基于脉冲响应函数和虚拟脉冲响应函数的挡土墙结构损伤诊断

为了诊断挡墙结构的损伤,基于脉冲响应函数及虚拟脉冲响应函数创建损伤特征向量谱、提出损伤识别指标。基于损伤特征向量谱和损伤指标,提出了一种用于挡墙结构的损伤诊断方法。为了验证该损伤诊断方法的可行性和有效性,对某桩板式挡墙进行了脉冲激励和环境激励下的振动测试,通过损伤特征向量谱和损伤指标诊断其损伤。试验结果表明:基于损伤特征向量谱可敏感判别挡墙损伤状态,通过损伤指标走势曲面图可有效诊断挡墙损伤位置,通过损伤指标与损伤程度间的定量关系可定量识别挡墙损伤程度。受激励影响,脉冲激励下基于脉冲响应函数的损伤指标稳定性相对较差,而环境激励下基于虚拟脉冲响应函数的损伤指标稳定性相对较强。     

基于椭球凸模型的结构模糊可靠性分析

结构工程中不仅存在随机不确定性,还存在模糊不确定性.针对结构模糊可靠性问题,提出了一种基于模糊分解定理的超椭球凸模型响应面法,适用于隐式结构功能函数的模糊可靠性求解问题.首先,通过在置信水平[0,1]内遍历隶属度值确定结构可靠度的可能性分布函数,将模糊变量转化成在置信水平[0,1]下的区间变量;其次,建立超椭球凸集模型...     

基于插值fast Fourier transform谐波分析的桥梁状态评估方法

桥梁的环境振动信号包含了各种环境噪声成分,如何从噪声影响中提取桥梁的真实自振频率,并进行桥梁状态评估是亟待解决的问题.本文对环境激励下的大跨桥梁响应信号进行了研究,根据环境激励在低频段近于平白噪声以及线性系统在环境激励下,各输出点测量信号之间相关函数与结构的脉冲响应函数具有相同的数学表达式——均是主频正弦函数的叠加这一特点,建立了插值fast Fourier transform(FFT)频谱校正技术分析各测点相关函数的方法.该方法能在白噪声背景下精确提取桥梁振动频率、幅度和相位等模态参数,简单实用,不仅能在线识别参数,而且对桥梁单点激励和多点同时激励均适用.将校正后的主频与三维有限元计算结果相对比,能对桥梁结构整体状态和工作性能进行评估.最后,一座实桥动力试验和计算结果证明了该方法的能有效用于运营条件下桥梁状态的评估.     

基于HHT的结构损伤特征量与异常诊断

Hilbert-Huang Transform(HHT)是一种新的适用于非线性、非平稳信号且具有自适应性的数据处理方法.提出了一种基于HHT的结构损伤识别方法,该方法利用结构动态响应信号的HHT边际谱构造出损伤特征量--模态成分向量,进而定义结构异常指数.通过比较结构同一位置不同状态下模态成分向量的匹配度来识别结构特性变化,实现损伤辨识.数值模拟分析表明,该方法具有有效性和实用性.     

模糊数学评判方法在桥梁结构受损状态评定中的应用

运用模糊数学中的模糊评判方法,建立结构损伤度函数及隶属函数模型,结合专家提供的各评估对象的因素权重,对在役桥梁结构损伤的状态进行模糊综合评判,通过比较桥梁损伤度隶属函数值的大小来确定其对应的受损程度等级.结合实例分析结果表明,糊数学评判方法可以较好地运用于桥梁结构受损状态评判,且其评判结果与中国公路桥梁管理系统(简称CBMS)应用软件计算的结果一致.     

基于小波包能量曲率的环境激励下简支梁损伤识别方法

为了识别环境激励下简支梁的损伤时刻及损伤位置,提出一种基于小波包能量的简支梁损伤识别方法.首先采用小波包技术处理环境激励下健康状态和未知状态的简支梁位移响应时程数据,获得其小波包能量;然后根据各子频带的能量占比筛选出最优频带,并进行归一化处理得到能量曲率;最后以健康状态下的小波包能量曲率计算的损伤识别指标作为参考,对比未知状态下简支梁的损伤识别指标,获得结构中的单点或多点损伤状况,包括损伤时刻、损伤位置和相对损伤程度.简支梁数值模拟结果表明,该方法在信噪比≥40 dB条件下可以准确识别结构的损伤状况.     

基于加速度内积向量和灰云模型的结构损伤识别

为了解决测量噪声等引起的损伤识别不确定性问题,提出了基于加速度内积向量和灰云模型相结合的损伤识别方法。描述了云模型和云发生器的基本理论和公式,计算了结构在随机激励荷载下的加速度响应,并利用互相关函数和二阶差分法构造出加速度内积向量损伤指标,最后,基于灰云模型建立了内积向量和损伤区间的前件云和后件云。考虑随机测量噪声等引起的不确定性,利用多种模式下的加权和均化计算,建立了基于灰云模型的损伤识别方法。数值计算结果表明,所提出的基于灰云模型损伤识别方法,可以较好地进行含噪数据的损伤识别,其识别效果优于单纯的加速度内积向量损伤指标。     

结构非概率-模糊混合可靠性分析方法

研究了非概率不确定性量和模糊变量共存时的结构可靠性问题.以结构极限状态函数和模糊变量隶属函数为条件,基于可能性理论导出了结构的模糊失效域和模糊安全域及其隶属函数,将原混合可靠性问题转化为模糊失效准则下的非概率可靠性问题;在结构非概率可靠性模型的基础上,建立了模糊失效准则下的结构非概率可靠性指标;提出了一般性的非概率不确定性量和模糊变量共存时的结构可靠性分析方法,该方法能同时考虑非概率不确定性波动和模糊变量的可能性分布,更合理地评价结构可靠性.     

运营环境下混凝土简支梁桥裂缝的非线性损伤识别

针对混凝土简支梁桥常见的开裂病害,基于改进的Hilbert-Huang变换(HHT)提出裂缝的非线性损伤识别方法。选取曲率曲线型呼吸裂缝模型并将其融入车桥耦合共振系统,以更真实地模拟运营环境下裂缝的非线性开闭现象。引入镜像延拓法和集合经验模态分解法分别改进传统HHT算法的端点发散和模态混叠问题,提取桥梁加速度响应的能量时程曲线,将能量时程曲线尖峰出现时刻和相对幅值比分别作为损伤定位和定量的特征指标,从而建立简支梁裂缝的非线性损伤识别方法。数值算例表明,采用单一传感器便可通过文中方法识别简支梁开裂的部位和程度,为混凝土简支梁的损伤识别提供技术支撑。     

饮用水源污染风险评价的模糊-随机模型研究

为了综合量化富营养化水体的随机不确定性和模糊不确定性,评价水源污染风险,该文以微囊藻毒素为风险指示物,采用随机数值模拟预报水体中污染物浓度,并用模糊隶属度函数表征污染物的环境质量标准和毒性标准,建立了模糊-随机风险评价模型.针对污染物存在的环境风险、健康风险和生态风险,建立模糊集规则以获取综合风险水平,从而得到风险水平与决策行动的关系.将该模型用于某饮用水源2种不同环境质量标准的情景分析,证明了模型的可行性和有效性.     

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.     

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