An increase in RE element content in Mg alloys promotes the grain boundary precipitate,which affects the mechanical properties.However,the influence of grain boundary precipitates on microstructure of Mg-RE alloys dur...An increase in RE element content in Mg alloys promotes the grain boundary precipitate,which affects the mechanical properties.However,the influence of grain boundary precipitates on microstructure of Mg-RE alloys during ageing and their role on ductility of the aged alloy is unclear.In this work,hot extrusion and ageing treatment were performed for Mg-9Gd-2Y-xNd-0.2Zr(x=1 wt.%and 3 wt.%)alloys,and grain boundary precipitates were formed in the extruded Mg-9Gd-2Y-3Nd-0.2Zr alloy due to the increase of Nd content.The extruded alloys exhibit a complete dynamic recrystallization(DRX)microstructure and a texture with the<0001>orientation parallel to the extrusion direction(ED).In addition,a large amount of fiber microstructures distributed by the second phase along the ED were formed in the Mg-9Gd-2Y-3Nd-0.2Zr alloy,while only a small amount of the second phase was observed in the Mg-9Gd-2Y-1Nd-0.2Zr alloy.After ageing treatment,a large amount ofβ'phase precipitated inside the grains.The strength of the Mg-9Gd-2Y-1Nd-0.2Zr alloy increased from 202 MPa to 275 MPa but the elongation decreased from 12.8%to 2.6%,and the strength of the Mg-9Gd-2Y-3Nd-0.2Zr alloy increased from 212 MPa to 281 MPa but the elongation decreased from 13.7%to 6.2%.Among them,the Mg-9Gd-2Y-3Nd-0.2Zr alloy showed good overall mechanical properties,especially the elongation of the aged alloy was 58%higher than that of the Mg-9Gd-2Y-1Nd-0.2Zr alloy.The increase in ductility of the aged Mg-9Gd-2Y-3Nd-0.2Zr alloy attributed to the grain boundary precipitate promotes the formation of a large number of precipitation free zones(PFZs)with widths of 130-150 nm during ageing treatment.展开更多
Pb(Zr,Ti)O_(3)-Pb(Zn_(1/3)Nb_(2/3))O_(3) (PZT-PZN) based ceramics, as important piezoelectric materials, have a wide range of applications in fields such as sensors and actuators, thus the optimization of their piezoe...Pb(Zr,Ti)O_(3)-Pb(Zn_(1/3)Nb_(2/3))O_(3) (PZT-PZN) based ceramics, as important piezoelectric materials, have a wide range of applications in fields such as sensors and actuators, thus the optimization of their piezoelectric properties has been a hot research topic. This study investigated the effects of phase boundary engineering and domain engineering on (1-x)[0.8Pb(Zr_(0.5)Ti_(0.5))O_(3)-0.2Pb(Zn_(1/3)Nb_(2/3))O_(3)]-xBi(Zn_(0.5)Ti_(0.5))O_(3) ((1-x)(0.8PZT-0.2PZN)- xBZT) ceramic to obtain excellent piezoelectric properties. The crystal phase structure and microstructure of ceramic samples were characterized. The results showed that all samples had a pure perovskite structure, and the addition of BZT gradually increased the grain size. The addition of BZT caused a phase transition in ceramic samples from the morphotropic phase boundary (MPB) towards the tetragonal phase region, which is crucial for optimizing piezoelectric properties. By adjusting content of BZT and precisely controlling position of the phase boundary, the piezoelectric performance can be optimized. Domain structure is one of the key factors affecting piezoelectric performance. By using domain engineering techniques to optimize grain size and domain size, piezoelectric properties of ceramic samples have been significantly improved. Specifically, excellent piezoelectric properties (piezoelectric constant d_(33)=320 pC/N, electromechanical coupling factor kp=0.44) were obtained simultaneously for x=0.08. Based on experimental results and theoretical analysis, influence mechanisms of phase boundary engineering and domain engineering on piezoelectric properties were explored. The study shows that addition of BZT not only promotes grain growth, but also optimizes the domain structure, enabling the polarization reversal process easier, thereby improving piezoelectric properties. These research results not only provide new ideas for the design of high-performance piezoelectric ceramics, but also lay a theoretical foundation for development of related electronic devices.展开更多
This paper presents a brief summary of the three development stages of investigation on the transpiration cooling and its control for aircraft, missiles and electromagnetic gun, then the control problem of the distrib...This paper presents a brief summary of the three development stages of investigation on the transpiration cooling and its control for aircraft, missiles and electromagnetic gun, then the control problem of the distributed parameters system with a moving boundary is derived. It introduces the mathematical model of the transpiration cooling control, its control characteristics, and the present situation of the experimental and theoretical study on this problem. This paper also describes the main study results and the existing problems. The prospective application is also reported. The major references in every developing stage are listed systematically for further study.展开更多
Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique opportunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous maj...Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique opportunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous major global geological events.The basin had been undergone three stages of tectonic evolution during展开更多
A class of singularly perturbed initial boundary value problems for the reaction diffusion equations in a part of domain are considered. Using the operator theory the asymptotic behavior of solution for the problems i...A class of singularly perturbed initial boundary value problems for the reaction diffusion equations in a part of domain are considered. Using the operator theory the asymptotic behavior of solution for the problems is studied.展开更多
The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of th...The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of vortices.In this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving body.We designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered to recover high-value warheads.展开更多
As to solve the online monitoring of the inner temperatur e and freezing profile of the reaction shaft of flash smelting furnace, simulation of the wall in the reaction shaft in a flash smelting furnace was made throu...As to solve the online monitoring of the inner temperatur e and freezing profile of the reaction shaft of flash smelting furnace, simulation of the wall in the reaction shaft in a flash smelting furnace was made through numerical computation. The computational results are very near the data got in s ite. The error of the moving boundary is approximately 3%, and that of the tempe rature is less than 5%. It is proved that the simulation software is applicable for practice to monitor the temperature and moving boundary inside the hearth on line. Based on a large number of the data computed, the relation between the cha nge of the moving boundary and inner temperature is summarized, and the great in fluence of the cooling system on the forming and stability of the moving boundar y inside the hearth is emphasized, which provide the theoretical bases for optim izing the flash smelting operation.展开更多
A spiro-type quaternary ammonium salt, spiro-(1,1′)-bipyrrolidinium tetrafluoroborate(SBP-BF4) was successfully prepared by an economical and efficient three-step process comprising the cyclization reaction of 1,4-di...A spiro-type quaternary ammonium salt, spiro-(1,1′)-bipyrrolidinium tetrafluoroborate(SBP-BF4) was successfully prepared by an economical and efficient three-step process comprising the cyclization reaction of 1,4-dibromobutane and pyrrolidine, and subsequent ion exchange pathway with KOH followed by neutralization reaction via HBF4 in the system of ethanol solution. 1H NMR, 13 C NMR, FI-IR and XPS analyses showed the structure of SBP-BF4. The as-obtained SBP-BF4 was dissolved in AN and used as the electrolyte for supercapacitor. Electrochemical measurements demonstrate that, compared with commercial electrolyte TEMA-BF4/AN, SBP-BF4/AN exhibits high ionic conductivity, lower resistance and improved cycling performance, which is due to its smaller ion size and stable symmetry structure.展开更多
The temperature distribution in laminated beams underging thermal boundary conditions has been investigated.The thermal boundary conditions are general and include various combinations of prescribed heat fluxes and te...The temperature distribution in laminated beams underging thermal boundary conditions has been investigated.The thermal boundary conditions are general and include various combinations of prescribed heat fluxes and temperatures at the edges.An analytical solution of temperature for the laminated beam is present on the basis of the heat conduction theory in this paper.The proposed method is applicable to the beams with arbitrary thickness and layer numbers.Due to the complexity of the boundary conditions,the temperature field to be determined was considered from two sources.The first part was the temperature field from the complex temperature conditions at two edges of the laminated beam.The solution for the temperature of the first part was constructed to satisfy temperature boundary conditions at two edges.The second part was the temperature field from the upper and lower surface temperatures without taking account of the thermal conditions at two edges.In this part,the exact solution for the temperature was obtained based on the heat conduction theory.The convergence of the solution was examined by analyzing terms of Fourier series.The validity and feasibility of the proposed method was verified by comparing theoretical results with numerical results due to the equivalent single layer approach and the finite element method(FEM).The influences of surface temperatures,beam thicknesses,layer numbers and material properties with respects to the solution of the temperature field of the beam were investigated via a series of parametric studies.展开更多
Lacus sediments developed in Sebei Formation of Quaternary in Tainan Area,Qindam Basin,which is along one of the low uplift growing dome in the center of the depression basin.Because the sediments are weakly cemented ...Lacus sediments developed in Sebei Formation of Quaternary in Tainan Area,Qindam Basin,which is along one of the low uplift growing dome in the center of the depression basin.Because the sediments are weakly cemented as siltstone and mudstone,it is very difficult to acquire the normal data for classifying and predicting precipitation facies and reservoir beds originally.Data from core cored under展开更多
We present kinematic constraints on the direction of Quaternary extension within the tectonically thickened crust of the Pamir,based on seismicity and fault\|slip data.The Pamir mountain belt of Central Asia is a dire...We present kinematic constraints on the direction of Quaternary extension within the tectonically thickened crust of the Pamir,based on seismicity and fault\|slip data.The Pamir mountain belt of Central Asia is a direct consequence of the collision of the NW\|corner of the Indian indenter with Asia.It comprises Asian crust that is wedged between two opposite\|dipping continental subduction zones in the N and S,laterally blunted by strike\|slip and transgressive fault zones,and locally more than 70km thick (e.g.,Burtman and Molnar,1993).Active deformation in the Pamir is concentrated on compression and transgression along its margins.However,recently published seismic and neotectonic data also presented evidence for approximately E—W directed extension,roughly parallel to the main structural trends within the Pamir,along a N—S trending belt within the high terrain in the interior of the orogen (Strecker et al.,1995).or the central and southern portions of this N—S belt,preliminary kinematic analyses of seismic data from the Harvard moment tensor catalog indicate an extension direction of about 74=B0.This direction is based on presently available focal mechanisms for shallow earthquakes,weighted by their seismic moment;the extension directions calculated for the individual earthquakes vary between 52=B0 and 92=B0=46 or the northern most portion of this belt,earthquake focal mechanisms are not available.展开更多
This paper presents an efficient numerical method for solving the Euler equations on rectilinear grids. Wall boundary conditions on the surface of an airfoil are implemented by using their first order expansions on th...This paper presents an efficient numerical method for solving the Euler equations on rectilinear grids. Wall boundary conditions on the surface of an airfoil are implemented by using their first order expansions on the airfoil chord line, which is placed along a grid line. However, the method is not restricted to flows with small disturbances since there are no restrictions on the magnitude of the velocity or pressure perturbations. The mathematical formulation and the numerical implementation of the wall boundary conditions in a finite volume Euler code are described. Steady transonic flows are calculated about the NACA 0006, NACA 0012 and NACA 0015 airfoils, corresponding to thickness ratios of 6%, 12%, and 15%, respectively. The computed results, including surface pressure distributions, the lift coefficient, the wave drag coefficient, and the pitching moment coefficient, at angles of attack from 0° to 8° are compared with solutions at the same conditions by FLO52, a well established Euler code using body fitted curvilinear grids. Results demonstrate that the method yields acceptable accuracies even for the relatively thick NACA 0015 airfoil and at high angles of attack. This study establishes the potential of extending the method to computing unsteady fluid structure interaction problems, where the use of a stationary rectilinear grid offers substantial advantages in both computer time and human work since it would not require the generation of time dependent body fitted grids.展开更多
Heat transfer of an SI engine's piston is calculated by employing three different methods based on resistor-capacitor model with the help of MATLAB code, and then the piston is thermo-mechanically analyzed using c...Heat transfer of an SI engine's piston is calculated by employing three different methods based on resistor-capacitor model with the help of MATLAB code, and then the piston is thermo-mechanically analyzed using commercial ANSYS code. The results of three methods are compared to study their effects on the piston thermal behavior. It is shown that resistor-capacitor model with less number of equations and consequently less solution time, is an appropriate method for solving problems of engine piston heat transfer. In the second part, the thermal stresses due to non-uniform temperature distribution, and mechanical stresses due to mechanical loads are calculated. Finally, the temperature distributions as a thermal load along with mechanical loads are applied to the piston to determine the total stress distribution and critical fracture zones. It is found that the amount of thermal stresses is considerable.展开更多
This article studies the inhomogeneous Moisil-Theodorsco system in the space R3, gives the integral expression of its solution, proves the Holder continuity of the solution. Moreover the author studies the Riemann-Hil...This article studies the inhomogeneous Moisil-Theodorsco system in the space R3, gives the integral expression of its solution, proves the Holder continuity of the solution. Moreover the author studies the Riemann-Hilbert boundary value problem for the Moisil-Theodorsco system in a cylindrical domain of R3, and gives the solvability conditions and the integral expressions of solutions. The Holder continuity of the solutions is proved.展开更多
The unsaturated quaternary ammonium salt diethyldiallylammonium chloride(DEDAAC) was synthesized in a two-step synthetic method. The influences of the adding method of raw materials and temperature on the yields of di...The unsaturated quaternary ammonium salt diethyldiallylammonium chloride(DEDAAC) was synthesized in a two-step synthetic method. The influences of the adding method of raw materials and temperature on the yields of diethylallylamine (DEAA), and drying and temperature on the synthesis of DEDAAC were investigated. The content of in-process product DEAA was determined by non-aqueous titration. The structure of product DEDAAC was identified with IR, 1 H NMR and elemental analysis. The results show that adding allyl chloride and sodium hydroxide alternately can increase the yield of DEAA and decrease by-products. In further synthesizing of DEDAAC from DEAA, the step of drying DEAA is very necessary. When DEAA is dried by solid sodium hydroxide, good columnar crystals with a high purity(mp 199.5-201.0 ℃) are obtained; when DEAA is undried or the content of water in DEAA is above 20%, only platelets with bad quality are obtained even without crystals. The suitable synthesis conditions for DEAA and DEDAAC are 35 ℃, 6 h and 40 ℃, 36 h, respectively, and their yields are 69.7% and 67.3%, respectively.展开更多
An analysis of unsteady boundary layer flow and heat transfer over an exponentially shrinking porous sheet filled with a copper-water nanofluid is presented.Water is treated as a base fluid.In the investigation,non-un...An analysis of unsteady boundary layer flow and heat transfer over an exponentially shrinking porous sheet filled with a copper-water nanofluid is presented.Water is treated as a base fluid.In the investigation,non-uniform mass suction through the porous sheet is considered.Using Keller-box method the transformed equations are solved numerically.The results of skin friction coefficient,the local Nusselt number as well as the velocity and temperature profiles are presented for different flow parameters.The results showed that the dual non-similar solutions exist only when certain amount of mass suction is applied through the porous sheet for various unsteady parameters and nanoparticle volume fractions.The ranges of suction where dual non-similar solution exists,become larger when values of unsteady parameter as well as nanoparticle volume fraction increase.So,due to unsteadiness of flow dynamics and the presence of nanoparticles in flow field,the requirement of mass suction for existence of solution of boundary layer flow past an exponentially shrinking sheet is less.Furthermore,the velocity boundary layer thickness decreases and thermal boundary layer thickness increases with increasing of nanoparticle volume fraction in both non-similar solutions.Whereas,for stronger mass suction,the velocity boundary layer thickness becomes thinner for the first solution and the effect is opposite in the case of second solution.The temperature inside the boundary layer increases with nanoparticle volume fraction and decreases with mass suction.So,for the unsteadiness and for the presence of nanoparticles,the flow separation is delayed to some extent.展开更多
The electrokinetic properties and flotation of diaspore, kaolinite, pyrophyllite and illite with quaternary ammonium salts collectors were studied. The results of flotation tests show that the collecting ability of qu...The electrokinetic properties and flotation of diaspore, kaolinite, pyrophyllite and illite with quaternary ammonium salts collectors were studied. The results of flotation tests show that the collecting ability of quaternary ammonium salts for the four minerals is in the order（from strong to weak） ofoctadecyl dimethyl benzyl ammonium chloride（ODBA）, cetyl trimethyl ammonium bromide（CTAB）, dodecyl trimethyl ammonium chloride（DTAC）. Under the condition of alkalescence, it is possible to separate the diaspore from the silicate minerals such as kaolinite, illite and pyrophyllite using quaternary ammonium salts as collector. Isoelectric points （IEP） of diaspore, kaolinite, pyrophyllite and illite are pH=6.0, 3.4, 2.3 and 3.2, respectively. Quaternary ammonium salts can change ζ-potential of the aluminosilicate minerals obviously. The flotation mechanisms were explained by ζ-potential and Fourier transform infrared spectrum （FT-IR） measurements. The results demonstrate that only electrostatic interaction takes place between aluminosilicate minerals （diaspore, kaolinite, pyrophyllite and illite） and quaternary ammonium salts.展开更多
Boundary conditions for the classical solution of the Terzaghi one-dimensional consolidation equation conflict with the equation＇s initial condition. As such, the classical initial-boundary value problem for the Terz...Boundary conditions for the classical solution of the Terzaghi one-dimensional consolidation equation conflict with the equation＇s initial condition. As such, the classical initial-boundary value problem for the Terzaghi one-dimensional consolidation equation is not well-posed. Moreover, the classical boundary conditions of the equation can only be applied to problems with either perfectly pervious or perfectly impervious boundaries. General boundary conditions are proposed to overcome these shortcomings and thus transfer the solution of the Terzaghi one-dimensional consolidation equation to a well-posed initial boundary value problem. The solution for proposed general boundary conditions is validated by comparing it to the classical solution. The actual field drainage conditions can be simulated by adjusting the values of parameters b and c given in the proposed general botmdary conditions. For relatively high coefficient of consolidation, just one term in series expansions is enough to obtain results with acceptable accuracy.展开更多
The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates,temperatures and strains were studied.The microstructure evolution was quantitatively characterized and analyzed,including recrystalliz...The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates,temperatures and strains were studied.The microstructure evolution was quantitatively characterized and analyzed,including recrystallization fraction,grain sizes,local misorientation,geometrically necessary dislocation and stored strain energy during hot deformation and subsequent heat treatment.The results show that the dislocation density and energy storage are linear with ln Z during hot deformation and subsequent heat treatment,indicating continuous recrystallization occurring in both processes.With higher ln Z,the dislocation density declines more sharply during subsequent heat treatment.When ln Z is less than 28,dislocation density becomes more stable with less reduction during subsequent heat treatment after hot deformation.As these dislocations distribute along low angle grain boundaries,the subgrain has good stability during subsequent heat treatment.The main recrystallization mechanism during hot deformation is continuous dynamic recrystallization,accompanied by geometric dynamic recrystallization at higher ln Z.展开更多
基金Project(2021YFB3701103) supported by the National Key R&D Program of China。
文摘An increase in RE element content in Mg alloys promotes the grain boundary precipitate,which affects the mechanical properties.However,the influence of grain boundary precipitates on microstructure of Mg-RE alloys during ageing and their role on ductility of the aged alloy is unclear.In this work,hot extrusion and ageing treatment were performed for Mg-9Gd-2Y-xNd-0.2Zr(x=1 wt.%and 3 wt.%)alloys,and grain boundary precipitates were formed in the extruded Mg-9Gd-2Y-3Nd-0.2Zr alloy due to the increase of Nd content.The extruded alloys exhibit a complete dynamic recrystallization(DRX)microstructure and a texture with the<0001>orientation parallel to the extrusion direction(ED).In addition,a large amount of fiber microstructures distributed by the second phase along the ED were formed in the Mg-9Gd-2Y-3Nd-0.2Zr alloy,while only a small amount of the second phase was observed in the Mg-9Gd-2Y-1Nd-0.2Zr alloy.After ageing treatment,a large amount ofβ'phase precipitated inside the grains.The strength of the Mg-9Gd-2Y-1Nd-0.2Zr alloy increased from 202 MPa to 275 MPa but the elongation decreased from 12.8%to 2.6%,and the strength of the Mg-9Gd-2Y-3Nd-0.2Zr alloy increased from 212 MPa to 281 MPa but the elongation decreased from 13.7%to 6.2%.Among them,the Mg-9Gd-2Y-3Nd-0.2Zr alloy showed good overall mechanical properties,especially the elongation of the aged alloy was 58%higher than that of the Mg-9Gd-2Y-1Nd-0.2Zr alloy.The increase in ductility of the aged Mg-9Gd-2Y-3Nd-0.2Zr alloy attributed to the grain boundary precipitate promotes the formation of a large number of precipitation free zones(PFZs)with widths of 130-150 nm during ageing treatment.
基金National Natural Science Foundation of China (52202139, 52072178)。
文摘Pb(Zr,Ti)O_(3)-Pb(Zn_(1/3)Nb_(2/3))O_(3) (PZT-PZN) based ceramics, as important piezoelectric materials, have a wide range of applications in fields such as sensors and actuators, thus the optimization of their piezoelectric properties has been a hot research topic. This study investigated the effects of phase boundary engineering and domain engineering on (1-x)[0.8Pb(Zr_(0.5)Ti_(0.5))O_(3)-0.2Pb(Zn_(1/3)Nb_(2/3))O_(3)]-xBi(Zn_(0.5)Ti_(0.5))O_(3) ((1-x)(0.8PZT-0.2PZN)- xBZT) ceramic to obtain excellent piezoelectric properties. The crystal phase structure and microstructure of ceramic samples were characterized. The results showed that all samples had a pure perovskite structure, and the addition of BZT gradually increased the grain size. The addition of BZT caused a phase transition in ceramic samples from the morphotropic phase boundary (MPB) towards the tetragonal phase region, which is crucial for optimizing piezoelectric properties. By adjusting content of BZT and precisely controlling position of the phase boundary, the piezoelectric performance can be optimized. Domain structure is one of the key factors affecting piezoelectric performance. By using domain engineering techniques to optimize grain size and domain size, piezoelectric properties of ceramic samples have been significantly improved. Specifically, excellent piezoelectric properties (piezoelectric constant d_(33)=320 pC/N, electromechanical coupling factor kp=0.44) were obtained simultaneously for x=0.08. Based on experimental results and theoretical analysis, influence mechanisms of phase boundary engineering and domain engineering on piezoelectric properties were explored. The study shows that addition of BZT not only promotes grain growth, but also optimizes the domain structure, enabling the polarization reversal process easier, thereby improving piezoelectric properties. These research results not only provide new ideas for the design of high-performance piezoelectric ceramics, but also lay a theoretical foundation for development of related electronic devices.
基金The Project is Supported by Nation Natural Science Foundation of China
文摘This paper presents a brief summary of the three development stages of investigation on the transpiration cooling and its control for aircraft, missiles and electromagnetic gun, then the control problem of the distributed parameters system with a moving boundary is derived. It introduces the mathematical model of the transpiration cooling control, its control characteristics, and the present situation of the experimental and theoretical study on this problem. This paper also describes the main study results and the existing problems. The prospective application is also reported. The major references in every developing stage are listed systematically for further study.
文摘Well-preserved Cretaceous lacustrine deposits in Songliao Basin NE China provide a unique opportunity both for building the terrestrial type stage of Cretaceous in China and for studying the response of Cretaceous major global geological events.The basin had been undergone three stages of tectonic evolution during
文摘A class of singularly perturbed initial boundary value problems for the reaction diffusion equations in a part of domain are considered. Using the operator theory the asymptotic behavior of solution for the problems is studied.
文摘The gun-track launch system is a new special launch device that connects the track outside the muzzle.Because it is constrained by the track,the characteristics of development of the muzzle jet differ from those of the traditional muzzle jet.Specifically,it changes from freely developing to doing so in a constrained manner,where this results in an asymmetric direction of flow as well as spatio-temporal coupling-induced interference between various shock waves and the formation of vortices.In this background,the authors of this article formulate and consider the development and characteristics of evolution of the muzzle jet as it impacts a constrained moving body.We designed simulations to test the gun-track launch system,and established a numerical model based on the dynamic grid method to explore the development and characteristics of propagation of disturbances when the muzzle jet impacted a constrained moving body.We also considered models without a constrained track for the sake of comparison.The results showed that the muzzle jet assumed a circumferential asymmetric shape,and tended to develop in the area above the muzzle.Because the test platform was close to the ground,the muzzle jet was subjected to reflections from it that enhanced the development and evolution of various forms of shock waves and vortices in the muzzle jet to exacerbate its rate of distortion and asymmetric characteristics.This in turn led to significant differences in the changes in pressure at symmetric points that would otherwise have been identical.The results of a comparative analysis showed that the constrained track could hinder the influence of reflections from the ground on the muzzle jet to some extent,and could reduce the velocity of the shock waves inducing the motion of the muzzle as well as the Mach number of the moving body.The work here provides a theoretical basis and the requisite technical support for applications of the gun-track launch system.It also sheds light on the technical bottlenecks that need to be considered to recover high-value warheads.
文摘As to solve the online monitoring of the inner temperatur e and freezing profile of the reaction shaft of flash smelting furnace, simulation of the wall in the reaction shaft in a flash smelting furnace was made through numerical computation. The computational results are very near the data got in s ite. The error of the moving boundary is approximately 3%, and that of the tempe rature is less than 5%. It is proved that the simulation software is applicable for practice to monitor the temperature and moving boundary inside the hearth on line. Based on a large number of the data computed, the relation between the cha nge of the moving boundary and inner temperature is summarized, and the great in fluence of the cooling system on the forming and stability of the moving boundar y inside the hearth is emphasized, which provide the theoretical bases for optim izing the flash smelting operation.
基金Project(51371198)supported by the National Natural Science Foundation of China
文摘A spiro-type quaternary ammonium salt, spiro-(1,1′)-bipyrrolidinium tetrafluoroborate(SBP-BF4) was successfully prepared by an economical and efficient three-step process comprising the cyclization reaction of 1,4-dibromobutane and pyrrolidine, and subsequent ion exchange pathway with KOH followed by neutralization reaction via HBF4 in the system of ethanol solution. 1H NMR, 13 C NMR, FI-IR and XPS analyses showed the structure of SBP-BF4. The as-obtained SBP-BF4 was dissolved in AN and used as the electrolyte for supercapacitor. Electrochemical measurements demonstrate that, compared with commercial electrolyte TEMA-BF4/AN, SBP-BF4/AN exhibits high ionic conductivity, lower resistance and improved cycling performance, which is due to its smaller ion size and stable symmetry structure.
基金Projects(52108148,51878319,51578267)supported by the National Natural Science Foundation of ChinaProject(2021M701483)supported by the China Postdoctoral Research Funding Program+1 种基金Project(2021K574C)supported by the Jiangsu Postdoctoral Research Funding Program,ChinaProject(BK20190833)supported by the Natural Science Foundation of Jiangsu Province,China。
文摘The temperature distribution in laminated beams underging thermal boundary conditions has been investigated.The thermal boundary conditions are general and include various combinations of prescribed heat fluxes and temperatures at the edges.An analytical solution of temperature for the laminated beam is present on the basis of the heat conduction theory in this paper.The proposed method is applicable to the beams with arbitrary thickness and layer numbers.Due to the complexity of the boundary conditions,the temperature field to be determined was considered from two sources.The first part was the temperature field from the complex temperature conditions at two edges of the laminated beam.The solution for the temperature of the first part was constructed to satisfy temperature boundary conditions at two edges.The second part was the temperature field from the upper and lower surface temperatures without taking account of the thermal conditions at two edges.In this part,the exact solution for the temperature was obtained based on the heat conduction theory.The convergence of the solution was examined by analyzing terms of Fourier series.The validity and feasibility of the proposed method was verified by comparing theoretical results with numerical results due to the equivalent single layer approach and the finite element method(FEM).The influences of surface temperatures,beam thicknesses,layer numbers and material properties with respects to the solution of the temperature field of the beam were investigated via a series of parametric studies.
文摘Lacus sediments developed in Sebei Formation of Quaternary in Tainan Area,Qindam Basin,which is along one of the low uplift growing dome in the center of the depression basin.Because the sediments are weakly cemented as siltstone and mudstone,it is very difficult to acquire the normal data for classifying and predicting precipitation facies and reservoir beds originally.Data from core cored under
文摘We present kinematic constraints on the direction of Quaternary extension within the tectonically thickened crust of the Pamir,based on seismicity and fault\|slip data.The Pamir mountain belt of Central Asia is a direct consequence of the collision of the NW\|corner of the Indian indenter with Asia.It comprises Asian crust that is wedged between two opposite\|dipping continental subduction zones in the N and S,laterally blunted by strike\|slip and transgressive fault zones,and locally more than 70km thick (e.g.,Burtman and Molnar,1993).Active deformation in the Pamir is concentrated on compression and transgression along its margins.However,recently published seismic and neotectonic data also presented evidence for approximately E—W directed extension,roughly parallel to the main structural trends within the Pamir,along a N—S trending belt within the high terrain in the interior of the orogen (Strecker et al.,1995).or the central and southern portions of this N—S belt,preliminary kinematic analyses of seismic data from the Harvard moment tensor catalog indicate an extension direction of about 74=B0.This direction is based on presently available focal mechanisms for shallow earthquakes,weighted by their seismic moment;the extension directions calculated for the individual earthquakes vary between 52=B0 and 92=B0=46 or the northern most portion of this belt,earthquake focal mechanisms are not available.
文摘This paper presents an efficient numerical method for solving the Euler equations on rectilinear grids. Wall boundary conditions on the surface of an airfoil are implemented by using their first order expansions on the airfoil chord line, which is placed along a grid line. However, the method is not restricted to flows with small disturbances since there are no restrictions on the magnitude of the velocity or pressure perturbations. The mathematical formulation and the numerical implementation of the wall boundary conditions in a finite volume Euler code are described. Steady transonic flows are calculated about the NACA 0006, NACA 0012 and NACA 0015 airfoils, corresponding to thickness ratios of 6%, 12%, and 15%, respectively. The computed results, including surface pressure distributions, the lift coefficient, the wave drag coefficient, and the pitching moment coefficient, at angles of attack from 0° to 8° are compared with solutions at the same conditions by FLO52, a well established Euler code using body fitted curvilinear grids. Results demonstrate that the method yields acceptable accuracies even for the relatively thick NACA 0015 airfoil and at high angles of attack. This study establishes the potential of extending the method to computing unsteady fluid structure interaction problems, where the use of a stationary rectilinear grid offers substantial advantages in both computer time and human work since it would not require the generation of time dependent body fitted grids.
文摘Heat transfer of an SI engine's piston is calculated by employing three different methods based on resistor-capacitor model with the help of MATLAB code, and then the piston is thermo-mechanically analyzed using commercial ANSYS code. The results of three methods are compared to study their effects on the piston thermal behavior. It is shown that resistor-capacitor model with less number of equations and consequently less solution time, is an appropriate method for solving problems of engine piston heat transfer. In the second part, the thermal stresses due to non-uniform temperature distribution, and mechanical stresses due to mechanical loads are calculated. Finally, the temperature distributions as a thermal load along with mechanical loads are applied to the piston to determine the total stress distribution and critical fracture zones. It is found that the amount of thermal stresses is considerable.
基金Supported partially by the Key Project Foundation of the Education Department of Sichuan Province
文摘This article studies the inhomogeneous Moisil-Theodorsco system in the space R3, gives the integral expression of its solution, proves the Holder continuity of the solution. Moreover the author studies the Riemann-Hilbert boundary value problem for the Moisil-Theodorsco system in a cylindrical domain of R3, and gives the solvability conditions and the integral expressions of solutions. The Holder continuity of the solutions is proved.
文摘The unsaturated quaternary ammonium salt diethyldiallylammonium chloride(DEDAAC) was synthesized in a two-step synthetic method. The influences of the adding method of raw materials and temperature on the yields of diethylallylamine (DEAA), and drying and temperature on the synthesis of DEDAAC were investigated. The content of in-process product DEAA was determined by non-aqueous titration. The structure of product DEDAAC was identified with IR, 1 H NMR and elemental analysis. The results show that adding allyl chloride and sodium hydroxide alternately can increase the yield of DEAA and decrease by-products. In further synthesizing of DEDAAC from DEAA, the step of drying DEAA is very necessary. When DEAA is dried by solid sodium hydroxide, good columnar crystals with a high purity(mp 199.5-201.0 ℃) are obtained; when DEAA is undried or the content of water in DEAA is above 20%, only platelets with bad quality are obtained even without crystals. The suitable synthesis conditions for DEAA and DEDAAC are 35 ℃, 6 h and 40 ℃, 36 h, respectively, and their yields are 69.7% and 67.3%, respectively.
基金the National Board for Higher Mathematics (NBHM),Department of Atomic Energy,Government of India for the financial support in pursuing this workthe financial support from MOHE and the Research Management Center-UTM through FRGS and RUG vote number 4F109 and 02H80 for this research
文摘An analysis of unsteady boundary layer flow and heat transfer over an exponentially shrinking porous sheet filled with a copper-water nanofluid is presented.Water is treated as a base fluid.In the investigation,non-uniform mass suction through the porous sheet is considered.Using Keller-box method the transformed equations are solved numerically.The results of skin friction coefficient,the local Nusselt number as well as the velocity and temperature profiles are presented for different flow parameters.The results showed that the dual non-similar solutions exist only when certain amount of mass suction is applied through the porous sheet for various unsteady parameters and nanoparticle volume fractions.The ranges of suction where dual non-similar solution exists,become larger when values of unsteady parameter as well as nanoparticle volume fraction increase.So,due to unsteadiness of flow dynamics and the presence of nanoparticles in flow field,the requirement of mass suction for existence of solution of boundary layer flow past an exponentially shrinking sheet is less.Furthermore,the velocity boundary layer thickness decreases and thermal boundary layer thickness increases with increasing of nanoparticle volume fraction in both non-similar solutions.Whereas,for stronger mass suction,the velocity boundary layer thickness becomes thinner for the first solution and the effect is opposite in the case of second solution.The temperature inside the boundary layer increases with nanoparticle volume fraction and decreases with mass suction.So,for the unsteadiness and for the presence of nanoparticles,the flow separation is delayed to some extent.
基金Project(2005CB623701) supported by the National Key Fundamental Research and Development Program of China
文摘The electrokinetic properties and flotation of diaspore, kaolinite, pyrophyllite and illite with quaternary ammonium salts collectors were studied. The results of flotation tests show that the collecting ability of quaternary ammonium salts for the four minerals is in the order（from strong to weak） ofoctadecyl dimethyl benzyl ammonium chloride（ODBA）, cetyl trimethyl ammonium bromide（CTAB）, dodecyl trimethyl ammonium chloride（DTAC）. Under the condition of alkalescence, it is possible to separate the diaspore from the silicate minerals such as kaolinite, illite and pyrophyllite using quaternary ammonium salts as collector. Isoelectric points （IEP） of diaspore, kaolinite, pyrophyllite and illite are pH=6.0, 3.4, 2.3 and 3.2, respectively. Quaternary ammonium salts can change ζ-potential of the aluminosilicate minerals obviously. The flotation mechanisms were explained by ζ-potential and Fourier transform infrared spectrum （FT-IR） measurements. The results demonstrate that only electrostatic interaction takes place between aluminosilicate minerals （diaspore, kaolinite, pyrophyllite and illite） and quaternary ammonium salts.
基金Foundation item： Project（50608038） supported by the National Natural Science Foundation of China
文摘Boundary conditions for the classical solution of the Terzaghi one-dimensional consolidation equation conflict with the equation＇s initial condition. As such, the classical initial-boundary value problem for the Terzaghi one-dimensional consolidation equation is not well-posed. Moreover, the classical boundary conditions of the equation can only be applied to problems with either perfectly pervious or perfectly impervious boundaries. General boundary conditions are proposed to overcome these shortcomings and thus transfer the solution of the Terzaghi one-dimensional consolidation equation to a well-posed initial boundary value problem. The solution for proposed general boundary conditions is validated by comparing it to the classical solution. The actual field drainage conditions can be simulated by adjusting the values of parameters b and c given in the proposed general botmdary conditions. For relatively high coefficient of consolidation, just one term in series expansions is enough to obtain results with acceptable accuracy.
基金Project(2016YFB0300901)supported by the National Key R&D Program of ChinaProject(TC190H3ZV/2)supported by the National Building Project of Application Demonstration Platform on New Materials Products,ChinaProject(15308469779)supported by Key Laboratory of National Science and Technology for Equipment Pre-research,China。
文摘The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates,temperatures and strains were studied.The microstructure evolution was quantitatively characterized and analyzed,including recrystallization fraction,grain sizes,local misorientation,geometrically necessary dislocation and stored strain energy during hot deformation and subsequent heat treatment.The results show that the dislocation density and energy storage are linear with ln Z during hot deformation and subsequent heat treatment,indicating continuous recrystallization occurring in both processes.With higher ln Z,the dislocation density declines more sharply during subsequent heat treatment.When ln Z is less than 28,dislocation density becomes more stable with less reduction during subsequent heat treatment after hot deformation.As these dislocations distribute along low angle grain boundaries,the subgrain has good stability during subsequent heat treatment.The main recrystallization mechanism during hot deformation is continuous dynamic recrystallization,accompanied by geometric dynamic recrystallization at higher ln Z.
