• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.6
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• pp.785-795
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• 2009

In this paper, new type of finite element models for the analysis of nonlinear beam bending are developed by using unconventional residual minimizing method to increase accuracy of finite element solutions and overcome some of computational drawbacks. Developing procedures of the new models are presented along with the comparison of the numerical results of existing beam bending models.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.23-29
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• 2009

For the purpose of high outlet pressure, compactness and low vibration and noise, 2 stage reciprocating air compressors can have various cylinder arrangement: opposed, in-line, and V type. This paper presents an effective method to calculate the inertia forces and to design counter weight. This method is based on the complex representation for the orbital behavior of the compressor shaft. This method helps to find the optimal balancing rate easily to reduce the inertial force or moment. This paper shows that the residual inertia forces of the single throw shafts and the residual inertia moments of the double throw shafts remain to be imbalanced.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.620-625
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• 1995

Finite element analysis tool was developed to analyze the casting process. Generally, casting processes consists of mold filling and solifification. In order to investigate the effects of process variables and to predict the defects, both filling and solidiffication process were simulated simultaneously. At filling process, especiallywe consider thermal coupling to investigate thermal history of material during the filling stage. And thermal condition at the final stage of filling is used as the initial conditions in a solidification process for the exact simulation of the actual casting processes. At mold filling process, Lagrangian-type finite element method with automatic remashing scheme was used to find the material flow. To avoid numerical instability in low viscous fluid, a perturbation method with artificial viscosity is adopted. At solififfication process, enthalpy-based finite element method was used to solve the heat transfer problem with phase change. And elastic stress analysis has been performed to predict the thermal residual stress. Through the FE analysis, solidiffication time, position of solidus line, liquidus line and thermal residual stress are studied. Finite element tools developed in this study will be used process design of casting process and maybe basic structure for total CAE system of castigs which will be constructed afterward.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.11
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• pp.883-890
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• 2003

Two GOS (Generalized Observer Scheme) type Fault Detection Isolation Schemes (FDIS), employing the bank of unknown input functional observers (UIFO) as a residual generator, are proposed to make the practical use of the multiple observer based FDIS. The one is IFD (Instrument Fault Detection) scheme and the other is PFD (Process Fault Detection) scheme. A design method of UIFO is suggested for robust residual generation and reducing the size of the observer bank. Several design objectives that can be achieved by the FDI schemes and the design methods to meet the objectives are described. An IFD system is constructed for the Boeing 929 Jetfoil boat system to show the effectiveness of the propositions. Major contributions of this paper are two folds. Firstly, the proposed UIFO approaches considerably reduce the size of residual generator in the GOS type FDI systems. Secondly, the FDI schemes, in addition to the basic functions of the conventional observer-based FDI schemes, can reconstruct the failed signal or give the estimates of fault magnitude that can be used for compensating fault effects. The schemes are directly applicable to the design of a fault tolerant control systems.

• Current Optics and Photonics
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• v.3 no.3
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• pp.193-198
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• 2019

We propose a novel method to design a dispersion map for a WDM (Wavelength Division Multiplexing) ring network with the capability of wavelength reconfiguration. The method is simple, but gives us an optimum set of DCMs (Dispersion Compensation Modules) which satisfies a given value of the tolerable residual dispersion. The proposed method does not depend on compensation method, fiber type, or modulation format. We also demonstrate numerically how it works with an example 10-node ring network.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.4
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• pp.213-217
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• 1999

The river bank is one of the most important structure of fluvial hydraulic structure. Because the breaking of river bank is the cause of calamity, the durability and stability of river bank an very important factors. The breaking of river bank is the cause of the overflow of flood and the leakage of river bank. In this study, we investigated the leakage of river bank using the resistivity probing and estimated the volume of leakage using the weighted residual method The study basin of this study is the upstream of Sumji river basin and the factor of river bank is length 300 m and berm 2.0 m and width 4.5 m and height 4 m. We evaluated the leakage of river basin using using the resistivity probing and estimated the leakage volume using the weighted residual method. The result of this study, the leakage of river bank generated at the point of 39~45 m 80~90 m. 218~222 m. 214~250 m and the type of leakage is the rectangle and the polygon. And the leakage volume of this points evaluated 2.7$\times$$10^{-3}$ $\textrm{m}^3$/sec.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.2
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• pp.89-99
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• 1997

Although discontinuously reinforced metal matrix composite(MMC) is one of the most promising materials for applications of aerospace, automotive industries, the thermal residual stresses developed in the MMC due to the mismatch in coefficients of thermal expansion between the matrix and the fiber under a temperature change has been pointed out as one of the serious problem in practical applications. There are very limited nondestructive techniques to measure the residual stress of composite materials. However, many difficulties have been reported in their applications. Therefore it is important to establish analytical model to evaluate the thermal residual stress of MMC for practical engineering application. In this study, an elastic model is developed to predict the average thermal residual stresses in the matrix and fiber of a misoriented short fiber composite. The thermal residual stresses are induced by the mismatch in the coefficient of the thermal expansion of the matrix and fiber when the composite is subjected to a uniform temperature change. The model considers two-dimensional in-plane fiber misorientation. The analytical formulation of the model is based on Eshelby's equivalent inclusion method and is unique in that it is able to account for interactions among fibers. This model is more general than past models to investigate the effect of parameters which might influence thermal residual stress in composites. The present model is to investigate the effects of fiber volume fraction, distribution type, distribution cut-off angle, and aspect ratio on thermal residual stress for in-plane fiber misorientation. Fiber volume fraction, aspect ratio, and distribution cut-off angle are shown to have more significant effects on the magnitude of the thermal residual stresses than fiber distribution type for in-plane misorientation.

• Journal of applied mathematics & informatics
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• v.8 no.2
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• pp.327-343
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• 2001

This is a survey article on finite element a posteriori error estimates with an emphasize on gradient recovery type error estimators. As an example, the error estimator based on the ZZ patch recovery technique will be discussed in some detail.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2183-2187
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• 2005

In this paper we propose a new fault detection and isolation (FDI) method for those faults of parameter change type. First, we design a residual generator based on the ${\delta}$-operator model of the plant by using the stable pseudo inverse system. Second, the parameter change is estimated by using the property of the block Hankel operator. Third, reliability with respect to stability is quantified. Fourth, the limitations for the meaningful diagnosis in our method are given. The numerical examples demonstrate the effectiveness of the proposed method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.93-101
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• 1987

Residual stresses have remained around welding areas of a steel structure member after welding operation. The major causes to occur these residual stresses are the local heat due to a welding, the heat stresses due to a irregular and rapid cooling condition, the material and rigidity of a steel structure. Ultimatly, these residual stresses have been known to decrease a brittle fracture strength, a fatigue strength, a buckling strength, dynamic properties, and the corrosion resistance of the material. This paper deals with the residual stresses on a steel structure member through experimental studies. SWS 58 plates were welded by the method of X-groove type. These plates were layed on the heat treatment at four different temperatures; $350^{\circ}C$, $500^{\circ}C$, $650^{\circ}C$ and $800^{\circ}C$. The resulting residual Stresses were measured by hole drilling method, and the followings were obtained. The residual stresses on the vicinity of a welding point were relieved most effectively at the temperature of $650^{\circ}C$, and these stresses relieved completly when the ratio of a hole diamerter to a hole depth became unity. Hardness test shows that the higher value of hardness at the heat affected zone dropped to belower as the temperature went up from $350^{\circ}C$ to $800^{\circ}C$. The Welding input heats have not influenced the magnitude of residual stresses at the input heat range between above and below one forth than standard.