拟船舶在波浪中的回转操纵运动…王建华,万德成（1）[2]船舶运动与液舱晃荡耦合频域计算方法…孙雷,罗贤成,刘昌凤,姜胜超（9）[3]浮体浅水波浪载荷数值计算方法研究…杨鹏,寇冠元,朱学康,刘成义,高长华（19）[4]滑行艇阻力计算方法对比研究…孙源,卢晓平,李井煜,王中（27）[5]偏转工况下吊舱推进器的水动力和空泡性能…李善成,熊鹰,王展智（33）[6]艇桨一体的螺旋桨激振力和水动力噪声数值预报…王诗洋,汤佳敏,王文全,张祥瑞（43）[7]后燃烧效应对约束空间内爆炸载荷的影响规律…徐维铮,吴卫国（52）[8]含负刚度动力吸振的混合隔振系统振动冲击响应特性分析…苏智伟,黄修长,吴静波,华宏星（59）[9]弹性隔离安装设备抗冲击设计指标影响因素分析…史少华,冯麟涵,杜志鹏,计晨（66）[10]含空腔点阵增强夹芯结构的固有振动分析方法…王祖华,殷洪（72）[11]金属表面点蚀的稳态过程数值研究…崔静,杨帆,杨霆浩,杨广峰（80）[12]双壳船体结构在楔形物撞击下的损伤特性试验及数值仿真分析…张新宇,曹俊伟,骆伟,张敏（89）[13]焊接缺陷对铝合金板架疲劳寿命影响的试验分析…缪素菲,刘敬喜,刘元丹,王秀兰（95）[14]矩形耐压舱预应力支柱优化设计…陈静,余恩恩,卢骏锋,程远胜（102）[15]船舶推进轴系纵向振动共振转换器的优化设计…胡泽超,何琳,徐伟,李正民,赵兴乾（107）[16]营运船舶主机能效和碳排放等级评定方法…丛岩,宋立国,潘新祥,池华方,韩志伟,吴晓光（114）[17]基于GSE平台的蒸汽试验系统边界的动态控制仿真…苑龙飞,宋杨,赵观辉,吴毅,黄杰,黄威霖（120）[18]脉冲性负荷柴油发电机组特性分析…吴骏,庞宇,赵凡琪（125）[19]船舶中压直流电力系统中模块化多电平逆变器的谐波性能仿真研究…郭燚,邵德东,郭将驰,张权宝,李艺（134）[20]I²C总线技术在舰船能量管理系统I/O端口扩展中的应用…许智豪,李维波,华逸飞,徐聪,范磊（144）[21]基于Lyapunov稳定性的船舶航向保持控制器非线性反馈改进…马超,张显库,杨光平（150）[22]基于长基线和超短基线联合的拖曳目标定位技术…吴静波,程淑萍,赵鹏铎（156）     

分层递阶控制理论与地铁环控系统构建

从理论体系上,结合分层递阶控制理论中高阶产生式系统,提出地铁环境与设备监控系统(building automatic system,BAS)是一个具有递阶和分散控制结构的大系统,且二者之间存在紧密的、类似理论与实践的相互促进关系.将仿人智能控制理论(HSIC)引入地铁的BAS中,为其设计提供新的系统运行模型.根据实践需要,提出改进的分层递阶控制系统的体系结构,并对其可靠性进行分析.     

基于随车声强法的公路隧道水泥混凝土路面噪声特性

应用随车声强法测试了高速公路混凝土路面与沥青路面的噪声, 采用统计产品与服务解决方案软件(SPSS)分析了噪声样本数据, 研究了横向刻槽、纵向刻槽、纵横组合式刻槽及露石混凝土等具有不同抗滑纹理的隧道混凝土路面的A计权声压级和1/3倍频谱噪声特性, 并与普通沥青混凝土路面(AC)、沥青玛蹄脂碎石混凝土路面(SMA)和超薄磨耗层的噪声特性进行了对比。研究结果表明: 横向刻槽与横向组合式刻槽混凝土路面的噪声范围集中在100~104 dB(A), 纵向刻槽混凝土路面的噪声范围集中在99~102 dB(A), 露石混凝土路面、普通沥青路面、SMA路面、超薄磨耗层的噪声范围集中在97~100 dB(A); 各种路面的1/3倍频程峰值频率均出现在1 000Hz附近, 但是露石混凝土路面、普通AC路面、SMA路面、超薄磨耗层峰值频率对应的噪声水平比横向刻槽混凝土路面高出3~5 dB(A)。可见, 路表纹理形式是影响隧道混凝土路面噪声的重要因素, 合理地选择路面纹理有助于降低隧道混凝土路面的噪声。     

Consumers’ willingness to pay for alternative fuel vehicles: A comparative discrete choice analysis between the US and Japan

This paper conducts a comparative discrete choice analysis to estimate consumers’ willingness to pay (WTP) for electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) on the basis of the same stated preference survey carried out in the US and Japan in 2012. We also carry out a comparative analysis across four US states. We find that on average US consumers are more sensitive to fuel cost reductions and alternative fuel station availability than are Japanese consumers. With regard to the comparative analysis across the four US states, consumers’ WTP for a fuel cost reduction in California is considerably greater than in the other three states. We use the estimates obtained in the discrete choice analysis to examine the EV/PHEV market shares under several scenarios. In a base case scenario with relatively realistic attribute levels, conventional gasoline vehicles still dominate both in the US and Japan. However, in an innovation scenario with a significant purchase price reduction, we observe a high penetration of alternative fuel vehicles both in the US and Japan. We illustrate the potential use of a discrete choice analysis for forward-looking policy analysis, with the future opportunity to compare its predictions against actual revealed choices. In this case, increased purchase price subsidies are likely to have a significant impact on the market shares of alternative fuel vehicles.     

基于维修规划的舰船船体腐蚀防护经济性分析

  目的  碳钢在海洋环境下的腐蚀速率预测非常复杂和模糊。针对碳钢腐蚀速率的灰色预测模型精度普遍不高的现状,为提高腐蚀速率预测模型的精度,  方法  通过船用碳钢腐蚀速率和海洋环境因素的灰关联分析,得到影响船用碳钢腐蚀速率的关键因素,进而建立具有较高精度的GM（1,N）腐蚀速率预测模型。  结果  实例分析表明,在青岛、厦门、舟山和榆林海域影响船用碳钢腐蚀速率的主要环境因素是海水温度、海生物附着量、pH值和海水盐度,在此基础上建立的GM（1,5）模型具有较高的精度且计算量较小。  结论  GM（1,N）模型可以有效预测碳钢等船用金属的腐蚀速率,可为船用金属腐蚀寿命的研究提供理论支撑,具有一定的参考价值。