• 한국방재학회 논문집
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• 제7권3호
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• pp.9-18
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• 2007

대부분의 중규모 이하 댐은 홍수에 취약한 필댐으로 대책마련이 시급한 상황이나 시설물의 중요도 및 예산형편 등을 이유로 안전의 사각지대에 놓여있다. 이러한 문제점에 대한 현실적인 대책으로 여수로 월류부만을 부분 개축할 경우 방류능력을 어느 정도 증대시킬 수 있는지 분석하였다. 월류부 개축모형은 래버린스 웨어(labyrinth weir)와 가동 웨어를 선정하였고, 소규모 댐을 임의 선정하여 수리모형실험과 Flow-3D를 이용한 3차원수치해석을 통해 월류수심별 방류량을 산정하였다. 개축모형별 개선효과를 분석하기 위하여 빈도별 확률홍수량과 가능최대홍수량(PMF)을 산정하였고, 저수지홍수추적을 실시하여 개축 전 후의 최고수위를 비교하였다.

• 지질공학
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• 제17권4호
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• pp.567-576
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• 2007

디지털 영상을 통한 터널 내공의 3차원 절대변위 계측의 현장 적용성 검토를 위해 OO터널 현장에 계획된 내공변위 계측단면 상에 위치한 광파 타겟의 변위를 측정하고자 하였다. 디지털 영상 계측을 위한 3차원 입체모델 생성을 위해 측정위치마다 3개의 측선까지의 타겟만 고려하였다. 하나의 입체모델의 생성을 위해서 각 위치에서 3장 이상의 디지털 영상을 획득하여 입체모델을 구성하였으며, 마지막 2개 측선에서의 6개 타겟(천단, 좌우 측벽)을 계속 중첩시켜가며 다음 입체 모델을 구성하여 6개 이상의 정합점이 두 입체모델에서 공유될 수 있도록 하였다. 광파 계측과 디지털 영상계측을 통한 터널 시공 중 암반의 3차원 절대변위 계측 방법을 비교하기 위해 10회에 걸쳐 디지털 영상 계측과 광파 계측을 동일한 구간에 동시에 적용하였다. 각 방법을 사용한 계측에 소요되는 시간과 계측결과를 비교하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제25권4호
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• pp.295-303
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• 1999

Presented in this paper are the experimental results that measure rapid prototyping (RP) errors in 3D medical models. We identified various factors that can cause dimensional errors when producing RP models, specifically in maxillofacial areas. For the experiment, we used a human dry skull. A number of linear measurements based on landmarks were first obtained on the skull. This was followed by CT scanning, 3D model reconstruction, and RP model fabrication. The landmarks were measured again on both the reconstructed models and the physical RP models, and these were compared with those on dry skull. We focused on major sources of errors, such as CT scanning, conversion from CT data to STL models, and RP model fabrication. The results show that the overall error from skull to RP is $0.64{\times}0.36mm(0.71{\times}0.66%)$ in absolute value. This indicates that the RP technology can be acceptable in the real clinical applications. A clinical case that has applied RP models successfully for treatment planning and surgical rehearsal is presented. Although the use of RP models is rare in the medical area yet, we believe RP is promising in that it has a great potential in developing new tools which can aid diagnosis, treatment planning, surgical rehearsal, education, and so on.

• Journal of International Society for Simulation Surgery
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• 제3권2호
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• pp.77-79
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• 2016

Osteoma is one of the benign tumor that occurs on the bones all over the body. Mostly the simple excision is known to be enough. However, sometimes we encounter the troublesome situation where the osteoma is located in very challenging area, which results in the recurrence. 26 year female presented with the intractable intracranial osteoma. Given the disease entity of the osteoma, the simple excision would be enough or conservative management. But this osteoma turned out to be huge and recurrent in spite of the endoscopic resections, which causes the facial disappearance accompanied by the orbital vertical dystopia. Moreover, the patient's main concern was the pain. We performed the intracranial resection of the whole lesion and reconstructed the skull base and frontal bone as well as the part of the orbital wall. In order to restore the original bony anatomy, the 3D printing model was used based on the titanium mesh. I report this unusual case of the intractable intracranial huge osteoma. This report may be helpful for the other surgeons to make a decision on their similar cases in the future.

• 제어로봇시스템학회논문지
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• 제8권1호
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• pp.21-27
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• 2002

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three-dimensional surfaces. However, those conventional visual or optical methods have inherent shortcomings such as occlusion and variant surface reflection. X-ray vision system can be a good solution to these conventional problems, since we can extract the volume information including both the surface geometry and the inner structure of any objects. In the x-ray system, the surface condition of an object, whether it is lambertian or specular, does not affect the inherent characteristics of its x-ray images. In this paper, we propose a three-dimensional x-ray imaging method to reconstruct a three dimensional structure of an object out of two dimensional x-ray image sets. To achieve this by the proposed method, two or more x-ray images projected from different views are needed. Once these images are acquired, the simultaneous algebraic reconstruction technique(SART) is usually utilized. Since the existing SART algorithms have several shortcomings such as low performance in convergence and different convergence within the reconstruction volume of interest, an advanced SART algorithm named as USART(uniform SART) is proposed to avoid such shortcomings and improve the reconstruction performance. Because, each voxel within the volume is equally weighted to update instantaneous value of its internal density, it can achieve uniform convergence property of the reconstructed volume. The algorithm is simulated on various shapes of objects such as a pyramid, a hemisphere and a BGA model. Based on simulation results the performance of the proposed method is compared with that of the conventional SART method.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제30권6호
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• pp.513-517
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• 2008

Purpose: This study aimed to evaluate distribution and maximal value of mechanical stresses on the reconstruction plate, bridging mandibular symphysis defect, and to optimize the most appropriate locations of the plate to distribute the stress causing the fracture of the plate. Materials and methods: Four types of reconstruction were constructed by different number and location of the reconstruction plates on the 3 D finite element model (FEM) of a human edentulous mandible; Type I: one plate on the inferior border of the anterior mandible, Type II: one plate on the middle of the anterior mandible, Type III: one plate on the superior border of the anterior mandible, and Type IV: two plates on the inferior and superior border of the anterior mandible. Results: The results showed that the maximal stress of type I (234.29 Mpa) was lower than that of type II (260.91 Mpa) and type III (247.37 Mpa), but higher than that of type IV (186.64 Mpa). We could also observe that the stresses are tending to focus on the inner side and inferior part of the plate which connected proximal segment from the vertical load. Conclusions: On the basis of the findings, it was concluded that using a plate on the inferior border of mandible or two plates on the inferior and superior border of mandible are more favorable to distribute mechanical stresses, which could reduce the fracture of the plate.

• 한국정보과학회논문지:소프트웨어및응용
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• 제35권12호
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• pp.780-788
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• 2008

손 포즈 모델링 및 추적은 컴퓨터 시각 분야에서 어려운 문제로 알려져 있다. 손 포즈 3차원 복원을 위한 방법에는 사용되는 카메라의 수에 따라 다중 카메라 또는 스테레오 카메라 기반 방식과 단일카메라 기반 방식이 있다. 다중 카메라의 경우 여러 대의 카메라를 설치하거나 동기화를 시키는 등에 대한 제약사항이 따른다. 본 논문에서는 확률 그래프 모델에서 신뢰 전파 (Belief Propagation) 알고리즘을 이용하여 단안 카메라에서 획득된 2차원 입력 영상으로부터 3차원 손 포즈를 추정하는 방법을 제안한다. 또한, 은닉 마르코프 모델(Hidden Markov Model)을 인식기로 하여 손가락 클릭 동작을 인식한다. 은닉 노드로 손가락의 관절 정보를 표현하고, 2차원 입력 영상에서 추출된 특징을 관측 노드로 표현한 확률 그래프 모델을 정의한다. 3차원 손 포즈 추적을 위해 그래프 모델에서의 신뢰 전파 알고리즘을 이용한다. 신뢰 전파 알고리즘을 통해 3차원 손 포즈를 추정 및 복원하고, 복원된 포즈로부터 손가락의 움직임에 대한 특징을 추출한다. 추출된 정보는 은닉 마르코프 모델의 입력값이 된다. 손가락의 자연스러운 동작을 위해 본 논문에서는 한 손가락의 클릭 동작 인식에 여러 손가락의 움직임을 함께 고려한다. 제안한 방법을 가상 키패드 시스템에 적응한 결과 300개의 동영상 테스트 데이타에 대해 94.66%의 높은 인식률을 보였다.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2006년도 학술대회 1부
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• pp.33-39
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• 2006

Home modification has come to be recognized as an important intervention strategy to manage health care conditions, maintain or improve functioning, ensure safety, and reduce the wheelchair user's dependency on others. However, the availability of skilled professionals with experience in home modifications for accessibility is limited. A system that enables accurate remote assessments would be an important tool to improve our ability to perform home assessments more easily and at decreased cost. A Remote Wheelchair Accessibility Assessment System (RWAAS) using Virtualized Reality(VR) technology was developed that enabled clinicians to assess the wheelchair accessibility of users' built environments from a remote location. Characteristics of the camera and 3D reconstruction program chosen for the system significantly affect its overall reliability. In this study, we performed two reliability analyses on the hardware and software components: 1) Verification that commercial software can construct sufficiently accurate 3D models by analyzing the accuracy of dimensional measurements in a virtualized environment; 2) comparison of dimensional measurements with four camera settings. Based on these two analyses, we were able to specify a consumer level digital camera and the Photomodeler Pro software for this system. And we then tested the feasibility of the selected software and hardware in an actual environment. Lastly, A field evaluation was performed to test whether this new system is comparable to the traditional method of accessibility assessment to evaluate its ability to assess the accessibility of a wheelchair user's typical built environment. The results of field trials showed high congruence between the assessments by two methods. Findings suggested that the RWAAS assessments have the potential to enable specialists to assess potential accessibility problems in built environments regardless of the location of the client, home, or specialist.

• 한국측량학회지
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• 제25권6_1호
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• pp.545-555
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• 2007

3D buildings are the most prominent feature comprising urban scene. A few of mega-cities in the globe are virtually reconstructed in photo-realistic 3D models, which becomes accessible by the public through the state-of-the-art online mapping services. A lot of research efforts have been made to develop automatic reconstruction technique of large-scale 3D building models from remotely sensed data. However, existing methods still produce irregular building polygons due to errors induced partly by uncalibrated sensor system, scene complexity and partly inappropriate sensor resolution to observed object scales. Thus, a geometric regularization technique is urgently required to rectify such irregular building polygons that are quickly captured from low sensory data. This paper aims to develop a new method for regularizing noise building outlines extracted from airborne LiDAR data, and to evaluate its performance in comparison with existing methods. These include Douglas-Peucker's polyline simplication, total least-squared adjustment, model hypothesis-verification, and rule-based rectification. Based on Minimum Description Length (MDL) principal, a new objective function, Geometric Minimum Description Length (GMDL), to regularize geometric noises is introduced to enhance the repetition of identical line directionality, regular angle transition and to minimize the number of vertices used. After generating hypothetical regularized models, a global optimum of the geometric regularity is achieved by verifying the entire solution space. A comparative evaluation of the proposed geometric regulator is conducted using both simulated and real building vectors with various levels of noise. The results show that the GMDL outperforms the selected existing algorithms at the most of noise levels.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.250-255
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• 2003

The position of a 3-dimensional(3D) point can be measured by using calibrated stereo camera. To obtain more accurate measurement ,more accurate camera calibration is required. There are many existing methods to calibrate camera. The simple linear methods are usually not accurate due to nonlinear lens distortion. The nonlinear methods are accurate more than linear method, but it increase computational cost and good initial guess is needed. The multi step methods need to know some camera parameters of used camera. Recent years, these explicit model based camera calibration work with the development of more precise camera models involving correction of lens distortion. But these explicit model based camera calibration have disadvantages. So implicit camera calibration methods have been derived. One of the popular implicit camera calibration method is to use neural network. In this paper, we propose implicit stereo camera calibration method for 3D reconstruction using support vector machine. SVM can learn the relationship between 3D coordinate and image coordinate, and it shows the robust property with the presence of noise and lens distortion, results of simulation are shown in section 4.