规则波作用下方形排柱附近水流特性数值模拟

为研究规则波作用下方形排柱附近流动特性,基于计算流体力学软件FLOW-3D,运用质量源造波方法,离散RNG k-ε方程控制下的雷诺时均Navier-Stokes方程建立无反射三维数值波浪水槽.与物理模型试验结果对比,建立的数值模型性能良好.运用数值计算结果,分析排柱周围自由表面三维运动特征和方形排柱周围速度场与涡量场分...     

多发脑梗死血浆内皮素的动态变化及补肾化瘀中药的影响

采用放射免疫分析（ＲＩＡ）对多发脑梗死模型组大鼠和补肾益脑、活血化瘀中药治疗组血浆内皮素（Ｅｎｄｏｔｈｅｌｉｎ, ＥＴ）进行动态测定,并用水迷宫试验评价其分辨性学习记忆能力。结果表明：多发脑梗死血浆ＥＴ存在先迅速升高,７ｄ 达峰后迅速下降,至１４ｄ 达正常水平的时相变化;补肾益脑、活血化瘀中药组各时期ＥＴ水平均显著低于模型组（ Ｐ＜ ０．０５）,且前者学习记忆能力缺损轻于后者（ Ｐ＜ ０．０５）。提示补肾益脑、活血化瘀中药通过降低局部ＥＴ而改善脑梗死的结局     

汽车尾气路面净化材料研究进展与思考

汽车尾气的排放严重影响空气质量,危害人类身体健康。为了减少尾气排放,汽车领域做了很多努力,包括机内净化与机外净化。作为尾气排放后最近的接触源,从道路角度切入进行治理,也被认为是行之有效的途径,近年来一直是国际上研究的热点领域。为了深入了解汽车尾气路面净化材料的发展,系统地梳理并回顾了汽车尾气净化过程中使用的催化材料的研究进展、面临的问题以及应用前景。催化材料主要包括二氧化钛基催化剂、贵金属催化剂、ABO₃钙钛矿结构催化剂、介孔材料催化剂以及其他催化剂,分析了不同催化剂的作用机理以及优缺点。由于道路实际的开放条件、尾气净化材料与尾气接触不够充分、易于达到自身净化极限等问题,从梳理高效路面尾气净化材料的改善技术出发,提出了路面汽车尾气净化材料研究的发展方向,即降低贵金属用量、开发新型稀土复合氧化光催化材料,以及多元化、功能化发展等。这一领域的研究,显示出路面尾气净化技术的光明应用前景。     

基于尺度方法的AC-13沥青混合料弹性力学特性研究

运用尺度方法预测随机复合材料沥青混合料弹性力学性能:弹性模量E及泊松比μ。通过CT扫描技术获取AC-13沥青混合料细观图像,统计不同粒径骨料随机分布特性。根据统计的随机骨料分布特性,在有限元软件内建立AC-13沥青混合料骨料特性的二维细观模型,选取70 mm×70 mm区域作为计算尺度。对集料及基体材料赋予参数,运用尺度算法程序计算沥青混合料模型;预测得出沥青混合料的弹性力学参数E、μ。     

分布式光纤技术在隧道变形监测中的应用

目前,隧道的安全服役离不开安全监测和预警,分布式光纤技术为隧道的安全运营提供一种全新的技术保障手段。为解决隧道的差异性沉降监测难题,从实验室内光纤轴向拉伸监测变形和Z字形布线方式监测差异沉降的原理及其在某隧道内的应用效果2个方面,阐述分布式光纤监测技术在隧道工程中的应用。无论室内的等级光纤拉伸和还是Z字形布线方式,位移和应变的对应关系都呈现出良好的线性比例关系,为工程实际应用提供理论依据。从工程监测结果来看,分布式定点应变感测光缆能实现对管片接缝变形的准确定位和毫米级接缝宽度感知,Z字形光缆布设方式也能对隧道内管片差异沉降实现精准感知,充分体现分布式光纤监测技术在隧道结构健康监测中的鲜明优势。     

Constrained nested logit model: formulation and estimation

A model of traveller behaviour should recognise the exogenous and endogenous factors that limit the choice set of users. These factors impose constraints on the decision maker, which constraints may be considered implicitly, as soft constraints imposing thresholds on the perception of changes in attribute values, or explicitly as hard constraints. The purpose of this paper is twofold: (1) To present a constrained nested logit-type choice model to cope with hard constraints. This model is derived from the entropy-maximizing framework. (2) To describe a general framework to deal with (dynamic) non-linear utilities. This approach is based on Reproducing Kernel Hilbert Spaces. The resulting model allows the dynamic aspect and the constraints on the choice process to be represented simultaneously. A novel estimation procedure is introduced in which the utilities are viewed as the parameters of the proposed model instead of attribute weights as in the classical linear models. A discussion on over-specification of the proposed model is presented. This model is applied to a synthetic test problem and to a railway service choice problem in which users choose a service depending on the timetable, ticket price, travel time and seat availability (which imposes capacity constraints). Results show (1) the relevance of incorporating constraints into the choice models, (2) that the constrained models appear to be a better fit than the counterpart unconstrained choice models; and (3) the viability of the approach, in a real case study of railway services on the Madrid–Seville corridor (Spain).     

Methods for forecasting the market penetration of electric drivetrains in the passenger car market

Current car technologies will not solve upcoming challenges of mitigating greenhouse gas emissions in road transport. Projections of the market penetration by alternative drive train technologies are controversial regarding both forecast market shares and applied scientific methods. Accepting this latter challenge, we provide a (so far missing) overview of methods applied in this field and give some recommendations for further work. Our focus is to classify the applied methods into a convenient pattern and to analyse models from the recent scientific literature which consider the electrification of light-duty vehicles. We differentiate the following bottom-up approaches: Econometric models with disaggregated data (such as discrete choice), and agent-based simulation models. The group of top-down models are subdivided into econometric models with aggregated data (e.g. vehicle stock data), system dynamics, as well as integrated assessment models with general equilibrium models. It becomes obvious that some methods have a stronger methodological background whereas others require comprehensive data sets or can be combined more flexibly with other methods. Even though there is no dominant method, we can identify a trend in the literature towards data-driven hybrid approaches, which considers micro and macro aspects influencing the market penetration of electric vehicles.     

The taxi industry: working conditions and health of drivers,a literature review

The taxi industry plays an important role in urban transportation systems, both in economic and mobility terms. In the case of the former, it provides employment for a large number of people and circulates significant amounts of money. In the case of the latter, it is a flexible means of transportation capable of arriving at any destination. Although the way the taxi industry is organised varies across countries and even within countries, some factors are shared at varying latitudes of the globe. Working conditions, habits, health, and exposure to road crashes have been a subject of interest for researchers from various disciplines, including medicine, psychology, and economics. However, much of this research focuses on a part of the problem and is not mutually referential. A review of the literature may be useful not only to researchers of diverse disciplines but also to industry representatives and those public officials responsible for transportation, road safety and health policy. This article provides a comprehensive review of the working conditions of taxi drivers, their relationship to road risk exposure and their consequences on the health of workers. It also includes information on coping strategies and protective behaviors. The review is based on a Scopus database search. The search covered the period from 1990 to 2015. This initial search was complemented with other database searches, which yielded some additional studies. Our goal was to summarise existing knowledge, identify possible lines of research and suggest some practical recommendations. It would be important (a) to reduce the workload, establish adequate time for breaks, and provide access to healthcare, (b) to implement actions to promote and maintain healthy habits, (c) to diagnose, detect and treat indicators of occupational fatigue and stress, and (d) to develop programs that make it possible to evaluate work concerns and broaden coping strategies to foster positive changes.     

FPSO码头舾装靠泊装置设计及结构强度分析

浮式生产储油卸油装置(FPSO)的建造过程包括设计、建造、加工、安装、调试和试生产等,涉及多个学科和专业,需由船体上部组块设计单位、工程项目组、建造方等多家单位配合协调才能完成,其码头舾装也更为复杂和重要。FPSO码头舾装靠泊装置可使码头舾装更安全、施工空间更充足,并且显著提高建造效率、缩短建造周期。文中借助有限元软件对该装置的重要部件——护舷驳船结构进行分析、建模,证明其使用安全性。该装置对于其他大型船舶的码头舾装也有较好的参考价值。     

Global maritime domain awareness: a sustainable development perspective

The International Maritime Organization defines maritime domain awareness as the effective understanding of any activity that could impact upon the security, safety, economy or environment. The traditional approach to manage it is based on state sovereignty over national territorial waters where authorities exercise their responsibilities within the defined specific area. Lately, new issues of transboundary dimension (i.e. piracy, overfishing, pollution) are changing the high seas from an open space governed by the rule of freedom into a common domain requiring new governance approach to manage its complex international problems. This paper investigates the use of sustainable development methodology to explore governance solutions within the socio-technical domain of maritime awareness. The outcome suggests that the use of sustainable development tools can and should be used to support the development and implementation of cooperative governance models which are more appropriate for creating global maritime domain awareness than the traditional state-centric and sector-based models. A modelling diagram for potential governance framework under International Maritime Organization’s leadership is included.