• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.251-256
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• 2018

In the case of a radar repeater that used for the trajectory tracking of a high-speed aircraft, it emits pulses of short width. For phase displacement of these signals a branch type phase shifter is used. The phase on the transmission line is changed by utilizing the variable reactance at the end of the displacement branch transmission line. Further, it is easy to control the high output signal, and there is an advantage that the insertion loss is not large even when the reactance fails. In this paper, we will discuss the fabrication test results of a 400 W class phase shifter that sequentially displaces the phase at $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $90^{\circ}$.

• Journal of IKEEE
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• v.24 no.3
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• pp.713-718
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• 2020

The method of measuring skin active points is a technique for obtaining a lot of biometric information because it is measured with convenience, low cost and non-invasive methods. In this paper, we used in a three electrode measure method that has the advantage of measuring the impedance of the APs under the skin. The impedance measuring method is well illustrated by a simple model of an equivalent electrical circuit that correlates well with experimental results. The characteristic frequencies of APs are about 15-30HZ higher than that of surrounding skin and the values of measured reactance are about 35-77KΩ smaller. This technology analyzed accurately and objectively the reactance and characteristic frequency of APs and the surrounding skin using a non-invasive measuring system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.329-338
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• 2001

In this paper, we designed microstrip patch antenna to enhance the weak point of general microstrip patch antenna that has narrow bandwidth and analyzed that. To reduce reactance in probe feed antenna, capacitive gap added to the patch. Using single patch and auxiliary wire, makes dual frequency resonant. So bandwidth is improved and gain also becomes higher. To verify with experiment, PCS band antenna is designed, fabricated. For PCS band antenna, bandwidth is 180 MHz in VSWR<1.5 and gain is 8.6 dBi.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.225-231
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• 2009

In this paper, it is shown that Carson's equation can still be applied for the calculation of the series reactance of transmission lines with no ground return current as well as the one with ground return. It is proved in the following method. First two voltage drop equations for three-phase three wire transmission line are derived, one without considering ground return and the other using Carson's equation. The impedance matrix of the two equations are different from each other. But if we put the condition of zero ground current, $I_a+I_b+I_c=0$, those two equations becomes the identical equations. Therefore even a transmission line is not grounded, its line parameters can still be obtained using the Carson's equation. It has been confused whether or not Carson's equation can be used for an ungrounded system. It is because where ever Carson's equation is shown in the book, it also says that the system has ground return current paths as a premise. It is also verified with EMTP studies on the test circuit.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.2
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• pp.65-72
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• 2001

This paper presents the design and test results of a 10kVA single phase HTS transformer which is operating at 77K. Double pancake windings with BSCCO -2223 HTS tape and GFRP cryostat with room temperature bore are used in the transformer. Four double pan cake windings were used in pancake windings are connected in parallel to conduct the secondary current of 45.4A. the rated voltages of each winding are 440/220V. Numerical calculation using Finite Element Method was used to evaluated the performance of each arrangement. Considering the magnetizing reactance, leakage reactance, electrical insulation and the circulating current in low voltage winding which had two windings in parallel, HLLH arrangement was finally chosen. Estimation of the AC loss, magnetizing loss and self field loss, in the design stage, where effects of perpendicular field and parallel field are considered. Room temperature bore type cryostat has been constructed and its heat loss was measured.

• Journal of Power Electronics
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• v.19 no.2
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• pp.580-590
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• 2019

The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG's controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.32-36
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• 2007

On the contrary of a conventional motor with very narrow air-gap. it is difficult to calculate the accurate magnetic field distribution and the performance of an air-cored superconducting motor by 2 dimensional analysis. which does not use high permeability material except outer machine shield. This paper aims to do analysis of magnetic field and force distribution from the 3 dimensional modelling of a 1MW class superconducting synchronous motor. Especially. the field coil composed of Bi-2223 high-temperature superconductor and the outer machine shield are modelled by finite element analysis software according to their structures and the self-inductance and Lorentz force are calculated based on the 3 dimensional magnetic field calculation. Moreover. the influence of an important parameter, synchronous reactance, has been analyzed on the machine performances such as voltage variation and output power.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1686-1696
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• 2022

The impedance matching circuit design technique based on the phasor plot introduced in this paper is based on the impedance triangle of electric circuit. It is a technique that designs through the construction of a phasor figure using the values given to the matching circuit design. The design pattern is based on L-type, inverted L-type, T-type, and 𝜋-type, and unknown reactance elements are determined through phasor shapes. In this paper, using a design by phasor plot, we design several cases, such as the case where the input and output ports are pure resistance and have reactance. It was confirmed that the design value was verified by serial-parallel equivalent conversion to achieve matching. This design technique can immediately grasp the phase or size of input/output power, so it is expected to be applied mainly in a low frequency band due to rapid design change and application.

• Fashion & Textile Research Journal
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• v.26 no.3
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• pp.239-250
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• 2024

This study aims to investigate the factors influencing donation intention when the option to donate is presented during a purchase decision. Through an experimental design, we examined how price differences and reference group effects impact donation intention. We created stimuli with three price difference conditions (high, low, and control) and two levels of referent power (high and low), and involved 480 Korean consumer panels in the experiments. After controlling for psychological reactance levels, a two-way MANCOVA confirmed the main effects of price difference and referent power but found no interaction effect between these variables. Notably, consumers were less likely to feel guilty for not selecting the donation option when its price was slightly higher than that of the non-donation option, compared to the scenario where the prices were the same. Additionally, consumers exposed to high referent power experienced greater irritation, guilt, and shame if they did not choose the donation option compared to the low referent power group. Multiple regression results showed that guilt significantly influenced the intention to purchase a donation option, whereas irritation and shame did not. These findings suggest that understanding situational factors such as price differences and referent power can help develop effective marketing strategies and encourage voluntary participation in donations.

• Tuberculosis and Respiratory Diseases
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• v.71 no.6
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• pp.431-437
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• 2011

Background: We tried to examine the small airway diseases which can be found early, in workers exposed to inorganic dusts. This is measured in normal breath by using the impulse oscillometry (IOS). Methods: The Pulmonary function test (forced vital capacit [FVC], forced expiratory volume in one second [$FEV_1$], forced expiratory flow between 25% and 75% of vital capacity [$FEF_{25-75}$]), IOS resistance (Rrs at 5, 10, 15, 20, 25, 35 Hz) and reactance (Xrs at 5, 10, 15, 20, 25, 35 Hz) were measured for 454 workers. The subjects were classified into 173 workers of normal (38.1%) and 281 patients with pneumoconiosis (61.9%). Results: There were significant differences between normal and patients with FVC ($3.82{\pm}0.61$ vs. $3.53{\pm}0.56L$), $FEV_1$ ($2.67{\pm}0.63$ vs. $2.35{\pm}0.48L$), and $FEF_{25-75}$ ($1.88{\pm}0.95$ vs. $1.47{\pm}0.80L/sec$) between groups (p<0.05). And as for IOS, there was no significant difference in resistance (Rrs) (p>0.05), and there were significant differences between normal and patients with reactance (Xrs) 15 Hz ($0.003{\pm}0.05$ vs. $-0.006{\pm}0.04kPa/L/s$), 20 Hz ($0.043{\pm}0.05$ vs. $0.031{\pm}0.04kPa/L/s$), and 35 Hz ($0.141{\pm}0.05$ vs. $0.131{\pm}0.05kPa/L/s$) between groups (p<0.05). Conclusion: We could find out that 15 Hz, 20 Hz, and 35 Hz values of reactance were significantly influenced by pneumoconiosis. When usefulness and reproducibility to carry out the IOS are considered, it is thought that in future work will be required to draw the reference values for normal Korean persons.