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유형선(H.S.Yoo),김용성(Y.S.Kim) 한국자동차공학회 1983 오토저널 Vol.5 No.4
전탄성유체 유동에 대하여 일반적으로 U.C맥스웰 모델 또는 올두로이드 B모델이 사용되지만 이러한 모델들은-매우 큰 전단율 영역인 윤활문제에서 믿기 힘든-수직응력의 크리가 전단율의 제곱에 비례함을 나타내므로, 본 연구에서는 수직응력 계수들(??)이 가정될 수 있는 Cri-minale-Ericksen-Filbey 모델이 사용되었다. 2차수직응력계수는 다른 문제들에서와 같이 무시되었으며 Weissenberg수가 포함된 특수레이놀즈식이 유도되었다.<br/> 이 모델의 속도분포는-2차원 약한점탄성 유체에 대하여 증명된 바와 같이-뉴우톤 유체와 같이 가정되었다. 유도된 특수레이놀즈 식은 We-issenberg수를 1까지 계산되었으며 그 결과 점탄성유체가 유한저어널 베어링에서 유리한 것으로 나타났지만 그 차가 미소하여 일반베이링에서 점탄성 윤활유의 영향이 무시됨을 보였다.
유형덕 ( H . D . Yoo ) 한국화학공학회 1977 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.15 No.1
The underground storage of hydrocarbons is the most economical engineering method known to store a large volume of hydrocarbons and has been widely practiced else where in the world. Because of the recovery difficulties, however, this storage technique is confined to light hydrocarbons. Usually, depleted oil and gas reservoirs are converted to underground gas storages where the underline aquifer behavior controls the storage volume and the pressure. Actual case study examples are described in this paper together with the engineering design and model analysis. Because of the growing Korea`s need for bulk volume gas storage, development plans are necessary to apply some of these techniques to Korea. Three different underground storage possibilities are proposed. The utilization of dry holes resulted from petroleum exploration work is a possibility for gas storage if an impermeable rock structure extends over an aquifer. Alternatively, the low temperature geothermal well could similarly be converted to a small gas storage under same assumptions, after a successful energy recovery operation for a moderate economic gain. Lastly, the Jejudo Manjanggool natural cave is a good prospect for a constant volume LPG storage. Because of the many uncertainties and engineering difficulties, sufficient development work must be carried out before attempting to put these into actual practices.
유형덕 ( H . D . Yoo ) 한국화학공학회 1977 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.15 No.4
The recovery of low temperature geothermal energy (40∼80℃) in Korea is investigated by injecting air seasonally for local community heating without heat exchangers, when a gas storage development is planned. A preliminary design was conducted to study the feasibility of the scheme. Safety, economics, reserve estimation, and aquifer dynamics were studied. Other recovery methods and power generation have been briefly reviewed. Conversion to a small gas storage system upon depletion of geothermal energy, because of the Korea`s pressing need for underground storage system and the overall economic advantage, plays a very significant role to make the energy recovery attractive.
유형선(H.S.Yoo),안상호(S.H.An) 한국자동차공학회 1988 오토저널 Vol.10 No.6
During recent years, a great deal of interest has emerged on the use of adaptive approaches and a posteriori estimates in finite element method. The results are intended to be used to improve the quality of finite element solution by changing the location of the nodes within a fixed number of degrees of freedom-so called r method-, and by increasing the order of polynomial approximation with the new degrees of freedom-p method.<br/> This paper deals with error analysis that contains the basic theory and method of deriving error estimates and adaptive processes applied to finite element solutions underlying the rp method that is the combination of r and p method of finite element. It is shown that we can obtain more accurate solution by applying the method to the 2-dimensional heat transfer problem.
김규한(K.H. Kim),유형석(H.S. Yoo),편종근(C.K. Pyun) 한국해양환경·에너지학회 2005 한국해양환경공학회 학술대회논문집 Vol.2005 No.11
Unyeo beach placed in west coast has been eroded for a long time because of several reasons. In this study, erosion characteristics of Unyeo beach that coastal sand dunes was widely branched out and pre-existed data were investigated. And sediment movement due to environmental change of Unyeo beach was carefully analyzed using result of pre-existed data study and 3D topographical change model test showed present case. In addition, applicable countermeasures for beach erosion in Unyeo Beach were examined by 3D topographical change model test and 2D movable hydraulic model test.
저장벽 양자우물구조와 비태칭 패브리 - 페로 공명기 구조에 의한 고성능 2×4 S-SEED Array 구현
권오균(O. K. Kwon),최영완(Y. W. Choi),김광준(K. J. Kim),이일항(E. H. Lee),이상훈(S. H. Lee),원용협(Y. H. Won),유형모(H. M. Yoo) 한국광학회 1994 한국광학회지 Vol.5 No.1
GaAs/Al_(0.04)Ga_(0.96)As 다중양자우물 구조를 이용한 반사형 PIN 다이오우드 S-SEED의 설계에 있어 낮은 동작전압, 높은 포화에너지 및 높은 반사율 on/off 강도비를 얻고자 저장벽 양자우물구조와 비대칭 페브리-페로 공명구조를 결합하였다. 2×4 array를 구성하는 S-SEED들은 역방향 동작전압 5V에서 평균적으로 13 이상의 반사율 on/off 강도비 (CR)와 약 24%의 반사율차 (ΔR) 및 91% 이상의 광쌍안정폭 (Δ)을 나타내었다. 공명구조를 이용함으로서 PIN 다이오우드 진성영역내의 양자우물의 주기수를 줄일 수 있어 외부동작전압 없이도 CR~4.7, R~9.2%, ~22%의 향상된 무전압 광쌍안정 동작특성을 얻었다. We designed and fabricated a 2×4 symmetric self electro-optic effect device array using GaAs/Al_(0.04)Ga_(0.96)As extremely shallow quantum wells grown by a molecular beam epitaxy. By employing ESQW and asymmetric Fabry-Perot cavity structure simultaneously, we improved the performances of S-SEED such as on/off contrast ratio (CR), reflectivity change (ΔR), and optical bistability loop width (Δ). The average values of the elements of the 2×4 S-SEED array were CR~13.1, R~24%, and Δ~91%. It was found that the AFP cavity structure enhances the self-biased optical bistability in ESQW-SEED under no external bias. That is due to the decreased intrisic region thickness in AFP-SEED structures, and which increases the built-in electric fields. The zero-biased S-SEED showed CR of ~4.7, R~9%, and Δ~22%.