利用偏振约束对最小信息准则方法自动拾取微震初至的改进

初至拾取是影响微震事件分析精度的重要因素之一。本文结合微震事件偏振特性和最小信息准则(akaike information criterion,AIC)函数特性,提出了一种利用偏振约束实现AIC初至拾取的改进方法:可以将偏振特征值拾取微震初至的应用扩展至单分量的微震数据,该方法将单分量微震数据视为三分量微震数据的一种特殊形式,利用三分量微震数据协方差矩阵的最大值序列对AIC方法进行约束,从而快速准确的拾取到微震数据的初至。文中应用该方法对不同信噪比的合成数据和实测数据进行了验证,同时与长短时平均(short time average/long time average,STA/LTA)、Maeda-AIC和偏振特征值方法进行了对比,结果显示该算法速度略低于上述3种方法,但精度和可靠性优于其他三种方法,同时与其他改进算法对比,不用设置阈值,并且选取时窗的长短对拾取结果几乎没有影响,可极大地提高算法的自动化程度。     

基于U-Net的矿山微震初至拾取研究

初至到时拾取是微震数据处理中基础而又重要的环节,关系到整个微震监测系统的精度与可靠性。因此,为了解决传统初至拾取方法存在拾取效率低和拾取精度差的问题,引入深度学习方法,构建U型神经网络(U-Net)来预测三分量矿山微震数据P波、S波和噪声的概率分布,并根据概率峰值提取其初至到达时间。实验结果表明：本文算法的拾取结果准确度高且误差范围较小,与AR pick (auto regression pick)算法相比,其拾取结果具有明显的优越性。所构建的初至拾取模型可用于矿山动力灾害微震监测,解决微震监测的瓶颈问题,为矿山安全生产风险智能监测预警提供强力技术支撑。     

人工智能在拾取地震P波初至中的应用 ——以汶川地震余震序列为例

为了准确而迅速地拾取大量地震事件的P波初至, 将深度学习方法引入微地震P波初至到时拾取研究中, 对卷积神经网络的结构进行改造, 以便适应地震波形数据的特点 P波初至拾取的要求。该算法只需要输入10 s窗口的三分量地震波形数据, 就可以自动地判定P波初至时刻, 无需扫描连续波形, 运算时间远远小于长短窗、模板匹配等传统方法。使用该算法训练汶川地震主震后2008年7—8月7467条人工拾取的余震P波初至到时, 将得到的模型对测试集中 1867条数据的计算结果与人工拾取结果对比, 误差小于0.5 s者占比达到98.9%。在低信噪比条件下, 该方法仍能保持较好的拾取能力。     

基于 Shearlet-AIC 算法的微地震初至拾取

初至拾取是微地震数据处理的基本步骤及重要环节,在低信噪比情况下,传统的初至拾取方法性能不佳,无法满足实际需求。为此,提出一种新算法,该算法将时域 微 地 震 数 据 映 射 到 Shearlet 域,利 用 AIC(Akaike Information Criterion) 模型对 Shearlet 域各尺度层的数据实现初步识别,最小 AIC 值作为初至时刻。通过 大量实验验证 Shearlet-AIC 算法在低至 － 13 dB 信噪比下自动拾取的准确性,证实该算法优于传统初至拾取算法,解决了传统初至拾取算法在低信噪比时难以有效拾取微地震初至的难题。     

一种微震震相到时自动拾取方法

震相初至到时的自动拾取是微震监测中一个关键问题,是实现震源定位及震源机制解释的前提和基础。针对微震信号固有的低信噪比、非线性、非平稳等特征,提出了一种震相初至自动拾取方法。首先,应用小波阈值降噪法对采集到的含噪微震信号进行降噪处理,降低人工采集时机械类振动噪声对微震震相初至拾取的干扰;然后使用STA/LTA对降噪后的微震信号进行预拾取,获得震相初至的大致时刻;以该时刻为基准,分别向前向后各截取500个采样点构成一个时间窗口,在该时间窗口内应用AIC准则法精确求取震相初至。为验证本文方法的有效性,以人工拾取的到时为基准,误差在±10ms之内视为准确拾取。实验结果显示,本文方法对低信噪比微震信号拾取的准确率为95.79%,较单纯使用STA/LTA及AIC方法准确率分别提高了9.78%及10.08%。     

基于改进的STA/LTA方法的微地震P波自动拾取技术

基于STA/LTA方法,提出了一种改进的自动拾取P波到时算法.引入权重因子K,构建了一种新的特征函数,提出寻找STA/LTA曲线上的最大值对应时刻为P波到时的方法,并运用Matlab对冬瓜山铜矿微震事件进行初至拾取分析.结果表明:该方法能够准确地拾取微地震P波初至,减少了传统的STA/LTA算法需要调整触发阈值(Thr)的过程,克服了固定阈值不能适应复杂多变信号到时拾取的缺点,具有抗噪性强、稳定性强、拾取精确度高等优势.     

基于深度学习的井间地震CT初至自动拾取方法

井间地震CT方法能够有效探测岩溶等不良地质,而拾取地震波的初至对其反演结果至关重要.以往井间地震CT初至拾取通过手动标定,效率低,无法满足模型训练要求.本文基于人工源地震初至的时距特征,提出了一种基于深度学习的地震初至训练样本库快速标定方法.利用人工合成数据训练初始网络模型,采用少量人工标定实测数据进一步训练,基于该网络模型对未标定的井间地震实测数据剖面进行初至拾取,采用长短时窗比法修正曲线拟合结果,对仍不理想的拾取结果进行人工判别和改正,并将准确标定数据加入训练集,形成新的网络模型;通过迭代实现数据集再生成并获得后续阶段的网络模型.基于上述方法完成了80 000道数据的初至拾取,在充分训练后神经网络具备较高的拾取精度,采用3840组数据对该模型进行测试,发现预测结果与人工拾取结果对比的绝对误差值小于0.2ms的数据占91.8%,说明该方法是一种切实有效且高效的井间地震CT初至拾取方法.     

单分量微地震信号的P波S波到时自动拾取方法

 单分量传感器依然是目前矿山中应用最广泛的传感器。针对矿山每天采集到的大量信号,提出了一种针对单分量微地震信号的P 波S 波到时拾取算法。长短时窗均值比法(STA/LTA)可以用来检测信号的变化趋势,结合改进的特征函数对信号的几何特征予以加强,进而可以提高震相识别的精度。随着长短时窗的滑动,信号的变化趋势表现在走势图上,再利用震相到时判别阈值可以初步定位到P 波S 波的到时区间。初步确定到时区间后,分别在P 波S 波的到时区间内应用AR-AIC 准则,可以计算出信号发生突变的位置,这两个点即对应着P 波S 波的到时。结合时差阈值判别和时频图谱,对拾取的结果再次做检验。经过两次判别,有效地提高了该算法的拾取精度。通过对1000 多条单分量微地震信号进行验证,自动拾取能拾取到71%的P 波到时和79%的S 波到时,相同条件下,自动拾取的结果不低于手动拾取的精度,满足矿山应用的要求。     

联合改进STA/LTA与MLoG算子的微震P波到时自动拾取方法

在非常规低渗油气藏开发过程中,微震P波震相到时的精确拾取是实时监测诱导水力压裂动态变化的一项关键技术.然而,传统的STA/LTA震相拾取方法存在低效率、低精度等问题.为提高低信噪比微震事件到时拾取的准确性和分辨率,提出一种联合改进型STA/LTA算法和MLoG算子的微震P波震相到时自动拾取方法.先通过MLoG算子对微震...     

改进双向LSTM的地震震相拾取算法

为了更好地提升识别精度和算法的适应性,针对传统波形检测算法存在依赖人工设定阈值以及震相拾取的精度偏低等问题,提出了一种基于改进双向LSTM的震相拾取算法。该方法利用滤波、归一化、加噪等方式对原始波形数据进行预处理,通过双向LSTM模型对地震信号数据进行自适应深层特征提取;同时为解决双向LSTM模型存在的过拟合问题,引入Spatial-Dropout机制在随机区域对双向LSTM模型进行稀疏性约束;最后引入Time-Distributed机制从时域维度针对事件-噪声的二分类问题自动判定P波到时,并在相关地震数据集上进行对比实验。结果表明:模型对P波拾取的准确率达90%,P波拾取的精确度达80%,与LSTM和GRU等传统RNN网络模型相比,精确度分别提高了6%和5%.同时,该模型不需要人工设定阈值,并且对复杂波形数据的P波拾取问题具有较强的鲁棒性。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with