The North China Plain often su ers heavy haze pollution events in the cold season due to the rapid industrial development and urbanization in recent decades.In the winter of 2015,the megacity cluster of Beijing Tianji...The North China Plain often su ers heavy haze pollution events in the cold season due to the rapid industrial development and urbanization in recent decades.In the winter of 2015,the megacity cluster of Beijing Tianjin Hebei experienced a seven-day extreme haze pollution episode with peak PM2.5(particulate matter(PM)with an aerodynamic diameter≤2.5μm)concentration of 727μg m 3.Considering the in uence of meteorological conditions on pollu-tant evolution,the e ects of varying initial conditions and lateral boundary conditions(LBCs)of the WRF-Chem model on PM2.5 concentration variation were investigated through ensemble methods.A control run(CTRL)and three groups of ensemble experiments(INDE,BDDE,INBDDE)were carried out based on difierent initial conditions and LBCs derived from ERA5 reanalysis data and its 10 ensemble members.The CTRL run reproduced the meteorological conditions and the overall life cycle of the haze event reasonably well,but failed to capture the intense oscillation of the instantaneous PM2.5 concentration.However,the ensemble forecasting showed a considerable advantage to some extent.Compared with the CTRL run,the root-mean-square error(RMSE)of PM2.5 concentration decreased by 4.33%,6.91%,and 8.44%in INDE,BDDE and INBDDE,respectively,and the RMSE decreases of wind direction(5.19%,8.89%and 9.61%)were the dominant reason for the improvement of PM2.5 concentration in the three ensemble experiments.Based on this case,the ensemble scheme seems an e ective method to improve the prediction skill of wind direction and PM2.5 concentration by using the WRF-Chem model.展开更多
Most aspects of construction projects mainly fall under contractual regime. However, when things go wrong such as when the project is abandoned for various reasons, they may create two different scenarios： a contract...Most aspects of construction projects mainly fall under contractual regime. However, when things go wrong such as when the project is abandoned for various reasons, they may create two different scenarios： a contract that is breached and a fixed structure that is left on the land which may constitute an incomplete benefit that is acquired by one of the parties. The transfer of such benefit is initially made with a legal ground, but that ground has since ceased to exist. If some aspect of that benefit cannot be recovered under a contract, enrichment rules may be competent to solve the problem. How to measure the different aspects of that enrichment is however a problem that may have different interpretations according to different conceptions of the foundations of enrichment liability in a particular legal system. This article explores the measures of enrichment in such cases of failed bilateral contracts scenarios working from South African perspective. It argues that in cases of failed bilateral contracts generating an enrichment situation, sanctioning a dual measure of enrichment in a legal system may be an appropriate avenue.展开更多
Let X,Y be UMD-spaces that have property (α), 1< p< ∞ and let M be anR-bounded subset in L(X, Y). It is shown that {T(M_k)_(k∈z): M_k, k(M_(k+l)-M_k) ∈M for k∈Z} is an R-bounded subset of L(L^p (0,2π; X), ...Let X,Y be UMD-spaces that have property (α), 1< p< ∞ and let M be anR-bounded subset in L(X, Y). It is shown that {T(M_k)_(k∈z): M_k, k(M_(k+l)-M_k) ∈M for k∈Z} is an R-bounded subset of L(L^p (0,2π; X), L^p(0,2π; Y)), where T(M_m)_(k∈zdenotes the L^p-multiplier given by the sequence (M_k)_(k∈z), This generalizes a resultof Venni [10]. The author uses this result to study the strongly L^p-well-posedness ofevolution equations with periodic boundary condition. Analogous results for operator-valued L^p-multipliers on R are also given.展开更多
基金supported by the National Basic Research(973)Program of China [grant number2015CB954102]the National Natural Science Foundation of China [grant number 41475043]the National Key R&D Program of China [grant number 2018YFC1507403]
文摘The North China Plain often su ers heavy haze pollution events in the cold season due to the rapid industrial development and urbanization in recent decades.In the winter of 2015,the megacity cluster of Beijing Tianjin Hebei experienced a seven-day extreme haze pollution episode with peak PM2.5(particulate matter(PM)with an aerodynamic diameter≤2.5μm)concentration of 727μg m 3.Considering the in uence of meteorological conditions on pollu-tant evolution,the e ects of varying initial conditions and lateral boundary conditions(LBCs)of the WRF-Chem model on PM2.5 concentration variation were investigated through ensemble methods.A control run(CTRL)and three groups of ensemble experiments(INDE,BDDE,INBDDE)were carried out based on difierent initial conditions and LBCs derived from ERA5 reanalysis data and its 10 ensemble members.The CTRL run reproduced the meteorological conditions and the overall life cycle of the haze event reasonably well,but failed to capture the intense oscillation of the instantaneous PM2.5 concentration.However,the ensemble forecasting showed a considerable advantage to some extent.Compared with the CTRL run,the root-mean-square error(RMSE)of PM2.5 concentration decreased by 4.33%,6.91%,and 8.44%in INDE,BDDE and INBDDE,respectively,and the RMSE decreases of wind direction(5.19%,8.89%and 9.61%)were the dominant reason for the improvement of PM2.5 concentration in the three ensemble experiments.Based on this case,the ensemble scheme seems an e ective method to improve the prediction skill of wind direction and PM2.5 concentration by using the WRF-Chem model.
文摘Most aspects of construction projects mainly fall under contractual regime. However, when things go wrong such as when the project is abandoned for various reasons, they may create two different scenarios： a contract that is breached and a fixed structure that is left on the land which may constitute an incomplete benefit that is acquired by one of the parties. The transfer of such benefit is initially made with a legal ground, but that ground has since ceased to exist. If some aspect of that benefit cannot be recovered under a contract, enrichment rules may be competent to solve the problem. How to measure the different aspects of that enrichment is however a problem that may have different interpretations according to different conceptions of the foundations of enrichment liability in a particular legal system. This article explores the measures of enrichment in such cases of failed bilateral contracts scenarios working from South African perspective. It argues that in cases of failed bilateral contracts generating an enrichment situation, sanctioning a dual measure of enrichment in a legal system may be an appropriate avenue.
基金Project supported by the National Natural Science Foundation of China (No.10271064) and the Excel-lent Young Teachers Program of the Ministry of Education of China
文摘Let X,Y be UMD-spaces that have property (α), 1< p< ∞ and let M be anR-bounded subset in L(X, Y). It is shown that {T(M_k)_(k∈z): M_k, k(M_(k+l)-M_k) ∈M for k∈Z} is an R-bounded subset of L(L^p (0,2π; X), L^p(0,2π; Y)), where T(M_m)_(k∈zdenotes the L^p-multiplier given by the sequence (M_k)_(k∈z), This generalizes a resultof Venni [10]. The author uses this result to study the strongly L^p-well-posedness ofevolution equations with periodic boundary condition. Analogous results for operator-valued L^p-multipliers on R are also given.
