Wave scattering by undulating bed topography in a two-layer ocean

The problem of wave scattering by undulating bed topography in a two-layer ocean is investigated on the basis of linear theory. In a two-layer fluid with the upper layer having a free surface, there exist two modes of waves propagating at both the free surface of the upper layer and the interface between the two layers. Due to a wave train of a particular mode incident on an obstacle which is bottom-standing on the lower layer, reflected and transmitted waves of both modes are created by the obstacle. For small undulations on the bottom of the lower layer, a perturbation method is employed to obtain first-order reflection and transmission coefficients of both modes for incident wave trains of again both modes in terms of integrals involving the bed-shape function. For sinusoidal undulations, numerical results are presented graphically to illustrate the energy transfer between the waves of different modes by the undulating bed. U. BASU was born in 1949. She is a professor in the Department Applied Mathematics, Calcutta University, India. Her current research interests include water wave problems, continuum mechanics, etc.     

Development of the Inner Spherical CVT for a motorcycle

An Inner Spherical CVT (ISCVT) transfers engine power by utilizing the traction force of the lubricant fluid film on the contact point between concave and convex spherical rolling bodies. Since the concave and the convex contact surfaces of the ISCVT are exactly spherical parts, they have a large circular (not elliptic) contact area, and the ISCVT mechanism has a larger torque capacity, less spin loss, and better stability than other traction drive mechanisms. The IVT (Infinitely Variable Transmission) performances also can easily be embodied in the ISCVT. In this work, we developed a prototype of the ISCVT for a motorcycle with a 125cc single cylinder engine having a maximum torque of 13.73 Nm at 8,000 rpm. The design parameters were determined, and the transmission performances were evaluated by optimal design procedure. The transmission efficiency, the life time, the maximum severe stresses on each part of the ISCVT, and the work needed for varying speed ratio were theoretically investigated, and the efficiency performances were experimentally measured. The manufactured prototype was installed in an actual motorcycle, which was fixed on the test-bench equipped with a dynamometer. The parasitic loss of the prototype and the cross-sectional road load performance were tested. The power efficiency of the simulated prototype was between 87∼92%, and the life span was more than 50,000 hours. The tested overall power efficiency was around 70∼92% under frequent driving conditions, which is an impressive performance in a motorcycle transmission despite the small difference from the simulation.     

When the internet is not enough: toward an understanding of carpool services for service workers

For much of the twentieth century, the economies of Canada and the United States have increasingly focused on service provision. During this same time period, cities have grown into expansive urban regions characterized by dispersed workplaces complemented by a wide array of commuting patterns, dominated by single occupancy vehicle use. This study aims to understand how service worker engagement with an Internet-based carpool formation software, known as Carpool Zone, and workplace transport policies, jointly enable carpool formation and use. The piece also explores the question of difference in carpool formation between female and male service workers. The study area is the Greater Golden Horseshoe, Canada??s largest metropolitan region. Data were drawn from Carpool Zone and a 2007 survey of commuter satisfaction. Extending past work, logistic regression analysis clarifies the importance of specific workplace policies, enacted within suburban firms, to the carpool formation process, including: provision of carpool spaces and availability of an emergency ride home service. The findings indicate that the Internet may not be enough, powerful enabling tools should be situated within expert networks of human capital developed to ameliorate the negative effects of commuting.     

No longer in the driver’s seat: How do affective motivations impact consumer interest in automated vehicles?

Transportation - Emerging advancements in automated vehicles may dramatically change how transportation system users engage cars as symbols and tools to exert control over their lives, time use,...     

A Critical Analysis of DEA Applications to Seaport Economic Efficiency Measurement

Abstract

The significant increase in the adoption of Data Envelopment Analysis (DEA) for seaport efficiency measurement renders a literature synthesis and critical analysis of the application of the technique relevant and worthwhile. This paper provides a thorough review and critical analysis of the major studies undertaken to date, and highlights some problems and limitations in the application of the technique in the seaport context particularly in the specification of parameters, the sampling domain and the type of DEA to be applied. The paper informs the decision process as to the merits and limitations of DEA approaches for seaport efficiency measurement and makes a contribution towards methodological improvement by considering variations not yet applied to the port sector.     

Safety outcomes of internationalization of domestic road haulage: a review of the literature

Abstract

The European Union (EU) promotes gradual lifting of restrictions on foreign hauliers involved in domestic road transport of goods (cabotage), and a major deregulation was scheduled in 2014. Due to complaints from several member states facing competition from new EU-countries with lower labour costs, this process was postponed until 2015. An important aspect related to such a deregulatory reform includes potential consequences for transport safety and accident risk factors. The main aims of the current paper are therefore to examine the potential transport safety outcomes of increasing internationalization of domestic road haulage, and to examine potential accident risk factors of foreign hauliers. This is done by reviewing the research literature. This paper shows that the heavy goods vehicle (HGV) accident risk varies with a factor of up to 10 in European countries, and that the accident risk of foreign HGVs is approximately two times higher than that of domestic HGVs in the studied European countries. The paper points to several risk factors and concludes that better data on accident risk and risk factors must be gathered in order to enable European authorities to correctly analyse and respond to this important traffic safety challenge.     

Analysis of factors affecting the choice of route of pedestrians

Pedestrians as compared to vehicular traffic enjoy a high degree freedom of movement even in heavily congested areas. Consequently, there are more alternative links available to pedestrians between a given origin‐destination (O‐D) pair. This paper describes a study done by the University of Calgary to evaluate the factors affecting the choice of route on intra‐CBD trips or trips within the Central Business District (CBD).

An origin destination survey conducted in downtown Calgary, Alberta enabled the identification of the most significant factors influencing the choice. These factors were analyzed in relation to the physical characteristics of the location, personal characteristics of the trip maker and the type of the trip.

It appears that most people chose the shortest link and factors such as the level of congestion, safety or visual attractions were only secondary. This suggests that the length should be made a major consideration when planning and designing pedestrian links.     

Experimental study of performance and emission characteristics of DEE-assisted minimally processed ethanol fuelled HCCI engine

The homogeneous charge compression ignition (HCCI) is an alternative combustion concept for reciprocating engines. This study investigates an HCCI engine fuelled with Diethyl ether (DEE) ignition assisted wet ethanol (ethanol with 20% water content). The direct use of wet ethanol could reduce the associated energy required for distillation and dehydration of ethanol. The HCCI engine offers significant benefits in terms of its high efficiency and ultra low emissions. The experiment is conducted with various DEE flow rates and at different air-fuel ratios, for which stable HCCI combustion is achieved. Incylinder pressure, heat release analysis and exhaust emissions were observed. In this study, the effect of DEE on combustion parameters, thermal efficiency and emissions is analysed and discussed in detail. The experimental results indicate that the DEE flow rates have a significant effect on the maximum in-cylinder pressure and its position, thermal efficiency, maximum rate of pressure rise and the heat release rate. Results show that for all stable operating points, brake thermal efficiency is higher than reference mode at lower loads and almost same at higher loads. The emission parameters such as NO, HC and CO are lower than the dual fuel mode which is considered as a reference model for this experiment.     

A methodology to estimate travel time using dynamic traffic assignment (DTA) under incident conditions

This paper presents results from a research case study that examined the distribution of travel time of origin–destination (OD) pairs on a transportation network under incident conditions. Using a transportation simulation dynamic traffic assignment (DTA) model, incident on a transportation network is executed under normal conditions, incident conditions without traveler information availability, and incident conditions assuming that users had perfect knowledge of the incident conditions and could select paths to avoid the incident location. The results suggest that incidents have a different impact on different OD pairs. The results confirm that an effective traveler information system has the potential to ease the impacts of incident conditions network wide. Yet it is also important to note that the use of information may detriment some OD pairs while benefiting other OD pairs. The methodology demonstrated in this paper provides insights into the usefulness of embedding a fully calibrated DTA model into the analysis tools of a traffic management and information center.     

大型加强板结构焊接顺序的效果研究(英文)

Welding sequence has a significant effect on distortion pattern of large orthogonally stiffened panels normally used in ships and offshore structures. These deformations adversely affect the subsequent fitup and alignment of the adjacent panels. It may also result in loss of structural integrity. These panels primarily suffer from angular and buckling distortions. The extent of distortion depends on several parameters such as welding speed, plate thickness, welding current, voltage, restraints applied to the job while welding, thermal history as well as sequence of welding. Numerical modeling of welding and experimental validation of the FE model has been carried out for estimation of thermal history and resulting distortions. In the present work an FE model has been developed for studying the effect of welding sequence on the distortion pattern and its magnitude in fabrication of orthogonally stiffened plate panels.