• Journal of Biomedical Engineering Research
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• v.13 no.2
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• pp.133-140
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• 1992

Bioelectrical Impedance method for measuring human body composition is based upon the principle that the electrical conductivity of the fat-free mass (FFM) is far greater than that of the (at. Deter- mination o( impedance was nlade in 30 healthy and obese men aged $40.9{\pm}14.7$yr (mean${\pm}$SD) and 25 healthy and obese women aged $44.0{\pm}10.2$ yr. A commercial impedance body fat analyzer was used with a four electrode arrangement that introduced a painless constant current(ImA at 50 kHz) into the body. Linear relationships were found between impudence values and FFM(r=-0.786) and between weight and FFM(r=0.837). Signigicant increases in the correlation coefficients were ob served when the predicator Hta/z was regressed against FFM(r=0.912) where Ht Is height and Z Is impedance. A linear regression equation, FFM=0.586(Htf/z) +0.317(Weight) -1.674(r=0.977), was found. The correlation coefficient of % body fat between the impedance and infrared methods was 0.898. These data Indicate that the bioelectrical impedance technique is a reliable and valld approach for the estimation of human body composition. This method Is safe, noninvasivr, prouides rapld measure menu, requires little operator skill and subject cooperation, and Os portable. Finally measurement of percent body fat was made possible using both the regression equation and a developed impedance measuring device which measures impedance between wrist and ankle.

• Corrosion Science and Technology
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• v.4 no.6
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• pp.217-221
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• 2005

In the present investigation, holographic interferometry was utilized for the first time to monitor in situ the thickness of the oxide film of aluminium samples during anodization processes in boric acid solutions. The anodization process (oxidation) of the aluminium samples was carried out by the technique of the electrochemical impedance spectroscopy(EIS), in different concentrations of boric acid (0.5-5.0% $H_3BO_3$) at room temperature. In the mean time, the real-time holographic interferometry was used to measure the thickness of anodized (oxide) film of the aluminium samples in solutions. Consequently, holographic interferometry is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film of the aluminium samples can be determined without any physical contact. In addition, measurements of electrochemical values such as the alternating current (A.C) impedance(Z), the double layer capacitance($C_{dl}$), and the polarization resistance(Rp) of anodized films of aluminium samples in boric acid solutions were made by the electrochemical impedance spectroscopy(EIS). Attempts to measure electrochemical values of Z, Cdl, and Rp were not possible by holographic interferometry in boric acid especially in low concentrations of the acid. This is because of the high rate of evolutions of interferometric fringes during the anodization process of the aluminium samples in boric acid, which made measurements of Z, Cdl, and Rp are difficult.

• 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.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.449-451
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• 2001

This study presents a study on modified algorithm to operating train simulation of AT feeding systems. In this study equivalent impedance is constructed by $Z_c,\;Z_r,\;Z_f,\;Z_{cr},\;Z_{rf},\;Z_{fc}$. The train current flows through the all auto-transformer corresponding to track impedance. To calculate train voltage from analyzing the railway systems, the algorithm is based on the K. C. L, K. V. L, superposition and circuit separation method. Multi-train's voltages are determined by calculating the catenary voltage at each train's position and adding up these train's voltage drop. Case studies use a field operational data, show that the proposed method is easily applied.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.223-224
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• 2011

This paper presents the method to design the inductor and capacitor value considering the ripple component that may be generated by three operating states of the Quasi Z source inverter at the impedance network. Based on the analysis of each operation mode, the equations of the capacitor voltage and inductor current are derived. In order to simplify the design processing, design equations of the impedance network are derived where the capacitor voltage and inductor current are lineared. The validity of the design method is verified with the simulation result using PSIM.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1195-1202
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• 2017

This paper presents a novel topology named a modified capacitor-assisted Z-source inverter (MCA-ZSI) based on the traditional ZSI. The impedance network of the proposed MCA-ZSI consists of two symmetrical cells coupled with two capacitors with an X-shape structure, and each cell has two inductors, two capacitors, and one diode. Compared with other topologies based on switched ZSI with the same number of components used at impedance network, the proposed topology provides higher boost ability, lower voltage stress across inverter switching devices, and lower capacitor voltage stress. The improved performances of the proposed topology are demonstrated in the simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.203-204
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• 2012

This paper presents the method to design the inductor and capacitor value considering the ripple component that may be generated by three operating states of the Quasi Z-source inverter at the impedance network. Based on the analysis of each operation mode, the equations of the capacitor voltage and inductor current are derived. In order to simplify the design processing, design equations of the impedance network are derived where the capacitor voltage and inductor current are lineared. The validity of the design method is verified with the simulation result using PSIM and experimental result using 32-bit DSP.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.123-130
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• 2013

This paper proposes the switched trans Z-source inverter(STZSI) which combined the characteristics of the trans Z-source inverter(TZSI) and the switched inductor Z-source inverter(SLZSI). The proposed STZSI has the same performance compared with the SLZSI which is improved the voltage boost performance of the conventional typical X-shaped ZSI, and it has advantage that circuit structure of Z-impedance network is more simple. And, in order to step up the voltage boost factor under the condition of the same duty ratio, unlike the SLZSI adding the inductors and diodes, the proposed method is dune by changing the turn ratio of trans primary winding of Z-impedance network. To confirm the validity of the proposed method, PSIM simulation and a DSP(TMS320F28335) based experiment were performed using trans with turn ratio 1 and 2 under the condition of the input DC voltage VI=50V, duty ratio D=0.1 and D=0.15. As a result, under the same input/ouput condition, the inverter arm voltage stress of the proposed method is reduced to about 15%-22% as compared with typical X-shaped ZSI, and the elements in Z-impedance network of the proposed method is reduced as compared with the SLZSI.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.129-137
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• 2015

The Cu(radius ra = $95{\mu}m$)/$Ni_{80}Fe_{20}$(outer radius $r_b$ = $120{\mu}m$) core/shell composite wire is fabricated by electrodeposition. The two diagonal components of impedance tensor for the Cu/$Ni_{80}Fe_{20}$ core/shell composite wire in cylindrical coordinates, $Z_{zz}$ and $Z_{{\theta}{\theta}}$, are measured as a function of frequency in 10 kHz~10 MHz and external static magnetic field in 0 Oe~200 Oe. The equations expressing the diagonal $Z_{zz}$ and $Z_{{\theta}{\theta}}$ in terms of diagonal components of complex permeability tensor, ${\mu}^*_{zz}$ and ${\mu}^*_{{\theta}{\theta}}$, are derived from Maxwell's equations. The real and imaginary parts of ${\mu}^*_{zz}$(f) and ${\mu}^*_{{\theta}{\theta}}$(f) spectra are extracted from the measured $Z_{zz}$(f) and $Z_{{\theta}{\theta}}$(f) spectra, respectively. It is presened that the extraction of ${\mu}^*_{zz}$(f) and ${\mu}^*_{{\theta}{\theta}}$(f) spectra from the diagonal impedance spectra can be a versatile tool to investigate dymanic magnetization process in the core/shell composite wire.

• Journal of the Korean Ceramic Society
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• v.27 no.4
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• pp.529-535
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• 1990

This paper describes the factors which control the impedance-relative humidity characteristics of the TiO2-V2O5 humidity sensor. To obtain the quantitative relationships between impedance and many manufacturing parameters such as V2O5mol%, the sintering time and temperature, various sets of samples are preared and tested. With changing relative hymidity from 20% to 80%, it is measrued that the corresponding capacitance and impedance from the semicircles which complex impedance plots make. As a result we found that the impedance-relative humidity characteristics are mainly controlled by the doping amount of V2O5 total pore volume and bulk resistence of the elements. We can assume the equivalent circuits of each samples and finally control the sintering time to get a linear humidity impedance response curve which plays an important role in device making. 4mol% V2O5-TiO2 specimen sintered at 90$0^{\circ}C$ for 10min. show liear log(Z) vs. RH characteristics and 10mol% V2O5-TiO2 specimen sintered at the same temp. for 20min. show linear (Z) vs. RH.