This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micr...This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole bandwidth.Compared to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.展开更多
An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface ar...An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.展开更多
Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420°C and strain rate range of 0.01-10 s-1.A physically-bas...Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420°C and strain rate range of 0.01-10 s-1.A physically-based model was developed to accurately predict the flow stress.Meanwhile,processing maps were established to optimize hot working parameters.It is found that decreasing the strain rate or increasing the deformation temperature reduces the flow stress.The high activation energy is closely related to the pinning of dislocations from Si-containing dispersoids.Moreover,the deformed grains and the Si-containing dispersoids in the matrix are elongated perpendicular to the compression direction,and incomplete dynamic recrystallization(DRX)is discovered on the elongated boundaries in domain with peak efficiency.The flow instability is mainly attributed to the flow localization,brittle fracture of eutectic Si phase,and formation of adiabatic shear band.The optimum hot working window is 380-420°C and 0.03-0.28 s-1.展开更多
A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influ...A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area.展开更多
A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented. Then a microstructure model and a set of rheological constitutive relations for sott clays, which describe how t...A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented. Then a microstructure model and a set of rheological constitutive relations for sott clays, which describe how the rheological consolidation settlement develops, are established in the framework of the catastrophe theory. The validity of this model is verified by a series of rheological consolidation experiments with different loading rates. The experimental data show that creep deformation can be clearly observed in these tests, and the consolidation settlement is loading rate dependent. The characteristics of the deformation can be explained and reproduced successfully using the model. It can be concluded that only the biggest set of voids would collapse for one load increment. Parameters in the model, k and η, are gained by curve fitting. With only two free parameters, good fits of the data are achieved.展开更多
In order to characterizc large fluctuations of the financial markets and optimize financial portfolio, a new dynamic asset control strategy was proposed in this work. Firstly, a random process item with variable jump ...In order to characterizc large fluctuations of the financial markets and optimize financial portfolio, a new dynamic asset control strategy was proposed in this work. Firstly, a random process item with variable jump intensity was introduced to the existing discrete microstructure model to denote large price fluctuations. The nonparametric method of LEE was used for detecting jumps. Further, the extended Kalman filter and the maximum likelihood method were applied to discrete microstructure modeling and the estimation of two market potential variables： market excess demand and liquidity. At last, based on the estimated variables, an assets allocation strategy using evolutionary algorithm was designed to control the weight of each asset dynamically. Case studies on IBM Stock show that jumps with variable intensity are detected successfully, and the assets allocation strategy may effectively keep the total assets growth or prevent assets loss at the stochastic financial market.展开更多
The measurement of thickness of material removed between serial sections is a crucial step of three-dimensional reconstruction. Active contour model is an efficient method for contour detection of objects on an image....The measurement of thickness of material removed between serial sections is a crucial step of three-dimensional reconstruction. Active contour model is an efficient method for contour detection of objects on an image. Based on the segmentation of the FeAl/ZrO2 composite image by using adaptive threshold, the gradient vector flow (GVF) snake was used to detect the contour of the indent. The horizontal diagonal length and the vertical diagonal length of the indent contour were acquired by measuring the distance from the uppermost snaxel to the lowermost snaxel and that from the leftmost snaxel to the rightmost snaxel respectively. Then the final diagonal length was gotten by averaging the vertical diagonal length and the horizontal diagonal length. The Vickers indenter was made by a square pyramidal-shaped diamond with opposite faces at an angle of 136°, so the geometrical relation was established between the thickness of material removed between two successive serial sections and the difference of diagonal length on the two serial sections. Based on the relation, the thickness of material removed between two successive serial sections was calculated using the two successive diagonals.展开更多
A novel solid support adsorbent for CO2capture was developed by loading pentaethylenehexamine(PEHA)on commercially available mesoporous molecular sieve MCM-41 using wet impregnation method.MCM-41 samples before and af...A novel solid support adsorbent for CO2capture was developed by loading pentaethylenehexamine(PEHA)on commercially available mesoporous molecular sieve MCM-41 using wet impregnation method.MCM-41 samples before and after PEHA loading were characterized by X-ray powder diffraction,N2adsorption/desorption,thermal gravimetric analysis and scanning electron microscope to investigate the textural and thermo-physical properties.CO2adsorption performance was evaluated in a fixed bed adsorption system.Results indicated that the structure of MCM-41 was preserved after loading PEHA.Surface area and total pore volume of PEHA loaded MCM-41 decreased with the increase of loading.The working adsorption capacity of CO2could be significantly improved at 60%of PEHA loading and 75°C.The effect of the height of adsorbent bed was investigated and the best working adsorption capacity for MCM-41-PEHA-60 reached 165 mg·(g adsorbent)-1at 75°C.Adsorption/desorption circle showed that the CO2working adsorption capacity of MCM-41-PEHA kept stable.展开更多
The properties of the high spin states of the neutron-rich 98-102Sr and 100-104Zr isotopes have been st udied using the projected shell model. In particular, the upbending phenomenon is investigated for these isotopes...The properties of the high spin states of the neutron-rich 98-102Sr and 100-104Zr isotopes have been st udied using the projected shell model. In particular, the upbending phenomenon is investigated for these isotopes along the yrast line. The results show that the occurrence of upbending phenomenon is attributed to the band crossing between ground state band and 2-qp neutron band having configuration 2vh11/2[-3/2, 5/2], K = 1. Furthermore, the neutron two-quasi-particle structure of side bands in 98SR-102Zr is discussed in this paper.展开更多
By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for produ...By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for producing both regular and irregular three dimensional(3 D) microstructures. It was found that there was a dramatic coupling effect between the confined etching process and the slow-rate mechanical motion because of the concentration distribution of electrogenerated etchant caused by the latter. In this article, the coupling effect was investigated systemically by comparing the etchant diffusion, etching depths and profiles in the non-confined and confined machining modes. A two-dimensional(2 D) numerical simulation model was proposed to analyze the diffusion variations during the ECMM process, which is well verified by the machining experiments. The results showed that, in the confined machining mode, both the machining resolution and the perpendicularity tolerance of side faces were improved effectively. Furthermore, the theoretical modeling and numerical simulations were proved valuable to optimize the technical parameters of the ECMM process.展开更多
A common phenomenon of fatigue test data reported in the open literature such as S-N curves exhibits the scatter of points for a group of same specimens under the same loading condition.The reason is well known that t...A common phenomenon of fatigue test data reported in the open literature such as S-N curves exhibits the scatter of points for a group of same specimens under the same loading condition.The reason is well known that the microstructure is different from specimen to specimen even in the same group.Specifically,a fatigue failure process is a multi-scale problem so that a fatigue failure model should have the ability to take the microscopic effect into account.A physically-based trans-scale crack model is established and the analytical solution is obtained by coupling the micro-and macro-scale.Obtained is the trans-scale stress intensity factor as well as the trans-scale strain energy density(SED)factor.By taking this trans-scale SEDF as a key controlling parameter for the fatigue crack propagation from micro-to macro-scale,a trans-scale fatigue crack growth model is proposed in this work which can reflect the microscopic effect and scale transition in a fatigue process.The fatigue test data of aluminum alloy LY12 plate specimens is chosen to check the model.Two S-N experimental curves for cyclic stress ratio R=0.02 and R=0.6 are selected.The scattering test data points and two S-N curves for both R=0.02 and R=0.6 are exactly re-produced by application of the proposed model.It is demonstrated that the proposed model is able to reflect the multiscaling effect in a fatigue process.The result also shows that the microscopic effect has a pronounced influence on the fatigue life of specimens.展开更多
文摘This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole bandwidth.Compared to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.
基金Project(60806006) supported by the National Natural Science Foundation of China
文摘An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.
基金Project(51375502)supported by the National Natural Science Foundation of ChinaProject(2015CX002)supported by the Innovation-driven Plan in Central South University,China+2 种基金Project(2016RS2006)supported by the Science and Technology Leading Talent in Hunan Province,ChinaProject(Q2015140)supported by the Program of Chang Jiang Scholars of Ministry of Education,ChinaProject(2016JJ1017)supported by the Natural Science Foundation for Distinguished Young Scholars of Hunan Province,China
文摘Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420°C and strain rate range of 0.01-10 s-1.A physically-based model was developed to accurately predict the flow stress.Meanwhile,processing maps were established to optimize hot working parameters.It is found that decreasing the strain rate or increasing the deformation temperature reduces the flow stress.The high activation energy is closely related to the pinning of dislocations from Si-containing dispersoids.Moreover,the deformed grains and the Si-containing dispersoids in the matrix are elongated perpendicular to the compression direction,and incomplete dynamic recrystallization(DRX)is discovered on the elongated boundaries in domain with peak efficiency.The flow instability is mainly attributed to the flow localization,brittle fracture of eutectic Si phase,and formation of adiabatic shear band.The optimum hot working window is 380-420°C and 0.03-0.28 s-1.
基金Supported by the National Key Basic R&D Program ("973" Program, No. 2009CB219905 and 2009CB219907)the Program for Changjiang Scholars and Innovative Research Teams in Universities (No. IRT0936)
文摘A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area.
基金Project(51079126) supported by the National Natural Science Foundation of ChinaProject(Y1090971) supported by the Natural Science Foundation of Zhejiang Province, China
文摘A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented. Then a microstructure model and a set of rheological constitutive relations for sott clays, which describe how the rheological consolidation settlement develops, are established in the framework of the catastrophe theory. The validity of this model is verified by a series of rheological consolidation experiments with different loading rates. The experimental data show that creep deformation can be clearly observed in these tests, and the consolidation settlement is loading rate dependent. The characteristics of the deformation can be explained and reproduced successfully using the model. It can be concluded that only the biggest set of voids would collapse for one load increment. Parameters in the model, k and η, are gained by curve fitting. With only two free parameters, good fits of the data are achieved.
基金Projects(71271215,71221061) supported by the National Natural Science Foundation of ChinaProject(2011DFA10440) supported by the International Science&Technology Cooperation Program of ChinaProject(CX2012B067) supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘In order to characterizc large fluctuations of the financial markets and optimize financial portfolio, a new dynamic asset control strategy was proposed in this work. Firstly, a random process item with variable jump intensity was introduced to the existing discrete microstructure model to denote large price fluctuations. The nonparametric method of LEE was used for detecting jumps. Further, the extended Kalman filter and the maximum likelihood method were applied to discrete microstructure modeling and the estimation of two market potential variables： market excess demand and liquidity. At last, based on the estimated variables, an assets allocation strategy using evolutionary algorithm was designed to control the weight of each asset dynamically. Case studies on IBM Stock show that jumps with variable intensity are detected successfully, and the assets allocation strategy may effectively keep the total assets growth or prevent assets loss at the stochastic financial market.
基金Sponsored by the National Natural Science Foundation of China (Grant No.60873089)the Doctoral Fund of Shandong Province( Grant No.2007BS04018)
文摘The measurement of thickness of material removed between serial sections is a crucial step of three-dimensional reconstruction. Active contour model is an efficient method for contour detection of objects on an image. Based on the segmentation of the FeAl/ZrO2 composite image by using adaptive threshold, the gradient vector flow (GVF) snake was used to detect the contour of the indent. The horizontal diagonal length and the vertical diagonal length of the indent contour were acquired by measuring the distance from the uppermost snaxel to the lowermost snaxel and that from the leftmost snaxel to the rightmost snaxel respectively. Then the final diagonal length was gotten by averaging the vertical diagonal length and the horizontal diagonal length. The Vickers indenter was made by a square pyramidal-shaped diamond with opposite faces at an angle of 136°, so the geometrical relation was established between the thickness of material removed between two successive serial sections and the difference of diagonal length on the two serial sections. Based on the relation, the thickness of material removed between two successive serial sections was calculated using the two successive diagonals.
基金Supported by the National Natural Science Foundation of China(20836008,21176132)the Special Research Fund for the Doctoral Program of the Ministry of Education of China(20101012174)
文摘A novel solid support adsorbent for CO2capture was developed by loading pentaethylenehexamine(PEHA)on commercially available mesoporous molecular sieve MCM-41 using wet impregnation method.MCM-41 samples before and after PEHA loading were characterized by X-ray powder diffraction,N2adsorption/desorption,thermal gravimetric analysis and scanning electron microscope to investigate the textural and thermo-physical properties.CO2adsorption performance was evaluated in a fixed bed adsorption system.Results indicated that the structure of MCM-41 was preserved after loading PEHA.Surface area and total pore volume of PEHA loaded MCM-41 decreased with the increase of loading.The working adsorption capacity of CO2could be significantly improved at 60%of PEHA loading and 75°C.The effect of the height of adsorbent bed was investigated and the best working adsorption capacity for MCM-41-PEHA-60 reached 165 mg·(g adsorbent)-1at 75°C.Adsorption/desorption circle showed that the CO2working adsorption capacity of MCM-41-PEHA kept stable.
基金Supported by the Natural Science Foundation of China under Grant Nos. 10975051, 10979024, 10905021the Natural Science Foundation of Zhejiang province, China under Grant No. Y6090210the Natural Science Foundation of Huzhou under Grant No. 2010YZll
文摘The properties of the high spin states of the neutron-rich 98-102Sr and 100-104Zr isotopes have been st udied using the projected shell model. In particular, the upbending phenomenon is investigated for these isotopes along the yrast line. The results show that the occurrence of upbending phenomenon is attributed to the band crossing between ground state band and 2-qp neutron band having configuration 2vh11/2[-3/2, 5/2], K = 1. Furthermore, the neutron two-quasi-particle structure of side bands in 98SR-102Zr is discussed in this paper.
基金supported by the National Natural Science Foundation of China (21573054, 21327002, 91323303, 21621091)the Joint Funds Key Project of the National Natural Science Foundation of China (U1537214)+2 种基金the State Key Program of National Natural Science of China (51535003)Self-Planned Task (SKLRS201606B) of State Key Laboratory of Robotics and System (HIT)the Open Project of the State Key Laboratory for Manufacturing Systems Engineering (Xi'an Jiaotong University)
文摘By introducing the mechanical motion into the confined etchant layer technique(CELT), we have developed a promising ultraprecision machining method, termed as electrochemical mechanical micromachining(ECMM), for producing both regular and irregular three dimensional(3 D) microstructures. It was found that there was a dramatic coupling effect between the confined etching process and the slow-rate mechanical motion because of the concentration distribution of electrogenerated etchant caused by the latter. In this article, the coupling effect was investigated systemically by comparing the etchant diffusion, etching depths and profiles in the non-confined and confined machining modes. A two-dimensional(2 D) numerical simulation model was proposed to analyze the diffusion variations during the ECMM process, which is well verified by the machining experiments. The results showed that, in the confined machining mode, both the machining resolution and the perpendicularity tolerance of side faces were improved effectively. Furthermore, the theoretical modeling and numerical simulations were proved valuable to optimize the technical parameters of the ECMM process.
基金supported by the National Natural Science Foundation of China(Grant No.51378081)
文摘A common phenomenon of fatigue test data reported in the open literature such as S-N curves exhibits the scatter of points for a group of same specimens under the same loading condition.The reason is well known that the microstructure is different from specimen to specimen even in the same group.Specifically,a fatigue failure process is a multi-scale problem so that a fatigue failure model should have the ability to take the microscopic effect into account.A physically-based trans-scale crack model is established and the analytical solution is obtained by coupling the micro-and macro-scale.Obtained is the trans-scale stress intensity factor as well as the trans-scale strain energy density(SED)factor.By taking this trans-scale SEDF as a key controlling parameter for the fatigue crack propagation from micro-to macro-scale,a trans-scale fatigue crack growth model is proposed in this work which can reflect the microscopic effect and scale transition in a fatigue process.The fatigue test data of aluminum alloy LY12 plate specimens is chosen to check the model.Two S-N experimental curves for cyclic stress ratio R=0.02 and R=0.6 are selected.The scattering test data points and two S-N curves for both R=0.02 and R=0.6 are exactly re-produced by application of the proposed model.It is demonstrated that the proposed model is able to reflect the multiscaling effect in a fatigue process.The result also shows that the microscopic effect has a pronounced influence on the fatigue life of specimens.
