• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.42-47
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• 1993

Importance of separation of a nonlinear dynamical system into nonlinear static part and linear dynamical part was insisted in designing a controller for the nonlinear system. We further proposed compensation techniques for oscillation of controlled variables caused by system time delay and compensation of steady state errors caused by modelling errors of the systems. The proposed principle of designing procedure and the compensation methods were discussed by applying them for temperature and level control of an actual tanked water system.

• 방사성폐기물학회지
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• 제20권2호
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• pp.185-192
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• 2022

A compacted bentonite buffer is a major component of engineered barrier systems, which are designed for the disposal of high-level radioactive waste. In most countries, the target temperature required to maintain safe functioning is below 100℃. If the target temperature of the compacted bentonite buffer can be increased above 100℃, the disposal area can be dramatically reduced. To increase the target temperature of the buffer, it is necessary to investigate its properties at temperatures above 100℃. Although some studies have investigated thermal-hydraulic properties above 100℃, few have evaluated the water suction of compacted bentonite. This study addresses that knowledge gap by evaluating the water suction variation for compacted Korean bentonite in the 25-150℃ range, with initial saturations of 0 and 0.22 under constant saturation conditions. We found that water suction decreased by 5-20% for a temperature increase of 100-150℃.

• 한국광학회지
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• 제10권4호
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• pp.273-278
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• 1999

광섬유 Fabry-Perot 간섭계를 센서로 하는 TDM 다중화 광섬유 압력/온도 센서시스템을 개발하고, 이 시스템을 이용하여 수위와 온도 측정실험을 행하였다. 측정시스템의 측정속도는 측정데이타를 저장하지 않는 경우 최대 초당 4500회이며, 센서의 응답속도는 ~1 ms로 추정된다. 압력센서와 온도센서의 특성은 이론적 추정치와 비교하여 각각 +13.7%,-18%의 차이를 보였으며, 반복실험을 통하여 선형화한 후의 선형화 오차는 1%이내, 온도의 변화가 $<0.1>^{\circ}C$이내 일 때 수위측정의 오차는 $\pm$0.3cm이며, 수위측정에 대한 시스템 잡음은 측정하지 않았다. 온도센서의 시스템 잡음은 0.1$^{\circ}C$이내였으며, 이 시스템을 이용하여 수위 및 온도 변화량에 대한 고속 측정실험을 수행할 결과 예상된 결과를 얻을 수 있었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.404-410
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• 2001

A new thermal type fluid level transmitter was designed and tested at the HITROL R&D institute. The relation of heat transfer and electric resistance was adopted as an operation principle. The length of a fabricated level transmitter was two meters and a water under normal temperature was used as a working fluid for the experiment Finally, the new product could have a high precision, acceptable accuracy and reasonable response time. Foreign-made level transmitter of this type is under in use for measuring water level of containment building in nuclear power plants so far. It is expected that new product will substitute it.

• 환경정책연구
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• 제13권2호
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• pp.21-38
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• 2014

지구의 온난화로 인하여 기온이 상승하고 이에 대응하여 수온 증가가 감지되고 있다. 하천의 수온 변화는 수질과 생태계, 특히 용존산소변화와 생물체의 이동으로 이어진다. 기온 변화가 하천의 수질과 생태 환경에 미치는 영향을 추정하기 위해서 수온 상승의 시기와 하천 어종에 대한 이해가 필요한데 이를 위하여 미래의 수온을 예측할 필요가 있다. 환경부 산하 국립환경과학원에서 설치한 국가수질관측망 자료와 기상청 기상관측소의 기온 자료를 활용하여 기온-수온 비선형 상관관계모형을 구축하였다. 기온-수온 대표 관계인 비선형 로지스틱(Logistic) 함수에 포함된 4개의 매개변수를 결정하기 위하여 SCE최적화 기법을 이용하였다. 기온-수온 상관관계는 시간규모에 따른 최대 온도와 최소 온도에 차이가 있으나 수질 또는 생태 반응의 적당한 시간규모에 해당하는 주 평균 온도를 이용하여 분석하였다. 전반적으로 우리나라 하천의 기온-수온 관계는 선형보다는 비선형 모형에서 NSC와 RMSE가 더 우수하여 비선형 모형이 적합한 것으로 나타났다. 연구 결과는 미래의 기온 상승 변화에 반응하는 수질, 수문 및 생태반응에 대비하여 공학기술자 또는 정책입안자에게 적절한 기후변화 대책 방향을 설정하는 데 지침을 제공할 것이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.471-474
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• 2002

A fuel tank contains water at the bottom under the fuel. The water comes from humidity by temperature change of inside and outside of tank. So it is necessary to measure both level to check precise amount of oil. But measuring instrument for level of water and fuel is not available yet. Since the fuel is inflammable, the sensor system must not include any electric circuits in the fuel tank. Optical cable sensor can satisfy this non-explosive condition. The displacement of a float changing by water level makes bending curvature of optical cable different. As the float rise up, the optical cable is bent more and the light signal in the cable decreases. The reduction of light signal is detected and it is converted into the change of water level. The output signal from a photo diode shows the proportional relation of water level. The increase of sensor voltage as a unit of ㎷ follows the level position of the float that is located between water and gasoline in the tank.

• 한국전자통신학회논문지
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• 제16권2호
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• pp.371-378
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• 2021

본 연구에서는 한국 남동해역에 발생하는 냉수대의 공간적인 분포를 구분하기 위해 2016 ~ 2018년의 고리, 양포의 해양 관측 부이 수온자료와 GHTSST Level 4 재분석 해수면 온도자료를 K-means clustering 기법을 활용하여 분석하였다. 부이자료는 남동해역에서 고리와 양포 지점의 수온변화 및 냉수대 발생을 파악하기 위해 활용하였다. 그 결과 냉수대 발생 시점에 고리와 양포의 수온이 동일하게 감소하였다. 이에 냉수대 발생시 SST의 변화를 보기 위해 수온의 역수와 SST의 분산을 비교하였다. 수온이 변화하는 시점에 SST의 분산도 증가하는 것을 나타내었는데 이를 통해 냉수대 발생시 해역의 SST의 수온분포에 변화가 있다는 것을 알 수 있었다. 냉수대 발생해역을 분류하기 위해 K-means clustering을 활용하였다. Elbow 기법을 활용하여 분류를 위한 최적의 K값을 찾아낸 후 분류를 진행한 결과 연안의 차가운 해수가 존재하는 지역을 찾아낼 수 있었다. 이를 통해 냉수대 발생해역의 공간적인 분포 및 확산범위를 추정하여 향후 냉수대로 인한 피해 파악 및 공간적인 확산 예측연구에 활용할 수 있을 것이라 판단된다.

• Journal of Biosystems Engineering
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• 제25권4호
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• pp.273-278
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• 2000

The hybrid heat pump system of the air to air and / or air to water was composed and its COP was analyzed with the ambient temperature on the opened and closed loop system respectively. The results be indicated by the equation(7) that the COP(Coefficient of Performance) of air-source(air to air and / or air-water) heat pump is effected with the ambient air temperature and AVACTHE.(Automatic Variable Area Capillary Type Heat Exchanger) 2. The COP of air-to-water heat pump without AVACTHE decreased in accordance with the ambient temperature decrease, however in case of the heat pump with AVACTHE the COP was maintained at 2.8∼3.0 level when the ambient temperature decrease from -$5^{\circ}C$ to $-11^{\circ}C$. 3. The COP of the air-to-water heat pump operated on the open loop was higher 40∼58% than that of the heat pump operated on the close loop. 4. The lower ambient temperature air effect on the COP of the air-to-air heat pump operated on the semi closed loop could be controlled using the AVACTHE, and at the high ambient air temperature the COP increased using the Bypass circuit.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2204-2220
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• 2020

An open-pool type research reactor is designed and operated considering the accessibility around the pool top area to enhance the reactor utilization. The reactor structure assembly is placed at the bottom of the pool and filled with water as a primary coolant for the core cooling and radiation shielding. Most radioactive materials are generated from the fuel assemblies in the reactor core and circulated with the primary coolant. If the primary coolant goes up to the pool surface, the radiation level increases around the working area near the top of the pool. Hence, the hot water layer is designed and formed at the upper part of the pool to suppress the rising of the primary coolant to the pool surface. The temperature gradient is established from the hot water layer to the primary coolant. As this temperature gradient suppresses the circulation of the primary coolant at the upper region of the pool, the radioactive primary coolant rising up directly to the pool surface is minimized. Water mixing between these layers is reduced because the hot water layer is formed above the primary coolant with a higher temperature. The radiation level above the pool surface area is maintained as low as reasonably achievable since the radioactive materials in the primary coolant are trapped under the hot water layer. The key to maintaining the stable hot water layer and keeping the radiation level low on the pool surface is to have a stable flow of the primary coolant. In the research reactor with a downward core flow, the primary coolant is dumped into the reactor pool and goes to the reactor core through the flow guide structure. Flow fields of the primary coolant at the lower region of the reactor pool are largely affected by the dumped primary coolant. Simple, circular, and duct type discharge headers are designed to control the flow fields and make the primary coolant flow stable in the reactor pool. In this research, flow fields of the primary coolant and hot water layer are numerically simulated in the reactor pool. The heat transfer rate, temperature, and velocity fields are taken into consideration to determine the formation of the stable hot water layer and primary coolant flow. The bulk Richardson number is used to evaluate the stability of the flow field. A duct type discharge header is finally chosen to dump the primary coolant into the reactor pool. The bulk Richardson number should be higher than 2.7 and the temperature of the hot water layer should be 1 ℃ higher than the temperature of the primary coolant to maintain the stability of the stratified thermal layer.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.638-641
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• 2008

Geothermal water at moderate temperature in a range between 30 to $50^{\circ}C$ exists sparse in surroundings. Mostly they are utilized as heat or water source at spar zones in Korea. However, a large portion of used water is discarded due to its poor recovery quality and inferior application technologies. In this research, an innovative heat pump system based on the hybrid concept that combinate compression cycle and absorption cycle was investigated mathematically. The hybrid heat pump aims to recycle various kind of the heat sources at moderate temperature including geothermal water effectively. The prime objective of the simulation is to design a compression/absorption hybrid heat pump system which can make high temperature above the level of $90^{\circ}C$ and low temperature of $20^{\circ}C$ as well at the same using $50^{\circ}C$ geothermal heat water. As a result, primitive data was provided as a basis to design a prototype 3 RT class hybrid heat pump.