• ETRI Journal
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• v.44 no.5
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• pp.715-732
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• 2022

Despite the successful launch of Advanced Television Systems Committee (ATSC) 3.0 broadcasting worldwide, broadcasters are facing obstacles in constructing void-less large-scale single-frequency networks (SFNs). The bottleneck is the absence of decent on-channel repeater (OCR) solutions necessary for SFNs. In the real world, OCRs suffer from the maleficent feedback interference (FI) problem, which overwhelms the desired input signal. Moreover, the undesired multipaths between studio-linked transmitters and the OCR deteriorate the forward signals' quality as well. These problems crucially restrict the feasibility of conventional OCR systems, arousing the strong need for cost-worthy advanced OCR solutions. This paper presents an ATSC 3.0-specific solution of advanced OCR that solves the FI problem and refines the input signal. To this end, the FI canceler and channel equalizer functionalities are carefully implemented into the OCR system. The presented OCR system is designed to be fully compliant with the ATSC 3.0 specifications and performs a fast and efficient signal processing by exploiting the specific frame structure. The real product of ATSC 3.0 OCR is fabricated as well, and its feasibility is verified via field and laboratory experiments. The implemented solution is installed at a commercial on-air site and shown to provide substantial coverage gain in practice.

• ETRI Journal
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• v.45 no.5
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• pp.887-898
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• 2023

Aerial base stations (ABSs) seem promising to enhance the coverage and capacity of fifth-generation and upcoming networks. With the flexible mobility of ABSs, they can be positioned in air to maximize the number of users served with a guaranteed quality of service (QoS). However, ABSs may be overloaded or underutilized given inefficient placement, and user association has not been well addressed. Hence, we propose a three-dimensional ABS placement scheme with a delay-QoS-driven user association to balance loading among ABSs. First, a load balancing utility function is designed based on proportional fairness. Then, an optimization problem for joint ABS placement and user association is formulated to maximize the utility function subject to statistical delay QoS requirements and ABS collision avoidance constraints. To solve this problem, we introduce an efficient modified gray wolf optimizer for ABS placement with a greedy user association strategy. Simulation results demonstrate that the proposed scheme outperforms baselines in terms of load balancing and delay QoS provisioning.

• Journal of Computing Science and Engineering
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• v.8 no.2
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• pp.107-118
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• 2014

One interesting problem regarding wireless local area network (WLAN) ad-hoc networks is the effective mitigation of hidden nodes. The WLAN standard IEEE 802.11 provides request to send/clear to send (RTS/CTS) as mitigation for the hidden node problem; however, this causes the exposed node problem. The first 802.11 standard provided only two transmission rates, 1 and 2 Mbps, and control frames, such as RTS/CTS assumed to be sent at 1 Mbps. The 802.11 standard has been enhanced several times since then and now it supports multi-rate transmission up to 65 Mbps in the currently popular 802.11n (20 MHz channel, single stream with long guard interval). As a result, the difference in transmission rates and coverages between the data frame and control frame can be very large. However adjusting the RTS/CTS transmission rate to optimize network throughput has not been well investigated. In this paper, we propose a method to decrease the number of exposed nodes by increasing the RTS transmission rate to decrease RTS coverage. Our proposed method, Asymmetric Range by Multi-Rate Control (ARMRC), can decrease or even completely eliminate exposed nodes and improve the entire network throughput. Experimental results by simulation show that the network throughput in the proposed method is higher by 20% to 50% under certain conditions, and the proposed method is found to be effective in equalizing dispersion of throughput among nodes.

• Journal of the Korean Society for Library and Information Science
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• v.12
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• pp.39-86
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• 1985

The main purpose of the present study is to survey the major iudexing bulletins of national nature in Korea, to define such problem areas as lacunae, duplicates and limitation in coverage in the indexing services currently available in Korea, and to make some suggestions for action for improving the existing indexing services in the light of general principles and the tradition and constraints unique to Korea. The major findings and conclusions reached at this study are summarised as follows: (A) A new indexing bulletin of general nature covering the entire field needs to be created in each of the following fields without an established indexing service available for the outcome of research and development activities in Korea. (1) Philosophy (2) Religion (3) Pure sciences (4) Art (5) Language (6) Literature (7) History (B) A new specialised indexing bulletin needs to be created in each of the following fields where indexing services are heavily utilised but no, or only partial, indexing service is available. (1) Social sciences (a) Statistics (b) Sociology (c) Folklore (d) Military science (2) Pure sciences (a) Mathematics (b) Physics (c) Chemistry (d) Astronomy (e) Geology (f) Mineralogy (g) Life sciences (h) Botany (i) Zoology (3) Applied sciences (a) Medicine (b) Agriculture (c) Civil engineering (d) Architectural engineering (e) Mechanical engineering (f) Electrical engineering (g) Chemical engineering (h) Domestic science (C) Publication of the indexing bulletins suggested in A and B above may be ideally carried on by a qualified and dependable learned society established in the respective fields and designated by the Minister of Education, and should be financially supported from the public fund under the provisions of Art. 27 of the Scientific Research Promotion Act of 1979. (D) The coverage and contents of the four indexing bulletins in the field of banking and financing published by the Library of the Bank of Korea are similar and considerably duplicated. It is, therefore, suggested that the four indexing bulletins are combined in one to form a more comprehensive and efficient bibliographical tool in the field and it is further developed into a general guide to the literature produced in the entire field of economics in Korea by gradually expanding its subject coverage. (E) For the similar reasons stated in D, the Index to the Articles on North Korea and the Catalogue of Theses on North Korea, both publisheds by the Ministry of Unification Library, are suggested to make into one. The Index to the Articles of the Selected North Korean Journals and the Index to the Articles of the North Korean Journals in Microfilm Housed in the Ministry of Unification Library, both published by the same Library, are also suggested to be combined in one. (F) The contents of the Catalogue of the Reports Submitted by Government Officials Who Have Travelled Abroad, published by the National Archives are included in the Index to the Information Materials Related to Government Administration, published by the National Archives. The publication of the former is hardly justified. (G) The contents of the Index to Legal Literature published by the Seoul National University Libraries and those of the Law Section of the Index to Scholastic Works published by the National Central Library are nearly identical. One of the two indexes should cease to be published. (H) Though five indexes are being published in the field of political science and four in the field of public administration, their subject coverage is limited. Naturally, these indexes are little usable to many other researchers in the two fields. A comprehensive index covering all the specialised areas in each field needs to be developed on one or all the existing indexes. (I) It is suggested that the Catalogue of the Scholastic Works on Curricula published by the National Central Library expands its subject coverage to become a more usable and effective index to all the researchers in the field of education. (J) The bimonthly Index to Periodical Articles and the specialised index by subject series published by the National Assembly Library, and the Index to Scholastic Works published by the National Central Library are expected to increase their coverage and frequency of publication to be used more effectively and more efficiently by all users in all fields till the indexing bulletins suggested in this study will fully be available in Korea.

• The Journal of the Korean life insurance medical association
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• v.30 no.2
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• pp.8-11
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• 2011

Insurance medicine has been known to medical risk selection. The role of insurance medicine is sound maintenance of insurance system. So it's function is medical underwriting of life risks. However, emerging market has insufficient medical epidemiological research that is necessary for estimation of extra-risk and such market is usually lack of full understanding of life insurance among insurance customers. This problem makes difficult of performing the medical underwriting, as an original insurance medicine. Medical contributions at the stage of claims adjudication comparing the coverage provided in the product, with the information provided in the claims, based on medical records and the agreement between them. This is called medical verification. The insurance doctors can also use their medical knowledge to help the claims staff with informing claimants about the medical basis of claims decisions.

• Journal of Contemporary Eastern Asia
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• v.12 no.2
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• pp.19-34
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• 2013

Previous research assessed media reporting on nuclear accidents and risks, whilst studies about the Fukushima accident focused on the impact of the Internet on coverage of the incident. However, little research has addressed news framing or comparisons of the perceptions of journalists in relation to reporting nuclear accidents. The aim of this study is to apply framing analysis to news content in The New York Times, the Los Angeles Times, and USA Today about the Fukushima accident. It explores the question of how journalists view reporting on complex events. Content analysis of these three newspapers shows that conflict, responsibility, and economic consequences were the most frequently used frames. According to the journalists interviewed, the biggest problem was the inability to assess information due to contrary positions held by experts. It is argued that the Fukushima accident was framed as a conflict of experts and officials' opinions, utility and government officials' responsibility, and economic consequences for the United States. Adherence to professional norms of objectivity and impartiality was signified as the best approaches to risk reporting.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1069-1072
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• 1998

Recently the development of design and automation technology and manufacturing method, has reduced the cost of chip, but it becomes more difficult to test IC chip because test technique doesn't keep up with these techniques. In case of IC testing, obtaining test vectors to be able to detect good chip or bad one is very important, but according to increasing complexity, it is very complex and difficult. Another problem is that during testing, there could be capability of physical and electrical damage on chip. Also there is difficulty in synchronization between CUT (circuit under test) and Test equipment〔1〕. Because of these difficulties, built in self test has been proposed. Not only obtaining test vectors but also reducing test time becomes hot issues nowadays. This paper presents a new test BIST(built in self test) method. Proposed BIST implementation reduces test time and obtains high fault coverage. By searching internal nodes in which are inserted test_point_cells〔2〕and allocating TPG(test pattern generation) stages, test length becomes much shorter.

• Economic and Environmental Geology
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• v.33 no.6
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• pp.557-563
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• 2000

Subsidence hazard has never been considered seriously until recent yews in Korea, although its socioeconomic impact on Korea becomes more and more enormous. There have been a few studies for the application of GIS analysis technique to the prediction of subsidence hazard. For GIS analysis, several factors, which are represented by coverage, are considered and selected for building a GIS model. Numerical method was used to quantify the importance of each factor in GIS model and the result from numerical modeling using FLAC was compared with that from previous research based on empirical methods. Analysis in 3-D needs more computer resources (i.e. memory). Therefore that in 2.5-D was considered to overcome the problem. Not only maximum vertical subsidence but also maximum horizontal strain and maximum slope have been considered for the assessment of subsidence hazard. The model can be easily modified for the purpose of applications in any subsidence area, especially cavern or abandoned mines under thick soil layer.

• Archives of Reconstructive Microsurgery
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• v.22 no.2
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• pp.90-93
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• 2013

Old post burn contractures on feet still remain challenging problem for reconstructive surgeon. A 43-year-old male visited Hallym University Sacred Heart Hospital with the complain of foot deformity and difficulties in shoe fitting. His right 4th and 5th toes were inverted at dorsal foot. We released the contracture of 4, 5th metatarsophalangeal joint and lengthened extensor tendon by Z-plasty, and covered the resultant defect with the anterolateral thigh flap. The flap was successful and the deformity was corrected. As there have been few reports on reconstruction of foot dorsum, especially on post burn extension contractures in the toes, we report a rare case of contracture release and coverage by free flap.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.5
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• pp.81-90
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• 2004

This paper presents new testability measure based on learning, which can be useful in the deterministic process of test pattern generation algorithms. This testability measure uses the structural information that are obtained by teaming. The proposed testability measure searches for test pattern that can early detect the conflict in case of the hardest decision problems. On the other hand in case of the easiest decision problem, it searches for test pattern that likely results in the least conflict. The proposed testability measure reduces CPU time to generate test pattern that accomplishes the same fault coverage as that of the distance-based measure.