Technology Choice and Productivity in the Turkish merchant fleet in the last two decades

Sea transportion has become a significant sector in Turkey since the early 1980s. It has developed due to the domestic subsidies provided and also because of the favourable conjuncture in the world ship Sale and Purchase markets in this period. In the 1990s this sector has started to gain some self-confidence and has completed the 'Infant Inudustry' period. However, bacause its structure is open to international competition, the protection policies available in the 1980s have been found to be inadequate. The capacity of the Turkish merchant fleet has expanded to a considerable extent in the last two decades, but it is comprised of over-aged and old fashioned ships built using outdated technology. and a sudden and cat-astrophic crisis could be approaching. A precaution in the long run could be to have special types of ships carrying convenient loads at minimum costs.     

Influence of wheel and rail profile shape on the initiation of rolling contact fatigue cracks at high axle loads

The influence of wheel and rail profile shape features on the initiation of rolling contact fatigue (RCF) cracks is evaluated based on the results of multi-body vehicle dynamics simulations. The damage index and surface fatigue index are used as two damage parameters to assess the influence of the different features. The damage parameters showed good agreement to one another and to in-field observations. The wheel and rail profile shape features showed a correlation to the predicted RCF damage. The RCF damage proved to be most sensitive to the position of hollow wear and thus bogie tracking. RCF initiation and crack growth can be reduced by eliminating unwanted shape features through maintenance and design and by improving bogie tracking.     

Determining the Monetary Value of Quality Attributes in Freight Transportation Using a Stated Preference Approach

It is commonly accepted that the modal choice of a shipper is influenced not only by the pure economic attributes of transportation – time and cost – but also by more qualitative factors. These quality attributes relate to frequency, reliability, flexibility, transport duration and risk of loss or damage; they are usually difficult to quantify in monetary terms. Different techniques exist that help to understand better how these different quality attributes of freight transportation influence modal choice. In this paper we apply a stated preference design. Using real business data, the aim is then to derive partial utility functions that allow us to calculate monetary values for these different quality attributes.     

Investigation of hardware-in-the-loop for use in suspension development

Hardware-in-the-loop (HiL) is a testing method in which real-time measurements on physical hardware replace the mathematical model of the particular hardware during simulation. The development of a semi-active suspension prompted the need for such capability. HiL, implemented on a PC with a dSpace^TM board in conjunction with a hydrodynamic actuator, was compared to software simulations of single degree of freedom (DOF) and two DOF systems. HiL was also compared to a physical (ballast-based) two DOF system, comprising the rear suspension of a motorcycle. Comparisons between the HiL and software responses showed its suitability for testing suspension systems, thus providing a viable alternative to ballast-based suspension tests, using available hardware. The research also showed that actuator dynamics, filter types and amounts, and signal reference levels required special consideration.     

The status of German railway operations management in research and practice

The German railway operations management uses probabilistic and simulation methods in research and practice. The probabilistic methods are based on queuing theory. There are synchronous or asynchronous algorithms for the simulation of time tables, schedule, operation, and disposition. Models were also developed for the simulation of the operation in many parts of the network for the connection between the structure of the track and the capacity of lines and stations, for the evaluation of operating cost depending from the quality of service, and for the design of integrated timetables.     

Scrutinizing individuals’ leisure-shopping travel decisions to appraise activity-based models of travel demand

Activity-based models for modeling individuals’ travel demand have come to a new era in addressing individuals’ and households’ travel behavior on a disaggregate level. Quantitative data are mainly used in this domain to enable a realistic representation of individual choices and a true assessment of the impact of different Travel Demand Management measures. However, qualitative approaches in data collection are believed to be able to capture aspects of individuals’ travel behavior that cannot be obtained using quantitative studies, such as detailed decision making process information. Therefore, qualitative methods may deepen the insight into human’s travel behavior from an agent-based perspective. This paper reports on the application of a qualitative semi-structured interview method, namely the Causal Network Elicitation Technique (CNET), for eliciting individuals’ thoughts regarding fun-shopping related travel decisions, i.e. timing, shopping location and transport mode choices. The CNET protocol encourages participants to think aloud about their considerations when making decisions. These different elicited aspects are linked with causal relationships and thus, individuals’ mental representations of the task at hand are recorded. This protocol is tested in the city centre of Hasselt in Belgium, using 26 young adults as respondents. Response data are used to apply the Association Rules, a fairly common technique in machine learning. Results highlight different interrelated contexts, instruments and values considered when planning a trip. These findings can give feedback to current AB models to raise their behavioral realism and to improve modeling accuracy.     

Why Cost Benefit Analysis is perceived as a problematic tool for assessment of transport plans: A process perspective

Academic discussions on Cost Benefit Analysis (CBA) as an appraisal instrument for integrated land use and transportation plans tend to focus on its technical aspects. However, many issues of CBA also arise from process related matters, especially when assessing integrated plans. Using an inductive research design, we explored how these process related issues play out in Dutch planning practices. In two applied research techniques, focus group sessions and open in depth interviews, we focused on process related issues as perceived by CBA participants ranging from plan makers to CBA testers. This article presents the different perceptions of issues in CBA processes. Through these collected perspectives, we found that these issues are multi-layered and present a number of fundamental dilemmas. After relating our empirical data to theory, we conclude that the biggest challenge lies in decreasing the level of mistrust and communication deficits revealed between plan owners and CBA calculators and their respective frames of thinking when assessing complex integrated land use and transportation plans.     

Towards port infrastructure adaptation: a global port climate risk analysis

In this paper, a new concept of “port climate risk exposure function along the sea–land boundary axis” is introduced as a critical component towards port adaptation. This concept derived from a global survey which was conducted over 29 countries to assess perceived climate risks to port infrastructure from relevant experts. The methodology used 48 climate scenarios developed based on existing data. Ultimately, this paper serves as a global climate risk indicator to guide further adaptive initiatives in ports.     

汽车交流发电机与调节器搭铁极性及其应用

从汽车交流发电机结构与搭铁极性角度,简述了汽车交流发电机与调节器配套工作和在使用维修及研中的实际意义。     

Long-term wear and rolling contact fatigue behaviour of a conformal wheel profile designed for large radius curves

There are many reasons to optimise the wheel–rail interface through redesign or maintenance. Minimising wear and rolling contact fatigue (RCF) initiation on wheels and/or rails is often at the forefront of such considerations. This paper covers the design of a conformal wheel profile and its long-term wear and RCF performance to optimise the wheel–rail interface and subsequently reduce the occurrence of surface-initiated RCF on South Africa’s iron ore export line. A comparative study is performed using multibody dynamics simulation together with numerical wheel wear and RCF predictions. The advantages of a conformal wheel profile design are illustrated by evaluating the worn shape and resulting contact conditions of the conformal design. The conformal design has a steadier equivalent conicity progression and a smaller conicity range compared with the current wheel profile design over the wheel’s wear life. The combination of a conformal wheel profile design with 2?mm hollow wear and inadequate adherence to grinding tolerances often result in two-point contact, thereby increasing the probability of RCF initiation. The conformal wheel profile design proved to have wear and potential RCF benefits compared with the current wheel profile design. However, implementation of such a conformal wheel profile must be accompanied by improved rail grinding practices to ensure rail profile compliance.