Full wave seismic exploration technology

Reflected wave seismology has the following defects:the acquisition design is based on the assumption of layered media,the signal processing suppresses weak signals such as diffracted wave and scattered wave,and the seismic wave band after the image processing is narrow.They limit the full utilization of broadband raw data.The concept of full wave seismic exploration is redefined based on the idea of balanced utilization of reflected wave,diffracted wave and scattered wave information,its characteristics and adaptive conditions are clarified.A set of key technologies suitable for full wave seismic exploration are put forward.During seismic acquisition period,it is necessary to adopt multi geometry,i.e.embed small bin,small offset and small channel interval data in conventional geometry.By discretizing of common midpoint(CMP)gathers,small offset with high coverage,the weak signals such as diffracted wave and scattered wave in the raw seismic data can be enhanced.During seismic processing,the signal and noise in the original seismic data need to be redefined at first.The effective signals of seismic data are enhanced through merging of multi-geometry data.By means of differential application of data with different bin sizes and different arrangement modes,different regimes of seismic waves can be effectively decomposed and imaged separately.During seismic interpretation stage,making the most of the full wave seismic data,and adopting well-seismic calibration on multi-scale and multi-dimension,the seismic attributes in multi-regimes and multi-domains are interpreted to reveal interior information of complex lithology bodies and improve the lateral resolution of non-layered reservoirs.

Full Wave Solution for Hydrodynamic Behaviors of Pile Breakwater

Rayleigh expansion is used to study the water-wave interaction with a row of pile breakwater in finite water depth. Evanescent waves, the wave energy dissipated on the fluid resistance and the thickness of the breakwater are totally included in the model. The formulae of wave reflection and transmission coefficients are obtained. The accuracy of the present model is verified by a comparison with existing results. It is found that the predicted wave reflection and transmission coefficients for the zero order are all highly consistent with the experimental data （Hagiwara, 1984; Isaacson et al., 1998） and plane wave solutions （Zhu, 2011）. The losses of the wave energy for the fluid passing through slits play an important role, which removes the phenomena of enhanced wave transmission.

The phase relations between the first arrivals of compressional and shear waves, and their signification to full wave logging

这篇论文描述在完整的波浪实验观察的三现象：1。振幅(绝对值) 第一有压缩性并且砍到达有一样的变化规则；2。阶段第一有压缩性并且砍到达对对方总是相反；并且 3。振幅变化时期第一有压缩性并且砍到达是 2 π 。完整的分析和解释指出这些现象应该在记载状况的完整的波浪下面出现。因此，使用阶段差别从完整的波浪提取有用信息的基础被发现。

Acoustic Based Crosshole Full Waveform Slowness Inversion in the Time Domain

We develop a new full waveform inversion (FWI) method for slowness with the crosshole data based on the acoustic wave equation in the time domain. The method combines the total variation (TV) regularization with the constrained optimization together which can inverse the slowness effectively. One advantage of slowness inversion is that there is no further approximation in the gradient derivation. Moreover, a new algorithm named the skip method for solving the constrained optimization problem is proposed. The TV regularization has good ability to inverse slowness at its discontinuities while the constrained optimization can keep the inversion converging in the right direction. Numerical computations both for noise free data and noisy data show the robustness and effectiveness of our method and good inversion results are yielded.

Time-Domain Full Waveform Inversion Using the Gradient Preconditioning Based on Transmitted Wave Energy

The gradient preconditioning approach based on seismic wave energy can effectively avoid the huge memory consumption of the gradient preconditioning algorithms based on the Hessian matrix. However, the accuracy of this approach is prone to be influ- enced by the energy of reflected waves. To tackle this problem, the paper proposes a new gradient preconditioning method based on the energy of transmitted waves. The approach scales the gradient through a precondition factor, which is calculated by the ‘ap- proximate transmission wavefield’ simulation based on the nonreflecting acoustic wave equation. The method requires no computing nor storing of the Hessian matrix and its inverse matrix. Furthermore, the proposed method can effectively eliminate the effects of geometric spreading and disproportionality in the gradient illumination. The results of model experiments show that the time-domain full waveform inversion (FWI) using the gradient preconditioning based on transmitted wave energy can achieve higher inversion accuracy for deep high-velocity bodies and their underlying strata in comparison with the one using the gradient preconditioning based on seismic wave energy. The field marine seismic data test shows that our proposed method is also highly applicable to the FWI of field marine seismic data.

Study of full waveform inversion based on L-BFGS algorithm

Full waveform inversion is mainly used to obtain high resolution velocity models of subsurface. The size of full waveform inversion will lead to a gigantic computation cost. Under the available computer resource and the limitation of full waveform inversion,the authors propose L-BFGS algorithm as the optimization method to solve this problem. In order to demonstrate the flexibility of the method,three different numerical experiments have been done to analyze the properties of full waveform inversion based on L-BFGS.

Elastic Full Waveform Inversion Based on the Trust Region Strategy

In this paper, we investigate the elastic wave full-waveform inversion (FWI) based on the trust region method. The FWI is an optimization problem of minimizing the misfit between the observed data and simulated data. Usually, the line search method is used to update the model parameters iteratively. The line search method generates a search direction first and then finds a suitable step length along the direction. In the trust region method, it defines a trial step length within a certain neighborhood of the current iterate point and then solves a trust region subproblem. The theoretical methods for the trust region FWI with the Newton type method are described. The algorithms for the truncated Newton method with the line search strategy and for the Gauss-Newton method with the trust region strategy are presented. Numerical computations of FWI for the Marmousi model by the L-BFGS method, the Gauss-Newton method and the truncated Newton method are completed. The comparisons between the line search strategy and the trust region strategy are given and show that the trust region method is more efficient than the line search method and both the Gauss-Newton and truncated Newton methods are more accurate than the L-BFGS method.

Fracture detection by using full azimuth P wave attributes

特定的折断的烃水库的一种类型，页岩折断了水库，在 Shengli 油矿存在。由于这种类型，到石油化学的性质参数的变化的低敏感，和强壮的 anisotropy 的很小的孔，为他们探索是很困难的。到目前为止，没有为由综合分析的破裂的方向，分发，和密度的识别的成熟方法的集合地质，地球物理，井木头，钻的数据，和等等。这篇论文与方位角(IPVA ) 为声学的阻抗变化论述一个新方法，基于存在破裂察觉方法。地震获得，处理，并且识别技术为在 Luojia 区域与页岩破裂的地震、地质的特征在联合用多方位角 P 波浪数据检测方向性的垂直破裂被开发。IPVA 研究为认识到基于有方位角(VVA ) 的速度变化和有为完整的方位角 P 的方位角(AVA ) 的振幅变化的学习的破裂的分发，罢工，和密度在不同 CMP 位置挥动数据被执行。通过在 Luojia 区域的实际申请，主要结果被获得了它证实 IPVA 方法为平行、高角度的量的察觉提供好潜力，页岩破裂。

Analysis of the radiation Resistance and Gain of Full-Wave Dipole Antenna for Different Feeding Design

This paper demonstrates the analysis of antenna pattern and gain for different designs of full-wave dipole antenna feeding techniques. Seven such techniques were studied and analyzed;symmetrical dual feeding in phase, symmetrical dual feeding out of phase, asymmetrical dual feeding in phase, asymmetrical dual feeding out of phase, symmetrical triple feeding in phase and symmetrical triple feeding out of phase. Symmetrical dual feeding in phase produced high gain as compared to the single and center-fed antennas. An improvement of about 3 to 3.5 dB was achieved comparing to center tap fed and off center fed. It was found that an asymmetrical dual feeding in-phase provides good performance, considering the directivity, pattern, and input impedance. A 2.46 dB gain has been attained. It was found that a symmetrical triple feeding provides an overall best performance with respect to gain, radiation pattern, beam width and input impedance.

STABILITY OF STEADY MULTI-WAVE CONFIGURATIONS FOR THE FULL EULER EQUATIONS OF COMPRESSIBLE FLUID FLOW

We are concerned with the stability of steady multi-wave configurations for the full Euler equations of compressible fluid flow. In this paper, we focus on the stability of steady four-wave configurations that are the solutions of the Riemann problem in the flow direction, consisting of two shocks, one vortex sheet, and one entropy wave, which is one of the core multi-wave configurations for the two-dimensional Euler equations. It is proved that such steady four-wave configurations in supersonic flow are stable in structure globally, even under the BV perturbation of the incoming flow in the flow direction. In order to achieve this, we first formulate the problem as the Cauchy problem （initial value problem） in the flow direction, and then develop a modified Glimm difference scheme and identify a Glimm-type functional to obtain the required BV estimates by tracing the interactions not only between the strong shocks and weak waves, but also between the strong vortex sheet/entropy wave and weak waves. The key feature of the Euler equations is that the reflection coefficient is always less than 1, when a weak wave of different family interacts with the strong vortex sheet/entropy wave or the shock wave, which is crucial to guarantee that the Glimm functional is decreasing. Then these estimates are employed to establish the convergence of the approximate solutions to a global entropy solution, close to the background solution of steady four-wave configuration.

Simulation of Fully Nonlinear 3-D Numerical Wave Tank

A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order boundary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.

Full-wave Analyses of Scattering of Electromagnetic Wave from the Weakly Ionized Plasma in Plane Geometry

The purpose of the present work is to present a full-wave analysis of scattering from the weakly ionized plasma in the plane geometry. We have yielded an approximate solution in an analytic form to the electromagnetic wave scattering from the weakly ionized plasma. In the normal and oblique incidence, the analytic solution works well, as compared with the exact solution and the solution based on the Wenzell-Kramers-Brillouin-Jeffreys (WKBJ) approximation to the uniform density profile.

Full-waveform Velocity Inversion Based on the Acoustic Wave Equation

Full-waveform velocity inversion based on the acoustic wave equation in the time domain is investigated in this paper. The inversion is the iterative minimization of the misfit between observed data and synthetic data obtained by a numerical solution of the wave equation. Two inversion algorithms in combination with the CG method and the BFGS method are described respectively. Numerical computations for two models including the benchmark Marmousi model with complex structure are implemented. The inversion results show that the BFGS-based algorithm behaves better in inversion than the CG-based algorithm does. Moreover, the good inversion result for Marmousi model with the BFGS-based algorithm suggests the quasi-Newton methods can provide an important tool for large-scale velocity inversion. More computations demonstrate the correctness and effectives of our inversion algorithms and code.

Quasi-Dynamic Green’s Functions for Efficient Full-Wave Integral Formulations for Microstrip Interconnects

Integral formulations are widely used for full-wave analysis of microstrip interconnects. A weak point of these formulations is the inclusion of the proper planar-layered Green’s Functions (GFs), because of their computational cost. To overcome this problem, usually the GFs are decomposed into a quasi-dynamic term and a dynamic one. Under suitable approximations, the ?rst may be given in closed form, whereas the second is approximated. Starting from a general criterion for this decomposition, in this paper we derive some simple criteria for using the closed-form quasi-dynamic GFs instead of the complete GFs, with reference to the problem of evaluating the full-wave current distribution along microstrips. These criteria are based on simple relations between frequency, line length, dielectric thickness and permittivity. The layered GFs have been embedded into a full-wave transmission line model and the results are ?rst benchmarked with respect to a full-wave numerical 3D tool, then used to assess the proposed criteria.

A Simplified Full-Wave Analysis for Microstrip Patch Antennas

The spectral domain integral equation(SDIE) provides an accurate and efficient method for computing the resonant frequency, radiation patterns, etc . Using continuous Fourier transform, the formulation utilizes the singular integral equations via the Glerkin's method to derive the deterministic equation with fewer mathematical manipulations. In contrast, discrete Fourier transform(DFT) requires intricate mathematical labor. The present scheme requires a small size, i.e ., (2×2) matrix, and it is possible to extract higher order modal solutions conveniently. Moreover, computation is reduced with the same convergence properties. Based on the present scheme, some results for resonant frequency and radiation patterns compared with available data and computed current distribution on the patch are presented.

Full-wave synthetic acoustic logs in porous media

In order to investigate the permeability of porous media,it is necessary to figure out the property of wave propagation in this medium. The authors calculated the full waveforms and the 2-dimensional spectrum of fluid saturated porous media,analyzed the wave propagation characteristics of different permeable stratums. From the theoretical acoustic pressure waveform received at the well-axis and the 2-D spectrum it is revealed that longitudinal-,transverse-,Stoneley-,pseudo-Rayleigh-,longitudinal mode-and transverse mode waves are different in characters in various permeable strata. Stoneley wave is sensitive to the change of permeability,and its frequency range and amplitude attenuation are influenced by permeability.

A New Current Conveyor Full-Wave Rectifier for Low Frequency/Small Signal Medical Applications

This paper presents a new current conveyor (CCII+) full-wave rectifier for low frequency/small signal medical applications. The proposed rectifier is based on the current conveyor full-wave rectifier proposed previously, but the proposed rectifier is better in view of no need diodes to rectify, and no need bias sources to overcome the zero crossing error. It needs only two CCII+s, two resistors, and three simple current mirrors, which is easy for IC implementation and for building in many countries. The PSPICE simulation with the current conveyor CCII+ in the current feedback opamp AD844 IC and the 2N2222 bipolar current mirror shows the good low frequency/small signal rectification, the operation voltage of down to 6 .

Precision Full-Wave Rectifier Using Two DDCCs

A new precision full-wave rectifier employing only two differential difference current conveyors, which is very suitable for CMOS technology implementation, is presented. The proposed rectifier is the voltage-mode circuit, which offers high-input and low-output impedance hence it can be directly connected to load without using any buffer circuits. PSPICE is used to verify the circuit performance. Simulated rectifier results based-on a 0.5 μm CMOS technology with ±2.5 V supply voltage demonstrates high precision rectification and excellent temperature stability. In addition, the application of proposed rectifier to pseudo RMS-to-DC conversion is also introduced.

超材料天线罩雷达散射截面特性分析

以超材料为代表的新技术迅速崛起,大大推进了天线罩的技术进步,与往常天线罩不同的是,超材料天线罩改进了天线系统的散射特性。多年来,人们注重于天线罩的传输特性而忽略了散射特性研究,一方面原因是控制天线罩的散射性能的需求不甚迫切,另一方面原因则是准确分析耗时费力,难度很大,特别是电大尺寸的天线罩的散射特性几乎无法精确计算。虽然高频光学近似在分析天线罩传输特性方面,精度较高,基本满足设计需求,但是在分析天线罩散射特性方面,偏差较大,很难满足设计需求。针对超材料天线罩雷达散射特性分析需求,文中首先分析比较了不同方法对于介质天线罩雷达散射截面(RCS)的计算结果的差别,分析了产生的原因,采用特征模型结合全波分析方法,计算了超材料天线罩散射特性,并与测试结果进行了比较,仿真和试验结果的包络符合较好,验证了在天线罩中采取吸收措施能明显降低其RCS,可供超材料天线罩设计师参考。

纸基复合吸波超材料吸波性能的等效电路分析方法研究

纸基复合吸波超材料是一种较为理想的宽带雷达吸波材料。以某种具有六边形环结构的纸基复合吸波超材料为例,借助等效电路方法对该材料的吸波性能进行分析。结果表明:借助等效电路方法可以较为直观、准确地得到纸基吸波超材料的吸波性能分析结果,与一般的全波仿真分析方法相比具有更强的实用性。