• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.503-511
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• 2002

Heat flow characteristics during hot water extraction process was studied experimentally. Data were taken at various outlet port type for the fixed inlet port type, inlet-outlet temperature differences and mass flow rates. In this study, the temperature distribution in a storage tank and an outlet temperature were measured to predict a degree of stratification in the storage tank, and a useful rate of hot water was analysed with respect to the variables dominating a extraction process. Experimental results show that the degree of stratification and useful rate of hot water are all high in a low flow rate in case of using modified distributor I (MDI) as the outlet port type.

• The Magazine for Energy Service Companies
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• s.33
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• pp.46-53
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• 2005

열병합발전의 도입에서는 건물의 규모나 용도에 따라 시스템의 선정, 발전전력$\cdot$배열의 이용률을 올리기 위한 설계가 중요하다. 발전전력에 대해서는 상용전력과 계통연계를 하는 것에 의해 건물 전체의 전력부하를 공급대상으로 하는 것이 가능하기 때문에 점차 정격용량의 발전을 할 수 있다. 최근의 열병합발전에서는 전주열종(電主熱從) 운전이 주류이며 일부 소형시스템 이외는 계통연계이기 때문에 발전전력의 유효이용은 비교적 용이하다. 그러므로 열병합발전시스템의 종합효율을 올리고, 시스템을 성공시키기 위해서는 배열을 잘 이용할 수 있는 시스템 설계를 하는 것이 포인트이다. 배열이용 설계를 하려면 우선 도입을 계획하고 있는 건물의 용도, 규모에 가장 적합한 배열이용시스템을 선정할 필요가 있다. 민생용 열병합발전에서는 모두 배열을 온수로 이용하는 가스엔진시스템이므로 가스엔진배열온수의 이용시스템에 대해 설명한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1829-1836
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• 2010

The district heating system distributes the heat generated from a cogeneration plant to wider locations. In this process, the district heating pipe (DHP) is subjected to internal and external loadings. The internal loadings are generally caused by the operating conditions such as water temperature and internal pressure. Frictional interactions between the pipes and the soil contribute to the external loadings. Thus, investigation of the mechanisms of failure of DHPs will help to guarantee both mechanical stability and heating efficiency. In this study, we investigate the local buckling of DHPs using limit state design (LSD). Two methods are considered: the use of the limit state for the width-thickness ratio and the use of the limit state for the strain. The results are used to confirm that the DHP is stable under local buckling. Finally, we suggest a minimum preheating temperature for avoiding local buckling.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.93-98
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• 2009

Cogeneration means the highly energy-efficient generation system that improves energy ratio by generating electricity and heat, and it really affects the improvement of overall efficiency by using industrial process, district heating, and hot-water supply etc. after the energy produced through supplying power to system collects. This thesis indicates the screen of cogeneration flow in LabVIEW and the heat power control system that can be in long-distance control of a district energy system using TCP/IP. We simulated on four computers so that the heat power control system proves long-distance control possible.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1011-1015
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• 2005

본 실험에서는 부력 조건이 달라질 때 단공방류구에서 정체수역으로 수평방류되는 부력제트의 거동을 규명하였다. LIF (Laser Induced Fluorescence) 시스템을 이용하여 수행하였는데, LIF 시스템은 고해상도의 이미지를 취득할 수 있어 데이터의 정확도가 높으며, 동시에 한 평면상의 농도장을 일시에 측정할 수 있는 장점이 있는 기술이다. LIF 시스템은 크게 세부분으로 구성되어 있는데 방출시스템, 포착시스템, 처리시스템이 그것이다. 실험 조건을 고려해서 온수를 이용하여 주변수와의 밀도차를 재현하였으며, LIF 시스템의 추적입자로 형광염료 Rhodamine B를 사용하였다. 또한, 실험 데이터 취득과정에서 필요한 검정과정을 수행하였는데, LIF 시스템에서 검정과정은 레이저 입사광의 강도가 불균등한 분포를 가지는 점과 주변수의 매질에 의한 근의 감쇠가 발생하는 문제를 해결하기 위한 것이다. LIF 시스템은 부력제트의 농도장을 매우 정밀하게 측정할 수 있는데, 방류밀도 Froude 수가 변함에 따라 측정된 순간이미지를 통해 제트의 진화과정을 상세하고 가시적으로 확인할 수 있었다. 검정과정을 거친 농도 종단면에서 중심선의 연장선이 LIF 시스템에 의해 측정된 순간이미지의 중심선 궤적과 거의 일치하는 것도 알 수 있었다. 또한 LIF 시스템을 통해서 취득된 단일수평부력제트의 궤적과 중심선 희석률을 기존의 상용모형인 VISJET과 CORMIX1에 의해 예측된 결과와 비교$\cdot$분석한 결과, 제트 중심선 궤적의 경우, LIF 시스템을 이용한 측정값은 대체로 VISJET 모형의 결과와 일치하는 것으로 밝혀졌다. 중심선 희석률의 경우, LIF 측정값은 대체로 CORMIX1 모형, Cederwall(1968)의 경험식과 일치하는 경향을 보였다.0\%$일 때가 밸브를 $60\%$와 $80\%$ 개폐시켰을 때보다 $0.3kg/cm^2,\;0.29kg/cm^2$ 낮게 나타나 밸브를 전체 개방 했을 때 관로내의 수압이 상수설계기준에 적합한 수압을 유지함을 알 수 있다. 상수관로 설계 기준에서는 관로내 수압을 $1.5\~4.0kg/cm^2$으로 나타내고 있는데 $6kg/cm^2$보다 과수압을 나타내는 경우가 $100\%$로 밸브를 개방하였을 때보다 $60\%,\;80\%$ 개방하였을 때가 더 빈번히 발생하고 있으므로 대상지역의 밸브 개폐는 $100\%$ 개방하는 것이 선계기준에 적합한 것으로 나타났다. 밸브 개폐에 따른 수압 변화를 모의한 결과 밸브 개폐도를 적절히 유지하여 필요수량의 확보 및 누수방지대책에 활용할 수 있을 것으로 판단된다.8R(mm)(r^2=0.84)$로 지수적으로 증가하는 경향을 나타내었다. 유거수량은 토성별로 양토를 1.0으로 기준할 때 사양토가 0.86으로 가장 작았고, 식양토 1.09, 식토 1.15로 평가되어 침투수에 비해 토성별 차이가 크게 나타났다. 이는 토성이 세립질일 수록 유거수의 저항이 작기 때문으로 생각된다. 경사에 따라서는 경사도가 증가할수록 증가하였으며 $10\% 경사일 때를 기준으로 $Ro(mm)=Ro_{10}{\times}0.797{\times}e^{-0.021s(\%)}$로 나타났다.천성 승모판 폐쇄 부전등을 초래하는 심각한 선천성 심질환이다. 그러나 진단 즉시 직접 좌관상동맥-대동맥 이식술로 수술적 교정을 해줌으로써 좋은 성적을 기대할 수 있음을 보여주었다.특히

• Plant Journal
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• v.18 no.1
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• pp.43-49
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• 2022

In this study, the operational characteristics of the 7.48 MW fuel cell power plant consisting of 17 units of 440 kW Phosphoric Acid Fuel Cell (PAFC) in operation since its commercial operation in December 2017 were explained and the heat recovery process of the plat using Organic Rankine Cycle (ORC)was simulated. The fuel cell system performance improvement and economic assessment were analyzed by calculating the amount of heat recovery and electric power available when connecting a 125 kW XLT Model ORC for hot water heat sources with 105℃, 40.8 t/h. The result of the study shows that integrating the 125 kW ORC to PAFC power plant would improve generating efficiency by about 0.6% through annually 851,472 kWh of electricity produced by ORC, and fuel cell and ORC integrated systems were calculated to have a 0.35% higher Internal Return Ratio and more Net Present Value of 1,249 million KRW than not installing ORC despite installation costs.

• Clinical and Experimental Pediatrics
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• v.45 no.5
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• pp.629-636
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• 2002

Purpose : Our study was aimed to investigate the characteristics of seizures as well as to determine whether the expression of neuronal nitric oxide synthase expression(nNOS) of hippocampus has an affect in the hyperthermic seizure in developing rat. Methods : Hyperthermic seizures were repeatedly induced twice a week for four weeks in 20-day old Spraque-Dowley rats. Fifty two rats were used as a hyperthermic group and 30 rats used as a normothermic control group. Hyperthermic seizures were induced in a water bath at $45^{\circ}C{\pm}1$ for 4 min. The characteristics of seizures were recorded. Using western blot, hippocampal nNOS expression was measured in normothermic control, hyperthermic non-seizure, and hyperthermic seizure groups, respectively. Results : Eighty seven percent of hyperthermia exposed rats showed generalized tonic-clonic seizure most frequently. The duration of seizure was ranged from 12 to 145 sec(mean 55 sec) and the latency to seizure ranged from 158 to 240 sec(mean 204 sec). The duration of seizure was prolonged but there was no significant difference in the seizure latency as the rat exposed more number of hyperthermia. Interestingly, the expression level of hippocampal nNOS in hyperthermic seizure and hyperthermic non-seizure groups was not different from each other, however, the expression in these groups was lower than that of the control group. Conclusion : Our results indicate that nNOS do not have an affect in this repeated hyperthermic seizures. Further studies are required to clarify a role of nNOS in hyperthermic seizure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.379-383
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• 2011

Electro-osmotic pumps were fabricated by using two types of porous glass frits. The performance of these pumps was characterized in terms of maximum flow rate, current, and pressure using deionized water and 1 mM sodium tertraborate decahydrate buffer. Maximum flow rate and current when ROBU porous glass frits were used were higher than those when DURAN porous glass frits were used because of the high porosity of the ROBU glass frits. However, the maximum pressure when ROBU glass frits were used was similar to that when DURAN glass frits were used. The therrmodynamic efficiency of a pump with ROBU porous glass frits is approximately twice that of a pump with DURAN porous glass frits. Further, the maximum flow rate at maximum current in the case of ROBU porous glass frits is high. However, it is lower than the maximum pressure at maximum current in the case of DURAN porous glass frits. Further, in this study, we also verified the effectiveness of ROBU glass frits when high flow rate is required and of DURAN glass frits when a high pressure is required.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.91-98
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• 2009

Recently, production cost of ready mixed concrete has been increased due to the rising cost of raw materials such as cement and aggregate etc. cause by the upturn of oil price and increase of shipping charge. The delivery cost of ready mixed concrete companies, however, has been decreased owing to their excessive competition in sale. Consequently, ready mixed concrete companies began to manufacture the concrete by mixing ground granulated blast furnace slag(GGBF) and fly-ash in order to lower the production cost. Therefore, the objective of this study was to predict 28 days strength of GGBF slag concrete by early strength(warm and hot water curing method) for the sake of managing with ease the quality of ready mixed concrete. In experimental results, the prediction equation for 28 days compressive strength of GGBF slag concrete could be produced through the linear regression analysis of early strength and 28 days strength. In order to acquire the reliability, all mixture were repeated as 3 times and each mixture order was carried out by random sampling. The prediction equation for 28 days strength of GGBF slag concrete by 1 day compressive strength(accelerated testing) according to warm and hot water curing method won the good reliability.

• Journal of Animal Environmental Science
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• v.7 no.1
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• pp.1-12
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• 2001

This study was conducted to develope an automatic liquid feeder for early weaning piglets and to test the efficacy of the system. The liquid feeder consists of water heating and discharge unit, dry diet storing and discharge unit, mixing and discharge unit, mixed liquid feed-delivering unit, and the central control part which control each unit, feeding frequency and the amount of feeding. For investigating the possibility of practical use, a feeding trial was carried out using eighteen three way crossbred piglets weaned on 19 days of age for the experimental period of six weeks. Experimental diet was provided in liquid form using the automatic liquid feeder for the first three weeks and in dry form for the later three weeks. The water heating and discharge unit exactly supplied warm water by 27 $m\ell$/s, into the mixing unit. The dry diet storing and discharge unit supplied dry feed by 3.7g/s, into the mixing unit. Being compared with the standard growth rate suggested by NRC, average daily gain of the piglets during the first three weeks of liquid feeding was lower by 10%, while it was higher during three weeks of dry feeding and over the whole experimental period by 24 and 17%, respectively. Feed/gain was 1.09, 2.14 and 1.89 for the first 3 weeks, later 3 weeks, and whole period, respectively. Diarrhea was observed for three days from day 3 to day 7 after feeding liquid diet, but no pig died of it. In conclusion, a preliminary test for the newly developed an automatic liquid feeder using 19 days of age weaning piglets showed that the unit was successfully operated without any major problems. Piglets raised on a liquid diet through the unit developed grew less during the first three weeks, but their growth and feed intake were greatly improved thereafter, indicating the developed automatic liquid feeder may be practically used in swine industry.