고온 초전도체 Y₁-x Gdx Ba₂Cu₃O7-y의 임계전류밀도에 관한 연구

전인,송승기,최덕,김영호 명지대학교자연과학연구소 1991 자연과학논문집 Vol.9 No.-

고온 초전도체 Y₁-??Nd??Ba₂Cu₃O??-??(x=00.1, 0.2, 0.3,...,1.0)를 고상 반응법을 이용하여 제작하였다. 온도에 따른 전기적 비저항의 측정과 자기적 감수율의 측정을 통하여 구한 초전도 전이온도는 92.1∼93.5K 사이에 존재하였다. 77K에서 시료의 자기적 감수율은 -5.06∼-6.83Χ10??emu/㎤ㆍOe 사이에 존재하였으며, 상온에서의 비저항은 x=0.6인 시료를 제외하고 x가 증가함에 따라 감소하였다. 수송 임계전류밀도는 자기장이 0일때 51.6∼80.6 A/㎠사이에서 측정되었으며 x가 증가함에 따라 대체로 증가하였다. 자기장을 가해준 상태에서 측정한 수송 임계전류밀도 는 자기장이 증가함에 따라 급격히 감소하였다. 자기 이력곡선으로부터 Bean의 공식을 이용하여 구한 임계전류밀도는 수송 임계전류밀도의 0.8∼2.7Χ10??배로 크게 나타났다. High-Tc superconductors Y₁-??Nd??Ba₂Cu₃O??-??(x=0.1, 0.2, 0.3,…,1.0) have been prepared by solid state reaction method. The superconduction transition temperatures determined by the temperature dependence of electric resistivity and magnetic susceptibility are in the range between 92.1 and -6.83Χ10??emu/㎤·Oe and the resistivities at room temperature are decreased as increasing Gd contents except for the value of x=0.6 sample. Transport critical current densities have the value of 51.6∼80.6 A/㎠ and are generally increased with increasing the magnetic field. Magnetic critical current densities obtained from the magnetization curve using the Bean's law are about 0.8∼2.7Χ10??times of the transport J??.

ZnSe 단결정에 대한 열자극 발광과 열자극 전류의 동시측정

전경남,유승철,고석룡,신용규,김택성,이춘호 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-

두 종류의 ZnSe 분말을 사용하여 sublimation 방법으로 성장한 ZnSe 단결정(as grown)에 대하여 TSC와 TSL을 동시 측정하였으며, PL과 DLTS를 측정하였다. PL 측정으로 I_1, I_2와 DAP 발광을 관측하였으며 DLTS에 의한 깊은준위를 관측하였다. TSL과 TSC의 동시 측정으로부터 얻은 그로우 곡선을 점근 해법으로 분해하여 세개의 준위를 얻었으며 그들의 활성화에너지값은 0.22 eV, 0.30 eV, 0.39 eV이었다. PL spectrum과 열자극 완화과정의 동시 측정 결과로부터 0.22 eV 근방에 impurity에 의한 주게준위와 native defect에 의한 받게준위가 각각 전도대의 아래와 가전자대의 위에 존재하는 것으로 판명되었다. DLTS 측정과 동시측정 결과로부터 0.30 eV와 0.39 eV의 준위는 V_se vacancy와 관련되는 주게 준위임을 알았다. Simultaneous measurements of TSL were carried out on ZnSe single crystals grown by high pressure Bridgman technique and the PL and DLTS signals were observed. Photoluminescence spectrum at 10 K on the ZnSe crystal reveals I_1 and I_2 lines, as well as DAP emission line. DLTS spectrum on the ZnSe crystal show electron trap at 0.33 eV. Two TSC and TSL peaks were observed near 215 K and 230 K, which are identified as having originated from two donor trap levels at 0.30 eV and 0.39 eV, respectively, below the bottom of the conduction band. We also observed single TSL and TSC peaks at 150 K which were identified as having originated from a donor and acceptor trap levels at about 0.22 eV below the conduction band and over the top of the valence band, respectively.

대전광역시 사업체인지 변화 동향에 관한 연구

전승창,이건호 牧園大學校 建築·都市硏究센터 1999 建築·都市環境硏究 Vol.7 No.-

This study analyzes the locational distribution & change of the industrial establishment trend with the city is expanding to the suburb and activity of the downtown becomes severe. The results of this study are following this, First, industrial establishments are expanding to the area where under urban development projects. Second, in the industrial establishment respects, finance and insurance businesses are expanding to the new development area with keeping their existing enterprises. Whole sale and retails are moving from existing C.B.D area with weak competitive power to new development area with strong competitive power. In manufacturing industry respects, large scale manufacturing enterprises are keeping their places. Third, as a result of shift-share method, industrial establishments are moving from tong-gu and Chung-gu with weak competitive power to so-gu and yusung-gu where under new development.

Cr,Cu,Fe가 첨가된 MgO 단결정의 열자극 발광 스펙트럼 분석

田耕南,兪昇喆,杜夏榮,李春鎬 全北大學校 1994 論文集 Vol.38 No.-

On the MgO single crysital doped artificially with Cr, Cu, Fe we observed thermally stimulated luminescence(TSL) glow curves and spectra, and analyzed them in the temperatured range from 500 to 77 k after excitation with UV or X-ray irradiation. TSL glow curves obtained from these samples show five peaks at 136.5K, 223.5 K, 390 K, 440 K, and their estimated activation energies are 1.08 eV, 0.27 eV, 0.63 eV, 1.19 eV, and 1.33 eV, respectively. When we measured TSL spectrum at the range of 200 nm to 650 nm, we also analysed the peak wavelength which obtained at 345 nm, 375 nm, and 410 nm from measurement of TSL spectrum and described their luminescence mechanisms.

고온 초전도체 Y₁Ba₂Cu₃O_7-δ(CdO)_x의 핵사중극 상호작용 연구

전인,김복수,노태호,김영훈,서용문,송승기,박영민 명지대학교 자연과학연구소 2000 자연과학논문집 Vol.19 No.-

CdO가 첨가된 고온 초전도체 Y1Ba2CU3O7-δ(CdO)x(x=0.00,0.09,0.22,0.34,0.42,0.49)를 고상 반응법으로 제작하여 상온에서 Cu 핵사중극 공명 실험을 하였다. 구리-산소 평면에 있는 63Cu(2)의 핵사중극 공명 진동수는 31.13∼31.39 MHz이고, 65Cu(2)의 공명 진동수는 28.82∼29.06 MHz이었다. 이러한 공명 진동수는 χ가 증가할수록 높은 진동수 방향으로 이동하였다. 63Cu(2)과 65Cu(2)의 NQR 공명 진동수의 비는 모든 시료가 1.08로 63Cu과 65Cu의 핵 사중극 모멘트의 비와 같았다. 구리-산소 사슬에 있는 63Cu(1)의 공명 진동수는 22.15~22.36 MHz에서 관측되었는데, χ에 따른 공명 진동수의 이동 경향은 63Cu(2)과 65Cu(2)의 경우와 비슷하였다. 선폭은 63Cu(2)과 65Cu(2)그리고 63Cu(1)의 경우 모두 약 200∼300 kHz고, 전반적으로 χ가 증가할 수록 감소하였다. 스핀-에코 방법으로 구한 스핀-스핀 이완 시간 T2는 χ가 증가함에 따라 약간씩 증가하였다. We have studied Cu-NQR in CdO-mixed high-Tc superconductor Y1Ba2Cu3O7-δ(CdO)x(x=0.00, 0.09, 0.22, 0.34, 0.42, 0.49) at room temperature prepared by solid state reaction method. In the Cu-O plane, 63Cu(2)-NQR frequencies were measured to be in the range of 31.13-31.39 MHz and those of 65Cu(2) were in the range of 28.82-29.06 MHz. The position of spectrum-peaks shifted to the higher frequency with increasing χ. The ratio of 63Cu(2) and 65Cu(2)-NQR frequencies have the value of 1.08 which is equal to the ratio of 63Cu(2) and 65Cu(2) nuclear quadrupole moment for all samples. The resonance frequencies of 63Cu(1) in the Cu-O chain have been observed in the range of 22.15-22.36 MHz and the tendency of resonance frequency behaviour with χ were nearly the same for both 63Cu(2) and 65Cu(2). The line-widths of 63Cu(2), 65Cu(2) and 63Cu(1) were observed to the value of 200∼300 kHz and they decreased with increasing χ. The spin-spin relaxation time T2 obtained by spin-echo method increased slightly with increasing χ.

물류체계의 상대적 효율성 평가모형

전승호,노승종 한국경영과학회 1999 韓國經營科學會誌 Vol.24 No.4

We propose a series of methodologies that can evaluate relative efficiency of logistics units(centers) in three categories, managerial, cost, and operational efficiency. Inputs and outputs of logistics systems are first defined. Appropriate quantitative and qualitative measures for the three categories are then selected Employed also are Analytic Hierarchy Process. Weighted Scoring Method, Stochastic Frontier Model, and Data Envelopment Analysis for the development of a comprehensive assessment scheme. Our scheme not only assesses the degree of relative efficiency of logistics units but also identify the sources of inefficiency in each unit. The methodologies are applied to a large telecommunications company which operates 12 distribution centers nation wide. Relative efficiency of the centers are compared using 1995-1997 performance data. Summarized are the level of efficiency of each distribution center for each of the tree categories. The degree and sources of inefficiency of each distribution center are also discussed.

C₄유분을 이용한 옥텐류의 합성에 있어서 1,3-Butadiene의 함량에 따른 이량화 촉매의 수명에 관한 연구

전종기,한원희,조정호,고승태,노상균 동양대학교 2001 동양대학교 논문집 Vol.7 No.1

Selective hydrogenation of 1,3-butadiene in C4 raffinate was carried out in fixed bed reactor using Pd/a1unina catalysts, Concentration of 1,3-butadiene in C4 raffinate could be reduced under 100 ppm.The life of dimerization catalyst using C4 raffinate after selective hydrogenation was longer than that of dimerization catalyst without selective hydrogenation.It was found that dilution of olefin concentration in feed was effective to increase dimerization catalyst life.

유치 매복에 관한 증례보고

이제호,이종갑,최병재,전승준 大韓小兒齒科學會 1995 大韓小兒齒科學會誌 Vol.22 No.2

The term impaction is defined as a tooth has failed to erupt into normal position beyond the time usually expected for such appearance. Most of the cases of unerupted and impacted teeth reported in the literature are of permanent teeth. Impactions of mandibular primary second molars, however, are as numerous as all other primary impactions combined. Early detection of impaction is necessary during periodic oral examination and also radiographic examination and proper management is needed, because impaction of primary tooth may lead to obstruction of successive permanent tooth, space loss, and cystic change of tooth follicle. In these cases, 5 cases of primary teeth impaction are presented. Impaction teeth of each cases are maxillary primary incisor, maxillary and mandibular second primary molar, mandibular first primary molar. Following results were achieved by these cases; 1. In this cases, the cause of primary tooth impaction are abnormal eruption path, odontoma and fibrotic gingiva. 2. In this cases, impaction of primary tooth results in eruption problem of successive permanent tooth and failure of space maintenance. 3. Proper treatment plan should be established after through consideration of impacted tooth and it's relation with successive permanent tooth, and periodic examination and proper treatment about successive permanent tooth and eruptive condition is needed.

AISI D2강 위에 다층으로 증착된 WC-Ti_(1-X)Al_(X)N 코팅의 국부부식 거동에 관한 연구

안승호,이정호,김호건,김정구,한전건 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9

Multilayered WC-Ti_(1-x)Al_(x)N coatings are characterized by periodically repeated structures of lamellae of WC-Ti/WC-Ti_(1-x)Al_(x)N. WC-Ti_(1-x)Al_(x)N coatings of changing Al concentration were deposited on AISI D2 steel by high-ionization sputtered plasma vapor deposition (PVD). The Al concentration could be controlled by using evaporation source for Al and fixing the evaporating rate of other metals. Four kinds of WC-Ti_(1-x)Al_(x)N coatings were prepared: WC-Ti_(0.6)Al_(0.4)N, WC-Ti_(0.53)Al_(0.47)N, WC-Ti_(0.5)Al_(0.5)N and WC-Ti_(0.43)Al_(0.57)N. The corrosion behavior of WC-Ti_(1-x)Al_(x)N coatings was investigated using electrochemical techniques in deaerated 3.5% NaCl electrolyte (galvanic corrosion test, potentiodynamic polarization test, electrochemical impedance spectroscopy and Mott-Schottky method) and surface analyses (GDOES, SEM and EDS). Particular attention was paid to the effect of growth defects on the coating properties related to the corrosion behavior. The results of the coating and substrate galvanic corrosion test showed low galvanic current densities. In the potentiodynamic polarization test and EIS measurement, the corrosion current density of WC-Ti_(0.5)Al_(0.5)N was lower than others and presented higher R_(ct) values than others after 240 h immersion time. This could be attributed to the formation of a Ti oxide, which promotes partial closing of the defects. Capacitance values obtained from EIS as a function of different potentials (C^(-2) vs E) showed that the oxide layer exhibited an n-type semiconductor behavior.

철근 이음형 PC 보-기둥 내부 접합부의 구조적 거동에 관한 실험적 연구

김승훈,하상수,문정호,이리형,이강철,전병갑 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)

In this study, new moment-resisting precast concrete beam-column joint is proposed for moderate seismic regions. It has the connection reinforcing bars, penetrated the joint and lap-spliced with the bottom bars of precast U-beam. An experimental study was carried out to investigate the joint behavior subjected to reverse cyclic loading and constant axial compressive load. Three precast beam-column interior were tested. The variables examined were the type of connection reinforcing bars and presence of transverse reinforcement in joint. Joint performance is evaluated on the basis of connection .strength, stiffness, energy dissipation, and drift capacity. Based on the test results, the precast connection is capable of matching or exceeding the performance of the monolithic connection and thereby provides the sufficient moment-resisting behavior to be applicable for moderate seismic regions.