• Journal of Biomedical Engineering Research
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• v.37 no.5
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• pp.168-177
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• 2016

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

• The Journal of the Korea Contents Association
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• v.11 no.12
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• pp.317-325
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• 2011

This study aims to develop the stance-control typed 4-bar linkage orthotic knee joint that replace the locked orthotic knee joint for the disabled with poliomyelitis and muscle weakness of lower limb. Unlike the existing stance-control orthotic knee joint, there are no needs of electric power, connecting circuit, bulky compomnets, etc, because this 4-bar linkage orthotic knee joint is controled by geometric locking. To evaluate the 4-bar linkage orthotic knee joint, a subject participated in this study who has been diagnosed with lower limb poliomyelitis and have used locked type orthotic knee joint. In the results of analysis of subject's gait using 3-dimentional motion analysis system, this 4-bar linkage orthotic knee joint provide the stability during stance phase and knee flexion during swing phase.

• The Journal of the Korea Contents Association
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• v.6 no.4
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• pp.1-10
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• 2006

In this paper, a broadband RF module is designed and tested for 2.4GHz band applications. The RF module is composed of a low noise amplifier (LNA) with a three stage amplifier, a single ended gate mixer, matching circuits, a hairpin line band pass filter and a Chebyshev low pass filter to convert the radio frequency (RF) into the intermediate frequency (IF). The LNA has a high gain and stability, and the single ended gate mixer has a high conversion gain and wide dynamic range. In the analysis of the broadband RF module, the composite harmonic balance technique is used to analyze the operating characteristics of an RF module circuit. The RF module has a 55.2dB conversion gain with a 1.54dB low noise figure, $-120{\sim}-60dBm$ wide RF power dynamic range, -60dBm low harmonic spectrum and a good isolation factor among the RF, IF, and local oscillator (LO) ports.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.380-382
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• 2018

In this study, we developed software for portable lifter using Android application for stability of portable lifter which can load freight easily. Arduino Uno R3 boards were used for this purpose. The existing portable lifts were disassembled to mount the Arduino Uno R3 board and circuit, and to send and receive signals via Bluetooth communication. This study can be expected to contribute greatly to the safety work of logistics activities.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.80-83
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• 2017

In this paper, the X-band reconfigurable frequency selective surface having flexible geometry was proposed. The proposed RFSS is composed of patterns of cross-shaped loop with inductive stub, which can control the frequency response for C-Band and X-band by ON/OFF state of PIN diode. To minimize the parasitic effect and to obtain the high level of isolation between the unit cell of FSS and the bias circuit, we designed the grid type bias line on bottom layer through via hole. The measured transmission characteristics show good agreement with the simulation results and good stability of frequency response for different incident angles and curvatures of surface.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.710-714
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• 2007

LSGM$(La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.2}O_{3-{\delta}})$ is the very promising electrolyte material for lower-temperature operation of SOFCs, especially when realized in anode-supported cells. But it is notorious for reacting with other cell components and resulting in the highly resistive reaction phases detrimental to cell performance. LDC$(La_{0.4}Ce_{0.6}O_{1.8})$, which is known to keep the interfacial stability between LSGM electrolyte and anode, was adopted in the anode-supported cell, and its effect on the interfacial reactivity and electrochemical performance of the cell was investigated. No severe interfacial reaction and corresponding resistive secondary phase was found in the cell with LDC buffer layer, and this is due to its ability to sustain the La chemical potential in LSGM. The cell exhibited the open circuit voltage of 0.64V, the maximum power density of 223 $mW/cm^2$, and the ohmic resistance of $0.17{\Omega}cm^2$ at $700^{\circ}C$. These values were much improved compared with those from the cell without any buffer layer, which implies that formation of the resistive reaction phases in LSGM and then deterioration of the cell performance is resulted mainly from the La diffusion from LSGM electrolyte to anode.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.102-112
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• 2005

In this work, we developed fully integrated broadband MMIC chip set employing CSP(Chip Size Package) for K/Ka band applications. By utilizing an ACF for the RF-CSP, the fabrication process for the packaged amplifier MMIC could be simplified and made cost effective. $STO(SrTi_{3})$ capacitors were employed to integrate the DC biasing components on the MMIC, and LC parallel circuits were employed for DC feed and ESD protection. A pre-matching technique and RC parallel circuit were used to achieve a broadband matching and good stability fer the amplifier MMIC in K/Ka band. The amplifier CSP MMIC exhibited good RF performance over a wide frequency range in K/Ka band. This work is the first report of a fully integrated CSP amplifier MMIC successfully operating in the K/Ka band.

• Journal of IKEEE
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• v.3 no.2 s.5
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• pp.221-225
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• 1999

In this paper, a new type of predistortion linearizer has been studied. It employs a series feedback amplifier with a large source inductance as a predistortion linearizer, which provides positive amplitude and negative phase deviations for input Power and can compensate for AM-AM and AM-PM distortions of power amplifier. This predistortion lineariaer consists of only one CaAs FET, large source inductor, input output matching networks and bias circuits. Because of its simple circuit, the linear can be operated over a broad bandwidth and has good thermal stability The characteristics of this linearizer can be easily tuned using source inductor, its gate bias condition. In fabricated linearizer, the third-order intermodulation distortion(IMD) for main amplifier alone is 10.61dBc, and the $IM_3$ for main amplifier with predistorter is 21.91dBc. Therefore, the $IM_3$ characteristic results an improvement of approximately 11dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.9
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• pp.713-722
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• 2017

In the future battlefield, the role of the unmanned vehicle is very important. Currently, charging and management systems for unmanned vehicles are all wired. However, for convenience and stability, it is desirable that the charging of the unmanned vehicle uses wireless power transfer system. In this paper, we have studied the application of wireless power transfer system to the charging of unmanned vehicles. Considering the size of the unmanned vehicle and the required power, the transmission coil and the receiving coil are designed through the finite element analysis based magnetic field simulation. The coil was made according to the simulation results and the circuit simulation was performed through the measured parameter values. Finally, we show that wireless power transmission can be applied to unmanned mobile charging through actual experiments.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.309-312
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• 2008

In this paper, we investigated electric safety manager's PL recognition and accident occurrence of electric power facilities(power cable, transformer, circuit breaker) in electric installation for private use. The target of questionnaire survey is 450 electric installations for private use, 154 responded the questionnaire among these and it occupied 35.8%. Most of receiving voltage were 22.900kV. The questionnaire survey says that 58% of electric safety manager knew well about PL contents and 42% of them did not recognize about PL contents, About the PL application of electrical facility accidents, 82.4% of them must applied PL law, 5.8% of them did not need the PL law. Reason of PL application occupied 64% for stability of electrical facility and product, 19% for prevention of same accident. The accident of transformer occupied most and the power cable accident were much next. The questionnaire survey results, electric safety managers are interested in PL content. thev expected necessity of PL application about electrical accident strongly.