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
The past few years have seen work on the maintenance and decaying mechanisms of tropical cyclones （TCs） over land. Statistic study has been on the landfall frequency and location of TCs and their maintenance, decayi...The past few years have seen work on the maintenance and decaying mechanisms of tropical cyclones （TCs） over land. Statistic study has been on the landfall frequency and location of TCs and their maintenance, decaying, transition, intensification and dissipation for the past 32 years and that （1） the deeper water accumulates on land, the more favorable it would be for the maintenance of low pressures and vast lakes, and the surface of large rivers and large- sized reservoirs can slow down the decaying of TC lows, （2） the descending and intrusion of cold air from mid- and upper- tropospheric and warm advection from lower troposphere are responsible for TCs transition; and （3） after landfall, TCs tend to accelerate towards areas of intense convection to the northwest, etc. Being mainly numerical simulation and diagnostic analyses for cases covering much detail and depth, most of the studies cannot tell anything in common about how TCs maintain and decay over land. There has been little work on the difference of land track of TCs, which travel with the underlying surface changing from sea to land. The energy supply from the tropical ocean is severely reduced or completely cut off on the one hand, rough land surface is both a blocking and frictional force for TCs to dissipate their energy on the other. In fact, landfall TCs can either maintain for only a few hours and cover a distance of less than 100 km or stay active tbr more than 100 hours and go as farther away as a few thousand km inland. Why do they differ so much？ Why do TCs follow routes that differ dramatically when they land at or near the same sites with identical or similar underlying surface？ It is obvious that the environmental field is one of the essential factors for TCs after landfall. The aim of this paper is to discuss the effect of the environmental field on TCs track over land and to know whicch, synoptic systems or factors play key roles in it so as to provide basis for the forecasting of land track of TCs after landfall.展开更多
Taking Beijing as an example and based on the census data,macro-level population statistical data and 2004~2013 marriage registration data,this paper makes a contrastive analysis on the characteristics and changing tr...Taking Beijing as an example and based on the census data,macro-level population statistical data and 2004~2013 marriage registration data,this paper makes a contrastive analysis on the characteristics and changing trends of local residents,migrants and temporary migrants. Relative to the local residents,the migrants generally have household registry of central districts and higher educational level and occupational layer. Temporary migrants have relatively complicated population structure but differentiate during the process of marriage matching. 'Two-place marriages'form a stable group of new permanent migrants and meanwhile imply a sizable group of latent dependent migrants. This will produce great infl uences on the general population structure and the aging process,which may also lead to some confl icts and problems. The government should be prepared with policy responses so as to promote the benign development of population diversifi cation in megalopolis.展开更多
Supposing that the overall situation is dug out from the distributed monitoring nodes, there should be two critical obstacles, heterogenous schema and instance, to integrating heterogeneous data from different monitor...Supposing that the overall situation is dug out from the distributed monitoring nodes, there should be two critical obstacles, heterogenous schema and instance, to integrating heterogeneous data from different monitoring sensors. To tackle the challenge of heterogenous schema, an instance-based approach for schema mapping, named instance-based machine-learning （IML） approach was described. And to solve the problem of heterogenous instance, a novel approach, called statistic-based clustering （SBC） approach, which utilized clustering and statistics technologies to match large scale sources holistically, was also proposed. These two algorithms utilized the machine-leaning and clustering technology to improve the accuracy. Experimental analysis shows that the IML approach is more precise than SBC approach, reaching at least precision of 81% and recall rate of 82%. Simulation studies further show that SBC can tackle large scale sources holisticalty with 85% recall rate when there are 38 data sources.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.
基金A project from the Ministry of Science and Technology of China (2005DIB3j104)
文摘The past few years have seen work on the maintenance and decaying mechanisms of tropical cyclones （TCs） over land. Statistic study has been on the landfall frequency and location of TCs and their maintenance, decaying, transition, intensification and dissipation for the past 32 years and that （1） the deeper water accumulates on land, the more favorable it would be for the maintenance of low pressures and vast lakes, and the surface of large rivers and large- sized reservoirs can slow down the decaying of TC lows, （2） the descending and intrusion of cold air from mid- and upper- tropospheric and warm advection from lower troposphere are responsible for TCs transition; and （3） after landfall, TCs tend to accelerate towards areas of intense convection to the northwest, etc. Being mainly numerical simulation and diagnostic analyses for cases covering much detail and depth, most of the studies cannot tell anything in common about how TCs maintain and decay over land. There has been little work on the difference of land track of TCs, which travel with the underlying surface changing from sea to land. The energy supply from the tropical ocean is severely reduced or completely cut off on the one hand, rough land surface is both a blocking and frictional force for TCs to dissipate their energy on the other. In fact, landfall TCs can either maintain for only a few hours and cover a distance of less than 100 km or stay active tbr more than 100 hours and go as farther away as a few thousand km inland. Why do they differ so much？ Why do TCs follow routes that differ dramatically when they land at or near the same sites with identical or similar underlying surface？ It is obvious that the environmental field is one of the essential factors for TCs after landfall. The aim of this paper is to discuss the effect of the environmental field on TCs track over land and to know whicch, synoptic systems or factors play key roles in it so as to provide basis for the forecasting of land track of TCs after landfall.
文摘Taking Beijing as an example and based on the census data,macro-level population statistical data and 2004~2013 marriage registration data,this paper makes a contrastive analysis on the characteristics and changing trends of local residents,migrants and temporary migrants. Relative to the local residents,the migrants generally have household registry of central districts and higher educational level and occupational layer. Temporary migrants have relatively complicated population structure but differentiate during the process of marriage matching. 'Two-place marriages'form a stable group of new permanent migrants and meanwhile imply a sizable group of latent dependent migrants. This will produce great infl uences on the general population structure and the aging process,which may also lead to some confl icts and problems. The government should be prepared with policy responses so as to promote the benign development of population diversifi cation in megalopolis.
基金Projects(2007AA01Z126, 2007AA01Z474) supported by the National High-Tech Research and Development Program of ChinaProject(NCET-06-0928) supported by the Program for New Century Excellent Talents in University
文摘Supposing that the overall situation is dug out from the distributed monitoring nodes, there should be two critical obstacles, heterogenous schema and instance, to integrating heterogeneous data from different monitoring sensors. To tackle the challenge of heterogenous schema, an instance-based approach for schema mapping, named instance-based machine-learning （IML） approach was described. And to solve the problem of heterogenous instance, a novel approach, called statistic-based clustering （SBC） approach, which utilized clustering and statistics technologies to match large scale sources holistically, was also proposed. These two algorithms utilized the machine-leaning and clustering technology to improve the accuracy. Experimental analysis shows that the IML approach is more precise than SBC approach, reaching at least precision of 81% and recall rate of 82%. Simulation studies further show that SBC can tackle large scale sources holisticalty with 85% recall rate when there are 38 data sources.
