The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow.This work was analyzed and ...The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow.This work was analyzed and researched by combining theory,numerical and experimental methods.The direct simulation Monte Carlo(DSMC)method and the finite element analysis method were combined to reveal the random collision of particles during the precision machining of abrasive flow.Under different inlet velocity,volume fraction and abrasive particle size,the dynamic pressure and turbulence flow energy of abrasive flow in elbow were analyzed,and the machining mechanism of particles on the wall and the influence of different machining parameters on the precision machining quality of abrasive flow were obtained.The test results show the order of the influence of different parameters on the quality of abrasive flow precision machining and establish the optimal process parameters.The results of the surface morphology before and after the precision machining of the inner surface of the elbow are discussed,and the surface roughness Ra value is reduced from 1.125μm to 0.295μm after the precision machining of the abrasive flow.The application of DSMC method provides special insights for the development of abrasive flow technology.展开更多
CSE (China's Standards of English) is China's first English proficiency assessment standard covering all semester. Its abilitygrading reflects the correspondence between the English level of students in each s...CSE (China's Standards of English) is China's first English proficiency assessment standard covering all semester. Its abilitygrading reflects the correspondence between the English level of students in each scholastic school and the ability to describe thedescriptors, and it is targeted and instructive for college English teaching. As an English assessment reform that benefits allChinese English learners, the Chinese English Proficiency Rating Scale has an epoch-making significance. One of the core tasks ofthe construction of foreign language assessment system is to formulate a unified competency assessment standard, and to provide ascientific competency index system and accurate Competency Scale for various foreign language examinations. CSE provides acommon reference framework for English learning, teaching and assessment in China, and combines English learning, Englishteaching and English assessment system. Improving the quality of teaching is a concern of every English teacher. The introductionof CSE undoubtedly provides authoritative criteria and powerful impetus for the deepening and refinement of College Englishreform.展开更多
基金Projects(51206011,U1937201)supported by the National Natural Science Foundation of ChinaProject(20200301040RQ)supported by the Science and Technology Development Program of Jilin Province,China+1 种基金Project(JJKH20190541KJ)supported by the Education Department of Jilin Province,ChinaProject(18DY017)supported by Changchun Science and Technology Program of Changchun City,China。
文摘The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow.This work was analyzed and researched by combining theory,numerical and experimental methods.The direct simulation Monte Carlo(DSMC)method and the finite element analysis method were combined to reveal the random collision of particles during the precision machining of abrasive flow.Under different inlet velocity,volume fraction and abrasive particle size,the dynamic pressure and turbulence flow energy of abrasive flow in elbow were analyzed,and the machining mechanism of particles on the wall and the influence of different machining parameters on the precision machining quality of abrasive flow were obtained.The test results show the order of the influence of different parameters on the quality of abrasive flow precision machining and establish the optimal process parameters.The results of the surface morphology before and after the precision machining of the inner surface of the elbow are discussed,and the surface roughness Ra value is reduced from 1.125μm to 0.295μm after the precision machining of the abrasive flow.The application of DSMC method provides special insights for the development of abrasive flow technology.
文摘CSE (China's Standards of English) is China's first English proficiency assessment standard covering all semester. Its abilitygrading reflects the correspondence between the English level of students in each scholastic school and the ability to describe thedescriptors, and it is targeted and instructive for college English teaching. As an English assessment reform that benefits allChinese English learners, the Chinese English Proficiency Rating Scale has an epoch-making significance. One of the core tasks ofthe construction of foreign language assessment system is to formulate a unified competency assessment standard, and to provide ascientific competency index system and accurate Competency Scale for various foreign language examinations. CSE provides acommon reference framework for English learning, teaching and assessment in China, and combines English learning, Englishteaching and English assessment system. Improving the quality of teaching is a concern of every English teacher. The introductionof CSE undoubtedly provides authoritative criteria and powerful impetus for the deepening and refinement of College Englishreform.
