The formula for a magnetic fluid's apparent density is derived based on Bernoulli's equation of magnetic fluid,and the distribution of the magnetic fluid's apparent density is measured by the intelligent a...The formula for a magnetic fluid's apparent density is derived based on Bernoulli's equation of magnetic fluid,and the distribution of the magnetic fluid's apparent density is measured by the intelligent apparatus of measuring a magnetic fluid's apparent density in an applied perpendicular magnetic field.Magnetic particle chain-like alignments are observed by a transmission electron microscope(TEM).Without an applied magnetic field,the magnetic fluid's density is equal everywhere and the distribution of magnetic particles is homogeneous and unordered.When magnetic induction and magnetic induction gradient gather strength in an applied perpendicular magnetic field,the magnetic fluid's apparent density increases gradually,and more chain-like structures are formed and aligned with the direction of the magnetic field.The results of magnetic particle alignments are correspondent with the distribution of the magnetic fluid's apparent density.Both of them result from particle-particle interactions and particle-carrier liquid interactions,which are eventually controlled by the applied magnetic induction and magnetic induction gradient distribution.展开更多
We study the quantum discord dynamics of a bipartite composite system in the presence of a dissipative environment and investigate the effect of the interaction between the two subsystems.The results show that the int...We study the quantum discord dynamics of a bipartite composite system in the presence of a dissipative environment and investigate the effect of the interaction between the two subsystems.The results show that the interaction can influence the sudden transition between the quantum correlation and the classical correlation and for the maximally mixed marginals initial states,the sudden transition regime will always exist.The entanglements are also discussed in comparison to the quantum discord in describing the quantum correlations.展开更多
We investigate the temporal evolution of the current pulses from an ac Fie cold plasma jet at atmospheric pressure and with driving frequency in the range 14.76-15.30 kHz. The driving frequency is used as the plasma s...We investigate the temporal evolution of the current pulses from an ac Fie cold plasma jet at atmospheric pressure and with driving frequency in the range 14.76-15.30 kHz. The driving frequency is used as the plasma system＇s bifurcation parameter in analogy with the evolution in which the current pulses undergoes multiplication and chaos. Such time-domain nonlineaxity is important for controlling instabilities in atmospheric glow discharges. In addition, the observation can provide some data to support the simulation results reported previously [Appl. Phys. Lett. 90 （2007） 071501].展开更多
By combining first-principles calculations with the particle swarm optimization algorithm, we predicted a hexagonal Pˉ3m1 structure for Tc B, which is energetically more favorable than the previously reported WC-type...By combining first-principles calculations with the particle swarm optimization algorithm, we predicted a hexagonal Pˉ3m1 structure for Tc B, which is energetically more favorable than the previously reported WC-type and Cmcm structures.The new phase is mechanically and dynamically stable, as confirmed by its phonon and elastic constants calculations.The calculated mechanical properties show that it is an ultra-incompressible and hard material. Meanwhile, the elastic anisotropy is investigated by the shear anisotropic factors and ratio of the directional bulk modulus. Density of states analysis reveals that the strong covalent bonding between Tc and B atoms plays a leading role in forming a hard material. Additionally, the compressibility, bulk modulus, Debye temperature, Gruneisen parameter, specific heat, and thermal expansion coefficient of Tc B are also successfully obtained by using the quasi-harmonic Debye model.展开更多
The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the disch...The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period-n discharge becomes more and more unstable with the increase of n. The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied.It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation.展开更多
Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of th...Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of the GaN films are characterized by x-ray diffraction, reflection high energy electron diffraction and atomic force microscopy. The results indicate that the structure and morphology of the films are strongly dependent on the deposition temperature. The most significant improvements in morphological and structural properties of GaN films are obtained under the proper deposition temperature of 400°C.展开更多
The characteristics of radio frequency atmospheric pressure discharge in nitrogen and oxygen mixture gases are investigated by using a one-dimensional fluid model.The model consists of equations of particle continuity...The characteristics of radio frequency atmospheric pressure discharge in nitrogen and oxygen mixture gases are investigated by using a one-dimensional fluid model.The model consists of equations of particle continuity,Poisson's equation,and the electron energy equation.The effect of the concentrations of O_(2) in N_(2) on the discharge characteristics is analyzed.The results show that when the concentration of O_(2) in N_(2) is less than 12%,as the amount of O_(2) grows,the electron density and the N4+ion density decrease;the main negative particles are electrons.When the concentration of O_(2) in N_(2) is greater than 12%,the electron density and the N_(4)^(+) ion density increase with the increasing admixture of oxygen;the main negative particle is the O^(-) ion.Moreover,the O^(-) ion density,the O_(2)^(+) ion density,the electron temperature and the mixture gases electronegativity increase with growth of O_(2) in the range from 4%to 20%and with density of O_(2) in N_(2).展开更多
The molecular dynamics （MD） method is used to simulate the interactions of energetic C20 clusters with the dense plasma targets within the framework of the linear Vlasov-Poisson theory. The influences of various clu...The molecular dynamics （MD） method is used to simulate the interactions of energetic C20 clusters with the dense plasma targets within the framework of the linear Vlasov-Poisson theory. The influences of various clusters （H2, N2, C20 and C60 respectively） on stopping power are discussed. The simulation results show that the vicinage effects in the Coulomb explosion dynamics and the stopping power are strongly affected by the variations in the cluster speed and the plasma parameters. Coulomb explosions are found to proceed faster for higher speeds, lower plasma densities and higher electron temperatures. In addition, the cluster stopping power is strongly enhanced in the early stages of Coulomb explosions due to the vicinage effect, but this enhancement eventually diminishes, after the cluster constituent ions are sufficiently separated. For the large and heavy clusters, the stopping power ratio reaches much higher values in the early stage of Coulomb explosion owing to the constructive interferences in the vicinage effect.展开更多
We examine the interferometry results of identical pion and kaon for the granular sources of quark-gluon plasma droplets for the Au + Au collisions at S_(NN)^(1/2) = 200 GeV.The effects of particle absorptions of pion...We examine the interferometry results of identical pion and kaon for the granular sources of quark-gluon plasma droplets for the Au + Au collisions at S_(NN)^(1/2) = 200 GeV.The effects of particle absorptions of pion and kaon on the results are investigated.We find that the absorptions lead to the decrease of the interferometry radii.After considering the absorptions,the interferometry radii of pion and kaon of the granular sources are in better agreement with the experimental data of the Au + Au collisions.展开更多
Abstract A hybrid sheath model, including a fluid model and a Monte Carlo （MC） method, is proposed to study ion energy distributions （IEDs） driven by a radiofrequency （RF） with a tailed pulse-bias on an insulati...Abstract A hybrid sheath model, including a fluid model and a Monte Carlo （MC） method, is proposed to study ion energy distributions （IEDs） driven by a radiofrequency （RF） with a tailed pulse-bias on an insulating substrate, where a charging effect is obviously caused by the ions accumulated. This surface charging effect will significantly affect the IEDs on the insulating substrate. In this paper, a voltage compensation method is employed to eliminate the charging effect by making the pulse-bias waveform have a certain gradient. Furthermore, we investigate the IEDs under the condition of different pulse-bias duty ratios, waveforms, amplitudes, and cycle proportions. It is found that the parameters of the pulsed source can effectively modulate the IEDs on the insulating substrate and the charging effect, and more desired IEDs are obtained by using the voltage compensation method with modulations of pulse parameters.展开更多
A two-dimensional hybrid simulation scheme is proposed to study the characteristics of dual-frequency （DF） capacitively coupled plasma （CCP） discharge based on the geometry of real device. Given the experimental p...A two-dimensional hybrid simulation scheme is proposed to study the characteristics of dual-frequency （DF） capacitively coupled plasma （CCP） discharge based on the geometry of real device. Given the experimental parameters for argon plasma, the output from the fluid module such as ion density, number flux, electron temperature and the Monte-Carlo collision （MCC） results of ion energy distribution function （IEDF） as well as electron energy distribution function （EEDF） are obtained and discussed in detail. A novel complete floating double probe is designed to measure both density and temperature of electron and a quadrupole mass spectrometer is also equipped for IEDF investigations. The measurements on the density of bulk plasma, electron temperature and IEDF agree well, qualitatively, with the simulated results. A comparison with experimental results indicates that, since the structure of real device is taken into account, this model is capable of describing the global dynamic characteristics occurred in DF-CCP and presenting more reliable results than the model with an ideal chamber structure.展开更多
We study theoretically how to produce and detect the ultracold ground-state Cs2 molecule from Feshbach state. Nu- merical calculations are performed by solving the quantum Liouville equation based on multilevel Bloch ...We study theoretically how to produce and detect the ultracold ground-state Cs2 molecule from Feshbach state. Nu- merical calculations are performed by solving the quantum Liouville equation based on multilevel Bloch model. The producing efficiency reaches 55% and the detecting efficiency is 31%. The producing and detecting efficiencies are closely related to the Rabi frequencies of laser pulses. The decay of relevant electronic and vibrational states obviously reduces the producing and detecting efficiencies.展开更多
In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the seconda...In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the secondary electron emission in the Hall thruster, by the particle-in-cell （PIC） method. The numerical results show that when the electron temperature is relatively low, the change of sheath potential drop is relatively large, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is relatively high, the surface potential maintains a persistent oscillation, and the stability of the sheath reduces. As the electron temperature increases, the secondary electron emission coefficient on the wall increases. For three kinds of propellants （At, Kr, and Xe）, as the ion mass increases the sheath potentials and the secondary electron emission coefficients reduce in sequence.展开更多
A new type of two-dimensional self-consistent fluid model that couples an equivalent circuit module is used to in- vestigate the mode transition characteristics and hysteresis in hydrogen inductively coupled plasmas a...A new type of two-dimensional self-consistent fluid model that couples an equivalent circuit module is used to in- vestigate the mode transition characteristics and hysteresis in hydrogen inductively coupled plasmas at different pressures, by varying the series capacitance of the matching box. The variations of the electron density, temperature, and the circuit electrical properties are presented. As cycling the matching capacitance, at high pressure both the discontinuity and hysteresis appear for the plasma parameters and the transferred impedances of both the inductive and capacitive discharge components, while at low pressure only the discontinuity is seen. The simulations predict that the sheath plays a determi- native role on the presence of discontinuity and hysteresis at high pressure, by influencing the inductive coupling efficiency of applied power. Moreover, the values of the plasma transferred impedances at different pressures are compared, and the larger plasma inductance at low pressure due to less collision frequency, as analyzed, is the reason why the hysteresis is not seen at low pressure, even with a wider sheath. Besides, the behaviors of the coil voltage and current parameters during the mode transitions are investigated. They both increase （decrease） at the E to H （H to E） mode transition, indicating an improved （worsened） inductive power coupling efficiency.展开更多
In this paper, the double-discharge plasma generated by radio frequency （RF） and direct current （DC） has been investigated. In comparison with their single-frequency counterpart, the interaction between the two ex...In this paper, the double-discharge plasma generated by radio frequency （RF） and direct current （DC） has been investigated. In comparison with their single-frequency counterpart, the interaction between the two excitations is significant and beneficial. The results show that the RF discharge can effectively increase the DC discharge current and decrease the DC voltage; meanwhile the DC discharge is favorable to feed abundant high energy seed electrons to the ICP discharge sustaining at 13.56 MHz for the latter to acquire higher plasma density and lower plasma potential by increasing the ionization rate. The innovative design has been demonstrated to facilitate more homogeneous performance with higher plasma density.展开更多
We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya （DM） interaction, and investigate the effect of the DM interaction on the quantum phase ...We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya （DM） interaction, and investigate the effect of the DM interaction on the quantum phase transition （QPT） of such spin chains. The results show that the DM interaction could influence the distribution of the regions of QPTs but could not produce new critical points for the spin-chain. This study extends the relation between geometric phases and QPTs.展开更多
Electric field enhancement distributions encountered in feed gap of opposing bi-Au cone-tips is studied using a frequency-domain three-dimensional finite element method to solve Maxwell＇s equations of electric field ...Electric field enhancement distributions encountered in feed gap of opposing bi-Au cone-tips is studied using a frequency-domain three-dimensional finite element method to solve Maxwell＇s equations of electric field distributions. Both the influences of cone-tip length and surrounding medium on electric field enhancement are investigated. The maximal enhancement value is discussed in terms of a simple physical model based on a standing wave on the tip surface associated with the antenna effect and surface plasmon. Simulated results demonstrate the enhancement is sensitive to the tip length. By selecting a suitably matched scale according to the incident wavelength, a large enhancement value can be observed within a small focused spot between the opposing tips permitting a high spatial resolution. The relative position of the opposing tips is also found for the optimum enhancement. All of the results suggest that our configuration is suitable for the site-specific Raman spectroscopic analysis at nanoscale.展开更多
We propose the schemes for implementing hyperentangled state analysis and generating four-electron high entan-gled states （including cluster state, ｜X） state, and symmetric Dicke state） based on the charge detecti...We propose the schemes for implementing hyperentangled state analysis and generating four-electron high entan-gled states （including cluster state, ｜X） state, and symmetric Dicke state） based on the charge detection of free electrons. These schemes are deterministic and rely only on charge detection and single-spin rotations. This method, which uses noninteracting electrons, is not only efficient but also saves on quantum resources.展开更多
e movable limiter at the mid-plane of the Experimental Advanced Superconducting Tokamak （EAST） with carbon coatings on the surface was exposed to edge plasma to study the material erosion and re-deposition.After the...e movable limiter at the mid-plane of the Experimental Advanced Superconducting Tokamak （EAST） with carbon coatings on the surface was exposed to edge plasma to study the material erosion and re-deposition.After the experiments,the carbon erosion and re-deposition is modelled using the 3D Monte Carlo code ERO.The geometry of the movable limiter,3D configuration of the plasma parameters and electromagnetic fields under both limiter and divertor configurations have been implemented into the code.In the simulations,the main uncertain parameters such as carbon concentration ρc in the background plasma and cross-field transport coefficient D⊥ in the vicinity of surface according to the ‘funneling model＇,have been studied in comparison with experiments.The parameter ρc mainly influences the net erosion and deposition profiles of the two sides of the movable limiter,while D ⊥ mostly changes the profiles on the top surface.展开更多
Using the quasi-classical trajectory(QCT)method,the product polarization at the collision energy of 46 kcal/mol is investigated for the reactions of F+LiH(v=0,j=0)→LiF+H and F+LiD(v=0,j=0)→LiF+D on the 2A'ground...Using the quasi-classical trajectory(QCT)method,the product polarization at the collision energy of 46 kcal/mol is investigated for the reactions of F+LiH(v=0,j=0)→LiF+H and F+LiD(v=0,j=0)→LiF+D on the 2A'ground state potential energy surface(PES)[J.Chem.Phys.106(1997)1013).The distribution of P(θr),which represents the K and J'correlation,the dihedral angle distribution of K-K'-J'P(φr),the angular distribution P(θr,φr)and the four PDDCSs[(2π/σ)(dσ00/dωt),(2πr/σ)(dσ20/dωt),(2π/σ)(dσ22+/dωt),(2π/σ)(dσ21-/dωt)]are presented and discussed.In addition,isotope effects are investigated.The results indicate that at the collision energy of 46 kcal/mol,with isotopic mass substitution,the orientation degree of LiF perpendicular to the scattering degree becomes stronger while the polarization degree of LiF perpendicular to K keeps almost changeless.In addition,the angular distribution of LiF strongly prefers forward scattering.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 51077006.
文摘The formula for a magnetic fluid's apparent density is derived based on Bernoulli's equation of magnetic fluid,and the distribution of the magnetic fluid's apparent density is measured by the intelligent apparatus of measuring a magnetic fluid's apparent density in an applied perpendicular magnetic field.Magnetic particle chain-like alignments are observed by a transmission electron microscope(TEM).Without an applied magnetic field,the magnetic fluid's density is equal everywhere and the distribution of magnetic particles is homogeneous and unordered.When magnetic induction and magnetic induction gradient gather strength in an applied perpendicular magnetic field,the magnetic fluid's apparent density increases gradually,and more chain-like structures are formed and aligned with the direction of the magnetic field.The results of magnetic particle alignments are correspondent with the distribution of the magnetic fluid's apparent density.Both of them result from particle-particle interactions and particle-carrier liquid interactions,which are eventually controlled by the applied magnetic induction and magnetic induction gradient distribution.
基金by the National Natural Science Foundation of China under Grant Nos 10905007 and 61078011 and the Fundamental Research Funds for the Central Universities.
文摘We study the quantum discord dynamics of a bipartite composite system in the presence of a dissipative environment and investigate the effect of the interaction between the two subsystems.The results show that the interaction can influence the sudden transition between the quantum correlation and the classical correlation and for the maximally mixed marginals initial states,the sudden transition regime will always exist.The entanglements are also discussed in comparison to the quantum discord in describing the quantum correlations.
文摘We investigate the temporal evolution of the current pulses from an ac Fie cold plasma jet at atmospheric pressure and with driving frequency in the range 14.76-15.30 kHz. The driving frequency is used as the plasma system＇s bifurcation parameter in analogy with the evolution in which the current pulses undergoes multiplication and chaos. Such time-domain nonlineaxity is important for controlling instabilities in atmospheric glow discharges. In addition, the observation can provide some data to support the simulation results reported previously [Appl. Phys. Lett. 90 （2007） 071501].
基金Project supported by the Science Foundation of Baoji University of Arts and Sciences of China(Grant No.ZK11061)the Natural Science Foundation of the Education Committee of Shaanxi Province,China(Grant Nos.2013JK0637,2013JK0638,and 2014JK1044)
文摘By combining first-principles calculations with the particle swarm optimization algorithm, we predicted a hexagonal Pˉ3m1 structure for Tc B, which is energetically more favorable than the previously reported WC-type and Cmcm structures.The new phase is mechanically and dynamically stable, as confirmed by its phonon and elastic constants calculations.The calculated mechanical properties show that it is an ultra-incompressible and hard material. Meanwhile, the elastic anisotropy is investigated by the shear anisotropic factors and ratio of the directional bulk modulus. Density of states analysis reveals that the strong covalent bonding between Tc and B atoms plays a leading role in forming a hard material. Additionally, the compressibility, bulk modulus, Debye temperature, Gruneisen parameter, specific heat, and thermal expansion coefficient of Tc B are also successfully obtained by using the quasi-harmonic Debye model.
基金supported by the National Natural Science Foundation of China(Grant Nos.11447244 and 11405208)the Science Foundation of Hengyang Normal University,China(Grant No.14B41)the Hunan Provincial Applied Basic Research Base of Optoelectronic Information Technology,China(Grant No.GDXX010)
文摘The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period-n discharge becomes more and more unstable with the increase of n. The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied.It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation.
基金Supported by the National Natural Science Foundation of China under Grant No 60976006, the Key Laboratory Project of Liaoning Provincial Department of Education, and the Science and Technology Research Projects of the Higher Education Department of Liaoning Province.
文摘Prefer-oriented and fine grained polycrystalline GaN films are prepared by plasma enhanced metal organic chemical vapour deposition on nucleation surfaces of freestanding thick diamond films. The characteristics of the GaN films are characterized by x-ray diffraction, reflection high energy electron diffraction and atomic force microscopy. The results indicate that the structure and morphology of the films are strongly dependent on the deposition temperature. The most significant improvements in morphological and structural properties of GaN films are obtained under the proper deposition temperature of 400°C.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11075030,11105065,11275041the National Basic Research Program of China under Grant Nos 2008CB717801,2008CB787103,2009GB105004,2010GB106002the Fundamental Research Funds for the Central Universities of China under Grant Nos DUT12ZD(G)01,DUT12ZD201.
文摘The characteristics of radio frequency atmospheric pressure discharge in nitrogen and oxygen mixture gases are investigated by using a one-dimensional fluid model.The model consists of equations of particle continuity,Poisson's equation,and the electron energy equation.The effect of the concentrations of O_(2) in N_(2) on the discharge characteristics is analyzed.The results show that when the concentration of O_(2) in N_(2) is less than 12%,as the amount of O_(2) grows,the electron density and the N4+ion density decrease;the main negative particles are electrons.When the concentration of O_(2) in N_(2) is greater than 12%,the electron density and the N_(4)^(+) ion density increase with the increasing admixture of oxygen;the main negative particle is the O^(-) ion.Moreover,the O^(-) ion density,the O_(2)^(+) ion density,the electron temperature and the mixture gases electronegativity increase with growth of O_(2) in the range from 4%to 20%and with density of O_(2) in N_(2).
基金Supported by the National Natural Science Foundation of China under Grant No 10705007, and the Doctorial Start-up Foundation of Liaoning Province under Grant No 20071067.
文摘The molecular dynamics （MD） method is used to simulate the interactions of energetic C20 clusters with the dense plasma targets within the framework of the linear Vlasov-Poisson theory. The influences of various clusters （H2, N2, C20 and C60 respectively） on stopping power are discussed. The simulation results show that the vicinage effects in the Coulomb explosion dynamics and the stopping power are strongly affected by the variations in the cluster speed and the plasma parameters. Coulomb explosions are found to proceed faster for higher speeds, lower plasma densities and higher electron temperatures. In addition, the cluster stopping power is strongly enhanced in the early stages of Coulomb explosions due to the vicinage effect, but this enhancement eventually diminishes, after the cluster constituent ions are sufficiently separated. For the large and heavy clusters, the stopping power ratio reaches much higher values in the early stage of Coulomb explosion owing to the constructive interferences in the vicinage effect.
基金supported by the National Natural Science Foundation of China(No.11275037)
文摘We examine the interferometry results of identical pion and kaon for the granular sources of quark-gluon plasma droplets for the Au + Au collisions at S_(NN)^(1/2) = 200 GeV.The effects of particle absorptions of pion and kaon on the results are investigated.We find that the absorptions lead to the decrease of the interferometry radii.After considering the absorptions,the interferometry radii of pion and kaon of the granular sources are in better agreement with the experimental data of the Au + Au collisions.
基金supported by National Natural Science Foundation of China(No.11375040)the Important National Science&Technology Specific Project of China(No.2011ZX02403-001)
文摘Abstract A hybrid sheath model, including a fluid model and a Monte Carlo （MC） method, is proposed to study ion energy distributions （IEDs） driven by a radiofrequency （RF） with a tailed pulse-bias on an insulating substrate, where a charging effect is obviously caused by the ions accumulated. This surface charging effect will significantly affect the IEDs on the insulating substrate. In this paper, a voltage compensation method is employed to eliminate the charging effect by making the pulse-bias waveform have a certain gradient. Furthermore, we investigate the IEDs under the condition of different pulse-bias duty ratios, waveforms, amplitudes, and cycle proportions. It is found that the parameters of the pulsed source can effectively modulate the IEDs on the insulating substrate and the charging effect, and more desired IEDs are obtained by using the voltage compensation method with modulations of pulse parameters.
基金supported by National Natural Science Foundation of China (No. 10635010)Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20090041110026)
文摘A two-dimensional hybrid simulation scheme is proposed to study the characteristics of dual-frequency （DF） capacitively coupled plasma （CCP） discharge based on the geometry of real device. Given the experimental parameters for argon plasma, the output from the fluid module such as ion density, number flux, electron temperature and the Monte-Carlo collision （MCC） results of ion energy distribution function （IEDF） as well as electron energy distribution function （EEDF） are obtained and discussed in detail. A novel complete floating double probe is designed to measure both density and temperature of electron and a quadrupole mass spectrometer is also equipped for IEDF investigations. The measurements on the density of bulk plasma, electron temperature and IEDF agree well, qualitatively, with the simulated results. A comparison with experimental results indicates that, since the structure of real device is taken into account, this model is capable of describing the global dynamic characteristics occurred in DF-CCP and presenting more reliable results than the model with an ideal chamber structure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974024 and 11274056)
文摘We study theoretically how to produce and detect the ultracold ground-state Cs2 molecule from Feshbach state. Nu- merical calculations are performed by solving the quantum Liouville equation based on multilevel Bloch model. The producing efficiency reaches 55% and the detecting efficiency is 31%. The producing and detecting efficiencies are closely related to the Rabi frequencies of laser pulses. The decay of relevant electronic and vibrational states obviously reduces the producing and detecting efficiencies.
基金supported by the National Natural Science Foundation of China(Grant Nos.10975026,11275034,and 11175052)the Key Project of Science andTechnology of Liaoning Province,China(Grant No.2011224007)the Fundamental Research Funds for the Central Universities of Ministry of Educationof China(Grant No.3132014328)
文摘In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the secondary electron emission in the Hall thruster, by the particle-in-cell （PIC） method. The numerical results show that when the electron temperature is relatively low, the change of sheath potential drop is relatively large, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is relatively high, the surface potential maintains a persistent oscillation, and the stability of the sheath reduces. As the electron temperature increases, the secondary electron emission coefficient on the wall increases. For three kinds of propellants （At, Kr, and Xe）, as the ion mass increases the sheath potentials and the secondary electron emission coefficients reduce in sequence.
基金supported by the National Natural Science Foundation of China(Grant Nos.11175034,11205025,11305023,and 11075029)
文摘A new type of two-dimensional self-consistent fluid model that couples an equivalent circuit module is used to in- vestigate the mode transition characteristics and hysteresis in hydrogen inductively coupled plasmas at different pressures, by varying the series capacitance of the matching box. The variations of the electron density, temperature, and the circuit electrical properties are presented. As cycling the matching capacitance, at high pressure both the discontinuity and hysteresis appear for the plasma parameters and the transferred impedances of both the inductive and capacitive discharge components, while at low pressure only the discontinuity is seen. The simulations predict that the sheath plays a determi- native role on the presence of discontinuity and hysteresis at high pressure, by influencing the inductive coupling efficiency of applied power. Moreover, the values of the plasma transferred impedances at different pressures are compared, and the larger plasma inductance at low pressure due to less collision frequency, as analyzed, is the reason why the hysteresis is not seen at low pressure, even with a wider sheath. Besides, the behaviors of the coil voltage and current parameters during the mode transitions are investigated. They both increase （decrease） at the E to H （H to E） mode transition, indicating an improved （worsened） inductive power coupling efficiency.
基金supported by National Natural Science Foundation of China(No.11475038)
文摘In this paper, the double-discharge plasma generated by radio frequency （RF） and direct current （DC） has been investigated. In comparison with their single-frequency counterpart, the interaction between the two excitations is significant and beneficial. The results show that the RF discharge can effectively increase the DC discharge current and decrease the DC voltage; meanwhile the DC discharge is favorable to feed abundant high energy seed electrons to the ICP discharge sustaining at 13.56 MHz for the latter to acquire higher plasma density and lower plasma potential by increasing the ionization rate. The innovative design has been demonstrated to facilitate more homogeneous performance with higher plasma density.
基金Project supported by National Natural Science Foundation of China (Grant Nos. 10847108 and 10775023)
文摘We study geometric phases of the ground states of inhomogeneous XY spin chains in transverse fields with Dzyaloshinski--Moriya （DM） interaction, and investigate the effect of the DM interaction on the quantum phase transition （QPT） of such spin chains. The results show that the DM interaction could influence the distribution of the regions of QPTs but could not produce new critical points for the spin-chain. This study extends the relation between geometric phases and QPTs.
基金Supported by National Natural Science Foundation of China under Grant Nos 30270367.
文摘Electric field enhancement distributions encountered in feed gap of opposing bi-Au cone-tips is studied using a frequency-domain three-dimensional finite element method to solve Maxwell＇s equations of electric field distributions. Both the influences of cone-tip length and surrounding medium on electric field enhancement are investigated. The maximal enhancement value is discussed in terms of a simple physical model based on a standing wave on the tip surface associated with the antenna effect and surface plasmon. Simulated results demonstrate the enhancement is sensitive to the tip length. By selecting a suitably matched scale according to the incident wavelength, a large enhancement value can be observed within a small focused spot between the opposing tips permitting a high spatial resolution. The relative position of the opposing tips is also found for the optimum enhancement. All of the results suggest that our configuration is suitable for the site-specific Raman spectroscopic analysis at nanoscale.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11165015,61068001,and 11264042)the Natural Science Foundationof Jilin Province,China(Grant No.201115226)
文摘We propose the schemes for implementing hyperentangled state analysis and generating four-electron high entan-gled states （including cluster state, ｜X） state, and symmetric Dicke state） based on the charge detection of free electrons. These schemes are deterministic and rely only on charge detection and single-spin rotations. This method, which uses noninteracting electrons, is not only efficient but also saves on quantum resources.
基金Supported by the National Magnetic Confinement Fusion Science Programof China(Nos.2013GB107004 and 2013GB105003)National Natural Science foundation of China(Nos.11375010,11675218 and 11005125)the Sino-German Center for Research Promotion under contract NoGZ769
文摘e movable limiter at the mid-plane of the Experimental Advanced Superconducting Tokamak （EAST） with carbon coatings on the surface was exposed to edge plasma to study the material erosion and re-deposition.After the experiments,the carbon erosion and re-deposition is modelled using the 3D Monte Carlo code ERO.The geometry of the movable limiter,3D configuration of the plasma parameters and electromagnetic fields under both limiter and divertor configurations have been implemented into the code.In the simulations,the main uncertain parameters such as carbon concentration ρc in the background plasma and cross-field transport coefficient D⊥ in the vicinity of surface according to the ‘funneling model＇,have been studied in comparison with experiments.The parameter ρc mainly influences the net erosion and deposition profiles of the two sides of the movable limiter,while D ⊥ mostly changes the profiles on the top surface.
基金Supported by the National Natural Science Foundation of China under Grant No 21003062.
文摘Using the quasi-classical trajectory(QCT)method,the product polarization at the collision energy of 46 kcal/mol is investigated for the reactions of F+LiH(v=0,j=0)→LiF+H and F+LiD(v=0,j=0)→LiF+D on the 2A'ground state potential energy surface(PES)[J.Chem.Phys.106(1997)1013).The distribution of P(θr),which represents the K and J'correlation,the dihedral angle distribution of K-K'-J'P(φr),the angular distribution P(θr,φr)and the four PDDCSs[(2π/σ)(dσ00/dωt),(2πr/σ)(dσ20/dωt),(2π/σ)(dσ22+/dωt),(2π/σ)(dσ21-/dωt)]are presented and discussed.In addition,isotope effects are investigated.The results indicate that at the collision energy of 46 kcal/mol,with isotopic mass substitution,the orientation degree of LiF perpendicular to the scattering degree becomes stronger while the polarization degree of LiF perpendicular to K keeps almost changeless.In addition,the angular distribution of LiF strongly prefers forward scattering.
