• Korean Journal of Optics and Photonics
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• v.31 no.2
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• pp.59-70
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• 2020

We discuss a modified numerical model based on the Monte Carlo radiative transfer (MCRT) method, i.e., the MCRT matrix method, for the analysis of atmospheric scattering effects in three-dimensional flash LIDAR systems. Based on the MCRT method, the radiative transfer function for a LIDAR signal is constructed in a form of a matrix, which corresponds to the characteristic response. Exploiting the superposition and convolution of the characteristic response matrices under the paraxial approximation, an extended computer simulation model of an overall flash LIDAR system is developed. The MCRT matrix method substantially reduces the number of tracking signals, which may grow excessively in the case of conventional Monte Carlo methods. Consequently, it can readily yield fast acquisition of the signal response under various scattering conditions and LIDAR-system configurations. Using the computational model based on the MCRT matrix method, we carry out numerical simulations of a three-dimensional flash LIDAR system operating under different atmospheric conditions, varying the scattering coefficient in terms of visible distance. We numerically analyze various phenomena caused by scattering effects in this system, such as degradation of the signal-to-noise ratio, glitches, and spatiotemporal spread and time delay of the LIDAR signals. The MCRT matrix method is expected to be very effective in analyzing a variety of LIDAR systems, including flash LIDAR systems for autonomous driving.

• Composites Research
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• v.29 no.1
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• pp.16-23
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• 2016

In this paper, numerical results of sectional analysis, stress recovery and energy release rate were compared with the results of VABS, 3-D FEM through the blade analysis library. The result of stress recovery analysis for one-dimensional model including the stiffness matrix is compared with stress results of three-dimensional FEM. We discuss the configuration of the blade analysis library and compare verifications of numerical analysis results of VABS. Blade analysis library through dimensional reduction and stress recovery is intended to be utilized in conjunction with pre- and post-processing of the analysis program of the composite blade, high-altitude uav's wing, wind blades and tilt rotor blade.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.1
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• pp.111-121
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• 2006

Recently, many studies have been performed to apply airborne LIDAR data to extracting urban models. In order to model efficiently the man-made objects which are the main components of these urban models, it is important to extract automatically planar patches from the set of the measured three-dimensional points. Although some research has been carried out for their automatic extraction, no method published yet is sufficiently satisfied in terms of the accuracy and completeness of the segmentation results and their computational efficiency. This study thus aimed to developing an efficient approach to automatic segmentation of planar patches from the three-dimensional points acquired by an airborne LIDAR system. The proposed method consists of establishing adjacency between three-dimensional points, grouping small number of points into seed patches, and growing the seed patches into surface patches. The core features of this method are to improve the segmentation results by employing the variable threshold value repeatedly updated through a statistical analysis during the patch growing process, and to achieve high computational efficiency using priority heaps and sequential least squares adjustment. The proposed method was applied to real LIDAR data to evaluate the performance. Using the proposed method, LIDAR data composed of huge number of three dimensional points can be converted into a set of surface patches which are more explicit and robust descriptions. This intermediate converting process can be effectively used to solve object recognition problems such as building extraction.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.39-42
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• 2009

본 논문에서는 콤팩트 세라믹 메탈핼라이드 램프용 가로등 기구의 반사판에 대해 2차원 설계법을 기반으로 한 3차원 설계로 150W single-ended type 콤팩트 세라믹 메탈핼라이드 램프 전용의 가로등용 반사판을 설계하였다.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.514-516
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• 2004

국내 및 국외에서 많은 시뮬레이션 환경이 개발되어 다양한 시뮬레이터 개발에 활용되고 있다. 이러한 시뮬레이션 환경은 다양한 기능을 갖추고 있어 시뮬레이터 개발편의를 도모하고 있다. 이러한 시뮬레이션 환경에서는 시뮬레이션 스케줄링(Scheduling), 데이터베이스(Database), 모델 컴파일 그리고 디버거(모니터링 및 제어기능 툴)등을 제공한다. 이미 국내 및 국외 업체에서 시뮬레이션 환경이 개발되어 왔지만, 3차원적인 시뮬레이션을 필요로 하는 시뮬레이션 환경은 미비한 상태로 로봇공학이나 3차원 시뮬레이션이 필요한 산업에 앞으로 더욱더 개발이 필요한 실점이다. 본 논문에서는 3차원 시뮬레이션을 하기 위한 방안으로 개발된 3D 모델빌더와 시뮬레이션 환경인 3DSIM(3D Simulation Environment)을 소개한다. 3DSIM은 현재 사용되고 있는 시뮬레이션 환경과는 다른 형식의 구조를 갖추고 있어 일반 시뮬레이션 환경과의 차이점에 대해 알아본다. 일반적인 시뮬레이션 환경은 서버와 클라이언트로 나뉘어 서버에서는 특정 모델에 대한 연산을 수행하기 위한 환경을 제공하며, 클라이언트에서는 서버에서 수행된 연산을 효율적으로 분석하기 쉽도록 보여주는 환경으로 나된다. 하지만, 3차원 시뮬레이션 환경인 3DSIM은 3차원 객체를 디자인하는 과정이 필요하며, 3차원 객체를 디자인하였을 경우, 각각의 파라미터를 통하여 시뮬레이션 되어야 한다는 점에서 일반적인 시뮬레이션 환경과의 구조가 다르게 된다. 3DSIM개발을 통하여 3차원 시뮬레이터 개발을 보다 편하게 개발할 수 있도록 하였으며, 시뮬레이션 모니터링 및 제어가 용이하도록 개발하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.71-76
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• 2017

In BIM design, the construction and use of a library are very important. Since the existing contents can be re-used, the design can be executed more effectively and efficiently. Unlike the construction, the civil engineering, in particular, the railroad sees an inappropriate development and standardization of libraries. Thus, this study aims to develop and standardize the 3D object library in the railroad facility. We first gather and analyze the railroad facility breakdown structure and relevant drawings. We then match the items of analyzed standard drawings and the breakdown structure items. It was reviewed whether the library was required according to all items, and if required, it was reviewed what software was proper. Available software were found to be Civil 3D, Revit, etc. Based on this analysis, we will design the attribute items and specifications of the 3D railroad infrastructure library, as well as construct the library thereof.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.139-140
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• 2008

지상라이다는 고정도의 3차원 영상을 제공하고 레이저 빔을 현장이나 대상물에 발사하여 짧은 시간에 수백만점의 3차원좌표를 기록할 수 있는 최신 측량장비로서 다양한 응용분야에서 두각을 나타내고 있다. 본 연구에서는 지상라이다를 이용한 건축물의 3자윈 자동 윤곽선 추출을 다룬다. 지상라이다는 건축물의 3차원 윤곽선을 신속하게 추출할 수 있지만 지상기반 시스템이므로 여러 가지 장애물 때문에 건국물의 하단부에서는 추출이 쉽지 않다. 기존 항공라이다를 이용한 알고리즘에서는 사진의 색상차나 모폴로지 특성에 의존하여 범위를 제한하고, 이를 기반으로 윤곽선을 추출하였다. 하지만 지상라이다의 경우 항공라이다에 비해 분해능이 월등히 높다. 또한, 지상라이다는 지상에서 측정하기 때문에 항공라이다에서 어려운 건축물의 측면이나 정면도 윤곽선 추출이 가능하기 때문에 본 논문에서는 사진을 이용하지 않고 전처리를 하지 않은 데이터를 직접 이용하여 건물의 정면 윤곽선을 추출하는 것을 제안한다. 건물의 크기와 데이터 수 즉, 라이다로 측정한 포인트 수를 고려한 효율적인 Decimation방법을 제안하고 또한, Decimation된 데이터이서 지역적으로 제일 큰 값과 작은 값을 찾아낸다. 그 중 많이 벗어난 점을 편차를 이용하여 제거한다. 이렇게 찾아낸 건축물의 외곽점들을 이어 만든 윤곽선을 최종적으로 보간하여 좀 더 현실과 가까운 윤곽선 추출 방법을 제안한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.461-468
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• 2017

The introduction of BIM in domestic construction industry has become more active. Library development and standardization in civil-engineering are unexhausted. This research develop and standardize prototype library for railway infrastructure. We define target facility for library based on railway standard drawings and select BIM software according characteristic of each facility. In this research, we develop libraries composed of 199 files and 489 types for alignment, roadbed and track and make specifications as defined attribution item and description. As we consider for application to diverse use case, develop prototype library in low LoD. We expect that library can increase 3D design productivity and ensure consistency of quality.

• Journal of the Korea Computer Graphics Society
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• v.25 no.3
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• pp.143-152
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• 2019

This paper presents two new techniques for solving the two problems of the water curtain: 'shape distortion' caused by gravity and 'resolution degradation' caused by fine satellite droplets around the shape. In the first method, when the user converts a three-dimensional model to a vertical sequence of slices, the slices are evenly spaced. The method is to adjust the time points at which the equi-distance slices are created by the nozzle array. In this method, even if the velocity of a water drop increases with time by gravity, the water drop slices maintain the equal interval at the moment of forming the whole shape, thereby preventing distortion. The second method is called the minimum time interval technique. The minimum time interval is the time between the open command of a nozzle and the next open command of the nozzle, so that consecutive water drops are clearly created without satellite drops. When the user converts a three-dimensional model to a sequence of slices, the slices are defined as close as possible, not evenly spaced, considering the minimum time interval of consecutive drops. The slices are arranged in short intervals in the top area of the shape, and the slices are arranged in long intervals in the bottom area of the shape. The minimum time interval is pre-determined by an experiment, and consists of the time from the open command of the nozzle to the time at which the nozzle is fully open, and the time in which the fully open state is maintained, and the time from the close command to the time at which the nozzle is fully closed. The second method produces water drop sculptures with higher resolution than does the first method.

• Korean Journal of Remote Sensing
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• v.30 no.5
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• pp.559-570
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• 2014

Backscatter signal observed from the space-borne Light Detection And Ranging (LIDAR) system is providing unique 3-dimensional spatial distribution as well as temporal variations for atmospheric aerosols. In this study, the continuous observations for aerosol profiles were analyzed during a years of 2012 by using a Cloud-Aerosol LIDAR with Orthogonal Polarization (CALIOP), carried on the Cloud-Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) satellite. The statistical analysis on the particulate extinction coefficient and depolarization ratio for each altitude was conducted according to time and space in order to estimate the variation of optical properties of aerosols over Northeast Asia ($E110^{\circ}-140^{\circ}$, $N20^{\circ}$ $-50^{\circ}$). The most frequent altitudes of aerosols are clearly identified and seasonal mean aerosol profiles vary with season. Since relatively high particle depolarization ratios (>0.5) are found during all seasons, it is considered that the non-spherical aerosols mixed with pollution are mainly exists over study area. This study forms initial regional 3-dimensional aerosol information, which will be extended and improved over time for estimation of aerosol climatology and event cases.