• 한국정밀공학회지
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• 제12권1호
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• pp.78-86
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• 1995

$H_{\infty}$ Controller of seeker scan-loop is designed using LSDP proposed by McFarlane. The performance and robustness of $H_{\infty}$ controller are analyzed using robustness theorems by Lehtomaki and compared with those of the LQG/LTR controller. Especially, structured singular value .mu. -test of Doyle is used to evaluate robust performance of seeker scan-loop. It is demonstated that seeker scan-loop by $H_{\infty}$ controller is very robust to model uncertainties described by additive and multiplicative perturbations.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.335-338
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• 1998

This paper presents calculated results for the infinite phased arrays of the probe-fed rectagualr microstrip patches. A numerical model that is based on a rigorous Green's function and galerkin solutionsis is described. In an arbitrary scan plane, the input impedance and the input reflection coefficient versus the scand angle are calculated. The effects of substrate parameters on the phased arry antenna are considered. The scan blindness phenomenon due to the surface wave is observed and the input impedance bandwidth in the arbitrary scan plane is calculated.

• 대한토목학회논문집
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• 제42권5호
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• pp.689-699
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• 2022

최근 다양한 산업에서 첨단기술의 적용으로 높은 생산성 향상을 이루고 있지만 건설산업의 경우 생산성 향상이 비교적 낮게 조사되어, 이를 극복하기 위한 첨단기술 연구가 빠르게 진행되고 있다. 여러 첨단기술 중 3차원 스캔 기술은 실제 대상물을 손쉽게 디지털화 할 수 있다는 점에서 건설현장의 3차원 디지털 지형 모델 생성을 위한 기술로 널리 활용되고 있다. 특히 3차원 디지털 지형 모델은 토공 중장비의 자동제어 및 가이던스 등과 같은 건설 자동화의 기초자료가 될 수 있어 지형 스캔데이터의 높은 품질이 요구되고 있다. 3차원 디지털 지형 모델의 품질은 3D 스캐너의 성능 및 취득환경뿐 아니라 지형 스캔데이터 취득 후 3차원 디지털 지형 모델 생성을 위한 전처리 과정인 노이즈제거, 정합 및 병합과정 등 또한 많은 영향을 끼치고 있어, 지형 스캔데이터 처리의 성능 증진이 필요할 것으로 보인다. 본 연구에서는 3차원 디지털 지형 모델 생성을 위한 전처리 과정 중 정합과정에서 발생하는 지형 스캔데이터의 밀도 불균일 문제를 해결하고자 한다. 이를 위해 본 연구에서 개발한 정합 후처리 기술인 '픽셀기반 점군비교 알고리즘'을 제시하였으며, 실제 토공현장에서 취득한 지형 스캔데이터를 활용해 개발한 알고리즘의 성능검증을 수행하여 지형 스캔데이터 정합 후 불균일 문제의 개선 가능성을 검증하고 밀도 별 지형 스캔데이터에 대한 알고리즘의 최적 파라미터를 제시하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.303-304
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• 2007

• 비파괴검사학회지
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• 제20권6호
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• pp.538-544
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• 2000

강구조물의 내부를 영상화 하여 비파괴 평가를 할 수 있는 위상배열 초음파 탐상 시스템을 의료용 영상진단기를 개조함으로 개발하였다. 선택된 의료용 시스템은 64개의 독립된 송수신채널로 이루어져있으며 최고 128개의 배열초음파 탐촉자를 구동하여 초음파영상을 획득할 수 있도록 되어있다. 개조를 위해 주되게 고려된 사항은 속도의 변화로 인한 시스템의 개조와 강구조물에 적합한 탐촉자의 제작 그리고 비파괴 탐상에서 필요한 A-scan 신호를 획득하는 것이었다. 강구조물에 적합한 배열탐촉자를 설계하고 제작하기위해 경계회절파모델(Boundary Diffraction Wave Model)을 이용하여 초음파의 방사되는 음장을 시뮬레이션 하였다. 그리고 A-scan신호를 획득하기위한 장치를 제작하여 주어진 영상에서 선택된 주사선(scan line)의 RF신호를 획득하도록 하였다. 또한 강구조물에서 적절하게 송수신집속이 될 수 있도록 지연시간을 조절하였다. 개발된 시스템과 제작된 배열 탐촉자의 성능평가를 위해 인위결함 시험편에서 실험한 결과, 시험편의 내부의 영상과 선택한 주사선에 대한 A-scan신호를 실시간으로 획득할 수 있었다.

• The Journal of Advanced Prosthodontics
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• 제12권3호
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• pp.107-113
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• 2020

PURPOSE. The aim of this study was to examine the importance of the defect-free scanning of a scan body by assessing the accuracy of virtual implant positioning in computer-aided design (CAD) software when the scan body image is improperly scanned. MATERIALS AND METHODS. A scan body was digitized in a dentiform model using an intraoral scanner, and scanned images with differing levels of image deficiency were generated: 5%, 10%, and 15% deficiency in the flat or rounded area. Using a best-fit image matching algorithm on each of the deficient scan body images, corresponding virtual implants were created. The accuracy of the implant position was evaluated by comparing the linear and angular discrepancies between the actual and virtual positions of the implant. Kruskal-Wallis tests and Mann-Whitney U tests with Bonferroni correction were used to determine the statistical differences among the seven scanned image deficiency groups (α=.05). RESULTS. In general, the linear and angular discrepancies of the implant position in the software increased as the deficiency of the scan body images increased. A 15% scan body image deficiency generated larger discrepancies than deficiency of 5% and 10%. The difference of scan defect position, flat or rounded area, did not affect the accuracy of virtual implant orientation at 5% and 10% deficiency level, but did affect the accuracy at 15% deficiency level. CONCLUSION. Deficiencies in the scanned images of a scan body can decrease the accuracy of the implant positioning in CAD software when the defect is large, thus leading to the incorrect fabrication of implant prostheses.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1634-1637
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• 2003

Any given object on the motor-driven turntable is pictured from 8 to 72 different views with a digital camera. 3D shape reconstruction is performed with the integrated software called by Scanware from these multiple digital photographs. There are several steps such as configuration, calibration, capturing, segmentation, shape creation, texturing and merging process during the shape reconstruction process. 3D geometry data can be exported to cad data such as Autocad input file. Also 3D image model is generated from 3D geometry and texture data, and is used to advertise the model in the internet environment. Consumers can see the object realistically from wanted views by rotating or zooming in the internet browsers with Scanbull spx plug-in. The spx format allows a compact saving of 3D objects to handle or download. There are many types of scan equipments such as laser scanners and photogrammetric scanners. Line or point scan methods by laser can generate precise 3D geometry but cannot obtain color textures in general. Reversely, 3D image modeling with photogrammetry can generate not only geometries but also textures from associated polygons. We got various 3D image models and introduced the process of getting 3D image model of an internet-connected watchdog robot.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.541-545
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• 1997

This paper presents a modified geometric active contour model or edge detection and segmentation of computed tomography(CT) scan images. The method is based on the level setup approach developed by Osher and Sethian and the modeling of propagation fronts with curvature dependent speeds by Malladi. Based on above algorithms, the geometric active contour is obtained through a particular level set of hypersurface lowing along its gradient force and curvature force. This technique retains the attractive feature which is topological and geometric flexibility of the contour in recovering objects with complex shapes and unknown topologies. But there are limitations in this algorithm which are being not able to separate the object with weak difference from neighbor object. So we use speed limitation filter to overcome those problems. We apply a 2D model to various synthetic cases and the three cases of real CT scan images in order to segment objects with complicated shapes and topologies. From the results, the presented model confirms that it attracts very naturally and efficiently to the desired feature of CT scan images.

• Advances in biomechanics and applications
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• 제1권1호
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• pp.67-76
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• 2014

Bone properties are one of the key components when constructing models that can simulate the mechanical behavior of a mandible. Due to the complexity of the structure, the tooth, ligaments, different bones etc., some simplifications are often considered and bone properties are one of them. The objective of this study is to understand if a simplification of the problem is possible and assess its influence on mandible behavior. A cadaveric toothless mandible was used to build three computational models from CT scan information: a full cortical bone model; a cortical and cancellous bone model, and a model where the Young's modulus was obtained as function of the pixel value in a CT scan. Twelve muscle forces were applied on the mandible. Results showed that although all the models presented the same type of global behavior and proximity in some locations, the influence of cancellous bone can be seen in strain distribution. The different Young's modulus defined by the CT scan gray scale influenced the maximum and minimum strains. For modeling general behavior, a full cortical bone model can be effective. However, when cancellous bone is included, maximum values in thin regions increase the strain distribution. Results revealed that when properties are assigned to the gray scale some peaks could occur which did not represent the real situation.

• 한국의류산업학회지
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• 제12권3호
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• pp.354-363
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• 2010

The purpose of this study was to provide some preliminary results on application of 3D scan data of head shapes to the hat design and pattern-making. This paper defined necessary measurement items and concepts in 3-dimensional images of head shapes. And also it presented the methodology to pattern-making of 6-piece crown hat based on 3D data. It used the data of Size Korea to pick up and choose a head shape model with the average head size of Korean women in their twenties. Main results were: 1. The 3D scan data of head shape was better than the 1 dimensional measurement data. Because I could establish a hat pattern-making theory by the 3D scan data of head. 2. The 3D scan data provided the basis for conceptualization of basic measurement points and items for a better fit of hats as well as the definition of the basic hat circumference. 3. This presented a methodology for analyzing out head shape by 3D scan data, and allowed the derivation of the basic hat circumference from the maximum head circumference. 4. As the 6-piece Crown cloche hat made by this method fitted the head shape model perfectly, this methodology could suggest potential applicability to various hat design.