• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.793-799
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• 2004

In track a third weakness point is joint part, turnout part, curve part. One of them joint part of rail have been known to the most weak point by loosen of joint bar and fish bolt due to impulse and vibration by wheel contact at times. In addition happen to deformation and failure at end of rail, failure and miniature of ballast gravel. Finally impact between wheel and rail become origin cause of a welded rail, noise and vibration. riding condition deterioration, besides track failure. In the present domestic, Thermite and Gas pressure weldings have been used to continuous welded rail(CWR), however stiffness and confidence in quality is lower than Flash butt welding method. FRW have the excellent capacity, however have a shortcoming large scale of machine and power equipment. Therefore we will introduce Mobile Flash Butt Welder can weld in track.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.23-25
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• 1994

A simple analytical method that allows direct monitoring of small amount of CO$_2$ in a CO$_2$ discharge tube which utilizes the optoacoustic detection technique is described. The dependence of the optoacoustic signal on the mole fraction of CO$_2$ was shown that the system responded linearly to the amount of CO$_2$ present in the miniature discharge cavity equipped with Cu electrodes. It was also found that fraction of dissociated CO$_2$ varied from 14 to 37% of the initial concentration which depended on the current and the pressure in the tube. This simple and easy detection method has proven to possess the practical advantages over the conventional systems for the study of CO$_2$ laser electrodes.

• The Korean Journal of Physiology and Pharmacology
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• 제2권6호
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• pp.687-693
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• 1998

This study was performed to examine the mean arterial pressure and nociceptive jaw opening reflex after microinjection of glutamate into the amygdala in freely moving rats, and to investigate the mechanisms of antinociceptive action of amygdala. Animals were anesthetized with pentobarbital sodium (40 mg/kg, ip). A stainless steel guide cannula (26 gauge) was implanted in the amygdala and lateral ventricle. Stimulating and recording electrodes were implanted into each of the incisor pulp and anterior digastric muscle. Electrodes were led subcutaneously to the miniature cranial connector sealed on the top of the skull with acrylic resin. After 48 hours of recovery from surgery, mean arterial pressure and digastric electromyogram (dEMG) were monitored in freely moving rats. Electrical shocks (200 ${\mu}sec$ duration, $0.5{\sim}2$ mA intensity) were delivered at 0.5 Hz to the dental pulp every 2 minutes. After injection of 0.35 M glutamate into the amygdala, mean arterial pressure was increased by $8{\pm}2$ mmHg and dEMG was suppressed to $71{\pm}5%$ of the control. Injection of 0.7 M glutamate elevated mean arterial pressure by $25{\pm}5$ mmHg and suppressed dEMG to $20{\pm}7%$ of the control. The suppression of dEMG were maintained for 30 minutes. Naloxone, an opioid receptor antagonist, inhibited the suppression of dEMG elicited by amygdaloid injection of glutamate from $28{\pm}4\;to\;68{\pm}5%$ of the control. Methysergide, a serotonin receptor antagonist, also inhibited the suppression of dEMG from $33{\pm}5\;to\;79{\pm}4%$ of the control. However, phentolamine, an ${\alpha}-adrenergic$ receptor antagonist, did not affect the suppression of dEMG. These results suggest that the amygdala can modulate both cardiovascular and nociceptive responses and that the antinociception of amygdala seems to be attributed to an augmentation of descending inhibitory influences on nociceptive pathways via serotonergic and opioid pathways.

• Journal of Electrical Engineering and information Science
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• 제3권2호
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• pp.239-244
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• 1998

Piezoelectric pressure sensors and pyroelectric infrared detectors based on ZnO thin film have been integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers. Surface micromachining techniques have been applied in a GaAs MESFET process to form both microsensors and electronic circuits. The on-chip integration of microsensors such as pressure sensors and infrared detectors with GaAs integrated circuits is attractive because of the higher operating temperature up to 200 oC for GaAs devices compared to 125 oC for silicon devices and radiation hardness for infrared imaging applications. The microsensors incorporate a 1${\mu}$m-thick sputtered ZnO capacitor supported by a 2${\mu}$m-thick aluminum membrane formed on a semi-insulating GaAs substrate. The piezoelectric pressure sensor of an area 80${\times}$80 ${\mu}$m2 designed for use as a miniature microphone exhibits 2.99${\mu}$V/${\mu}$ bar sensitivity at 400Hz. The voltage responsivity and the detectivity of a single infrared detector of an area 80${\times}$80 $\mu\textrm{m}$2 is 700 V/W and 6${\times}$108cm$.$ Hz/W at 10Hz respectively, and the time constant of the sensor with the amplifying circuit is 53 ms. Circuits using 4${\mu}$m-gate GaAs MESFETs are fabricated in planar, direct ion-implanted process. The measured transconductance of a 4${\mu}$m-gate GaAs MESFET is 25.6 mS/mm and 12.4 mS/mm at 27 oC and 200oC, respectively. A differential amplifier whose voltage gain in 33.7 dB using 4${\mu}$m gate GaAs MESFETs is fabricated for high selectivity to the physical variable being sensed.

• 대한기계학회논문집A
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• 제39권4호
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• pp.429-435
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• 2015

벨로우즈는 줄-톰슨 소형 극저온 냉각기에서 온도조절장치로 사용하는 중요한 부품이다. 벨로우즈는 매우 얇은 쉘로 제작되었으며 내부는 질소기체로 충전되어 있다. 또한 재료는 니켈-코발트 합금이며 이 재질은 $300^{\circ}C$에서 극저온까지 탄성계수와 강도가 변하지 않는 금속이다. 벨로우즈 내부의 기체는 온도가 바뀌면 기체의 압력과 부피가 변하고 결과적으로 벨로우즈가 길이 방향으로 수축 또는 팽창한다. 이 현상을 해석하기 위하여 주어진 온도에서 기체의 상태방정식이 만족될 때까지 수정된 압력하에서 벨로우즈의 변형과 변형된 내부 체적을 반복적으로 계산하였다. 현 연구에서 기체의 온도-부피-압력 상태를 정의하는 식으로 MBWR 상태 방정식이 채택되었다. 제안한 해석 방법론의 타당성을 증명하기 위하여 실험을 수행하였고 비교결과 수치 해는 실험값과 잘 일치하였다.

• 한국지반신소재학회논문집
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• 제10권4호
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• pp.49-59
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• 2011

본 연구에서는 보강토 옹벽 구조물의 지진저항 특성을 파악하기 위하여 대표단면을 기초로 하여 축소모형의 비율에 해당하는 상사법칙을 고려하여 1:10의 상사비로 토조를 제작하였다. 그리고 국내 설계기준에 준하여 장주기인 Hachinohe파, 단주기인 Ofunato파, 인공지진파를 가진하여 실험 대상단면에 대해 가속도변화, 토압, 변위를 측정하고, 측정된 결과를 통하여 보강토 옹벽의 지진 시 외적안정성을 평가하였다. 실험결과 보강재를 설치하지 않은 옹벽구조물에서는 지진가속도 0.2g에서 파괴되었으나 보강재를 설치한 보강토 옹벽에서는 안정성을 확보하는 것으로 평가되었다. 토압계 측정결과 하부보다 상부에서 지진에 의한 토압의 증가량이 크게 발생되는 경향을 보였으며, 이는 기존의 이론과 비슷한 거동특성을 보이는 것으로 평가되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.1-4
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• 2008

Fuel cells have the potential of providing several times higher energy storage densities than those possible using current state-of-the-art lithium-ion batteries, but current energy density of fuel cell system is not better than that of lithium-ion batteries. To achieve the high energy density, volume and weight of fuel cell system need to be reduced by miniaturizing system components such as stack, fuel tank, and balance-of-plant. In this paper, the thin flexible PCB (Printed circuit board) is used as a current collector to reduce the stack volume. Two end plates are made from light weight aluminum alloy plate. The plate surface is wholly oxidized through the anodizing treatment for electrical insulation. The opening rate of cathode plate hole is optimized through unit cell performance measurement of various opening rates. The performances are measured at room temperature and ambient pressure condition without any repulsive air supply. The active area of MEA is 10.08 $cm^2$ and active area per a unit cell is 1.68 $cm^2$. The peak power density is about 210 mW/$cm^2$ and the air-breathing planar stack of 2 Wis achieved as a small volume of 18 cc.

• 산업기술연구
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• 제22권B호
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• pp.191-197
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• 2002

This paper is experimental and numerical research results of performing centrifuge model tests to investigate the geotechnical engineering behavior of slag compaction pile as a substitute of sand compaction pile. In order to find the geotechnical engineering characteristics of the soft clay and the slag used in centrifuge model experiments, basic soil property tests, consolidation test, permeability tests and triaxial compression tests were performed. For centrifuge model tests, slags with changing relative density were used and their bearing capacity, stress concentrations in between pile and soft clay, settlement characteristics, and failure modes were investigated. As a results of centrifuge model tests, it was found that the bearing, capacity of model was increased with increasing density of slag pile and general shear failures were occured. Miniature soil pressure gauges were installed on model pile and soft ground respectively and thus vertical stress acting on them were measured. Stress concentration ratio was found to be in the range of 2.0~3.0. Bearing capacity obtained from the model test with slag was greater than that from the model test with a sand having the identical layout to each other. Thus it was confirmed the slag was an appropriate substitution of pile for sand.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.561-568
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• 2000

본 연구의 목적은 Piezocone 관입시험을 이용한 연약지반의 OCR 평가에 있어 기존의 여러 가지 해석방법들과 최근에 새롭게 제안된 방법들을 실내 모형토조에서 실측된 피에조콘 관입 실험치에 적용하여 각 해석방법들의 차이와 장단점들을 비교 분석하는데 있다. 본 연구의 연구실험방법으로는, Piezocone 관입을 위한 연약 모형지반 조성을 위하여 초대형 Slurry Consolidometer에 Free Stress 상태의 Slurry를 45일간 압밀시킨후 Automatic Computer Control Calibration Chamber (LSU/CALCHAS; Louisiana Slate University Calibration Chamber System)에 옮긴후 다시한번 압밀시키는 Two-Stage Consolidation Method를 사용하였다. 모형지반은 여러 가지 Boundary Condition들과 Stress Condition 그리고 Stress History등을 달리하여 총 5개의 지반을 조성하였다. 관입시험은 총 25개의 Piezocone 관입이 수행되어졌고, 그중 4개는 Standard 10 cm2 Piezocone이고, 나머지 21개는 Miniature Piezocone이 사용되었다. Piezocone 실험치들에 대한 여러 가지 OCR 해석방법 적용결과, Schmertmann방법은 5개 모형지반 모두에서 과다한 OCR평가를 보였으며, $B_{q}$ 방법은 일부모형지반에서 음의 OCR값으로 계산되어졌다. 그러나, Critical-Stale Soil Mechanics 와 Cavity Expansion 이론에 근거하여 Mayne(1991), Kurup(1993), Tumay et al (1995) 들이 제안한 OCR 평가방법들은 실험치와 잘맞는 경향을 보여주었다. 이와같은 이론 모델값들의 차이는 응력조건(Stress Condition)과 경계조건(Boundary Condition)들에 대한 각 해석방법들의 고려정도에 따른 결과로 판단된다.

• 한국지반환경공학회 논문집
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• 제13권5호
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• pp.13-24
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• 2012

국토의 효율적 이용과 기간시설 수용을 위한 대단위 부지 확충 및 대규모 항만배후부지 개발이 계획 중에 있으며, 이에 따라 해안지역의 준설매립은 지속적으로 이루어지고 있다. 슬러리 상태의 초연약 상태인 준설매립 지반은 오랜 시간에 걸쳐 침강 및 자중압밀 과정을 거치게 되며 투기한 준설토를 압밀 촉진시켜 침하시킬 수 있다면 기존 처분지의 수명을 연장시킬 수 있으므로 경제적으로 유용하리라 판단된다. 재하중 없이 공기를 단축시키고 매립 물량을 증대시키기 위하여 small column test와 medium column을 보완, 개발한 medium column test를 실시하여 PBD와 침투압이 동시에 작용하였을 PBD의 효과 및 침투압의 침강 및 자중압밀 촉진 효과를 검토하였다. 연구 결과, 기존의 자중압밀 공법에 비하여 침투압과 PBD를 적용한 지반은 배수재의 배수거리 단축에 따른 투수 상승 효과와 침투압에 의한 침투 압밀의 효과가 활발히 이루어지는 것으로 나타났다. 이를 통해 매립 직후나 매립 도중에 연직드레인을 직접 타설하여 침강 및 자중압밀 과정을 단축시키면 전체 매립공사 공기를 단축시킬 수 있으며 압밀촉진에 따라 확보된 여유고 만큼 준설토 투기가 가능해져 투기 준설토량을 경제적으로 증대시킬 수 있을 것으로 기대된다.