• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.570-572
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• 2005

This paper is proposed adaptive hybrid artificial intelligent(HAI) controller for high performance of induction motor drive. The design of this algorithm based on fuzzy-neural network(FNN) controller that is implemented using fuzzy control and neural network. This controller uses fuzzy rule as training patterns of a neural network. Also, this controller uses the back-propagation method to adjust the weights between the neurons of neural network in order to minimize the error between the command output and actual output. A model reference adaptive scheme is proposed in which the adaptation mechanism is executed by fuzzy logic based on the error and change of error measured between the motor speed and output of a reference model. The control performance of the adaptive FNN controller is evaluated by analysis for various operating conditions. The results of experiment prove that the proposed control system has strong high performance and robustness to parameter variation, and steady-state accuracy and transient response.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.640-648
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• 1998

A numerical study has been conducted to investigate the effect of inflow supply air temperature and velocity on ventilation effectiveness in an underfloor air conditioning space. A low Reynolds number k-$\varepsilon$ model is implemented to calculate steady state turbulent velocity distributions. A step-down injection method is used to calculate local and room mean ages from transient concentrations based on the concept of the age of air. Results show that there is a significant effect of Archimedes number on ventilation effectiveness especially for cooling conditions. Reynolds number shows relatively minor effect on velocity distribution and ventilation effectiveness especially for isothermal and heating conditions. It can be concluded that underfloor air conditioning system provides good ventilation characteristics for cooling conditions because of temperature stratification in the space.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1026-1031
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• 2001

In this paper. the dynamic characteristics of a super high-speed tilting-pad air bearing(TPGB) used in a turbo expander with high expansion ratio are analyzed. The dynamic behavior and stability of a rotary system supported by two journal air bearings are investigated numerically. The transient response of the shaft is obtained by simultaneously solving the equation of motion of the shaft and the dynamic Reynolds equation. The stiffness and damping coefficients of the bearing are calculated from the loading coefficients of the bearing are calculated from the loading capacity. shaft velocity and displacement by using a curve fitting method. The natural frequencies of the 1st and 2nd rigid modes can be calculated from these coefficients. The theoretical method of a rigid rotor system is verified by experimentsut.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.19-31
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• 2022

Lithium-ion battery development is one of the most active contemporary research areas, gaining more attention in recent times, following the increasing importance of energy storage technology. The galvanostatic intermittent titration technique (GITT) has become a crucial method among various electrochemical analyses for battery research. During one titration step in GITT, which consists of a constant current pulse followed by a relaxation period, transient and steady-state voltage changes were measured. It draws both thermodynamic and kinetic parameters. The diffusion coefficients of the lithium ion, open-circuit voltages, and overpotentials at various states of charge can be deduced by a series of titration steps. This mini-review details the theoretical and practical aspects of GITT analysis, from the measurement method to the derivation of the diffusivity equation for research cases according to the specific experimental purpose. This will shed light on a better understanding of electrochemical reactions and provide insight into the methods for improving lithium-ion battery performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.132-139
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• 1997

It is difficult for most of passenger cars to attach various types of suspensions. The modular experimental vehicle, which is designed to exchange suspension systems, has been developed to evaluate the effect of design changes of a suspension upon ride and handling characteristics of a vehicle. In order to enable the assemblage between modules, the experimental vehicle design is based on a space frame construction through finite element analysis. Moreover, module frames and brackets are designed using three-dimensional solid modeler to check the interference between each part of a vehicle. Steady-state and transient road tests were performed. Multibody dynamic model and simplified linear vehicle model are made to compare with the tests. The results of simulations and tests show the performance and validity of this experimental vehicle.

• Journal of Mechanical Science and Technology
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• v.18 no.12
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• pp.2190-2203
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• 2004

A combined procedure for two-dimensional Delaunay mesh generation algorithm and an adaptive remeshing technique with higher-order compressible flow solver is presented. A pseudo-code procedure is described for the adaptive remeshing technique. The flux-difference splitting scheme with a modified multidimensional dissipation for high-speed compressible flow analysis on unstructured meshes is proposed. The scheme eliminates nonphysical flow solutions such as the spurious bump of the carbuncle phenomenon observed from the bow shock of the flow over a blunt body and the oscillation in the odd-even grid perturbation in a straight duct for the Quirk's odd-even decoupling test. The proposed scheme is further extended to achieve higher-order spatial and temporal solution accuracy. The performance of the combined procedure is evaluated on unstructured triangular meshes by solving several steady-state and transient high-speed compressible flow problems.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.70-76
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• 1998

A switch-mode AC/DC converter with high input power factor and sinusoidal input current waveforms is analyzed and modelled for computer simulation. The developed mathematical model for this converter can be used to examine the transient and steady-state performance for selecting the proper ratings of filter, boost inductor and semiconductor devices or the effects of this converter under normal and fault operating conditions on the associated power systems. The proposed model and computer programs are confirmed by comparing with the experimental results.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3038-3043
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• 2008

Tumble or swirl flow is used adequately to promote mixing of air and fuel in the cylinder and to enlarge turbulent intensity in the late time of compression stroke. However, since in-cylinder flow is a kind of transient state with rapid flow variation, that is, non-steady state flow, swirl or tumble flow has not been analyzed sufficiently and not been recognized whether they are available for combustion theoretically yet. In the investigation of intake turbulent characteristics using PIV method, different flow characteristics were showed according to SCV figures. SCV installed engine had higher vorticity, turbulent strength by fluctuation and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder. Consequently, as swirl flow was added to existing tumble flow, it was found that fluctuation component increased and flow energy was conserved effectively through the experiment.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.399-406
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• 2000

In this study, using the CRS consolidation tests on reconstituted marine clay, the characteristics of C$\sub$v/, k, e and $\varepsilon$, the anisotropic characteristics of specimen according to the rate of strain were estimated. Also, the validity of the Wissa et al.(1971) consolidation theory on CRS(Constant Rate of Strain) consolidation tests were reviewed. From that results, it was shown that the value of C$\sub$v/, k and u$\sub$b/ was increased as the rate of strain was increased. While the difference of the value( C$\sub$v/, k and u$\sub$b/) between vertically reconstituted specimen and horizontally reconstituted specimen became small as the rate of strain was increased. It is known that k is different due to the hydraulic gradient(i) during the CRS consolidation tests. The subject of this study is to distinguish steady state from transient state in CRS consolidation tests. Consequently, the difference of the value(C$\sub$v/ and k) is higher in case of vertically reconstituted specimen than horizontally reconstituted specimen.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.131-138
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• 2001

In this paper, performance of a dry CVT vehicle with torque cam is investigated. Based on belt transmission mechanism and torque cam actuator characteristics, an algorithm which is able to calculate the speed ratio from given thrust and load torque is suggested and a 3-D map is constructed for the speed ratio-thrust-torque. Using the 3-D map, a steady state characteristic of torque cam and a transient response of a dry CVT vehicle are investigated by simulation. It is found that initial spring compression plays a key role in determining the sliding criteria and the speed ratio velocity.