• 한국정밀공학회지
• /
• 제16권3호통권96호
• /
• pp.198-207
• /
• 1999

This paper presents an accurate algorithm for geometric calibration of X-ray imaging system. Calibration is a very important process for improving an imaging system performance. There has been a lot of previous works using linear camera modeling technique, where lens distortion is neglected and/or center of distortion is assumed to be known. Geometrical distortion of image intensifier, however, is very large and its center of distortion should be calculated. This paper presents a new calibration method to estimate the intensifier position and orientation, scale factor, distortion coefficient, magnification factor, and center of distortion using the least square method. We investigate the properties of the algorithm by computer simulation. Simulation results show that the parameters can be estimated accurately using the proposed algorithm.

• Journal of Advanced Research in Ocean Engineering
• /
• 제1권2호
• /
• pp.106-114
• /
• 2015

In the fabrication of offshore oil and gas facilities, the significance of dimension control is growing continuously. But, it is difficult to determine the deformation of the structure during fabrication by simple lab tests due to the large size and the complicated shape. Strain-boundary method (a kind of shrinkage method) based on the shell element was proposed to predict the welding distortion of a structure effectively. Modeling of weld geometry in shell element is still a difficult task. In this paper, a concept of imaginary temperature pair is introduced to handle the effect of geometric factors such as groove shape, plate thickness and pass number, etc. Single pass imaginary temperature pair formula is derived from the relation between the groove area and the FE mesh size. By considering the contribution of each weld layer to the whole weldment, multi-pass imaginary temperature is also derived. Since the temperature difference represents the distortion increment, cumulative distortion curve can be drawn by integrating the temperature difference. This curve will be a useful solution when engineers meet some problems occurred in the shipyard. A typical example is shown about utilization of this curve. Several verifications are conducted to examine the validity of the proposed methodology. The applicability of the model is also demonstrated by applying it to the fabrication process of the heavy ship block. It is expected that the imaginary temperature model can effectively solve the modeling problem in shell element. It is also expected that the cumulative distortion curve derived from the imaginary temperature can offer useful qualitative information about angular distortion without FE analysis.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
• /
• pp.23-26
• /
• 2004

This paper analyzed time delay and phase distortion that generates in multipath and the degree of distortion due to power attenuation factor when UWB system is applied at indoor environment and the effects of indoor structure and material on distortion factors. Based on these distortion factors, channel model similar to actual environment is mathematically described and multipath and the degree of signal distortion generated when UWB system is applied to random environment is tested through channel model simulation and varies distortion factor that UWB system needs to consider in different indoor environment is analyzed.

• 대한조선학회논문집
• /
• 제49권4호
• /
• pp.304-311
• /
• 2012

One of the main features of Drillship or FPSO is a moonpool structure. The moonpool structures have various accuracy tolerances according to their functions and targets. This study is mainly interested in roundness of a circular moonpool structure in FPSO. Because this structure needs abrasion-resistance at which bearing of machine touches on inner wall of moonpool, we should do over-lay welding widely and deeply by using Inconel weld material. But a general over-lay can cause a severe distortion at ship block structure. If we can analyze the roundness by thermal distortion under Inconel over-lay, we can establish a special erection policy by the results. In this study, we designed stress-strain curve for strain-boundary condition analysis by an elasto-plastic material property. The results made us to decide an appropriate ship-block size and policy of crane manipulation will follow for its capacity. If a structure that needs over-lay is not large, solid elements also are not a bad choice for FEM modeling. Therefore we also developed a standard of using strain-boundary method that shell elements are used as over-lay on solid element modeling.

• 한국통신학회논문지
• /
• 제38C권10호
• /
• pp.911-919
• /
• 2013

방사 왜곡이 홀로그래픽 스테레오그램에 미치는 영향을 알아보기 위해, 가상의 3차원 객체를 렌더링하고, 이 객체로부터 원근 투영 이미지를 획득하였다. 획득된 원근 투영 이미지를 재배열 하여 hogel 이미지를 만들고 복원되는 영상을 확인하기 위해 홀로그래픽 스테레오그램의 수학적 복원 알고리즘을 제안하였다. 광학 엔진에 의해 발생 할 수 있는 방사 왜곡을 포함하는 hogel 이미지를 왜곡 정도를 달리하여 만들고, 수학적 복원 알고리즘을 이용하여 복원 하였고, 복원된 영상을 PSNR을 이용하여 비교 하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
• /
• pp.2193-2194
• /
• 2006

This paper presents the results of a grid-connected photovoltaic (PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD). The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.561-562
• /
• 2006

This paper presents the results of a grid-connected photovoltaic(PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power Quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD) The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
• /
• pp.1227-1228
• /
• 2006

This paper presents the results of a grid-connected photovoltaic(PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that can occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD). The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
• /
• pp.1687-1688
• /
• 2006

This paper presents the results of a grid-connected photovoltaic (PV) system modeling that contain incremental conductance MPPT(Maximum Power Point Tracking) controller by PSCAD/EMTDC simulator and investigates the influence that tan occur in the grid-connected PV system from aspect of power quality, i.e. voltage drop, total harmonic distortion(THD) and total demand distortion(TDD). The measured data the PV array modeling of PSCAD/EMTDC in Cheongwadae, Seoul, Korea is used in the paper.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1997년도 추계학술대회 논문집
• /
• pp.225-229
• /
• 1997

This paper describes the camera calibration based-neural network with a camera modeling that accounts for major sources of camera distortion, namely, radial, decentering, and thin prism distortion. Radial distortion causes and inward or outward displacement of a given image point from its ideal location. Actual optical systems are subject to various degrees of decentering, that is, the optical centers of lens elements are not strictly collinear. Thin prism distortion arises from imperfection in lens design and manufacturing as well as camera assembly. It is our purpose to develop the vision system for the pattern recognition and the automatic test of parts and to apply the line of manufacturing. The performance of proposed camera calibration is illustrated by simulation and experiment.