It is necessary to reduce the currents of poloidal field(PF) coils as small as possible, during the static equilibrium design procedure of Experimental Advanced Superconductive Tokamak(EAST). The quasi-snowflake(QSF) ...It is necessary to reduce the currents of poloidal field(PF) coils as small as possible, during the static equilibrium design procedure of Experimental Advanced Superconductive Tokamak(EAST). The quasi-snowflake(QSF) divertor configuration is studied in this paper. Starting from a standard QSF plasma equilibrium, a new QSF equilibrium with 300 kA total plasma current is designed. In order to reduce the currents of PF6 and PF14, the influence of plasma shape on PF coil current distribution is analyzed. A fixed boundary equilibrium solver based on a non-rigid plasma model is used to calculate the flux distribution and PF coil current distribution. Then the plasma shape parameters are studied by the orthogonal method. According to the result, the plasma shape is redefined, and the calculated equilibrium shows that the currents of PF6 and PF14 are reduced by 3.592 kA and 2.773 kA, respectively.展开更多
It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in ke...It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in keyhole plasma arc welding is determined firstly, and then the dynamic force-balance condition on the interface between the plasma jet and the molten metal is dealt with in describing the keyhole formation inside the weld pool. The effects of welding current on the shape and size of keyhole are numerically analyzed. The sharp transformation from a partial keyhole to a full-penetration keyhole is quantitatively demonstrated.展开更多
The formation of plasma bullets’ring-shaped structure in atmospheric pressure helium is analyzed by using a coupled fluid model.The model consists of a two-dimension neutral gas flow module and a one-dimension plasma...The formation of plasma bullets’ring-shaped structure in atmospheric pressure helium is analyzed by using a coupled fluid model.The model consists of a two-dimension neutral gas flow module and a one-dimension plasma dynamics module.The obtained radial distributions of the electron’s number density and the nitrogen’s metastable number density have different structures under different types of reactions or air contents in the model.It shows that total electron impact ionization plays an important role in sustaining the discharge,and together with Penning process,they lead to the shifted-off structure of electron number density.Meanwhile,the ring structure of plasma bullets forms mainly due to the excitation reaction of nitrogen molecule on air contents.展开更多
Platelet-free plasma of human blood (sodium citrate and EDTA as an anticoagulant) and serum were stored at 4°C, room temperature (25°C) and at 37°C for 24 hours. RBC aggregation decreased after incubati...Platelet-free plasma of human blood (sodium citrate and EDTA as an anticoagulant) and serum were stored at 4°C, room temperature (25°C) and at 37°C for 24 hours. RBC aggregation decreased after incubation of plasma and serum at 37°C for 4 hours. The RBC shape was changed at the same time: discocytes transformed to echinocytes. Storage of plasma and serum at 4°C and room temperature did not lead to significant alterations of RBC aggregation. The RBC shape did not change in influence of such plasma and serum. The most considerable decrease of RBC aggregation and change of their shapes were observed in the plasma and serum incubated at 37°C for 24 hours. Dilution of incubated plasma by fresh plasma led to consistent restoration of erythrocyte shape and their aggregation.展开更多
Physical engineering capability on the superconducting magnetic system of EAST was tested and first divertor plasma configuration in EAST was obtained. The extrapolation of the safety limit has verified the reliabilit...Physical engineering capability on the superconducting magnetic system of EAST was tested and first divertor plasma configuration in EAST was obtained. The extrapolation of the safety limit has verified the reliability of the system for long pulse operation. A stably controlled diverted plasmas configuration with an elongation n in excess of 1.8 and plasma current of up to 500 kA, by using the （copper） internal coils to control the vertical displacement instability was obtained by an optimized plasma control algorithm. Highly shaped plasma at various configurations, which almost covers all designed configurations for EAST, was generated stably. A number of operational issues, such as plasma initiation, ramp up and configuration control with constraints of superconducting coils, were successfully investigated. All of the results obtained proved both the capability of the superconducting poloidal magnets for operation under steady-state condition and effectiveness of the plasma control algorithm for EAST.展开更多
To unveil the characteristics and available propagation mechanism of coaxial-type microwave excited line-shape plasma, the effects of parameters including microwave power, working pressure, dielectric constant, and ex...To unveil the characteristics and available propagation mechanism of coaxial-type microwave excited line-shape plasma, the effects of parameters including microwave power, working pressure, dielectric constant, and external magnetic field on the plasma distribution were numerically investigated by solving a coupled system of Maxwell＇s equations and continuity equations. Numerical results indicate that high microwave power, relatively high working pressure, low dielectric constant, and shaped magnetic field profiles will help produce a high-density and uniform plasma source. Exciting both ends by microwave contributed to the high-density and uni- form plasma source as well. Possible mechanisms were analyzed by using the polarization model of low temperature plasma. The generation and propagation processes of the line-shape plasma mainly depend on the interaction of three aspects, i.e. the transmitted part, penetration part and absorptive part of the electromagnetic field. The numerical results were qualitatively consistent with available experimental results from literature. More elaborate descriptions of the three aspects and corresponding interactions among them need to be investigated further to improve the properties of the line-shape plasma.展开更多
Discharge with a plasma current of 1 MA at a line-averaged density of 1.8× 10^19 m^-3 was realized in EAST, a fully superconducting tokamak. The key issues to achieve the discharge with 1 MA plasma current includ...Discharge with a plasma current of 1 MA at a line-averaged density of 1.8× 10^19 m^-3 was realized in EAST, a fully superconducting tokamak. The key issues to achieve the discharge with 1 MA plasma current include both early shaping and LHCD assistance during start-up phase to extend the voltage margin of poloidal field （PF） coils for easier plasma control, an optimization of the control methodology for PF coils to avoid over-current fault and a very good wall condition. A better wall condition was achieved mainly by extensive Lithium coating. Both stationary H- mode and diverted plasma discharge of 100 s were also obtained.展开更多
Analytical theories of the geodesic acoustic mode （GAM） are reviewed in the small- and large-orbit drift width limits, respectively. Different physics pictures in these two limits are displayed. As an example, these...Analytical theories of the geodesic acoustic mode （GAM） are reviewed in the small- and large-orbit drift width limits, respectively. Different physics pictures in these two limits are displayed. As an example, these two analytical methods are employed to investigate the plasma shaping effect on the frequency and collisionless damping rate of the GAM.展开更多
The plasma arc pressure plays an important role in determining the keyhole formation and size. So it is of great significance to choose adaptive distribution mode of the plasma arc pressure for determining keyhole sha...The plasma arc pressure plays an important role in determining the keyhole formation and size. So it is of great significance to choose adaptive distribution mode of the plasma arc pressure for determining keyhole shape and size. In this study, through employing a double-elliptic distribution mode of plasma arc pressure, three-dimensional keyhole was numerically simulated. The unsymmetric feature of the keyhole inside the weld pool was described. The development of keyhole was demonstrated under different levels of welding current. The critical current required to form an open keyhole was obtained for the study cases .展开更多
A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and S...A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.展开更多
NiTi shape memory alloys(SMAs) was developed using the spark-plasma sintering(SPS) process with different average particle size(45 μm and 10 μm) under various temperature. The influence of particle size and temperat...NiTi shape memory alloys(SMAs) was developed using the spark-plasma sintering(SPS) process with different average particle size(45 μm and 10 μm) under various temperature. The influence of particle size and temperature on the density, microstructure, and corrosion behavior of the NiTi in simulated body fluid was examined. The porosity decreased with increasing sintering temperature and decreasing particle size, which resulted in an increase in density of the alloy. Increasing the sintering temperature led to the formation of Ni-and Ti-rich intermetallic such as Ni3Ti and NiTi2. The formation of these secondary phases influenced the corrosion behavior of NiTi by changing its chemical composition. The planar structure of NiTi was transformed into a dendritic structure at 900℃, which resulted in the formation of uniform oxide and phosphate layers on the entire surface. A high corrosion potential and low corrosion current density were achieved with NiTi prepared with 10 μm particles at 900℃, which exhibited superior corrosion resistance.展开更多
The surface shape of liquid water is well controlled during nanosecond pulse laser ablation plasma propulsion. In this study, we measured the effect of the shape on the coupling coefficient and the specific impulse. W...The surface shape of liquid water is well controlled during nanosecond pulse laser ablation plasma propulsion. In this study, we measured the effect of the shape on the coupling coefficient and the specific impulse. We found that the coupling coefficient and specific impulse could be optimized by varying the surface convexity. Based on the analysis of the surface radius curvature, we demonstrate that the convex surface changes the laser focal positions to achieve high efficiency.展开更多
An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular c...An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.展开更多
The microstructural, phase transformation and magnetic properties of Ni Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed si...The microstructural, phase transformation and magnetic properties of Ni Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed sintered specimens exhibit typical martensitic transformation behaviours. The martensite of the sintered specimen after annealing exhibits a ferromagnetic nature. Moreover, study of the fracture surface indicates that the transgranular fracture con- tributes to the higher ductility of sintered Ni-Mn-Ga alloy. In addition, the transformation strain in sintered Ni-Mn-Ga alloy is studied for the first time.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51677051)the Institute of Plasma Physics,Chinese Academy of Sciences
文摘It is necessary to reduce the currents of poloidal field(PF) coils as small as possible, during the static equilibrium design procedure of Experimental Advanced Superconductive Tokamak(EAST). The quasi-snowflake(QSF) divertor configuration is studied in this paper. Starting from a standard QSF plasma equilibrium, a new QSF equilibrium with 300 kA total plasma current is designed. In order to reduce the currents of PF6 and PF14, the influence of plasma shape on PF coil current distribution is analyzed. A fixed boundary equilibrium solver based on a non-rigid plasma model is used to calculate the flux distribution and PF coil current distribution. Then the plasma shape parameters are studied by the orthogonal method. According to the result, the plasma shape is redefined, and the calculated equilibrium shows that the currents of PF6 and PF14 are reduced by 3.592 kA and 2.773 kA, respectively.
文摘It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in keyhole plasma arc welding is determined firstly, and then the dynamic force-balance condition on the interface between the plasma jet and the molten metal is dealt with in describing the keyhole formation inside the weld pool. The effects of welding current on the shape and size of keyhole are numerically analyzed. The sharp transformation from a partial keyhole to a full-penetration keyhole is quantitatively demonstrated.
基金Project supported by National Natural Science Foundation of China （10775026 11275042）, Hebei Provincial Natural Science Foundation of China （A2012201015）.
文摘The formation of plasma bullets’ring-shaped structure in atmospheric pressure helium is analyzed by using a coupled fluid model.The model consists of a two-dimension neutral gas flow module and a one-dimension plasma dynamics module.The obtained radial distributions of the electron’s number density and the nitrogen’s metastable number density have different structures under different types of reactions or air contents in the model.It shows that total electron impact ionization plays an important role in sustaining the discharge,and together with Penning process,they lead to the shifted-off structure of electron number density.Meanwhile,the ring structure of plasma bullets forms mainly due to the excitation reaction of nitrogen molecule on air contents.
文摘Platelet-free plasma of human blood (sodium citrate and EDTA as an anticoagulant) and serum were stored at 4°C, room temperature (25°C) and at 37°C for 24 hours. RBC aggregation decreased after incubation of plasma and serum at 37°C for 4 hours. The RBC shape was changed at the same time: discocytes transformed to echinocytes. Storage of plasma and serum at 4°C and room temperature did not lead to significant alterations of RBC aggregation. The RBC shape did not change in influence of such plasma and serum. The most considerable decrease of RBC aggregation and change of their shapes were observed in the plasma and serum incubated at 37°C for 24 hours. Dilution of incubated plasma by fresh plasma led to consistent restoration of erythrocyte shape and their aggregation.
基金the National Natural Science Foundation of China(No.10235010)
文摘Physical engineering capability on the superconducting magnetic system of EAST was tested and first divertor plasma configuration in EAST was obtained. The extrapolation of the safety limit has verified the reliability of the system for long pulse operation. A stably controlled diverted plasmas configuration with an elongation n in excess of 1.8 and plasma current of up to 500 kA, by using the （copper） internal coils to control the vertical displacement instability was obtained by an optimized plasma control algorithm. Highly shaped plasma at various configurations, which almost covers all designed configurations for EAST, was generated stably. A number of operational issues, such as plasma initiation, ramp up and configuration control with constraints of superconducting coils, were successfully investigated. All of the results obtained proved both the capability of the superconducting poloidal magnets for operation under steady-state condition and effectiveness of the plasma control algorithm for EAST.
基金supported by National Natural Science Foundation of China(Nos.11205201 and 61205139)the Scientific Foundation of Ministry of Education of China(No.N130405008)
文摘To unveil the characteristics and available propagation mechanism of coaxial-type microwave excited line-shape plasma, the effects of parameters including microwave power, working pressure, dielectric constant, and external magnetic field on the plasma distribution were numerically investigated by solving a coupled system of Maxwell＇s equations and continuity equations. Numerical results indicate that high microwave power, relatively high working pressure, low dielectric constant, and shaped magnetic field profiles will help produce a high-density and uniform plasma source. Exciting both ends by microwave contributed to the high-density and uni- form plasma source as well. Possible mechanisms were analyzed by using the polarization model of low temperature plasma. The generation and propagation processes of the line-shape plasma mainly depend on the interaction of three aspects, i.e. the transmitted part, penetration part and absorptive part of the electromagnetic field. The numerical results were qualitatively consistent with available experimental results from literature. More elaborate descriptions of the three aspects and corresponding interactions among them need to be investigated further to improve the properties of the line-shape plasma.
基金supported by National Natural Science Foundation of China (Nos. 10725523, 10990212 and 10721505)
文摘Discharge with a plasma current of 1 MA at a line-averaged density of 1.8× 10^19 m^-3 was realized in EAST, a fully superconducting tokamak. The key issues to achieve the discharge with 1 MA plasma current include both early shaping and LHCD assistance during start-up phase to extend the voltage margin of poloidal field （PF） coils for easier plasma control, an optimization of the control methodology for PF coils to avoid over-current fault and a very good wall condition. A better wall condition was achieved mainly by extensive Lithium coating. Both stationary H- mode and diverted plasma discharge of 100 s were also obtained.
基金supported by National Natural Science Foundation of China (No. 10990214)the Major State Basic Research Development Program of China (Nos. 2009GB105002, 2008GB717804)the JSPS-CAS Core University Program in Plasma and Nuclear Fusion
文摘Analytical theories of the geodesic acoustic mode （GAM） are reviewed in the small- and large-orbit drift width limits, respectively. Different physics pictures in these two limits are displayed. As an example, these two analytical methods are employed to investigate the plasma shaping effect on the frequency and collisionless damping rate of the GAM.
基金Acknowledgement The authors are grateful to the financial support for this project from the National Natural Science Foundation of China under grant No. 50540420570.
文摘The plasma arc pressure plays an important role in determining the keyhole formation and size. So it is of great significance to choose adaptive distribution mode of the plasma arc pressure for determining keyhole shape and size. In this study, through employing a double-elliptic distribution mode of plasma arc pressure, three-dimensional keyhole was numerically simulated. The unsymmetric feature of the keyhole inside the weld pool was described. The development of keyhole was demonstrated under different levels of welding current. The critical current required to form an open keyhole was obtained for the study cases .
基金National Natural Science Foundation of China(No.10405014)
文摘A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.
文摘NiTi shape memory alloys(SMAs) was developed using the spark-plasma sintering(SPS) process with different average particle size(45 μm and 10 μm) under various temperature. The influence of particle size and temperature on the density, microstructure, and corrosion behavior of the NiTi in simulated body fluid was examined. The porosity decreased with increasing sintering temperature and decreasing particle size, which resulted in an increase in density of the alloy. Increasing the sintering temperature led to the formation of Ni-and Ti-rich intermetallic such as Ni3Ti and NiTi2. The formation of these secondary phases influenced the corrosion behavior of NiTi by changing its chemical composition. The planar structure of NiTi was transformed into a dendritic structure at 900℃, which resulted in the formation of uniform oxide and phosphate layers on the entire surface. A high corrosion potential and low corrosion current density were achieved with NiTi prepared with 10 μm particles at 900℃, which exhibited superior corrosion resistance.
基金supported by National Natural Science Foundation of China(No.10905049)Fundamental Research Funds for the Central Universities of China(Nos.53200859165,2562010050)
文摘The surface shape of liquid water is well controlled during nanosecond pulse laser ablation plasma propulsion. In this study, we measured the effect of the shape on the coupling coefficient and the specific impulse. We found that the coupling coefficient and specific impulse could be optimized by varying the surface convexity. Based on the analysis of the surface radius curvature, we demonstrate that the convex surface changes the laser focal positions to achieve high efficiency.
文摘An electrohydrodynamic （EHD） method, which is based on glow discharge plasma, is presented for flow control in an S-shaped duct. The research subject is an expanding channel with a constant width and a rectangular cross section. An equivalent divergence angle and basic function are introduced to build the three-dimensional model. Subsequently, the plasma physical models are simplified as the effects of electrical body force and work （done by the force） on the fluid near the wall. With the aid of FLUENT software, the source terms of momentum and energy are added to the Navier-Stokes equation. Finally, the original performance of three models （A, B and C） is studied, in which model A demonstrates better performance. Then EHD control based on model A is discussed. The results show that the EHD method is an effective way of reducing flow loss and improving uniformity at the duct exit. The innovation in this study is the assessment of the EHD control effect on the flow in an S-shaped duct. Both the parametric modeling of the S-shaped duct and the simplified models of plasma provide valuable information for future research on aircraft inlet ducts.
基金supported by the National Natural Science Foundation of China (Grant No. 50971052)the Scientific Research Fund of Heilongjiang Provincial Education Department of China (Grant No. 11531059)
文摘The microstructural, phase transformation and magnetic properties of Ni Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed sintered specimens exhibit typical martensitic transformation behaviours. The martensite of the sintered specimen after annealing exhibits a ferromagnetic nature. Moreover, study of the fracture surface indicates that the transgranular fracture con- tributes to the higher ductility of sintered Ni-Mn-Ga alloy. In addition, the transformation strain in sintered Ni-Mn-Ga alloy is studied for the first time.
