• 드라이브 ㆍ 컨트롤
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• 제14권2호
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• pp.1-8
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• 2017

The spool displacement of a directional control valve can be considered as the standard signal for the measurement of its bandwidth frequency. When the spool displacement is not available, the metering-orifice system is suggested in this study as an alternative way to measure the - 3 dB amplitude-ratio bandwidth frequency of the hydraulic directional-control valve. The amplitude ratio of the metering-orifice pressure can be adjusted to equal that of the spool displacement through the controlling of the metering-orifice opening area. A series of experiments were conducted to verify the effectiveness of the metering-orifice system. The metering orifice was confirmed as adequate for the measurement of the - 3 dB amplitude-ratio bandwidth frequency.

• 한국자동차공학회논문집
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• 제22권7호
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• pp.57-62
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• 2014

This study presented the feasibility of a coolant heat-source heat pump system as an alternative heating system for electrically driven vehicles. Heat pumps are among the most environmentally friendly and efficient heating technologies in residential buildings. In various countries, electric mobiles devices such as EV, PHEV, and FCEV, have been mainly concerned with heat pumps for new mobile markets. The experiments herein were conducted for various ambient temperatures and coolant temperatures to reflect the winter season. The system, a coolant heat-source heat pump, consisted of an inside heat exchanger, an outside heat exchanger, a motor driven compressor, an electronic expansion valve, and plumbing parts. For the experimental results, the maximum heating capacity and air discharge temperature are up to 6.3 kW and $62^{\circ}C$ respectively at an ambient temperature of $10^{\circ}C$, and coolant at $10^{\circ}C$. However, at $-20^{\circ}C$ ambient temperature and $-10^{\circ}C$ coolant temperature, conditions were insufficient to warm the cabin as the air discharge temperature was $13^{\circ}C$.

• 설비공학논문집
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• 제27권4호
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• pp.213-219
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• 2015

A thermal storage tank with internal heat exchange coils is commonly used in solar thermal systems with a collector area below $100m^2$. The coils are installed in the lower part of the tank because the temperature of the upper part of the tank can drop if the outlet temperature of the collector becomes lower than the upper temperature of the tank, which is a kind of temperature reversal. As an alternative to the well-mixed storage tank with lower coil only, we have proposed a tank with lower and upper coils and have achieved superior thermal stratification in the tank, which results in increased collector efficiency and solar fraction. But, the phenomenon of temperature reversal was often observed in the tank when the load or solar radiation changed rapidly. In the present work, revised control was successfully applied, i.e., to heat only the lower coil using a three way valve if temperature reversal occurs and to operate the collector at a low flow rate when the quality of solar radiation is not good.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.42-48
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• 1999

A control method for a robot hand grasping a object in a partially unknown environment will be proposed, where a proximate sensor detecting the distance between the fingertip and object was used. Particularly, the finger joints were driven servo-pneumatically in this study. Based on the proximate sensor signal the finger motion controller could plan the grasping process divided in three phases ; fast aproach, slow transitional contact and contact force control. That is, the fingertip approached to the object with full speed, until the output signal of the proximate sensor began to change. Within the perating range of the proximate sensor, the finger joint was moved by a state-variable feedback position controller in order to obtain a smooth contact with the object. The contact force of fingertip was then controlled using the blocked-line pressure sensitivity of the flow control servovalve for finger joint control. In this way, the grasping impact could be reduced without reducing the object approaching speed. The performance of the proposed grasping method was experimentally compared with that of a open loop-controlled one.

• 한국정밀공학회지
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• 제21권3호
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• pp.100-108
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• 2004

Contamination of environment induces the shortage of drinkables. In this trend, the leakage of water that occurs by breakage or erosion of rubber valve seats is serious problem. Rubber is apt to cause breakage between two materials when they contact with each other. The possible way to avoid leakage of water by damage and breakdown of rubber is to replace that with metal. Because of this reason, nowadays, rubber is being substituted with metal as valve seat materials for water works. In tribology, a severe from of wear is characterized by local, macroscopic material transfer, removal, or formation of surface protrusions when two solid surfaces experience relative sliding under load. One of the major problems in sliding of metals is galling due to bad surface quality. Experimentally, there are various elements which influence on incipient galling, such as hardness, surface roughness, temperature, load, velocity and external environments. This paper is aimed at verifying the galling tendencies according to hardness, surface roughness, load and velocity and showing how much effect the factors have on the galling tendencies.

• Journal of Chest Surgery
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• 제19권3호
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• pp.457-463
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• 1986

Truncus Arteriosus is uncommon, accounting for 0.4%-2.8% of all congenital cardiac malformations. Truncus arteriosus has a poor prognosis in early infancy and defined as "a single arterial trunk that leaves the heart by way of a single arterial valve and that gives rise to the coronary, systemic and one or both pulmonary arteries directly." Through antemortem study of patients with truncus arteriosus the development of surgical techniques for palliation and correction was established. Recently we had surgical experience of truncus arteriosus - Collett '||'&'||' Edwards type 2. The main pulmonary artery was originated from truncus at right posterolateral aspect. Truncal valve was tricuspid with good coaptation. Ventricular septal defect was subarterial type of 2.0 cm in diameter. After detachment of the main pulmonary artery from truncus, truncus was repaired directly. Ventricular septal defect was closed with Dacron patch. Extracardiac valved conduit [Carpentier-Edwards: 16mm] was employed for making continuity between right ventricular outflow tract and pulmonary artery. Postoperatively, incomplete right bundle branch block on electrocardiogram was continued. Patient was died due to respiratory failure in postoperative 40 days.s.

• 한국산학기술학회논문지
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• 제20권2호
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• pp.1-6
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• 2019

본 연구의 목적은 100kW급 연료전지 시스템의 열관리 성능을 실도로 운전조건에서 분석하여, 성능 해석 모델링을 개발하는 것이다. 개발된 모델을 적용하여, 열관리 시스템의 운전조건 변화에 따른 성능 변화를 고찰하고자 한다. 해석 모델링은 핵심부품들에 대한 성능 평가 데이터를 바탕으로, 성능에 영향을 주는 변수들로 개발하였다. 개발된 연료전지 열관리 시스템 해석 모델링으로 다양한 실차 운전조건에서의 최적 열관리 시스템에 대한 전력소비량을 분석하였다. 주요하게, 연료전지 열관리시스템 핵심부품(워터펌프, 냉각 팬, 3 Way Valve, 라디에이터)에 대한 성능 특성 분석 후 모델링을 진행하였다. 개발된 모델링으로 운전조건에 따른 유량 예측을 하였고, 실험값과 예측값과의 비교분석을 통하여서, 해석 모델링에 대한 검증을 진행하였다. 과도해석을 통하여서, 냉시동시 냉각수 온도가 특정온도까지의 소요시간을 예측하였다. 스택 운전조건에서 스택 입출구 온도가 적정 수준에서 움직이기 위한 열관리 시스템 운전조건에 대한 예측을 진행하였다. 그 결과를 바탕으로, 소모전력과 열방출량과의 비교분석을 하였다. 개발된 해석 모델링은 핵심부품들의 성능 변화시 연료전지 시스템 운전에 대한 영향도를 분석할 수 있도록 활용할 예정이다.

• Journal of Chest Surgery
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• 제42권5호
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• pp.597-603
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• 2009

배경: 기능적 단심 실에서 방실판막 폐쇄부전은 폰탄수술 후 사망과 그 만기성적의 중요한 위험인자로 알려져 있다. 단심실의 공통방실판 페쇄부전에 대한 이분성형술(bivavaltion valvuloplasty)의 중단기 성적을 조사하였다. 대상 및 방법: 1999년부터 2007년까지 판막 이분성형술을 시행한 기능적 단심실 환자 11명을 대상으로 하였다. 공통방실판 역류의 정도는 color Doppler 심초음파로 결정하였다 (경미(trivial); 1, 경도(mild); 2, 중등도(moderate); 3, 고도(severe); 4). 판막 수술 당시 평균 나이는 생후 $6.9{\pm}7.0$개월(중간 값 4개월, 범위 24일$\sim$21개월)이었고 평균 체중은 $6.2{\pm}2.8\;kg$ (범위: $3.1{\sim}11.3\;kg$)이었다. 9명의 환자가 심방이형증(atrial isomerism)을 갖고 있었으며 이 중 두 명은 총폐정맥연결 이상을 동반하였다. 1예를 제외한 모든 예에서 동시에 다른 수술이 함께 시행되었다. 판막 이분성형술 이외에 같이 시행된 판막 술식은 3예에서 교련봉합술, 또 다른 3예에서 교련부 판륜성형술을 시행하였다. 결과: 병원사망이 1예 있었는데 술 전 인공호흡이 필요하였던 생후 32일된 환아로, 폐동맥교약술과 함께 판막 이분성형술을 시행한 후 4.3개월에 기도와 폐 질환으로 사망하였다. 평균 추적기간은 40개월(범위: $4.3{\sim}114$개월)이었다. 평균 수술 전 공통방실판 역류는 $3.3{\pm}0.6$이었고 이는 수슬 후 $1.9{\pm}0.7$로 개선되었다(p<0.0001). 이 잔존 역류는 평균 14.3개월 후 $2.2{\pm}0.4$로 조금 증가하였으나 통계학적 유의성은 없었다. 6명(60%)의 환아에서 잔존 역류로 인해 양방성 상공정맥-폐동맥 단락술이나 폰탄수술 시에 판막에 대한 재수술이 필요하였다. 1예는 우측 방실판막에 엡스타인기형 형태를 갖고 있었던 환아로 방실판 협착 및 역류로 인해 판막치 환술을 시행하였다. 다른 1명의 환아는 우측 방실판막에 가장자리 봉합술(edge-to-edge technique)을 시행하였으며 나머지 4명의 환아에게는 전후 브리징판엽(bridging leaflet)사이에 봉합을 추가하였다. 모든 환자에서 마지막 추적 초음파에서 경미 혹은 경도의 역류를 보였다. 결론: 기능적 단심실의 공통판막 역류에서 판막 이분성형 술은 효과적이고 안전한 술식이다. 그러나 많은 환자에서 잔존 역류를 가지고 있었으며 반수 이상의 환자에서 다음 단계의 수술에서 판막의 재수술이 필요하다 공통판 역류의 진행에 대한 장기적 추적조사가 꼭 필요할 것으로 생각된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1122-1126
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• 1991

As microcomputers have become widespread and the high speed solenoid valves have been developed, digitally controlled hydraulic systems are used in many applications. This study deals with position control of hydraulic cylinder operated by two port 3-way high speed solenoid valve using a self-learning strategy. This was done by developing a control algorithm for the microcomputer which always automatically adjust the length of control pulse to the optimum value in accordance with the error regardless of changes in the operating condition and physical differences between components. Tests carried out in the laboratory indicate that a positional accuracy could be improved.

• 에너지공학
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• 제14권3호
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• pp.180-186
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• 2005

실험에 사용된 엔진은 $3000\~12000$ RPM의 광범위한 회전수범위를 가지고 있어 엔진성능을 향상시키기 위해서는 다양한 제어장치가 필요하다. SCV는 저회전수에서 엔진의 성능을 개선시키기 위한 방법 중의 하나로 자주 언급되어지고 있다. 본 연구에서는 소형고속엔진에 SCV를 장착하여 저회전수 범위에서 SCV가 엔진에 미치는 영향에 대해 조사하였다. 실험에서는 4valve SOHC 공랭식 단기통 엔진에 SCV의 형상에 따른 스월 강도, 출력, 연료소비율, 배기가스를 조사하였다 그 결과 SCV의 사용 가능 범위 5000 RPM에서 연료소비율 $9\%$의 저감효과를 보았다.