Using Euler’s first-order explicit(EE)method and the peridynamic differential operator(PDDO)to discretize the time and internal crystal-size derivatives,respectively,the Euler’s first-order explicit method–peridyna...Using Euler’s first-order explicit(EE)method and the peridynamic differential operator(PDDO)to discretize the time and internal crystal-size derivatives,respectively,the Euler’s first-order explicit method–peridynamic differential operator(EE–PDDO)was obtained for solving the one-dimensional population balance equation in crystallization.Four different conditions during crystallization were studied:size-independent growth,sizedependent growth in a batch process,nucleation and size-independent growth,and nucleation and size-dependent growth in a continuous process.The high accuracy of the EE–PDDO method was confirmed by comparing it with the numerical results obtained using the second-order upwind and HR-van methods.The method is characterized by non-oscillation and high accuracy,especially in the discontinuous and sharp crystal size distribution.The stability of the EE–PDDO method,choice of weight function in the PDDO method,and optimal time step are also discussed.展开更多
Fujian cuisine is a distinctive Chinese cuisine.Today,there are many faults and mistakes in the translation of the dish names,which leads to the failure and inconvenience of cross-cultural communication.The paper is a...Fujian cuisine is a distinctive Chinese cuisine.Today,there are many faults and mistakes in the translation of the dish names,which leads to the failure and inconvenience of cross-cultural communication.The paper is an attempt to probe into the appropriate translation of Fujian dish names by the employment of explicitation.展开更多
Based on corpus-related software and strategic framework of explicitation translation in applied texts,this paper uses Report on the Work of the Government as an example and explore the explicitation in political text...Based on corpus-related software and strategic framework of explicitation translation in applied texts,this paper uses Report on the Work of the Government as an example and explore the explicitation in political texts.According to the research results,political texts have shown explicitation in four sectors of the framework,especially the sector of first person plural pronouns,with quantity,language,culture,and others as influential factors.展开更多
In this work,a method is put forward to obtain the dynamic solution efficiently and accurately for a large-scale train-track-substructure(TTS)system.It is called implicit-explicit integration and multi-time-step solut...In this work,a method is put forward to obtain the dynamic solution efficiently and accurately for a large-scale train-track-substructure(TTS)system.It is called implicit-explicit integration and multi-time-step solution method(abbreviated as mI-nE-MTS method).The TTS system is divided into train-track subsystem and substruc-ture subsystem.Considering that the root cause of low effi-ciency of obtaining TTS solution lies in solving the alge-braic equation of the substructures,the high-efficient Zhai method,an explicit integration scheme,can be introduced to avoid matrix inversion process.The train-track system is solved by implicitly Park method.Moreover,it is known that the requirement of time step size differs for different sub-systems,integration methods and structural frequency response characteristics.A multi-time-step solution is pro-posed,in which time step size for the train-track subsystem and the substructure subsystem can be arbitrarily chosen once satisfying stability and precision demand,namely the time spent for m implicit integral steps is equal to n explicit integral steps,i.e.,mI=nE as mentioned above.The numeri-cal examples show the accuracy,efficiency,and engineering practicality of the proposed method.展开更多
We propose efficient numerical methods for nonseparable non-canonical Hamiltonian systems which are explicit,K-symplectic in the extended phase space with long time energy conservation properties. They are based on ex...We propose efficient numerical methods for nonseparable non-canonical Hamiltonian systems which are explicit,K-symplectic in the extended phase space with long time energy conservation properties. They are based on extending the original phase space to several copies of the phase space and imposing a mechanical restraint on the copies of the phase space. Explicit K-symplectic methods are constructed for two non-canonical Hamiltonian systems. Numerical tests show that the proposed methods exhibit good numerical performance in preserving the phase orbit and the energy of the system over long time, whereas higher order Runge–Kutta methods do not preserve these properties. Numerical tests also show that the K-symplectic methods exhibit better efficiency than that of the same order implicit symplectic, explicit and implicit symplectic methods for the original nonseparable non-canonical systems. On the other hand, the fourth order K-symplectic method is more efficient than the fourth order Yoshida’s method, the optimized partitioned Runge–Kutta and Runge–Kutta–Nystr ¨om explicit K-symplectic methods for the extended phase space Hamiltonians, but less efficient than the the optimized partitioned Runge–Kutta and Runge–Kutta–Nystr ¨om extended phase space symplectic-like methods with the midpoint permutation.展开更多
This study aimed to identify the effectiveness of explicit vocabulary instruction on productive vocabulary learning in writing among intermediate school learners in Saudi Arabia,verify the existence of any statistical...This study aimed to identify the effectiveness of explicit vocabulary instruction on productive vocabulary learning in writing among intermediate school learners in Saudi Arabia,verify the existence of any statistically significant differences at the significance level of 0.01 between the mean scores of the post-test of the control group and the experimental group in the vocabulary test,and verify the existence of any statistically significant differences at the significance level of 0.01 between the mean scores of the pre-and post-test of the experimental group in the vocabulary test in favor of the post-test.The study community consisted of all intermediate school students in the Kingdom of Saudi Arabia,while the study sample included 30 students.The experimental method was adopted to identify the effectiveness of explicit vocabulary instruction on productive vocabulary learning in writing and the achievement test was used as the study tool.The study reached many results including there were no statistically significant differences at the significance level of 0.01 between the mean scores of the post-test of the control group and the experimental group in the vocabulary test and there were no statistically significant differences at the significance level of 0.01 between the mean scores of the pre-and post-test of the experimental group in the vocabulary test in favor of the post-test.According to these results,some recommendations and proposals were made including training English teachers at the intermediate school level in the Kingdom of Saudi Arabia,on explicit vocabulary instruction and conducting future researches on the trends of English teachers at the intermediate school level,in the Kingdom of Saudi Arabia,regarding the adoption of explicit vocabulary instruction while teaching the English language.展开更多
This paper presents an explicit difference scheme with accuracy and branching stability for solving onedimensional parabolic type equation by the method of undetermined parameters and its truncation error is O(△t4+△...This paper presents an explicit difference scheme with accuracy and branching stability for solving onedimensional parabolic type equation by the method of undetermined parameters and its truncation error is O(△t4+△x4). The stability condition is r=a△t/△x2<1/2.展开更多
More researchers have been attempting to clarify some appropriate approaches in teaching and learning grammar especially in the implicit or explicit way. I would attempt to find out some hints in the grammar course of...More researchers have been attempting to clarify some appropriate approaches in teaching and learning grammar especially in the implicit or explicit way. I would attempt to find out some hints in the grammar course offered by a senior teacher of a senior high in order to provide some ideas and inspirations toward future teaching and researches.展开更多
Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical(H-M) interaction of fluid flow and deformation induced by structures built above and under sat...Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical(H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit(ADE)scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in nonuniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourthorder finite difference(FD) approximation to the spatial derivatives of the axisymmetric fluid-diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps,giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua(FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%-50% that of FLAC’s basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%-1.8%.展开更多
Combining with the research on the linear complexity of explicit nonlinear generators of pseudorandom sequences, we study the stability on linear complexity of two classes of explicit inversive generators and two clas...Combining with the research on the linear complexity of explicit nonlinear generators of pseudorandom sequences, we study the stability on linear complexity of two classes of explicit inversive generators and two classes of explicit nonlinear generators. We present some lower bounds in theory on the k-error linear complexity of these explicit generatol＇s, which further improve the cryptographic properties of the corresponding number generators and provide very useful information when they are applied to cryptography.展开更多
It has long been in dispute about whether explicit grammar teaching is more effective in second language learning or implicit grammar teaching is.However,there are more than one factor to take into consideration while...It has long been in dispute about whether explicit grammar teaching is more effective in second language learning or implicit grammar teaching is.However,there are more than one factor to take into consideration while discussing which way is better for L2 learners.This short essay aims at depicting three respects concerning grammar teaching,namely learning context,language learners'beliefs and needs,and grammar instruction.When educators and practitioners try to adopt grammar instruction either implicitly or explicitly in L2 learners'writing development,they probably need to consider the above three factors and to find out the best way to produce more effective teaching results among their students.展开更多
An economical explicit scheme of time integration is implemented in a regional model over Indian region to achieve computational economy. The model is also integrated by explicit Leap-Frog Scheme. The performance of e...An economical explicit scheme of time integration is implemented in a regional model over Indian region to achieve computational economy. The model is also integrated by explicit Leap-Frog Scheme. The performance of economical explicit scheme is evaluated by comparing the forecast results with those produced by leap-frog scheme. The results show that the economical explicit scheme produces more or less similar forecasts as compared to those produced with leap-frog scheme. However, application of the economical explicit scheme saves substantial amount of computer time. The scheme is found nearly four times economical as compared to explicit leap-frog scheme.展开更多
Implicit and explicit learning strategies of SL vocabulary acquisition are summarized based on precious studies and experiments. It is concluded that implicit learning strategies dolittlehelpto SL vocabulary acquisiti...Implicit and explicit learning strategies of SL vocabulary acquisition are summarized based on precious studies and experiments. It is concluded that implicit learning strategies dolittlehelpto SL vocabulary acquisition, but explicit learning strategies play a very important part in SL vocabulary acquisition. Besides, an assumption is proposed: the more obvious explicit learning is in vocabulary acquisition, the more words learners can acquire. It is hoped that this research has certain implications for SL learners and teaching.展开更多
This study investigated the effect of explicit instruction about DCs in argumentative writings by 15 Chinese learners of English. This study involved in a 4-week experiment. Pre-and post-writing tests were quantitativ...This study investigated the effect of explicit instruction about DCs in argumentative writings by 15 Chinese learners of English. This study involved in a 4-week experiment. Pre-and post-writing tests were quantitatively analyzed to examine whether the explicit instruction about DCs had a significant effect on the students'argumentative writing. The findings revealed that the ex-plicit instruction of the target DCs facilitated the improvement of the participants in their argumentative writing .展开更多
The teachers use explicit learning in the traditional teaching of English grammar, which pays great attention to the master of grammar knowledge points. Nowadays, some English teachers excessively emphasize the import...The teachers use explicit learning in the traditional teaching of English grammar, which pays great attention to the master of grammar knowledge points. Nowadays, some English teachers excessively emphasize the importance of teaching grammar imperceptibly, but neglect to explain the rules of grammar. The diametrically isolation of implicit and explicit learning doesn＇t correspond with the English grammar teaching. So the teachers should combine the two learning styles in order to make the best use of them to teach English grammar.展开更多
A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions,motion control over guide rolls,and mass scaling.The method has the following feature...A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions,motion control over guide rolls,and mass scaling.The method has the following features:1)the elastic-plastic dynamic explicit approach instead of the static implicit approach is adopted to solve the process so as to greatly improve computational efficiency without sacrificing computational accuracy;2)the coupled thermal-mechanical effect is considered as opposed to the conventional isothermal assumption,which is more practical;3)in contrast to the simplified 2D or local 3D ring model,the full 3D ring is modeled to simulate the process.Based on the FE modeling method,two cases of hot plain ring rolling are simulated in the FEA software ABAQUS/Explicit.The simulation results are compared with the experimental measurements and the good agreement between them is observed regarding the material flow and the temperature distribution of the ring.展开更多
Ecosystem service is an emerging concept that grows to be a hot research area in ecology.Spatially explicit ecosystem service values are important for ecosystem service management.However,it is difficult to quantify e...Ecosystem service is an emerging concept that grows to be a hot research area in ecology.Spatially explicit ecosystem service values are important for ecosystem service management.However,it is difficult to quantify ecosystem services.Remote sensing provides images covering Earth surface,which by nature are spatially explicit.Thus,remote sensing can be useful for quantitative assessment of ecosystem services.This paper reviews spatially explicit ecosystem service studies conducted in ecology and remote sensing in order to find out how remote sensing can be used for ecosystem service assessment.Several important areas considered include land cover,biodiversity,and carbon,water and soil related ecosystem services.We found that remote sensing can be used for ecosystem service assessment in three different ways:direct monitoring,indirect monitoring,and combined use with ecosystem models.Some plant and water related ecosystem services can be directly monitored by remote sensing.Most commonly,remote sensing can provide surrogate information on plant and soil characteristics in an ecosystem.For ecosystem process related ecosystem services,remote sensing can help measure spatially explicit parameters.We conclude that acquiring good in-situ measurements and selecting appropriate remote sensor data in terms of resolution are critical for accurate assessment of ecosystem services.展开更多
Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this...Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this paper, for the sake of illustrating in detail how dynamic explicit finite element method is applied to the numerical simulation of the autobody panel forming process,an example of optimization of stamping process pain meters of an inner door panel is presented. Using dynamic explicit finite element code Ls-DYNA3D, the inner door panel has been optimized by adapting pa- rameters such as the initial blank geometry and position, blank-holder forces and the location of drawbeads, and satisfied results are obtained.展开更多
文摘Using Euler’s first-order explicit(EE)method and the peridynamic differential operator(PDDO)to discretize the time and internal crystal-size derivatives,respectively,the Euler’s first-order explicit method–peridynamic differential operator(EE–PDDO)was obtained for solving the one-dimensional population balance equation in crystallization.Four different conditions during crystallization were studied:size-independent growth,sizedependent growth in a batch process,nucleation and size-independent growth,and nucleation and size-dependent growth in a continuous process.The high accuracy of the EE–PDDO method was confirmed by comparing it with the numerical results obtained using the second-order upwind and HR-van methods.The method is characterized by non-oscillation and high accuracy,especially in the discontinuous and sharp crystal size distribution.The stability of the EE–PDDO method,choice of weight function in the PDDO method,and optimal time step are also discussed.
文摘Fujian cuisine is a distinctive Chinese cuisine.Today,there are many faults and mistakes in the translation of the dish names,which leads to the failure and inconvenience of cross-cultural communication.The paper is an attempt to probe into the appropriate translation of Fujian dish names by the employment of explicitation.
文摘Based on corpus-related software and strategic framework of explicitation translation in applied texts,this paper uses Report on the Work of the Government as an example and explore the explicitation in political texts.According to the research results,political texts have shown explicitation in four sectors of the framework,especially the sector of first person plural pronouns,with quantity,language,culture,and others as influential factors.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.52008404,U1934217 and 11790283)Science and Technology Research and Development Program Project of China Railway Group Limited(Major Special Project,No.2020-Special-02)the National Natural Science Foundation of Hunan Province(Grant No.2021JJ30850).
文摘In this work,a method is put forward to obtain the dynamic solution efficiently and accurately for a large-scale train-track-substructure(TTS)system.It is called implicit-explicit integration and multi-time-step solution method(abbreviated as mI-nE-MTS method).The TTS system is divided into train-track subsystem and substruc-ture subsystem.Considering that the root cause of low effi-ciency of obtaining TTS solution lies in solving the alge-braic equation of the substructures,the high-efficient Zhai method,an explicit integration scheme,can be introduced to avoid matrix inversion process.The train-track system is solved by implicitly Park method.Moreover,it is known that the requirement of time step size differs for different sub-systems,integration methods and structural frequency response characteristics.A multi-time-step solution is pro-posed,in which time step size for the train-track subsystem and the substructure subsystem can be arbitrarily chosen once satisfying stability and precision demand,namely the time spent for m implicit integral steps is equal to n explicit integral steps,i.e.,mI=nE as mentioned above.The numeri-cal examples show the accuracy,efficiency,and engineering practicality of the proposed method.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11901564 and 12171466)。
文摘We propose efficient numerical methods for nonseparable non-canonical Hamiltonian systems which are explicit,K-symplectic in the extended phase space with long time energy conservation properties. They are based on extending the original phase space to several copies of the phase space and imposing a mechanical restraint on the copies of the phase space. Explicit K-symplectic methods are constructed for two non-canonical Hamiltonian systems. Numerical tests show that the proposed methods exhibit good numerical performance in preserving the phase orbit and the energy of the system over long time, whereas higher order Runge–Kutta methods do not preserve these properties. Numerical tests also show that the K-symplectic methods exhibit better efficiency than that of the same order implicit symplectic, explicit and implicit symplectic methods for the original nonseparable non-canonical systems. On the other hand, the fourth order K-symplectic method is more efficient than the fourth order Yoshida’s method, the optimized partitioned Runge–Kutta and Runge–Kutta–Nystr ¨om explicit K-symplectic methods for the extended phase space Hamiltonians, but less efficient than the the optimized partitioned Runge–Kutta and Runge–Kutta–Nystr ¨om extended phase space symplectic-like methods with the midpoint permutation.
文摘This study aimed to identify the effectiveness of explicit vocabulary instruction on productive vocabulary learning in writing among intermediate school learners in Saudi Arabia,verify the existence of any statistically significant differences at the significance level of 0.01 between the mean scores of the post-test of the control group and the experimental group in the vocabulary test,and verify the existence of any statistically significant differences at the significance level of 0.01 between the mean scores of the pre-and post-test of the experimental group in the vocabulary test in favor of the post-test.The study community consisted of all intermediate school students in the Kingdom of Saudi Arabia,while the study sample included 30 students.The experimental method was adopted to identify the effectiveness of explicit vocabulary instruction on productive vocabulary learning in writing and the achievement test was used as the study tool.The study reached many results including there were no statistically significant differences at the significance level of 0.01 between the mean scores of the post-test of the control group and the experimental group in the vocabulary test and there were no statistically significant differences at the significance level of 0.01 between the mean scores of the pre-and post-test of the experimental group in the vocabulary test in favor of the post-test.According to these results,some recommendations and proposals were made including training English teachers at the intermediate school level in the Kingdom of Saudi Arabia,on explicit vocabulary instruction and conducting future researches on the trends of English teachers at the intermediate school level,in the Kingdom of Saudi Arabia,regarding the adoption of explicit vocabulary instruction while teaching the English language.
文摘This paper presents an explicit difference scheme with accuracy and branching stability for solving onedimensional parabolic type equation by the method of undetermined parameters and its truncation error is O(△t4+△x4). The stability condition is r=a△t/△x2<1/2.
文摘More researchers have been attempting to clarify some appropriate approaches in teaching and learning grammar especially in the implicit or explicit way. I would attempt to find out some hints in the grammar course offered by a senior teacher of a senior high in order to provide some ideas and inspirations toward future teaching and researches.
基金the support from the University Transportation Center for Underground Transportation Infrastructure at the Colorado School of Mines for partially funding this research under Grant No. 69A3551747118 of the Fixing America's Surface Transportation Act (FAST Act) of U.S. DoT FY2016
文摘Explicit solution techniques have been widely used in geotechnical engineering for simulating the coupled hydro-mechanical(H-M) interaction of fluid flow and deformation induced by structures built above and under saturated ground, i.e. circular footing and deep tunnel. However, the technique is only conditionally stable and requires small time steps, portending its inefficiency for simulating large-scale H-M problems. To improve its efficiency, the unconditionally stable alternating direction explicit(ADE)scheme could be used to solve the flow problem. The standard ADE scheme, however, is only moderately accurate and is restricted to uniform grids and plane strain flow conditions. This paper aims to remove these drawbacks by developing a novel high-order ADE scheme capable of solving flow problems in nonuniform grids and under axisymmetric conditions. The new scheme is derived by performing a fourthorder finite difference(FD) approximation to the spatial derivatives of the axisymmetric fluid-diffusion equation in a non-uniform grid configuration. The implicit Crank-Nicolson technique is then applied to the resulting approximation, and the subsequent equation is split into two alternating direction sweeps,giving rise to a new axisymmetric ADE scheme. The pore pressure solutions from the new scheme are then sequentially coupled with an existing geomechanical simulator in the computer code fast Lagrangian analysis of continua(FLAC). This coupling procedure is called the sequentially-explicit coupling technique based on the fourth-order axisymmetric ADE scheme or SEA-4-AXI. Application of SEA-4-AXI for solving axisymmetric consolidation of a circular footing and of advancing tunnel in deep saturated ground shows that SEA-4-AXI reduces computer runtime up to 42%-50% that of FLAC’s basic scheme without numerical instability. In addition, it produces high numerical accuracy of the H-M solutions with average percentage difference of only 0.5%-1.8%.
基金the Natural Science Foundation of Fujian Province (2007F3086)the Funds of the Education Department of Fujian Prov-ince (JA07164)the Open Funds of Key Laboratory of Fujian Province University Network Security and Cryptology (07B005)
文摘Combining with the research on the linear complexity of explicit nonlinear generators of pseudorandom sequences, we study the stability on linear complexity of two classes of explicit inversive generators and two classes of explicit nonlinear generators. We present some lower bounds in theory on the k-error linear complexity of these explicit generatol＇s, which further improve the cryptographic properties of the corresponding number generators and provide very useful information when they are applied to cryptography.
文摘It has long been in dispute about whether explicit grammar teaching is more effective in second language learning or implicit grammar teaching is.However,there are more than one factor to take into consideration while discussing which way is better for L2 learners.This short essay aims at depicting three respects concerning grammar teaching,namely learning context,language learners'beliefs and needs,and grammar instruction.When educators and practitioners try to adopt grammar instruction either implicitly or explicitly in L2 learners'writing development,they probably need to consider the above three factors and to find out the best way to produce more effective teaching results among their students.
文摘An economical explicit scheme of time integration is implemented in a regional model over Indian region to achieve computational economy. The model is also integrated by explicit Leap-Frog Scheme. The performance of economical explicit scheme is evaluated by comparing the forecast results with those produced by leap-frog scheme. The results show that the economical explicit scheme produces more or less similar forecasts as compared to those produced with leap-frog scheme. However, application of the economical explicit scheme saves substantial amount of computer time. The scheme is found nearly four times economical as compared to explicit leap-frog scheme.
文摘Implicit and explicit learning strategies of SL vocabulary acquisition are summarized based on precious studies and experiments. It is concluded that implicit learning strategies dolittlehelpto SL vocabulary acquisition, but explicit learning strategies play a very important part in SL vocabulary acquisition. Besides, an assumption is proposed: the more obvious explicit learning is in vocabulary acquisition, the more words learners can acquire. It is hoped that this research has certain implications for SL learners and teaching.
文摘This study investigated the effect of explicit instruction about DCs in argumentative writings by 15 Chinese learners of English. This study involved in a 4-week experiment. Pre-and post-writing tests were quantitatively analyzed to examine whether the explicit instruction about DCs had a significant effect on the students'argumentative writing. The findings revealed that the ex-plicit instruction of the target DCs facilitated the improvement of the participants in their argumentative writing .
文摘The teachers use explicit learning in the traditional teaching of English grammar, which pays great attention to the master of grammar knowledge points. Nowadays, some English teachers excessively emphasize the importance of teaching grammar imperceptibly, but neglect to explain the rules of grammar. The diametrically isolation of implicit and explicit learning doesn＇t correspond with the English grammar teaching. So the teachers should combine the two learning styles in order to make the best use of them to teach English grammar.
基金Project(50335060) supported by the National Natural Science Foundation for Key Program of ChinaProject(50225518) supported by the National Science Fund of China for Distinguished Young Scholars
文摘A new FE modeling method of hot ring rolling was presented by solving key technologies such as contact and heat boundary conditions,motion control over guide rolls,and mass scaling.The method has the following features:1)the elastic-plastic dynamic explicit approach instead of the static implicit approach is adopted to solve the process so as to greatly improve computational efficiency without sacrificing computational accuracy;2)the coupled thermal-mechanical effect is considered as opposed to the conventional isothermal assumption,which is more practical;3)in contrast to the simplified 2D or local 3D ring model,the full 3D ring is modeled to simulate the process.Based on the FE modeling method,two cases of hot plain ring rolling are simulated in the FEA software ABAQUS/Explicit.The simulation results are compared with the experimental measurements and the good agreement between them is observed regarding the material flow and the temperature distribution of the ring.
基金Under the auspices of National Basic Research Priorities Program of China (No 2009CB421104)National Natural Science Foundation of China (No 40801070)+1 种基金Knowledge Innovation Programs of Chinese Academy of Sciences (No KZCX2-YW-421)the CAS/SAFEA International Partnership Program for Creative Research Teams of 'Ecosystem Processes and Services'
文摘Ecosystem service is an emerging concept that grows to be a hot research area in ecology.Spatially explicit ecosystem service values are important for ecosystem service management.However,it is difficult to quantify ecosystem services.Remote sensing provides images covering Earth surface,which by nature are spatially explicit.Thus,remote sensing can be useful for quantitative assessment of ecosystem services.This paper reviews spatially explicit ecosystem service studies conducted in ecology and remote sensing in order to find out how remote sensing can be used for ecosystem service assessment.Several important areas considered include land cover,biodiversity,and carbon,water and soil related ecosystem services.We found that remote sensing can be used for ecosystem service assessment in three different ways:direct monitoring,indirect monitoring,and combined use with ecosystem models.Some plant and water related ecosystem services can be directly monitored by remote sensing.Most commonly,remote sensing can provide surrogate information on plant and soil characteristics in an ecosystem.For ecosystem process related ecosystem services,remote sensing can help measure spatially explicit parameters.We conclude that acquiring good in-situ measurements and selecting appropriate remote sensor data in terms of resolution are critical for accurate assessment of ecosystem services.
文摘Taking CPU time cost and analysis accuracy into account, dynamic explicit finite ele- ment method is adopted to optimize the forming process of autobody panels that often have large sizes and complex geometry. In this paper, for the sake of illustrating in detail how dynamic explicit finite element method is applied to the numerical simulation of the autobody panel forming process,an example of optimization of stamping process pain meters of an inner door panel is presented. Using dynamic explicit finite element code Ls-DYNA3D, the inner door panel has been optimized by adapting pa- rameters such as the initial blank geometry and position, blank-holder forces and the location of drawbeads, and satisfied results are obtained.
