• Nuclear Engineering and Technology
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• 제26권3호
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• pp.355-366
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• 1994

미국원자력규제위원회에서는 최근 안전해석에 최적전산코드의 사용을 허용하는 개정된 비상노심냉각계통 평가 규정을 제시하였다. 당 규정에서는 계통해석에 최적전산코드를 사용할 경우 불확실성 평가를 수행할 것을 요구하고 있다. 본 논문에서는 이러한 비상노심냉각계통의 규제요건을 만족하는 실제적인 최적평가방법론을 개발하여 대형냉각재상실사고에 적용하였다. 최적평가전산코드로는 RELAP5/MOD3.1을 개선한 RELAP5/MOD3/KAERI를 사용하였으며, 코드의 불확실성은 수개의 분리효과 및 총체효과 실험에 대한 평가를 수행함으로써 정량화 하였다. 적용대상 발전소로는 고리 3 & 4호기를 선정하였다. 민감도 분석을 통하여 응답방정식을 구성하였으며 각 응답방정식에 대하여 무작위 추출방식, Monte Carlo 방식으로 확률밀도함수를 구하였다. 최종 불확실성은 95%의 신뢰도로 정량화 하였으며 대형냉각재 상실사고시의 안전여유도에 대하여 논의하였다.

• 한국자동차공학회논문집
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• 제19권1호
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• pp.51-57
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• 2011

Information of the lateral velocity and the sideslip angle in a vehicle is very useful in many active vehicle safety applications such as yaw stability control and rollover prevention. Because cost-effective sensors to measure the lateral velocity and the sideslip angle are not available, reliable algorithms to estimation them are necessary. In this paper, a sliding mode observer is designed to estimate the lateral velocity. The side slip angle is estimated using the recursive least square with the disturbance observer and the pseudo integral. The estimated parameters from the combined estimation method are updated recursively to minimize the discrepancy between the model and the physical plant, and any possible effects caused by disturbances. The performance of the proposed monitoring system is evaluated through simulations and experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.565-569
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• 2003

In this paper, a robust filter is proposed to effectively estimate the system states in the case where system model uncertainties as well as disturbances are present. The proposed robust filter is constructed based on the linear approximation methods for a general nonlinear uncertain system with an integral quadratic constraint. We also derive the important characteristic of the proposed filter, a modified $H_{\infty}$ performance index. Analysis results show that the proposed filter has robustness against disturbances, such as process and measurement noises, and against parameter uncertainties. Simulation results show that the proposed filter effectively improves the performance.

• Korea-Australia Rheology Journal
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• 제20권2호
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• pp.51-58
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• 2008

This paper describes a two-step Tikhonov regularization procedure for converting the steady shear data generated by parallel-disk viscometers, in the presence of wall slip, into a shear stress-shear rate function and a wall shear stress-slip velocity functions. If the material under test has a yield stress or a critical wall shear stress below which no slip is observed the method will also provide an estimate of these stresses. Amplification of measurement noise is kept under control by the introduction of two separate regularization parameters and Generalized Cross Validation is used to guide the selection of these parameters. The performance of this procedure is demonstrated by applying it to the parallel disk data of an oil-in-water emulsion, of a foam and of a mayonnaise.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1991년도 가을 학술발표회 논문집
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• pp.75-80
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• 1991

The purpose of this study is to ascertain the robustness of p-version model with hierarchic intergrals of Legendre shape functions in various applications including plane stress/strain, axisymmetric and shell problems. The most important symptoms of accuracy failure in modern finite elements are spurious mechanisms and a phenomenon known as locking which are exhibited for incompressible materials and irregular shapes which contain aspect ratios(R/t, a/b), tapered ratio(d/b), and skewness. The condition numbers and energy norms are used to estimate numerical errors, convergence characteristics and algorithmic efficiencies for verifying the aforementioned symptoms of accuracy failure. Numerical results from p-version models are compared wi th those from NASTRAN, SAP90, and Cheung's hybrid elements.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.31-36
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• 2004

Defective components of interest include not only homogeneous components, but also components with weldments where tensile properties vary across the weldment. Noting that the region near the weldment is the most vulnerable place for crack initiation and subsequent growth, defect assessment methods for homogeneous structure. Moreover, weldment width and crack location also affects the deformation and fracture behavior of the welded joints. These weld characteristics can evaluate using plastic limit load. So in this paper, evaluate plastic limit load both full circumference part-throughwall cracked pipes and circumference through-wall cracked pipes considering weld characteristics. And using evaluate results, proposed J-integral and crack opening displacement(COD) estimate method based on reference stress method.

• 대한수학회지
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• 제37권6호
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• pp.1043-1057
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• 2000

This paper is devoted to the investigation of mixed Fourier-Bessel transformation (※Equations, See Full-text) We apply the method of [6] which provides the estimate for weighted L(sub)$\infty$-norm of the spherical mean of │f│$^2$ via its weighted L$_1$-norm (generally it is wrong without the requirement of the non-negativity of f). We prove that in the case of Fourier-Bessel transformatin the mentioned method provides (in dependence on the relation between the dimension of the space of non-special variables n and the length of multiindex ν) similar estimates for weighted spherical means of │f│$^2$, the allowed powers of weights are also defined by multiindex ν. Further those estimates are applied to partial differential equations with singular Bessel operators with respect to y$_1$, …, y(sub)m and we obtain the corresponding estimates for solutions of the mentioned equations.

• Journal of Electrical Engineering and Technology
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• 제6권2호
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• pp.226-232
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• 2011

The $H_{\infty}$ approach, adopted in this paper, is based on loop shaping using a normalized coprime factor combined with a field-oriented control to control induction motor. We develop two loops. The first one, the inner loop, controls the stator current by $H{\infty}$ controller in order to obtain good performance. The second loop, the outer one, guarantees stability and tracking performance of speed and rotor flux using a proportional integral controller. When the rotor flux cannot be measured, we introduce a flux observer to estimate the rotor flux. Simulation and experimental results are presented to validate the effectiveness and the good performance of this control technique.

• 대한수학회보
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• 제55권6호
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• pp.1783-1789
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• 2018

This paper treats the class of normalized logharmonic mappings $f(z)=zh(z){\overline{g(z)}}$ in the unit disk satisfying ${\varphi}(z)=zh(z)g(z)$ is analytically typically real. Every such mapping f admits an integral representation in terms of its second dilatation function and a function of positive real part with real coefficients. The radius of starlikeness and an upper estimate for arclength are obtained. Additionally, it is shown that f maps the unit disk into a domain symmetric with respect to the real axis when its second dilatation has real coefficients.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1350-1358
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• 2001

During the last decade, a number of experiments and numerical analyses had been performed in conjunction with the development of simplified analytical methods to estimate the fracture behavior of cracked piping in nuclear power plant. However, the necessity of further investigation for the analytical methods was issued because of the discrepancies with the experimental data. The objective of this paper is to find out the optimum methods to evaluate the load-carrying capacities for cracked pipes. To do this, numerous analytical and finite element analyses were carried out for various pipe and crack geometries and materials. These results were synthesized for crack shapes and can be used as basic data for leak before analyses and risk informed inspections.