Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this...Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.展开更多
In this paper, we completely determine the structure of the unit group of the group algebra of some dihedral groups D2 n over the finite field Fpk, where p is a prime.
Representing the appeals of its industry,the high-tech interest group has recently become an emerging political force in the United States.With abundant financial resources and proficiency in political communication,t...Representing the appeals of its industry,the high-tech interest group has recently become an emerging political force in the United States.With abundant financial resources and proficiency in political communication,the group rapidly grows to be a significant force in the American political sphere.It has started to affect the internal and foreign affairs of the U.S.and played a proactive role in the latest presidential election.Since the high-tech interest group has already become and will continue to be a big player in Sino-U.S.relations,China should carefully deal with its appeals and conflict of interests,and try to develop this group into a stabilizer between the two countries.展开更多
OUR"COVER GIRL"for this issue is a young woman of the Lisu minority who lives in the Nu River valley of China's southwestern Yunnan Province.A number of color pictures,together with two articles in the i...OUR"COVER GIRL"for this issue is a young woman of the Lisu minority who lives in the Nu River valley of China's southwestern Yunnan Province.A number of color pictures,together with two articles in the issue,outline changes that have taken place in Yunnan,the province with the largest diversity of China's ethnic minorities.展开更多
This is a pedagogical introduction to the theory of buildings of Jacques Tits and to some applications of this theory.This paper has 4 parts.In the first part we discuss incidence geometry,Coxeter systems and give two...This is a pedagogical introduction to the theory of buildings of Jacques Tits and to some applications of this theory.This paper has 4 parts.In the first part we discuss incidence geometry,Coxeter systems and give two definitions of buildings.We study in the second part the spherical and affine buildings of Chevalley groups.In the third part we deal with Bruhat-Tits theory of reductive groups over local fields.Finally we discuss the construction of the p-adic flag manifolds.展开更多
The effects of different yaw angles on the aerodynamic performance of city electric multiple units(EMUs)were investigated in a wind tunnel using a 1:16.8 scaled model.Pressure scanning valve and six-component box-type...The effects of different yaw angles on the aerodynamic performance of city electric multiple units(EMUs)were investigated in a wind tunnel using a 1:16.8 scaled model.Pressure scanning valve and six-component box-type aerodynamic balance were used to test the pressure distribution and aerodynamic force of the head car respectively from the 1.5-and 3-coach grouping city EMU models.Meanwhile,the effects of the yaw angles on the pressure distribution of the streamlined head as well as the aerodynamic forces of the train were analyzed.The experimental results showed that the pressure coefficient was the smallest at the maximum slope of the main shape-line.The side force coefficient and pressure coefficient along the head car cross-section were most affected by crosswind when the yaw angle was 55°,and replacing a 3-coach grouping with a 1.5-coach grouping had obvious advantages for wind tunnel testing when the yaw angle was within 24.2°.In addition,the relative errors of lift coefficient C_(L),roll moment coefficient C_(Mx),side force coefficient C_(S),and drag coefficient C_(D) between the 1.5-and 3-coach cases were below 5.95%,which all met the requirements of the experimental accuracy.展开更多
When R satisfies (strong unit) 1-stable range and M is a R-R-bimodule, the authors calculate that K_1(R(?) M)≌U(R(?) M)/L(R(?) M). As applications, the authors also calculate some Whitehead groups for exchange rings ...When R satisfies (strong unit) 1-stable range and M is a R-R-bimodule, the authors calculate that K_1(R(?) M)≌U(R(?) M)/L(R(?) M). As applications, the authors also calculate some Whitehead groups for exchange rings with artinian primitive factors.展开更多
文摘Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.
文摘In this paper, we completely determine the structure of the unit group of the group algebra of some dihedral groups D2 n over the finite field Fpk, where p is a prime.
文摘Representing the appeals of its industry,the high-tech interest group has recently become an emerging political force in the United States.With abundant financial resources and proficiency in political communication,the group rapidly grows to be a significant force in the American political sphere.It has started to affect the internal and foreign affairs of the U.S.and played a proactive role in the latest presidential election.Since the high-tech interest group has already become and will continue to be a big player in Sino-U.S.relations,China should carefully deal with its appeals and conflict of interests,and try to develop this group into a stabilizer between the two countries.
文摘OUR"COVER GIRL"for this issue is a young woman of the Lisu minority who lives in the Nu River valley of China's southwestern Yunnan Province.A number of color pictures,together with two articles in the issue,outline changes that have taken place in Yunnan,the province with the largest diversity of China's ethnic minorities.
文摘This is a pedagogical introduction to the theory of buildings of Jacques Tits and to some applications of this theory.This paper has 4 parts.In the first part we discuss incidence geometry,Coxeter systems and give two definitions of buildings.We study in the second part the spherical and affine buildings of Chevalley groups.In the third part we deal with Bruhat-Tits theory of reductive groups over local fields.Finally we discuss the construction of the p-adic flag manifolds.
基金Project(2020YFA0710903) supported by the National Key R&D Program of ChinaProjects(2020zzts111, 2020zzts117)supported by the Graduate Student Independent Innovation Project of Central South University,ChinaProject(202037)supported by Transport Department of Hunan Province Technology Innovation Project,China。
文摘The effects of different yaw angles on the aerodynamic performance of city electric multiple units(EMUs)were investigated in a wind tunnel using a 1:16.8 scaled model.Pressure scanning valve and six-component box-type aerodynamic balance were used to test the pressure distribution and aerodynamic force of the head car respectively from the 1.5-and 3-coach grouping city EMU models.Meanwhile,the effects of the yaw angles on the pressure distribution of the streamlined head as well as the aerodynamic forces of the train were analyzed.The experimental results showed that the pressure coefficient was the smallest at the maximum slope of the main shape-line.The side force coefficient and pressure coefficient along the head car cross-section were most affected by crosswind when the yaw angle was 55°,and replacing a 3-coach grouping with a 1.5-coach grouping had obvious advantages for wind tunnel testing when the yaw angle was within 24.2°.In addition,the relative errors of lift coefficient C_(L),roll moment coefficient C_(Mx),side force coefficient C_(S),and drag coefficient C_(D) between the 1.5-and 3-coach cases were below 5.95%,which all met the requirements of the experimental accuracy.
基金This research is supported by the National Natural Science Foundation of China (19801012)the Ministry of Education of China([2000]65)
文摘When R satisfies (strong unit) 1-stable range and M is a R-R-bimodule, the authors calculate that K_1(R(?) M)≌U(R(?) M)/L(R(?) M). As applications, the authors also calculate some Whitehead groups for exchange rings with artinian primitive factors.
