• 대한기계학회논문집B
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• 제21권4호
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• pp.570-578
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• 1997

At design stage of new motor or when taking remedial action of old motor, a lot of information can be obtained from thermal parameters analysis. This study focused on the temperature rise of TEFC induction motor with respect to various thermal parameters. Frame heat transfer had the most important effect on coil temperature rise. But those of air gap and rotor fan had no effect. This fact shows fan action is more important than fin action in the case of rotor fan. Coil temperature can be more decreased by cooling near the heat sources than any other parts from the results of thermal conductivity and loss tests. Variation of cooling air flow rate and motor volume effects on coil temperature were also tested. These tests suggest that improvement of cooling fan performance is important in reducing the coil temperature rise. Thermal equivalent program was verified by comparison of some experimental results.

• 한국전자통신학회논문지
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• 제12권6호
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• pp.997-1002
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• 2017

무선전파를 사용하는 지상통신과는 달리 1500[m/s] 속도의 음향채널이 사용되는 수중통신은 수중온도, 염도를 비롯한 통신환경에 민감할 뿐 아니라 3D 공간의 영향을 받는다. 3D 수중통신은 통신공간의 복잡성과 더불어 음파의 전파손실, 해저환경에서 발생되는 음향잡음 등에 민감하다. 본 연구에서는 이와 같은 3D 수중통신환경의 특성을 고려하여 3D 수중통신환경에서 운용되는 MANET을 대상으로 전송성능을 측정 분석하고 이를 토대로 수중 MANET 운용조건을 제시한다. 본 연구는 NS-2를 기반으로 구축한 수중통신 시뮬레이터를 사용하여 수행하며, 성능파라미터로는 처리율, 전송지연, 패킷손실율 및 소비에너지를 사용한다.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.155-164
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• 2002

저널과의 마찰과 마멸을 줄이기 위하여 저널베어링이 사용된다. 저널베어링은 유체 윤활 상대에서 사용되나, 압력이 지나치게 높거나 회전 속도가 작아지면 탄성 유체 윤활 상태의 유막이 파괴되어 접촉부의 돌기가 접촉되는 경계 윤활 상태가 된다. 따라서 혼합 윤활 상태가 되면 저널베어링의 마멸량이 증가하게 된다 본 논문은 마멸율을 최소화함으로 저널베어링의 수명을 연장하는 최적설계를 수행하였다 목적 함수로 혼합 윤활 영역에서 적용되는 마멸을 함수를 사용하였고, 저널베어링 설계에서 고려할 성능 인자들인 마찰 손실, 안정 한계 속도, 유막 파라미터 등을 제약 함수로 사용하였다. 저널베어링 형상을 나타내는 베어링 반경, 축 반경, 베어링 폭 등에서 본 연구는 베어링 반경을 설계 변수로 하였다. 정식화한 설계인자를 이용하여 저널베어링의 최적 설계를 순차 이차 계획법인 PLBA알고리즘을 사용하여 수행하였다.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.3176-3183
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• 2011

무선 센서 네트워크에서 트래픽과 혼잡제어는 처리율과 QoS (Quality of Service)를 결정하는 중요한 파라미터이다. 본 논문에서는 무선 센서 네트워크에서 디지털 콘텐츠 스트리밍 서비스를 위한 전송율 우선순위 기반의 트래픽 제어 기법을 제안한다. 제안된 기법에서 전송율 우선순위는 버스트 시간과 크기에 따른 실시간 트래픽과 비실시간 트래픽에 의해 결정된다. 전송율 기반 우선순위는 지연을 줄이고 신뢰성을 향상시킴으로서 스트림이 요청될 때 트래픽이 효율적으로 제어되게 된다. 트래픽 제어는 트래픽 탐지 과정, 트래픽 공지, 그리고 트래픽 제어 조절 과정을 거쳐 스트리밍 서비스가 차별화 되도록 하였다. 시뮬레이션 결과 제안된 기법이 CCF (Congestion Control and Fairness)기법, WCA (Weight-based Clustering Algorithm)기법에 비해서 전송지연, 패킷손실, 그리고 처리율에 대한 성능이 효율적임을 보였다.

• IEIE Transactions on Smart Processing and Computing
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• 제3권6호
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• pp.388-392
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• 2014

This paper proposes an early termination method of a block vector search for fast encoding of high efficiency video coding (HEVC) screen content coding (SCC). In the proposed algorithm, two blocks indicated by two block vector predictors (BVPs) were first employed as an intra block copy (IBC) search. If the sum of absolute difference (SAD) value of the block is less than a threshold defined empirically, an IBC BV search is terminated early. The initial threshold for early termination is derived by statistical analysis and it can be modified adaptively based on a quantization parameter (QP). The proposed algorithm is evaluated on SCM-2.0 under all intra (AI) coding configurations. Experimental results show that the proposed algorithm reduces IBC BV search time by 29.23% on average while the average BD-rate loss is 0.41% under the HEVC SCC common test conditions (CTC).

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.287-289
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• 1995

In this paper, We applied the $\mu$-stepping method on the Phase Excitation Sequence of Hybrid type LPM. Linear Pulse Motor can opeate in an open loop control as an effective positioning actuator. PWM driver was used for low power loss and automatically adjusted voltage at rate current. Finally we find that through the position-velocity for timing Triangular and Trapezoidal Profile are very affected by velocity and acceleration parameter.

• 한국멀티미디어학회논문지
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• 제18권12호
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• pp.1475-1482
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• 2015

In network routers, buffers are used to resolve congestion and reduce packet loss rate whenever congestion occurs at bottleneck link. Most of the existing methods to manage such buffers focus only on queue-length-based control as one loop which have some issues of low link utilization and system stability. In this paper, we propose a novel framework which exploits two-loop control method, e.g. queue-length and congestion window size, combined with optimal margin method to facilitate parameter choices. Simulation results in ns-2 demonstrate that bottleneck link performance can be improved with higher link utilization (85%) and shorter queue length (22%) than the current deployed scheme in commercial routers (RED and DropTail).

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1997년도 학술대회
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• pp.63-67
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• 1997

The ISO(International Standard Organization) has standardized MPEG-2 audio. The MPEG-2 audio compression algorithm is based upon subband analysis and exploits the human auditory characteristics to achieve a low bit rate with minimum perceptual loss of audio signal quality. This thesis presents an enhanced MPEG-2 audio encoder using multiple TMS320C30 general purpose DSP's. The developed system is made up of five slave boards and one master board. Each slave board performs susband analysis psychoacoustic parameter calculation for one channel, and the master board manages bit allocation, quantization, and bit-stream formatting for all channels. Parallel processing and pipelining techniques are used in hardware structure and fast algorithms are applied in each subroutine to implement a real-time process. The implemented system supports multichannel up to 5.1 and various bitrates.

• 천문학회지
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• 제29권2호
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• pp.93-105
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• 1996

We have solved the radiative transfer problem using a Sobolev approximation with an escape probability method in case of the supersonic expansion of a stellar envelope to an ambient medium. The radiation from the expanding envelope turns out to produce a P-Cygni type profile. In order to investigate the morphology of the theoretical P-Cygni type profile, we have treated $V_\infty,\;V_{sto},\;\beta$ (parameters for the velocity field), it and E(parameter for collisional effect) as model parameters. We have investigated that the velocity field and the mass loss rate affect the shapes of the P-Cygni type profiles most effectively. The secondarily important factors are $V_\infty,\;V_{sto}$. The collisional effect tends to make the total flux increased but not so much in magnitude. We have infered some physical parameters of 68 Cyg, HD24912, and $\xi$ persei such as $V_\infty,\;M$ from the model calculation, which shows a good agreenment with the observational results.

• 한국물환경학회지
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• 제26권5호
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• pp.802-809
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• 2010

An automatic calibration tool of Hydrological Simulation Program-Fortran (HSPF), Parameter Estimation (PEST) program, was applied at the Imha lake watershed to get optimal hydrological parameters of HSPF. Calibration of HSPF parameters was performed during 2004 ~ 2008 by PEST and validation was carried out to examine the model's ability by using another data set of 1999 ~ 2003. The calibrated HSPF parameters had tendencies to minimize water loss to soil layer by infiltration and deep percolation and to atmosphere by evapotranspiration and maximize runoff rate. The results of calibration indicated that the PEST program could calibrate the hydrological parameters of HSPF with showing 0.83 and 0.97 Nash-Sutcliffe coefficient (NS) for daily and monthly stream flow and -3% of relative error for yearly stream flow. The validation results also represented high model efficiency with showing 0.88 and 0.95, -10% relative error for daily, monthly, and yearly stream flow. These statistical values of daily, monthly, and yearly stream flow for calibration and validation show a 'very good' agreement between observed and simulated values. Overall, the PEST program was useful for automatic calibration of HSPF, and reduced numerous time and effort for model calibration, and improved model setup.