变厚度板中水平剪切波的传播特性分析

为研究超声导波在储罐壁板等变壁厚结构中的传播特性，建立了SH波在空间自由边界中的传播模型，基于各向同性弹性介质Navier-Stokes方程，推导了变厚度板中SH波的频散方程，分析了变厚度板中水平剪切波走时t与倾斜角θ间的相互作用关系；通过简谐点源的远场响应并引入板厚与传播位移的非线性关系，得出了变厚度板中SH波的远场响应方程。在此基础上，仿真分析和实验验证了水平剪切波在不同倾斜角变厚度板中的传播特性，结果表明：在变厚度板的薄端激励水平剪切波并沿结构表面传播时，无频散现象，且无波包分离现象；但随着变厚度板倾斜角θ增大，水平剪切波的走时和接收信号幅值均逐渐递减，且呈非线性关系。     

Robust user equilibrium model based on cumulative prospect theory under distribution-free travel time

The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value(CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities.Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.     

Black hole entropy,the black hole information paradox,and time travel paradoxes from a new perspective

ABSTRACT

Relatively simple but apparently novel ways are proposed for viewing three related subjects: black hole entropy, the black hole information paradox, and time travel paradoxes. (1) Gibbons and Hawking have completely explained the origin of the entropy of all black holes, including physical black holes – nonextremal and in 3-dimensional space – if one can identify their Euclidean path integral with a true thermodynamic partition function (ultimately based on microstates). An example is provided of a theory containing this feature. (2) There is unitary quantum evolution with no loss of information if the detection of Hawking radiation is regarded as a measurement process within the Everett interpretation of quantum mechanics. (3) The paradoxes of time travel evaporate when exposed to the light of quantum physics (again within the Everett interpretation), with quantum fields properly described by a path integral over a topologically nontrivial but smooth manifold.     

Customers segmentation in eco-friendly hotels using multi-criteria and machine learning techniques

This study aims to investigate the travellers' choice behaviour towards green hotels through existing online travel reviews on TripAdvisor. Accordingly, a method combining segmentation and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) techniques was developed to segment travellers based on their provided reviews and to prioritize green hotel attributes based on their level of importance in each segment. The data were taken from travellers' online reviews of Malaysian eco-friendly hotels on TripAdvisor. The results showed that the sleep quality was one of the most imporant factors for eco-hotel selection in the majority of segments. The developed method in this study was able to analyse travellers’ reviews and ratings on eco-friendly hotels to identify the future choice behaviour and aid travellers in their decision-making process. The study provides new insights for hotel managers and green policy makers on developing environmental-friendly practices.     

流形元覆盖系统的有向图遍历生成算法研究

在裂隙切割块体生成算法的基础上，结合现有的有限元自适应网格生成技术，系统地探讨了一种基于有向图遍历理论的平面流形元覆盖系统的生成算法。该算法将有限元网格作为流形元覆盖系统的生成所需的数学网格，利用有向图的关联矩阵并结合块体搜索算法，形成最终的流形元覆盖系统。同时，该算法能有效地在现有的各种有限元单元的基础上，形成流形元法所需的流形单元。     

大城市空间系统的组织优化——一种基于交通行为选择的规划技术思路

基于"大城市病"与土地利用方式之间的关联性,以及城市空间系统阐述,指出:对于中国大城市的建成区和半建成区,需要确立"空间组织优化"的规划主题。在此主题下,论述了出行尺度、出行方式和组织层次等三个空间组织方面的优化内容;提出,大城市空间规划需要基于交通行为选择调查,遵循一种"渐进式"的规划技术思路。     

基于实时数据的网状城市快速路行驶时间预测方法研究

基于城市快速路实时管理和控制的思路,利用观测断面的数据,给出动态预测网状城市快速路上的交通状态和任意两点间行驶时间的方法。具体做法是,依据时序列数据、状态空间模型和自回归模型进行模型参数自拟合,并且预测出将来几个时段的交通状态,然后计算出行驶时间。最后,给出应用于城市快速路网的实例计算结果。结果表明,提出的方法可以用于预测路网上的交通状态和行驶时间,并为城市快速路的信息服务和交通诱导提供一种方法。     

对高速公路行车安全影响因素的分析

通过对高速公路交通事故影响因素的分析，发现人的因素在交通事故中占有最重要的位置，阐述了车辆，道路以及天气情况对事故的发生起着不可忽视的作用，并据此提出预防交通事故发生应采取的对策。     

Learning from the extreme River Tyne flood in January 2005

Extreme floods often demonstrate unanticipated characteristics that pose problems for management and response. The floods on the Tyne and Eden in January 2005 provided numerous examples of such unexpected response. This paper describes characteristics of storm rainfall and runoff generation on the River Tyne catchment, flood effects and damage. Unusual aspects of hydrological behaviour are highlighted as a basis for assessing what lessons can be learned for flood risk management. These include problems associated with coincidence of extreme wind speeds and rainfall, the retarding influence of floodplain storage on flood wave travel time in extreme flows, the influence of critical storm duration on the severity of the resulting flood on headwaters and main river, and the variety of mechanisms of flood occurrence. The occurrence of such an extreme flood provides the opportunity to validate and enhance the review process of the Environment Agency's flood zone maps.     

城市主干道交叉口连续交通仿真分析

利用VISSIM微观仿真系统对采用连续交通组织方式的城市主干道交叉口进行了仿真分析,研究了道口车辆路段行程时间随交织段长度、车流量的变化规律,得出了综合效益最佳的交织段长度。最后对道路设计和管理给出了几点建议。