• 약학회지
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• 제22권1호
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• pp.8-14
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• 1978

The method that changes sodium cloxacillin from amorphous form to hydrate form was investigated. Using organic solvents of which dielectric constants are greater than 9, the amorphous sodium cloxacillin could be changed to hydrate form. The difference of water content of sodium cloxacillin hydrate caused the differences of ir spectrum at $3,350~3,360cm_{-1}$, and owing to the decrease of water content, hydrate form was changed to the morphous form, which could be identified by x-ray diffraction pattern. Regarding the stability of sodium cloxacillin in activity, the hydrate form was stable but the amorphous form was very unstable. Moreover, the stable hydrate form was scarcely hygroscopic, while the other form was hygroscopic, becoming a fused state ar $50^{\circ}$. and R.H. 50%.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.658-663
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• 1987

The new controller developed here, which is the facility with only one measurement, is a new concept for the level controller of the existing nuclear steam generator. A MACS (Microcomputer-based Adaptive Control System of a Steam Generator) is quite practical and efficient, and has also simple structure and higher flexibility in the installment for actual plant. A key ingredient of this system is adaptive regulator which can calculate adaptive, optimal valve position in response to changes in the dynamics of the process and the disturbances. In spite of many difficulties in the steam generator water level control at low power, it can be concluded from the experimental and simulation results, that the MACS can provide optimal, robust steam generator level control from zero to full power. The amount of the control input effort can be reduced by adjusting the weighting factor. However, the steady state water level errors are generated. To avoid the steady errors, the different adaptive algorithm should be investigated in the future. The 3 second sampling time is acceptable for this system. However, action should be taken to shorten the sampling time for better digital control.

• The Korean Journal of Physiology
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• 제21권2호
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• pp.297-304
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• 1987

A study was carried out to find out the relationship between arginine vasopressin (AVP) release and plasma osmolality in 15 young men (age: 21.4 yr). After an overnight fasting, wale. (20 ml/kg) was imbibed, and venous blood and urine samples were collected every 30 min for 90 min. then 5% saline was infused (0.06 ml/min/kg) for 120 min. AVP was extracted on Sep-Pak column and measured by radioimmunoassay. Under basal condition, plasma osmolality (pOsm), AVP (pAVP) and aldosterone (pAldo) levels were 286.5 mOsm/kg, 1.1 pg/ml, and 140 pg/ml, respectively. pAVP became undetectable during maximum water diuresis, and increased in response to hypertonic saline infusion. pAVP level began to increase when pOsm was above 280 mOsm/kg. Changes in urinary AVP excretion (uAVP) was parallel to pAVP levels. The fall in pAVP was followed by a decrease in uAVP, uOsm and an increase in free water clearance, while the later rise in pAVP was followed by an increase in uAVP, uOsm and a decrease in free water clearance. When pooling all data together, relationships between pAVP and pOsm, and uAVP and uOsm were best expressed by an exponential relationship (r=0.78, 0.86, respectively). pAldo level decreased to 71 pg/ml after water ingestion, and decreased further to 30 pg/ml 2 hr after 5% saline infusion. Even at the same pNa, pAldo level during dehydration state was significantly higher than during hydration state. Negative exponential relation (r=-0.59) was observed between pAldo and pNa. Response to change in body fluid volume was greater in aldosterone than in AVP release.

• Advances in Energy Research
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• 제6권2호
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• pp.103-129
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• 2019

While global demand for energy increases annually, at the same time the demand for carbon-free, sulphur-free and NO_x-free energy sources grows considerably. This state poses a challenge in the research for newer sources like biomass and shale gas as well as renewable energy resources such as solar, wind, geothermal and hydraulic energy. Although wave energy also is a form of renewable energy it has not fully been exploited technically and economically so far. This study tries to explain those reasons in which it is beyond doubt that the demand for wave energy will soon increase as fossil energy resources are depleted and environmental concerns gain more importance. The electrical energy supplied to the grid shall be produced from wave energy whose conversion devices can basically work according to three different systems. i. Systems that exploit the motions or shape deformations of their mechanisms involved, being driven by the energy of passing waves. ii. Systems that exploit the weight of the seawater stored in a reservoir or the changes of water pressure by the oscillations of wave height, iii. Systems that convert the wave motions into air flow. One of the aims of this study is to present the classification deficits of the wave energy converters (WECs) of the "wave developers" prepared by the European Marine Energy Center, which were to be reclassified. Furthermore, a new classification of all WECs listed by the European Marine Energy Center was arranged independently. The other aim of the study is to assess the technological state of the art of these WECs designed and/or produced, to obtain an overview on them.

• 환경영향평가
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• 제28권1호
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• pp.49-62
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• 2019

환경변화는 생물의 성장과 번식 등의 생활사에 영향을 주며, 생물은 살아가는 서식환경에서 생태적 적합도를 가장 극대화 시킬 수 있도록 적응되어 왔다. 본 연구에서는 동적상태의존모델을 이용하여 수온과 용존산소량의 변화가 어류의 초기 성장과 체내 스트레스 누적 과정에 미치는 영향을 분석하였다. 본 연구에서 제시한 어류의 생활사 모델은 취식 행동이 성장과 체내 스트레스 누적에 영향을 받는다고 가정하였다. 또한 수온과 용존산소량의 임계점은 가장 빠른 성장속도를 유도하는 수온과 용존산소량으로 가정하였다. 이에 모델은 수온과 용존산소량의 임계점에서 성장속도가 가장 빨랐으며 임계점보다 크거나 낮은 경우 성장속도는 느렸다. 용존산소량의 저산소 상태는 체내에 누적된 스트레스양의 증가로 성장속도는 느렸고, 고산소 상태는 성장속도를 향상 시켰으나 누적된 스트레스로 신체 크기를 감소시켰다. 본 연구를 통해 환경변화가 생물에 미치는 영향을 예측하는데 있어 단일 또는 독립적인 환경요인 보다 복합적 요인들의 영향이 높음을 보였다. 따라서 환경영향평가에서 환경변화에 대한 영향 예측을 향상시키기 위하여 생리생태학적 측면에서의 복합적 환경 요인을 평가에 도입이 필요하고 또한 관련된 기법 개발에 대한 연구가 후속 되어야 한다.

• 한국지반신소재학회논문집
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• 제9권3호
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• pp.87-93
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• 2010

저수지의 수위변화는 저수지 주변 강기슭 사면파괴의 주요 요인이다. 중국의 삼협댐 저수위는 홍수량 조절을 위해 145m와 175m사이에서 변화한다. 삼협댐 저수위의 정상적 운영상태에서 저수위 변동속도는 0.67m~3.0m의 범위에 있다. 마지아고 사면은 자시강의 2.1km 상류 좌측기슭에 위치한다. 자시강은 삼협지역내에 있는 양츠강의 지류이다. 2003년 저수위가 95m에서 135m로 상승한 직후, 마지아고 사면의 후면부에서 길이 20m, 폭 3~10의 균열이 발생하였다. 지금은 균열 보수 후 특별한 징후는 보이지 않고는 있으나, 이 큰 균열은 마지아고 사면의 산사태 가능성을 암시하고 있었다. 이 연구에서는 침투해석에서 얻어진 간극수압을 저수위 변동에 따른 안전율 변화를 평가하기 위해 사용되었다. 안전율 평가는 한계평형해석에 의한 사면안정해석에 의해 수행되었다. 한계평형해석에서 전단강도에 미치는 부의 간극수압 효과는 불포화 흙에 대한 프레드런드의 전단강도식을 사용하여 고려하였다. 연구결과 강기슭사면의 안전율은 저수위의 상승, 하강에 따라 감소와 증가의 경향을 보이나, 가장 위험한 상태는 저수위가 최대높이를 장기간 유지할 때인 것으로 나타났다.

• 한국방재안전학회논문집
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• 제16권1호
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• pp.81-89
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• 2023

최근 이상기후의 영향으로 전 지구적 온난화 및 도시화로 인해 세계적으로 기상이변이 늘어나고 있다. 도시화 및 난개발로 인한 불투수 면적의 증가 같은 문제로 홍수량이 증가함에 따라 홍수피해를 줄이기 위한 다양한 방안이 제시되고 있다. 본 연구에서는 사행하천 구간에 설치되는 횡월류 위어 유입각의 변화에 따라 3차원 CFD 모형인 FLOW-3D를 이용하여 흐름 특성과 월류량을 분석하여 횡월류 위어 유입각에 대한 수공구조물의 월류능력 평가 및 유량계수 산정을 위한 기초 연구를 수행하였다. 분석 결과, 횡월류 위어 유입각이 작을수록 횡월류부 통과 후 주수로 흐름의 수위가 감소하고 유속이 증가하였으며, 유입각이 증가할수록 수위가 상승하였고, 유속이 감소하는 경향을 보였다. 또한, 횡월류 위어 유입각이 40° 이상인 경우 직하류 유속이 상류 유속과 비교하여 감소하는 것을 확인할 수 있었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.272-273
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• 2014

Existing the free-form concrete segments (FCS) mold is produced by state of solid such as steel, wood, Styrofoam that can not be recycled. Using FCS mold result in delay on schedule and decrease of productivity because it consists of irregular curved variety and it requires more time than fixed mold. Thus, FCS mold should be developed which can reduce the costs and also it can be used as semipermanent. The aim of this study is to suggest of flexible mold production process for using the phase change materials(PCM). PCM is maintain that its solid state at low temperature but it changes phase to liquid state by heating. PCM is suitable material for flexible mold due to change of phase in relatively high temperature compare to other phase change materials such as water. Flexible mold is possible that reuse semi-permanently made by PCM. Thus, this study is proposed the process of flexible mold production for using the PCM. The study results will be used as the basic theory for studies on production and installation of FCS.

• 한국항만학회지
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• 제14권4호
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• pp.451-461
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• 2000

The design and maintenance of navigation channel and water facilities of an harbor which is located at the mouth of river or at the estuary area are difficult due to the complexity of estuarial water and sediment circulation. Effects of deepening navigable waterways, of changing coastline configurations, or of discharging dredged material to the open sea are necessary to be investigated and predicted in terms of water quality and possible physical changes to the coastal environment. A borad analysis of the transport mechanism in the estuary area was made in terms of sediment property, falling velocity, concentration and flow characteristics. In order to simulate the transport processes, a two-dimensional finite element model is developed, which includes erosion, transport and deposition mechanism of suspended sediments. Galerkin’s weighted residual method is used to solve the transient convection-diffusion equation. The fluid domain is subdivided into a series of triangular elements in which a quadratic approximation is made for suspended sediment concentration. Model could deal with a continuous aggregation by stipulating the settling velocity of the flocs in each element. The model provides suspended sediment concentration, bed shear stress, erosion versus deposition rate and bed profile at the given time step.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.248-251
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• 2003

In this paper, it was experimented about thermal and mechanical insulation properties of a elastic epoxy specimen. We made elastic epoxy specimen adding a ratio of 0[phr], 20[phr], 35[phr] and 53[phr] with modifier to existing epoxy. Each specimen was absorbed by 25h, 196h, 361h 484h with water. In water-absorption state, it was experimented a change of heat flows by temperature of elastic epoxy and changes of thermal expansion coefficient. Also, a hardness-change of each specimen was experimented by change of water-absorption time. In this experiment DSC (Differential Scanning Calorimetry) and TMA (Thermomechanical Analysis) were used. A temperature range of DSC was changed from -0[$^{\circ}C$] to 200[$^{\circ}C$], TMA was changed from -0[$^{\circ}C$] to 350[$^{\circ}C$]. In addition, we investigated structural analysis of water absorbed specimen using SEM (Scanning electron microscope).