The evolution of dislocation loops in austenitic steels irradiated with Fe^(+)is investigated using cluster dynamics(CD)simulations by developing a CD model.The CD predictions are compared with experimental results in...The evolution of dislocation loops in austenitic steels irradiated with Fe^(+)is investigated using cluster dynamics(CD)simulations by developing a CD model.The CD predictions are compared with experimental results in the literature.The number density and average diameter of the dislocation loops obtained from the CD simulations are in good agreement with the experimental data obtained from transmission electron microscopy(TEM)observations of Fe~+-irradiated Solution Annealed 304,Cold Worked 316,and HR3 austenitic steels in the literature.The CD simulation results demonstrate that the diffusion of in-cascade interstitial clusters plays a major role in the dislocation loop density and dislocation loop growth;in particular,for the HR3 austenitic steel,the CD model has verified the effect of temperature on the density and size of the dislocation loops.展开更多
With continuous growth in scale,topology complexity,mission phases,and mission diversity,challenges have been placed for efficient capability evaluation of modern combat systems.Aiming at the problems of insufficient ...With continuous growth in scale,topology complexity,mission phases,and mission diversity,challenges have been placed for efficient capability evaluation of modern combat systems.Aiming at the problems of insufficient mission consideration and single evaluation dimension in the existing evaluation approaches,this study proposes a mission-oriented capability evaluation method for combat systems based on operation loop.Firstly,a combat network model is given that takes into account the capability properties of combat nodes.Then,based on the transition matrix between combat nodes,an efficient algorithm for operation loop identification is proposed based on the Breadth-First Search.Given the mission-capability satisfaction of nodes,the effectiveness evaluation indexes for operation loops and combat network are proposed,followed by node importance measure.Through a case study of the combat scenario involving space-based support against surface ships under different strategies,the effectiveness of the proposed method is verified.The results indicated that the ROI-priority attack method has a notable impact on reducing the overall efficiency of the network,whereas the O-L betweenness-priority attack is more effective in obstructing the successful execution of enemy attack missions.展开更多
The two-parameter Weibull model is used to describe the fiber strength distribution.The stress carried by the intact and fracture fibers on the matrix crack plane during unloading/reloading is determined based on the ...The two-parameter Weibull model is used to describe the fiber strength distribution.The stress carried by the intact and fracture fibers on the matrix crack plane during unloading/reloading is determined based on the global load sharing criterion.The axial stress distribution of intact fibers upon unloading and reloading is determined based on the mechanisms of fiber sliding relative to matrix in the interface debonded region.The interface debonded length,unloading interface counter slip length,and reloading interface new slip length are obtained by the fracture mechanics approach.The hysteresis loops corresponding to different stresses considering fiber failure are compared with the cases without considering fiber failure.The effects of fiber characteristic strength and fiber Weibull modulus on the fiber failure,the shape,and the area of the hysteresis loops are analyzed.The predicted quasi-static unloading/reloading hysteresis loops agree well with experimental data.展开更多
CC chemokine receptor 4（CCR4） is a G-protein-coupled receptor which plays a pivotal role in allergic inflammation. In the present study, three extracellular loops（EL1-3） of CCR4 were synthesized, and the interacti...CC chemokine receptor 4（CCR4） is a G-protein-coupled receptor which plays a pivotal role in allergic inflammation. In the present study, three extracellular loops（EL1-3） of CCR4 were synthesized, and the interactions between the extracellular loops and compound S009 were investigated using capillary zone electrophoresis（CZE）. Both qualitative and quantitative characterizations of the compound-peptide binding were carried out. The experimental data indicated that compound S009 exhibited interactions with EL3, and a binding constant of（12.5±0.19）×10^4 M^-1 was determined using the Scatchard plot. Our study identified the specific domains of CCR4 that could be targeted by small molecules and provided insights for the discovery of novel CCR4 antagonists.展开更多
Hard/soft permanent magnets have attracted a lot of attention because of their rich magnetic properties and their potential for realizing giant energy products. However, energy products obtained by scientists in exper...Hard/soft permanent magnets have attracted a lot of attention because of their rich magnetic properties and their potential for realizing giant energy products. However, energy products obtained by scientists in experiments are much smaller than the theoretical values, which has been studied by various analytical and numerical methods. The famous Stoner-Wohlfarth model(S-W model) is too simple to give the hysteresis loops whereas the intensively used variational method is too complicated to reveal the underlying mechanism in a simple form. The analytical model proposed in this paper maintains a balance between simplicity and precision, where the spins in the soft layer rotate fast and coherently with the applied field while those in the hard layer response to the applied field much slower but also coherent. An exchange coupling is provided to maintain the exchange spring which drags the spins in the hard layer to follow those in the soft layer. Similar to the more sophisticated model, the calculated hysteresis loops display three typical magnetic phases, i.e., the rigid composite magnet, the exchange spring and decoupled magnet, whereas the simple SW model can only give one single phase, i.e., the rigid composite one. In addition to the hysteresis loop, the energy product and the nucleation fields have been calculated and compared with those calculated by other methods, which justifies our model.Careful comparisons show that our calculations are in good agreement with the experimental results and other theoretical results, especially for the important coercivity value and the related mechanism.展开更多
Two models are established to reveal the underlying coercivity mechanism for SmCo/Fe films,where one model considers a transition layer between hard and soft layers,while the other model does not consider this layer.B...Two models are established to reveal the underlying coercivity mechanism for SmCo/Fe films,where one model considers a transition layer between hard and soft layers,while the other model does not consider this layer.Based on the two models,hysteresis loops,nucleation fields and coercivity are obtained by one-dimensional(1 D)and three-dimensional(3 D)micromagnetic methods.In particular,the calculated nucleation fields(H_N)and coercivity(H_C)match very well with the experimental data.It is found that the increase in the soft phase thickness(Ls)leads to a transition of the coercivity mechanism from nucleation to pinning.Such a pinning is inherently related to nucleation and has both attributes of traditional nucleation and pinning,called as a hybrid coercivity mechanism here.It is general for all hard/soft composites and can be extended to single-phased permanent magnets where defects are inevitable.展开更多
Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures.The annealing process made the defects develop into large dislocation loops. The nature of the disloc...Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures.The annealing process made the defects develop into large dislocation loops. The nature of the dislocation loops formed after annealing was studied by the evolution of loops under in situ electron irradiation in high-voltage electron microscope.It indicated that only interstitial-type loops were observed when annealed at 550 °C and below, but vacancy-type loops started to form at the temperature higher than 600 °C. According to the previous study of our group, the presence of chromium element made the formation temperature of vacancy-type loops higher than that in pure iron. The effect of alloying elements on the formation temperature of the vacancy-type loops was discussed.展开更多
Compact accelerator-based neutron source facilities are garnering attention and play an important and expanding role in material and engineering sciences,as well as in neutron science education and training.Neutrons a...Compact accelerator-based neutron source facilities are garnering attention and play an important and expanding role in material and engineering sciences,as well as in neutron science education and training.Neutrons are produced by bombarding a low-energy proton beam onto a beryllium or lithium target.In such an acceleratorbased neutron source,a radio frequency quadrupole(RFQ)is usually utilized to accelerate a high-intensity proton beam to a few MeV.This study mainly covers the highfrequency structure design optimizations of a 4-vane RFQ with pi-mode stabilizer loops(PISLs)and its RF stability analysis.A 176 MHz RFQ accelerator is designed to operate at a 10%duty factor and could accelerate an80 mA proton beam from 65 keV to 2.5 MeV within a length of 5.3 m.The adoption of PISLs ensures high RF stability,eases the operation of the accelerator,and implies less stringent alignment and machining tolerances.展开更多
By use of the recursive formulation of flexible multibody system with closed loops,this paper studies the dynamic simulation of complicated multibody system.The conception of static correction modes in structural dyna...By use of the recursive formulation of flexible multibody system with closed loops,this paper studies the dynamic simulation of complicated multibody system.The conception of static correction modes in structural dynamics is introduced to present the local deformation effects due to reaction forces at kinematic joints.A space four bar mechanism is utilized here as an example to describe the method of selecting static correction modes.Compared with vibration normal modes, static correction modes are demonstrated to be effective in numerical simulation.展开更多
In this paper we study the properties of homotopy inverses of comultiplications and Mgebraic loops of co-H-spaces based on a wedge of spheres. We also investigate a method to construct new comultiplications out of old...In this paper we study the properties of homotopy inverses of comultiplications and Mgebraic loops of co-H-spaces based on a wedge of spheres. We also investigate a method to construct new comultiplications out of old ones by using a group action. We are primarily interested in the algebraic loops which have inversive, power-associative and Moufang properties for some comultiplications.展开更多
AL-6XN stainless steels, one of the candidate structure materials for supercritical water-cooled reactor, were irradiated from 0.5 to 5 dpa using 100 keV H2＋ ions at 290 and 380 ℃. Microstructures were characterized...AL-6XN stainless steels, one of the candidate structure materials for supercritical water-cooled reactor, were irradiated from 0.5 to 5 dpa using 100 keV H2＋ ions at 290 and 380 ℃. Microstructures were characterized by transmission electron microscopy （TEM）. Dislocation loops were the dominant radiation-induced defects. All the dislocation loops had 1/3 〈111〉 type Burgers vector. Number density and size of the loops have been measured. Nucleation and evolution of dislocation loops were also investigated. Voids were observed only in the condition of 5 dpa at 380 ℃. Different evolution mechanisms of the radiation-induced dislocation loops were discussed. Effects of hydrogen and elevated temperature on the microstructural evolution were also investigated. Besides, the formed voids have a further effect on the evolution of dislocation loops.展开更多
A conformal restriction measure is a probability measure which is used to describe the law of a random connected subset in a simply connected domain that satisfies a certain conformal restriction property. Usually the...A conformal restriction measure is a probability measure which is used to describe the law of a random connected subset in a simply connected domain that satisfies a certain conformal restriction property. Usually there are three kinds of conformal restriction measures: one (called the chordal restriction measure) has two given boundary points of the random set, the second (called the radial restriction measure) has one boundary point and one interior point in the random set, and the third (called the tri-chordal restriction measure) has three boundary points in the random set. In this article, we will define a new probability measure such that the random set associated to it contains one given interior point and does not intersect with the boundary. Furthermore, we will show that this measure can be characterized by one parameter;we will also construct this one-parameter family of measures in two ways and obtain several properties.展开更多
We propose a bulk negative refractive index （NRI） metamaterial composed of periodic array of tightly coupled metallic cross-pairs printed oR the six sides of a cube for applications of superlenses. The structural ch...We propose a bulk negative refractive index （NRI） metamaterial composed of periodic array of tightly coupled metallic cross-pairs printed oR the six sides of a cube for applications of superlenses. The structural characteristics of the three-dimensional （3D） metamaterial consist in the high symmetry and the superposition of metallic cross-pairs, which can increase the magnetic inductive coupling between adjacent cross-pairs and realize a broadband and isotropic NRI. The proposed 3D structure is simulated using the CS~ Microwave Studio 2006 to verify the design validity. The simulation results show that the proposed structure can not only realize simultaneously an electric and magnetic response to an incident electromagnetic （EM） wave, but also exhibit a broadband NRI whose relative bandwidth can reach up to 56.7%. In addition, the NRI band is insensitive to tile polarization and the incident angle of the incident EM wave. Therefore, the proposed metamaterial is a good candidate material as three-dimensional broadband isotropic NRI metamaterial.展开更多
Magnetic hysteresis and compensation behavior of a mixed spin-（1, 3/2） Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The e...Magnetic hysteresis and compensation behavior of a mixed spin-（1, 3/2） Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The effect of random crystal field, ferromagnetic and ferrimagnetic exchange interaction on hysteresis loops and compensation phenomenon are discussed. A number of characteristic phenomena have been reported such as the observation of triple hysteresis loops at low temperatures and for negative values of random crystal field. Critical and double compensation temperatures have been also found. The obtained results are also compared to some previous works.展开更多
Based on the transverse Ising model in the framework of the mean field approximation, this paper discusses a ferroelectric bilayer film with the surface transition layers within each constituent slab and an antiferroe...Based on the transverse Ising model in the framework of the mean field approximation, this paper discusses a ferroelectric bilayer film with the surface transition layers within each constituent slab and an antiferroelectric interracial coupling between two slabs. The hysteresis loop of a bilayer film is investigated. The results show that the surface transition layer in a ferroelectric bilayer film plays a significant role in realizing the multiple-state memory.展开更多
The plasma shape and other paremeters such as /3P, li is important for the tokamak deveice where the plasma has a non-circular cross-section of sufficient elongation. The measuered signals of magnetic probes and flux ...The plasma shape and other paremeters such as /3P, li is important for the tokamak deveice where the plasma has a non-circular cross-section of sufficient elongation. The measuered signals of magnetic probes and flux loops are used to reconstruct the plasma shape and the current profile in device operation and plasma shape feed back control system. So the number and positions of magnetic probes and flux loops provides the basis of the plasma reconstruction. This paper instroduce how to use EFIT code (equilibrium fitting code) to determine the number and positions of the magnetic probes and flux loops. The simulation result is given also.展开更多
The phenomenon of stochastic resonance of a bistable system subjected to linear time-delayed feedback loops driven by multiplieative Gaussian coloured noise and additive Gaussian white noise is investigated. Firstly, ...The phenomenon of stochastic resonance of a bistable system subjected to linear time-delayed feedback loops driven by multiplieative Gaussian coloured noise and additive Gaussian white noise is investigated. Firstly, the analytic expression of the quasi-steady distribution function Ps （x, t） is derived by applying the unified coloured noise approximation and the Novikov Theorem; Secondly, the expression of the signal-to-noise ratio （SNR） is obtained in the adiabatic limit to quantify the stochastic resonance. Finally, tile effects of the linear coefficient a, the nonlinear coefficient b, the linear time-delayed feedback coefficient c and the delay time r on Ps（x,t） and SNR^± are discussed. It is found that the effects of the linear coefficient and the nonlinear coefficient, the positive linear time-delayed feedback coefficient and the negative linear time-delayed feedback coefficient, the positive delayed time and the negative delayed time on Ps（x,t） and SNR^± are different, respectively. This discussion would be helpful to the study of the system reliability and controlling stochastic resonance.展开更多
Bernoulli’s law is applied to the closed streamlines of a smoke ring, and the centrifugal force of the curved flow is balanced by a pressure gradient. Two equations in two unknowns, pressure and velocity, are combine...Bernoulli’s law is applied to the closed streamlines of a smoke ring, and the centrifugal force of the curved flow is balanced by a pressure gradient. Two equations in two unknowns, pressure and velocity, are combined into one equation in one unknown, velocity. Solving the governing equation algebraically produces a radial shear in the velocity such that the speed decreases outward inversely as the radius increases, which is the main result. Measurements are needed to verify the predicted structure of the velocity field.展开更多
基金supported by the National Natural Science Foundation of China(No.U1967212)the Fundamental Research Funds for the Central Universities(No.2021MS032)the Nuclear Materials Innovation Foundation(No.WDZC-2023-AW-0305)。
文摘The evolution of dislocation loops in austenitic steels irradiated with Fe^(+)is investigated using cluster dynamics(CD)simulations by developing a CD model.The CD predictions are compared with experimental results in the literature.The number density and average diameter of the dislocation loops obtained from the CD simulations are in good agreement with the experimental data obtained from transmission electron microscopy(TEM)observations of Fe~+-irradiated Solution Annealed 304,Cold Worked 316,and HR3 austenitic steels in the literature.The CD simulation results demonstrate that the diffusion of in-cascade interstitial clusters plays a major role in the dislocation loop density and dislocation loop growth;in particular,for the HR3 austenitic steel,the CD model has verified the effect of temperature on the density and size of the dislocation loops.
文摘With continuous growth in scale,topology complexity,mission phases,and mission diversity,challenges have been placed for efficient capability evaluation of modern combat systems.Aiming at the problems of insufficient mission consideration and single evaluation dimension in the existing evaluation approaches,this study proposes a mission-oriented capability evaluation method for combat systems based on operation loop.Firstly,a combat network model is given that takes into account the capability properties of combat nodes.Then,based on the transition matrix between combat nodes,an efficient algorithm for operation loop identification is proposed based on the Breadth-First Search.Given the mission-capability satisfaction of nodes,the effectiveness evaluation indexes for operation loops and combat network are proposed,followed by node importance measure.Through a case study of the combat scenario involving space-based support against surface ships under different strategies,the effectiveness of the proposed method is verified.The results indicated that the ROI-priority attack method has a notable impact on reducing the overall efficiency of the network,whereas the O-L betweenness-priority attack is more effective in obstructing the successful execution of enemy attack missions.
基金Supported by the National Natural Science Foundation of China(51075204)the Graduate Innovation Foundation of Jiangsu Province(CX08B-133Z)the Doctoral Innovation Foundation of Nanjing University of Aeronautics and Astronautics(BCXJ08-05)~~
文摘The two-parameter Weibull model is used to describe the fiber strength distribution.The stress carried by the intact and fracture fibers on the matrix crack plane during unloading/reloading is determined based on the global load sharing criterion.The axial stress distribution of intact fibers upon unloading and reloading is determined based on the mechanisms of fiber sliding relative to matrix in the interface debonded region.The interface debonded length,unloading interface counter slip length,and reloading interface new slip length are obtained by the fracture mechanics approach.The hysteresis loops corresponding to different stresses considering fiber failure are compared with the cases without considering fiber failure.The effects of fiber characteristic strength and fiber Weibull modulus on the fiber failure,the shape,and the area of the hysteresis loops are analyzed.The predicted quasi-static unloading/reloading hysteresis loops agree well with experimental data.
基金National Natural Science Foundation(Grant No.81072612,31270915 and 81071749)Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.201 10001110021 and 20120001110001)the Open Foundation of State Key Laboratory of Natural and Biomimetic Drugs(Grant No.K20110109)
文摘CC chemokine receptor 4（CCR4） is a G-protein-coupled receptor which plays a pivotal role in allergic inflammation. In the present study, three extracellular loops（EL1-3） of CCR4 were synthesized, and the interactions between the extracellular loops and compound S009 were investigated using capillary zone electrophoresis（CZE）. Both qualitative and quantitative characterizations of the compound-peptide binding were carried out. The experimental data indicated that compound S009 exhibited interactions with EL3, and a binding constant of（12.5±0.19）×10^4 M^-1 was determined using the Scatchard plot. Our study identified the specific domains of CCR4 that could be targeted by small molecules and provided insights for the discovery of novel CCR4 antagonists.
基金Project supported by National Natural Science Foundation of China(11074179,51771127,51571126,51772004)the Scientific Research Fund of Sichuan Provincial Education Department(18TD0010,16CZ0006)
文摘Hard/soft permanent magnets have attracted a lot of attention because of their rich magnetic properties and their potential for realizing giant energy products. However, energy products obtained by scientists in experiments are much smaller than the theoretical values, which has been studied by various analytical and numerical methods. The famous Stoner-Wohlfarth model(S-W model) is too simple to give the hysteresis loops whereas the intensively used variational method is too complicated to reveal the underlying mechanism in a simple form. The analytical model proposed in this paper maintains a balance between simplicity and precision, where the spins in the soft layer rotate fast and coherently with the applied field while those in the hard layer response to the applied field much slower but also coherent. An exchange coupling is provided to maintain the exchange spring which drags the spins in the hard layer to follow those in the soft layer. Similar to the more sophisticated model, the calculated hysteresis loops display three typical magnetic phases, i.e., the rigid composite magnet, the exchange spring and decoupled magnet, whereas the simple SW model can only give one single phase, i.e., the rigid composite one. In addition to the hysteresis loop, the energy product and the nucleation fields have been calculated and compared with those calculated by other methods, which justifies our model.Careful comparisons show that our calculations are in good agreement with the experimental results and other theoretical results, especially for the important coercivity value and the related mechanism.
基金financially supported by the National Natural Science Foundation of China(Nos.51771127,51571126 and 51772004).
文摘Two models are established to reveal the underlying coercivity mechanism for SmCo/Fe films,where one model considers a transition layer between hard and soft layers,while the other model does not consider this layer.Based on the two models,hysteresis loops,nucleation fields and coercivity are obtained by one-dimensional(1 D)and three-dimensional(3 D)micromagnetic methods.In particular,the calculated nucleation fields(H_N)and coercivity(H_C)match very well with the experimental data.It is found that the increase in the soft phase thickness(Ls)leads to a transition of the coercivity mechanism from nucleation to pinning.Such a pinning is inherently related to nucleation and has both attributes of traditional nucleation and pinning,called as a hybrid coercivity mechanism here.It is general for all hard/soft composites and can be extended to single-phased permanent magnets where defects are inevitable.
基金supported by the National Natural Science Foundation of China (Grant No. 51471026)
文摘Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures.The annealing process made the defects develop into large dislocation loops. The nature of the dislocation loops formed after annealing was studied by the evolution of loops under in situ electron irradiation in high-voltage electron microscope.It indicated that only interstitial-type loops were observed when annealed at 550 °C and below, but vacancy-type loops started to form at the temperature higher than 600 °C. According to the previous study of our group, the presence of chromium element made the formation temperature of vacancy-type loops higher than that in pure iron. The effect of alloying elements on the formation temperature of the vacancy-type loops was discussed.
文摘Compact accelerator-based neutron source facilities are garnering attention and play an important and expanding role in material and engineering sciences,as well as in neutron science education and training.Neutrons are produced by bombarding a low-energy proton beam onto a beryllium or lithium target.In such an acceleratorbased neutron source,a radio frequency quadrupole(RFQ)is usually utilized to accelerate a high-intensity proton beam to a few MeV.This study mainly covers the highfrequency structure design optimizations of a 4-vane RFQ with pi-mode stabilizer loops(PISLs)and its RF stability analysis.A 176 MHz RFQ accelerator is designed to operate at a 10%duty factor and could accelerate an80 mA proton beam from 65 keV to 2.5 MeV within a length of 5.3 m.The adoption of PISLs ensures high RF stability,eases the operation of the accelerator,and implies less stringent alignment and machining tolerances.
文摘By use of the recursive formulation of flexible multibody system with closed loops,this paper studies the dynamic simulation of complicated multibody system.The conception of static correction modes in structural dynamics is introduced to present the local deformation effects due to reaction forces at kinematic joints.A space four bar mechanism is utilized here as an example to describe the method of selecting static correction modes.Compared with vibration normal modes, static correction modes are demonstrated to be effective in numerical simulation.
基金supported by Basic Science Research Program through the National Research Foundation of Korea (NRF)the Ministry of Education,Science and Technology (2010-0022035)
文摘In this paper we study the properties of homotopy inverses of comultiplications and Mgebraic loops of co-H-spaces based on a wedge of spheres. We also investigate a method to construct new comultiplications out of old ones by using a group action. We are primarily interested in the algebraic loops which have inversive, power-associative and Moufang properties for some comultiplications.
基金financial supports from the International Science and Technology Cooperation Program of China (No. 2015DFR60370)the National Natural Science Foundation of China (Nos. 11275140 and U1532134)
文摘AL-6XN stainless steels, one of the candidate structure materials for supercritical water-cooled reactor, were irradiated from 0.5 to 5 dpa using 100 keV H2＋ ions at 290 and 380 ℃. Microstructures were characterized by transmission electron microscopy （TEM）. Dislocation loops were the dominant radiation-induced defects. All the dislocation loops had 1/3 〈111〉 type Burgers vector. Number density and size of the loops have been measured. Nucleation and evolution of dislocation loops were also investigated. Voids were observed only in the condition of 5 dpa at 380 ℃. Different evolution mechanisms of the radiation-induced dislocation loops were discussed. Effects of hydrogen and elevated temperature on the microstructural evolution were also investigated. Besides, the formed voids have a further effect on the evolution of dislocation loops.
文摘A conformal restriction measure is a probability measure which is used to describe the law of a random connected subset in a simply connected domain that satisfies a certain conformal restriction property. Usually there are three kinds of conformal restriction measures: one (called the chordal restriction measure) has two given boundary points of the random set, the second (called the radial restriction measure) has one boundary point and one interior point in the random set, and the third (called the tri-chordal restriction measure) has three boundary points in the random set. In this article, we will define a new probability measure such that the random set associated to it contains one given interior point and does not intersect with the boundary. Furthermore, we will show that this measure can be characterized by one parameter;we will also construct this one-parameter family of measures in two ways and obtain several properties.
基金supported by the National Natural Science Foundation of China (Grant No. 51005001)the National Science Foundation for Post-doctoral Scientists in China (Grant No. 20090450226)+1 种基金the Research Foundation of Education Bureau of Heilongjiang Province, China (Grant No. 11551098)the Youth Foundation of Harbin University of Science and Technology, China (Grant No. 2009YF024)
文摘We propose a bulk negative refractive index （NRI） metamaterial composed of periodic array of tightly coupled metallic cross-pairs printed oR the six sides of a cube for applications of superlenses. The structural characteristics of the three-dimensional （3D） metamaterial consist in the high symmetry and the superposition of metallic cross-pairs, which can increase the magnetic inductive coupling between adjacent cross-pairs and realize a broadband and isotropic NRI. The proposed 3D structure is simulated using the CS~ Microwave Studio 2006 to verify the design validity. The simulation results show that the proposed structure can not only realize simultaneously an electric and magnetic response to an incident electromagnetic （EM） wave, but also exhibit a broadband NRI whose relative bandwidth can reach up to 56.7%. In addition, the NRI band is insensitive to tile polarization and the incident angle of the incident EM wave. Therefore, the proposed metamaterial is a good candidate material as three-dimensional broadband isotropic NRI metamaterial.
文摘Magnetic hysteresis and compensation behavior of a mixed spin-（1, 3/2） Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The effect of random crystal field, ferromagnetic and ferrimagnetic exchange interaction on hysteresis loops and compensation phenomenon are discussed. A number of characteristic phenomena have been reported such as the observation of triple hysteresis loops at low temperatures and for negative values of random crystal field. Critical and double compensation temperatures have been also found. The obtained results are also compared to some previous works.
文摘Based on the transverse Ising model in the framework of the mean field approximation, this paper discusses a ferroelectric bilayer film with the surface transition layers within each constituent slab and an antiferroelectric interracial coupling between two slabs. The hysteresis loop of a bilayer film is investigated. The results show that the surface transition layer in a ferroelectric bilayer film plays a significant role in realizing the multiple-state memory.
基金The project supported by the National Meg-Science Engineering Project of the Chinese Government
文摘The plasma shape and other paremeters such as /3P, li is important for the tokamak deveice where the plasma has a non-circular cross-section of sufficient elongation. The measuered signals of magnetic probes and flux loops are used to reconstruct the plasma shape and the current profile in device operation and plasma shape feed back control system. So the number and positions of magnetic probes and flux loops provides the basis of the plasma reconstruction. This paper instroduce how to use EFIT code (equilibrium fitting code) to determine the number and positions of the magnetic probes and flux loops. The simulation result is given also.
基金supported by National Natural Science Foundation of China under Grant Nos.10472091 and 10332030
文摘The phenomenon of stochastic resonance of a bistable system subjected to linear time-delayed feedback loops driven by multiplieative Gaussian coloured noise and additive Gaussian white noise is investigated. Firstly, the analytic expression of the quasi-steady distribution function Ps （x, t） is derived by applying the unified coloured noise approximation and the Novikov Theorem; Secondly, the expression of the signal-to-noise ratio （SNR） is obtained in the adiabatic limit to quantify the stochastic resonance. Finally, tile effects of the linear coefficient a, the nonlinear coefficient b, the linear time-delayed feedback coefficient c and the delay time r on Ps（x,t） and SNR^± are discussed. It is found that the effects of the linear coefficient and the nonlinear coefficient, the positive linear time-delayed feedback coefficient and the negative linear time-delayed feedback coefficient, the positive delayed time and the negative delayed time on Ps（x,t） and SNR^± are different, respectively. This discussion would be helpful to the study of the system reliability and controlling stochastic resonance.
文摘Bernoulli’s law is applied to the closed streamlines of a smoke ring, and the centrifugal force of the curved flow is balanced by a pressure gradient. Two equations in two unknowns, pressure and velocity, are combined into one equation in one unknown, velocity. Solving the governing equation algebraically produces a radial shear in the velocity such that the speed decreases outward inversely as the radius increases, which is the main result. Measurements are needed to verify the predicted structure of the velocity field.
