• Journal of Biosystems Engineering
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• 제14권2호
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• pp.128-136
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• 1989

The purpose of this study was to develop a computer operated automatic drip irrigation system for application in vinyl-house cultivation. The results can be summarized as follows: 1) The T-type ice compensation wire was used to measure the temperature. The voltage level measured up to 0.02 volt was used as input to an 8-bit A/D converter. 2) A specially devised tensiometer was used to content the watering system. When the needle of the pressure gauge reaches the lower threshold position it turns on the pumping system and turns off when it reaches higher threshold position. 3) In order to use the multiple gypsum blocks for one transducer, reed relays and a D/O board were used to make the sequential switching possible. 4) It was possible to automate the trickle irrigation system for the whole growth period of vinyl-house crops with the help of microcomputer. 5) In terms of furrow irrigation, the irrigation water consumption was the smallest, 2.8 times less than conventional method of surface trickle irrigation, 3.4 times less than subsurface trickle irrigation method. 6) In terms of productivity of cucumber, there was a drop in productivity when compared to furrow irrigation method, 7.2% for surface trickle irrigation, 27.4% for subsurface irrigation method.

• 동력기계공학회지
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• 제17권2호
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• pp.95-102
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• 2013

For vessels operating in the cold climate regions, the ballast water inside or hopper tanks above the waterline may be frozen, starting at the top of the tank and at the side walls. Therefore, countermeasures against freeze-up of the ballast tank such as air-bubbling system, hot steam injecting system, heating coil system and water circulating system are taken to prevent freeze-up phenomenon; however, there are no rigorous investigations of anti-freezing to examine the effectiveness and validity of systems against freeze-up of the ballast tank, in which the temperatures are about $-25^{\circ}C$ (ambient air temperature) and $0^{\circ}C$ (sea water), respectively. In this paper, to ensure reasonable specifications for cold regions if the measures from the above-mentioned systems against freeze-up are effective, the phenomenon of ballast tank freeze-up is simulated and discussed in low temperature conditions. With the results using the commercial CFD code, CFX 14, the most cost-effective solution is conducted to prevent being frozen along the outer surface.

• 한국지반환경공학회 논문집
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• 제17권1호
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• pp.49-54
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• 2016

동토지반을 구성하는 지층 중 표층에 분포하는 활동층은 계절에 따라 동결과 융해를 반복하여 지표면의 동상을 야기한다. 동상 높이는 활동층의 두께에 큰 영향을 받으므로, 동토지반 상부 인프라시설의 안전한 설계 및 시공을 위하여 활동층의 두께 산정은 매우 중요한 부분을 차지한다. 본 연구에서는 경량화된 원위치 관입시험 방법인 동적 콘 관입기를 이용하여 동토지반에서 활동층이 분포하는 심도를 평가하고자 하였다. 동적 콘 관입시험을 적용하기 위한 대상현장으로서 알래스카에 위치한 솔로몬 지역의 동토지반이 선택되었으며, 해당 지역의 두 개소에서 지중온도계측 및 동적 콘 관입시험이 수행되었다. 적용실험 결과 동적 콘 관입시험으로부터 획득된 동적 콘 관입지수는 활동층 및 영구동토층에서 서로 상이한 값을 나타내는바 동적 관입특성에 따른 활동층과 영구동토층의 경계부 심도가 산정되었으며, 경계부 심도에서 아이스 렌즈층으로 판단되는 구간이 감지되었다. 해당 개소에서 획득된 지중온도분포도에서 영상 및 영하 온도의 경계 심도는 본 연구의 동적 콘 관입시험으로부터 획득된 활동층 분포 심도와 부합하는 결과를 보였다. 본 연구에서 적용된 동적 콘 관입기는 대형장비의 접근 및 적용에 한계가 있는 극한지 동토 지역의 활동층 심도평가를 위하여 활용될 수 있을 것이라 기대된다.

• 한국제4기학회:학술대회논문집
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• 한국제4기학회 2004년도 추계학술대회
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• pp.37-43
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• 2004

The response of the CCCma coupled climate model to the imposition of LGM conditions is investigated. The global mean SAT and SST decrease by about $10^{\circ}C$ and $5.6^{\circ}C$ in the coupled model. Tropical SST decreases by $6.5^{\circ}C$, whereas CLIMAP reconstructions suggest that the tropics cool by only about $1.7^{\circ}C$, although the larger tropical cooling is consistent with the more recent proxy estimates. With the incorporation of a full ocean component, the coupled model gives a realistic spatial SST pattern, capturing features associated with ocean dynamics that are seen in the CLIMAP reconstructions. The larger decrease of the surface temperature in the model is associated with a reduction in global precipitation rate (about 15%). The tropical Pacific warm pool retreats to the west and a mean La $Ni\tilde{n}a$-like response is simulated with less precipitation over the central Pacific and more in the western tropical Pacific. The more arid ocean climate in the LGM results in an increase in SSS almost everywhere. This is particularly the case in the Arctic Ocean where large SSS increase is due to a decrease in river discharge to the Arctic Ocean associated with the accumulation of snow over the ice sheet, but in the North Atlantic by contrast SSS decreases markedly. This remarkable reduction of SSS in the North Atlantic is attributed to an increase in fresh water supply by an increase in discharges from the Mississippi and Amazon rivers and an increase in P-E over the North Atlantic ocean itself. The discharges increase in association with the wetter LGM climate south of the Laurentide ice sheet and in South America. The fresh water capping of the northern North Atlantic results in a marked reduction of deep convection and consequently a marked weakening of the North Atlantic overturning circulation. In the LGM, the maximum overturning stream function associated with the NADW formation decreases by about 60% relative to the control run, while in the Southern Ocean, oceanic convection is stronger in the LGM due to reduced stratification associated with an increase in SSS and a decrease in SST and the overturning stream function associated with the formation of AABW and the outflow increases substantially.

• 한국수산과학회지
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• 제29권4호
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• pp.497-502
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• 1996

1990년 3월, 경상북도 영덕군 강구면에 위치한 오십천과 경상남도 밀양시 밀양강에서 채집하여 인공수정한 난을 실험실로 운반하여 난발생과정과 부화자어의 성장에 따른 형태변화를 관찰한 결과는 다음과 같다. 1. 빙어의 수정난은 구형의 침성부착난으로 무색 투명하며, 난경은 $0.85\~1.05mm$ (평균 0.97mm, n=50)이다. 2. 부화에 소요된 시간은 평균 $16.5^{\circ}C$에서 약 170시간만에 부화한다. 3. 부화직후의 자어는 전장 $3.85\~4.25mm$ (평균 4.05 mm, n=10)로, 아직 입과 항문이 열려 있지 않고, 눈에 색소포가 착색되어 있으며, 근절수는 $52\~54$개이다. 4. 부화 $4\~5$일째의 자어는 전장이 $5.20\~5.65mm$ (평균 5.37mm, n=10)로 난황은 거의 흡수되고, 눈의 색소는 더욱 짙어진다. 5. 부화 20일째의 후기자어는 전장이 $8.20\~8.55\;mm$(평균 8.38mm, n=10)로 척색말단이 $45^{\circ}$ 각도로 위로 굽어진다. 6. 부화 25일째의 후기자어는 전장이 $9.15\~9.75mm$ (평균 9.63mm, n=10)로 등지느러미와 뒷지느러미에 각각 융기하기 시작하여 원기가 나타난다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.561-564
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• 2008

콘크리트의 동결융해 작용에 의한 내구성능 저하는 콘크리트 내부의 수분이 동결융해 작용을 반복적으로 받아 균열이 발생하거나 표층부가 박리함으로서 표면부분으로 부터 점차적으로 떨어져나가 콘크리트의 내구성능이 저하되는 현상을 말한다. 우리나라에의 경우 겨울철에 대부분 일평균기온이 0$^{\circ}C$이하로 되는 경우가 많으므로 거의 모든 지역이 매년 동결융해의 피해를 받고 있다고 볼 수 있으며, 다소 정도의 차이는 있으나 전국적으로 대부분의 콘크리트 구조물이 동결융해 및 제설제의 염해 피해 함께 받아 복합적인 열화를 받고 있다고 볼 수 있다. 그중 콘크리트포장 고속도로의 경우 기상작용 및 자동차에 의한 지속적인 피해를 받기 때문에 콘크리트구조물에 비해 더욱 많은 피해를 입고 있으며, 이로 인한 보수 및 보강에 대한 비용이 해마다 증가하는 추세이다. 본 연구에서는 고속도로 구조물의 용도로 가장 많이 사용되고 있는 40, 27, 21 MPa, 포장용 콘크리트로 현행 표준 배합비를 바탕으로 포장콘크리트의 동결융해 특성을 평가하기 제설제에 따른 동결융해 시험을 통해 동결융해저항성 및 중량감소율을 비교 분석하였다.

• 한국지열·수열에너지학회논문집
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• 제2권1호
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• pp.1-7
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• 2006

This paper was studied for optimum design of the used vaporizer at a satellite station. Generally, the cold air is created by temperature drop on the vaporizer surface. In addition, the frost creates ice deposit layer, therefore, heat transfer on vaporizer decreases into the adiabatic condition. By this reason, recent vaporizer system is installed as parallel type, and it takes three times of vaporizer capacity. But this vaporizer system requires much installation costs and restricted by some space. It is very important to solve this problem. This study paper is regarding $LN_2$ vaporizer where the utilization increases recently. There are three variable conditions which are used in this study research. First, fin lengths of 4000mm, 6000mm, 8000mm and 0, 4, 8 fin types were applied rut each vaporizer. Second, we applied four season condition which consist of humidity, temperature and air velocity to the experimental environment. Finally, pressure was applied to get flow rate during experiment. This paper objective is to propose vaporizer type and length data for best performance of vaporizer through experiment.

• 설비공학논문집
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• 제18권11호
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• pp.915-922
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• 2006

Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around $-20^{\circ}C$, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with $N_2$ gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around $-20^{\circ}C$. It was observed that the gas loaded one had succeeded in chilling start-up operation.

• 통합자연과학논문집
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• 제7권3호
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• pp.214-218
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• 2014

The main objective of this study is to analyse the influence factors of snowfall enhancement by glaciogenic seeding in a mountainous area. Twenty-five seeding experiments have been conducted during the period of February to April 2010. To use two rates seeding experiments (SR1: $1.04g\;min^{-1}$, SR2: $2.08g\;min^{-1}$) have been tested to get an appropriate ratio for snowfall enhancement at Daegwallyeong area. The conditions of seeding are able as followings: surface temperature <$0^{\circ}C$, wind speed <5 m/s, wind direction between 0 and $130^{\circ}$. The experiment results indicated that in the case of SR1 was more effective than SR2. The number of small ice particles below 1.0 mm was increased during seeding period measured by PARSIVEL disdrometer near generator. Most of snowfall enhancement by seeding was observed the inflow of the easterly wind blew in toward Gangwon regions from the East Sea and the supersaturated supercooled liquid water due to orographic effect.

• 동굴
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• 제63호
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• pp.61-79
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• 2004

프랜츠 요셉 빙하는 해발고도 250 m의 낮은 고도에 위치한다. 프랜츠 요셉 빙하는 낮은 고도에도 불구하고 타즈만해에서 불어오는 습윤한 편서풍과 고산의 지형적 특색으로 빙하가 존재한다. 지난 소빙기를 끝으로 지구의 기후 온난화로 빙하는 점점 후퇴하고 있으며 2002년과 2003년 사이에도 빙하는 후퇴했다. 후퇴의 원인을 기후요소로 비교 분석하여 후퇴의 원인이 기후에 있음을 확인하였다 빙하 주변에 알파인 단층이 지나가며 변성암이 분포하고 빙하 후퇴의 흔적으로 찰흔과 그루브가 다수 관찰되고 있다