• Explosives and Blasting
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• v.26 no.1
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• pp.57-66
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• 2008

It has been proven that the pre-cracking notches in a blasting hole are applicable to control crack growth along specific direction. This study compared the roughnesses of the fracture plane resulting from test blasts using a regular charge hole and notched charge hole to investigate the effect of the notches of charge hole on the formation of fracture plane. A notch bit system was used to drill the notched hole in the rock specimens. The surfaces of the fracture planes were reconstructed as Digital Elevation Model (DEM) using digital photogrammetric method and the roughnesses of the surfaces were estimated with Surface Roughness Profile Index (SRp).

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.2
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• pp.104-115
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• 2018

Purpose: The purpose of this study is to evaluate the image acquisition ability of intraoral scanners by analyzing the comprehensiveness of scanned images from standardized model, and to identify problems of the model. Materials and Methods: Cast models and 3D-printed models were prepared according to international standards set by ISO12836 and ANSI/ADA no. 132, which were then scanned by model scanner and two different intraoral scanners (TRIOS3 and CS3500). The image acquisition performance of the scanners was classified into three grades, and the study was repeated with varying surface conditions of the models. Results: Model scanner produced the most accurate images in all models. Meanwhile, CS3500 showed good image reproducibility for angled structures and TRIOS3 showed good image reproducibility for rounded structures. As for model ingredients, improved plaster model best reproduced scan images regardless of the type of scanner used. When limited to 3D-printed model, powdered surface condition resulted in higher image quality. Conclusion: When scanning structures beyond FOV (field of view) in standardized models (following ISO12836 and ANSI/ADA 132), lack of reference points to help distinguish different faces confuses the scanning and matching process, resulting in inaccurate display of images. These results imply the need to develop a new standard model not confined to simple pattern repetition and symmetric structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.30-39
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• 2023

Large dams, which are critical infrastructures for disaster prevention, are exposed to various risks such as aging, floods, and earthquakes. Better dam safety inspection and diagnosis using digital transformation technologies are needed. Traditional visual inspection methods by human inspectors have several limitations, including many inaccessible areas, danger of working at heights, and know-how based subjective inspections. In this study, drone photogrammetry was performed on two large dams to evaluate the applicability of digital data-based dam safety inspection and propose a data management methodology for continuous use. High-quality 3D digital models with GSD (ground sampling distance) within 2.5 cm/pixel were generated by flat double grid missions and manual photography methods, despite reservoir water surface and electromagnetic interferences, and severe altitude differences ranging from 42 m to 99.9 m of dam heights. Geometry profiles of the as-built conditions were easily extracted from the generated 3D mesh models, orthomosaic images, and digital surface models. The effectiveness of monitoring dam deformation by photogrammetry was confirmed. Cracks and deterioration of dam concrete structures, such as spillways and intake towers, were detected and visualized efficiently using the digital 3D models. This can be used for safe inspection of inaccessible areas and avoiding risky tasks at heights. Furthermore, a methodology for mapping the inspection result onto the 3D digital model and structuring a relational database for managing deterioration information history was proposed. As a result of measuring the labor and time required for safety inspection at the SYG Dam spillway, the drone photogrammetry method was found to have a 48% productivity improvement effect compared to the conventional manpower visual inspection method. The drone photogrammetry-based dam safety inspection is considered very effective in improving work productivity and data reliability.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.106-114
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• 2010

Mesh parameterization is the process of finding one-to-one mapping between an input mesh and a parametric domain. It has been considered as a fundamental tool for digital geometric processing which is required to develop several applications of digital geometries. In this paper, we propose a novel 3D volume parameterization by means that a harmonic mapping is established between a 3D volume mesh and a unit solid cube. To do that, we firstly partition the boundary of the given 3D volume mesh into the six different rectangular patches whose adjacencies are topologically identical to those of a surface cube. Based on the partitioning result, we compute the boundary condition as a precondition for computing a volume mesh parameterization. Finally, the volume mesh parameterization with a low-distortion can be accomplished by performing a harmonic mapping, which minimizes the harmonic energy, with satisfying the boundary condition. Experimental results show that our method is efficient enough to compute 3D volume mesh parameterization for several models, each of whose topology is identical to a solid sphere.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1629-1632
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• 2004

입체는 특수 장비에 의해 디지털 데이터화 되어 3차원 물체의 표면을 메쉬나 다각형 등으로 표현하며 입체의 세부구조인 다각형은 면적, 각 정점의 토폴로지, 변의 길이, 내각과 같은 고유 기하정보 요소를 가진다. 본 연구에서는 3차원 입체를 특징짓는 다각형의 기하학적 정보를 이용하여 3차원 모델을 2차원 평면으로 전개하는 방법을 제안한다. 이와 같은 기술은 옷이나 신발과 같은 2차원 형태의 부품을 결합하여 입체형태의 제품을 만들어 내는 분야에 매우 유용하게 쓰이며 나아가 3차원 모델에 최소의 왜곡을 가지는 텍스쳐를 적용시켜 3차원 모델의 사실성을 높이는데 기여할 수 있다.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.500-506
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• 2007

얼굴에 대한 시각적 인지는 오랫동안 인간에게 중요한 문제로 인식되어 왔다. 수 세기 동안 이루어져 왔던 미용 화장과 성형, 치아 교정 등의 다양한 연구는 사람의 얼굴을 감성적 측면에서 어떻게 하면 아름답게 만들 수 있는 가에 초점을 두었다. 본 논문에서는 휴먼 입출력 인터페이스로서 햅틱 장치와 스테레오 디스플레이를 혼합한 다중 감각 인터랙션 기반의 감성적인 3차원 얼굴 메이크업 시뮬레이션 프레임워크를 개발한다. 본 연구는 3차원 스캐너 장비로부터 사용자의 얼굴 모델을 추출하고, 그 데이터를 이용하여 자연스럽고 직관적인 얼굴 메이크업 시뮬레이션을 수행하는 것을 목표로 하고 있다. 이를 위하여 본 연구에서는 surface elements 표현 기반의 3차원 얼굴 필터링 방법과 얼굴 메이크업을 지원하는 페인팅 방법을 개발한다. 우선 사용자의 얼굴 모델을 3차원 스캐너로 획득한 후, 전처리 얼굴 필터링을 수행하여 조명, 그리고 사용자 얼굴 피부 상태에 기인하는 에러 및 속성들을 보정하고 피부 톤을 사용자가 선호하는 색으로 변경한다. 최종적으로 사용자는 햅틱 및 스테레오 디스플레이 장치를 이용하여 두 개의 레이어로 구성된 페인팅 표면 모델에 메이크업을 수행한다. 본 연구에서 적용한 surface elements 표현 기반의 그래픽 렌더링은 일반적인 메쉬 기반 페인팅의 문제점인 텍스쳐 왜곡 현상을 완화하고, 3차원 스캐너 장치에 기인하는 표면 에러를 보정한다. 그리고 전처리 얼굴 필터링과 메이크업 페인팅 방법은 사용자 중심의 감성적인 3차원 얼굴을 재구성하도록 한다. 결과적으로 본 연구에서 개발한 이러한 기술들이 다중 감각 인터페이스 기반의 메이크업 시뮬레이터의 기본 프레임워크가 되어, 차후 메이크업이나 코디네이션 분야 등의 디지털 콘텐츠 산업에서 활용될 수 있음을 확인하였다.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.375-383
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• 2020

This study aimed to propose a methodology for quantitatively analyzing problems resulting from the performance and combination of the ionization chamber when using an automatic exposure control (AEC) and to optimize the performance of the digital radiography (DR). In the experimental method, the X-ray quality of the parameters used for the examination of the abdomen and pelvis was evaluated by percentage average error (PAE) and half value layer (HVL). Then, the stability of the radiation output and the image quality were analyzed by calculating the entrance surface dose (ESD) and entropy when the three ionization chambers were combined. As a result, all of the X-ray quality of the digital radiography used in the experiment showed a percentage average error and a half value layer in the normal range. The entrance surface dose increased in proportion to the combination of chambers, and entropy increased in proportion to the combination of ionization chambers except when three chambers were combined. In conclusion, analysis using entrance surface dose and entropy was found to be a useful method for evaluating the performance and combination problems of the ionization chamber, and the optimal performance of the digital radiography can be maintained when two or less ionization chambers are combined.

• Journal of Korea Game Society
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• v.16 no.2
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• pp.97-110
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• 2016

Digital game is an entertainment content as well as a cultural content so that digital game can deliver social messages to make people confront with current problems. Based on Gonzalo Frasca's expanded model theory, this study aims to analyze independent games parodying reality on the level of the narrative and the gameplay to demonstrate that digital game can be a powerful medium to represent a satire on society. Parody games describe irrational side of society as being comical and provoke players' repetitive gameplay. Therefore, players can experience serious theme through casual play in the first-person, and realize the tragic reality directly.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.369-380
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• 2005

This study describes image-based approach for efficient and objective evaluation method of the rock slope stability. Three-dimensional rock slope model was reconstructed by processing stereo digital images. The model provided fundamental information for geospatial analysis of the rock slope. Methods to extract three-dimensional information about discontinuity on the rock slope and to estimate roughness of the rock surfaces were suggested. The results show that stereo digital images have potential to provide information for both quantitative and qualitative analysis of rock slope. In addition, visualization of the results increases efficiency and benefit in evaluating rock slope stability.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.1
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• pp.1-9
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• 2007

3D data are in great demand for pedestrian navigation recently. For pedestrian navigation, we needs to reconstruct 3D model in detail from people's eye. In order to present spatial features in detail for pedestrian navigation, it is indispensable to develop 3D model not only in outdoor environment but also in indoor environment such as underground shopping complex. However, it is very difficult to acquire 3D data efficiently by mobile mapping without GPS. In this research, 3D shape was acquired by Laser scanner, and texture by CCD(Charge Coupled Device) sensor. Continuous changes position and attitude of sensors were measured by IMU(Inertial Measurement Unit). Moreover, IMU was corrected by relative orientation of CCD images without GPS(Global Positioning System). In conclusion, Reliable, quick, and handy method for acquiring 3D data for indoor environment is proposed by a combination of a digital camera and a laser scanner with IMU.