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Metal-support interaction controlled migration and coalescence of supported particles

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Science China(Technological Sciences) 2019年第5期62卷 762-772页

作者： HU SuLei LI wei-xue Department of Chemical Physics School of Chemistry and Materials ScienceiCHeMCAS Excellence Center for NanoscienceUniversity of Science and Technology of ChinaHefei 230026China Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China

The particle migration and coalescence(PMC) kinetics of a supported metal are the main deactivation mechanisms restricting the successful industrialization of nanoparticles, but the theoretical insights regarding these kinetics are lacking. One key issue is the lack of a physical model to predict the effects of metal-support interaction(MSI) on PMC kinetics. In this paper, we report a theoretical study of PMC kinetics and their dependence on MSI. A new particle diffusion model is proposed based on the surface premelting hypothesis that considers the contact angle of a hemispherical particle on the support. Enhanced MSI suppresses PMC by increasing the radius of curvature and the interfacial adhesion energy, even though the accompanying reduction in the geometry factor partially promotes PMC kinetics. The increased surface energy increases the chemical potential of the atoms in the particle, which is conducive to PMC; an increased surface energy also results in enhanced MSI, which suppresses PMC. The competition between these two contradictory effects leads to a critical contact angle where the surface energy has no influence on the diffusion and resulting PMC kinetics. The proposed diffusion theory mode lincluding the effects of the support and the corresponding kinetic simulations, shed light onto the support-dependence of PMC kinetics and provide a foundation for further optimization and design of supported particles with better stability.

关键词： particle migration and coalescence metal-support interaction supported particles diffusion coefficient Smoluchowski

Degradation and Self-recovery of Polycrystalline Silicon TFT CMOS Inverters Under NBTI Stress

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Chinese Journal of Electronics 2019年第4期28卷 884-888页

作者： GUO Jian YU Zhinong YAN wei SHI Dawei xue Jianshe xue wei School of Optics and Photonics and Beijing Engineering Research Center of Mixed Reality and Advanced Display Beijing Institute of Technology

Degradation and self-recovery of polycrystalline Silicon(poly-Si) Thin film transistor(TFT) by using complementary metal oxide semiconductor(CMOS)inverter were investigated. Under DC stress, degradation mechanisms were clarified by comparing the Voltage transfer characteristics(VTC) of fresh and stressed inverters. It is determined that Negative bias temperature instability(NBTI) of p-TFT dominates the degradation of the inverter under zero bias DC stress. After removing the stress, the VTC continues to be degraded, because the interface trap-states and the grain boundary trapstates increase due to hydrogen species diffusion. It is found out that the VTC is shifted to its right side severely with negative bias stress of VIN. The NBTI of p-TFT is enhanced and the NBTI of n-TFT also plays a role on the degradation. When removing the negative bias stress, the self-recovery of NBTI of nTFT and the continuing degradation of NBTI of p-TFT become competing mechanisms, together controlling the VTC after-stress behavior. Consequently, the continuing degradation of NBTI of p-TFT is restrained by selfrecovery of NBTI of n-TFT.

关键词： Negative bias temperature instability(NBTI) Self-recovery Inverter Polycrystalline silicon Voltage transfer characteristics(VTC)

Reverse-time type nonlocal Sasa–Satsuma equation and its soliton solutions

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Communications in Theoretical Physics 2023年第7期75卷 48-57页

作者： xue-wei Yan Yong Chen School of Mathematics Harbin Institute of TechnologyHarbin150001China

In this work,we study the Riemann–Hilbert problem and the soliton solutions for a nonlocal Sasa–Satsuma equation with reverse-time type,which is deduced from a reduction of the coupled Sasa–Satsuma *** the coupled Sasa–Satsuma system can describe the dynamic behaviors of two ultrashort pulse envelopes in birefringent fiber,our equation presented here has great physical *** classification of soliton solutions is studied in this nonlocal model by considering an inverse scattering transform to the Riemann–Hilbert ***,we find that the symmetry relations of discrete data in the special nonlocal model are very ***,the eigenvectors in the scattering data are determined by the number and location of ***,multi-soliton solutions are not a simple nonlinear superposition of multiple *** exhibit some novel dynamics of solitons,including meandering and sudden position ***,they have the bound state of multi-soliton entanglement and its interaction with solitons.

关键词： nonlocal Sasa-Satsuma equation Riemann-Hilbert problem soliton solution

LINEAR FINITE ELEMENT APPROXIMATIONS FOR THE TIMOSHENKO BEAM AND THE SHALLOW ARCH PROBLEMS

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Journal of Computational Mathematics 2002年第1期20卷 15-22页

作者： Xiao-liang Cheng wei-min xue Department of Mathematics Zhejiang UniversityXixi CampusHangzhou 310028China Department of Mathematics Hong Kong Baptist UniversityKowloon TongHong Kong

Focuses on a study that discusses the linear finite element approximations for the Timoshenko beam and the shallow arch problems with shear dampening and reduced integration. Information on the Timoshenko beam; Detail... 详细信息

关键词： Timoshenko beam shallow arch shear dampening reduced integration

Preferred search over encrypted data

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Frontiers of Computer Science 2018年第3期12卷 593-607页

作者： Zhirong SHEN Jiwu SHU wei xue Department of Computer Science and Technology Tsinghua University Beijing 100084 China

Cloud computing provides elastic data storage and processing services. Although existing research has proposed preferred search on the plaintext files and encrypted search, no method has been proposed that integrates the two techniques to efficiently conduct preferred and privacypreserving search over large datasets in the cloud. In this paper, we propose a scheme for preferred search over encrypted data （PSED） that can take users＇ search preferences into the search over encrypted data. In the search process, we ensure the confidentiality of not only keywords but also quantified preferences associated with them. PSED constructs its encrypted search index using Lagrange coefficients and employs secure inner-product calculation for both search and relevance measurement. The dynamic and scalable property of cloud computing is also considered in PSED. A series of experiments have been conducted to demonstrate the efficiency of the proposed scheme when deploying it in realworld scenarios.

关键词： preferred search encrypted data secure innerproduct calculation

Cooperative Optimization of Reconfigurable Machine Tool Configurations and Production Process Plan

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Chinese Journal of Mechanical Engineering 2012年第5期25卷 982-989页

作者： XIE Nan LI Aiping xue wei Sino-German College of Applied Science Tongji University Shanghai 201804 China Institute of AdvancedManufacturing Technology Tong/i University Shanghai 201804 China College of Mechanical & Electrical Engineering Wenzhou University Wenzhou 325000 China

The production process plan design and configurations of reconfigurable machine tool （RMT） interact with each other. Reasonable process plans with suitable configurations of RMT help to improve product quality and reduce production cost. Therefore, a cooperative strategy is needed to concurrently solve the above issue. In this paper, the cooperative optimization model for RMT configurations and production process plan is presented. Its objectives take into account both impacts of process and configuration. Moreover, a novel genetic algorithm is also developed to provide optimal or near-optimal solutions： firstly, its chromosome is redesigned which is composed of three parts, operations, process plan and configurations of RMTs, respectively; secondly, its new selection, crossover and mutation operators are also developed to deal with the process constraints from operation processes （OP） graph, otherwise these operators could generate illegal solutions violating the limits; eventually the optimal configurations for RMT under optimal process plan design can be obtained. At last, a manufacturing line case is applied which is composed of three RMTs. It is shown from the case that the optimal process plan and configurations of RMT are concurrently obtained, and the production cost decreases 6.28% and nonmonetary performance increases 22%. The proposed method can figure out both RMT configurations and production process, improve production capacity, functions and equipment utilization for RMT.

关键词： reconfigurable manufacturing system reconfigurable machine tool configuration process plan cooperative optimization model

Preparation of ferronickel from nickel laterite via coal-based reduction followed by magnetic separation

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International Journal of Minerals,Metallurgy and Materials 2018年第7期25卷 744-751页

作者： Lun-wei Wang xue-ming Mei Liu Zhi-xiong You xue-wei Chen-guang Bai college of materials science and engineering chongqing universityChongqing 400044China engineer of cisdi thermal&environmental engineering co. ltd.Chongqing 401122China

The sticking phenomenon between molten slag and refractory is one of the crucial problems when preparing ferronickel from laterite ore using rotary hearth fulnace or rotary kiln processes. This study aims to ameliorate sticking problems by using silicon dioxide （SiO2） to adjust the melting degree of file briquette during reduction roasting. Thermodynamic analysis indicates that the melting temperature of the slag gradually increases with an increase in the SiO2 proportion （SiO2/（SiO2 ＋ A1203 ＋ MgO） mass ratio）. Experimental validations also prove that the briquette retains its original shape when the SiO2 proportion is greater than 75wt%, and sticking problems axe avoided during reduction. A ferronickel product with 8.33wt% Ni and 84.71wt% Fe was prepared via reductive roasting at 1500~C for 90 min with a SiO2 proportion of 75wt% and a C/O molar ratio of 1.0 followed by dry magnetic separation; the corresponding recoveries of Ni and Fe reached 75.70% and 77.97%, respectively. The micro stxucture and phase txmlsformation of reduced briquette reveals that the aggregation and growth of ferroinckel particles were not significantly affected after adding SiO2 to the reduction process.

关键词： nickel laterite caxbot^ermal reduction ferronickel magnetic separation

First-principles kinetics study of carbon monoxide promoted Ostwald ripening of Au particles on FeO/Pt(111)

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Journal of Energy Chemistry 2019年第3期28卷 108-113页

作者： Sulei Hu Runhai Ouyang wei-xue Li State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina Department of Chemical Physics School of Chemistry and Materials ScienceiCHeMCAS Excellence Center for NanoscienceUniversity of Science and Technology of ChinaHefei 230026AnhuiChina Hefei National Laboratory for Physical Sciences at the Microscale Hefei 230026AnhuiChina University of Chinese Academy of Sciences Beijing 100049China

The dynamic and kinetic evolution of supported metal particles in the presence of reactants is decisive in shaping the nature of the catalytic active sites and the deactivation process. Ostwald ripening of FeO/Pt(111) supported Au particles in the presence of carbon monoxide is addressed here by firstprinciples kinetics. It is found that CO stabilizes the ripening monomer(Au atom) by forming favorable Au carbonyls with lower total activation energy, and corresponding phase diagram at wide range of temperature and CO pressures is constructed. Evolution of particle number, dispersion and particle size distribution of supported Au particles are explored. Great influence of CO promotion on ripening kinetics is revealed and explored in details, and mbar range of CO can lower the onset temperature of ripening by a few hundred kelvins. The present work reveals the crucial role of the metal-reactant complexes formed under reaction conditions on ripening of metal catalysts.

关键词： Carbon monoxide Au particles Ostwald ripening First-principles kinetics FeO/Pt(111)

Atmospheric corrosion behavior of low-alloy steels in a tropical marine environment

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Journal of Iron and Steel Research International 2019年第12期26卷 1315-1328页

作者： Zhao-liang Li Kui Xiao Chao-fang Dong xue-qun Cheng wei xue wei Yu Corrosion and Protection Center University of Science and Technology BeijingBeijing 100083China Institute of Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China Engineering Research Institute University of Science and Technology BeijingBeijing 100083China

The corrosion behavior of carbon steels and weathering steels was investigated in a tropical marine *** both exhibited similar corrosion weight-loss behavior in tropical marine *** weight loss(W)as a function of exposure time(t)can be calculated using the power function,W=A^*** values of the initial corrosion rate,A,and corrosion tendency,n,can be easily obtained by taking the logarithm of the power ***,the corrosion rust-layer structure of the two materials was quite *** rust layer of carbon steel presents a single-layer ***,the rust layer of weathering steel exhibits a single-layer structure after exposure for about 24 months and then gradually evolves into a double-layer *** main corrosion products of the steels areβ-FeOOH,γ-FeOOH,and Fe3O4 in the initial stage of *** the rust layers,α-FeOOH appeared after 12 months of exposure.

关键词： Marine environment Atmospheric corrosion Carbon steel Weathering steel Rust