Packet size is restricted due to the error-prone wireless channel which drops the network energy utilization. Furthermore, the frequent packet retransmissions also lead to energy waste. In order to improve the energy ...Packet size is restricted due to the error-prone wireless channel which drops the network energy utilization. Furthermore, the frequent packet retransmissions also lead to energy waste. In order to improve the energy efficiency of wireless networks and save the energy of wireless devices, EEFA （Energy Efficiency Frame Aggregation）, a frame aggregation based energy-efficient scheduling algorithm for IEEE 802.11n wireless network, is proposed. EEFA changes the size of aggregated frame dynamically according to the frame error rate, so as to ensure the data transmission and retransmissions completed during the TXOP and reduce energy consumption of channel contention. NS2 simulation results show that EEFA algorithm achieves better performance than the original frame-aggregation algorithm.展开更多
In Nigeria, like some other developing countries, income tax administration is characterized by noncompliance problem and this has been hindering tax revenue performance. Although a number of factors may be responsibl...In Nigeria, like some other developing countries, income tax administration is characterized by noncompliance problem and this has been hindering tax revenue performance. Although a number of factors may be responsible for such phenomenon, the literature has suggested that the relationship between tax compliance behavior and its determinants may be moderated by other factors. In order to account for situational and environmental peculiarity of Nigeria, this study extends tax compliance model to incorporate moderating effects of taxpayers＇ financial condition and risk preference. However, the study investigates the moderating effects of financial condition and risk preference on the relationship between noncompliance opportunity and tax compliance behavior. The study was conducted through a survey of individual taxpayers＇ opinions and the data collected were statistically treated using multiple regression technique. The study reveals among others that the effects of financial condition and risk preference significantly moderated the influences of taxpayers＇ source of income and occupation on tax compliance behavior. These findings pose some theoretical and policy implications.展开更多
Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quanti...Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quantitative relationship with thermal environment are still poorly understood, resulting in ineffective application in urban ecological planning and management.Through the integration of "spatial structure theory" in urban geography and "surface energy balance" in urban climatology, we proposed a new concept of urban surface structure and thermal environment regulation to reveal the mechanism between urban spatial structure and surface thermal environment. We developed the EcoCity model for regulating urban land cover structure and thermal environment, and established the eco-regulation thresholds of urban surface thermal environments. Based on the comprehensive analysis of experimental observation, remotely sensed and meteorological data, we examined the spatial patterns of urban habitation, industrial, infrastructure service, and ecological spaces. We examined the impacts of internal land-cover components(e.g., urban impervious surfaces, greenness, and water) on surface radiation and heat flux. This research indicated that difference of thermal environments among urban functional areas is closely related to the proportions of the land-cover components.The highly dense impervious surface areas in commercial and residential zones significantly increased land surface temperature through increasing sensible heat flux, while greenness and water decrease land surface temperature through increasing latent heat flux. We also found that different functional zones due to various proportions of green spaces have various heat dissipation roles and ecological thresholds. Urban greening projects in highly dense impervious surfaces areas such as commercial, transportation, and residential zones are especially effective in promoting latent heat dissipation efficiency of vegetation, leading to strongly cooling effect of unit vegetation coverage. This research indicates that the EcoCity model provides the fundamentals to understand the coupled mechanism between urban land use structure and surface flux and the analysis of their spatiotemporal characteristics. This model provides a general computational model system for defining urban heat island mitigation, the greening ratio indexes, and their regulating thresholds for different functional zones.展开更多
基金the National Natural Science Foundation of China under Grant No.61363067，Guangxi Nature Science Foundation，Guangxi Ministry of Education Foundation
文摘Packet size is restricted due to the error-prone wireless channel which drops the network energy utilization. Furthermore, the frequent packet retransmissions also lead to energy waste. In order to improve the energy efficiency of wireless networks and save the energy of wireless devices, EEFA （Energy Efficiency Frame Aggregation）, a frame aggregation based energy-efficient scheduling algorithm for IEEE 802.11n wireless network, is proposed. EEFA changes the size of aggregated frame dynamically according to the frame error rate, so as to ensure the data transmission and retransmissions completed during the TXOP and reduce energy consumption of channel contention. NS2 simulation results show that EEFA algorithm achieves better performance than the original frame-aggregation algorithm.
文摘In Nigeria, like some other developing countries, income tax administration is characterized by noncompliance problem and this has been hindering tax revenue performance. Although a number of factors may be responsible for such phenomenon, the literature has suggested that the relationship between tax compliance behavior and its determinants may be moderated by other factors. In order to account for situational and environmental peculiarity of Nigeria, this study extends tax compliance model to incorporate moderating effects of taxpayers＇ financial condition and risk preference. However, the study investigates the moderating effects of financial condition and risk preference on the relationship between noncompliance opportunity and tax compliance behavior. The study was conducted through a survey of individual taxpayers＇ opinions and the data collected were statistically treated using multiple regression technique. The study reveals among others that the effects of financial condition and risk preference significantly moderated the influences of taxpayers＇ source of income and occupation on tax compliance behavior. These findings pose some theoretical and policy implications.
基金financially supported by the Major Projects of the National Natural Science Foundation of China (Grant No. 41590842)General Program of the National Natural Science Foundation of China (Grant No. 41371408)
文摘Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quantitative relationship with thermal environment are still poorly understood, resulting in ineffective application in urban ecological planning and management.Through the integration of "spatial structure theory" in urban geography and "surface energy balance" in urban climatology, we proposed a new concept of urban surface structure and thermal environment regulation to reveal the mechanism between urban spatial structure and surface thermal environment. We developed the EcoCity model for regulating urban land cover structure and thermal environment, and established the eco-regulation thresholds of urban surface thermal environments. Based on the comprehensive analysis of experimental observation, remotely sensed and meteorological data, we examined the spatial patterns of urban habitation, industrial, infrastructure service, and ecological spaces. We examined the impacts of internal land-cover components(e.g., urban impervious surfaces, greenness, and water) on surface radiation and heat flux. This research indicated that difference of thermal environments among urban functional areas is closely related to the proportions of the land-cover components.The highly dense impervious surface areas in commercial and residential zones significantly increased land surface temperature through increasing sensible heat flux, while greenness and water decrease land surface temperature through increasing latent heat flux. We also found that different functional zones due to various proportions of green spaces have various heat dissipation roles and ecological thresholds. Urban greening projects in highly dense impervious surfaces areas such as commercial, transportation, and residential zones are especially effective in promoting latent heat dissipation efficiency of vegetation, leading to strongly cooling effect of unit vegetation coverage. This research indicates that the EcoCity model provides the fundamentals to understand the coupled mechanism between urban land use structure and surface flux and the analysis of their spatiotemporal characteristics. This model provides a general computational model system for defining urban heat island mitigation, the greening ratio indexes, and their regulating thresholds for different functional zones.
