The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.Th...The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM.The monsoon indexes for East Asian summer monsoon and land-sea thermal difference,which characterize the intensity of the EASM,show an obvious increase during the onset period of the EASM.Moreover,the land-sea thermal difference is more sensitive to warmer SST.Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China,South China Sea,and the Western Pacific Ocean to the east of the Philippines.While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China,precipitation increases notably in northern China,the South China Sea,the East China Sea,the Yellow Sea,and the Western Pacific to the east of the Philippines.North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent.The surface air temperature shows a warming trend.The warming in the entire troposphere between 30oN and 50oN increases the land-sea thermal contrast,which plays an important role in the enhancement of the EASM.Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension.展开更多
This paper provides an overview of the state of art of reverse logistics and current status of waste management problems with special emphasis on developing countries. Logistics activities have been practiced and play...This paper provides an overview of the state of art of reverse logistics and current status of waste management problems with special emphasis on developing countries. Logistics activities have been practiced and played a fundamental role in the global economic development for over 5,000 years. It has then been transformed into different logistics branches and elaborates the emergency of reverse logistics as one of the most important. The paper presents the evolution of logistics into reverse logistics and how it relates to waste management both in the developed and developing world. Reverse logistics is a relatively new phenomenon in the research area which is mainly referring to damaged goods, the take back of products that should be returned to the manufacturers or distributors. Reverse logistics is relatively more practiced in an organized way in the developed world than in the developing countries in that the latter provided less value additions on reversed products.展开更多
The early stage of a boundary layer bypass transition induced by the direct impingement of a circular cylinder wake is experimentally investigated in water tunnel,with the primary interest in both the evolution of coh...The early stage of a boundary layer bypass transition induced by the direct impingement of a circular cylinder wake is experimentally investigated in water tunnel,with the primary interest in both the evolution of coherent structures and their effects on the disturbance growth inside the boundary layer.It is found that spanwise vortices with small scale first form in the near-wall region around the leading-edge,which are either the residual of the wake rollers cut by the leading-edge or the high-order structures induced by the wake rollers.The formation of these spanwise vortices leads to the first rapid disturbance growth inside the boundary layer.On the other hand,streamwise vortices,which result from the impingement of longitudinal braids onto the leading-edge,are also observed inside the boundary layer.They lead to the three dimensional destabilization and the subsequent dispersion of spanwise vortices,and soon become the most dominant coherent structures inside the transitional boundary layer.It is suggested that the formation and evolution of these streamwise vortices contribute to the secondary disturbance growth stage and thus promote the completion of the transition process.The difference between the present transition scenario triggered by direct wake impingement and that by indirect wake-vortex inducement is further discussed.展开更多
A basic equation system for meridional throughflow fields in multistage axial flow compressors has been deduced, containing many unknown correlation terms,which describe different kinds of spanwise mixing mechanism in...A basic equation system for meridional throughflow fields in multistage axial flow compressors has been deduced, containing many unknown correlation terms,which describe different kinds of spanwise mixing mechanism in a unified form.The equation system shows that spanwise mixing of meridional flows in compressors is attributed to three kinds of mechanism:molecular motion,turbulent diffusion,and circumferential non-uniformities,the last of which includes secondary flow effects and others.Therefore the equation system unifies the two models for spanwise mixing analyses by Adkins & Smith (1981) and Gallimore & Cumpsty (1986).With three kinds of apparent mixing coefficients defined and introduced into the basic equation system,a novel,much simpler equation system,without additional unknown correlation terms included,has been obtained.This novel equa- tion system makes throughflow computations including mixing far easier for multistage compressors.It has been rigorously shown that these apparent mixing coefficients contain full information of all the three kinds of mixing mechanism,so that the simpler equation system can also be taken as a unified model for meridional flows with all the kinds of the mixing effects.Calculations of the flow through multistage machines have been made by incorporating the new model into a streamline curvature throughflow calculation method and the improved agreement with experimental data has been obtained.It is believed that the simpler equation system can be applied to the flows not only in subsonic but in transonic and supersonic compressors if an appropriate model is proposed for the apparent mixing coefficients.展开更多
Necessary and sufficient conditions are given for the finiteness of the generalized exponents expD(k), f(D, k) and F(D, k) for digraphs which are not necessarily primitive. Also the largest finite value of the general...Necessary and sufficient conditions are given for the finiteness of the generalized exponents expD(k), f(D, k) and F(D, k) for digraphs which are not necessarily primitive. Also the largest finite value of the generalized exponent expD(k) for digraphs of order n is determined and the complete characterizations of the extreme digraphs are given.展开更多
基金National Program on Key Basic Research Project of China (973 Program) (2007CB411805 2010CB428505)National Natural Science Foundation of China (40830958)
文摘The impact of anomalous sea surface temperature (SST) warming in the Kuroshio Extension in the previous winter on the East Asian summer monsoon (EASM) was investigated by performing simulation tests using NCAR CAM3.The results show that anomalous SST warming in the Kuroshio Extension in winter causes the enhancement and northward movement of the EASM.The monsoon indexes for East Asian summer monsoon and land-sea thermal difference,which characterize the intensity of the EASM,show an obvious increase during the onset period of the EASM.Moreover,the land-sea thermal difference is more sensitive to warmer SST.Low-level southwesterly monsoon is clearly strengthened meanwhile westerly flows north (south) of the subtropical westerly jet axis are strengthened (weakened) in northern China,South China Sea,and the Western Pacific Ocean to the east of the Philippines.While there is an obvious decrease in precipitation over the Japanese archipelago and adjacent oceans and over the area from the south of the Yangtze River in eastern China to the Qinling Mountains in southern China,precipitation increases notably in northern China,the South China Sea,the East China Sea,the Yellow Sea,and the Western Pacific to the east of the Philippines.North China is the key area where the response of the EASM to the SST anomalous warming in the Kuroshio Extension is prominent.The surface air temperature shows a warming trend.The warming in the entire troposphere between 30oN and 50oN increases the land-sea thermal contrast,which plays an important role in the enhancement of the EASM.Atmospheric circulation and precipitation anomalies in China and its adjacent regions have a close relationship with the enhancement of the Western Pacific subtropical high and its northward extension.
文摘This paper provides an overview of the state of art of reverse logistics and current status of waste management problems with special emphasis on developing countries. Logistics activities have been practiced and played a fundamental role in the global economic development for over 5,000 years. It has then been transformed into different logistics branches and elaborates the emergency of reverse logistics as one of the most important. The paper presents the evolution of logistics into reverse logistics and how it relates to waste management both in the developed and developing world. Reverse logistics is a relatively new phenomenon in the research area which is mainly referring to damaged goods, the take back of products that should be returned to the manufacturers or distributors. Reverse logistics is relatively more practiced in an organized way in the developed world than in the developing countries in that the latter provided less value additions on reversed products.
基金supported by the National Natural Science Foundation of China (Grant No. 10832001)
文摘The early stage of a boundary layer bypass transition induced by the direct impingement of a circular cylinder wake is experimentally investigated in water tunnel,with the primary interest in both the evolution of coherent structures and their effects on the disturbance growth inside the boundary layer.It is found that spanwise vortices with small scale first form in the near-wall region around the leading-edge,which are either the residual of the wake rollers cut by the leading-edge or the high-order structures induced by the wake rollers.The formation of these spanwise vortices leads to the first rapid disturbance growth inside the boundary layer.On the other hand,streamwise vortices,which result from the impingement of longitudinal braids onto the leading-edge,are also observed inside the boundary layer.They lead to the three dimensional destabilization and the subsequent dispersion of spanwise vortices,and soon become the most dominant coherent structures inside the transitional boundary layer.It is suggested that the formation and evolution of these streamwise vortices contribute to the secondary disturbance growth stage and thus promote the completion of the transition process.The difference between the present transition scenario triggered by direct wake impingement and that by indirect wake-vortex inducement is further discussed.
文摘A basic equation system for meridional throughflow fields in multistage axial flow compressors has been deduced, containing many unknown correlation terms,which describe different kinds of spanwise mixing mechanism in a unified form.The equation system shows that spanwise mixing of meridional flows in compressors is attributed to three kinds of mechanism:molecular motion,turbulent diffusion,and circumferential non-uniformities,the last of which includes secondary flow effects and others.Therefore the equation system unifies the two models for spanwise mixing analyses by Adkins & Smith (1981) and Gallimore & Cumpsty (1986).With three kinds of apparent mixing coefficients defined and introduced into the basic equation system,a novel,much simpler equation system,without additional unknown correlation terms included,has been obtained.This novel equa- tion system makes throughflow computations including mixing far easier for multistage compressors.It has been rigorously shown that these apparent mixing coefficients contain full information of all the three kinds of mixing mechanism,so that the simpler equation system can also be taken as a unified model for meridional flows with all the kinds of the mixing effects.Calculations of the flow through multistage machines have been made by incorporating the new model into a streamline curvature throughflow calculation method and the improved agreement with experimental data has been obtained.It is believed that the simpler equation system can be applied to the flows not only in subsonic but in transonic and supersonic compressors if an appropriate model is proposed for the apparent mixing coefficients.
文摘Necessary and sufficient conditions are given for the finiteness of the generalized exponents expD(k), f(D, k) and F(D, k) for digraphs which are not necessarily primitive. Also the largest finite value of the generalized exponent expD(k) for digraphs of order n is determined and the complete characterizations of the extreme digraphs are given.
