Design and optimization of an LPG roller vane pump for suppressing cavitation

A roller vane type liquefied petroleum gas (LPG) pump was developed for a liquid phase LPG injection (LPLi) engine. Most of the LPG pumps used in the current LPLi engines are installed inside of the LPG tank, but this pump is intended to be installed outside of the LPG tank to overcome the difficulty of fixing an in-tank pump. Because LPG has a low boiling point and high vapor pressure, it usually causes cavitation in the pump and consequently deteriorates the flow rate of the pump. The purpose of this work is to optimize the design of the roller vane pump in order to suppress cavitation and increase the fuel flow rate by using a computational fluid dynamics (CFD) analysis. In order to achieve these goals, the intake port configuration and the rotor of the roller vane pump were redesigned and simulated using STAR-CD code. Computation was performed for six different models to obtain the optimized design of the roller vane pump at a constant speed of 2600 rpm and a constant pressure difference between the inlet and outlet of 5 bar. The computation results show that an increased intake port cross-section area can suppress cavitation, and the pump can achieve a higher flow rate when the rotor configuration is changed to increase its chamber volume. When the inlet pressure difference is 0.1 bar higher than the fluid saturation pressure, the pump reaches its maximum flow rate.     

快速公交系统离散仿真框架 的设计和实施

世界范围内,快速公交系统是缓解许多城市交通拥挤问题的有效方法之一.然 而,系统的成功与否依赖多种因素,如服务规划、基础设施、车站设计、乘客信息系统及系 统的集成和接口等.本文基于离散事件系统,构建了快速公交系统（BRT）的计算机仿真 框架.这种方法在评估各种变量对BRT 运行效果的影响时能够节约成本.结果表明,一部 分子系统能够直接用于模拟典型的BRT 系统.数值试验证明,开发的子系统能够合理地 再现实际BRT 系统中的常见情况.     

素砼桩复合地基处理拓宽路堤软基的现场试验研究

以在建的佛开高速公路谢边至三堡段扩建工程软基试验段为依托,在新老路堤采用合理的拼接措施,软土地基采用素砼桩复合地基进行处理的基础上,结合现场监测数据,分析研究素砼桩复合地基处理高速公路拓宽工程软基的沉降变形特性。     

浅谈影响超声回弹综合法检测精度的主要因素

列举了影响超声回弹综合法检测精度的主要因素,并结合部分试验数据进行分析说明,为现场检测工作提供指导。     

大学物理网络辅助教学平台建设的探索与研究

本文阐述了大学物理网络辅助教学平台建设的内容,总结了网络辅助教学平台建设的特点,提出了网络辅助教学平台建设存在的J＊--ltt~解决的对策。     

Advances in port studies: the contribution of 40 years Maritime Policy & Management

Port economics, management and policy have progressively emerged as a distinctive research field, and a core part of maritime economics. This paper provides an analysis of all the 267 port studies published in Maritime Policy & Management (MPM) since its inception in 1973. This paper provides a content analysis for seven interrelated research theme categories including main research topics and methods, authorship distribution and citation counts. It is demonstrated that MPM played, and continues to play, a key role in publishing research on seaports. The published research increasingly applies established analytical frameworks to ports. The paper concludes with a discussion on current challenges for port-related research.     

A study of factors influencing the severity of road crashes involving drunk drivers and non drunk drivers

In this study, an attempt has been made to develop Multinomial Logit (MNL) model by analysing the drunken and non drunken drivers involved in road crashes on Indian highways. Multinomial Logit model has been deployed to assess the influence of various parameters like vehicular, environment and geometric factors on the set of drivers who were found to be drunk at the time of getting involved in the road crash and those who were not under the influence of alcohol at the time of meeting with the road crash. The total economic cost of road crashes in the case of non-drunk driver road crash is Rs. 1046.27 million whereas in the case of drunk driver road crashes it is estimated to be Rs. 204.50 million. Further, it can be observed that economic cost of drunk driver road crashes is varying from 13 to 19 % across different types of road crashes.     

Some economic aspects of conflicts over land use in the coastal zone

Abstract

Recent land use legislation pays particular attention to the coastal zone where age‐old conflicts have recently accelerated. Flexibility is required in policy because visible conflicts are tied into complex physical and social systems which may require changing patterns of land use over time. Public policy is altering property rights and a thorough understanding of the economic and social roles played by those rights is required. Economic models can be used to understand some major changes such as types of alteration of the environment, but may be ignored or misused unless a better understanding of coastal decision processes is developed.     

冲压荷载下水泥路面土基的变形及应力分析

通过建立有限元模型,采用瞬态动力学加载方法,模拟冲击压路机破裂稳固旧水泥混凝土路面的冲压效果,探讨冲压荷载作用下土基中的应力传递规律和沉降变形．结果表明：在土基顶面以下5 m深度处由冲压荷载引起的土基竖向应力和位移均接近于0,冲压荷载的影响深度不超过5 m;冲压荷载作用下路基的工作区为2．25 m深度范围内,埋深超过2．25 m的构造物理论上不受冲压荷载的影响．     

A three-stage least squares approach to the analysis of airline strategies for aircraft size and airline frequency on the north Atlantic: an airline case study

In response to increasing demand, airlines may increase capacity by increasing the frequency of flights or they may choose to increase aircraft size. This may yield operating cost economies. If the airports they operate from are capacity constrained, they will be limited in the extent that they can change frequency which will limit their ability to compete with the number of frequencies offered. This article focuses on this trade-off and pays particular attention to the practices of a specific airline. Conclusions are offered on the impact of inter alia competition, changes in aircraft technology, 9/11 and the impact of slot constraints. It appears that changes in size are more important than frequency, which is consistent with the presence of slot constraints and there is a significant impact of competition. As the concentration of carriers increases, so aircraft size falls. 9/11 also has a significant impact on traffic whereas the introduction of the Boeing 777, as an illustration of a change in technology, does not.