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농용(農用) 디이젤 엔진 연료(燃料)로서의 에타놀 이용(利用)에 관(關)한 연구(硏究)
유관희,배영환,유수남,Ryu, Kwan Hee,Bae, Yeong Hwan,Yoo, Soo Nam 한국농업기계학회 1982 바이오시스템공학 Vol.6 No.2
The objective of this study was to find out the technical feasibility of ethanol-diesel fuel blends as a diesel engine fuel. Fuel properties essential to the proper operation of a diesel engine were determined for blends containing several concentrations of ethanol in No. 2 diesel fuel. A single-cylinder diesel engine for a power tiller was used for the engine tests, in which load, speed and fuel consumption rate were measured. The fuels used in tests were No. 2 diesel fuel and a blend containing 10-percent ethanol and 90-percent No. 2 diesel fuel. The results of the study are summarized as follows. 1. It was not possible to blend ethanol and No. 2 diesel fuel as a homogeneous solution even though anhydrous ethanol was used. The problem of blending ethanol in No. 2 diesel fuel could be solved by adding butanol about 5% of the amount of ethanol in the blends. 2. Because ethanol had a much lower boiling point ($78.3^{\circ}C$ under atmospheric pressure) than a diesel fuel, it was necessary to store ethanol-diesel fuel blends airtight in order to prevent them from evaporation losses of ethanol. 3. The addition of ethanol to No. 2 diesel fuel lowered the fuel viscosity and the cetane rating, but a blend of 10% ethanol and 90% diesel fuel had a viscosity and a cetane rating well above the KS minimum values for No. 2 diesel fuel. 4. At the rated speed, the specific fuel consumption of No.2 diesel fuel was lower than that of the 10% ethanol blend for the almost entire range of load. However, under the overload condition the specific fuel consumption was lower for the 10% ethanol blend. 5. Under the variable-speed full-load tests, both fuels produced approximately the same torque and power. At the speeds of 1600rpm or below, the specific fuel consumption of No. 2 diesel fuel was lower than that of the 10% ethanol blend. At the speeds of 1600rpm or above, however, the specific fuel consumption was lower for the 10% ethanol blend. 6. At the ambient temperature above $15^{\circ}C$, the use of the 10% ethanol blend in the engine created a vapor lock in the fuel injection pump and stalled the engine. The vapor locking problem was overcome by chilling the surroundings of the fuel injection pump and the cylinder head with water.
삼차원 메쉬에 대한 기하학 라이브와이어와 기하학 라이브레인
유관희,Yoo Kwan-Hee 한국정보처리학회 2005 정보처리학회논문지 A Vol.12 No.1
이차원 영상에서 정의된 에지와 유사하게 삼차원 메쉬에서도 주요 부위의 경계를 표현하는 기하학 특징을 정의할 수 있다. 삼차원 메쉬에서 기하학 특징은 메쉬 단순화, 메쉬 변형과 메쉬 편집 등과 같은 여러 응용에 기본적인 항목으로 사용되고 있다. 본 논문에서는 삼차원 메쉬의 기학적 특징을 효과적으로 찾기 위하여 이차원 영상의 라이브와이어와 라이브레인 기법을 삼차원 메쉬로 확장한 기하학 라이브와이어와 기하학하 라이브레인 기법을 제안한다. 제안된 기법에서는 메쉬의 기하학 특징을 나타내기 위하여 근사곡률을 사용하였고 메쉬 그 자체를 정의된 비용함수를 에지의 가중치고 가지는 가중치 방향그래프로 나타내었다. 그리고 만들어진 가중치 방향그래프에 대해 잘 알려진 최단경로 탐색 알고리즘을 이용하여 사용자에 의해 지정된 점들 사이에 존재하는 삼차원 메쉬에서의 기하학 특징을 추출하였다. 본 논문에서는 사람 얼굴, 소, 신발과 치어 메쉬 모델에 나타나는 기하학 특징을 추출하기 위하여 제안한 기법을 적용하여 얻어진 결과를 가시화한다. Similarly to the edges defined in a 2D image, we can define the geometric features representing the boundary of the distinctive parts appearing on 3D meshes. The geometric features have been used as basic primitives in several applications such as mesh simplification, mesh deformation, and mesh editing. In this paper, we propose geometric livewire and geometric livelane for extracting geometric features in a 3D mesh, which are the extentions of livewire and livelane methods in images. In these methods, approximate curvatures are adopted to represent the geometric features in a 3D mesh and the 3D mesh itself is represented as a weighted directed graph in which cost functions are defined for the weights of edges. Using a well-known shortest path finding algorithm in the weighted directed graph, we extracted geometric features in the 3D mesh among points selected by a user. In this paper, we also visualize the results obtained from applying the techniques to extracting geometric features in the general meshes modeled after human faces, cows, shoes, and single teeth.
동적 X3D 콘텐츠의 영상 품질 향상을 위한 다중텍스쳐링 기법의 적용
유관희,하종성,Yoo Kwan-Hee,Ha Jong-Sung 한국콘텐츠학회 2006 게임&엔터테인먼트논문지 Vol.2 No.1
본 논문은 텍스쳐와 같은 물체의 속성이 동적으로 변하는 인터넷 3D 콘텐츠에서 영상 품질을 향상시키기 위한 다중텍스쳐링 기법에 관한 것이다. 다중텍스쳐링과 관련된 X3D 노드들을 최근의 X3D 뷰어를 중심으로 실험하여 이들의 활용 방법과 제약점을 알아보고 이를 바탕으로 향후 사용자 요구 및 그래픽가속기의 발전에 따른 차세대 X3D 뷰어의 개발 방향에 대하여 논의한다. This paper is concerned with the techniques of multitexturing for increasing the image quality of 3D contents in the Internet, where the attributes of objects such as textures are dynamically changed. First we explain the empirical results of implementing the X3D nodes related with the multitexturing in the recent X3D viewers. Next we discuss the directions for developing the next-generation of X3D viewers that satisfy the user requirements and the advanced graphics accelerators.
유관희(Kwan-Hee Yoo),좌경룡(Kyung-Yong chwa) 한국정보과학회 1988 정보과학회논문지 Vol.15 No.6
단순 다각형(sunple polygon) P의 L₁-중심은 P 내부에 존재하는 어떤 점 x에서 P에 포함되는 다른 점까지의 최장 직교 내부 거리가 최소인 점들의 집합이다. 본 논문에서는 n개의 꼭지점(vertex)으로 구성된 P의 L₁-중심을 구하는 문제에 대해 P(n log n) 시간과 O(n) space가 소요되는 알고리즘을 제시한다. The L₁-center of a simple polygon P is the set of points x inside P at which the maximum rectilinear internal distance from x to any other points in P is minimized. This paper presents an algorithm which calculates the L₁-center of P with n vertices in O(n log n) time and O(n) space.