• 상하수도학회지
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• 제12권2호
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• pp.127-139
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• 1998

The objectives of this study is at the development of the channel routing model which can be used for flood prediction. Among the routing models, the hydraulic technique of the implicit scheme in the dynamic equation is selected to route the unsteady varied flow in the open channel. The channel routing model is catchment runoff which computed by the conceptual and transfer function model. The conceptual and transfer function model can simulate the catchment runoff accurately. As a result of investigating the channel routing model, the optimal weighting factor ${\theta}$ which fixes two points between time line is chosen, and also, the optimal error tolerance which satisfies computing time and converge of solution is determined in this study.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1351-1359
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• 2003

This study presents a numerical procedure to optimize shape of streamwise periodic ribs mounted on both of the principal walls to enhance turbulent heat transfer in a rectangular channel flow. The response surface method is used as an optimization technique. The optimization is based on Navier-Stokes analysis of flow and heat transfer with $k-{\varepsilon}$ turbulence model. The width-to-height ratio of a rib, rib height-to-channel height ratio and rib pitch to rib height ratio are chosen as design variables. The object function is defined as a function of heat transfer coefficient and friction drag coefficient with weighting factor. Optimum shapes of the rib have been obtained for the range of 0.02 to 0.1 of weighting factor.

• 대한기계학회논문집B
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• 제38권9호
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• pp.773-779
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• 2014

가스터빈 희박 예혼합 연소기에서 발생하는 연소 불안정 현상을 모델링하기 위해서는 화염의 동 특성에 대한 정량적, 정성적 분석이 필수적이다. 이를 위하여 화염전달함수가 전산유체역학을 통하여 모델링되었다. 기존 화염전달함수의 연구 결과로부터, 화염전달함수의 결과는 화염의 구조에 크게 의존하는 것으로 알려졌다. 본 연구에서는 실제 계측된 화염의 구조와 유사한 형상을 갖도록 열전달 조건을 최적화한 후, 동일 조건에서 화염전달함수가 모델링되었다. 화염의 형상을 정확하게 예측할 수 있다면, 이로부터 전달함수의 이득값과 위상차의 모델링 결과 역시 실험값과 유사한 거동을 확인할 수 있었다.

• 드라이브 ㆍ 컨트롤
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• 제15권4호
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• pp.67-73
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• 2018

The paper deals with an approach to time domain simulation for closed end at the downstream of pipe, hydraulic lines terminating into a tank and series lines with change of cross sectional area. Time domain simulation of a fluid power systems containing hydraulic lines is very complex and difficult if the transfer functions consist of hyperbolic Bessel functions which is the case for the distributed parameter dissipative model. In this paper, the magnitudes and phases of the complex transfer functions of hydraulic lines are calculated, and the MATLAB Toolbox is used to formulate a rational polynomial approximation for these transfer functions in the frequency domain. The approximated transfer functions are accurate over a designated frequency range, and used to analyze the time domain response. This approach is usefully to simulate fluid power systems with hydraulic lines without to approximate the frequency dependent viscous friction.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.920-927
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• 2008

This study deals with modeling of Head-Related Transfer Functions (HRTFs) using Principal Components Analysis (PCA) in the time and frequency domains. Four PCA models based on Head-Related Impulse Responses (HRIRs), complex-valued HRTFs, augmented HRTFs, and log-magnitudes of HRTFs are investigated. The objective of this study is to compare modeling performances of the PCA models in the least-squares sense and to show the theoretical relationship between the PCA models. In terms of the number of principal components needed for modeling, the PCA model based on HRIR or augmented HRTFs showed more efficient modeling performance than the PCA model based on complex-valued HRTFs. The PCA model based on HRIRs in the time domain and that based on augmented HRTFs in the frequency domain are shown to be theoretically equivalent. Modeling performance of the PCA model based on log-magnitudes of HRTFs cannot be compared with that of other PCA models because the PCA model deals with log-scaled magnitude components only, whereas the other PCA models consider both magnitude and phase components in linear scale.

• Nuclear Engineering and Technology
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• 제47권5호
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• pp.567-578
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• 2015

In a nuclear reactor containment, wall condensation forms with noncondensable gases and their accumulation near the condensate film leads to a significant reduction in heat transfer. In the framework of nuclear reactor safety, the film condensation in the presence of noncondensable gases is of high relevance with regards to safety concerns as it is closely associated with peak pressure predictions for containment integrity and the performance of components installed for containment cooling in accident conditions. In the present study, CUPID code, which has been developed by KAERI for the analysis of transient two-phase flows in nuclear reactor components, is improved for simulating film condensation in the presence of noncondensable gases. In order to evaluate the condensate heat transfer accurately in a large system using the two-fluid model, a mass diffusion model, a liquid film model, and a wall film condensation model were implemented into CUPID. For the condensation simulation, a wall function approach with a heat/mass transfer analogy was applied in order to save computational time without considerable refinement for the boundary layer. This paper presents the implemented wall film condensation model, and then introduces the simulation result using the improved CUPID for a conceptual condensation problem in a large system.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1035-1044
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• 2010

머리관련 전달함수는 음원으로부터 이도의 입구까지 소리의 전달함수로 인간이 소리의 위치를 판단하는 데 중요한 역할을 하는 함수이다. HRTF 는 개인간의 편차가 크게 나는 것으로 알려져 있다. 본 논문에서는 한국인의 평균두형에 관해서 HRTF 를 해석하는 경계요소해석 모델을 개발하고 해석 결과와 실험결과와의 비교를 통해서 모델을 검증하였다. 또한 특정 성인에 대하여 CT 촬영을 통하여 두형, 귓바퀴 및 이도의 형상을 획득하여 이를 바탕으로 이도 내의 음향응답을 전 가청주파수에서 해석할 수 있는 모델을 개발하고 실험과의 비교를 통하여 모델을 검증하였다. 개발된 모델을 이용, 경계요소 해석을 수행하고 한국인 HRTF 의 특성에 영향을 미치는 인자를 살펴보았다.

• 한국철도학회논문집
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• 제12권4호
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• pp.506-511
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• 2009

본 연구에서는 대차에서 계측한 가속도 데이터를 사용하여 궤도틀림을 식별하기 위한 알고리즘을 제안하였다. 등가 SISO 모델에 의한 정상궤도틀림 상태에서의 대차진동과 궤도틀림과의 주파수영역 전달함수를 정의하고, 이를 역으로 이용하여 대차에서 계측한 가속도 데이터로 궤도틀림을 예측하였다. 예측된 값과 기준값과의 잔차의 분산 비로정의되는 틀림지수를 사용하여 궤도틀림의 이상을 분석하였다. 궤도틀림을 시간에 따라 변하는 변위 경계조건으로 고려하여 3차원 수치예제를 수행하였으며, 제안된 알고리즘의 타당성을 검증하였다.

• 응용통계연구
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• 제36권1호
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• pp.21-32
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• 2023

한국 소비자원의 의료 분야 처리금액 자료에 대한 시계열 모형을 이용한 실증 분석을 연구하였다. 의료분야 처리금액 시계열 자료는 상담 처리금액, 피해 구제금액, 분쟁 조정 처리금액으로 나뉜 3개 변수를 사용하였고 분석에 사용된 시계열 모형은 ARIMA 모형, 벡터 자기회귀 모형 그리고 전이 함수를 이용한 시계열 모형이다. 이들 중 전이 함수를 이용한 시계열 모형이 단기 예측면에서 가장 우수한 예측력을 보였고 벡터자기회귀 모형도 변수간 영향력과 기간을 파악하는데 유용한 정보를 제공하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.731-736
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• 2004

In this study, a linearized model of pneumatic cylinder position control system including transmission line is proposed. The transmission line using compressible fluid has a nonlinear transfer characteristics because that the frequency response of it is changed by the flowing state of the fluid. But, when the pressure difference between both sides of transmission line is low, the effect of resonance characteristics of it under high frequency range can be neglected because of the friction force and low pass characteristics of the position control system. Therefore, the transmission line can be modeled by second order transfer function and the natural frequency, damping ratio and gain are changed by the diameter and length of it. The effectiveness of the proposed model is proved by comparison of simulation results using proposed model with experimental results and simulation results using conventional model.