The integration of industry and education in vocational education is related to the direction of vocational education reform and thequality of personnel training. Nowadays, there are institutional obstacles to the int...The integration of industry and education in vocational education is related to the direction of vocational education reform and thequality of personnel training. Nowadays, there are institutional obstacles to the integration of industry and education in VocationalEducation in China in terms of government power boundary, governance system, governance model, safeguard measures andenvironmental atmosphere. Therefore, the author makes an analysis and Discussion on the new ideas and strategies for eliminatingthe obstacles to the integration of industry and education in Vocational education. The study found that during the social transitionperiod, the survival and development of vocational and technical education became crucial. And the results of the research showthat the integration of production and education in vocational education is an inevitable requirement for the establishment of amodern vocational education system. It is not an activity under the administrative instruction, but an inherent requirement for thedevelopment of vocational education.展开更多
Einstein aimed to find a unified theoretical model to explain various interactions in nature,and the relationship between gravitational and electric fields was particularly important.For the first time,this paper prov...Einstein aimed to find a unified theoretical model to explain various interactions in nature,and the relationship between gravitational and electric fields was particularly important.For the first time,this paper provides the internal relationship equations of the electric and magnetic fields.Further,the relationship between the magnetic and gravity fields is analyzed,and the relationship equations of the electric,magnetic,and gravity fields are established.On this basis,a general formula for calculating the radius of charged particles is derived.Simultaneously,we also discussed and made predictions on black holes,providing convenience for future research and experimental detection.展开更多
Four different welding sequences of double-pulse MIG welding were conducted for 6061-T6 aluminum alloy automobile bumpers by using nonlinear elastoplasticity finite element method based on ABAQUS software.The post-wel...Four different welding sequences of double-pulse MIG welding were conducted for 6061-T6 aluminum alloy automobile bumpers by using nonlinear elastoplasticity finite element method based on ABAQUS software.The post-welding residual stress and deformation were definitely different among the four welding sequences.The results showed that the highest temperature in Solution A was approximately 200℃higher than the melting point of base metal.High residual stress was resulted from this large temperature gradient and mainly concentrated on the welding vicinity between beam and crash box.The welding deformation primarily occurred in both of the contraction of two-ends of the beam and the self-contraction of crash box.Compared with other welding sequences,the residual stress in Solution A was the smallest,whereas the welding deformation was the largest.However,the optimal sequence was Solution B because of the effective reduction of residual stress and good assembly requirements.展开更多
To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established b...To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established based on HyperXtrude software using Arbitrary Lagrangian–Eulerian(ALE)algorithm.The velocity distribution on the cross-section of the extrudate at the die exit and pressure distribution at different heights in the welding chamber were quantitatively analyzed.To obtain an uniformity of metal flow velocity at the die exit,the porthole die structure was optimized by adding baffle plates.After optimization,maximum displacement in the Y direction at the bottom of profile decreases from 1.1 to 0.15 mm,and the concave defects are remarkably improved.The research method provides an effective guidance for improving extrusion defects and optimizing the metal flow of complex hollow aluminium profiles during porthole die extrusion.展开更多
6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and tim...6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and time was investigated by transmission electron microscopy and scanning electron microscopy. The mechanical properties were examined by hardness test and tensile test. The results showed that the micro-hardness was sensitive to heat treatment temperature and time. Increasing temperature was beneficial to the shortening of peak aging time. There were a large number of dislocations and few precipitates in the welded joints. With the increase of post-weld heat treatment temperature and time, the density of dislocation decreased. Meanwhile, the strengthening phase precipitated and grew up gradually. When the post-weld heat treatment temperature increased up to 200℃, large Q' phases were observed. And they were responsible for the peak value of the micro-hardness in the welded joints.展开更多
The railway tunnel concrete lining exposed to sulfate-bearing groundwater beyond 40 years in southwest of China was investigated. Field investigation, sulfate ions content and corroded products analysis, macro/microsc...The railway tunnel concrete lining exposed to sulfate-bearing groundwater beyond 40 years in southwest of China was investigated. Field investigation, sulfate ions content and corroded products analysis, macro/microscopic test were carried out. Results show that under the tunnel concrete lining structure and its served environmental conditions, sulfate solutions permeate concrete lining and accumulate on windward-side of concrete lining, resulting in the increase of sulfate ions content on windward-side and the diffusion of sulfate ions from windward-side to waterward-side, which cause the concrete lining of windward-side damaged seriously but the waterward-side of concrete lining is still in perfect condition. It is confirmed that structural characteristic of tunnel and environmental conditions lead to physical attack with the leaching of concrete and sodium sulfate crystallization as well as chemical corrosion with formation of gypsum in high sulfate concentration and formation of thaumasite in proper temperature rather than formation of ettringite. These achievements can provide academic and technical supports for understanding the deterioration mechanism of concrete lining as well as constructing railway tunnel under sulfate attack.展开更多
The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was de...The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment.展开更多
A certain amount of ammonia reducer were directly injected into the 4102BZLQ Diesel engine's combustion chamber when the combustion temperature decreases to 1573-1073K, NOx generated could be reduced to 1.11g/(kW&...A certain amount of ammonia reducer were directly injected into the 4102BZLQ Diesel engine's combustion chamber when the combustion temperature decreases to 1573-1073K, NOx generated could be reduced to 1.11g/(kW·h). Based on PRF combustion mechanism, NO was tested by using the heavy-duty diesel engine test cycle of ESC thirteen conditions[1], the ammonia spray angle and amount were tested and optimized in different conditions. The test results show that the thermal efficiency of Diesel engine does not decrease while NO exhaust decreases.展开更多
In the process of protected protocol recognition,an improved AGglomerative NESting algorithm( IAGNES) with high adaptability is proposed,which is based on the AGglomerative NESting algorithm( AGNES),for the challengin...In the process of protected protocol recognition,an improved AGglomerative NESting algorithm( IAGNES) with high adaptability is proposed,which is based on the AGglomerative NESting algorithm( AGNES),for the challenging issue of how to obtain single protocol data frames from multiprotocol data frames. It can improve accuracy and efficiency by similarity between bit-stream data frames and clusters,extract clusters in the process of clustering. Every cluster obtained contains similarity evaluation index which is helpful to evaluation. More importantly,IAGNES algorithm can automatically recognize the number of cluster. Experiments on the data set published by Lincoln Laboratory shows that the algorithm can cluster the protocol data frames with high accuracy.展开更多
In the minimum degree vertex deletion problem,we are given a graph,a distinguished vertex in the graph,and an integer κ,and the question is whether we can delete at most κ vertices from the graph so that the disting...In the minimum degree vertex deletion problem,we are given a graph,a distinguished vertex in the graph,and an integer κ,and the question is whether we can delete at most κ vertices from the graph so that the distinguished vertex has the unique minimum degree.The maximum degree vertex deletion problem is defined analogously but here we want the distinguished vertex to have the unique maximum degree.It is known that both problems areΨ-hard and fixed-parameter intractable with respect to some natural parameters.In this paper,we study the(parameterized)complexity of these two problems restricted to split graphs,p-degenerate graphs,and planar graphs.Our study provides a comprehensive complexity landscape of the two problems restricted to these special graphs.展开更多
Discomfort caused by long-term sitting decreases the passenger experience and may lead to musculoskeletal diseases, and this hasbecome one of the main problems for passengers of high-speed railways. However, the comfo...Discomfort caused by long-term sitting decreases the passenger experience and may lead to musculoskeletal diseases, and this hasbecome one of the main problems for passengers of high-speed railways. However, the comfort degradation mechanism during longtermsitting in high-speed railways is still unknown. This study aimed to reveal passengers’ sitting comfort degradation mechanismin high-speed railways. By carrying out long-term sitting tests on high-speed trains running on the Shanghai-Kunming line, the dynamicinterface pressure and subjective comfort including overall and regional comfort of seven participants were obtained.Machinelearning models and statistical analysis methods were combined for data analysis to reveal the effect of regional comfort and thecontribution of sitting duration during the process of sitting comfort degradation. The results show that overall comfort is most significantlyinfluenced by the comfort of the shoulders, waist and buttocks. The seats play different roles before and after 20 minutesduring long-term sitting and there is a lag between the fatigue occurring and being offset. Therefore, the structure of seats affectsoverall comfort by affecting important regional comfort, and a long-term sitting test is necessary for accurate seat assessment. Thecomfort degradation mechanism can be used to define standards for long-term sitting comfort or provide guidance for seat evaluation,and the design and evaluation plan mentioned in this article for second-class seats can be applied to other cases with limitedaccommodating space.展开更多
文摘The integration of industry and education in vocational education is related to the direction of vocational education reform and thequality of personnel training. Nowadays, there are institutional obstacles to the integration of industry and education in VocationalEducation in China in terms of government power boundary, governance system, governance model, safeguard measures andenvironmental atmosphere. Therefore, the author makes an analysis and Discussion on the new ideas and strategies for eliminatingthe obstacles to the integration of industry and education in Vocational education. The study found that during the social transitionperiod, the survival and development of vocational and technical education became crucial. And the results of the research showthat the integration of production and education in vocational education is an inevitable requirement for the establishment of amodern vocational education system. It is not an activity under the administrative instruction, but an inherent requirement for thedevelopment of vocational education.
基金supported by the Hunan Provincial Natural Science Foundation(No.2016JJ3034).
文摘Einstein aimed to find a unified theoretical model to explain various interactions in nature,and the relationship between gravitational and electric fields was particularly important.For the first time,this paper provides the internal relationship equations of the electric and magnetic fields.Further,the relationship between the magnetic and gravity fields is analyzed,and the relationship equations of the electric,magnetic,and gravity fields are established.On this basis,a general formula for calculating the radius of charged particles is derived.Simultaneously,we also discussed and made predictions on black holes,providing convenience for future research and experimental detection.
基金Projects(31665004,31715011) supported by the Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,Hunan University,ChinaProject(15C0450) supported by the Educational Commission of Hunan Province of China
文摘Four different welding sequences of double-pulse MIG welding were conducted for 6061-T6 aluminum alloy automobile bumpers by using nonlinear elastoplasticity finite element method based on ABAQUS software.The post-welding residual stress and deformation were definitely different among the four welding sequences.The results showed that the highest temperature in Solution A was approximately 200℃higher than the melting point of base metal.High residual stress was resulted from this large temperature gradient and mainly concentrated on the welding vicinity between beam and crash box.The welding deformation primarily occurred in both of the contraction of two-ends of the beam and the self-contraction of crash box.Compared with other welding sequences,the residual stress in Solution A was the smallest,whereas the welding deformation was the largest.However,the optimal sequence was Solution B because of the effective reduction of residual stress and good assembly requirements.
基金Project(U1664252) supported by the National Natural Science Foundation of ChinaProjects(31665004,31715011) supported by the Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,China
文摘To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established based on HyperXtrude software using Arbitrary Lagrangian–Eulerian(ALE)algorithm.The velocity distribution on the cross-section of the extrudate at the die exit and pressure distribution at different heights in the welding chamber were quantitatively analyzed.To obtain an uniformity of metal flow velocity at the die exit,the porthole die structure was optimized by adding baffle plates.After optimization,maximum displacement in the Y direction at the bottom of profile decreases from 1.1 to 0.15 mm,and the concave defects are remarkably improved.The research method provides an effective guidance for improving extrusion defects and optimizing the metal flow of complex hollow aluminium profiles during porthole die extrusion.
基金Projects(2019JJ70077,2019JJ50510) supported by the National Science Foundation of Hunan Province,ChinaProject(31665004) supported by Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,ChinaProjects(18B552,18B285) supported by Scientific Research Fund of Hunan Provincial Education Department,China
文摘6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and time was investigated by transmission electron microscopy and scanning electron microscopy. The mechanical properties were examined by hardness test and tensile test. The results showed that the micro-hardness was sensitive to heat treatment temperature and time. Increasing temperature was beneficial to the shortening of peak aging time. There were a large number of dislocations and few precipitates in the welded joints. With the increase of post-weld heat treatment temperature and time, the density of dislocation decreased. Meanwhile, the strengthening phase precipitated and grew up gradually. When the post-weld heat treatment temperature increased up to 200℃, large Q' phases were observed. And they were responsible for the peak value of the micro-hardness in the welded joints.
基金Project(51108463) supported by the National Natural Science Foundation of ChinaProject(11B041) supported by Scientific Research Fund of Hunan Provincial Education Department of ChinaProject(NCET-10-0839) supported by Ministry Education of China
文摘The railway tunnel concrete lining exposed to sulfate-bearing groundwater beyond 40 years in southwest of China was investigated. Field investigation, sulfate ions content and corroded products analysis, macro/microscopic test were carried out. Results show that under the tunnel concrete lining structure and its served environmental conditions, sulfate solutions permeate concrete lining and accumulate on windward-side of concrete lining, resulting in the increase of sulfate ions content on windward-side and the diffusion of sulfate ions from windward-side to waterward-side, which cause the concrete lining of windward-side damaged seriously but the waterward-side of concrete lining is still in perfect condition. It is confirmed that structural characteristic of tunnel and environmental conditions lead to physical attack with the leaching of concrete and sodium sulfate crystallization as well as chemical corrosion with formation of gypsum in high sulfate concentration and formation of thaumasite in proper temperature rather than formation of ettringite. These achievements can provide academic and technical supports for understanding the deterioration mechanism of concrete lining as well as constructing railway tunnel under sulfate attack.
基金the financial supports from the National Natural Science Foundation of China(No.52005244)the Scientific Research Fund of Hunan Provincial Education Department,China(Nos.18B285,18B552)+1 种基金the Natural Science Foundation of Hunan Provincial,China(Nos.2019JJ50510,2019JJ70077)Young Scholars Program of Furong Scholar Program,China.
文摘The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment.
基金Sponsored by the Hunan Science and Technology Agency Science Research Program 09(2009GK3091)the Hunan Provincial Education Department Science Research Program 09(09C1138)
文摘A certain amount of ammonia reducer were directly injected into the 4102BZLQ Diesel engine's combustion chamber when the combustion temperature decreases to 1573-1073K, NOx generated could be reduced to 1.11g/(kW·h). Based on PRF combustion mechanism, NO was tested by using the heavy-duty diesel engine test cycle of ESC thirteen conditions[1], the ammonia spray angle and amount were tested and optimized in different conditions. The test results show that the thermal efficiency of Diesel engine does not decrease while NO exhaust decreases.
基金Supported by the National Natural Science Foundation of China(No.F020704)
文摘In the process of protected protocol recognition,an improved AGglomerative NESting algorithm( IAGNES) with high adaptability is proposed,which is based on the AGglomerative NESting algorithm( AGNES),for the challenging issue of how to obtain single protocol data frames from multiprotocol data frames. It can improve accuracy and efficiency by similarity between bit-stream data frames and clusters,extract clusters in the process of clustering. Every cluster obtained contains similarity evaluation index which is helpful to evaluation. More importantly,IAGNES algorithm can automatically recognize the number of cluster. Experiments on the data set published by Lincoln Laboratory shows that the algorithm can cluster the protocol data frames with high accuracy.
文摘In the minimum degree vertex deletion problem,we are given a graph,a distinguished vertex in the graph,and an integer κ,and the question is whether we can delete at most κ vertices from the graph so that the distinguished vertex has the unique minimum degree.The maximum degree vertex deletion problem is defined analogously but here we want the distinguished vertex to have the unique maximum degree.It is known that both problems areΨ-hard and fixed-parameter intractable with respect to some natural parameters.In this paper,we study the(parameterized)complexity of these two problems restricted to split graphs,p-degenerate graphs,and planar graphs.Our study provides a comprehensive complexity landscape of the two problems restricted to these special graphs.
基金the National Natural Science Foundation of China(Grant No.52075553)the Hunan Science Foundation for Distinguished Young Scholars of China(Grant No.2021JJ10059)the School Enterprise Cooperation Program of Central South University(Grant No.2021XQLH011).
文摘Discomfort caused by long-term sitting decreases the passenger experience and may lead to musculoskeletal diseases, and this hasbecome one of the main problems for passengers of high-speed railways. However, the comfort degradation mechanism during longtermsitting in high-speed railways is still unknown. This study aimed to reveal passengers’ sitting comfort degradation mechanismin high-speed railways. By carrying out long-term sitting tests on high-speed trains running on the Shanghai-Kunming line, the dynamicinterface pressure and subjective comfort including overall and regional comfort of seven participants were obtained.Machinelearning models and statistical analysis methods were combined for data analysis to reveal the effect of regional comfort and thecontribution of sitting duration during the process of sitting comfort degradation. The results show that overall comfort is most significantlyinfluenced by the comfort of the shoulders, waist and buttocks. The seats play different roles before and after 20 minutesduring long-term sitting and there is a lag between the fatigue occurring and being offset. Therefore, the structure of seats affectsoverall comfort by affecting important regional comfort, and a long-term sitting test is necessary for accurate seat assessment. Thecomfort degradation mechanism can be used to define standards for long-term sitting comfort or provide guidance for seat evaluation,and the design and evaluation plan mentioned in this article for second-class seats can be applied to other cases with limitedaccommodating space.
