We present a discrete time single-server two-level mixed service polling systems with two queue types, one center queue and N normal queues. Two-level means the center queue will be successive served after each normal...We present a discrete time single-server two-level mixed service polling systems with two queue types, one center queue and N normal queues. Two-level means the center queue will be successive served after each normal queue. In the first level, server visits between the center queue and the normal queue. In the second level, normal queues are polled by a cyclic order. Mixed service means the service discipline are exhaustive for center queue, and parallel 1-limited for normal queues. We propose an imbedded Markov chain framework to drive the closed-form expressions for the mean cycle time, mean queue length, and mean waiting time. Numerical examples demonstrate that theoretical and simulation results are identical the new system efficiently differentiates priorities.展开更多
We present a weak-coupling theory of semiclassical periodically driven two-level systems. The explicit analytical approximating solution is shown to reproduce highly accurately the exact results well beyond the regime...We present a weak-coupling theory of semiclassical periodically driven two-level systems. The explicit analytical approximating solution is shown to reproduce highly accurately the exact results well beyond the regime of the rotating-wave approximation.展开更多
In this article, on the basis of two-level discretizations and multiscale finite element method, two kinds of finite element algorithms for steady Navier-Stokes problem are presented and discussed. The main technique ...In this article, on the basis of two-level discretizations and multiscale finite element method, two kinds of finite element algorithms for steady Navier-Stokes problem are presented and discussed. The main technique is first to use a standard finite element discretization on a coarse mesh to approximate low frequencies, then to apply the simple and Newton scheme to linearize discretizations on a fine grid. At this process, multiscale finite element method as a stabilized method deals with the lowest equal-order finite element pairs not satisfying the inf-sup condition. Under the uniqueness condition, error analyses for both algorithms are given. Numerical results are reported to demonstrate the effectiveness of the simple and Newton scheme.展开更多
Fractures of the lesser tuberosity of the humerus are typically met in combination with other injuries of the shoulder. Case reports of isolated lesser tuberosity fractures are particularly rare and, consequently,ther...Fractures of the lesser tuberosity of the humerus are typically met in combination with other injuries of the shoulder. Case reports of isolated lesser tuberosity fractures are particularly rare and, consequently,therapeutic protocols have not yet been completely clarified. Conservative as well as surgical treatment has been recommended, while several operative techniques have been applied. We present a case of a 39-yearold man with an isolated lesser tuberosity fracture who was treated surgically in our institution. Due to fracture comminution, a two-level reconstruction technique with headless screws and buttress plate was applied. As far as we know, this method of fixation of this type of fracture has not been previously described in the literature.The patient tolerated the procedure well and excellent results were obtained at the latest follow-up.展开更多
BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic charac...BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.展开更多
Two uncoupleable distributions, assigning missions to robots and allocating robots to home stations, accompany the use ofmobile service robots in hospitals.In the given problem, two workload-related objectives and fiv...Two uncoupleable distributions, assigning missions to robots and allocating robots to home stations, accompany the use ofmobile service robots in hospitals.In the given problem, two workload-related objectives and five groups of constraints areproposed.A bio-mimicked Binary Bees Algorithm (BBA) is introduced to solve this multiobjective multiconstraint combinatorialoptimisation problem, in which constraint handling technique (Multiobjective Transformation, MOT), multiobjectiveevaluation method (nondominance selection), global search strategy (stochastic search in the variable space), local searchstrategy (Hamming neighbourhood exploitation), and post-processing means (feasibility selection) are the main issues.TheBBA is then demonstrated with a case study, presenting the execution process of the algorithm, and also explaining the change ofelite number in evolutionary process.Its optimisation result provides a group of feasible nondominated two-level distributionschemes.展开更多
The purpose of the study is to measure the "growth drag" according to the characteristic of Chinese land resource.Romer model (2001) holds that every country is inevitably affected by the "growth drag&q...The purpose of the study is to measure the "growth drag" according to the characteristic of Chinese land resource.Romer model (2001) holds that every country is inevitably affected by the "growth drag" due to the limitation of land resource.So it's of profound strategic significance to measure the "growth drag" according to the character of Chinese land resource.Modified two-level CES production function was employed,and this paper modified the hypothesis of the model.The result indicates that the limitation of Chinese land resource casts shadow over the economic development of China,and the growth rate is 0.4618% lower than that without the limitation of land resource.Through implementing the land resource protection policy along with the technology improvement and the substitute effect of other factors to the land resource,China will keep a steady and balanced economic growth.展开更多
We discuss the effects of dissipation on the behavior of single photon transport in a system of coupled cavity arrays, with the two nearest cavities nonlocally coupled to a two-level atom. The single photon transmissi...We discuss the effects of dissipation on the behavior of single photon transport in a system of coupled cavity arrays, with the two nearest cavities nonlocally coupled to a two-level atom. The single photon transmission amplitude is solved exactly by employing the quasi-boson picture. We investigate two different situations of local and nonlocal couplings, respectively. Comparing the dissipative case with the nondissipative one reveals that the dissipation of the system increases the middle dip and lowers the peak of the single photon transmission amplitudes, broadening the line width of the transport spectrum. It should be noted that the influence of the cavity dissipation to the single photon transport spectrum is asymmet- ric. By comparing the nonlocal coupling with the local one, one can find that the enhancement of the middle dip of single photon transmission amplitudes is mostly caused by the atom dissipation and that the reduced peak is mainly caused by the cavity dissipation, no matter whether it is a nonlocal or local coupling case. Whereas in the nonlocal coupling case, when the coupling strength gets stronger, the cavity dissipation has a greater effect on the single photon transport spectrum and the atom dissipation affection becomes weak, so it can be ignored.展开更多
We study the optical properties of a two-level atomic ensemble controlled by a high-finesse cavity. Even though the cavity is initially in the vacuum state in the absence of external driving, the probe response of the...We study the optical properties of a two-level atomic ensemble controlled by a high-finesse cavity. Even though the cavity is initially in the vacuum state in the absence of external driving, the probe response of the atomic ensemble can be dramatically modified. When the collectively enhanced atom–cavity coupling is strong enough and the cavity decay rate is much smaller than the atomic damping rate, an electromagnetically induced transparency-like coherent phenomenon emerges with a dip absorption for the response of the two-level atoms in the cavity without driving, and thus is called vacuum induced transparency. We also show the slow light with very low group velocity in such an atomic ensemble.展开更多
From the viewpoint of quantum information, this paper proposes a concept and a definition of the atomic optimal entropy squeezing sudden generation （AOESSG） for the system of an effective two-level moving atom which...From the viewpoint of quantum information, this paper proposes a concept and a definition of the atomic optimal entropy squeezing sudden generation （AOESSG） for the system of an effective two-level moving atom which entangles with the two-mode coherent fields. It also researches the relationship between the AOESSG and entanglement sudden death of the atom-fields, and discusses the influences of atomic initial state on the AOESSG and obtains the system parameter which controls the AOESSG.展开更多
There exist many two-level group consensus problems with different psychological behaviors of decision makers.To deal with these group consensus problems and reach a stable consensus,based on the principles and method...There exist many two-level group consensus problems with different psychological behaviors of decision makers.To deal with these group consensus problems and reach a stable consensus,based on the principles and methods of grey system,utility theory and group consensus,we use grey utility function to describe and reflect decision makers’opinion preferences in different subgroups and different levels,and then we construct a two-level group consensus method with a moderator,and exploit it to solve the negotiation problems of the natural gas subsidy.展开更多
Recent studies of the space debris environment in Low Earth Orbit(LEO)have shown that the critical density of space debris has been reached in certain regions.The Active Debris Removal(ADR)mission,to mitigate the spac...Recent studies of the space debris environment in Low Earth Orbit(LEO)have shown that the critical density of space debris has been reached in certain regions.The Active Debris Removal(ADR)mission,to mitigate the space debris density and stabilize the space debris environment,has been considered as a most effective method.In this paper,a novel two-level optimization strategy for multi-debris removal mission in LEO is proposed,which includes the low-level and high-level optimization process.To improve the overall performance of the multi-debris active removal mission and obtain multiple Pareto-optimal solutions,the ADR mission is seen as a Time-Dependant Traveling Salesman Problem(TDTSP)with two objective functions to minimize the total mission duration and the total propellant consumption.The problem includes the sequence optimization to determine the sequence of removal of space debris and the transferring optimization to define the orbital maneuvers.Two optimization models for the two-level optimization strategy are built in solving the multi-debris removal mission,and the optimal Pareto solution is successfully obtained by using the non-dominated sorting genetic algorithm II(NSGA-II).Two test cases are presented,which show that the low level optimization strategy can successfully obtain the optimal sequences and the initial solution of the ADR mission and the high level optimization strategy can efficiently and robustly find the feasible optimal solution for long duration perturbed rendezvous problem.展开更多
In this paper,we first propose a new stabilized finite element method for the Stokes eigenvalue problem.This new method is based on multiscale enrichment,and is derived from the Stokes eigenvalue problem itself.The co...In this paper,we first propose a new stabilized finite element method for the Stokes eigenvalue problem.This new method is based on multiscale enrichment,and is derived from the Stokes eigenvalue problem itself.The convergence of this new stabilized method is proved and the optimal priori error estimates for the eigenfunctions and eigenvalues are also obtained.Moreover,we combine this new stabilized finite element method with the two-level method to give a new two-level stabilized finite element method for the Stokes eigenvalue problem.Furthermore,we have proved a priori error estimates for this new two-level stabilized method.Finally,numerical examples confirm our theoretical analysis and validate the high effectiveness of the new methods.展开更多
A two-level stabilized finite element method for the Stokes eigenvalue problem based on the local Gauss integration is considered. This method involves solving a Stokes eigenvalue problem on a coarse mesh with mesh si...A two-level stabilized finite element method for the Stokes eigenvalue problem based on the local Gauss integration is considered. This method involves solving a Stokes eigenvalue problem on a coarse mesh with mesh size H and a Stokes problem on a fine mesh with mesh size h -- O（H2）, which can still maintain the asymptotically optimal accuracy. It provides an approximate solution with the convergence rate of the same order as the usual stabilized finite element solution, which involves solving a Stokes eigenvalue problem on a fine mesh with mesh size h. Hence, the two-level stabilized finite element method can save a large amount of computational time. Moreover, numerical tests confirm the theoretical results of the present method.展开更多
To fit the complicated geographic conditions of the Three Gorges Reservoir area, a two-level multi-objective monitoring system was developed to monitor the atmosphere of the area. Statistical analysis of environmental...To fit the complicated geographic conditions of the Three Gorges Reservoir area, a two-level multi-objective monitoring system was developed to monitor the atmosphere of the area. Statistical analysis of environmental monitoring data and the macro control principle were employed to configure the upper layer. The lower layer was designed by the application of the thumb rule to a local terrain and specific point sources of pollution therein. The optimized two-level system comprises an upper layer of 16 monitoring stations distributed at places of diverse geographical, ecological, economical and social characteristics, and a lower layer of ]6 sub-machines at each monitoring station of the upper layer. This optimal outcome fits the complicated conditions of the Three Gorges Reservoir area, substantially cuts down the installation cost and the operation cost, and provides accurate monitoring data of atmosphere over the entire area with a high resolution.展开更多
Electron-positron pair production rate created from vacuum in the presence of an elliptically polarized laser field is investigated.By applying the technique of two level transition amplitude,a routine for obtaining p...Electron-positron pair production rate created from vacuum in the presence of an elliptically polarized laser field is investigated.By applying the technique of two level transition amplitude,a routine for obtaining pair production rate is presented,and approximate analytical expressions are given both for the low frequency strong field regime and the high frequency weak field regime.We found that for an elliptically polarized field,the electron-positron pair production rate decrease when the elliptic eccentricity increase in the high frequency weak field regime,however,in the low frequency strong field regime,there is almost the same electron-positron pair production rate as in the constant electric field case.展开更多
In recent years, it has shown that a generalized thresholding algorithm is useful for inverse problems with sparsity constraints. The generalized thresholding minimizes the non-convex p-norm based function with p <...In recent years, it has shown that a generalized thresholding algorithm is useful for inverse problems with sparsity constraints. The generalized thresholding minimizes the non-convex p-norm based function with p < 1, and it penalizes small coefficients over a wider range meanwhile applies less bias to the larger coefficients.In this work, on the basis of two-level Bregman method with dictionary updating(TBMDU), we use the modified thresholding to minimize the non-convex function and propose the generalized TBMDU(GTBMDU) algorithm.The experimental results on magnetic resonance(MR) image simulations and real MR data, under a variety of sampling trajectories and acceleration factors, consistently demonstrate that the proposed algorithm can efficiently reconstruct the MR images and present advantages over the previous soft thresholding approaches.展开更多
We generalize the Wu-Yang strong-coupling theory to solve analytically periodically driven two-level systems in the weak-coupling and low-frequency regimes for single- and multi-period periodic driving of continuous-w...We generalize the Wu-Yang strong-coupling theory to solve analytically periodically driven two-level systems in the weak-coupling and low-frequency regimes for single- and multi-period periodic driving of continuous-wave-type and pulse-type including ultrashort pulses of a few cycles.We also derive a general formula of the AC Stark shift suitable for such diverse situations.展开更多
基金Supported by the National Natural Science Foundation of China (No. 61072079)Science Foundation of Yunnan Provincial Department (No. 2011Y117)
文摘We present a discrete time single-server two-level mixed service polling systems with two queue types, one center queue and N normal queues. Two-level means the center queue will be successive served after each normal queue. In the first level, server visits between the center queue and the normal queue. In the second level, normal queues are polled by a cyclic order. Mixed service means the service discipline are exhaustive for center queue, and parallel 1-limited for normal queues. We propose an imbedded Markov chain framework to drive the closed-form expressions for the mean cycle time, mean queue length, and mean waiting time. Numerical examples demonstrate that theoretical and simulation results are identical the new system efficiently differentiates priorities.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10575040, 90503010, 60478029, and 10634060, and by the State Key Basic Research Program under Grant No. 2005CB724508
文摘We present a weak-coupling theory of semiclassical periodically driven two-level systems. The explicit analytical approximating solution is shown to reproduce highly accurately the exact results well beyond the regime of the rotating-wave approximation.
文摘In this article, on the basis of two-level discretizations and multiscale finite element method, two kinds of finite element algorithms for steady Navier-Stokes problem are presented and discussed. The main technique is first to use a standard finite element discretization on a coarse mesh to approximate low frequencies, then to apply the simple and Newton scheme to linearize discretizations on a fine grid. At this process, multiscale finite element method as a stabilized method deals with the lowest equal-order finite element pairs not satisfying the inf-sup condition. Under the uniqueness condition, error analyses for both algorithms are given. Numerical results are reported to demonstrate the effectiveness of the simple and Newton scheme.
文摘Fractures of the lesser tuberosity of the humerus are typically met in combination with other injuries of the shoulder. Case reports of isolated lesser tuberosity fractures are particularly rare and, consequently,therapeutic protocols have not yet been completely clarified. Conservative as well as surgical treatment has been recommended, while several operative techniques have been applied. We present a case of a 39-yearold man with an isolated lesser tuberosity fracture who was treated surgically in our institution. Due to fracture comminution, a two-level reconstruction technique with headless screws and buttress plate was applied. As far as we know, this method of fixation of this type of fracture has not been previously described in the literature.The patient tolerated the procedure well and excellent results were obtained at the latest follow-up.
文摘BACKGROUND The technique of percutaneous endoscopic lumbar discectomy(PELD)as a transforaminal approach has been used to treat highly migrated lower lumbar disc herniations.However,due to the different anatomic characteristics of the upper lumbar spine,conventional transforaminal PELD may fail to remove the highly migrated upper lumbar disc nucleus pulposus.Therefore,the purpose of this study was to describe a novel surgical technique,two-level PELD,for the treatment of highly migrated upper lumbar disc herniations and to report its related clinical outcomes.CASE SUMMARY A 60-year-old male presented with a complaint of pain at his lower back and right lower limb.The patient received 3 mo of conservative treatments but the symptoms were not alleviated.Physical examination revealed a positive femoral nerve stretch test and a negative straight leg raise test for the right leg,and preoperative visual analog scale(VAS)score for the lower back was 6 points and for the right leg was 8 points.Magnetic resonance imaging(MRI)demonstrated L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.According to physical examination and imaging findings,surgery was the primary consideration.Therefore,the patient underwent surgical treatment with two-level PELD.The pain symptom was relieved and the VAS score for back and thigh pain was one point postoperatively.The patient was asymptomatic and follow-up MRI scan 1 year after operation revealed no residual nucleus pulposus.CONCLUSION Two-level PELD as a transforaminal approach can be a safe and effective procedure for highly migrated upper lumbar disc herniation.
文摘Two uncoupleable distributions, assigning missions to robots and allocating robots to home stations, accompany the use ofmobile service robots in hospitals.In the given problem, two workload-related objectives and five groups of constraints areproposed.A bio-mimicked Binary Bees Algorithm (BBA) is introduced to solve this multiobjective multiconstraint combinatorialoptimisation problem, in which constraint handling technique (Multiobjective Transformation, MOT), multiobjectiveevaluation method (nondominance selection), global search strategy (stochastic search in the variable space), local searchstrategy (Hamming neighbourhood exploitation), and post-processing means (feasibility selection) are the main issues.TheBBA is then demonstrated with a case study, presenting the execution process of the algorithm, and also explaining the change ofelite number in evolutionary process.Its optimisation result provides a group of feasible nondominated two-level distributionschemes.
基金founded by the Excellent Young Teachers Program of Shanghai Municipal Education Commission (Grant No. B8101090039)the Project for Doctoral Research Fund of Shanghai Ocean University (Grant No.A2400080314)
文摘The purpose of the study is to measure the "growth drag" according to the characteristic of Chinese land resource.Romer model (2001) holds that every country is inevitably affected by the "growth drag" due to the limitation of land resource.So it's of profound strategic significance to measure the "growth drag" according to the character of Chinese land resource.Modified two-level CES production function was employed,and this paper modified the hypothesis of the model.The result indicates that the limitation of Chinese land resource casts shadow over the economic development of China,and the growth rate is 0.4618% lower than that without the limitation of land resource.Through implementing the land resource protection policy along with the technology improvement and the substitute effect of other factors to the land resource,China will keep a steady and balanced economic growth.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10704031,10874235,11274148,and 10934010)
文摘We discuss the effects of dissipation on the behavior of single photon transport in a system of coupled cavity arrays, with the two nearest cavities nonlocally coupled to a two-level atom. The single photon transmission amplitude is solved exactly by employing the quasi-boson picture. We investigate two different situations of local and nonlocal couplings, respectively. Comparing the dissipative case with the nondissipative one reveals that the dissipation of the system increases the middle dip and lowers the peak of the single photon transmission amplitudes, broadening the line width of the transport spectrum. It should be noted that the influence of the cavity dissipation to the single photon transport spectrum is asymmet- ric. By comparing the nonlocal coupling with the local one, one can find that the enhancement of the middle dip of single photon transmission amplitudes is mostly caused by the atom dissipation and that the reduced peak is mainly caused by the cavity dissipation, no matter whether it is a nonlocal or local coupling case. Whereas in the nonlocal coupling case, when the coupling strength gets stronger, the cavity dissipation has a greater effect on the single photon transport spectrum and the atom dissipation affection becomes weak, so it can be ignored.
基金Project supported by the National Natural Science Foundation of China(Grant No.11304010)
文摘We study the optical properties of a two-level atomic ensemble controlled by a high-finesse cavity. Even though the cavity is initially in the vacuum state in the absence of external driving, the probe response of the atomic ensemble can be dramatically modified. When the collectively enhanced atom–cavity coupling is strong enough and the cavity decay rate is much smaller than the atomic damping rate, an electromagnetically induced transparency-like coherent phenomenon emerges with a dip absorption for the response of the two-level atoms in the cavity without driving, and thus is called vacuum induced transparency. We also show the slow light with very low group velocity in such an atomic ensemble.
基金Project supported by the National Natural Science Foundation of China (Grant No 19874020)the Natural Science Foundation of Hunan Province,China (Grant No 09JJ3012)the Scientific Research Fund of the Education Department of Hunan Province of China (Grant No 07c543)
文摘From the viewpoint of quantum information, this paper proposes a concept and a definition of the atomic optimal entropy squeezing sudden generation （AOESSG） for the system of an effective two-level moving atom which entangles with the two-mode coherent fields. It also researches the relationship between the AOESSG and entanglement sudden death of the atom-fields, and discusses the influences of atomic initial state on the AOESSG and obtains the system parameter which controls the AOESSG.
基金supported by the National Natural Science Foundation of China (71503103)the Outstanding Youth in Social Sciences of Jiangsu Provincethe Jiangsu Qinglan Project and the Tender Project from Wuxi Federation of Philosophy and Social Sciences(WXCK22-A-03).
文摘There exist many two-level group consensus problems with different psychological behaviors of decision makers.To deal with these group consensus problems and reach a stable consensus,based on the principles and methods of grey system,utility theory and group consensus,we use grey utility function to describe and reflect decision makers’opinion preferences in different subgroups and different levels,and then we construct a two-level group consensus method with a moderator,and exploit it to solve the negotiation problems of the natural gas subsidy.
基金the Open Research Foundation of Science and Technology in Aerospace Flight Dynamics Laboratory of China(GF2018005).
文摘Recent studies of the space debris environment in Low Earth Orbit(LEO)have shown that the critical density of space debris has been reached in certain regions.The Active Debris Removal(ADR)mission,to mitigate the space debris density and stabilize the space debris environment,has been considered as a most effective method.In this paper,a novel two-level optimization strategy for multi-debris removal mission in LEO is proposed,which includes the low-level and high-level optimization process.To improve the overall performance of the multi-debris active removal mission and obtain multiple Pareto-optimal solutions,the ADR mission is seen as a Time-Dependant Traveling Salesman Problem(TDTSP)with two objective functions to minimize the total mission duration and the total propellant consumption.The problem includes the sequence optimization to determine the sequence of removal of space debris and the transferring optimization to define the orbital maneuvers.Two optimization models for the two-level optimization strategy are built in solving the multi-debris removal mission,and the optimal Pareto solution is successfully obtained by using the non-dominated sorting genetic algorithm II(NSGA-II).Two test cases are presented,which show that the low level optimization strategy can successfully obtain the optimal sequences and the initial solution of the ADR mission and the high level optimization strategy can efficiently and robustly find the feasible optimal solution for long duration perturbed rendezvous problem.
基金supported by the National Key R&D Program of China(2018YFB1501001)the NSF of China(11771348)China Postdoctoral Science Foundation(2019M653579)。
文摘In this paper,we first propose a new stabilized finite element method for the Stokes eigenvalue problem.This new method is based on multiscale enrichment,and is derived from the Stokes eigenvalue problem itself.The convergence of this new stabilized method is proved and the optimal priori error estimates for the eigenfunctions and eigenvalues are also obtained.Moreover,we combine this new stabilized finite element method with the two-level method to give a new two-level stabilized finite element method for the Stokes eigenvalue problem.Furthermore,we have proved a priori error estimates for this new two-level stabilized method.Finally,numerical examples confirm our theoretical analysis and validate the high effectiveness of the new methods.
基金Project supported by the National Natural Science Foundation of China(Nos.10901131,10971166, and 10961024)the National High Technology Research and Development Program of China (No.2009AA01A135)the Natural Science Foundation of Xinjiang Uygur Autonomous Region (No.2010211B04)
文摘A two-level stabilized finite element method for the Stokes eigenvalue problem based on the local Gauss integration is considered. This method involves solving a Stokes eigenvalue problem on a coarse mesh with mesh size H and a Stokes problem on a fine mesh with mesh size h -- O（H2）, which can still maintain the asymptotically optimal accuracy. It provides an approximate solution with the convergence rate of the same order as the usual stabilized finite element solution, which involves solving a Stokes eigenvalue problem on a fine mesh with mesh size h. Hence, the two-level stabilized finite element method can save a large amount of computational time. Moreover, numerical tests confirm the theoretical results of the present method.
基金This work was based on a previous article presented in 1st Three Gorges Research Forum on Environment and Economy, TGRF2007, at Chongqing University, July 18-19, 2007.
文摘To fit the complicated geographic conditions of the Three Gorges Reservoir area, a two-level multi-objective monitoring system was developed to monitor the atmosphere of the area. Statistical analysis of environmental monitoring data and the macro control principle were employed to configure the upper layer. The lower layer was designed by the application of the thumb rule to a local terrain and specific point sources of pollution therein. The optimized two-level system comprises an upper layer of 16 monitoring stations distributed at places of diverse geographical, ecological, economical and social characteristics, and a lower layer of ]6 sub-machines at each monitoring station of the upper layer. This optimal outcome fits the complicated conditions of the Three Gorges Reservoir area, substantially cuts down the installation cost and the operation cost, and provides accurate monitoring data of atmosphere over the entire area with a high resolution.
基金Supported by the National Natural Science Foundation of China (NNSFC) under the grant Nos. 10875015,11175023,10965006,11165014partially by the Fundamental Research Funds for the Central Universities (FRFCU)
文摘Electron-positron pair production rate created from vacuum in the presence of an elliptically polarized laser field is investigated.By applying the technique of two level transition amplitude,a routine for obtaining pair production rate is presented,and approximate analytical expressions are given both for the low frequency strong field regime and the high frequency weak field regime.We found that for an elliptically polarized field,the electron-positron pair production rate decrease when the elliptic eccentricity increase in the high frequency weak field regime,however,in the low frequency strong field regime,there is almost the same electron-positron pair production rate as in the constant electric field case.
基金the National Natural Science Foundation of China(Nos.6136200161365013 and 51165033)+3 种基金the Natural Science Foundation of Jiangxi Province(Nos.20132BAB211030 and 20122BAB211015)the Technology Foundation of Department of Education in Jiangxi Province(Nos.GJJ 13061 and GJJ14196)the National Postdoctoral Research Funds(No.2014M551867)the Jiangxi Advanced Projects for Postdoctoral Research Funds(No.2014KY02)
文摘In recent years, it has shown that a generalized thresholding algorithm is useful for inverse problems with sparsity constraints. The generalized thresholding minimizes the non-convex p-norm based function with p < 1, and it penalizes small coefficients over a wider range meanwhile applies less bias to the larger coefficients.In this work, on the basis of two-level Bregman method with dictionary updating(TBMDU), we use the modified thresholding to minimize the non-convex function and propose the generalized TBMDU(GTBMDU) algorithm.The experimental results on magnetic resonance(MR) image simulations and real MR data, under a variety of sampling trajectories and acceleration factors, consistently demonstrate that the proposed algorithm can efficiently reconstruct the MR images and present advantages over the previous soft thresholding approaches.
基金supported by the Natural Science Foundation of Jiangxi Province under Grant Nos.0612006 and 2007GZW0819the Scientific Research Foundation of the Education Department of Jiangxi Province under Grant No.[2007]191Funds from East China Jiaotong University
文摘We generalize the Wu-Yang strong-coupling theory to solve analytically periodically driven two-level systems in the weak-coupling and low-frequency regimes for single- and multi-period periodic driving of continuous-wave-type and pulse-type including ultrashort pulses of a few cycles.We also derive a general formula of the AC Stark shift suitable for such diverse situations.
