The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom...The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom and the micro vibration test bed. The result of stimulational experiment indicates that the isolation of vibration of this system is satisfactory. The design method of vibration can be used as the reference to ultra precision machine tool, super micro orientation machanism and so on.展开更多
The beyond-dripline oxygen isotopes^(27,28)O were recently observed at RIKEN,and were found to be unbound decaying into^(24)O by emitting neutrons.The unbound feature of the heaviest oxygen isotope,^(28)O,provides an ...The beyond-dripline oxygen isotopes^(27,28)O were recently observed at RIKEN,and were found to be unbound decaying into^(24)O by emitting neutrons.The unbound feature of the heaviest oxygen isotope,^(28)O,provides an excellent test for stateof-the-art nuclear models.The atomic nucleus is a self-organized quantum manybody system comprising specific numbers of protons Z and neutrons N.展开更多
Knowledge of the mechanical behavior of planetary rocks is indispensable for space explorations.The scarcity of pristine samples and the irregular shapes of planetary meteorites make it difficult to obtain representat...Knowledge of the mechanical behavior of planetary rocks is indispensable for space explorations.The scarcity of pristine samples and the irregular shapes of planetary meteorites make it difficult to obtain representative samples for conventional macroscale rock mechanics experiments(macro-RMEs).This critical review discusses recent advances in microscale RMEs(micro-RMEs)techniques and the upscaling methods for extracting mechanical parameters.Methods of mineralogical and microstructural analyses,along with non-destructive mechanical techniques,have provided new opportunities for studying planetary rocks with unprecedented precision and capabilities.First,we summarize several mainstream methods for obtaining the mineralogy and microstructure of planetary rocks.Then,nondestructive micromechanical testing methods,nanoindentation and atomic force microscopy(AFM),are detailed reviewed,illustrating the principles,advantages,influencing factors,and available testing results from literature.Subsequently,several feasible upscaling methods that bridge the micro-measurements of meteorite pieces to the strength of the intact body are introduced.Finally,the potential applications of planetary rock mechanics research to guiding the design and execution of space missions are environed,ranging from sample return missions and planetary defense to extraterrestrial construction.These discussions are expected to broaden the understanding of the microscale mechanical properties of planetary rocks and their significant role in deep space exploration.展开更多
Group testing is a method that can be used to estimate the prevalence of rare infectious diseases,which can effectively save time and reduce costs compared to the method of random sampling.However,previous literature ...Group testing is a method that can be used to estimate the prevalence of rare infectious diseases,which can effectively save time and reduce costs compared to the method of random sampling.However,previous literature only demonstrated the optimality of group testing strategy while estimating prevalence under some strong assumptions.This article weakens the assumption of misclassification rate in the previous literature,considers the misclassification rate of the infected samples as a differentiable function of the pool size,and explores some optimal properties of group testing for estimating prevalence in the presence of differential misclassification conforming to this assumption.This article theoretically demonstrates that the group testing strategy performs better than the sample by sample procedure in estimating disease prevalence when the total number of sample pools is given or the size of the test population is determined.Numerical simulation experiments were conducted to evaluate the performance of group tests in estimating prevalence in the presence of dilution effect.展开更多
Sophisticated systems for the testing of fibres and advanced materials were showcased by key members of the British Textile Machinery Association(BTMA)at the forthcoming Techtextil 2024 exhibition which takes place in...Sophisticated systems for the testing of fibres and advanced materials were showcased by key members of the British Textile Machinery Association(BTMA)at the forthcoming Techtextil 2024 exhibition which takes place in Frankfurt,Germany,from April 23-26.展开更多
Method of testing for dynamic output forces from jet elements is studied, the handwidth is large in testing with this method. By establishing a model of the test system and simulating it, principles of how inherent fe...Method of testing for dynamic output forces from jet elements is studied, the handwidth is large in testing with this method. By establishing a model of the test system and simulating it, principles of how inherent features of the test system affect the dynamic force test are found out. Thus a theoretical foundation is given for the design and error modification to the actual test system.展开更多
This paper presents a method based on riblet surfaces. Its advantage lies in that it is more with testing methods using instruments such as a the Spalding formula for testing drag-reduction on convenient and yields mo...This paper presents a method based on riblet surfaces. Its advantage lies in that it is more with testing methods using instruments such as a the Spalding formula for testing drag-reduction on convenient and yields more precise data compared scale. With this method, data is obtained from the velocity distribution within the inner layer, nearest the riblet surface. Precision of measurement of the velocity distribution is the key factor affecting the precision of the testing.展开更多
A set-up based on a special shadow method, pinhole method, was made and some experiments were done. The results show that this novel method is simple, easy to operate,and suitable for testing large aspherical surfaces...A set-up based on a special shadow method, pinhole method, was made and some experiments were done. The results show that this novel method is simple, easy to operate,and suitable for testing large aspherical surfaces quantitatively.展开更多
To analyze the errors of processing data, the testing principle for jet elements is introduced and the property of testing system is theoretically and experimentally studied. On the basis of the above, the method of p...To analyze the errors of processing data, the testing principle for jet elements is introduced and the property of testing system is theoretically and experimentally studied. On the basis of the above, the method of processing data is presented and the error formulae, which are the functions of the testing system property, are derived. Finally, the methods of reducing the errors are provided. The measured results are in correspondence with the theoretical conclusion.展开更多
Speaking,as a productive skill,is a priority for many foreign-language learners.They often evaluate their success in language learning on the basis of how much they feel they have improved in their spoken language pro...Speaking,as a productive skill,is a priority for many foreign-language learners.They often evaluate their success in language learning on the basis of how much they feel they have improved in their spoken language proficiency.Consequently,testing of oral skills has hardly been neglected in college English examination.The communicative testing theory in 1970s greatly influenced language testing,especially the oral tests.This essay briefly explores the theory of communicative language testing and discusses the methods of TOEFL oral test and college English oral test and proposes ways to the latter one for further improve ment.展开更多
This article is mainly talked about CET English writing tests from the perspective of language testing.Writing tests designed to test the language proficiency,have direct and integrative characteristics.Writing requir...This article is mainly talked about CET English writing tests from the perspective of language testing.Writing tests designed to test the language proficiency,have direct and integrative characteristics.Writing requires the candidates to use language accurately,fluently and appropriately.展开更多
Language testing is an important link in language teaching,in this paper,the two important criteria of language test the reliability and validity has carried on the detailed elaboration,in order to a language teacher ...Language testing is an important link in language teaching,in this paper,the two important criteria of language test the reliability and validity has carried on the detailed elaboration,in order to a language teacher proposition and evaluation test more scientific.展开更多
This paper is to investigate whether the CET-4 writing section has positive effect in terms of Communicative Language Testing.The questionnaire survey method is adopted to carry out the research to collect data.It is ...This paper is to investigate whether the CET-4 writing section has positive effect in terms of Communicative Language Testing.The questionnaire survey method is adopted to carry out the research to collect data.It is concluded that currently the CET-4 writing section has certain harmful effect upon English learning of college non-English major students.Further reforms and improvement from the perspective of communicative language testing concerning the scoring criteria and the design of the task should be the focus of the future.展开更多
In this paper,some basic theories and terms of language testing,like types of language tests and qualities of good tests were briefly discussed.Then CET3(College English Test Band3) in Beijing was analyzed from three ...In this paper,some basic theories and terms of language testing,like types of language tests and qualities of good tests were briefly discussed.Then CET3(College English Test Band3) in Beijing was analyzed from three perspectives:design principles,item formats and test content. In the end,some suggestions were given to improve this test.展开更多
This paper shows some points of view on communicative language ability and issues of processing an effective communicative language test. Different considerations are given in different stages both from aspects of val...This paper shows some points of view on communicative language ability and issues of processing an effective communicative language test. Different considerations are given in different stages both from aspects of validity and reliability. All the processes are involved in considering the characteristics of communicative language test and special needs from communicative language ability. Different from other kinds of tests, it pays much more attention to context, precision measurement and criterion.展开更多
With the development of wireless communication technology,the fifth generation mobile communications system(5 G) emerges at a historic moment and devotes itself to open the curtain of the information age.Recently,in o...With the development of wireless communication technology,the fifth generation mobile communications system(5 G) emerges at a historic moment and devotes itself to open the curtain of the information age.Recently,in order to satisfy the requirement of different applications,various advanced 5 G technologies have been developed in full swing.However,before applying these 5 G related technologies in practical systems,effective testing methods are needed to evaluate these technologies in a real,comprehensive,rapid and flexible manner.However,the testing methods are faced with new challenges along with the continuous development of the new 5 G technologies.In this paper,we present a survey of 5 G testing,including solutions and opportunities.In particular,two cases are considered,i.e.,channel modelling and overthe-air(OTA) testing of antenna systems.Specifically,a non-stationary channel model is proposed to characterize and test massive multiple-input multiple-output(MIMO) channel.In addition,we propose two probe subset selection algorithms for three-dimensional(3 D) OTA testing,which minimizes the number of probe antennas while ensuring the accuracy of the target channel emulation.Finally,future research directions and challenges on 5 G testing are given.展开更多
文摘The relation of mass, stiffness and rate of damping is obtained by using the mechanical analysis of the obstructive vibration system of two dimensions for the design of the obstructive vibration system of more freedom and the micro vibration test bed. The result of stimulational experiment indicates that the isolation of vibration of this system is satisfactory. The design method of vibration can be used as the reference to ultra precision machine tool, super micro orientation machanism and so on.
基金This work was supported by the National Natural Science Foundation of China(Nos.12335007,11835001,11921006,12035001 and 12205340)the State Key Laboratory of Nuclear Physics and Technology,Peking University(No.NPT2020KFY13)Gansu Natural Science Foundation(No.22JR5RA123).
文摘The beyond-dripline oxygen isotopes^(27,28)O were recently observed at RIKEN,and were found to be unbound decaying into^(24)O by emitting neutrons.The unbound feature of the heaviest oxygen isotope,^(28)O,provides an excellent test for stateof-the-art nuclear models.The atomic nucleus is a self-organized quantum manybody system comprising specific numbers of protons Z and neutrons N.
基金supported by China Postdoctoral Science Foundation(No.2023TQ0247)Shenzhen Science and Technology Program(No.JCYJ20220530140602005)+2 种基金the Fundamental Research Funds for the Central Universities(No.2042023kfyq03)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515111071)the Postdoctoral Fellowship Program(Grade B)of China Postdoctoral Science Foundation(No.GZB20230544).
文摘Knowledge of the mechanical behavior of planetary rocks is indispensable for space explorations.The scarcity of pristine samples and the irregular shapes of planetary meteorites make it difficult to obtain representative samples for conventional macroscale rock mechanics experiments(macro-RMEs).This critical review discusses recent advances in microscale RMEs(micro-RMEs)techniques and the upscaling methods for extracting mechanical parameters.Methods of mineralogical and microstructural analyses,along with non-destructive mechanical techniques,have provided new opportunities for studying planetary rocks with unprecedented precision and capabilities.First,we summarize several mainstream methods for obtaining the mineralogy and microstructure of planetary rocks.Then,nondestructive micromechanical testing methods,nanoindentation and atomic force microscopy(AFM),are detailed reviewed,illustrating the principles,advantages,influencing factors,and available testing results from literature.Subsequently,several feasible upscaling methods that bridge the micro-measurements of meteorite pieces to the strength of the intact body are introduced.Finally,the potential applications of planetary rock mechanics research to guiding the design and execution of space missions are environed,ranging from sample return missions and planetary defense to extraterrestrial construction.These discussions are expected to broaden the understanding of the microscale mechanical properties of planetary rocks and their significant role in deep space exploration.
基金supported by the National Natural Science Foundation of China(Grant No.72091212).
文摘Group testing is a method that can be used to estimate the prevalence of rare infectious diseases,which can effectively save time and reduce costs compared to the method of random sampling.However,previous literature only demonstrated the optimality of group testing strategy while estimating prevalence under some strong assumptions.This article weakens the assumption of misclassification rate in the previous literature,considers the misclassification rate of the infected samples as a differentiable function of the pool size,and explores some optimal properties of group testing for estimating prevalence in the presence of differential misclassification conforming to this assumption.This article theoretically demonstrates that the group testing strategy performs better than the sample by sample procedure in estimating disease prevalence when the total number of sample pools is given or the size of the test population is determined.Numerical simulation experiments were conducted to evaluate the performance of group tests in estimating prevalence in the presence of dilution effect.
文摘Sophisticated systems for the testing of fibres and advanced materials were showcased by key members of the British Textile Machinery Association(BTMA)at the forthcoming Techtextil 2024 exhibition which takes place in Frankfurt,Germany,from April 23-26.
文摘Method of testing for dynamic output forces from jet elements is studied, the handwidth is large in testing with this method. By establishing a model of the test system and simulating it, principles of how inherent features of the test system affect the dynamic force test are found out. Thus a theoretical foundation is given for the design and error modification to the actual test system.
基金Supported by National Natural Science Foundation (50835009 and 10672136)Science and Technology Innovation Foundation of NWPU(2008KJ02012)
文摘This paper presents a method based on riblet surfaces. Its advantage lies in that it is more with testing methods using instruments such as a the Spalding formula for testing drag-reduction on convenient and yields more precise data compared scale. With this method, data is obtained from the velocity distribution within the inner layer, nearest the riblet surface. Precision of measurement of the velocity distribution is the key factor affecting the precision of the testing.
文摘A set-up based on a special shadow method, pinhole method, was made and some experiments were done. The results show that this novel method is simple, easy to operate,and suitable for testing large aspherical surfaces quantitatively.
文摘To analyze the errors of processing data, the testing principle for jet elements is introduced and the property of testing system is theoretically and experimentally studied. On the basis of the above, the method of processing data is presented and the error formulae, which are the functions of the testing system property, are derived. Finally, the methods of reducing the errors are provided. The measured results are in correspondence with the theoretical conclusion.
文摘Speaking,as a productive skill,is a priority for many foreign-language learners.They often evaluate their success in language learning on the basis of how much they feel they have improved in their spoken language proficiency.Consequently,testing of oral skills has hardly been neglected in college English examination.The communicative testing theory in 1970s greatly influenced language testing,especially the oral tests.This essay briefly explores the theory of communicative language testing and discusses the methods of TOEFL oral test and college English oral test and proposes ways to the latter one for further improve ment.
文摘This article is mainly talked about CET English writing tests from the perspective of language testing.Writing tests designed to test the language proficiency,have direct and integrative characteristics.Writing requires the candidates to use language accurately,fluently and appropriately.
文摘Language testing is an important link in language teaching,in this paper,the two important criteria of language test the reliability and validity has carried on the detailed elaboration,in order to a language teacher proposition and evaluation test more scientific.
文摘This paper is to investigate whether the CET-4 writing section has positive effect in terms of Communicative Language Testing.The questionnaire survey method is adopted to carry out the research to collect data.It is concluded that currently the CET-4 writing section has certain harmful effect upon English learning of college non-English major students.Further reforms and improvement from the perspective of communicative language testing concerning the scoring criteria and the design of the task should be the focus of the future.
文摘In this paper,some basic theories and terms of language testing,like types of language tests and qualities of good tests were briefly discussed.Then CET3(College English Test Band3) in Beijing was analyzed from three perspectives:design principles,item formats and test content. In the end,some suggestions were given to improve this test.
文摘This paper shows some points of view on communicative language ability and issues of processing an effective communicative language test. Different considerations are given in different stages both from aspects of validity and reliability. All the processes are involved in considering the characteristics of communicative language test and special needs from communicative language ability. Different from other kinds of tests, it pays much more attention to context, precision measurement and criterion.
基金supported by the National Natural Science of Foundation for Creative Research Groups of China(No.61421061)
文摘With the development of wireless communication technology,the fifth generation mobile communications system(5 G) emerges at a historic moment and devotes itself to open the curtain of the information age.Recently,in order to satisfy the requirement of different applications,various advanced 5 G technologies have been developed in full swing.However,before applying these 5 G related technologies in practical systems,effective testing methods are needed to evaluate these technologies in a real,comprehensive,rapid and flexible manner.However,the testing methods are faced with new challenges along with the continuous development of the new 5 G technologies.In this paper,we present a survey of 5 G testing,including solutions and opportunities.In particular,two cases are considered,i.e.,channel modelling and overthe-air(OTA) testing of antenna systems.Specifically,a non-stationary channel model is proposed to characterize and test massive multiple-input multiple-output(MIMO) channel.In addition,we propose two probe subset selection algorithms for three-dimensional(3 D) OTA testing,which minimizes the number of probe antennas while ensuring the accuracy of the target channel emulation.Finally,future research directions and challenges on 5 G testing are given.
