• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1429-1435
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• 2004

In this work, high performance broadband amplifier MMIC including all the matching and biasing components, and electrostatic discharge (ESD) protection circuit was developed for K/Ka band applications. Therefore, external biasing or matching components were not required for the operation of the MMIC. STO (SrTiO3) capacitors were employed to integrate the DC biasing components on the MMIC, and miniaturized LC parallel ESD protection circuit was integrated on MMIC, which increased ESD breakdown voltage from 10 to 300 V. A pre-matching technique and RC parallel circuit were used for the broadband design of the amplifier MMIC. The amplifier MMIC exhibited good RF performances and good stability in a wide frequency range. The chip size of the MMICs was $1.7{\pm}0.8$ mm2.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.560-563
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• 2000

In this paper we proposed AC/DC boost converter to improve input current harmonic reduction in TIG welder. The proposed harmonic reduction circuit with UC2854AN acting on constant switching frequency average current control has a three-loop control structure : the inner current loop the line voltage feed-forward loop and th outer voltage loop. Also we applied the constant current strategy on full bridge IGBT inverter to stabilized the output current using the analog PI controller. To demonstrate the practical significance of the proposed methods some simulation studies and experimental results are presented.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.678-684
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• 2013

This paper describes a low-power baseband circuit for SAW-less LTE-Advanced transmitters. The proposed transmitter baseband circuit consists of a 2nd-order Tow-Thomas type active RC-LPF and a 1st-order passive RC LPF. It can provide a 7 multi-channel cut-off frequencies and wide gain control range of -41 dB ~ 0 dB with a 1-dB step. The proposed 2nd-order active RC-LPF adopts an op-amp in which three other sub-op amps are in parallel connected to reduce DC current for different cutoff frequency. In addition, each sub-op amp adopts both Miller and feed-forward phase compensation method to achieve an UGBW of more than 1-GHz with a small DC power consumption. The proposed baseband circuit is implemented in 65-nm CMOS technology, consuming DC power from 6.3 mW to 24.1 mW from a 1.2V supply voltage for each different cut-off frequency.

• 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 Radiation Protection and Research
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• v.24 no.1
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• pp.9-15
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• 1999

In order to separate $Sr^{2+}$ selectively from environmental sample solutions containing $Ca^{2+}$, supported liquid membranes(SLM) were prepared and their characteristics of separation were investigated. The contents of carriers, DC18C6 and DNNS, in SLM affected the permeabilities of metal ions and selectivities of $Sr^{2+}$. The selectivity of $Sr^{2+}$ reached to 93.3% in a SLM with 0.1 M DC18C6 and 25 mM DNNS. When the ratio of $Sr^{2+}$ to $Ca^{2+}$ concentration in the feed solution was in the range of 1/25 to 1/50, the selectivity of $Sr^{2+}$ was greater than 90 %. Therefore, it is considered that the SLM prepared in this study is capable of treating environmental sea-water samples for strontium measurement.

• Journal of IKEEE
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• v.24 no.1
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• pp.368-371
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• 2020

In this paper, we propose a linear tapered slot rectifying antenna for a portable UHF-band RFID system. Since the proposed rectifying antenna does not use a dielectric substrate, the planar antenna is implemented with a thin metal thickness. The rectifier circuit converts input RF power into output DC voltage using a voltage doubler circuit based on two anti-parallel schottky diodes. The rectifying antenna is integrated by the voltage doubler circuit into a linear tapered slot antenna. For conjugate impedance matching of the rectifying circuit and the linear tapered slot antenna, the source-pull method was utilized by adjusting the angle of the tapered slot and the length of the antenna feed line. The proposed antenna prototype has been verified with the electrical and radiation characteristics through RF-DC conversion and far-field radiation test in open space measurement environment. Finally, the proposed antenna is realized to 0.23-wavelength (75 mm) and 0.18-wavelength (60 mm) at 915 MHz center frequency.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.1
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• pp.25-30
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• 2011

We investigated the effect of a lactic acid extract of Sargassum horneri (ExSL) as a calcium supplement on bone formation in 48 female Sprague-Dawley rats for 4 weeks of their growth phase. The rats were divided into four groups based on diet: two calcium-sufficient and two calcium-deficient diets. The normal control group (NC) was fed AIN-93G; the NCS group was fed the same diet containing 1% extract; the calcium-deficient control (DC) diet was based on AIN-93G; and the DCS group received the same calcium-deficient diet plus 1% extract. Bone formation in the rats was evaluated using the wet weight, length, diameter, and bone mineral density (BMD) of the femur. Serum parameters were also examined. The food intake among the groups did not differ significantly (P<0.05). The NCS group gained the most body weight, while the DC group gained much less weight than the other groups. The feeding efficiencies of the groups that received the extract (NCS and DCS) were slightly higher than those of the control groups (NC and DC). The calcium intakes of all groups depended on the amount of calcium in the feed; the NCS and DCS diets contained 12.15 mg more calcium than the NC and DC diets. The calcium absorption was lower in NCS than in DC and DCS, but significantly higher than in NC (P<0.05). The BMDs in the calcium-sufficient groups were not significantly different (P<0.05), while in the calcium-deficient groups the BMD was significantly higher in DCS than in DC (P<0.05). The serum calcium and phosphorus levels in all groups were not associated with markers of bone growth related to the extract. The osteocalcin content and alkaline phosphatase (ALPase) activity were higher in the calcium-deficient groups than in the normal groups (P<0.05). Ultimately, the osteocalcin content and ALPase activity were lower in DCS compared to DC. These results suggest that the addition of ExSL promotes bone formation and calcium absorption in growing rats.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2668-2670
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• 1999

In the past, the PWM converter had a large switching loss by hard switching and difficult to high frequency operation. The resonance converter to decrease the switching loss and EMI is required the frequency control and needed to reduce the voltage or current stress at each parts. So, this paper propose the 3-phase boost converter and the method to compensated input power factor by control the amplitude - an instantaneous value of the DC inductor current -and control the switching frequency that a modulation error by the ripple of the DC inductor current. The proposed 3-phase PWM boost converter of single phase control type can takes higher capacity and compensate the power factor by using Feed back controller at each phase for the existing 3-phase bridge rectifier type. Moreover the 3-phase full bridge type using the rectifier at each 3-phase circuit will be small size reactor and compensate input power factor by minimize harmonic components of each phase.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.507-515
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• 2013

This paper proposes a compensation method for the $2^{nd}$-order harmonic of single-phase grid-connected wind power generation systems. Theoretically, a single-phase grid-connected inverter system has no choice but to cause the $2^{nd}$-order harmonic to DC-link voltage. The reference active current is affected by the DC-link voltage. The output current from the reference active current is distorted by the $1^{st}$ and $3^{rd}$-order harmonic. The proposed method can compensate, conveniently, the reference active current with the $2^{nd}$-order harmonic. To reduce the $2^{nd}$-order ripple in the reference active current, proposed method takes a PR controller as a feed-forward compensator. PR controllers can implement selective harmonic compensation without excessive computational requirements; the use of these controllers simplifies the method. Both the simulation and experimental results agree well with the theoretical analysis.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.359-360
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• 2012

This paper proposes a scheme of auto-tuning fuzzy PI controller and input voltage feed forward to control the output voltage of a three-phase Z-source inverter (ZSI). The proposed scheme adjusts the ts (Kp and Ki) in real time in order to find the most suitable Kp and Ki for PI controller and to simplify the controller design. The proposed scheme is verified the validity by experiment and co-simulation in PSIM and MATLAB/SIMULINK both load step change and input DC voltage variation in Z-source inverter, and has compared with the conventional PID control scheme. The experiment results involve of three-phase output voltage, Z-network capacitor voltage and dc-link peak voltage value. By those analysis and comparison, the availability of the proposed method in output voltage transient response quality improving has been verified. Compared with conventional PID method, the proposed method showed a more effective and robust control performance for coping with the severe disturbance conditions.