• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.144-144
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• 2000

Air balance hoists are widely used in handling of heavy materials in industry. Currently used air balance hoists adopt manual switches for vertical motion, thus the operator has a difficulty in operating of the switches and handling of material simultaneously. To overcome this difficulty, this study develops a weightless air-balance-hoist system using compressed air. This system memorizes the weight of material in terms of pneumatic pressure with a pneumatic circuit. Such memory of the material weight is used for achieving weightless handling of materials. Through a series of experiments, handling forces and the response of the system for various material weights are analyzed. The results show that the developed system can be used for weightless handling o( heavy materials.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.380-380
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• 2000

We have developed a design/analysis tool for use with Mat lab whick is named as "Parametric Robust Control and Identification(PROCI)". The tool is composed of three parts: Part i) consists of the identification of the continuous time transfer function by using either time domain input-output data or frequency response data, which might be experimentally obtained. Part ii) is the CDM synthesis of classical controller such as PID, Lead/Lag compensators. In part iii), the analysis of robustness of overall system can be dealt with. This tool allows us to analyze completely most of robustness issues with respect to the interval uncertaintyncertainty

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.233-233
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• 2000

Direct torque control (DTC) scheme provides a very quick torque response without the complex field-orientation block and inner current regulation loop. DTC is known as an appropriate scheme for high power induction motet drives because it can be used at lower switching frequency. There are two major drawbacks with the application of DTC schemes : one is large current harmonics due to flux drooping in a low speed range, the other is that the inverter switching frequency is varying according to motor parameters and operating speed. Switching devices in the power electronics drives should be supported for relatively high switching frequency. In this paper, a P-type fuzzy controller to realize the variable switching sector scheme and a PID-type fuzzy switching frequency regulator are adopted. A meaningful contribution of this paper is to propose a simple realization scheme of the fuzzy switching frequency regulator. Simulation results show the effectiveness of those propositions.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.318-318
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• 2000

Current signal square based on switch current is presented in this article. This is the new technique that can design current signal square circuit by using switch-current memory cell, current square and sample and hold technique, which have been presented by the general switch-current. This principle which is present have the good electrical characteristics such as the low input impedance, high output impedance and high frequency response. The system can also operate in the audio frequency range to the high frequency current signal. The system application of this technique can be apply to the current signal multiplier by quarter square technique. The experimental results agree well with the theory as high accuracy and linearity.

• Communications for Statistical Applications and Methods
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• v.9 no.1
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• pp.141-154
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• 2002

Foreign investors'shares and their influences on the Korean stock market have never been larger and greater before since the market was completely open to foreign investors in 1992 Quantitatively and qualitatively as well, as a result, changes in the patterns of foreign investments have caused enormous effects on the interactions of major macroeconomic indices of the Korean economy. This paper is intended to investigate the causal relations of the four variables, foreigners'buy-sell ratios, stock returns, ￦/＄ exchange rates and $\yen$/＄ exchange rates, over the two time periods of the pre-IMF (1996.1.1-1997.8.15) and the post-IMF (1997.8.16-2000.6.15) based on the daily data of the variables. Granger Causality Test, Forecast Error Variance Decomposition(FEVD) using VAR model and Impulse Response Function were implemented for the empirical analysis.

• Childhood Kidney Diseases
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• v.4 no.2
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• pp.166-169
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• 2000

Tubulointerstitial nephritis and uveitis (TINU) is a rare syndrome of unknown etiology involving the kidney and the eye. This is the first case reput of TINU in Korea. The diagnosis of TINU was confirmed in a 15-year-old girl on the basis of pathologically proven tubulointerstitial nephritis and bilateral uveitis. Although the renal symptoms disappeared spontaneously, uveitis showed only partial response to topical steroid treatment and persisted fir more than 11 months. TINU should be included in the differential diagnosis of tubulointerstitial nephritis of unknown etiology.

• Journal of KSNVE
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• v.10 no.6
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• pp.949-954
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• 2000

Applicability of the vibration signal phase for predicting the modal damping properties of structures is investigated. For uniform plates with different internal damping levels, the phase delay as a function of the frequency span as well as a function of the distance between the excitation and response measurement points are experimentally obtained. Dependence of the phase characteristics on the amount of structural damping is elucidated -more heavily damped plate shows notably reduced phase delay at intermediate distances. The experimental results compare favorably with analytical predictions, and show much promise for further refinement as a tool for estimating structural properties.

• Journal of KSNVE
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• v.10 no.6
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• pp.977-984
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• 2000

Vibration of disk drive spindle is one of the major limiting factors in achieving higher track densities in hard disk drives. Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. In this paper, radial magnetic forces for symmetric and asymmetric BLDC motor are calculated with respect to the various rotor eccentricity using analytic method. Based on the results of the radial magnetic forces, transient whirl responses of the spindle motor are analyzed using finite element and transfer matrices. Results show that an asymmetric motor has a worse effects on unbalanced magnetic forces and vibration when mechanical and magnetic coupling exists.

• Journal of KSNVE
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• v.10 no.6
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• pp.1041-1047
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• 2000

The main objectives of this study are to examine the random response of a vibration absorber system with autoparametric coupling in the neighborhood of internal resonance by Gaussian closure and to compare the results with those obtained by Monte Carlo simulation. The numerical simulation is found to support the main features of the nonlinear modal interaction in the neighborhood of internal resonance conditions. While the Gaussian closure exhibits regions of multiple solutions in the neighborhood of internal resonance, the numerical simulation gives only one solution depending on the assigned initial conditions. The on-off intermittency phenomena of the cantilever mode is observed in the Monte Carlo simulation over a small range of parameter.

• Journal of Korean Society for Quality Management
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• v.28 no.2
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• pp.57-69
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• 2000

This paper discusses the local influence approach to the linear regression models with AR(2) errors. Diagnostics for the linear regression models with AR(2) errors are proposed and developed when simultaneous perturbations of the response vector are allowed- That is, the direction of maximum curvature of local influence analysis is obtained by studying the curvature of a surface associated with the overall discrepancy measure.