• The KIPS Transactions:PartC
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• v.14C no.2
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• pp.139-146
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• 2007

Mobile Sensor Network(MSN) is actively studied due to the advent of mobile sensors such as Robomote and Robotic Sensor Agents(RSAs), However, existing studies on MSN have mainly focused on coverage hole problem which occurs in Stationary Sensor Network(SSN). To address coverage hole problem, these studies make mobile sensors move temporarily so that they do not make the best use of the mobility of mobile sensors, Thus, a mechanism utilizing the continuous movement of mobile sensors is proposed to improve the network coverage performance. However, this mechanism is presently immature and does not explain how to make routing path and send data from mobile sensors to a sink node, Therefore, to efficiently make routing path and send data from mobile sensors to a sink node, we propose a communication protocol for mobile sensor network where mobile sensors continuously move. The proposed protocol deploys not only mobile sensors but also stationary sensors which send sensing data to a sink node instead of mobile sensors. Simulation results show that the proposed protocol improves the performance in terms of network coverage and traffic overhead, compared to conventional SSN protocols.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11b
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• pp.1491-1494
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• 2002

Ad Hoc 네트웍은 유선 기반망을 배제한 완전한 모바일 네트웍이다. 이동성이 큰 Ad Hoc 네트웍 안에서는 주기적으로 라우팅 패킷을 전송함으로써 네트웍의 성능을 저하시킬 수 있다 네트웍의 오버헤드를 줄이고 노드 에너지 보존을 위해서 주로 소스 기반의 요구 기반 라우팅 기법이 사용되는데, 기존의 기법은 모든 노드의 자원과 능력을 동일시하여 경로 설정이 이루어진다. 본 논문에서는 모바일 노드들의 에너지와 전파 전송 범위가 서로 다른 점에 착안하여 요구 기반 라우팅에서 서로 다른 데이터 전송 범위를 갖는 노드를 설정하였다. 노드의 정지 시간과 전파 전송 범위를 달리하여 시뮬레이션한 결과 기존의 요구 기반 라우팅 방법에 비해 현저히 라우팅 패킷의 수를 줄여 데이터 패킷 전송률을 높이고 네트웍의 오버헤드를 줄일 수 있었다.

• Proceedings of the Korean Society for Information Management Conference
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• 1995.08a
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• pp.105-108
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• 1995

본 연구는 이동도서관에서 집중적으로 많이 이용되는 도서의 특성을 조사하고 이용자의 유형을 조사하였다. 본 연구를 통하여 얻은 결론은 도서 대출 분포는 브랫포드의 분산법칙, 지프의 법칙같은 현상이 존재한다는 것이다. 즉, 대출 횟수의 약 80%가 장서의 약 30%이내에서 오며 도서 대출 경향에서 수확 체감 현상이 나타났다. 그리고, 도서의 내용, 출판 후 경과 년수, 대출 경과 일수, 인구학적 특성이 장서의 이용에 영향을 준다. 즉, 아동 도서, 한국 소설, 외국 소설 순으로 많이 대출되며 출판 후 경과년수가 5-6년 이내의 도서가 핵심 도서이며 출판 후 경과년수가 짧은 도서일수록 대출횟수가 많다. 그러나, 아동 도서, 한국 소설, 외국 소설이 대출 횟수는 많지만 도서 이용가치수명은 기타 도서의 1/2에 불과하다. 대출 도서의 대부분(80%)은 6주이내에 최종 대출되며 이용자는 여자가 30, 40대가, 가정주부가, 고졸이상이 많이 이용한다.

• International Area Studies Review
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• v.16 no.3
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• pp.119-134
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• 2012

This paper examines the shift to service economy in the developed countries including Korea and analyzes whether Baumol's cost disease hypothesis could explain the labor productivity growth in the developed countries even though the share of service industry is rising rapidly. We have found the following results: First, the shift to service economy is widely observed in the developed countries. Second, the productivity gap between manufacturing and service industry is widening as a result of stagnant productivity growth in service industry. Third, however, the productivity in the whole economy is still growing because of the large productivity differences among the sub-industries in service industry. Fourth, we have found that the productivities of some service industries, such as finance, communication, business service, etc., are almost same or larger than the productivity of manufacturing industry. From this fact it is likely that the productivity of the whole economy could grow in spite of the stagnant productivity growth in service industry.

• Survey Research
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• v.12 no.1
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• pp.119-139
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• 2011

This paper analyzes the effects of college students' preparing for government official recruitment exams on their employment and job characteristics. To this end, Graduates Occupational Mobility Survey(GOMS) data were used. The main results of this study are summarized as follows. (1) college students preparing for the exams extend their college enrollment period; (2) college students preparing for the exams delay their employment; (3) college students preparing for the exams lower their wages and job satisfactions if they are employed in private sectors. In general, these results are consistent with common concerns. However, the sizes of the effects are less than common concerns.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.886-890
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• 1995

최근 몇년사이에 산업 전분야에서 로보트의 이용이 증가하고 있는데, 로보트 시스템의 주요목적은 작업영역내에서 작업물을 빠르고 정확하게 다른 장소로 이동시키는 것이다. 이러한 로보트의 이용에 있어서의 어려움 중 하나는 로보트가 목표점으로 움직이는 동안에 작업장내에 있는 장애물, 즉 각종 공구, 시설등의 물체와의 충돌을 피할 수 있도록 프로그램 되어야 하며, 이를 위해서 많은 시간이 소요된다는 것이다. 본 연구에서는 SOM 네트워크를 이용하여 장애물이 존재하는 작업 공간에서 로보트가 장애물과 충돌없이 움직일 수 있는 경로를 구하기 위한 SOM의 응용방안을 소개한다. 본 연구에서는 SOM의 최적 size, 학습계수 요인을 고려하여 2관절 로보트의 충돌회피 경로 발견을 위한 시뮬레이션을 수행하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.6
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• pp.458-464
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• 2013

This paper presents an algorithm for autonomous landing approach of a unmanned aerial vehicle. The main purpose of the autonomous landing approach in this study is to help a safe landing at night. From any initial position of the aircraft when this function is engaged, a flight path command is generated from the initial position. The shortest combination of an initial circular arc, a straight line segment, and a final circular arc is chosen for the flight path that will lead the aircraft to one end of runway for a landing. The algorithm is initially validated through numerous simulations with various initial conditions of aircraft. Then it is successfully validated through a number of flight tests.

• Journal of Navigation and Port Research
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• v.44 no.6
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• pp.447-452
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• 2020

Extratropical cyclone in winter season is very important in safe operation of ships because it is a major cause of marine accidents due to its strong power. In this study, we used meteorological data, to analyze extratropical cyclones occurring near the 1st Pacific polar front from December 2019 to February 2020. The analysis results are as follows. During those three months, we recorded 41 extratropical cyclones, 8 of which were remarkably developed. The central pressure of the strongest cyclone was 947hPa. The highest number of cyclones were generated in the East P acific Ocean around J apan (16), followed by the areas around Korea, the East China Sea, and the southern Sea of J apan. The cyclones followed five major tracks with a common northeast pattern. We thus concluded that the optimal route for a ship encountering an extratropical cyclone in the North P acific in winter would be south of the cyclone's center traveling eastbound and north of the center traveling westbound.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.1
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• pp.31-37
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• 2008

In this paper, we propose an entropy-based routing protocol to effectively support both stable route construction and route lifetime in Mobile Ad-hoc Wireless Sensor Networks (MAWSN). The basic idea and feature of the proposed routing protocol are as follows. First, we construct the stable routing routes based on entropy concept using mobility of mobile nodes. Second, we consider a realistic approach, in the points of view of the MAWSN, based on mobile sensor nodes as well as fixed sensor nodes in sensor fields while the conventional research for sensor networks focus on mainly fixed sensor nodes. The performance evaluation of the proposed routing protocol is performed via simulation using OPNET(Optimized Network Engineering Tool) and analysis. The results of the performance evaluation show that the proposed routing protocol can efficiently support both the construction of stable route and route lifetime in mobile ad-hoc wireless networks.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.344-345
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• 2000

근해안강망어업에서 주로 어획되는 수산자원은 참조기, 갈치, 아귀등의 저서성어류로서, 겨울에는 월동장인 우리나라 서해남부 및 동중국해 북부해역으로 남하회유하고 봄이 되면 황해 및 중국 연안의 산란장으로 북상이동하는 계절회유를 한다. 따라서 근해안강망어업의 주간어황은 황해 및 동중국해에 서식하는 대상어업자원의 자원량변동의 영향을 받으며, 해황의 변동에 따른 회유경로의 경년변동 및 계절회유에 의한 주 서식처의 변동, 조석의 변동, 어장의 일기등의 영향을 받는다. (중략)