Unsteady finite-depth effects during resistance tests on a ship model in a towing tank

This paper covers an extension of the study of Doctors et al. (J Ship Res 52(4):263–273, 2008) on oscillations in wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model to the case of relatively shallow water. We demonstrate here that the unsteady effects are very prominent and that it is essentially impossible to achieve a steady-state resistance curve in a towing tank of typical proportions for a water-depth-to-model-length ratio of 0.25. This statement is particularly true in the speed region near a depth Froude number of unity. However, on the positive side, we show here that an application of unsteady linearized wave-resistance theory provides an excellent prediction of the measured total resistance, when one accounts for the form factor in the usual manner. Finally, a simple application of the results to the planning and analysis of towing-tank tests is presented.     

郁江口及羊栏滩汇流段船舶对会条件改善措施研究

长洲枢纽建成后只能渠化其上游159 km航道,水浅流急的羊栏滩处于水库脱水段。在贵港至梧州二级航道整治工程中对羊栏滩进行了整治,但未根本改善回水末端的郁江口及羊栏滩河段的船舶双向通航条件,按照《航道整治工程技术规范》(JTJ312-2003),加宽后的设计方案航道尺度根本无法满足设计船队的双线通航要求,严重影响航道的通过能力。文章分析了郁江口汇流段及羊栏滩河床形态和通航水流条件的特殊性,通过物理模型试验和自航船模试验相结合的方法,提出并研究了满足船舶对会的工程方案,并对现行规范中弯道双向航道尺度的计算方法提出了建议。     

考虑驾驶人风格的换道轨迹规划与控制（双语出版）

基于自动换道控制技术中融合个性化驾驶人风格的研究，建立考虑驾驶人风格的车辆换道轨迹规划及控制模型以提高换道规划控制模型对不同风格驾驶人的适用性，在保证安全性的基础上进一步满足驾驶人的个性化需求。首先通过问卷调查的方式采集得到了212份驾驶人风格量表数据，采用主成分分析法和K均值（K-means）聚类分析法将驾驶人按驾驶风格分为激进型、普通型和谨慎型，并通过驾驶模拟器试验采集不同风格驾驶人分别在自车道前车、目标车道前车和目标车道后车影响下的换道行为数据。然后对椭圆车辆模型进行改进，以描述不同风格驾驶人的行车安全区域，并据此构建3种典型工况下不同风格驾驶人的换道最小安全距离模型，结合驾驶舒适性约束、车辆几何位置约束以及不同风格驾驶人的换道行为数据，以换道纵向位移最短为目标，实现适应驾驶人风格的换道轨迹规划。最后以基于预瞄的路径跟踪模型作为前馈量，设计基于动力学的线性二次型最优（LQR）反馈控制器，通过调节控制权重矩阵实现3种工况下不同驾驶人风格的换道轨迹跟踪。PreScan和MATLAB/Simulink联合仿真结果表明：所设计的考虑驾驶人风格的换道轨迹规划及跟踪控制模型能够实现不同驾驶风格的自动换道轨迹规划及跟踪控制，可满足驾驶人个性化换道需求。     

砂砾地层盾构隧道受力光弹试验

为满足城市地下管廊、城际快速地下交通网的建设需求，中国隧道工程的应用率与日俱增。砂砾地层因黏聚力较低，与其他地质条件地层相比工程特性明显。在分析类似地质情况下的盾构隧道受力时，连续性介质假设已不能满足实际需求，应从非连续介质角度分析隧道及其周围岩石介质的受力分布。通过光弹试验观测砂砾地层中隧道-围岩系统内的力链强弱及其分布形式，并应用数字图像处理方法提取力链信息。在光弹颗粒中设置圆形管道以模拟盾构隧道，并通过改变内置管道的直径大小，改变上部及侧部载荷大小，以及在管道底部进行光弹颗粒释放，来分析砂砾地层中隧道直径、埋深变化及隧道底部的地层破坏、流动对隧道-围岩系统中力链分布的影响。利用颗粒元软件PFC对试验过程进行数值模拟，对比分析模拟结果与试验结果以验证试验的可靠性。结果表明：力链是砂砾地层与隧道之间载荷传递的主要方式，围岩与隧道间的接触力分布具有非对称性；隧道的椭圆化程度及其周围砂砾岩层中的力链密度，均随着隧道直径和埋深的增加而增大；当砂砾地层破坏、流动时，隧道-围岩系统内的力链也被破坏并重新分布，地层内维持系统稳定的“环状”强力链退化成为“拱形”强力链，系统自稳性产生破坏，此时应采取措施强化系统的稳定性。     

Ant Colony Routing algorithm for freeway networks

Dynamic traffic routing refers to the process of (re)directing vehicles at junctions in a traffic network according to the evolving traffic conditions. The traffic management center can determine desired routes for drivers in order to optimize the performance of the traffic network by dynamic traffic routing. However, a traffic network may have thousands of links and nodes, resulting in a large-scale and computationally complex non-linear, non-convex optimization problem. To solve this problem, Ant Colony Optimization (ACO) is chosen as the optimization method in this paper because of its powerful optimization heuristic for combinatorial optimization problems. ACO is implemented online to determine the control signal – i.e., the splitting rates at each node. However, using standard ACO for traffic routing is characterized by four main disadvantages: 1. traffic flows for different origins and destinations cannot be distinguished; 2. all ants may converge to one route, causing congestion; 3. constraints cannot be taken into account; and 4. neither can dynamic link costs. These problems are addressed by adopting a novel ACO algorithm with stench pheromone and with colored ants, called Ant Colony Routing (ACR). Using the stench pheromone, the ACR algorithm can distribute the vehicles over the traffic network with less or no traffic congestion, as well as reduce the number of vehicles near some sensitive zones, such as hospitals and schools. With colored ants, the traffic flows for multiple origins and destinations can be represented. The proposed approach is also implemented in a simulation-based case study in the Walcheren area, the Netherlands, illustrating the effectiveness of the approach.     

Using repeated cross-sectional travel surveys to enhance forecasting robustness: Accounting for changing mode preferences

Transportation system capacity and performance, urban form and socio-demographics define the influences and constraints conditioning the preferences of urban residents for different transport modes. Changes in characteristics of urban areas are likely to lead to changes in preferences for alternative modes of transport over time; as a consequence, statistical models to forecast mode choice need to be sensitive to both purposeful changes to urban systems as well as exogenous shocks. We make use of the 1996, 2001 and 2006 household surveys conducted in the Greater Toronto and Hamilton Area to study mode preference evolution and model forecasting performance. These repeated cross-sectional household surveys provide an opportunity to investigate aggregate structural changes in commuting mode preferences over time, in a manner sensitive to changes in the urban area. We focus on commuting mode choices because these trips are prime determinants of peak period congestion and peak spreading. We then address how to combine the three cross-sections econometrically in a robust way that allows for use of a single mode choice model across the entire period. Using independent data from 2012, we are able to compare the individual year and combined models in terms of forecasting performance to demonstrate the combined model’s more robust forecasting performance into the future.     

21世纪世界新秩序——几种基本理论模式述评

在人类进入21世纪之后，世界需要建立什么样的新秩序才能更好地服务于人类社会?这个问题激发了政治家和思想家们的极大兴趣，他们提出了各种各样的“理论”和“模式”。其中，较具代表性的有：“地球村”模式，世界政府模式，“和平区”与“动乱区”模式，“三大经济区”模式，“明冲突”模式，“单极霸权”或“单极主导下的多极合作”模式，两极或多极均势模式，等等。这些模式各以其独特的视角，试图勾勒出后冷战时代世界新秩序的“地图”。     

我国城市现阶段经济、社会功能定位新探

在我国当前的经济建设中，城市面临着模式转型的过程，同时也面对着不断产生的一系列新矛盾和新要求。文章着重对此加以探讨，并就我国新时期城市功能的新定位提出了建设性意见。     

不同钢内衬加固钢筋混凝土管涵力学特性试验研究

为研究不同钢内衬加固钢筋混凝土管涵的加固效果及其力学特性,对不加固的钢筋混凝土管、10 mm厚平钢管内衬加固钢筋混凝土管、波纹钢管内衬加固钢筋混凝土管3个试件进行两点加载试验,测试P—Δ曲线及截面应变。试验结果表明:采用直接加固方式时,波纹钢管内衬加固钢筋混凝土管、平钢管内衬加固钢筋混凝土管的极限承载力分别比未加固圆管的极限承载力提高240%、22%;加固形成的钢筋混凝土—内填混凝土—内衬波纹钢管截面为部分组合截面;钢筋混凝土—内填混凝土—内衬平钢管截面接近非组合截面,其受力过程与未加固管截面受力过程相似。