• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.238-241
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• 1996

New porous BaTiO$_3$ thermistors were fabricated using graphite powders (0 to 10 wt. %) and their porosities were in the range of 9.1% to 16.2%. As results of impedance analysis, it was confirmed that the pores affected the grain-boundary resistance and the bulk (grain interior) resistance was constant as about 25 $\Omega$ at room temperature. The magnitude of PTCR effect $(p_{max}/p)$ markedly increased from 3 orders to 7 orders without addition of any acceptor dopant such as Mn or Cr.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.3
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• pp.3-9
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• 1991

Validity and limitation of conventional methods for analyzing the characteristics of nonuniform transmission lines are discussed here. It is found that uniqueness of cal- culated input impedance of an exponential transmission line by employing conventional methods is not assured in general but only under secific conditions. And the calculated input impedance of an angled two-plane transmission line based on the conventional planar TEM mode devices from its rigorous solution.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.227-234
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• 2000

The human sensibility caused by the motion of an object grasped by a human operator is defined as kinesthetic sense of arm. Due to nonlinearity and ambiguity of human sense, there is no absolute standard for quantification of kinesthetic sense. In this research, a so-called 2-dimensional arm motion generator is developed to present various mechanical impedance (i.e., stiffness or damping) characteristics to a human arm. The kinesthetic words representing arm kinesthetic sense are selected and then the subject's satisfaction levels on these words for given impedance values are measured and processed by the SD method and factor analysis. In addition, the quantification method using neural network is proposed to take into account the individual difference between the mean sensibility and each subject's sensibility. Through this proposed algorithm, the sensibility of human motion described qualitatively can be converted into engineering data ensuring objectivity, reproducibility, and universality.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.200-202
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• 2006

A impedance model simulating the electrical characteristics of the Electrodeless fluorescent lamp operated at high frequency is proposed. The model is constructed from a two parameter equation which is derived based on a set of two measurements. This is a readily constructed and computer simulator oriented model which is suitable for a preliminary design of electronic ballasts. Simulated and experimental results are used to verify the analytical discussions, and moreover, an electronic ballast design example using the proposed model is presented to further demonstrate ist applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.4
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• pp.335-341
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• 1991

We derive the radiation field equation at the naar field region to analyse EMI by the rectangular horn antenna. The EMI loadk current calculated from the load current induced on the transmission line being close to the rectangular horn antenna using the field theory and the transmission line theory. We find the conditions minimizing the EMI from the load current transfer function of distance, frequency and impedances at sending and receiving end. The smaller sending end impedance, the larger EMI load current and the larger sending impedance, the smaller EMI load current.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.353-356
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• 2005

A loop RFID tag antenna and a dipole RFID antenna with a T-matching method have been designed. The characteristic of loop and dipole with T-matching antenna structures of RFID tag antennas have been studied. The impedance of different sizes of loop and dipole antenna structures are found. This paper shows parametric research of loop RFID antenna structure and RFID dipole antenna with T-matching method to match the impedance of commercially available RFID chips.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.182-187
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• 2018

A low profile asymmetrical fractal boundary patch antenna based on reactive impedance surface (RIS) and a mushroom unit cell (MUC) is proposed and studied for dual band operation. The sides of the square patch antenna are replaced with asymmetrical half circled fractal curves for circular polarization operation at patch mode band. The fractal patch antenna is loaded with MUC for dual band operation. The antenna radiation characteristics are investigated and illustrated with both simulated and experimental results in detail. The 10-dB return loss bandwidth are 8.48% (3.21-3.49 GHz) and 2.59% (2.30-2.36 GHz) at upper and lower resonance frequencies, respectively. The 3-dB axial ratio bandwidth is 4.26% (3.21-3.35 GHz). A close agreement between simulation data with experimental results is observed.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.375-380
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• 2004

This paper presents the basic quench protection idea for the HTS(High-Temperature Superconducting) cable. In Korea power system, the transfer capability of transmission line is limited by the voltage stability, and HTS cable could be one of the countermeasure to solve the transfer limit as its higher current capacity and lower impedance[1]. However, the quench characteristic of HTS cable makes HTS cable to loss its superconductivity, and therefore change the impedance of the line and power system operating condition dramatically. This pheonominum threats not only HTS cable safety but also power system security, therefore a proper protection scheme and security control counterplan have to be established before HTS cable implementation. In this paper, the quench characteristics of HTS cable for the fault current based on heat balance equation was established and a proper protection method by FCL(Fault Current Limiter) was suggested.

• Journal of information and communication convergence engineering
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• v.14 no.2
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• pp.65-70
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• 2016

This paper proposes and experimentally tests a modified circular slot antenna fed by a fork-like tuning stub for ultra-wideband (UWB) operation. The proposed antenna consists of a modified circular slot model and fork-like tuning stub. The proposed antenna is printed on a 34.0 mm × 30.0 mm FR4 substrate with thickness of 1.0 mm and relative permittivity of 4.4. The effect of various parameters of the circular slot and fork-like tuning stub is investigated for UWB operation. The modified circular slot and fork-like tuning stub are fabricated on the substrate to achieve wideband operation and good impedance matching. Experimental results demonstrated that the measured return loss exhibits an acceptable agreement with the simulated return loss and satisfies the -10 dB impedance bandwidth requirement while simultaneously covering the UWB bands. In addition, the proposed antenna shows good radiation characteristics and gains in the UWB bands.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1491_1492
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• 2009

The impedance of a vertical grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of thr vertical grounding electrode which shows the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertical grounding electrodes are calculated by using the distributed parameter circuit model. The adequacy of the simulations has been confirmed by comparing the simulated results with the measured results.