Odor pollution in landfill area has attracted more social attention in China. It is very important to control the generation of odor pollutants in situ. Analyzing odorous materials production form buried waste, simula...Odor pollution in landfill area has attracted more social attention in China. It is very important to control the generation of odor pollutants in situ. Analyzing odorous materials production form buried waste, simulated columns of different volatile solid (VS) content and different buried period waste were designed. Gas compounds produced from the columns were collected and analyzed by comprehensive two-dimensional gas chromatography (GC × GC) method. It has remarkable relationship between VS content and concentrations of odorous material. When VS content more than 40%, the total amount of odorous compounds increases remarkably. It can be inferred that reduced VS content of original waste may effective decreasing odorous materials production in landfill area. The old rubbish produced more odorous compounds than that of fresh one in simulated columns.展开更多
The incidence rate of diabetes in pregnancy is about 20%,and diabetes in pregnancy will have a long-term impact on the metabolic health of mothers and their offspring.Mothers may have elevated blood glucose,which may ...The incidence rate of diabetes in pregnancy is about 20%,and diabetes in pregnancy will have a long-term impact on the metabolic health of mothers and their offspring.Mothers may have elevated blood glucose,which may lead to blood pressure disease,kidney disease,decreased resistance and secondary infection during pregnancy.The offspring may suffer from abnormal embryonic development,intrauterine growth restriction,obesity,autism,and other adverse consequences.Resveratrol(RSV)is a natural polyphenol compound,which is found in more than 70 plant species and their products,such as Polygonum cuspidatum,seeds of grapes,peanuts,blueberries,bilberries,and cranberries.Previous studies have shown that RSV has a potential beneficial effect on complex pregnancy,including improving the indicators of diabetes and pregnancy diabetes syndrome.This article has reviewed the molecular targets and signaling pathways of RSV,including AMP-activated protein kinase,mitogen-activated protein kinases,silent information regulator sirtuin 1,miR-23a-3p,reactive oxygen species,potassium channels and CX3C chemokine ligand 1,and the effect of RSV on gestational diabetes mellitus(GDM)and its complications.RSV improves the indicators of GDM by improving glucose metabolism and insulin tolerance,regulating blood lipids and plasma adipokines,and modulating embryonic oxidative stress and apoptosis.Furthermore,RSV can ameliorate the GDM complications by reducing oxidative stress,reducing the effects on placentation,reducing the adverse effects on embryonic development,reducing offspring's healthy risk,and so on.Thus,this review is of great significance for providing more options and possibilities for further research on medication of gestational diabetes.展开更多
This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam...This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam as an example,and the deformation and stress distribution of the beam were analyzed using FET.The results showed that using color stress nephograms and color U nephograms can improve students’learning outcomes in mechanics classroom.The high levels of satisfaction and interest in incorporating new techniques into the classroom suggest that there is a need to explore and develop innovative teaching methods in mechanics and related fields.This approach may inspire educators to develop more effective ways of teaching material mechanics,and our research can contribute to the advancement of mechanics education.展开更多
Vocational education is an important part of the overall education system.The development of higher vocational education is one of the guiding principles of education in China.The development of teachers is an importa...Vocational education is an important part of the overall education system.The development of higher vocational education is one of the guiding principles of education in China.The development of teachers is an important support for the development of vocational education.Teachers who can teach theoretically and guide students in practical work are known as“double-qualified”teachers.Building a highly qualified and professional double-qualified teaching team is the fundamental task in modernizing vocational education.Firstly,this paper discusses the importance of“double-qualified”teachers by describing the relevant policies of the Ministry of Education in China.Secondly,it reviews the research works of early scholars.Thirdly,it analyzes the main problems of teacher training in higher education institutions.Fourthly,it proposes five suggestions for the development of a“double-qualified”teaching team in higher education institutions.A high level and professional teaching team is an important support for the high-quality development of vocational institutions.School leaders must attach great importance to the construction of a“double-qualified”teaching team and increase the support in terms of policies,institutional protection,and financial investment.展开更多
Skilled talents are the main support for the strategic development of science and technology in China.The quality of talents is an important guarantee for the transformation and upgrading of national industries.By ana...Skilled talents are the main support for the strategic development of science and technology in China.The quality of talents is an important guarantee for the transformation and upgrading of national industries.By analyzing and studying Huang Yanpei’s thought on vocational education,this paper focuses on the cultivation of students’craftsmanship in vocational schools.First,we analyze the results of previous research and then elaborate on the connotations of Huang Yanpei’s education thought and craftsmanship spirit.Lastly,we propose five suggestions for the cultivation of craftsmanship.Our research work carries certain reference value to the study of craftsmanship cultivation in Huang Yanpei’s education thought.展开更多
The spirit of craftsmanship is gaining increasing attention from both society and the education community.Along with professional knowledge,continuous research,and innovation have become decisive factors in determinin...The spirit of craftsmanship is gaining increasing attention from both society and the education community.Along with professional knowledge,continuous research,and innovation have become decisive factors in determining the quality of products.In this context,vocational colleges strive to cultivate high-quality skilled talents,making the cultivation of craftsmanship spirit a crucial component of vocational education.This study explores the cultivation path of craftsmanship spirit through the lens of skills competitions,with a special emphasis on developing students’perseverance.The research conclusions of this article hold significant reference value for the implementation of vocational education policies.展开更多
Engineering mechanics is as a basic course,and the learning effect of this course directly affects the learning of subsequent professional courses.However,the teaching quality of engineering mechanics in vocational co...Engineering mechanics is as a basic course,and the learning effect of this course directly affects the learning of subsequent professional courses.However,the teaching quality of engineering mechanics in vocational colleges has been subpar for a long time.In this study,we explored the teaching situation of engineering mechanics by using questionnaires,pointing out the challenges faced in the teaching of engineering mechanics and putting forward four targeted suggestions,which include stimulating students’interest and increasing the investment in laboratory equipment,to improve the teaching quality.The findings of this study may provide some reference for the teaching reform of engineering mechanics.展开更多
With the continuous progress of science and technology,the speed of technology iteration in enterprise production line and the demand for comprehensive quality among workers are increasing.Companies not only require t...With the continuous progress of science and technology,the speed of technology iteration in enterprise production line and the demand for comprehensive quality among workers are increasing.Companies not only require their employees to have excellent skills,but also require them to be rigorous and meticulous,possess excellence,and carry out continuous innovation of the craftsman spirit.The talent training goal in vocational colleges is to supply high-quality skilled talents to the society.Vocational colleges have an important duty to cultivate the spirit of craftsmanship in students through multiple paths.Through in-depth analysis of previous research results,we carried out a study on the cultivation path of craftsmanship spirit.The results of this study may provide reference for the development of moral education in vocational colleges.展开更多
The quality of the teaching staff is crucial to the development of vocational education.Skilled and knowledgeable teachers can provide students with specialized technical knowledge and practical skills.In addition to ...The quality of the teaching staff is crucial to the development of vocational education.Skilled and knowledgeable teachers can provide students with specialized technical knowledge and practical skills.In addition to teaching,teachers also act as mentors in providing guidance and support in all areas to students.However,the development of young teachers faces many problems,such as unclear career plans and a lack of attention to operational skills.This paper analyzes the research findings of past scholars and uses a questionnaire to analyze the problems faced by young teachers in their career development.Based on this,this paper puts forward some targeted suggestions,which can provide guidelines for the career development of young teachers.展开更多
This study investigates the challenges encountered by vocational colleges when preparing for innovative skills competitions and proposes effective countermeasures.It highlights issues concerning students’motivation,l...This study investigates the challenges encountered by vocational colleges when preparing for innovative skills competitions and proposes effective countermeasures.It highlights issues concerning students’motivation,limited financial resources and hardware,teacher capacity limitations,inadequate reward systems,and curriculum misalignment.Through meticulous research and analysis,this paper presents practical recommendations to mitigate these challenges.Suggestions encompass strategies to enhance students’motivation,increase financial support,provide professional development opportunities for teachers,revamp the reward system,and align the curriculum with competition requirements.By implementing these measures,vocational colleges can cultivate active student participation,elevate teaching quality,bridge the gap between education and industry demands,and equip students for success in innovative skills competitions.展开更多
Vocational education and general education are two different types of education that are equally important.The orientation of talent training in vocational education is to nurture skilled talents to serve the society....Vocational education and general education are two different types of education that are equally important.The orientation of talent training in vocational education is to nurture skilled talents to serve the society.The practical ability of students is both the focus of teaching in vocational colleges and the requirement of enterprise posts.The various types of skills competitions provide a“stage”for students to showcase their abilities.First,this paper explores students’problem-solving ability while preparing for these competitions,expounding the importance of vocational education and skills competitions.Second,this paper summarizes the views of different scholars.Third,based on a specific case,this paper describes the improvement in students’ability while preparing for these competitions.Fourth,this paper analyzes the results of the questionnaire survey conducted to investigate the improvement in students’ability.Lastly,this paper puts forward several suggestions that appeal for vocational colleges to pay more attention to skills competitions.展开更多
This paper analyzes the key challenges faced by vocational college students when participating in national skills competitions.It identifies problems such as limited resources,insufficient training,lack of mentorship,...This paper analyzes the key challenges faced by vocational college students when participating in national skills competitions.It identifies problems such as limited resources,insufficient training,lack of mentorship,academic workload constraints,and inadequate equipment.Targeted solutions are proposed,including improving resource access,providing structured skill training,implementing expert mentorship programs,offering flexible schedules,and upgrading experimental equipment.Implementing these recommendations through a collaborative effort among stakeholders can significantly empower vocational students to excel in skills competitions by enabling access to resources,building practical skills,obtaining guidance,managing time effectively,and gaining hands-on experience.展开更多
The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The res...The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The results show that minor Er in the studied alloy exists in the form of Al 3Er,only a few of Er in α Al based solid solution .Primary Al 3Er particles formed during solidification were often found at the center of aluminum grains and acted as heterogeneous nucleus, also increased the rate of nucleation, therefore the grain are remarkably refined. Trace Er addition to high pure aluminum is able to increase the mechanical properties of high pure Al, which is caused by fine grain strengthening, substructure strengthening and precipitation strengthening. The recrystallization temperature of Er doped aluminum increases above 50 ℃, which is caused by the pinning effect of highly dispersed fine Al 3Er precipitates on dislocations and sub grain boundaries.展开更多
To realize stable rotating spray transfer in the region of high constant current is the key of realizing high deposition rate MAG welding process without helium in shielding gas and extending the welding current range...To realize stable rotating spray transfer in the region of high constant current is the key of realizing high deposition rate MAG welding process without helium in shielding gas and extending the welding current range of traditional MAG welding process. In this paper, the magnetic control mechanism of the rotating spray transfer is stated and mathematical model is given. Theoretic basis is established, which implements high deposition rate MAG welding process with magnetic control instead of helium in shielding gas.展开更多
The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficu...The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficulty arises when the algorithm is used for non-homogeneous dynamic systems, due to the inverse matrix calculation and the simulation accuracy of the applied loading. By combining the Gaussian quadrature method and state space theory with the calculation technique of matrix exponential function in the precise time step integration method, a new modified precise time step integration method (e.g., an algorithm with an arbitrary order of accuracy) is proposed. In the new method, no inverse matrix calculation or simulation of the applied loading is needed, and the computing efficiency is improved. In particular, the proposed method is independent of the quality of the matrix H. If the matrix H is singular or nearly singular, the advantage of the method is remarkable. The numerical stability of the proposed algorithm is discussed and a numerical example is given to demonstrate the validity and efficiency of the algorithm.展开更多
The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the en...The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La 2O 3 in the La 2O 3 Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo 2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.展开更多
The TiB2 dispersion-reinforced copper-matrix composite used as electrode material in resistance spot welding of zinc coated steels was studied. The service life of the composite electrode reaches （7700） welds, whi...The TiB2 dispersion-reinforced copper-matrix composite used as electrode material in resistance spot welding of zinc coated steels was studied. The service life of the composite electrode reaches （7700） welds, which is 4 times that of the conventional Cu-Cr-Zr electrode. Little gross deformation is observed on the composite （electrodes） because of the higher thermal strength; therefore, it is believed that wear is the only mechanism for the composite （electrode） deterioration. However, both wear and plastic deformation are responsible for the large increase in the tip diameter of the Cu-Cr-Zr electrodes. Moreover, the large deformation of the Cu-Cr-Zr electrodes may contribute to the increased wear rate of the tips.展开更多
In order to confirm which process is the most important in the bloodcoagulation cascade,a dynamic model on the function of platelets in blood coagulationis presented based on biochemical experiments.Based on qualitati...In order to confirm which process is the most important in the bloodcoagulation cascade,a dynamic model on the function of platelets in blood coagulationis presented based on biochemical experiments.Based on qualitative analysis andmathematical simulation,a series of conclusions about the influence of the activationrate of factor VIII and factor IX on the generation of thrombin（IIa）are drawn.It isevident that the pro-coagulation stimulus must exceed a threshold value to initiate thecoagulation cascade.The value is related to the binding constant d<sub>2</sub> of the platelet.The stability of the equilibrium value is also related to the pro-coagulation stimulus.This article also evaluates the influence of the stimulus strength and the activated rateparameter of platelets on thrombin.The proportion of platelets activated at any giventime is designated c.To each c,we obtain a maximum concentration of thrombin.Itis evident that when the level of factor IX is below 1% of the normal level,the rateof thrombin generation reduces dramatically,resulting in severe bleeding tendency.展开更多
文摘Odor pollution in landfill area has attracted more social attention in China. It is very important to control the generation of odor pollutants in situ. Analyzing odorous materials production form buried waste, simulated columns of different volatile solid (VS) content and different buried period waste were designed. Gas compounds produced from the columns were collected and analyzed by comprehensive two-dimensional gas chromatography (GC × GC) method. It has remarkable relationship between VS content and concentrations of odorous material. When VS content more than 40%, the total amount of odorous compounds increases remarkably. It can be inferred that reduced VS content of original waste may effective decreasing odorous materials production in landfill area. The old rubbish produced more odorous compounds than that of fresh one in simulated columns.
基金Supported by the Innovative Talents Support Program of Liaoning Province,No.LR2018047the Natural Science Foundation of Liaoning Province,No.2021-MS-150+1 种基金the Support Plan for the Construction of High-level Teachers in Beijing Municipal Colleges and Universities,No.CIT&TCD 201904047the Research on National Reference Material and Product Development of Natural Products in Beijing Polytechnic,No.SG030801.
文摘The incidence rate of diabetes in pregnancy is about 20%,and diabetes in pregnancy will have a long-term impact on the metabolic health of mothers and their offspring.Mothers may have elevated blood glucose,which may lead to blood pressure disease,kidney disease,decreased resistance and secondary infection during pregnancy.The offspring may suffer from abnormal embryonic development,intrauterine growth restriction,obesity,autism,and other adverse consequences.Resveratrol(RSV)is a natural polyphenol compound,which is found in more than 70 plant species and their products,such as Polygonum cuspidatum,seeds of grapes,peanuts,blueberries,bilberries,and cranberries.Previous studies have shown that RSV has a potential beneficial effect on complex pregnancy,including improving the indicators of diabetes and pregnancy diabetes syndrome.This article has reviewed the molecular targets and signaling pathways of RSV,including AMP-activated protein kinase,mitogen-activated protein kinases,silent information regulator sirtuin 1,miR-23a-3p,reactive oxygen species,potassium channels and CX3C chemokine ligand 1,and the effect of RSV on gestational diabetes mellitus(GDM)and its complications.RSV improves the indicators of GDM by improving glucose metabolism and insulin tolerance,regulating blood lipids and plasma adipokines,and modulating embryonic oxidative stress and apoptosis.Furthermore,RSV can ameliorate the GDM complications by reducing oxidative stress,reducing the effects on placentation,reducing the adverse effects on embryonic development,reducing offspring's healthy risk,and so on.Thus,this review is of great significance for providing more options and possibilities for further research on medication of gestational diabetes.
文摘This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam as an example,and the deformation and stress distribution of the beam were analyzed using FET.The results showed that using color stress nephograms and color U nephograms can improve students’learning outcomes in mechanics classroom.The high levels of satisfaction and interest in incorporating new techniques into the classroom suggest that there is a need to explore and develop innovative teaching methods in mechanics and related fields.This approach may inspire educators to develop more effective ways of teaching material mechanics,and our research can contribute to the advancement of mechanics education.
基金This work was supported by the Project of Beijing Office for Education Sciences Planning(Project Number:AFDB21206).
文摘Vocational education is an important part of the overall education system.The development of higher vocational education is one of the guiding principles of education in China.The development of teachers is an important support for the development of vocational education.Teachers who can teach theoretically and guide students in practical work are known as“double-qualified”teachers.Building a highly qualified and professional double-qualified teaching team is the fundamental task in modernizing vocational education.Firstly,this paper discusses the importance of“double-qualified”teachers by describing the relevant policies of the Ministry of Education in China.Secondly,it reviews the research works of early scholars.Thirdly,it analyzes the main problems of teacher training in higher education institutions.Fourthly,it proposes five suggestions for the development of a“double-qualified”teaching team in higher education institutions.A high level and professional teaching team is an important support for the high-quality development of vocational institutions.School leaders must attach great importance to the construction of a“double-qualified”teaching team and increase the support in terms of policies,institutional protection,and financial investment.
基金The Project of China Vocational Education Association(Project Number:ZJS2022YB024)The Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project Number:2022X305-SXZC).
文摘Skilled talents are the main support for the strategic development of science and technology in China.The quality of talents is an important guarantee for the transformation and upgrading of national industries.By analyzing and studying Huang Yanpei’s thought on vocational education,this paper focuses on the cultivation of students’craftsmanship in vocational schools.First,we analyze the results of previous research and then elaborate on the connotations of Huang Yanpei’s education thought and craftsmanship spirit.Lastly,we propose five suggestions for the cultivation of craftsmanship.Our research work carries certain reference value to the study of craftsmanship cultivation in Huang Yanpei’s education thought.
基金The Project of China Vocational Education Association(Project number:ZJS2022YB024)the Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project number:2022X305-SXZC).
文摘The spirit of craftsmanship is gaining increasing attention from both society and the education community.Along with professional knowledge,continuous research,and innovation have become decisive factors in determining the quality of products.In this context,vocational colleges strive to cultivate high-quality skilled talents,making the cultivation of craftsmanship spirit a crucial component of vocational education.This study explores the cultivation path of craftsmanship spirit through the lens of skills competitions,with a special emphasis on developing students’perseverance.The research conclusions of this article hold significant reference value for the implementation of vocational education policies.
基金supported by the Project of China Vocational Education Association(Project number:ZJS2022YB024)the Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project number:2022X305-SXZC)+1 种基金the Project of Beijing Municipal Social Science Foundation(Project number:22XCC015)the Project of Key Program of Beijing Polytechnic(Project number:2023X018-SXZ).
文摘Engineering mechanics is as a basic course,and the learning effect of this course directly affects the learning of subsequent professional courses.However,the teaching quality of engineering mechanics in vocational colleges has been subpar for a long time.In this study,we explored the teaching situation of engineering mechanics by using questionnaires,pointing out the challenges faced in the teaching of engineering mechanics and putting forward four targeted suggestions,which include stimulating students’interest and increasing the investment in laboratory equipment,to improve the teaching quality.The findings of this study may provide some reference for the teaching reform of engineering mechanics.
基金The Project of China Vocational Education Association(Project number:ZJS2022YB024)The Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project number:2022X305-SXZC).
文摘With the continuous progress of science and technology,the speed of technology iteration in enterprise production line and the demand for comprehensive quality among workers are increasing.Companies not only require their employees to have excellent skills,but also require them to be rigorous and meticulous,possess excellence,and carry out continuous innovation of the craftsman spirit.The talent training goal in vocational colleges is to supply high-quality skilled talents to the society.Vocational colleges have an important duty to cultivate the spirit of craftsmanship in students through multiple paths.Through in-depth analysis of previous research results,we carried out a study on the cultivation path of craftsmanship spirit.The results of this study may provide reference for the development of moral education in vocational colleges.
文摘The quality of the teaching staff is crucial to the development of vocational education.Skilled and knowledgeable teachers can provide students with specialized technical knowledge and practical skills.In addition to teaching,teachers also act as mentors in providing guidance and support in all areas to students.However,the development of young teachers faces many problems,such as unclear career plans and a lack of attention to operational skills.This paper analyzes the research findings of past scholars and uses a questionnaire to analyze the problems faced by young teachers in their career development.Based on this,this paper puts forward some targeted suggestions,which can provide guidelines for the career development of young teachers.
基金The Project of China Vocational Education Association(Project number:ZJS2022YB024)the Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project number:2022X305-SXZC).
文摘This study investigates the challenges encountered by vocational colleges when preparing for innovative skills competitions and proposes effective countermeasures.It highlights issues concerning students’motivation,limited financial resources and hardware,teacher capacity limitations,inadequate reward systems,and curriculum misalignment.Through meticulous research and analysis,this paper presents practical recommendations to mitigate these challenges.Suggestions encompass strategies to enhance students’motivation,increase financial support,provide professional development opportunities for teachers,revamp the reward system,and align the curriculum with competition requirements.By implementing these measures,vocational colleges can cultivate active student participation,elevate teaching quality,bridge the gap between education and industry demands,and equip students for success in innovative skills competitions.
基金This work was supported by the Project of China Vocational Education Association(Project Number:ZJS2022YB024)the Project of Innovation and Development Center of Ideological and Political Work(Beijing Polytechnic),Ministry of Education(Project Number:2022X305-SXZC).
文摘Vocational education and general education are two different types of education that are equally important.The orientation of talent training in vocational education is to nurture skilled talents to serve the society.The practical ability of students is both the focus of teaching in vocational colleges and the requirement of enterprise posts.The various types of skills competitions provide a“stage”for students to showcase their abilities.First,this paper explores students’problem-solving ability while preparing for these competitions,expounding the importance of vocational education and skills competitions.Second,this paper summarizes the views of different scholars.Third,based on a specific case,this paper describes the improvement in students’ability while preparing for these competitions.Fourth,this paper analyzes the results of the questionnaire survey conducted to investigate the improvement in students’ability.Lastly,this paper puts forward several suggestions that appeal for vocational colleges to pay more attention to skills competitions.
基金The Project of China Vocational Education Association(Project number:ZJS2022YB024).
文摘This paper analyzes the key challenges faced by vocational college students when participating in national skills competitions.It identifies problems such as limited resources,insufficient training,lack of mentorship,academic workload constraints,and inadequate equipment.Targeted solutions are proposed,including improving resource access,providing structured skill training,implementing expert mentorship programs,offering flexible schedules,and upgrading experimental equipment.Implementing these recommendations through a collaborative effort among stakeholders can significantly empower vocational students to excel in skills competitions by enabling access to resources,building practical skills,obtaining guidance,managing time effectively,and gaining hands-on experience.
文摘The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The results show that minor Er in the studied alloy exists in the form of Al 3Er,only a few of Er in α Al based solid solution .Primary Al 3Er particles formed during solidification were often found at the center of aluminum grains and acted as heterogeneous nucleus, also increased the rate of nucleation, therefore the grain are remarkably refined. Trace Er addition to high pure aluminum is able to increase the mechanical properties of high pure Al, which is caused by fine grain strengthening, substructure strengthening and precipitation strengthening. The recrystallization temperature of Er doped aluminum increases above 50 ℃, which is caused by the pinning effect of highly dispersed fine Al 3Er precipitates on dislocations and sub grain boundaries.
文摘To realize stable rotating spray transfer in the region of high constant current is the key of realizing high deposition rate MAG welding process without helium in shielding gas and extending the welding current range of traditional MAG welding process. In this paper, the magnetic control mechanism of the rotating spray transfer is stated and mathematical model is given. Theoretic basis is established, which implements high deposition rate MAG welding process with magnetic control instead of helium in shielding gas.
基金financial support from Hunan Provincial Natura1 Science Foundation of China,Grant Number:02JJY2085,for this study
文摘The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficulty arises when the algorithm is used for non-homogeneous dynamic systems, due to the inverse matrix calculation and the simulation accuracy of the applied loading. By combining the Gaussian quadrature method and state space theory with the calculation technique of matrix exponential function in the precise time step integration method, a new modified precise time step integration method (e.g., an algorithm with an arbitrary order of accuracy) is proposed. In the new method, no inverse matrix calculation or simulation of the applied loading is needed, and the computing efficiency is improved. In particular, the proposed method is independent of the quality of the matrix H. If the matrix H is singular or nearly singular, the advantage of the method is remarkable. The numerical stability of the proposed algorithm is discussed and a numerical example is given to demonstrate the validity and efficiency of the algorithm.
文摘The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La 2O 3 in the La 2O 3 Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo 2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.
文摘The TiB2 dispersion-reinforced copper-matrix composite used as electrode material in resistance spot welding of zinc coated steels was studied. The service life of the composite electrode reaches （7700） welds, which is 4 times that of the conventional Cu-Cr-Zr electrode. Little gross deformation is observed on the composite （electrodes） because of the higher thermal strength; therefore, it is believed that wear is the only mechanism for the composite （electrode） deterioration. However, both wear and plastic deformation are responsible for the large increase in the tip diameter of the Cu-Cr-Zr electrodes. Moreover, the large deformation of the Cu-Cr-Zr electrodes may contribute to the increased wear rate of the tips.
基金The project supported by The Beijing Municipal Natural Sciences Foundation (3982005)
文摘In order to confirm which process is the most important in the bloodcoagulation cascade,a dynamic model on the function of platelets in blood coagulationis presented based on biochemical experiments.Based on qualitative analysis andmathematical simulation,a series of conclusions about the influence of the activationrate of factor VIII and factor IX on the generation of thrombin（IIa）are drawn.It isevident that the pro-coagulation stimulus must exceed a threshold value to initiate thecoagulation cascade.The value is related to the binding constant d<sub>2</sub> of the platelet.The stability of the equilibrium value is also related to the pro-coagulation stimulus.This article also evaluates the influence of the stimulus strength and the activated rateparameter of platelets on thrombin.The proportion of platelets activated at any giventime is designated c.To each c,we obtain a maximum concentration of thrombin.Itis evident that when the level of factor IX is below 1% of the normal level,the rateof thrombin generation reduces dramatically,resulting in severe bleeding tendency.
