三电平逆变器供电的感应电动机转差频率控制系统

本文研究了三电平逆变器的原理、及其空间电压矢量(SVPWM)调制方案、并利用SVPWM策略决定电压向量的开关顺序和相应的输出电压的方法.提出基于SVPWM的三电平逆变器转差频率控制的异步电动机的矢量控制系统,并进行了仿真,仿真结果显示,所设计的感应电动机转差频率控制系统具有较好的实用价值.     

基于自抗扰控制器的猎雷声纳基阵姿态稳定系统研究

依据声纳基阵姿态控制稳定回路数学模型及工作环境的特点,采用具有非线性结构的自抗扰控制器实现了声纳基阵姿态稳定系统的控制.仿真结果说明,稳定系统的动、静态性能满足指标要求;与经典的PID控制效果相比,控制性能得到了全面改善.     

高墩箱梁悬臂浇筑0号块托架施工技术

通过工程实践,介绍了高墩箱梁悬臂浇筑0号块施工采用的一种较新颖的三角托架,从结构形式、与传统托架比较、结构计算、构造要点等方面作了较详细的介绍,可供类似工程借鉴。     

柱式塔同向回转斜拉-悬索体系桥梁设计关键技术

安徽某跨江通道方案设计中,提出主桥采用主跨1620 m的斜拉-悬索协作体系桥梁。为解决该体系刚度低、主梁压力间断、边吊杆应力幅大等传统疑问,以及因不能设置辅助墩而引起的边跨刚度小、尾索应力幅高的特殊问题,设计采用单柱式桥塔、空间化悬索构建整体结构,并对结构的合理性、可行性进行理论和计算验证。设计针对体系形成的主要过程,提出边孔悬吊辅助跨构造,采用四索面斜拉索和空间双悬索四索面吊索。借助四索面拉吊融合方式在横向转换的便利、同向回转拉索对不对称布索的支持,使调整在更大空间内进行,实现两种体系更加平顺的融合。采用斜置阻尼约束系统使结构纵、横向动力性能满足规范要求。     

浅析怎样搞好汽车维修全面质量管理

汽车维修全面质量管理是汽车维修企业管理中的重要内容,也是汽车维修服务工作的关键环节。当代汽车维修质量管理就是运用现代科学的手段和方法来保证和提高汽车维修质量,全面汽车维修质量管理的范围是客户接待、进厂检验、故障诊断、配件供应、维修作业、中间检验、检验试车、交车全过程。企业相关部门都要参与全面质量管理,形成全面质量管理体系,并使之有效运行,促进企业发展。     

Transshipment hub port selection for shipping carriers in a dual hub-port system

ABSTRACT

This paper investigates the factors affecting transshipment (T/S) hub port selection by a feeder port and helps shipping carriers make a decision about T/S hub port selection in a dual hub-port system. By employing established evaluation factors, a case study is conducted to weigh the priority of factors and to select an alternative T/S hub port, such as between the Shanghai and Ningbo ports from the Nanjing feeder port in the Yangtze River delta (YRD). A combined multi-criteria decision-making (MCDM) framework utilizing the analytic hierarchy process (AHP) and the consistent fuzzy preference relations (CFPR) method is employed to both reduce the number of pairwise comparisons by AHP and to obtain experts’ knowledge in the decision-making process. The result indicates that the cost, availability of hub port’s space allocation, and the connectivity between feeder port and hub port are crucial factors for T/S hub port selection by shipping carriers. In the case study, Shanghai is selected as the T/S hub port from the Nanjing feeder port. Nevertheless, Ningbo port has the advantage of cost, and if the relationship with feeder port can be improved, Ningbo port would be preferred over Shanghai as a T/S hub port for shipping carriers in a dual hub-port system.     

Transition to a cyclable city: Latent variables affecting bicycle commuting

An understanding of the key factors influencing bicycle commuting is essential for developing effective policies towards a cyclable city. This paper contributes to this line of research by proposing a methodology for including cycling-related indicators in mobility surveys based on the Theory of Planned Behaviour (TPB), and applying an exploratory factor analysis (EFA) to evaluate the structure of latent variables associated with bicycle commuting. The EFA identified six cycling latent variables: Lifestyle, Safety and comfort, Awareness, Direct disadvantages, Subjective norm, and Individual capabilities. These were complemented with a latent variable related to habit: Non-commuting cycling habit. Statistical differences and regression analysis were applied with the cycling latent variables. The study also includes the relationship between objective factors and bicycle commuting, which reveals minor associations. This methodology was applied to the “starter cycling city” of Vitoria-Gasteiz (Spain). The results confirm that in this context – in transition to a cyclable city – safety and comfort issues are not the main barriers for all commuters, although more progress needs to be made to normalise cycling. A set of customised policy initiatives is recommended in the light of the research findings, including marketing campaigns to encourage non-commuting cycling trips, bicycle measures to target social groups as opposed to individuals, bicycle-specific programs such as “Bike-to-work Days”, and cycling courses.     

瞬间即永恒:济慈《希腊古瓮颂》浅析

济慈在《希腊古瓮颂》这首诗中,为古瓮留下的瞬间画面赋予了双面性:永恒的爱情和永恒的寂寞。热烈的爱情与寂寥的生活看似对立,却是生活的真谛。现实是残酷的,艺术是理想化的,只有把艺术与现实结合起来,才是生活中的真美,美是永恒的。     

社会剧变期的畸形儿——西门庆新评

《金瓶梅》里西门庆的发家史，是封建社会后期财产再分配的新的经济形态的体现；西门庆集商人、官僚、恶霸于一身的新的社会角色，反映了金钱对权力的渗入和对道德的颠覆；西门庆人欲横流的生存方式，则是金钱异化了的人性的赤裸裸的展露。读懂了西门庆，也就懂得了资本主义在中国最终不能成功的原因。     

浅谈冬季公路雪阻的防治

简要介绍了冬季公路预防风雪流常用的几类设施的适应性及设置要求。对雪阻的治理应综合考虑各种因素 ,因地制宜