• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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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.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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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.

• Journal of Ecology and Environment
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• v.48 no.3
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• pp.382-394
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• 2024

Background: Humbo Farmer Managed Natural Regeneration (FMNR) forest is managed through direct involvement of the local community and funded by the World Vision Australia through World Vision Ethiopia under framework of the Kyoto Protocol's Clean Development Mechanism on greenhouse gas emissions. Understanding the amount and distribution of carbon stored in forests across different elevations will enhance ability to anticipate how forests will react to future climate conditions and carbon levels. The aim of the study was to quantify the amount of carbon stocks along altitudinal gradients in the Humbo FMNR forest in southern Ethiopia. A total of 54 nested sample plots of 20 m × 20 m were established on transects of elevation gradients. Inventories of woody species and soil samples (0-10 cm and 10-20 cm depth) were collected within each nested sample plot. Carbon stocks in woody biomass and soil were compared by three elevation classes. Results: The total carbon stocks significantly (p < 0.05) differed among the three altitudinal gradients. There is no significant difference in biomass carbon stocks between the middle (1,610-1,750 m above sea level [a.s.l.]) and lower (1,470-1,610 m a.s.l.) elevations. However, both of these elevations significantly differ (p < 0.05) from the higher (1,750-1,890 m a.s.l.) elevation, despite an increase in carbon stocks from lower to higher elevations. The highest ecosystem carbon stock was contributed by soil carbon. The higher proportion of C stocks at the higher elevations may be associated to the species composition and dominance with larger wood density. Conclusions: It was concluded that even though soil carbon contributed higher carbon to the total carbon stock, biomass is stronger impact than soil carbon when it comes to carbon stock variation by altitudinal gradients. We recommend that carbon-related awareness creation on reducing emission for the local people and promotion of knowledge on carbon stock credits accounting and to be claimed in future for financing, which could be considered as additional possible option for sustainable forest management.

• Journal of Korean Society of Forest Science
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• v.97 no.6
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• pp.656-660
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• 2008

This study is carried out to minimize the damage to the forest road when locating strip roads in the future for stability of timberland after afforestation by assessing the factors that affect the damage on the forest road surface and making appropriate constructing standards. Major factors that influence damage to the strip road surface were location, longitudinal gradients, soil types, cross-section shape in order of influence on damage. it is considered that structural road factors like longitudinal gradients, road width, location factors such as construction location, slope gradients and road material like soil types were greatly related to occurrence of road surface damage. Damage occurrences in the forest road were severe at the valley, longitudinal gradients of over 24%, weathered granite soil, concave of road position, road width of over 3.0 m. stability was high at longitudinal gradients of 4~24%, road width of under 3.0 m, ridge of road position, straight slope, soil materials. The evaluation table of damage possibility on forest road was manufactured by discriminant analysis using Quantification theory(II). The results showed that the discriminant ratios was 79.4% and this table was available for forest manager.

• Korean Journal of Remote Sensing
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• v.30 no.4
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• pp.537-546
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• 2014

In this paper, we propose a method to detect interesting objects in inaccessible areas using high resolution satellite images. We define the interesting objects as a set of objects which have conceptually similar image patterns, not having exact sizes or shapes. In this paper, we developed a learning and classifier of Support Vector Machine (SVM) that extracts characteristic data for inputted images using Histogram of Gradients (HOG) feature and detects similar objects in other images using the characteristic data. As automatic search of interesting objects in our proposed method, we identify that our method provides reduced time and efforts for manual searching similar objects.

• Journal of Mechanical Science and Technology
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• v.15 no.8
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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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• v.18 no.1
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• pp.7-14
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• 2001

On the basis of data obtained from forest road collapsed due to a heavy rainfall, this study carried out to evaluate the cutting slope failure factors of forest road by using Quantification theory(II). The results were summarized as follows. The factors on cutting slope failure was ranked in the order of cutting slope length, soil type, aspect, cutting slope gradients and slope gradients. And the slope failure was mainly occurred under such conditions as cutting slope length longer than 8m, soil type with soil, aspect of N, cutting slope gradients steeper than 600 and slope gradients greater than $35{\sim}40^{\circ}$.

• Journal of Radiation Protection and Research
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• v.36 no.4
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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.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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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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• v.15 no.4
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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.