• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.316-318
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• 2002

클러스터 파일 시스템은 고가용성(high availability) 및 결함내성(fault tolerance)을 만족하고 확장성이 뛰어나기 때문에 멀티미디어 서비스 등으로 활용범위를 넓혀왔다. 클러스터 시스템에서 일반적으로 제공되는 단일 시스템 이미지 (single system image) 기술은 저장된 위치에 관계없이 디렉토리나 파일에 접근할 수 있는 장점을 제공하지만 실제 저장된 위치에 따라 접근 시간의 편차가 발생된다. 본 논문에서는 파일이나 디렉토리에 관한 메타정보를 캐쉬에 저장함으로써 클러스터 파일 시스템에서의 접근 시간을 단축하기 위한 방법을 제안한다. 파일과 디렉토리의 접근 형태에 적합한 캐쉬 배치(placement) 기법과 재배치(replacement) 기법을 제시하고 캐쉬 일관성 유지를 위한 알고리즘을 보인다. 제안된 방법은 멀티미디어 서비스 등의 응용에서 효과적으로 접근시간을 단축할 수 있을 것으로 예상된다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.572-574
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• 2015

최근 스마트폰 내장 카메라와 플래시를 사용하여 PPG 신호를 측정하고 생체정보를 측정하는 연구가 많이 진행되고 있다. 그러나 스마트폰 카메라를 사용하여 측정하는 PPG신호는 스마트폰 카메라와 플래시 위치에 따라 각 측정 영역의 신호의 세기가 다르다. 본 논문에서는 스마트폰 카메라와 플래시 위치에 따라 강한 PPG 신호를 가지는 ROI를 찾기 위해 비교, 분석하였다. ROI를 계산하기 위해 PPG 신호를 측정하고 ROI를 선정할 수 있는 스마트폰 애플리케이션을 개발하여 각 ROI의 PPG 신호의 편차를 계산하고 가장 최적의 영역을 실험을 통해 비교분석하였다.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1125-1139
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• 2022

In an unmanned aerial vehicles (UAVs) system, a physical offset can be existed between the global positioning system/inertial measurement unit (GPS/IMU) sensor and the observation sensor such as a hyperspectral sensor, and a lidar sensor. As a result of the physical offset, a misalignment between each image can be occurred along with a flight direction. In particular, in a case of multi-sensor system, an observation sensor has to be replaced regularly to equip another observation sensor, and then, a high cost should be paid to acquire a calibration parameter. In this study, we establish a precise sensor model equation to apply for a multiple sensor in common and propose an independent physical offset estimation method. The proposed method consists of 3 steps. Firstly, we define an appropriate rotation matrix for our system, and an initial sensor model equation for direct-georeferencing. Next, an observation equation for the physical offset estimation is established by extracting a corresponding point between a ground control point and the observed data from a sensor. Finally, the physical offset is estimated based on the observed data, and the precise sensor model equation is established by applying the estimated parameters to the initial sensor model equation. 4 region's datasets(Jeon-ju, Incheon, Alaska, Norway) with a different latitude, longitude were compared to analyze the effects of the calibration parameter. We confirmed that a misalignment between images were adjusted after applying for the physical offset in the sensor model equation. An absolute position accuracy was analyzed in the Incheon dataset, compared to a ground control point. For the hyperspectral image, root mean square error (RMSE) for X, Y direction was calculated for 0.12 m, and for the point cloud, RMSE was calculated for 0.03 m. Furthermore, a relative position accuracy for a specific point between the adjusted point cloud and the hyperspectral images were also analyzed for 0.07 m, so we confirmed that a precise data mapping is available for an observation without a ground control point through the proposed estimation method, and we also confirmed a possibility of multi-sensor fusion. From this study, we expect that a flexible multi-sensor platform system can be operated through the independent parameter estimation method with an economic cost saving.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.4
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• pp.405-412
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• 2012

After the spatial discrepancy between SLI(Street-Level Imagery) and vector map is removed by their conflation, the corresponding building regions can be found based on SLI parameters. The building region correspondence, however, is not perfect even after the conflation. This paper aims to improve the correspondence of building regions by region splitting of an SLI. Regions are initialized by the seed lines, projection of building objects onto SLI scene. First, sky images are generated by filtering, segmentation, and sky region detection. Candidates for split lines are detected by edge detector, and then images are splitted into building regions by optimal split lines based on color difference and sky existence. The experiments demonstrated that the proposed region splitting method had improved the accuracy of building region correspondence from 83.3% to 89.7%. The result can be utilized effectively for enhancement of SLI services.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.6
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• pp.593-599
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• 2011

With increasing user applicability of geospatial data, user demand for manifold and accurate information has increased. The usefulness of these services derives from their combination of the advantages of as-built geospatial data in making new content. There is a spatial inconsistency and shape disagreement in fusing heterogeneous data. Conflation, defined as the combining of information from diverse sources so as to reconcile spatial inconsistencies and shape disagreement, is possible solution to the problem. In this research, we developed the technique for removing shape disagreement between aerial image and road map removed spatial inconsistency in advanced research. The process includes four processes: producing of a road candidate image, extraction of vertices, and generation of a graph by connecting the vertices. We could remove the shape disagreement using the extracted road that was derived from finding the road possible path.

• Journal of radiological science and technology
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• v.25 no.2
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• pp.83-83
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• 2002

국내 35개 병원의 44대의 CT장치를 대상으로 CT장치의 성능을 크게 7가지의 항목별로 구분하여 평가한 결과는 다음과 같았다. 물의 평균 CT number는 -18.9HU와 +68.6HU의 범위에 속했으며, 전체 장치의 평균은 $2.4{\pm}13.0\;HU$였다. 물의 평균 CT number의 권장수준을 -6과 +6로 하였을 경우 이에 적합한 장치는 35대(79.5%)였다. Contrast scale은 장치의 종류에 따라 많은 차이를 나타내었으나 평균은 $2.02{\pm}10^{-4}{\sim}1.665{\pm}10^{-5}$이었다. 직선성을 나타내는 상관계수는 0.984에서 0.992의 분포를 나타내었으며 평균은 $0.990{\pm}0.002$였다. 공간분해능은 0.60 m에서 1.25 mm의 분포를 나타내었으며 전체 장치의 65.9%에 해당되는 29대에서 0.75 mm의 공간 해상능을 나타내었다. 대조도 분해능은 3.2 mm(1/8인치)에서 19.1 mm(3/4인치)의 분포를 나타내었으며, 대조도 분해능의 권장수준을 6.4 mm 이하로 하였을 경우 측정 대상장치 44대 중 이에 적합한 장치는 37대(84.1%)였다. 슬라이스 두께의 설정치가 1 mm인 경우 측정치의 평균은 $2.0{\pm}0.6\;mm$이였으며, 설정치가 2 mm와 3 mm인 경우 측정치는 각각 $3.0{\pm}0.7\;mm$와 $3.5{\pm}0.6\;mm$이였다. 설정치가 5 mm와 7 mm인 경우 측정치는 각각 $5.1{\pm}0.6\;mm$, $7.0{\pm}0.5mm$이였다. 그리고 10 mm의 설정치에서는 $9.8{\pm}0.7\;mm$의 측정치를 나타내었다. 위치잡이용 중심선의 좌우방향의 편차는 -4.7 mm에서 +41.7 mm의 범위였으며, 상하방향의 편차는 -3.7 mm에서 +4.6 mm의 범위였다. 위치잡이용 중심선의 좌우 및 상하방향의 권장수준을 ${\pm}3.0\;mm$과 ${\pm}3.0\;mm$ 이하로 하였을 경우 41대의 측정 대상장치에서 이에 적합한 장치는 33대(80.5 %)였다.

• Journal of Navigation and Port Research
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• v.35 no.10
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• pp.785-791
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• 2011

This paper describes the evaluation and selection of MEMS(Micro-Elect Mechanical System) based inertial sensor to fit to implement the Inertial Measurement Unit(IMU) for a small-sized vessel at sea. At first, the error model and the noise model of the inertial sensors are defined with Euler's equations and then, the inertial sensor evaluation is carried out with Allan Variance techniques and Monte Carlo simulation. As evaluation results for the five sensors, ADIS16405, SAR10Z, SAR100Grade100, LIS344ALH and ADXL103, the combination of gyroscope and accelerometer of ADIS16405 is shown minimum error having around 160 m/s standard deviation of velocity error and around 35 km standard deviation of position error after 600 seconds. Thus, we select the ADIS16405 inertial sensor as a MEMS-based inertial sensor to implement IMU and, the error reducing method is also considered with the search for reference papers.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.490-490
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• 2015

산림 사면에서의 토양층 수문반응은 물순환을 이해하는데 중요하다. 본 연구에서는 토양수분자료를 이용하여 토양수분의 계절적, 공간적 변화를 분석하였다. 연구대상지역은 경기도 파주시 적성면 설마리의 설마천 유역 내에 위치한 범륜사사면과 충청북도 음성군의 청미천 유역내의 수레의산사면이다. 정밀측량을 통해 획득한 수치고도모형(Digital Elevation Model, DEM)을 이용하여 관측지점들을 각각 선정하였다. 대상사면에 토양층별 토양수분의 분포변화를 분석하기 위해 각 지점별 10, 30, 60cm에서 토양수분량 측정시스템(Time Domain Reflectometry, TDR)방식의 토양수분측정장비(miniTRASE)를 설치하여 2시간 간격으로 2014년 3월부터 12월까지 토양수분을 측정하였다. 각 지점별 사면에서 획득된 토양수분 시계열자료는 토양수분의 시공간적 분포특성을 파악하기 위해 지점별 토양수분량의 통계분석(평균, 표준편차, 변동계수)를 수행하였다. 설마천유역의 범륜사사면에서는 2014년도에 특히 강우량이 적어 토양수분의 평균과 표준편차의 월별 변화에서는 기저토양수분 값을 주로 유지하고 강우에 대한 변동성이 크지 않은 것으로 나타났고, 청미천유역의 수레의산 사면에서는 시간적 토양수분변화는 계절적 강우분포 패턴에 따라 반응이 나타났다. 청미천유역의 토양수분자료를 이용하여 토양수분의 계절적, 공간적 변화를 분석한 결과 지표근처 토양층(10, 30cm)와 저층(60cm)에서의 공간적 변화특성이 다르게 나타났다. 이는 저층(60cm)에서의 지표하 흐름, 기반암 존재의 영향차이에 의한 것으로 판단되고, 사면의 위치에 따라 토양수분의 안정화 정도가 다른 것을 확인할 수 있다.

• Journal of Advanced Navigation Technology
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• v.21 no.2
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• pp.163-170
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• 2017

MLAT which is an independent cooperative surveillance system is applied to increase the positon resoultin of secondary survelliance radar. MLAT uses the hyperboic or hyperboloid position mesurement algorithm. Central processing unit of MLAT calculates target position using time difference of arrival (TDOA) which can be solved from time of arrival (TOA) information of each receivers (at least 4 receivers). To increase position resolution of MLAT which use TDOA, TOA which is transfer time from tranmitter to receiver shold be calculated with precision time resolution in receiver. This paper explained the MLAT system briefly and explained ATD which is one of means of calcuating pulse position. ATD is applied to solve the deviation of pulse position due to different amplitude of signals in mulitiple receivers. In this paper, to analysis the performance of ATD, the simulation result of LAS and CDS was compared with the simulation result of basic threshold method.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.4
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• pp.420-430
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• 2008

Statement of problem & Purpose: Articulators are very important for education and overall clinical situation in the field of prosthodontics, however preexisting articulators are designed and built based on maxillofacial structures and mean values of mandibular movement of Western people. Purpose of this research is to find out a adequate basis for applicating these articulators, presently used for clinical education, for Korean. Material and methods: 59 Korean adults (41 males, 18 females), aged between 24 to 41, where selected for this study. Two pairs of both maxillary and mandibular models were made for each examinee. These models where attached to both KaVo PROTARevo 7 and Hanau Modular semiadjustable articulators by using facebow transfer, than sagittal condylar inclination, occlusal plane inclination and position of mandibular on the articulator where measured. Result and conclusion: 1. Mean sagittal condylar inclination for KaVo PROTAR semiadjustable articulator was $33.75^{\circ}$(standard deviation $12.46^{\circ}$) meanwhile Hanau Modular semiadjustable articulator showed $40.72^{\circ}$(standard deviation $12.09^{\circ}$) for mean sagittal condylar inclination. 2. Mean occlusal plane inclination for KaVo PROTAR semiadjustable articulator was $-2.76{\circ}$(standard deviation $3.63^{\circ}$) meanwhile Hanau Modular semiadjustable articulator showed $11.87^{\circ}$ (standard deviation $3.63^{\circ}$) for mean occlusal plane inclination. 3. On the average center of the mandibular dentition were in the range of 5 to 7 mm of the central position of the articulator. Both anterior and posterior dentition were positioned at the center of the articulator vernacularly for KaVo PROTAR semiadjustable articulators, meantime for Hanau Modular semiadjustable articulator, anterior dentition was positioned 5 mm downwards and 3mm upwards for posterior dentition from vertically central position of the articulator.