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Three-dimensional analysis of micro defect morphologies in cement-based materials using focused ion beam tomography

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Science China(Technological Sciences) 2012年第6期55卷 1539-1544页

作者： wan KeShu SUN Wei tang ChunKai RONG ZhiDan Jiangsu Key Laboratory of Construction Materials Nanjing 211189China School of Materials Science and Engineering Southeast UniversityNanjing 211189China

Although there has been much research of cracks of the cement-based materials using optical and electron microscopy two-dimensional (2D) imaging methods, the real three-dimensional (3D) crack shapes have not previously been revealed. Thanks to the focused ion beam (FIB) tomography and the follow-up image processing, two 3D subsurface cracks and a cluster of inner cracks were picked out and discussed in this research. It was found that the subsurface crack (its length is about 15 part, width about 1-5 prn, and opening about 1 ~tm) was much larger than the inner crack (its length and width are about 1-5 pro, opening is from 200 nm to 1 pan), which arose from the sample preparation process. Besides, it was revealed that most of the inner cracks were in the form of clusters.

关键词： focused ion beam (FIB) microstructure crack cement-based materials tomography

Carboxyl-modified hierarchical wrinkled mesoporous silica supported TiO2 nanocomposite particles with excellent photocatalytic performances

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Progress in Natural Science:Materials International 2018年第6期28卷 683-688页

作者： Xuejuan wan Haoqi Ke Guanghui yang Jiaoning tang Shenzhen Key Laboratory of Polymer Science and Technology College of Materials Science and Engineering Shenzhen University

Titanium dioxide（TiO2） is a common photocatalyst for organic pollutants degradation. However, in practical application, the poor adsorption capacity of pure TiO2seriously impeded its efficiency in the degradation of organic molecules. In this work, a series of hierarchical wrinkle mesoporous silica supported TiO2nano-composite particles（TiO2@WMS-COOH） were successfully prepared. Thanks to their high surface areas, large pore volumes and mesoporous structures, these materials showed high adsorption capacity and excellent photocatalytic performance towards dye molecules, which is comparable to or even better than commercial catalyst P25. Moreover, their photocatalytic efficiency can be further enhanced by increasing the calcination temperature during preparation process. Therefore it can be concluded that the TiO2@WMS-COOH particles may find promising applications in the photodegradation of organic pollutants.

关键词： Hierarchical wrinkled mesoporous silica Titanium dioxide Photocatalytic performance Organic pollutants

Study of the pressure transient behavior of directional wells considering the effect of non-uniform flux distribution

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Petroleum Science 2024年第3期21卷 1765-1779页

作者： yan-Zhong Liang Bai-Lu Teng wan-Jing Luo School of Energy Resources China University of Geosciences(Beijing)Beijing100083China

During the production,the fluid in the vicinity of the directional well enters the wellbore with different rates,leading to non-uniform flux distribution along the directional ***,in all existing studies,it is oversimplified to a uniform flux distribution,which can result in inaccurate results for field ***,this paper proposes a semi-analytical model of a directional well based on the assumption of non-uniform flux ***,the direction well is discretized into a carefully chosen series of linear sources,such that the complex well trajectory can be captured and the nonuniform flux distribution along the wellbore can be considered to model the three-dimensional flow *** using the finite difference method,we can obtain the numerical solutions of the transient flow within the *** the aid of Green's function method,we can obtain the analytical solutions of the transient flow from the matrix to the *** complete flow behavior of a directional well is perfectly represented by coupling the above two types of transient ***,on the basis of the proposed model,we conduct a comprehensive analysis of the pressure transient behavior of a directional *** computation results show that the flux variation along the direction well has a significant effect on pressure *** addition,the directional well in an infinite reservoir may exhibit the following flow regimes:wellbore afterflow,transition flow,inclined radial flow,elliptical flow,horizontal linear flow,and horizontal radial *** horizontal linear flow can be observed only if the formation thickness is much smaller than the well ***,a dip region that appears on the pressure derivative curve indicates the three-dimensional flow behavior near the wellbore.

关键词： Directional well Pressure transient behavior Semi-analytical model Non-uniform flux

Studies on the influence of spar position on aeroelastic optimization of a large aircraft wing

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Science China(Technological Sciences) 2012年第1期55卷 117-124页

作者： wan ZhiQiang LIU DongYue tang ChangHong yanG Chao School of Aeronautic Science and Engineering Beihang University Beijing 100191 China

Aeroelastic problems are encountered at the preliminary design stage of flexible wings for large aircraft. A three-dimensional finite element model of a high-aspect-ratio wing was built, and the influence of the front and rear spar positions on the results of the aeroelastic analysis and optimization was studied to improve the wing structure desgin. The most feasible and optimal solutions were effectively obtained by aeroelastic optimization. In particular, the position parameter of the front spar has a greater influence on the aeroelastic analysis and optimization than the rear spar. In addition, some key constraints became re- strictive leading to a rapid increase in the structural weight. Therefore, reasonable constraints were necessary for the optimization of results.

关键词： large aircraft aeroelasticity optimization design high-aspect-ratio wing spar

Photo-grafting Poly(acrylic acid) onto Poly(lactic acid) Chains in Solution

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Chinese Journal of Polymer Science 2020年第2期38卷 137-142,I0005页

作者： Jia-Xing wang yan-Bin Huang wan-Tai yang Department of Chemical Engineering Tsinghua University

Poly(lactic acid)(PLA)is one of the most important bio-plastics,and chemical modification of the already-polymerized poly(lactic acid)chains may enable optimization of its material properties and expand its application *** this study,we demonstrated that poly(lactic acid)can be readily dissolved in acrylic acid at room temperature,and acrylic acid can be graft-polymerized onto poly(lactic acid)chains in solution with the help of photoinitiator benzophenone under 254 nm ultraviolet(UV)*** photo-grafting polymerization of acrylic acid(PAA)has only been studied before in the surface modification of polymer *** graft ratio could be controlled by various reaction parameters,including irradiation time,benzophenone content,and monomer/polymer *** photo-grafting reaction resulted in high graft ratio(graft ratio PAA/PLA up to 180%)without formation of homopolymers of acrylic *** the PAA/PLA graft ratio was higher than 100%,the resulting PLA-g-PAA polymer was found dispersible in *** pros and cons of the photo-grafting reaction were also discussed.

关键词： Photo-grafting Polymer modification Poly(acrylic acid) Poly(lactic acid)

Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at *** Observatory(China)

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Particuology 2015年第3期13卷 24-31页

作者： Xiangdong Zheng Chengde Shen Guojiang wan Jie tang Kexin Liu Key Laboratory of Atmospheric Chemistry Chinese Academy of Meteorological Sciences State Key Laboratory of Isotope Geochronology and Geochemistry Guangzhou Institute of GeochemistryChinese Academy of Sciences State Key Laboratory of Environment Geochemistry Institute of GeochemistryChinese Academy of Sciences Center of Meteorological Sounding Chinese Meteorological Administration State Key Laboratory of Nuclear Physics and Technology and Institute of Heavy Ion Physics Peking University

Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan （WLG） site. The overall average WlRC mass concentration was （1183 ± 120）ng/m3 （n = 79）, while seasonal averages were 2081 ± 1707 （spring）, 454±205 （summer）, 650 ±411 （autumn）, and 1019 ± 703 （winter） ng/m3. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ13C PDB value （-25.3 ± 0.8）%0 determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion. No seasonal change in δ13C PDB was evident. The average percent Modern Carbon （pMC） for 14C in WIRC for winter and spring was （67.2 ± 7.7）% （n = 29）. Lower pMC values were associated with air masses trans- ported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.

关键词： Water-insoluble refractory carbon (WIRC)Mass concentration813C14CMt. Waliguan (WLG)

Distributional Chaos Occurring on the Set of Proper Positive Upper Banach Density Recurrent Points of One-sided Symbolic Systems

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Acta Mathematica Sinica,English Series 2020年第1期36卷 66-76页

作者： yan Jie tang Jian Dong YIN Department of Mathematics Nanchang University

The purpose of this paper is to show that for one-sided symbolic systems,there exists an uncountable distributionally scrambled set contained in the set of proper positive upper Banach density recurrent points.

关键词： Distributional chaos positive upper Banach density recurrent point one-sided symbolic system

Adsorption of 2-mercaptobenzothiazole from aqueous solution by organo-bentonite

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Journal of Environmental Sciences 2013年第6期25卷 1139-1144页

作者： Ping Jing Meifang Hou Ping Zhao Xiaoyan tang Hongfu wan South China Botanical Garden Chinese Academy of Sciences Graduate School of Chinese Academy of Sciences School of Ecological Technology and Engineering Shanghai Institute of Technology Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control Guangdong Institute of Eco-environmental and Soil Sciences

The adsorption behavior of 2-mercaptobenzothiazole onto organo-bentonite was investigated. Natural bentonite from Gaozhou in Guangdong Province, China was collected. Organo-bentonite was prepared by intercalation of cetyltrimethyl ammonium bromide into the natural bentonite. The physicochemical properties of the prepared organo-bentonite were characterized by X-ray diffraction, N2 adsorption-desorption isotherm and Fourier transform infrared spectroscopy. The results showed that montmorillonite is the main component of the natural bentonite. The basal spacing of the natural bentonite is 1.47 nm, which increased to 1.98 nm on intercalation with cetyltrimethyl ammonium bromide. Moreover, both the surface area and pore volume increased with intercalation. Clear CH2 stretching （3000-2800 cm-1） and scissoring （1480-1450 cm-1） modes of the intercalated surfactants were observed for organo- bentonite. Compared with the pseudo first-order kinetic model, the pseudo second-order kinetic model is more suitable to describe the adsorption kinetics of 2-mercaptobenzothiazole onto organo-bentonite. The adsorption capacity of 2-mercaptobenzothiazole onto organo-bentonite increased with increasing initial concentration of 2-mercaptobenzothiazole, but decreased with increasing adsorbent dosage. The adsorption isotherm of 2-mercaptobenzothiazole onto organo-bentonite fits well with the Langmuir model. The maximum adsorption capacity of organo-bentonite for 2-mercaptobenzothiazole was 33.61 mg/g, indicating that organo-bentonite is a promising adsorbent for 2-mercaptobenzothiazole.

关键词： 2-mercaptobenzothiazole bentonite intercalation adsorption

Performance evaluation from stochastic statecharts representation of flexible reactive systems:a simulation approach

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Journal of Systems Engineering and Electronics 2014年第1期25卷 150-157页

作者： Junqiao Li Jun tang Shuang wan Wenbo Zhou Jianfeng Xu Department of Electronic Engineering Tsinghua University Key Lab of Underwater Acoustic Countermeasure China Electronic Science Research Institute

This paper focuses on the performance analysis of flexible reactive systems. The performance analysis consists of two phases： first system modeling, second performance evalua-tion. The paper models the flexible reactive system by the stochas-tic statecharts method, and uses the simulation method to evalu-ate the performance. To make use of the feature of event-triggered state transitions in the statecharts, a new method of simulation is proposed based on the techniques of the discrete-event system simulation. The new method solves the problem of computer imple-mentation of stochastic events, probabilistic transition, concurrent states, paral el actions, and broadcast communication mechanism in the stochastic statecharts. An example of a flexible manufactur-ing system is presented. The simulation result of the example is consistent with the analytical result, which shows the feasibility of the proposed new simulation method.

关键词： performance analysis stochastic statecharts simulation approach flexible reactive systems.