Spectrum analysis of the plasma has over the years been growing both in methods and instrument, which makes it become a widely used non-contact detection method, without disturbing the arc plasma itself. With noticeab...Spectrum analysis of the plasma has over the years been growing both in methods and instrument, which makes it become a widely used non-contact detection method, without disturbing the arc plasma itself. With noticeable developments in the industry application of the method, a need for careful analysis of the plasma with both time and space identification is desirable. Therefore, a spectral measurement system is developed in this paper for diagnosing arc plasma with time and space identification. With a new hollow probe scanning method, the instrument can be used to provide information like energy distribution of plasma, temperature within the arc plasma, which are of great significance with the requirement of space identification. Furthermore, the system can also be used to capture the instant state of the arc plasma with the synchronic triggering system, which uses high speed photo and electrical signal as the time criterion. The industry applications prove that the system works well for online detection of the arc plasma.展开更多
Based on the reliability budget and percentile travel time(PTT) concept, a new travel time index named combined mean travel time(CMTT) under stochastic traffic network was proposed. CMTT here was defined as the convex...Based on the reliability budget and percentile travel time(PTT) concept, a new travel time index named combined mean travel time(CMTT) under stochastic traffic network was proposed. CMTT here was defined as the convex combination of the conditional expectations of PTT-below and PTT-excess travel times. The former was designed as a risk-optimistic travel time index, and the latter was a risk-pessimistic one. Hence, CMTT was able to describe various routing risk-attitudes. The central idea of CMTT was comprehensively illustrated and the difference among the existing travel time indices was analyzed. The Wardropian combined mean traffic equilibrium(CMTE) model was formulated as a variational inequality and solved via an alternating direction algorithm nesting extra-gradient projection process. Some mathematical properties of CMTT and CMTE model were rigorously proved. Finally, a numerical example was performed to characterize the CMTE network. It is founded that that risk-pessimism is of more benefit to a modest(or low) congestion and risk network, however, it changes to be risk-optimism for a high congestion and risk network.展开更多
The effects of semi-solid isothermal process parameters on the microstructure evolution of Mg-Gd rare earth alloy produced by strain-induced melt activation(SIMA)were investigated.The formation mechanism of the partic...The effects of semi-solid isothermal process parameters on the microstructure evolution of Mg-Gd rare earth alloy produced by strain-induced melt activation(SIMA)were investigated.The formation mechanism of the particles in the process of the isothermal treatment was also discussed.The results show that the microstructure of the as-cast alloy consists ofα-Mg solid solution, Mg5RE and Mg24RE5(Gd,Y,Nd)phase.After being extruded with an extrusion ratio of 14:1 at 380℃,the microstructure of Mg-Gd alloy changes from developed dendrites to near-equiaxed grains.The liquid volume fraction of the semisolid slurry gradually increases with elevating isothermal temperature or prolonging isothermal time during the partial remelting.To obtain an ideal semisolid slurry,the optimal process parameters for the Mg-Gd alloy should be 630℃for isothermal temperature and 30 min for the corresponding time,respectively,where the volume fraction of the liquid phase is 52%.展开更多
The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailab...The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value(CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities.Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.展开更多
We study the Cauchy problem of a semilinear parabolic equation. We construct an appropriate Harnack quantity and get a differential Harnack inequality. Using this inequality, we prove the finite-time blow-up of the po...We study the Cauchy problem of a semilinear parabolic equation. We construct an appropriate Harnack quantity and get a differential Harnack inequality. Using this inequality, we prove the finite-time blow-up of the positive solutions and recover a classical Harnack inequality. We also obtain a result of Liouville type for the elliptic equation.展开更多
This article discusses computational methods for the numerical simulation of unsteady Bingham visco-plastic flow. These methods are based on time-discretization by operator-splitting and take advantage of a characteri...This article discusses computational methods for the numerical simulation of unsteady Bingham visco-plastic flow. These methods are based on time-discretization by operator-splitting and take advantage of a characterization of the solutions involving some kind of Lagrange multipliers. The full discretization is achieved by combining the above operator-splitting methods with finite element approximations, the advection being treated by a wave-like equation 'equivalent' formulation easier to implement than the method of characteristics or high order upwinding methods. The authors illustrate the methodology discussed in this article with the results of numerical experiments concerning the simulation of wall driven cavity Bingham flow in two dimensions.展开更多
To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch(POS),we have made measurements of the line-integrated plasma density during switch operation using a time-...To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch(POS),we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer.The conduction current and conduction time in experiments are about 120 kA and 1 s,respectively.As a result,more than 85%of conduction current has been transferred to an inductive load with rise time of 130 ns.The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters.During the conduction phase,the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns.The current conduction is observed to cause a radial redistribution of the switch plasma.A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor,which is consistent with the location where magnetic pressure is the largest,allowing current to be transferred from the POS to the load.展开更多
We study the existence and uniqueness of the solution to a forward-backward stochastic differential equation with subdifferential operator in the backward equation. This kind of equations includes, as a particular cas...We study the existence and uniqueness of the solution to a forward-backward stochastic differential equation with subdifferential operator in the backward equation. This kind of equations includes, as a particular case, multi-dimensional forward-backward stochastic differential equation where the backward equation is reflected on the boundary of a closed convex(time-independent) domain. Moreover, we give a probabilistic interpretation for the viscosity solution of a kind of quasilinear variational inequalities.展开更多
基金Research Project Supported by Shanxi Scholarship Council of China(No.2012-69)Selected Research Project by Department of Human Resources and Social Security of Shanxi
文摘Spectrum analysis of the plasma has over the years been growing both in methods and instrument, which makes it become a widely used non-contact detection method, without disturbing the arc plasma itself. With noticeable developments in the industry application of the method, a need for careful analysis of the plasma with both time and space identification is desirable. Therefore, a spectral measurement system is developed in this paper for diagnosing arc plasma with time and space identification. With a new hollow probe scanning method, the instrument can be used to provide information like energy distribution of plasma, temperature within the arc plasma, which are of great significance with the requirement of space identification. Furthermore, the system can also be used to capture the instant state of the arc plasma with the synchronic triggering system, which uses high speed photo and electrical signal as the time criterion. The industry applications prove that the system works well for online detection of the arc plasma.
基金Project(2012CB725403-5)supported by National Basic Research Program of ChinaProject(71131001-2)supported by National Natural Science Foundation of China+1 种基金Projects(2012JBZ005)supported by Fundamental Research Funds for the Central Universities,ChinaProject(201170)supported by the Foundation for National Excellent Doctoral Dissertation of China
文摘Based on the reliability budget and percentile travel time(PTT) concept, a new travel time index named combined mean travel time(CMTT) under stochastic traffic network was proposed. CMTT here was defined as the convex combination of the conditional expectations of PTT-below and PTT-excess travel times. The former was designed as a risk-optimistic travel time index, and the latter was a risk-pessimistic one. Hence, CMTT was able to describe various routing risk-attitudes. The central idea of CMTT was comprehensively illustrated and the difference among the existing travel time indices was analyzed. The Wardropian combined mean traffic equilibrium(CMTE) model was formulated as a variational inequality and solved via an alternating direction algorithm nesting extra-gradient projection process. Some mathematical properties of CMTT and CMTE model were rigorously proved. Finally, a numerical example was performed to characterize the CMTE network. It is founded that that risk-pessimism is of more benefit to a modest(or low) congestion and risk network, however, it changes to be risk-optimism for a high congestion and risk network.
基金Projects(2006BA104B04-1,2006BAE04B07-3)supported by the National Science and Technology supporting Program of ChinaProject(2007KZ05)supported by the Science and Technology Foundation of Changchun City,China+1 种基金Project supported by"985 Project"of Jilin University,ChinaProject supported by the Open Subject of State Key Laboratory of Rare Earth Resource Utilization(2008)
文摘The effects of semi-solid isothermal process parameters on the microstructure evolution of Mg-Gd rare earth alloy produced by strain-induced melt activation(SIMA)were investigated.The formation mechanism of the particles in the process of the isothermal treatment was also discussed.The results show that the microstructure of the as-cast alloy consists ofα-Mg solid solution, Mg5RE and Mg24RE5(Gd,Y,Nd)phase.After being extruded with an extrusion ratio of 14:1 at 380℃,the microstructure of Mg-Gd alloy changes from developed dendrites to near-equiaxed grains.The liquid volume fraction of the semisolid slurry gradually increases with elevating isothermal temperature or prolonging isothermal time during the partial remelting.To obtain an ideal semisolid slurry,the optimal process parameters for the Mg-Gd alloy should be 630℃for isothermal temperature and 30 min for the corresponding time,respectively,where the volume fraction of the liquid phase is 52%.
基金Project(2012CB725400)supported by the National Basic Research Program of ChinaProjects(71271023,71322102,7121001)supported by the National Natural Science Foundation of China
文摘The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value(CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities.Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.
文摘We study the Cauchy problem of a semilinear parabolic equation. We construct an appropriate Harnack quantity and get a differential Harnack inequality. Using this inequality, we prove the finite-time blow-up of the positive solutions and recover a classical Harnack inequality. We also obtain a result of Liouville type for the elliptic equation.
文摘This article discusses computational methods for the numerical simulation of unsteady Bingham visco-plastic flow. These methods are based on time-discretization by operator-splitting and take advantage of a characterization of the solutions involving some kind of Lagrange multipliers. The full discretization is achieved by combining the above operator-splitting methods with finite element approximations, the advection being treated by a wave-like equation 'equivalent' formulation easier to implement than the method of characteristics or high order upwinding methods. The authors illustrate the methodology discussed in this article with the results of numerical experiments concerning the simulation of wall driven cavity Bingham flow in two dimensions.
基金supported by the National Natural Science Foundation of China(Grant No.51177155)
文摘To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch(POS),we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer.The conduction current and conduction time in experiments are about 120 kA and 1 s,respectively.As a result,more than 85%of conduction current has been transferred to an inductive load with rise time of 130 ns.The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters.During the conduction phase,the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns.The current conduction is observed to cause a radial redistribution of the switch plasma.A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor,which is consistent with the location where magnetic pressure is the largest,allowing current to be transferred from the POS to the load.
基金supported by Australian Research Council’s Discovery Projects Funding Scheme(Grant No.DP120100895)
文摘We study the existence and uniqueness of the solution to a forward-backward stochastic differential equation with subdifferential operator in the backward equation. This kind of equations includes, as a particular case, multi-dimensional forward-backward stochastic differential equation where the backward equation is reflected on the boundary of a closed convex(time-independent) domain. Moreover, we give a probabilistic interpretation for the viscosity solution of a kind of quasilinear variational inequalities.
