• Ocean and Polar Research
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• 제39권4호
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• pp.293-300
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• 2017

Various approaches have been tried in an effort to improve the power performance of a flapping tidal stream turbine after it was introduced as an alternative to conventional rotary turbines. Among the different approaches, researches on mimicking the morphology and behavior of animals have been conducted. In this study, we utilized a flapper to mimic the multi-joint pectoral fin of a Manta-ray and investigated its effect on power generation. Experiments were conducted by a dual flapping apparatus with rigid and flexible flappers in a towing tank facility. First, in order to determine the conditions that can produce high power generation, the performances of the dual rigid flappers were compared when input arm angles and frequencies are changed, and the two conditions $40^{\circ}$, 0.2 Hz and $40^{\circ}$, 0.3 Hz for the input arm angle, frequency were selected. When the mimicked flexible flapper was used instead of the front rigid flapper and the rear one, the power was improved by an average of 22% and 38% in the experimental conditions, respectively. Moreover, it was recognized from the apparent camber observed during the experiment that the flexible flapper had been successfully applied. If the feasibility of the Manta-Ray mimicked flapper is improved through subsequent researches, the flapping tidal turbine can be a viable alternative to rotary turbines in the near future.

• 한국관개배수논문집
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• 제17권2호
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• pp.71-81
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• 2010

Stream Pilot Project, which began in May 2003 and finished in December 2003, was selected to develop effective methods applicable to nature-like streams. Stream restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. Fields environmental monitoring such as flow discharge and precipitation were conducted along the Idong stream for amount of channel zone change in 2007. This study selected three monitoring positions to measure the water level and discharge of flowing water. A stage-discharge relation is obtained from direct discharge measurements for three stations by fitting an empirical relationship to the data set. Since discharge measures are made only for low flow conditions, a curve of discharge against stage can then be built by fitting these data with a power curve. And this study used data obtained from floodmark checkup as well as HEC-RAS model to analyze the hydrodynamic characteristics of monitoring sites. Reach-averaged hydraulic parameters for the supply reach were calculated from the small area's HEC-RAS model for Idong stream, and a HEC-RAS model used to analyze hydraulics for a period in 2007, after the stream was considered bank stabilization.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2670-2689
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• 2022

STREAM - a lattice transport calculation code with method of characteristics for the purpose of light water reactor analysis - has been developed by the Computational Reactor Physics and Experiment laboratory (CORE) of the Ulsan National Institute of Science and Technology (UNIST). Recently, efforts have been taken to develop a photon module in STREAM to assess photon heating and the influence of gamma photon transport on power distributions, as only neutron transport was considered in previous STREAM versions. A multi-group photon library is produced for STREAM based on the ENDF/B-VII.1 library with the use of the library-processing code NJOY. The developed photon solver for the computation of 2D and 3D distributions of photon flux and energy deposition is based on the method of characteristics like the neutron solver. The photon library and photon module produced and implemented for STREAM are verified on VERA pin and assembly problems by comparison with the Monte Carlo code MCS - also developed at UNIST. A short analysis of the impact of photon transport during depletion and thermal hydraulics feedback is presented for a 2D core also from the VERA benchmark.

• 전력전자학회논문지
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• 제23권6호
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• pp.415-423
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• 2018

This study uses a level selection algorithm with fixed sampling frequency for modular multilevel converter (MMC) systems. Theoretically, the proposed method increases the level infinitely while the sampling time remains the same. The proposed method called cluster stream buffer (CSB) consists of several clusters, wherein each cluster is composed of 32 submodules that depend on the level of the submodules in the MMC system. To increase the level of the MMC system, additional clusters are used, and the sampling time between clusters is determined from the sampling time between levels needed for utilizing the entire level from the MMC system. This method is crucial in the control of MMC-type HVDC systems because it improves scalability and precision.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.119-121
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• 2008

Pattern matching is increasingly being employed in various researches as health care service, RFID-based system, facility management, and surveillance. Geosensor filter correlates a data stream to match specific patterns in distribution environments. In this paper, we present a geosensor query language to represent efficiently declarative geosensor query. Geosensor operators are proposed to use for fast query processing in terms of spatial and temporal area in distribution environments. We also propose a geosensor filter to match new query predicates into incoming stream predicates. Our filter can reduce the volume of transmission data and save power consumption of sensors. It can be utilized the stream data mining system to process in real-time various data as location, time, and geosensor information in distribution environments.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.3-5
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• 2007

Many continuous queries are important to be process efficiently in a data stream environment. It is applied a query index technique that takes linear performance irrespective of the number and width of intervals for processing many continuous queries. Previous researches are not able to support the dynamic insertion and deletion to arrange intervals for constructing an index previously. It shows that the insertion and search performance is slowed by the number and width of interval inserted. Many intervals have to be inserted and searched linearly in a data stream environment. Therefore, we propose Hashed Multiple Lists in order to process continuous queries linearly. Proposed technique shows fast linear search performance. It can be utilized the systems applying a sensor network, and preprocessing technique of spatiotemporal data mining.

• 한국정보통신학회논문지
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• 제11권8호
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• pp.1519-1527
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• 2007

센서 네트워크에서는 다양하고 폭 넓은 응용 프로그램을 위해서 경제적으로 실행 가능한 모니터링 솔루션을 제공한다. 대부분의 연구에서는 값싼 노드들을 겨냥해서 연구가 진행된다. 센서 네트워크들이 노출되는 보안위협들과 맞서기 위해서, 암호 프로토콜은 센서 노드들 사이에서 점대점 암호화 방식으로 암호화를 실행한다. 알려진 파괴와 속임 위협들은 전송시에 데이터를 암호화 하는 것과 동시에 데이터 소스를 인증하는 것에 의해서 막을 수 있다. 제한된 자원을 가진 노드들에서 저 전력 장치들에게 효과적이라고 알려진 대칭키 알고리즘이 사용된다. 데이터보호는 Dragon Stream Cipher 대칭키 암호화와 새롭게 디자인된 Dragon-MAC Message Authentication Code를 짜 넣는 것에 의한 방법에 의해서 완전하게 된다. 제안된 알고리즘은 MAC 알고리즘에 의해서 요구되는 동작 계산값을 최소화 하기 위한 목적으로써 Dragon Stream Cipher을 기초로 한 계산된 몇몇의 데이터를 사용하기 위해서 디자인 되었다. 빠른 키 스트림 생성을 가진 문자 기반의 Stream Cipher 인 Dragon을 목표로 하여, 한정된 환경에 적합하다. 무선센서 노드에서 권한 암호화의 이행을 통한 실제 인증과 메시지 인증을 겨냥해서 우리의 프로토콜은 계획되었다.

• 한국위성정보통신학회논문지
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• 제6권1호
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• pp.19-27
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• 2011

본 논문에서는 블록 대각화 프리코딩 기법을 사용하는 다중 사용자 MIMO 하향링크 시스템에서 전체 채널 용량을 최대화하기 위한 데이터 스트림 할당 기법을 제안한다. 기존의 블록 대각화 프리코딩 기법은 모든 사용자에게 동일한 수의 데이터 스트림을 할당하고 water-filling에 의한 전력제어 만으로 전체 채널 용량을 최대화함으로써 데이터 스트림의 수의 차이에 의한 채널 용량의 이득을 스스로 제한했다. 제안하는 블록 대각화 프리코딩의 데이터 스트림 할당 기법은 시스템의 전체 채널 용량을 최대화하기 위하여 평균 채널이득, 순시 채널 이득의 크기를 비교하여 채널 이득이 좋은 사용자에게 많은 수의 데이터 스트림을 할당하고 water-filling을 통한 전력 제어를 하는 방법으로 채널 이득에 대한 채널 용량을 최대화 시킨다. 본 논문에서 제안된 데이터 스트림 할당 기법을 이용하여 시스템의 성능을 향상시킬 수 있음을 모의실험을 통해 증명했다.

• 대한토목학회논문집
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• 제4권1호
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• pp.79-92
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• 1984

Unit Stream Power(USP)의 이론(理論)에 의하여 총유사량해석(總流砂量解析)이 수행(遂行)되어졌다. 부유사(浮遊砂)에 관한 USP함수(凾數)로부터 Einstein의 기준점농도(基準點濃度)와 Stokes의 침강속도(沈降速度)를 적용(適用)하여 $S_R$에 관한 무차원(無次元) USP 방정식(方程式)을 유도(誘導)하였다. 또한 유량(流量)과 Reynolds수간(數間)의 관계식(關係式)을 유도(誘導)하고 USP와의 관계(關係)를 밝혔으며, 양자(兩者)는 서로 밀접(密接)한 관계(關係)가 있음을 보여주었다. $S_R$식(式)의 계수(係數)들을 한강하류부실험자료(漢江下流部實驗資料)와 Mantz의 실험자료(實驗資料)로부터 구(求)하여 우리 나라의 수개(數個) 하천(河川) 관측지점(觀測地點)에 적용(適用)하였다. 이로써 USP는 부유사(浮遊砂)와 $S_R$에 대하여 좋은 상관성(相關性)을 보여주었으며, 이 USP는 난류강도(亂流强度)가 증가(增加)함에 따라 같은 경향(傾向)을 보여 주었다. 본(本) 연구결과(硏究結果)는 총유사량추정(總流砂量推定)에 기여(寄與)될 수 있을 것으로 판단(判斷)된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.166.1-166.1
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• 2011

The rotor design is fundamental to the performance and dynamic response of the Counter-rotating marine tidal current turbine. The wind industry has seen significant advancement single rotor blade technology, offering considerable knowledge and making it easy to transfer to tidal stream energy converters. In this paper, 3D flow and performance an alysis on a 100 kW counter-rotating marine current turbine blade was carried out by using the 3-D Navier-Stokes commercial solver(ANSYS CFX-11.0) to provide more efficient design techniques to design engineers. The front and rear rotor diameter is 8m and the rotating speed is 24.72rpm. Hexahedral meshing was generated by ICEM-CFD to achieve better quality of results. The rated power and its approaching stream velocity for design are 100 kW and 2 m/s respectively. The pressure distribution on the blade's suction side tells us that the pressure becomes low at the leading edge of the airfoil as it moves from the hub to the tip.