With its rapid development in the wireless markets, IEEE 802.11 WLAN is experiencing a huge popularity. However, due to the limitation of frequency bandwidth of WLANs, it is essential that the available radio resource...With its rapid development in the wireless markets, IEEE 802.11 WLAN is experiencing a huge popularity. However, due to the limitation of frequency bandwidth of WLANs, it is essential that the available radio resource should be fully utilized to offer different services to multiple users. In order to maximize system throughput while still guaranteeing the fairness among users, a proportional fairness based algorithm is proposed in this work. Since most of the previous resource allocation algorithms were simply based on the channel conditions without taking into account user's demand, in this paper, we introduce the theory of fuzzy synthetic evaluation(FSE) which also allows us to consider user's demand as an important factor. As such, the fairness among users can be improved based on different users' requirements for services. In addition, a channel state information based rate adaptation scheme is also proposed. Through simulation studies, the results clearly validate that our proposed scheme shows advantages on providing user fairness while still improving the system throughput.展开更多
Lab scale biological treatment system was constructed from acrylic and operated using synthetic wastewater to evaluate the nitrification performance using different media. The media used for were Ceramic Ring A （CRA...Lab scale biological treatment system was constructed from acrylic and operated using synthetic wastewater to evaluate the nitrification performance using different media. The media used for were Ceramic Ring A （CRA）, Ceramic Ring B （CRB）, Japanese Filter Mat （JFM）, and Filter Wool （FW）. Laboratory studies were conducted, in order to evaluate the nitrification performance of different media types, at different synthetic wastewater flow rates, ranging from 0.03 to 0.045 m3/hr. The results from experiments suggest that at higher water flow rates, there was a decrease in nitrification for all media types. Based on the ammonia and nitrite removal rates, FW media gave the optimum nitrification, of up to 0.46 g/m2/day and 0.09 g/m2/day, respectively. Besides, in this study, the surface texture of the media is the main factor that affected the volumetric ammonia and nitrite conversion rates （VTR and VNR）. JFM gave the greatest VTR and VNR performance, compared with the other media展开更多
Background:At 10 a.m.on January 23,2020 Wuhan,China imposed a 76-day travel lockdown on its 11 million residents in order to stop the spread of COVID-19.This lockdown represented the largest quarantine in the history ...Background:At 10 a.m.on January 23,2020 Wuhan,China imposed a 76-day travel lockdown on its 11 million residents in order to stop the spread of COVID-19.This lockdown represented the largest quarantine in the history of public health and provides us with an opportunity to critically examine the relationship between a city lockdown on human mobility and controlling the spread of a viral epidemic,in this case COVID-19.This study aims to assess the causal impact of the Wuhan lockdown on population movement and the increase of newly confirmed COVID-19 cases.Methods:Based on the daily panel data from 279 Chinese cities,our research is the first to apply the synthetic control approach to empirically analyze the causal relationship between the Wuhan lockdown of its population mobility and the progression of newly confirmed COVID-19 cases.By using a weighted average of available control cities to reproduce the counterfactual outcome trajectory that the treated city would have experienced in the absence of the lockdown,the synthetic control approach overcomes the sample selection bias and policy endogeneity problems that can arise from previous empirical methods in selecting control units.Results:In our example,the lockdown of Wuhan reduced mobility inflow by approximately 60%and outflow by about 50%.A significant reduction of new cases was observed within four days of the lockdown.The increase in new cases declined by around 50%during this period.However,the suppression effect became less discernible after this initial period of time.A 2.25-fold surge was found for the increase in new cases on the fifth day following the lockdown,after which it died down rapidly.Conclusions:Our study provided urgently needed and reliable causal evidence that city lockdown can be an effective short-term tool in containing and delaying the spread of a viral epidemic.Further,the city lockdown strategy can buy time during which countries can mobilize an effective response in order to better prepare.Therefore,in spite of initial widespread skepticism,lockdowns are likely to be added to the response toolkit used for any future pandemic outbreak.展开更多
基金partially supported by the Academy of Finland (Decision No. 284748, 288473)
文摘With its rapid development in the wireless markets, IEEE 802.11 WLAN is experiencing a huge popularity. However, due to the limitation of frequency bandwidth of WLANs, it is essential that the available radio resource should be fully utilized to offer different services to multiple users. In order to maximize system throughput while still guaranteeing the fairness among users, a proportional fairness based algorithm is proposed in this work. Since most of the previous resource allocation algorithms were simply based on the channel conditions without taking into account user's demand, in this paper, we introduce the theory of fuzzy synthetic evaluation(FSE) which also allows us to consider user's demand as an important factor. As such, the fairness among users can be improved based on different users' requirements for services. In addition, a channel state information based rate adaptation scheme is also proposed. Through simulation studies, the results clearly validate that our proposed scheme shows advantages on providing user fairness while still improving the system throughput.
文摘Lab scale biological treatment system was constructed from acrylic and operated using synthetic wastewater to evaluate the nitrification performance using different media. The media used for were Ceramic Ring A （CRA）, Ceramic Ring B （CRB）, Japanese Filter Mat （JFM）, and Filter Wool （FW）. Laboratory studies were conducted, in order to evaluate the nitrification performance of different media types, at different synthetic wastewater flow rates, ranging from 0.03 to 0.045 m3/hr. The results from experiments suggest that at higher water flow rates, there was a decrease in nitrification for all media types. Based on the ammonia and nitrite removal rates, FW media gave the optimum nitrification, of up to 0.46 g/m2/day and 0.09 g/m2/day, respectively. Besides, in this study, the surface texture of the media is the main factor that affected the volumetric ammonia and nitrite conversion rates （VTR and VNR）. JFM gave the greatest VTR and VNR performance, compared with the other media
文摘Background:At 10 a.m.on January 23,2020 Wuhan,China imposed a 76-day travel lockdown on its 11 million residents in order to stop the spread of COVID-19.This lockdown represented the largest quarantine in the history of public health and provides us with an opportunity to critically examine the relationship between a city lockdown on human mobility and controlling the spread of a viral epidemic,in this case COVID-19.This study aims to assess the causal impact of the Wuhan lockdown on population movement and the increase of newly confirmed COVID-19 cases.Methods:Based on the daily panel data from 279 Chinese cities,our research is the first to apply the synthetic control approach to empirically analyze the causal relationship between the Wuhan lockdown of its population mobility and the progression of newly confirmed COVID-19 cases.By using a weighted average of available control cities to reproduce the counterfactual outcome trajectory that the treated city would have experienced in the absence of the lockdown,the synthetic control approach overcomes the sample selection bias and policy endogeneity problems that can arise from previous empirical methods in selecting control units.Results:In our example,the lockdown of Wuhan reduced mobility inflow by approximately 60%and outflow by about 50%.A significant reduction of new cases was observed within four days of the lockdown.The increase in new cases declined by around 50%during this period.However,the suppression effect became less discernible after this initial period of time.A 2.25-fold surge was found for the increase in new cases on the fifth day following the lockdown,after which it died down rapidly.Conclusions:Our study provided urgently needed and reliable causal evidence that city lockdown can be an effective short-term tool in containing and delaying the spread of a viral epidemic.Further,the city lockdown strategy can buy time during which countries can mobilize an effective response in order to better prepare.Therefore,in spite of initial widespread skepticism,lockdowns are likely to be added to the response toolkit used for any future pandemic outbreak.
