• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.324-330
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• 2005

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• 한국유체기계학회 논문집
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• 제9권4호
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• pp.13-19
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• 2006

For axial-type turbines which operate at partial admission, a performance prediction model is developed. In this study, losses generated within the turbine are classified to windage loss, expansion loss and mixing loss. The developed loss model is compared with experimental results. Particularly, if a turbine operates at a very low partial admission rate, a circular-type nozzle is more efficient than a rectangular-type nozzle. For this case, a performance prediction model is developed and an experiment is conducted with the circular-type nozzle. The predicted result is compared with the measured performance, and the developed model quite well agrees with the experimental results. So the developed model could be applied to predict the performance of axial-type turbines which operate at various partial admission rates or with different nozzle shape.

• Journal of Advanced Marine Engineering and Technology
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• 제28권1호
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• pp.98-108
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• 2004

This study concerns a large eddy simulation (LES) of turbulent flow around a bluff body inside a sudden expansion cylindrical chamber, a configuration which resembles a premixed gas turbine combustor The simulation code is constructed by using the general coordinate system based on the physical contravariant velocity components. The Smagorinsky model is employed and the calculated Reynolds number is 5,000 based on the bulk velocity and the diameter of the inlet pipe. The combined grid technique and cylindrical grid are tested in the numerical simulation with complex geometry. The predicted turbulent statistics are evaluated by comparing with LDV measurement data. The numerical flow visualizations depict the behavior of turbulent mixing process behind the flame holder.

• Composites Research
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• 제30권6호
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• pp.410-415
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• 2017

본 연구에서는 탄소섬유강화 복합재의 제작 시 열 잔류응력으로 인한 변형을 유한요소 프로그램 ABAQUS에서 User Subroutine을 이용한 유한요소 해석을 통해 예측한다. 탄소섬유강화 복합재의 변형에 영향을 주는 다양한 요인 중 온도구배, 제품 형상, 적층각 및 적층순서, 수지의 화학수축, 열 잔류응력을 고려한 복합재 성형을 해석하였다. 같은 형상의 실제 모델과 해석 모델의 결과를 비교한다. 또한 해석 결과를 분석하여 실제 제작의 오차에 적용하여 실제 제작에서의 성형 완성도를 높이는데 목적이 있다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제13권4호
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• pp.291-297
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• 2013

Chaotic dynamics have been studied by many researchers in the fields of biology, physics, and engineering. Interest in chaos is also expanding to the social sciences such as politics, economics, and others, including the prediction of societal events. The concept of leisure has developed from a passive concept correlated with relaxation, entertainment, and ideology formation into a positive concept that assumes a more active role. As information and communications technology develops, digital leisure activity is expected to continue spreading. This expansion of digital leisure function correctly, as well as. Traditional leisure activity functions correctly more, whereas digital leisure activity is predicted to function incorrectly more often. In this paper, we propose a mathematical addiction model of digital leisure that deals with its dysfunctions such as addiction to digital leisure, including computer games, internet search, internet chatting, and social media. Herein, to solve addiction to digital leisure, we propose a model derived from a nicotine addiction.

• 한국음향학회지
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• 제40권4호
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• pp.278-289
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• 2021

본 연구에서는 함정에서 발생하는 배관소음을 줄이기 위해 크기 대비 성능이 우수한 흡음형 소음기의 음향성능을 수치해석 방법을 이용하여 예측 및 분석하였다. 이를 위해 단일확장형 소음기의 음향성능을 실험 및 수치해석 방법을 이용하여 검증하였다. 음향성능은 자체 성능을 나타내는 지표인 투과손실을 이용하여 나타내었고, 실험은 배관 끝단 임피던스를 바꿔서 측정하는 two-load method를 통해 결과를 도출하였다. 수치해석은 범용 유한요소해석 프로그램을 사용하여 실시하였고, 흡음재 유동저항을 입력 매개변수로 하는 Delany-Bazley-Miki 모델을 적용하였다. 최종적으로, 단순확장형 및 흡음형 소음기 음향성능 각각에 대한 실험·모의 결과를 비교하여 결과의 일치성을 확인하였으며, 흡음재 물성치에 따라 4가지 경우로 분류하여 각각에 대한 시뮬레이션 결과를 예측 및 분석하였다.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1053-1064
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• 2009

The existence of a large sodium pool in the KALIMER, a pool-type LMR developed by the Korea Atomic Energy Research Institute, plays an important role in reactor safety and operability because it determines the grace time for operators to cope with an abnormal event and to terminate a transient before reactor enters into an accident condition. A two-dimensional hot pool model has been developed and implemented in the SSC-K code, and has been successfully applied for the assessment of safety issues in the conceptual design of KALIMER and for the analysis of anticipated system transients. The other important models of the SSC-K code include a three-dimensional core thermal-hydraulic model, a reactivity model, a passive decay heat removal system model, and an intermediate heat transport system and steam generation system model. The capability of the developed two-dimensional hot pool model was evaluated with a comparison of the temperature distribution calculated with the CFX code. The predicted hot pool coolant temperature distributions obtained with the two-dimensional hot pool model agreed well with those predicted with the CFX code. Variations in the temperature distribution of the hot pool affect the reactivity feedback due to an expansion of the control rod drive line (CRDL) immersed in the pool. The existing CRDL reactivity model of the SSC-K code has been modified based on the detailed hot pool temperature distribution obtained with the two-dimensional pool model. An analysis of an unprotected transient over power with the modified reactivity model showed an improved negative reactivity feedback effect.

• 한국농공학회지
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• 제38권3호
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• pp.70-81
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• 1996

Solutions of geotechnical engineering problems require predictions of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such predictions even for complicated problems. To get accurate results, realistic stress-strain relationships of soils are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate stress-strain and volume change characteristics of Lade's single work hardening model dependant on the stress path. In order to predicted of stress-strain and volumetric strain behavior were determined the values of parameters for the mode by the computer program based on the regression analysis. Predicted stress-strain behavior of triaxial compression tests and optional stress path tests for increasing confining pressure with parameters obtained conventional triaxial compression tests agreed with several test results but the prediction results for decreasing confining pressure reduced triaxial compression tests make a little difference with test results.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.1117-1121
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• 2010

Several isotropic compression-expansion tests and a series of drained conventional traxial tests with various confining pressures for relative density of Beakma river sand 25%, 50%, 80% and 100% selecting Lade's Single Work-Hardening constitutive model. This examination materials use regression analysis as a basis, depending on the relative density of soil parameters change statement attributes. Yield fuction represent the soil parameters h and $\alpha$ is not affected by the changes in the relative density. $\eta_1$ could be replaced by fomula. And Numerical analysis results predicted very good and could confirm that.

• 기술혁신연구
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• 제27권4호
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• pp.21-48
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• 2019

기초연구 분야는 정부의 적극적인 지원으로 양적 확대가 큰 폭으로 이루어지는 반면, 체계적인 투자계획이나 데이터에 기반한 재정소요를 제시하는 연구 및 정책자료가 전무하여 관련 연구가 요구되는 시점이다. 이에 본 연구는 시계열 예측모형을 활용하여 기초연구지원사업의 향후 재정소요를 전망하였다. 기초연구분야의 특성을 포함한 다양한 요인들을 종합적으로 고려하기 위하여 시간에 따른 단일 종속변수의 값을 예측하는 ARIMA 모형이 아닌, 다변수의 영향을 반영할 수 있는 ARIMAX 모형을 선택하였다. 모형 적합성 판단을 위해 ARIMAX 모형과 ARIMA 모형의 예측값을 비교한 결과 ARIMAX 모형에서 예측오차율이 개선됨을 확인하였다. ARIMAX 모형에 기반하여 2017년에서 2021년까지 5년 간의 기초연구지원사업 재정소요를 전망하였다. 본 연구는 기초연구지원사업의 재정소요를 통계적 접근방법인 시계열모형을 적용해 전망한 시범적 연구를 수행하였다는 점과, 단변량이 아닌 다변량을 고려하여 예측력을 개선했다는 점에서 의의를 지닌다. 또한 현 정부 국정과제인 '기초연구 예산 2배 확대' 등 기초연구 투자의 중요성이 꾸준히 강조되는 정책기조를 고려할 때 향후 기초연구 투자전략 수립 시 참고자료로 활용 될 수 있다.