A new design of LHM(left-handed material)is suggested,in which the wave vectork and the energy flowS(the Poynting vector)are in the opposite direction.Metallic cores or lines are coated with ferromagnetic layers to ob...A new design of LHM(left-handed material)is suggested,in which the wave vectork and the energy flowS(the Poynting vector)are in the opposite direction.Metallic cores or lines are coated with ferromagnetic layers to obtain negative permittivity and permeability.This design may bring some improvements over the binary design,such as higher homogeneity,smaller volume size,lower power loss,higher convenience and economy.The analytical expressions for the permittivityεand permeabilityμare shown to be negative in certain direction and frequency regions.Two specific structures are theoretically discussed and proved to be left-handed.Key words left-handed materials-negative refraction-NIM-LHM-artificial crystal CLC number O 438 Foundation item:Supported by the National Natural Science Foundation of China(10344002)Biography:SU Hua(1978-),male,Master candidate,research direction:information optics.展开更多
We have used chemical bond parameters and pattern recognition method to investigatethe regularities of the crystal type of alloy phase,and achieved good results.Theparameters used,however,are semi-empirical paramters,...We have used chemical bond parameters and pattern recognition method to investigatethe regularities of the crystal type of alloy phase,and achieved good results.Theparameters used,however,are semi-empirical paramters,which are not very strict fromtheoretical viewpoint.In this letter,we use the numbers describing atomic structure(thenumbers of valence electrons Z<sub>1</sub>,Z<sub>2</sub>,the principal quantum numbers of valence electrons n<sub>1</sub>,展开更多
In this study,we employed a three-dimensional mesoscale cold-cloud seeding model to simulate the microphysical impacts of artificial ice crystals used as cloud seeding catalysts.Our objective was to elucidate the mech...In this study,we employed a three-dimensional mesoscale cold-cloud seeding model to simulate the microphysical impacts of artificial ice crystals used as cloud seeding catalysts.Our objective was to elucidate the mechanism of snowfall enhancement in stratiform clouds in the Bayanbulak test area of Xinjiang,China.The results indicated that the optimal seeding time was the early stages of weather system development.In this case,the optimal seeding zone was identified as the northwest of the test area,especially near the cloud top(altitudes between 3500 and 4000 m,temperatures range−11 to−15℃),and the ideal concentration of catalyst was with ice crystal density of 1.0×10^(7)kg^(−1)within the target area.Under such conditions,the total precipitation rate in the seeding-affected area increased to 50.1 mm h^(−1).The results also showed that the favorable seeding region was featured by high content of supercooled water and low population of natural ice crystals,where artificial ice crystals could substantially increase the snowfall.This augmentation typically appeared in a unimodal pattern,with the peak formed within 2–3 h after seeding.Seeding in the ice–water mixed zone of a supercooled cloud facilitated rapid ice crystal growth to snow-flake pieces via the Bergeron process,which in turn consumed more supercooled water via collision–coalescence with cloud water droplets.Simultaneously,the intensive consumption of supercooled water impeded the riming process and reduced the formation of graupel particles within the cloud.The dispersion of artificial ice crystals extended over tens of kilometers horizontally;however,in the vertical direction most particles remained approximately 1 km below the seeding layer,due to limited vertical ascent rate in the stratiform clouds restricting upward movement of artificial ice crystals.The above results help better understand the snowfall enhancement mechanism in stratiform clouds and facilitate related weather modification practice.展开更多
基金Supported by the National Natural Science Foundation of China(10344002)
文摘A new design of LHM(left-handed material)is suggested,in which the wave vectork and the energy flowS(the Poynting vector)are in the opposite direction.Metallic cores or lines are coated with ferromagnetic layers to obtain negative permittivity and permeability.This design may bring some improvements over the binary design,such as higher homogeneity,smaller volume size,lower power loss,higher convenience and economy.The analytical expressions for the permittivityεand permeabilityμare shown to be negative in certain direction and frequency regions.Two specific structures are theoretically discussed and proved to be left-handed.Key words left-handed materials-negative refraction-NIM-LHM-artificial crystal CLC number O 438 Foundation item:Supported by the National Natural Science Foundation of China(10344002)Biography:SU Hua(1978-),male,Master candidate,research direction:information optics.
文摘We have used chemical bond parameters and pattern recognition method to investigatethe regularities of the crystal type of alloy phase,and achieved good results.Theparameters used,however,are semi-empirical paramters,which are not very strict fromtheoretical viewpoint.In this letter,we use the numbers describing atomic structure(thenumbers of valence electrons Z<sub>1</sub>,Z<sub>2</sub>,the principal quantum numbers of valence electrons n<sub>1</sub>,
基金Supported by the Scientific Research Project of the Bayingol Mongolian Autonomous Prefecture in Xinjiang(202318)China Meteorological Administration(CMA)Weather Modification Centre Innovation Team Project(WMC2023IT01)CMA Key Innovation Team Project(CMA2022ZD10).
文摘In this study,we employed a three-dimensional mesoscale cold-cloud seeding model to simulate the microphysical impacts of artificial ice crystals used as cloud seeding catalysts.Our objective was to elucidate the mechanism of snowfall enhancement in stratiform clouds in the Bayanbulak test area of Xinjiang,China.The results indicated that the optimal seeding time was the early stages of weather system development.In this case,the optimal seeding zone was identified as the northwest of the test area,especially near the cloud top(altitudes between 3500 and 4000 m,temperatures range−11 to−15℃),and the ideal concentration of catalyst was with ice crystal density of 1.0×10^(7)kg^(−1)within the target area.Under such conditions,the total precipitation rate in the seeding-affected area increased to 50.1 mm h^(−1).The results also showed that the favorable seeding region was featured by high content of supercooled water and low population of natural ice crystals,where artificial ice crystals could substantially increase the snowfall.This augmentation typically appeared in a unimodal pattern,with the peak formed within 2–3 h after seeding.Seeding in the ice–water mixed zone of a supercooled cloud facilitated rapid ice crystal growth to snow-flake pieces via the Bergeron process,which in turn consumed more supercooled water via collision–coalescence with cloud water droplets.Simultaneously,the intensive consumption of supercooled water impeded the riming process and reduced the formation of graupel particles within the cloud.The dispersion of artificial ice crystals extended over tens of kilometers horizontally;however,in the vertical direction most particles remained approximately 1 km below the seeding layer,due to limited vertical ascent rate in the stratiform clouds restricting upward movement of artificial ice crystals.The above results help better understand the snowfall enhancement mechanism in stratiform clouds and facilitate related weather modification practice.
