Search

It is well known that high-rise buildings affect the surrounding pedestrian-level wind environment. In recent years, awareness and concern has increased about the creation of low wind speed areas around buildings which may lead to poor out-door air ventilation. Moreover, many modern building developments are not restricted to a single building but may comprise a group of buildings. There are very few systematic studies focused on the low wind speed areas around a group of buildings. In this research, a series of parametric wind tunnel studies was carried out to investigate the effects of building width, height and the gap width between buildings on the pedestrian-level wind environment. Mean wind speeds were used to determine the low wind speed areas where poor air ventilation may exist, and Gust Equivalent Mean (GEM) wind speeds were used to indicate the high wind speed areas for discomfort under strong wind conditions.

Rail transit systems are great assets to metropolitan areas, for they provide efficient, reliable, convenient, and environmentally friendly transit services. In many modem cities, rail transit is not financially sustainable; however, in Hong Kong, the situation is different. It is believed that the extremely high population density provides a suitable environment for the rail transit system to be financially sustainable. In this study, a preliminary analysis on the demand and supply of the rail transit service was undertaken to shed light on the threshold density below which the rail service cannot be sustainable without subsidy, considering its operations vis-Avis the competing modes' fares and services. We investigated to the Mass Transit Rail (MTR) line in the new town Tseung Kwan O (TKO) in Hong Kong. We collected data including the population density and distribution in TKO, and the travel characteristics for home-based trips in 2003. The result showed that the operation schedule of the MTR TKO line can be financially self-sustainable under the requirement of high population density (at least 90% of the present density in TKO). This result is preliminary as we did not have access to all the information required for this study, but the general trend seems to be comparable with the real situation. The result also showed that the profit was very sensitive to the competing modes' fares and services.

A schedule coordination problem involving two train services provided by different operators is modeled as an optimization of revenue intake. The coordination is achieved through the adjustment of commencement times of the train services by negotiation. The problem is subject to constraints regarding to passenger demands and idle costs of rolling-stocks from both operators. This paper models the operators as software agents having the flexibility to incorporate one of the two (and potentially more) proposed negotiation strategies. Empirical results show that agents employing different combination of strategies have significant impact on the quality of solution and negotiation time.

Many infrastructure and necessity systems such as electricity and telecommunication in Europe and the Northern America were used to be operated as monopolies, if not state-owned. However, they have now been disintegrated into a group of smaller companies managed by different stakeholders. Railways are no exceptions. Since the early 1980s, there have been reforms in the shape of restructuring of the national railways in different parts of the world. Continuous refinements are still conducted to allow better utilisation of railway resources and quality of service. There has been a growing interest for the industry to understand the impacts of these reforms on the operation efficiency and constraints. A number of post-evaluations have been conducted by analysing the performance of the stakeholders on their profits (Crompton and Jupe 2003), quality of train service (Shaw 2001) and engineering operations (Watson 2001). Results from these studies are valuable for future improvement in the system, followed by a new cycle of post-evaluations. However, direct implementation of these changes is often costly and the consequences take a long period of time (e.g. years) to surface. With the advance of fast computing technologies, computer simulation is a cost-effective means to evaluate a hypothetical change in a system prior to actual implementation. For example, simulation suites have been developed to study a variety of traffic control strategies according to sophisticated models of train dynamics, traction and power systems (Goodman, Siu and Ho 1998, Ho and Yeung 2001). Unfortunately, under the restructured railway environment, it is by no means easy to model the complex behaviour of the stakeholders and the interactions between them. Multi-agent system (MAS) is a recently developed modelling technique which may be useful in assisting the railway industry to conduct simulations on the restructured railway system. In MAS, a real-world entity is modelled as a software agent th

Sol-gel derived lead zirconate titanate (PZT) films have been prepared on STOpassivated silicon substrates. The STO buffer layer of thickness about 55 nm is prepared by rf-magnetron sputtering. XRD results reveal that the PZT film has wellcrystallized perovskite phase, indicating that the thin STO layer can effectively prevent reaction and inter-diffusion between the PZT film and silicon substrate. Interdigitated electrodes (IDEs) have then been deposited on the PZT film by magnetron sputtering and patterned using the standard photolithography. With the IDEs, the dielectric and ferroelectric properties of the PZT film under transverse or in-plane electric fields have been investigated. By assuming a uniform distribution of electric field (in-plane electric field model), the estimated relative permittivity of the PZT film is about 2100, while the dielectric loss is less than 1 %. Good in-plane polarization hysteresis loop is observed, showing an observed remanent polarization value of 21 *mC/cm2, which is comparable to that of a PZT film with both top and bottom electrodes. The in-plane polarized PZT/STO/SiO2/Si film can be used to fabricate d33-mode unimorph bending transducers, which will have much better performance than the conventional bending transducers driven electromechanically through the piezoelectric d31, mode.