• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.93-100
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• 2012

The interest in 3-dimensional information and its practical use are rapidly increasing and thus some goods with stereoscopic views are being released. Mobile phones, unlike other units, are being closely utilized in everyday life and their applications are undoubtedly limitless. In this study, taking photographs with the stereo-camera of mobile phones has been accomplished and also the possibility of getting the quantitative information has been examined. In addition, this study aims to evaluate the quantitative practical use of mobile phones, evaluating the accuracy of the obtained quantitative information. Thus, interior orientation parameters were decided through the calibration of the lens of two cameras equipped with mobile phones. Using the determined interior orientation parameters, the 3-dimensional coordinates on the targets of the test field were calculated and then compared with precisely observed coordinates. Moreover, the performance of the orientation on the arbitrary building resulted in the standard deviation of $X={\pm}0.0674m$, $Y={\pm}0.25319$, and $Z={\pm}0.4983m$. The result also shows that the plot is possible. As a result, smart phones could be utilized for the acquisition of the quantitative information at close range and small measurement in which the high-accuracy on the basis of centimeters is not required.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.4_1
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• pp.363-371
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• 2014

Most space-borne optical scanning systems adopt linear arrayconfigurations. The well-knownthree different types of space-borne sensors arealong-track line scanner, across-track linescanner, and three line scanner. To acquire accurate location information of an object on the ground withthose sensors, the exterior and interior orientation parameters are critical factors for both of space-borne and airborne missions. Since the imaging geometry of sensors mightchange time to time due to thermal influence, vibration, and wind, it is very important to analyze the Interior Orientation Parameters (IOP) effects on the ground. The experiments based on synthetic datasets arecarried out while the focal length biases are changing. Also, both high and low altitudes of the imagingsensor were applied. In case with the along-track line scanner, the focal length bias caused errors along the scanline direction. In the other case with the across-track one, the focal length bias caused errors alongthe scan line and vertical directions. Lastly, vertical errors were observed in the case ofthree-line scanner. Those results from this study will be able to provide the guideline for developing new linearsensors, so as for improving the accuracy of laboratory or in-flight sensor calibrations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.780-788
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• 2009

AE technique was applied to the static structural test of the composite wing structure to evaluate the structural integrity and damage. During the test, strain and displacements measurement technique were used to figure out for static structural strength. AE parameter analysis and source location technique were used to evaluate the internal damage and find out damage source location. Design limit load test, the 1st and 2nd design ultimate load tests and fracture test were performed. Main AE source was detected by an sensor attached on skin near by front lug. Especially, at the 1st design ultimate test, strain and displacements results didn't show internal damage but AE signal presented a phenomenon that the internal damage was formed. At the fracture test, AE activities were very lively, and strain and displacements results showed a tendency that the load path was changed by severe damage. The internal damage initiation load and location were accurately evaluated during the static structural test using AE technique. It is certified from this paper that AE technique is useful technique for evaluation of internal damage at static structural strength test.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.543-544
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• 2015

GIS(Gas Insulated Switchgear:가스절연 개폐장치)는 절연성능이 뛰어난 $SF_6$가스로 절연되어 초고압 전력의 제어(차단,투입)를 담당하는 중요한 장치이다. GIS는 절연성능을 검증하기 위하여 현장 운전전에 공장검수시험(내전압시험)과 현장 가압 시험을 수행한다. 이 때 GIS의 조립/운반/설치의 오류로 인한 절연성능 저하로 절연파괴(내부아크)가 발생될 수 있다. 그러나 GIS는 $SF_6$가스로 밀폐되어 있어 절연파괴를 정확히 알 수 없을 뿐만 아니라 사고 위치를 확인하기 어렵다는 단점을 가지고 있다. 따라서 본 논문에서는 이런 문제를 해결하기 위하여 GIS 내부에서 발생되는 사고를 신속하게 탐지하고 위치를 정확하게 표정할 수 있도록 개발된 GIS 절연파괴 위치 추정 시스템의 현장 적용연구를 수행하였다. 이를 통해 GIS 절연파괴 위치 추정 시스템의 성능을 확인하였다.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.318-321
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• 2001

클래딩은 주요 산업분야에 내마모성, 내부식성의 향상을 위해 사용되고 있다. 그러나 클래딩 공정에서는 모재와 클래딩 재료의 물리적, 화학적 특성의 차이와 여러 가지 공정 변수의 영향으로 제품의 사용에 치명적인 손상을 줄 수 있는 균열, 슬래그 개재물, 기공등의 불연속이 발생하기 쉽다. 본 연구에서는 클래딩 시에 발생되는 불연속을 실시간으로 검출하는데 아주 우수한 검출능력을 갖고 있는 비파괴 검사 방법인 음향방출시험을 적용하고 검출된 신호에 대한 주파수 분석과 2차원 위치표정을 실시하여 균열, 기공 등의 불연속을 검출하였고 이를 주사전자현미경을 통하여 확인하였다. 음향방출법에 의해 클래딩부에서 발생하는 결함에 대한 실시간 평가가 가능함을 입증하였으며, 특히 다층 클래딩이나 넓은 면적의 클래딩시에 불연속을 가장 신속하게 감지할 수 있으므로 이를 생산공정에 활용한다면 클래딩 또는 용접부 품질감시를 위한 효과적인 방법이 될 것이다.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.478-481
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• 2008

오늘날 비즈니스의 글로벌화, 사업장의 분산화는 필연적으로 영상회의의 활성화를 가져왔으나, 기 구축된 SD(Standard Definition)급 화질의 영상회의는 실감성 및 장시간 사용시 피로감 등에 따른 이용율 저조로 기대 만큼의 성화를 이루지 못하였다. 또한 기존 영상회의 시스템에서의 dec는 보조적 채널, 시스템 조작과 운영의 복잡성, 낮은 해상도로 인한 표정 및 눈짓 등의 요소 포착이 어려운 한계를 극복하지 못하였고, 기업들은 기업 내부 및 국내외 타기업들과의 협업을 위해 막대한 비용과 시간이 요구되고 있는 실정이다. KT는 기존 영상회의 문제 극복을 위해 서울<->대전 연구소간 전용선 연결, 비용 및 여러 site 확장을 위한 VPN으로의 전환 방안등 최상의 영상회의 구축을 위한 검토를 통해 Full HD실감 화질의 영상회의를 구축하였으며, 향후에는 Full HD 데이터 압축 기술 향상 및 데이터 전송 방안에 대한 더 많은 연구가 필요하다고 판단된다. 본 고에서는 KT에서 구축한 영상회의 사례를 중심으로 기본적인 기술과 구조, 국내외 시장의 현황 및 활용 방안에 대해 논하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.555-562
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• 2019

This paper presents soil deformation measurement in model chamber based on photogrammetry. We created an aluminum framed acrylic model chamber with soil inside and applied photogrammetry to measure soil deformation caused by loading tests. The soil consists of 40% black and 60% regular sand to create image contrast in soil images. In preprocessing, the self camera calibration was carried out for IOPs (Interior Orientation Parameters), followed by the space resection to estimate EOPs (Exterior Orientation Parameters) using control points located along the aluminum frame. Image matching was applied to measure the soil displacement. We tested different matching window sizes and the effect of image smoothing. Experimental results showed that 65x65 pixels of window size produced better soil deformation map and the image smoothing was useful to suppress the matching outliers. In conclusion, photogrammetry was able to efficiently generated soil deformation map.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.1
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• pp.68-76
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• 2011

Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect any further growth or expansion of preexisting defects or to characterize failure mechanisms. Recently, this kind of technique, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures like a huge wind turbine blade. Therefore, it is required to find a symptom of damage propagation before catastrophic failure through a continuous monitoring. In this study, a new damage location method has been proposed by using signal mapping algorithm, and an experimental verification is conducted by using small wind turbine blade specimen; a part of 750 kW real blade. The results show that this new signal mapping method has high advantages such as a flexibility for sensor location, improved accuracy, high detectability. The newly proposed method was compared with traditional AE source location method based on arrival time difference.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.3 s.21
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• pp.17-27
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• 2002

It is desirable to use a photogrammetric scanner to minimize the errors from the scanning procedure in case of building aerial photo image DB. The photogrammetric scanner, however, is highly expensive to have only limited number of scanners available, therefore the general-purpose scanners have been considered as an alternative. This study has mainly been focused to see the possibility of the general-purpose scanner to be used for scanning aerial photographs. For that, the analysis of the image coordinates were made as well as the accuracy evaluation of each phase. In addition to that, as the application of the orthophoto images has been increased, the magnitudes of the errors from the DEM generation and orthophoto projection were analyzed. Also, the calibration program was developed to verify the geometric distortion of the automatic scanner to contribute to enhance the quality of the aerial photo image DB.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2D
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• pp.277-285
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• 2008

X-ray images are wildly used in medical applications, and these can be more efficiently find scoliosis which is appearing during the growth of human skeleton than others. This research is focused on the calibration of X-ray image and three-dimensional coordinate determination of objects. Three-dimensional coordinate of objects taken by X-ray are determined by two step procedure. Firstly, interior and exterior orientation parameters are determined by camera calibration using Primary Calibration Object (PCO) which has two sides with embedded radiopaque steel ball. Secondly, calibration cage coordinates which is composed of two acrylic sheets that are perpendicular to X-ray source are determined by the parameters. Three-dimensional coordinates of calibration cage determined by photogrammetric technique are compared with that of Coordinate Measuring Machine (CMM). Though the accuracy analysis, X direction which is parallel to X-ray source error values are relatively higher than those of Y and Z directions. But, the accuracies of Y and Z axis are approximately -3 mm to 3 mm. From the research results, it is considered that photogrammetric technique is applied to determine three-dimensional coordinates of patients or assist to make medical devices.