Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green func...Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.展开更多
A self-adaptive precise algorithm in the time domain was employed to solve 2-D nonlinear coupled heat and moisture transfer problems. By expanding variables at a discretized time interval, the variations of variables ...A self-adaptive precise algorithm in the time domain was employed to solve 2-D nonlinear coupled heat and moisture transfer problems. By expanding variables at a discretized time interval, the variations of variables can be described more precisely,and a nonlinear coupled initial and boundary value problem was converted into a series of recurrent linear boundary value problems which are solved by FE technique. In the computation, no additional assumption and the nonlinear iteration are required, and a criterion for self-adaptive computation is proposed to maintain sufficient computing accuracy for the change sizes of time steps. In the numerical comparison, the variations of material properties with temperature, moisture content, and both temperature and moisture content are taken into account, respectively. Satisfactory results have been obtained, indicating that the proposed approach is capable of dealing with complex nonlinear problems.展开更多
We consider the one-dimensional bio-heat transfer equation with quadratic temperature-dependent blood perfusion, which governs the temperature distribution inside biological tissues. Using an extended mapping method w...We consider the one-dimensional bio-heat transfer equation with quadratic temperature-dependent blood perfusion, which governs the temperature distribution inside biological tissues. Using an extended mapping method with symbolic computation, we obtain the exact analytical thermal traveling wave solution, which describes the non-uniform temperature distribution inside the bodies. The found exact solution is used to investigate the temperature distribution in the tissues. It is found that the surrounding medium with higher temperature does not necessarily imply that the tissue will quickly (after a short duration of heating process) reach the desired temperature. It is also found that increased perfusion causes a decline in local temperature.展开更多
In this paper,we present a unified finite volume method preserving discrete maximum principle(DMP)for the conjugate heat transfer problems with general interface conditions.We prove the existence of the numerical solu...In this paper,we present a unified finite volume method preserving discrete maximum principle(DMP)for the conjugate heat transfer problems with general interface conditions.We prove the existence of the numerical solution and the DMP-preserving property.Numerical experiments show that the nonlinear iteration numbers of the scheme in[24]increase rapidly when the interfacial coefficients decrease to zero.In contrast,the nonlinear iteration numbers of the unified scheme do not increase when the interfacial coefficients decrease to zero,which reveals that the unified scheme is more robust than the scheme in[24].The accuracy and DMP-preserving property of the scheme are also veri ed in the numerical experiments.展开更多
Stochastic temperature distribution should be carefully inspected in the thermal-failure design of heterogeneous solids with unexpected random energy excitations.Stochastic multiscale modeling for these problems invol...Stochastic temperature distribution should be carefully inspected in the thermal-failure design of heterogeneous solids with unexpected random energy excitations.Stochastic multiscale modeling for these problems involve multiscale and highdimensional uncertain thermal parameters,which remains limitation of prohibitive computation.In this paper,we propose a multi-modes based constrained energy minimization generalized multiscale finite element method(MCEM-GMsFEM),which can transform the original stochastic multiscale model into a series of recursive multiscale models sharing the same deterministic material parameters by multiscale analysis.Thus,MCEM-GMsFEM reveals an inherent low-dimensional representation in random space,and is designed to effectively reduce the complexity of repeated computation of discretized multiscale systems.In addition,the convergence analysis is established,and the optimal error estimates are derived.Finally,several typical random fluctuations on multiscale thermal conductivity are considered to validate the theoretical results in the numerical examples.The numerical results indicate that the multi-modes multiscale approach is a robust integrated method with the excellent performance.展开更多
The presence of non-gray radiative properties in a reheating furnace’s medium that absorbs,emits,and involves non-gray creates more complex radiative heat transfer problems.Furthermore,it adds difficulty to solving t...The presence of non-gray radiative properties in a reheating furnace’s medium that absorbs,emits,and involves non-gray creates more complex radiative heat transfer problems.Furthermore,it adds difficulty to solving the coupled conduction,convection,and radiation problem,leading to suboptimal efficiency that fails to meet real-time control demands.To overcome this difficulty,comparable gray radiative properties of non-gray media are proposed and estimated by solving an inverse problem.However,the required iteration numbers by using a least-squares method are too many and resulted in a very low inverse efficiency.It is necessary to present an efficient method for the equivalence.The Levenberg-Marquardt algorithm is utilized to solve the inverse problem of coupled heat transfer,and the gray-equivalent radiative characteristics are successfully recovered.It is our intention that the issue of low inverse efficiency,which has been observed when the least-squares method is employed,will be resolved.To enhance the performance of the Levenberg-Marquardt algorithm,a modification is implemented for determining the damping factor.Detailed investigations are also conducted to evaluate its accuracy,stability of convergence,efficiency,and robustness of the algorithm.Subsequently,a comparison is made between the results achieved using each method.展开更多
On the basis of clarifying and defining rural land transfer, the necessity of rural land transfer is analyzed. Land transfer is the necessity in terms of promoting agricultural scale operation and improving production...On the basis of clarifying and defining rural land transfer, the necessity of rural land transfer is analyzed. Land transfer is the necessity in terms of promoting agricultural scale operation and improving production efficiency; proving opportunities for narrowing urban and rural gap; realizing rural surplus labor transfer and facilitating urbanization. Major problems in the existing rural land transfer are analyzed:unclear laws and regulations and rural land transfer lacks relevant legal protection;rural social security system is imperfect and can not solve farmers' worries after land transfer; farmers and local governments are restricted by traditional ideas and it is hard to carry out the land transfer policies; rural system construction is relatively backward and the rural land transfer market is immature. Countermeasures on the governmental behaviors in rural land transfer are put forward: stipulating relevant administrative laws and regulations and perfecting the political system of rural land transfer; perfecting rural social security system and solving farmers' worries after land transfer; changing the ideas and working style of local officials and leading farmers to form the scientific land transfer outlook;and vigorously promoting the construction of system and positively cultivating rural land transfer market.展开更多
This paper emphasizes the urgency of solving the problems of farmers' employment under the condition of land transfer,indicating that solving the problems of farmers' employment is the necessary requirement of...This paper emphasizes the urgency of solving the problems of farmers' employment under the condition of land transfer,indicating that solving the problems of farmers' employment is the necessary requirement of land transfer,the actual requirement of constructing well-off society comprehensively,and the objective requirement of transforming developmental model.The characteristics of the problems of farmers' employment under the condition of land transfer are as follows:the rural surplus labor forces increase,and the ubiquitous unemployment is urgent;the employment room of farmers is narrow,and the structural unemployment is serious;the ability of farmers' employment is poor,and recessive unemployment has a large proportion;the situation of farmers' employment is not so sanguine,and the policy unemployment is frequent.This paper points out the causes of farmers' employment problems under the situation of land transfer as follows:in terms of analysis of subjective factors,farmers' self-employment ability is yet to be underpinned;in terms of analysis of objective factors,the relevant mechanism of government is unsound.Finally,corresponding countermeasures and suggestions are put forward as follows:establish the mechanism of farmer traceability analysis under the condition of land transfer;strengthen the training of farmers' skills;reinforce the publicity and education of farmers' employment concept;promote the process of urbanization and construct the employment vehicle of farmers;adjust the industrial structure in rural areas and expand the internal employment in rural areas;improve macro regulation and improve the employment environment for farmers.展开更多
The present work deals with the calculation of transition probability between two diabatic potentials coupled by any arbitrary coupling. The method presented in this work is applicable to any type of coupling while fo...The present work deals with the calculation of transition probability between two diabatic potentials coupled by any arbitrary coupling. The method presented in this work is applicable to any type of coupling while for numerical calculations we have assumed the arbitrary coupling as Gaussian coupling. This arbitrary coupling is expressed as a collection of Dirac delta functions and by the use of the transfer matrix technique the transition probability from one diabatic potential to another diabatic potential is calculated. We examine our approach by considering the case of two constant potentials coupled by Gaussian coupling as an arbitrary coupling.展开更多
Negative language transfer is a common phenomenon in Chinese college students 'English writing. Influenced by our native language, Chinese college students tend to apply Chinese language rules to English writing. ...Negative language transfer is a common phenomenon in Chinese college students 'English writing. Influenced by our native language, Chinese college students tend to apply Chinese language rules to English writing. This paper primarily focuses on the negative language transfer in College English writing. It tries to illustrate and analyze the negative language transfer in college students'English writing in terms of lexicon, syntax, discourse, and pragmatics. Based on the above analysis, it proceeds to put forward some suggestions on how to teach English writing effectively and efficiently.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 50776097)
文摘Analytically solving a three-dimensional （3-D） bioheat transfer problem with phase change during a freezing process is extremely difficult but theoretically important. The moving heat source model and the Green function method are introduced to deal with the cryopreservation process of in vitro biomaterials. Exact solutions for the 3-D temperature transients of tissues under various boundary conditions, such as totally convective cooling, totally fixed temperature cooling and a hybrid between them on tissue surfaces, are obtained. Furthermore, the cryosurgical process in living tissues subject to freezing by a single or multiple cryoprobes is also analytically solved. A closed-form analytical solution to the bioheat phase change process is derived by considering contributions from blood perfusion heat transfer, metabolic heat generation, and heat sink of a cryoprobe. The present method is expected to have significant value for analytically solving complex bioheat transfer problems with phase change.
文摘A self-adaptive precise algorithm in the time domain was employed to solve 2-D nonlinear coupled heat and moisture transfer problems. By expanding variables at a discretized time interval, the variations of variables can be described more precisely,and a nonlinear coupled initial and boundary value problem was converted into a series of recurrent linear boundary value problems which are solved by FE technique. In the computation, no additional assumption and the nonlinear iteration are required, and a criterion for self-adaptive computation is proposed to maintain sufficient computing accuracy for the change sizes of time steps. In the numerical comparison, the variations of material properties with temperature, moisture content, and both temperature and moisture content are taken into account, respectively. Satisfactory results have been obtained, indicating that the proposed approach is capable of dealing with complex nonlinear problems.
文摘We consider the one-dimensional bio-heat transfer equation with quadratic temperature-dependent blood perfusion, which governs the temperature distribution inside biological tissues. Using an extended mapping method with symbolic computation, we obtain the exact analytical thermal traveling wave solution, which describes the non-uniform temperature distribution inside the bodies. The found exact solution is used to investigate the temperature distribution in the tissues. It is found that the surrounding medium with higher temperature does not necessarily imply that the tissue will quickly (after a short duration of heating process) reach the desired temperature. It is also found that increased perfusion causes a decline in local temperature.
基金National Natural Science Foundation of China(11971069,12071045)Foundation of CAEP(CX20210042)Science Challenge Project(No.TZ2016002).
文摘In this paper,we present a unified finite volume method preserving discrete maximum principle(DMP)for the conjugate heat transfer problems with general interface conditions.We prove the existence of the numerical solution and the DMP-preserving property.Numerical experiments show that the nonlinear iteration numbers of the scheme in[24]increase rapidly when the interfacial coefficients decrease to zero.In contrast,the nonlinear iteration numbers of the unified scheme do not increase when the interfacial coefficients decrease to zero,which reveals that the unified scheme is more robust than the scheme in[24].The accuracy and DMP-preserving property of the scheme are also veri ed in the numerical experiments.
基金the Natural Science Foundation of Shanghai(No.21ZR1465800)the Science Challenge Project(No.TZ2018001)+2 种基金the Interdisciplinary Project in Ocean Research of Tongji University,the Aeronautical Science Foundation of China(No.2020001053002)the National Key R&D Program of China(No.2020YFA0713603)the Fundamental Research Funds for the Central Universities.
文摘Stochastic temperature distribution should be carefully inspected in the thermal-failure design of heterogeneous solids with unexpected random energy excitations.Stochastic multiscale modeling for these problems involve multiscale and highdimensional uncertain thermal parameters,which remains limitation of prohibitive computation.In this paper,we propose a multi-modes based constrained energy minimization generalized multiscale finite element method(MCEM-GMsFEM),which can transform the original stochastic multiscale model into a series of recursive multiscale models sharing the same deterministic material parameters by multiscale analysis.Thus,MCEM-GMsFEM reveals an inherent low-dimensional representation in random space,and is designed to effectively reduce the complexity of repeated computation of discretized multiscale systems.In addition,the convergence analysis is established,and the optimal error estimates are derived.Finally,several typical random fluctuations on multiscale thermal conductivity are considered to validate the theoretical results in the numerical examples.The numerical results indicate that the multi-modes multiscale approach is a robust integrated method with the excellent performance.
基金supported by the Na⁃tional Natural Science Foundation of China(No.12172078)the Fundamental Research Funds for the Central Univer⁃sities(No.DUT24MS007).
文摘The presence of non-gray radiative properties in a reheating furnace’s medium that absorbs,emits,and involves non-gray creates more complex radiative heat transfer problems.Furthermore,it adds difficulty to solving the coupled conduction,convection,and radiation problem,leading to suboptimal efficiency that fails to meet real-time control demands.To overcome this difficulty,comparable gray radiative properties of non-gray media are proposed and estimated by solving an inverse problem.However,the required iteration numbers by using a least-squares method are too many and resulted in a very low inverse efficiency.It is necessary to present an efficient method for the equivalence.The Levenberg-Marquardt algorithm is utilized to solve the inverse problem of coupled heat transfer,and the gray-equivalent radiative characteristics are successfully recovered.It is our intention that the issue of low inverse efficiency,which has been observed when the least-squares method is employed,will be resolved.To enhance the performance of the Levenberg-Marquardt algorithm,a modification is implemented for determining the damping factor.Detailed investigations are also conducted to evaluate its accuracy,stability of convergence,efficiency,and robustness of the algorithm.Subsequently,a comparison is made between the results achieved using each method.
文摘On the basis of clarifying and defining rural land transfer, the necessity of rural land transfer is analyzed. Land transfer is the necessity in terms of promoting agricultural scale operation and improving production efficiency; proving opportunities for narrowing urban and rural gap; realizing rural surplus labor transfer and facilitating urbanization. Major problems in the existing rural land transfer are analyzed:unclear laws and regulations and rural land transfer lacks relevant legal protection;rural social security system is imperfect and can not solve farmers' worries after land transfer; farmers and local governments are restricted by traditional ideas and it is hard to carry out the land transfer policies; rural system construction is relatively backward and the rural land transfer market is immature. Countermeasures on the governmental behaviors in rural land transfer are put forward: stipulating relevant administrative laws and regulations and perfecting the political system of rural land transfer; perfecting rural social security system and solving farmers' worries after land transfer; changing the ideas and working style of local officials and leading farmers to form the scientific land transfer outlook;and vigorously promoting the construction of system and positively cultivating rural land transfer market.
文摘This paper emphasizes the urgency of solving the problems of farmers' employment under the condition of land transfer,indicating that solving the problems of farmers' employment is the necessary requirement of land transfer,the actual requirement of constructing well-off society comprehensively,and the objective requirement of transforming developmental model.The characteristics of the problems of farmers' employment under the condition of land transfer are as follows:the rural surplus labor forces increase,and the ubiquitous unemployment is urgent;the employment room of farmers is narrow,and the structural unemployment is serious;the ability of farmers' employment is poor,and recessive unemployment has a large proportion;the situation of farmers' employment is not so sanguine,and the policy unemployment is frequent.This paper points out the causes of farmers' employment problems under the situation of land transfer as follows:in terms of analysis of subjective factors,farmers' self-employment ability is yet to be underpinned;in terms of analysis of objective factors,the relevant mechanism of government is unsound.Finally,corresponding countermeasures and suggestions are put forward as follows:establish the mechanism of farmer traceability analysis under the condition of land transfer;strengthen the training of farmers' skills;reinforce the publicity and education of farmers' employment concept;promote the process of urbanization and construct the employment vehicle of farmers;adjust the industrial structure in rural areas and expand the internal employment in rural areas;improve macro regulation and improve the employment environment for farmers.
基金This work was partially supported by NSFC Project （Grant No. 11031006, 91130002, 11171281）, the Key Project of Scientific Research Fund of Hunan Provincial Science and Technology Department （Grant No. 2011FJ2011）, Hunan Provincial Natural Science Foundation of China （Grant No. 12JJ3010）.
文摘The present work deals with the calculation of transition probability between two diabatic potentials coupled by any arbitrary coupling. The method presented in this work is applicable to any type of coupling while for numerical calculations we have assumed the arbitrary coupling as Gaussian coupling. This arbitrary coupling is expressed as a collection of Dirac delta functions and by the use of the transfer matrix technique the transition probability from one diabatic potential to another diabatic potential is calculated. We examine our approach by considering the case of two constant potentials coupled by Gaussian coupling as an arbitrary coupling.
文摘Negative language transfer is a common phenomenon in Chinese college students 'English writing. Influenced by our native language, Chinese college students tend to apply Chinese language rules to English writing. This paper primarily focuses on the negative language transfer in College English writing. It tries to illustrate and analyze the negative language transfer in college students'English writing in terms of lexicon, syntax, discourse, and pragmatics. Based on the above analysis, it proceeds to put forward some suggestions on how to teach English writing effectively and efficiently.
