• 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.211-211
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• 2000

The multiple targets tracking problem has been one of main issues in the radar applications area in the last decade. Besides the standard Kalman filtering, various methods including the variable dimension filter, input estimation filter, interacting multiple model (IMM) filter, federated variable dimension filter with input estimation, probable data association (PDA) filter etc. have been proposed to address the tracking and sensor fusion issues. In this paper, two existing tracking algorithms, i.e. the IMMPDA filter and the variable dimension filter with input estimation (VDIE), are combined for the purpose of improving the tracking performance of maneuvering targets in clutter. To evaluate the tracking performance of the proposed algorithm, three typical maneuvering patterns i.e. Waver, Pop-Up, and High-Diver motions, are defined and are applied to the modified IMMPDA filter considered as well as the standard IMM filter. The smaller RMS tracking errors, in position and velocity, of the modified IMMPDA filter than the standard IMM filter are demonstrated through computer simulations.

• Journal of the Korea Fashion and Costume Design Association
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• v.4 no.2
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• pp.31-45
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• 2002

The purpose of this study was designed to investigate if self-monitoring variable among various individual trait theories and demographic variable would be variables which can explain about the importance differences of consumer service level of retailing in the garment product. The survey was conducted from Feb, 6 to 16, 2002. For this survey, the 118 data were analysed with spss window 9.0 version and Cronbach's, Factor analysis, one-way ANOVA, Duncan test, Frequency, mean, percentage were applied. The results of this study were as follows; 1. Consumer service was classified in attitude/confidence/expert knowledge of salesperson, product display, product information, product assortment, shopping environment, lighting setup. 2. As a result of analyzing the importance differences per consumer service dimension depending on self-monitoring levels, it was not significant differences. 3. As a result of analyzing the importance differences per consumer service dimension depending on demographic variables, it was not significant differences.

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.205-212
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• 2006

Three-dimensional numerical study was carried out for the investigation of the detonation wave structures propagating in tubes. Fluid dynamics equations and conservation equation of reaction progress variable were analyzed by a MUSCL-type TVD scheme and four stage Runge-Kutta time integration. Chemical reaction was modeled by using a simplified one-step irreversible kinetics model. The variable gas properties between unburned and burned states were considered by using variable specific heat ratio formulation. The unsteady computational results in three-dimension show the detailed mechanisms of rectangular and diagonal mode of detonation wave instabilities resulting same cell length but different cell width in smoked-foil record. The results for the small reaction constant shows the spinning mode of three-dimensional detonation wave dynamics, which was rarely observed in the previous numerical simulation of the detonation waves.

• Communications for Statistical Applications and Methods
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• v.10 no.1
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• pp.239-246
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• 2003

Statisticians, or data miners, are often requested to assess the importances of input variables in the given supervised learning model. For the purpose, one may rely on separate ad hoc measures depending on modeling types, such as linear regressions, the neural networks or trees. Consequently, the conceptual consistency in input variable importance measures is lacking, so that the measures cannot be directly used in comparing different types of models, which is often done in data mining processes, In this short communication, we propose a unified approach to the importance measurement of input variables. Our method uses sensitivity analysis which begins by perturbing the values of input variables and monitors the output change. Research scope is limited to the models for continuous output, although it is not difficult to extend the method to supervised learning models for categorical outcomes.

• 전기의세계
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• v.30 no.6
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• pp.375-385
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• 1981

New algorithms are derived for nonlinear programming problems which are characterized by their large variables and equality and inequality constraints. The algorithms are based upon the introduction of the Dependent-Variable-Elimination method, Independent-Variable-Reduction method, Optimally-Ordered-Triangular-Factorization method, Equality-Inequality-Sequential-Satisfaction method, etc. For a case study problem relating to the optimal determination of load flow in a 10-bus, 13-line sample power system, several approaches are undertaken, such as SUMT, Lagrange's Multiplier method, sequential applications of linear and quadratic programming method. For applying the linear programming method, the conventional simplex algorithm is modified to the large-system-oriented one by the introduction of the Two-Phase method and Variable-Upper-Bounding method, thus resulting in remarkable savings in memory requirements and computing time. The case study shows the validity and effectivity of the algorithms presented herein.

• Journal of the Korean Professional Engineers Association
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• v.16 no.4
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• pp.4-14
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• 1983

when one is designing a continuous bridge with variable cross sections, it is very troublesome to integrate explicitly load terms and various factor under consideration so that it has different moment of inertia at each cross section. In this paper to obtain the influence line of a arbitary-span continuous beam with variable cross sections, the value of some particular function due to a load at any point can be carried out by numerical integration instead of definite integral. The ordinate of the influence line equals the product of the magnitude of the final moment at each support due to unit moment at any support and the load terms due to unit load, measured at the point of application of the load. It is concluded that this method can be easily used to design continuous bridges with arbitary cross sections.

• Journal of the Korean Data and Information Science Society
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• v.28 no.2
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• pp.443-449
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• 2017

Estimation of population proportion like the distribution rate of LED TV and the prevalence of a disease are often estimated based on survey sample data. Population proportion is generally considered as a special form of population mean. In complex sampling like stratified multistage sampling with unequal probability sampling, the denominator of mean may be random variable and it is estimated like ratio estimator. In this research, we examined the estimation of distribution rate based on stratified multistage sampling, and determined some numerical outcomes using stratified random sample data with about 25% of missing observations. In the data used for this research, the survey weight was determined by deterministic way. So, the weights are not random variable, and the population distribution rate and its variance estimator can be estimated like population mean estimation. When the weights are not random variable, if one estimates the variance of proportion estimator using ratio method, then the variances may be inflated. Therefore, in estimating variance for population proportion, we need to examine the structure of data and survey design before making any decision for estimation methods.

• ETRI Journal
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• v.28 no.3
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• pp.386-388
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• 2006

Monolithic SiGe heterojunction bipolar transistor (HBT) variable gain amplifiers (VGAs) with a feedforward configuration have been newly developed for 5 GHz applications. Two types of the feedforward VGAs have been made: one using a coupled-emitter resistor and the other using an HBT-based current source. At 5.2 GHz, both of the VGAs achieve a dynamic gain-control range of 23 dB with a control-voltage range from 0.4 to 2.6 V. The gain-tuning sensitivity is 90 mV/dB. At $V_{CTRL}$= 2.4 V, the 1 dB compression output power, $P_{1-dB}$, and dc bias current are 0 dBm and 59 mA in a VGA with an emitter resistor and -1.8 dBm and 71mA in a VGA with a constant current source, respectively.

• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.131-150
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• 2006

Exact analytical solutions for in-plane static problems of planar curved beams with variable curvatures and variable cross-sections are derived by using the initial value method. The governing equations include the axial extension and shear deformation effects. The fundamental matrix required by the initial value method is obtained analytically. Then, the displacements, slopes and stress resultants are found analytically along the beam axis by using the fundamental matrix. The results are given in analytical forms. In order to show the advantages of the method, some examples are solved and the results are compared with the existing results in the literature. One of the advantages of the proposed method is that the high degree of statically indeterminacy adds no extra difficulty to the solution. For some examples, the deformed shape along the beam axis is determined and plotted and also the slope and stress resultants are given in tables.