• Title/Summary/Keyword: Free-formed

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Preparation of Crack-free HTS YBCO Films by EPD Method

  • Soh, Dea-Wha;Li Yingmei;Nataly Korobova
    • Transactions on Electrical and Electronic Materials
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    • v.4 no.5
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    • pp.6-9
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    • 2003
  • Electrophoretic deposition (EPD) of alcohol YBCO suspensions on the Ag wire electrode is studied. Polyethyleneglycol was coordinated to a structure formed by the EPD process with YBCO particles. The d.c electric fields of 200-300 V/cm are applied for 1-10 min. The optimal condition for the EPD allows modifying the properties and microstructure of the deposited films. Superconducting coatings with nanometer-sized pores and a preferred orientation along the caxis were prepared from the result with chemically modified precursor solution. In contrast, YBCO coatings of submicrometer-sized pores and randomly orientated grains were prepared from the solution without PEG.

Low-temperature Dyeing of Silk Fabrics using a Glyoxal/Hydrogen peroxide Redox System (Glyoxal/Hydrogen peroxide-Redox System을 사용한 견직물의 저온염색)

  • 이내연;백두현;임종열;임영훈
    • Textile Coloration and Finishing
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    • v.6 no.1
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    • pp.1-7
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    • 1994
  • A low-temperature dyeing system for silk fabrics based on a redox system has been investigated. Some factors affecting dyeing of silk fabrics with levelling acid dyes in the absence and presence of certain redox system were investigated under different conditions. The variables studied were; type and concentration of redox system, dyeing conditions, i. e. temperature and time, dye concentration, material-to-liquor ration(LR) and colour fastness. The colour strength(K/S value) is outstandingly higher in the presence than in the absence of redox system. A comparison between the colour strength values of such dyeings abtained the three redox system would call for the following order ; Glyoxal/hydrogen peroxide>thiourea/hydrogen peroxide>glucose/hydrgen peroxide> nothing. In the presence of redox system, free radicals are supposed to be formed in both the fiber and the dye and the interaction between these free radicals bring about covalent fixation beside the usual electrostatic bonds, hydrogen bonds and Van der Waals forces.

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Analysis of Gas Injection System based on Flow Visualization (가시화를 통한 Gas Injection System에 관한 연구)

  • Seo Dong-pyo;Oh Yool-kwon
    • 한국가시화정보학회:학술대회논문집
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    • 2002.11a
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    • pp.85-88
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    • 2002
  • In order to visually analyze the flow characteristics, gas was injected into the liquid bath through nozzle installed at the center of bottom of the bath. When gas was injected into the liquid bath, several flow patterns were observed bubble-liquid plumb, the spout flow that occurred at the free surface, liquid circulation flow by bubble's behavior, etc. Various bubbles, from small bubbles to Taylor bubbles, consisted of the bubble-liquid plumb. In the pure liquid region, the large and small several vortices were formed and irregularly circulated. These irregular repetition and circulation play a important role of mixing in the bath. The vortices were developed in the upper and the side wall regions and the movement of flow in the low region was very small. It is known as 'dead zone'.

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Anisotropic Phase Transitions of Hard-Spheres Confined in Hard Walls

  • Yun, Byeong Jip
    • Bulletin of the Korean Chemical Society
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    • v.22 no.12
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    • pp.1375-1379
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    • 2001
  • Monte Carlo simulations of hard-spheres confined in parallel hard walls have been carried out extensively at various densities and for various wall distances. The compressibility factors in the directions parallel and normal to the wall have been calculated from the radial free space distribution function (RFSDF) with the results showing that the compressibility factors normal to the wall are smaller than those in parallel direction and that a solid phase is formed in the direction normal to the wall while a fluid phase remains in the parallel direction. An order parameter is found to classify the phases whether a system (or a molecule) is in a fluid or a solid state. The compressibility factors of narrow wall are very small compared to those when the wall is put away. A plausible mechanism of the rise of sap in xylem vessel has been proposed.

Condensation of independent variables in free vibration analysis of curved beams

  • Mochida, Yusuke;Ilanko, Sinniah
    • Advances in aircraft and spacecraft science
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    • v.3 no.1
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    • pp.45-59
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    • 2016
  • In this paper, the condensation method which is based on the Rayleigh-Ritz method, is described for the free vibration analysis of axially loaded slightly curved beams subject to partial axial restraints. If the longitudinal inertia is neglected, some of the Rayleigh-Ritz minimization equations are independent of the frequency. These equations can be used to formulate a relationship between the weighting coefficients associated with the lateral and longitudinal displacements, which leads to "connection coefficient matrix". Once this matrix is formed, it is then substituted into the remaining Rayleigh-Ritz equations to obtain an eigenvalue equation with a reduced matrix size. This method has been applied to simply supported and partially clamped beams with three different shapes of imperfection. The results indicate that for small imperfections resembling the fundamental vibration mode, the sum of the square of the fundamental natural and a non-dimensional axial load ratio normalized with respect to the fundamental critical load is approximately proportional to the square of the central displacement.

Fabrication and Characterization of Free-Standing DBR Porous Silicon Film

  • Um, Sungyong;Sohn, Honglae
    • Journal of Integrative Natural Science
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    • v.7 no.1
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    • pp.1-4
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    • 2014
  • Distributed Bragg reflector porous silicon of different characteristics were formed to determine their optical constants in the visible wavelength range using a periodic square wave current between low and high current densities. The surface and cross-sectional SEM images of distributed Bragg reflector porous silicon were obtained using a cold field emission scanning electron microscope. The surface image of distributed Bragg reflector porous silicon indicates that the distributions of pores are even. The cross-sectional image illustrates that the multilayer of distributed Bragg reflector porous silicon exhibits a depth of few microns and applying of square current density during the etching process results two distinct refractive indices in the contrast. Distributed Bragg reflector porous silicon exhibited a porosity depth profile that related directly to the current-time profile used in etch. Its free-standing film was obtained by applying an electro-polishing current.

Comparative Study on Red Blood Cell Hemolysis and Yeast Test by Photosensitizing Compounds (광예민성화합물에 의한 적혈구 용혈현상과 Yeast 시험 비교연구)

  • 김봉희;백광흠
    • Environmental Analysis Health and Toxicology
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    • v.5 no.1_2
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    • pp.45-50
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    • 1990
  • In order to investigate the phototoxicity of five phenothiazine derivatives and one thioxanthen derivative were examined by using in vitro method based on growth inhibition of Candida albicans and red blood cell hemolysis. Effects of the test compounds on RBCs were monitored with a spectrophotometer and a drug PI in the Candida albicans was calculated on the basis of the lowest concentration giving a yeast-free zone. All phenothiazines phototoxic in the red blood cell hemolysis method were positive in the yeast test except promethazine. It was also observed that toxic photo-products were formed by perphenazine and chlorpromazine in the red blood cell hemolysis.

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Cu-doped Programmable Metallization Cell의 스위칭 특성 연구

  • Nam, Gi-Hyeon;Jeong, Hong-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.57-57
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    • 2009
  • Programmable Metallization Cell (PMC) is a memory device based on the electrolytical characteristic of chalcogenide materials. We investigated the nature of thin films formed by photo doping of Cu ions into chalcogenide materials for use in solid electrolyte of PMC. We were able to do more economical approach by using copper which play an electrolyte ions role. The results imply that a Cu-rich phase separates owing to the reaction of Cu with free atoms from chalcogenide materials.

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Rotation-Free Transformation of the Coupling Matrix with Genetic Algorithm-Error Minimizing Pertaining Transfer Functions

  • Kahng, Sungtek
    • Journal of electromagnetic engineering and science
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    • v.4 no.3
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    • pp.102-106
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    • 2004
  • A novel Genetic Algorithm(GA)-based method is suggested to transform a coupling matrix to another, without the procedure of Matrix Rotation. This can remove tedious work like pivoting and deciding rotation angles needed for each of the iterations. The error function for the GA is simply formed and used as part of error minimization for obtaining the solution. An 8th order dual-mode elliptic integral function response filter is taken as an example to validate the present method.

A Study of Preventing Chevron Crack in Cold Extrusion (냉간 압출시 Chevron Crack 방지에 대한 고찰)

  • 최영순;이정환
    • Transactions of Materials Processing
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    • v.6 no.3
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    • pp.221-226
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    • 1997
  • Chevron crack in cold extrusion has been studied in view of deformation conditions and material characteristics. There is V formed chevron crack is occasionally occurred in core part of shaft by multistage free extrusion. Although many research results were reported and theoretical analyses were accompanied, in this study we discussed practical method to prevent chevron crack in the field of working conditions and material characteristics. We have found that chevron crack is eliminated under condition of high hydrostatic state in deformation and decreased segregation, refinement of micro structure of materials.

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