Analytical method for the distributions of axial-load and stress is based on elastic assumption, but the threaded connections are often in plastic deformation stage in practice. Meanwhile the strain in the threaded co...Analytical method for the distributions of axial-load and stress is based on elastic assumption, but the threaded connections are often in plastic deformation stage in practice. Meanwhile the strain in the threaded connection is difficult to measure. So it is necessary to study the reliable numerical method. At present neither the convergence analysis of the computational results nor the elastic-plastic analysis in the loading-unloading process are studied. In this paper, von Mises plasticity and kinematic hardening model is used to describe the material response. A new convergence criterion for nonlinear finite element analysis of the loading-unloading process is proposed. An axisymmetric finite element model according to the proposed convergence criterion is developed and used to analyze the distributions of axial-load and stress. It can be conclude that the stress distribution analysis is more dependent on the mesh density than the axial-load distribution analysis. The stress distribution result indicates that with increasing of applied load, the engaged threads close to the nut-bearing surface become plastic firstly. The axial-load distribution result reveals that the load percentage carried by single thread depends on the position of thread and load intensity. When the load is relatively small, the applied load is mainly carried by the engaged threads near the nut-bearing surface, when the load is larger, the differences of percentages for all threads become small. The proposed convergence analyzing procedure is applicable for other nonlinear analyses. The obtained distributions of axial-load and stress can be a reference of engineering application.展开更多
In order to improve the threading stability and the head thickness precision in tandem hot rolling process, an adaptive threading strategy was proposed. The proposed strategy was realized by the rolling characteristic...In order to improve the threading stability and the head thickness precision in tandem hot rolling process, an adaptive threading strategy was proposed. The proposed strategy was realized by the rolling characteristics analysis, and factors which affect the rolling force and the final thickness were determined and analyzed based on the influence coefficients calculation process. An objective function consisting of the influenced factors was founded, and the disturbance quantity was obtained by minimizing the function with the Nelder-Mead simplex method, and the proposed adaptive threading strategy was realized based on the calculation results. The adaptive threading strategy has been applied to one 7-stand hot tandem mill successfully, actual statistics data show that the predicted rolling force prediction in the range of +/- 5.0% is improved to 97.8%, the head thickness precision in the range of +/- 35 mu m is improved to 98.5%, and the threading stability and the head thickness precision are enhanced to a high level.展开更多
BACKGROUND： What are the successful factors of the establishment of the thread-blocking method for focal cerebral ischemia/reperfusion mouse models？ OBJECTIVE： To study the effects of strain, body mass, and thread ...BACKGROUND： What are the successful factors of the establishment of the thread-blocking method for focal cerebral ischemia/reperfusion mouse models？ OBJECTIVE： To study the effects of strain, body mass, and thread tip preparation for the establishment of focal cerebral ischemia mouse models by using middle cerebral artery occlusion （MCAO）. DESIGN： Observational contrast animal study. SETTING： Gulou Hospital, Medical College of Nanjing University. MATERIALS： （1） The following experiment was performed at the Animal Experimental Center, Gulou Hospital Affiliated to Medical College of Nanjing University from December 2006 to April 2007. Sixty male white Kunming mice, whose body masses were 18-22 g （n =40）, 25-29 g （n =10） and 30-33 g （n =10）, as well as 10 male C57BL/6J mice, whose body mass was 18-22 g, were provided by the Animal Experimental Center, Gulou Hospital Affiliated to Medical College of Nanjing University. All mice were 10-12 weeks old. The project received confirmed consent from the local ethics committee. （2）Experimental materials： tripheryltetrazolium hydrochloride （TTC） and 0.1% poly-L-lysine were provided by Sigma Company, USA; citromint was provided by Shanghai Lingfeng Chemical Company Limited. METHODS： （1） Strain comparison： Ten white Kunming mice （weighing 18-22 g） and ten C57BL/6J mice （weighing 18 - 22 g） were selected. （2） Comparison of body mass： Thirty white Kunming mice, whose body masses were 18-22 g （n =10）, 25-30 g （n =10）, and 30-35 g （n =10）, were divided into groups. （3） Comparison of thread tip preparation： White Kunming mice weighing 18-22 g were divided into a poly-L-lysine line group and general line group, with 10 mice in each group. Mice in these two groups, which were respectively treated with poly-L-lysine or nothing, underwent MCAO. （4） All experimental mice received MCAO. Three hours after ischemia, and 24 hours after reperfusion, neurological deficit scores were measured and a success rate of model establishment was calculated. In addition, after sacrifice, sample tissues were cut into coronal sections to calculate the cerebral infarction area. MAIN OUTCOME MEASURES： （1） Success rate of model establishment and cerebral infarction area. （2） Neurological deficit scores. RESULTS： Sixty white Kunming mice and 10 C57BL/6J mice were included in the final analysis. （1） Strain comparison： The cerebral infarction area of white Kunming mice was larger than the C57BL/6J mice, and the neurological deficit scores of white Kunming mice were greater than those of the C57BL/6J mice （P 〈 0.05）. （2） Comparison of body mass： A success rate of model establishment in white Kunming mice weighing 18-22 g was higher than in white Kunming mice weighing 25-30 g or 30-35 g （P 〈 0.05）. （3） Comparison of thread tip preparation： The cerebral infarction area of mice in the poly-L-lysine line group was larger than in mice in the general line group. The neurological deficit scores of mice in the poly-L-lysine line group were greater than in mice in the general line group （P 〈 0.05）. CONCLUSION： Strain, body mass, and thread tip preparation can affect the establishment success rate of a focal cerebral ischemia mouse model using MCAO.展开更多
The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filt...The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.展开更多
In order to realize the efficiency, reliability and safety tests on the complex cable network of an electronic system, an efficient cable network resistance tester is designed. Firstly, the design background and hardw...In order to realize the efficiency, reliability and safety tests on the complex cable network of an electronic system, an efficient cable network resistance tester is designed. Firstly, the design background and hardware structure are briefly described. Then aiming at the multi task parallelism considering real time measurement of parameters and real time control of the system in the tester testing, a real time muhi task control software is developed by using multi thread testing technology in parallel test to realize multi task complex control. Finally, the least squares method is used to improve the test accuracyof the tester. The test results show that the test error is basically within 0.3%, and the test speed can reach 345 point/min.展开更多
基金supported by Vehicular Diesel Engine Development Program of China (Grant No. DEDP0202)
文摘Analytical method for the distributions of axial-load and stress is based on elastic assumption, but the threaded connections are often in plastic deformation stage in practice. Meanwhile the strain in the threaded connection is difficult to measure. So it is necessary to study the reliable numerical method. At present neither the convergence analysis of the computational results nor the elastic-plastic analysis in the loading-unloading process are studied. In this paper, von Mises plasticity and kinematic hardening model is used to describe the material response. A new convergence criterion for nonlinear finite element analysis of the loading-unloading process is proposed. An axisymmetric finite element model according to the proposed convergence criterion is developed and used to analyze the distributions of axial-load and stress. It can be conclude that the stress distribution analysis is more dependent on the mesh density than the axial-load distribution analysis. The stress distribution result indicates that with increasing of applied load, the engaged threads close to the nut-bearing surface become plastic firstly. The axial-load distribution result reveals that the load percentage carried by single thread depends on the position of thread and load intensity. When the load is relatively small, the applied load is mainly carried by the engaged threads near the nut-bearing surface, when the load is larger, the differences of percentages for all threads become small. The proposed convergence analyzing procedure is applicable for other nonlinear analyses. The obtained distributions of axial-load and stress can be a reference of engineering application.
基金Project(51504061)supported by the National Natural Science Foundation of China
文摘In order to improve the threading stability and the head thickness precision in tandem hot rolling process, an adaptive threading strategy was proposed. The proposed strategy was realized by the rolling characteristics analysis, and factors which affect the rolling force and the final thickness were determined and analyzed based on the influence coefficients calculation process. An objective function consisting of the influenced factors was founded, and the disturbance quantity was obtained by minimizing the function with the Nelder-Mead simplex method, and the proposed adaptive threading strategy was realized based on the calculation results. The adaptive threading strategy has been applied to one 7-stand hot tandem mill successfully, actual statistics data show that the predicted rolling force prediction in the range of +/- 5.0% is improved to 97.8%, the head thickness precision in the range of +/- 35 mu m is improved to 98.5%, and the threading stability and the head thickness precision are enhanced to a high level.
基金the Six Talent Projects of Jiangsu Province, No. 06-B-002
文摘BACKGROUND： What are the successful factors of the establishment of the thread-blocking method for focal cerebral ischemia/reperfusion mouse models？ OBJECTIVE： To study the effects of strain, body mass, and thread tip preparation for the establishment of focal cerebral ischemia mouse models by using middle cerebral artery occlusion （MCAO）. DESIGN： Observational contrast animal study. SETTING： Gulou Hospital, Medical College of Nanjing University. MATERIALS： （1） The following experiment was performed at the Animal Experimental Center, Gulou Hospital Affiliated to Medical College of Nanjing University from December 2006 to April 2007. Sixty male white Kunming mice, whose body masses were 18-22 g （n =40）, 25-29 g （n =10） and 30-33 g （n =10）, as well as 10 male C57BL/6J mice, whose body mass was 18-22 g, were provided by the Animal Experimental Center, Gulou Hospital Affiliated to Medical College of Nanjing University. All mice were 10-12 weeks old. The project received confirmed consent from the local ethics committee. （2）Experimental materials： tripheryltetrazolium hydrochloride （TTC） and 0.1% poly-L-lysine were provided by Sigma Company, USA; citromint was provided by Shanghai Lingfeng Chemical Company Limited. METHODS： （1） Strain comparison： Ten white Kunming mice （weighing 18-22 g） and ten C57BL/6J mice （weighing 18 - 22 g） were selected. （2） Comparison of body mass： Thirty white Kunming mice, whose body masses were 18-22 g （n =10）, 25-30 g （n =10）, and 30-35 g （n =10）, were divided into groups. （3） Comparison of thread tip preparation： White Kunming mice weighing 18-22 g were divided into a poly-L-lysine line group and general line group, with 10 mice in each group. Mice in these two groups, which were respectively treated with poly-L-lysine or nothing, underwent MCAO. （4） All experimental mice received MCAO. Three hours after ischemia, and 24 hours after reperfusion, neurological deficit scores were measured and a success rate of model establishment was calculated. In addition, after sacrifice, sample tissues were cut into coronal sections to calculate the cerebral infarction area. MAIN OUTCOME MEASURES： （1） Success rate of model establishment and cerebral infarction area. （2） Neurological deficit scores. RESULTS： Sixty white Kunming mice and 10 C57BL/6J mice were included in the final analysis. （1） Strain comparison： The cerebral infarction area of white Kunming mice was larger than the C57BL/6J mice, and the neurological deficit scores of white Kunming mice were greater than those of the C57BL/6J mice （P 〈 0.05）. （2） Comparison of body mass： A success rate of model establishment in white Kunming mice weighing 18-22 g was higher than in white Kunming mice weighing 25-30 g or 30-35 g （P 〈 0.05）. （3） Comparison of thread tip preparation： The cerebral infarction area of mice in the poly-L-lysine line group was larger than in mice in the general line group. The neurological deficit scores of mice in the poly-L-lysine line group were greater than in mice in the general line group （P 〈 0.05）. CONCLUSION： Strain, body mass, and thread tip preparation can affect the establishment success rate of a focal cerebral ischemia mouse model using MCAO.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61874148,61974141,and 61674020)the Beijing Natural Science Foundation,China(Grant No.4192043)+3 种基金the National Key Research and Development Program of China(Grant No.2018YFB2200104)the Fund from the Beijing Municipal Science&Technology Commission,China(Grant No.Z191100004819012)the Project of the State Key Laboratory of Information Photonics and Optical Communications,Beijing University of Posts and Telecommunications,China(Grant No.IPOC2018ZT01)the 111 Project of China(Grant No.B07005).
文摘The threading dislocations(TDs)in GaAs/Si epitaxial layers due to the lattice mismatch seriously degrade the performance of the lasers grown on silicon.The insertion of InAs quantum dots(QDs)acting as dislocation filters is a pretty good alternative to solving this problem.In this paper,a finite element method(FEM)is proposed to calculate the critical condition for InAs/GaAs QDs bending TDs into interfacial misfit dislocations(MDs).Making a comparison of elastic strain energy between the two isolated systems,a reasonable result is obtained.The effect of the cap layer thickness and the base width of QDs on TD bending are studied,and the results show that the bending area ratio of single QD(the bending area divided by the area of the QD base)is evidently affected by the two factors.Moreover,we present a method to evaluate the bending capability of single-layer QDs and multi-layer QDs.For the QD with 24-nm base width and 5-nm cap layer thickness,taking the QD density of 10^(11) cm^(-2) into account,the bending area ratio of single-layer QDs(the area of bending TD divided by the area of QD layer)is about 38.71%.With inserting five-layer InAs QDs,the TD density decreases by 91.35%.The results offer the guidelines for designing the QD dislocation filters and provide an important step towards realizing the photonic integration circuits on silicon.
文摘In order to realize the efficiency, reliability and safety tests on the complex cable network of an electronic system, an efficient cable network resistance tester is designed. Firstly, the design background and hardware structure are briefly described. Then aiming at the multi task parallelism considering real time measurement of parameters and real time control of the system in the tester testing, a real time muhi task control software is developed by using multi thread testing technology in parallel test to realize multi task complex control. Finally, the least squares method is used to improve the test accuracyof the tester. The test results show that the test error is basically within 0.3%, and the test speed can reach 345 point/min.
