• Journal of Korean Institute of Industrial Engineers
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• v.27 no.3
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• pp.281-288
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• 2001

We consider in this article a multi-objective part-machine grouping problem in which parts have alternative process plans and expected annual demand of each part is known. This problem is characterized as optimally determining part sets and corresponding machine cells such that total sum of distance (or dissimilarity) between parts and total sum of load differences between machines are simultaneously minimized. Two heuristic algorithms are proposed, and examples are given to compare the performance of the algorithms.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.10
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• pp.553-558
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• 2009

Energy demand characteristics of hotel, hospital, and office building are compared to provide guidelines for combining building in community energy system design. The annual, monthly, and daily energy demand patterns for electricity, heating, hot water and cooling are qualitatively compared and important features are delineated based on the energy demand models. Key statistical values such as the mean, the maximum are also provided. Important features of the hourly demand patterns are summarized for weekdays and weekends. Substantial variations in both magnitudes and patterns are observed among the 3 building types and smart grouping or combination of building type and size is essential for a successive energy supply.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.338-346
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• 2016

In order for the optimal solution of generators’ annual maintenance scheduling to be applicable to the actual power system it is crucial to incorporate the constraints related to the equivalent operation hours (EOHs) in the optimization model. However, most of the existing researches on the optimal maintenance scheduling are based on the assumption that the maintenances are to be performed periodically regardless of the operation hours. It is mainly because the computation time to calculate EOHs increases exponentially as the number of generators becomes larger. In this paper an efficient algorithm based on demand grouping method is proposed to calculate the approximate EOHs in an acceptable computation time. The method to calculate the approximate EOHs is incorporated into the optimization model for the maintenance scheduling with consideration on the EOHs of generators. The proposed method is successfully applied to the actual Korean power system and shows significant improvement when compared to the result of the maintenance scheduling algorithm without consideration on EOHs.

• Korea Trade Review
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• v.46 no.4
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• pp.219-234
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• 2021

Armington elasticity has been a methodology for analyzing how much imports could increase in response to importing price cuts, assuming the possibility of incomplete substitution of domestic and imported products. This study calculates Armington elasticity values in Korean fisheries sector and presents an analysis method for classifying items based on price and preference differences. The model is modified reflecting the characteristics of the fisheries market along with the typical OLS, PAM, and ECM models. The result's implication is that products with a high import growth rate do not necessarily show a high Armington value, but it could be seen that price is not the only factor facilitating fisheries imports increase. Considering the items of which demand increases due to importing price cuts have an indiscriminate demand between domestic and imported products, the results could be interpreted that the Korean fisheries importing market has been easily affected by the changes in import prices. Fisheries grouping by price and preference demonstrates that explanatory variables other than price should be considered when estimating import demand.

• ETRI Journal
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• v.44 no.2
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• pp.244-259
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• 2022

Bicycle- or bike-sharing systems (BSSs) have received increasing attention as a secondary transportation mode due to their advantages, for example, accessibility, prevention of air pollution, and health promotion. However, in BSSs, due to bias in bike demands, the bike rebalancing problem should be solved. Various methods have been proposed to solve this problem; however, it is difficult to apply such methods to small cities because bike demand is sparse, and there are many practical issues to solve. Thus, we propose a demand prediction model using multiple classifiers, time grouping, categorization, weather analysis, and station correlation information. In addition, we analyze real-world relocation data by relocation managers and propose a relocation algorithm based on the analytical results to solve the bike rebalancing problem. The proposed system is compared experimentally with the results obtained by the real relocation managers.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.861-866
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• 2022

Seoul introduced the shared bicycle system, "Seoul Public Bike" in 2015 to help reduce traffic volume and air pollution. Hence, to solve various problems according to the supply and demand of the shared bicycle system, "Seoul Public Bike," several studies are being conducted. Most of the research is a strategic "Bicycle Rearrangement" in regard to the imbalance between supply and demand. Moreover, most of these studies predict demand by grouping features such as weather or season. In previous studies, demand was predicted by time-series-analysis. However, recently, studies that predict demand using deep learning or machine learning are emerging. In this paper, we can show that demand prediction can be made a little better by discovering new features or ordering the importance of various features based on well-known feature-patterns. In this study, by ordering the selection of new features or the importance of the features, a better coefficient of determination can be obtained even if the well-known deep learning or machine learning or time-series-analysis is exploited as it is. Therefore, we could be a better one for demand prediction.

• Journal of Korean Society on Water Environment
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• v.39 no.5
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• pp.377-389
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• 2023

Chungcheongnam-do has been measuring the flow rate and water quality of streams in the province once a month since 2011 in order to water environment policies. Based on the results, after evaluating the coefficient of variation and the tendency of the water quality trend by using the Mann-Kendall test and Sen's Slope for each stream, the streams subject to priority introduction of Total Pollution Load Management at Tributaries were selected through the Stream Grouping Method. The water quality trend analysis results for 125 streams using the Mann-Kendall test and Sen's Slope were evaluated as streams showing a tendency of deteriorating water quality Biochemical oxygen demand (BOD): 13 streams, Total Phosphorus (T-P): 16 streams). Streams with deteriorating water quality were classified into A-D groups using the Stream Grouping Method. Group A, which has a high flow rate and high water quality, is a stream that requires priority management, and was selected as a stream for introduction of Total Pollution Load Management at Tributaries. There are 7 streams that need to be introduced into the BOD category, and there are 7 streams that need to be introduced into the T-P category. In this study, based on flow and water quality monitoring data accumulated over a long period of time (2011-2022), statistical techniques are used to select watersheds in which water quality is deteriorating. Accordingly, it is expected that it will be useful in establishing a water quality improvement plan in the future.

• Journal of Labour Economics
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• v.32 no.3
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• pp.27-59
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• 2009

Using Korea Education Longitudinal Study and administrative school data, this paper analyzes school characteristics that influence the demand for private education. Among other findings, it should be noted that private education expenditure tends to be decreased when student evaluation of teacher effectiveness is high, the average education level of teachers is high, and individualized education is offered through subject-based classroom. These results suggest that the demand for private education could be dropped by a better quality and high effort of teachers, which would be attained through an improved education system for teaching profession and student-oriented teacher evaluation. In addition, ability grouping within school via subject-based classrooms with different levels appears to be helpful to overcome uniformity of school equalization system without inducing an increasing demand for private education.

• Journal of KIISE:Information Networking
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• v.27 no.4
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• pp.489-497
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• 2000

주문형 비디오(Video On Demand)서버의 구현은 현재까지도 많은 부분에 한계를 가지고 있으며 이를 해결하기 위한 연구들이 활발히 진행되고 있다. 주문형 비디오 서비스의 한계는 대부분이 자원(디스크, 버퍼)의 제한 때문에 발생하고 있으며 디스크어레이(Disk Array)나, 메모리 뱅크(Memory Bank)와 같은 특수한 하드웨어를 사용하여 해결하고 있다. 또한 이와 아울러 그룹핑이나 버퍼 공유기법과 같은 소프트웨어적인 방법도 제안되었다. 본논문에서는 주분형 비디오 서버의 한계 중 디스크대역폭과 버퍼공간의 한계점에 의한 문제를 해결하기위하여 개선된 그룹핑 방법과 버퍼 공유 및 관리 방법을 제안한다. 제안하는 그룹핑 방법은 비디오의 인기도에 기반을 둔 방법을 사용하며 버퍼 공유방법은 버퍼의 크기 및 디스크의 대역폭 가용량에 따라 적응적으로 병합 분할하는 방법을 사용한다, 제안하는 병합 분할 방법은 피기백킹(piggy-backing)개념을 도입하였으며 시뮬레이션을 통해 제안하 방법의 우수성을 보였다.

• Industrial Engineering and Management Systems
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• v.8 no.1
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• pp.54-65
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• 2009

The existence of Internet revolutionized the computer and communications world. With the rising demand for accessing the Internet, the mobile technology has incorporated the use of Internet in mobile phones. Wireless Application Protocol (WAP) has combined two of the widest utilized technology today: mobile phones and Internet. This study aims to assess the existing WAP pages offered by the top service providers in the Philippines through usability testing experiments. The paper also aims to identify existing problems in WAP interface by focusing on the errors committed by the users. From the usability study, it was found out that common usability problems are wrong selection of links, unclear grouping of categories, wrong feedback, and redundant links. The type of service provider used is significant in determining the performance of users while experience in accessing WAP is insignificant.