Experimental study on mobility of a vehicle with CTIS in soft soil

Recently, the domestic military vehicles currently being developed are installed with a central tire inflation system (CTIS) to control the pressure of tires to increase the contact area between the tires and the ground and improve mobility on soft soils. On the other hand, it is difficult to find technical data based on experiments for designing a CTIS. In this study, to obtain the technical data to set proper pressures according to road conditions a range of mobility tests were performed on soft soil roads, such as sand and clay, according to the CTIS operating modes to obtain the technical data to set proper pressures according to the road conditions. The characteristics of the mobility and its correlation with the tire pressures in each operating mode were analyzed. The results confirmed that a wheeled vehicle with a CTIS showed better performance on soft soil than a vehicle without a CTIS.     

主桩套板结构受力特性研究

主桩套板结构作为一种板桩墙结构形式,各构件受力情况较复杂。结合工程算例应用NL法进行水平承载力计算,并利用ABAQUS有限元分析软件建立3D桩土模型进行数值模拟,以验证理论方法的可靠性,发现主桩承担了绝大部分荷载,套板所受横向弯矩较竖向要大得多。基于ABAQUS研究不同套板尺寸下主桩的力学特性,着重分析当套板宽度、厚度和入土深度发生变化时主桩的弯矩变化,结果表明主桩的受力情况深受套板宽度的影响,其跨中最大弯矩随套板宽度的增加而明显增加,而套板厚度和入土深度对主桩的影响相对较小,在实际工程中可以根据需要做适当调整。     

基于 GMap ．N ET 的无人机航迹再现设计与应用磁

三维的飞行仿真技术,数据庞大,建立模型复杂,对计算机要求高,建立针对无人机飞参数据分析的简易航迹再现系统,将有很大的实用价值。为此论文研究了基于GMap ．NET 框架的离线地图嵌入技术,探讨了离线地图数据库的建立原理以及GM apProvider接口原理,并成功应用到无人机航迹再现系统中,实现了多种离线地图的浏览与转换,拓展实现了无人机的航线预置与二维动态演示功能,达到了飞参数据分析的目的。使用结果表明,该系统对资源需求低,可靠性高,操作简洁,易于部署,能够满足对无人机飞参数据分析的需要。     

Accounting for travel time variability in the optimal pricing of cars and buses

A number of studies have shown that in addition to travel time and cost as the common influences on mode, route and departure time choices, travel time variability plays an increasingly important role, especially in the presence of traffic congestion on roads and crowding on public transport. The dominant focus of modelling and implementation of optimal pricing that incorporates trip time variability has been in the context of road pricing for cars. The main objective of this paper is to introduce a non-trivial extension to the existing literature on optimal pricing in a multimodal setting, building in the role of travel time variability as a source of disutility for car and bus users. We estimate the effect of variability in travel time and bus headway on optimal prices (i.e., tolls for cars and fares for buses) and optimal bus capacity (i.e., frequencies and size) accounting for crowding on buses, under a social welfare maximisation framework. Travel time variability is included by adopting the well-known mean–variance model, using an empirical relationship between the mean and standard deviation of travel times. We illustrate our model with an application to a highly congested corridor with cars, buses and walking as travel alternatives in Sydney, Australia. There are three main findings that have immediate policy implications: (i) including travel time variability results in higher optimal car tolls and substantial increases in toll revenue, while optimal bus fares remain almost unchanged; (ii) when bus headways are variable, the inclusion of travel time variability as a source of disutility for users yields higher optimal bus frequencies; and (iii) including both travel time variability and crowding discomfort leads to higher optimal bus sizes.     

A meta-model of vehicle ownership choice parameters

This paper builds a meta-model of vehicle ownership choice parameters to predict how their values might vary across extended periods as a function of macroeconomic variables. Multinomial logit models of vehicle ownership are estimated from repeated cross-sectional data between 1971 and 1996 for large urban centers in Ontario. Three specifications are tested: a varying constants (VC) model where the alternative specific constants are allowed to vary each year; a varying scales (VS) model where the scale parameter varies instead; and a varying scales and constants model. The estimated parameters are then regressed on macroeconomic variables (e.g., employment rate, gas prices, etc.). The regressions yield good fit and statistically significant results, suggesting that changes in the macroeconomic environment influence household decision making over time, and that macroeconomic information could potentially help predict how model parameters evolve. This implies that the common assumption of holding parameters constant across forecast horizons could potentially be relaxed. Furthermore, using a separate validation dataset, the predictive power of the VC and VS models outperform conventional approaches providing further evidence that pooling data from multiple periods could also produce more robust models.     

Study and application of calculation method for temporary consolidation beside piers in pc cantilever casting beamEI北大核心

Research purposes: The temporary consolidation at top piers is regarded as rigid body in continuous girder cantilever construction. And the calculation theory and method are mature. Whereas, temporary consolidation beside piers should be regarded as elastic body. And the calculation methods about it are insufficient. Through the mechanical analysis of temporary consolidation beside piers, a simple calculation method is proposed and can be applied in various construction conditions. Research conclusions: (1) Simplify the temporary consolidation beside piers as elastic three fulcrums model which is consistent with practical force-baring conditions. (2) Calculation method based on elastic three fulcrums model can be well applied in various construction conditions. (3) Calculation of axial forces temporary consolidation beside piers is well related to their tension-compression stiffness, and we should choose calculation formula based on their tension-compression stiffness and force-baring conditions. (4) The calculation method proposed can be the base and accordance for design of temporary consolidation beside piers in PC cantilever casting girders.     

Dynamic system‐optimal traffic assignment for a city using the continuum modeling approach

This paper presents a continuum dynamic traffic assignment model for a city in which the total cost of the traffic system is minimized: the travelers in the system are organized to choose the route to their destinations that minimizes the total cost of the system. Combined with the objective function, which defines the total cost and constraints such as certain physical and boundary conditions, a continuum model can be formulated as an optimization scheme with a feasible region in the function space. To obtain an admissible locally optimal solution to this problem, we first reformulate the optimization in discrete form and then introduce a heuristic method to solve it. This method converges rapidly with attractive computational cost. Numerical examples are used to demonstrate the effectiveness of the method. Copyright © 2013 John Wiley & Sons, Ltd.     

A review of shipboard large-scale energy storage systems北大核心CSCD

储能系统是船舶中的重要设备,可为各类船舶负荷提供能源。随着电力推进技术的成熟,全电船舶已成为未来船舶设计的主要方向。在此背景下,储能系统将由主要为辅助负荷供能逐步发展到为多类型船舶负荷供能,特别是作为船舶动力系统的重要组成部分与各类船舶主/辅机配合,在满足船舶各类负荷需求的前提下提高船舶的经济/环保特性。功能角色的转变加速了大规模储能系统接入船舶,带来了储能系统的状态估计、能量管理、优化规划等一系列问题。首先,对目前的储能技术进行分类;然后,介绍典型全电船舶的分类方法并指出储能系统的应用场景;最后,提出大容量储能系统接入船舶后带来的若干亟待解决的技术问题,即船舶储能系统分布式控制、船舶储能系统适应性规划与优化,以及船舶储能系统状态评估。所做研究可为未来大规模储能系统在电力化船舶上的应用研究提供参考方向。     

Thermal anaysis of an electric water pump for internal combustion engine vehicles

An electric water pump for engine cooling system has an advantage which particularly in the cold start, the use of the electric water pump saves fuel and leads to a corresponding reduction in emissions. However, the electric water pump for internal combustion engine generates much more heat loss than that for hybrid electric vehicle or electric vehicle since it is operated by electric power of high current and low voltage. In this study, the fluid flow and thermal characteristics of the canned type electric water pump with an inverter integrated has been investigated under the effects of heat generation. The analysis conditions such as outdoor air temperature of 125°C, water pump speed of 6000 rpm, coolant temperature of 106°C and coolant flow rate of 120 L/min were used as a standard condition. Therefore, the thermal performance of the canned type electric water pump’s motor and inverter was evaluated by comparison with that of mechanical seal type. In the motor, the temperature reduced by over 10°C, and in the inverter, the amount of temperature decrease equaled to the maximum temperature difference, about 18.7°C. Also, canned type electric water pumps of variable materials were compared for the evaluation of thermal transfer performance for variable thermal conductivity of a can. The motor and inverter were cooled lower to 42°C at motor and about 40°C at inverter for reasonable selection of can’s thermal conductivity.     

Vibration path analysis and optimal design of the suspension for brake judder reduction

Brake judder is abnormal vibration, which is mainly generated by uneven contact between the brake disc and pad. The abnormal vibration from BTV (Brake Torque Variation) is transferred to the suspension and the steering system during braking. In this paper, judder simulation is carried out using a multi-body dynamic analysis program to analyze the relationship between judder and the transfer mechanism, which consists of the suspension and the steering system. In order to verify the analytical model, test results are compared with the simulation results. A sensitivity analysis is also carried out. In addition, an optimization method is presented for judder reduction, using the design of experiments.