• 한국측량학회지
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• 제24권1호
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• pp.1-8
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• 2006

효율적인 3차원 모델링은 건설, 기계 그리고 디자인과 같은 폭넓은 설계분야에서 필수적으로 되고 있다. 특히, 역설계를 가능케 하는 툴로써 발전하고 있다. 3차원 모델링은 신속성, 정확성 그리고 명확성이 요구된다. 모델링을 위한 데이터 획득은 접촉식 좌표측정기, 레이져스캐너, 패턴스캐너 그리고 수치사진측량방법을 이용한다. 본 연구에서는 모델링 기법을 분석하고 패턴스캐너를 이용한 3차원 모델링기법을 소개하고자 한다. 또한, 본 연구는 OPTO-Top 패턴스캐너를 이용하여 3차원 모델링을 시도하고 신속성과 효율성을 수치사진측량기법과 비교분석하였다. 아울러 3차원으로 사용자가 웹환경에서 시뮬레이션 할 수 있는 환경구축을 시도하였다.

• 한국전산유체공학회지
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• 제19권2호
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• pp.58-65
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• 2014

The adaptive wavelet method is studied for the enhancement of computational efficiency of three-dimensional flows. For implementation of the method for three-dimensional Euler equation, wavelet decomposition process is introduced based on the previous two-dimensional adaptive wavelet method. The order of numerical accuracy of an original solver is preserved by applying modified thresholding value. In order to assess the efficiency of the proposed algorithm, the method is applied to the computation of flow field around ONERA-M6 wing in transonic regime with 4th and 6th order interpolating polynomial respectively. Through the application, it is confirmed that the three-dimensional adaptive wavelet method can reduce the computational time while conserving the numerical accuracy of an original solver.

• 한국기계가공학회지
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• 제16권6호
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• pp.139-145
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• 2017

It is necessary to analyze the exact contact position and contact stress of the wheel-rail in order to predict damage to the wheel and rail. This study presents a wheel-rail contact analysis model that considers the deformation of the axle. When a wheel-rail contact analysis is performed using a full three-dimensional model of the wheelset and rail, the analytical model becomes very inefficient due to the increase in analysis time and cost. Therefore, modeling the element-coupling model of the wheel and rail as a three-dimensional element and the axle as a one-dimensional element is proposed. The wheel-rail contact characteristics in the proposed analysis model for straight and curved lines were analyzed and compared with the conventional three-dimensional analysis model. Considering the accuracy of the analysis results and time, the result shows that the proposed analytical model has almost the same accuracy as a full three-dimensional model, but the computational effort is significantly reduced.

• 대한치과보철학회지
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• 제30권1호
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• pp.1-14
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• 1992

The purpose of this study was to evaluate the accuracy of reproduction of stone casts made from complete-arch impressions using different trays. The trays used were : 1) nonperforated custom tray, 2) perforated custom tray, 3) nonperforated Rim-Lock tray, 4) perforated stock tray. Impressions were made from an dentulous acrylic resin model with metal inserts in first premolars and second molars. Transverse distance, sagittal distance and diagonal distance were measured using 4 landmarks. Measurements were made by using 3 dimensional measuring machine. The impression material used was an addition silicone. Impressions were poured at once with a Type IV dental stone. Data were analyzed using ANOVA and student t-test with a sample size of five. The results were as follows : 1. There were statistical differences in amount of dimensional change in according to the tray types. In amount of mean dimensional change, perforated custom tray was the first smallest, nonperforated custom tray was the second, nonperforated Rim-Lock tray and perforated stock tray were the largest. 2. There were statistical differences in amount of dimensional change between nonperforated custom tray and nonperforated Rim-Lock tray, and between perforated custom tray perforated stock tray. 3. There were satistical differences in amount of dimensional change between nonperforated custom tray and perforated custom tray, but there was not a statistical difference between nonperforated Rim-Lock tray and perforated stock tray. 4. There was not a statistical difference in amount of dimensional change between upper and lower arch in all tray types.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.382-387
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• 1992

In order to obtain desired arc welding performance, we already developed an arc welding robot system that enabled coordinated motions of dual arm robots. In this system one robot arm holds a welding target as a positioning device, and the other robot moves the welding torch. Concerning to such a dual arm robot system, the positioning accuracy of robots is one important problem, since nowadays conventional industrial robots unfortunately don't have enough absolute accuracy in position. In order to cope with this problem, our robot system employed teaching playback method, where absolute error are compensated by the operator's visual feedback. Due to this system, an ideal arc welding considering the posture of the welding target and the directions of the gravity has become possible. Another problem still remains, while we developed an original teaching method of the dual arm robots with coordinated motions. The problem is that manual teaching tasks are still tedious since they need fine movements with intensive attentions. Therefore, we developed a 3-dimensional vision guided robot control method for our welding robot system with coordinated motions. In this paper we show our 3-dimensional vision sensor to guide our arc welding robot system with coordinated motions. A sensing device is compactly designed and is mounted on the tip of the arc welding robot. The sensor detects the 3-dimensional shape of groove on the target work which needs to be weld. And the welding robot is controlled to trace the grooves with accuracy. The principle of the 3-dimensional measurement is depend on the slit-ray projection method. In order to realize a slit-ray projection method, two laser slit-ray projectors and one CCD TV camera are compactly mounted. Tactful image processing enabled 3-dimensional data processing without suffering from disturbance lights. The 3-dimensional information of the target groove is combined with the rough teaching data they are given by the operator in advance. Therefore, the teaching tasks are simplified

• 한국의학물리학회지:의학물리
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• 제34권3호
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• pp.23-32
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• 2023

Purpose: In radiomics analysis, to evaluate features, and predict genetic characteristics and survival time, the pixel values of lesions depicted in computed tomography (CT) and magnetic resonance imaging (MRI) images are used. CT and MRI offer three-dimensional images, thus producing three-dimensional features (Features_3d) as output. However, in reports, the superiority between Features_3d and two-dimensional features (Features_2d) is distinct. In this study, we aimed to investigate whether a difference exists in the prediction accuracy of radiomics analysis of lung cancer using Features_2d and Features_3d. Methods: A total of 38 cases of large cell carcinoma (LCC) and 40 cases of squamous cell carcinoma (SCC) were selected for this study. Two- and three-dimensional lesion segmentations were performed. A total of 774 features were obtained. Using least absolute shrinkage and selection operator regression, seven Features_2d and six Features_3d were obtained. Results: Linear discriminant analysis revealed that the sensitivities of Features_2d and Features_3d to LCC were 86.8% and 89.5%, respectively. The coefficients of determination through multiple regression analysis and the areas under the receiver operating characteristic curve (AUC) were 0.68 and 0.70 and 0.93 and 0.94, respectively. The P-value of the estimated AUC was 0.87. Conclusions: No difference was found in the prediction accuracy for LCC and SCC between Features_2d and Features_3d.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1549-1554
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• 2010

플라스틱 나사는 경량성, 내식성, 열 및 전기절연성이 우수하여 최근 금속나사 대체용도로 사용 되고 있다. 플라스틱 나사는 사출성형에 의해 제작되며 성형과정에서 수축이 발생하여 형상정밀도가 저하된다. 특히 소형 정밀나사의 경우 마이크로미터 단위의 정밀도를 요구하는 관계로 소성가공에 의해 제작되는 금속나사를 대체하기 위해서는 많은 어려움이 따른다. 본 연구에서는 사출성형 공정의 수치해석을 통해 금형설계 인자를 결정하였고, 실험계획법을 적용하여 변형량을 최소화하기 위한 성형조건을 도출함으로써 플라스틱 나사의 형상정밀도 향상을 위한 연구를 수행하였다.

• 대한기계학회논문집A
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• 제35권1호
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• pp.33-37
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• 2011

디스플레이, 광학, 에너지 분야 부품의 미세형상화, 대면적화, 저가격화 요구에 대응하기 위하여 대면적 롤금형의 미세형상 가공기술개발에 대한 필요성이 대두되고 있다. 롤금형은 기존의 평판금형에 비해서 금형의 납기가 빠르고, 대면적화에 용이하며, 연속성형이 가능하다는 장점을 갖고 있다. 본 연구는 롤금형에 미세형상을 가공할 때 발생하는 형상오차의 원인을 규명하는 것을 목적으로 하고 있으며, 가공 현장에서 개선 가능한 요소로서 롤금형의 동적밸런싱 보정방안을 제시하고 있다. 기존보다 정밀한 동적밸런싱 보정을 통하여 롤금형의 질량불평형이 최대 90%까지 감소되었고, 롤금형의 진동량이 0.044 mm/sec (RMS)에서 0.004mm/sec (RMS)로 감소하였으며, 결과적으로 미세패턴의 형상정밀도가 개선되는 것을 확인할 수 있었다.

• Imaging Science in Dentistry
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• 제48권2호
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• pp.111-119
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• 2018

Purpose: This study was conducted to evaluate the accuracy of linear measurements of 3-dimensional (3D) images generated by cone-beam computed tomography (CBCT) and facial scanning systems, and to assess the effect of scanning parameters, such as CBCT exposure settings, on image quality. Materials and Methods: CBCT and facial scanning images of an anthropomorphic phantom showing 13 soft-tissue anatomical landmarks were used in the study. The distances between the anatomical landmarks on the phantom were measured to obtain a reference for evaluating the accuracy of the 3D facial soft-tissue images. The distances between the 3D image landmarks were measured using a 3D distance measurement tool. The effect of scanning parameters on CBCT image quality was evaluated by visually comparing images acquired under different exposure conditions, but at a constant threshold. Results: Comparison of the repeated direct phantom and image-based measurements revealed good reproducibility. There were no significant differences between the direct phantom and image-based measurements of the CBCT surface volume-rendered images. Five of the 15 measurements of the 3D facial scans were found to be significantly different from their corresponding direct phantom measurements(P<.05). The quality of the CBCT surface volume-rendered images acquired at a constant threshold varied across different exposure conditions. Conclusion: These results proved that existing 3D imaging techniques were satisfactorily accurate for clinical applications, and that optimizing the variables that affected image quality, such as the exposure parameters, was critical for image acquisition.

• 산업경영시스템학회지
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• 제38권4호
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• pp.177-183
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• 2015

Incremental sheet metal forming is a manufacturing process to produce thin parts using sheet metals by a series of small incremental deformation. The process rarely needs dedicated dies and molds, thus, preparation time for the process is relatively short as to be compared to conventional metal forming. Spring back in sheet metal working is very common, which causes critical errors in dimensions. Incremental sheet metal forming is not fully investigated yet. Hence, incremental sheet metal forming frequently produces inaccurate parts. This paper proposes a method to minimize dimensional errors to improve shape accuracy of products manufactured by incremental forming. This study conducts experiments using an exclusive incremental forming machine and the material for these experiments are sheets of aluminum AL1015. This research defines a process parameter and selects a few factors for the experiments. The parameters employed in this paper are tool feed rate, tool diameter, step depth, material thickness, forming method, dies applied, and tool path method. In addition, their levels for each factor are determined. The plan of the experiments is designed using orthogonal array $L_8$ ($2^7$) which requires minimum number of experiments. Based on the measurements, dimensional errors are collected both on the tool contacted surfaces and on the non-contacted surfaces. The distances between the formed surfaces and the CAD models are scanned and recorded using a commercial software product. These collected data are statistically analyzed and ANOVAs (analysis of variances) are drawn up. From the ANOVAs, this paper concludes that the process parameters of tool diameter, forming depth, and forming method are the significant factors to reduce the errors on the tool contacted surface. On the other hand, the experimental factors of forming method and dies applied are the significant factors on the non-contacted surface. However, the negative forming method always produces better accuracy than the positive forming method.