• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.255-257
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• 1995

In this paper, a new speed estimation method of induction motors based on the very quick torque control is proposed to realize speed sensorless control. The proposed method can be realized very simply by detecting primary motor current and voltage command at every sampling time. As the method need not the differential value of primary current in a arithmetic of voltage command, it can be expected to promote the precision of speed estimation in low speed area, especially. Through the numerical simulation, the validity of the proposed method was successfully confirmed.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.3
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• pp.42-55
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• 1999

A mathematical model for biological nutrient removal in a sequencing batch reactor process, which is based on the IAWQ Activated Sludge Model No. 2 with a few modifications, has been developed. Twenty water quality components and twenty three kinetic equations are incorporated in the model. The model is structured in the matrix form based on the law of mass conservation using stoichiometry and kinetic equations. Stoichiometric coefficients and kinetic parameters included in the model equations are chosen from the literature. A multistep predictor-corrector algorithm of variable step-size is adopted for solving the vector nonlinear ordinary differential equations. The simulation for experimental results is conducted to evaluate the validity of the model and to calibrate coefficients and parameters. The simulation using the model well represents the experimental results from laboratory. The mathematical model developed in this study may be utilized for the design and operation of a sequencing batch reactor process under the steady and unsteady-state at various environmental conditions.

• Honam Mathematical Journal
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• v.43 no.3
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• pp.373-383
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• 2021

In this study, a numerical method deals with the Chebyshev wavelet collocation and Adomian decomposition methods are proposed for solving Korteweg-de Vries equation. Integration of the Chebyshev wavelets operational matrices is derived. This problem is reduced to a system of non-linear algebraic equations by using their operational matrix. Thus, it becomes easier to solve KdV problem. The error estimation for the Chebyshev wavelet collocation method and ADM is investigated. The proposed method's validity and accuracy are demonstrated by numerical results. When the exact and approximate solutions are compared, for non-linear or linear partial differential equations, the Chebyshev wavelet collocation method is shown to be acceptable, efficient and accurate.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.2
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• pp.92-98
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• 2019

Accurate estimation of motor parameters is required in some motor control applications. For example, the value of stator resistance is required for stator flux-oriented control mostly used in doubly fed induction generator systems. Stator resistance is not a constant value and continuously changes due to the rise in temperature during motor operation. Estimation errors degrade the control performance. Hence, this study proposes a simple stator resistance estimation method. In this scheme, the differential components of voltage and current values are used to eliminate the dead-time effect, and Kalman filter algorithm is applied to reduce the error according to measurement noise. Simulation and experimental results obtained with a permanent magnet motor show the validity of the proposed algorithm.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.46-51
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• 2017

Recent controller design techniques often discretize the target system and implement a discrete controller that is digitized to match the target system. When constructing such a discrete system, it is necessary to first determine the sampling time. The smaller the sampling time is, the more advantageous it can be made similar to the original system, but the cost is a problem when realizing such a configuration as hardware. On the other hand, the longer the time, the more different the system is from the original system, and eventually the control becomes impossible. In this paper, we consider the above problem and propose a more logical approach to determine the sampling time in the discrete system and investigate the relation with the differential controller. We also apply this process to a nonlinear system called ARAGO disc and verify its validity through computer simulation.

• Journal of Korean Association for Spatial Structures
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• v.21 no.2
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• pp.89-97
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• 2021

This paper describes an adaptive hybrid evolutionary firefly algorithm for a topology optimization of truss structures. The truss topology optimization problems begins with a ground structure which is composed of all possible nodes and members. The optimization process aims to find the optimum layout of the truss members. The hybrid metaheuristics are then used to minimize the objective functions subjected to static or dynamic constraints. Several numerical examples are examined for the validity of the present method. The performance results are compared with those of other metaheuristic algorithms.

• Journal of the military operations research society of Korea
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• v.13 no.1
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• pp.1-18
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• 1987

This paper presents several adaptive linear predictive coding techniques based upon extension of recursive ladder filters. A 2-D recursive ladder filter is extended to a 3-D case which can adaptively track the variation of both spatial and temporal changes of moving images. Using the 2-D/3-D ladder filter and a previous farme predictor, two types of adaptive predictor-control schemes are proposed in which the prediction error at each pel can be obtained at or close to a minimum level. We also investigate several modifications of the basic encoding methods. Performance of the 2-D/3-D ladder filters, their adaptive control schemes, and variations in coding methods are evaluated by computer simulations on a real sequence and compared to the results of motion compensation and frame differential coders. As a validity test of the ladder filters developed, the error signals for the different predictors are compared and evaluated.

• Journal of Sasang Constitution and Immune Medicine
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• v.33 no.3
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• pp.54-71
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• 2021

Objectives The purpose of this study was to revise Sasang Digestive Function Inventory (SDFI) and improve its validity and reliability using clinical data. Methods The Sasang type and Cold-Heat pattern differentiation by certified clinical specialist and responses to SDFI items were acquired from 419 hospital patients. The revision of SDFI was performed using item analysis and Explorative Factor Analysis (EFA). Furthermore, the validity and reliability of the revised SDFI (rSDFI) were investigated using Confirmatory Factor Analysis (CFA), Internal Consistency and Item Response Theory (IRT). And, clinical significance of the rSDFI was examined for the differentiation of Sasang types and Cold-Heat patterns. Results The number of the SDFI items were modified from 21 to 15. And, the validity and reliability of the rSDFI subscale structure were found to be acceptable. The scores of rSDFI-total and rSDFI-E significantly decreased in the order of Tae-Eum (TE), So-Yang (SY), So-Eum (SE) types, and the rSDFI score of SE type was significantly lower than that of TE and SY types. The rSDFI-total score could differentiate Cold-Heat pattern in both SY and SE types. And the difference of digestive function between Cold and Heat pattern of SE type could be explained with the rSDFI-D score. The rSDFI-total score in Cold pattern significantly decreased in the order of TE, SY, and SE types, and the rSDFI-total score of TE type is significantly higher than that of SE type in Heat pattern. Conclusions Current results demonstrated the reliability, validity and clinical usefulness of the rSDFI in clinical patients. Therefore, rSDFI can be utilized as an objective clinical measure supporting the differential diagnosis of Sasang typology.

• The Journal of Internal Korean Medicine
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• v.25 no.4
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• pp.346-355
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• 2004

Background & Object : The aim of this study was to investigate the usefulness of electrogastrography on differential diagnosis of deficiency or excess Condition in patients with functional dyspepsia Methods : Selected symptoms for diagnosis of deficiency and excess in functional dyspepsia have been reviewed in some literatures, notably within Oriental medicine, Donguibogam and Gogeumdoseojipseong-uibujeolrok. This is what was investigated in this study. 93 patients (male 32, female 61) were divided into three groups; Non-pain group, Pre-treatment pain group (chief complain was abdominal pain at the first medical examination), and Mid-treatment pain group(they had no pain at the time of first medical examination, but showed abdominal pain within two weeks). 10 healthy people participated as normal controls. Gastric motility were recorded and analyzed using electrogastrography during fasting and postprandial period. In assessment, effectiveness was divided into validity, sensitivity and specificity. Results : Epigastric pain reflected the tendency for excess condition in comprehensive diagnosis, which was linked with postprandial arrhythmia in electrogastrography(p=0.001). Postprandial arrhythmia detected abdominal pain with a validity of 78.6%, a sensitivity of 79.2%, and a specificity of 78%(p<0.001). Conclusions : Results 1Tom Postprandial arrhythmia in electrogastrography support that the index of excess condition in the comprehensive diagnosis of symptoms is useful for patients with functional dyspepsia.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.1
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• pp.38-43
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• 1993

A Hybrid Finite Element Method(HFEM) is applied to solve the electrormagnetic scattering from multi-layered dielectric cylinders. An unbounde region is divided into local boundary regions where a practical differential equation solution is obtained, with the remaining unbounded region represented by a boundary integral equation. If sources, media inhomogeneities, and anisotropies are local, a surgace may be defined to enclose them. Therefore the integral region so defined is bounded, and differential techniques may be used there. Also, in the re- maining unbounded region a boundary integral equation may be formulated using only a simple free - space green's function. Therefore, The local boundary is represented by a boundary - value problem with boundary conditions and solved by the finite element method. The advantage of the proposed method is simple and efficient in the work of electromagnetic scattering. The validity of the results have been verified by comparing results of other method(boundary element method). Examples has been presented to calculate the scattered fields of lossy dielectric cylinders of arbitray cross section.