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Dynamic Protective Control Strategy for Distributed Generation System with Fixed-speed Wind Turbines

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电力系统自动化 2012年第8期36卷 178-184页

作者： mu WEI Zhe CHEN Department of Energy Technology Aalborg UniversityAalborg 9220Denmark

The characteristics of induction generator based fixed-speed wind turbines(FSWT)are *** impacts of different execution time in protective operations are studied under different fault duration and various wind velocity situations,e.g.,FSWT stabilities of load shedding in distribution *** on this research,a dynamic protective control strategy for a distributed generation system(DGS)with FSWT is ***,simulation results demonstrate the effectiveness of the strategy.

关键词：分布式发电系统控制策略动态保护风力发电机组速度执行时间风力涡轮机异步发电机

Enhancement of Performance by Blade Optimization in Two-Stage Ring Blower

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Journal of Thermal Science 2010年第5期19卷 383-389页

作者： Choon-Man Jang gi-Young Han Plant Research Division Korea Institute of Construction Technology dh-m co. ltd.626-5Bulmo-dongSeo-guIncheon404-270Korea

This paper describes the shape optimization of an impeller used for two-stage high pressure ring *** shape variables,which are used to define an impeller shape,are introduced to increase the blower *** pressure of a blower is selected as an object function,and the blade optimization is performed by a response surface ***-dimensional Navier-Stokes equations are introduced to analyze the internal flow of the blower and to find the value of object function for the training *** good agreement between experimental measurements and numerical simulation is obtained in the present *** the shape optimization,it is found that a hub height is effective to increase pressure in the ring *** pressure rise for the optimal two-stage ring blower is successfully increased up to 1.86% compared with that of reference at the design flow *** recirculation flow having low velocity is formed in both sides of the impeller outlet by different flow direction of the inlet and outlet of the *** flow field inside the ring blower is also analyzed and discussed.

关键词： Ring blower Blower performance Numerical simulation Blade optimization Response surface method

Rational design and synthesis of hierarchically structured SnO2 microspheres assembled from hollow porous nanoplates as superior anode materials for lithium-ion batteries

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Nano Research 2018年第3期11卷 1301-1312页

作者： gi Dae Park Yun Chan Kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seoul 136-713 Republic of Korea

Herein, hierarchically structured SnO2 microspheres are designed and synthesized as an efficient anode material for lithium-ion batteries using hollow SnO2 nanoplates. Three-dimensionally ordered macroporous （3-DOM） SnOx-C microspheres synthesized by spray pyrolysis are transformed into hierarchically structured SnO2 microspheres by a two-step post-treatment process. Sulfidation produces hierarchically structured SnS-SnS2-C microspheres comprising tin sulfide nanoplate and carbon building blocks. A subsequent oxidation process produces SnO2 microspheres from hollow SnO2 nanoplate building blocks, which are formed by Kirkendall diffusion. The discharge capacity of the hierarchically structured SnO2 microspheres at a current density of 5 Ag^-1 for the 600th cycle is 404 mA·h·g^-1. The hierarchically structured SnO2 microspheres have reversible discharge capacities of 609 and 158 mA·h·g^-1 at current densities of 0.5 and 30 Ag^-1, respectively. The ultrafine nanosheets contain empty voids that allow excellent lithium-ion storage performance, even at high current densities.

关键词： Kirkendall diffusion nanoplate tin oxide lithium-ion batter spray pyrolysis

Precipitation kinetics of carbides during cyclical and isothermal aging of 2.25Cr–1Mo steel and its effect on mechanical properties

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Journal of Iron and Steel Research International 2021年第10期28卷 1282-1290页

作者： Maribel Leticia Saucedo-muñoz ESIQIE Instituto Politécnico NacionalMexico07300Mexico

The carbide precipitation was analyzed during aging of 2.25Cr–1Mo steel at 550℃.The as-received steel was aged in two different manners:the first treatment was an isothermal aging at 550℃ for time up to 1000 h,and the second one was carried out by a cyclical aging,which consisted of aging at 550℃ for 1 h,water quenching at room temperature and then newly heating at 550℃.This procedure was repeated up to 300 *** M_(23)C_(6) and M6C carbide precipitation took place intragranularly and intergranularly for both aging *** carbide coarsening was detected to occur with the increasing aging ***,the growth kinetics of precipitation occurred more rapidly in the case of cyclical *** specimen hardness decreased with the aging time in both cases;however,it occurred in shorter aging time for the cyclical *** testing indicated the increase in ductility with the aging time,and the cyclically aged specimens showed larger ductility than the isothermally aged specimens.

关键词： 2.25Cr-1Mo steel Precipitation Isothermal heating Cyclical heating Mechanical property

Mapping the trends and prospects of battery cathode materials based on patent landscape

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Frontiers in Energy 2023年第6期17卷 822-832页

作者： Chen YANG Xin-Yu mu School of Japanese Culture and Economy Xi’an International Studies UniversityXi’an 710128China The Northeast Asian Research Center Xi’an International Studies UniversityXi’an 710128China

Advancing portable electronics and electric vehicles is heavily dependent on the cutting-edge lithium-ion (Li-ion) battery technology, which is closely linked to the properties of cathode materials. Identifying trends and prospects of cathode materials based on patent analysis is considered a kernel to optimize and refine battery related markets. In this paper, a patent analysis is performed on 6 popular cathode materials by comprehensively considering performance comparison, development trend, annual installed capacity, technology life cycle, and distribution among regions and patent assignees. In the technology life cycle, the cathode materials majorly used in electric vehicle have entered maturity stage, while the lithium cobalt oxide (LCO) cathode that is widely used in portable electronics is still in the growth stage. In global patent distributions, China holds more than 50% of total patents. In the top 10 patent assignees of 6 cathode materials, 2 institutes are from China with the rest being Japan (6) and Republic of Korea (2), indicating that the technology of cathode materials in China is relatively scattered while cathode research is highly concentrated in Japan and Republic of Korea. Moreover, the patent distribution has to consider practical issues as well as the impacts of core patents. For example, the high cost discourages the intention of applying international patents. This paper is expected to stimulate battery research, understand technical layout of various countries, and probably forecast innovative technology breakthroughs.

关键词： patent analysis cathode batteries technology life cycle

Bilateral Hardy-type Inequalities

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Acta Mathematica Sinica,English Series 2013年第1期29卷 1-32页

作者： mu Fa CHEN School of Mathematical Sciences Beijing Normal University Laboratory of Mathematics and Complex Systems Beijing Normal University Ministry of Education

This paper studies the Hardy-type inequalities on the intervals （may be infinite） with two weights, either vaaishing at two endpoiats of the interval or having mean zero. For the first type of inequalities, in terms of new isoperimetric constants, the factor of upper and lower bounds becomes smaller than the known ones. The second type of the inequalities is motivated from probability theory and is new ia the analytic context. The proofs are now rather elementary. Similar improvements are made for Nash inequality, Sobolev-type inequality, and the logarithmic Sobolev inequality on the intervals.

关键词： Hardy-type inequality vanishing at two endpoints mean zero splitting technique normedlinear space Nash inequality logarithmic Sobolev inequality

Lower bounds of principal eigenvalue in dimension one

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Frontiers of Mathematics in China 2012年第4期7卷 645-668页

作者： mu-Fa CHEN School of Mathematical Sciences Beijing Normal UniversityLaboratory of Mathematics andComplex Systems(Beijing Normal University)Ministry of EducationBeijing 100875China

For the principal eigenvalue with bilateral Dirichlet boundary condition, the so-called basic estimates were originally obtained by capacitary method. The Neumann case （i.e., the ergodic case） is even harder, and was deduced from the Dirichlet one plus a use of duality and the coupling method. In this paper, an alternative and more direct proof for the basic estimates is presented. The estimates in the Dirichlet case are then improved by a typical application of a recent variational formula. As a dual of the Dirichlet case, the refine problem for bilateral Neumann boundary condition is also treated. The paper starts with the continuous case （one-dimensional diffusions） and ends at the discrete one （birth-death processes）. Possible generalization of the results studied here is discussed at the end of the paper

关键词： Principal eigenvalue lower estimate variational formula one- dimensional diffusion birth-death process

Addressing the issue of fog and haze:A promising perspective from meteorological science and technology

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Science China Earth Sciences 2014年第1期57卷 1-2页

作者： mu mu ZHANG RenHe Key Laboratory of Ocean Circulation and Waves Institute of Oceanology Chinese Academy of Sciences State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences

Fog and haze are two kinds of weather *** is referred to as water droplets suspended in the air near earth’s surface,which reduces the visibility to less than 1 km.A fog consisting of ice crystals is called ice *** is the particles suspended in the air that reduce visibility by scattering the light,and is usually a mixture of aerosol and photochemical *** and haze usually *** occurrence and evolution of haze and fog are closely related with meteorological conditions.

关键词：天气现象气象科学霾技术低能见度光化学烟雾地球表面气象条件

Hermitizable,isospectral complex matrices or differential operators

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Frontiers of Mathematics in China 2018年第6期13卷 1267-1311页

作者： mu-Fa CHEN School of Mathematical Sciences Beijing Normal UniversityLaboratory of Mathematics and Complex Systems (Beijing Normal University)Ministry of EducationBeijing 100875China

The main purpose of the paper is looking for a larger class of matrices which have real spectrum. The first well-known class having this property is the symmetric one, then is the Hermite one. This paper introduces a new class, called Hermitizable matrices. The closely related isospectral problem, not only for matrices but also for differential operators is also studied. The paper provides a way to describe the discrete spectrum, at least for tridiagonal matrices or one-dimensional differential operators. Especially, an unexpected result in the paper says that each Hermitizable matrix is isospectral to a birth-death type matrix (having positive sub-diagonal elements, in the irreducible case for instance). Besides, new efficient algorithms are proposed for computing the maximal eigenpairs of these class of matrices.

关键词： Real spectrum symmetrizable Hermitizable isospectral matrix differential operator