• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.57-59
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• 2003

Digital surface model generation from IKONOS stereo imagery is a new challenge in photogrammetric community, especially when the satellite company does not provide the raw data as well as their ancillary ephemeris data. In this paper we utilized an estimated relief displacement azimuth and the nominal collection elevation data included in the metadata file to correct the relief displacement of GCPs, together with a linear transformation for geometric modeling of IKONOS imagery. Space intersection is performed by the trigonometric intersection assuming a parallel projection of IKONOS imagery due to its small FOV and frame size. In the experiment, less than 2-meters of RMSE in orbit modeling is achieved denoting the potential positioning accuracy of the IKONOS stereo imagery.

• 한국정밀공학회지
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• 제26권2호
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• pp.133-140
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• 2009

Presented in this paper is a method to generate round-endmill toolpaths for sculptured surfaces represented as a triangular mesh model. The proposed method is applicable in toolpath generation for ball-endmills and flat-endmills because the round-endmill is a generalized tool in three-axis NC (numerical control) milling. The method uses a wireframe model as the offset model that represents a cutter location surface. Since wireframe models are relatively simple and fast to calculate, the proposed method can process large models and keep high precision. Intersection points with the wireframe offset model and a tool guide plane are calculated, and intersection curves are constructed by tracing the intersection points. The final step of the method is extracting regular curves from the intersection curves including degenerate and self-intersected segments. The proposed method is implemented and tested, and a practical example is presented.

• International Journal of CAD/CAM
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• 제4권1호
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• pp.11-17
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• 2004

In this paper, an exponential bound of the distance between a Loop subdivision surface and its control mesh is derived based on the topological structure of the control mesh. The exponential bound is independent of the process of recursive subdivisions and can be evaluated without subdividing the control mesh actually. Using the exponential bound, we can predict the depth of recursion within a user-specified tolerance as well as the error bound after n steps of subdivision. The error-estimating approach can be used in many engineering applications such as surface/surface intersection, mesh generation, NC machining, surface rendering and the like.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1080-1085
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• 2003

The flow of electrical current through a microscopic actual contact spot between two conductors is influenced by the flow through adjacent contact spots. A smoothed version of this interaction effect is developed and used to predict the contact resistance when the statistical size and spatial distribution of contact spots is known. To illustrate the use of the method, an idealized fractal rough surface is defined using the random midpoint displacement algorithm and the size distribution of contact spots is assumed to be given by the intersection of this surface with a constant height plane. With these assumptions, it is shown that including finer scale detail in the fractal surface, equivalent to reducing the sampling length in the measurement of the surface, causes the predicted resistance to approach the perfect contact limit.

• 대한기계학회논문집A
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• 제24권1호
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• pp.173-181
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• 2000

Depending upon the method of the surface generation and the quality of the boundary curves provided, the resulting surfaces may have global or local irregularities in many cases. Thus it would be necessary for the designer to evaluate the surface quality and to modify the surface. This capability is very important because the defect of the surface requires the rework of the dies that causes a big loss in cost and delivery time. To simulate the reflection line test in the actual production line, a faster generation algorithm is presented. Among., various surface interrogation methods using reflection lines, Blinn-Newell type of reflection mapping is applied to generate reflection lines on the trimmed NURBS surface. The generation of reflection lines is formulated as a surface-plane intersection problem, and solved by surface-contouring techniques. In addition, a modified reflection map is proposed to eliminate the discontinuity of reflection lines due to the configuration of the reflection map. A fast reflection line algorithm is developed utilizing an efficient traced contouring technique, and proved to be well suited for real-time quality-assessment task.

• 한국정보통신학회논문지
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• 제10권1호
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• pp.127-135
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• 2006

영상 기반 3차원 모델링은 카메라로부터 획득된 영상을 입력으로 하여 3차원 그래픽 모델을 생성하는 기술로 고가형 3D 스캐너의 대체 기술로 연구되어지고 있다. 본 논문에서는 피라미드 볼륨 교차기법을 이용한 영상 기반 3차원 모델링 시스템을 제안한다. 3차원 모델을 생성하기 위한 제안 알고리즘은 카메라 보정 단계, 3차원 형상 복원단계, 3차원 표면 생성 단계로 이루어진다. 카메라 보정 단계에서는 영상 획득용 카메라에 대한 카메라 행렬을 계산하며 3차원 형상 복원 단계에서는 실루엣 기반 피라미드 볼륨 교차 기법에 의해 실 3차원 형상을 생성한다. 3차원 표면 생성 단계에서는 3차원 형상 복원 단계의 결과인 복원 복셀 공간을 그물망 형태의 3차원 표면을 생성시킨다. 실험 결과 제안 알고리즘이 비교적 정확하게 3차원 모델을 생성함을 확인하였다.

• 한국ITS학회 논문지
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• 제20권4호
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• pp.95-105
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• 2021

도로 노면 파손 탐지는 쾌적한 주행 환경과 안전사고의 예방을 위해 필요하다. 도로 관리 기관은 자동화 기술 기반의 검사 장비와 시스템을 활용하고 있다. 이러한 자동화 기술 중에서도 도로 노면의 파손을 탐지하는 기술은 중요한 역할을 수행한다. 최근 들어 딥러닝을 이용한 기술에 대한 연구가 활발하게 진행 중이다. 이러한 딥러닝 기술 개발을 위해서는 도로 영상과 라벨 영상이 필요하다. 하지만 라벨 영상을 확보하기 위해서는 많은 시간과 노동력이 요구된다. 본 논문에서는 이러한 문제를 해결하기 위하여 준지도 학습 기법 중 하나인 적대적 학습 방법을 제안했다. 이를 구현하기 위해서 5,327장의 도로 영상과 1,327장의 라벨 영상을 사용하여 경량화 심층 신경망 모델을 학습했다. 그리고 이를 400장의 도로 영상으로 실험한 결과 80.54%의 mean intersection over union과 77.85%의 F1 score를 갖는 모델을 개발하였다. 결과적으로 라벨 영상 없이 도로 영상만을 학습에 추가하여 인식 성능을 향상시킬 수 있는 기술을 개발하였고, 향후 도로 노면 관리를 위한 기술로 활용되길 기대한다.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.160-171
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• 2001

Depending upon the method of the surface generation and the quality of the designed boundary curves, the resulting surfaces may have global or local irregularities in many cases. Thus, it would be necessary for the designer to evaluate the surface quality and to modify the surface. This is very important because the defect of the surface causes the rework of the dies, increasing cost and delivery time significantly. To simulate the reflection line test in the actual production line, a faster algorithm for generating reflection lines is presented. In this paper, among various surface interrogation methods using reflection lines, Blinn-Newell type of reflection mapping is applied to generate the reflection lines on the trimmed NURBS surfaces. The derivation of reflection lines is formulated as a surface-plane intersection problem (Jung 1994) and is solved by surface-contouring techniques. Also, for eliminating the discontinuity of reflection lines due to the configuration of reflection map, a modified reflection map is proposed. An efficient traced contouring technique is utilized for the computational efficiency and proves to be well suited for the real-time quality-assessment task.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.399-404
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• 2002

An efficient method of machining impeller is presented. In the roughing process, the cutting area is divided into two regions to reduce cutting time and select cutting tools. The regions are determined by characteristic point on the geometry of impeller blade. Then, the tool of the maximum radius is selected in each area. Tool interference in cutting areas is avoided by checking the intersection between cooing tool axis and ruling line on blade surface.

• 대한조선학회지
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• 제22권3호
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• pp.19-26
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• 1985

This paper deals with the representation and fairing of ship hull using a B-spline surface which is known as a 3-D model in computer aided free-form design. The first part of this paper is devoted to the fundamental concepts of B-spline theory and its geometrical characteristics. In its second part are described the facillities for efficient application, fast rendering of B-spline surface, and intersection of B-spline surfaces. The examples are presented with actual application to a real ship in the last part. And also a new concept of evaluating the surface fairness by the Gaussian curvature isolines is briefly discussed and its examples are presented.