基于传播模型的非机动车违规过街行为研究

为研究信号交叉口非机动车违规过街行为，选取西安市的7个信号交叉口，通过视频拍摄获取资料，应用复杂网络来分析非机动车网络的结构特征和演化规律.建立了交叉口非机动车网络，基于SI模型的基本思想，提出了非机动车违规过街行为的传播模型.并通过python程序进行模拟分析，在不同的网络结构和不同的传播率下，获取了非机动车违规过街的行为趋势.结果表明：随着等待时间的增加，一旦有骑行者闯红灯，更多的骑行者将加入到违规过街的行列；在内向度和外向度方面，电动自行车均高于普通自行车；非机动车违规行为随着传播率及非机动车流量的增加而增加.     

Real-time trip purpose prediction using online location-based search and discovery services

The use of smartphone technology is increasingly considered a state-of-the-art practice in travel data collection. Researchers have investigated various methods to automatically predict trip characteristics based upon locational and other smartphone sensing data. Of the trip characteristics being studied, trip purpose prediction has received relatively less attention. This research develops trip purpose prediction models based upon online location-based search and discovery services (specifically, Google Places API) and a limited set of trip data that are usually available upon the completion of the trip. The models have the potential to be integrated with smartphone technology to produce real-time trip purpose prediction. We use a recent, large-scale travel behavior survey that is augmented by downloaded Google Places information on each trip destination to develop and validate the models. Two statistical and machine learning prediction approaches are used, including nested logit and random forest methods. Both sets of models show that Google Places information is a useful predictor of trip purpose in situations where activity- and person-related information is uncollectable, missing, or unreliable. Even when activity- and person-related information is available, incorporating Google Places information provides incremental improvements in trip purpose prediction.     

混凝土工程中裂缝的起因及控制与处理

对水泥混凝土工程中常见的裂缝问题进行分析,提出了一些预防、控制及处理措施。     

流线型钢箱梁涡激振动机理与气动控制措施

以某主跨390 m的独塔流线型钢箱梁斜拉桥为工程依托，采用风洞试验与计算流体动力学（Computational Fluid Dynamics，CFD）相结合的方法对流线型钢箱梁涡激振动机理与气动控制措施进行研究。首先，采用几何缩尺比为1∶30的主梁节段模型进行主梁涡振性能与气动控制措施优化研究；其次，采用CFD方法对主梁涡振响应进行流固耦合计算，将Newmark-β算法嵌入ANSYS Fluent用户自定义函数（User Defined Functions，UDFs）实现主梁结构振动响应求解，同时结合动网格技术实现主梁断面流固耦合分析；并根据判断条件来检索箱梁壁面上的网格单元，以获得主梁断面振动过程中的表面压力，然后结合主梁结构振动响应、表面压力以及流场特征等对主梁涡激振动机理进行分析。结果表明：该桥主梁原设计方案存在涡激共振现象，将梁底检修车轨道内移120 cm可有效抑制主梁涡振响应；主梁涡激振动响应的数值模拟结果与风洞试验结果吻合较好；检修车轨道内移120 cm后主要改变了箱梁下表面平均压力系数分布特性，且箱梁表面各测点脉动压力卓越频率不一致，有效减小了主梁涡激振动响应；流线型箱梁靠近迎风侧的“被动区域”对结构涡振响应贡献较小，背风侧“驱动区域”发生周期性旋涡脱落是影响流线型箱梁涡振的主要因素。     

浅埋顶管沉井周边土体的三维破坏形状及沉降研究

为研究顶管沉井及周边土体在顶进力作用下的形变范围与大小，以加固旋喷桩作为沉井周围加固体建立ABAQUS软件计算模型，并将模拟结果与工程实例、PLAXIS 3D软件所得结果进行对比分析。同时，采用广州地区花岗岩残积土进行室内沉井模型试验，并通过试验结果对数值模拟结论进行验证，得出结论如下： 1）在开挖基坑前达到设计强度的旋喷桩能有效减小基坑周边土体塌陷变形、坑底隆起。2）在施加工作顶推力下，前侧主动区首先出现贯通裂缝，竖向位移斜率增大出现明显拐点；继续增大顶推力，土体位移会急剧增大导致地表沉降严重。3）对于后背土体，在顶推力作用下，地表破裂线的切线角度从0°逐渐增大至45°+φ/2，导致破裂范围也不断扩大；达到45°+φ/2处后，继续施加顶推力会导致短轴方向破坏范围扩大的速度较长轴方向的速度更快；三维空间中被动区破坏土体在地表处产生形状为椭圆的破坏面，椭圆长轴方向为顶推轴线方向，被动破坏体呈现为牛角状椭圆楔体。     

Interactive travel choices and traffic forecast in a doubly dynamical system with user inertia and information provision

This study models the joint evolution (over calendar time) of travelers’ departure time and mode choices, and the resulting traffic dynamics in a bi-modal transportation system. Specifically, we consider that, when adjusting their departure time and mode choices, travelers can learn from their past travel experiences as well as the traffic forecasts offered by the smart transport information provider/agency. At the same time, the transport agency can learn from historical data in updating traffic forecast from day to day. In other words, this study explicitly models and analyzes the dynamic interactions between transport users and traffic information provider. Besides, the impact of user inertia is taken into account in modeling the traffic dynamics. When exploring the convergence of the proposed model to the dynamic bi-modal commuting equilibrium, we find that appropriate traffic forecast can help the system converge to the user equilibrium. It is also found that user inertia might slow down the convergence speed of the day-to-day evolution model. Extensive sensitivity analysis is conducted to account for the impacts of inaccurate parameters adopted by the transport agency.     

高速路网不停车收费车道优化布设方法

合理设置高速公路收费站ETC (Electronic Toll Collection)车道数量，对高速公路通行效率至关重要。针对目前路网中ETC与MTC (Manual Toll Collection)车辆混行的情况，考虑ETC的普及率，结合多用户路网均衡模型和排队论方法，建立基于双层规划模型的高速路网ETC车道优化布设方法。上层模型以车辆总通行时间最小为目标，优化设置进出收费站的ETC车道数量；下层模型为多用户路网均衡模型，反映ETC和MTC车辆的路径和收费车道选择行为。下层模型通过设计收费站的等价拓扑结构，表征收费站的车道使用规则及车辆的收费车道选择行为，并采用排队论方法估计ETC和MTC车道的收费排队时间。根据模型的特点设计了基于主动集的启发式算法，利用参数二进制与拉格朗日函数法确定迭代下降方向，解决了下降方向与步长难以计算的问题；通过内嵌优化函数的方式，保证在主动集转化过程中上层约束均不会失效，且避免了迭代过程中的模型解退化问题。基于上海市绕城高速进行实证分析，结果表明：随着ETC普及率的提升，收费排队时长按照负指数趋势下降；与按比例布设ETC车道的方法相比，所提方法最高可降低57.4%的收费排队时间，且该方法可以避免ETC车道布设过多对于MTC车道通行能力挤压造成的负面效果。研究成果可以有效指导高速路网ETC车道的布设，提高路网通行效率。     

Investigating Causal Pathways Linking Site-Level Characteristics,Compliance, and Ecological Performance in Caribbean MPAs

A rapidly growing body of empirical evidence has linked improved ecological performance of social–ecological systems (SES) with better compliance with rules governing human activities. Researchers have proposed several key factors that motivate an individual to comply with resource use rules, including deterrence, social pressures, moral inclinations, and perceived legitimacy of rules and responsible authorities. Much of the research on compliance proposes causal mechanisms at the individual human level, but few studies test causal paths with empirical data particularly at the site level. This study tested a proposed pathway for explaining overall compliance rates and ecological performance in SES using data from structured surveys of community members, key informant interviews, policy documents, and coral reef surveys at marine protected areas (MPAs) and their associated human communities in the wider Caribbean. Findings indicate that compliance and other active MPA management interventions positively affect ecological performance, and site-level contextual factors (level of community development and being part of a political network) positively influence significant predictors of overall compliance rates, which include active MPA management and enforced punishments.     

Promoting public bike-sharing: A lesson from the unsuccessful Pronto system

In 2014, Seattle implemented its own bike-sharing system, Pronto. However, the system ultimately ceased operation three years later on March 17th, 2017. To learn from this failure, this paper seeks to understand factors that encourage, or discourage, bike-sharing trip generation and attraction at the station level. This paper investigates the effects of land use, roadway design, elevation, bus trips, weather, and temporal factors on three-hour long bike pickups and returns at each docking station. To address temporal autocorrelations and the nonlinear seasonality, the paper implements a generalized additive mixed model (GAMM) that incorporates the joint effects of a time metric and time-varying variables. The paper estimates models on total counts of pickups and returns, as well as pickups categorized by user types and by location. The results clarify that effects of hilly terrain and the rainy weather, two commonly perceived contributors to the failure. Additionally, results suggest that users in the University District, presumably mostly university students, tend to use shared bikes in neighborhoods with a higher household density and a higher percentage of residential land use, and make bike-sharing trips regardless workdays or non-workdays. The paper also contributes to the discussion on the relationship between public transportation service and bike-sharing. In general, users tend to use bike-sharing more at stations that have more scheduled bus trips nearby. However, some bike-sharing users may shift to bus services during peak hours and rainy weather. Several strategies are proposed accordingly to increase bike ridership in the future.     

公路工程的水土保持生态补偿

就公路工程中所遇到的环境问题,结合设计施工中的解决办法,阐述公路工程的水土保持生态补偿,从而减小因道路施工给沿线自然地形、地貌造成的各种破坏,保护和改善当地环境,提高公路的使用效果,更好地发挥公路的各项功能。