To guarantee the computational accuracy of the finite element model,the strain-compensated Arrhenius-type model,modified Fields-Backofen(m-FB)model and modified Zerilli-Armstrong(m-ZA)model were established to predict...To guarantee the computational accuracy of the finite element model,the strain-compensated Arrhenius-type model,modified Fields-Backofen(m-FB)model and modified Zerilli-Armstrong(m-ZA)model were established to predict the hightemperature flow stress of as-cast low alloyed Al-0.5Cu,Al-1Si,and Al-1Si-0.5Cu.To determine the material constants of these three constitutive models,isothermal compression tests of the three aluminum alloys were carried out on a Gleeble-3800 thermal simulator.The prediction results of the constitutive model were compared with the experimental results to evaluate the prediction accuracy of the constitutive models,and to provide a basis for selecting the most suitable constitutive models(parameters)for the three alloys mentioned above.It is found that the strain-compensated Arrhenius model and m-ZA model can be regarded as the most suitable constitutive models for Al-0.5Cu and Al-1Si alloys,respectively,and these two constitutive models also can be applied to Al-1Si-0.5Cu alloy.However,the m-FB model can be applied to Al-0.5Cu,Al-1Si and Al-1Si-0.5Cu alloys only under high temperature and medium strain conditions.展开更多
Four key stress thresholds exist in the compression process of rocks,i.e.,crack closure stress(σ_(cc)),crack initiation stress(σ_(ci)),crack damage stress(σ_(cd))and compressive strength(σ_(c)).The quantitative id...Four key stress thresholds exist in the compression process of rocks,i.e.,crack closure stress(σ_(cc)),crack initiation stress(σ_(ci)),crack damage stress(σ_(cd))and compressive strength(σ_(c)).The quantitative identifications of the first three stress thresholds are of great significance for characterizing the microcrack growth and damage evolution of rocks under compression.In this paper,a new method based on damage constitutive model is proposed to quantitatively measure the stress thresholds of rocks.Firstly,two different damage constitutive models were constructed based on acoustic emission(AE)counts and Weibull distribution function considering the compaction stages of the rock and the bearing capacity of the damage element.Then,the accumulative AE counts method(ACLM),AE count rate method(CRM)and constitutive model method(CMM)were introduced to determine the stress thresholds of rocks.Finally,the stress thresholds of 9 different rocks were identified by ACLM,CRM,and CMM.The results show that the theoretical stress−strain curves obtained from the two damage constitutive models are in good agreement with that of the experimental data,and the differences between the two damage constitutive models mainly come from the evolutionary differences of the damage variables.The results of the stress thresholds identified by the CMM are in good agreement with those identified by the AE methods,i.e.,ACLM and CRM.Therefore,the proposed CMM can be used to determine the stress thresholds of rocks.展开更多
The effects of leaching temperature(60−105°C),NH4Cl concentration(3−7 mol/L),liquid/solid ratio(4:1−12:1 mL/g),stirring speed(150−750 r/min),and leaching time(5−90 min)on the leaching rates of Zn and Pb were inve...The effects of leaching temperature(60−105°C),NH4Cl concentration(3−7 mol/L),liquid/solid ratio(4:1−12:1 mL/g),stirring speed(150−750 r/min),and leaching time(5−90 min)on the leaching rates of Zn and Pb were investigated.The leaching kinetics of Zn-and Pb-rich fuming dust with a NH4Cl solution was also studied.The leaching rates of Zn and Pb respectively reached 98.2%and 75.6%at leaching temperature of 100°C,an NH4Cl concentration of 7.0 mol/L,a liquid/solid ratio of 10:1 mL/g,a stirring speed of 450 r/min and leaching time of 60 min.The kinetics results indicate that the leaching of Zn and Pb conforms to the shrinking unreacted core model and is controlled by the internal diffusion of NH4Cl through the reacted fuming dust layer and external diffusion of NH4Cl through the leaching solution boundary layer,respectively.The apparent activation energies of Zn and Pb are 23.922 and 19.139 kJ/mol,respectively.This study demonstrates that the use of NH4Cl solution,without ammonia,is an environmentally friendly method for simultaneous extracting Zn and Pb from the fuming dust of lead blast furnace slag.展开更多
The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical ...The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical aluminum alloy 7050-T7451. Combined high-speed orthogonal cutting experiments with the cutting process simulations, the data relationship of high temperature, high strain rate and large strain in high-speed cutting is modified. The Johnson-Cook empirical model considering the effects of strain hardening, strain rate hardening and thermal softening is selected to describe the data relationship in high-speed cutting, and the material constants of flow stress constitutive model for aluminum alloy 7050-T7451 are determined. Finally, the constitutive model of aluminum alloy 7050-T7451 is established through experiment and simulation verification in high-speed cutting. The model is proved to be reasonable by matching the measured values of the cutting force with the estimated results from FEM simulations.展开更多
By the constant stress tensile creep test method, creep tests were performed on aluminum silicate short fiber-reinforced AZ91D magnesium matrix composite with volume fraction of 30% and its matrix alloy AZ91D under di...By the constant stress tensile creep test method, creep tests were performed on aluminum silicate short fiber-reinforced AZ91D magnesium matrix composite with volume fraction of 30% and its matrix alloy AZ91D under different temperatures and stresses. The results indicate that the composite and the matrix have the same true stress exponent and true activation energy for creep, which are 3 and 144.63 kJ/mol, respectively. The creep of the composite is controlled by the creep of its matrix, which is mainly the controlling of viscous slip of dislocation, and the controlling of grain boundary slippage as a supplement. The creep constitutive model obtained from the experiment data can well describe the creep deformation pattern of the composite.展开更多
Hot deformation behavior ofX20Cr13 martensitic stainless steel was investigated by conducting hot compression tests on Gleeble-1500D thermo-mechanical simulator at the temperature ranging from 1173 to 1423 K and the s...Hot deformation behavior ofX20Cr13 martensitic stainless steel was investigated by conducting hot compression tests on Gleeble-1500D thermo-mechanical simulator at the temperature ranging from 1173 to 1423 K and the strain rate ranging from 0.001 to 10 s^-1. The material constants of a and n, activation energy Q and A were calculated as a function of strain by a fifth-order polynomial fit. Constitutive models incorporating deformation temperature, strain rate and strain were developed to model the hot deformation behavior of X20Cr13 martensitic stainless steel based on the Arrhenius equation. The predictable efficiency of the developed constitutive models of X20Cr13 martensitic stainless steel was analyzed by correlation coefficient and average absolute relative error which are 0.996 and 3.22%, respectively.展开更多
Isothermal compression tests in a wide range of temperatures （300-500 ℃） and strain rates （0.001-10 s^-1）, were performed on 2099 alloy to reveal the hot deformation characteristics. In order to give a precise pr...Isothermal compression tests in a wide range of temperatures （300-500 ℃） and strain rates （0.001-10 s^-1）, were performed on 2099 alloy to reveal the hot deformation characteristics. In order to give a precise prediction of flow behavior, the obtained experimental data were modified by friction and temperature correction and then employed to derive the constitutive modeling. The effects of the temperature and strain rate on hot deformation behavior can be expressed by Zener-Hollomon parameter including Arrhenius term. Furthermore, the influence of strain was incorporated in the constitutive analysis by considering the effect of strain on material constants （i.e. a, n, Q and A）. Consequently, the flow stress curves predicted by the developed modeling show a good agreement with the corrected ones, which indicates that the developed constitutive modeling could give an accurate and precise prediction for the flow stress of 2099 alloy.展开更多
[Objective] The paper was to study adsorption dynamics of calyx aroma onto basic tea in scenting process of calyx-scented tea, so as to increase aroma and quality of products. [Method] Adsorption experiment was carrie...[Objective] The paper was to study adsorption dynamics of calyx aroma onto basic tea in scenting process of calyx-scented tea, so as to increase aroma and quality of products. [Method] Adsorption experiment was carried out in a hermetic container, and the effect of calyx amount, contact time, moisture content of basic tea and temperature on the scenting process was studied. [Result] The optimal moisture and temperature for scenting process was 4% and 10 ℃, respectively. [Conclusion] The scenting process accorded pseudo-first-order kinetic model, and the adsorption dynamic data of total process could better fit pseudo-second-order kinetic model.展开更多
The effect of realistic topology configuration of intercellular connections on the response ability in coupled cell system is numerically investigated by using the Hindmarsh-Rose model. For the proper coupling intensi...The effect of realistic topology configuration of intercellular connections on the response ability in coupled cell system is numerically investigated by using the Hindmarsh-Rose model. For the proper coupling intensity, we set the control parameter to be near the critical value, and the external stimulus is introduced to the first cell in coupled system. It is found that, on one hand, when the cells are coupled with some proper topological structures, the external stimulus could transmit through the system, and shows better response ability and higher sensitivity. On the other hand, the influence of topological configuration on the synchronous ability and selection effect of neural system are also discussed. Our results display that the topology of coupled system may play an important role in the process of signal propagation, which could help us to understand the coordinated performance of cells in tissue.展开更多
Effects of four factors on thin sheet metal flow stress were considered, including grain size d, thickness t, grain number across thickness （t/d ratio） and surface property. Surface model was adopted to quantitative...Effects of four factors on thin sheet metal flow stress were considered, including grain size d, thickness t, grain number across thickness （t/d ratio） and surface property. Surface model was adopted to quantitatively describe the effect of t/d ratio on flow stress for pure copper. It is predicted that when t/d ratio is larger than a critical value, effect of t/d ratio on flow stress can be neglected. Existence of critical t/d ratio changes the Hall-Petch relationship and evolution of flow stress with thickness. A criterion was proposed to determine critical t/d ratio. Then a comprehensive constitutive model was developed to consider all the four factors, with parameters determined by fitting experimental data of high purity Ni. The predicted results show the same tendencies with experiment results. Particularly when t/d ratio decreases, Hall-Petch relationship and evolution of true stress show varied slopes with two transition points.展开更多
The nonlinear mixed-effects model with stochastic differential equations （SDEs） is used to model the population pharmacokinetic （PPK） data that are extended from ordinary differential equations （ODEs） by adding ...The nonlinear mixed-effects model with stochastic differential equations （SDEs） is used to model the population pharmacokinetic （PPK） data that are extended from ordinary differential equations （ODEs） by adding a stochastic term to the state equation. Compared with the ODEs, the SDEs can model correlated residuals which are ubiquitous in actual pharmacokinetic problems. The Bayesian estimation is provided for nonlinear mixed-effects models based on stochastic differential equations. Combining the Gibbs and the Metropolis-Hastings algorithms, the population and individual parameter values are given through the parameter posterior predictive distributions. The analysis and simulation results show that the performance of the Bayesian estimation for mixed-effects SDEs model and analysis of population pharmacokinetic data is reliable. The results suggest that the proposed method is feasible for population pharmacokinetic data.展开更多
Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the invest...Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.展开更多
In order to investigate the hot deformation behavior of superalloy GH696, isothermal compression experiments were carried out at deformation temperatures of 880?1120 °C and strain rates of 0.01?10 s?1. And the de...In order to investigate the hot deformation behavior of superalloy GH696, isothermal compression experiments were carried out at deformation temperatures of 880?1120 °C and strain rates of 0.01?10 s?1. And the deformation amount of all the samples was 50%. The strain rate sensitivity exponent (m) and strain hardening exponent (n) under different deformation conditions were calculated, meanwhile the effects of the processing parameters on the values ofm andn were analyzed. The results show that the flow stress increases with the increase of strain rate and the decrease of deformation temperature. The value ofm increases with the increase of deformation temperature and decreases with the increase of strain rate, while the value ofn decreases with the increase of deformation temperature. A novel flow stress model during hot deformation of superalloy GH696 was also established. And the calculated flow stress of the alloy is in good agreement with the experimental one.展开更多
Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolut...Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al-l.lMn-0.3Mg-0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440-450 ℃ and strain rate of 0.01 s-1.展开更多
In accordance to the anisotropic feature of turbulent flow, ananisotropic algebraic stress model is adopted to predict theturbulent flow field and turbulent characteristics generated by aRushton disc turbine with the ...In accordance to the anisotropic feature of turbulent flow, ananisotropic algebraic stress model is adopted to predict theturbulent flow field and turbulent characteristics generated by aRushton disc turbine with the improved inner-outer iterativeprocedure. The predicted turbulent flow is compared with experimentaldata and the simulation by the standard k-ε turbulence model. Theanisotropic algebraic stress model is found to give better predictionthan the standard k-ε turbulence model. The predicted turbulent flowfield is in accordance to experimental data and the trend of theturbulence intensity can be effectively reflected in the simulation.展开更多
The aim of this work is to evaluate how the building distribution influences the cooling effect of water bodies. Different turbulence models, including the S-A, SKE, RNG, Realizable, Low-KE and RSM model, were evaluat...The aim of this work is to evaluate how the building distribution influences the cooling effect of water bodies. Different turbulence models, including the S-A, SKE, RNG, Realizable, Low-KE and RSM model, were evaluated, and the CFD results were compared with wind tunnel experiment. The effects of the water body were detected by analyzing the water vapor distribution around it. It is found that the RNG model is the most effective model in terms of accuracy and computational economy. Next, the RNG model was used to simulate four waterfront planning cases to predict the wind, thermal and moisture environment in urban areas around urban water bodies. The results indicate that the building distribution, especially the height of the frontal building, has a larger effect on the water vapor dispersion, and indicate that the column-type distribution has a better performance than the enclosed-type distribution.展开更多
The hot deformation behaviors of GCr15 bearing steel were investigated by isothermal compression tests, performed on a Gleeble-3800 thermal-mechanical simulator at temperatures between 950 ℃ and 1 150 ℃ and strain r...The hot deformation behaviors of GCr15 bearing steel were investigated by isothermal compression tests, performed on a Gleeble-3800 thermal-mechanical simulator at temperatures between 950 ℃ and 1 150 ℃ and strain rates between 0.1 and 10 s-1. The peak stress and peak strain as functions of processing parameters were obtained. The dependence of peak stress on strain rate and temperature obeys a hyperbolic sine equation with a Zener-Hollomon parameter. By regression analysis, in the temperature range of 950-1 150 ℃ and strain rate range of 0.1?10 s?1, the mean activation energy and the stress exponent were determined to be 351kJ/mol and 4.728, respectively. Meanwhile, models of flow stress and dynamic recrystallization (DRX) grain size were also established. The model predictions show good agreement with experimental results.展开更多
To realize numerical simulation of rolling and obtain the hot forming process parameters for X70 HD steel, the flow stress behaviors of X70 HD steel were investigated under different temperatures（820-1100 ℃ and stra...To realize numerical simulation of rolling and obtain the hot forming process parameters for X70 HD steel, the flow stress behaviors of X70 HD steel were investigated under different temperatures（820-1100 ℃ and strain rates（0.01-10 s-1） on a Gleeble-3500 thermo-simulation machine. A new flow stress model was established. The linear and exponential relationship methods were applied to the parameters with respect to temperature and deformation rates. The rise of curve ends under certain conditions was analyzed. The flow stress of X70 HD steel predicted by the proposed model agrees well with the experimental results. So, it greatly improves the precision of the metal thermoplastic processing through finite element method and practical application of engineering.展开更多
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China“Study on constitutive behavior of Al-xSi-yCu high purity aluminum alloy billets for target materials”(2020D01C023).
文摘To guarantee the computational accuracy of the finite element model,the strain-compensated Arrhenius-type model,modified Fields-Backofen(m-FB)model and modified Zerilli-Armstrong(m-ZA)model were established to predict the hightemperature flow stress of as-cast low alloyed Al-0.5Cu,Al-1Si,and Al-1Si-0.5Cu.To determine the material constants of these three constitutive models,isothermal compression tests of the three aluminum alloys were carried out on a Gleeble-3800 thermal simulator.The prediction results of the constitutive model were compared with the experimental results to evaluate the prediction accuracy of the constitutive models,and to provide a basis for selecting the most suitable constitutive models(parameters)for the three alloys mentioned above.It is found that the strain-compensated Arrhenius model and m-ZA model can be regarded as the most suitable constitutive models for Al-0.5Cu and Al-1Si alloys,respectively,and these two constitutive models also can be applied to Al-1Si-0.5Cu alloy.However,the m-FB model can be applied to Al-0.5Cu,Al-1Si and Al-1Si-0.5Cu alloys only under high temperature and medium strain conditions.
基金Projects(2021RC3007,2020RC3090)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProjects(52374150,52174099)supported by the National Natural Science Foundation of China。
文摘Four key stress thresholds exist in the compression process of rocks,i.e.,crack closure stress(σ_(cc)),crack initiation stress(σ_(ci)),crack damage stress(σ_(cd))and compressive strength(σ_(c)).The quantitative identifications of the first three stress thresholds are of great significance for characterizing the microcrack growth and damage evolution of rocks under compression.In this paper,a new method based on damage constitutive model is proposed to quantitatively measure the stress thresholds of rocks.Firstly,two different damage constitutive models were constructed based on acoustic emission(AE)counts and Weibull distribution function considering the compaction stages of the rock and the bearing capacity of the damage element.Then,the accumulative AE counts method(ACLM),AE count rate method(CRM)and constitutive model method(CMM)were introduced to determine the stress thresholds of rocks.Finally,the stress thresholds of 9 different rocks were identified by ACLM,CRM,and CMM.The results show that the theoretical stress−strain curves obtained from the two damage constitutive models are in good agreement with that of the experimental data,and the differences between the two damage constitutive models mainly come from the evolutionary differences of the damage variables.The results of the stress thresholds identified by the CMM are in good agreement with those identified by the AE methods,i.e.,ACLM and CRM.Therefore,the proposed CMM can be used to determine the stress thresholds of rocks.
基金financial supports from the National Natural Science Foundation of China(No.51704107)the Department of Education Scientific Research of Hunan Province,China(No.22A0401)the Natural Science Foundation of Hunan Province,China(No.2024JJ7160).
文摘The effects of leaching temperature(60−105°C),NH4Cl concentration(3−7 mol/L),liquid/solid ratio(4:1−12:1 mL/g),stirring speed(150−750 r/min),and leaching time(5−90 min)on the leaching rates of Zn and Pb were investigated.The leaching kinetics of Zn-and Pb-rich fuming dust with a NH4Cl solution was also studied.The leaching rates of Zn and Pb respectively reached 98.2%and 75.6%at leaching temperature of 100°C,an NH4Cl concentration of 7.0 mol/L,a liquid/solid ratio of 10:1 mL/g,a stirring speed of 450 r/min and leaching time of 60 min.The kinetics results indicate that the leaching of Zn and Pb conforms to the shrinking unreacted core model and is controlled by the internal diffusion of NH4Cl through the reacted fuming dust layer and external diffusion of NH4Cl through the leaching solution boundary layer,respectively.The apparent activation energies of Zn and Pb are 23.922 and 19.139 kJ/mol,respectively.This study demonstrates that the use of NH4Cl solution,without ammonia,is an environmentally friendly method for simultaneous extracting Zn and Pb from the fuming dust of lead blast furnace slag.
文摘The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical aluminum alloy 7050-T7451. Combined high-speed orthogonal cutting experiments with the cutting process simulations, the data relationship of high temperature, high strain rate and large strain in high-speed cutting is modified. The Johnson-Cook empirical model considering the effects of strain hardening, strain rate hardening and thermal softening is selected to describe the data relationship in high-speed cutting, and the material constants of flow stress constitutive model for aluminum alloy 7050-T7451 are determined. Finally, the constitutive model of aluminum alloy 7050-T7451 is established through experiment and simulation verification in high-speed cutting. The model is proved to be reasonable by matching the measured values of the cutting force with the estimated results from FEM simulations.
基金Project(10151170003000002)supported by the National Science Foundation of Guangdong Province,China
文摘By the constant stress tensile creep test method, creep tests were performed on aluminum silicate short fiber-reinforced AZ91D magnesium matrix composite with volume fraction of 30% and its matrix alloy AZ91D under different temperatures and stresses. The results indicate that the composite and the matrix have the same true stress exponent and true activation energy for creep, which are 3 and 144.63 kJ/mol, respectively. The creep of the composite is controlled by the creep of its matrix, which is mainly the controlling of viscous slip of dislocation, and the controlling of grain boundary slippage as a supplement. The creep constitutive model obtained from the experiment data can well describe the creep deformation pattern of the composite.
基金Project(51005150)supported by the National Natural Science Foundation of ChinaProject(2011CB012903)supported by the National Basic Research Program of China
文摘Hot deformation behavior ofX20Cr13 martensitic stainless steel was investigated by conducting hot compression tests on Gleeble-1500D thermo-mechanical simulator at the temperature ranging from 1173 to 1423 K and the strain rate ranging from 0.001 to 10 s^-1. The material constants of a and n, activation energy Q and A were calculated as a function of strain by a fifth-order polynomial fit. Constitutive models incorporating deformation temperature, strain rate and strain were developed to model the hot deformation behavior of X20Cr13 martensitic stainless steel based on the Arrhenius equation. The predictable efficiency of the developed constitutive models of X20Cr13 martensitic stainless steel was analyzed by correlation coefficient and average absolute relative error which are 0.996 and 3.22%, respectively.
文摘Isothermal compression tests in a wide range of temperatures （300-500 ℃） and strain rates （0.001-10 s^-1）, were performed on 2099 alloy to reveal the hot deformation characteristics. In order to give a precise prediction of flow behavior, the obtained experimental data were modified by friction and temperature correction and then employed to derive the constitutive modeling. The effects of the temperature and strain rate on hot deformation behavior can be expressed by Zener-Hollomon parameter including Arrhenius term. Furthermore, the influence of strain was incorporated in the constitutive analysis by considering the effect of strain on material constants （i.e. a, n, Q and A）. Consequently, the flow stress curves predicted by the developed modeling show a good agreement with the corrected ones, which indicates that the developed constitutive modeling could give an accurate and precise prediction for the flow stress of 2099 alloy.
基金Supported by Special Major Build of China and Nature Science Research Foundations of Sichuan Agricultural University(06370101)~~
文摘[Objective] The paper was to study adsorption dynamics of calyx aroma onto basic tea in scenting process of calyx-scented tea, so as to increase aroma and quality of products. [Method] Adsorption experiment was carried out in a hermetic container, and the effect of calyx amount, contact time, moisture content of basic tea and temperature on the scenting process was studied. [Result] The optimal moisture and temperature for scenting process was 4% and 10 ℃, respectively. [Conclusion] The scenting process accorded pseudo-first-order kinetic model, and the adsorption dynamic data of total process could better fit pseudo-second-order kinetic model.
文摘The effect of realistic topology configuration of intercellular connections on the response ability in coupled cell system is numerically investigated by using the Hindmarsh-Rose model. For the proper coupling intensity, we set the control parameter to be near the critical value, and the external stimulus is introduced to the first cell in coupled system. It is found that, on one hand, when the cells are coupled with some proper topological structures, the external stimulus could transmit through the system, and shows better response ability and higher sensitivity. On the other hand, the influence of topological configuration on the synchronous ability and selection effect of neural system are also discussed. Our results display that the topology of coupled system may play an important role in the process of signal propagation, which could help us to understand the coordinated performance of cells in tissue.
基金Projects(50835002,50975174,50821003)supported by the National Natural Science Foundation of ChinaProjects(200802480053,20100073110044)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Effects of four factors on thin sheet metal flow stress were considered, including grain size d, thickness t, grain number across thickness （t/d ratio） and surface property. Surface model was adopted to quantitatively describe the effect of t/d ratio on flow stress for pure copper. It is predicted that when t/d ratio is larger than a critical value, effect of t/d ratio on flow stress can be neglected. Existence of critical t/d ratio changes the Hall-Petch relationship and evolution of flow stress with thickness. A criterion was proposed to determine critical t/d ratio. Then a comprehensive constitutive model was developed to consider all the four factors, with parameters determined by fitting experimental data of high purity Ni. The predicted results show the same tendencies with experiment results. Particularly when t/d ratio decreases, Hall-Petch relationship and evolution of true stress show varied slopes with two transition points.
基金The National Natural Science Foundation of China(No.11171065,81130068)the Natural Science Foundation of Jiangsu Province(No.BK2011058)the Fundamental Research Funds for the Central Universities(No.JKPZ2013015)
文摘The nonlinear mixed-effects model with stochastic differential equations （SDEs） is used to model the population pharmacokinetic （PPK） data that are extended from ordinary differential equations （ODEs） by adding a stochastic term to the state equation. Compared with the ODEs, the SDEs can model correlated residuals which are ubiquitous in actual pharmacokinetic problems. The Bayesian estimation is provided for nonlinear mixed-effects models based on stochastic differential equations. Combining the Gibbs and the Metropolis-Hastings algorithms, the population and individual parameter values are given through the parameter posterior predictive distributions. The analysis and simulation results show that the performance of the Bayesian estimation for mixed-effects SDEs model and analysis of population pharmacokinetic data is reliable. The results suggest that the proposed method is feasible for population pharmacokinetic data.
基金Project(2009ZX04004-031-04) supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China
文摘Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.
文摘In order to investigate the hot deformation behavior of superalloy GH696, isothermal compression experiments were carried out at deformation temperatures of 880?1120 °C and strain rates of 0.01?10 s?1. And the deformation amount of all the samples was 50%. The strain rate sensitivity exponent (m) and strain hardening exponent (n) under different deformation conditions were calculated, meanwhile the effects of the processing parameters on the values ofm andn were analyzed. The results show that the flow stress increases with the increase of strain rate and the decrease of deformation temperature. The value ofm increases with the increase of deformation temperature and decreases with the increase of strain rate, while the value ofn decreases with the increase of deformation temperature. A novel flow stress model during hot deformation of superalloy GH696 was also established. And the calculated flow stress of the alloy is in good agreement with the experimental one.
基金Project(31115014)supported by the of Open Research Fund Program of State Key Laboratory of Advanced Design and Manufacture forVehicle Body(Hunan University)Project(12JJ9017)supported by the Natural Science Foundation of Hunan Province,China
文摘Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al-l.lMn-0.3Mg-0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440-450 ℃ and strain rate of 0.01 s-1.
基金the National Natural Science Foundation of China (No. 29792074).
文摘In accordance to the anisotropic feature of turbulent flow, ananisotropic algebraic stress model is adopted to predict theturbulent flow field and turbulent characteristics generated by aRushton disc turbine with the improved inner-outer iterativeprocedure. The predicted turbulent flow is compared with experimentaldata and the simulation by the standard k-ε turbulence model. Theanisotropic algebraic stress model is found to give better predictionthan the standard k-ε turbulence model. The predicted turbulent flowfield is in accordance to experimental data and the trend of theturbulence intensity can be effectively reflected in the simulation.
基金Project(51438005)supported by the National Natural Science Foundation of China
文摘The aim of this work is to evaluate how the building distribution influences the cooling effect of water bodies. Different turbulence models, including the S-A, SKE, RNG, Realizable, Low-KE and RSM model, were evaluated, and the CFD results were compared with wind tunnel experiment. The effects of the water body were detected by analyzing the water vapor distribution around it. It is found that the RNG model is the most effective model in terms of accuracy and computational economy. Next, the RNG model was used to simulate four waterfront planning cases to predict the wind, thermal and moisture environment in urban areas around urban water bodies. The results indicate that the building distribution, especially the height of the frontal building, has a larger effect on the water vapor dispersion, and indicate that the column-type distribution has a better performance than the enclosed-type distribution.
基金Project(2001-122) supported by the Youth Science and Technology Elitist Foundation of Dalian, China
文摘The hot deformation behaviors of GCr15 bearing steel were investigated by isothermal compression tests, performed on a Gleeble-3800 thermal-mechanical simulator at temperatures between 950 ℃ and 1 150 ℃ and strain rates between 0.1 and 10 s-1. The peak stress and peak strain as functions of processing parameters were obtained. The dependence of peak stress on strain rate and temperature obeys a hyperbolic sine equation with a Zener-Hollomon parameter. By regression analysis, in the temperature range of 950-1 150 ℃ and strain rate range of 0.1?10 s?1, the mean activation energy and the stress exponent were determined to be 351kJ/mol and 4.728, respectively. Meanwhile, models of flow stress and dynamic recrystallization (DRX) grain size were also established. The model predictions show good agreement with experimental results.
基金Project(51304171)supported by the National Natural Science Foundation of ChinaProject(E2013203248)supported by Natural Science Foundation of Hebei Province of ChinaProject(NECSR-201209)supported by Open Foundation of the National Engineering Research Center for Equipment and Technology of Cold Rolling Strip,China
文摘To realize numerical simulation of rolling and obtain the hot forming process parameters for X70 HD steel, the flow stress behaviors of X70 HD steel were investigated under different temperatures（820-1100 ℃ and strain rates（0.01-10 s-1） on a Gleeble-3500 thermo-simulation machine. A new flow stress model was established. The linear and exponential relationship methods were applied to the parameters with respect to temperature and deformation rates. The rise of curve ends under certain conditions was analyzed. The flow stress of X70 HD steel predicted by the proposed model agrees well with the experimental results. So, it greatly improves the precision of the metal thermoplastic processing through finite element method and practical application of engineering.
