W-SPSA in practice: Approximation of weight matrices and calibration of traffic simulation models

The development and calibration of complex traffic models demands parsimonious techniques, because such models often involve hundreds of thousands of unknown parameters. The Weighted Simultaneous Perturbation Stochastic Approximation (W-SPSA) algorithm has been proven more efficient than its predecessor SPSA (Spall, 1998), particularly in situations where the correlation structure of the variables is not homogeneous. This is crucial in traffic simulation models where effectively some variables (e.g. readings from certain sensors) are strongly correlated, both in time and space, with some other variables (e.g. certain OD flows). In situations with reasonably sized traffic networks, the difference is relevant considering computational constraints. However, W-SPSA relies on determining a proper weight matrix (W) that represents those correlations, and such a process has been so far an open problem, and only heuristic approaches to obtain it have been considered.This paper presents W-SPSA in a formally comprehensive way, where effectively SPSA becomes an instance of W-SPSA, and explores alternative approaches for determining the matrix W. We demonstrate that, relying on a few simplifications that marginally affect the final solution, we can obtain W matrices that considerably outperform SPSA. We analyse the performance of our proposed algorithm in two applications in motorway networks in Singapore and Portugal, using a dynamic traffic assignment model and a microscopic traffic simulator, respectively.     

云计算技术及应用浅谈

从云技术的含义出发,概括云技术的特点,研究云技术环境下的面向个人、企业、运营商的各种应用,总结各自应用的特点。     

Much Ado about Nothing? - An analysis of economic impacts and ecologic effects of the EU-emission trading scheme in the aviation industry

From 2012 on, all CO₂ emissions from flights departing from or arriving at airports within the European Union have to be offset. We analyze the economic and ecological impacts that are caused by an inclusion of the aviation industry into the proposed emissions trading scheme (ETS). Building on the now fixed system design we employ a simulation model to estimate the impacts of the scheme. Our results indicate that financial impacts are highly dependant on external settings, such as allowance prices and demand growth. We show that the financial burden on the aviation industry will be rather modest in the first years after the introduction of the system and therefore induce only low competition distortions. Likewise, emission reductions within air transportation will be comparably low. While aviation will induce a decline of emissions in other sectors, significant absolute reductions within air transportation can only be reached by a more restrictive system design.     

Real time detection of driver attention: Emerging solutions based on robust iconic classifiers and dictionary of poses

Real time monitoring of driver attention by computer vision techniques is a key issue in the development of advanced driver assistance systems. While past work mostly focused on structured feature-based approaches, characterized by high computational requirements, emerging technologies based on iconic classifiers recently proved to be good candidates for the implementation of accurate and real-time solutions, characterized by simplicity and automatic fast training stages.In this work the combined use of binary classifiers and iconic data reduction, based on Sanger neural networks, is proposed, detailing critical aspects related to the application of this approach to the specific problem of driving assistance. In particular it is investigated the possibility of a simplified learning stage, based on a small dictionary of poses, that makes the system almost independent from the actual user.On-board experiments demonstrate the effectiveness of the approach, even in case of noise and adverse light conditions. Moreover the system proved unexpected robustness to various categories of users, including people with beard and eyeglasses. Temporal integration of classification results, together with a partial distinction among visual distraction and fatigue effects, make the proposed technology an excellent candidate for the exploration of adaptive and user-centered applications in the automotive field.     

化学复合镀及其应用

化学复合镀是一种新型表面处理技术。探讨了复合镀的机理及其应用 ,主要包括耐磨复合镀层 ,如Ni -P -SiC复合镀等 ,还有自润滑复合镀层 ,如Ni -P -PTFE复合化学镀层等。最后对化学复合镀在机车车辆制造业方面的应用作了展望。     

高速列车通信网的技术及其在机车车辆上的应用

高速、安全和舒适是旅客列车发展的方向。列车通信网在高速列车中是必不可少的。本文从拓扑结构、信息特征、介质访问形式、可靠性措施和列车初运行等五个方面分析了列车通信网的技术特点,及其在机车车辆上的具体应用。     

工字钢组合梁架空设备稳定性检算及应用

主要介绍了在营业线架空线路施工中常用的工字梁安全稳定性的检算依据、方法,并用实例进行了计算,对其应用条件、特点及改进措施作了阐述。     

简支槽形梁-拱组合桥在宁启线的应用研究

宁启线增建二线跨越新建沪通铁路时因纵断面受限,采用64m简支槽形梁-拱组合的大跨、低高度新型桥式,有效地解决了立交跨越问题。文章通过对该结构与其他桥式进行综合比较,阐述采用简支槽形梁-拱组合桥式的可行性、经济性及优越性,为类似工点提供设计借鉴。     

基于课元相关运算的高校排课算法

在分析高校课表编排所遵循的基本原则和模糊性原则的基础上，定义了课元之间关于教师的相关关系和关于自然班的相关关系，提出以课元相关运算和课元的候选时空片计算为核心的计算机排课算法。还给出了用关系数据库描述课表问题及实现排课算法的方法。经应用表明，该排课软件具有较好的适应性和实用性。     

汽车排气管设计中QFD与FMEA的集成应用研究

在汽车产品质量管理过程中,QFD和FMEA作为两个核心工具得到广泛应用,这两种工具的结合,既可以分析出最大限度的满足顾客需求的关键技术特性和质量特性,又可以将顾客需求与企业实际生产能力相结合,找出对产品质量影响较大的潜在的质量缺陷和失效模式,合理的调整相应的设计参数。本论文以汽车排气管设计为例,集成应用QFD与FMEA分析工具,从排气管产品的关键技术特性和关键零部件特性方面对产品进行了改善,对企业产品开发中的质量管理具有实际指导意义。