Diaphragm structures with micron scale play a significant role in microtransducers and micro-nano devices, and the performance of these devices depends mainly on the dynamic behaviour of diaphragms. Micro-diaphragms a...Diaphragm structures with micron scale play a significant role in microtransducers and micro-nano devices, and the performance of these devices depends mainly on the dynamic behaviour of diaphragms. Micro-diaphragms are treated commonly as membranes and in some cases as plates or plates in tension (called TD plates for short), but they also show in many cases the behaviour of plates in tension and supported by air spring (called TDK plates for short). Therefore, it is necessary to perform systematic research on the dynamic behaviour of micro-diaphragms, and establish a characterized mathematical description. This paper focuses on the TDK plates since they possess universality, gives the corresponding basic equations, and then derives analytical solutions of TDK circular plates under clamped and simply supported boundary conditions. This paper also gives a 3D plot representation of characteristic curved surfaces, revealing the transition from the TDK and TD plate to the pure plate or pure membrane behaviour; and further uses the value φ to determine the property of diaphragms. Its two extreme cases, i.e. φ = 0 and φ = ∞ , correspond to pure plate or pure membrane, respectively. Thus, membrane, plate and TD plate can be treated as special cases of TDK plate. In addition, this paper reveals that the presence of air-spring not only enhances the restoring force of diaphragm such that increases its natural frequencies, but also results in the resonance of a dynamic system consisting of diaphragm and air-spring. These analytical and computational results are significant for the understanding of the operation mechanism of capacitive microtransducers and their optimized design.展开更多
Micro-arc oxidation is a recently developed surface treatment technology under anodic oxidation. Through micro-arc oxidation, a ceramic coating is directly formed on the surface of magnesium alloy, by which its surfac...Micro-arc oxidation is a recently developed surface treatment technology under anodic oxidation. Through micro-arc oxidation, a ceramic coating is directly formed on the surface of magnesium alloy, by which its surface property is significantly improved. In this paper, a dense ceramic oxide coating was prepared on an AZ31 magnesium alloy by micro-arc oxidation in a NaOH-Na2SiO3-NaB407-（NaPO3）6 electrolytic solution. Micro-structure, surface morphology and phase composition were analysed using scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The tribological behavior of the micro-arc oxidation ceramic coating under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results showed that the AZ31 alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface micro-arc oxidation ceramic coating experienced much abated adhesion wear and scuffing under the same testing conditions. The micro-arc oxidation ceramic coating showed good friction-reducing and fair antiwear ability in dry sliding against the steel.展开更多
The dynamic recrystallization refinement of magnesium alloy AZ80 by compression tests was studied,and its effect on the mechanical properties was investigated.It is observed that the microstructure of the as-cast bill...The dynamic recrystallization refinement of magnesium alloy AZ80 by compression tests was studied,and its effect on the mechanical properties was investigated.It is observed that the microstructure of the as-cast billet with grain size of 240μm becomes refined to about 120,110,94 and 50μm after upsetting at 350℃ under strain rates of 0.01,0.1,1 and 10 s -1 respectively.The changes in the mechanical properties according to grain size show that yield strength significantly decreases with grain size increasing,while strain hardening exponent and micro hardness increase very sharply.Further,the grain size vs strain rate and change in Vickers micro hardness according to the various strain rates show that grain size and micro hardness decrease with strain rate increasing.展开更多
This article presents a study of vehicle acceleration distribution at a traffic signal stop line in an urban environment. Accurate representation of vehicle acceleration behavior provides important inputs to traffic s...This article presents a study of vehicle acceleration distribution at a traffic signal stop line in an urban environment. Accurate representation of vehicle acceleration behavior provides important inputs to traffic simulation models especially when traffic related emissions need to be estimated. A smart eye TDS （traffic data sensor） system was used to record vehicle trajectories, which were extracted to calculate vehicle acceleration profiles. This paper presents the acceleration distributions obtained from over 300 passenger-car acceleration cycles observed on site from the stop line up to a maximum speed of 40 km/h. These distributions are compared with the outputs from a traffic micro simulation tool modeling a similar stop line scenario. The comparison shows that measured accelerations present wider distribution and lower values than the micro simulation. This result highlights the importance of using acceleration distribution calibrated with real-world measured data rather than default values in order to estimate accurate emission levels.展开更多
Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addr...Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies.This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro-and photo-thermal energy conversion and also storage systems.A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6(GPA6)and Ti_(3)C_(2)T_(x)MXene/silver nanowire with Cellulose Micro/NanoFibers(CMNF)cryogens by using spark plasma sintering(SPS)based high-pressure hydrothermal treatment model.An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500℃to850℃.The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems,to increase energy output while minimizing losses.The silver nanowire is with a heat transfer coefficient of 78%,a mass remaining rate of 98.7%,and an energy storage efficiency of 23.8%.This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses,and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 60774053 and 60374044)
文摘Diaphragm structures with micron scale play a significant role in microtransducers and micro-nano devices, and the performance of these devices depends mainly on the dynamic behaviour of diaphragms. Micro-diaphragms are treated commonly as membranes and in some cases as plates or plates in tension (called TD plates for short), but they also show in many cases the behaviour of plates in tension and supported by air spring (called TDK plates for short). Therefore, it is necessary to perform systematic research on the dynamic behaviour of micro-diaphragms, and establish a characterized mathematical description. This paper focuses on the TDK plates since they possess universality, gives the corresponding basic equations, and then derives analytical solutions of TDK circular plates under clamped and simply supported boundary conditions. This paper also gives a 3D plot representation of characteristic curved surfaces, revealing the transition from the TDK and TD plate to the pure plate or pure membrane behaviour; and further uses the value φ to determine the property of diaphragms. Its two extreme cases, i.e. φ = 0 and φ = ∞ , correspond to pure plate or pure membrane, respectively. Thus, membrane, plate and TD plate can be treated as special cases of TDK plate. In addition, this paper reveals that the presence of air-spring not only enhances the restoring force of diaphragm such that increases its natural frequencies, but also results in the resonance of a dynamic system consisting of diaphragm and air-spring. These analytical and computational results are significant for the understanding of the operation mechanism of capacitive microtransducers and their optimized design.
基金supported by Scientific Research Common Program of Beijing Municipal Commission of Education (No.KM200510017005)Beijing Excellent Talent Nurture and Sponsor Project(20061D0500500151)
文摘Micro-arc oxidation is a recently developed surface treatment technology under anodic oxidation. Through micro-arc oxidation, a ceramic coating is directly formed on the surface of magnesium alloy, by which its surface property is significantly improved. In this paper, a dense ceramic oxide coating was prepared on an AZ31 magnesium alloy by micro-arc oxidation in a NaOH-Na2SiO3-NaB407-（NaPO3）6 electrolytic solution. Micro-structure, surface morphology and phase composition were analysed using scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The tribological behavior of the micro-arc oxidation ceramic coating under dry sliding against GCr15 steel was evaluated on a ball-on-disc test rig. The results showed that the AZ31 alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface micro-arc oxidation ceramic coating experienced much abated adhesion wear and scuffing under the same testing conditions. The micro-arc oxidation ceramic coating showed good friction-reducing and fair antiwear ability in dry sliding against the steel.
基金Project(cstc2009aa3012-1)supported by Science and Technology Committee of Chongqing,ChinaProject(20100470813)supported by China Postdoctoral Science FoundationProject(2010011511)supported by Sharing Fund of Chongqing University’s Large-Scale Equipment,China
文摘The dynamic recrystallization refinement of magnesium alloy AZ80 by compression tests was studied,and its effect on the mechanical properties was investigated.It is observed that the microstructure of the as-cast billet with grain size of 240μm becomes refined to about 120,110,94 and 50μm after upsetting at 350℃ under strain rates of 0.01,0.1,1 and 10 s -1 respectively.The changes in the mechanical properties according to grain size show that yield strength significantly decreases with grain size increasing,while strain hardening exponent and micro hardness increase very sharply.Further,the grain size vs strain rate and change in Vickers micro hardness according to the various strain rates show that grain size and micro hardness decrease with strain rate increasing.
文摘This article presents a study of vehicle acceleration distribution at a traffic signal stop line in an urban environment. Accurate representation of vehicle acceleration behavior provides important inputs to traffic simulation models especially when traffic related emissions need to be estimated. A smart eye TDS （traffic data sensor） system was used to record vehicle trajectories, which were extracted to calculate vehicle acceleration profiles. This paper presents the acceleration distributions obtained from over 300 passenger-car acceleration cycles observed on site from the stop line up to a maximum speed of 40 km/h. These distributions are compared with the outputs from a traffic micro simulation tool modeling a similar stop line scenario. The comparison shows that measured accelerations present wider distribution and lower values than the micro simulation. This result highlights the importance of using acceleration distribution calibrated with real-world measured data rather than default values in order to estimate accurate emission levels.
文摘Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies.This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro-and photo-thermal energy conversion and also storage systems.A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6(GPA6)and Ti_(3)C_(2)T_(x)MXene/silver nanowire with Cellulose Micro/NanoFibers(CMNF)cryogens by using spark plasma sintering(SPS)based high-pressure hydrothermal treatment model.An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500℃to850℃.The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems,to increase energy output while minimizing losses.The silver nanowire is with a heat transfer coefficient of 78%,a mass remaining rate of 98.7%,and an energy storage efficiency of 23.8%.This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses,and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials.
