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클래스 불균형 문제가 있는 다중클래스 텍스트 분류에서의 특징 선택 방법
서민지(Minji Seo),안길승(Gilseung Ahn),허선(Sun Hur) 대한산업공학회 2019 대한산업공학회지 Vol.45 No.2
A text classification model in which one of the class variables is biased to the majority class typically classifies most documents into the majority class to enhance the overall classification accuracy. It is called a class imbalance problem. This study proposes a feature selection method based on simplified chi-square statistics to select features in each class for developing a robust model to the problem. Proposed method and typical feature selection methods are compared by Reuter21578 data. Experiment shows that the proposed method is superior to typical feature selection methods in terms of naïve Bayes and support vector machine which are robust to the class imbalance problem.
남극에서의 위성기반 순복사 장기변화와 알베도 사이의 상관성 분석
서민지 ( Minji Seo ),이경상 ( Kyeong-sang Lee ),최성원 ( Sungwon Choi ),이다래 ( Darae Lee ),김홍희 ( Honghee Kim ),권채영 ( Chaeyoung Kwon ),진동현 ( Donghyun Jin ),이은경 ( Eunkyung Lee ),한경수 ( Kyung-soo Han ) 대한원격탐사학회 2017 大韓遠隔探査學會誌 Vol.33 No.2
남극은 기후변화를 이해하는데 있어 중요한 지역 중 하나이며, 선행연구에 따르면 온난화뿐만 아니라 냉각화도 일어나는 복합적인 지역이다. 그렇기 때문에 남극 에너지 수지의 장기간 변화에 대한 파악이 필요하다. 에너지 수지 요소 중 하나인 순복사는 알베도의 영향을 받으며, 이때 알베도는 negative radiative forcing을 일으키는 요소로 작용한다. 남극의 기후 변화 및 얼음-알베도 피드백에서 두 요소 사이의 관계를 면밀하게 분석하기 위해서는 두 요소 사이의 상관관계를 분석할 필요가 있다. 본 연구에서는 위성 자료를 활용하여 남극에서의 순복사량을 계산하고, 장기간 변화를 분석하였다. 순복사는 연구기간 동안 내륙에서 음의 분포를 보였으며, 해양에서는 양의 분포를 보였다. 순복사의 연간 변화의 경우 해양에서 알베도와 반대되는 변화가 관측되었다. 시계열 패턴은 알베도와 순복사가 서로 대칭되어 나타났으며, 두 요소 사이의 상관관계는 남극 내륙에서 -0.73의 높은 음의 상관관계를 보였으며 해양에서는 -0.32의 음의 상관관계를 보였다. Antarctica is important area in order to understand climate change. In addition, this area is complex region where indicate warming and cooling trend according to previous studies. Therefore, it is necessary to understand the long-term variability of Antarctic energy budget. Net radiation, one of energy budget factor, is affected by albedo, and albedo cause negative radiative forcing. It is necessary to analyze a relationship between albedo and net radiation in order to analyze relationship between two factors in Antarctic climate changes and ice-albedo feedback. In this study, we calculated net radiation using satellite data and performed an analysis of long-term variability of net radiation over Antarctica. In addition we analyzed correlation between albedo. As a results, net radiation indicates a negative value in land and positive value in ocean during study periods. As an annual changes, oceanic trend indicates an opposed to albedo. Time series pattern of net radiation is symmetrical with albedo. Correlation between the two factors indicate a negative correlation of -0.73 in the land and -0.32 in the ocean.
서민지 ( Minji Seo ),이종세 ( Jongse Yi ),김주연 ( Jooyun Kim ) 한국공간디자인학회 2015 한국공간디자인학회논문집 Vol.10 No.4
(Background and Purpose)Surface spaces that embrace a range of environmental variables play a mediating role that directly connects with humans and enables continuous morphological change. Understanding the context and relations between spaces and surfaces and trends by theoretically studying holonic structure will provide a framework. This framework does not adhere to the outdated conception that drawing boundaries is a finishing material, and lays a foundation for understanding a ubiquitous surface that can respond to all environmental conditions. In this regard, this study analyzes “elements of relations” in terms of how designs can be created according to human expectations and environmental conditions. (Method) By understanding the quadrant elements of holons, surfaces can be seen to have physical functions that adapt to the demands and expanded language of roles, which can trigger social and cultural value. All types of holons can be formed and destroyed by certain relations, so understanding quadrant traits within these relations is crucial. As such, although a surface is an artificial system of cortical functions established by human needs, since surfaces are closely related to concepts and institutional change, they can evolve into open systems that can immediately respond to surroundings. By understanding quadrants, thus, surfaces can be regarded as organisms, or “live systems;” therefore, this study examines surfaces from the perspective of philosophers who questioned existence. This study classifies the elements of surfaces as live systems and analyzes module systems using an intelligent methodology that incorporates a variable, structural, expressive, and functional approach. In addition, this study attempts to understand the relative traits of surfaces by using the characteristics of intentional, behavioral, social, and cultural aspects that arise within quadrants. (Results) Six surface construction cases are analyzed using a module approach in terms of the virtual side and physical side, which exposes the hypothetical nature of shapes, including tectonics “knowledge” and “demonstration,” and the “interior side” and “exterior side” of holon quadrants. The results show, first, that surfaces with correlative characteristics play a connecting role. Surfaces that used to have single function now play the role of organic media with hypothetical and physical capabilities. Second, surfaces can easily accelerate change or restructuring using module systems; thus, surfaces have existing values as sensitizers, which can lead to lasting change. (Conclusions) By correlatively and contextually understanding the influence on each other, the potential value of a surface can be estimated. Surfaces are continuously involved in a process of physical change according to conditions. Based on this understanding, it is predicted that surfaces can gradually transform to open systems that can sensitively read the environment. By setting up a module system within a space structure that is difficult to keep up with temporality, the system can be design methodology with variability. In this regard, vitalization of surfaces using the module system can be expected.