• 한국음향학회지
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• 제19권1호
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• pp.61-66
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• 2000

본 논문에서는 다중 3차원 근거리표적의 위치를 효과적으로 추정하는 기법을 제안하였다. 제안한 기법은 세 개의 부분 센서배열을 이용하여 기존의 3D MUSIC에서의 3차원 탐색을 3번의 1차원 탐색으로 대치함으로써 연산량을 감소시켰다. 각각의 부분센서배열에서 얻은 센서신호로부터 표적이 원거리에 있다고 가정하고 원거리 입체각을 추정하면 추정된 입체각은 실제 근거리 표적의 위치인 방위각, 고각, 거리의 함수로 주어진다. 그러므로 세 개의 부분센서배열로부터 얻은 세 개의 함수를 연립하여 풀면 실제 근거리표적의 위치를 추정할 수 있다. 또한 다중 표적의 경우, 추정치에 대하여 3차원 MUSIC 스펙트럼 값을 비교함으로써 연관 문제를 해결하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.57-59
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• 1998

For medical students and doctors, knowledge of the three-dimensional (3D) structure of brain is very important in diagnosis and treatment of brain diseases. Two-dimensional (2D) tools (ex: anatomy book) or traditional 3D tools (ex: plastic model) are not sufficient to understand the complex structures of the brain. However, it is not always guaranteed to dissect the brain of cadaver when it is necessary. To overcome this problem, the virtual dissection programs of the brain have been developed. However, most programs include only 2D images that do not permit free dissection and free rotation. Many programs are made of radiographs that are not as realistic as sectioned cadaver because radiographs do not reveal true color and have limited resolution. It is also necessary to make the virtual dissection programs of each race and ethnic group. We attempted to make a virtual dissection program using a 3D image of the brain from a Korean cadaver. The purpose of this study is to present an educational tool for those interested in the anatomy of the brain. The procedures to make this program were as follows. A brain extracted from a 58-years old male Korean cadaver was embedded with gelatin solution, and serially sectioned into 1.4 mm-thickness using a meat slicer. 130 sectioned specimens were inputted to the computer using a scanner ($420\times456$ resolution, true color), and the 2D images were aligned on the alignment program composed using IDL language. Outlines of the brain components (cerebrum, cerebellum, brain stem, lentiform nucleus, caudate nucleus, thalamus, optic nerve, fornix, cerebral artery, and ventricle) were manually drawn from the 2D images on the CorelDRAW program. Multimedia data, including text and voice comments, were inputted to help the user to learn about the brain components. 3D images of the brain were reconstructed through the volume-based rendering of the 2D images. Using the 3D image of the brain as the main feature, virtual dissection program was composed using IDL language. Various dissection functions, such as dissecting 3D image of the brain at free angle to show its plane, presenting multimedia data of brain components, and rotating 3D image of the whole brain or selected brain components at free angle were established. This virtual dissection program is expected to become more advanced, and to be used widely through Internet or CD-title as an educational tool for medical students and doctors.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권4호
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• pp.212-222
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• 2003

The ability to efficiently and robustly recover accurate 3D terrain models from sets of stereoscopic images is important to many civilian and military applications. A stereo matching has been an important tool for reconstructing three dimensional terrain. However, there exist many factors causing stereo matching error, such as occlusion, no feature or repetitive pattern in the correlation window, intensity variation, etc. Among them, occlusion can be only resolved by true multi-image stereo. In this paper, we present multi-image stereo method using DEM fusion as one of efficient and reliable true multi-image methods. Elevations generated by all pairs of images are combined by the fusion process which accepts an accurate elevation and rejects an outlier. We propose three fusion schemes: THD(Thresholding), BPS(Best Pair Selection) and MS(Median Selection). THD averages elevations after rejecting outliers by thresholding, while BPS selects the most reliable elevation. To determine the reliability of a elevation or detect the outlier, we employ the measure of self-consistency. The last scheme, MS, selects the median value of elevations. We test the effectiveness of the proposed methods with a quantitative analysis using simulated images. Experimental results indicate that all three fusion schemes showed much better improvement over the conventional binocular stereo in natural terrain of 29 Palms and urban site of Avenches.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.107-117
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• 2016

We develop a new method to globally calibrate the feature points that are derived from the binocular systems at different positions. A three-DOF (degree of freedom) global calibration system is established to move and rotate the 3D calibration board to an arbitrary position. A three-DOF global calibration model is constructed for the binocular systems at different positions. The three-DOF calibration model unifies the 3D coordinates of the feature points from different binocular systems into a unique world coordinate system that is determined by the initial position of the calibration board. Experiments are conducted on the binocular systems at the coaxial and diagonal positions. The experimental root-mean-square errors between the true and reconstructed 3D coordinates of the feature points are 0.573 mm, 0.520 mm and 0.528 mm at the coaxial positions. The experimental root-mean-square errors between the true and reconstructed 3D coordinates of the feature points are 0.495 mm, 0.556 mm and 0.627 mm at the diagonal positions. This method provides a global and accurate calibration to unity the measurement points of different binocular vision systems into the same world coordinate system.

• Asian-Australasian Journal of Animal Sciences
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• 제20권7호
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• pp.1092-1099
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• 2007

Two experiments were conducted to determine the additivity of apparent or true digestibility of phosphorus (P) in soybean meal (SBM), peas, faba beans, corn, oats, broken rice meal, rough rice meal, buckwheat, and sorghum for growing pigs. Chromic oxide (0.3%) was used as a digestion marker in both experiments. Each experiment lasted for 12 d, which consisted of a 7-d dietary adaptation period followed by a 5-d fecal collection period. Experiment 1 involved 6 diets: the SBM-based control diet; 4 diets with corn, oats, rough rice meal and broken rice meal substituted for SBM; and an additional diet with a representative mixture of the 5 ingredients. In Experiment 2, 6 diets were prepared similarly, except that the tested ingredients besides SBM were faba beans, peas, buckwheat, and sorghum. In each experiment, six barrows with an initial average individual BW of 20.5 kg were fed one of the six diets according to a $6{\times}6$ Latin square design. The apparent and true P digestibility values for the nine tested ingredients were determined by the substitution method. There were no differences (p>0.05) between the determined and the predicted true P digestibility values for the mixture of ingredients in Experiments 1 and 2. However, the determined and the predicted apparent P digestibility values for the mixture of ingredients differed (p = 0.059) in Experiment 1, but not in Experiment 2. These results indicate that true P digestibility values are additive in ingredients containing low levels of phytate phosphorus and anti-nutritional factors, whereas the apparent P digestibility values are not always additive in single feed ingredients for growing pigs.

• 대한치과교정학회지
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• 제50권1호
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• pp.3-12
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• 2020

Objective: This study compared three prominent midsagittal planes (MSPs) to identify the MSP that best approximates the true symmetrical MSP. Methods: Forty-three patients (mean age, 23.0 ± 8.20 years) were grouped as follows: group 1 consisted of 10 patients with skeletal Class I and a menton (Me) deviation of < 2 mm; group 2, 11 patients with skeletal Class III and a Me deviation < 2 mm; group 3, nine patients with skeletal Class III and a Me deviation of 2 to less than 4 mm; and group 4, 13 patients with skeletal Class III and an Me deviation ≥ 4 mm. The candidate MSPs were established by three-dimensional (3D) cone beam computed tomography (CBCT) reorientation methods (RMs): (1) the MSP perpendicular to the Frankfort horizontal (FH) plane while passing through the crista galli and basion; (2) the MSP including the nasion, incisive foramen, and basion; (3) the MSP including the nasion, anterior nasal spine, and posterior nasal spine. The mean absolute distances (MADs) to the MSPs were calculated from the coordinates of 1,548 points on 129 CBCT images. The differences in the values of the 3D coordinates among RMs were compared. Results: The MADs of the three RMs showed significant differences (p < 0.05). Most of the differences in values of the coordinates were not significant among RMs. Conclusions: Although the differences in distance among the three MSPs were minor, the MSP perpendicular to the FH plane while passing through the crista galli and basion best approximated the true symmetrical MSP.

• 한국산업정보학회논문지
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• 제5권1호
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• pp.37-46
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• 2000

본 연구는 작업자 효율 균형화, 생산성 향상등과 같은 시스템 수행도를 개선하기 위해 자동차 부품 조립라인의 시뮬레이션 모델을 개발하였다. 시뮬레이션 모델은 완벽한 3D환경을 제공하는 이산사건모델링 도구인 QUEST를 이용하였으며, 이를 이용하여 현재의 생산라인의 수행도를 분석하였으며, 작업자효율을 균형화시키면서 생산성을 향상시킬 수 있는 방안을 제시하였다.

• Geomechanics and Engineering
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• 제14권2호
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• pp.195-202
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• 2018

Many laboratory experiments on crack propagation under uniaxial loading and biaxial loading have been conducted in the past using transparent materials such as resin, polymethyl methacrylate (PMMA), etc. However, propagation behaviors of three-dimensional (3D) cracks in rock or rock-like materials under tri-axial loading are often considerably different. In this study, a series of true tri-axial loading tests on the rock-like material with two semi-ellipse pre-existing cracks were performed in laboratory to investigate the acoustic emission (AE) characteristics and propagation characteristics of 3D crack groups influenced by intermediate principal stress. Compared with previous experiments under uniaxial loading and biaxial loading, the tests under true tri-axial loading showed that shear cracks, anti-wing cracks and secondary cracks were the main failure mechanisms, and the initiation and propagation of tensile cracks were limited. Shear cracks propagated in the direction parallel to pre-existing crack plane. With the increase of intermediate principal stress, the critical stress of crack initiation increased gradually, and secondary shear cracks may no longer coalesce in the rock bridge. Crack aperture decreased with the increase of intermediate principal stress, and the failure is dominated by shear fracturing. There are two stages of fracture development: stable propagation stage and unstable failure stage. The AE events occurred in a zone parallel to pre-existing crack plane, and the AE zone increased gradually with the increase of intermediate principal stress, eventually forming obvious shear rupture planes. This shows that shear cracks initiated and propagated in the pre-existing crack direction, forming a shear rupture plane inside the specimens. The paths of fracturing inside the specimens were observed using the Computerized Tomography (CT) scanning and reconstruction.

• The Journal of Advanced Prosthodontics
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• 제6권4호
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• pp.259-265
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• 2014

PURPOSE. The purpose of this study was to develop a dental image processing system using a three-dimensional (3D) camera and stereovision technology. The reliability of the system for measuring axial wall convergence angles was evaluated. MATERIALS AND METHODS. The new system predicted 3D coordinate points from 2D images and calculated distances and angles between points. Two examiners measured axial wall convergence angles for seven artificial abutments using a traditional tracing-based method (TBM) and the stereovision-based method (SVBM). Five wax abutment models of simplified abutment forms were made and axial wall convergence angles of wax models were measured by both methods. The data were statistically analyzed at the level of significance, 0.05. RESULTS. Intraclass correlation coefficients showed excellent intra-examiner and inter-examiner reliabilities for both methods. Bland-Altman plots and paired t-tests showed significant differences between measurements and true values using TBM; differences were not significant with SVBM. CONCLUSION. This study found that the SVBM reflected true angle values more accurately than a TMB and illustrated an example of 3D computer science applied to clinical dentistry.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.837-839
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• 2014

레이다 시스템에서 3차원 궤적 정보는 목표물 추적을 위해 필수적이다. 이때 3차원 레이다는 수신 신호를 통해 방위각, 고각 및 거리를 추정하여 3차원 궤적 정보를 얻게 된다. 수신 신호에 따라 추정된 각도들과 거리는 오차를 가지게 되며 이 오차의 정도에 따라 3차원 레이다 시스템의 성능에 미치는 영향에 대한 분석이 요구되어진다. 본 논문에서는 3차원 레이다 시스템의 각도 및 거리 오차에 따라 추정된 3차원 궤적 정보와 실제 궤적 정보에 대해 RMSE (Root Mean Square Error)를 통해 성능을 분석한다.