This study aims to construct a virtual twin testing framework for the safety of the intended functionality of intelligent connected vehicles to address the safety requirements of intelligent driving and transportation...This study aims to construct a virtual twin testing framework for the safety of the intended functionality of intelligent connected vehicles to address the safety requirements of intelligent driving and transportation systems.The research methods include the construction of a theoretical model of safety for intelligent connected vehicles based on the concept of virtual twins,the correlation study between key concepts and functional safety,and the application research of virtual twin technology in the safety testing of intelligent connected vehicles.The results reveal that the virtual twin testing framework can effectively enhance the functional safety of intelligent connected vehicles,reduce development costs,and shorten the product launch cycle.The conclusion suggests that this framework provides strong support for the healthy development of the intelligent connected vehicle industry and has a positive impact on the safety and efficiency of intelligent transportation systems.展开更多
The methods for designing listening comprehension tests appeared in recent years will be also reviewed.For each kind of testing method,no matter what its scale and how its importance,can influence teaching and learnin...The methods for designing listening comprehension tests appeared in recent years will be also reviewed.For each kind of testing method,no matter what its scale and how its importance,can influence teaching and learning in varied range.Therefore,to discuss how to use the principle of authenticity to improve and ensure the reliability and validity of test can create a positive effect on teaching and learning.展开更多
Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solv...Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solve the loading problems of large-tonnage cranes during testing, an equivalency test is proposed based on the similarity theory and BP neural networks. The maximum stress and displacement of a large bridge crane is tested in small loads, combined with the training neural network of a similar structure crane through stress and displacement data which is collected by a physics simulation progressively loaded to a static load test load within the material scope of work. The maximum stress and displacement of a crane under a static load test load can be predicted through the relationship of stress, displacement, and load. By measuring the stress and displacement of small tonnage weights, the stress and displacement of large loads can be predicted, such as the maximum load capacity, which is 1.25 times the rated capacity. Experimental study shows that the load reduction test method can reflect the lift capacity of large bridge cranes. The load shedding predictive analysis for Sanxia 1200 t bridge crane test data indicates that when the load is 1.25 times the rated lifting capacity, the predicted displacement and actual displacement error is zero. The method solves the problem that lifting capacities are difficult to obtain and testing accidents are easily possible when 1.25 times related weight loads are tested for large tonnage cranes.展开更多
To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient...To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.展开更多
This study presents a Bayesian methodology for de- signing step stress accelerated degradation testing （SSADT） and its application to batteries. First, the simulation-based Bayesian de- sign framework for SSADT is p...This study presents a Bayesian methodology for de- signing step stress accelerated degradation testing （SSADT） and its application to batteries. First, the simulation-based Bayesian de- sign framework for SSADT is presented. Then, by considering his- torical data, specific optimal objectives oriented Kullback-Leibler （KL） divergence is established. A numerical example is discussed to illustrate the design approach. It is assumed that the degrada- tion model （or process） follows a drift Brownian motion; the accele- ration model follows Arrhenius equation; and the corresponding parameters follow normal and Gamma prior distributions. Using the Markov Chain Monte Carlo （MCMC） method and WinBUGS software, the comparison shows that KL divergence is better than quadratic loss for optimal criteria. Further, the effect of simulation outiiers on the optimization plan is analyzed and the preferred sur- face fitting algorithm is chosen. At the end of the paper, a NASA lithium-ion battery dataset is used as historical information and the KL divergence oriented Bayesian design is compared with maxi- mum likelihood theory oriented locally optimal design. The results show that the proposed method can provide a much better testing plan for this engineering application.展开更多
For a long time, it has been generally believed that spin-spin interactions can only exist in a theory where Lorentz symmetry is gauged, and a theory with spin-spin interactions is not perturbatively renormalizable. B...For a long time, it has been generally believed that spin-spin interactions can only exist in a theory where Lorentz symmetry is gauged, and a theory with spin-spin interactions is not perturbatively renormalizable. But this is not true. By studying the motion of a spinning particle in gravitational field, it is found that there exist spin-spin interactions in gauge theory of gravity. Its mechanism is that a spinning particle will generate gravitomagnetic field in space-time, and this gravitomagnetic field will interact with the spin of another particle, which will cause spin-spin interactions. So, spin-spin interactions are transmitted by gravitational field. The form of spin-spin interactions in post Newtonian approximations is deduced. This result can also be deduced from the Papapetrou equation. This kind of interaction will not affect the renormalizability of the theory. The spin-spin interactions will violate the weak equivalence principle, and the violation effects are detectable. An experiment is proposed to detect the effects of the violation of the weak equivalence principle.展开更多
This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during e...This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during examinees prior testing. Disadvantage of the mentioned item calibration method is the item exposure; when test items become familiar to the examinees. To reduce the item exposure, automatic item generation method is used, where item models are being constructed based on already calibrated test items without losing already estimated item parameters. A technic of item model extraction method from the already calibrated and therefore exposed test items described, which can be used by the test item development specialists to integrate automatic item generation principles with the existing testing applications.展开更多
Classical Solar System tests of photons coupled to Weyl tensor with two polarizations were studied in a recent work. A coupling strength parameter α in this model was firstly obtained as |α| 4 × 10^(11) m^2 by ...Classical Solar System tests of photons coupled to Weyl tensor with two polarizations were studied in a recent work. A coupling strength parameter α in this model was firstly obtained as |α| 4 × 10^(11) m^2 by using available datasets in the Solar System. In this paper, a new test called by gravitational time advancement is proposed and investigated to test such the coupling. This new test, which is quite different from Shapiro time delay, depends strongly on round-trip proper time span(not coordinate time one) of flight of radio pulses between an observer on the Earth and a distant spacecraft. For ranging a spacecraft getting far away from the Sun, two special cases(the superior/inferior conjunctions) are used to analyse the observability in the advancement contributed by the Weyl coupling. We found that the situation of the inferior conjunction is more suitable for detecting the advancement caused by such the Weyl coupling.In either case, two kinds of polarizations make the advancement in the model smaller or larger than the one of general relativity. Although the observability in the advancement could be out of the reach of already existing technology, the implement of planetary laser ranging and optical clocks might provide us more insights on such the Weyl coupling in the near future.展开更多
Background: Zimbabwe recorded a 55% increase in HIV testing from 2011 to 2018 but with decreasing HIV-testing yields from 20% to 6% respectively as we aim to identify the narrowing gap of undiagnosed people living wit...Background: Zimbabwe recorded a 55% increase in HIV testing from 2011 to 2018 but with decreasing HIV-testing yields from 20% to 6% respectively as we aim to identify the narrowing gap of undiagnosed people living with HIV. As such adoption of screening tools during targeted HIV testing services improves efficiency by identifying individuals who are likely to test positive. Effective utilization of screening tools requires an understanding of health care worker perception and willingness to use the tools. Methods: We conducted a qualitative study among healthcare workers at 8 selected primary healthcare facilities in Zimbabwe. Interviewer-guided, in-depth interviews were conducted with healthcare workers and their immediate supervisors. Thematic analysis was performed following a framework built around the grounded theory model to describe perspectives that influence the utilization of HIV screening tools and suggestions for improved eligibility screening. Results: Behavioural factors facilitating the utilisation of the screening tool included motivation to adhere to standard practice, awareness of screening in targeting testing, and its ability to manage workload through screening out ineligible clients. This was evident across service delivery levels. Barriers included limited healthcare capacity, confidentiality space, multiple screening tools and opaque screening in/out criteria and the potential of clients not responding to screening questions truthfully. Conclusions: Across geographical and service delivery levels, placing screening tools at HIV testing entry points, healthcare worker knowledge on screening in/out criteria emerged as enablers for correct and consistent utilization. Further, standardizing the tools and adopting a decision aid algorithm would improve the accurate utilisation of screening tools.展开更多
Security testing is a key technology for software security.The testing results can reflect the relationship between software testing and software security,and they can help program designers for evaluating and improvi...Security testing is a key technology for software security.The testing results can reflect the relationship between software testing and software security,and they can help program designers for evaluating and improving software security.However,it is difficult to describe by mathematics the relationship between the results of software functional testing and software nonfunctional security indexes.In this paper,we propose a mathematics model(MSMAM)based on principal component analysis and multiattribute utility theory.This model can get nonfunctional security indexes by analyzing quantized results of functional tests.It can also evaluate software security and guide the effective allocation of testing resources in the process of software testing.The feasibility and effectiveness of MSMAM is verified by experiments.展开更多
Coutsourides derived an ad hoc nuisance paratmeter removal test for testing equality of two multiple correlation matrices of two independent p variate normal populations under the assumption that a sample of size ...Coutsourides derived an ad hoc nuisance paratmeter removal test for testing equality of two multiple correlation matrices of two independent p variate normal populations under the assumption that a sample of size n is available from each population. This paper presents a likelihood ratio test criterion for testing equality of K multiple correlation matrices and extends the results to the testing of equality of K partial correlation matrices.展开更多
A systematic method is developed to studY the classical motion of a mass point in gravitational gauge field. First, by using Mathematica, a spherical symmetric solution of the field equation of gravitational gauge fie...A systematic method is developed to studY the classical motion of a mass point in gravitational gauge field. First, by using Mathematica, a spherical symmetric solution of the field equation of gravitational gauge field is obtained, which is just the traditional Schwarzschild solution. Combining the principle of gauge covariance and Newton＇s second law of motion, the equation of motion of a mass point in gravitational field is deduced. Based on the spherical symmetric solution of the field equation and the equation of motion of a mass point in gravitational field, we can discuss classical tests of gauge theory of gravity, including the deflection of light by the sun, the precession of the perihelia of the orbits of the inner planets and the time delay of radar echoes passing the sun. It is found that the theoretical predictions of these classical tests given by gauge theory of gravity are completely the same as those given by general relativity.展开更多
As only a little information can be obtained from torpedo's lake and sea tests,and the torpedo's life does not distribute typically. If conventional methods are used to convert the environment factor for torpe...As only a little information can be obtained from torpedo's lake and sea tests,and the torpedo's life does not distribute typically. If conventional methods are used to convert the environment factor for torpedo's lake and sea tests,their results can not reflect the actual conditions. A conversion model of the environment factor for torpedo's lake and sea tests is set up based on the GM(1,2) model of the grey system theory. For the merit of the grey system,the problem of uncertain life distributions and few samples can be solved. The calculation results show that the method is easy,realistic and high precise.展开更多
Communication of the various testing methods of COVID-19 is vital for English speakers within China and with the outside world.This research is set to find out the appropriate translation of the Chinese phrases referr...Communication of the various testing methods of COVID-19 is vital for English speakers within China and with the outside world.This research is set to find out the appropriate translation of the Chinese phrases referring to COVID-19 tests in English,in light of functional equivalence theory,which is expected to help correct mistakes and facilitate understanding between people speaking the two languages.展开更多
Reading is a complex process of communication between writer and reader.Relevance theory proposes that communication is an ostensive-inferential process from the cognitive perspective.The thesis studies the English re...Reading is a complex process of communication between writer and reader.Relevance theory proposes that communication is an ostensive-inferential process from the cognitive perspective.The thesis studies the English reading teaching approach for higher vocational students and applies it to the question type of reading comprehension test in PRETCO-A.It proposes three research questions in view of actual condition of teaching English reading.By the questionnaires and tests,the relevant data are collected,analyzed and discussed.Three research results are proved to be effective in reading teaching.展开更多
The 110-mining method,a rising and revolutionary non-pillar longwall mining method,can obviously expand coal extraction ratio and minimize roadway incidents.However,in case of composite hard roof,problems such as diff...The 110-mining method,a rising and revolutionary non-pillar longwall mining method,can obviously expand coal extraction ratio and minimize roadway incidents.However,in case of composite hard roof,problems such as difficulty in commanding the entry steadiness and insufficient fragmentation and bulking of the goaf gangue are prevalent.In this study,a 110-mining method for roadway surrounding rock stability control technology based on a compensation mechanism was proposed.First,the composite hard roof cutting short cantilever beam(SCB)model was built and the compensation mechanism including stress and space dual compensation was studied.Subsequently,the controllable elements influencing the roadway steadiness were confirmed to consequently put forward a control technology based on stress compensation for entry support and space compensation for the fragmentation and bulking of goaf gangue.The control technology was finally verified through onsite engineering experiments in terms of composite hard roof.The adoption of the 110-mining method with compensation control technology indicated good support effect on the roadway.The initial and residual expansion coefficients of the goaf gangue increased by 0.6 and 0.6,respectively,and the maximum and average working resistances of the working face support decreased by 10.9%and 13.8%,respectively.Consequently,the deformations of reserved entry decreased,and entry steadiness was enhanced.The presented technique and effects got probably have practical values for non-pillar mining functions in comparable field.展开更多
文摘This study aims to construct a virtual twin testing framework for the safety of the intended functionality of intelligent connected vehicles to address the safety requirements of intelligent driving and transportation systems.The research methods include the construction of a theoretical model of safety for intelligent connected vehicles based on the concept of virtual twins,the correlation study between key concepts and functional safety,and the application research of virtual twin technology in the safety testing of intelligent connected vehicles.The results reveal that the virtual twin testing framework can effectively enhance the functional safety of intelligent connected vehicles,reduce development costs,and shorten the product launch cycle.The conclusion suggests that this framework provides strong support for the healthy development of the intelligent connected vehicle industry and has a positive impact on the safety and efficiency of intelligent transportation systems.
文摘The methods for designing listening comprehension tests appeared in recent years will be also reviewed.For each kind of testing method,no matter what its scale and how its importance,can influence teaching and learning in varied range.Therefore,to discuss how to use the principle of authenticity to improve and ensure the reliability and validity of test can create a positive effect on teaching and learning.
基金Supported by National "Twelfth Five-Year" Plan for Science&Technology Support of China(Grant No.2011BAK06B05)National High-tech Research and Development Program of China(863 Program,Grant No.2013AA040203)Shanxi Scholarship Council of China(Grant No.2015-088)
文摘Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solve the loading problems of large-tonnage cranes during testing, an equivalency test is proposed based on the similarity theory and BP neural networks. The maximum stress and displacement of a large bridge crane is tested in small loads, combined with the training neural network of a similar structure crane through stress and displacement data which is collected by a physics simulation progressively loaded to a static load test load within the material scope of work. The maximum stress and displacement of a crane under a static load test load can be predicted through the relationship of stress, displacement, and load. By measuring the stress and displacement of small tonnage weights, the stress and displacement of large loads can be predicted, such as the maximum load capacity, which is 1.25 times the rated capacity. Experimental study shows that the load reduction test method can reflect the lift capacity of large bridge cranes. The load shedding predictive analysis for Sanxia 1200 t bridge crane test data indicates that when the load is 1.25 times the rated lifting capacity, the predicted displacement and actual displacement error is zero. The method solves the problem that lifting capacities are difficult to obtain and testing accidents are easily possible when 1.25 times related weight loads are tested for large tonnage cranes.
基金Supported by National Natural Science Foundation of China(Grant No.51275042)
文摘To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.
基金supported by the National Natural Science Foundation of China(61104182)
文摘This study presents a Bayesian methodology for de- signing step stress accelerated degradation testing （SSADT） and its application to batteries. First, the simulation-based Bayesian de- sign framework for SSADT is presented. Then, by considering his- torical data, specific optimal objectives oriented Kullback-Leibler （KL） divergence is established. A numerical example is discussed to illustrate the design approach. It is assumed that the degrada- tion model （or process） follows a drift Brownian motion; the accele- ration model follows Arrhenius equation; and the corresponding parameters follow normal and Gamma prior distributions. Using the Markov Chain Monte Carlo （MCMC） method and WinBUGS software, the comparison shows that KL divergence is better than quadratic loss for optimal criteria. Further, the effect of simulation outiiers on the optimization plan is analyzed and the preferred sur- face fitting algorithm is chosen. At the end of the paper, a NASA lithium-ion battery dataset is used as historical information and the KL divergence oriented Bayesian design is compared with maxi- mum likelihood theory oriented locally optimal design. The results show that the proposed method can provide a much better testing plan for this engineering application.
文摘For a long time, it has been generally believed that spin-spin interactions can only exist in a theory where Lorentz symmetry is gauged, and a theory with spin-spin interactions is not perturbatively renormalizable. But this is not true. By studying the motion of a spinning particle in gravitational field, it is found that there exist spin-spin interactions in gauge theory of gravity. Its mechanism is that a spinning particle will generate gravitomagnetic field in space-time, and this gravitomagnetic field will interact with the spin of another particle, which will cause spin-spin interactions. So, spin-spin interactions are transmitted by gravitational field. The form of spin-spin interactions in post Newtonian approximations is deduced. This result can also be deduced from the Papapetrou equation. This kind of interaction will not affect the renormalizability of the theory. The spin-spin interactions will violate the weak equivalence principle, and the violation effects are detectable. An experiment is proposed to detect the effects of the violation of the weak equivalence principle.
文摘This paper studies the technics of reducing item exposure by utilizing automatic item generation methods. Known test item calibration method uses item parameter estimation with the statistical data, collected during examinees prior testing. Disadvantage of the mentioned item calibration method is the item exposure; when test items become familiar to the examinees. To reduce the item exposure, automatic item generation method is used, where item models are being constructed based on already calibrated test items without losing already estimated item parameters. A technic of item model extraction method from the already calibrated and therefore exposed test items described, which can be used by the test item development specialists to integrate automatic item generation principles with the existing testing applications.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11773080,11473072,and 11533004
文摘Classical Solar System tests of photons coupled to Weyl tensor with two polarizations were studied in a recent work. A coupling strength parameter α in this model was firstly obtained as |α| 4 × 10^(11) m^2 by using available datasets in the Solar System. In this paper, a new test called by gravitational time advancement is proposed and investigated to test such the coupling. This new test, which is quite different from Shapiro time delay, depends strongly on round-trip proper time span(not coordinate time one) of flight of radio pulses between an observer on the Earth and a distant spacecraft. For ranging a spacecraft getting far away from the Sun, two special cases(the superior/inferior conjunctions) are used to analyse the observability in the advancement contributed by the Weyl coupling. We found that the situation of the inferior conjunction is more suitable for detecting the advancement caused by such the Weyl coupling.In either case, two kinds of polarizations make the advancement in the model smaller or larger than the one of general relativity. Although the observability in the advancement could be out of the reach of already existing technology, the implement of planetary laser ranging and optical clocks might provide us more insights on such the Weyl coupling in the near future.
文摘Background: Zimbabwe recorded a 55% increase in HIV testing from 2011 to 2018 but with decreasing HIV-testing yields from 20% to 6% respectively as we aim to identify the narrowing gap of undiagnosed people living with HIV. As such adoption of screening tools during targeted HIV testing services improves efficiency by identifying individuals who are likely to test positive. Effective utilization of screening tools requires an understanding of health care worker perception and willingness to use the tools. Methods: We conducted a qualitative study among healthcare workers at 8 selected primary healthcare facilities in Zimbabwe. Interviewer-guided, in-depth interviews were conducted with healthcare workers and their immediate supervisors. Thematic analysis was performed following a framework built around the grounded theory model to describe perspectives that influence the utilization of HIV screening tools and suggestions for improved eligibility screening. Results: Behavioural factors facilitating the utilisation of the screening tool included motivation to adhere to standard practice, awareness of screening in targeting testing, and its ability to manage workload through screening out ineligible clients. This was evident across service delivery levels. Barriers included limited healthcare capacity, confidentiality space, multiple screening tools and opaque screening in/out criteria and the potential of clients not responding to screening questions truthfully. Conclusions: Across geographical and service delivery levels, placing screening tools at HIV testing entry points, healthcare worker knowledge on screening in/out criteria emerged as enablers for correct and consistent utilization. Further, standardizing the tools and adopting a decision aid algorithm would improve the accurate utilisation of screening tools.
基金Supported by the National Natural Science Foundation of China (91018008,61003268,61103220,91118003)the National Natural Science Foundation of Hubei Province (2010cdb08601)the Fundamental Research Funds for the Central Universities (3101038)
文摘Security testing is a key technology for software security.The testing results can reflect the relationship between software testing and software security,and they can help program designers for evaluating and improving software security.However,it is difficult to describe by mathematics the relationship between the results of software functional testing and software nonfunctional security indexes.In this paper,we propose a mathematics model(MSMAM)based on principal component analysis and multiattribute utility theory.This model can get nonfunctional security indexes by analyzing quantized results of functional tests.It can also evaluate software security and guide the effective allocation of testing resources in the process of software testing.The feasibility and effectiveness of MSMAM is verified by experiments.
文摘Coutsourides derived an ad hoc nuisance paratmeter removal test for testing equality of two multiple correlation matrices of two independent p variate normal populations under the assumption that a sample of size n is available from each population. This paper presents a likelihood ratio test criterion for testing equality of K multiple correlation matrices and extends the results to the testing of equality of K partial correlation matrices.
文摘A systematic method is developed to studY the classical motion of a mass point in gravitational gauge field. First, by using Mathematica, a spherical symmetric solution of the field equation of gravitational gauge field is obtained, which is just the traditional Schwarzschild solution. Combining the principle of gauge covariance and Newton＇s second law of motion, the equation of motion of a mass point in gravitational field is deduced. Based on the spherical symmetric solution of the field equation and the equation of motion of a mass point in gravitational field, we can discuss classical tests of gauge theory of gravity, including the deflection of light by the sun, the precession of the perihelia of the orbits of the inner planets and the time delay of radar echoes passing the sun. It is found that the theoretical predictions of these classical tests given by gauge theory of gravity are completely the same as those given by general relativity.
文摘As only a little information can be obtained from torpedo's lake and sea tests,and the torpedo's life does not distribute typically. If conventional methods are used to convert the environment factor for torpedo's lake and sea tests,their results can not reflect the actual conditions. A conversion model of the environment factor for torpedo's lake and sea tests is set up based on the GM(1,2) model of the grey system theory. For the merit of the grey system,the problem of uncertain life distributions and few samples can be solved. The calculation results show that the method is easy,realistic and high precise.
基金2021 Undergraduate Innovation and Entrepreneurship Training Program(No.XJ2021284)。
文摘Communication of the various testing methods of COVID-19 is vital for English speakers within China and with the outside world.This research is set to find out the appropriate translation of the Chinese phrases referring to COVID-19 tests in English,in light of functional equivalence theory,which is expected to help correct mistakes and facilitate understanding between people speaking the two languages.
文摘Reading is a complex process of communication between writer and reader.Relevance theory proposes that communication is an ostensive-inferential process from the cognitive perspective.The thesis studies the English reading teaching approach for higher vocational students and applies it to the question type of reading comprehension test in PRETCO-A.It proposes three research questions in view of actual condition of teaching English reading.By the questionnaires and tests,the relevant data are collected,analyzed and discussed.Three research results are proved to be effective in reading teaching.
基金This work described herein was supported by the Program of China Scholarship Council(202206430008)the National Natural Science Foundation of China(NSFC)(52074300 and 52304111)+1 种基金the Yueqi Young Scholars Project of China University of Mining and Technology Beijing(2602021RC84)the Guizhou province science and technology planning project([2020]3007 and[2020]2Y019).
文摘The 110-mining method,a rising and revolutionary non-pillar longwall mining method,can obviously expand coal extraction ratio and minimize roadway incidents.However,in case of composite hard roof,problems such as difficulty in commanding the entry steadiness and insufficient fragmentation and bulking of the goaf gangue are prevalent.In this study,a 110-mining method for roadway surrounding rock stability control technology based on a compensation mechanism was proposed.First,the composite hard roof cutting short cantilever beam(SCB)model was built and the compensation mechanism including stress and space dual compensation was studied.Subsequently,the controllable elements influencing the roadway steadiness were confirmed to consequently put forward a control technology based on stress compensation for entry support and space compensation for the fragmentation and bulking of goaf gangue.The control technology was finally verified through onsite engineering experiments in terms of composite hard roof.The adoption of the 110-mining method with compensation control technology indicated good support effect on the roadway.The initial and residual expansion coefficients of the goaf gangue increased by 0.6 and 0.6,respectively,and the maximum and average working resistances of the working face support decreased by 10.9%and 13.8%,respectively.Consequently,the deformations of reserved entry decreased,and entry steadiness was enhanced.The presented technique and effects got probably have practical values for non-pillar mining functions in comparable field.
