We study the heat equation with non-periodic coefficients in periodically perforated domains with a homogeneous Neumann condition on the holes. Using the time-dependent unfolding method, we obtain some homogenization ...We study the heat equation with non-periodic coefficients in periodically perforated domains with a homogeneous Neumann condition on the holes. Using the time-dependent unfolding method, we obtain some homogenization and corrector results which generalize those by Donato and Nabil(2001).展开更多
An accurate energy calibration of a 5＂× 2＂ BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measure...An accurate energy calibration of a 5＂× 2＂ BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with 22Na, 137Cs and 54Mn photon sources and simulated using the GRESP code, which was developed at the Physiknlisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in toknmak experiments.展开更多
Ultra-large plate forgings are foundation of heavy machinery,but many parts of the type cannot be made by conventional technologies due to the characters of extreme manufacturing in terms of size and quality requireme...Ultra-large plate forgings are foundation of heavy machinery,but many parts of the type cannot be made by conventional technologies due to the characters of extreme manufacturing in terms of size and quality requirements.This paper introduced a systematically method called cylinder unfolding method(CUM)for producing large plate forgings,by using a serial of operations including“splitting”,“unfolding”,and“flattening”of a thick cylinder obtained from saddle forging.The technological route of CUM was presented in detail with an example of plate forging with the horizontal sizes of 6100 mm and thickness of 300 mm.The deformation features of saddle forging for fabricating transitional cylinders were analyzed,and then the subsequent handling steps including splitting,unfolding and flattening of the cylinder,as well as the auxiliary processing,were addressed.The practice proved that CUM can provide an efficient way for manufacturing ultra-large plate forgings and meet the strict requirements in geometry and mechanical performance,without highly increasing the investments of forming equipment and tooling.展开更多
Objective: to explore the application value of expanded teaching method in pediatric clinical teaching practice. Methods: 100 children's department interns received from the hospital from January 2016 to February ...Objective: to explore the application value of expanded teaching method in pediatric clinical teaching practice. Methods: 100 children's department interns received from the hospital from January 2016 to February 2020 were selected as the research object, and they were randomly divided into two groups, with 50 interns in each group. The control group implemented the conventional classroom explanation teaching method for pediatric clinical teaching, and the observation group adopted the exhibition teaching method for learning guidance, and during and after the teaching. The teaching effect, classroom easy memory rate and the improvement rate of clinical processing ability of the two groups were evaluated. Results: teaching results: the effective rate of the observation group was significantly better than that of the control group. Easy memory rate of interns in class: the easy memory rate of students in the observation group was significantly higher than that in the control group. Improvement rate of clinical treatment ability: in clinic, the students in the observation group have stronger ability to deal with emergencies in clinic, and their clinical treatment ability is improved more significantly compared with the control group. There was significant difference between the two groups in three indexes (teaching efficiency, easy memory rate of interns in class and improvement rate of clinical processing ability) (P < 0.05). Conclusion: in the clinical teaching practice of pediatrics, the application of expansion teaching method can effectively improve the teaching efficiency, help interns remember relevant knowledge more quickly, and give more play to its application value in clinical practice teaching.展开更多
In this paper, we study a class of hyperbolic-parabolic problems in periodically perforated domains with a homogeneous Neumann condition on the boundary of holes. We focus on the homogenization of these equations, whi...In this paper, we study a class of hyperbolic-parabolic problems in periodically perforated domains with a homogeneous Neumann condition on the boundary of holes. We focus on the homogenization of these equations, which generalizes those achieved by Bensoussan- Lions-Papanicolau and Migorski. The proof is based on the periodic unfolding method in perforated domains.展开更多
We are concerned with a class of parabolic equations in periodically perforated domains with a homogeneous Neumann condition on the boundary of holes.By using the periodic unfolding method in perforated domains, we ob...We are concerned with a class of parabolic equations in periodically perforated domains with a homogeneous Neumann condition on the boundary of holes.By using the periodic unfolding method in perforated domains, we obtain the homogenization results under the conditions slightly weaker than those in the corresponding case considered by Nandakumaran and Rajesh（Nandakumaran A K, Rajesh M. Homogenization of a parabolic equation in perforated domain with Neumann boundary condition. Proc. Indian Acad. Sci.（Math. Sci.）, 2002, 112（1）： 195–207）. Moreover,these results generalize those obtained by Donato and Nabil（Donato P, Nabil A. Homogenization and correctors for the heat equation in perforated domains. Ricerche di Matematica L. 2001, 50： 115–144）.展开更多
Making use of the periodic unfolding method,the authors give an elementary proof for the periodic homogenization of the elastic torsion problem of an infinite 3dimensional rod with a multiply-connected cross section a...Making use of the periodic unfolding method,the authors give an elementary proof for the periodic homogenization of the elastic torsion problem of an infinite 3dimensional rod with a multiply-connected cross section as well as for the general electroconductivity problem in the presence of many perfect conductors(arising in resistivity well-logging).Both problems fall into the general setting of equi-valued surfaces with corresponding assigned total fluxes.The unfolding method also gives a general corrector result for these problems.展开更多
基金supported by National Natural Science Foundation of China(Grant No.11401595)
文摘We study the heat equation with non-periodic coefficients in periodically perforated domains with a homogeneous Neumann condition on the holes. Using the time-dependent unfolding method, we obtain some homogenization and corrector results which generalize those by Donato and Nabil(2001).
基金supported by the State Key Development Program for Basic Research of China (Nos. 2008CB717803, 2009GB107001,2007CB209903)the Research Fund for the Doctoral Program of Higher Education of China (No. 200610011023)National Natural Science Foundation of China (No. 10875002)
文摘An accurate energy calibration of a 5＂× 2＂ BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with 22Na, 137Cs and 54Mn photon sources and simulated using the GRESP code, which was developed at the Physiknlisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in toknmak experiments.
基金Project(cstc2018jcyjAX0159)supported by the Natural Science Foundation of Chongqing,ChinaProject(51575066)supported by the National Natural Science Foundation of China。
文摘Ultra-large plate forgings are foundation of heavy machinery,but many parts of the type cannot be made by conventional technologies due to the characters of extreme manufacturing in terms of size and quality requirements.This paper introduced a systematically method called cylinder unfolding method(CUM)for producing large plate forgings,by using a serial of operations including“splitting”,“unfolding”,and“flattening”of a thick cylinder obtained from saddle forging.The technological route of CUM was presented in detail with an example of plate forging with the horizontal sizes of 6100 mm and thickness of 300 mm.The deformation features of saddle forging for fabricating transitional cylinders were analyzed,and then the subsequent handling steps including splitting,unfolding and flattening of the cylinder,as well as the auxiliary processing,were addressed.The practice proved that CUM can provide an efficient way for manufacturing ultra-large plate forgings and meet the strict requirements in geometry and mechanical performance,without highly increasing the investments of forming equipment and tooling.
文摘Objective: to explore the application value of expanded teaching method in pediatric clinical teaching practice. Methods: 100 children's department interns received from the hospital from January 2016 to February 2020 were selected as the research object, and they were randomly divided into two groups, with 50 interns in each group. The control group implemented the conventional classroom explanation teaching method for pediatric clinical teaching, and the observation group adopted the exhibition teaching method for learning guidance, and during and after the teaching. The teaching effect, classroom easy memory rate and the improvement rate of clinical processing ability of the two groups were evaluated. Results: teaching results: the effective rate of the observation group was significantly better than that of the control group. Easy memory rate of interns in class: the easy memory rate of students in the observation group was significantly higher than that in the control group. Improvement rate of clinical treatment ability: in clinic, the students in the observation group have stronger ability to deal with emergencies in clinic, and their clinical treatment ability is improved more significantly compared with the control group. There was significant difference between the two groups in three indexes (teaching efficiency, easy memory rate of interns in class and improvement rate of clinical processing ability) (P < 0.05). Conclusion: in the clinical teaching practice of pediatrics, the application of expansion teaching method can effectively improve the teaching efficiency, help interns remember relevant knowledge more quickly, and give more play to its application value in clinical practice teaching.
基金Supported by the National Natural Science Foundation of China(Grant No.11401595)
文摘In this paper, we study a class of hyperbolic-parabolic problems in periodically perforated domains with a homogeneous Neumann condition on the boundary of holes. We focus on the homogenization of these equations, which generalizes those achieved by Bensoussan- Lions-Papanicolau and Migorski. The proof is based on the periodic unfolding method in perforated domains.
基金The NSF(11401595)of Chinathe Nationalities Innovation Foundation(2018sycxjj113)of South-central University for Postgraduate
文摘We are concerned with a class of parabolic equations in periodically perforated domains with a homogeneous Neumann condition on the boundary of holes.By using the periodic unfolding method in perforated domains, we obtain the homogenization results under the conditions slightly weaker than those in the corresponding case considered by Nandakumaran and Rajesh（Nandakumaran A K, Rajesh M. Homogenization of a parabolic equation in perforated domain with Neumann boundary condition. Proc. Indian Acad. Sci.（Math. Sci.）, 2002, 112（1）： 195–207）. Moreover,these results generalize those obtained by Donato and Nabil（Donato P, Nabil A. Homogenization and correctors for the heat equation in perforated domains. Ricerche di Matematica L. 2001, 50： 115–144）.
基金Supported by the National Natural Science Foundation of China (No. 11121101)the National Basic Research Program of China (No. 2013CB834100)
文摘Making use of the periodic unfolding method,the authors give an elementary proof for the periodic homogenization of the elastic torsion problem of an infinite 3dimensional rod with a multiply-connected cross section as well as for the general electroconductivity problem in the presence of many perfect conductors(arising in resistivity well-logging).Both problems fall into the general setting of equi-valued surfaces with corresponding assigned total fluxes.The unfolding method also gives a general corrector result for these problems.
