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Three-scale stochastic homogenization of elastic recycled aggregate concrete based on nano-indentation digital images

Chen WANG, Yuching WU, Jianzhuang XIAO

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 461-473 doi: 10.1007/s11709-017-0441-7

摘要： In this paper, three-scale stochastic elastic finite element analyses are made for recycled aggregate concrete (RAC) based on nano-indentation digital images. The elastic property of RAC contains uncertainties across scales. It has both theoretical and practical values to model and predict its mechanical performance. Based on homogenization theory, effective stochastic elastic moduli of RAC at three different scales are obtained using moving window technique, nano-indentation digital images, and Monte-Carlo method. It involves the generation of a large number of random realizations of microstructure geometry based on different volume fraction of the inclusions and other parameters. The mean value, coefficient of variation and probability distribution of the effective elastic moduli are computed considering the material multiscale structure. The microscopic randomness is taken into account, and correlations of RAC among five phases are investigated. The effective elastic properties are used to obtain the global behavior of a composite structure. It is indicated that the response variability can be considerably affected by replacement percentage of recycled aggregates.

关键词： RAC nano-indentation digital image multiscale microscopic randomness homogenization

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气体多孔电极反应微观机理及宏观现象的研究

朱梅,徐献芝,杨基明

《中国工程科学》 2005年第7卷第5期页码 79-83

摘要：

提出多孔电极研究的新思路、新方法，探索电极反应的微观机理及宏观现象，试图为制造高效多孔电极提供理论参考。通过锌空气电池实验对比了立式多孔碳电极相对于传统多孔碳电极在放电中的优点。通过实验观察了三相界面的形成形态随时间变化的3个宏观过程，根据3个宏观过程对应的电化学过程定义了电极反应中所形成的2种有代表性的三相界面。分析了电解液在多孔电极中运动的微观机理并得出理想突变界面是气体电极的最佳工作状态的结论。

关键词：多孔电极三相界面锌空气电池

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Aerobic granulation of pure bacterial strain

ADAV Sunil S., LEE Duu-Jong

《环境科学与工程前沿（英文）》 2008年第2卷第4期页码 461-467 doi: 10.1007/s11783-008-0066-0

摘要： The objective of this study is to cultivate aerobic granules by pure bacterial strain, , in a sequencing batch reactor. Stable granules sized 2.0–2.2 mm were formed in the reactor after a five-week cultivation. These granules exhibited excellent settling attributes, and degraded phenol at rates of 1.49 and 1.19 g phenol/(g VSS·d) at 250 and 1500 mg/L of phenol concentration, respectively. Confocal laser scanning microscopic test results show that was distributed over the initial small aggregates, and the outer edge of the granule was away from the core regime in the following stage.

关键词： following excellent settling phenol/ sequencing microscopic

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Molecular dynamic simulation on the conformation of mouse muscle type nAChR

Shengai SUN, Rilei YU, Yanhui ZHANG, Yanni LI,

《化学科学与工程前沿（英文）》 2010年第4卷第3期页码 348-352 doi: 10.1007/s11705-009-0284-4

摘要： A mouse muscle type nAChR model ((α1)βδγ) was built based on the cryoelectron microscopic structure of intact nAChR and the high resolution crystal structure of nAChR-α1 subunit. The conformation of the pentameric nAChR model was investigated by molecular dynamic simulation. The function of water molecule in the hydrophilic interior was clarified. The reason for Tyr127 showing two alternative conformations was discussed in detail.

关键词： pentameric hydrophilic Tyr127 cryoelectron microscopic conformation

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A solution to stochastic unit commitment problem for a wind-thermal system coordination

B. SARAVANAN,Shreya MISHRA,Debrupa NAG

《能源前沿（英文）》 2014年第8卷第2期页码 192-200 doi: 10.1007/s11708-014-0306-x

摘要： Unit commitment (UC) problem is one of the most important decision making problems in power system. In this paper the UC problem is solved by considering it as a real time problem by adding stochasticity in the generation side because of wind-thermal co-ordination system as well as stochasticity in the load side by incorporating the randomness of the load. The most important issue that needs to be addressed is the achievement of an economic unit commitment solution after solving UC as a real time problem. This paper proposes a hybrid approach to solve the stochastic unit commitment problem considering the volatile nature of wind and formulating the UC problem as a chance constrained problem in which the load is met with high probability over the entire time period.

关键词： unit commitment (UC) randomness wind generation univariate chance constrained

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Analysis of behavior of melted dark green silty soil

TANG Yiqun, ZHOU Nianqing, YANG Ping, SHEN Feng

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 242-245 doi: 10.1007/s11709-008-0022-x

摘要： The behavior of dark green silty soil of the 6th storey is studied by means of scanning electron microscopy (SEM). The shape, size and contact condition of the basic elements of the soil microstructure, and the shape and the size of the pore are further studied. In addition, a comparative study is made to analyze the experiment results of Cu and dynamic test. The mechanic characteristics of common soil and those of melted soil are presented and their influences on dark silty soil after being frozen are theoretically illustrated from a microscopic perspective.

关键词： electron microscopy mechanic microscopic perspective addition dynamic

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Stochastic analysis of laminated composite plate considering stochastic homogenization problem

S. SAKATA,K. OKUDA,K. IKEDA

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 141-153 doi: 10.1007/s11709-014-0286-2

摘要： This paper discusses a multiscale stochastic analysis of a laminated composite plate consisting of unidirectional fiber reinforced composite laminae. In particular, influence of a microscopic random variation of the elastic properties of component materials on mechanical properties of the laminated plate is investigated. Laminated composites are widely used in civil engineering, and therefore multiscale stochastic analysis of laminated composites should be performed for reliability evaluation of a composite civil structure. This study deals with the stochastic response of a laminated composite plate against the microscopic random variation in addition to a random variation of fiber orientation in each lamina, and stochastic properties of the mechanical responses of the laminated plate is investigated. Halpin-Tsai formula and the homogenization theory-based finite element analysis are employed for estimation of effective elastic properties of lamina, and the classical laminate theory is employed for analysis of a laminated plate. The Monte-Carlo simulation and the first-order second moment method with sensitivity analysis are employed for the stochastic analysis. From the numerical results, importance of the multiscale stochastic analysis for reliability evaluation of a laminated composite structure and applicability of the sensitivity-based approach are discussed.

关键词： stochastic homogenization multiscale stochastic analysis microscopic random variation laminated composite plate

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Reliability and variance-based sensitivity analysis of arch dams during construction and reservoir impoundment

M. Houshmand KHANEGHAHI, M. ALEMBAGHERI, N. SOLTANI

《结构与土木工程前沿（英文）》 2019年第13卷第3期页码 526-541 doi: 10.1007/s11709-018-0495-1

摘要： The static performance of arch dams during construction and reservoir impoundment is assessed taking into account the effects of uncertainties presented in the model properties as well as the loading conditions. Dez arch dam is chosen as the case study; it is modeled along with its rock foundation using the finite element method considering the stage construction. Since previous studies concentrated on simplified models and approaches, comprehensive study of the arch dam model along with efficient and state-of-the-art uncertainty methods are incorporated in this investigation. The reliability method is performed to assess the safety level and the sensitivity analyses for identifying critical input factors and their interaction effects on the response of the dam. Global sensitivity analysis based on improved Latin hypercube sampling is employed in this study to indicate the influence of each random variable and their interaction on variance of the responses. Four levels of model advancement are considered for the dam-foundation system: 1) Monolithic dam without any joint founded on the homogeneous rock foundation, 2) monolithic dam founded on the inhomogeneous foundation including soft rock layers, 3) jointed dam including the peripheral and contraction joints founded on the homogeneous foundation, and 4) jointed dam founded on the inhomogeneous foundation. For each model, proper performance indices are defined through limit-state functions. In this manner, the effects of input parameters in each performance level of the dam are investigated. The outcome of this study is defining the importance of input factors in each stage and model based on the variance of the dam response. Moreover, the results of sampling are computed in order to assess the safety level of the dam in miscellaneous loading and modeling conditions.

关键词： concrete arch dams reliability randomness improved Latin hypercube sampling variance-based sensitivity analysis exceedance probability Sobol′ index

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超光速研究中的几个理论问题

黄志洵,耿天明

《中国工程科学》 2007年第9卷第4期页码 6-17

摘要：

宇宙早期的强子时期，光速比c大，实际上可达v＝75c。故光速随时间缓慢减小，从v降低到今天的值（c）。另一方面，根据对128个类星体吸收线的测量，在过去的6～12Ga期间，精细结构常数α平均增大了6×10^－6，科学家们认为可能是光速变化造成的。对上述效应进行研究以了解宇宙的过去是有趣的。还深入讨论了超光速研究中的一些问题———微观粒子速度的定义，引力速度，量子纠缠态作用速度以及超距作用。对这些概念有了更准确的理解。

关键词：可变光速超光速微观粒子速度引力速度量子纠缠态作用速度超距作用