城市公交区间车与全程车组合调度问题研究

为提高城市公交区间车线路上闲置车辆的利用率,对区间车设置及其组合调度可行性、工作流程进行了全面分析.针对区间车线路上车辆的运行特点,构建了区间车线路上发车场站的一组逆差函数,通过发车场站内部调度和场站之间插入空驶车次,实现了以最小的车队规模运行区间车线路的所有车次.研究了大连市某公交区间车线路.结果表明,区间车与全程车组合调度后的运行区间车线路的车辆数目获得了优化.

预算限制下的单线公交车辆组合调度模型

针对单条公交线路双向及单向客流分布的不均衡性,考虑我国大城市公交企业普遍依靠政府补贴,在实际运营中存在预算限制的情况,以社会总体效益最优为目标,建立了对区间车和双向全程车的发车频率及区间车折返位置同时进行优化的组合调度模型,探讨了预算限制对优化调度的影响,证明了预算限制相当于减少了乘客的时间价值,分析了预算限制下组合调度最优发车频率、折返点位置和系统成本的关系,并与单一调度进行对比。结果表明:在客流分布不均衡和预算限制的情况下,相比单一调度,组合调度能有效减少系统成本和乘客平均出行时间,节省运力,降低车辆拥挤,提高服务水平。在预算限制下,可以通过组合策略的实施,使出行乘客和运营企业都获益。

基于异质性出行需求的公交线路组合调度研究

为进一步研究异质性需求公交线路的组合调度,设计全程车、区间车和大站快车组合调度研究模型:以公交线路总成本(包括用户成本和运营成本)为目标函数,以各种调度模式发车频率、大站快车跳过站点为优化参数,以满足乘客出行需求为约束条件。模型首先基于Logit模型计算换乘比例,将乘客的出行需求进行分类,然后对组合调度方案进行建模。设计一种混合遗传算法的布谷鸟算法求解算例,获得最优解,并对模型参数进行敏感性分析。计算分析结果表明:此组合调度方法相较于全程车、全程车+区间车调度模式,总成本分别减少24.3%和14.4%;并优化乘客出行方式;乘客时间价值和单位运营成本对结果影响较大。通过这种组合调度优化方法,为公交运营企业调度方案提供一种新思路。

Analysis of bicyclist-vehicle crash at intersection area considering behavior prior to crash:A random parameter ordinal probit approach

In order to analyze the risky factors that affect vehicle-cyclist crash injury severity at the intersection area,especially the factors relating to the road users behaviors,an empirical study was conducted by collecting accident records from 2011 to 2015 from the General Estimates System.After preliminary screening,the variables were classified into 5 main categories including cyclists characteristic and behavior,drivers characteristic and behavior,vehicle characteristic,intersection condition,and time.The random parameter ordinal probit(RPOP)was used to study the significant influencing factors and corresponding heterogeneity.The results show that failing to obey traffic signals,failing to yield to right-of-way,dash and drinking before cycling can increase the injury severity for cyclists,and the corresponding fatal injury likelihoods increase by 53.2%,40.0%,86.3%,and 211.5%,respectively.Moreover,drivers inattention,speeding,going straight and left turning increase the risk of crashing for cyclists.The corresponding fatal injury likelihoods increase by 134.5%,186.5%,69.3%,and 22.7%,respectively.Other indicators such as age,gender,vehicle type,traffic signal and intersection type can also affect injury severity.

Dual cycloid gear mechanism for automobile safety pretensioners

The most conventional vehicle pretensioner system consists of an internal gear pair with involute teeth. However, it has been well known that the corresponding gear pairs are relatively weak under the situation of impact loadings. To improve this phenomenon, a new pretensioning gear system with cycloid teeth rather than the involute ones was proposed, and dual cycloidal gear mechanisms were designed for satisfying geometric constraints and dynamic loading conditions. The simulations of the prototypes were conducted by LS-DYNA program and the experiments for a prototype were performed for a dynamic model with impact loading devices. The results show that the better operation and the smoother motion are confirmed in the proposed cycloidal gear system rather than the conventional one without interferences between gear teeth under the impact of a crash.

Collaborative Reversing of Input Formats and Program Data Structures for Security Applications

Reversing the syntactic format of program inputs and data structures in binaries plays a vital role for understanding program behaviors in many security applications.In this paper,we propose a collaborative reversing technique by capturing the mapping relationship between input fields and program data structures.The key insight behind our paper is that program uses corresponding data structures as references to parse and access different input fields,and every field could be identified by reversing its corresponding data structure.In details,we use a finegrained dynamic taint analysis to monitor the propagation of inputs.By identifying base pointers for each input byte,we could reverse data structures and conversely identify fields based on their referencing data structures.We construct several experiments to evaluate the effectiveness.Experiment results show that our approach could effectively reverse precise input formats,and provide unique benefits to two representative security applications,exploit diagnosis and malware analysis.

Crash Severity Modeling in Urban Highways Using Backward Regression Method

Identifying and classifying intersections according to severity is very important problem for implementation of safety related counter measures and effective models are needed to compare and assess the severity. Highway safety organizations have considered intersection safety among their priorities. In spite of significant advances in highways safety, the large numbers of crashes with high severities still occur in the highways. Investigation of influential factors on crashes enables engineers to carry out calculations in order to reduce crash severity. In the previous studies, there are no perfect models which are capable to illustrate the influence of human factors, road, vehicle, weather conditions and traffic features including traffic volume and flow speed on the crash severity. Therefore, this paper is aimed to develop the models for illustration of the simultaneous influence of these variables on the crash severity in urban highways. The models represented in this study have been developed using binary Logit Models. SPSS software has been used to calibrate the models. It must be mentioned that backward regression method in SPSS was used to identify the significant variables in the model. Consider to obtained results it can be concluded that the main factor in increasing of crash severity in urban highways are driver age, movement with reverse gear, technical defect of the vehicle, vehicle collision with motorcycle and bicycle, bridge, frontal impact collisions, frontal-lateral collisions and multi-vehicle crashes in urban highways which always increase the crash severity in urban highways. Obtained results show the effectiveness and capability of the developed models.

Review of Supply Chain Partnership Process in Joint Ventures Example as Chinese Automotive Industry

Under the environment of economic globalization, there has seen a global transfer of manufacturing into China and China＇s automotive industry engage in global trade. China faces unprecedented opportunities for development, although there are many challenges it must face, It has become a strategic choice for all automotive enterprises to implement supply chain management in order to achieve competitive advantages. At present, most researches on supply chain partnerships have been carried out based on enterprises in developed countries. Very few theoretical and empirical studies have been based on developing countries, and in particular, only a few scholars have examined supply chain partnerships in China. Based on the joint ventures, this paper is a review of partner theories and process of partner relationship. With respect to the supply chain partnership strategy and process and partners＇ capability literature, there is limited research on the special background such as joint ventures or Chinese automotive industry. Some literature on partners＇ capabilities is based in favor of the operational aspects.

Seismic stability of loess tunnels under the effects of rain seepage and a train load

Loess tunnels are widely used in transportation engineering and are irreplaceable parts of transportation infrastructure. In this paper, a dynamic finite element method is used to analyze the coupled effects of a train vibration load and rainfall seepage. By calculating the variation in the safety factor of a loess tunnel because of the effects of various factors, such as different rainfall intensities and soil thicknesses, the dynamic stability of the loess tunnel is studied under the condition of a near-field pulse-like earthquake. The results show that the security and stability of the tunnel decrease gradually with decreasing burial depth. In addition, the plastic strain of the tunnel is mainly distributed on both sides of the vault and the feet, and the maximum value of the critical strain occurs on both sides of the arch feet. Because of the effects of the train vibration load and rainfall seepage, the safety factor of the loess tunnel structure decreases to a certain degree. Moreover, the range and maximum value of the plastic strain increase to various degrees.

An engineering approach to improve the accuracy of one-step simulation for vehicle forming-to-crashworthiness integrated evaluation

To improve the accuracy of the vehicle crashworthiness simulation, it is necessary as well as important to integrate the valid forming effects of key parts. It has been agreed by many that one-step simulation results should be used only as a qualitative trend of the part but not as an engineering result for further structural analysis, especially for a relatively complex part. The study shows that it is inaccurate to analyze the forming effects with one-step simulation based on the geometry of the final part through comparison with the incremental simulation and verification with the actual part, whether in thickness or in plastic strain. However, incremental simulation is very time consuming and infeasible in the early stage of vehicle design due to lack- ing of forming tools and process parameters. An engineering approach is proposed to meet the requirement of accuracy as well as the time efficiency, where one-step simulation is conducted based on the geometry of the transformed part instead of the fi- nN part. The geometry of the transformed part is generated by simple die design engineering and proves to offer much more accuracy than the one-step simulation based on the final part geometry.