一种数据驱动的面波预测和自适应衰减方法

面波压制是地震数据处理的重要环节,为了在压制过程中确保信号保真度,减少空间假频的影响,近年来基于频散特征的面波预测与压制方法受到青睐。该方法利用面波固有的频散属性,通过分析计算得到的频散关系预测面波,并将其从原始数据中消减,以达到压制的目的。但该方法也存在频散谱精度不高、面波预测欠准确,或频散谱精度虽然较高但计算耗时长等问题,导致该方法未能广泛应用。文中介绍一种经过改良的频散面波压制策略,即通过使用自适应面波数据提取技术、随炮检距变化的面波重建方法及面波模型匹配相减,结合高精度的频散谱分析方法对面波噪声进行准确预测,使该方法在对海量数据的处理中得到有效应用。实际资料测试结果表明,该方法能有效去除面波,最大限度地保护有效信号,在面波发育区有广泛应用前景。

Heat transfer model for microwave hot in-place recycling of asphalt pavements

In order to solve for temperature fields in microwave heating for recycling asphalt mixtures, a two-dimensional heat transfer model for the asphalt mixtures within the heating range is built based on the theory of unsteady heat conduction. Four onedimensional heat transfer models are established for the asphalt mixtures outside the heating range, which are simplified into four half-infinite solids. The intensity of the radiation electric field is calculated through experiment by using heating water loads. It is suggested that the mathematical model of boundary conditions can be established in two ways, which are theoretical deduction and experimental reverse. The actual temperature field is achieved by fitting temperatures of different positions collected in the heating experiment. The simulant temperature field, which is solved with the Matlab PDE toolbox, is in good agreement with the actual temperature field. The results indicate that the proposed models have high precision and can be directly used to calculate the temperature distribution of asphalt pavements.

Mathe matical model and calculation for heat transfer during condensation on surfaces of corrugated plates

A mathematical model was established for condensation on surfaces of verticalcorrugated plates based on the mechanism of heat transfer enhancement to thin down the liquid filmdue to surface tension effect between corrugated plate surfaces and liquid films. The relative heattransfer coefficients of condensation on corrugation plates were calculated in contrast withequivalent vertical plane ones. The heat transfer enhancement effects for the main geometricparameters such as pitch, height, corrugation angle, tilt angle, and fillet radii of corrugationswere analyzed to guide the optimization of corrugation structure for application. A two-scalecorrugation is suggested, which can compromise both the enhanced heat transfer effect and adequatecross section area for flows, and it makes the heat transfer coefficient 1 to 2 times more than thatof an equivalent plane one.

Design and Realization of CPW Circuits Using EC-ANN Models for CPW Discontinuities

Novel accurate and efficient equivalent circuit trained artificial neural-network （EC-ANN） models,which inherit and improve upon EC model and EM-ANN models＇ advantages,are developed for coplanar waveguide （CPW） discontinuities. Modeled discontinuities include ： CPW step, interdigital capacitor, symmetric cross junction, and spiral inductor, for which validation tests are performed. These models allow for circuit design, simulation, and optimization within a CAD simulator. Design and realization of a coplanar lumped element band pass filter on GaAs using the developed CPW EC-ANN models are demonstrated.

A Hydrodynamic Modei for Slug Frequency in Horizontal Gas-Liquid Two-Phase Flow

The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrody-namic modei was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the modei was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30m long and its inner diameter is 24 mm. It is observed experimentally that the interfacial wave frequency at the inlet is about l to 3 times the frequency of stable slug. The slug frequencies predicted by the modei fit well with Tronconi (1990) modei and the experimental data. The combination of the hydrodynamic modei and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the miniraum frequency of interfacial wave.

Waveforms analysis and optimization of new electro-hydraulic excitation technology

A new electro-hydraulic exciter that consists of rotary valve and micro-displacement double-functioned hydraulic cylinder was proposed to realize different kinds of waveforms.Calculated fluid dynamics(CFD) simulation of rotary valve orifice reveals that orifice exists the two-throttle phenomenon.According to the finding,the revised flow area model was established.Vibration waveforms analysis was carried out by means of mathematic model and the related experiments were validated.Furthermore,as a new analysis indicator,saturation percentage was introduced first.The experimental results indicate that the revised flow area model is more accurate compared to the original one,and vibration waveforms can be optimized through suitable spool parameters and the revised cylinder structure.

A Wave Modulation Model of Ripples over Long Surface Waves

A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modula-tion model is proposed. In this model, the wind surface stress modulation is related to the modulation of ripple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the ripple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.

Scattering loss in optical waveguide with trapezoidal cross section

To get the scattering loss of the trapezoidal core waveguide,a new analysis model is presented based on the perturbation equivalent method and modified effective-index method.Firstly,the trapezoidal core waveguide is successfully equivalent to the rectangular one with both restricting the same optical field energy by adopting the perturbation method,Then,the equivalent rectangular core waveguide is decomposed into two slab waveguides by employing the modified effective-index method,The trapezoidal core waveguide scattering theory model is established based on the slab waveguide scattering theory.With the sidewalls surface roughness in the range from 0 to 100 nm in the single model trapezodial core waveguide,optical simulation shows excellent agreement with the results from the scattering loss model presented.The relationship between the dimension and side-wall roughness with the scattering loss can be determined in the trapezoidal core waveguide by the scattering loss model.

Characteristic Analysis of Diffraction from the Restricted Output End Surface of Single Mode Planar Waveguide

As for single mode symmetric step refractive index structure dielectric planar optical waveguide, when its output end is restricted, the diffractive field distribution is derived. It can be expressed as the convolution between the Dirac function and the Sinc and Lorenz functions. It is helpful to deepen the recognition of the restricted diffraction. The characteristic of the diffractive field is discussed. The variational curve of the full angle width at half maximum intensity of central bright fringe versus the half width of slit is presented by numerical calculation, and the fitting curve with the exponential function is close to it.

3D surface topography formation in ultra-precision turning

The generation process of 3D surface topography in ultra-precision turning is analyzed, as the result of superimposing between actual roughness surface,waviness surface and geometrical form texture surface. From the viewpoints of machine technical system and manufacturing process,factors influencing on roughness surface, waviness surface and geometrical form texture surface in ultra-precision turning are discussed further.The 3D topography of ideal roughness surface and actual surface affected by cutting vibration are simulated respectively.

Energy dissipation through wind-generated breaking waves

Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.

Analysis of wave propagation on human body based on stratified media model

Human body communication(HBC) is a promising near-field communication(NFC) method emerging in recent years. But existing theoretical models of HBC are too simple to simulate the wave propagation on human body. In this work, in order to clarify the propagation mechanism of electromagnetic wave on human body, a surface waveguide HBC theoretical model based on stratified media cylinder is presented. A numerical model analyzed by finite element method(FEM) is used for comparing and validating the theoretical model. Finally, results of theoretical and numerical models from 80 MHz to 200 MHz agree fairly well, which means that theoretical model can characterize accurate propagation mechanism of HBC signal. Meanwhile, attenuation constants derived from two kinds of models are within the range from 1.64 to 3.37, so that HBC signal can propagate effectively on human body. The propagation mechanism derived from the theoretical model is useful to provide design information for the transmitter and the modeling of the propagation channel in HBC.

Near-surface model reconstruction using pseudo well-surface simultaneous travel time tomographic inversion

The static correction of a near-surface model may be improved by using travel time tomographic inversion.We discuss unfavorable factors in the inversion of surface seismic waves that have been analyzed by the first break.These factors show that sources and geophones arranged on the surface,or close to the surface,give a first break that only includes the direct wave and the up going wave from the down going to up going transition.These up going waves have weak directivity when they arrive at a geophone and so the rays passing through the grids have small directional differences and a narrow azimuth.Drawing lessons from the advantages of Vertical Seismic Profiling(VSP) acquisition mode we describe a pseudo well-surface simultaneous travel time tomographic inversion of a near-surface model.The well depth should be increased in the surface seismic study to produce a pure up going wave,to enhance the verticality of the rays and to increase the azimuth and shorten path length of the rays.Simulations of the effect of well depth on a pseudo well-surface simultaneous travel time tomographic inversion model are reported.The results show that the static corrections are improved significantly when the well depth extends below the weathered or sub-weathered layers.The root mean square error of the statics is 1.14 or 0.93 ms for these two situations,respectively.

Influence of Structure Plane Size on Seismic Response of Soil-Structure Interaction

The influence of the change of structure plane size on seismic response was studied for a soil-structure interaction system.Based on the finite element method,a soil-structure interaction calculation model was established to analyze the seismic response by changing the structure plane size and choosing different earthquake waves for different soil fields.The results show that when the natural periods of vibration for different structure plane sizes are close,under the same earthquake wave,the total displacement on the top layer of the structure and the foundation rotation displacement decrease with the increase of structure plane size,and the proportion of superstructure elastic selfdeformation displacement to the total displacement increases with the increase of structure plane size.While for different types of sites and seismic waves,under the horizontal and vertical seismic waves,the seismic responses of different plane sizes have a similar change rule.

Analytical estimation of mixing coefficient induced by surface wave-generated turbulence based on the equilibrium solution of the second-order turbulence closure model

Based on the equations of motion and the assumption that ocean turbulence is of isotropy or quasi-isotropy, we derived the closure equations of the second-order moments and the variation equations for characteristic quantities, which describe the mechanisms of advection transport and shear instability by the sum of wave-like and eddy-like motions and circulation. Given that ocean turbulence generated by wave breaking is dominant at the ocean surface, we presented the boundary conditions of the turbulence kinetic energy and its dissipation rate, which are determined by energy loss from wave breaking and entrainment depth respectively. According to the equilibrium solution of the variation equations and available data of the dissipation rate, we obtained an analytical estimation of the characteristic quantities of surface-wave-generated turbulence in the upper ocean and its related mixing coefficient. The derived kinetic dissipation rate was validated by field measurements qualitatively and quantitatively, and the mixing coefficient had fairly good consistency with previous results based on the Prandtl mixing length theory.

Acoustic Goos-H?nchen effect

We report two models of the lateral displacement of acoustic-wave scattering on a fluid-solid interface that reveal an acoustic analog of the Goos-Hainchen effect in optics. This acoustic analog is called the acoustic Goos-Hainchen effect. Using newly proposed models, we made numerical calculations for the system ofa water-Perspex interface. Specifically, in the post-critical-angle region, we observed a lateral displacement （and transition time） of the reflected P-wave with respect to the incident P-wave. The first arrival of the acoustic signal from the interface is found to be a reflected P-wave rather than the sliding-refraction P-wave usually described in traditional acoustic-logging sliding P-wave theory. For both proposed models, the effective propagation speed of the reflected P-wave along the interface depends on not only the physical properties of the interracial media but also the incident angle. These observations are intriguing and warrant further investigation.

Exhaustive Classification of the Invariant Solutions for a Specific Nonlinear Model Describing Near Planar and Marginally Long-Wave Unstable Interfaces for Phase Transition

Problems of thermodynamic phase transition originate inherently in solidification, combustion and various other significant fields. If the transition region among two locally stable phases is adequately narrow, the dynamics can be modeled by an interface motion. This paper is devoted to exhaustive analysis of the invariant solutions for a modified Kuramoto-Sivashinsky equation in two spatial and one temporal dimensions is presented. This nonlinear partial differential equation asymptotically characterizes near planar interfaces, which are marginally long-wave unstable. For this purpose, by applying the classical symmetry method for this model the classical symmetry operators are attained.Moreover, the structure of the Lie algebra of symmetries is discussed and the optimal system of subalgebras, which yields the preliminary classification of group invariant solutions is constructed. Mainly, the Lie invariants corresponding to the infinitesimal symmetry generators as well as associated similarity reduced equations are also pointed out. Furthermore,the nonclassical symmetries of this nonlinear PDE are also comprehensively investigated.

Inversion of excitation source in ground vibration from urban railway traffic

Urban trains running on ground surface lead to evironmental ground vibrations in the vicinity of railwaylines. The complicated vibration source of the system can hardly be measured directly. The inversion methodology in engineering seismology is borrowed here to study the dynamic exciting sourec, i.e., the wheel-rail unevenness. A dynamic coupled train-track-3D ground model is combined with a genetic algorithm for the inversion. The solution space of the inversion variables, the objective function and the solving genetic strategy of the inversion are determined, and a joint inversion for the wheel-rail unevenness source function and some track structure parameters is therefore designed. The wheel-rail unevenness PSD, being the source function of No. 13 Beijing urban railway, is obtained by the inversoin based on observed data in the field. The result indicates that the source function discribes the track unevenness in the range of wavelength over 1.2 m, and reflects properly wheel irregularites in the range of wavelength shorter than 1.2 m. It should be noticed that the urban rail traffic is not very fast, and this range of short wavelength is exactly corresponding to the main frequency band of environmental vibrations from the traffic. The unevenness of wavelength under 1.2 m is underestimated, and the ground vibration in the main frequency band must be underestimated consequently, if the track unevenness spectrum is taken as the source function. Rather than the track spectrum reflecting just the evenness of track, the wheel-rail spectrum expresses both the track unevenness and the irregularities of wheels, and therefore is more suitable to be the source function of urban railway traffic. It is also convinced that the exciting source inversion according to observed ground vibrations is an effective way to detect quantitatively the combined wheel-rail unevenness.