• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1275-1280
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• 2004

This paper presents the construction of an active suspension system of a one-wheel car model by using fuzzy reasoning. The car model is approximately described by a nonlinear two degrees freedom system subject to excitation from a road profile, and the active control force is constructed by actuating a pneumatic actuator, and the degradation of the performance due to the delay of the pneumatic actuator is improved by inserting a compensator. The fuzzy control is obtained by single input rule modules fuzzy reasoning, and the excitation from the road profile is estimated by using a disturbance observer. The experimental result shows that the proposed active suspension system much improves the performance in the vibration suppression of the car model.

• Geomechanics and Engineering
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• v.14 no.6
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• pp.509-517
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• 2018

This paper proposes a numerical methodology for capturing the complete curve of a pressuremeter test including initial or disturbed parts and loops through a stiffness-based approach adopted in three dimensional finite difference code, FLAC3D. In order to enable this, a new hyperbolic model was used to replace the conventional linear elastic model prior to peak strength of Mohr-Coulomb soil model and update or degradation of shear modulus was considered. Presented modeling approach and implemented constitutive model are impressively successful. It leads to obtain the whole set of parameters for characterizing sands and seems promising for modeling the most of geotechnical structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1386-1390
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• 2007

This paper presents the equipment condition monitoring technology for the process or the equipment using statistical techniques. The equipment condition monitoring system consists of an empirical model to estimate the expected sensor values of process variables and a diagnose model to detect the abnormal condition and to identify the root source of the problem. The empirical model is constructed by the analysis of historic data. The diagnose model uses the sequential probability ratio test (SPRT) technique. The monitoring system was tested with real operating data acquired from the Reactor Coolant Pump Seal in the Nuclear Power Plant. It can detect the system degradation or failure at the early stage since it is able to catch the subtle deviation of process variables from normal condition.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.8
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• pp.49-56
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• 1993

In this paper, we present a new lifetime prediction model for PMOSFET by using the correlation between transconductance degradation and substrate current influence. The suggested model is applied to a different channel structured PMOSFET, dgm/gm of both SC-PMOSFET and BC-PMOSFET appear with one straigth line about Qbib, therefore, this model is independent of channel structure. The suggested model is applied to a different drain structured SC-PMOSFET. Unlike S/D structured SC-PMOSFET, dgm/gm of LDD structured SC-PMOSFET appears with one straight line about Qb, therefore, this model is dependent of drain structure.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.711-712
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• 2002

A numerical study of a hemodynamical model for the tumor angiogenesis is carried out. The tumor angiogenesis process is comprised of a sequence of events; secretion of tumor angiogenesis factor(TAF) from the solid tumor, degradation of the basement membrane of nearby blood vessels, migration and proliferation of the endothelial cells. The model takes into account the effect of TAF concentration and endothelial cell density, and their conservation equations are represented as a set of one-dimensional initial boundary value problems. These equations are discretized by using a finite difference method in which the second order schemes both in time and in space are used. The effects of the parameters contained in the model are Investigated extensively through the numerical simulation of the discretized model. The result for the typical case compares very well with the known result.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.145-152
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• 2005

This paper presents a deformable strut-and-tie model of determining the shear strengths and ultimate deformations of the shear-dominant reinforced concrete members. The proposed model originates from the strut-and-tie model concept and satisfies equilibrium, compatibility, constitutive laws, and the geometric conditions of shear deformation. This study attempts to apply deformation patterns to strut-and-tie models. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. The validity and accuracy of the proposed model is then tested against available experimental data. The parameters reviewed include the ratios of truss action and arch action, the reinforcement ratios, and the shear span-depth ratio. It is expected that this model can be applied to displacement-based design methods.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.884-891
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• 2009

This study investigates some of swarm intelligence algorithms to tackle a traditional damage detection problem having stiffness degradation or damage in mechanical structures. Particle swarm(PSO) and ant colony optimization(ACO) methods have been exploited for localizing and estimating the location and extent damages in a structure. Both PSO and ACO are population-based, stochastic algorithms that have been developed from the underlying concept of swarm intelligence and search heuristic. A finite element (FE) model updating is implemented to minimize the difference in a set of natural frequencies between measured and baseline vibration data. Stiffness loss of certain elements is considered to simulate structural damages in the FE model. It is numerically shown that PSO and ACO algorithms successfully completed the optimization process of model updating in locating unknown damages in a truss structure.

• Structural Engineering and Mechanics
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• v.30 no.2
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• pp.147-164
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• 2008

Recently, many researches have been done to examine the behavior of fiber reinforced concrete (FRC) subjected to the static loading. However, a few studies have been devoted to cyclic behaviors of FRC. A main objective of this paper is to investigate the cyclic behavior of FRC through theoretical method. A new cyclic bridging model was proposed for the analysis of fiber reinforced cementitious composites under cyclic loading. In the model, non-uniform degradation of interfacial bonding under cyclic tension was considered. Fatigue test results for FRC were numerically simulated using proposed models and the proposed model is achieving better agreement than the previous model. Consequently, the model can establish a basis for analyzing cyclic behavior of fiber reinforced composites.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.139-142
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• 2005

This paper presents a deformable strut-and-tie model of determining the shear strengths and ultimate deformations of the shear-dominant reinforced concrete members. The proposed model originates from the strut-and-tie model concept and satisfies equilibrium, compatibility, constitutive laws, and the geometric conditions of shear deformation. This study attempts to apply deformation patterns to strut-and-tie models. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. The validity and accuracy of the proposed model is then tested against available experimental data. The parameters reviewed include the ratios of truss action and arch action, the reinforcement ratios, and the shear span-depth ratio. It is expected that this model can be applied to displacement-based design methods.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1199-1203
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• 2008

It has been recognized that unsaturated soil behavior plays an importantrole in geomechanics. In the last decade several constitutive models have been proposed and used in the analysis. Many of them, however, are constructed in the frame work of rate independent model such as elasto-plastic one. Although rate dependency is an important characteristics of soil for both saturated and unsaturated soils, very few models have been developed taking account of rate dependency. In the present paper, we have developed an elasto-viscoplastic model considering an effect of suction based on the overstress-type viscoplasticity with soil structure degradation. In the model, we have adopted an averaged pore pressure composed of pore water pressure and air pressure to determine the effective stress.