• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.11 s.254
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• pp.1401-1407
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• 2006

In a haptic interface system with a nanoscale virtual environment (NVE) using an atomic force microscope (AFM), impedance scaling is important. In order to explicitly derive the relationship between performance and impedance scaling factors, a nanoscale virtual coupling (NSVC) concept and a selection method of scaling factors of velocity (or position) and force are introduced. An available scaling factor region is represented based on Llewellyn's absolute stability criteria and the physical limitation of the haptic device. Experiments have been performed for tele-nanomanipulation tasks such as positioning, indenting and nanolithography with available force scaling factor in the NVE.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.201-205
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• 2005

This work presents a study on development of a practical and quantitative technique for assessment of the structural health condition by piezoelectric Impedance-based technique associated with longitudinal wave propagaation. The natural frequency of the object has a tendency of frequency shifting according to hole size corresponded to real structure crack and crack size. In order to estimate the damage condition numerically, we suggest the evaluation method of Impedance peak frequency shift hF in this paper.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.74_76
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• 2009

This paper presents a discrete wavelet analysis based algorithm to address the fault impedance calculation under transient state in radial power distribution networks. The fault impedances have been derived under different fault conditions. Furthermore, a recursive fault distance estimation method is proposed utilizing the measured fault impedance and power line parameters. The proposed scheme can resolve the errors caused by the non-homogeneous power lines, the presence of lateral loads since, the fault impedance will always be updated with the recursive form. For the verification of the proposed scheme, a filed test has been peformed with varying fault resistances in the 22.9(kV) radial system. Power meters and fault locators were installed at the substation. It was figured out that the performance of the discrete wavelet and the recursive scheme are very good even for high fault resistance condition.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.610-612
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• 2013

A novel balanced distributed amplifier (DA) was proposed using novel impedance transforming MEMS baluns. The impedance transforming MEMS balun is matched to $50{\Omega}$ at one input port and $25{\Omega}$ at two output ports. It is based on the electric field mode-change method, thus it is strongly independent of frequency and very compact. The novel balanced DA consists of two $25{\Omega}$-matched DAs and these are combined by $50{\Omega}$-to-$25{\Omega}$ baluns. Theoretically, it has two times wider bandwidth and power capability than the conventional DA. So as to verify the proposed concept, we designed and fabricated a conventional DA and the proposed one using 0.15-${\mu}m$ GaAs pHEMT technology.

• Journal of Electrical Engineering and Technology
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• v.7 no.1
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• pp.86-90
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• 2012

A two-dimensional nonlocal heating theory of planar-type inductively coupled plasma source has been previously reported with a filamentary antenna current model. However, such model yields an infinite value of electric field at the antenna position, resulting in the infinite self-inductance of the antenna. To overcome this problem, a surface current model of antenna should be adopted in the calculation of the electromagnetic fields. In the present study, the reactor impedance is calculated based on the surface current model and the dependence on various discharge parameters is studied. In addition, a simpler method is suggested and compared with the surface current calculation.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.123-128
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• 2004

In electrical impedance tomography (EIT), the internal resistivity distribution of the unknown object is computed using the boundary voltage data induced by different current patterns using various reconstruction algorithms. This paper presents a new image reconstruction algorithm based on the genetic algorithm (GA) via a two-step approach for the solution of the EIT inverse problem, in particular for the reconstruction of "static" images. The computer simulation for the 32 channels synthetic data shows that the spatial resolution of reconstructed images in the proposed scheme is improved compared to that of the modified Newton-Raphson algorithm at the expense of an increased computational burden.rden.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.329-334
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• 2016

In this paper, we demonstrate a Non-Foster matching method for an electrically small antenna to improve the signal-to-noise ratio (SNR) of communication link. For the experiment, we used a general FM antenna whose resonance frequency is about 52-57 MHz and a floating type Linvill negative impedance converter(NIC)-based circuit as a Non-Foster matching element. By implementing the Non-Foster circuit to cover FM band, we can achieve a wide bandwidth matching covers 40-200 MHz. Our measurement shows 3-7 dB improvement of SNR for the same bandwidth though there are several spikes which means no improvement of SNR in the band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.860-863
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• 2005

This work presents a study on development of a practical and quantitative technique for assessment of the structural health condition by PZT impedance-based technique associated with longitudinal wave propagation. The bolt fastening condition is adjusted by torque wrench In order to estimate the damage condition numerically, we suggest the evaluation method of impedance peak frequency shift $\Delta$F in this paper.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.3
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• pp.53-64
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• 2007

Considering a sinusoidally varying blood pressure In left ventricle in Cho - Kensey's Windkessel model, we expressed the impedance elements in terms of the phase differences among the pressure and flow rates in the artery and the peripherical tubes. The relationships were further simplified for the real human cardiac system. We expect that the results would give some valuable information for examination and treatment in oriental medicine as well as in western medicine.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.677-679
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• 1996

This paper describes a method to improve the speed of a distance relay based on a differential equation of transmission lines using feedforward artificial neural networks (ANN) on an EHV system. For the impedance calculation an integration approximation to the differential equation is used and then an ANN is trained with the impedance convergence characteristic. The ANN predicts the fault distance with some calculated resistances and reactances before they reach trip zone. Thus, the proposed method can improve the speed of distance relays, significantly if a high sampling rate such as 48 samples per cycle is employed.