The dynamic behavior of a two-degree-of-freedom oblique impact system consisted of two pendulums with non-fixed impact positions is investigated. The relations between the restitution coefficient, the friction coeffic...The dynamic behavior of a two-degree-of-freedom oblique impact system consisted of two pendulums with non-fixed impact positions is investigated. The relations between the restitution coefficient, the friction coefficient, as well as other parameters of the system and the states before or after impact, are clarified in this oblique impact process. The existence criterion of single impact periodic-n subharrnonic motions is deduced based on the Poincare map method and the oblique impact relations with non-fixed impact positions. The stability of these subharrnonic periodic motions is analyzed by the Floquet theory, and the formulas to calculate the Flocluet multipliers are given. The validity of this method is shown through numerical simulation. At the same time, the probability distribution of impact positions in this oblique system with nonfixed impact positions is analyzed.展开更多
Alkyl dinitrites have at-tracted attention as an im-portant type of nitrosating agent and a pollution source in atmosphere.The reac-tivity and chemistry of alkyl dinitrites induced by the two ONO functional groups are...Alkyl dinitrites have at-tracted attention as an im-portant type of nitrosating agent and a pollution source in atmosphere.The reac-tivity and chemistry of alkyl dinitrites induced by the two ONO functional groups are relatively unknown.In this work,decompositions of 1,3-cyclohexane dinitrite and 1,4-cyclohexane dinitrite are studied by electron impact ionization mass spectroscopy(EI-MS).Apart from NO^(+)(m=z=30),fragment ions m=z=43 and 71 are the most abundant for the 1,3-isomer.On the other hand,fragments m=z=29,57,85,and 97 stand out in the EI-MS spectrum of 1,4-isomer.Possible dissociation mechanisms of the two dinitrites are proposed by theoretical calculations.The results reveal that the ring-opening of 1,3-cyclohexane dinitrite mainly starts from the intermediate ion(M-NO)^(+)by cleavage of twoαC-βC bonds.For 1,4-cyclohexane dinitrite,in addition to the decomposition via intermediate(M-NO)^(+),cleavage ofβC-βC bonds can occur directly from the parent cation(M)^(+).The results will help to understand the structural related chemistry of alkyl dinitrites in atmosphere and in NO transfer process.展开更多
The regional ecological positioning of one area is based on the region’s ecological orientation by the country or a larger region.Combined with the region’s natural geographical features,ecological background,main e...The regional ecological positioning of one area is based on the region’s ecological orientation by the country or a larger region.Combined with the region’s natural geographical features,ecological background,main ecological problems,regional ecological structure,pattern,process,function and service,etc.,the position of a certain area in ecological space,structure,process,function and service,etc.is determined through the analysis and research.Regional ecological positioning is an important prerequisite and core basis for regional ecological impact assessment.However,in the current regional ecological impact assessment,most of them have not analyzed and studied the regional ecological positioning.Due to the lack of research on regional ecological positioning,it is rare to apply the research results of regional ecological positioning to the establishment of regional ecological objectives and the construction of index system.Regional ecological positioning does not guide the direction of regional ecological protection and construction well,and there is a general tendency of regional ecological positioning being one-sided and slogan-based.This paper analyzes the necessity and importance of research of regional ecological positioning,puts forward the technology framework of study on regional ecological positioning.With regional ecological positioning research in planning ecological impact assessment of the Chengdu-Chongqing Economic Zone as an example,how to carry out the study on the regional ecological positioning and how to apply the results of the study on the regional ecological positioning in regional ecological impact assessment are explained and illustrated.展开更多
Language testing is of great value in language teaching. This paper is intended to deal with its washback effects in the following aspects. On one hand, it explores the impacts of language testing on objects invovled....Language testing is of great value in language teaching. This paper is intended to deal with its washback effects in the following aspects. On one hand, it explores the impacts of language testing on objects invovled. On the other hand, it directs at the positive and negative washback effects of testing on language teaching.展开更多
文摘The dynamic behavior of a two-degree-of-freedom oblique impact system consisted of two pendulums with non-fixed impact positions is investigated. The relations between the restitution coefficient, the friction coefficient, as well as other parameters of the system and the states before or after impact, are clarified in this oblique impact process. The existence criterion of single impact periodic-n subharrnonic motions is deduced based on the Poincare map method and the oblique impact relations with non-fixed impact positions. The stability of these subharrnonic periodic motions is analyzed by the Floquet theory, and the formulas to calculate the Flocluet multipliers are given. The validity of this method is shown through numerical simulation. At the same time, the probability distribution of impact positions in this oblique system with nonfixed impact positions is analyzed.
基金This work was supported by the the National Nat-ural Science Foundation of China(No.21773011 and No.21373033).
文摘Alkyl dinitrites have at-tracted attention as an im-portant type of nitrosating agent and a pollution source in atmosphere.The reac-tivity and chemistry of alkyl dinitrites induced by the two ONO functional groups are relatively unknown.In this work,decompositions of 1,3-cyclohexane dinitrite and 1,4-cyclohexane dinitrite are studied by electron impact ionization mass spectroscopy(EI-MS).Apart from NO^(+)(m=z=30),fragment ions m=z=43 and 71 are the most abundant for the 1,3-isomer.On the other hand,fragments m=z=29,57,85,and 97 stand out in the EI-MS spectrum of 1,4-isomer.Possible dissociation mechanisms of the two dinitrites are proposed by theoretical calculations.The results reveal that the ring-opening of 1,3-cyclohexane dinitrite mainly starts from the intermediate ion(M-NO)^(+)by cleavage of twoαC-βC bonds.For 1,4-cyclohexane dinitrite,in addition to the decomposition via intermediate(M-NO)^(+),cleavage ofβC-βC bonds can occur directly from the parent cation(M)^(+).The results will help to understand the structural related chemistry of alkyl dinitrites in atmosphere and in NO transfer process.
基金Supported by Special Projects in Key Fields of Ordinary Colleges and Universities in Guangdong Province(Science and Technology Serving Rural Revitalization)(2021ZDZX4023)Construction Item of Teaching Quality and Teaching Reform Project in Guangdong Provincial Undergraduate Universities in 2021(YUEJIAOGAOHAN[2021]29)+3 种基金Quality Engineering and Teaching Reform Project of Zhaoqing University(zlgc 201931)Ideological and Political Construction Project of Environmental Engineering Courses,Curriculum Ideological and Political Construction Project of Zhaoqing University in 2020(ZHAOXUEYUAN[2020]95)Ideological and Political Construction Project of"Physical Pollution Control Engineering"Courses,Curriculum Ideological and Political Construction Project of Zhaoqing University in 2020(ZHAOXUEYUAN[2020]95)Innovation and Entrepreneurship Training Program for College Students of Zhaoqing University in 2022(X 202210580130)。
文摘The regional ecological positioning of one area is based on the region’s ecological orientation by the country or a larger region.Combined with the region’s natural geographical features,ecological background,main ecological problems,regional ecological structure,pattern,process,function and service,etc.,the position of a certain area in ecological space,structure,process,function and service,etc.is determined through the analysis and research.Regional ecological positioning is an important prerequisite and core basis for regional ecological impact assessment.However,in the current regional ecological impact assessment,most of them have not analyzed and studied the regional ecological positioning.Due to the lack of research on regional ecological positioning,it is rare to apply the research results of regional ecological positioning to the establishment of regional ecological objectives and the construction of index system.Regional ecological positioning does not guide the direction of regional ecological protection and construction well,and there is a general tendency of regional ecological positioning being one-sided and slogan-based.This paper analyzes the necessity and importance of research of regional ecological positioning,puts forward the technology framework of study on regional ecological positioning.With regional ecological positioning research in planning ecological impact assessment of the Chengdu-Chongqing Economic Zone as an example,how to carry out the study on the regional ecological positioning and how to apply the results of the study on the regional ecological positioning in regional ecological impact assessment are explained and illustrated.
文摘Language testing is of great value in language teaching. This paper is intended to deal with its washback effects in the following aspects. On one hand, it explores the impacts of language testing on objects invovled. On the other hand, it directs at the positive and negative washback effects of testing on language teaching.
