• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.57-60
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• 2008

Maglev is a system that a train runs levitated above a rail. Therefore it is very important to maintain a constant levitation gap for achieving serviceability and ride comfort. This study is a cooperation research subject of the 3-1 subject, performance improvement of maglev track structures, of the Center for Urban Maglev Program in Korea, started in 2006. The aim of this study is development of rapid constructions of bridge superstructure for maglev. At present, precast deck is widely used because of its superiority to cast-in-place concrete on quality and the term of works. The research group suggested basic systems of maglev guideway with PSC-U type and trapezoidal open steel box type girder, and precast deck, cooperating with Korea Railroad Research Institute, the managing institute of the 3-1 subject. In this study, a mock-up consisted of girders, decks and rail was fabricated and test was performed for constructability, serviceability and maintenance evaluation of PSC U-type girder, precast deck, and new guide rail system.

• Journal of Satellite, Information and Communications
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• v.6 no.1
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• pp.19-27
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• 2011

In this paper, we propose the data stream allocation algorithms for maximizing sum capacity of downlink multiuser MIMO (Multiple-input Multiple-output) systems with BD (Block Diagonalization). The conventional BD precoding algorithms maximize the capacity by controlling power against channel gain of each user. In multiuser MIMO systems, however, the number of data streams for each user can be used to as another control parameter, which determines the capacity. This paper proposes the data stream allocation algorithm of BD for increasing capacity in multiuser MIMO systems. The proposed algorithm allocates unequal bit stream to each user based on channel matrix of each user for maximizing sum capacity. It is proved that proposed algorithm can achieve the significantly improved sum capacity by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.714-721
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• 2005

In this parer, we analyze the preamble model in the OFDMA/TDD(OFDM-FDMA/Time Division Duplexing). Besides, under AWGN, ITU-R M.1225 Ped-B and Veh-A channel environments, we analyze capabilities of symbol timing & carrier frequency offset and performance of cell searching capabilities applied to OFDM/TDD system through computer simulation. The performance using Detection Probability, False Alarm Probability, Missing Probability, Mean Acquisition Time and MSE(Mean Square Error) is analyzed. Especially, in the case of symbol timing offset estimation, the preamble structure and its algorithm with enhanced performance are proposed and then compared with existing ones.

• Korea Information Processing Society Review
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• v.5 no.4
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• pp.75-81
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• 1998

최근 모든 내장형 응용들이 급속히 웹기반으로 바뀌어 가고 있다 사무자동화 과학의료 멀티미디어 보안시스템 등 망에 접속된 모든 최종사용자들은 같은 공간안에 접속된 모든 최종사용자들은 같은 공간안에 있는 같은 건물내에 있든 혹은 다른 도시에 위치하든 인터넷 이나 인트라넷에의 접속장치를 사용하게 된다 예를 들어 대형 출판물사업에서도 원고의 접수나 작업일정을 원격으로 처리하기 시작했고 새로운 의료장치들은 의사들이 원격지나 오지에 있는 환자의 상태를 웹을 통해 진단 할 수 있게 되었다 자동화된 건물이나 원격보안 시스템은 LAN이나 WAN 상에서 건물내의 모든 출입문을 상태를 감시할 수가 있게 되는 등 그 활용성은 무한하다. Agrant, Spyglass 그리고 프리웨어인 Apache 등 많은 내장형 서버 솔루션이 이미 HTTP 서버를 도입하고 있다 내장형 어플리케이션에서의 HTTP 서비스 CGI와 API, memory footprint HTML 및 applet compression OS threading model security 그리고 licensing등에 대해 알아본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.250-258
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• 2005

An initial carrier frequency offset estimation algorithm is proposed for a multi-user frequency bowing orthogonal frequency division modulation-frequency division multiple access (FH-OFDMA) system with a single preamble symbol. To mitigate the effect of the frequency offset, every mobile station needs to accurately and rapidly acquire synchronization. The proposed algorithm uses only one preamble symbol in which two kinds of subcarriers are designed for coarse and fine frequency offset estimation. The non-data aided estimation using the energy spectrum is exploited for fine offset estimation, and maximum likelihood estimation using correlation for coarse offset estimation. By combining the two estimation results, an accurate frequency offset can be estimated with a single symbol. Through simulations, the performance of the proposed algorithm is evaluated by comparing estimation error variance with a conventional method.

• Composites Research
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• v.14 no.4
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• pp.8-14
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• 2001

The satellite system experiences severe mechanical loads during the launch period. Therefore, the positive margin of safety of the satellite system must be demonstrated for every possible mechanical loading conditions during the launch period. This paper presents modal and stress analysis results due to quasi-static loads for the satellite antenna system. The failure tendency fur the sandwich construction of the satellite antenna system has been studied with various lamination angles of unidirectional prepreg.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.343-351
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• 2011

Nuclear containment building is the last barrier for being secure from any nuclear power plant accident. Therefore, it is very important to understand the ultimate capacity of nuclear containment building to loads associated with severe accidents. LOCA (loss of coolant accident) is considered as the basic accidental load and CANDU-type containment building is considered as a target structure in order to conduct the numerical analysis for the structural safety of a containment building. The CANDU-type containment building is a prestressed concrete shell structure which has the dome and the cylindrical wall and is reinforced with bonded tendons. In this paper, the evaluation of ultimate internal pressure capacity was carried out by nonlinear analysis of a prestressed concrete containment building using 3-dimensional structural analysis system.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.3-11
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• 2014

Multiple antennas can provide huge capacity gains when the transmitter knows the channel state information (CSI). Precoding is a technique that exploits CSI at the transmitter side. In this paper, an adaptive precoding scheme is proposed, called a hybrid multiple-input multiple-output (MIMO) precoding (HMP). HMP is a combination of linear and nonlinear precoding. The number of transmit antennas less than or equal to four is as same as the conventional antenna selection scheme. Therefore, the HMP scheme uses more than four transmit antennas. The good channel means that the channels must be selected to maximize the channel capacity among the given channels, and the rest channels are called bad channel. In HMP scheme, we use the nonlinear precoding in the good channels and the linear precoding in the bad channels. The well-known Tomlinson-Harashima precoding (THP) is considered as nonlinear precoding. The system throughput and MSE (minimum square error) are shown for the performance of HMP scheme compared to the conventional schemes which are BD (block diagonalization), antenna selection and THP.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.721-727
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• 2012

Since a conventional multi-cell transmit diversity scheme depends on the feedback from the user for the channel gain information, its performance gets to severely degrade when the channel varies fast due to the high mobility of the user. Also, transmit power of the base station cannot be fully used in the conventional scheme because only one transmit antenna is used for data transmission. In this paper, we propose a multi-cell transmit diversity scheme appropriate for fast fading channel. In the proposed scheme, channel-independent precoding vector is applied over all transmit antennas and different precoding vectors are applied for neighboring subcarriers so that the received signal is avoided to experience deep fading over multiple neighboring subcarriers. Simulation results show that the proposed scheme has better detector output signal-to-noise ratio (SNR) and bit error rate (BER) performances than the conventional scheme.

• Digital Contents
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• no.4 s.131
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• pp.100-104
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• 2004

처음 웨더뉴스 사이트에 대한 분석 요청을 받을 때 기자로부터의 요구사항은 사이트의 다른 부분, 이를테면 프리젠테이션 영역이나 수집방법, 비즈니스 로직보다는 데이터베이스 그 자체에 초점을 맞춰달라는 것이었다. 실상‘데이터베이스’라는 것은‘데이터’ 와는 조금 다른 성향을 가지고 있다. ‘데이터’는 세상의 모든 사물, 모든 사물이 운동하는 형상, 인간의 감각기관이나 그 외의 다양한 방법으로 인지할 수 있는 모든 수치화될 수 있거나 그렇지 못한 것까지를 포함하는 포괄적인 개념이다. 그러나‘데이터베이스’는 이러한 추상적인 개념과는 근본적으로 달리 현상에 있는 수많은 데이터중 필요한 데이터를 수집하는 것이 기본이며, 이를 저장하고 필요에 의해 원하는 방법대로 꺼내어 볼 수 있도록 하는 것까지를 모두 갖춰 하나의 시스템이 되어야만 비로소 하나의 데이터베이스가 되는 근본 요소가 갖춰졌다고 할 수 있는 것이다. 이번 글에서는 웨더뉴스사가 날씨 정보를 실시간으로 또한 안정적으로 운영하기 위한 노력과 이를 비즈니스화 한 방안, 그리고 다양한 디스플레이 방법을 살펴보도록 하겠다.