Superpave沥青混合料级配优化与路面离析防治

为了减小混合料离析造成的路面早期病害,以泰州长江公路大桥镇江段高速公路SUP-25下面层施工为例,分析了离析产生的原因,总结了路面离析的种类,研究了混合料级配的优化,提出了集料堆放、拌和、运输、摊铺、碾压等各个施工环节中预防离析的处理措施,保证最大限度地减少离析现象,确保沥青路面的质量.     

Multi-channel spectrum sensing in cognitive ad-hoc networks: An energy-efficient manner

Cognitive radio,which is capable of enabling dynamic spectrum access,is a promising technology in future wireless communication.The feasibility of cognitive radio network greatly depends on the energy efciency and reliability of spectrum sensing technology.In this paper,spectrum sensing in cognitive ad-hoc network（CAN）with wide-band dynamic spectrum is considered.A cognitive cluster head（CCH）is set and responsible for dividing the wide-band spectrum into multiple sub-channels;it can either sense sub-channels in a centralized manner,or make use of sensing modules to sense sub-channels in a distributed manner.Then cognitive users（CUs）can get sensing results and access to the available sub-channel.We take the cost of control message into consideration and formulate the energy consumption of CAN in terms of sub-channel sampling rate and whole-band sensing time.We define energy efciency intuitively and solve the energy efciency optimization problem with sensing reliability constraints by constructing a parametric problem and obtain the optimal sampling rate and the wholeband sensing time.Power dissipation model of a practical A/D convertor（ADC）is introduced,and numerical results are given to show the energy efciency performance of two diferent sensing manners.     

Optimization of Fare Structure and Service Frequency for Maximum Profitability of Transit Systems

Abstract

Providing efficient public transportation has been recognized as a potential way of alleviating congestion, improving mobility, mitigating air pollution, and reducing energy consumption. Many people use public transportation systems for their daily commute, while others use different transportation modes (e.g. cars, taxis, carpools, etc.). Inexpensive fares with good transit service encourages ridership, and the resulting revenue may be used to provide better service. Optimization of transit service frequency and its associated fare structure is desirable in order to increase revenue at reasonable transit operating expenditure. The objective of the study reported here is to maximize profit subject to service capacity constraint, while elastic demand is considered. The solution methodology is developed and applied to solve the profit maximization problem in a case study based on Newark, NJ, USA. Numerical results, including optimal solutions and sensitivity analyses, are presented. It is found that an optimal temporal headway and differential fare structure that maximizes total profit for the studied subway system can be efficiently solved.     

多行星排机电复合传动特性分析

针对车辆常用机电复合无级传动的分速汇矩、分矩汇速和分速汇速3种功率耦合机构,分析了多行星排分流传动的转速、转矩和分流比特性,并对不同分流形式组合进行了分析。结果表明:多行星排分流特性与两行星排分流传动特性相同,分速汇矩式分流传动有一个机械点,在机械点之前分流比较小,适用于低速起步阶段;分矩汇速式分流有一个机械点,分流比成对称分布,传动比小于机械点时,成分流工况,效率高,适合于高速阶段。分速汇速式分流传动有两个机械点,在两个机械点之间分流比较小,适用于中高速阶段。对于多模式机电复合传动,低速起步采用分速汇矩式分流传动,中高速采用分速汇速式分流传动比较好,可实现电机无速差切换。     

基于Pro/Engineer建立客车骨架类三维通用件库的方法

对Pro/Engineer标准件、通用件作简要介绍,详细探讨客车设计中骨架类通用件构建方法及其拓展应用功能。     

Urea-SCR system optimization with various combinations of mixer types and decomposition pipe lengths

The demand for NO_x after-treatment system has increased dramatically due to the stricter NO_x emission regulations for diesel vehicles. The urea-SCR system is one of the NO_x after-treatment methods found to be quite effective to meet the regulation requirement enforced by various authorities including the Euro-6. In order to develop an effective urea-SCR system, it is critical to establish an even distribution of reductant over the catalyst surface since this favorable distribution can increase reduction reaction and in turn, improve NO_x conversion efficiencies. In the current study, a number of design variations of the urea-SCR system which included two mixer types and three decomposition pipe lengths, were evaluated systematically using CFD analysis and experimental measurements. The purpose of the CFD analysis was to estimate the distribution of reductant within the urea-SCR system with a specific configuration and the purpose of the engine emission test was to measure the amount of NO_x reduction, respectively. The results from the systematic analysis revealed the relation between the reductant distribution over the SCR and the performance of the NO_x reduction.     

Simulation of flow in diesel particulate filter system using metal fiber filter media

Metal fiber is introduced as a new filter media in wall-flow Diesel Particulate Filter (DPF) system. This technology has high temperature durability which is required for filter regeneration, and can maintain the mechanical strength even in the extreme exhaust-related vibrations of vehicles. However, the regeneration near the wall (outer layer) is more difficult because of the heat loss and reduced gas flow near the wall. In this study, a flow is simulated to determine the flow control method for the more uniform flow in all filter layer. By using Star CCM+ commercial software, we obtain local velocity, streamline, and pressure distributions in the filter, which are typically difficult to obtain from measurements. The major control factors are the filter porosity, size and location of the distribution plate, and the number of blades of the swirler. By placing the distribution plate in front of the filter, the flow velocity near the wall was increased. The optimum location and size of the flat plate were chosen. By attaching the blade on the plate the flow velocity near the wall was increased more. Therefore, the regeneration efficiency is increased by using the swirler-type metal fiber DPF system.     

Intrusion detection model with twin support vector machines

Intrusion detection system （IDS） is becoming a critical component of network security. However, the performance of many proposed intelligent intrusion detection models is still not competent to be applied to real network security. This paper aims to explore a novel and effective approach to significantly improve the performance of IDS. An intrusion detection model with twin support vector machines （TWSVMs） is proposed. In this model, an etficient algorithm is also proposed to determine the parameter of TWSVMs. The performance of the proposed intrusion detection model is evaluated with KDD＇99 dataset and is compared with those of some recent intrusion detection models. The results demonstrate that the proposed intrusion detection model achieves remarkable improvement in intrusion detection rate and more balanced performance on each type of attacks. Moreover, TWSVMs consume much less training time than standard support vector machines （SVMs）.     

Construction Risk Management for Deep Excavation Adjacent to In operation Bored Tunnels

营运中的盾构隧道在邻近施工时周围地盘的应力可能因扰动而重新分布,使得盾构隧道暴露在因变形或位移衍生的结构损坏或营运中断等高风险下。为降低相关风险发生的可能性或后果的严重性,高雄计划将高雄车站段地下化工程捷运-R11永久站施工纳入风险管理,通过风险辨识、分析、评估以及以监测、巡检及沟通为基础的风险追踪查核等手段执行风险管理。依本计划执行成果,位于基地两侧营运中的盾构隧道在永久站主体工程开挖施工期间,各项风险均受到妥善的追踪、管控及处置。     

船用三相异步电动机常见故障的检查及维修

为了让船舶电子电气员(ETO)掌握正确分析、判断船用三相异步电动机的故障及进行相应的维修,在此以举例的形式将船用三相异步电动机常见故障的检查步骤和维修方法进行总结,希望可以为ETO在实际工作过程中解决常见故障提供分析依据及作为参考使用。