• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.364-366
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• 2005

최신 동영상 압축 표준인 H.264는 압축 효율을 높이기 위해 기존의 표준과는 다른 1/2 화소 생성 방법을 사용한다. 그러므로 기존의 동영상 압축표준으로 압축된 비트열을 DCT 상에서 H.264로 트랜스코딩(transcoding)하기 위해서는 추가적인 보정 작업이 필요하다. 본 논문에서는 MPEG-2로 압축된 비트열을 DCT 상에서 H.264로 트랜스코딩 할 때 두 표준 간 1/2 화소 값의 차이를 보정하는 기법을 제안한다. 제안된 1/2 화소 보정 기법에서는 DCT 상태의 창조 프레임을 이용하여 두 표준 간의 차이 값을 구하여 입력으로 들어온 블록의 값에 더하여 보정한다. 픽셀 기반에서 보정하는 기법과 성능을 비교한 결과 제안하는 기법이 화질 면에서 우수하며 움직임이 빠른 비디오의 경우 계산량이 높아지는 것으로 나타났다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.3B
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• pp.302-314
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• 2001

많은 비전 응용에서 카메라의 광축은 영상 평면과 직교한다는 가정을 한다. 그러나 가정아래 전통적인 왜곡 영상 보정 방법은 렌즈의 방사(radial) 왜곡과 이탈(decentering) 왜곡만을 고려하고 있다. 그러나 렌즈의 광축(optical axis)과 영상 켈리브레이션 평면이 직교하지 않을 경우는 평면 투명 변환과 카메라 자체의 렌즈 왜곡이 복합되어 나타나게 되므로 기존 방법만으로는 이러한 복합왜곡을 보정할 수 없다. 본 논문에서는 일방 방사왜곡 뿐만 나이라 평면 투명변환과 렌즈왜곡이 동시 존재하는 영상 시스템에서도 적용 가능한 왜곡 영상 자동 보정 방법을 제한한다. 제안한 복합 왜곡 모델은 평면 투명 변환 모델과 렌즈의 방사 왜곡 모델로부터 유도하고, 계수 추출 알고리듬은 비 선형 최소화 기법인 Levenberg-Marquart 방법에 기반을 둔다. 실험은 이상형 격자 영상에 임의 왜곡 계수를 적용한 영상과 WebCam 카메라의 실제 왜곡 영상을 가지고 실시하였고, 기존 방법과 제안한 방법의 보정율을 비교 평가하였다. 실험결과 제안한 방법은 렌즈 왜곡만 있는 경우에도 기존 방법보다 우수하였으며, 복합왜곡 환경에서도 97% 이상의 보정율로 아주 견고하게 적용 가능한 것으로 나타났다.

• The korean journal of orthodontics
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• v.33 no.2 s.97
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• pp.103-111
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• 2003

The Purpose of this study was to evaluate the effect of occlusion on the mechanical strength of periodontal fibers during retention periods after experimental tooth movement. In the Sprague-Dawley male rats weighing 200g or more, the ntraoral elastics were inserted into the both right and left interproximal space between upper first and second molars for tooth movement. kiter 4 days later, the left lower first, second, and third molars were extracted for differentiating the non-occlusal side from the occlusal side in the same mouth. At the same time the elastics were removed and then light cured resin was Placed in the space between upper first and second molars following undercut was made for retention bilaterally. From the beginning of retention, 7 rats were sacrificed at 0, 4, 8, 12, 16, 20 days respectively. For evaluating of magnitude on the mechanical strength of periodontal tissue, the maximal shear load of the upper first molars were measured bilateraly during extraction using Instron Universal Testing Machine. The results of this study were obtained as follows : 1. In the occlusal side, the maximal shear load was increased from no retention to retention 20 days group as time was going and statistically difference was shown from retention 12 days group (p<0.05). 2. In the non-occlusal side, the maximal shear load was increased slightly from no retention to 20 days group as time was going but there was no statistically difference (p>0.05). 3. The result compared with the maximal shear load between occlusal and nonocclusal side showed no statistically difference until retention 8 day group (p>0.05), but showed statistically difference from retention 12 day to 20day group (P<0.05). These results show that occlusion had an effect on mechanical strength of the periodontal fibers during retention periods after experimental tooth movement; therefore, it is suggested that occlusion should be considered while the retainer types and retention period are planned.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.438-438
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• 2015

기후변화 시나리오는 다양한 자연조건에 대한 불완전한 이해, 연산능력 등의 제한으로 매우 높은 불확실성이 내포되어 있으며, 국내의 다양한 연구에서도 제시되어 있듯이 매우 과소 추정되어 있는 문제점이 있다. 이러한 문제로 인하여 다양한 편의보정 기법을 통해 기후변화 시나리오의 불확실성을 줄이고자 하는 노력이 수행되었다. 그러나 편의보정 기법은 적용 방법이 서로 상이하기 때문에 보정에 따른 강우 특성이 다르게 나타나는 문제점이 있다. 이에 본 연구에서는 편의보정 기법에 따른 강우-유출 특성을 갑천유역을 대상으로 분석하였다. Change Factor(CF)와 Quantile Mapping(QM) 그리고 CF와 QM을 연계한 편의보정기법(CQ)에 따른 강우-유출 특성을 갑천유역을 대상으로 Change Factor(CF)에서 연평균(CF_Y)/월평균(CF_M) 교정계수를 이용하는 방법과 Quantile Mapping(QM)을 총 편의보정기간(QM_E)과 우기와 비우기(QM_P)를 구분하여 누적확률분포를 고려하는 방법, 그리고 CF와 QM을 연계한 편의보정기법(CQ) 총 5가지에 대해서 편의보정을 수행하고 유출특성을 SWAT모형을 이용하여 분석하였다. 과거 기간에 대해 CF_M과 QM_P는 첨두유량이 실측 첨두유량에 비해 2배 이상 크게 나타났으며, 특히 QM_P는 최대 강우 발생 월이 다른 편의보정 기법과는 다르게 나타나 월별 유출 분석시 큰 오류가 발생될 것으로 판단된다. 5가지의 편의보정 기법 중에 CQ가 과거 강수 크기, 발생 분포 및 빈도 재현을 가장 잘 반영하며, 미래기간에 대한 기간별(2030s, 2050s, 2070s, 2090s) 평균유량을 비교한 결과 본 연구에서 사용한 SRES A1B 시나리오의 이산화탄소 배출 시나리오의 특성을 유지한 미래 강우-유출해석이 이루어지는 것으로 나타났다. 기후변화 시나리오에 편의보정 기법 적용으로 자연적인 현상을 정확하게 모의하기에는 어려움이 많고 불확실성 역시 매우 크지만, 과거 강수발생 경향이나 편의보정의 특성을 알고 활용목적에 맞는 편의보정을 수행한다면 수자원 관리 계획 수립 등에 큰 도움이 될것으로 판단된다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.3
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• pp.247-258
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• 2004

Two 3-dimensional data processing techniques to predict the fractured zone ahead of a tunnel face by the tunnel seismic survey were proposed so that the geometric formation of the fractured zone could be estimated. The first 3-dimensional data processing technique was developed based on the principle of ellipsoid, The input data needed for the 3D migration can be obtained from the 2-dimensional tunnel seismic prediction (TSP) test where the TSP test should be performed in each sidewall of a tunnel. The second 3-dimensional migration technique that was developed based on the concept of wave travel plane was proposed. This technique can be applied when the TSP is operated with sources in one sidewall of a tunnel while the receivers are installed in both sidewalls. New migration technique was applied to an in-situ tunnelling site. The 3-dimensional migration was performed using measured TSP data and its results were compared with the geological investigation results that were monitored during tunnel construction. This comparison revealed that the proposed migration technique could reconstruct the discontinuity planes reasonably well.

• The Journal of the Korea Contents Association
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• v.16 no.7
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• pp.31-41
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• 2016

Atmospheric correction as a preprocessing work should be performed to conduct accurately landcover/landuse classification using hyperspectral imagery. Atmospheric correction on airborne hyperspectral images was conducted and then the effect of atmospheric correction by comparing spectral reflectance characteristics before and after atmospheric correction for a few landuse classes was analyzed. In addition, land cover classification was first conducted respectively by the maximum likelihood method and the spectral angle mapper method after atmospheric correction and then the results were compared. Applying the spectral angle mapper method, the sea water area were able to be classified with the minimum of noise at the threshold angle of 4 arc degree. It is considered that object-based classification method, which take into account of scale, spectral information, shape, texture and so forth comprehensively, is more advantageous than pixel-based classification methods in conducting landcover classification of the coastal area with hyperspectral images in which even the same object represents various spectral characteristics.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.391-399
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• 2019

In this study, an analytical method was proposed to correct the analysis results and minimize the errors between column shortening predictions and real values in high-rise buildings. In this regard, the construction sequence analysis of 41-story reinforced concrete buildings was performed and the results were compared to four assumed field measurements that were divided into the column and the core. The analysis correction was applied at a stage over the error limit in the column and at all stages in the core. Since the error occurred continuously after the analysis was corrected, additional corrections of the analysis resulted in a smaller error. By applying the proposed analytical correction method, it was confirmed that the long-term shortening value can be accurately predicted.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.20 no.3
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• pp.283-291
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• 2002

Since GPS's SA cancellation, the interest is converged in correction of errors such as atmospheric delay and multipath that weight had been small relatively, which can improve the accuracy of positioning through modelling research. The aim of this study have an extensive comparison of the various tropospheric delay models (Goad&Goodman, A&K, Hopfield and Sasstamoinen) and mapping functions(Niell, Chao, and Marini). Expecially, the tropospheric delay amounts by change of the GPS satellite elevations, and the delay by various combination between zenith delay models and mapping functions, compared and examined. For this, programmed the total delay models and the combined models which can be described as a product of the delay at the zenith and a mapping function. The result of study, especially, as the minimum elevation of included data is reduced under $10^{\circ}$, it was considered to be reasonable that the prediction of tropospheric delay considering combination and mapping character of functions about the transition of the zenith delay to a delay with arbitrary zenith angle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3692-3697
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• 2012

Landsat 7 ETM+ sensor is getting imageries in the SLC-off state since May 31, 2003 due to mechanical defect of SLC(Scan Line Corrector). Therefore additional correction works are required to use these imageries. In this study, Landsat 7 SLC-off imageries were corrected using Gapfill function and compared with Landsat 5 around the same time. Most of pixels in omitted areas due to SLC-off by producing SLC-off imageries and imageries without visual incompatibility could be achieved as there were not unnatural noises. Also, the corrected imageries were performed land cover classification which was compared with the classification result using reference image. To do this, it could be suggested the possibility of SLC-off imagery. Landsat 7 SLC-off corrected imageries will improve the difficult conditions to detect changes of large areas and be used to detect changes of large areas and classify imageries as well as to recover imagery loss arising regionally such as small scale cloud, etc.

• Tunnel and Underground Space
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• v.34 no.4
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• pp.283-300
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• 2024

Due to the revitalization of urban development, the number of cases of excavating tunnels adjacent to existing subways is increasing. This may affect the structure and track of the existing subway, resulting in reduced stability and usability. In this study, we verified the adequacy of the proximity evaluation range to ensure the stability of new tunnels and existing subways when excavating adjacent to tunnels, and proposed a quantitative correction rate considering various conditions. Conditions for applying the correction rate considered rock grade, geologically weak section, structurally weak section, and structural deterioration section. It is hoped that a more accurate proximity evaluation will be performed by applying a quantitative correction rate that considers rock and geological conditions, structure status, etc. to the proximity evaluation standard.