• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.309-311
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• 1997

In this paper, it is proposed that a algorithm which is applicable to the transient analysis by combined use of the Laplace transform and the finite element method. The proposed method removes the time terms using the Laplace transform and then solves the associated equation with the finite element method. The solution which is solved at frequency domain is transformed into time domain by use of the Laplace inversion. To verify proposed algorithm, heat conduction problem is analysed and found a good agreement with analytic solution.

• 성인간호학회지
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• 제15권1호
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• pp.137-145
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• 2003

Purpose: This research is a descriptive study to explore "patient respect" in nursing. Respect was analyzed as a concept in the domain of the patient. The Hybrid Model suggested by Schwartz-Barcott and Kim was used in this study. Method: For the theoretical phase, nursing and other literature were reviewed to analyze attributes and develop a working definition of the concept, respect. For the fieldwork phase, four subjects in two general hospitals in Seoul participated. With the participants' permission, the data was collected between January and April, 2002, through in-depth interview and participant observation. The data analysis progressed at the same time as the fieldwork. Data analysis proceeded according to the analysis method of Strauss and Corbin. Result: The final attributes of patient respect are suggested by consideration, recognition, cordial treatment, concern, honesty, acceptance. The final definition of patient respect as a concept in the domain the of patient is suggested by "Patient respect is that the patient is recognized as an individual with worth and is accepted, and considered to be that kind of an individual person. In addition, the patient is recognized to be an independent person and is treated with concern and honesty." Conclusion: The results of the analyses is helpful in integrating into a comprehensive description of the concept, Patient Respect.

• 항공우주시스템공학회지
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• 제14권5호
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• pp.1-8
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• 2020

구조적 특성 및 공력의 상호작용과 조종면 작동기의 제어 시스템의 영향을 고려한 서보공력탄성 해석을 수행하였다. 공탄성 안정성 해석을 위해서 선행되어야 하는 구조모델의 자유진동 해석은 유한요소 해석 프로그램 MSC Nastran을 사용하였다. 비정상 공기력 계산에 ZAERO를 사용하였다. 비정상 공기력 검증에 Doublet Hybrid Method를 사용하였다. Karpel의 최소상태근사법을 이용하여 주파수 영역의 공기력을 라플라스 영역으로 근사하였다. 공탄성 상태방정식을 구동기의 동역학 상태방정식과 결합하여 서보 공탄성 모델의 상태공간방정식을 구성하였다. 고세장비 모델의 승강타 입력에 따른 안정성 해석을 수행하였다. 근궤적법과 시간적분법을 사용하여 주파수영역과 시간영역에서의 서보공탄성 안정성 해석을 수행하였다.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.950-960
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• 2006

An output time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via a digital computer. A new method for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed in this paper. This method is applied to the sampled-data representation of a nonlinear system with a constant output time-delay. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. In addition, 'hybrid' discretization schemes resulting from a combination of the 'scaling and squaring' technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. A performance of the proposed method is evaluated using two nonlinear systems with time-delay output.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.132-139
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• 2000

This paper presents a new hybrid approach for nonlinear dynamic analysis of the soil-structure interaction system in the time domain. It employs, in a practical manner, a linear SSI program and a general-purpose nonlinear finite element program. In order to demonstrate the validity and applicability of the proposed method, seismic response analyses are carried out for a free-field problem and a 2-D subway station. The results indicate that the proposed methodology gives reasonable solution for the linear/nonlinear SSI problem utilizing a general-purpose finite element program. Some further studies will endorse the applicability of the method to various soil-structure interaction problems.

• 대한기계학회논문집A
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• 제25권8호
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• pp.1253-1260
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• 2001

Transient thermal analysis of a three-dimensional axisymmetric automotive disk brake is presented in this paper. Temperature fields are obtained using a hybrid FFT-FEM scheme that combines Fourier transform techniques and finite element method. The use of a fast Fourier transform algorithm can avoid singularity problems and lead to inexpensive computing time. The transformed problem is solved with finite element scheme for each frequency domain. Inverse transforms are then performed for time domain solution. Numerical examples are presented for validation tests. Comparisons with analytical results show very good agreement. Also, a 3-D simulation, based upon an automotive brake disk model is performed.

• 대한조선학회논문집
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• 제51권4호
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• pp.328-333
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• 2014

A hybrid particle-mesh method based on the vorticity-velocity formulation for solving the incompressible Navier-Stokes equations is a combination of the Vortex-In-Cell(VIC) method for convection and the penalization method for diffusion. The key feature of the numerical methods is to determine velocity and vorticity fields around a solid body on a temporary grid, and then the time evolution of the flow is computed by tracing the convection of each vortex element using the Lagrangian approach. Assuming that the vorticity and velocity fields are to be computed in time domain analysis, pressure fields are estimated through a complete set of solutions at present time step. It is possible to obtain vorticity and velocity fields prior to any pressure calculation since the pressure term is eliminated in the vorticity-velocity formulation. Therefore, pressure field is explicitly treated by solving a suitable Poisson equation. In this paper, we propose a simple way to numerically implement the vorticity-velocity-pressure formulation including a penalty term. For validation of the proposed numerical scheme, we illustrate the early development of viscous flows around an impulsive started circular cylinder for Reynolds number of 9500.

• Earthquakes and Structures
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• 제5권2호
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• pp.161-205
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• 2013

We study seismically induced, anti-plane strain wave motion in a non-homogeneous geological region containing tunnels. Two different scenarios are considered: (a) The first models two tunnels in a finite geological region embedded within a laterally inhomogeneous, layered geological profile containing a seismic source. For this case, labelled as the first boundary-value problem (BVP 1), an efficient hybrid technique comprising the finite difference method (FDM) and the boundary element method (BEM) is developed and applied. Since the later method is based on the frequency-dependent fundamental solution of elastodynamics, the hybrid technique is defined in the frequency domain. Then, an inverse fast Fourier transformation (FFT) is used to recover time histories; (b) The second models a finite region with two tunnels, is embedded in a homogeneous half-plane, and is subjected to incident, time-harmonic SH-waves. This case, labelled as the second boundary-value problem (BVP 2), considers complex soil properties such as anisotropy, continuous inhomogeneity and poroelasticity. The computational approach is now the BEM alone, since solution of the surrounding half plane by the FDM is unnecessary. In sum, the hybrid FDM-BEM technique is able to quantify dependence of the signals that develop at the free surface to the following key parameters: seismic source properties and heterogeneous structure of the wave path (the FDM component) and near-surface geological deposits containing discontinuities in the form of tunnels (the BEM component). Finally, the hybrid technique is used for evaluating the seismic wave field that develops within a key geological cross-section of the Metro construction project in Thessaloniki, Greece, which includes the important Roman-era historical monument of Rotunda dating from the 3rd century A.D.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.41-64
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• 2014

The main objective of this article is the exploitation of a stochastic hybrid mesh-free method based on stochastic generalized finite difference (SGFD), Newmark finite difference (NFD) methods and Monte Carlo simulation for thermoelastic wave propagation and coupled thermoelasticity analysis based on GN theory (without energy dissipation). A thick hollow cylinder with Gaussian uncertainty in mechanical properties is considered as an analyzed domain for the problem. The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in details. Also, the time histories and distribution on thickness of cylinder of maximum, mean and variance values of temperature and radial displacement are studied for various coefficients of variations (COVs).

• 한국음향학회지
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• 제32권5호
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• pp.369-376
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• 2013

Lowson의 음향상사식을 이용하여 시간영역에서 풍력터빈의 저주파수 소음을 예측 하였고, 관련 소음원들의 기여도를 분석하였다. 소음원으로서 날개-깃 상 평균 압력 분포를 구하기 위하여 XFOIL를 이용하였다. 이 때, 소음 예측 시 입력 값 인 유한 요소 상의 힘을 계산하기 위해 날개-깃을 여러 개의 요소로 분할하였다. 소음원을 힘 섭동항, 가속도항, 속도항으로 분리하여 주파수 기여도를 분석하였다. 끝으로, 예측 스펙트럼을 운용 중 인 풍력터빈에 대하여 측정한 저주파수 소음과 비교하였고, 그 결과 풍속 증가에 따라 힘 섭동 성분이 저주파수에서 크게 기여하는 것을 확인하였다.