佛开高速公路软基路堤拓宽沉降控制标准研究

以在建的佛开高速公路拓宽工程为背景,分析在拓宽路基边载的作用下,新老路基的沉降变形规律.在此分析的基础上,根据新老路基路面结构路用性能以及变形稳定的要求,并结合现场观测资料,对软基上高速公路拓宽工程的沉降控制标准进行了研究.研究表明,对于拓宽工程软基应采用“三指标”的控制标准,即:拓宽路基施工期老路容许的横坡度变化率、新老路基工后容许横坡度变化率、拓宽路基的容许工后沉降量.     

发动机缸内高温燃气热电偶温度测试误差研究

根据发动机气缸内高温燃气温度静态和动态的不同情况,对热电偶测头和热电偶套管在静态下的辐射热损失以及动态响应过程进行了推导与计算。结果表明,静态情况下热电偶读数误差增加幅度较小,动态响应过程中热电偶读数误差主要决定于热电偶测头及热电偶套管的辐射热损失,且其辐射热损失又受热电偶测头的滞后时间常数τ0的限制。     

Numerical investigation of turbolag reduction in HD CNG engines by means of exhaust valve variable actuation and spark timing control

Turbocharging port-injected Natural Gas (NG) engines allows them to recover gaseous-fuel related power gap with respect to gasoline engines. However, turbolag reduction is necessary to achieve high performance during engine transient operations and to improve vehicle fun-to-drive characteristics. Significant support for the study of turbocharged Compressed Natural Gas (CNG) engines and guidelines for the turbo-matching process can be provided by 1-D numerical simulation tools. However, 1-D models are predictive only when a careful tuning procedure is set-up and carried out on the basis of the experimental data. In this paper, a 1-D model of a Heavy-Duty (HD) turbocharged CNG engine was set up in the GT-POWER (Gamma Technologies Inc., Westmont, IL, US) environment to simulate transient operations and to evaluate the turbolag. An extensive experimental activity was carried out to provide experimental data for model tuning. The model buildup and tuning processes are described in detail with specific reference to the turbocharger model, whose correct calibration is a key factor in accounting for the effects of turbine flow pulsations. The second part of the paper focuses on the evaluation of different strategies for turbolag reduction, namely, exhaust valve variable actuation and spark timing control. Such strategies were aimed at increasing the engine exhaust-gas power transferred to the turbine, thus reducing the time required to accelerate the turbocharger group. The effects of these strategies were examined for tip-in maneuvers at a fixed engine speed. Depending on the engine speed and the applied turbolag reduction strategy, turbolag reductions from 70% to 10% were achieved.     

Transport policy for London in 2001 The case for an integrated approach

The paper reports the results of a series of studies conducted to enable the London Planning Advisory Committee to provide advice on strategic transport policy for London. The analytical approach combined the use of an area-based, multi-modal strategic model (LAM) and professional judgment. The performance of LAM as a basis for providing rapid advice on complex issues in transport policy is assessed.The resulting policy advice advocated a coherent approach, involving new infrastructure, particularly for rail; improved management of the road and public transport networks; the use of subsidy to enhance public transport service levels; and road user charges to reduce the impact of private vehicles on congestion and the environment. Road user charges emerged as the pivotal issue in the policy; the paper discusses their role, and the questions which still need to be resolved before they can be implemented.The main message of the study is that no one element of transport policy can tackle London's problems alone; an integrated policy in which infrastructure provision, management and pricing are used to complement one another is shown to be far more effective.     

Adaptive Ride Control In Active Suspension Systems

The paper describes the development of an adaptive control algorithm for active suspension systems based on optimal regulation methods. The objective is to design an algorithm which will automatically tune at start-up to changed vehicle conditions and adaptively re-tune to changes in driving conditions (in particular road generated disturbances). The proposed algorithm is a self-tuning regulator based on generalised minimum variance (GMV) control. Simulation results obtained for a 3 degree-of-freedom (DOF) quarter car suspension demonstrate potential benefits of fully adaptive control in automotive suspensions.     

Aggregation effects on the network design problem

This article examines the effects of various network extraction schemes on the network design problem. Given an original network, many criteria can be used to identify subnetworks on which the network design problem is solved. For the purposes of this article, these subnetworks are obtained using an extraction algorithm which preserves the magnitude of the user equilibrium flows on the links of these subnetworks. The results of the implementation of the network design problem on the original and the extracted subnetworks are presented and compared. We conclude that very good solutions to the network design problem can be obtained from the use of highly aggregate networks.     

多孔无桥台斜腿刚架桥斜腿倾角优化研究

多孔无桥台斜腿刚架桥是一种高次超静定结构,结构优化潜力较大。结合具体工程实践,根据不同的荷载组合,从结构的控制截面内力和位移两个方面对斜腿倾角进行了优化分析。研究结果表明:多孔无桥台斜腿刚架桥与拱桥的连拱情况有相似之处,斜腿倾角在45°~55°较为合适。     

汽车动力传动系弯曲振动及减振措施

本文建立了动力传动系弯曲振动的理论模型，运用该模型可以讨论传动轴，变速器输出轴结构参数、中间支承的刚度，手制动器的位置等对动力传动系弯曲振动的影响。还运用理论模型对轻型车、厢式车以及大客车的动力传动系弯曲振动进行了分析，提出了减振措施，解决了上述车型车身振动严重的问题。     

Economic and commercial considerations affecting the maritime transportation of tropical produce

This paper discusses the pattern of sea transport and loading in the ECAP and ESCAP areas, particularly the bulk trades in such commodities as sawn hardwood, plywood and rubber. The effects of port development and organization are examined, especially the difficulties of instituting bulk services and containerization in an area with a fragmented pattern of trade.