Short‐term travel time forecasts for transport information system in hong kong

In this paper, a case study is carried out in Hong Kong for demonstration of the Transport Information System (TIS) prototype. A traffic flow simulator (TFS) is presented to forecast the short‐term travel times that can be served as a predicted travel time database for the TIS in Hong Kong. In the TFS, a stochastic deviation coefficient is incorporated to simulate the minute‐by‐minute fluctuation of traffic flows within the peak hour period. The purposes of the case study are: 1) to show the applicability of the TFS for larger‐scale road network; and 2) to illustrate the short‐term forecasting of path travel times in practice. The results of the case study show that the TFS can be applied to real network effectively. The predicted travel times are compared with the observed travel times on the selected paths for an OD pair. The results show that the observed path travel times fall in the 90% confidence interval of the predicted path travel times.     

A stability analysis of tandem offloading systems at sea

In this article, we analyze the linear stability of tandem offloading systems in wind, current, and waves. The wind and current forces are evaluated with the help of published experimental data, while the hydrodynamic coefficients and wave drift forces are rigorously estimated by using a three-dimensional singularity distribution method based on potential theory. The bow hawser and mooring lines are described quasistatically by elastic catenary equations. In order to examine the linear static and dynamic stability of the system, the equations for surge, sway, and yaw are linearized. The effect of design parameters such as turret position, mooring stiffness, and hawser length and stiffness on stability is investigated based on linearized model. The stability analysis clarifies the mechanism of the limit cycle for tandem offloading systems, which is known as fishtailing motion. The theoretical results of the shape and amplitude of the limit cycle are found to be in good agreement with those of simulations and experiments.     

Rail line length in a crosstown corridor with many-to-many demand

An analytical model that determines the optimal location and length of rail line along a crosstown transportation corridor with the objective of minimizing the total transportation cost is presented. A general, many-to-many passenger demand pattern is considered. The objective function, which includes the rail and bus riding costs, rail and bus operating costs, rail fleet costs and rail line costs, is minimized by using the classical optimization method with the aid of a computer program developed for the model. The model is applied to the Northwest-South transportation corridor in Calgary, Alberta, and the sensitivity of the optimal rail line location and length to the unit cost and demand parameters at their reasonable ranges is tested. It is found that although the total passenger demand, unit rail line cost, and unit bus operating cost have greater influence than the unit bus and rail riding costs, and unit rail fleet and operating costs, the optimal line length is generally insensitive to all these parameters. It is also found that the length of the existing LRT line in the corridor is comparable to the optimal line length obtained from the model, but the existing line should be extended further south in order to meet the heavier demand in that direction optimally.     

Development of a Remotely Controlled Testing Platform with Low-drag Air-ventilated Hull

This paper addresses the development and testing of a remotely controlled boat platform with an innovative air-ventilated hull. The application of air cavities on the underside of ship hulls is a promi...     

Metropolitan railways: present characteristics and future prospects

Urban bus operation in Chile is totally deregulated. This is the only example in the world where access to the urban bus transport market is totally free, and where the government does not exercise any control over the fares. This policy has been implemented progressively since 1979. Ten years later, it is possible to draw some conclusions from the experience. To summarize these conclusions, one could say that (i) the impact of deregulation has been almost exactly the opposite of what was expected: fares have risen and the diversity of services has been reduced, (ii) the reasons for this discrepancy lie less in the action of a cartel than in the specifics of urban transport supply and (iii) there is probably more to be expected from a refined deregulation policy, taking into account these specifics, than from a drive back to the traditional regulation system.     

CANDY statement of methods

This paper presents a detailed overview of CANDY, a catenary–pantograph dynamic interaction software. Authors describe the main key points of the formulation, focusing on its time-integration scheme, the pantograph and contact models as well as the solution of the initial equilibrium problem. Nonetheless one of the most important features of CANDY is its moving finite element mesh, which enables accurate results without excessive computational cost. The validation of the model against the European Standard EN 50318 and some conclusions and comments about the results of the benchmark are also included.     

Hydrological changes in the Mediterranean Sea in relation to changes in the freshwater budget: A numerical modelling study

The response of the Mediterranean Sea and the various sub-basins to changes in the freshwater budget are investigated in a process-oriented study, using the POM model. The model is first integrated using values of the Nile and Ebro rivers runoff, as well as of the Dardanelles freshwater input, typical of the fifties. The model reaches a steady state representative of that existing in the Mediterranean prior to the major damming period after 90 years of integration. Then the model is integrated using the reduced river runoff values typical of the after-damming period. The additional impact of decadal scale trends in the precipitation rate as well as of intense surface cooling periods/events on the thermohaline circulation during the last 40 years were also examined. The model results show that the dramatic reduction of the Nile freshwater input and to a lesser extent the reduction of the freshwater input from the Dardanelles Straits induced a large increase in the sea surface salinity in the Aegean and Levantine basins in the late sixties/early seventies, in agreement with observations. Furthermore, the Ebro runoff reduction during the same period further enhanced the salinity increase in the Levantine basin as higher salinity surface waters of the western basin reached the eastern basin via the Atlantic Water circulation. This saltier surface layer in the vicinity of the Rhodes Gyre favoured the preconditioning for the formation of the Levantine Intermediate Water, resulting in about 40% increase of its formation rate. This in turn resulted in the production of saltier and larger amounts of deep waters in the various deep-water formation sites. According to the model, the river damming and decreased precipitation since the eighties explain about 95% of the observed salinity increase in the Western Mediterranean Deep Water over the last 40 years. The major contributor to this increase was proved to be the Nile damming. The salt increase in the surface layer is proved to be insufficient to produce alone the two climatic transient events in the deep waters of the Eastern Mediterranean in the late sixties and early nineties, respectively. Surface cooling was found to be important, resulting in large deep water formation and thus allowing the propagation of the increased surface salinity signal to the deep layers. However, model results demonstrate that the river damming played an important role in the long-term salt preconditioning of the surface/intermediate layers, thus contributing in triggering the two events.     

Wave responses of a coastal cargo ship consisting of unit modules

This article discusses the dynamic responses of a coastal cargo ship that consists of unit modules with advance forward speed in waves. We introduce a simple way of connecting the modules that has enough capability to link the modular parts of the ship as a unified whole. The flexible connection consists of male and female rubber fenders with additional pretensioned ropes. This kind of connection system is proposed for use in coastal regions with relatively calm waters wherein the modular ship can move at a moderate speed. The modules are assumed to be rigid compared to the connections. Computations were performed to investigate the vertical elastic responses of four modules connected end-to-end with the assumption that in the simple hinge, no gaps occur in the flexible rubber connections between adjacent modules. A simple method, which is an extension of the computational analysis we reported previously, is presented to study the hydroelasticity and rope tension forces of the modular ship with forward speed in waves. Experiments with a three-dimensional model at Froude numbers of 0 and 0.16 in head waves were performed to evaluate the effectiveness of the calculation method. In the experiments, deflections for each part were measured using calibrated potentiometers. Force transducers were used to measure the rope tension force between the modules of the articulated cargo ship. Some slight differences were observed, but generally the calculated results showed the same trends as the experimental values.     

A minimization theory in Hilbert space and its application to two-dimensional cavity flow with a numerical study

A minimization theory, which is based on the Hilbert space theory, is proposed and applied to two-dimensional cavity flow past a strut with the assumption of potential flow. That is, the minimization of the cavity drag of the strut on the cavity flow is studied with the help of the optimization theory proposed. To accelerate the optimization process, the Euler beam theory is introduced to generate a small variation in the strut. The introduction of the Euler beam theory makes the mathematical formulation for the present theory ill-conditioned. To overcome this condition, the Tikhonov regularization and the Morozov's discrepancy principle are used to regularize the present optimal theory. From the numerical study, it is shown that the proposed minimization theory is able to find an optimized shape for the given strut and corresponding optimized cavity drag. Received: June 22, 2000 / Accepted: January 30, 2001