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Wide speed range for traction motor in braking force of electric braking control system

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Journal of Central South University 2014年第10期21卷 3837-3843页

作者： young-Choon kim Moon-Taek Cho Division of Mechanical and Automotive Engineering College of EngineeringKongju National University Department of Electrical & Electric Engineering Daewon University College

A vehicle stopping method using an electric brake until a traction motor is stopped is studied. At the moment of vehicle stop, electric brake is changed to control mode where torque is reduced at a low speed. Gradient is controlled by estimating the load torque of motor, thereby traction motor is not rotated after stop. In addition, coasting operation and brake test are performed from normal-opposite operation and start using a small-scale model comprising the inertial load equipment and the power converter. Further, traction motor is made to be equipped with a suspension torque. Pure electric braking that makes traction motor stop by an air brake at the time of stop is also implemented. Constant torque range and constant power range are expanded during braking so that braking force is secured with the electric brakes even in high speed region. Therefore, vehicle reduction effect can be expected by reducing parts related with an air brake which is not used frequently by using a pure electric brake in the M car in wide speed region. Further, maintenance of brake system can be reduced. Besides, ride comfort of passenger in the electric rail car, energy efficiency improvement, and noise reduction effect can be additionally expected. Further, an improved brake method that uses only an electric brake till motor stop is proposed by comparing those in the blending brake that uses an air brake while reducing brake torque at vehicle stop.

关键词： wide speed range electric braking control traction motor

Effects of Processing Parameters on Microstructure and Properties of Ultra High Strength Linepipe Steel

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Journal of Materials Science & Technology 2012年第10期28卷 889-894页

作者： Xiaodan Wu Hakcheol Lee young Min kim Nack J.kim University of Pittsburgh Pittsburghl PA 15213USA Pohang University of Science and Technology Pohang 790-784Korea

To examine the effect of processing parameters on microstructural evolution and to obtain the excellent combination of strength and toughness, simulation of thermo-mechanical processing was conducted using the Gleeble machine. Trial production was then conducted under the conditions obtained by Gleeble tests. Based on the results of microstructure analysis and mechanical property evaluation, the relationship between microstructural features and mechanical properties was elucidated. The result shows that the volume fraction of constituted phases can be controlled through adjusting the cooling rate and finish cooling temperature in order to get different strength levels. As cooling rate increases, the volume fraction of upper bainite increases, which leads to the increase of strength. The upper shelf energy （USE） increases with increasing volume fraction of acicular ferrite in bainite base because of the small effective acicular ferrite grain size. Ductile-brittle transition temperature （DBTT） decreases with increasing acicular ferrite volume fraction. High reduction in the rough stage has great influence on grain refinement.

关键词： Linepipe steel Microstructure Gleeble test TMCP (thermomechanicalcontrol process)

Fabrication of Dual-pore Scaffolds Using a Combination of Wire-Networked Molding （WNM） and Non-solvent Induced Phase Separation （NIPS） Techniques

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Journal of Bionic Engineering 2015年第4期12卷 565-574页

作者： Dong Guk Sohn Myoung Wha Hong young Yul kim young-Sam Cho Division of Mechanical and Automotive Engineering College of Engineering Wonkwang University 460 Iksandae-ro Iksan Jeonbuk 570-749 Republic of Korea Department of Orthopedics Daejeon St. Mary's Hospital Catholic University of Korea 64 Daeheung-ro Jung-gu Daejeon 301-723 Republic of Korea

In this study, to fabricate dual-pore scaffolds with interconnected pores, Non-solvent Induced Phase Separation （NIPS） and Wire-Network Molding （WNM） techniques were combined. First, a mold with uniform slits was prepared, and needles were inserted into the mold. Subsequently, polycaprolactone （PCL） pellets were dissolved in tetrahydrofuran （THF） at a specified ratio. The slurry was mixed using hot plate stirrer at 1200 rpm for 24 hours at 40 ~C. The PCL slurry was subsequently injected into the mold. Thereafter, to exchange the THF （solvent） with the ethanol （non-solvent）, the mold was soaked in an ethanol bath. After removing the mold from the ethanol bath, the needles were removed from the mold. Consequently, dual-pore scaffold with interconnected pores was obtained. The surface morphology of the fabricated scaffolds were observed using Scanning Electron Microscope （SEM）. Moreover, cell culture experiments were performed using the CCK-8 assay, and the characteristics of cells grown on the dual-pore scaffolds were assessed and were compared with the NIPS-based 3D plotting scaffold.

关键词： tissue engineering scaffold polycaprolactone (PCL) Wire-Network Molding (WNM) Non-solvent Induced Phase Separation (NIPS)

Geometrical and Geotechnical Characteristics of Landslides in Korea under Various Geological Conditions

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Journal of Mountain Science 2015年第5期12卷 1267-1280页

作者： Kyeong-Su kim young-Suk SONG Geologic Environment Division Korea Institute of Geoscience and Mineral Resources

The goal of this study is to determine the geometrical and geotechnical characteristics of landslides under various geological conditions using detailed field surveys, laboratory soil tests and precipitation records. Three study areas are selected to consider different rocks, including gneiss in Jangheung, granite in Sangju and sedimentary rocks in Pohang, South Korea. Many landslides have occurred in these three areas during the rainy *** records indicate that landslides occurring in the gneiss area of Jangheung and granite area of Sangju may be influenced by the hourly rainfall intensity rather than cumulative ***, landslides occurring in the sedimentary rock area of Pohang may be influenced by hourly rainfall intensity and cumulative rainfall. To investigate the factors that influence these types of landslides, a detailed landslide survey was performed and a series of laboratory soil tests were *** to the detailed field survey, most landslides occurred on the flanks of mountain slopes, and the slope inclination where they occurred mostly ranged from 26 to 30 degrees, regardless of the geological conditions. The landslide in the gneiss area of Jangheung is larger than the landslides in the granite area of Sangju and sedimentary rock area of ***, the landslide in the sedimentary rock area is shorter and shallower than the landslides in the gneiss and granite areas. Thus, the shape and size of the landslide are clearly related to the geological conditions. According to the integrated soil property and landslide occurrence analyses results, the average dry unit weight of the soils from the landslide sites is smaller than that of the soils obtained from the nonlandslide site. The average coefficient of permeability of soils obtained from the landslide sites is greater than that of soils obtained from the non-landslide sites with the same geology. These results indicate that the soils from the landslide site

关键词： Landslides Geological condition Geometrical characteristics Precipitation Soilproperties South Korea

SOME RESULTS ON GENERALIZED EQUILIBRIUM PROBLEMS INVOLVING STRICTLY PSEUDOCONTRACTIVE MAPPINGS

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Acta Mathematica Scientia 2011年第5期31卷 2041-2057页

作者： Jong Kyu kim Sun young Cho Department of Mathematics Educations Kyungnam UniversityMasan 631-701Korea Department of Mathematics Gyeongsang National UniversityChinju 660-701Korea

In this paper,we consider an iterative sequence for generalized equilibrium problems and strictly pseudocontractive *** show that the iterative sequence converges strongly to a common element of the solution set of ge... 详细信息

关键词： equilibrium problem nonexpansive mapping inverse-strongly monotone mapping strictly pseudocontractive mapping

User Profile System Based on Sentiment Analysis for Mobile Edge Computing

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Computers, Materials & Continua 2020年第2期62卷 569-590页

作者： Sang-Min Park young-Gab kim Korea University 145 Anam-roSeongbuk-guSeoul02841Korea Sejong University 209Neungdong-roGwangjin-guSeoul05006Korea

Emotions of users do not converge in a single application but are scattered across diverse *** devices are the closest media for handling user data and these devices have the advantage of integrating private user information and emotions spread over different *** this paper,we first analyze user profile on a mobile device by describing the problem of the user sentiment profile system in terms of data granularity,media diversity,and server-side ***-grained data requires additional data and structural analysis in mobile *** diversity requires standard parameters to integrate user data from various applications.A server-side solution presents a potential risk when handling individual privacy ***,in order to overcome these problems,we propose a general-purposed user profile system based on sentiment analysis that extracts individual emotional preferences by comparing the difference between public and individual data based on particular *** proposed system is built based on a sentiment hierarchy,which is created by using unstructured data on mobile *** can compensate for the concentration of single media,and analyze individual private data without the invasion of privacy on mobile devices.

关键词： User profile sentiment analysis mobile edge computing social network

Microstructural evolution and grain growth mechanism of pre-twinned magnesium alloy during annealing

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Journal of Magnesium and Alloys 2021年第4期9卷 1238-1251页

作者： Ye Jin kim Jong Un Lee young Min kim Sung Hyuk Par School of Materials Science and Engineering Kyungpook National JJniversityDaegu 41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChanson 51508Republic of Korea

The microstructural evolution and underlying grain growth mechanism of a{1012}-twin-containing Mg alloy during annealing are investigated through quasi in situ electron backscatter diffraction measurements of a rolled AZ31 alloy subjected to precompression along the rolling direction(RD).The precompressed material shows a partially twinned structure consisting of a twinned region and a residual matrix region,and this structure changes to an almost twin-free structure consisting of grown grains with serrated grain boundaries in twinand matrix-originated regions after annealing at 250℃ for 1 *** addition,the average grain size almost doubles and the internal strain energy decreases significantly after *** microstructural variations are induced mainly by grain growth through the strain-induced migration of high-angle grain boundaries without the movement of twin *** twinned region of the precompressed material has higher stored strain energy than the residual matrix region because the crystallographic orientation of the former region is favorable for basal slip and because of the occurrence of the dislocation transmutation reaction in the *** reducing the total strain energy accumulated in the precompressed material,the residual matrix region—having lower stored strain energy—preferentially grows while consuming the twinned regions formed in the surrounding grains during *** a result,the area fraction of grains with a matrix texture increases whereas that of grains with a twin texture decreases after *** twin texture intensity increases significantly and this texture becomes more concentrated along the RD because the highly RD oriented twins tend to grow during annealing on account of their fairly low stored strain energy.

关键词： Magnesium Twin Annealing Grain growth Strain energy

Pebbling numbers of some graphs

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Science China Mathematics 2002年第4期45卷 470-478页

作者：冯荣权 Ju young kim School of Mathematical Sciences Peking University Beijing 100871 China Department of Mathematics Catholic University of Daegu Kyongsan 713-702 Korea

Chung defined a pebbling move on a graphG as the removal of two pebbles from one vertex and the addition of one pebble to an adjacent vertex. The pebbling number of a connected graphG, f(G), is the leastn such that any distribution ofn pebbles onG allows one pebble to be moved to any specified but arbitrary vertex by a sequence of pebbling moves. Graham conjectured that for any connected graphsG andH, f(G xH) ≤ f(G)f(H). In the present paper the pebbling numbers of the product of two fan graphs and the product of two wheel graphs are computed. As a corollary, Graham’s conjecture holds whenG andH are fan graphs or wheel graphs.

关键词： pebbling, Graham's conjecture, Cartesian product, fan graph, wheel graph.

Surface properties of Al-doped ZnO thin film before and after CF_4/Ar plasma etching

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Plasma Science and Technology 2022年第7期24卷 194-200页

作者： young-Hee JOO Gwan-Ha kim Doo-Seung UM Chang-Il kim School of Electrical and Electronics Engineering Chung-Ang UniversitySeoul 06974Republic of Korea Department of Semiconductor Materials and Applications Korea PolytechnicSeongnam 13122Republic of Korea Department of Electrical Engineering Sejong UniversitySeoul 05006Republic of Korea

Al-doped ZnO(AZO) is considered as an alternative to transparent conductive oxide *** and achieving a stable surface are important challenges in the development and optimization of dry etching processes, which must be overcome for the application of AZO in various devices. Therefore, in this study, the etch rate and surface properties of an AZO thin film after plasma etching using the adaptive coupled plasma system were investigated. The fastest etch rate was achieved with a CF_(4)/Ar ratio of 50:50 sccm. Regardless of the ratio of CF_(4) to Ar,the transmittance of the film in the visible region exceeded 80%. X-ray photoelectron spectroscopy analysis of the AZO thin film confirmed that metal-F bonding persists on the surface after plasma etching. It was also shown that F eliminates O vacancies. Consequently, the work function and bandgap energy increased as the ratio of CF-4 increased. This study not only provides information on the effect of plasma on AZO thin film, but identifies the cause of changes in the device characteristics during device fabrication.

关键词： Al-doped ZnO plasma etching F-based plasma surface characteristics X-ray photoelectron spectroscopy ultraviolet photoelectron spectroscopy