Micro-tubes manufactured by hydro-forming techniques have now been widely used in medical and microelectronics applica- tions. One of the difficulties in forming such parts is the control of localized necking in the i...Micro-tubes manufactured by hydro-forming techniques have now been widely used in medical and microelectronics applica- tions. One of the difficulties in forming such parts is the control of localized necking in the initial stages of the deformation/forming process. A lack of microstructural information causes conventional macro-mechanics finite element(FE) tools to break down when used to investigate the localized microstructure evolution and necking encountered in micro-forming. An effort has been made to create an integrated crystal plasticity finite element(CPFE) system that enables micro-forming process simulations to be carried out easily, with the important features in forming micro-parts captured by the model. Based on Voronoi tessellation and probability theory, a virtual GRAIN(VGRAIN) system is created for generating grains and grain boundaries for micro-materials. Numerical procedures are devel- oped to link the physical parameters of a material to the control variables in a Gamma distribution. A script interface is developed so that the virtual microstructure can be input to the commercial FE code, ABAQUS, for mesh generation. A simplified plane strain CPFE modeling technique is developed and used to capture localized thinning and failure features for hydro-forming of micro-tubes. Grains within the tube workpiece, their distributions and orientations are generated automatically by using the VGRAIN system. A set of crystal viscoplasticity constitutive equations are implemented in ABAQUS/Explicit by using the user-defined material subroutine, VUMAT. Lo- calized thinning is analyzed for different microstructures and deformation conditions of the material using the CPFE modeling technique. The research results show that locations of thinning in forming micro-tubes can be random, which are related to microstructure and grain orientations of the material. The proposed CPFE technique can be used to predict the locations of thinning in forming micro-tubes.展开更多
Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro...Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro-double gear with central shaft.In the paper,a novel hy-brid-forming process with two kinds of piercing method have been proposed to manufacture the micro-double gear using micro forming technology.The tests of hybrid forming process were carried out with two steps and the micro-double gear was successfully manufactured with good surface quality.The results also show that the hybrid micro-forming process with central piercing method can improve the defects of inclining shaft generated by double-ended piercing method.The quality evaluation of micro-double gear was conducted with surface roughness,micro-hardness and impact tests.The results show that the micro-double gear with good mechanical properties can meet the requirements of application for milli-machines.展开更多
Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a dis...Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.展开更多
Micro-pored CA6 -MA lightweight material with CAM: MA mass ratio of 7:3 was prepared using Al(OH) 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite + sweet potato starch...Micro-pored CA6 -MA lightweight material with CAM: MA mass ratio of 7:3 was prepared using Al(OH) 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite + sweet potato starch as pore forming agent (PFA) with an addition of 10 mass%, 20 mass% and 30 mass%, respectively. The starting materials were dry mixed, wet co-milled in a ball mill for 1 h. slip cast into cylindrical specimens with a diameter of 60 ram. and then calcined at 1 450 ℃ for 3 h. With the increase of PFA addition,, apparent porosity increases, and bulk density decreases. The influence of different PFAs on properties of the micro-pored LW CAM -MA aggregate was investigated. The achieved CAM - MA, by adding 30% sweet potato starch, has a porosity of 76. 8%, bulk density of 0. 78 g · cm^ - 3 and median pore size of 1.90 μm.展开更多
A low-power CO_2 laser is used to deposit Fe powder and mixture of Fe andcarbon powder on substrates respectively, and the macro and micro-structure of the formed samplesare investigated. It is demonstrated that most ...A low-power CO_2 laser is used to deposit Fe powder and mixture of Fe andcarbon powder on substrates respectively, and the macro and micro-structure of the formed samplesare investigated. It is demonstrated that most grains of these samples are equi-axed. This isderived from the high nucleation velocity in the shallow melt pool besides rapid solidification ofthe liquid-state alloy or metal. Bainitic structure, combination of pearlite and ferrite structureand ferrite structure are seen respectively in the samples involving various amounts of carbon owingto no martensitic transformation in these small samples.展开更多
Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the m...Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method(FEM). The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metallographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.展开更多
In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's ...In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks' scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick's sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140-170 μm are sintered at 900-950℃ for 30-60 min in practical manufacturing. In addition, two approaches to improve wick's porosity are also proposed through theoretical analysis, which suggests that the larger the wick's porosity, the better the heat transfer capabilities of the MHP.展开更多
Micro compression and micro extrusion experiments of ultrafine grained titanium cylindrical specimens in diameters of 4, 2, and 1 mm prepared by equal channel angular pressing(ECAP) were conducted on the micro plast...Micro compression and micro extrusion experiments of ultrafine grained titanium cylindrical specimens in diameters of 4, 2, and 1 mm prepared by equal channel angular pressing(ECAP) were conducted on the micro plastic forming test machine. The effects of specimen size, grain size, deformation temperature and extrusion speed on the flow stress and forming properties of the ultrafine grained pure titanium were investigated. The flow stress of ultrafine grained pure titanium specimen decreases with decreasing specimen size. The yield limit of pure titanium with refined grain prepared by ECAP is significantly greater than that of coarse grained specimen. Also the research results show that the flow stress of specimen increases with decreasing deformation temperature and with the increase of the strain rate, and the ultrafine grained pure titanium possesses good micro forming properties at deformation temperature of 300 ℃.展开更多
Layer-block tectonics (LBT) concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history o...Layer-block tectonics (LBT) concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea (SCS). Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei (Rifleman bank)-Andu (Ardasier bank) and Liyue (Reed bank) North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei- Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip detachment of basemental layerblock and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei Andu and Liyue-North Palawan intra-plate basin groups, respectively.展开更多
To obtain the form error of micro-structured surfaces robustly and accurately, a form er- ror evaluation method was developed based on the real coded genetic algorithm (RCGA). The meth- od employed the average squar...To obtain the form error of micro-structured surfaces robustly and accurately, a form er- ror evaluation method was developed based on the real coded genetic algorithm (RCGA). The meth- od employed the average squared distance as the matching criterion. The point to surface distance was achieved by use of iterative method and the modeling of RCGA for the surface matching was also presented in detail. Parameter selection for RCGA including the crossover rate and population size was discussed. Evaluation results of series simulated surfaces without form error show that this method can achieve the accuracy of root mean square deviation ( Sq ) less than 1 nm and surface pro- file error ( St ) less than 4 nm. Evaluation of the surfaces with different simulated errors illustrates that the proposed method can also robustly obtain the form error with nano-meter precision. The e- valuation of actual measured surfaces further indicates that the proposed method is capable of pre- cisely evaluating micro-structured surfaces.展开更多
In this paper,^(99m)Tc-TRODAT-1 Micro-SPECT (single-photon emission computed tomography) was used for imaging dopamine transporter (DAT) in retinas and to investigate the changes of DAT in retinas of guinea pigs with ...In this paper,^(99m)Tc-TRODAT-1 Micro-SPECT (single-photon emission computed tomography) was used for imaging dopamine transporter (DAT) in retinas and to investigate the changes of DAT in retinas of guinea pigs with form deprivation myopia.Pigmented guinea pigs aged 3 weeks were derided into form deprivation myopia (FDM) group (n=6) and normal control group (n=6).The test group wore translucent goggles randomly for 4 weeks, and both groups underwent biometric measurement (refraction and axial length) before and after the experiment. Micro-SPECT retinas imaging was performed at the 4^(th) week after injection of ^(99m)Tc-TRODAT-1.The retinas were clearly resolved in the images.The ratio of ^(99m)Tc-TRODAT-1 uptake in the myopic retinas (11.55±2.80) was 3.64±1.40 lower than that in the control eye (15.20±1.98),and 2.35±1.05 lower than that in the fellow eyes (13.90±2.04).The results showed that ^(99m)Tc-TRODAT-1 Micro-SPECT eye imaging can be used to trace the distribution and changes of DAT in retina,and DAT in the myopic retinas were lower than that in the normal control eyes and fellow eyes.Micro-SPECT may provide a new approach for further studies on the role of dopamine system in the experimental myopia.展开更多
The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel (abbreviated to V4 steel). Its microstructure, hot rolling process, and annealing treatment have been investigate...The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel (abbreviated to V4 steel). Its microstructure, hot rolling process, and annealing treatment have been investigated. Observed from the optical and electron microscopes, the as-sprayed V4 steel had the finer microstructure of uniform and equiaxial grains ,while after hot rolling for densification and spheroidized annealing, the V4 steel obtained an excellent spheroidized structure that is favorable to subsequent quenching and tempering treatment. The spheroidized structure and level of annealed hardness of the V4 steel are almost the same as expensive imported powder metallurgy the V4 steel. It is difficult to produce V4 steel with the conventional ingot metallurgical technique, so the multi-step and high-cost powder metallurgy method is generally used at present. Compared to the powder metallurgy technique, using the spray forming technique to produce the V4 steel has obvious advantages and potential market competitiveness in reducing production costs, simplifying working process, and shortening the production cycle.展开更多
Metallic glasses(MGs)are considered as the ideal materials for miniature fabrication because of their excellent micro thermoplastic forming ability in the supercooled liquid region.The understanding and controlling ...Metallic glasses(MGs)are considered as the ideal materials for miniature fabrication because of their excellent micro thermoplastic forming ability in the supercooled liquid region.The understanding and controlling of micro filling process are fundamental for miniature fabrication and their applications,yet presently remain unresolved issues.A universal kinetic equation was proposed to describe the filling kinetics of viscous metallic glass supercooled liquid in micro molds with general cross sectional shapes by using a Pdbased MG as the modeling material and a series of potential applications based on the micro thermoplastic forming of the MG were developed.展开更多
Micro channel of T2 copper were molding through electronic-magnetic forming experiments.Laser scanning confocal microscope and contourgraph were used to measure the section profile and sheet thickness.The effects of v...Micro channel of T2 copper were molding through electronic-magnetic forming experiments.Laser scanning confocal microscope and contourgraph were used to measure the section profile and sheet thickness.The effects of voltage,shape of channel and discharge cycles on laws of metal flow were studied.Results showed that forming depth of micro channel and thinning of sheet thickness increased as the increasing of the voltage.Mold-filling capacity of components formed by two molds with different structures had been increased when the voltage was increased.Mold with semicircle structure facilitate the material flow and the forming depth of parts was relative large.Semicircle structure was better than taper structure in mold-filling capacity.A number of small pulse discharges can improve the forming quality and deformation,but local thinning in sheet metal leads to non-uniform distribution of thickness.展开更多
基金supported by the EuropeanFP6-IP Project"Integration of Manufacturing Systems for Mass-manufacture of Miniature/Micro-Products(MASMICRO)"
文摘Micro-tubes manufactured by hydro-forming techniques have now been widely used in medical and microelectronics applica- tions. One of the difficulties in forming such parts is the control of localized necking in the initial stages of the deformation/forming process. A lack of microstructural information causes conventional macro-mechanics finite element(FE) tools to break down when used to investigate the localized microstructure evolution and necking encountered in micro-forming. An effort has been made to create an integrated crystal plasticity finite element(CPFE) system that enables micro-forming process simulations to be carried out easily, with the important features in forming micro-parts captured by the model. Based on Voronoi tessellation and probability theory, a virtual GRAIN(VGRAIN) system is created for generating grains and grain boundaries for micro-materials. Numerical procedures are devel- oped to link the physical parameters of a material to the control variables in a Gamma distribution. A script interface is developed so that the virtual microstructure can be input to the commercial FE code, ABAQUS, for mesh generation. A simplified plane strain CPFE modeling technique is developed and used to capture localized thinning and failure features for hydro-forming of micro-tubes. Grains within the tube workpiece, their distributions and orientations are generated automatically by using the VGRAIN system. A set of crystal viscoplasticity constitutive equations are implemented in ABAQUS/Explicit by using the user-defined material subroutine, VUMAT. Lo- calized thinning is analyzed for different microstructures and deformation conditions of the material using the CPFE modeling technique. The research results show that locations of thinning in forming micro-tubes can be random, which are related to microstructure and grain orientations of the material. The proposed CPFE technique can be used to predict the locations of thinning in forming micro-tubes.
基金Funded by the Technology Research and Development Program of China (2006AA04Z331)Young Scholars of Heilongjiang Province (JC-05-11 and JC-06-07)
文摘Micro-gear is an important actuating component used widely in the micro electro mechanical systems(MEMS) devices.The technologies of micro-forming and precision assembly are urgently developed to manufacture the micro-double gear with central shaft.In the paper,a novel hy-brid-forming process with two kinds of piercing method have been proposed to manufacture the micro-double gear using micro forming technology.The tests of hybrid forming process were carried out with two steps and the micro-double gear was successfully manufactured with good surface quality.The results also show that the hybrid micro-forming process with central piercing method can improve the defects of inclining shaft generated by double-ended piercing method.The quality evaluation of micro-double gear was conducted with surface roughness,micro-hardness and impact tests.The results show that the micro-double gear with good mechanical properties can meet the requirements of application for milli-machines.
文摘Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.
文摘Micro-pored CA6 -MA lightweight material with CAM: MA mass ratio of 7:3 was prepared using Al(OH) 3, MgCO3 and CaCO3 as starting materials, and anthracite. sweet potato starch and anthracite + sweet potato starch as pore forming agent (PFA) with an addition of 10 mass%, 20 mass% and 30 mass%, respectively. The starting materials were dry mixed, wet co-milled in a ball mill for 1 h. slip cast into cylindrical specimens with a diameter of 60 ram. and then calcined at 1 450 ℃ for 3 h. With the increase of PFA addition,, apparent porosity increases, and bulk density decreases. The influence of different PFAs on properties of the micro-pored LW CAM -MA aggregate was investigated. The achieved CAM - MA, by adding 30% sweet potato starch, has a porosity of 76. 8%, bulk density of 0. 78 g · cm^ - 3 and median pore size of 1.90 μm.
文摘A low-power CO_2 laser is used to deposit Fe powder and mixture of Fe andcarbon powder on substrates respectively, and the macro and micro-structure of the formed samplesare investigated. It is demonstrated that most grains of these samples are equi-axed. This isderived from the high nucleation velocity in the shallow melt pool besides rapid solidification ofthe liquid-state alloy or metal. Bainitic structure, combination of pearlite and ferrite structureand ferrite structure are seen respectively in the samples involving various amounts of carbon owingto no martensitic transformation in these small samples.
基金supported by National Natural Science Foundation of China(Grant No.50675049)
文摘Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method(FEM). The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metallographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.
基金Key Project(50436010, U0834002) supported by the National Natural Science Foundation of ChinaProjects(50675070, 50705031) supported by the National Natural Science Foundation of China+1 种基金Project(8151064101000058) supported by the Natural Science Foundation of Guangdong Province,ChinaProject(E200909) supported by the Natural Science Foundation of Heilongjiang Province, China
文摘In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks' scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick's sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140-170 μm are sintered at 900-950℃ for 30-60 min in practical manufacturing. In addition, two approaches to improve wick's porosity are also proposed through theoretical analysis, which suggests that the larger the wick's porosity, the better the heat transfer capabilities of the MHP.
基金Funded by the National Natural Science Foundation of China(No.51474170)the SAN JIN Scholars Program
文摘Micro compression and micro extrusion experiments of ultrafine grained titanium cylindrical specimens in diameters of 4, 2, and 1 mm prepared by equal channel angular pressing(ECAP) were conducted on the micro plastic forming test machine. The effects of specimen size, grain size, deformation temperature and extrusion speed on the flow stress and forming properties of the ultrafine grained pure titanium were investigated. The flow stress of ultrafine grained pure titanium specimen decreases with decreasing specimen size. The yield limit of pure titanium with refined grain prepared by ECAP is significantly greater than that of coarse grained specimen. Also the research results show that the flow stress of specimen increases with decreasing deformation temperature and with the increase of the strain rate, and the ultrafine grained pure titanium possesses good micro forming properties at deformation temperature of 300 ℃.
基金The National Basic Research Program of China ("973") under contract Nos 2009CB2194 and 2007CB411700the Major Knowledge Innovation Programs of the Chinese Academy of Sciences under contract No. kzcx2-yw-203-01+2 种基金the National Natural Science Foundation of China of China under contract No. 40676039the National Program of Sustaining Science and Technology of China under contract No. 2006BAB19B02the Program of the Ministry of Land and Natural Resources of China under contract No. GT-YQ-QQ-2008-1-02
文摘Layer-block tectonics (LBT) concept, with the core of pluralistic geodynamic outlook and multilayer-sliding tectonic outlook, is one of new keys to study 3-dimensional solid and its 4-dimensional evolution history of global tectonic system controlled by global geodynamics system. The LBT concept is applied to study the lithospheric tectonics of the southern South China Sea (SCS). Based on the analysis of about 30 000 km of geophysical and geological data, some layer-blocks in the Nansha micro-plate can be divided as Nansha ultra-crustal layer-block, Zengmu crustal layer-block, Nanwei (Rifleman bank)-Andu (Ardasier bank) and Liyue (Reed bank) North Palawan crustal layer-blocks, Andu-Bisheng and Liyue-Banyue basemental layer-blocks. The basic characteristics of the basemental layer-blocks have been dicussed, and three intra-plate basin groups are identified. The intra-plate basins within Nansha micro-plate can be divided into three basin groups of Nanwei- Andu, Feixin-Nanhua, and Liyue-North Palawan based on the different geodynamics. In the light of pluralistic geodynamic concept, the upheaving force induced by the mid-crust plastic layer is proposed as the main dynamical force which causes the formation of the intra-plate basins within the Nansha micro-plate. Finally, models of a face-to-face dip-slip detachment of basemental layerblock and a unilateral dip-slip-detachment of basemental layer-block are put forward for the forming mechanisms of the Nanwei Andu and Liyue-North Palawan intra-plate basin groups, respectively.
基金Supported by the Programme of Introducing Talents of Discipline to Universities (B07018)
文摘To obtain the form error of micro-structured surfaces robustly and accurately, a form er- ror evaluation method was developed based on the real coded genetic algorithm (RCGA). The meth- od employed the average squared distance as the matching criterion. The point to surface distance was achieved by use of iterative method and the modeling of RCGA for the surface matching was also presented in detail. Parameter selection for RCGA including the crossover rate and population size was discussed. Evaluation results of series simulated surfaces without form error show that this method can achieve the accuracy of root mean square deviation ( Sq ) less than 1 nm and surface pro- file error ( St ) less than 4 nm. Evaluation of the surfaces with different simulated errors illustrates that the proposed method can also robustly obtain the form error with nano-meter precision. The e- valuation of actual measured surfaces further indicates that the proposed method is capable of pre- cisely evaluating micro-structured surfaces.
文摘In this paper,^(99m)Tc-TRODAT-1 Micro-SPECT (single-photon emission computed tomography) was used for imaging dopamine transporter (DAT) in retinas and to investigate the changes of DAT in retinas of guinea pigs with form deprivation myopia.Pigmented guinea pigs aged 3 weeks were derided into form deprivation myopia (FDM) group (n=6) and normal control group (n=6).The test group wore translucent goggles randomly for 4 weeks, and both groups underwent biometric measurement (refraction and axial length) before and after the experiment. Micro-SPECT retinas imaging was performed at the 4^(th) week after injection of ^(99m)Tc-TRODAT-1.The retinas were clearly resolved in the images.The ratio of ^(99m)Tc-TRODAT-1 uptake in the myopic retinas (11.55±2.80) was 3.64±1.40 lower than that in the control eye (15.20±1.98),and 2.35±1.05 lower than that in the fellow eyes (13.90±2.04).The results showed that ^(99m)Tc-TRODAT-1 Micro-SPECT eye imaging can be used to trace the distribution and changes of DAT in retina,and DAT in the myopic retinas were lower than that in the normal control eyes and fellow eyes.Micro-SPECT may provide a new approach for further studies on the role of dopamine system in the experimental myopia.
文摘The material selected for this work was the spray formed Vanadis4 high alloy cold working mould steel (abbreviated to V4 steel). Its microstructure, hot rolling process, and annealing treatment have been investigated. Observed from the optical and electron microscopes, the as-sprayed V4 steel had the finer microstructure of uniform and equiaxial grains ,while after hot rolling for densification and spheroidized annealing, the V4 steel obtained an excellent spheroidized structure that is favorable to subsequent quenching and tempering treatment. The spheroidized structure and level of annealed hardness of the V4 steel are almost the same as expensive imported powder metallurgy the V4 steel. It is difficult to produce V4 steel with the conventional ingot metallurgical technique, so the multi-step and high-cost powder metallurgy method is generally used at present. Compared to the powder metallurgy technique, using the spray forming technique to produce the V4 steel has obvious advantages and potential market competitiveness in reducing production costs, simplifying working process, and shortening the production cycle.
基金The financial support of the Science and Technology Innovation Commission Shenzhen(Grant Nos.JCYJ20150625102923775 and JCYJ20160520164903055)
文摘Metallic glasses(MGs)are considered as the ideal materials for miniature fabrication because of their excellent micro thermoplastic forming ability in the supercooled liquid region.The understanding and controlling of micro filling process are fundamental for miniature fabrication and their applications,yet presently remain unresolved issues.A universal kinetic equation was proposed to describe the filling kinetics of viscous metallic glass supercooled liquid in micro molds with general cross sectional shapes by using a Pdbased MG as the modeling material and a series of potential applications based on the micro thermoplastic forming of the MG were developed.
基金Item Sponsored by the National Natural Science Foundation of China[No.5083500250805035]
文摘Micro channel of T2 copper were molding through electronic-magnetic forming experiments.Laser scanning confocal microscope and contourgraph were used to measure the section profile and sheet thickness.The effects of voltage,shape of channel and discharge cycles on laws of metal flow were studied.Results showed that forming depth of micro channel and thinning of sheet thickness increased as the increasing of the voltage.Mold-filling capacity of components formed by two molds with different structures had been increased when the voltage was increased.Mold with semicircle structure facilitate the material flow and the forming depth of parts was relative large.Semicircle structure was better than taper structure in mold-filling capacity.A number of small pulse discharges can improve the forming quality and deformation,but local thinning in sheet metal leads to non-uniform distribution of thickness.