WTO与交通企业发展

刘光溪:入世谈判过程本身具有重大意义 入世谈判的过程对于中国经济的发展、中国经济体制改革的深化是一个巨大的教育过程.这次谈判不光是经济和贸易的交锋,还是两种文化、两种理念的碰撞,对中华民族价值取向、理性思维将产生深远的影响.     

Revisiting the application of simultaneous perturbation stochastic approximation towards signal timing optimization

Simultaneous Perturbation Stochastic Approximation (SPSA) has gained favor as an efficient optimization method for calibrating computationally intensive, “black box” traffic flow simulations. Few recent studies have investigated the efficiency of SPSA for traffic signal timing optimization. It is important for this to be investigated, because significant room for improvement exists in the area of signal optimization. Some signal timing methods and products perform optimization very quickly, but deliver mediocre solutions. Other methods and products deliver high-quality solutions, but at a very slow rate. When using commercialized desktop signal timing products, engineers are often forced to choose between speed and solution quality. Real-time adaptive control products, which must optimize timings within seconds on a cycle-by-cycle basis, have limited time to reach a high-quality solution. The existing literature indicates that SPSA provides the potential for upgrading both off-line and on-line solutions alike, by delivering high-quality solutions within seconds. This article describes an extensive set of optimization tests involving SPSA and genetic algorithms (GAs). The final results suggest that GA was slightly more efficient than SPSA. Moreover, the results suggest today's signal timing solutions could be improved significantly by incorporating GA, SPSA, and “playbooks” of preoptimized starting points. However, it may take another 5–10 years before our computers become fast enough to simultaneously optimize coordination settings (i.e., cycle length, phasing sequence, and offsets) at numerous intersections, using the most powerful heuristic methods, at speeds that are compatible with real-time adaptive solutions.     

自动化实时监测系统在中国台湾高速铁路浅埋隧道的应用

中国台湾高速铁路新竹二高隧道以覆土深度9～12m穿越台湾北部第二高速公路。为了考虑高速公路下方隧道穿越施工时的行车安全,采用自动化监测系统,监控隧道施工产生之顶部路面沉降与隧道侧墙土层之变位。监测系统采用捷仪工程科技公司GeoAuto自动化实时监测软件系统,该系统分前端、中端、后端三部分。前端部分在隧道顶部沿隧道方向安装有自动量测水平倾斜计、在隧道两侧各安装有自动量测垂直倾斜计与伸张仪,另沿高速公路方向安装3排路面沉降点以全站仪自动监测,前述各类仪器皆连接至资料集录器;中端部分为ADSL、直接联机与无线传输等方式进行数据传输;后端部分为GeoAuto自动监测软件系统,所有路面沉降、土层变位等现场数据,皆由前端仪器量测、经中端传输,最后将所有现场有关沉降、变位等数据,皆显现于后端电脑显示器上。在自动监测系统配合下,有效协助浅埋隧道凿进,顺利完成隧道施工。     

Two-Dimensional Motion of Four-Wheel Vehicles

This paper deals with two-dimensional motion of vehicles. Since the general four-wheel vehicle model is statically indeterminate, the motion of vehicles has been analyzed by replacing the vehicle with the equivalent two-wheel one proposed by E. Marquard. Because this approximation is based on the axisymmetry of vehicles, it causes significant errors in the general case. To improve the accuracy of the analysis of vehicle motion, a four-wheel model is suggested. In this model, it is assumed that the chassis remains in a flat plane during motion. By introducing this condition, the motion of the vehicle can be analyzed. Several results from the four-wheel model and the equivalent two-wheel model are shown for comparison, and the vehicle trajectories with time are discussed.     

The anachronism in maritime law that is general average

The concept of general average is of great antiquity. It has fruitfully served the maritime community of the last two millennia, but the justification for its continued existence in the 21^st century is questionable. This article examines the proposition that general average is an anachronism and should be abolished — a cry that has been heard for well over a hundred years but has failed to materialise. In the article, the arguments for retaining general average are marshalled alongside the demands for its demise. Current developments in the revision of the York-Antwerp Rules are discussed. In conclusion, the resilience of general average as an age-old equitable maritime principle is recognized. But the author points to the sophistication in the modern regime of marine insurance in support of discarding general average and allowing maritime losses to lie where they fall; to be indemnified independently by the insurer of each interest in a maritime adventure without contribution from co-adventurers or their insurers.     

Estimation of a time‐dependent origin‐destination matrix for congested highway networks

This paper presents a time‐dependent origin‐destination (O‐D) matrix estimation procedure embedded with a dynamic traffic assignment model, in which the predictive dynamic user optimal conditions in congested networks are maintained. Two solution algorithms are proposed, namely: an iterative (ITR) scheme and a method of successive averages (MSA) scheme. It is found that the MSA scheme outperforms the ITR scheme. As a prior O‐D matrix is an important input for the problem, its quality is essential for the reliability of the matrix estimation procedure. Empirical constraints are set in relation to the quality of the prior O‐D matrix for the estimation procedure. Numerical examples are used to demonstrate the effectiveness of the proposed methodology.     

Customer loads of two-wheeled vehicles

Customer usage profiles are the most unknown influences in vehicle design targets and they play an important role in durability analysis. This publication presents a customer load acquisition system for two-wheeled vehicles that utilises the vehicle's onboard signals. A road slope estimator was developed to reveal the unknown slope resistance force with the help of a linear Kalman filter. Furthermore, an automated mass estimator was developed to consider the correct vehicle loading. The mass estimation is performed by an extended Kalman filter. Finally, a model-based wheel force calculation was derived, which is based on the superposition of forces calculated from measured onboard signals. The calculated wheel forces were validated by measurements with wheel–load transducers through the comparison of rainflow matrices. The calculated wheel forces correspond with the measured wheel forces in terms of both quality and quantity. The proposed methods can be used to gather field data for improved vehicle design loads.     

Measurement of soot oxidation with No<Subscript>2</Subscript>-O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O in a flow reactor simulating diesel engine DPF

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO₂-O₂-H₂O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of NO₂-O₂ oxidation, which was 60±3 kJ/mol. When NO₂ exists with O₂ and H₂O, the reaction rate increases in proportion to NO₂. It increases nonlinearly with O₂ or H₂O concentration when the other two oxidants are fixed.     

Cooperative control for friction and regenerative braking systems considering dynamic characteristic and temperature condition

The braking system of hybrid electric vehicle (HEV) is composed of friction and regenerative braking system, meaning that braking torque is generated by the collaboration of the friction and regenerative braking system. With the attributes, there are two problems in the HEV braking system. First, rapid deceleration occurs due to dynamic characteristic difference when shifting the friction and regenerative braking systems. Second, the friction braking torque alters with temperature because the friction coefficient changes with the temperature. These problems cause the vehicle to be unstable. In this paper, the concurrence control and compensation control were proposed to solve these problems. And also, the concurrence control and compensation control were combined for the stability of the braking system. In order to confirm the effect of these control algorithms, the experiment and simulation were conducted. Consequently, it was confirmed that the control algorithm of this study improved the vehicle safety and stability.