This paper uses the relation of the cosmic scale factor and scalar field to solve Wheeler-De Witt equation,gives the tunnel effect of the cosmic scale factor a and quantum potential well of scalar field, and makes it ...This paper uses the relation of the cosmic scale factor and scalar field to solve Wheeler-De Witt equation,gives the tunnel effect of the cosmic scale factor a and quantum potential well of scalar field, and makes it fit with the physics of cosmic quantum birth. By solving Wheeler-De Witt equation we achieve a general probability distribution of the cosmic birth, and give the analysis of cosmic quantum birth.展开更多
We discuss, giving all necessary details, the boundary-bulk propagators. We do it for a scalar field, with and without mass, for both the Feynman and the Wheeler cases. Contrary to standard procedure, we do not need h...We discuss, giving all necessary details, the boundary-bulk propagators. We do it for a scalar field, with and without mass, for both the Feynman and the Wheeler cases. Contrary to standard procedure, we do not need here to appeal to any unfounded conjecture (as done by other authors). Emphasize that we do not try to modify standard ADS/CFT procedures, but use them to evaluate the corresponding Feynman and Wheeler propagators. Our present calculations are original in the sense of being the first ones undertaken explicitly using distributions theory (DT). They are carried out in two instances: 1) when the boundary is a Euclidean space and 2) when it is of Minkowskian nature. In this last case we compute also three propagators: Feynman’s, Anti-Feynman’s, and Wheeler’s (half advanced plus half retarded). For an operator corresponding to a scalar field we explicitly obtain, for the first time ever, the two points’ correlations functions in the three instances above mentioned. To repeat, it is not our intention here to improve on ADS/CFT theory but only to employ it for evaluating the corresponding Wheeler’s propagators.展开更多
Due to the less stringent emission technology requirement,motorized two and three-wheelers(2&3W)generate more pollutants than cars.About 20%of the world's registered motorcycles are known to be in Africa.Vehic...Due to the less stringent emission technology requirement,motorized two and three-wheelers(2&3W)generate more pollutants than cars.About 20%of the world's registered motorcycles are known to be in Africa.Vehicle pollution is one of the major causes of death and health problems in Africa.The electrification of transportation provides an opportunity for E2&3W in Africa.To assess this transition,this study quantifies the number of E2&3W present in some African countries.Surveys of electric vehicle start-ups,drivers,and owner experiences are used to determine the E2&3W's technical feasibility and ability to compete with petrol scooters(p-scooters).SimaPro 9.4 software together with Ecoinvent 3.8 database was used to conduct a cradle-to-the-grave analysis of the environmental impact of using electric scooters(e-scooters).The research found that Africa's E2&3W's have a 0.2%market share compared to gasoline versions.The main disadvantage of e-scooters is their limited range and battery life.The average range and speed are 50 km and 50 km/h,respectively.Overloading of E2&3W caused damage to traction motors and was of major concern to distributors.The main advantages of E2&3W are their low operating costs and low environmental impact.In South Africa,the total environmental impact of e-scooters outweighed that of p-scooters.Emissions that have a direct impact on human health,were significantly lower for e-scooters than for p-scooters.The lack of battery performance standards,battery swapping station standards,and charging station standards negatively affects the quality of imported e-scooters.African countries need to implement electric vehicle standards,and battery recycling policies,and establish electric vehicle training and research centers.展开更多
The ownership of motorised two wheelers(MTWs)has been on the rise across various countries across the globe.The growth has been especially higher in developing countries which have typical traffic characteristics and ...The ownership of motorised two wheelers(MTWs)has been on the rise across various countries across the globe.The growth has been especially higher in developing countries which have typical traffic characteristics and higher populations.This steady rise has resulted in increased accident and fatalities.This abrupt increase warranted attention from the researchers to carry out specific studies for MTWs,which have a very different behaviour as compared to cars in terms of physical and dynamic parameters.Moreover,the unique traffic patterns usually found in the developing countries pose an additional challenge to the researchers,since the conventional focus of transportation safety researchers was a homogeneous car-based traffic.Many such studies have been attempted,especially in the recent decades,which have considered various risk factors related to MTW safety.However,the studies have considered different sets of risk factors and have given surprising and even conflicting results.Therefore,a comprehensive review of the diverse studies needs to be carried out which incorporates all the risk factors considered in previous research.This study reviews such research papers which have analysed various risk factors related to safety of MTWs,especially in heterogeneous,non-lane based traffic.Specifically,this paper aims to incorporate results from those studies and highlight the conclusions from state of the art.The paper also discusses about the research gaps that are crucial for MTW safety in mixed traffic conditions.The review will be useful for researchers working in the field of MTW safety and for policy implementation and analysis.展开更多
基金Acknowledgments 0ne of the authors （Y.C. Huang） is grateful to Profs R.G. Cai and D.H. Zhang for useful discussions.
文摘This paper uses the relation of the cosmic scale factor and scalar field to solve Wheeler-De Witt equation,gives the tunnel effect of the cosmic scale factor a and quantum potential well of scalar field, and makes it fit with the physics of cosmic quantum birth. By solving Wheeler-De Witt equation we achieve a general probability distribution of the cosmic birth, and give the analysis of cosmic quantum birth.
文摘We discuss, giving all necessary details, the boundary-bulk propagators. We do it for a scalar field, with and without mass, for both the Feynman and the Wheeler cases. Contrary to standard procedure, we do not need here to appeal to any unfounded conjecture (as done by other authors). Emphasize that we do not try to modify standard ADS/CFT procedures, but use them to evaluate the corresponding Feynman and Wheeler propagators. Our present calculations are original in the sense of being the first ones undertaken explicitly using distributions theory (DT). They are carried out in two instances: 1) when the boundary is a Euclidean space and 2) when it is of Minkowskian nature. In this last case we compute also three propagators: Feynman’s, Anti-Feynman’s, and Wheeler’s (half advanced plus half retarded). For an operator corresponding to a scalar field we explicitly obtain, for the first time ever, the two points’ correlations functions in the three instances above mentioned. To repeat, it is not our intention here to improve on ADS/CFT theory but only to employ it for evaluating the corresponding Wheeler’s propagators.
文摘Due to the less stringent emission technology requirement,motorized two and three-wheelers(2&3W)generate more pollutants than cars.About 20%of the world's registered motorcycles are known to be in Africa.Vehicle pollution is one of the major causes of death and health problems in Africa.The electrification of transportation provides an opportunity for E2&3W in Africa.To assess this transition,this study quantifies the number of E2&3W present in some African countries.Surveys of electric vehicle start-ups,drivers,and owner experiences are used to determine the E2&3W's technical feasibility and ability to compete with petrol scooters(p-scooters).SimaPro 9.4 software together with Ecoinvent 3.8 database was used to conduct a cradle-to-the-grave analysis of the environmental impact of using electric scooters(e-scooters).The research found that Africa's E2&3W's have a 0.2%market share compared to gasoline versions.The main disadvantage of e-scooters is their limited range and battery life.The average range and speed are 50 km and 50 km/h,respectively.Overloading of E2&3W caused damage to traction motors and was of major concern to distributors.The main advantages of E2&3W are their low operating costs and low environmental impact.In South Africa,the total environmental impact of e-scooters outweighed that of p-scooters.Emissions that have a direct impact on human health,were significantly lower for e-scooters than for p-scooters.The lack of battery performance standards,battery swapping station standards,and charging station standards negatively affects the quality of imported e-scooters.African countries need to implement electric vehicle standards,and battery recycling policies,and establish electric vehicle training and research centers.
文摘The ownership of motorised two wheelers(MTWs)has been on the rise across various countries across the globe.The growth has been especially higher in developing countries which have typical traffic characteristics and higher populations.This steady rise has resulted in increased accident and fatalities.This abrupt increase warranted attention from the researchers to carry out specific studies for MTWs,which have a very different behaviour as compared to cars in terms of physical and dynamic parameters.Moreover,the unique traffic patterns usually found in the developing countries pose an additional challenge to the researchers,since the conventional focus of transportation safety researchers was a homogeneous car-based traffic.Many such studies have been attempted,especially in the recent decades,which have considered various risk factors related to MTW safety.However,the studies have considered different sets of risk factors and have given surprising and even conflicting results.Therefore,a comprehensive review of the diverse studies needs to be carried out which incorporates all the risk factors considered in previous research.This study reviews such research papers which have analysed various risk factors related to safety of MTWs,especially in heterogeneous,non-lane based traffic.Specifically,this paper aims to incorporate results from those studies and highlight the conclusions from state of the art.The paper also discusses about the research gaps that are crucial for MTW safety in mixed traffic conditions.The review will be useful for researchers working in the field of MTW safety and for policy implementation and analysis.
