Magnetoelectric effect in layered disk-shaped magnetostrictive–piezoelectric structures: Theory and experiment

Theoretical and experimental studies of the magnetoelectric effect in a disk-shaped magnetostrictive–piezoelectric structure in the electromechanical resonance region are presented. An expression for the magnetoelectric voltage coefficient is derived based on the simultaneous solution of elastodynamic and electrostatic equations separately for magnetostrictive and piezoelectric layers. The conditions at the interface were taken into account based on the premise that the interaction between layers is implemented by shear. It is shown that the inhomogeneity of the voltage and strain distribution over the sample thickness, caused by the interface, leads to a significant contribution to the effect in the case of thick layers. The theoretical and experimental dependences of the frequency characteristic of the effect are presented for the permendur–lead zirconate-titanate–permendur structure. The theoretical calculations are in good agreement with experimental data.     

New theory on turbulence generation and structure—DNS and experiment

<正>(1)Turbulence is a world puzzle.After over one century research effort,"Turbulence"is still a world puzzle(Wikipedia website at http://en.wikipedia.org/wiki/Turbulence).Nobel Laureate Richard Feynman described turbulence as"the most important unsolved problem of classical physics".According     

Spatiotemporal self-organization in the oscillatory HCOOH oxidation on a Pt ribbon electrode – Theory and experiments

Since the current density near the edges of ribbon and disk electrodes is enhanced, the resulting stationary and non-stationary double layer potential is generally inhomogeneous in all electrochemical reactions. We investigate the impact of this edge effect induced spatial inhomogeneity on the pattern formation of the oscillatory formic acid oxidation on thin Pt ribbon electrodes. In order to be able to theoretically describe the spatiotemporal behavior of the double layer potential distribution, we derive and discuss the properties of the electrochemical ribbon coupling function for various distances of the reference electrode. The resulting reaction–migration equation is analyzed in connection with a chemical model accounting for the specific reaction mechanism of the formic acid oxidation. The interaction of structural inhomogeneity, chemically induced temporal instability and nonlocal spatial coupling due to ion migration gives rise to novel types of spatiotemporal behavior. The results compare favorably with experiments conducted so far, which are presented as well and can be explained within the framework of reaction–migration equations.     

Schrödinger equation for a particle on a curved surface in an electric and magnetic field

We derive the Schr?dinger equation for a spinless charged particle constrained to move on a curved surface in the presence of an electric and magnetic field. The particle is confined on the surface using a thin-layer procedure, which gives rise to the well-known geometric potential. The electric and magnetic fields are included via the four potential. We find that there is no coupling between the fields and the surface curvature and that, with a proper choice of the gauge, the surface and transverse dynamics are exactly separable. Finally, we derive an analytic form of the Hamiltonian for spherical, cylindrical, and toroidal surfaces.     

Pseudo-Gaussian cylindrical acoustical beam – Axial scattering and radiation force on an elastic cylinder

Making use of the addition theorem for the cylindrical wave functions and the complex-source-point method in cylindrical coordinates, an exact solution to the Helmholtz equation is derived, which corresponds to a tightly focused (or collimated) cylindrical quasi-Gaussian beam with arbitrary waist. The solution is termed “quasi-Gaussian” to make a distinction from the standard Gaussian beam solution obtained in the paraxial approximation. The advantage of introducing this new solution is the efficient and fast computational modeling of tightly focused or quasi-collimated cylindrical wave-fronts depending on the dimensionless waist parameter kw₀, where k is the wavenumber of the acoustical radiation. Moreover, a closed-form partial-wave series expansion is obtained for the incident field, which has the property that the axial scattering (i.e. along the direction of wave propagation) and the axial acoustic radiation force (which is a time-averaged quantity) on a cylinder, can be calculated without any approximations in the limit of linear acoustical waves in a nonviscous fluid. Examples are found where the extinction in the radiation force function plot is found to be correlated with conditions giving reduction of the backscattering from an elastic cylinder. Those results are useful in beam-forming design, particle manipulation in acoustic tweezers operating with focused cylindrical beams, and the prediction of the scattering and radiation forces on a cylindrical particle or liquid bridges.     

Constraints on unparticle interactions from particle and antiparticle oscillations

Unparticles have dramatic effects on particle and antiparticle oscillations in meson–antimeson and muonium–antimuonium systems. Unlike the usual tree-level contributions to meson oscillations from heavy-particle exchange, which results in a small Γ ₁₂, the unparticle may have sizeable contributions to both M ₁₂ and Γ ₁₂ due to the fractional dimension of the unparticle. If the unparticle effect dominates the contributions (which may happen in D ⁰– mixing) to the meson mixing parameters x and y, we find that . The mass difference Δm in meson mixing can provide interesting constraints on the unparticle interactions. The unparticle interaction can significantly enhance the CP asymmetry in meson mixing, which can be tested in more accurate experiments in the future. Interesting constraints on unparticle and particle interactions can also be obtained using muonion and antimuonion oscillation data.     

Noncommutative Geometry¶and Gauge Theory on Fuzzy Sphere

The differential algebra on the fuzzy sphere is constructed by applying Connes' scheme. The U(1) gauge theory on the fuzzy sphere based on this differential algebra is defined. The local U(1) gauge transformation on the fuzzy sphere is identified with the left U(N+1) transformation of the field, where a field is a bimodule over the quantized algebra . The interaction with a complex scalar field is also given. Received: 21 January 1998 / Accepted: 4 February 2000     

Stern–Gerlach experiment as the pioneer – and probably the simplest – quantum entanglement test?

Two output beams of a Stern–Gerlach (SG) apparatus for spin 1/2 particles should not show interference when appropriately superposed (i.e. by means of a `half-reversible SG setup' that is described in this letter). The reason is that an entanglement between energy level and path selection occurs.     

Study on the physical basis of pressure and particle velocity combine processing

1 Introductiontraditional sonar system only processes the iDformation of pressure in the soUnd field sinceLongevin, one blanch physicist, invented the first sonar device in 1918. Hydrophone is the mere receiver of sonar system. What'8 more, the eXPerimental research of Underwateracoustic physics focus mainly on the pressure field of the aCOuStic channel in the sea. wave just has two vector field wed are electronic field and the magnetic field, while the soundheld has both scale field and ve…     

Influences of magnetic particle–particle interactions on orientational distributions and rheological properties for a colloidal dispersion composed of rod-like particle with a magnetic moment normal to the particle axis

We have investigated mainly the influences of magnetic particle–particle interactions on the orientational distribution and viscosity of a semi-dense dispersion, which is composed of rod-like particles with a magnetic moment magnetized normal to the particle axis. In addition, the influences of the magnetic field strength, shear rate, and random forces on the orientational distribution and rheological properties have been clarified. The mean field approximation has been applied to take into account magnetic interactions between rod-like particles. The basic equation of the orientational distribution function has been derived from the balance of torques and solved by the numerical analysis method. The results obtained here are summarized as follows. For a strong magnetic field, the rotational motion of the rod-like particle is restricted in a plane normal to the shearing plane since the magnetic moment of the particle is restricted in the magnetic field direction. Under circumstances of a very strong magnetic interaction between particles, the magnetic moment is strongly restricted in the magnetic field direction, so that the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. For a strong shear flow, a directional characteristic of rod-like particles is enhanced, and this leads to a more significant one-peak-type distribution of the orientational distribution function. Magnetic interactions between particles do not contribute to the increase in the viscosity because the mean-field vector has only a component along the magnetic field direction.     

Parametric resonance and cooling on an atom chip

This paper observes the parametric excitation on atom chip by measuring the trap loss when applying a parametric modulation. By modulating the current in chip wires, it modulates not only the trap frequency but also the trap position. It shows that the strongest resonance occurs when the modulation frequency equals to the trap frequency. The resonance amplitude increases exponentially with modulation depth. Because the Z-trap is an anharmonic trap, there exists energy selective excitation which would cause parametric cooling. We confirm this effect by observing the temperature of atom cloud dropping.     

Two image denoising approaches based on wavelet neural network and particle swarm optimization

Two image denoising approaches based on wavelet neural network (WNN) optimized by particle swarm optimization (PSO) are proposed. The noisy image is filtered by the modified median filtering (MMF). Feature values are extracted based on the MMF and then normalized in order to avoid data scattering. In approach 1, WNN is used to tell those uncorrupted but filtered by MMF and then the pixels are restored to their original values while other pixels will retain. In approach 2, WNN distinguishes the corrupted pixels and then these pixels are replaced by MMF results while other pixels retain. WNN can be seen as a classifier to distinguish the corrupted or uncorrupted pixels from others in both approaches. PSO is adopted to optimize and train the WNN for its low requirements and easy employment. Experiments have shown that in terms of peak signal-to-noise ratio (PSNR) and subjective image quality, both proposed approaches are superior to traditional median filtering.     

Quality control and database on resistive plate chambers for the BESⅢ experiment

The chamber production and installation of the BESⅢ MUON identifier system have been finished. The cosmic ray test result after installation shows that the average efficiency is bigger than 95% and can meet the requirement of the design report. A database including all the chamber parameters and performance data has been constructed and is accessible online. The quality control procedures during the production and the database are described.     

Analyse and sound image localization experiment study on multi-channel planar surround sound system

I.IntroductionAnidealplanarsurroundsoundsystemshouldreproduceanaturalanddistinctimageandshouldnothavetheeffectofAnagepositi9ndistortion.Itshouldalsohaveagoodeffectoverawidelisteningarea)agoodcompatibilitywith8tereosystem.ItshouldnotrequiremanytransInissionchannels.InthispaPeritisproposedthataseriesofplanarsurroundsoundsystemstomeetaboverequlremellts.II-ThereproductionsignalsoftheperfectplanarsurroundsoundsystemFirstthecharacteristicsofaperfectplanarsurroundsoundsystemareanalysed.There-prod…     

High dense views auto-stereoscopic three-dimensional display based on frontal projection with LLA and diffused screen

We present a high dense views auto-stereoscopic three-dimensional display method with the projectors array and lenticular lens array(LLA) screen. The principle and configuration are demonstrated. This display method utilizes lenticular screen to modulate the information of projectors. To increase the dense of views, we propose a novel arrangement way of projectors array. In the experiment, the viewer can obtain smooth motion parallax and evident stereo feeling at optimal distance. Through analyzing and observation, the maximum display depth is found to be more than 50 cm.     

Field localization and particle confinement effects on pair creation by Schwinger’s mechanism

Solutions of the Dirac equation in the presence of a static uniform electric fieldɛ in thez-direction and a linear confining potentialAz, are obtained. Generalized reflection and transmission coefficients are derived for such divergent potentials forɛ >A/e. The eigenspectrum and corresponding localized eigenfunctions forɛ <A/e are obtained from the reflection coefficient and the continuum solutions respectively. The rate for the electric field to decay into pairs is derived from the transmission coefficient. Neglecting nonabelian effects in quantum chromodynamics we identify the fieldɛ with a colour electric field and the produced particles with a quark and an antiquark. By considering a cylindrical geometry, we thus obtain a generalization of Schwinger’s formula, for the fieldɛ in a finite spatial region with the quark (antiquark) being confined in thez direction by the linear potentialAz and in the perpendicular direction by the MIT bag boundary condition. The result is used to qualitatively study Schwinger’s mechanism of quark-gluon plasma (QGP) formation in ultrarelativistic heavy ion collisions. It is found that the critical strength of the field required to create pairs is enhanced,ɛ _c(A) >ɛ _c(A = 0). The rate of pair creation for constantɛ, decreases for non-zeroA, implying longer QGP formation times. Because ofɛ _c(A) >ɛ _c(0), QGP is predicted to be formed in the early stages of the nuclear collision. The finite size effects and the MIT bag boundary condition effects on QGP formation are also discussed.     

Low frequency ultrasonic multi-mode Lamb wave method for characterizing the ultra-thin transversely isotropic laminate composite: Theory and experiment

1 IntroductionThe transversely isotropic laIninate composites, such as the eddirectional fiber-reinforcedcomposites and the whdirectional 8tretched high polymers, are widely used in many fields suchas aerospace, information science and biomedical engineering. Recelltly) more and more attention has been attracted to quatitative, nondestructive and insitu evaluating of the acoustical,mechanical and interfaCiaJ characters of the transversely isotropic 1aIninate composites.The traditional ultras…