旧金山-奥克兰海湾桥抗震安全设计

美国奥克兰海湾桥位于州际公路上,1936年通车.为上下行分离桥面,共10条车道,每天有超过28万辆车通过.Loma Prieta地震造成E9号墩上的两跨双向桥面部分坍塌.新建东跨奥克兰海湾桥项目由四个不同结构组成,第一部分从奥克兰到Yerba Buena岛,为奥克兰部分;第二部分以"高架桥"闻名,是一个平行的混凝土箱梁结构;第三部分为自锚式悬索桥,是当前在建的主要结构;最后一部分是一系列多室后张拉箱梁桥.本文将着重对东奥克兰海湾大桥新建项目为震后"生命线服务"进行的设计和施工进行论述.     

计量模型在“十五”四川省 交通运输量预测中的应用

在阐述科学预测交通运输量的意义的基础上,利用计量经济模型对四川省的“十五”交通运输量进行了预测,并给出了一般性的模型检验流程.     

CONSTRUCTING POLYCOMPETITOR CDNAS FOR QUANTITATIVE PCR

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INTERFERON γ－INDEPENDENT EFFECTS OF INTERLEUKIN 12 ADMINISTERED DURING ACUTE OR ESTABLISHED INFECTION DUE TO LEISHMANIAMAJOR

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Computer modeling and validations of steel gear heat treatment processes using commercial software DANTE

The heat treatment process of a gear made of AISI 9310 carburized steel is modeled using the commercial heat treatment simulation software DANTE. Both carburization and quenching processes affect the residual stress distribution and distortion of heat-treated parts, which are important to service quality and fatigue life. DANTE/VCARB is used to design the boost/diffuse schedule of a vacuum carburization process. Oil quenching is modeled following the vacuum carburization process. Thermal gradient and phase transformation are two main sources of distortion and residual stresses in quenched parts. The relation of the carbon distribution, thermal gradient, and phase transformations during quenching is studied through the gear modeling example. Because of geometry, the residual stress distribution after quenching is non-uniform along the gear surface. In general, the root fillet has higher residual compression than either the root or tooth face locations after traditional oil quenching of carburized gears. The predicted residual stresses from the oil quenching model are imported into a single tooth fatigue bending model. The gear stresses under bending load indicate the possible cracking locations during the bending fatigue test. The importance of heat treatment residual stresses during gear design is pointed out, and it is commonly ignored in the gear design and manufacturing industry.     

Structural optimization of a circumferential friction disk brake with consideration of thermoelastic instability

This research suggests a new disk brake design using circumferential friction on the disk of a front-wheel-drive passenger car. The paper compares mechanical performance between the conventional and suggested disk brakes under dynamic braking conditions. Thermoelastic instability is considered in simulation of the test condition. An optimization technique using a metamodel is introduced to minimize the weight of the suggested disk brake. To achieve this goal, the response defined in the optimization formulation is expressed in a mathematically explicit form with respect to the design variables by using a kriging surrogate model, resulting in a simple optimization problem. Then, the simulated annealing algorithm is utilized to find the global optimum. The design results obtained by the kriging method are compared with those obtained from ANSYS analysis.     

Research on the electro-hydraulic variable valve actuation system based on a three-way proportional reducing valve

As the internal combustion engine moves into the 21st century, fully flexible valve actuation systems are being proposed as an enabling technology for advanced internal combustion engine concepts. Electro-hydraulic valve actuator systems are being considered as a potential variable valve technology. Compared to the servo control system, the system using a proportional valve has the advantages of low price, high anti-pollution ability and high reliability. Our research focuses on exploring the dynamic characteristic of the electro-hydraulic variable valve system, which is based on three-way proportional reducing valve. In this paper, the structure and working principles of the system are described. The dynamic mathematical model of the system is derived. From the analysis of a linearized model and dynamic simulation, it is demonstrated that the system will be stable only if the proportional reducing valve has a positive opening. Some structural factors that affect the system’s dynamic characteristics, such as input signal, the stiffness of the return spring and the pre-tightening force of the return spring, are studied using AMESim. The experimental results coincide with the theoretical and simulated analyses. Further study shows that the dynamic response can be improved effectively by adopting closed-loop control of valve lift.     

带舭龙骨柱体的横摇阻尼的粘性流计算

文章用RANSE求解器计算在自由面上带舭龙骨二维柱体的横摇水动力系数(附加惯量和阻尼).采用有限体积法(VOF)和两相流技术在时间域内求解柱体横摇强迫振荡所扰动的带自由面粘性流场.由柱体所受到的横摇水动力矩的时间历程导出横摇水动力系数.文中所给算例与已公开发表的试验结果吻合令人满意.     

Distribution of drifting seaweeds in eastern East China Sea

In offshore waters with relatively low primary production, drifting seaweeds composed of Sargassum species form an identical ecosystem such as an oasis in desert. Commercially important pelagic fishes such as jack mackerel (Trachurus japonicus) and yellow tail (Seriola quinqueradiata) spawn in East China Sea pass their juvenile period accompanying drifting seaweeds. Therefore drifting seaweeds are very important not only in offshore ecosystem but also fishery resources. However the distribution of drifting seaweeds in East China Sea has scarcely known. Then we conducted two research cruises of R/V Hakuho–Maru in May 2002 and in March 2004. During the cruises, drifting seaweeds were visually observed from the bridge and sampled with a towing net. The observation revealed that the drifting seaweeds were distributed along the front between the Kuroshio Current and coastal waters and mainly composed of one seaweed species, Sargassum horneri (Turner) C. Agardh from spring to early summer. There are no reports on geographical distribution of this species in the coasts south of southern Kyushu Island in Japan. Kuroshio Current flows northeastward there. Buoys with GPS attached to drifting seaweeds released off Zhejiang Province, China, in March 2005 to track their transport. Their positions monitored by ORBCOM satellite showed that they were transported to the area in East China Sea, where the drifting seaweeds were observed during the cruises, in 2 months. These facts suggest that S. horneri detached from Chinese coast in March or months earlier than March could be transported to fringe area of continental shelf and waters influenced by Kuroshio Current from March to May. Therefore the Sargassum forests, especially S. horneri, along the Chinese coast play a very important role in the ecosystem of the East China Sea as a source of drifting seaweeds.     

Port competition between Shanghai and Ningbo

The objective of this paper is to analyse the relative competitiveness of the neighbouring container ports of Shanghai and Ningbo in China and to develop a view of the likely future outcome of the competition between them. After assessing the demand for their services within what is hypothesized as a shared hinterland, current supply and future expansion plans are detailed and considered within the two ports' wider development strategies. The relative competitiveness of the two ports is then evaluated on the basis of price and quality of service, as embodied within the concept of generalized cost as incurred by customers. A critical political dimension is a necessary element of this analysis. It is concluded that continued economic development in the hinterland, central government policies on regional development and China's accession to the World Trade Organization (WTO) will all contribute to growing demand for port services. However, Ningbo will continue to gain greater market share as the result of advantages in its natural endowments (particularly depth of water), price (especially in terms of recovering the cost of capacity expansions) and quality of service improvements that are predicted to emerge as the result of currently planned enhancements to inland transport infrastructure and logistical systems.