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Long-Term Structural Responses of Orifices in Gravity Dams Considering Thermal and Creep Effects

JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES 2016年第3期30卷

作者： Zhang, Sherong Yu, Mao Xiao, Feng Wang, Chao Wang, Gaohui Tianjin Univ State Key Lab Hydraul Engn Simulat & Safety Tianjin 300072 Peoples R China Midsouth Design & Res Inst State Engn Changsha 410004 Hunan Peoples R China Wuhan Univ State Key Lab Water Resources & Hydropower Engn S Wuhan 430072 Peoples R China

A numerical simulation method is presented to analyze the thermal and creep effects on structural performance of orifices in gravity dams during construction and operation period. Time-dependent conditions such as the changes of gravity load and water pressure, the concrete viscoelastic material properties, and the variations of environment temperature are all considered for numerical modeling. Compared temperature results obtained from heat transfer analysis with the monitored data around orifice, proposed model is verified to be a reliable tool for thermal-structural coupling analysis. This paper discusses temperature distributions of orifice concrete surfaces in contact with water or air. Tensile stress evolutions arising from temperature variations are investigated correspondingly. Subsequently, cracking risks of orifice with different environments and locations are calculated to evaluate orifice structural performance. Thermal and creep effects on the distributions of tensile stress and cracking risk are studied simultaneously. Results show that long-term thermal and creep effects play important roles in the structural performance of orifice, and orifice concrete surface in contact with air located at the middle part of the dam has a higher cracking risk than surfaces in contact with air or water close to the upstream or downstream of dam. (C) 2015 American Society of Civil Engineers.

关键词： Gravity dam Orifice Structural performance Thermal effects Creep effects Cracking risk

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Cs₂CO₃-Promoted Carboxylation of N-Tosylhydrazones with Carbon Dioxide toward α-Arylacrylic Acids

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JOURNAL OF ORGANIC CHEMISTRY 2015年第5期80卷 2855-2860页

作者： Sun, Song Yu, Jin-Tao Jiang, Yan Cheng, Jiang Changzhou Univ Sch Petrochem Engn Jiangsu Key Lab Adv Catalyt Mat & Technol Jiangsu Prov Key Lab Fine Petrochem Engn Changzhou 213164 Peoples R China Nanjing Univ State Key Lab Coordinat Chem Nanjing 210093 Jiangsu Peoples R China

A Cs2CO3-promoted carboxylation of N-tosylhydrazones and CO2 has been developed. The reaction proceeded efficiently at 80 degrees C under atmospheric CO2, gave the corresponding a-arylacrylic acids in moderate to good yields. This method was featured with (1) the employment of Cs2CO3 rather than nBuLi as the base;(2) a reaction temperature of 80 degrees C rather than -78 degrees C.

关键词： Column chromatography Silica Ethers Gels Ethyl groups

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Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons

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Chinese Physics B 2015年第2期24卷 302-312页

作者：陈兆权殷志祥夏广庆洪伶俐胡业林刘明海胡希伟 A.A.Kudryavtsev College of Electrical & Information Engineering Anhui University of Science and Technology Faculty of Physics St. Petersburg State University State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient *** plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric *** electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon ***,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric *** addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.

关键词： pulsed microwave discharge surface plasmon polaritons atmospheric argon cold plasma jet distinctive plasma plume patterns

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Hyperspectral image classification based on volumetric texture and dimensionality reduction

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Frontiers of Earth Science 2015年第2期9卷 225-236页

作者： Hongjun SU Yehua SHENG Peijun DU Chen CHEN Kui LIU School of Earth Sciences and Engineering Hohai University Nanjing 210098 China Key Laboratory of Satellite Mapping Technology and Application National Administration of Surveying Mapping and Geoinformation Nanjing University Nanjing 210046 China Key Laboratory of Virtual Geographic Environment (Ministry of Education) Nanjing Normal University Nanjing 210023 China Department of Electrical Engineering the University of Texas at Dallas Richardson TX 75080-3021 USA

A novel approach using volumetric texture and reduced-spectral features is presented for hyperspectral image classification. Using this approach, the volumetric textural fea^res were extracted by volumetric gray-level co-occurrence matrices （VGLCM）. The spectral features were extracted by minimum estimated abundance covar- iance （MEAC） and linear prediction （LP）-based band selection, and a semi-supervised k-means （SKM） cluster- ing method with deleting the worst cluster （SKMd） band- clustering algorithms. Moreover, four feature combination schemes were designed for hyperspectral image classifica- tion by using spectral and textural features. It has been proven that the proposed method using VGLCM outper- forms the gray-level co-occurrence matrices （GLCM） method, and the experimental results indicate that the combination of spectral information with volumetric textural features leads to an improved classification performance in hyperspectral imagery.

关键词： hyperspectral imagery image classification,volumetric textural feature spectral feature fusion

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Dynamic Coordinated Condition-Based Maintenance for Multiple Components With External Conditions

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IEEE TRANSACTIONS ON POWER DELIVERY 2015年第5期30卷 2362-2370页

作者： Wang, Chong Hou, Yunhe Qin, Zhijun Peng, Chaoyi Zhou, Hui Univ Hong Kong Dept Elect & Elect Engn Hong Kong 999077 Hong Kong Peoples R China Zhejiang Power Grid Corp Hangzhou 310007 Zhejiang Peoples R China

This paper proposes a method to establish an optimal dynamic coordinated condition-based maintenance strategy that considers harsh external conditions, for example, harsh weather conditions. Component deterioration is modeled as a Markov process based on physical characteristics, with the effects of harsh external conditions represented as probabilistic models. The proposed model involves interactions between different maintenance strategies on various components, as well as influences on the operation of the entire system. The optimal maintenance strategies are obtained by optimizing the proposed model with the cost to go, including system reliability cost and maintenance cost. This proposed model is solved using a backward induction algorithm associated with a search space reduction approach developed to reduce the simulation time. Two IEEE systems and one actual system validate the proposed model. The results show that this optimal maintenance strategy model that considers harsh external conditions provides insight for scheduling appropriate maintenance activities.

关键词： Backward induction condition-based maintenance coordinated scheduling harsh external conditions Markov decision processes

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Ultra-thin SiC layer covered graphene nanosheets as advanced photocatalysts for hydrogen evolution

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JOURNAL OF MATERIALS CHEMISTRY A 2015年第20期3卷 10999-11005页

作者： Zhou, Xunfu Gao, Qiongzhi Li, Xin Liu, Yingju Zhang, Shengsen Fang, Yueping Li, Jun South China Agr Univ Inst Biomat Coll Mat & Energy Guangzhou 510642 Guangdong Peoples R China Kansas State Univ Dept Chem Manhattan KS 66506 USA

Herein, for the first time, ultra-thin SiC nanoparticles or ultra-thin layer covered graphene nanosheets were successfully prepared via using a facile in situ vapor-solid reaction. The samples were characterized by Xray diffraction, UV-visible spectroscopy, photoluminescence spectra analysis, Raman spectra, transient photocurrent responses and transmission electron microscopy. The photocatalytic activities were also evaluated by H-2 evolution from pure water or water containing Na2S as an electron donor. The resulting SiC-graphene hybrids show enhanced photocatalytic H-2-evolution activities in the presence of an electron donor. Especially, the graphene nanosheet and SiC nanocrystal hybrids show the highest photocatalytic activity in H-2 production under visible light, which is about 10 times higher than that of the SiC nanocrystals. The enhanced activities of the SiC-graphene hybrids can be attributed to their 2D nanosheet structures, large surface area, enhanced visible-light absorption and rapid interfacial charge transfer from SiC to graphene. Our results can provide an effective approach to synthesize graphene-based heterogeneous nanocomposites for a wide variety of potential applications in solar energy conversion and storage, separation, and purification processes.

关键词： Graphene

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Yield of Y, La, Ce in high temperature alloy during electroslag remelting process

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METALLURGICAL RESEARCH & technology 2016年第4期113卷

作者： Ren, Ying Zhang, Lifeng Yu, Le Fang, Wen Univ Sci & Technol Beijing Sch Met & Ecol Engn Beijing 100083 Peoples R China Carnegie Mellon Univ Dept Mat Sci & Engn Ctr Iron & Steelmaking Res Pittsburgh PA 15213 USA Wuhan Iron & Steel Co Ltd Ironmaking Plant Wuhan 430083 Peoples R China 4 CISDI R&D Co Ltd Chongqing 401122 Peoples R China

In the current study, samples of ingots and slags after electroslag remelting (ESR) were analyzed to investigate the reoxidation of the rare earth (Re) metals Y, La and Ce from high temperature alloys during remelting. The yield of Y, La and Ce in high temperature alloys during ESR is enhanced by increasing the concentrations of their oxides in the slag, and by adding CaO to the slag. Alumina in the slag should be avoided during ESR, since Y, La and Ce are easily oxidized by Al2O3, and because Al2O3 lowers the activity of the rare-earth element oxides. The effect of Re2O3, CaO and Al2O3 content in the slag on the activity of Re2O3 was estimated using the Temkin model.

关键词： Electroslag remelting rare earth high temperature alloys thermodynamic calculation

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Dynamical analysis and numerical simulation of bloch chaotic system

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COMPLEXITY 2016年第S2期21卷 201-206页

作者： Zhang, Fuchen Liao, Xiaofeng Zhang, Guangyun Mu, Chunlai Lin, Da Chongqing Technol & Business Univ Coll Math & Stat Chongqing 400067 Peoples R China Southwest Univ Coll Elect & Informat Engn Chongqing 400716 Peoples R China Chongqing Technol & Business Univ Int Business Sch Chongqing 400067 Peoples R China Chongqing Univ Coll Math & Stat Chongqing 401331 Peoples R China Sichuan Univ Sci & Engn Sch Automat & Elect Informat Zigong 643000 Peoples R China

In this article, some dynamics of Bloch chaotic system have been studied. Based on Lagrange multiplier method, optimization theory, and the generalized positively definite and radially unbound Lyapunov functions with respect to the parameters of the system, we derive the ultimate bound and a family of mathematical expressions of globally exponentially attractive sets for this system with respect to the parameters of system. The results obtained in this article provides theory basis for chaotic synchronization, chaotic control, Hausdorff dimension, and Lyapunov dimension of chaotic attractors of Bloch chaotic system. (c) 2016 Wiley Periodicals, Inc. Complexity 21: 201-206, 2016

关键词： Bloch chaotic system chaotic attractor Lyapunov stability Lagrange multiplier method optimization theory

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Synthesis and Characterization of Polybenzimidazole/α-Zirconium Phosphate Composites as Proton Exchange Membrane

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POLYMER engineering AND SCIENCE 2016年第6期56卷 622-628页

作者： Zhang, Qi Liu, Hui Li, Xun Xu, Rong Zhong, Jing Chen, Ruoyu Gu, Xuehong Changzhou Univ Jiangsu Key Lab Adv Catalyt Mat & Technol Sch Petrochem Engn Changzhou 213164 Jiangsu Peoples R China Nanjing Univ Technol State Key Lab Mat Oriented Chem Engn Nanjing 210009 Peoples R China

To improve the high-temperature performance of proton exchange membranes, the polybenzimidazole (PBI)/alpha-zirconium phosphate (alpha-Zr(HPO4)(2)center dot nH(2)O, alpha-ZrP) proton exchange composite membranes were prepared in this study. PBI polymer containing a large amount of ether units has been synthesized from 3,30-diaminobenzidine (DAB) and 4,40-oxybis (benzoic acid) by a direct polycondensation in polyphosphoric acid. The polymer exhibited a good solubility in most polar solvents. Inorganic proton conductor alpha-ZrP nanoparticles have been obtained using a synthesis route involving separate nucleation and aging steps (SNAS). The effects of alpha-ZrP doping content on the composite membrane performance were investigated. It was found that the introduction of ZrP improved the thermal stability of the composite membranes. The PBI/ZrP composite membranes exhibited excellent mechanical strength. The composite membrane with 10 wt% ZrP showed the highest proton conductivity of 0.192 S cm(-1) at 160 degrees C under anhydrous condition. The proton conducting mechanism of the PBI/ZrP composite membranes was proposed to explain the proton transport phenomena. The experimental results suggested that the PBI/ZrP composite membranes may be a promising polymer electrolyte used in high temperature proton exchange membrane fuel cells (HT-PEMFCs) under anhydrous condition. (C) 2016 Society of Plastics Engineers

关键词： Composite membranes

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Graph clustering by congruency approximation

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IET COMPUTER VISION 2015年第6期9卷 841-849页

作者： Ren, Weiya Li, Guohui Tu, Dan Natl Univ Def Technol Coll Informat Syst & Management Changsha 410073 Hunan Peoples R China

The authors consider the general problem of graph clustering. Graph clustering manipulates the graph-based data structure and the entries of the solution vectors are only allowed to take non-negative discrete values. Finding the optimal solution is NP-hard, so relaxations are usually considered. Spectral clustering retains the orthogonality rigorously but ignores the non-negativity and discreteness of the solution. Sym non-negative matrix factorisation can retain the non-negativity rigorously but it is hard to reach the orthogonality. In this study, they proposed a novel method named congruent approximate graph clustering (CAC), which can retain the non-negativity rigorously and can reach the orthogonality properly by congruency approximation. Furthermore, the solution obtained by CAC is sparse, which is approximate with the ideal discrete solution. Experimental results on several real image benchmark datasets indicate that CAC achieves encouraging results compared with state-of-the-art methods.

关键词： graph theory pattern clustering computational complexity matrix decomposition congruency approximation graph-based data structure solution vectors nonnegative discrete values NP-hard optimal solution spectral clustering nonnegative matrix factorisation congruent approximate graph clustering CAC ideal discrete solution real image benchmark datasets

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