• Journal of the Korean Society of Radiology
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• v.12 no.4
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• pp.475-480
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• 2018

In lower abdominal MRI scan, patients have been tested by physically contacting with the body array coil. In this study, we have designed the acrylic assistant equipment (ACR) which allows the contactless scan of the patient to the coil and evaluated the feasibility by comparing the acquired images with ACR to those obtained without ACR. We tested 10 cases (F: 5, m: 5) by using the Ingenia $3.0T^{TM}$ MR system and dStreamTM torso coil (Philips Healthcare, Netherlands). We implemented T1 AX TSE and eTHRIVE (GRE) techniques. The scanned images were quantitatively and qualitatively assessed. In qualitatively, the TSE shows 4.44 and 4.56 mean values with and without the ACR and 4.34 and 4.28 at the GRE, respectively. In quantitatively, the TSE shows 12.15 CNR, 17.95 SNR and 12.71 CNR, 18.96 SNR with and without the ACR. And GRE shows 17.72 CNR, 22.59 SNR and 18.26 CNR, 24.47 SNR with and without the ACR, respectively. We have designed and implemented the acrylic assistant equipment to lower abdominal patients. Our data indicate that it is possible to obtain similar image qualities to current lower abdominal MRI scan without the physical contact to the patient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.37-43
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• 2017

This review investigates the basic principle of physical interactions and failure mechanisms introduced in the materials and inner parts of semiconducting components under electromagnetic pulses (EMPs). The transfer process of EMPs at the semiconducting component level can be explained based on three layer structures (air, dielectric, and conductor layers). The theoretically absorbed energy can be predicted by the complex reflection coefficient. The main failure mechanisms of semiconductor components are also described based on the Joule heating energy generated by the coupling between materials and the applied EMPs. Breakdown of the P-N junction, burnout of the circuit pattern in the semiconductor chip, and damage to connecting wires between the lead frame and semiconducting chips can result from dielectric heating and eddy current loss due to electric and magnetic fields. To summarize, the EMPs transferred to the semiconductor components interact with the chip material in a semiconductor, and dipolar polarization and ionic conduction happen at the same time. Destruction of the P-N junction can result from excessive reverse voltage. Further EMP research at the semiconducting component level is needed to improve the reliability and susceptibility of electric and electronic systems.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.264-272
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• 2012

In this paper, we report THz generation and detection characteristics investigated by InGaAs semiconductor epilayers, as results of a basic study obtained from the InGaAs-based THz transmitter/receiver (Tx/Rx). High-temperature and low-temperature (LT) grown InGaAs epilayers were prepared by the molecular beam epitaxy technique for the characterization of THz generation and detection, respectively, and the surface emission based on the photo-Dember effect was tried for THz generation. THz wave was generated by irradiation of a Ti:Sapphire fs pulse laser (60 ps/83 MHz), and a LT-GaAs Rx was used for the THz detection. The frequency band shown in the spectral amplitudes Fourier-transformed from the measured current signals was ranging in 0.5~2 THz, and the signal currents were exponentially increased with the Tx beam power. The THz detection characteristics of LT-InGaAs were investigated by using an Rx with dipole (5/20 ${\mu}m$) antenna, and the cutoff frequency was ~2 THz.

• Carbon letters
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• v.28
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• pp.31-37
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• 2018

This paper examines a simple one-step and catalyst-free method for synthesizing carbon nanoparticles from aliphatic alcohols and n-hexane with linear molecule formations by using a stable solution plasma process with a bipolar pulse and an external resistor. When the external resistor is adopted, it is observed that the current spikes are dramatically decreased, which induced production of a more stable discharge. Six aliphatic linear alcohols (methanol-hexanol) containing carbon with oxygen sources are studied as possible precursors for the massive production of carbon nanoparticles. Additional study is also carried out with the use of n-hexane containing many carbons without an oxygen source in order to enhance the formation of carbon nanoparticles and to eliminate unwanted oxygen effects. The obtained carbon nanoparticles are characterized with field emission-scanning electron microscopy, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The results show that with increasing carbon ratios in alcohol content, the synthesis rate of carbon nanoparticles is increased, whereas the size of the carbon nanoparticles is decreased. Moreover, the degree of graphitization of the carbon nanoparticles synthesized from 1-hexanol and n-hexane with a high carbon (C)/oxygen (O) ratio and low or no oxygen is observed to be greater than that of the carbon nanoparticles synthesized from the corresponding materials with a low C/O ratio.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.71-79
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• 2010

This paper presents a design of a LLC resonant controller IC. LLC resonant controller IC controls the voltage of the 2nd side by adjusting frequency the input frequency of the external resonant circuit. The clock generator is integrated to provide the pulse to the resonant circuit and its frequency is controlled by the external resistor. Also, the frequency of the VCO is adjusted by the feedback voltage. The protection circuits such as UVLO(Under Voltage Lock Out), brown out, fault detector are implemented for the reliable and stable operation. The HVG, and LVG drivers can provide the high current and voltage to the IGBT. The designed LLC resonant controller IC is fabricated with the 0.35 um 2P3M BCD process. The overall die size is $1400um{\times}1450um$, and supply voltage is 5V, 15V.

• Economic and Environmental Geology
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• v.40 no.1 s.182
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• pp.129-140
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• 2007

CFC(CFC-12, CFC-11 and CFC-113) analytical system for air and water was constructed using a customized purge and trap extraction device and a gas chromatograph with an electron capture detector. Sampling methods of air and water for CFCs were also established. The analytical system was experimentally optimized to result in reproducibilities of triplicates less than 2% for current air samples and less than 5% for groundwater samples with CFC-12 concentration of 160 to 180 pg/kg, and verified with respect to the CFC system in USGS, which showed analytical results were in agreement within 10%. CFCs in air were monitored at three sites over 19-month period in the central part of South Korea, and the result indicates no significant local sources of CFCs in those areas. For groundwater in Jeju Island, CFCs were measured over a year with a two-month interval. The time-series data showed seasonal fluctuations which could be interpreted by the effect of recharge pulse derived from large amount of rainfall during monsoon period with a few month delay, which indicates high permeability of basaltic rocks in Jeju Island.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.151-156
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• 2004

The purpose of this study was to develop EMG triggered FES system for restoration of upper extremity function in chronic hemiplegic patients and to identify the optimal location of electrode application for the EMG triggered FES system which produces effective muscle contraction and detects EMG activity for extension in the wrist and finger joints. The stimulus system was composed of EMG measuring component, constant current component and the program for muscle contraction by EMG triggered FES and passive FES. Parameter of electrical stimulation was 35 ㎐ in frequency, 150 ${\mu}\textrm{s}$ in pulse width and symmetric bi-phasic wave. In 15 hemiplegic patients, EMG triggered FES was applied to the proximal half of forearm which was divided into 12 areas. The most sensitive area for measuring EMG activities during extension of the wrist and fingers was area 4, 5 and the optimal location of electrical stimulation for producing extension of the wrist and fingers was area 4, 5, 7, 8. These results suggest that the area 4 and 5 was considered as the most optimal location of electrode application for measuring EMG activities as well as producing extension of the wrist and fingers by EMG triggered FES system.

• Childhood Kidney Diseases
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• v.12 no.1
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• pp.99-104
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• 2008

Microscopic polyangiitis(MPA) is a systemic necrotizing vasculitis that involves many organ systems including the skin, joint, kidneys, and lungs. In spite of early diagnosis and intensive care, the five-year actuarial patient and kidney survival rates are 65% and 55%. We experienced a case in 7-year-old girl of microscopic polyangiitis presenting with rapidly progressive glomerulonephritis which was confirmed by renal biopsy and positive serum perinuclear antineutrophil cytoplasmic autoantibodies(p-ANCA). The diagnosis of patients first renal biopsy was MPA, p-ANCA-associated crescentic glomerulonephritis. The patients second renal biopsy was done 5 years 6 months later since first renal biopsy, and pathologic diagnosis was chronic sclerosing glomerulonephritis, advanced, due to MPA. We began methylprednisolone pulse therapy, combined with a low dose of cyclophosphamide and plasmapheresis therapy. ACE inhibitor, angiotensin II receptor blocker, and cyclophosphamide were used until now and the patients current age is 14 years old. On admission, the patients laboratory findings showed BUN 117 mg/dL and Cr 2.3 mg/dL, while on the hospital day BUN and Cr values fell to 20.8 mg/dL and 1.6 mg/dL. But renal function was progressed to chronic failure with latest laboratory data BUN 51.7 mg/dL and Cr 3.2 mg/dL. ACE inhibitor, angiotensin II receptor blocker and small dose of immunosuppressant with close observation is the key to maintain the patient survival.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.62-62
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• 2018

Pt is still considered as one of the most active electrocatalysts for ORR in alkaline fuel cells. However, the high cost and scarcity of Pt hamper the widespread commercialization of fuel cells. As a strong candidate for the replacement of Pt catalyst, silver (Ag) has been extensively studied due to its high activity, abundance, and low cost. Ag is more stable than Pt in the pH range of 8~14 as the equilibrium potential of Ag/Ag+ being ${\approx}200mV$ higher than that of Pt/PtO. However, Ag is the overall catalytic activity of Ag for oxygen reduction reaction(ORR) is still not comparable to Pt catalyst since the surface Ag atoms are approximately 10 times less active than Pt atoms. Therefore, further enhancement in the ORR activity of Ag catalysts is necessary to be competitive with current cutting-edge Pt-based catalysts. We demonstrate the architectural design of Ag catalysts, synthesized using plasma discharge in liquid phase, for enhanced ORR kinetics in alkaline media. An attractive feature of this work is that the plasma status controlled via electric-field could form the Ag nanowires or dendrites without any chemical agents. The plasma reactor was made of a Teflon vessel with an inner diameter of 80 mm and a height of 80 mm, where a pair of tungsten(W) electrodes with a diameter of 2 mm was placed horizontally. The stock solutions were made by dissolving the 5-mM AgNO3 in DI water. For the synthesis of Agnanowires, the electricfield of 3.6kVcm-1 in a 200-ml AgNO3 aqueous solution was applied across the electrodes using a bipolar pulsed power supply(Kurita, Seisakusyo Co. Ltd). The repetition rate and pulse width were fixed at 30kHz and 2.0 us, respectively. The plasma discharge was carried out for a fixed reaction time of 60 min. In case of Ag nanodendrites, the electric field of 32kVcm-1 in a 200-ml AgNO3 aqueous solution was applied and other conditions were identical to the plasma discharge in water in terms of electrode configuration, repetition rate and discharge time. Using SEM and STEM, morphology of Ag nanowires and dendrites were investigated. With 3.6 kV/cm, Ag nanowire was obtained, while Ag dendrite was constructed with 32 kV/cm. The average diameter and legth of Ag nanowireses were 50 nm and 3.5 um, and thoes values of Ag dendrites were 40 nm and 3.0 um. As a results of XPS analysis, the surface defects in the Ag nanowires facilitated O2 incorporation into the surface region via the interaction between the oxygen and the electron cloud of the adjacent Ag atoms. The catalytic activity of Ag for oxygen reduction reaction(ORR) showed that the catalytic ORR activity of Ag nanowires are much better than Ag nanodendrites, and electron transfer number of Ag nanowires is similar to that of Pt (${\approx}4$).

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.579-588
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• 1999

Monitoring of patients is essential in assuring the safety of sedation in the dental office. The purpose of this study was to explore the utilization and preferences of sedation, utilization of monitoring methods, and the preparation for emergencies during sedation. Members of the Korean Academy of Pediatric Dentistry were surveyed(n=245) from 1998. 10. 1 to 1998. 12. 20 to establish current trends in the use of sedation practices and monitoring methods in Korea. Findings of the survey include: 1. Twenty nine percent of pediatric dentists use sedative agents in their practices. Seventy one percent of pediatric dentists do not use any sedative agents in their practices 2. Thirty nine percent of pediatric dentists who use sedative agents do so without monitoring devices 3. Nitrous oxide inhalation sedation was the most frequently utilized sedation method by pediatric dentists and chloral hydrate was the most frequently utilized sedative by pediatric dentists. Pulse oximeter was the most frequently utilized monitoring method during sedation in dental office. 4. Only twenty eight percent of pediatric dentists obtain the informed consent of the child's legal guardian. 5. Only sixty percent of pediatric dentists prepare for emergencies during sedation.