• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1137-1147
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• 2022

River and groundwater stages are the main elements in the hydrologic cycle. They are spatially correlated and can be used to evaluate hydrological and agricultural drought. Stochastic simulation is often performed independently on hydrological variables that are spatiotemporally correlated. In this setting, interdependency across mutual variables may not be maintained. This study proposes the Bayesian vector autoregression model (VAR) to capture the interdependency between multiple variables over time. VAR models systematically consider the lagged stages of each variable and the lagged values of the other variables. Further, an autoregressive model (AR) was built and compared with the VAR model. It was confirmed that the VAR model was more effective in reproducing observed interdependency (or cross-correlation) between river and ground stages, while the AR generally underestimated that of the observed.

• Journal of Intelligence and Information Systems
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• v.26 no.2
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• pp.27-42
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• 2020

Traditional companies with offline stores were unable to secure large display space due to the problems of cost. This limitation inevitably allowed limited kinds of products to be displayed on the shelves, which resulted in consumers being deprived of the opportunity to experience various items. Taking advantage of the virtual space called the Internet, online shopping goes beyond the limits of limitations in physical space of offline shopping and is now able to display numerous products on web pages that can satisfy consumers with a variety of needs. Paradoxically, however, this can also cause consumers to experience the difficulty of comparing and evaluating too many alternatives in their purchase decision-making process. As an effort to address this side effect, various kinds of consumer's purchase decision support systems have been studied, such as keyword-based item search service and recommender systems. These systems can reduce search time for items, prevent consumer from leaving while browsing, and contribute to the seller's increased sales. Among those systems, recommender systems based on association rule mining techniques can effectively detect interrelated products from transaction data such as orders. The association between products obtained by statistical analysis provides clues to predicting how interested consumers will be in another product. However, since its algorithm is based on the number of transactions, products not sold enough so far in the early days of launch may not be included in the list of recommendations even though they are highly likely to be sold. Such missing items may not have sufficient opportunities to be exposed to consumers to record sufficient sales, and then fall into a vicious cycle of a vicious cycle of declining sales and omission in the recommendation list. This situation is an inevitable outcome in situations in which recommendations are made based on past transaction histories, rather than on determining potential future sales possibilities. This study started with the idea that reflecting the means by which this potential possibility can be identified indirectly would help to select highly recommended products. In the light of the fact that the attributes of a product affect the consumer's purchasing decisions, this study was conducted to reflect them in the recommender systems. In other words, consumers who visit a product page have shown interest in the attributes of the product and would be also interested in other products with the same attributes. On such assumption, based on these attributes, the recommender system can select recommended products that can show a higher acceptance rate. Given that a category is one of the main attributes of a product, it can be a good indicator of not only direct associations between two items but also potential associations that have yet to be revealed. Based on this idea, the study devised a recommender system that reflects not only associations between products but also categories. Through regression analysis, two kinds of associations were combined to form a model that could predict the hit rate of recommendation. To evaluate the performance of the proposed model, another regression model was also developed based only on associations between products. Comparative experiments were designed to be similar to the environment in which products are actually recommended in online shopping malls. First, the association rules for all possible combinations of antecedent and consequent items were generated from the order data. Then, hit rates for each of the associated rules were predicted from the support and confidence that are calculated by each of the models. The comparative experiments using order data collected from an online shopping mall show that the recommendation accuracy can be improved by further reflecting not only the association between products but also categories in the recommendation of related products. The proposed model showed a 2 to 3 percent improvement in hit rates compared to the existing model. From a practical point of view, it is expected to have a positive effect on improving consumers' purchasing satisfaction and increasing sellers' sales.

• Korean Journal of Construction Engineering and Management
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• v.21 no.2
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• pp.15-21
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• 2020

The relationship between keywords, found in all productivity related papers published in the KSCE journal for last 15 years, were analyzed in order to reveal a research trend in the area using text mining and A-Priori algorithm. As the results, it is found that the word of 'productivity' is most closely related to the words of 'work' and 'labor'. Futhermore, the word is somewhat related to those of 'factor', 'model', simulation', and 'work time'. It is also revealed that, on the other hand, the words of 'machine' and 'equipment' have little relationships with the keyword. This research will be a great help for academia to understand a research trend in the area of construction productivity.

• The Journal of Aerospace Industry
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• s.69
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• pp.88-98
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• 2007

서머타임은 1784년 벤자민 프랭클린에 의해 최초 제안된 이후, 제1차 세계대전중인 1916년 5월 1일 독일과 오스트리아에서 최초 도입되었고, 현재 전세계적으로 86개국 이상이 서머타임을 실시하고 있다. 우리나라의 경우 1948년 처음 도입하여 1960년까지 시행 하였으며, 이후 1987년 산업의 고도화와 올림픽 개최에 맞추어 동 재도를 재실시하였으나 여러가지 긍정적 영향에도 불구, 권위주의 정부의 국민의견 수렴이 없는 일방적 결정과 당시 미성숙된 노동자 근무여건, 특히 올림픽 경기의 외국 TV 방송시간에 맞추기 위한 올림픽용이라는 비판 등 국민적 거부감으로 시행 2년 후인 1989년 폐지되었다. 최근 사회적 여건의 성숙에 따라 서머타임 도입이 재 논의 되고 있으며, 서머타임이 도입될 경우 약 31만명의 외국인 관광객 추가 방한과 연간 약 4,340억원 이상의 추가 관광수입을 얻을 수 있을 것으로 예상된다. 특히 항공운송산업의 경우 100만명 이상의 국제선 탑승객 증가와 약 1,537억원의 항공운임 수입증가 효과를 거둘 수 있을 것으로 예상된다. 또한 항공운송산업 직접연관산업에서 약 400여명, 간접연관산업에서 3,000여명 등 항공운송산업 전체에서 총 3,400여명의 고용 효과를 유발할 것이다. 반면 서머타임 도입에 따라 CRS, GDS, 항공기 스케쥴, 운항·항행 시스템 및 각 공항별 Curfew 조정이 필요하나, 이미 전세계 항공 선진국 대부분이 수십여년간 서머타임을 도입하고 있어, 서머타임 도입에 따른 失이나 혼란보다는 得과 효용이 더 클 것으로 생각된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.355-355
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• 2011

이론적으로 단일벽 탄소나노튜브(SWNT)는 무산란 전도가 가능하여 실리콘을 대체할 차세대 나노소자의 기본소재로서 많은 각광을 받아왔다. 이러한 SWNT의 전기전자적 특성을 좌우하는 주요인자로는 직경과 비틀림도(chirality)가 있으며, 이를 제어하기 위한 많은 방법들이 제시되어왔다. 특히, SWNT 합성 시 필요한 촉매 나노입자의 크기와 튜브직경과의 연관성이 제기된 후부터, 합성단계에서 촉매 나노입자의 형태(또는 크기)를 제어함으로써 SWNT의 직경을 제어하고자 하는 직접적인 방법들도 주요방법의 한 축으로 이어지고 있다. 한편, SWNT의 합성촉매로는 철, 코발트, 니켈 등의 전이금속이 주로 사용되어 왔으나, 최근에는 금, 은, 루테늄, 팔라듐, 백금 등의 귀금속에서부터 다양한 금속산화물 나노입자에 이르기까지 그 범위가 확장되었다. 본 연구에서는, 촉매 나노입자의 크기제어를 통하여 SWNT의 직경을 제어할 목적으로, 전이금속에 비해 상대적으로 융점이 낮아 비교적 낮은 온도의 열처리를 통해서도 입자의 크기를 제어할 수 있는 금 나노입자를 선정하여 SWNT의 합성거동을 살펴보았다. 합성은 메탄을 원료가스로 하는 CVD방법을 이용하였고, 합성되는 SWNT의 다발화(bundling) 등을 방지하기 위하여 수평배향 성장을 도모하였으며, 이를 위하여 퀄츠 웨이퍼를 사용하였다. 우선, 콜로이드상인 금 나노입자의 스핀코팅 조건을 최적화하여 퀄츠 위에 단분산(monodispersion) 된 금 나노입자를 얻었으며, 열처리 온도 및 시간의 제어를 통하여, 1~5 nm 범위 내에서 특정 직경을 갖는 금 나노입자를 얻는 것이 가능하게 되었다. 합성 후 금 나노입자의 크기와 합성된 SWNT 직경과의 관계를 면밀히 조사한 결과, 튜브보다 나노입자의 크기가 약간 큰 것을 확인할 수 있었으며, 금 나노입자의 크기에 따라 SWNT의 합성효율이 크게 좌우되는 것을 확인하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.392-392
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• 2016

다량의 토사가 유입된 하천에서의 유사 이송 및 퇴적 과정을 이해하고 하상재료 분포 특성을 파악하는 것은 안정하도설계를 위해 대단히 중요하다. 2006년 7월경 태풍으로 인한 수증기가 강원도내의 산악지형과 만나면서 내륙산간 지역 집중호우로 인해 지방하천에 토석류 홍수 피해가 크게 발생하였다. 인제군에 위치한 한계천은 그러한 피해를 경험한 하천 중에 하나이다. 토석류가 발생한 한계천과 토석류가 발생하지 않은 인근지역 하천인 영실천의 하천 특성을 비교하였다. 토석류 발생 이후 2008년, 2010년, 2012년의 위성영상을 비교한 결과 영실천의 하천 유심부의 위치는 거의 변화가 없는 반면, 한계천의 경우 유사이송에 의해 하천의 유심부 위치가 지속적으로 변화하고 있음을 확인할 수 있었다. 또한 시간 경과에 따라 유사이송 구간의 하상재료 크기가 256~2,048mm 범위인 전석(boulder)이 점차적으로 빈번하게 관측되었다. 토석류 유입 하천의 하상재료의 분포 특성을 분석하고자 하천 구간별 전석의 크기와 빈도를 조사하였다. 하천에서의 토석류 유입은 하상재료 전석의 빈도와 크기에 영향을 미치는 것을 확인 할 수 있었다. 전석의 공간적 분포를 조사한 결과 전석의 빈도와 크기는 하류로 갈수록 감소하였다. 또한 구간별 하상 경사, 하폭, 그리고 유속 등에 따라 전석의 공간적 크기와 빈도가 연관성을 보이는 것을 확인하였다.

• Korean Journal of Cognitive Science
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• v.25 no.3
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• pp.259-276
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• 2014

Artists such as Duchamp and Balla tried to portray moving objects on static canvases by superimposing snapshots of moving objects. Previously, our group showed the influence of prior experience on brain responses within a motion-sensitive area MT+ to abstr act paintings with or without implied motion. In the present study, we went further to investigate whether the differential MT+activation between observers is originated from differential eye movement patterns. Prior experience was defined operationally with major in art. In addition, we examined whether perceiver's awareness of artist's intention concerning the implied motion, as well as expertise in art, affects the way he/she views the artwork. Results showed that the number and the duration of fixation on the abstract paintings tended to differ between participants based on art major. The awareness of artist's intention was not related to such differences. In contrast, observers' awareness of artist's intention of implying motion affected eye movement patterns in specific regions of the abstract paintings where the motion was portrayed. In other words, observers with awareness focused more on the parts of paintings portraying motion and moved their eyes in the direction corresponding to the direction of moving objects than observers without awareness. Expertise was not related to such specific eye movement patterns. The present study implies that art expertise and awareness of artist's intention play differential roles in observers' perception of paintings with implied motion. Namely, it suggests that expertise is related to the overall perception of paintings, while awareness of implied motion is related to perception of the specific spatial information in those paintings.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.65-71
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• 2006

The number of elevator installation increases every year about 15,000. The number of confine-disease of elevator increases every year and then sudden in, sudden stop, error of level indication, stand; those can bring to uneasiness of elevator passenger and malfunction related life accident is increasing. Therefore we researched elevator repair diary of elevator repairing company, APT management office and 119 life rescue for elevator confine-disease during 2004. 1. 1.${\sim}$12. 31. we analyzed the content and the time type and cause of the malfunction and fault for APT elevator. Form the result of 119 life rescue, only power reset is 24[%] and only power failure is 8.2[%] by cause of confine-disease. This paper will be used data of the analysis for mutual relation between Power Quality and malfunction and fault of elevator.

• 한국체육학회지인문사회과학편
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• v.54 no.5
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• pp.727-737
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• 2015

The study investigated the relationship between vitamin D status and lifestyle risk factors in office workers. A total of 515 office workers(336 men and 179 women) aged 30 years or older were voluntarily recruited from S-city. Along with serum vitamin D levels, lifestyle risk factors including obesity index, physical fitness, metabolic risk factors, lipids profile and sedentary behavior were measured using standardized protocols. Subjects were classified as deficiency (<20ng/mL), insufficiency (20-29ng/mL), and sufficiency (≥30ng/mL) based on serum vitamin D levels. Linear contrast analysis using one-way ANOVA showed significant linear decreases in mean body fat (p=.030) and sedentary behavior (p<.001) and significant linear increases in skeletal muscle (p=.037), cardiorespiratory fitness (p<.001) and HDL-C (p=.013) across incremental serum vitamin D levels. Compared with the low cardiorespiratory fitness group, the high cardiorespiratory fitness group had a significantly higher odds ratio (men OR=2.144, p=.042, women OR=1.971, p=.045) for having vitamin D insufficiency or deficiency even adjustment after age. Compared to the shortest sitting time group, the longest sitting time group had a significantly higher odds-ratio in a group of female office workers (OR=1.262, p=.043) for having vitamin D insufficiency or deficiency even adjustment after age. The current findings of the study showed that poor physical fitness and sedentary behavior were the risk factors of low serum vitamin D levels, implying the urgent need for a healthy lifestyle modification along with vitamin D supplementation.

• Journal of the Korean Society for information Management
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• v.39 no.1
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• pp.257-280
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• 2022

In this study, we analyzed comments on news articles of representative companies of the three industries (i.e., semiconductor, secondary battery, and bio industries) that had been listed as national strategic technology projects of South Korea to identify public opinions towards them. In addition, we analyzed the relationship between changes in public opinion and stock price. 'Samsung Electronics' and 'SK Hynix' in the semiconductor industry, 'Samsung SDI' and 'LG Chem' in the secondary battery industry, and 'Samsung Biologics' and 'Celltrion' in the bio-industry were selected as the representative companies and 47,452 comments of news articles about the companies that had been published from January 1, 2020, to December 31, 2020, were collected from Naver News. The comments were grouped into positive, neutral, and negative emotions, and the dynamic topics of comments over time in each group were analyzed to identify the trends of public opinion in each industry. As a result, in the case of the semiconductor industry, investment, COVID-19 related issues, trust in large companies such as Samsung Electronics, and mention of the damage caused by changes in government policy were the topics. In the case of secondary battery industries, references to investment, battery, and corporate issues were the topics. In the case of bio-industries, references to investment, COVID-19 related issues, and corporate issues were the topics. Next, to understand whether the sentiment of the comments is related to the actual stock price, for each company, the changes in the stock price and the sentiment values of the comments were compared and analyzed using visual analytics. As a result, we found a clear relationship between the changes in the sentiment value of public opinion and the stock price through the similar patterns shown in the change graphs. This study analyzed comments on news articles that are highly related to stock price, identified changes in public opinion trends in the COVID-19 era, and provided objective feedback to government agencies' policymaking.