• ETRI Journal
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• v.34 no.3
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• pp.319-329
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• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.319-325
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• 2015

This paper presents an efficient vibration energy harvester with a piezoelectric (PE) cantilever. The proposed PE energy harvester increases the efficiency through minimization of hardware complexity and hence reduction of power dissipation of the circuit. Two key features of the proposed energy harvester are (i) incorporation synchronized switches with a simple control circuit, and (ii) a feed-forward buck converter with a simple control circuit. The chip was fabricated in $0.18{\mu}m$ CMOS processing technology, and the measured results indicate that the proposed rectifier achieves the efficiency of 77%. The core area of the chip is 0.2 mm2.

• IE interfaces
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• v.19 no.1
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• pp.53-61
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• 2006

We propose a new supply chain planning methodology for both a manufacturer and a distributor in order to find a global supply chain plan for functional product markets. Functional products as opposed to innovative products include the staples that people buy regularly from their nearby places to satisfy basic needs. In the functional product market, the distributor has an initiative of supply chain control and planning with a freedom to request any profit maximizing order quantities until the manufacturer refuses, whereas the manufacturer may not provide more than requested. In this paper, two independent agents on behalf of the manufacturer and the distributor are introduced, and supply chain planning can be conducted by collaboration between them. In addition, mathematical models and a numerical example are presented to show the possibility of the proposed methodology.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.238-239
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• 2012

본 논문에서는 ESS를 위한 3상 인터리브드 양방향 DC-DC 컨버터의 단일 전류센서 기반 상전류 검출 방법을 제안한다. 제안하는 방법은 직류 링크 단에 하나의 전류 센서를 이용하여 전류를 측정하고 스위칭 상태에 따라 각 상의 전류를 복원한다. 따라서 기존의 각 상 전류 센서 이용 시 잠재적으로 내포하고 있는 센서 간 출력특성 불균일 문제에서 자유롭고, 보다 경제적인 시스템 구성이 가능하다. 제안한 방법을 3kW ESS용 컨버터에 적용하여 실험적으로 그 유용성을 검증하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.582-588
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• 2008

Microgrids are new distribution level power networks that consist of various electronically-interlaced generators and sensitive loads. The important control object of Microgrids is to supply reliable and high-quality power even during the faults or loss of mains(islanding) cases. This paper presents power control methods to coordinate multiple distributed generators(DGs) against abnormal cases such as islanding and load power variations. Using speed-droop and voltage-droop characteristics, multiple distributed generators can share the load power based on locally measured signals without any communications between them. This paper adopts the droop controllers for multiple DG control and improved them by considering the generation speed of distribution level generators. Dynamic response of the proposed control scheme has been investigated under severe operation cases such as islanding and abrupt load changes through PSCAD/EMTDC simulations.

• Journal of Korean Society of Water and Wastewater
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• v.16 no.6
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• pp.710-716
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• 2002

A General Pipe Break Prediction Model that incorporates linear and exponential models in its form is developed. The model is capable of fitting pipe break trends that have linear, exponential or in between of linear and exponential trend by using a weighting factor. The weighting factor is adjusted to obtain a best model that minimizes the sum of squared errors of the model. The model essentially plots a best curve (or a line) passing through "cumulative number of pipe breaks" versus "break times since installation of a pipe" data points. Therefore, it prevents over-predicting future number of pipe breaks compared to the conventional exponential model. The optimal replacement time equation is derived by using the Threshold Break Rate equation by Loganathan et al. (2002).

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.300-304
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• 2013

Novel breakthrough random-hole optical fibers (RHOFs) are fabricated in a draw tower facility, by tapering an optical fiber preform packed with a silica powder mixture capable of producing air holes in situ at the high temperature of tens of hundreds in degrees Celsius. Structural and propagation characteristics of the porous RHOF are explained briefly. Experimental investigations of the invented RHOF are performed for pressure sensor applications. Remarkable results are obtained for the RHOF with desirable pressure sensitivity independent of temperature, as is required for harsh conditions as in oil reservoirs.

• Journal of Smart Tourism
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• v.1 no.1
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• pp.19-30
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• 2021

Smart tourism technologies are becoming ever more pervasive and an increasing number of destinations and hospitality establishments are investing in smart tourism initiatives. However, while governments and businesses around the world are aggressively pushing the smart tourism agenda forward, smart tourism research initiatives are still in their infancy and seem to not fully cover the whole spectrum of smart tourism-related issues and questions. This paper conducts a systematic review of existing smart tourism literature to determine the status quo of smart tourism research and to identify research gaps. Considering the steep growth of smart tourism initiatives starting at the beginning of this decade, this paper reviews publications on smart tourism over the last 8 years. All publications for which the keyword "smart tourism" appears in the title, keywords or abstract were included in the sample.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.616-619
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• 2009

새로운 미디어와 창의적인 발상으로 유비쿼터스 기반 상거래에 대한 요구는 날로 증가하고 있다. 사용자 참여형 U-commerce 비즈니스 시나리오를 구성하고, 이에 따라 디지털 아이템 상거래에 필요한 요구사항을 정의한다. 이를 위하여, 각 단계 별로 수익모델을 중심으로 서비스 흐름을 고찰하고, IPTV를 비롯한 휴대폰, 텔레매틱 단말, PDA 등 각종 U-Commerce 서비스가 가능한 단말에서의 양방향 서비스를 고찰하며, 설계된 분류체계를 SOA 기반 U-commerce의 실질적인 운영에 이를 활용가능하게 하는 것을 목적으로 한다. 특히, 본 논문에서는 UCC와 같은 P2P를 중심으로 하여 SOiVA(Service Oriented interactive Video Application)를 활용한 U-commerce 운영 서비스 요구사항을 연구하였다.

• Asia pacific journal of information systems
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• v.27 no.4
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• pp.216-232
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• 2017

This study's objective is to use the construal-level theory (CLT) to explore the effect of the utility of online travel reviews on tourists' perception. To accomplish this goal, online travel reviews are divided into two different categories based on concreteness, and the usefulness of each review is compared with the temporal dimension of psychological distance. The results show that close future tourists are more influenced by concrete reviews than abstract reviews; however, the far future tourists are more influenced by abstract reviews than concrete reviews. Based on these results, theoretical and practical implications are discussed, and suggestions are made for future research.