• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.394-401
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• 2013

Recently there have been much interest in the performance improvement of maritime communication system. In the maritime communication system, the wireless channel is likely to be time-invariant and the retransmission scheme is not proper because it does not provide time diversity. For the improvement of reliability, we consider MIMO ARQ scheme using Alamouti-type signal which can provide space and time diversity. In this paper, we also propose the criterion of optimal retransmission order and provide its performance of error probability and packet throughput. The proposed MIMO ARQ scheme with optimal retransmission order has performance gain over random ordered MIMO ARQ and conventional Chase combining method. Therefore we expect that it can be adapted to the next generation maritime communication system.

• Culinary science and hospitality research
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• v.20 no.4
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• pp.296-309
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• 2014

This study aimed to identify the relationship between the control and purchasing methods of food items and the restaurant business performance. To achieve the purpose of this study, it reviewed the theoretical background about the control of food items, purchasing methods of those items and restaurant business performance. The result of this study was shown as follows. 1) Distribution method of food items has an effect on business performance. 2) Satisfaction with controlling food items and distribution method of food items have an effect on business performance. 3) Satisfaction with controlling food items and distribution method of food items have an effect on satisfaction with business performance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1994.06a
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• pp.40-41
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• 1994

본 연구에서는 윤활유에 해수가 혼입된 유화유중에서 음극방식에 의한 선박용 베어링 합금재의 침식-부식억제에 관한 연구를 위하여, 초음파 진동장치의 캐비네이션 발생장치에 의해 선박용 베어링 합금재의 캐비네이션 침식-부식방지를 위해 음극방식(Cathodic protection)실험을 실시하였다. 이실험을 토대로 하여 해수의 혼입에 따른 유화유중에서 음극방식에 의한 베어링 합금재의 침식-부식억제효과를 구명하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.103-105
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• 2002

802.11과 같은 무선 네트워크에서는 전송오류에 의한 패킷손실이 많이 발생한다. 802.11 MAC 프로토콜에서는 에러 복구를 위해 ARQ방식을 통한 재전송을 통하여 에러를 정정하나 채널 에러 율이 증가하면 재전송 방식의 효율은 급격히 저하된다. 또한 재전송을하는데 있어서 다시 RTS와 CTS를 전송하여 데이터를 보낼 수 있는 채널을 확보해야 하므로 상당한 전송부하가 발생한다. 이에 재전송 없이 효율적인 에러 복구를 위해서는 FEC방식이 필요하다. 그러나 정적인 FEC방식은 연속적으로 변화하는 무선 채널의 전송 오류율에알맞은 정정 코드를 채택하지 못해 과도한 대역폭 낭비로 인하여 효율이 떨어지는 문제가 있다. 이러한 문제를 개선하기 위해서는 채널의 상태에 따라 정정 코드를 동적으로 변경하는 것이 필요하다. 본 논문은 FEC방식을 802.11 MAC 프로토콜에 적용할 수 있는 방안에 대해서 기술하고 채널 에러 변화에 따라 능동적으로 정정 코드 양을 조절하여 재 전송하는적응적 FEC 알고리즘을 제안한다. 본 논문에서 제안한 적응적 FEC 알고리즘을 802.11 MAC 프로토콜에 적용하여 성능을 측정한 결과 최대 80%정도 성능이 향상된 것을 확인할 수 있었다.

• Journal of Korean Society for Geospatial Information Science
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• v.24 no.1
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• pp.99-107
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• 2016

Korea has been known as volcanic disaster free area. However, recent surveying result shows that Baekdu mountain located in northernmost in the Korean peninsula is not a dormant volcano anymore. When Baekdu mountain is erupting, various damages due to the volcanic ash are expected in South Korea area. Especially, volcanic ash in the air may cause big aviation accident because it can hurt engine or gauges in the airplane. Therefore, it is a crucial issue to interrupt airplane navigation, whose route is overlapped with volcanic ash, after predicting three dimensional dispersion of volcanic ash. In this paper, we deals with 3D visualization techniques for volcanic ash dispersion prediction results. First, we introduce the data acquisition of the volcanic ash dispersion prediction. Dispersion prediction data is obtained from Fall3D model, which is volcanic ash dispersion simulation program. Next, three 3D visualization techniques for volcanic ash dispersion prediction are proposed. Firstly proposed technique is so called 'Cube in the Air', which locates the semitransparent cubes having different color depends on its particle concentration. Second technique is a 'Cube in the Cube' which divide the cube in proportion to particle concentration and locates the small cubes. Last technique is 'Semitransparent Volcanic Ash Plane', which laminates the layer, whose grids present the particle concentration, and apply the semitransparent effect. Based on the proposed techniques, the user could 3D visualize the volcanic ash dispersion prediction results upon his own purposes.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.731-738
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• 1996

노심 손상이 일어나는 중대사고 발생시 고온의 노심 용융물이 윈자로 용기를 파손시키며 캐비티 내로 유출되는 경우, 노심 용융물과 냉각재의 폭발적 반응을 억제하고 잔열제거를 위한 효과적인 냉각수 주입 방법을 규명하는 실험을 수행하였다. 냉각수 주입 방법은 파이프 관을 이용한 단순 fouling 방식과 노즐을 이용한 Spray 방식, 그리고 반응용기의 옆면으로 냉각수를 주입하는 세 가지 방식을 채택하였다. 동일한 실험 조건에서 각각의 주입 방법에 따른 반응 형태 및 냉각 정도를 알아보는 실험을 수행하였다. 본 논문에서는 일차적으로 노심 용융물의 모사체로 사용한 주석 용융물에 Pouring 방식과 Spray 방식으로 냉각수를 주입한 경우의 실험 결과를 정리하였으며, 분석 결과 Spray 방식으로 냉각수를 주입한 경우에 폭발적 반응이 일어나지 않고 냉각됨을 알 수 있었다.

• Journal of Korea Multimedia Society
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• v.10 no.11
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• pp.1523-1529
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• 2007

In this paper, we describe a method which reuses DVB EPG informations for the generation of ATSC EPG. For the efficient reuse, we analyze the differences and similarities of ATSC and DVB EPG informations, classify the informations reusable and convert DVB SI to ATSC PSIP. We implemented a system for the conversion and tested the validity of the system using broadcasting test equipments.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.21-27
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• 2015

Due to the population growth and development of industry, waste from household and industries has increased. As the advanced countries experienced these problems, they have already started research on recycling methods of waste incineration ashes. Domestic recycling rate of incineration ash became up to 80 percent as high as the level of developed countries, but the recycling was limited to fly ash for admixture in concrete. In case of bottom ash, most of bottom ash was reclaimed in the landfills. Therefore, basic physical property and mechanical experiments for bottom ash were conducted in this study to evaluate the possibility of incineration bottom ash as an alternative construction materials. Bottom ashes from three different landfills with two different incineration methods were tested. Incineration methods are Stoker type Incinerator and Pyrolysis-Melting Treatment. Bottom ash can be used as an alternative granular material for construction based on the basic physical property and mechanical characteristics similar to those of sandy materials. However, the incineration method should be considered since it can affect the material and mechanical characteristics of the incineration bottom ash.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.95-104
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• 2010

In wireless communication system, a variety of retransmission algorithms are used in order to improve the quality of service of users. But the system may be inefficient because retransmission algorithms operate independently with other layers. Also, the quality of service can be degraded due to the unnecessary retransmission of packets. To solve these problems, the study on the cross-layer retransmission schemes have been widely performed. However, in order to apply cross-layer retransmission schemes to wireless communication system, whether the performance of cross-layer retransmission schemes meets QoS requirements of each service class has to be verified. Thus, this paper proposes the mathematical model for analyzing the performance of the cross-layer retransmission schemes and derives both the suitable retransmission scheme and the optimal retransmission parameter on each service class. The proposed mathematical model selects the MCS level based on channel state information and The performance analysis is comparatively easy in case that HARQ, ARQ, and AMC schemes are combined. The proposed mathematical model also enables the analysis of the packet transmission delay. To utilize the analytical model, this paper derives the suitable retransmission scheme and the optimal retransmission parameter for delay sensitive services in WiMAX system. Also, the proposed analytical model can be used to analyze the performance of wireless communication system such as LTE and WLAN.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.7
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• pp.1001-1005
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• 2002

In march 2002, Study Group on Long-Run Incremental Cost(LRIC) Model of Japan compiled its report. In this report shows there are three ways of inter-islands and island to land telecommunication service, radio communication, suboptic, communication satellite. Analysis of Japanese island network model is helpful in developing Korean island network model. The development of Korean island network model will make he useful costing of local loop unbundling, universal service fund and access charge.