Vehicular beaconing plays an important role to facilitate various applications in the paradigm of Internet of Vehicles(IoV). Due to high dynamic and resource limitation in IoV, how to schedule the vehicular beacon bro...Vehicular beaconing plays an important role to facilitate various applications in the paradigm of Internet of Vehicles(IoV). Due to high dynamic and resource limitation in IoV, how to schedule the vehicular beacon broadcast is challenging, especially in dense scenarios. In this paper, we investigate the beacon broadcast scheduling problem considering the Age of Information(AoI). We first propose an algorithm minimizing the expected sum of AoI considering the limited communication resource and vehicle mobility. Then the performance of the proposed algorithm is analyzed. With the proposed algorithm, the optimal solution can be obtained under certain conditions. Extensive simulations are conducted to verify the efficiency, effectiveness and fairness of the proposed solution.展开更多
In mapping out China’s future development,policymakers must bear in mind the challenges from a falling birthrate and aging society.Based on previous demographic censuses and original data of large sample surveys,this...In mapping out China’s future development,policymakers must bear in mind the challenges from a falling birthrate and aging society.Based on previous demographic censuses and original data of large sample surveys,this study employed an indirect method for estimating China’s total fertility rate(TFR)and a demographic forecast method based on the parity progression ratio(PPR).Our analysis details the socioeconomic implications behind demographic change,and we have proposed public policy countermeasures.The findings include:(i)China’s ultra-low fertility rate over the past three decades has led to an increasingly aging society,and China’s future fertility rate is likely to continue to decrease.(ii)Around 2024,China’s total population is expected to peak at 1.407 billion,followed by chronic negative population growth at an accelerating pace.By 2050,China’s newborn population will shrink to 8.73 million and the aging population will increase to roughly 30%of the total population resulting in the total dependency ratio above 50%.(iii)With a falling birthrate and aging society,China will face unprecedented challenges with respect to education,employment,and pension.(iv)As a public policy response,China should remove birth control altogether.If the fertility rate continues to stall,policymakers should consider issuing policies to encourage birth and create a birth-friendly society for all birth cycles.展开更多
Studies of competition in mangroves are mostly limited to seedlings and artificial settings like forestry projects.We conducted the first experimental study of intraspecific competition among adult mangroves in a natu...Studies of competition in mangroves are mostly limited to seedlings and artificial settings like forestry projects.We conducted the first experimental study of intraspecific competition among adult mangroves in a natural mangrove forest to examine how important competition is in determining tree size compared with abiotic conditions.We conducted a study near Port Aransas,TX,USA,which is near the geographical limit of mangroves and dominated by monospecific stands of‘scrub’form black mangroves,Avicennia germinans.We thinned 10 plots to create a gradient of mangrove cover,and quantified the effects of mangrove cover on the growth of tagged mangroves from 2013 to 2019,and the mangrove canopy height in 2019.The relative growth rate of tagged mangroves declined as mangrove cover increased,and plants in the plot with 100%mangrove cover did not grow,indicating that they had attained their maximum size.In plots with reduced mangrove cover,plant height increased sharply,with plants in the plot with 11%mangrove cover growing~52%taller over 6 years.Canopy height was~30%taller in the plot fringe than in the interior,and canopy height in both fringe and interior declined as mangrove cover increased.Measures of leaf chlorophyll concentration and light interception suggested that plants were primarily limited by nitrogen.Our results showed that scrub mangroves compete strongly despite being limited by abiotic conditions,and that the importance of competition was greater in magnitude than that of abiotic differences between the fringe and interior.展开更多
基金supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERC)China Scholarship Council (CSC)
文摘Vehicular beaconing plays an important role to facilitate various applications in the paradigm of Internet of Vehicles(IoV). Due to high dynamic and resource limitation in IoV, how to schedule the vehicular beacon broadcast is challenging, especially in dense scenarios. In this paper, we investigate the beacon broadcast scheduling problem considering the Age of Information(AoI). We first propose an algorithm minimizing the expected sum of AoI considering the limited communication resource and vehicle mobility. Then the performance of the proposed algorithm is analyzed. With the proposed algorithm, the optimal solution can be obtained under certain conditions. Extensive simulations are conducted to verify the efficiency, effectiveness and fairness of the proposed solution.
文摘In mapping out China’s future development,policymakers must bear in mind the challenges from a falling birthrate and aging society.Based on previous demographic censuses and original data of large sample surveys,this study employed an indirect method for estimating China’s total fertility rate(TFR)and a demographic forecast method based on the parity progression ratio(PPR).Our analysis details the socioeconomic implications behind demographic change,and we have proposed public policy countermeasures.The findings include:(i)China’s ultra-low fertility rate over the past three decades has led to an increasingly aging society,and China’s future fertility rate is likely to continue to decrease.(ii)Around 2024,China’s total population is expected to peak at 1.407 billion,followed by chronic negative population growth at an accelerating pace.By 2050,China’s newborn population will shrink to 8.73 million and the aging population will increase to roughly 30%of the total population resulting in the total dependency ratio above 50%.(iii)With a falling birthrate and aging society,China will face unprecedented challenges with respect to education,employment,and pension.(iv)As a public policy response,China should remove birth control altogether.If the fertility rate continues to stall,policymakers should consider issuing policies to encourage birth and create a birth-friendly society for all birth cycles.
基金supported by Institutional Grants(NA10OAR4170099,NA14OAR4170102,NA18OAR4170088)from the Texas Sea Grant College Program from the National Sea Grant Office,National Oceanic and Atmospheric Administration,U.S.Department of Commerce.
文摘Studies of competition in mangroves are mostly limited to seedlings and artificial settings like forestry projects.We conducted the first experimental study of intraspecific competition among adult mangroves in a natural mangrove forest to examine how important competition is in determining tree size compared with abiotic conditions.We conducted a study near Port Aransas,TX,USA,which is near the geographical limit of mangroves and dominated by monospecific stands of‘scrub’form black mangroves,Avicennia germinans.We thinned 10 plots to create a gradient of mangrove cover,and quantified the effects of mangrove cover on the growth of tagged mangroves from 2013 to 2019,and the mangrove canopy height in 2019.The relative growth rate of tagged mangroves declined as mangrove cover increased,and plants in the plot with 100%mangrove cover did not grow,indicating that they had attained their maximum size.In plots with reduced mangrove cover,plant height increased sharply,with plants in the plot with 11%mangrove cover growing~52%taller over 6 years.Canopy height was~30%taller in the plot fringe than in the interior,and canopy height in both fringe and interior declined as mangrove cover increased.Measures of leaf chlorophyll concentration and light interception suggested that plants were primarily limited by nitrogen.Our results showed that scrub mangroves compete strongly despite being limited by abiotic conditions,and that the importance of competition was greater in magnitude than that of abiotic differences between the fringe and interior.
