3D Characteristic Diagram of Acoustically Induced Surface Vibration with Different Landmines Buried

The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.

Adsorption and Vibration of Cl Atoms on Ni Low-index Surfaces

The 5-parameter Morse potential（5-MP） of the interactions between Cl atoms and Ni surfaces was constructed. The adsorption and diffusion of Cl atoms on Ni low index-surfaces were investigated with 5-MP in detail. All the critical characteristics of the system, such as adsorption site, adsorption geometry, binding energy, eigenvalues for vibration, etc. were obtained. The calculated results show that chlorine atoms are likely to be adsorbed on the high symmetry- sites. Cl atoms locate on the four-fold hollow sites of the intact Ni（100） surface, while they tend to occupy threefold sites on the Ni（ 111 ） surface. The four-fold hollow sites are the most stable adsorption sites on the Ni （110） surface for Cl, although the three-fold sites and the long-bridge sites are stable adsorption sites on the Ni（110） surface for the atoms of the first and second periods. For the Cl-Ni surface adsorption system, the surface binding energy of a Cl atom is relevant to the coarse degree of the cluster surface, and the binding energies have an order of Ni （ 111 ） 〈 Ni（100） 〈Ni（100）.

Methanol Adsorption on TiO2 Film Studied by Sum Frequency Generation Vibrational Spectroscopy

A broadband infrared surface sum frequency generation vibrational spectroscopy （SFG-VS） and an in situ UV excitation setup devoted to studying surface photocatalysis have been constructed. With a home-made compact high vacuum cell, organic contaminants on TiO2 thin film surface prepared by RF magnetron sputtering were in situ removed under 266 nm irradiation in 10 kPa 02 atmosphere. We obtained the methanol spectrum in the CH3 stretching vibration region on TiO2 surface with changing the methanol pressure at room temperature. Features of both molecular and dissociative methanol, methoxy, adsorbed on this surface were resolved. The CH3 symmetric stretching vibration frequency and Fermi resonance of molecular methanol is red-shifted by about 6-8 cm-1 from low to high coverage. Moreover, the recombination of dissociative methanol and H on Surfaces in vacuum was also observed. Our results suggest two equilibria exist： between molecular methanol in the gas phase and that on surfaces, and between molecular methanol and dissociative methanol on surfaces.

Dynamic analysis of new type elastic screen surface with multi degree of freedom and experimental validation

A feasible method was proposed to improve the vibration intensity of screen surface via application of a new type elastic screen surface with multi degree of freedom(NTESSMDF). In the NTESSMDF, the primary robs were coupled to the main screen structure with ends embedded into the elastomers, and the secondary robs were attached to adjacent two primary robs with elastic bands. The dynamic model of vibrating screen with NTESSMDF was established based on Lagrange's equation and the equivalent stiffnesses of the elastomer and elastic band were calculated. According to numerical simulation using the 4th order Runge-Kutta method, the vibration intensity of screen surface can be enhanced substantially with an averaged acceleration amplitude increasing ratio of 72.36%. The primary robs and secondary robs vibrate inversely in steady state, which would result in the friability of materials and avoid stoppage. The experimental results validate the dynamic characteristics with acceleration amplitude rising by62.93% on average, which demonstrates the feasibility of NTESSMDF.

Dynamics of a Rotating Sphere on Free Surface of Vibrated Granular Materials

We investigate the rotational dynamics of a low-density sphere on the free surface of a vertically vibrated granular material（VGM）. The dynamical behavior of the sphere is influenced by the external energy input from an electromagnetic shaker which is proportional to ε,where ε is equal to the ratio between the square of the dimensionless acceleration Γ and the square of the vibration frequency f of the container. Empirical results reveal that as the VGM transits from local-to-global convection,an increase in ε generally corresponds to an increase in the magnitudes of the rotational ω（RS） and translational v（CM） velocities of the sphere, an increase in the observed tilting angle θ（bed） of the VGM bed, and a decrease in the time t（wall） it takes the sphere to roll down the tilted VGM bed and hit the container wall. During unstable convection, an increase in ε results in a sharp decrease in the sphere＇s peak and mean ω（RS）,and a slight increase in t（wall）.For the range of ε values covered in this study, the sphere may execute persistent rotation, wobbling or jamming, depending on the vibration parameters and the resulting convective flow in the system.

Prediction of Outdoor Noise Propagation Induced By Single-Phase Power Transformers

Outdoor power transformers are one of the most pervasive noise sources in power transmission and distribution systems.Accurate prediction of outdoor noise propagation plays a dominant role for the evaluation and control of noise relevant to the transformer stations.In this paper surface vibration tests are carried out on a scale model of a single-phase transformer tank wall at different excitation frequencies.The phase and amplitude of test data are found to be randomly distributed when the excitation frequency exceeds the seventh mode frequency,which allows the single-phase power transformer to be simplified as incoherent point sources.An outdoor-coherent model is subsequently developed and incorporated with the image source method to investigate noise propagation from single-phase power transformers,due to the occurrence of multiple reflections and diffractions in the propagation path of each point source.The proposed model is used to calculate the sound field of the power transformer group by exploiting the additional phase information.In comparison with the ISO9613 model and the boundary element method,it is found that the proposed coherent image source method leads to more accurate prediction results,and hence better performance for the prediction of the outdoor noise induced by single-phase power transformers.

Shear Model of Metal Melt Flowing on Vibration Wall and Effect of Shear Stress on Solidification Microstructure

In this work,the shear model of metal melt flowing on vibration surface is established,and coupling effects of vibration and shear on the distribution of shear stress in melt and melt solidification microstructure are analyzed.Calculation results show that the transition of melt from laminar flow to turbulent flow occurs earlier with increasing vibration frequency and vibration amplitude.In the laminar flow melt,shear stress in melt decreases with increasing vertical length,but it decreases firstly and then stabilizes with increasing flow length.In the turbulent flow melt,shear stress decreases firstly and then stabilizes with increasing vertical length,but it increases with increasing flow length.With the increase in vibration frequency and amplitude,shear stress along flow direction in laminar flow melt increases,while shear stresses along both flow direction and vertical direction in turbulent flow melt increase.Shear stress in melt decreases with increasing length along vertical direction.With the increase in flow length,shear stress decreases firstly and then stabilizes in laminar flow melt,while it increases in turbulent flow melt.With the increase in vibration frequency and amplitude,shear stress increases in laminar flow melt,while it stabilizes in turbulent flow melt.Based on theoretical calculation,the maximum shear stress in melt during vibration shear flow is always much lower than the yield strength of a-Al grain,so the shear stress induced by vibration shear flow cannot break columnar crystal,which agrees with the experiment result.So,the model can explain the shear constitutive relation of melt flow on vibration surface relatively well.

Local characteristics and acoustical energy of radiation on vibrating surface: Ⅰ. Theory

From a point of view of the auto-spectrum, the local characteristics and the acous-tical energy of radiating on a vibrating surface are theoretically studied in this paper. The point radiation impedance at any point on a vibrating surface is defined a-s the ratio of the sound pressure to the vibrating velocity, which establishes the relation between the vibration of the surface and the sound field. Applying the Cauchy iategral theorem, the chromatic disper-sion relation between the real and imaginary components of the point radiation impedance is given, and some characteristics are discussed. The discussion about two typical sound sotirces,pulsating and oscillating spheres, supports the arguments of this paper.

Local characteristics and acoustical energy of radiation on vibrating surface: Ⅱ. application

Applying the theory put forward in Ref. [3], the radiation mechanism of sound energy on a vibrating steel plate was studied. Between the point radiation resistance efficiency and the point radiation reactance efficiency exists the chromatic dispersion relation that is one to one. The chromatic dispersion relation fits not only smooth curves, but also the dispersed curves with sharp-pointed peaks. While the vibrating surface radiates the sound energy into field, it absorbs some energy from the field.