适用于复杂试验条件下的声发射传感器布置装置设计

在岩石声发射实验中,合理布置声发射传感器至关重要.声发射传感器一般在夹具夹持情况下通过凡士林紧密贴合在岩样表面,常规方法操作比较繁琐,并且裸露在外的声发射传感器及其数据传输线很可能对其他实验和操作造成干扰.针对这一问题,研制了一套适用于多种试样尺寸的声发射传感器布置安装系统,并开展了相应的岩石直剪声发射试验和单轴压缩声...     

砂岩单轴循环加卸载过程中声发射信号特征与时空演化规律

为深入研究循环荷载作用下岩石内部微裂纹萌生、发展及贯通的时空演化规律,以砂岩为研究对象,开展了砂岩在单轴循环加卸载下的声发射试验。结果表明:借助不同方向的波速测试,可获得声波在岩石中的传播速度,为声发射定位提供合理的波速参数;通过合理布置传感器的位置,可准确定位破裂面的空间位置;加卸载过程中声发射事件数和能量呈现台阶状上升,表明声发射具有记忆效应;通过声发射事件空间定位与破坏岩样的对比,验证了两者的位置基本一致,表明声发射可有效获得岩石内部微裂纹发展的全过程。     

岩石声发射研究现状

声发射技术在岩土工程等领域得到了广泛的应用,通常根据Kaiser效应测试岩石地应力,根据声发射事件的时空分布分析岩石内部损伤状态.介绍岩石中形成声发射的原理及表征参数,阐述Kaiser效应地应力测试和岩石破裂空间定位的原理及影响测试结果的主要因素,系统分析基于声发射表征参数的岩石损伤力学及分形特性的研究进展.针对目前岩石声发射的研究现状,指出Kaiser效应地应力测试、岩石声发射空间定位和岩石损伤力学等方面存在的问题,主要表现在Kaiser效应地应力测试点显现度的影响因素复杂,岩石破裂的声发射空间定位精度有待提升,基于声发射的岩石损伤机理认识不足及分形维数临界值难以统一.     

声发射信号预测山体滑坡基础性试验研究

对现场取样并二次加工的岩石样本采用深梁三点加载方式在5种工况(变速加载、匀速加载、破坏形态改变、加载环境改变以及尺寸改变)下进行剪切加载至破坏,以模拟岩体滑坡.进而基于声发射理论,利用声发射传感器对试验样本破坏全过程中的声发射信号进行实时采集,并形成相应位置的声发射信号随时间变化曲线.最终通过声发射信号曲线变化特征识别区分出岩石样本加载破坏整个过程中的不同阶段.试验结果证明,基于传感器合理布置位置,通过观察声发射信号曲线变化特征可以对山体滑坡面中关键点破坏的预警提供较好的判断依据,从而通过对多个关键点破坏位置的预警来预测滑坡面的早期形态,为今后声发射信号预测山体滑坡的工程应用提供试验基础.     

空气传导新型声发射传感器的研究

提出了一种用于刀具破，磨损监测的新型非接触声发射传感器，它直接利用空气作为声发射信号传导介质，便于安装使用，实验证明，该传感器具有较高的灵敏度和抗干扰能力，并可应用于其它声发射监测的场合。     

声发射法测试岩石先期应力值的可行性

本文根据岩石声发射类型和一个试验实例,讨论了应用声发射法测量岩石先期地应力的可行性和精度。     

石灰岩声发射频谱特性演化及破裂阶段识别

为获得石灰岩受压破裂阶段声发射识别信息,开展石灰岩单轴压缩声发射试验,获得加载全过程的声发射特征参数及其波形信息,首先结合石灰岩应力与累积能量走势的特征选取 5 个岩石加载破坏过程中的关键点。通过频谱分析与小波包分析,找到石灰岩声发射频谱特征变化规律,获得适合的破裂阶段识别信息;其次利用小波包分解所提取的频带能量占比训练 BP 神经网络,为岩石破裂阶段预警提供双 重保证。研究结果表明：主频值整体呈现先上升后下降的趋势,频谱宽度变化为 200 kHz-300 kHz-200 kHz,频率由单一低频转化为低高频并存后又恢复单一低频;低频高幅为频谱特征的一种主要形态存在;小波包分解将信号频率分为 8 个频段,可将 1、2 低频段之和小于 30%的信号作为特征点,进行岩石破裂预测;以该特征点为界将石灰岩声发射信号划分为两类,训练后的 BP 神经网络能够实现这两类信号的快速准确识别与分类,对于预测岩石破裂阶段有一定价值。     

熔锥形光纤声发射传感器的实验研究

为克服传统的压电传感器体积大、质量大及易受电磁干扰等缺点,研制一种基于熔锥形光纤耦合器的新型光纤传感器。通过在铝板和碳纤维复合材料层板上进行断铅声发射探测实验,分析其频谱,得到频率响应为300kHz,比压电传感器的频率200kHz响应高。将该传感器对纤维缠绕压力容器打压时进行在线检测,得到水压分别为2．4和3MPa时的声发射信号,得出压力容器会发生基体开裂和界面损伤两种损伤模式。结果表明,该传感器具有制作简单、体积小和灵敏度高等优点,能够探测频率为几十千赫兹到几百千赫兹的声波。     

单轴载荷作用下岩石损伤演化及声发射特性研究

本文通过对两种不同岩石试样进行了单轴载荷破坏过程中声发射特性试验,得到了岩石全应力应变破坏过程中,声发射事件时间序列、事件累计数时间序列等声发射特性,分析了岩样损伤破裂不同阶段与声发射参数的内在联系与特征规律,研究表明,声发射信息反映岩石内部的损伤破坏情况,与其内部原生裂隙的压密及新裂隙的产生、扩展、贯通等演化过程密切相关,通过声发射事件数参数拟合出的理论应力应变曲线能够合理地反映岩石实际的应力应变和损伤演化特性,对预测预报岩石破坏失效的过程具有有着极其重要的理论价值和实际意义。     

供水管道在线泄露检测方法

针对水管泄漏检测难度大,提出了"节点式"光纤Bragg光栅声发射传感器安置方法,即将声发射传感器放在两段管道的节点处,对漏水的声发射信号进行收集,进而来判断水管的泄露程度.同时对声发射传感器进行了金属化封装,在实验室建立了供水管道的供水模型,在实验室进行模拟,采用声发射传感器采集声发射信号,对信号进行分析处理.实验结果表明:该检测系统能够详细提供供水系统的声发射信息分布情况,对漏水点实现准确报警,克服了以往声传感器在收集声发射信息过程中衰减和无法实现长距离传输的弊端.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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