Emission spectra of a (?)-type three-level atom in a Kerr medium

We investigate the emission spectra of a (?)-type three-level atom interacting with a single-mode optical field in an ideal cavity filled with a Kerr medium and discuss the structure of emission spectrum when the optical field is initially in a pure number state and a coherent state, respectively. It is shown that the structure of emission spectrum depends not only on the photon number distribution, but also on the strength of incident field and the coupling of Kerr medium to the field.     

Probing Shell Correction at High Spin by Neutron Emission of Doubly Magic Nuclei 208Pb and 132Sn

Shell effects in particle emission for two doubly magic nuclei ^132Sn and ^208pb were studied in the framework of Smoluchowski equation taking into account temperature and spin-dependent shell correction. It is shown that the shelle ffects in the emission of pre-scission neutrons are sensitive to the spin dependence of the shell correction at a moderate excitation energy. Therefore, we propose to use neutron multiplicity as an observable to probe the shell correction at high spins.     

Effects of Particle Size on Dilute Particle Dispersion in a Karman Vortex Street Flow

It is shown that in a Karman vortex street flow,particle size influences the dilute particle dispersion.Together with an increase of the particle size,there is an emergence of a period-doubling bifurcation to a chaotic orbit,as well as a decrease of the corresponding basins of attraction.A crisis leads the attractor to escape from the central region of flow.In the motion of dilute particles,a drag term and gravity term dominate and result in a bifurcation phenomenon.     

New Electroweak Model Without a Higgs Particle

A new unified electroweak model is proposed in this paper,In this unified electroweak model,Higgs echanism is not used.So no Higgs particle exists in the model.In order to keep the masses of intermediate gauge bosons non-zero,two sets of gauge fields will be introduced.In order to introduce symmetry breaking and to help to introduce the masses of all fileds.a vacuum potential is needed.Except for those terms concerning Higgs particle,the fundamental dynamical properties of this model are similar to those of the standard model.And in a proper limit,this model with approximately return to the standard model.The purpose of this paper is not to say that the Higgs particle does not exist in Nature,it is only to prove that,without a Higgs particle,we can also set up a unified electroweak model which is consistent with present experiments.     

Supersymmetric Quantum Mechanics and SUSY Dependent SU（2） Symmetry for a Spin-1/2 Charged Particle in a Magnetic Field

We find that in a supersymmetric quantum mechanics （SUSY QM） system, in addition to supersymmetric algebra, an associated SU（2） algebra can be obtained by using semiunitary （SUT） operator and projection operator, and the relevant constants of motion can be constructed. Two typical quantum systems are investigated as examples to demonstrate the above finding. The first example is the quantum system of a nonrelativistic charged particle moving in x-y plane and coupled to a magnetic field along z-axis. The second example is provided with the Dirac particle in a magnetic field. Similarly there exists an SUτ（2） SUσ（2） symmetry in the context of the relativistic Pauli Hamilt onian squared. We show that there exists also an SU（2） symmetry associated with the supersvmmetrv of the Dirac particle.     

Schrdinger Equation of a Particle on a Rotating Curved Surface

We derive the Schrdinger equation of a particle constrained to move on a rotating curved surface S.Using the thin-layer quantization scheme to confine the particle on S,and with a proper choice of gauge transformation for the wave function,we obtain the well-known geometric potential V_g and an additive Coriolis-induced geometric potential in the co-rotational curvilinear coordinates.This novel effective potential,which is included in the surface Schrdinger equation and is coupled with the mean curvature of S,contains an imaginary part in the general case which gives rise to a non-Hermitian surface Hamiltonian.We find that the non-Hermitian term vanishes when S is a minimal surface or a revolution surface which is axially symmetric around the rolling axis.     

Influence of a high-speed dielectric spherical particle''''s movement on its scattering characteristics

The scattered field and differential scattered section (DSS) of a moving spherical particle with a high speed are investigated numerically.The coordinate and vector transformations are used to establish a theoretical basis for studying the laser scattering of a moving particle.The DSS of a moving spherical particle is explained by the electric and magnetic field from Mie scattering theory.Assuming the laser wavelength of 1.06μm,we compute the ratio of the laser DSS of the moving dielectric spherical particle to that of the static dielectric spherical particle,which changes with radii,speeds and scattering angles of the particle.The numerical results show that the laser DSS of the moving spherical particle is tightly connected with its speed and scattering zenith angle.If a spherical particle moves with high speed,the laser DSS due to movement of the particle could not be neglected.If the speed of the dielectric spherical particle is fluctuating,the Doppler effect and the frequency spectrum expansion play important roles.     

Massive particles＇ tunnelling radiation from the black hole with a mass-quadruple moment

In this paper, we extend Zhang and Zhao's recent work to the black hole with a mass-quadruple moment. The behaviour of the tunnelling massive particles is investigated, and the emission rate at which massive particles tunnel across the event horizon of the black hole is calculated. The result is consistent with an underlying unitary theory, and takes the same functional form as that of a massless particle.     

Asymmetrical free diffusion with orientation-dependence of molecules in finite timescales

Using molecular dynamics simulations, we show that free diffusion of a nanoscale particle (molecule) with asymmetric structure critically depends on the orientation in a finite timescale of picoseconds to nanoseconds. In a timescale of ~100 ps, there are ~10% more possibilities for the particle moving along the initial orientation than moving opposite to the orientation; and the diffusion distances of the particle reach ~1 nm. We find that the key to this observation is the orientation-dependence of the damping force to the moving of the nanoscale particle and a finite time is required to regulate the particle orientation. This finding extends the work of Einstein to nano-world beyond random Brownian motion, thus will have a critical role in the understanding of the nanoscale world.     

Enhanced Laser Cooling of Rare-Earth-Ion-Doped Composite Material

We predict enhanced laser cooling performance of rare-earth-ions-doped glasses containing nanometre-sized ultrafine particles, which can be achieved by the enhanucement of locai field around rare earth ions, owing to the surface plasma resonance of small metallic particles. The influence of energy transfer between ions and the particle is theoretically discussed. Depending on the particle size and the ion emission quantum efficiency, the enhancement of the absorption is predicted. It is concluded that the absorption are greatly enhanced in these composite materials, the cooling power is increased as compared to the bulk material.     

Collective Modes of a Quasi-Two-Dimensional Superfluid Fermi Gas in BCS-BEC Crossover

We investigate the collective modes of a quasi-two-dimensional （Q2D） superfluid Fermi gas in Bardeen-Cooper-Schrieffer Bose-Einstein condensation （BCS-BEC） crossover. For solving a generalized Gross-Pitaevskii equation by using a time-dependent variational method, we take a trial wavefunction with the form of hybrid Gaussianparabolic type, which not only reflects the Q2D character of the system and also allows an essentially analytical approach of the problem. We present a Q2D criterion that is valid for various superfluid regimes and displays clearly the relation between the maximum condensed particle number and the parameters of trapping potential as well as atom-atom interaction. We show that due to the small particle number in the Q2D condensate, the contribution to oscillating frequencies by the quantum pressure in the strong confinement direction is significant and hence a Thomas-Fermi approximation can not be used.     

Vocal tract resonances tracking by auxiliary vector particle filters

An auxiliary vector particle filter was proposed to present the vocal tract resonances (VTRs) tracking.It uses particle filter based on a version of state-space model that describes the characteristics of speech signal.The speech model consists of a target-guided dynamic function and a non-linear prediction mapping from resonance frequencies and bandwidths to LPC cepstra(LPCC).There are two characteristics in the proposed method.First,particle filtering technique is put forth to solve the non-linear problem of speech model.Second,an auxiliary vector,embedded in the state function of speech model,is applied to incorporate the most current observations and to generate the proposal distribution of particle filter.The experimental results show that this method is able to track the VTRs of continuous speech utterance efficiently with a small number of particles and able to solve the problem of spurious peaks and merging peaks.     

Nearfield acoustic holography in a moving medium based on particle velocity input using nonsingular propagator

Nearfield acoustic holography in a moving medium is a technique which is typically suitable for sound sources identification in a flow.In the process of sound field reconstruction,sound pressure is usually used as the input,but it may contain considerable background noise due to the interactions between microphones and flow moving at a high velocity.To avoid this problem,particle velocity is an alternative input,which can be obtained by using laser Doppler velocimetry in a non-intrusive way.However,there is a singular problem in the conventional propagator relating the particle velocity to the pressure,and it could lead to significant errors or even false results.In view of this,in this paper,nonsingular propagators are deduced to realize accurate reconstruction in both cases that the hologram is parallel to and perpendicular to the flow direction.The advantages of the proposed method are analyzed,and simulations are conducted to verify the validation.The results show that the method can overcome the singular problem effectively,and the reconstruction errors are at a low level for different flow velocities,frequencies,and signal-to-noise ratios.     

Charged Particle Motion in Temporal Chaotic and Spatiotemporal Chaotic Fields

We investigate charged particle motion in temporal chaotic and spatiotemporal chaotic fields.In its steady wave frame a few key modes of the solution of the driven/damped nonlinear wave equation are used as the field.It is found that in the spatiotemporal chaotic field the particle drifts relative to the steady wave,in contrast to that in the temporal chaotic field where the particle motion is localized in a trough of the wave field.The result is of significance for understanding stochastic acceleration of particles.     

Structural response of aluminum core–shell particles in detonation environment

Natural aluminum particles have the core–shell structure. The structure response refers to the mechanical behavior of the aluminum particle structure caused by external influences. The dynamic behavior of the structural response of aluminum core–shell particles before combustion is of great importance for the aluminum powder burning mechanism and its applications. In this paper, an aluminum particle combustion experiment in a detonation environment is conducted and analyzed; the breakage factors of aluminum particles shell in detonation environment are analyzed. The experiment results show that the aluminum particle burns in a gaseous state and condenses into a sub-micron particle cluster. The calculation and simulation demonstrate that the rupture of aluminum particle shell in the detonation environment is mainly caused by the impact of the detonation wave. The detonation wave impacts the aluminum particles, resulting in shell cracking, and due to the shrinkage-expansion of the aluminum core and stripping of the detonation product, the cracked shell is fractured and peeled with the aluminum reacting with the detonation product.     

Measurement of anomalous nuclear reaction in deuterium-loaded metal

This paper reports on an experiment for testing natural nuclear fusion at low temperature searching for evidence of the origin of ³He from natural nuclear fusion in deep Earth. The experiment was carried out using deuterium-loaded titanium foil samples and powder sample. Detection of charged particle was carried out using a low-level charged particle spectrometer. An Al foil was used as an energy absorber for identification of charged particle. Although the counting rate is very low in the experiment, the emission of energetic particle from the sample is observed and the particle is identified as a proton having energy about 2.8 MeV after exiting the titanium sample. This work provides a positive result for the emission of charged particle in the deuterium-loaded titanium foil samples at low temperature, but a negative result for the deuterium-loaded titanium powder sample. The average reaction yield is deduced to be (0.46±0.08) protons/h for the foil samples. With the suggestion that the proton originates from d--d reaction, we calculate the reaction rate for d--d reaction, and the obtained result is 1.4× 10^-24 fusion/d--d\cdot sec. The negative result of the deuterium-loaded titanium powder sample suggests that the reaction yield might be correlated with the density or microscopic variables of deuterium-loaded titanium materials. The negative result also indicates that d--d reaction catalysed by μ-meson from cosmic ray can be excluded in the samples in this experiment.     

Spontaneous Emission of a Polarized Atom in a Medium Between Two Parallel Mirrors

Using the photon closed orbit theory, the spontaneous emission rate of a polarized atom in a medium between two parallel mirrors is derived and calculated. It is found that the spontaneous emission rate of a polarized atom between the mirrors is related to the atomic position and the polarization direction. The results show that in the vicinity of the mirror, the variation of the spontaneous emission rate depends crucially on the atomic polarization direction. With the increase of the polarization angle, the oscillation in the spontaneous emission rate becomes decreased. For the polarization direction parallel to the mirror plane, the oscillation is the greatest; while for the perpendicular polarization direction, the oscillation is nearly vanished. The agreement between our result and the quantum electrodynamics result suggests the correctness of our calculation. This study further verifies that the atomic spontaneous emission process can be effectively controlled by changing the polarization orientation of the atom.     

The photoluminescence of ZnSe bulk single crystals excited by femtosecond pulse

This paper reports on the photoluminescence spectra of ZnSe single crystal with trace chlorine excited by the femtosecond laser pulse. Three emission bands, including second-harmonic-generation, two-photon-excited peak and a broad band at 500--700nm, were detected. The thermal strain induced by femtosecond pulse strongly influences the photoluminescence of ZnSe crystal. The corresponding strain \va in ZnSe crystal is estimated to be about 8.8 \ti10^-3 at room temperature. The zinc-vacancy, as the main point defect induced by femtosecond pulse, is successfully used to interpret the broad emission at 500--700nm. The research shows that self-activated luminescence possesses the recombination mechanism of donor--vacancy pair, and it is also influenced by a few selenium defects and the temperature. The rapid decrease in photoluminescence intensity of two-photon-excited fluorescence and second-harmonic generation emission at lower temperature is attributed to the fact that more point defects result in the thermal activation of the two-photo-absorption energy converting to the stronger recombination emission of chlorine--zinc vacancy in 500--700nm. The experimental results indicate that the femtosecond exciting photoluminescence shows a completely different emission mechanism to that of He--Cd exciting luminescence in ZnSe single crystal. The femtosecond laser exhibits a higher sensitive to the impurity in crystal materials, which can be recommended as an efficient way to estimate the trace impurity in high quality crystals.     

Experimental Study on Transitional Flow in a Circular Microtube

We investigate the characteristics of the transition from laminar to turbulent flow in the microtube with a diameter of 310μm. The microscopic particle image velocimetry is used to measure the water flow at Re =1600-2500 in the microtube. It is found that the flow transition occurs at Re=1600-1900, and the streamwise streaks and vortices appear in the transitional flow fields. These experimental observations provide a validation for the theoretical prediction of unstable travelling waves in pipe flow.