Search

A good substation grounding grid is essential to ensure safety of personnel working in the substation, and also to protect the equipment to ensure continuous operation of the substation. The design of the substation grounding grid is often carried out to meet the IEEE Std 80-2000 requirements of grounding resistance, touch voltage and step voltage at an economical cost. However, the conventional grounding grid design is normally over calculated to meets these IEEE requirements without considering the total cost. The grounding grid is often costly to implement due to high number of grounding conductors and rods, and large area size of the interconnected bare conductors. In this study, Gravitational Search Algorithm (GSA) and Particle Swarm Algorithm (PSO) are proposed to achieve an effective grounding grid calculation. The reliability of these algorithms has been validated using a typical medium voltage substation grounding grid parameters. It was found both that GSA and PSO were capable to achieve a lower cost with of grounding grid with 29% cost saving as compared to the conventional calculation technique, without compromising the safety requirements of grounding grid.

This work estimates the distribution of a time-varying toll over a 24-hour period that minimizes the combined queue length of the three tunnels that traverse Hong Kong's Victoria Harbour, taking into account institutional constraints. Our results reveal that switching from a flat toll to a time-varying toll scheme would eliminate all existing tunnel queues. We argue that optimal tunnel tolling, coupled with the nonstop electronic toll collection mechanism already in place, could be the first step toward the implementation of electronic road pricing in Hong Kong. Optimal tolling would obviate the need to build a fourth harbor crossing in the near future.

Cardiac rehabilitation (CR) in post myocardial infarction (MI) patients reduces mortality and is a Class I indication in clinical practice guidelines. However the value of CR in the modern era of primary percutaneous coronary intervention (PPCI) has come into question especially for those low risk patients received prompt revascularization. We aim to identify any clinical predictor of improvement of exercise capacity in post MI survivors received PPCI after CR.

Particulate matters, being one of the major indoor contaminates, can lead to serious effect to our health, especially for those having the aerosol diameter less than 10µm (PM10), since those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. Therefore, concern should be paid to the indoor pollution from PM10. In this study, the particulate matters of an industrial workshop are suspected to be at a high concentration, therefore, an investigation has been performed to check the level of the particulate matters and the air flow path of them. The investigation is conducted by two means: experimental measurement for the particulate matter and computational simulation for the air flow field of the room. Experimental data showed that the particulate matters are much higher than the Hong Kong indoor air quality objective value which is 0.180mg/m3 [1] and simulation results showed that the particulates generated are spreading everywhere within the room before extracted away by the HVAC system. In order to protect the occupants inside the room, the HVAC system is proposed to be modified into a three-level negative pressure system. Performance of the three-level negative pressure system is verified by CFD tool and result showed that the new HVAC system can immediately extracted the contaminants away without contaminating the occupants inside.

Honoring David Boyce for his legendary contributions to the fields of transportation modeling and regional science, the chapters in this festschrift highlight and analyze state-of-the-art and state-of-the-practice methodologies and theories in transportation modeling, regional and urban planning.