THE ELASTIC FIELD CASED BY TWO INCLUSIONS WITH UNI- FORM DILATATIONAL EIGENSTRAINS IN DISSIMILAR MEDIA

IntroductionGuell and Dundurs[1] used the Papkovitch-Neuber displacementpotential and had the solutionfor a spherical inclusion in dissilmilar media whichundergoes homogeneous dilative eigenstrain. Itwas found that the displacements and stresses inthe region exterior to the sphere are the same asthose resulting from a center of dilatation of a cer-tian strength located at the center of the sphere.Using the solution of Mindlin and Cheng[2 ] inwhich the Galerkin vector was adopted and nucleiof…     

Equilibrium properties of taxi markets with search frictions

The equilibrium properties of an aggregate taxi market are investigated using a general bilateral searching and meeting function which characterizes the search frictions between vacant taxis and unserved customers. Three specific issues are analyzed for meeting functions that exhibit increasing, constant and decreasing returns to scale. Firstly, service quality in terms of customer wait/search time and average profit per taxi are examined jointly in relation to taxi fleet size, and a Pareto-improving win-win situation is identified, where an increase in taxi fleet size leads to improvements in both service quality and market profitability. Such a Pareto-improving situation is found to emerge if and only if the meeting functions show increasing returns to scale. Secondly, the properties of the socially optimal solution are examined. It is found that the taxi fleet size should be chosen such that the total cost of operating vacant taxis equals the total cost of customer waiting time multiplied by an asymmetric factor of the meeting function, and that taxi services should be subsidized at social optimum only when the meeting functions show increasing returns to scale. Thirdly, the Pareto-efficient services are examined for trade-offs between social welfare and profits in the light of partially conflicting objectives of the public sector and the private taxi firms using a bi-objective maximization approach. The taxi utilization rate and the customer wait/search time or service quality are proved to be constant along the Pareto frontier and equal to those at social optimum if the meeting functions show constant returns to scale. Extensions are made to the cases with increasing and decreasing returns to scale.     

THYL-80发动机台架试验系统技术升级功能拓展

对20世纪80年代引进的THYL-80发动机台架试验系统实施技术升级的设计开发．构建自主研制的发动机台架试验测控装置,设计数字标定接口电路提高扭矩、转速、油耗测量精度,增加变工况自动循环试验功能,通过技术升级拓展了该发动机台架试验系统的技术性能．满足国Ⅲ～国Ⅳ排放法规动态循环工况试验要求。     

新农村道路国防功能之管见

新农村道路便于通行、防护、隐蔽、修复,能够加大区域道路战时通行能力和通行几率,提升区域道路交通生存与使用能力。在科学界定新农村道路的内涵与特征的基础上,系统分析了新农村道路在未来高科技局部战争中的战略地位和作用,研究提出了确保新农村道路国防功能实现的对策和措施。     

舰船通信集成交互调影响评估方法

  目的  针对多艘船舶在间歇通信环境下的编队控制问题,提出了基于反步法的协调编队控制律,并给出编队形成的充分条件以满足编队的鲁棒性。  方法  首先,利用反步法设计正常通信时段的船舶编队控制律,加入误差观测器消除外部环境带来的误差,保证船舶在正常通信时段形成理想编队。然后,对于在间歇通信中通信缺失的时段,设计控制律。此外,在船舶编队的形成以及队形保持的过程中,通信时长必须满足一定的要求,并给出在间歇通信环境下实现编队的充分条件。最后,利用李雅普诺夫理论对船舶编队控制律的稳定性进行验证,并证明该充分条件的可靠性。  结果  仿真结果表明,采用该控制律且满足给出的充分条件,船舶能够在间歇通信环境下实现编队航行。  结论  在间歇通信或类似的周期性通信缺失情况下,对船舶编队控制的设计与研究有一定的参考价值。     

基于变换函数的船体曲面参数化修改技术研究

为实现基于CFD的船型自动优化,需要一种参数化的船体型线生成方法.文中改进了一种基于变换函数的船型参数化方法,以使变换船型更丰富、合理,该方法可以通过改变几个参数即可实现船体型线的自动生成.研究表明,只要选择合适的变换函数,参数的取值范围合理,则可以保证变化后的船型仍然满足光顺性等特征.以1 300 TEU集装箱船和戴维泰勒水池DTMB5415标模为例,阐述了基于变换函数的船体型线变换过程,结果表明,基于变换函数的船型变换方法可以应用于船型精细优化中.     

高校体育社会功能探析

通过文献资料法对高校体育在社会上所起的作用和具有的意义做出了总结,更深层次地对高校体育在社会政治、经济、文化等方面对社会所具有的作用做了细致的分析,并且研究了促进人才社会化等具有的影响。这一研究针对高校体育多层次、多元化和与时俱进的特征,为高校体育工作者提供一定的理论依据,以期对高校体育的社会功能有进一步的认识。     

汽车行驶记录仪与智能交通

简要介绍汽车行驶记录仪的国内外发展史,概述了汽车行驶记录仪在现代交通中的功用．及在智能交通管理中的应用.     

一类奇异积分算子与无界连续函数逼近

利用扩展乘数法建立了Мцракъян算子逼近全实轴上任意无界连续函数的收敛性定理,给出了具有一般性的结论,从而推广了前人的若干重要定理．     

Dynamic modeling and control of taxi services in large-scale urban networks: A macroscopic approach

Taxis are increasingly becoming a prominent mobility mode in many major cities due to their accessibility and convenience. The growing number of taxi trips and the increasing contribution of taxis to traffic congestion are cause for concern when vacant taxis are not distributed optimally within the city and are unable to find unserved passengers effectively. A way of improving taxi operations is to deploy a taxi dispatch system that matches the vacant taxis and waiting passengers while considering the search friction dynamics. This paper presents a network-scale taxi dispatch model that takes into account the interrelated impact of normal traffic flows and taxi dynamics while optimizing for an effective dispatching system. The proposed model builds on the concept of the macroscopic fundamental diagram (MFD) to represent the dynamic evolution of traffic conditions. The model considers multiple taxi service firms operating in a heterogeneously congested city, where the city is assumed to be partitioned into multiple regions each represented with a well-defined MFD. A model predictive control approach is devised to control the taxi dispatch system. The results show that lack of the taxi dispatching system leads to severe accumulation of unserved taxi passengers and vacant taxis in different regions whereas the dispatch system improves the taxi service performance and reduces traffic congestion by regulating the network towards the undersaturated condition. The proposed framework demonstrates sound potential management schemes for emerging mobility solutions such as fleet of automated vehicles and demand-responsive transit services.