• Electronics and Telecommunications Trends
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• v.22 no.4 s.106
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• pp.169-182
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• 2007

개인용 휴대 인터넷의 개념으로 세계에서 최초로 기술이 개발되고 본격적인 상용화를 개시한 WiBro는 기술개발 초기부터 서비스에 대한 수요예측 작업이 이루어져 왔고, 이는 HSDPA의 경우도 마찬가지이다. 그러나 초기의 수요예측 시점에 가정하였던 여러 가정들이 구체화되고, 정보통신 환경도 변화함에 따라 이제 보다 구체적이고 정확한 수요예측이 이루어질 시점에 도달하였다. 이에 따라 본 고에서는 변화된 여러 환경을 고려하여 WiBro 서비스에 대한 수요예측을 수행하고자 하였다.

• Elastomers and Composites
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• v.46 no.1
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• pp.54-59
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• 2011

One of the viscoelastic flow behaviors during profile extrusion is the swelling of extrudate. In this study, die swell of rubber compound in the capillary die have been investigated through experiment and computer simulation. Simplified viscoelastic model and non-linear differential viscoelastic model such as PTT model have been used in the computer simulation. The simulation results have been compared with experimental data. Experiment and simulation have been performed using fluidity tester and commercial CFD code, Polyflow respectively. Die swells predicted by two models showed good agreement with experimental results. Pressure and velocity distribution, and circulation flow at the corner of reservoir have been well predicted by PTT model. Simplified viscoelastic model can not predict circulation flow at the corner of reservoir. However this model has an advantage in computation time compare with full viscoelastic model, PTT model.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.253-255
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• 2005

DNA 연산 과정의 열역학적 통계 물리학적 예측 모델을 기술한다. 온도를 천천히 내리는 시험관에서의 DNA string 들의 결합은 Metropolis 알고리즘과 진화 연산의 일종인 simulated annealing 알고리즘으로 설명될 수 있다 본 논문에서는 정리 증명 문제를 통해 위의 통계 물리학적 모델이 DNA 연산에 적용될 수 있음을 보인다. 여섯 종류의 DNA 가닥들의 시뮬레이션 결과와 온도에 대한 실험적인 fluorescence intensity의 비교를 통해 이 모델이 유효함을 보인다. 또한 목표 DNA 개수를 시뮬레이션으로 예측하고 그 결과를 electrophoresis gel image 와 비교하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.139-146
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• 2002

This paper provides validations of the reference stress based J and $C^{*}$ estimations, proposed in Part I, for inner, circumferential surface cracked pipes under internal pressure and global bending against detailed 3-D elastic-plastic and elastic-creep FE results. For this purpose, actual tensile properties of two typical stainless steels (TP304 and TP316) are used for elastic-plastic FE analyses and two realistic creep laws are used for elastic-creep FE analyses. For a total of twenty cases considered in this paper, agreements between the proposed reference stress based J and $C^{*}$ estimations and the FE results are excellent. More important aspect of the proposed estimations is that they can be used to estimate J and $C^{*}$ not only at the deepest point of the surface crack but also at an arbitrary point along the crack front.front.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4364-4374
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• 2015

In this study, heat transfer and friction characteristics of compound enhanced fin-and-tube heat exchangers were experimentally investigated. Louver-finned heat exchangers were also tested for comparison purpose. The effect of fin pitch on j and f factor was negligible. The j factor decreased as number of tube row increased. However, f factor was independent of number of tube row. Louver fin samples yielded higher j and f factors than compound enhanced fin samples. For one row, j and f factors of louver fin were 23% and 27% higher than those of compound enhanced fin. For two row, those were 11% and 8%, and for three row, those were 10% and 9%. However, heat transfer capacities at the same pressure drop of the compound enhanced fins were 6.4% for one row, 11.1% for two row and 13.6% for three row larger than those of louver fins, Existing louver fin correlation overpredicted the present j factors and underpredicted the present f factors.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.88.1-88.1
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• 2011

본 연구에서는 SOFC 시스템 설계기술 개발을 위한 기초 연구로서 전산해석을 이용한 SOFC 성능예측 기법을 개발하였다. 기본설계 단계에서 SOFC의 성능을 개략적으로 예측할 수 있는 1차원 예측 모델을 정립하였으며, 온도, 조성, 전해질, 전극 두께 등을 비롯한 다양한 조건 변화에 따른 성능예측을 수행하여 실험값과 비교한 결과 최대전력밀도 조건에서 23%의 오차를 갖는 것으로 나타났다. 또한 Stack 제작단계에서 다양한 운전조건과 형상변화에 따른 SOFC 성능 변화를 예측할 수 있는 3차원 해석기법을 정립하였으며, 최대전력밀도에서 5.1%의 오차를 보였다. 포괄적인 열 및 물질 전달 현상과 전기화학반응을 3차원적으로 해석함으로써 보다 정확한 예측이 가능하였다. 또한 수소와 적당량의 수분을 함께 공급할 경우 SOFC 성능이 향상되는 것으로 나타났다. 본 연구에서 개발된 기술을 활용할 경우 시제품 제작 전에 전지시스템의 성능을 미리 예측할 수 있으므로, 향후 제품 개발시 제작비용 절감과 설계기간 단축에 기여할 수 있을 것으로 기대된다.

• Journal of Wetlands Research
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• v.21 no.3
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• pp.236-243
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• 2019

Hydrologic time series has been analyzed and forecasted by using classical linear models. However, there is growing evidence of nonlinear structure in natural phenomena and hydrologic time series associated with their patterns and fluctuations. Therefore, the classical linear techniques for time series analysis and forecasting may not be appropriate for nonlinear processes. Daily streamflow series at St. Johns river near Cocoa, Florida, USA showed an interesting result of a low dimensional, nonlinear dynamical system but daily inflow at Soyang reservoir, South Korea showed stochastic property. Based on the chaotic dynamical characteristic, DVS (deterministic versus stochastic) algorithm is used for short-term forecasting, as well as for exploring the properties of the system. In addition to the use of DVS algorithm, a neural network scheme for the forecasting of the daily streamflow series can be used and the two techniques are compared in this study. As a result, the daily streamflow which has chaotic property showed much more accurate result in short term forecasting than stochastic data.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.127-133
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• 2003

Pin-on-disk and hardness tests using mechanical components of M-20J aircraft braking system were performed to identify the friction and wear characteristics. The intention of this work was also to analyze a 5-year term maintenance record of an M-20J aircraft. used for flight training at Hankook Aviation University, and to determine the reliability of the brake system of an M-20J aircraft. The mean wear coefficients of the lining sliding against the brake disk were compared between the test and reliability estimation to obtain a predictive wear model.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.664-666
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• 2005

본 논문에서는 장거리 초고압 송전선로에서의 단상재폐로시에 발생가능한 과전압과 2차아크전류를 EMTP를 이용하여 예측계산 하였다. 예측계산결과로부터 과전압을 억제하고 재폐로 동작이 가능한 최적의 중성점 리액터와 400 kV 급 수평배열 1회선 선로를 단상으로 재폐로 하는데 필요한 재폐로 무전압시간을 구하였다.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.163-165
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• 1996

In this paper, we are proposed development of electric energy method and load curve. A daily electric energy is forecasted using artificial neural network. The load curve is obtained by combining forecasted electric energy and typical daily load patterns which are classified using KSOM and Fuzzy system. As a result, we know that we could get more accurate results and easier application than the results from based on the hourly historical data.