• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2D
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• pp.99-103
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• 2010

It is necessary to improve transfer impedance of express bus terminal users in order to increase the usage of public transportation. This study constructed a model for calculating transfer impedance based on bodily sensational transfer time in express bus terminal and calculated transfer impedance on major express bus terminals in Korea. The study results show that the addition of 100 meter exterior walking distance increases 3 minute travel time, 100 meter interior walking distance increases 5 minute travel time, 100 stairways increase 13 minute travel time, and escalators decreases 3 minute travel time. The calculated transfer impedance based on bodily sensational transfer time in this study can be utilized as objective criteria to compare transfer conditions of different bus terminals and to prioritize them for facility improvement. The calculated transfer impedance also can be used as facility guidelines for designing a new transit center.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.110-117
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• 1995

New formulas for the minimum noise figure and the optimum source impedance of microwave FETs are derived using the noise equivalent circuits obtained from the steady-state Nyquist theorem for multi-terminal semiconductor devices. The derived formulas manifest the relationships between the noise sources and the physical parameters of a noise equivalent circuit. Furthermore the formulas can explain the effect of gate leakage current on the minimum noise figure and the optimum source impedance. comparisons with the published experimental data confirm the validity and usability of our formula.

• Journal of electromagnetic engineering and science
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• v.8 no.1
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• pp.28-33
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• 2008

We have proposed a novel DVB-H(Digital Video Broadcast for Handheld) antenna for folder-type mobile handheld terminal by using a coupling element, a stub, and an L-type matching circuit. The L-type matching circuit consisting of two chip inductors is used for achieving an improved impedance matching over the DVB-H frequency band ($470{\sim}702\;MHz$). Simulated results showed the stub worked to more knot the lower and upper frequency ends of the input impedance curve. The antenna exhibits a flat gain characteristic from 2 to 2.8 dBi over the DVB-H frequency band. The radiation patterns are a stable Figure-of-eight radiation pattern in the frequency range.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.3
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• pp.1-5
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• 2011

In order to analyze the impedance properties of high integrated impedance network with multiple terminals, this paper introduces the concept of impedance relation matrix(IRM). The linear relation between the terminal voltages and currents is represented in the form of IRM and this matrix can be utilized to calculate the impedance between any two terminals. Furthermore, IRM representation for 2-port impedance network can be also defined. The whole impedance network is divided into the several 2-port sub-networks and each sub-network is analyzed in a form of the IRM representation. An illustrated example is given to show that the proposed method is simple and effective to analyze the impedance of a sensor array which has a very large number of impedance elements.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.6
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• pp.1-8
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• 1982

In this paper a new analytic method for Ladder networks by weighted tree is proposed. In contrast to conventional tree concept that represents only information structure, in this paper, a tree with hierarchical structure is established by giving wei체t of impedance Z and admittance Y to branch and representing each node of its branch as a pair of voltage and current. Then, by defining generation level from tree structure and by parsing between standand level and arbitrary level, driving point impedance, transfer function and transfer impedance are simultaneously obtained instead of complex calculation method by inspection. The validity of this method is proved by the reciprocal theorem and this method is applied to four-terminal constants and the feedback network.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.373-379
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• 2012

This paper presents a fault location algorithm based on the adaptively estimated value of the local sequence source impedance for faults on a parallel transmission line. This algorithm uses only the local voltage and current signals of a faulted circuit. The remote current signals and the zero-sequence current of the healthy adjacent circuit are calculated by using the current distribution factors together with the local terminal currents of the faulted circuit. The current distribution factors consist of local equivalent source impedance and the others such as fault distance, line impedance and remote equivalent source impedance. It means that the values of the current distribution factors can change according to the operation condition of a power system. Consequently, the accuracy of the fault location algorithm is affected by the two values of equivalent source impedances, one is local source impedance and the other is remote source impedance. Nevertheless, only the local equivalent impedance can be estimated in this paper. A series of test results using EMTP simulation data show the effectiveness of the proposed algorithm. The proposed algorithm is valid for a double-circuit transmission line system where the equivalent source impedance changes continuously.

• Journal of Power Electronics
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• v.18 no.1
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• pp.300-308
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• 2018

An online estimation method for wireless power transfer (WPT) systems is presented without using any measurement of the secondary side or the load. This parameter estimation method can be applied with a controlling strategy that removes both the receiving terminal controller and the wireless communication. This improves the reliability of the system while reducing its costs and size. In a wireless power transfer system with an LCCL impedance matching circuit under a rectifier load, the actual load value, voltage/current and mutual inductance can be reflected through reflected impedance measuring at the primary side. The proposed method can calculate the phase angle tangent value of the secondary loop circuit impedance via the reflected impedance, which is unrelated to the mutual inductance. Then the load value can be determined based on the relationships between the load value and the secondary loop impedance. After that, the mutual inductance and transfer efficiency can be computed. According to the primary side voltage and current, the load voltage and current can also be detected in real-time. Experiments have verified that high estimation accuracy can be achieved with the proposed method. A single-controller based on the proposed parameter estimation method is established to achieve constant current control over a WPT system.

• Journal of Power Electronics
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• v.16 no.1
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• pp.319-328
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• 2016

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.3 no.3
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• pp.2-13
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• 1966

The impedance characteristics of vertical antennas over a finite image plane were analyzed and measured. Two kinds of image plane, one rectangular and the other circular, were used for the mesurements. And the length of antennas was varied at fixed frequency. All kinds of terminal zone effects which possible raise questions because of antenna mounting system were discussed. It is observed from the results that the measured impedance of antennas over a comparativley large rectangular plane is approximatly identical with the theoretical value, and also the impedance of antennas over a comparatively small circular plane had similar characteristics to a comparatively thick antennas over an inifinite image plane.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.290-293
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• 2001

This paper presents the reach accuracy of a distance relay for protection of transmission line according to power system conditions. The apparent impedance of distance relay is considerably affected by source impedance, load current, power factor, fault point and resistance etc. For protective coordination on the variables power system parameters, trip characteristics of distance relay at sending and receiving terminal are discussed.