交通拥挤漂移的形成机理与预防技术

为了研究交通诱导信息对驾驶员驾驶行为的影响,从诱导比例、替代路径数量、替代路径合理性和路网交通负荷分布的角度,分析了在动态交通诱导条件下拥挤漂移现象的产生机理,提出了逐步增加诱导比例,在路阻数据中加入干扰因子与K最短路方法等3种预防交通拥挤漂移的技术,并采用Vissim交通仿真软件对其进行了模拟评价。模拟结果表明:在局部拥挤的道路网络中,所提出的3种方法都能够减轻或消除拥挤漂移现象,其中K最短路方法的效果最好,其次是逐步诱导方法,尽管在路阻数据中加入干扰因子的方法效果最不理想,但仍优于对车辆进行100%诱导和不采取任何诱导措施的情况。     

基于故障树分析法的DCT典型故障分析

本文针对双离合器式自动变速器(DCT)比较常见的典型故障,采用故障分析法,分别建立换挡异响故障树和挡位限制故障树,分析了两种典型故障案例的故障原因,并从故障现象和故障排除方面重点研究了挡位限制故障案例,研究中排除了离合器故障的可能性后,分析得到1-3挡拨叉的位置是主要故障原因,从而更换电液控制单元并进行相关匹配就能排除故障。本文的研究也可以应用到DCT其它故障分析中,为故障的排除提供理论指导。     

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有效的乘务调度能够为公交企业带来巨大的成本节约,但是,公交乘务调度问题因受制于一系列劳动法规的约束变得十分复杂.我国公交普遍存在"中式用餐"约束,进一步加大了问题的复杂性,使西方主流调度系统在国内实施面临困难.本文基于"生成与选择"方法解决乘务调度问题,关键在于"生成"阶段处理"中式用餐"难题;利用"中式用餐"约束和乘务问题特点,设计一种基于启发式规则的换班机会筛选方法;在所选换班机会集合的基础上构造能满足"中式用餐"约束的潜在乘务班次集合.对实际公交乘务调度问题中的12组实例进行测试,表明本文方法不仅能处理"中式用餐"约束,而且能极大减少所求问题的规模,因此适用于解决大规模的带有"中式用餐"约束的乘务调度问题.     

An exploration of shoppers travel mode choice in visiting convenience stores in the UK

Using data from over 2000 convenience store customers within and outside London, this paper explores how individuals access their convenience stores and how significant the influence of their socio-demographics, shopping types and trip chaining is to their mode choice in visiting the stores. Trip chaining is found to be crucial in influencing customers' mode choice and their visit frequency. The application of logit models also shows that frequent shoppers are the ones most likely to visit the stores on foot. Interestingly, the estimation results also show that the location's density, shopping types and the day of the week are not significant in influencing travel modes. Customers who live in the most deprived areas are less likely to use a private car in visiting the stores.     

叉车用集装箱内货物装卸吊臂的研制应用

为了解决件杂货码头拆装箱作业中存在的难题,有必要开展叉车用装卸吊臂的研制;介绍了叉车用集装内使用的吊臂的设计思路、技术性能和使用性能;并指出了吊臂的应用效果。     

基于DSP的信号高精度检测方法

在分析轨道电路FSK信号特点基础之上,提出了基于多相滤波器的频谱细化分析（ZOOM-FFT）技术接收并解调FSK信号的方法,结合数字信号处理技术,对FSK轨道电路信号进行频谱分析,可以有效地检测出轨道电路信号上下边频频率、中心频率和幅度,达到了实时性和精度高的要求。     

VDR雷达图像的ROI图像编码压缩算法

针对VDR雷达图像感兴趣区域压缩问题，提出了整数小波变换和非均匀移位的ROI图像编码压缩算法。该算法利用整数小波对图像进行变换，对量化后生成的小波系数进行非均匀移位，不仅能够保证感兴趣图像数据在低比特数据流中的优先恢复，还实现了使图像的渐进恢复过程更加适合人眼视觉特点的效果。通过对VDR雷达图像的压缩实验，该算法效果明显。     

基于MATLAB仿真的国产铁路移频信号分析

讨论了国产18信息轨道移频信号和UM71轨道移频信号的时域和频域特性，分析轨道移频信号的载频、低频调制频率及频率偏移等参数特征，用MATLAB软件对国产铁路移频信号进行仿真，确定了其参数特征。     

Topological constraints on the dynamics of wasp-waist ecosystems

Small pelagic fish species like anchovy or sardines are of high ecological and economical importance. As marine food webs are fished down, these small pelagics tend to be more exploited and overfished. It is not yet very well known what the possible effects of their collapse can be, therefore there is an urgent need to outline a theoretical framework for understanding their dynamics. These fish occupy very special position in food webs, ensuring energy transfer between species lower and higher levels, while forming narrow “wasp-waists” poor in number of species (but very abundant). Our purpose was to quantify the interaction structure of model food webs of equal complexity but different levels of “wasp-waistedness”. We analysed the topological properties of the webs by characterising every direct and indirect interactions between individual species, as well as by assessing the relative positional importance of each species in each web. We found that (1) the shorter the interaction pathways considered, the weaker the predictive power of node degree for positional importance, (2) the importance of species varies more in wasp-waist food webs, (3) if longer indirect chain effects are considered, indirect effects can well be stronger than direct ones, (4) interactions between coexisting wasp-waist species are stronger than the average, and (5) the “self-regulatory” looping effects are also stronger for wasp-waist species. Based on the topological properties of the networks, our results describe constraints acting on the dynamical behaviour of wasp-waist ecosystems. We give explanations, from this viewpoint, for regime shifts in which one WW species replaces another, and for the unpredictable dynamics of these fish stocks. From a marine conservation viewpoint, we illustrate that as the abundance of wasp-waist species decreases, the architecture of energy flows becomes highly vulnerable and unreliable. We provide an approach for quantifying these structural changes.     

Effects of the 1988/89 climatic regime shift on the structure and function of the southwestern Japan/East Sea ecosystem

In this study we compared the structure of the ecosystem and the role of major species before and after 1988/89 climatic regime shift (CRS) in the southwestern Japan/East Sea. The 1988/89 CRS event changed the biomass and production of fisheries resources in the southwestern Japan/East Sea. Total biomass of all species groups in the ecosystem increased by 59% after the CRS. These results indicate that there were substantial changes in the function of major species in the southwestern Japan/East Sea ecosystem. The relative contribution of walleye pollock, at trophic level (TL) III, to the total flow of energy decreased drastically from 33.0% in the pre-CRS period to 4.3% in the post-CRS period, while that of common squid, at the same TL, doubled from 34.2% to 72.2% during the periods.