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IEEE-Power-and-Energy-Society General Meeting (PESGM)

作者： Wang, Dong Hou, Yunhe Hu, Jiabing Univ Hong Kong Hong Kong Hong Kong Peoples R China Huazhong Univ Sci & Tec Wuhan Peoples R China

ISBN: (纸本)9781509041688

Dynamic stability issues of power converter interfaced devices integrating into the power grid have drawn increased attention. This paper studies DC-link voltage control stability for a weak-ac-grid connected wind farm, in which doubly-fed induction generator (DFIG) based wind turbines (WTs) operate in parallel. First, a reduced analytical model is proposed of separated dynamics for different time scales. Operating points of WTs, grid strengths and DC-link voltage control system dynamics are included in the model. Eigenvalue analysis for the proposed model shows that the mode, usually called common mode which represents the interconnection behavior between the overall wind farm and the grid, determines system stability. Damping of this common mode turns weak as grid strength decreases, and even negative thus leading system instability. Eigenvalue locus shows that tuning of phase-locked loop (PLL) has noticeable effect on this mode under weak ac grid, and larger PLL gain can effectively improve system damping. Time domain simulation with corresponding detailed model verifies the analysis.

关键词： Doubly fed induction generator (DFIG) DC-link voltage control stability weak ac grid common mode PLL

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ICL journal "Landslides" and the Kyoto 2020 Commitment

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LANDSLIDES 2018年第9期15卷 1705-1712页

作者： Sassa, Kyoji ICL Kyoto Japan

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Blockchainized Internet of Minds: A New Opportunity for Cyber-Physical-Social Systems

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IEEE TRANSACTIONS ON COMPUTATIONAL SOCIAL SYSTEMS 2018年第4期5卷 897-906页

作者： Wang, Fei-Yue Yuan, Yong Zhang, Jun Qin, Rui Smith, Michael H. Chinese Acad Sci Inst Automat State Key Lab Management & Control Complex Syst Beijing 100190 Peoples R China Qingdao Acad Intelligent Ind Qingdao 266109 Peoples R China Wuhan Univ Sch Elect Engn Wuhan 430072 Hubei Peoples R China Board Furaxa Inc Berkeley CA 94701 USA Univ Calif Berkeley Berkeley CA 94701 USA

Welcome to the last issue of the IEEE Transactions on Computational Social Systems (IEEE TCSS) in 2018. Starting from the first issue next year, our Transactions will be a bimonthly publication, entering a new stage f...

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Evidence for multi-gap symmetry from grain boundary effects in polycrystalline Ba_0.6K_0.4Fe₂As₂ microbridge

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SUPERCONDUCTOR SCIENCE & technology 2017年第1期30卷 015006-015006页

作者： Huang, Ya Zhou, Xian-Jing Gao, Zhao-Shun Wu, Hao He, Ge Yuan, Jie Jin, Kui Pereira, Paulo J. Ji, Min An, De-Yue Li, Jun Hatano, Takeshi Jin, Biao-Bing Wang, Hua-Bing Wu, Pei-Heng Nanjing Univ Res Inst Superconductor Elect Nanjing 210093 Jiangsu Peoples R China Natl Inst Mat Sci Tsukuba Ibaraki 3050047 Japan Chinese Acad Sci Inst Elect Engn Beijing 100190 Peoples R China Wuhan Univ Wuhan 430047 Peoples R China Chinese Acad Sci Inst Phys Condensed Matter Phys Beijing 100190 Peoples R China Katholieke Univ Leuven INPAC Inst Nanoscale Phys & Chem Celestijnenlaan 200 D B-3001 Leuven Belgium Katholieke Univ Leuven Theory Nanomat Grp B-3001 Leuven Belgium

We studied the grain boundaries within mechanically formed polycrystalline Ba0.6K0.4Fe2As2 micro-bridges. By tunneling current across grain boundaries, current-voltage characteristics (IVCs) demonstrated the typical Josephson weak links behavior in micro-bridges. Shapiro steps were observed for the junctions under the microwave radiation at 10 GHz. The temperature dependence of the critical current I-c was observed as a shoulder, corresponding to a multi-gap symmetry but not a single-gap s-wave or d-wave.

关键词： grain boundary effect Josephson junction multi-gap symmetry iron-based superconductors

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Hierarchical porous activated carbon in OER with high efficiency

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RSC ADVANCES 2016年第104期6卷 102422-102427页

作者： Pi, Yu-Tong Xing, Xiang-Ying Lu, Li-Ming He, Zhan-Bing Ren, Tie-Zhen Hebei Univ Technol Sch Chem Engn & Technol Tianjin 300130 Peoples R China Univ Sci & Technol Beijing State Key Lab Adv Met & Mat Beijing 100083 Peoples R China

The oxygen evolution reaction (OER) has attracted much attention as it can be used to produce clean energy. Hierarchical porous activated carbon (HPAC) shows potential applications for the OER. HPAC derived from fallen leaves (Fraxinus chinensis) is prepared using a facile method, in which KOH and/or K2CO3 are used as activators. Characterization reveals that HPAC in the system of KOH/K2CO3 has a high surface area and possesses abundant hierarchical pores, which are favorable for mass transfer and charge transfer in the oxygen evolution reaction (OER). Acid washed HPAC displays relatively low activity and electrochemical tests demonstrate that ash composition may contribute to the OER. HPAC is a potential carbon-based catalyst that has prominent OER activity and durability.

关键词： Activated carbon

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Effect of Nd on tin whisker growth in Sn-Zn soldered joint

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JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS 2016年第4期27卷 3742-3747页

作者： Xue, Peng Wang, Ke-Hong Zhou, Qi Huang, Jun Long, Wei-min Zhang, Qing-ke Nanjing Univ Sci & Technol Sch Mat Sci & Engn Nanjing 210016 Jiangsu Peoples R China Zhengzhou Res Inst Mech Engn Zhengzhou 450001 Peoples R China

In this paper the behavior and mechanism of tin whisker growth in Nd-doped Sn-Zn soldered joint were investigated, and the effect of Nd on the growth of tin whisker at 150 A degrees C thermal condition was studied in detail. It was found that spontaneous growth of tin whisker occurred on the surface of soldered joint with excessive Nd addition, and the maximum length of tin whisker exceeded the safety range after aging treatment. With the oxidation of NdSn3 phase, the compressive stress continuously drives the fresh tin atoms out from the fractures around NdSn3 phase until the NdSn3 phase was totally oxidized. The tin whisker growth from IMC in soldered joint was due to the diffusion-induced stress in the IMC layer between the Cu pad and the solder. As a result of stress release, voids and cracks formed in IMC layer and tin whisker sprout out from these fractures after aging treatment, which further decreased the mechanical property of soldered joint.

关键词： Tin

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A splicing-driven memetic algorithm for reconstructing cross-cut shredded text documents

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APPLIED SOFT COMPUTING 2016年 45卷 163-172页

作者： Gong, Yue-Jiao Ge, Yong-Feng Li, Jing-Jing Zhang, Jun Ip, W. H. Sun Yat Sen Univ Sch Data & Comp Sci Guangzhou Guangdong Peoples R China S China Normal Univ Sch Comp Sci Guangzhou Guangdong Peoples R China S China Univ Technol Sch Comp Sci & Engn Guangzhou Guangdong Peoples R China State Key Lab Math Engn & Adv Comp Wuxi Peoples R China Hong Kong Polytech Univ Dept Ind & Syst Engn Hong Kong Hong Kong Peoples R China

Reconstruction of cross-cut shredded text documents (RCCSTD) plays a crucial role in many fields such as forensic and archeology. To handle and reconstruct the shreds, in addition to some image processing procedures, a well-designed optimization algorithm is required. Existing works adopt some general methods in these two aspects, which may not be very efficient since they ignore the specific structure or characteristics of RCCSTD. In this paper, we develop a splicing-driven memetic algorithm (SD-MA) specifically for tackling the problem. As the name indicates, the algorithm is designed from a splicing-centered perspective, in which the operators and fitness evaluation are developed for the purpose of splicing the shreds. We design novel crossover and mutation operators that utilize the adjacency information in the shreds to breed high-quality offsprings. Then, a local search strategy based on shreds is performed, which further improves the evolution efficiency of the population in complex search space. To extract valid information from shreds and improve the accuracy of splicing costs, we propose a comprehensive objective function that considers both edge and empty row-based splicing errors. Experiments are carried out on 30 RCCSTD scenarios and comparisons are made against previous best-known algorithms. Experimental results show that the proposed SD-MA displays a significantly improved performance in terms of solution accuracy and convergence speed. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Reconstruction of cross-cut shredded text documents (RCCSTD) Memetic algorithm Evolutionary computation Information recovery Global optimization

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Recommendation System Based On Trusted Relation Transmission 12

Recommendation System Based On Trusted Relation Transmission

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12th International Conference on Intelligent Systems and Knowledge engineering (IEEE ISKE)

作者： Bian, Yixiong Li, Huakang Nanjing Univ Posts & Telecommun Jiangsu Key Lab Big Data & Secur & Intelligent Pr Nanjing 210023 Jiangsu Peoples R China Collaborat Innovat Ctr Econ Crime Investigat & Pr Nanjing Jiangxi Peoples R China State Key Lab Math Engn & Adv Comp Wuxi 214125 Peoples R China

ISBN: (纸本)9781538618295

With the rapid development of the internet, applications of recommendation systems for online shops and entertainment platforms become more and more popular. In order to improve the effectiveness of recommendation, external information has been incorporated into various algorithms, such as location and social relationship. However, most algorithms only focus on the introduction of external information without depth analysis of the intrinsic mechanism in the external information. This paper proposed a transfer model of social trusted relationship, and optimized the reliability of the transfer model using pruning algorithm based on original trust recommendation. A credible social relationship macro-transfer model based on iterations of new credible relationships is defined by the similarity of social relationships. With a certain interest topic as a source of information, a micro-transfer model achieves the theme of interest and credibility of the expansion using social information dissemination algorithm. To demonstrate the effectiveness of the macro and micro credible transfer models, we used the Mantra search tree pruning algorithm and the optimization algorithm of similar category replacing similar products. The experimental results show that the proposed method based on the macroscopic and microscopic transfer models of the trusted relationship enhances the success rate and stability of the recommended system.

关键词： Trust Recommendation Macro-transfer Model Micro-transfer Model Credible Delivery Pruning Optimization

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Investigation on the Effect of Nozzle Number on the Recirculation Rate and Mixing Time in the RH Process Using VOF plus DPM Model

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METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE 2016年第3期47卷 1950-1961页

作者： Ling, Haitao Li, Fei Zhang, Lifeng Conejo, Alberto N. Univ Sci & Technol Beijing Beijing Key Lab Green Recycling & Extract Met GRE Beijing 100083 Peoples R China Univ Sci & Technol Beijing Sch Met & Ecol Engn Beijing 100083 Peoples R China Morelia Technol Inst Grad Program Met Morelia Michoacan Mexico

A mathematical model has been developed to explain the effect of the number of nozzles on recirculation flow rate in the RH process. Experimental data from water modeling were employed to validate the mathematical model. The experimental data included the velocity fields measured with a particle image velocimetry technique and mixing time. The multiphase model volume of fluid was employed to allow a more realistic representation of the free surface in the vacuum chamber while injected argon bubbles were treated as discrete phase particles and modeled using the discrete phase model. Interfacial forces between bubbles and liquid phase were considered, including the lift force. The simulations carried out with the mathematical model involved changes in the gas flow rate from 12 to 36 L/min and a number of nozzles from 4 to 8. The results indicated a logarithmic increment in the recirculation rate as the gas flow rate increased and also corresponded with an exponential decrease in mixing time. The plume area and liquid velocities resulting from individual nozzles were computed. A maximum optimum recirculation rate was defined based on a mechanism proposed to explain the effect of gas flow rate and the number of nozzles on the recirculation rate.

关键词： Nozzles

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Mathematical Modeling on the Growth and Removal of Non-metallic Inclusions in the Molten Steel in a Two-Strand Continuous Casting Tundish

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METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE 2016年第5期47卷 2991-3012页

作者： Ling, Haitao Zhang, Lifeng Li, Hong USTB Beijing Key Lab Green Recycling & Extract Met GRE Beijing 100083 Peoples R China USTB Sch Met & Ecol Engn Beijing 100083 Peoples R China

In the current study, mathematical models were developed to predict the transient concentration and size distribution of inclusions in a two-strand continuous casting tundish. The collision and growth of inclusions were considered. The contribution of turbulent collision and Stokes collision was evaluated. The removal of inclusions from the top surface was modeled by considering the properties of inclusions and the molten steel, such as the wettability, density, size, and interfacial tension. The effect of composition of inclusions on the collision of inclusions was included through the Hamaker constant. Meanwhile, the effect of the turbulent fluctuation velocity on the removal of inclusions at the top surface was also studied. Inclusions in steel samples were detected using automatic SEM Scanning so that the amount, morphology, size, and composition of inclusions were achieved. In the simulation, the size distribution of inclusions at the end steel refining was used as the initial size distribution of inclusions at tundish inlet. The equilibrium time when the collision and coalescence of inclusions reached the steady state was equal to 3.9 times of the mean residence time. When Stokes collision, turbulent collision, and removal by floating were included, the removal fraction of inclusions was 16.4 pct. Finally, the removal of solid and liquid inclusions, such as Al2O3, SiO2, and 12CaO center dot 7Al(2)O(3), at the interface between the molten steel and slag was studied. Compared with 12CaO center dot 7Al(2)O(3) inclusions, the silica and alumina inclusions were much easier to be removed from the molten steel and their removal fractions were 36.5 and 39.2 pct, respectively.

关键词： Size distribution

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