景观道路的设计实践——广阳岛环岛路设计

广阳岛环岛路的主要功能是服务性景观路,跟环岛滨江公园一起,共同构筑广阳岛的滨江景观带。尝试引进了国外的宁静化设计,尽可能推行最生态的工程做法,努力创造人与自然相和谐的环境,并竭尽全力地将这些构想付诸实施。为了实现以上目标,道路、交通、排水、结构、桥梁和电照专业,在景观专业的组织下,共同展开了这条景观路的设计尝试。     

Effect of interference fits on the fatigue lives of bolted composite joints

The effect of interference fits on the fatigue lives of bolted composite joints is investigated by conducting mechanical tests. Static and fatigue tests are carried out on specimens made of carbon-bismaleimide composites joined together as double-lap single-bolt joints. The bolts having interference fits ranging of 0 (neat fit), 0.5%, 0.75% and 1% are performed. The results demonstrate the relationship between fatigue life and different values of interference fits. After the fatigue tests, non-destructive evaluation (NDE) and scanning electron microscope (SEM) are used to observe the damage of the surrender and surface of the hole. The test results show that the interference fitted specimens have improved fatigue life compared to the neat fitted specimen. The NDE and SEM results reveal that the damage degree of interference fitted specimen is weaker than that for the neat fitted one.     

考虑横向漂移的船舶路径跟踪自抗扰控制

针对船舶运动系统中内部动态不确定和外部干扰等问题,进行了欠驱动船舶路径跟踪的自抗扰方法研究。利用Backstepping设计参考航向角,并通过线性扩张状态观测器对流干扰和横向运动引起的横向漂移进行估计。其次,根据自抗扰算法对航向进行控制,采用线性扩张状态观测器对外界干扰及内部不确定项进行估计。最后仿真结果表明,在风流干扰下所设计的控制器仍能使船准确地跟踪上参考路径,验证了所提控制方案的有效性。     

Steering short-term demand for car-sharing: a mode choice and policy impact analysis by trip distance

Transportation - Car-sharing could have substantial benefits. However, there is not enough evidence about if more people choosing car-sharing would reduce private car usage or public transport...     

复合驱动仿生胸鳍机构设计与水动力研究

针对仿鱼型海洋探测机器人低速时的机动性问题,受鹞鲼鱼类依靠胸鳍摆动实现各种水下运动的启发,设计出一种基于共融理论的复合驱动刚-柔多体耦合仿生鱼胸鳍机构。通过构建基于三维非定常湍流控制方程组的柔性鳍摆动系统水动力学模型,研究仿生胸鳍柔性鳍面摆动时周围压力和速度场的变化情况,分析不同摆动幅度和频率下鳍面的水动力学特性,揭示仿生鹞鲼机器鱼的水下运动机理,对摆动胸鳍的水动力进行仿真。结论表明:鳍面摆动时周围的漩涡能够引起胸鳍面上推力、升力及侧向力按类似正弦变化,而推进力和侧向力的大小随摆动幅值和摆动频率增加而增大。     

Two degree of freedom flow-induced vibration of cylindrical structures in marine environments: frequency ratio effects

The flow-induced vibration of a cylindrical structure is a very common problem in marine environments such as undersea pipelines, offshore risers, and cables. In this study, the vortex-induced vibration (VIV) of an elastically mounted cylinder at a low Reynolds number is simulated by a transient coupled fluid–structure interaction numerical model. Considering VIV with low damping ratio, the response, hydrodynamic forces, and vortex shedding modes of the cylinder is systematically analyzed and summed up the universal rule under different frequency ratios. On the basis of the analysis, we find that the frequency ratio α is a very important parameter. It decides the locked-in, beat, and phase-switch phenomena of the cylinder, meanwhile, it also influence the vortex mode of the cylinder. The trajectory of the two degrees of freedom (2 DOF) case at different natural frequency ratios is discussed, with most trajectories having a “figure of 8” shape and a few having a “crescent” shape. A fast Fourier transformation technique is used to obtain the frequency characteristics of the vibration of the cylindrical structure. Using the 2 DOF cylinder model in place of the 1 DOF model presents several advantages in simulating the nonlinear characteristics of cylindrical structures, including the capacity to model the crosswise vibration generated by in-line vibration.     

New procedure for the analysis of speed trial results,with special attention to the correction of tidal current effect

Almost all the existing analysis methods of speed trial results were proposed before 1970s, and the actual analysis procedures are very old-fashioned with instructions like “plot the results on a chart and draw a smooth mean line”, “read a value from the mean line” and so on. Such instructions not only show up the analysis procedures old-fashioned, but also make them very ambiguous and unclear. They should be up-dated to a method which is clear not only in logic but also in calculation procedure, and also fits the present computing technology. At first, the author reviewed the major analysis methods and concluded that the logic of the up-dated analysis procedure can be composed of the logics of the existing ones. Then, the analysis procedure is composed of three stages; namely (1) correction of power and propeller revolution to the ones corresponding to no air condition, (2) correction of tidal current effect, and (3) correction of power and propeller revolution to the ones corresponding to no wind condition. For the stages (1) and (3), there seems to be no big issue except the estimation of the amount of environmentally added resistance in the stage (1). Then, the author focused on the correction of tidal current effect in this paper. For the correction of tidal current effect, the author considers the essential points for the up-date are in the direction of finding out appropriate functions for the variation of tidal current velocity and the ship speed through the water. Then, he investigated to find out such functions and made his proposal. Finally, the applicability of the new procedure is assessed by the analysis of simulated speed trial results of a VLCC.     

A finite pointset method for the numerical simulation of free surface flow around a ship

In this paper, we present a Finite pointset method (FPM) for the numerical simulation of free surface flow around a ship in calm water. It is a Lagrangian and meshless particle scheme which is applied to the projection method for the incompressible governing equations. This requires the solution of Poisson problems in each time step, so a moving least squares (MLS) interpolants is used for the spatial derivatives in order to discretize the Poisson equation with pressure-Dirichlet condition of free surface flow in meshless structure. Meanwhile, an additional problem of the periodic particle locations redistribution in the present approach is still handled by MLS interpolants. With the proposed FPM technique, problems associated with the free surface flow around a ship are circumvented. A verification of numerical modeling is made using the Wigley hull and the validity of the proposed methodology is examined by comparing the detail of wave profile and wave-making resistance with Series 60 model. The results demonstrate that FPM is able to perform efficient and stable simulations of free surface flow around a ship.     

Effects of built environment and weather on bike sharing demand: a station level analysis of commercial bike sharing in Toronto

Bike Share Toronto is Canada’s second largest public bike share system. It provides a unique case study as it is one of the few bike share programs located in a relatively cold North American setting, yet operates throughout the entire year. Using year-round historical trip data, this study analyzes the factors affecting Toronto’s bike share ridership. A comprehensive spatial analysis provides meaningful insights on the influences of socio-demographic attributes, land use and built environment, as well as different weather measures on bike share ridership. Empirical models also reveal significant effects of road network configuration (intersection density and spatial dispersion of stations) on bike sharing demands. The effect of bike infrastructure (bike lane, paths etc.) is also found to be crucial in increasing bike sharing demand. Temporal changes in bike share trip making behavior were also investigated using a multilevel framework. The study reveals a significant correlation between temperature, land use and bike share trip activity. The findings of the paper can be translated to guidelines with the aim of increasing bike share activity in urban centers.     

Market structures in coastal shipping: what to expect in Canada following the Comprehensive and Economic Trade Agreement with the European Union?

After several years of negotiation between Canada and the European Union, the Comprehensive and Economic Trade Agreement (CETA) was ratified in early 2017. The regime set out by the Canadian Coasting Trade Act that reserves shipments of cargo between Canadian ports to Canadian vessels remains mostly untouched under CETA. Minor, yet potentially significant, changes to the regime are introduced by the trade agreement. Provisions are made to liberalize the repositioning of empty containers within Canada. The liberalization of public markets now allows European firms to compete in the Canadian dredging market. Finally, EU vessels can undertake some transshipment activity in Canada but this is limited to international cargo on the specific Montreal-Halifax route. The paper attempts to highlight some possible CETA’s consequences for domestic Canadian shipping markets. It uses industrial economics analytical tools drawn from a Structure-Conduct-Performance (SCP) paradigm. From a literature review, it reconstructs different cases of deregulation that occurred internationally. The observed transformations are then characterized in terms of the SCP model. The paper identifies some common impacts which occurred in different transportation industries after a deregulation process. Using these findings, it concludes by discussing potential impacts for domestic shipping markets in Canada.