Lost foam casting(LFC)technology has been widely applied to cast iron and cast steel.However,the development of LFC for Al and Mg alloys was relatively slower than that for cast iron and cast steel.The application of ...Lost foam casting(LFC)technology has been widely applied to cast iron and cast steel.However,the development of LFC for Al and Mg alloys was relatively slower than that for cast iron and cast steel.The application of LFC to Al and Mg alloys needs more effort,especially in China.In this paper,the development history of LFC is reviewed,and the application situations of LFC to Al and Mg alloys are mainly discussed.Meanwhile,the key problems of LFC for Al and Mg alloys are also pointed out.Finally,the prospects for LFC technology are discussed,and some special new LFC technologies are introduced for casting Al and Mg alloys.In future,the development trends of green LFC technology mainly focus on the special new LFC methods,metal material,coating,heat treatment,new foam materials as well as purification technology of tail gas,etc.展开更多
The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship betwe...The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship between the spheroidization grade of liguid iron treated by different nodulizers and holding time were obtained. The results show that the more the remains of the rare earth, the longer the anti-degradation time, the liquid iron was treated either by Y-Mg-Si or by Ce-Mg-Si nodulizer. When the rare earth remains are above certain quantity, the spheroidization grade starts to decline. When liquid iron treated by either Y-Mg-Si or Ce-Mg-Si nodulizer with proper remains of rare earths about 0.04% 0.06%（mass fraction）, the anti-degradation is the best, and the remains of Mg being about 0.04% -0.07% （mass fraction）. Rare earths-Mg nodulizer with moderate RE remains is better than that of Mg-Si nodulizer in anti-degradation property. However, Y-Mg-Si nodulizer with moderate remins of Re is better than Ce-Mg-Si nodulizer. Sometimes Ce-Mg- Si nodulizer can be used for the production of heavy section nodular cast iron.展开更多
For measurement of component content in the extraction and separation process of praseodymium/neodymium(Pr/Nd), a soft measurement method was proposed based on modeling of ion color features, which is suitable for fas...For measurement of component content in the extraction and separation process of praseodymium/neodymium(Pr/Nd), a soft measurement method was proposed based on modeling of ion color features, which is suitable for fast estimation of component content in production field. Feature analysis on images of the solution is conducted,which are captured from Pr/Nd extraction/separation field. H/S components in the HSI color space are selected as model inputs, so as to establish the least squares support vector machine(LSSVM) model for Nd(Pr) content,while the model parameters are determined with the GA algorithm. To improve the adaptability of the model,the adaptive iteration algorithm is used to correct parameters of the LSSVM model, on the basis of model correction strategy and new sample data. Using the field data collected from rare earth extraction production, predictive methods for component content and comparisons are given. The results indicate that the proposed method presents good adaptability and high prediction precision, so it is applicable to the fast detection of element content in the rare earth extraction.展开更多
Tool wear has an important influence on the residual stress distribution on the machined surface.Also,it will influence the fatigue life of finished workpiece. In this research,the hard turning process of hardened die...Tool wear has an important influence on the residual stress distribution on the machined surface.Also,it will influence the fatigue life of finished workpiece. In this research,the hard turning process of hardened die steel Cr12 MoV was studied by using PCBN tool with considering tool wear. Based on the numerical treatment of residual stress,the dispersion and distribution curves of different tool wear were fitted,and the influence mechanism of tool wear on the residual stress distribution of machined surface was analyzed.Based on the theory of fatigue mechanics and mathematical statistics,the mathematical model for difference of stress dispersion and fatigue life was established. The rotating and bending tests were carried out on the standard parts after cutting process for the workpiece. The influence of tool wear on fatigue life was revealed by fracture surface morphology and fatigue life study. The results provide theoretical support for control of residual stress and the fatigue property of the machined surface under the actual working conditions.展开更多
The wavy interface for similar or the same metal explosive welding（EXW） and the universal mechanism of wavy interface formation in EXW were studied in this work. Based on a new established model, it was deduced that...The wavy interface for similar or the same metal explosive welding（EXW） and the universal mechanism of wavy interface formation in EXW were studied in this work. Based on a new established model, it was deduced that the evolution frequencies of the instability were constrained in a limited range. Then experiments of identical metal EXW were performed and welding interfaces were characterized for examining the final morphology. By calculating the fractal dimensions and multifractal spectra of welding interface, the fractal characteristics of interface were revealed and a quantitative description was achieved for EXW interface structure. Thus, the formation, evolution and final morphology of wavy interface were systemically researched.展开更多
ZnO whiskers observation on the surface of SnZn/Cu solder joints in concentrator silicon solar cells solder layer is reported. In the experiment,SnZn/Cu samples are left in laboratory after reflow soldering for two ye...ZnO whiskers observation on the surface of SnZn/Cu solder joints in concentrator silicon solar cells solder layer is reported. In the experiment,SnZn/Cu samples are left in laboratory after reflow soldering for two years before an examination by SEM,then ZnO whiskers can be observed obviously,which grows out from the rich-Zn phase of the samples and causes electrical short circuit in the electronics appliances,which demonstrates that the SnZn solder shows a risk for the short circuiting failure of an electronic device. Moreover,the growth mechanism of ZnO whiskers is researched based on cracked oxide theory,which provides the reference support for SnZn solders application.展开更多
The B Al permeation layers of Steel 45 were studied by means of SEM, TEM and XRD. The formation and growth model of permeation layer was proposed. The layer formation, growth and the migration behaviors of B were disc...The B Al permeation layers of Steel 45 were studied by means of SEM, TEM and XRD. The formation and growth model of permeation layer was proposed. The layer formation, growth and the migration behaviors of B were discussed. It is suggested that the diffusion of Al is deferred when the surface was covered by borides and aluminize compounds are surrounded by borides with the further growing of borides.展开更多
PI （proportional-integral） control algorithm is applied to control WlP （work-in-progress） in a discrete manufacturing system, where the cascade control of PI controllers is presented. It is in the frequency domain...PI （proportional-integral） control algorithm is applied to control WlP （work-in-progress） in a discrete manufacturing system, where the cascade control of PI controllers is presented. It is in the frequency domain that the PI controller is designed with constraints on sensitivity options to ensure the stability and robustness of its parameters. A case is evaluated on a motorcycle engine crankcase production system, whose simulation results confirm that demand fluctuations can be compensated by PI controllers under a normal demand. PI controllers also possess low sensitivity to the distribution of production times.展开更多
The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct ...The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant＇s thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant＇s local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc（ASHRAE） Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant＇s thermal responses, including the skin temperature and the thermal sensation. The skin temperaWa-e and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in real life traffic is presented. The investigation result indicates that the skin temperature is a robust index to evaluate the thermal sensation. Applying the skin temperature to designing and controlling parameters of the heating, ventilation and air conditioning（HVAC） system may benefit the thermal comfort and reducing energy consumption.展开更多
The microstructures and mechanical properties of the ductile cast iron （DI） specimens obtained by lost foam casting （LFC） with and without vibration were investigated. The results indicate that the number of the g...The microstructures and mechanical properties of the ductile cast iron （DI） specimens obtained by lost foam casting （LFC） with and without vibration were investigated. The results indicate that the number of the graphite nodule increases from 175 mm 2 of the specimens produced by LFC without vibration to 334 mm^-2 of the specimens produced by LFC with vibration, and the thickness of the ferrite shell increases. Meanwhile, the amount of the carbides decreases in the specimens produced by LFC with vibration and the granule structure then forms. These are mainly attributed to the ＂crystal shower＂ caused by the vibration. In addition, the tensile strength and elongation of DI specimens produced by LFC with vibration are improved due to the dispersion-strengthening of refined carbide and Dearlite colonv, uniform distribution of the graphite nodule, and increase of the amount of dimples and tearing edges.展开更多
To improve the characteristics of wet multi-disc brakes (WMDBs), the WMDBs of the drive axles of mining trucks were studied. A model was established to predict the phenomenon of drag characteristics during wet brake n...To improve the characteristics of wet multi-disc brakes (WMDBs), the WMDBs of the drive axles of mining trucks were studied. A model was established to predict the phenomenon of drag characteristics during wet brake non-engagement by considering the combined effect of surface grooves, film shrinkage, and laminar Navier-Stokes (N-S) equations. The model was used to study drag torque and temperature variation of the wet brakes for different volume flows, dynamic viscosities, and friction pair clearances. The simulation results indicated that the peak torque decreased when the clearance of the friction pair increased. Additionally, the peak torque increased when the volume flow increased and when the cooling liquid dynamic viscosity increased. The model was more accurate than a traditional forecasting system when considering the role of surface grooves and oil film shrinkage in actual working conditions.展开更多
The paper is concerned with stabilization problem for a class of stochastic switching systems with time-delay in the detection of switching signal. By using binomial model,Poisson process,and Wiener process to describ...The paper is concerned with stabilization problem for a class of stochastic switching systems with time-delay in the detection of switching signal. By using binomial model,Poisson process,and Wiener process to describe time-delay, switching signal, and exogenous disturbance, respectively, the system under investigation is entirely set in a stochastic framework. The influence of the random time-delay is combined into reconstructing the switching signal of overall closed-loop system and changes the distribution property of switching points. Therefore,based on the asymptotical behaviors of Poisson processes and Wiener processes,the almost surely exponential stability conditions are established. Furthermore,a design methodology is posed for solving the stabilization control.展开更多
The compensation current of the arc-suppressing coil makes the phase and amplitude of zero-sequence measurement current of the earthed fault feeder to vary. It is very hard to detect the fault feeder by using existing...The compensation current of the arc-suppressing coil makes the phase and amplitude of zero-sequence measurement current of the earthed fault feeder to vary. It is very hard to detect the fault feeder by using existing detectors based on single method. In this paper, integrative feeder selection strategy—zero sequence current increment method and the direction of transient current— is put forward. Based on the integrative feeder selection strategy, the design of fault-feeder selection device for one-phase-to ground fault on resonance grounding system is presented. For the purpose of testing and validating the operating principle of the device, the experiment of single-phase-to-ground fault has been carried out on the simulation of 1.2 kV power network. The results from many repeat experiments show that stability of the fault selection device is satisfactory.展开更多
Hillock Sn whiskers in Sn0.3Ag0.7Cu solder are investigated in 20 seconds in corrosive climate(95% methanol and 5% nitric acid),and the growth mechanism of hillock Sn whiskers is studied.The results indicate that hill...Hillock Sn whiskers in Sn0.3Ag0.7Cu solder are investigated in 20 seconds in corrosive climate(95% methanol and 5% nitric acid),and the growth mechanism of hillock Sn whiskers is studied.The results indicate that hillock Sn whiskers are formed near the interface of Sn0.3Ag0.7Cu/Cu solder joints,and small corrosion pits provide conceive sites for Sn whiskers. Moreover,compressive stress induced by IMC reaction and oxidation for the whisker growth may be suggested as the driving force.展开更多
So far,Maisotsenko cycle has been applied to many fields such as heating ventilation and air-conditioning,power industry,chemical production,and so on.A lot of researches about classical thermodynamic analyses of Mais...So far,Maisotsenko cycle has been applied to many fields such as heating ventilation and air-conditioning,power industry,chemical production,and so on.A lot of researches about classical thermodynamic analyses of Maisotsenko cycle have been made.A new cycle model of combined Diesel and Maisotsenko cycles considering heat transfer loss(HTL),piston friction loss(PFL)and internal irreversible loss(IIL)was proposed in this paper.By using the finite time thermodynamic(FTT)theory,the power and efficiency performances of the Maisotsenko-Diesel cycle(MDC)were studied.Effects of mass flow rate(MFR)of water injection in the Maisotsenko air saturator(MAS)and the other parameters related to the design of Diesel engine on the optimal cycle performances were analyzed.Furthermore,it was testified that irreversible MDC was superior than conventional irreversible Diesel cycle in both power output and thermal efficiency.The results can expand the application of Maisotsenko cycle(M-cycle)and provide some theoretical guidelines for the practical devices.展开更多
Solder bumps are widely used in surface mount components, which provide electrical and mechanical connection between the chip/package and the substrate. As the solder bump getting smaller in dimension and pitch, it be...Solder bumps are widely used in surface mount components, which provide electrical and mechanical connection between the chip/package and the substrate. As the solder bump getting smaller in dimension and pitch, it becomes more difficult to inspect the solder defects hidden in the IC package. In this paper, an intelligent inspection method using the scanning acoustic microscopy(SAM) and the fuzzy C-means(FCM) algorithm was investigated. A flip chip package of FA10 was chosen as the test sample. The SAM tests of FA10 were carried out in C-scan mode. The sub-image of every solder bump was segmented from the SAM image. The statistical features were then calculated and adopted for clustering of solder bumps using the FCM algorithm. The recognition results of FCM reached a high accuracy of 94.3%. The intelligent system is effective for defect inspection in high density packages.展开更多
This paper designs a 3 × 3 light emitting diode （LED） array with a total power of 9 W, presents a thermal analysis of plate fin, in-line and staggered pin fin heat sinks for a high power LED lighting system, an...This paper designs a 3 × 3 light emitting diode （LED） array with a total power of 9 W, presents a thermal analysis of plate fin, in-line and staggered pin fin heat sinks for a high power LED lighting system, and develops a 3D one-fourth finite element （FE） model to predict the system temperature distribution. Three kinds of heat sinks are compared under the same conditions. It is found that LED chip junction temperature is 48.978℃ when the fins of heat sink are aligned alternately.展开更多
Solder bump technology has been widely used in electronic packaging. With the development of solder bumps towards higher density and finer pitch, it is more difficult to inspect the defects of solder bumps as they are...Solder bump technology has been widely used in electronic packaging. With the development of solder bumps towards higher density and finer pitch, it is more difficult to inspect the defects of solder bumps as they are hidden in the package. A nondestructive method using the transient active thermography has been proposed to inspect the defects of a solder bump, and we aim at developing an intelligent diagnosis system to eliminate the influence of emissivity unevenness and non-uniform heating on defects recognition in active infrared testing. An improved fuzzy c-means(FCM) algorithm based on the entropy weights is investigated in this paper. The captured thermograms are preprocessed to enhance the thermal contrast between the defective and good bumps. Hot spots corresponding to 16 solder bumps are segmented from the thermal images. The statistical features are calculated and selected appropriately to characterize the status of solder bumps in FCM clustering. The missing bump is identified in the FCM result, which is also validated by the principle component analysis. The intelligent diagnosis system using FCM algorithm with the entropy weights is effective for defects recognition in electronic packages.展开更多
CeO2 nanocrystals with different morphologies were synthesized by adjusting the pH value of the starting solution in water-in-oil microemulsion. The obtained samples were characterized by transmission electron microsc...CeO2 nanocrystals with different morphologies were synthesized by adjusting the pH value of the starting solution in water-in-oil microemulsion. The obtained samples were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）. thermogravimetric analysis and different thermal analysis （TGA/DTA）, Brunauer-Emmet-Teller （BET） surface area measurement, ultraviolet-visible absorption （UV-vis） spectroscopy and photoluminescence （PL） spectroscopy. Results show that the mor- phologies of CeO2 were transformed from granular to spherical and to rod-like while the pH of the starting solution varied from 5 to 8 and to 11. All samples were indexed to the phase of Ce02 and Ce（OH）4, and the molar ratio of Ce02 to Ce（OH）4 was deduced to be about 0.25, The morphologies of CeO2 nanocrystals had but slight influence on their specific surface areas, UV-vis spectra and PL spectra, The band gap energies of different morphological samples were estimated by UV-vis spectroscopic method,展开更多
To obtain more accurate correlation dimension estimations for chaotic time series, a novel scaling region identification method is developed. First, points that obviously do not belong to the scaling region associated...To obtain more accurate correlation dimension estimations for chaotic time series, a novel scaling region identification method is developed. First, points that obviously do not belong to the scaling region associated with the whole double logarithm correlation integral curve are removed using the K-means algorithm. Second, a point-slope-error algorithm is developed to recognize a possible scaling region. Third, the K-means algorithm is used again to further remove a small interval of interfering points in the possible scaling region to obtain a more precise scaling region. The correlation dimension of four typical chaotic attractors and five curves generated by the Weierstrass-Mandelbrot fractal function were calculated using the proposed method. These calculated values were very close to the respective theoretical fractal dimensions. Moreover, the effectiveness of our method in identifying the scaling region was compared with existing methods. Results show that our method can distinguish the scaling region objectively, accurately, automatically and quickly, making estimations of the correlation dimension more precise and affording significant improvements in nonlinear analysis.展开更多
基金supported by the National Nature Science Foundation of China(NFSC)(No.50275058,50775085,51204124,51375187)the National High Technology Research and Development Program of China(No.2007AA03Z113)
文摘Lost foam casting(LFC)technology has been widely applied to cast iron and cast steel.However,the development of LFC for Al and Mg alloys was relatively slower than that for cast iron and cast steel.The application of LFC to Al and Mg alloys needs more effort,especially in China.In this paper,the development history of LFC is reviewed,and the application situations of LFC to Al and Mg alloys are mainly discussed.Meanwhile,the key problems of LFC for Al and Mg alloys are also pointed out.Finally,the prospects for LFC technology are discussed,and some special new LFC technologies are introduced for casting Al and Mg alloys.In future,the development trends of green LFC technology mainly focus on the special new LFC methods,metal material,coating,heat treatment,new foam materials as well as purification technology of tail gas,etc.
文摘The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship between the spheroidization grade of liguid iron treated by different nodulizers and holding time were obtained. The results show that the more the remains of the rare earth, the longer the anti-degradation time, the liquid iron was treated either by Y-Mg-Si or by Ce-Mg-Si nodulizer. When the rare earth remains are above certain quantity, the spheroidization grade starts to decline. When liquid iron treated by either Y-Mg-Si or Ce-Mg-Si nodulizer with proper remains of rare earths about 0.04% 0.06%（mass fraction）, the anti-degradation is the best, and the remains of Mg being about 0.04% -0.07% （mass fraction）. Rare earths-Mg nodulizer with moderate RE remains is better than that of Mg-Si nodulizer in anti-degradation property. However, Y-Mg-Si nodulizer with moderate remins of Re is better than Ce-Mg-Si nodulizer. Sometimes Ce-Mg- Si nodulizer can be used for the production of heavy section nodular cast iron.
基金Supported by the National Natural Science Foundation of China(51174091,61364013,61164013)Earlier Research Project of the State Key Development Program for Basic Research of China(2014CB360502)
文摘For measurement of component content in the extraction and separation process of praseodymium/neodymium(Pr/Nd), a soft measurement method was proposed based on modeling of ion color features, which is suitable for fast estimation of component content in production field. Feature analysis on images of the solution is conducted,which are captured from Pr/Nd extraction/separation field. H/S components in the HSI color space are selected as model inputs, so as to establish the least squares support vector machine(LSSVM) model for Nd(Pr) content,while the model parameters are determined with the GA algorithm. To improve the adaptability of the model,the adaptive iteration algorithm is used to correct parameters of the LSSVM model, on the basis of model correction strategy and new sample data. Using the field data collected from rare earth extraction production, predictive methods for component content and comparisons are given. The results indicate that the proposed method presents good adaptability and high prediction precision, so it is applicable to the fast detection of element content in the rare earth extraction.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51575147)the Science Funds for the Young Innovative Talents of HUST(Grant No.201507)
文摘Tool wear has an important influence on the residual stress distribution on the machined surface.Also,it will influence the fatigue life of finished workpiece. In this research,the hard turning process of hardened die steel Cr12 MoV was studied by using PCBN tool with considering tool wear. Based on the numerical treatment of residual stress,the dispersion and distribution curves of different tool wear were fitted,and the influence mechanism of tool wear on the residual stress distribution of machined surface was analyzed.Based on the theory of fatigue mechanics and mathematical statistics,the mathematical model for difference of stress dispersion and fatigue life was established. The rotating and bending tests were carried out on the standard parts after cutting process for the workpiece. The influence of tool wear on fatigue life was revealed by fracture surface morphology and fatigue life study. The results provide theoretical support for control of residual stress and the fatigue property of the machined surface under the actual working conditions.
基金Funded by the National Natural Science Foundation of China(Nos.11202093 and 11662010)
文摘The wavy interface for similar or the same metal explosive welding（EXW） and the universal mechanism of wavy interface formation in EXW were studied in this work. Based on a new established model, it was deduced that the evolution frequencies of the instability were constrained in a limited range. Then experiments of identical metal EXW were performed and welding interfaces were characterized for examining the final morphology. By calculating the fractal dimensions and multifractal spectra of welding interface, the fractal characteristics of interface were revealed and a quantitative description was achieved for EXW interface structure. Thus, the formation, evolution and final morphology of wavy interface were systemically researched.
基金Supported by the National Natural Science Foundation of China(No.51475220)State Foundation of Laboratory of Advanced Brazing Filler Metals&Technology(Zhengzhou Research Institute of Mechanical Engineering)(No.SKLABFMT-2015-03)High Level Talent Plan of Jiangsu Normal University(No.YQ2015002)
文摘ZnO whiskers observation on the surface of SnZn/Cu solder joints in concentrator silicon solar cells solder layer is reported. In the experiment,SnZn/Cu samples are left in laboratory after reflow soldering for two years before an examination by SEM,then ZnO whiskers can be observed obviously,which grows out from the rich-Zn phase of the samples and causes electrical short circuit in the electronics appliances,which demonstrates that the SnZn solder shows a risk for the short circuiting failure of an electronic device. Moreover,the growth mechanism of ZnO whiskers is researched based on cracked oxide theory,which provides the reference support for SnZn solders application.
文摘The B Al permeation layers of Steel 45 were studied by means of SEM, TEM and XRD. The formation and growth model of permeation layer was proposed. The layer formation, growth and the migration behaviors of B were discussed. It is suggested that the diffusion of Al is deferred when the surface was covered by borides and aluminize compounds are surrounded by borides with the further growing of borides.
基金Science Fund of Key Laboratory of Intel-ligent Control Theory and Application of High Academies in Liaoning Province (No.200521303)
文摘PI （proportional-integral） control algorithm is applied to control WlP （work-in-progress） in a discrete manufacturing system, where the cascade control of PI controllers is presented. It is in the frequency domain that the PI controller is designed with constraints on sensitivity options to ensure the stability and robustness of its parameters. A case is evaluated on a motorcycle engine crankcase production system, whose simulation results confirm that demand fluctuations can be compensated by PI controllers under a normal demand. PI controllers also possess low sensitivity to the distribution of production times.
基金supported by National Natural Science Foundation of China(Grant No.51375170)Open Fund of State Key Lab of Environmental Adaptability for Industrial Products of China
文摘The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant＇s thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant＇s local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc（ASHRAE） Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant＇s thermal responses, including the skin temperature and the thermal sensation. The skin temperaWa-e and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in real life traffic is presented. The investigation result indicates that the skin temperature is a robust index to evaluate the thermal sensation. Applying the skin temperature to designing and controlling parameters of the heating, ventilation and air conditioning（HVAC） system may benefit the thermal comfort and reducing energy consumption.
基金Item Sponsored by National High Technology Research and Development Program(863Program)of China(2007AA03Z113)
文摘The microstructures and mechanical properties of the ductile cast iron （DI） specimens obtained by lost foam casting （LFC） with and without vibration were investigated. The results indicate that the number of the graphite nodule increases from 175 mm 2 of the specimens produced by LFC without vibration to 334 mm^-2 of the specimens produced by LFC with vibration, and the thickness of the ferrite shell increases. Meanwhile, the amount of the carbides decreases in the specimens produced by LFC with vibration and the granule structure then forms. These are mainly attributed to the ＂crystal shower＂ caused by the vibration. In addition, the tensile strength and elongation of DI specimens produced by LFC with vibration are improved due to the dispersion-strengthening of refined carbide and Dearlite colonv, uniform distribution of the graphite nodule, and increase of the amount of dimples and tearing edges.
基金Supported by the National Natural Science Foundation of China(51375519)the Chongqing Graduate Education Innovation Fund Project(CYS18223)the Chongqing University of Arts and Sciences Graduate School Research Project(M2018ME16)
文摘To improve the characteristics of wet multi-disc brakes (WMDBs), the WMDBs of the drive axles of mining trucks were studied. A model was established to predict the phenomenon of drag characteristics during wet brake non-engagement by considering the combined effect of surface grooves, film shrinkage, and laminar Navier-Stokes (N-S) equations. The model was used to study drag torque and temperature variation of the wet brakes for different volume flows, dynamic viscosities, and friction pair clearances. The simulation results indicated that the peak torque decreased when the clearance of the friction pair increased. Additionally, the peak torque increased when the volume flow increased and when the cooling liquid dynamic viscosity increased. The model was more accurate than a traditional forecasting system when considering the role of surface grooves and oil film shrinkage in actual working conditions.
基金Sponsored by the Natural Science Foundation of Heilongjiang Province of China(Grant No.LC201428,F201429)
文摘The paper is concerned with stabilization problem for a class of stochastic switching systems with time-delay in the detection of switching signal. By using binomial model,Poisson process,and Wiener process to describe time-delay, switching signal, and exogenous disturbance, respectively, the system under investigation is entirely set in a stochastic framework. The influence of the random time-delay is combined into reconstructing the switching signal of overall closed-loop system and changes the distribution property of switching points. Therefore,based on the asymptotical behaviors of Poisson processes and Wiener processes,the almost surely exponential stability conditions are established. Furthermore,a design methodology is posed for solving the stabilization control.
文摘The compensation current of the arc-suppressing coil makes the phase and amplitude of zero-sequence measurement current of the earthed fault feeder to vary. It is very hard to detect the fault feeder by using existing detectors based on single method. In this paper, integrative feeder selection strategy—zero sequence current increment method and the direction of transient current— is put forward. Based on the integrative feeder selection strategy, the design of fault-feeder selection device for one-phase-to ground fault on resonance grounding system is presented. For the purpose of testing and validating the operating principle of the device, the experiment of single-phase-to-ground fault has been carried out on the simulation of 1.2 kV power network. The results from many repeat experiments show that stability of the fault selection device is satisfactory.
基金Supported by the National Natural Science Foundation of China(No.51475220)the State Foundation of Laboratory of Advanced Brazing Filler Metals & Technology(Zhengzhou Research Institute of Mechanical Engineering)(No.SKLABFMT-2015-03)High Level Talent Plan of Jiangsu Normal University(No.YQ2015002)
文摘Hillock Sn whiskers in Sn0.3Ag0.7Cu solder are investigated in 20 seconds in corrosive climate(95% methanol and 5% nitric acid),and the growth mechanism of hillock Sn whiskers is studied.The results indicate that hillock Sn whiskers are formed near the interface of Sn0.3Ag0.7Cu/Cu solder joints,and small corrosion pits provide conceive sites for Sn whiskers. Moreover,compressive stress induced by IMC reaction and oxidation for the whisker growth may be suggested as the driving force.
基金supported by The National Natural Science Foundation of China(Project No.51576207)
文摘So far,Maisotsenko cycle has been applied to many fields such as heating ventilation and air-conditioning,power industry,chemical production,and so on.A lot of researches about classical thermodynamic analyses of Maisotsenko cycle have been made.A new cycle model of combined Diesel and Maisotsenko cycles considering heat transfer loss(HTL),piston friction loss(PFL)and internal irreversible loss(IIL)was proposed in this paper.By using the finite time thermodynamic(FTT)theory,the power and efficiency performances of the Maisotsenko-Diesel cycle(MDC)were studied.Effects of mass flow rate(MFR)of water injection in the Maisotsenko air saturator(MAS)and the other parameters related to the design of Diesel engine on the optimal cycle performances were analyzed.Furthermore,it was testified that irreversible MDC was superior than conventional irreversible Diesel cycle in both power output and thermal efficiency.The results can expand the application of Maisotsenko cycle(M-cycle)and provide some theoretical guidelines for the practical devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.51675250&51705203)the Natural Science Foundation of Jiangsu Province(Grant No.BK20160183)the Open Foundation of State Key Lab of Digital Manufacturing Equipment&Technology(Grant No.DMETKF2016005)
文摘Solder bumps are widely used in surface mount components, which provide electrical and mechanical connection between the chip/package and the substrate. As the solder bump getting smaller in dimension and pitch, it becomes more difficult to inspect the solder defects hidden in the IC package. In this paper, an intelligent inspection method using the scanning acoustic microscopy(SAM) and the fuzzy C-means(FCM) algorithm was investigated. A flip chip package of FA10 was chosen as the test sample. The SAM tests of FA10 were carried out in C-scan mode. The sub-image of every solder bump was segmented from the SAM image. The statistical features were then calculated and adopted for clustering of solder bumps using the FCM algorithm. The recognition results of FCM reached a high accuracy of 94.3%. The intelligent system is effective for defect inspection in high density packages.
基金Project supported by the National Natural Science Foundation of China(No.60666002)
文摘This paper designs a 3 × 3 light emitting diode （LED） array with a total power of 9 W, presents a thermal analysis of plate fin, in-line and staggered pin fin heat sinks for a high power LED lighting system, and develops a 3D one-fourth finite element （FE） model to predict the system temperature distribution. Three kinds of heat sinks are compared under the same conditions. It is found that LED chip junction temperature is 48.978℃ when the fins of heat sink are aligned alternately.
基金supported by the National Natural Science Foundation of China(Grant Nos.51305179&51305177)the Natural Science Foundation of Jiangsu Higher Education Institutions(Grant No.13KJB510009)
文摘Solder bump technology has been widely used in electronic packaging. With the development of solder bumps towards higher density and finer pitch, it is more difficult to inspect the defects of solder bumps as they are hidden in the package. A nondestructive method using the transient active thermography has been proposed to inspect the defects of a solder bump, and we aim at developing an intelligent diagnosis system to eliminate the influence of emissivity unevenness and non-uniform heating on defects recognition in active infrared testing. An improved fuzzy c-means(FCM) algorithm based on the entropy weights is investigated in this paper. The captured thermograms are preprocessed to enhance the thermal contrast between the defective and good bumps. Hot spots corresponding to 16 solder bumps are segmented from the thermal images. The statistical features are calculated and selected appropriately to characterize the status of solder bumps in FCM clustering. The missing bump is identified in the FCM result, which is also validated by the principle component analysis. The intelligent diagnosis system using FCM algorithm with the entropy weights is effective for defects recognition in electronic packages.
文摘CeO2 nanocrystals with different morphologies were synthesized by adjusting the pH value of the starting solution in water-in-oil microemulsion. The obtained samples were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）. thermogravimetric analysis and different thermal analysis （TGA/DTA）, Brunauer-Emmet-Teller （BET） surface area measurement, ultraviolet-visible absorption （UV-vis） spectroscopy and photoluminescence （PL） spectroscopy. Results show that the mor- phologies of CeO2 were transformed from granular to spherical and to rod-like while the pH of the starting solution varied from 5 to 8 and to 11. All samples were indexed to the phase of Ce02 and Ce（OH）4, and the molar ratio of Ce02 to Ce（OH）4 was deduced to be about 0.25, The morphologies of CeO2 nanocrystals had but slight influence on their specific surface areas, UV-vis spectra and PL spectra, The band gap energies of different morphological samples were estimated by UV-vis spectroscopic method,
基金supported by the National Natural Science Foundation of China (50975276 and 50475164)the Ph.D. Programs Foundation of Ministry of Education of China (200802900513)
文摘To obtain more accurate correlation dimension estimations for chaotic time series, a novel scaling region identification method is developed. First, points that obviously do not belong to the scaling region associated with the whole double logarithm correlation integral curve are removed using the K-means algorithm. Second, a point-slope-error algorithm is developed to recognize a possible scaling region. Third, the K-means algorithm is used again to further remove a small interval of interfering points in the possible scaling region to obtain a more precise scaling region. The correlation dimension of four typical chaotic attractors and five curves generated by the Weierstrass-Mandelbrot fractal function were calculated using the proposed method. These calculated values were very close to the respective theoretical fractal dimensions. Moreover, the effectiveness of our method in identifying the scaling region was compared with existing methods. Results show that our method can distinguish the scaling region objectively, accurately, automatically and quickly, making estimations of the correlation dimension more precise and affording significant improvements in nonlinear analysis.
