• Korean Journal of Acupuncture
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• v.29 no.4
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• pp.563-572
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• 2012

Objectives : The aim of this study was to suggest a new method to estimate the resistance by acupoint compositions by using the multi-frequency bioelectrical impedance analysis(MF-BIA) of 5 kHz, 50 kHz and 200 kHz within 2 cm of acupoints as a local segment. Moreover, we try to confirm the relation to between measured resistance at skin surface and measured resistance by various manual acupuncture needle insertion depth. Methods : Ten male subjects participated in this study. We measured the resistance at left/right ST36 at skin surface and various manual acupuncture needle insertion depth(skin, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm and 30 mm). Results : It was also observed that the all measured resistances were the highest at 5 kHz and the lowest at 200 kHz. There were significant differences at 5 kHz, 50 kHz and 200 kHz between measured resistance at skin surface and measured resistance by various manual acupuncture needle insertion depth(p<0.05). There was no significant difference in the left and right identical acupoints under the identical condition(p>0.05). Conclusions : We conclude that the measured resistance at skin surface has limitation as to reflect the information of tissue. However, the measured resistance at each frequency was changed as similar pattern by different insertion depth. Hence, we confirmed the possibility of assumption on information of tissue which was expected to locate an acupoint.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.239-244
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• 2015

Lead zirconate titanate (PZT) thick films with thickness of $10{\sim}20{\mu}m$ were fabricated on silicon substrate by aerosol deposition method. As-deposited films on silicon were annealed at the temperatures of $700^{\circ}C$. The electrical properties of films deposited by PZT powders were characterized using impedance analyzer and Sawyer-Tower circuit. The PZT powder was prepared by both conventional solid reaction process and sol-gel process. The remanent polarization, coercive field, and dielectric constant of the $10{\mu}m$ thick film with solid reaction process were $20{\mu}C/cm^2$, 30 kV/cm and 1320, respectively. On the other hand, the PZT films by sol-gel process showed a poor dielectric constant of 635. The reason was probably due to the presence of pores produced from organic residue during annealing.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.119-126
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• 2015

The information about noise parameters is essential in the design of low noise amplifier. In the past, the noise parameters were measured using an impedance tuner and noise figure analyzer. Recently, the authors proposed the method of measuring the noise parameters using the 8-port network without the aid of the mechanically driven impedance tuner. However, the 8-port method still requires the noise source and causes the complexity in the measurements. In this paper, a novel measurement method of the noise parameters without the noise source using 6-port network is proposed. Based on the proposed 6-port method, the noise parameters of 10 dB attenuator whose noise parameters can be theoretically determined were measured and the measured noise parameters are compared with those measured using the previous 8-port network method. As a result, the accuracy of the measured noise parameters using 6-port network is found to be comparable to the previous 8-port network method.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.285-289
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• 2000

This study suggests a rebar detection technique for simultaneous detection of size and cover of embedded reinforcement in concrete. The structure of the probe made in this study is somewhat different from commercial ones. This probe has three sensing coils. Rebar size and cover depth can be evaluated by detecting and analyzing the signal from them. Amplitude and phase variation of each coil in the probe was investigated using an impedance analyzer and the loci of transfer functions of the coils were analyzed. The locus of transfer function from the sensing coil positioned inside excitation coil was simple as well known, but the others from the coils outside excitation coil were not so. Actual experiment on rebar detection was performed with our probe and an eddy current test system for various rebar sizes and depths. The signal shape according to variation of cover depths showed the same tendency with the transfer function loci acquired by impedance analyzer. The different variation pattern of signal enabled to evaluate rebar size and cover depth simultaneously.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.327-327
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• 2008

Lead-free $(K_{0.5}Na_{0.5})NbO_3$ 압전 세라믹스는 다양한 광소자로의 응용과 압전 특성, 초전 특성을 이용한 압전 소자로의 응용이 가능한 재료로 보고되고 있다. 그러나 KNN계 압전소재 특성상 판상 형태의 결정립으로 인해 낮은 소결 밀도를 갖게 되고, 그로인해 압전물성의 저하를 초래하는 문제점을 가지고 있다. 따라서, 본연구에서는 다양한 밀링 방법을 적용하여 입자 사이즈를 작게 하고 소성체의 결정립을 구형화 함으로써 저온소결에서의 압전물성을 개선시키고자 한다. $(K_{0.5}Na_{0.5})NbO_3$를 기계적 분쇄법에 의해 입자사이즈에 따라 변화되는 상의 분석과 압전체로서의 특성을 관찰하였다. 결정학적 상분석 및 미세 조직은 XRD, SEM을 이용하여 관찰하였고, Capacitance는 Impedance analyzer(HP4192A)로 측정하였으며, Impedance 주파수 특성은 Network Analyzer로 측정하여 Kp, Kt와 Qm을 측정하였다.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.80-86
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• 2007

We have investigated on the development of 2-2 type piezocomposites that have better piezoelectric activity and lower acoustic impedance than those of conventional piezoceramics. In this study, we have investigated the piezoelectric and acoustic properties of 2-2 type piezocomposites sensor which was fabricated using dice-and-fill technique for the different volume fraction of PZT. The specific acoustic impedance of 2-2 type piezocomposites decreased linearly when PZT volume fraction was decreased. The resonance characteristics measured by an impedance analyzer(HP4194A) were similar to the analysis of finite element method (FEM). The resonance characteristics and the electromechanical coupling factor were the best when the volume fraction PZT was 0.6. It also showed the highest result from the standpoint of sensitivity, bandwidth and ring-down property and so on at the same condition. The specific characteristics show that the 2-2 type piezocomposites turned out to be superior to the ultrasonic sensor composed by single phase PZT.

• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.5
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• pp.1-8
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• 1976

Microwave GaAs Metal Semiconductor Field effect Transistors (MESFET) with the gate-length of two micrometers are investigated. The scattering parameters of the transistors have been measured from 1GHz to 2GHz by Hp8545 Automatic network analyzer. From the measured data, an equivalent circuit is established which consists of an ntrinsic and. extrinsic transistor elements. In this paper, GaAb MESFET Amplifier is used in conjunction with conventional microstrip techniques to match into a 50 ohms high input/output impedances system. We found that Power gain is less than 8dB and VSWR is less than 1.5 in L-Band.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.8
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• pp.30-35
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• 2013

This paper describes the assessment method of deterioration condition for a power transformer using SFRA. Frequency Response Analysis(FRA) is a method to evaluate the mechanical and geometrical integrity of the core and windings within a power transformer by measuring the electrical transfer functions over a wide frequency range. SFRA is sweep frequency response analyzer for power transformer winding diagnosis. The FRA is a comparative method, that evaluates the transformer condition by comparing the obtained set of FRA results to reference results on the same, or a similar, unit. FRA techniques were widely used and much more sensitive than the traditional and internationally accepted method of impedance measurements, but that work was required on standardization and interpretation. In order to analyze the deterioration condition for power transformer, overvoltage test and mechanical distortion test were carried out. The deterioration condition for power transformer was evaluated by SFRA. It is intended to present the elemental technology of assessment method for power transformer using SFRA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.719-722
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• 2003

Ferroelectric $Pb(Zr_{1-x}Ti_x)O_3$ (PZT) films were deposited on (001) MgO single crystals using sol-gel method. Structural properties and surface morphologies of PZT films were investigated using an X-ray diffractometer and a scanning electron microscopy, respectively. The dielectric properties of PZT films were investigated with the dc bias field using interdigitated capacitors (IDC) which were fabricated on PZT films using a thick metal layer by photolithography and dry etching process. The small signal dielectric properties of PZT films were calculated by a modified conformal mapping method with low and high frequency data, such as capacitance measured by an impedance gain/phase analyzer at 100 kHz and reflection coefficient (S-parameter) measured by a HP 8510C vector network analyzer at 1 -20 GHz. The IDC on PZT films exhibited about 67% of capacitance change with an electric field of 135 kV/cm at 10 GHz. These PZT thin films can be applied to tunable microwave devices such as phase shifters, tunable resonators and tunable filters.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.1 s.139
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• pp.149-156
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• 2005

The purpose of this study was to produce the high quality of electromagnetic wave shielding fabrics. In this study, we have produced polyester fabrics by electroless Ag plating. The untreated polyester was etched with $4\%$ NaOH solution added accelerant(Benzyl Dimethyl Dodecyl Ammonium Chloride) then it was catalyzed by $SnCl_2$ solution and activated by $PdCl_2$ solution. Electroless Ag plating was carried out by changing conditions such as temperature. time, weight loss rate of polyester and kind of reducing agents. The electromagnetic wave shielding effectiveness of polyester fabric by electroless Ag plating was measured by RF Impedance Analyzer and element of electromagnetic wave shielding substance was measured using Electron probe micro analyzer. The results were as follows; The plating bath using potassium sodium tartrate by reducing agent was excellent electromagnetic wave shielding effectiveness. Element of electromagnetic wave shielding substance was silver. Electromagnetic wave shielding effectiveness was shown over 64dB at the temperature of $40^{\circ}C$, treating time 30min., weight loss rate $20\%$.