基于声速频散谱弛豫特征的油中溶解气体检测方法

针对传统气体检测方法难以满足电力运营部门大范围低成本实时监控油浸式电力设备问题,提出一种利用3个频率点声速测量值获取声速频散谱弛豫特征进行气体监测方法。首先,通过推导有效压缩系数与声弛豫过程理论公式,简化声速频散谱表达式。其次,根据不同频率点声速测量值重建声速频散谱,抽取油浸式电力设备故障气体声速频散谱弛豫声速和弛豫频率。最终,利用弛豫特征定性定量检测气体成分。仿真结果显示重建声速频散谱与实验数据相符,完成了CH_(4)、CO_(2)等多种气体检测,为实时在线监测电力设备油中溶解气体成分提供一种低成本、测量简单的声学方法。

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。

双相介质理论检测页岩裂缝及其油气

尝试用双相介质BISQ理论,在叠后地震数据上计算以频率为自变量的瞬时频散谱和瞬时吸收谱,用瞬时谱的频散和衰减信息检测页岩裂缝及油气。用迭代优化方法设计频宽为2Hz的25个分频算子,用分频算子对地震数据分频,用复数道分析技术对所有分频道进行"三瞬"计算,集合成瞬时振幅谱、瞬时频率谱、瞬时相位谱,用这3个瞬时谱计算瞬时频散谱和瞬时吸收谱。计算结果表明:在瞬时吸收谱的低频段可见到强吸收被弱吸收封闭的异常特征,在瞬时频散谱上伴有频散突变异常特征,两种异常共同构成检测页岩裂缝及油气的标志。用瞬时频散谱和瞬时吸收谱的衰减和频散的异常特征对8口已知井页岩储层的检测结果与钻井吻合。基于双相介质BISQ理论的瞬时频散谱和瞬时吸收谱可预测油气分布范围,提供钻探目标。

速度反转区的表层调查与静校正方法

高精度静校正方法是提高地震资料处理质量的重要环节。在复杂探区,尤其是因火成岩侵入、喷发等原因引起的近地表速度反转区,采用常规小折射调查法难以正确地建立近地表结构。基于面波的频散特性,利用不同波长面波反映近地表不同深度介质的物性参数,且不受速度反转的影响,是速度反转区表层结构调查的一种有效方法。将该方法应用于实际资料并做分析研究后认为:设计满足小折射空间域和时间域的观测方法,利用常规小折射资料进行面波和折射波联合解释,可显著提高速度反转区表层结构调查的精度,为后续处理提供精准的静校正量数据。

Wave field forward modeling and theoretical analysis of weakness in discrete media

The elasticity, viscosity, and the relationships derived from rheology weakness properties are taken into account in mechanics. Comparing with the corresponding relationships derived from damage mechanics, we find the weakness factor has the same significance as the damage factor. We simulate the wave field using a staggered-grid pseudospectral method to show the influence of the weakness factor qualitatively. Applying the analytical solution of plane waves, we give the velocity and attenuation coefficient of three body waves, which are affected by the wave frequency and the weakness factor of saturated discrete media. Our results show that velocity decreases with increasing weakness factor, the attenuation coefficient increases with an increase in the weakness factor, and that the influence of weakness depends on the mode of the body waves.

On Husimi Distribution for Systems with Continuous Spectrum

We propose a procedure to generalize the Husimi distribution to systems with continuous spectrum. We start examining a pioneering work, by Gazeau and Klauder, where the concept of coherent states for systems with discrete spectrum was extended to systems with continuous one. In the present article, we see the Husimi distribution as a representation of the density operator in terms of a basis of coherent states. There are other ways to obtain it, but we do not consider here. We specially discuss the problem of the continuous harmonic oscillator.

Timedelay based all-frequency correction method for discrete spectrum

Many spectrum correction methods have been developed, but their performance degrades significantly when they are applied to the correction of low frequency component （ LFC ）. It owns to that the model underlying the conventional approaches neglects the interference of the negative frequency in the real signal. A new approach for the correction of the LFC is proposed, which suits all kinds of symmetrical windows. It divides a signal into three sections and makes use of the first spectrum line of each section. Then this approach is modified so that it is also applicable to the correction of the high frequency component. Thus a timedelay-based all-frequency correction method is proposed. The simulation results show that this method is simple and feasible. By this method, the accurate frequency, amplitude and phase of the spectral line can be obtained whether it is close to or far from OHz.

New Positive and Negative Hierarchies of Integrable Differential-Difference Equations and Conservation Laws

Two hierarchies of nonlinear integrable positive and negative lattice equations are derived from a discrete spectrak problem. The two lattice hierarchies are proved to have discrete zero curvature representations associated with a discrete spectral problem, which also shows that the positive and negative hierarchies correspond to positive and negative power expansions of Lax operators with respect to the spectral parameter, respectively. Moreover, the integrable lattice models in the positive hierarchy are of polynomial type, and the integrable lattice models in the negative hierarchy are of rational type. Further, we construct infinite conservation laws about the positive hierarchy.

Analysis of Electroencephalogram Based on Wavelet Spectrum and Wavelet Entropy

Based on discrete wavelet transform, both relative wavelet energy （RWE） and segment wavelet entropy （SWE） of electroencephalogram （EEG） are defined in this paper. The RWE provides quantitatively the information about the relative energy associated with different frequency bands present in the EEG. The SWE carries information about the degree of order or disorder associated with different time segment of EEG evolution, which can determine the time-segment loealizations of abnormal dynamic processes of brain activity due to the localization characteristics of the wavelet transform. The experimental results show that the RWE and SWE are different between epileptic EEGs and normal EEGs, which demonstrate that the RWE and the SWE are helpful to analyze the dynamic behavior of different EEGs.

Suboptimal State Feedback H2/H∞ Controller Design with Spectrum Constraint for Discrete-time Stochastic Systems

With the aid of the spectnnn techique, a new concept named-α-stabilizability （0≤α≤1） is intnxhged and its suffident and necessary canditions are also prvposed. Especially, it is identical with the asymptotically mean square stabilizability when α = 1. As an application, the suboptimal state feedback H2/H∞ controller that satisfies the additional Spectrum canstmint via solving a convex optimization problem is delt with.

基于Mini-Sosie震源后置编码技术的面波探测方法研究

Mini-Sosie震源是城市环境主动源面波探测的理想震源,然而三元伪随机编码对控制系统和机械性能的高要求限制了其发展与应用.针对此问题,在野外数据采集阶段,采用Mini-Sosie震源的固定频率冲击模式,充分利用其简单、高效和强冲击力的优点;在室内数据处理阶段,对采集的长时序数据进行三元伪随机编码,提出了一种基于Mini-Sosie震源后置编码技术的面波探测方法.该方法首先从长时序地震记录中提取冲击序列,其次提出ABC三参数法将长时序地震记录分割成数以百计的脉冲式子记录,再次利用线性同余算法生成的三元伪随机序列对子记录进行编码,最后将冲击序列与编码地震记录进行互相关运算获得解码的地震记录.模拟与实测数据处理结果表明,该方法在编解码过程中产生的相干噪声较小,并能有效压制城市环境中的低频随机噪声,显著提高面波信噪比.三元伪随机冲击序列的频谱呈现白谱特征,无频率低切效应,能有效保护面波的低频信息,增大了主动源面波方法的探测深度.同时,该方法通过数学运算代替高精度的编码控制系统与机械性能需求,实现了Mini-Sosie震源的三元伪随机编码,具有先进性和推广价值.

Classification of hyperspectral remote sensing images using frequency spectrum similarity

An algorithm of hyperspectral remote sensing images classification is proposed based on the frequency spectrum of spectral signature.The spectral signature of each pixel in the hyperspectral image is taken as a discrete signal,and the frequency spectrum is obtained using discrete Fourier transform.The discrepancy of frequency spectrum between ground objects' spectral signatures is visible,thus the difference between frequency spectra of reference and target spectral signature is used to measure the spectral similarity.Canberra distance is introduced to increase the contribution from higher frequency components.Then,the number of harmonics involved in the proposed algorithm is determined after analyzing the frequency spectrum energy cumulative distribution function of ground object.In order to evaluate the performance of the proposed algorithm,two hyperspectral remote sensing images are adopted as experimental data.The proposed algorithm is compared with spectral angle mapper (SAM),spectral information divergence (SID) and Euclidean distance (ED) using the product accuracy,user accuracy,overall accuracy,average accuracy and Kappa coefficient.The results show that the proposed algorithm can be applied to hyperspectral image classification effectively.

Study on the interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate by the resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra and its analytical application

The interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate was investigated by ultravioletvisible absorption,resonance Rayleigh scattering(RRS),second-order scattering(SOS)and frequency doubling scattering (FDS)spectroscopy.In pH 5.3 Britton-Robinson(BR)buffer medium,chlorpromazine hydrochloride(CPZ)reacted with Pd(II) to form 2:1 cationic chelate,which further reacted with Na2WO4 to form a 1:1 ternary ion-association complex ([Pd(CPZ)2]·WO4).As a result,the signal intensities of RRS,SOS and FDS were enhanced greatly,and the enhancements of scattering were proportional to the CPZ concentration in a certain range.Their maximum wavelengths were located at 310 nm, 570 nm and 391 nm,respectively and the detection limits(3)were 1.6 ng/mL(RRS method),3.2 ng/mL(SOS method)and 5.6 ng/mL(FDS method).The optimum reaction conditions,the influences of coexisting substances and analytical application were mainly investigated by RRS method due to its highest sensitivity.A highly sensitive,simple,rapid and new method had been proposed to determine CPZ in the pharmaceutical form and residue of CPZ in pork.In addition,the Gibbs free energy change(△Gf)of ion-association reaction was computed by using B3LYP/3-21g*/LanL2dz method.The formation of ion-association and the reasons for the enhancement of RRS were also discussed.

A Model of Irregular Impurity at the Surface of Nanoparticle and Catalytic Activity

A problem of nanocatalyst improvement is considered. The existence of irregularities at the surface of nanoparticle leads to the increasing of the surface/volume ratio and, correspondingly, to the improvement of the catalytic activity. But this impurity gives one an additional effect due to the change of the electronic density at the surface. We suggest simple model for the description of this effect. The model allows one to find the discrete spectrum of the Schrdinger operator for nanoparticle. Due to this impurity induced bound states the electron density increases near the surface. It leads to the increase of the catalytic activity of nanoparticles with surface impurities.

Leaky modes and the first arrivals in cased boreholes with poorly bonded conditions

The generation mechanism of the first arrivals in the cased boreholes for the poorly bonded conditions is investigated. Based on the analyses of the Riemann surface structure of the characteristic function, the dispersion features, excitation spectra and contributions of modes excited in the cased boreholes with different cementing types are studied. The phase velocity dispersion studies of leaky modes show that high-order modes form "plateau" regions with one approximate velocity denoted by v separated by their cutoff frequencies, in which the phase velocity changes little with a considerable frequency range, while the group velocity keeps a relatively constant high value. Usually, the operation frequency range of a specific cementing evaluation acoustic logging tool is covered by such a "plateau" region. Mode excitation and contribution analyses show that the first arrivals in the cased boreholes for the poorly bonded conditions are the contributions from leaky modes, where the traveling velocity of the first arrivals processed by slowness time coherence(STC) method is equal to the approximated velocity v. Analyses on generation of leaky modes in the cased boreholes supplement the understanding of the generation mechanism of the first arrivals.

Simple aspects of femtosecond stimulated Raman spectroscopy

Femtosecond stimulated Raman spectroscopy （FSRS）, using an overlapping pair of narrow band Raman pump and broadband probe pulses with heterodyne detection along the probe pulse direction, is a new nonlinear spectroscopic technique to record vibrational spectra of even highly fluorescent molecules and to study vibrational dynamics on excited electronic states of molecules, as in photoisomerization. FSRS is described by diagrammatic third-order perturbation theory with wave packet analysis. The phase matching condition gives rise to forty-eight terms for FSRS, but the resonant condition reduces it to just eight terms, which can be depicted by Feynman dual time-line diagrams, or closed time path loop diagrams, or the complementary four-wave mixing energy level diagrams. The eight terms fall into four sets-SRS（I）, SRS（Ⅱ）, IRS（I）, IRS（Ⅱ）-where SRS stands for stimulated Raman scattering and IRS stands for inverse Raman scattering. The SRS（I） set can also account for spontaneous Raman scattering, but the remaining SRS（Ⅱ）, IRS（I） and IRS（Ⅱ） terms are only present in stimulated scattering with the presence of a probe field. The SRS（I） set accounts for the Stokes Raman lines while the IRS（I） term accounts for the anti-Stokes lines, relative to the Raman pump frequency, in the FSRS spectrum. The remaining SRS（Ⅱ） and IRS（Ⅱ） terms give rise to broad baselines. Using a harmonic oscillator model, analytic results are obtained for the four-time correlation functions in the third-order polarizations. The issue of high time and high frequency resolution in time-resolved FSRS spectra is discussed. Calculations are made with the theory to compare with experimental results for： （a） resonance FSRS of fluorescent Rhodamine 6G and （b） 2D-FSRS from a coherent vibrational state that has been prepared by an impulsive, off-resonant pump pulse on CDCl3. The calculated results compared well with experimental results, and in the case of 2D-FSRS on CDCl3 there is a dominant cascade effect contributing to the FSRS spectra.