Axial Strain Accelerations Approach for Damage Localization in Statically Determinate Truss Structures

This work proposes an efficient and reliable method for damage localization in truss structures. The damage is localized on the basis of measured acceleration signals of the structure followed by simple statistical signal processing. It has three main advantages over many existing methods. First, it can be directly applied to real engineering structures without the need of identifying modal parameters or solving any global optimization problem. Second, the proposed method has higher sensitivity to damage than some other frequently used methods and allows to localize damage as small as a few percentages. Third, it is a model‐free method, which does not require precise finite element model development or updating. Validation of the method has been conducted on numerical examples and laboratory‐scale trusses. Two types of frequently used trusses have been selected for this study, namely, Howe and Bailey trusses. The presented experimental validation of the method shows its efficiency and robustness for damage localization in truss structures.     

基于均匀设计法的碳纳米管纳米流体稳定性

研究碳纳米管质量分数、分散剂质量分数、pH值和超声振荡时间对碳纳米管纳米流体稳定性的交互影响和定量影响.配置12个碳纳米管纳米流体样品,测定各样品的Zeta电位值.样品的4因素取值通过均匀设计法确定,稳定性用Zeta电位表征.采用二次多项式逐步回归法处理数据,建立碳纳米管纳米流体稳定性与4个因素之间的回归模型.由模型分析可知,该4因素对碳纳米管纳米流体稳定性的影响是相互约束的.当超声振荡时间>3.411 h时,碳纳米管纳米流体的稳定性与碳纳米管质量分数正相关;当超声振荡时间<3.411 h时,碳纳米管纳米流体的稳定性与碳纳米管质量分数负相关.     

突出矿井掘进工作面瓦斯渗流模型及数值模拟

为了掌握挂耳钻场抽采影响下掘进巷道瓦斯涌出情况,指导矿井的巷道掘进工作,建立了综合考虑解吸、渗流、扩散、Klinkenberg效应的瓦斯运移数学模型,利用数值模拟软件对挂耳钻场瓦斯流动规律进行了数值分析。结果表明,随着抽采时间的增加,钻孔影响范围逐渐增大,钻场周围煤体瓦斯压力的变化与钻孔间距有直接关系,采用挂耳钻场的瓦斯抽采方式能够有效降低巷道暴露煤壁的瓦斯涌出量。     

钢框架-防屈曲开斜槽耗能钢板剪力墙装配式结构体系抗震性能分析

防屈曲开斜槽耗能钢板剪力墙(简称开斜槽钢板墙)是一种新提出的抗侧力构件,相比于普通钢板剪力墙,具有多个可调参数、耗能稳定且延性好的优点,并可作为装配式单元,通过组装单元的方式形成装配式剪力墙结构,进一步形成不同的装配式抗侧力体系。本文介绍了钢框架-开斜槽钢板墙装配式结构体系,包括开斜槽钢板墙设计方法,装配式剪力墙结构以及结构体系设计方法,并以20层办公大楼为例进行设计,对结构在小震和大震下的抗震性能进行分析。计算结果表明,开斜槽钢板墙可提供较大的抗侧刚度,能充分发挥耗能作用,保护主体结构安全,符合双重抗侧力体系的原则,该结构体系具有优越的抗震性能。     

水驱油田含水率预测方法研究及拓展

在新型油相相对渗透率曲线的基础上,结合物质平衡方程和Welge方程,导出了一种新型含水率预测模型,并在一定条件下可转化得到Logistic模型。新型含水率预测模型中待定系数与开发动态和地质静态参数变化关系明确,使得许多控水措施更具理论支持。同时,针对目前已有油水相渗曲线与Welge方程结合还无法得到Logistic模型、Goempertz模型以及Usher模型的问题,以及新模型推理过程中要保持开井数不变等条件限制,提出了联解法和直接法建立含水率预测模型。通过两种方法拓展,使得含水率预测模型丰富、多样,能够完全满足描述复杂多样的油田含水率与时间变化过程。后经实例应用,效果较好,值得其他油田借鉴。     

PeriScope随钻成像测井技术在水平井中的应用

PeriScope随钻成像测井仪是近年来在水平井随钻实时应用中非常成功的成像测井仪器,对水平井、复杂油气藏及薄层储层开发具有非常积极的作用。该技术在南美奥连特盆地K高含水油田利用水平井开发剩余油实践中,通过精细油藏描述研究,结合随钻测井技术,成功的完成16口水平井钻井,在油田开发中取得了非常理想的效果。通过K-11H水平井的实际钻探介绍了该仪器的实际应用。     

启发式教学法在"管理学"教学中的应用

启发式教学方法在不同科目和层次的课程中,其具体方法是多样的.本文认为在"管理学"的教学中,根据课程的特点可以采用诱导、讨论,案例以及课堂模拟等方法来迟到启发式教学的良好效果.     

Stress‐strain characteristics of the Taipei silty clay at small strain

Abstract

This study first developed a triaxial apparatus with the capability of small‐strain measurement. Then a series of undrained triaxial tests were carried out to investigate the stress‐strain behavior of the reconstituted Taipei silty clay at small strain. Test results show that the non‐linear behavior of the normally consolidated Taipei silty clay at small strain (?=10^–5～10^–3) is significant irrespective of the initial effective stress state and the shearing rate. The peak deviator stress occurs at strain of 10^–3～4×10^–3. The normalized initial elastic stiffness at strain of 10^–5 can reach 1600～2450, which is much higher than that measured by conventional triaxial tests.     

Classification of modulated signals using multifractal features

Abstract

In this paper we develop a novel modulation classification scheme based on multifractal dimensions. Theoretic analysis demonstrates that these features are robust to noise interference, and simulation results indicate the proposed scheme can classify modulated types accurately in a large range of SNR variation.