• 한국환경복원기술학회지
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• 제13권2호
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• pp.95-104
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• 2010

The purpose of this study is to analyze the correlation between physical stream characteristics and bed materials in natural rivers. Accordingly, four natural rivers were selected reference streams, they were Nam river, Sumjin River, Naesung River and Han River. Grain size distributions of bed materials were gravels, cobbles and boulders in Han river and Nam river, were sand, gravels, cobbles and boulders in Sumjin river and were sand in Naesung river. Four reference streams were divided into each two reference reaches (straight and bend) by plan and profile characteristics of naturally meandering stream. Therefore various reference reaches were chosen in the aspect of physical stream characteristics and grain size distributions. The results investigated and analyzed are as follows. The streams that grain sizes distributions of river bed materials were coarse were stable because they had variety of bed slope without sediment deposition, and then the riffles frequency and the physical characteristics were various. Also, velocitydepth regime were various in four kinds, and the response parts for water level change were small, so that channel flow status were stable and excellent condition. On the other hand, sand river that grain sizes distributions of river bed materials were fine had not the variety of parameters as velocity-depth regimes, sediment deposition, channel flow status and riffles frequency, so that the physical stream characteristics were not various.

• 한국환경과학회지
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• 제21권4호
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• pp.471-478
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• 2012

In this study, the flow characteristic analysis at the curved-channel of the actual channel section is compared and reviewed using the 2D RMA-2 model and the 3D FLOW-3D model. the curve section with curve rate 1.044 in the research section is analyzed applying the frequency of he project flood of 100 years. According to the result, the issue for the application of the FLOW-3D Model's three-dimensional numeric analysis result to the actual river is found to be reviewed with caution. Also, application of the 3D model to the wide basin's flood characteristic is determined to be somewhat risky. But, the applicability to the hydraulic property analysis of a partial channel section and the impact analysis and forecast of hydraulic structure is presumed to be high. In addition, if the parameters to reflect the vegetation of basin and the actual channel, more accurate topological measurement data and the topological data with high closeness to the current status are provided, the result with higher reliability is considered to be drawn.

• 한국환경복원기술학회지
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• 제11권3호
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• pp.74-86
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• 2008

To assessment the disturbances of the Namgang caused by dam construction, upstream area was selected for the reference reach and downstream area was selected for the comparison reach. And these reaches were surveyed and analyzed according to the assessment criteria of the river disturbances.The artificial factors of river disturbances were classified as river improvement works, dam construction and aggregate dredging. The indexes were physical factors as like epifaunal (bottom), embeddedness, velocity/depth regime, sediment deposition, channel flow status, channel alteration, frequency of riffles, bank stability, vegetative protection, riparian zone etc.The assessment results showed 46% of the assessment criteria which was serious status in dam downstream area and 89.5% of it which was excellent status in dam upstream.Finally, the results showed that physical river environment in downstream area was disturbed by the discharge control and the interception of sediment discharge by dam, consequently this disturbance give rise to impact of ecosystem in river.

• 전기학회논문지
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• 제61권9호
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• pp.1275-1282
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• 2012

This paper proposes the 16-channel LED Driver IC for Full color LED display system. The proposed LED driver IC in this paper can draw current independent of temperature and supply voltage in each channel. Current flow in the channel is configurable via an external resistor. LED brightness is adjusted by 12-Bit PWM(Pulse Width Modulation) and 8-Bit DC(Dot Correction). A real-time monitoring of IC temperature ($130^{\circ}C/150^{\circ}C$) and LED status (open/short) is provided by LED driver IC and the user can receive warning and get information on problems. A 16-channel LED driver IC is produced using 0.35 um BCD process and the size is $2.5mm{\times}2.5mm$. In this paper, channel current characteristic and channel current control function were measured in order to verify am embodied 16-channel LED driver IC by producing a single IC test board.

• 한국통신학회논문지
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• 제11권4호
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• pp.227-236
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• 1986

본 논문에서는 window flow 제어기능을 가진 음성과 데이터가 집적된 패킷 통신망을 폐쇄 multichain queueing 시스템으로 modeling하고 평균치해석 방법으로 성능을 분석하였다. 서로 다른 priority 등급을 가진 여러가지 메시지를 전송하기 위한 패킷망 성능해석을 위해서 본 논문에서는 평균치해석과 effective capacity개념에 의한 성능해석 방법을 사용하였다. 구체적으로 각 노드에서의 평균 buffer 점유율, virtual channel의 link throughput의 이용도, 각 메세지의 평균지연시간등 망의 통계적 특성들을 이론으로 분석하고 simulation으로 검증하였다. 제안된 해석방법을 사용할 경우 link의 데이타의 상태를 10%이내의 정확도로 예측할 수 있고 음성 메시지와 외부 데이타의 상태는 5% 이내으 ㅣ정확도로 예측할 수 있다.

• 한국수자원학회논문집
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• 제51권8호
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• pp.713-727
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• 2018

본 연구는 국내 하천의 고유성을 반영할 수 있는 물리적 환경평가 체계를 개발하는 것이다. 하천유형 분류, 평가구간 선정, 평가 항목 및 지표에 대하여 종합적으로 요약하였다. 하천의 물리적 구조는 하천 유수력에 의한 반응의 결과이므로 하도경사, 하상재료의 입경 및 하도지형의 특성에 따라 하천을 3가지 유형으로 분류하였다. 평가구간은 각 하천 유형의 대표적인 특징인 step 또는 여울출현 간격, 사행도에 따라 저수로 폭의 10배와 25배 기준으로 선정하였다. 평가지표는 하도 안정성, 흐름 상태, 횡단면 형상, 하안 안정성, 하도개수 및 하천횡단구조물과 같은 공통지표와 유효 서식지, 하상 매몰도, 흐름의 다양성 및 step과 여울 출현빈도와 같은 하천 유형별 특성지표로 구성되어 있다. 적용성 검토를 위하여 개발된 평가체계를 9개의 하천에 적용하고 그 결과를 제시하였다.

• 한국물환경학회지
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• 제27권6호
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• pp.822-829
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• 2011

The purpose of the present study is to estimate the ecological instream flow for conservation and restoration of fish habitat in running water ecosystem which has very important status for stream environment. Estimation of the ecological instream flow in the present study was carried out by application of a two-dimensional depth averaged model of river hydrodynamics, River2D model. It can model fish habitat in natural streams and rivers and assess the quality of physical habitat accoriding to the species preferences for habitat suitability. Zacco platypus and Zacco temmincki were selected as target fish species in the study area of the Seomjin river. The Habitat Suitability Criteria (HSC) developed by Sung et al. (2005) were used for target fish species, life stages and habitat conditions in the study. Weighted usable area (WUA) was computed by the River2D model considering preferences of target fish species for velocity, depth, and channel substrate. The result revealed that the ecological instream flow of $10.0m^3/s$ is needed to maintain the target fish habitat at each life stage in the river.

• 한국통신학회논문지
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• 제30권4B호
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• pp.202-209
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• 2005

본 논문에서는 first-hop 무선 채널을 갖는 무-유선망에서 채널 특성에 따라 코딩 비트율을 조절할 수 있는 동적 TCP-friendly 비트율 제어방식 (TFRC)을 제안한다. 제안되는 비트율 제어 기법은 무선망을 통해 전송되는 멀티미디어 플로우의 QoS 성능 저하 현상을 피하기 위해 패킷 손실 통계자료를 이용한 새로운 무선 손실 구별 알고리즘을 사용하고 있다. 이 알고리즘은 무-유선망에서 TCP 플로우와 함께 백본 대역폭을 공유하는 동안 TCP-friendly하도록 비트율을 생성한다. 실험 결과를 통해 제안하는 비트율 제어방식의 시스템은 TFRC 흐름 제어에서 무선 손실의 영향을 제거하고 신뢰성이 낮은 무선 링크에 의해서 발생되는 비디오 스트림의 갑작스런 품질 저하 현상을 상당히 줄일 수 있음을 알 수 있다.

• 한국컴퓨터정보학회논문지
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• 제22권9호
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• pp.49-55
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• 2017

Despite the Openflow's switch migration occurs after the channel was established in secure manner (optional), the current cryptography protocol cannot prevent the insider attack as the attacker possesses a valid public/private key pair. There are methods such as the certificate revocation list (CRL) or the online certificate status protocol (OCSP) that tries to revoke the compromised certificate. However, these methods require a management system or server that introduce additional overhead for the communication. Furthermore, these methods are not able to mitigate power abuse of an insider. In this paper, we propose a role-based identity-based cryptography (RB-IBC) that integrate the identity of the node along with its role so the nodes within the network can easily mitigate any role abuse of the nodes. Besides that, by combining with IBC, it will eliminate the need of exchanging certificates and hence improve the performance in a secure channel.

• 한국환경복원기술학회지
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• 제12권3호
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• pp.83-97
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• 2009

The objects of study is to propose criteria for physical river disturbance assessment and as case study to show the application results for river improvement. For this purpose, the river disturbance assessment method for past disturbance process and the present-day potential natural state of stream is proposed. To assess the disturbance of the Youngcheon River caused by river improvement, One ares of Nam River was selected for the reference reach and two areas of Youngcheon River were selected for the comparison reach. And these reaches were surveyed and analyzed according to applying criteria of the river disturbances assessment. The assessment indices were physical factors as like epifaunal (bottom), embededness, velocity/depth regime, sediment deposition, channel flow status, channel alteration, frequency of riffles, bank stability, vegetative protection and riparian zone etc. The results showed that physical river environment in Youngcheon River area was disturbed by artificial revetment and bed excavation, consequently this disturbance give rise to impact of ecosystem in river. Hereafter, the criteria for river disturbance assessment are needed to consider various river characters as bed materials and bed slop etc.