This paper considers a novel polling system with two classes of message which can experience an up-per bounded time before being served. The station serves these two classes with mixed service discipline, one class wi...This paper considers a novel polling system with two classes of message which can experience an up-per bounded time before being served. The station serves these two classes with mixed service discipline, one class with exhaustive service discipline, and the other with gated service discipline. Using iterative method, we have developed an approximation method to obtain the mean waiting time for each message class. The performance of approximation has been compared with the simulation results. The expression for the upper bound of waiting time is given too.展开更多
This paper examines trends in the impacts of disasters at the world scale and proposes explanations for them. It is concluded that statistics on natural hazards are questionable, in that changes in recording methods h...This paper examines trends in the impacts of disasters at the world scale and proposes explanations for them. It is concluded that statistics on natural hazards are questionable, in that changes in recording methods have artificially inflated the number of disasters and the seriousness of their impacts. Next, the paper examines the symbolic interpretation of disasters at various scales of analysis in terms of human cultures. It further applies this approach to the analysis of natural hazards using information technology methods such as GIS （Geographic Information Systems）. Returning to the global scale, deficiencies and inequalities in the world disaster relief system are considered. Thereafter, the paper investigates how global economic imbalances are thrown into sharp relief by catastrophes, with examples from the record of past earthquakes, landslides and floods. Finally, it considers the prospects for a major change in the direction of world policy on disasters and concludes that this will only occur if the international financial system is forced to adjust to a ＂super-disaster＂ event, which could possibly be seismic, volcanic or nuclear in origin.展开更多
Characteristic period is an important parameter of the seismic design response spectrum. There is important theoretical significance and engineering application value to the study of the characteristic period of seism...Characteristic period is an important parameter of the seismic design response spectrum. There is important theoretical significance and engineering application value to the study of the characteristic period of seismic design response spectrum of ultra high voltage （UHV） electrical equipment. In this paper, 1448 horizontal earthquake records within the world scope including the United States and Japan for Site Class m were analyzed. Results show that both magnitude and epicentral distance have great influence on the characteristic period. About 80 % of characteristic periods of strong earthquake records are about 0. 9s. Statistical analysis was conducted on the seismic hazard assessment results of 312 projects of China in recent years, and it is found that about 70 % of characteristic periods are about 0. 9s. Combined with the related code comparison and analysis, it is suggested that the characteristic period of the seismic design response spectrmn of UHV electrical equipment should select 0. 9s in order to effectively guarantee the seismic safety of UHV electrical equipment.展开更多
基金Supported by the High Technology Research and Development Program of China（2002AA412010-08） and the National Natural Science Foundation of China（60474031）.
文摘This paper considers a novel polling system with two classes of message which can experience an up-per bounded time before being served. The station serves these two classes with mixed service discipline, one class with exhaustive service discipline, and the other with gated service discipline. Using iterative method, we have developed an approximation method to obtain the mean waiting time for each message class. The performance of approximation has been compared with the simulation results. The expression for the upper bound of waiting time is given too.
文摘This paper examines trends in the impacts of disasters at the world scale and proposes explanations for them. It is concluded that statistics on natural hazards are questionable, in that changes in recording methods have artificially inflated the number of disasters and the seriousness of their impacts. Next, the paper examines the symbolic interpretation of disasters at various scales of analysis in terms of human cultures. It further applies this approach to the analysis of natural hazards using information technology methods such as GIS （Geographic Information Systems）. Returning to the global scale, deficiencies and inequalities in the world disaster relief system are considered. Thereafter, the paper investigates how global economic imbalances are thrown into sharp relief by catastrophes, with examples from the record of past earthquakes, landslides and floods. Finally, it considers the prospects for a major change in the direction of world policy on disasters and concludes that this will only occur if the international financial system is forced to adjust to a ＂super-disaster＂ event, which could possibly be seismic, volcanic or nuclear in origin.
基金founded by the Earthquake Science and Technology Spark Plan of China(XH12063)
文摘Characteristic period is an important parameter of the seismic design response spectrum. There is important theoretical significance and engineering application value to the study of the characteristic period of seismic design response spectrum of ultra high voltage （UHV） electrical equipment. In this paper, 1448 horizontal earthquake records within the world scope including the United States and Japan for Site Class m were analyzed. Results show that both magnitude and epicentral distance have great influence on the characteristic period. About 80 % of characteristic periods of strong earthquake records are about 0. 9s. Statistical analysis was conducted on the seismic hazard assessment results of 312 projects of China in recent years, and it is found that about 70 % of characteristic periods are about 0. 9s. Combined with the related code comparison and analysis, it is suggested that the characteristic period of the seismic design response spectrmn of UHV electrical equipment should select 0. 9s in order to effectively guarantee the seismic safety of UHV electrical equipment.
