• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.377-380
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• 2001

A recent trend in flexible manufacturing systems(FMS) is to compose of the identical versatile-machines and to use dynamic tool allocation strategy, sharing tools between machines with fast tool delivery system. Unlike a conventional FMS where parts are fed to the machines with the required tools, tools are acquired from other machines using a tool delivery system and parts can be finished on the same machine in these FMS. Therefore it is more important problem to plan tool flow using tool delivery system in these FMS rather than part flow in conventional FMS. According to existing study, in FMS 20~30 percent of the total management cost is the cost related with tools and it is possible to reduce the tool inventory by 40 percent using efficient tool allocation. In this study, in FMS under dynamic tool allocation strategy, a new method of part release considering tool flow at the stage of part release is proposed. In order to prove the efficiency of the proposed part release it is compared with other part release through simulation experiments. Performance measures in these experiments are the throughput and the number of tardy parts.

• Journal of Power Electronics
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• v.11 no.4
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• pp.576-582
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• 2011

This paper presents a novel control strategy for selective compensation of power quality (PQ) problems, depending upon the limited rating of voltage source inverters (VSIs), through a unified power quality conditioner (UPQC) in a three-phase four-wire distribution system. The UPQC is realized by the integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a three-phase, four-leg voltage source inverter (VSI), while a three-leg VSI is employed for the series APF of the three-phase four-wire UPQC. The proposed control scheme for the shunt APF, decomposes the load current into harmonic components generated by consumer and distorted utility. In addition to this, the positive and negative sequence fundamental frequency active components, the reactive components and harmonic components of load currents are decomposed in synchronous reference frame (SRF). The control scheme of the shunt APF performs with priority based schemes, which respects the limited rating of the VSI. For voltage harmonic mitigation, a control scheme based on SRF theory is employed for the series APF of the UPQC. The performance of the proposed control scheme of the UPQC is validated through simulations using MATLAB software with its Simulink and Power System Block set toolboxes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1514-1531
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• 2014

Femtocell provides better coverage and higher spectrum efficiency in areas rarely covered by macrocells. However, serious two-tier interference emerging from randomly deploying femtocells may create dead zones where the service is unavailable for macro-users. In this paper, we present adopting cognitive radio spectrum overlay to avoid intra-tier interference and incorporating spectrum underlay and overlay to coordinate cross-tier interference. It is a novel centralized control strategy appropriate for both uplink and downlink transmission. We introduce the application of proper spectrum sharing strategy plus optimal power allocation to address the issue of OFDM-based femtocells interference-limited downlink transmission, along with, a low-complexity suboptimal solution proposed. Simulation results illustrate the proposed optimal scheme achieves the highest transmission rate on successfully avoiding two-tier interference, and outperforms the traditional spectrum underlay or spectrum overlay, via maximizing the opportunity to transmit. Moreover, the strength of our proposed schemes is further demonstrated by comparison with previous classic power allocation methods, in terms of transmission rate, computational complexity and signal peak-to-average power ratio.

• The Research Journal of the Costume Culture
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• v.25 no.6
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• pp.893-912
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• 2017

Crowdsourcing models in which organizaions obtain needed product ideas and services from a crowd in a network-based society are rising as a global industry trend. The purpose of this study was to figure out the types and characteristics of crowdsourcing design shown in the domestic fashion brands, and to provide implications for design strategies using crowdsourcing. This study was based on qualitative research which was brand case studies on crowdsourcing design in the fashion industry from January 2006 to July 2017. Also, quantitative analysis using frequency and percentage was applied. The results were as follows: First, crowdsourcing design was used in almost all types of fashion brands, such as sports and outdoor wear, men's wear, women's wear, men's and women's casual wear, shoes, bags, school uniforms, jeans, accessories, etc. Crowdsourcing design in the fashion industry was classified into three types: crowdsourcing graphics and artwork; crowdsourcing customized designs; and crowdsourcing product designs. Of the three types, crowdsourcing graphics and artwork was used most. There were four methods to choose the best crowsourced design: review only by experts, voting by crowd and review by experts, crowdvoting, and crowdfunding. Second, the characteristics of crowdsourcing design were openness, participation, reward and acknowledgement, sharing and interaction, and individualized collective intelligence. Crowdsourcing design could be used as an open innovation strategy in the fashion industry, which could collect new and creative design ideas for product development, resulting in the satisfaction of consumers and benefitting the company.

• Journal of Distribution Science
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• v.17 no.1
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• pp.47-56
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• 2019

Purpose - This case study illustrates the story of eBay Korea, which owns two most leading Korean open market companies, AUCTION and Gmarket. The main concerns are to take over the Korean top domestic companies one by one, then, emerge these two giants through its well-developed post-merger Integration by eBay, an American multinational corporation. Research design, data, and methodology - This case explores various secondary resources such as periodicals, annual reviews, magazine, news articles, commentaries, even some interview materials related to 'eBay Korea' and industry source on condition of anonymity based on the critical reviewing of existing studies on these topics as well. Results - The findings of this study show the merger and acquisition of two market leaders in Korea is the only successful case in Asian Markets. The eBay's choice of entry mode is appropriate considering the timing, synergy and efficiency by sharing their resources. Conclusions - This study examines the successful entry and settlement process of foreign, multinational company through mergers and acquisitions in the Korean market. This would be a valuable in the studies of International Business and Global entry or distribution strategy in the e-commerce and open market dealing with M&A and its post-merger integration.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2873-2892
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• 2019

Reducing the interference to the licensed mobile users and obtaining the energy efficiency are key issues in cognitive heterogeneous networks. A corresponding rate loss constraint is proposed to be used for the sensing-based spectrum sharing (SBSS) model in cognitive heterogeneous networks in this paper. Resource allocation optimization strategy is designed for the maximum energy efficiency under the proposed interference constraint together with average transmission power constraint. An efficiency algorithm is studied to maximize energy efficiency due to the nonconvex optimal problem. Furthermore, the relationship between the proposed protection criterion and the conventional interference constraint strategy under imperfect sensing condition for the SBSS model is also investigated, and we found that the conventional interference threshold can be regarded as the upper bound of the maximum rate loss that the primary user could tolerate. Simulation results have shown the effectiveness of the proposed protection criterion overcome the conventional interference power constraint.

• Journal of Power Electronics
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• v.19 no.2
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• pp.580-590
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• 2019

The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG's controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.

• Korea Trade Review
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• v.47 no.5
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• pp.181-200
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• 2022

After the COVID-19 pandemic, a global economic downturn and a recession in the shipping market are expected, it is important for domestic shipping companies to establish appropriate strategy in response to the recession. Accordingly, domestic shipping companies should grow into integrated logistics companies that combine shipping and logistics in the future. And for this purpose, it is necessary to actively promote logistics integration with external shipping and logistics companies. This paper presents the direction of logistics integration for domestic shipping companies to develop as integrated logistics operators with competitiveness in the global shipping market, and presents detailed alternatives. Domestic shipping companies lack the infrastructure such as ships, port terminals, and warehouses, so they have a weak capacity to independently promote logistics integration. At the shipping company level, a logistics integration promotion strategy should be established, and accordingly, logistics infrastructure, service network, and logistics integration operating system should be established. The government should provide tax benefits for logistics integration, financial support for M&As led by domestic shipping companies, a standardized information sharing system, and preparation of educational courses for nurturing digital manpower.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.100-116
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• 2018

Recently, with the US protection trade trend, South Korea 's exports to the US have shrunk and the need to pioneer emerging markets in Eurasia has increased. Due to the bankruptcy of Hanjin Shipping, a large Korean national shipping company, the necessity of securing transportation that can replace the Asian - European shipping route has emerged. Moreover, as the international trade and logistics environment is rapidly changing due to the spread of electronic commerce, it is time to prepare for the environment where IT technology is applied to international logistics activities. Therefore, this study was carried out to establish information strategy of Eurasia logistics information sharing platform from Korean perspective through comparison of logistics information level of Eurasian countries. This study aims at standardization direction for supporting logistics activities between Eurasian countries, providing customs clearance and logistics services without interruption, providing information for expanding business of trade companies, and building information linkage infrastructure for expanding cooperation between logistics companies across countries. Through this study, it is expected that logistics activities through information sharing among countries will be actively carried out.

• Economic and Environmental Geology
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• v.54 no.1
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• pp.127-136
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• 2021

This study was carried out to understand China's earthquake governance and role-sharing, and to strategically use it for research cooperation in related fields with China. The characteristics of China's national earthquake governance and role-sharing are detailed in this study. First, unlike Korea, China's geoscience and earthquake research fields are separate, and are clearly distinguished from other fields of science and technology. They hold a higher status compared to other fields in China. Second, China's provincial earthquake agencies simultaneously carry out related tasks under the dual supervisory management system of the central and provincial governments. Third, the China Earthquake Administration (CEA) has the authority to do research and development, manpower training, and degree conferment, which are centered on directly affiliated institutions. Fourth, China carries out similar functions in directly affiliated institutions of the CEA and the China Geological Survey (CGS), and affiliated institutions of the Chinese Academy of Sciences (CAS), respectively. Fifth, the CEA is continuously expanding the seismic observation network that connects the vast land of the country. Sixth, China is considered to have detailed structures of earthquake-related laws and regulations. Given China's earthquake governance and role-sharing, it is considered that the possibility of success in research cooperation is high if Korea first determines whether it is under the jurisdiction of the CGS, CEA, and CAS, depending on the specific field.