• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.430-434
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• 2002

Recently, lot of researchers pay attention to custom power equipments for power quality improvement, especially, voltage stabilization equipment using PWM AC-AC converter. In this paper, voltage regulation system with PWM Buck-Boost AC-AC converter is proposed and then the system is modelled and analyzed by using of Circuit DQ transformation whereby steady state characteristics such as equations for voltage gain and power factor are obtained. The equations become guide line for system design by showing the effect on system operations. Finally, some experiment will show validity of analysis.

• Steel and Composite Structures
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• v.12 no.2
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• pp.129-147
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• 2012

In this paper, the thermal buckling analysis of rectangular composite laminated plates is investigated using the Differential Quadrature (DQ) method. The composite plate is subjected to a uniform temperature distribution and arbitrary boundary conditions. The analysis takes place in two stages. First, pre-buckling forces due to a temperature rise are determined by using a membrane solution. In the second stage, the critical temperature is predicted based on the first-order shear deformation theory. To verify the accuracy of the method, several case studies were used and the numerical results were compared with those of other published literatures. Moreover, the effects of several parameters such as aspect ratio, fiber orientation, modulus ratio, and various boundary conditions on the critical temperature were examined. The results confirm the efficiency and accuracy of the DQ method in dealing with this class of engineering problems.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.27-32
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• 2006

In this paper, a new scheme of current programmed control for three phase PWM AC-AC converter is presented. Compared to duty-ratio voltage control, current programmed control has several advantages such as reduction of system order, inherent current protection and robust output. By considering only the magnitude components, a similar scheme in the DC-DC converter can be extended to the three phase PWM AC-AC converter. The proposed current programmed control will be well adopted into various converter topologies though three phase PWM AC-AC boost converter is treated as an example. The converter analysis is carried out by applying the vector DQ transformation to obtain physical insight into the converter operation and to establish some important characteristic equations for control purpose. The experiment results show the validity of the proposed scheme.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1114-1116
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• 2003

Voltage sags are known as a serious problem causing mal-operation of equipment like computers, process controllers and adjustable-speed drives. In this paper, characterization of voltage sag and an overview of methods used in the mitigation of voltage sags are presented. Moreover a fast detection method for voltage disturbances is explored. The algorithm is based on the theory that allows a set of three-phase voltages be converted the d-q value. The utility input voltages are sensed and then converted to some quantities in the d-q transformation. And the difference between reference value and input value are showed that some disturbances happened in the system.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1637-1649
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• 2017

This paper describes an intensive analysis of a harmonic identification algorithm in non-ideal voltages source systems. The dq-axis Fourier with a positive sequence voltage detector (DQFP) is a novel harmonic identification algorithm for active power filters. A compensating current control system based on repetitive control is presented. A design and stability analysis of the proposed current control are also given. The aim of the paper is to achieve a robustness of the harmonic identification in a distorted and unbalanced voltage source. The proposed ideas are supported by a hardware in the loop technique based on a $eZdsp^{TM}$ F28335 and the Simulink program. The obtained results are presented to demonstrate the performance of the harmonic identification and the control strategy for the active power filter in non-ideal systems.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.79.1-79.1
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• 2003

Aster scaber T. (Asteraceae) has been used in traditional Korean and Chinese medicine to treat bruises, snakebites, headaches and dizziness. (-) 3,5-Dicaffeoyl-muco-quinic acid (DQ) isolated from Aster scaber induced neurite outgrowth in PC12 cells. It has been reported that the activation of the extracellular signal regulated kinase1/2 (Erk 1/2) and phosphoinositide 3 (P13) kinase plays a crucial role in the NGF-induced differentiation of PC12 cells. This study showed that the effect of DQ on neurite outgrowth is mediated via the Erk 1/2 and PI3 kinase-dependent pathways like NGF. (omitted)

• Bulletin of the Korean Mathematical Society
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• v.60 no.4
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• pp.1071-1083
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• 2023

The main motivation of this paper is to introduce and study the notions of strong Dedekind rings and semi-regular injective modules. Specifically, a ring R is called strong Dedekind if every semi-regular ideal is Q₀-invertible, and an R-module E is called a semi-regular injective module provided Ext¹_R(T, E) = 0 for every 𝓠-torsion module T. In this paper, we first characterize rings over which all semi-regular injective modules are injective, and then study the semi-regular injective envelopes of R-modules. Moreover, we introduce and study the semi-regular global dimensions sr-gl.dim(R) of commutative rings R. Finally, we obtain that a ring R is a DQ-ring if and only if sr-gl.dim(R) = 0, and a ring R is a strong Dedekind ring if and only if sr-gl.dim(R) ≤ 1, if and only if any semi-regular ideal is projective. Besides, we show that the semi-regular dimensions of strong Dedekind rings are at most one.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.121-127
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• 2016

We propose a algorithm to calculate power factor of fundamental waveform in an environment where the voltage and current have been distorted by harmonics. In the proposed power factor computation algorithm, voltage and current are converted to rotating DQ reference frame, and power factor is calculated from active power and reactive power. We compare the proposed method with the conventional power factor measurement method as mathematically. In a condition that voltage and current are distorted by harmonics, the proposed method accurately measure the power factor of fundamental wave, and it is confirmed by simulation using MATLAB. If the proposed power factor measurement method is applied to an automatic power factor control system, a power factor compensation performance can be maximized in harmonic distortion environment. As a result, it is possible to reduce electricity prices, reduce line loss, increase load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

• Journal of IKEEE
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• v.22 no.2
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• pp.258-265
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• 2018

This paper proposes an algorithm for reducing the starting current when the single-phase induction motor starts and analyzes its operation. Generally, the single-phase induction motors require several starters to generate the starting torque due to their structural characteristics. In this paper, a capacitor-start / capacitor-run method of the single-phase induction motor is basically adopted. This conventional method is efficient and has a large starting torque, but it generates about 5 ~ 6 times of inrush current at startup. As a result, the freezer starting device and peripheral devices are damaged and life time may be reduced. To reduce the inrush current, the current control algorithm based on the virtual dq model is presented to control the starting current. In addition, it validates the proposed algorithm through experiments to smooth transit from start-up operation to the rated operating region.

• Korean Journal of Plant Resources
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• v.29 no.1
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• pp.20-25
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• 2016

Five caffeoylquinic acids of Aster altaicus var. uchiyamae Kitamura (Compositae) leaves were identified using standard compounds by HPLC and determined as follows: 3,4-di-O-caffeoylquinic acid (4.92 ± 0.06 ㎎/g dried weight), 3,5-di-O-caffeoylquinic acid (3.95 ± 0.13 ㎎/g), 4,5-di-O-caffeoylquinic acid (1.39 ± 0.10 ㎎/g), 5-O-caffeoylquinic acid (chlorogenic acid, 8.05 ± 0.21 ㎎/g), 3-O-caffeoylquinic acid (4.97 ± 0.18 ㎎/g). The total content of five caffeoylquinic acids were calculated as 26.73 ± 0.26 ㎎/g dried weight while the percentage of the five compounds in the MeOH extract was calculated as 25.22 ± 0.25%. The IC₅₀ value of the MeOH extract scavenging peroxynitrite (ONOO⁻) was shown as 5.16 ± 0.15 ㎍/㎖.