A complex network approach to understand commercial vehicle movement

We introduce complex network analysis and use a commercial vehicle’s observed trip as a proxy for a business relation between two facilities in its activity chain. We extract facility locations by applying density-based clustering to GPS data of commercial vehicle activities. The network among the facilities is then extracted by analysing the activity chains of more than 25,000 commercial vehicles. Centrality metrics prove useful and novel in identifying and locating key logistics players. Transport planners and decision makers can benefit from such an approach as it allows them to design more targeted initiatives and policy interventions.     

Public transport in towns - Inevitably on the decline?

Bus transport in Linköping, a town of 140?000 people, was strongly on the increase up to the beginning of the 1980s, when a negative trend-break occurred. A demand model is developed which explains both the ongoing decline and the preceding increase. Based on this model, it is examined whether a change of the current bus transport policy towards an optimal pricing and investment policy from a social point of view could evoke a new and positive trend-break. Taking current trends in the exogenous factors into account it would. However, this could depend on a possible revival of bicycling in towns.     

Public opinion and the environment: Ecology,the coastal zone,and public policy

Abstract

In a public opinion survey conducted in Santa Barbara county, California, respondents were interviewed regarding their feelings on coastal zone development, within a context of broader environmental and political issues.

A high degree of expressed concern for the environment was found, but the data also indicate a widespread reluctance to allocate a greater share of personal income to improve environmental quality.

Among the issues dealt with are citizen views on environmental problems, the effectiveness of government in the environmental field, offshore oil drilling, and coastal zone development.

The results show that on each of the issues analyzed, a person's education, age, and the extent of his political participation are the major factors which determine his concern for the environment. Additional variables appear to have some significance in determining attitudes toward local environmental projects and perceptions of government.

Offered are implications of the findings for the future of organized action on environmental problems.     

Rail freight service productivity from the manager's perspective

To be beneficial to management, productivity concepts must be translated into terms that are meaningful to managers at all levels of the organization. Productivity per se is not nearly as important to these people as service quality and financial performance, especially since measured productivity can improve while profits or service levels decline. Productivity must, therefore, be related to an integrated set of performance measures that reflect costs, revenues, trip times and reliability, equipment availability and other matters of continuing concern to transportation companies. Planning and control are critical components of any program to improve productivity. The techniques required to measure and understand productivity are precisely those used in planning and in developing control systems. Furthermore, productivity is conceptually very close to cost analysis, which is a major focus of planning and control. Any transportation company has access to the data needed to develop a vast array of performance measures, including many productivity measures. This paper will illustrate the way that railroads can integrate productivity concepts within more global performance measurement systems. Specific attention will be given to terminal control systems, costing systems for origin-to-destination movements and life-cycle costing techniques for track maintenance planning.     

Modelling the effects of physical–biological interactions and spatial variability in spawning and nursery areas on transport and retention of sardine Sardinops sagax eggs and larvae in the southern Benguela ecosystem

A particle-tracking individual-based model (IBM) coupled with a 3-D hydrodynamic model was used to investigate how spatial variability in spawning and nursery grounds may influence transport and retention of sardine (Sardinops sagax) eggs and larvae in the southern Benguela ecosystem. A temperature-dependent Bělehrádek development model based on laboratory growth data was used to determine the duration of one egg and two larval stages. Successful transport/retention depended on each particle's stage of development rather than its age. Results show that recruitment could occur in two distinct nursery areas on the west and south coasts of South Africa. Three viable recruitment ‘systems’ were identified: two are retention-based (spawned and retained on the west coast (WC–WC) or the south coast (SC–SC)) and one is transport-based (spawned on the south coast and transported to the west coast (SC–WC)). In the WC–WC system, the vertical distribution of eggs influenced retention; at intermediate depths of spawning (25–50 m) eggs avoided both offshore Ekman drift and deep cold water. In the SC–SC system, the area of spawning was important; > 50% of eggs from the eastern Agulhas Bank (EAB) were retained in the south coast nursery grounds, whereas very few eggs were transported there from west of Cape Agulhas. In the SC–WC system, area of spawning was also important; 40% of the eggs spawned on the western Agulhas Bank (WAB) were transported to the west coast nursery ground. Sardine life history strategy could be divided between two main systems: the west coast system (spawning on the WAB and WC, and recruiting to the WC) and the Agulhas Bank system (spawning on the central and eastern Agulhas Bank, and recruiting to the SC).     

A Fisherman's Co-operative: Open System Theory applied ☆

In this paper the effects on the economic output, income and employment relating to Shetland are considered using an input—output model. The results are presented on the basis of an individual industry and appropriate multipliers are derived.     

Improving paratransit scheduling using ruin and recreate methods

Abstract

In this paper we study the effects of using ruin and recreate methods in a replanning phase of a dynamic dial-a-ride problem. Several such methods are proposed, and a modeling system is used to evaluate how they improve the quality of the solutions. We show that simple changes to existing planning methods can increase the efficiency of the service. Two cases, with different forms of costs inflicted on the vehicles, are evaluated and significant improvements are found in both cases. The best results of our study are found with ruin methods based on removal of sequences of requests.     

Dynamic Train-Track Interaction: Variability Attributable to Scatter in the Track Properties

A numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure. A perturbation technique has been used to investigate the influence of the scatter in selected track properties. The train-track interaction problem has been numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the whole track structure. All numerical simulations have been carried out in the time-domain with a moving mass model. Properties such as rail pad stiffness, ballast stiffness, dynamic ballast-subgrade mass and sleeper spacing have been studied. To obtain sufficient statistical information from track structures, full-scale measurements in the field and laboratory measurements have been carried out. The influence of scatter in the track properties on the maximum contact force between the rail and the wheel, the maximum magnitude of the vertical wheelset acceleration, and the maximum sleeper displacement have been studied. Mean values and standard deviations of these quantities have been calculated. The effects of the variation of the investigated track properties are discussed.     

Reduction of VIV using suppression devices—An empirical approach

Helical strakes are known to reduce and even eliminate the oscillation amplitude of vortex-induced vibrations (VIV). This reduction will increase the fatigue life. The optimum length and position of the helical strakes for a given riser will vary with the current profile.

The purpose of the present paper is to describe how data from VIV experiments with suppressing devices like fairings and strakes can be implemented into a theoretical VIV model. The computer program is based on an empirical model for calculation of VIV. Suppression devices can be accounted for by using user-defined data for hydrodynamic coefficients, i.e. lift and damping coefficients, for the selected segments.

The effect of strakes on fatigue damage due to cross flow VIV is illustrated for a vertical riser exposed to sheared and uniform current. Comparison of measured and calculated fatigue life is performed for a model riser equipped with helical strakes. A systematic study of length of a section with strakes for a set of current profiles is done and the results are also presented.