• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.111-117
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• 1996

The Delaunay triangulation technique was tested for complicated shapes of computational domain. While a simple geometry, both in topology and in geometry, was discretized well into triangular elements. a complex geometry often failed in triangularization. A complex geometry should be devided into smaller sub-domains whose shape is simple both topologically and geometrically. The present study developed the data structures not only for relationships among neibering elements but also for shape information, and coupled these into the Delaunay triangulation technique. This approach was able to enhance greatly the reliability of triangularization specially in complicated shapes of computational domains. The GUI (Graphic User Interface) and OOP (Object-Oriented Programming) were used in order to develop the user-friendly and efficient computer code.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2000년도 학술회의 논문집 3권2호
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• pp.139-153
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• 2000

지리 정보 시스템을 위한 공간 데이터베이스 관리시스템간의 이질성을 최소화하고 공간 데이터의 호환성이나 상호 연동성을 높일 수 있도록 OGC에서 OpenGIS의 사양을 정의하였다. 본 연구에서는 OpenGIS에서 정의된 공간 데이터 모델을 지원하는 컴포넌트를 구현한 것이다. 즉, OpenGIS에서 요구되어진 사양에 따라 SFG (Simple Feature Geometry) 컴포넌트를 구현하였다. 본 논문에서는 컴포넌트 구현상의 발생되었던 문제점과 이 해결 방법을 제시한다. 또한 구현 도중에 발견된 OpenGIS SFG의 사양 자체의 문제점도 함께 제시한다.

• 대한전자공학회논문지
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• 제24권5호
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• pp.818-822
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• 1987

Gate capacitances have been measured directly on small-geometry MOSFET's with the drain voltage as a parameter for various channel lengths and for p and n channel types and the characteristics have been compared with each other. The influence of 'hot carrier effect' of short channel devices on capaciatance has been compared with long channel devices. The results show that gate capacitance characteristics of short channel device deviate from those of long channel device. The accuracy of the measurement system is less than a few femto Farad, and the minimum geometry (W/L) of device for which reliable measurement can be obtained is 6/3.

• 대한원격탐사학회지
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• 제19권5호
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• pp.363-370
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• 2003

This paper describes a rectification procedure that relies on a polynomial model derived from the imaging geometry without loss of accuracy. By using polynomial model, one can effectively eliminate the iterative process to find an image pixel corresponding to each output grid point. With the imaging geometry and ephemeris data, a geo-location polynomial can be constructed from grid points that are produced by solving three equations simultaneously. And, in order to correct the local distortions induced by the geometry and terrain height, a distortion model has been incorporated in the procedure, which is a function of incidence angle and height at each pixel position. With this function, it is straightforward to calculate the pixel displacement due to distortions and then pixels are assigned to the output grid by re-sampling the displaced pixels. Most of the necessary information for the construction of polynomial model is available in the leader file and some can be derived from others. For validation, sample images of ERS-l PRI and Radarsat-l SGF have been processed by the proposed method and evaluated against ground truth acquired from 1:25,000 topography maps.

• Journal of Positioning, Navigation, and Timing
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• 제11권1호
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• pp.29-34
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• 2022

In this paper, we analyze the Non-Holonomic Constraint (NHC) satisfaction of Inertial Navigation System (INS) for vehicular navigation according to Inertial Measurement Unit (IMU) location. In INS-based vehicle navigation, NHC information is widely used to improve INS performance. That is, the error of the INS can be compensated under the condition that the velocity in the body coordinate system of the vehicle occurs only in the forward direction. In this case, the condition that the vehicle's wheels do not slip and the vehicle rotates with the center of the IMU must be satisfied. However, the rotation of the vehicle is rotated by the steering wheel which is controlled based on the Ackermann geometry, where the center of rotation of the vehicle exists outside the vehicle. Due to this, a phenomenon occurs that the NHC is not satisfied depending on the mounting position of the IMU. In this paper, we analyze this problem based on Ackermann geometry and prove the analysis result based on simulation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.952-956
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• 1995

It is known that the 3D Solid CAD system can provide various information which is useful for implementing CAPP and CAE. However the commercial 3D CAD systems available today do not support the handling of non-geometric information such as geometry tolerance and surface finish. It is impossible to input the non-geometric information during designof parts while CAPP needs the information for selecting machine tools. fiztures, inspection method, etc. In this paper the need of research on handling tolerance information In 3D CAD systems is considered. The development of inspection planning support system is also explained with an example. The development of inspection planning support systm receives the design geometry information from the 3D CAD system in the form of 2D draft and generates the inspection data base and the inspection sheet through the user interaction.

• 한국콘텐츠학회논문지
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• 제11권12호
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• pp.522-532
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• 2011

한의학에서 혀의 상태는 인체의 건강 상태를 진단하는 중요한 지표로 활용된다. 이러한 혀의 상태를 진단하는 설진은 편리할 뿐 아니라 비침습적이므로, 한의학에서 널리 활용되고 있다. 그러나 설진은 객관화와 표준화라는 관점에서 문제가 있으며, 한의사의 의사결정에 도움을 줄 수 있는 도구도 부족한 실정이다. 본 논문은 이러한 문제점을 해결하기 위해, 설진 유효 분석을 위한 혀의 기하정보를 자동으로 계산하는 방법을 제안한다. 제안된 방법은 개선된 스네이크(Snake) 방법을 통해 혀를 검출하고 컨벡스 헐(Convex Hull)과 인페인팅 방법을 이용하여 객관적인 기하 정보를 추출하였다. 제안 알고리즘의 성능평가로 치흔의 경우 7.2%, 균열의 경우 8.5%의 영역 차이 비율로 안정적인 결과가 도출되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권2호
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• pp.435-449
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• 2023

The state-of-the-art video-based point cloud compression(V-PCC) has a high efficiency of compressing 3D point cloud by projecting points onto 2D images. These images are then padded and compressed by High-Efficiency Video Coding(HEVC). Pixels in padded 2D images are classified into three groups including origin pixels, padded pixels and unoccupied pixels. Origin pixels are generated from projection of 3D point cloud. Padded pixels and unoccupied pixels are generated by copying values from origin pixels during image padding. For padded pixels, they are reconstructed to 3D space during geometry reconstruction as well as origin pixels. For unoccupied pixels, they are not reconstructed. The rate distortion optimization(RDO) used in HEVC is mainly aimed at keeping the balance between video distortion and video bitrates. However, traditional RDO is unreliable for padded pixels and unoccupied pixels, which leads to significant waste of bits in geometry reconstruction. In this paper, we propose a new RDO scheme which takes 3D-Distortion into account instead of traditional video distortion for padded pixels and unoccupied pixels. Firstly, these pixels are classified based on the occupancy map. Secondly, different strategies are applied to these pixels to calculate their 3D-Distortions. Finally, the obtained 3D-Distortions replace the sum square error(SSE) during the full RDO process in intra prediction and inter prediction. The proposed method is applied to geometry frames. Experimental results show that the proposed algorithm achieves an average of 31.41% and 6.14% bitrate saving for D1 metric in Random Access setting and All Intra setting on geometry videos compared with V-PCC anchor.

• Journal of Communications and Networks
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• 제16권3호
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• pp.249-257
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• 2014

This paper presents methods to the construction of regular and irregular low-density parity-check (LDPC) codes based on Euclidean geometries over the Galois field. Codes constructed by these methods have quasi-cyclic (QC) structure and large girth. By decomposing hyperplanes in Euclidean geometry, the proposed irregular LDPC codes have flexible column/row weights. Therefore, the degree distributions of proposed irregular LDPC codes can be optimized by technologies like the curve fitting in the extrinsic information transfer (EXIT) charts. Simulation results show that the proposed codes perform very well with an iterative decoding over the AWGN channel.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.901-905
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• 2012

In this study, we investigated the pure geometrical effect of porous materials in gas adsorption using the grand canonical Monte Carlo simulations of primitive gas-pore models with various pore geometries such as planar, cylindrical, and random pore geometries. Although the model does not possess atomistic level details of porous materials, our simulation results provided many insightful information in the effect of pore geometry on the adsorption behavior of gas molecules. First, the surface curvature of porous materials plays a significant role in the amount of adsorbed gas molecules: the concave surface such as in cylindrical pores induces more attraction between gas molecules and pore, which results in the enhanced gas adsorption. On the contrary, the convex surface of random pores gives the opposite effect. Second, this geometrical effect shows a nonmonotonic dependence on the gas-pore interaction strength and length. Third, as the external gas pressure is increased, the change in the gas adsorption due to pore geometry is reduced. Finally, the pore geometry also affects the collision dynamics of gas molecules. Since our model is based on primitive description of fluid molecules, our conclusion can be applied to any fluidic systems including reactant-electrode systems.