• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1058-1065
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• 2015

This paper present a current predicting control method for PMSM (permanent magnet synchronous motor) to improve the tracking performance of stator current, which regards the current vector as the control target. Solving the model state equation in the static frame (α-β frame), the dynamic change of current vector will be gained as three independent terms. These change terms, which contain the prediction of current vector, are discretized and simplified by Taylor series expansion and used to get the voltage vector as the predictive control quantity. SVPWM will transform the control voltage to the switching signal of inverter, which is newly deduced for the current vector. Simulation and experiment results are given to testy and verify the performance of this method.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.2
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• pp.93-101
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• 2016

This paper presents the results obtained using time-series-based methods for structural damage assessment. The methods are applied to a wind turbine blade structure subjected to fatigue loads. A 9 m CX-100 (carbon experimental 100 kW) blade is harmonically excited at its first natural frequency to introduce a failure mode. Consequently, a through-thickness fatigue crack is visually identified at 8.5 million cycles. The time domain data from the piezoelectric active-sensing techniques are measured during the fatigue loadings and used to detect incipient damage. The damage-sensitive features, such as the first four moments and a normality indicator, are extracted from the time domain data. Time series autoregressive models with exogenous inputs are also implemented. These features could efficiently detect a fatigue crack and are less sensitive to operational variations than the other methods.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.7
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• pp.1139-1152
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• 1997

Clothing consumption expenditure (UX) data of Korean consumers during the period of 1965 to 1993 were analyzed by time series analysis technique. According to the results of regression analysis, current income and UX of the year before showed most significant influences on the current UX. This means that the absolute and permanent income hypotheses can be accepted in case of clothing expenditures. However the effect of income decreased as the economy developed. The relative price of clothing had weak or no influence on clothing expenditures. It was also found out that CSX of the year before, the change of income, relative price of clothing ware the factors that affected clothing expenditures. From the estimation of Houthakker-Taylor state adjustment model, a negative stock coefficient was obtained. That is, clothing is subject to an inventor effect and Korean consumers regard clothing as one of the durable goods. To define whether clothing is a "luxury" or a "necessity", income and relative price elasticity of clothing expenditures were estimated. Income elasticity of clothing is slightly below 1.0 in case of national aggregate expenditures, and slightly above 1.0 in case of urban consumers' expenditures. Income elasticity has declined over time. Meanwhile the coefficient of price elasticity is not significant, indicating that the relative price of clothing have little connection with clothing expenditure.lothing expenditure.

• Journal of The Korean Astronomical Society
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• v.48 no.2
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• pp.139-154
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• 2015

We carry out three-dimensional hydrodynamic simulations of the supernova remnants (SNRs) produced inside molecular clouds (MCs) near their surface using the HLL code (Harten et al. 1983). We explore the dynamical evolution and the X-ray morphology of SNRs after breaking through the MC surface for ranges of the explosion depths below the surface and the density ratios of the clouds to the intercloud media (ICM). We find that if an SNR breaks out through an MC surface in its Sedov stage, the outermost dense shell of the remnant is divided into several layers. The divided layers are subject to the Rayleigh-Taylor instability and fragmented. On the other hand, if an SNR breaks through an MC after the remnant enters the snowplow phase, the radiative shell is not divided to layers. We also compare the predictions of previous analytic solutions for the expansion of SNRs in stratified media with our onedimensional simulations. Moreover, we produce synthetic X-ray surface brightness in order to research the center-bright X-ray morphology shown in thermal composite SNRs. In the late stages, a breakout SNR shows the center-bright X-ray morphology inside an MC in our results. We apply our model to the observational results of the X-ray morphology of the thermal composite SNR 3C 391.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.3
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• pp.52-61
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• 2012

The design method for cumulative sum (CUSUM) control charts, which can be robust to autoregressive moving average (ARMA) modeling errors, has not been frequently proposed so far. This is because the CUSUM statistic involves a maximum function, which is intractable in mathematical derivations, and thus any modification on the statistic can not be favorably made. We propose residual-based robust CUSUM control charts for monitoring autocorrelated processes. In order to incorporate the effects of ARMA modeling errors into the design method, we modify parameters (reference value and decision interval) of CUSUM control charts using the approximate expected variance of residuals generated in model uncertainty, rather than directly modify the form of the CUSUM statistic. The expected variance of residuals is derived using a second-order Taylor approximation and the general form is represented using the order of ARMA models with the sample size for ARMA modeling. Based on the Monte carlo simulation, we demonstrate that the proposed method can be effectively used for statistical process control (SPC) charts, which are robust to ARMA modeling errors.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.49-59
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• 2007

The purpose of this study is to investigate the seismic behavior of reinforced concrete bridge columns using shaking table tests. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. Solution of the equations of motion is obtained by numerical integration using Hither-Hughes-Taylor (HMT) algorithm. The proposed numerical method for the seismic behavior of reinforced concrete bridge columns using shaking table tests is verified by comparison with reliable experimental results.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.25-34
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• 2000

In this paper, we design a H^\infty servo controller for gauge control of tandem cold mill. To improve the performance of the AGC(Aotomatic Gauge Control) system based on the Taylor linearized model of tandem cold mill, the H^\infty servo controller is designed to satisfy robust stability, disturbance attenuation and robust tracking properties. The H^\infty servo controller problem is modified as an usual H^\infty control problem, and the solvability condition of the H^\infty servo problem depends on the solvability of the modified H^\infty control problem. Since this modified problem does not satisfied standard assumptions for the H^\infty control problem, it is solved by an LMI(Linear Matrix Inequality) technique. Consequently, the comparison between the H^\infty servo controller and the existing PID/FF(FeedForward) controller shows the usefulness of this study.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1215-1217
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• 2007

This paper is proposed a novel method to approximate the maximum power for a photovoltaic inverter system. It is designed for power systems application and utilities. The proposed Maximum Power Point Tracking(MPPT) control has the advantage to provide a new simple way to approximate the optimal or rated voltage, the optimal or rated current and maximum power rating produced by a solar panel and the photovoltaic inverter. And this straightforward method will be named linear reoriented coordinates method(LRCM) with the advantage that Pmax and $V_{op}$ can be approximated using the same variable as the dynamic model without using complicate approximations or Taylor series. This paper is proposed MPPT using LRMC method using weather condition of domestic moderate program technique. This paper is proposed the experimental results to verify the effectiveness of the new methods.

• Journal of Information Technology Application
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• v.3 no.3
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• pp.25-40
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• 2001

This paper deals with the problem of generating optimal polynomials using Genetic Programming(GP). The polynomial should approximate nonlinear response surfaces. Also, there should be a consideration regarding the size of the polynomial, It is not desirable if the polynomial is too large. To build small or medium size of polynomials that enable to model nonlinear response surfaces, we use the low order Tailor series in the function set of GP, and put the constrain on generating GP tree during the evolving process in order to prevent GP trees from becoming too large size of polynomials. Also, GAGPT(Group of Additive Genetic Programming Trees) is adopted to help achieving such purpose. Two examples are given to demonstrate our method.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.5
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• pp.1147-1154
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• 2021

The study aimed to investigate the impact of the microfinance program on loan borrowers' asset accumulation. In doing this, the study used descriptive and statistical methods to achieve the objectives. Primary data were collected from 192 respondents from Bangladesh using survey questionnaires. The data were analyzed using the multiple linear regression model. The result revealed that the majority of the borrowers said their assets such as farm, land, and livestock remained the same, which implies that microfinance borrowers still lag behind accumulating household assets. However, in the case of housing conditions and household appliances, there was a marginal increase. The regression result provides evidence that, among other factors, the amount of loan received from microfinance institutions and time duration with them is the most significant role-playing factor for borrower's sustainable well-being. The age and education level of borrowers are identified as positively related to asset accumulations, but not substantially so. Moreover, training provided by microfinance institutions is not effective and influential for microfinance borrowers' wealth accumulation, which is evidenced by the findings. This study's insights are worthwhile for any microfinance institution's decision-makers, development partners, and government to stress the shortcomings and accelerate the borrower's wealth status.