인버터 기반 신재생 에너지 발전 시스템의 계통 지원 운전을 위한 계통 전압 검출 방법

안현철(Ahn, Hyun-Chul),송승호(Song, Seung-Ho) 한국신재생에너지학회 2013 신재생에너지 Vol.9 No.2

The Grid code is being strengthen as increase of renewable energy ratio. Especially, the grid connection regulations are continuously being updated for stable operation of power grids. Static grid support and Dynamic grid support must make an accurate measure at Grid connected point because they needs control algorithm individually. It has to exactly measure voltage including switching ripple at the output of the inverter generating system. In addition, it is necessary to have an accurate voltage measurement when the situation rapidly changing the grid impedance is caused by the input of serial impedance of transformer and line impedance as well as Grid Fault Device. In this paper, We propose a new detection method of grid voltage to calculate accurately the r.m.s voltage of the grid connection point along the standard required by the low voltage regulation. We verified performance through simulation grid fault device.

지리산(智異山) 물박달나무림(林)의 식생구조(植生構造)와 동태(動態)

안현철,이정환,Ahn, Hyun-Chul,Lee, Jeong-Hwan 한국산림과학회 1998 한국산림과학회지 Vol.87 No.3

본 연구는 지리산 국립공원 오봉리 지역에서 집단적으로 분포하는 물박달나무림의 식생구조와 동태를 분석하여 물박달나무림의 경영과 분포지에 대한 정보를 제공하기 위하여 수행되었다. 그 결과 물박달나무림의 구조는 교목층(18종류), 아교목층(29종류), 관목층(43수종) 그리고 초본층(68종류)으로 구성되어 있다. 층위별 중요치는 교목층에서 물박달나무가 129.97%로 가장 높고 다음으로 물오리나무(49.04%), 밤나무(25.58%), 졸참나무(25.02%), 노각나무(14.49%), 아교목층에서 물박달나무(70.81%), 졸참나무(37.47%), 물푸레나무(25.35%), 비목나무(24.52%) 및 노각나무(18.86%)가 높은 우점을 보였고, 관목층에서는 조릿대(28.28%), 비목(24.94%), 개윷나무(20.42%), 국수나무(19.90%), 그리고 초본층에서는 오미자(18.51%), 참취(12.26%), 애기나리(10.63%)로 우점하고 있었다. 30개 조사방형구에서 전층을 대상으로 출현 비출현에 의한 17수종에 대한 $x^2$ 검정결과 굴참나무-상수리나무, 노각나무-검노린재나무, 당단풍-신갈나무간에는 고도의 유의성이 인정되었다. 또 밀도에 의한 Pearson 상관에서는 $x^2$ 검정에서 보다, 많은 7개 쌍의 유의성이 인정되었고, Spearman 상관에서는 모두 18개의 상관이 있는 쌍이 인정되었다. 물박달나무림에 대한 직경급의 분포는 물박달나무림의 지속이 계속될 것으로 예상되지만 치수 발생량이 거의 없어 앞으로 졸참나무, 노각나무 등 교목층과 아교목층을 형성하고 있는 활엽수종과 경쟁에 의하여 천이가 있을 것으로 사료된다. The present study focused on the vegetation structure and dynamics of Betula davurica forest were to provide the information for management, distribution and utilization of B. davurica forest in Mt. Chiri national park, southern Korea. The layer structure of B. davurica forest were consist of tree layer(18 species), middle layer(29 species), shrub layer(43 species) and herb layer(68 species). According to the importance value of stratification of layers, In tree layer, B. davurica dominant the highest value of 123.97%, Alnus hirsuta 49.04., Castanea crenata 25.58%, Quercus serrata 25.02%, Stewartia koreana 14.49%, in middle layer were B. davurica 70.81%, Q. serrata 37.74%, Fraxinus rhynchophylla 25.35% Lindera erythrocarpa 24.52%, S. koreana 18.86%, shrub layer were Sasa borealis 28.28%, L. erythrocarpa 24.94%, Rhus trichocarpa, 20.42%, Stephanandra incisa 19.90% and herb layer Schizandra chinensis 18.51%, Aster scaber 12.26%. Disporum smilacinum 10.63% etc, respectively. Results of chi-square test statistics based on presence-absence parameters, the positively associated species pair were Quercus variablis - Q. acutissima, Stewartia koreana - Symplocos paniculata, Acer pseudo-sieboldianum - Quercus mongolica. And covariation was calculated based on quantitative measure of density. The results showed that the association and covariation values among species not agreed with each other. The frequency distribution of DBH Betula davurica species showed reverse J-shaped, therefore it's seems to retrain as a dominant species. When predicting succession in Betula davurica forest, it is seedling and saplings were not richness, succession was governed by competition of hardwood species of subtree and tree layer.

계통 연계형 인버터의 LVRT제어 시 과도전류 분석

안현철(Hyun-Chul Ahn),송승호(Seung-Ho Song),최주엽(Ju-Yeop Choi) 전력전자학회 2013 전력전자학술대회 논문집 Vol.2013 No.7

스마트폰 환경에서 소셜커머스 사용에 대한 연구

안현철(Hyun chul Ahn),이형용(Hyoung Yong Lee) 한국IT서비스학회 2015 한국IT서비스학회지 Vol.14 No.1

Currently, Social Commerces have increasingly gained popularity with the growth of Social Network Services (SNS). As the applications of smartphones are being applied in widespread areas, social commerces in the smartphone environment have entered a new chapter. The applications of social commerces on smartphones are widely used, which has increased the market share of social commerces exponentially. Thus, we tried to find out factors which may affect the user acceptance of social commerces in the smartphone environment. We develop a research model to examine how social commerces in the smartphone environment are accepted by users based on the academic factors-switch costs, trend-seeking tendency, richness in media. The theoretical model is validated through an survey of social commerce users in the smartphone environment from the undergraduates and the graduates in Seoul, Korea. The structural equation analysis is conducted based on the partial least square (PLS) approach. The results reveal that the switch cost will have positive mediating influences to the intention to use social commerce in the smartphone environment. We also find that the perceived usefulness of the smartphone is affected by the media richness. The results also suggest that the trend-seeking tendency has no influences to the users of social commerces in the smartphone environment. Also, theoretical and practical implications are discussed. The findings are believed to increase our understanding an interesting mobile phenomenon, as well as making contributions.

지리산 물박달나무림의 식생구조와 동태

안현철,이정환 ( Hyun Chul Ahn,Jeong Hwan Lee ) 한국산림과학회 1998 한국산림과학회지 Vol.87 No.3

The present study focused on the vegetation structure and dynamics of Betula davurica forest were to provide the information for management, distribution and utilization of B. davurica forest in Mt. Chiri national park, southern Korea. The layer structure of B. davurica forest were consist of tree layer(18 species), middle layer(29 species), shrub layer(43 species) and herb layer(68 species). According to the importance value of stratification of layers, In tree layer, B. davurica dominant the highest value of 123.97%, Alnus hirsuta 49.04., Castanea crenata 25.58%, Quercus serrata 25.02%, Stewartia koreana 14.49%, in middle layer were B. davurica 70.81%, Q. serrata 37.74%, Fraxinus rhynchophylla 25.35% Lindera erythrocarpa 24.52% , S. koreana 18.86%, shrub layer were Sasa borealis 28.28%, L. erythrocarpa 24.94% . Rhus trichocarpa, 20.42%, Stephanandra incisa 19.90% and herb layer Schazandra chinensis 18.51%, Aster scaber 12.26%. Disporum smilacinum 10.63% etc, respectively. Results of chi-square test statistics based on presence-absence parameters, the positively associated species pair were Quercus variablis - Q. acutissima, Stewartia koreana - Symplocos paniculata, Acer pseudo-sieboldianum - Quercus mongolica. And covariation was calculated baste on quantitative measure of density. The results showed that the association and covariation values among species not agreed with each other. The frequency distribution of DBH Betula davurica species showed reverse J-shaped, therefore it`s seems to retrain as a dominant species. When predicting succession in Betula davurica forest, it is seedling and saplings were not richness, succession was governed by competition of hardwood species of subtree and tree layer.

다분류 Support Vector Machine을 이용한 한국 기업의 지능형 기업채권평가모형

안현철(Hyun Chul Ahn),김경재(Kyoung Jae Kim),한인구(In Goo Han) 한국경영학회 2006 經營學硏究 Vol.35 No.5

투자 의사결정 지원을 위한 유전자 알고리즘 기반의 다중 인공지능 기법 결합 모형

안현철(Hyun-Chul Ahn),이형용(Hyoung-Yong Lee) 국제e-비즈니스학회 2009 e-비즈니스 연구 Vol.10 No.1

사례기반추론의 유사 임계치 및 커버리지 최적화

안현철 ( Ahn Hyun Chul ) 한국정보처리학회 2013 정보처리학회논문지. 소프트웨어 및 데이터 공학 Vol.2 No.8

분석적 계층 프로세스(AHP) 기법을 이용한 e-CRM의 성공요인 분석

신동혁,김성진,안현철,Shin, Dong-Hyuk,Kim, Seong-Jin,Ahn, Hyun-Chul 한국CRM학회 2011 CRM연구 Vol.4 No.1

최근 기업들이 고객관계관리(CRM)의 도입과 확산에 많은 노력을 기울이고 있는 가운데, 정보통신기술의 발달과 인터넷 사용의 활성화로 인하여 온라인 채널을 활용하여 CRM을 구현하는 이른바 e-CRM에 대한 기업들의 관심 역시 높아지고 있다. 지금까지 많은 연구자들이 CRM의 성공요인들을 식별하고, 각 요인들의 우선순위를 알아보고자 노력을 기울여 왔다. 하지만, e-CRM 분야에 대한 성공요인 관련 연구는 지금까지 충분히 이루어지지 못했다. 이에 본 연구에서는 기업들이 성공적으로 e-CRM을 구현을 위한 준비를 할 수 있는 가이드라인을 제시하기 위해, 기존에 연구되었던 다양한 e-CRM구축의 성공요인들을 도출, 정리하고, 각 요인별 상대적 중요도를 전문가 설문을 통해 분석하여, 우선순위를 살펴보고자 하였다. 이 때 요인별 상대적 중요도는 전통적으로 많이 활용되고 검증되어 온 분석적 계층 프로세스(AHP) 기법을 이용하여 도출하였다. 기존의 연구들은 대부분 조직적인 요소와 기술적인 요소들로 성공요인을 분석하였지만 본 연구에서는 e-CRM의 기능적인 관점으로 성공요인을 도출하고자 하였다. 분석 결과, e-CRM의 성공을 위해서는 분석-운영-협업 CRM의 세 부분이 모두 균형 있게 관리되어야 하며, 특히 최고경영자의 전폭적인 지원과 양질의 고객정보 확보, 그리고 고객의 요구사항에 효과적으로 반응하는 우수한 온라인 처리능력의 확보가 중요한 것으로 나타났다. Recently, companies have interests in the adoption and diffusion of customer relationship management(CRM). And, as information and communication technologies and Internet technologies proliferate, they also have interests in e-CRM, which implements CRMusing online communication channels. Until now, many researchers have tried to identify the success factors of CRM and evaluate their relative importance. However, only a few studies have dealt with the success factors of e-CRM. For this reason, we aim at identifying and evaluating the success factors of e-CRM in order to provide the companies with the guideline for preparing the implementation of e-CRM. Our study adopts analytical hierarchy process(AHP) as a tool for evaluating these factors because it has been widely applied and validated for a long time. Whereas prior studies have analyzed the success factors from the organizational and technological perspective, our study analyzes them from the functional perspective. As a result, we found that the companies should manage all the CRM components including analytic-operational-collaborative CRM in good balance. Also, we found that the sufficient support from CEO, the acquisition of good quality customer data, and theonline processing capability for responding customers' requests effectively are important for the success of e-CRM.

절대 유사 임계값 기반 사례기반추론과 유전자 알고리즘을 활용한 시스템 트레이딩

한현웅 ( Han Hyun-woong ),안현철 ( Ahn Hyun-chul ) 한국정보시스템학회 2017 情報시스템硏究 Vol.26 No.3

Purpose This study proposes a novel system trading model using case-based reasoning (CBR) based on absolute similarity threshold. The proposed model is designed to optimize the absolute similarity threshold, feature selection, and instance selection of CBR by using genetic algorithm (GA). With these mechanisms, it enables us to yield higher returns from stock market trading. Design/Methodology/Approach The proposed CBR model uses the absolute similarity threshold varying from 0 to 1, which serves as a criterion for selecting appropriate neighbors in the nearest neighbor (NN) algorithm. Since it determines the nearest neighbors on an absolute basis, it fails to select the appropriate neighbors from time to time. In system trading, it is interpreted as the signal of `hold`. That is, the system trading model proposed in this study makes trading decisions such as `buy` or `sell` only if the model produces a clear signal for stock market prediction. Also, in order to improve the prediction accuracy and the rate of return, the proposed model adopts optimal feature selection and instance selection, which are known to be very effective in enhancing the performance of CBR. To validate the usefulness of the proposed model, we applied it to the index trading of KOSPI200 from 2009 to 2016. Findings Experimental results showed that the proposed model with optimal feature or instance selection could yield higher returns compared to the benchmark as well as the various comparison models (including logistic regression, multiple discriminant analysis, artificial neural network, support vector machine, and traditional CBR). In particular, the proposed model with optimal instance selection showed the best rate of return among all the models. This implies that the application of CBR with the absolute similarity threshold as well as the optimal instance selection may be effective in system trading from the perspective of returns.