• Journal of Power Electronics
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• v.15 no.2
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• pp.399-410
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• 2015

A 6.5 V/50 kA high-frequency switching power supply (HSPS) system composed of 10 power modules is developed to meet the requirements of copper-foil electrolysis. The power module is composed of a two-leg pulse width modulation (PWM) rectifier and a DC/DC converter. The DC/DC converter adopts two full-wave rectifiers in parallel to enhance the output. For the two-leg PWM rectifier, the ripple of the DC-link voltage is derived. A composite control method with a ripple filter is then proposed to effectively improve the performance of the rectifier. To meet the process demand of copper-foil electrolysis, the virtual impedance-based current-sharing control method with load current full feedforward is proposed for n-parallel DC/DC converters. The roles of load current feedforward and virtual impedance are analyzed, and the current-sharing control model of the HSPS system is derived. Virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance, which can effectively reduce current-sharing errors. Finally, simulation and experimental results verify the structure and control method.

• IE interfaces
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• v.20 no.1
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• pp.1-10
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• 2007

The main purpose of this research is to find out whether curriculums of industrial engineering (IE) departments meet the demand of IE graduates working in various fields. The research was conducted as an online questionnaire survey selecting IE Graduates working in industries as practising engineers. 1,324 participants were validated among 1,477 participants. 13 fields were selected and used in the survey. Those were; 1) Mathematical statistics, 2) Computer, 3) Purchase, 4) Production system, 5) Logistics, 6) Marketing, 7) Monetary, 8) Experiment methods, 9) Operations Research (OR), 10) Human Factors, 11) Quality, 12) Engineering management, and 13) Information systems. Using the 5-scale Likert rating, each education subject was assessed both in terms of its usefulness in practices and the amount it being taught in school. As a result, courses such as motion/time study, linear programming that IE has traditionally focused showed less usefulness in practices while it is taught in relatively large amount in schools. However, courses such as 6 sigma, CRM which are closely related to industrial practices showed high usefulness in practices compared with low degree of teaching in school. This was the first ever large scalesurvey conducted for IE graduates in Korea. The result of survey displayed many helpful information on current status and future direction of IE education in Korea.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.253-262
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• 2018

Recently, the energy industry is implementing renewable energy supply policy to reduce energy consumption. The purpose of this study is to build a database that can help promote the supply of geothermal energy system to prepare for the increase of renewable energy demand and to develop a method to evaluate the possibility of geothermal energy system installation by using database information. The data used in the study was reliable using open data provided by national agencies. We obtained information necessary for the possibility of geothermal energy system installation, constructed a dedicated database, and studied the method of calculating the geothermal well capacity by using the database information. In the future, this study will establish a local environmental evaluation standard and add information on other renewable energy to contribute to the activation of renewable energy supply.

• Journal of Information Technology Services
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• v.13 no.4
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• pp.109-122
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• 2014

Demand of spectrum resource is tremendously increasing recently and this trend will continues in the future due to the wide spread of IT services based on cloud computing and Internet of Things technology and as well as smart devices. Recently, spectrum sharing technology has drawn attention to the spectrum policy makers as a promising way to overcome the shortage problem of scarce spectrum resource. To succeed in commercialization of spectrum sharing technology, it is necessary to prospect the future business ecosystem of spectrum sharing and develop appropriate policies and laws at the same time along with the advance of spectrum sharing technology. The purpose of this paper is to analyze casual relationships between enablers in future business ecosystem of spectrum sharing and propose policies to vitalize spectrum sharing ecosystem based on a system dynamics causal map proposed in the previous research. With the causal map and system dynamics method, it is possible to analyze feedback loops exist in the business ecosystem of spectrum sharing and build policies which optimize positive dynamics in business ecosystem of spectrum sharing. As a result, policy leverages were found in four areas; spectrum supply, spectrum demand, spectrum quality and technology, and spectrum transaction cost. For those policy leverages, 13 policies were identified and intervention timing for each policy was discussed. Finally, the promotion policies of government and market participants to vitalize spectrum sharing ecosystem were discussed.

• Journal of the Korea Fashion and Costume Design Association
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• v.22 no.2
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• pp.29-43
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• 2020

This study investigated the luxury supply chain management called 'See now, Buy now'. This has been a new way of controlling the supply and demand for luxury brands in the fashion industry since 2016. In this study, we explored the backgrounds and impacts of 'See now, Buy now' in the digital era. 'See now, Buy now' was launched by the fashion brand, Burberry in February 2016. It was the first luxury brand to showcase its entire collection using 'See now, Buy now' among the brands which showcase in Paris, Milan, New York, and London fashion weeks. That has not only caused many controversies in the fashion world but also generated followers. In this study, we analyzed 'See now, Buy now' in three aspects, economics, efficiency, and management strategy, and this was done through a literature survey on articles pertaining to 'See now, Buy now' and empirical surveys on Burberry's collections. Based on 'See now, Buy now', Burberry tried a new process of supply and sale. In the era of SNS, the spread of information is getting faster. The speed of SNS and changes in the fashion market combining IT and mobile technology are major changes faced by the fashion industry. 'See now, Buy now', a model of the new supply and demand in luxury fashion brands, should be noted as a new directional aspect for the future of the fashion industry. Since it was a relatively recent trend that started from the September show of Burberry in 2016, there was still a lack of academic discussion or prior research on this phenomenon. Therefore this study aimed to predict future directions by recognizing the importance of 'See now, Buy now' in the fashion industry. Also, based on this research, the significance of this study was to present a management strategy that applies 'See now, Buy now' to the future of the fashion industry in the digital era.

• Journal of Korea Trade
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• v.25 no.4
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• pp.17-36
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• 2021

Purpose - This study provides useful information to stakeholders by forecasting the tramp shipping market, which is a completely competitive market and has a huge fluctuation in freight rates due to low barriers to entry. Moreover, this study provides the most effective parameters for Baltic Dry Index (BDI) prediction and an optimal model by analyzing and comparing deep learning models such as the artificial neural network (ANN), recurrent neural network (RNN), and long short-term memory (LSTM). Design/methodology - This study uses various data models based on big data. The deep learning models considered are specialized for time series models. This study includes three perspectives to verify useful models in time series data by comparing prediction accuracy according to the selection of external variables and comparison between models. Findings - The BDI research reflecting the latest trends since 2015, using weekly data from 1995 to 2019 (25 years), is employed in this study. Additionally, we tried finding the best combination of BDI forecasts through the input of external factors such as supply, demand, raw materials, and economic aspects. Moreover, the combination of various unpredictable external variables and the fundamentals of supply and demand have sought to increase BDI prediction accuracy. Originality/value - Unlike previous studies, BDI forecasts reflect the latest stabilizing trends since 2015. Additionally, we look at the variation of the model's predictive accuracy according to the input of statistically validated variables. Moreover, we want to find the optimal model that minimizes the error value according to the parameter adjustment in the ANN model. Thus, this study helps future shipping stakeholders make decisions through BDI forecasts.

• Korean Management Science Review
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• v.32 no.4
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• pp.19-28
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• 2015

This study presents a mathematical programming model to develop production planning in the manufacturing processes for photovoltaic silicon ingots and wafers. The model is formulated as a linear programming model that maximizes total growth margin, which is composed of production cost, inventory cost, shortage cost, and sales profit while considering the constraints associated with the production environments of photovoltaic materials. In order to demonstrate the utility of the model for production planning, we run operations for a planning horizon of a year for a case study. When the primary results of this mathematical programming are compared with the historical records, the model could have resulted in the considerable increase of the total growth margin by effectively reducing inventory cost if a decision maker had employed the model as a decision support system with perfect information for sales demand.

• Korean Management Science Review
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• v.19 no.2
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• pp.75-89
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• 2002

According to the fast-paced environment of information technology and improving customer services, the design activities of logistics systems improve customer centric services and delivery performance implementing e-logistics system. The fundamental design issues that arise in the delivery system planning are optimizing the system with minimum cost and maximum throughput and service level. This study is concerned with the integrated model development of delivery system with customer responsive service level for DCM, Demand Chain Management. We used a two-step approach for this study. First, we formulated the supply. center facility planning using stochastic set-covering problem and assigned the customers to the supply center using clustering algorithm. Second, we developed vehicle delivery planning for a supply center based on GIS, GIS-VRP. Also we developed a GUI-type computer program for proposed method for supply center problem using GIS and Geo-DataBase of Busan area. The computational results showed that the proposed method was very effective on a set of test problems.

• 전자공학회논문지 IE
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• v.46 no.1
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• pp.1-6
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• 2009

This paper presents the digital PLL architecture and design for improving the frequency detection range and locking time for wide-band frequency synthesizer applications. In this research, a wide-range digital logic quadricorrelator is used for wide-band and fast frequency detector and sigma-delta modulator with 2-bit up-down counter is adopted for DCO control. The proposed digital PLL reduces the phase noise from quantization effect and is suitable for implementation of wide-band fast-locking as well as low power features, which is in high demand for mobile multimedia applications.

• The Journal of Sustainable Design and Educational Environment Research
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• v.2 no.1
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• pp.1-15
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• 2002

New media is an emerging industry sector. It sits at the nexus of what has become a main vehicle of the Knowledge Based Economy. the crossroads where the use of interactive multimedia technology meets the traditional uses of media. The current Education information Act provided school with PC, multimedia labs and connection to internet. Having such a facility in schools encourage teachers and students to use computers more often. Teachers demand for more educational multimedia contents than they can find in the market. Although there are many good contents, teachers find them unfit or inflexible for their curriculum. The purpose of this study is to identify the elements of standard multimedia studio facilities to develop multimedia contents in primary and secondary schools. The result of this study will provide guidelines for schools to facilitate their multimedia studio for teaching and learning activities, and developing contents for effective use of their facilities.