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Chemical composition and formation mechanisms in the cathode-electrolyte interface layer of lithium manganese oxide batteries from reactive force field （ReaxFF） based molecular dynamics

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Frontiers in Energy 2017年第3期11卷 365-373页

作者： Sahithya REDDIVARI Christian LASTOSKIE Ruofei wu Junliang ZHANG Perimeter College Georgia State University Clarkston GA 30021 USA Department of Civil and Environmental Engineering University of Michigan Ann Arbor MI 48109-2125 USA Institute of Fuel Cells MOE Key Laboratory of Power & Machinery Engineering Shanghai Jiao Tong University Shanghai 200240 China

Lithium manganese oxide （LiMn2O4） is a principal cathode material for high power and high energy density electrochemical storage on account of its low cost, non-toxicity, and ease of preparation relative to other cathode materials. However, there are well-documented problems with capacity fade of lithium ion batteries containing LiMn2O4. Experimental observations indicate that the manganese content of the electrolyte increases as an electrochemical cell containing LiMn2O4 ages, suggesting that active material loss by dissolution of divalent manganese from the LiMn2O4 surface is the primary reason for reduced cell life in LiMn2O4 batteries. To improve the retention of manganese in the active material, it is key to understand the reactions that occur at the cathode surface. Although a thin layer of electrolyte decomposition products is known to form at the cathode surface, the speciation and reaction mechanisms of Mn^2＋ in this interface layer are not yet well understood. To bridge this knowledge gap, reactive force field （ReaxFF） based molecular dynamics was applied to investigate the reactions occurring at the LiMn2O4 cathode surface and the mechanisms that lead to manganese dissolution. The ReaxFFMD simulations reveal that the cathode-electrolyte interface layer is composed of oxida- tion products of electrolyte solvent molecules including aldehydes, esters, alcohols, polycarbonates, and organic radicals. The oxidation reaction pathways for the electro- lyre solvent molecules involve the formation of surface hydroxyl species that react with exposed manganese atoms on the cathode surface. The presence of hydrogen fluoride （HF） induces formation of inorganic metal fluorides and surface hydroxyl species. Reaction products predicted by ReaxFF-based MD are in agreement with experimentally identified cathode-electrolyte interface compounds. An overall cathode-electrolyte interface reaction scheme is proposed based on the molecular simulation results.

关键词： lithium manganese oxide batteries reactiveforce field (ReaxFF) cathode-electrolyte interface layer,molecular dynamics

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Nucleate pool boiling heat transfer measurements of HFC23/CFC13 system

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Journal of Thermal Science 2007年第4期16卷 370-375页

作者： Liqiang ZHANG Maoqiong GONG Jianfeng wu Lie XU Institute of Refrigeration and Cryogenics Shanghai Jiao Tong University Shanghai 200030 China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100080 China

Nucleate pool boiling heat transfer data of the HFC23/CFC13 system have been systematically measured in a wide range of pressures and heat fluxes. The experimental results are also compared with the measured data of R508A and R508B. It is found that the heat transfer coefficient of R503 （HFC23/CFC13=0.511/0.489） is higher than that of R508A and R508B. Furthermore, the measured data were compared with the predicted results with three well-known correlations. Correlation by Fujita and Tsutsui can provide acceptable results. Most of the data fall within ±20% of this correlation.

关键词： heat transfer pool boiling azeotropic system refrigerant mixtures.

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Aerodynamic Performance of a Flapping Foil with Asymmetric Heaving Motion near a Wall

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Journal of Bionic Engineering 2018年第4期15卷 636-646页

作者： Xingjian Lin Shuhao Guo Jie wu Jingwen Nan Department of Aerodynamics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The effect of asymmetric heaving motion on the aerodynamic performance of a two-dimensional flapping foil near a wall is studied numerically. The foil executes the heaving and pitching motion simultaneously. When the heaving motion is symmetric, the mean thrust coefficient monotonically increases with the decrease in mean distance between foil and wall. Meanwhile, the mean lift coefficient first increases and then decreases sharply. In addition, the negative mean lift coefficient appears when the foil is very close to the wall. After the introduction of asymmetric heaving motion, the influence of wall effect on the force behavior becomes complicated. The mean thrust coefficient is enhanced when the duration of upstroke is reduced. Moreover, more and more enhancement can be achieved when the foil approaches the wall gradually. On the other hand, the positive mean lift coefficient can be observed when the duration of downstroke is shortened. By checking the flow patterns around the foil, it is shown that the interaction between the vortex shed from the foil and the wall can greatly modify the pressure distribution along the foil surface. The results obtained here might be utilized to optimize the kinematics of the Micro Aerial Vehicles （MAVs） flying near a solid wall.

关键词： asymmetric heaving motion wall effect thrust enhancement positive mean lift

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Poincaréand Logarithmic Sobolev Inequalities for Nearly Radial Measures

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Acta Mathematica Sinica,English Series 2022年第8期38卷 1377-1398页

作者： Patrick CATTIAUX Arnaud GUILLIN Li Ming wu Institut de Mathématiques de Toulouse CNRS UMR 5219UniversitéPaul Sabatier118 Route de NarbonneF-31062 Toulouse Cedex 09 Laboratoire de Mathématiques Blaise Pascal CNRS UMR 6620UniversitéClermont-AuvergneAvenue des LandaisF-63177 Aubiere

Poincaréinequality has been studied by Bobkov for radial measures,but few are known about the logarithmic Sobolev inequality in the radial *** try to fill this gap here using different methods:Bobkov's argument and super-Poincaréinequalities,direct approach via L_(1)-logarithmic Sobolev *** also give various examples where the obtained bounds are quite *** bounds obtained by Lee–Vempala in the log-concave bounded case are refined for radial measures.

关键词： Radial measure log-concave measure Poincaréinequality logarithmic Sobolev inequality super-Poincaréinequality

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Ta-doped modified Gd2O3 film for a novel high k gate dielectric

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Journal of Materials Science & Technology 2019年第10期35卷 2305-2311页

作者： Shuan Li Yanqing wu Guoling Li Hongen Yu Kai Fu Yong wu Jie Zheng Wenhuai Tian Xingguo Li Department of Materials Physics and Chemistry University of Science and Technology BeijingBeijing 100083China Beijing National Laboratory of Molecular Sciences State Key Laboratory of Rare Earth Materials Chemistry and ApplicationsCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China College of Materials Science and Engineering Qingdao UniversityQingdao 266071China

Gadolinium oxide(Gd2O3) film has potential as a candidate gate dielectric to replace Hf O2. In this work,we provide a simple method by trace Ta(~1%) doping to significantly improve the dielectric properties of Gd2O3 film. And effects of annealing temperatures of Ta-doped Gd2O3(GTO) films are investigated in detail. Results show that GTO film annealed at 500℃ exhibits excellent performance as a novel gate dielectric material for integrated circuit, showing a small surface roughness of 0.199 nm, a large band gap of 5.45 e V, a high dielectric constant(k) of 21.2 and a low leakage current density(Jg) of 2.10 × 10^-3A/cm^*** properties of GTO films are superior to pure Gd2O3 films and these GTO films meet the requirements for next-generation gate dielectrics. In addition, impedance spectrum is first used to analyze the equivalent circuit of GTO based metal-oxide-semiconductor(MOS) capacitors, which represents a new insight to understand observed electrical behaviors.

关键词： Rare earth oxides High k film Magnetron sputtering Annealing temperature Gate dielectrics

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Double-cycle weighted imputation method for wastewater treatment process data with multiple missing patterns

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Science China(Technological Sciences) 2022年第12期65卷 2967-2978页

作者： HAN HongGui SUN MeiTing wu XiaoLong LI FangYu Faculty of Information Technology Beijing University of TechnologyBeijing 100124China Beijing Key Laboratory of Computational Intelligence and Intelligent System Beijing 100124China Engineering Research Center of Digital Community Ministry of EducationBeijing 100124China

Due to sensor malfunctions and communication faults,multiple missing patterns frequently happen in wastewater treatment process(WWTP).Nevertheless,the existing missing data imputation works cannot stand multiple missing patterns because they have not sufficiently utilized of data *** this article,a double-cycle weighted imputation(DCWI)method is proposed to deal with multiple missing patterns by maximizing the utilization of the available information in variables and *** proposed DCWI is comprised of two components:a double-cycle-based imputation sorting and a weighted K nearest neighbor-based imputation ***,the double-cycle mechanism,associated with missing variable sorting and missing instance sorting,is applied to direct the missing values ***,the weighted K nearest neighbor-based imputation estimator is used to acquire the global similar instances and capture the volatility in the local *** estimator preserves the original data characteristics as much as possible and enhances the imputation ***,experimental results on simulated and real WWTP datasets with non-stationarity and nonlinearity demonstrate that the proposed DCWI produces more accurate imputation results than comparison methods under different missing patterns and missing ratios.

关键词： wastewater treatment process multiple missing patterns data information imputation sorting imputation estimator

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Probability estimation based on grey system theory for simulation evaluation

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Journal of Systems Engineering and Electronics 2016年第4期27卷 871-877页

作者： Jianmin Wang Jinbo Wang Tao Zhang Yunjie wu Technology and Engineering Center for Space Utilization Chinese Academy of Sciences School of Automation Science and Electrical Engineering Beihang University

In the evaluation of some simulation systems, only small samples data are gotten due to the limited conditions. In allusion to the evaluation problem of small sample data, an interval estimation approach with the improved grey confidence degree is *** the basis of the definition of grey distance, three kinds of definition of the grey weight for every sample element in grey estimated value are put forward, and then the improved grey confidence degree is designed. In accordance with the new concept, the grey interval estimation for small sample data is deduced. Furthermore,the bootstrap method is applied for more accurate grey confidence interval. Through resampling of the bootstrap, numerous small samples with the corresponding confidence intervals can be obtained. Then the final confidence interval is calculated from the union of these grey confidence intervals. In the end, the simulation system evaluation using the proposed method is conducted. The simulation results show that the reasonable confidence interval is acquired, which demonstrates the feasibility and effectiveness of the proposed method.

关键词： small sample interval estimation simulation system evaluation probability grey system theory

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Modeling and Experimental Validation on Pressure Drop in a Reverse-flow Cyclone Separator at High Inlet Solid Loading

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Journal of Thermal Science 2011年第4期20卷 343-348页

作者： wu Xuezhi Liu Jie Xu Xiang Xiao Yunhan Key Laboratory of Advanced Energy and Power （Institute of Engineering Thermophysics） Chinese Academy of Sciences Beijing 100190 Graduate University of Chinese Academy of Sciences Beijing 100190

High inlet solid loading is one of the most important features of cyclone separators in high density circulating fluidized beds （CFB）. In this work, the effect of high solid loading on pressure drop in a reverse-flow cyclone was experimentally studied. The particles used were sand and 2zAl203. Art extended range of inlet solid loadings （M）, up to 30 kg of solids/kg of air was tested at different inlet air velocities （Vin=16~24 m/s）, well beyond the solid loading range reported before. The experiments showed that, in the tested range of solid loadings, the cyclone pressure drop decreased dramatically with increasing solid loading when M〈7.5 kg/kg and then almost remained constant. A new semi-empirical model for predicting cyclone pressure drop was also developed. The calculated and experimental results showed good agreement for particle free flow and particle laden flow.

关键词： high inlet solid loading pressure drop reverse-flow cyclone modeling.

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A Robust Self-healing Polyurethane Elastomer Enabled by Tuning the Molecular Mobility and Phase Morphology through Disulfide Bonds

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Chinese Journal of Polymer Science 2021年第10期39卷 1299-1309,I0007页

作者： Hai-Tao wu Bi-Qiang Jin Hao Wang Wen-Qiang wu Zhen-Xing Cao Zhao-Yang Yuan Yue Huang Wei-Hang Li Guang-Su Huang Lu-Sheng Liao Jin-Rong wu State Key Laboratory of Polymer Materials Engineering College of Polymer Science and EngineerngSichuan UniversityChengdu 610065China Guangdong Provincial Key Laboratory of Natural Rubber Processing Agricultural Products Processing Research Institute of Chinese Academy of Tropical Agricultural SciencesZhanjiang 524001China

Elastomers with outstanding strength,toughness and healing efficiency are highly promising for many emerging ***,it is still a challenge to integrate all these beneficial features in one ***,an asymmetric alicyclic structure adjacent to aromatic disulfide was tactfully introduced into the backbone of polyurethane(PU)***,such elastomer(PU-HPS)was fabricated by polycondensing polytetramethylene ether glycol(PTMEG),isophorone diisocyanate(IPDI)and p-hydroxydiphenyl disulfide(HPS)via one-pot *** molecular mobility and phase morphology of PU-HPS can be tuned by adjusting the HPS ***,the dynamic exchange of hydrogen and disulfide bonds in the hard segment domains can also be *** optimized sample manifests outstanding tensile strength(46.4 MPa),high toughness(109.1 MJ/m^(3)),high self-healing efficiency after fracture(90.3%),complete scratch recovery(100%)and good puncture ***,this work provides a facile strategy for developing robust self-healing polymers.

关键词： Self-healing Polyurethane Disulfide bonds Chain mobility Phase morphology

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Synthesis of oleanolic disaccharide derivatives

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Chinese Chemical Letters 2012年第4期23卷 403-406页

作者： Shu Chen Pei Jian Bo wu Fan Lei Shan Qian Li Hai Yong wu Key Laboratory of Drug Targeting and Drug Delivery System of the Education Ministry Department of Medicinal ChemistryWest China School of PharmacySichuan UniversityChengdu 610041China Bioengineering College Xihua UniversityChengdu 610039China

Oleanolic acid 1 exists widely in food,medicinal herbs and other plants and possesses many attractive biological activities. Recently,some oleanolic derivatives were reported to have interesting anti-tumor ***,using association principle of drug design,OA disaccharide 17 was designed and synthesized by coupling a-L-rhamnopyranosyl-（1→2）-a-L-arabinopyranosyl disaccharide moiety,which has proved to be a unique sugar sequence with strongly antitumor activity,and modified OA with a nitrile at C-17.

关键词： Oleanolic acid Rhamnopyranosyl Arabinopyranosyl Anti-tumor Association principle

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