• 천문학회보
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• 제44권1호
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• pp.76.2-76.2
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• 2019

Shells in early-type galaxies are low surface brightness tidal debris, which are wide concentric arcs of overdense stellar regions with large opening angles. The most widely accepted mechanism today for shell formation is the merger scenario, but the dominant merger type producing shells is not clearly understood yet: major/minor and wet/dry mergers. Since shells are regarded as smoking-gun evidence of merging events, detailed understanding of shell galaxies is very useful to constrain the formation process of early-type galaxies. In this study, we investigate the metallicity gradients of eight early-type shell galaxies using CALIFA IFU data to better understand the nature and origins of galaxy shells. We estimate simple stellar population properties out to three effective radius from the measurement of Lick/IDS absorption line indices. We compare the metallicity gradients of shell galaxies with those of normal early-type galaxies in the same mass range. In this presentation, we discuss how much the gradients of shell galaxies are different from those of normal early-type galaxies and what the existence of galaxy shells implies about galaxy formation.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2020년도 제61차 동계학술대회논문집 28권1호
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• pp.5-6
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• 2020

현대 의학에서 의료 영상은 수많은 영상처리 의료기기의 핵심이다. PACS(Picture Archiving Communication System)를 통해 관리되는 의료 영상 자료들은 요청에 따라 저장, 검색 및 전송을 수행하여 신속한 의료 서비스를 가능하게 한다. 그러나 만약에 관리자의 실수로 의료 영상 데이터가 바뀐다면 이는 사용자로 하여금 불편함과 낮은 신뢰성을 야기한다. 그리하여 본 논문에서는 서포트 벡터 머신 기반의 HOG(Histogram of Oriented Gradients) 특징 벡터를 이용하여 X-ray와 MRI(Magnetic Resonance Imaging) 사진을 분류하고 의료 영상 분류의 가능성을 제시하는 것을 목표로 한다.

• 한국산림과학회지
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• 제97권6호
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• pp.656-660
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• 2008

본 연구는 숲가꾸기 작업을 위하여 개설된 작업로를 대상으로 노면피해에 영향을 미치는 요인을 평가하여 작업로 노면의 피해예방을 위한 적정 시설기준의 기초자료를 제공하고자 실시하였다. 작업로 노면피해에 영향을 크게 미치는 요인은 시설위치, 종단기울기, 겉보기토질, 산지사면형상, 노폭의 순으로 나타났다. 따라서 종단기울기, 노폭 등 도로 구조적인 요인과 시설위치, 산지사면형상 등 입지적 요인 그리고 겉보기 토질과 같은 도로 구성물질이 노면 피해 발생과 밀접한 연관이 있는 것으로 나타났다. 또한 작업로의 피해발생은 계곡부, 종단기울기 24%이상, 마사토 토질, 요형사면, 노폭 3.0 m이상에서 심한 것으로 나타났고, 안정성은 능선부, 종단기울기 4~24%, 토사지역, 직선형(-)사면, 노폭 3.0 m이하에서 큰 것으로 나타났다. 수량화II류의 판별식의 판별적중률은 79.4%로 상당히 양호한 값으로 나타나 작업로 노면의 양부판정에 활용이 가능할 것으로 사료된다.

• 대한원격탐사학회지
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• 제30권4호
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• pp.537-546
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• 2014

본 논문은 비 접근 지역에 존재하는 관심물체의 위치를 고해상도 광학 위성영상을 이용하여 찾아내기 위한 방법을 제안한다. 관심물체는 정확하게 규정된 크기와 모양을 갖는 것이 아니라, 개념적으로 유사한 패턴을 가진 물체들의 집합이다. 본 논문에서는 유사 객체 검색에서 Histogram of Gradients (HOG) feature를 이용하여 입력 영상의 관심물체의 특징을 추출하고, 추출된 특징 데이터를 이용하여 다른 영상들의 관심물체를 탐색하는 Support Vector Machine (SVM) 학습 및 분류기를 개발하였다. 제안한 방법은 관심물체를 자동으로 찾아줌으로써, 넓은 영역에서 수동으로 관심물체를 탐색하는데 소요되는 시간과 노력을 줄일 수 있는 효과가 있음을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제15권8호
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• pp.1143-1155
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• 2001

In order to reduce the expensive CPU time for design sensitivity analysis in dynamic response optimization, this study introduces the design sensitivities approximated within estimated confidence radius in dynamic response optimization with ALM method. The confidence radius is estimated by the linear approximation with Hessian of quasi-Newton formula and qualifies the approximate gradient to be validly used during optimization process. In this study, if the design changes between consecutive iterations are within the estimated confidence radius, then the approximate gradients are accepted. Otherwise, the exact gradients are used such as analytical or finite differenced gradients. This hybrid design sensitivity analysis method is embedded in an in-house ALM based dynamic response optimizer, which solves three typical dynamic response optimization problems and one practical design problem for a tracked vehicle suspension system. The optimization results are compared with those of the conventional method that uses only exact gradients throughout optimization process. These comparisons show that the hybrid method is more efficient than the conventional method. Especially, in the tracked vehicle suspension system design, the proposed method yields 14 percent reduction of the total CPU time and the number of analyses than the conventional method, while giving similar optimum values.

• Journal of Forest and Environmental Science
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• 제18권1호
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• pp.7-14
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• 2001

본 연구는 집중호우로 인하여 절토사면의 붕괴가 발생한 임도를 대상으로 수량화이론(II)을 이용하여 붕괴요인을 평가하였다. 그 결과는 다음과 같다. 임도 절토사면의 붕괴발생에 미치는 요인의 영향은 절토사면길이, 겉보기 토질, 사면방위, 절토사변경사, 산지경사 등 5개 요인이 가장 크게 나타났다. 특히, 절토사면길이는 8m 이상, 겉보기 토질은 토사, 사면방위는 북사면, 절토사변경사는 $60^{\circ}$이상, 산지경사는 $35{\sim}40^{\circ}$ 사이에서 사면붕괴에 기여도가 가장 크게 나타났다.

• Journal of Radiation Protection and Research
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• 제36권4호
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• pp.183-189
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• 2011

To quantitatively evaluate how setup errors in conjunction with dose gradients contribute to the error in IMRT dose quality assurance (DQA) measurements. The control group consisted of 5 DQA plans of which all individual field dose differences were less than ${\pm}5%$. On the contrary, the examination group was composed of 16 DQA plans where any individual field dose difference was larger than ${\pm}10%$ even though their total dose differences were less than ${\pm}5%$. The difference in 3D dose gradients between the two groups was estimated in a cube of $6{\times}6{\times}6\;mm^3$ centered at the verification point. Under the assumption that setup errors existed during the DQA measurements of the examination group, a three dimensional offset point inside the cube was sought out, where the individual field dose difference was minimized. The average dose gradients of the control group along the x, y, and z axes were 0.21, 0.20, and 0.15 $cGy{\cdot}mm^{-1}$, respectively, while those of the examination group were 0.64, 0.48, and 0.28 $cGy{\cdot}mm^{-1}$, respectively. All 16 plans of the examination group had their own 3D offset points in the cube. The individual field dose differences recalculated at the offset points were mostly diminished and thus the average values of total and individual field dose differences were reduced from 3.1% to 2.2% and 15.4% to 2.2%, respectively. The offset distribution turned out to be random in the 3D coordinate. This study provided the quantitative data that support the large individual field dose difference mainly stems from possible geometric errors (e.g., random setup errors) under the influence of steep dose gradients of IMRT field.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.34.4-35
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• 2009

We have studied the radial g-r color gradients of early-type galaxies in the Sloan Digital Sky Survey (SDSS) DR6 in the redshift range 0.00 < z < 0.06. The color profiles of ~30 per cent of the galaxies in this sample show positive color gradients (centers being bluer). These positive gradient galaxies often show strong $H\beta$ absorption line strengths or emission line ratios that are consistent with star-forming populations. Combining the optical data with Galaxy Evolution Explorer (GALEX) UV photometry, we find that all positive gradient galaxies show blue UV-optical colors. They also exhibit a tendency of having a lower stellar velocity dispersion. Positive gradient galaxies tend to live in lower density regions than negative gradient galaxies and are likely to have a late-type companion galaxy. On the other hand, massive early-type galaxies show negative color gradients. A simplistic population analysis shows that these positive color gradients are visible only for half a billion years after a star burst. Although the effective radius decreases and mean surface brightness increases due to this centrally concentrated star formation, the positions of the positive gradient galaxies on the fundamental plane cannot be reproduced by any amount of recent star formation. Instead it required a lower velocity dispersion.

• The Korean Journal of Ecology
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• 제15권4호
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• pp.345-354
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• 1992

Allocation patterns of energy and mineral elements were investigated with phaseolus multiflorus grown in the environmental gradients. The result showed different energy allocation patterns according to relative light intensities and nutrients. The optimal switching time of energy allocation from vegetative to resproductive growth was delated as decreasing relative light intensity. The switch of the shift to reproduction was timed earlier in phosphorus treatment and delayed in nitrogen treatment. Analyzing the mineral elements to various organs, patterns of energy allocation were different from those of mineral allocation. There was no significant difference for allocation patterns in relative light intensity gradients. it was shown that n and p were distributed over the reproductive organs, k mainly in stems, ca in leaves and na in roots. mg was evenly distributed in each organs.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.201-210
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• 2003

In this paper, we propose a new binocular stereo correspondence method by maximizing a fitness formulated by integrating two constraints of edge similarity and disparity smoothness simultaneously. The proposed stereopsis focusing to measure distances to leading vehicles on roads uses intensity gradients as matching attribute. In contrast to the previous work of area-based stereo matching, in which matching unit is a pixel, the matching unit of the proposed method becomes an area itself which is obtained by selecting a series of pixels enclosed by two pixels on the left and right boundaries of an object. This approach allows us to cope with real-time processing and to avoid window size selection problems arising from conventional area-based stereo.