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排序方式: 共有973条查询结果,搜索用时 125 毫秒
941.
我国海洋外贸运输在全球外贸运输中发挥重大作用,而港口是国际物流运输的重要环节.基于状态空间模型,考察了金融危机之前及之后,国际、国内主要宏观因素对我国沿海港口外贸货物吞吐量的影响轨迹.结果发现:自金融危机以来,世界经济状况对我国沿海港口外贸货物吞吐量的边际正面影响在逐渐提高,外商直接投资的边际正面影响明显减弱,人民币实际有效汇率指数波动的边际负面影响在减弱,国内经济状况的边际正面影响逐渐减弱,沿海交通建设固定资产投资的边际正面影响在增强.基于实证结果,得出我国经济由外需拉动向内需推动转型的间接证据并提出政策建议. 相似文献
942.
长期以来受以车为主导的规划建设理念影响,中国许多城市新建、改建道路存在尺度失衡、品质降低、活力不足等问题。首先介绍纽约、伦敦、哥本哈根、莫斯科、墨尔本等世界级城市街道重建实践经验。以上海市黄浦区为例,采用公共生活—公共空间(PLPS)调研方法,对34处地点进行行人流量调查,并针对5个公共空间进行停留活动统计。由此分析黄浦区现状街道网络的主要问题与诉求,进而提出街道重建的规划设计策略及措施推进时序。以南京东路为示范项目,探讨其现存问题并提出具体改造方案。 相似文献
943.
A novel approach based on independent component analysis (ICA) for speckle filtering and target extraction of synthetic aperture radar (SAR) images is proposed using adaptive space separation with weighted information entropy (WIE) incorporated. First the basis and the independent components are respectively obtained by ICA technique, and WIE of the image is computed; then based on the threshold computed from function T-WIE (threshold versus weighted-information-entropy), independent components are adaptively separated and the bases are classified accordingly. Thus, the image space is separated into two subspaces: "clean" and "noise". Then, a proposed nonlinear operator ABO is applied on each component of the 'clean' subspace for further optimization. Finally, recovery image is obtained reconstructing this subspace and target is easily extracted with binarisation. Note that here T-WIE is an interpolated function based on several representative target SAR images using proposed space separation algorithm. 相似文献
944.
A lattice reduction aided (LRA) minimum mean square error (MMSE) Tomlinson-Harashima precoding (THP) was proposed based on vertical Bell Labs layered space time (VBLAST) algorithm for multiple input multiple output (MIMO) systems. The extended channel was used to provide optimal tradeoff between residual interference and noise amplification. The processing based on lattice reduction method helps achieve maximal diversity order. The VBLAST algorithm was applied to get the optimal processing ordering for successive interference cancellation (SIC) at transmitter. Simulation results show that the proposed algorithm outperforms conventional THP and the LRA zero-forcing (ZF) THP with full diversity order. 相似文献
945.
该文以欧拉弹性理论为基础,运用空间有限元法对高墩曲线连续刚构桥在施工最大悬臂状态下的T构进行稳定性分析。计算不同工况下的结构稳定特征值,以此对高墩曲线连续刚构桥的T构施工过程进行监控。 相似文献
946.
Yuan Yao Guosong Wu Yousef Sardahi 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(2):297-318
In this paper, we study a multi-objective optimal design of three different frame vibration control configurations and compare their performances in improving the lateral stability of a high-speed train bogie. The existence of the time-delay in the control system and its impact on the bogie hunting stability are also investigated. The continuous time approximation method is used to approximate the time-delay system dynamics and then the root locus curves of the system before and after applying control are depicted. The analysis results show that the three control cases could improve the bogie hunting stability effectively. But the root locus of low- frequency hunting mode of bogie which determinates the system critical speed is different, thus affecting the system stability with the increasing of speed. Based on the stability analysis at different bogie dynamics parameters, the robustness of the control case (1) is the strongest. However, the case (2) is more suitable for the dynamic performance requirements of bogie. For the case (1), the time-delay over 10?ms may lead to instability of the control system which will affect the bogie hunting stability seriously. For the case (2) and (3), the increasing time-delay reduces the hunting stability gradually over the high-speed range. At a certain speed, such as 200?km/h, an appropriate time-delay is favourable to the bogie hunting stability. The mechanism is proposed according to the root locus analysis of time-delay system. At last, the nonlinear bifurcation characteristics of the bogie control system are studied by the numerical integration methods to verify the effects of these active control configurations and the delay on the bogie hunting stability. 相似文献
947.
948.
本文介绍了遥感和GIS技术在防洪领域的应用 ,提出了洪水预警监测和损失评估系统的设计原则 ,并根据面向对象的思想设计系统的各功能模块 ,实现数据管理、影像处理、空间分析和模拟输出的功能 相似文献
949.
950.
Despite widespread growth in on-road public transport priority schemes, road management authorities have few tools to evaluate
the impacts of these schemes on all road users. This paper describes a methodology developed in Melbourne, Australia to assist
the road management authority, VicRoads, evaluate trade-offs in the use of its limited road-space for new bus and tram priority
projects. The approach employs traffic micro-simulation modelling to assess road-space re-allocation impacts, travel behaviour
modelling to assess changes in travel patterns and a social cost benefit framework to evaluate impacts. The evaluation considers
a comprehensive range of impacts including the environmental benefits of improved public transport services. Impacts on public
transport reliability improvements are also considered. Although improved bus and tram reliability is a major rationale for
traffic priority its use in previous evaluations is rare. The paper critiques previous approaches, describes the proposed
method and explores some of the results found in its application. A major finding is that despite a more comprehensive approach
to measuring the benefits of bus and tram priority, road-space reallocation is difficult to economically justify in road networks
where public transport usage is low and car usage high. Strategies involving the balanced deployment of bus and tram priority
measures where the allocation of time and space to PT minimises negative traffic impacts is shown to improve the overall management
of road-space. A discussion of the approach is also provided including suggestions for further methodology development.
相似文献
Bill YoungEmail: |