船舶操纵模拟器操纵仿真数学模型

系统地论述了船舶操纵仿真数学模型。包括船舶操纵基本模型、水动力、螺旋桨推力及扭距、主机扭距、舵力及其力矩、风、浪、流、锚、缆、拖轮的作用力、浅水影响及侧壁效应,最后给出了主要仿真结果和主要结论     

Influencing factors and heterogeneity in ridership of traditional and app-based taxi systems

The growth of app-based taxi services has disrupted the urban taxi market. It has seen significant demand shift between the traditional and emerging app-based taxi services. This study explores the influencing factors for determining the ridership distribution of taxi services. Considering the spatial, temporal, and modal heterogeneity, we propose a mixture modeling structure of spatial lag and simultaneous equation model. A case study is designed with 6-month trip records of two traditional taxi services and one app-based taxi service in New York City. The case study provides insights on not only the influencing factors for taxi daily ridership but also the appropriate settings for model estimation. In specific, the hypothesis testing demonstrates a method for determining the spatial weight matrix, estimation strategies for heterogeneous spatial and temporal units, and the minimum sample size required for reliable parameter estimates. Moreover, the study identifies that daily ridership is mainly influenced by number of employees, vehicle ownership, density of developed area, density of transit stations, density of parking space, bike-rack density, day of the week, and gasoline price. The empirical analyses are expected to be useful not only for researchers while developing and estimating models of taxi ridership but also for policy makers while understanding interactions between the traditional and emerging app-based taxi services.

     

夏季洒水降温减缓沥青混凝土路面车辙发展的研究

夏季高温是沥青路面产生车辙的主要因素。洒水养护因实施简易、可操作性强、养护费用低、性价比高的优势成为路面养护较常用的一种措施。分析了洒水降温的原理,通过埋设温度传感器,研究了沥青混凝土路面不同深度的温度变化规律,从而明确了洒水对路面的降温效果,并与微表处养护进行了经济效益对比分析,为洒水养护的应用提供了理论支撑。     

The Application of Virtual Reality Technology to Ear Microsurgery

The broad application of virtual reality (VR) to medicine has been of great value. The virtual surgery is one of technically difficult applications. With the expansion of the increasingly fine and complicated ear microsurgery, new methods are required to train the doctors. It is necessary and of practical significance to apply VR to the ear micro-operation, which is a functional operation with high precision and great difficulties. In this article,medical VR applications were reviewed. The application of VR to the ear microsurgery was discussed and the virtual ear microsurgery system was designed.     

有轨电车系统规划设计思考

作为城市轨道交通系统的组成部分,有轨电车系统规划设计的关键在于认清其在轨道交通系统中所处的功能地位和发挥的价值作用。从分析城市轨道交通的发展背景出发,解读有轨电车面临的发展机遇。探讨合理构建有轨电车系统的规划设计思路,以及有轨电车如何适应生态文明和社会文明的发展需要。重点阐述在有轨电车规划设计过程中如何实现与多层级轨道交通系统的协调、与城市空间用地的互动,以及与城市综合交通系统的衔接。     

城市轨道交通研究中心在京成立

由北方交通大学、北京市城建设计研究院共建的"城市轨道交通研究中心"于2001年1月4日在京成立.参加成立大会的有建设部、铁道部、北京市有关领导,我国城市轨道交通界的许多专家,国内外一些知名的城市轨道交通设备制造厂商的代表,以及"城市轨道交通高级研讨班"的学员等,成立大会气氛热烈,各地城市轨道交通建设部门也纷纷来电祝贺.     

船用无油润滑氦气增压机的研制及自动控制

本文介绍了ＣＴＺ型船用无油润滑氦气增压机的结构型式，基本参数，关键技术及自动控制。该机具有小型化，泄漏少等特点，且能在多工况下实现正常运转，以满足不同深度潜水作用的需要。     

群桩-土-承台结构共同作用的数值计算研究

群桩承载性状的数值计算,是在模型试验的基础上,为研究桩-土相互作用,采用一种既简单又符合土体成层、非均质实际情况的有限层计算模型。该文论述的计算模型不仅能满足工程实际的弹性计算要求,还研究了桩周土体的非线性特性。同时,还综合应用弹性理论法和荷载传递法的优点模拟桩的承载性状,利用有限元分析软件ANSYS建立其力学模型进行计算。数值计算结果与实测结果吻合良好,表明有限层方法计算超长群桩基础是可行的。     

Optimization of bus rollover strength by consideration of the energy absorption ability

Buses are an integral part of the national transportation system of each country. A rollover event is one of the most important hazards that concerns the safety of the passengers and the crew in a bus. In the past, it was observed after the accident that the deforming superstructure seriously threatens the lives of the passengers. Thus, the stiffness of the bus frame is the first thing that needs to be considered. The unfortunate side of strengthening the bus superstructure is that it usually causes the bus weight to increase. This paper presents an efficient and robust analysis method with which to design the bus superstructure for a reduction in occupant injuries from rollover accidents while the weight of the strengthened bus is maintained at the same level. First, the absorbed energy of the bus frame and its components during a rollover were investigated by using a LS-DYNA numerical study. The highest energy absorption region, which is the side section of the bus frame, was found and focused on for the investigation of a means to re-distribute the energy-absorption ability of the side frame component. Then the thickness parameters that were obtained from the re-distribution of the energy-absorption ability were used in the analysis to optimize the design. Finally, a prototype of the bus with a reasonable thickness for the window pillars and the side wall bars, which was based on the optimized parameters, was verified to ensure it satisfied ECE R66. In this paper, an effective usage of materials and an efficient and robust analysis method were presented to design the bus superstructure. Although the optimization process for increasing the stiffness is simple, this study improves the upper displacement by 39.9% and the lower displacement by 49.3% (versus the bus survivor space) while maintaining the bus weight at the existing level.     

基于形状记忆合金的半主动隔振研究

针对被动隔振器对低频段的隔振能力差,主动隔振器结构过于复杂等问题,设计了一种基于形状记忆合金(SMA)的半主动隔振器,带有SMA丝的悬臂梁充当弹性元件,根据SMA的弹性模量随温度改变而变化的特性,通过适时的改变通入悬臂梁的电流,从而调节系统的固有频率使其随外部激振力频率的变化而改变。本文对变刚度隔振器的原理及基于SMA的隔振器的模型进行了分析,通过仿真得到了较宽的隔振频带并避开共振峰的响应曲线。