• 대한치과기공학회지
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• 제41권4호
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• pp.287-293
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• 2019

Purpose: To evaluate the accuracy of the 3D printed die models and to investigate its clinical applicability. Methods: Stone die models were fabricated from conventional impressions(stone die model; SDM, n=7). 3D virtual models obtained from the digital impressions were manufactured as a 3D printed die models using a 3D printer(3D printed die models;3DM, n=7). Reference model, stone die models and 3D printed die models were scanned with a reference scanner. All dies model dataset were superimposed with the reference model file by the "Best fit alignment" method using 3D analysis software. Statistical analysis was performed using the independent t-test and 2-way ANOVA (α=.05). Results: The RMS value of the 3D printed die model was significantly larger than the RMS value of the stone die model (P<.001). As a result of 2-way ANOVA, significant differences were found between the model group (P<.001) and the part (P<.001), and their interaction effects (P<.001). Conclusion: The 3D printed die model showed lower accuracy than the stone die model. Therefore, it is necessary to further improve the performance of 3D printer in order to apply the 3D printed model in prosthodontics.

• The Journal of Advanced Prosthodontics
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• 제10권3호
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• pp.245-251
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• 2018

PURPOSE. To evaluate the accuracy of a model made using the computer-aided design/computer-aided manufacture (CAD/CAM) milling method and 3D printing method and to confirm its applicability as a work model for dental prosthesis production. MATERIALS AND METHODS. First, a natural tooth model (ANA-4, Frasaco, Germany) was scanned using an oral scanner. The obtained scan data were then used as a CAD reference model (CRM), to produce a total of 10 models each, either using the milling method or the 3D printing method. The 20 models were then scanned using a desktop scanner and the CAD test model was formed. The accuracy of the two groups was compared using dedicated software to calculate the root mean square (RMS) value after superimposing CRM and CAD test model (CTM). RESULTS. The RMS value ($152{\pm}52{\mu}m$) of the model manufactured by the milling method was significantly higher than the RMS value ($52{\pm}9{\mu}m$) of the model produced by the 3D printing method. CONCLUSION. The accuracy of the 3D printing method is superior to that of the milling method, but at present, both methods are limited in their application as a work model for prosthesis manufacture.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제34권5호
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• pp.555-561
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• 2008

Purpose: The goal of this study was to develop a technique for creating a computerized composite maxillofacial-dental model, based on point-based surface best fit algorithm and to test its accuracy. The computerized composite maxillofacial-dental model was made by the three dimensional combination of a 3-dimensional (3D) computed tomography (CT) bone model with digital dental model. Materials and Methods: This integration procedure mainly consists of following steps : 1) a reconstruction of a virtual skull and digital dental model from CT and laser scanned dental model ; 2) an incorporation of dental model into virtual maxillofacial-dental model by point-based surface best fit algorithm; 3) an assessment of the accuracy of incorporation. To test this system, CTs and dental models from 3 volunteers with cranio-maxillofacial deformities were obtained. And the registration accuracy was determined by the root mean squared distance between the corresponding reference points in a set of 2 images. Results and Conclusions: Fusion error for the maxillofacial 3D CT model with the digital dental model ranged between 0.1 and 0.3 mm with mean of 0.2 mm. The range of errors were similar to those reported elsewhere with the fiducial markers. So this study confirmed the feasibility and accuracy of combining digital dental model and 3D CT maxillofacial model. And this technique seemed to be easier for us that its clinical applicability can good in the field of digital cranio-maxillofacial surgery.

• 대한원격탐사학회지
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• 제25권3호
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• pp.205-214
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• 2009

This paper investigates stereo 3D viewing for linear pushbroom satellite images using the Orbit-Attitude Model proposed by Kim (2006) and using OpenGL graphic library in Digital Photogrammetry Workstation. 3D viewing is tested with KOMPSAT-2 satellite stereo images, a large number of GCPs (Ground control points) collected by GPS surveying and orbit-attitude sensor model as a rigorous sensor model. Comparison is carried out by two accuracy measurements: the accuracy of orbit-attitude modeling with bundle adjustment and accuracy analysis of errors in x and y parallaxes. This research result will help to understand the nature of 3D objects for high resolution satellite images, and we will be able to measure accurate 3D object space coordinates in virtual or real 3D environment.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.587-593
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• 2019

공간정보 관련 분야는 위치정보를 취득할 수 있는 센서 및 자료처리 기술의 발달로 빠른 속도로 변화하고 있으며, 이와 연관된 각종 산업과 사회적 활동에서 수요가 커지고 있는 실정이다. 누구나 보기 쉽고 이해가 빠른 3차원 공간정보의 구축과 활용은 관련 서비스의 품질과 신뢰도 향상에 필수적인 요소라 할 수 있다. 최근에는 3차원 공간정보 구축 기술로 3D 레이저 스캐너가 많이 활용되고 있지만 3D 레이저 스캐너는 대상물의 규모가 크거나 형상이 복잡한 경우, 데이터 취득이 되지 않는 음영지역이 발생할 수 있으며, 장비의 이동 및 설치 횟수가 많아질수록 작업의 효율이 떨어지는 단점이 있다. 이에 본 연구에서는 무인항공기를 이용하여 경사사진을 취득하고, 자료처리를 통해 대상물의 3차원 모델을 생성하고자 하였다. 연구대상지를 선정하고, 무인항공기를 이용해 경사사진을 취득하였으며, 자료처리를 통해 0.02m의 간격을 가지는 포인트클라우드 형태의 3D 모델을 생성하였다. 3D 모델의 정확도 평가 결과는 최대 0.19m, 평균 0.11m로 나타났으며, 축 방향에 따른 편차의 경향성은 나타나지 않았다. 향후, 촬영 및 자료처리 방법에 따른 정확도 평가와 카메라 종류에 따른 3D 모델 구축과 정확도 평가 및 분석이 이루어진다면 3D 모델의 정확도를 개선할 수 있을 것이며, 포인트클라우드 형태의 3D 모델은 거리 및 면적의 측정, 단면 생성, 대상물의 도면화 등 다양한 활용이 가능하여 공간정보 서비스 및 관련 업무의 작업 효율성을 향상시킬 수 있을 것이다.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.692-698
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• 2022

With the expansion of domestic hydrogen fuelling station infrastructure, it is necessary to secure reliability among hydrogen traders, and for this, technology to accurately measure hydrogen is important. In this study, 4 types of hydrogen trading volume calculation models (model 1-4) were presented to improve the accuracy of the hydrogen trading volume. In order to obtain the reference value of model 4, and experiment was conducted using a flow rate measurement equipment, and the error rate of the calculated value for each model was compared and analyzed. As a result, model 1 had the lowest metering accuracy, model 2 had the second highest metering accuracy and model 3 had the highest metering accuracy until a certain point. But after the point, model 2 had the highest metering accuracy and model 3 had the second metering accuracy.

• 방송공학회논문지
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• 제19권5호
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• pp.677-686
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• 2014

본 논문에서는 모바일폰 카메라를 이용하여 취득한 스테레오 영상으로부터 3차원 정보를 산출하고 이를 통해 3차원 정확도를 분석하고자 한다. 3차원 정확도 분석을 위해 스테레오 모델의 수렴각 변화에 따른 정확도 결과를 비교하였다. 본 논문에서는 내부 파라미터 산출과 영상의 왜곡보정 그리고 종속적 상대표정을 이용한 스테레오 영상의 기하구조 추정을 통해 모델 공간 상의 3차원 좌표를 계산하였으며, 이를 객체 공간 상의 좌표계로 변환함으로써 정량적인 3차원 정확도 분석을 수행하였다. 실험결과에서는 스테레오 모델의 수렴각이 약 $17^{\circ}$ 이상일 때, 상대적으로 높은 정확도를 갖는 3차원 정보가 생성됨을 확인하였다. 결과적으로 정확도 높은 3차원 정보 생성을 위해서는 촬영거리 및 기선거리를 고려하여 적절한 수렴각을 이루는 스테레오 모델 수립이 필요하다. 본 논문의 결과가 향후 모바일폰의 스테레오 영상을 이용한 입체영상 제작 및 3차원 객체 복원 등 관련 연구에 활용될 수 있을 것으로 기대된다.

• The Journal of Advanced Prosthodontics
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• 제15권3호
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• pp.145-154
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• 2023

PURPOSE. The objective of this study was to investigate how internal structures influence the overall and marginal accuracy of full arch preparations fabricated through additive manufacturing in different printing systems. MATERIALS AND METHODS. A full-arch preparation digital model was set up with three internal designs, including solid, hollow, and grid. These were printed using three different resin printers with nine models in each group. After scanning, each data was imported into the 3D data processing software together with the master cast, aligned and trimmed, and then put into the 3D data analysis software again to compare the overall and marginal deviation whose results are expressed using root mean square values and color maps. To evaluate the trueness of the resin model, the test data and reference data were compared, and the precision was evaluated by comparing the test data sets. Color maps were observed for qualitative analysis. Data were statistically analyzed by one-way analysis of variance and Bonferroni method was used for post hoc comparison (α = .05). RESULTS. The influence of different internal structures on the accuracy of 3D printed resin models varied significantly (P < .05). Solid and grid models showed better accuracy, while the hollow model exhibited poor accuracy. The color maps show that the resin models have a tendency to shrink inwards. CONCLUSION. The internal structure design influences the accuracy of the 3D printing model, and the effect varies in different printing systems. Irrespective of the kind of printing system, the printing accuracy of hollow model was observed to be worse than those of solid and grid models.

• Imaging Science in Dentistry
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• 제34권1호
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• pp.13-18
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• 2004

Purpose : This study was to evaluate the influence of slice thickness of computed tomography (CT) and rapid protyping (RP) type on the accuracy of 3-dimensional medical model. Materials and Methods: Transaxial CT data of human dry skull were taken from multi-detector spiral CT. Slice thickness were 1, 2, 3 and 4 mm respectively. Three-dimensional image model reconstruction using 3-D visualization medical software (V-works /sup TM/ 3.0) and RP model fabrications were followed. 2-RP models were 3D printing (Z402, Z Corp., Burlington, USA) and Stereolithographic Apparatus model. Linear measurements of anatomical landmarks on dry skull, 3-D image model, and 2-RP models were done and compared according to slice thickness and RP model type. Results: There were relative error percentage in absolute value of 0.97, 1.98,3.83 between linear measurements of dry skull and image models of 1, 2, 3 mm slice thickness respectively. There was relative error percentage in absolute value of 0.79 between linear measurements of dry skull and SLA model. There was relative error difference in absolute value of 2.52 between linear measurements of dry skull and 3D printing model. Conclusion: These results indicated that 3-dimensional image model of thin slice thickness and stereolithographic RP model showed relative high accuracy.

• 한국도로학회논문집
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• 제18권1호
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• pp.73-83
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• 2016

PURPOSES : The purpose of this study is to develop a method for improving the accuracy of analysis results obtained from a two-dimensional (2-D) numerical analysis model of continuously reinforced concrete pavement (CRCP). METHODS : The analysis results from the 2-D numerical model of CRCP are compared with those from more rigorous three-dimensional (3-D) models of CRCP, and the relationships between the results are recognized. In addition, the numerical analysis results are compared with the results obtained from field experiments. By performing these comparisons, the calibration factors used for the 2-D CRCP model are determined. RESULTS : The results from the comparisons between 2-D and 3-D CRCP analyses show that with the 2-D CRCP model, concrete stresses can be overestimated significantly, and crack widths can either be underestimated or overestimated by a slight margin depending on the assumption of plane stress or plane strain. The behaviors of crack width in field measurements are comparable to those obtained from the numerical model of CRCP. CONCLUSIONS : The accuracy of analysis results from the 2-D CRCP model can be improved significantly by applying calibration factors obtained from comparisons with 3-D analyses and field experiments.