• 센서학회지
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• 제20권5호
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• pp.317-321
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• 2011

A Micro platform for micro gas sensor consisted of micro heater, insulator, and sensing electrode on 2 ${\mu}m$ thick $SiN_x$ membrane. Three types of micro platforms were designed and fabricated with membrane sizes. Total size of micro platform was 2.6 mm by 2.6 mm. Measured power consumptions were 28 mW, 28 mW, and 32.5 mW for Type 1, Type 2, and Type 3. At this moment, temperatures of membranes on the platforms were $295^{\circ}C$, $297^{\circ}C$, and $296^{\circ}C$, respectively. Fabricated micro platform considered appropriate to apply for low power consumption micro gas sensor. Micro gas sensors were prepared by the sequence that $SnO_2$ nanopowder pastes were dropped on membrane of Type 1 platforms, dried in oven, heat-treated with micro heaters in platforms. One of the micro gas sensors was tested for gas response to 1157 ppm, 578 ppm, and 231 ppm of methane and 1.68 ppm, 0.84 ppm, and 0.42 ppm of $NO_2$.

• The Korean Journal of Pain
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• 제9권2호
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• pp.407-411
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• 1996

Stereotactic radiofrequency dorsal root ganglionotomy can be very useful procedures for the treatment of pain emanating from the lumbar segmental nerves. This procedure is reserved for patients who have failed conservative interventional treatments and in whom open surgical intervention is not an option. The advantages of the radiofrequency lesion method are presented, excellent control of the lesion process using temperature monitoring to quantify the lesion size, prevent boiling, and to produce differential destruction of neural tissue. The afferent fibers in the ventral root which are spared by dorsal rhizotomy but nerve fibers with their cells in the ganglion from either dorsal or ventral root can be destructed with stereotactic radiofrequency ganglionotomy. This technique is performed using a 100 mm cannula with a 5 mm active tip. Repeated lateral fluoroscopic view should be taken to make sure that cannlua still resides within the superior, dorsal quadrant or the foramen. With the cannula in this position, electrostimulation is performed and good paresthesia on the leg should be noted with 0.3 and 0.5 volt at 50 Hz stimulation. At 2Hz stimulation distinct dissociation between motor and sensory should be shown. Percutaneous lumbar ganglionotomy have carried out under local anesthesia on inpatient basis in 6 patients. A series of 5 patients with metastatic cancer pain and a patient with compression fracture have been relieved of pain without serious complications.

• 한국안전학회지
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• 제33권2호
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• pp.21-27
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• 2018

The expansion and stable operation of electric power facilities are important factors with development of industrial facilities in modern society. In high-voltage equipment such as GIS, the insulation characteristics may be deterioated by environment-friendly gas adaption and miniaturization. There is also the possibility of accidents due to insulation breakdown due to the deterioration of power facilities. Therefore, it is necessary to extend the diagnosis system to continuously monitor the danger signals of these power equipment and to prevent accidents. Most of the internal defects in the GIS system are conductive particles, floating electrode defects, protrusion defects, and the like. In this case, a partial discharge phenomenon is accompanied. These partial discharge signals occur irregularly and various noise signals are included in the field, so it is difficult to evaluate the reliability in the development of the diagnostic system. In this paper, a study was made on equipment capable of generating a partial discharge simulated signal that can be adjusted in size and frequency to be applied to a diagnostic device by electromagnetic wave detection method. The PD simulated pulse generator consists of a user interface module, a high-voltage charging module, a pulse forming circuit, a voltage sensor and an embedded controller. In order to simulate the partial discharge phenomenon similar to the actual GIS, a discharge cell was designed and fabricated. The application of the prototype pulse generator to the commercialized PD diagnosis module confirmed that it can be used to evaluate the performance of the diagnostic device. It can be used for the development of GIS diagnosis system and performance verification for reliability evaluation.

• 한국전기전자재료학회논문지
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• 제31권2호
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• pp.102-106
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• 2018

Recently, there has been an increasing interest in the use of graphene as electrode materials for supercapacitors. In this regard, graphene oxide (GO) films were prepared using GO slurry obtained by dispersing GO powder in deionized (DI) water. The degree of dispersion of GO powder in DI water depends on the concentration of GO slurry, pH, impurity content, GO particle size, types of functional groups contained in GO, and manufacturing method of GO powder. In this study, the dispersivity of the GO powder was improved by adjusting the pH using only DI water (without additives), and a uniform GO film was obtained. The GO film was reduced by exposure to xenon intense pulsed light for a few milliseconds, and the reduced GO film was used as electrodes of a supercapacitor. The supercapacitor was characterized using cyclic voltammetry (CV), charge-discharge cycle, and electrochemical impedance spectroscopy measurements, and the specific capacitance of the supercapacitor was found to be ~140 F/g from the CV data.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.112.1-112.1
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• 2011

The back contact solar cell (BCSC) has several advantages compared to the conventional solar cell since it can reduce grid shadowing loss and contact resistance between the electrode and the silicon substrate. This paper presents the effect of the surface texturing of the silicon BCSC by varying the texturing depth or the texturing gap in the commercially available simulation software, ATHENA and ATLAS of the company SILVACO. The texturing depth was varied from $5{\mu}m$ to $150{\mu}m$ and the texturing gap was varied from $1{\mu}m$ to $100{\mu}m$ in the simulation. The resulting efficiency of the silicon BCSC was evaluated depending on the texturing condition. The quantum efficiency and the I-V curve of the designed silicon BCSC was also obtained for the analysis since they are closely related with the solar cell efficiency. Other parameters of the simulated silicon BCSC are as follows. The substrate was an n-type silicon, which was doped with phosphorous at $6{\times}10^{15}cm^{-3}$, and its thickness was $180{\mu}m$, a typical thickness of commercial solar cell substrate thickness. The back surface field (BSF) was $1{\times}10^{20}\;cm^{-3}$ and the doping concentration of a boron doped emitter was $8.5{\times}10^{19}\;cm^{-3}$. The pitch of the silicon BCSC was $1250{\mu}m$ and the anti-reflection coating (ARC) SiN thickness was $0.079{\mu}m$. It was assumed that the texturing was anisotropic etching of crystalline silicon, resulting in texturing angle of 54.7 degrees. The best efficiency was 25.6264% when texturing depth was $50{\mu}m$ with zero texturing gap in case of low texturing depth (< $100{\mu}m$).

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.84-94
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• 2007

In order to collect information on local distribution of conductivity and permittivity underneath a scan probe, we developed a multi-frequency trans-admittance scanner (TAS). Applying a sinusoidal voltage with variable frequency on a chosen distal part of a human body, we measure exit currents from 320 grounded electrodes placed on a chosen surface of the subject. The electrodes are packaged inside a small and light scan probe. The system includes one voltage source and 17 digital ammeters. Front-end of each ammeter is a current-to-voltage converter with virtual grounding of a chosen electrode. The rest of the ammeter is a voltmeter performing digital phase-sensitive demodulation. Using resistor loads, we calibrate the system including the scan probe to compensate frequency-dependent variability of current measurements and also inter-channel variability among multiple. We found that SNR of each ammeter is about 85dB and the minimal measurable current is 5nA. Using saline phantoms with objects made from TX-151, we verified the performance of the lesion estimation algorithm. The error rate of the depth estimation was about 19.7%. For the size estimate, the error rate was about 15.3%. The results suggest improvement in lesion estimation algorithm based on multi-frequency trans-admittance data.

• 조명전기설비학회논문지
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• 제28권10호
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• pp.82-88
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• 2014

This paper presents the results of model tests for the attachment process of lightning leader to ground which is one of poorly understood processes of cloud-to-ground lightning discharges. In order to simulate the attachment process of lightning leader to ground, we investigated the discharge characteristics of air gap between the tip of needle-shaped electrode and the soil surface as a parameter of moisture content in soils when the positive and negative $1.2/50{\mu}s$ lightning impulse voltages are applied. The breakdown voltage and the discharge light were observed. As a result, the attachment processes of lightning leader to ground are strongly dependent on the grain size and the moisture content of soils. The time to breakdown was shortened with increasing the magnitude of incident impulse voltages. The delay time from application of the highest voltage to breakdown in sand is shortened with increasing the moisture content. The delay time from application of the voltage to breakdown in gravel varied from about $0.5{\mu}s$ to several ${\mu}s$. As the moisture content in soil increases, the breakdown voltages are decreased and the breakdown voltage versus time to breakdown curves are shifted toward the lower side. The results obtained in this work are similar to those for non-uniform air gap stressed by lightning impulse voltages.

• Transactions on Electrical and Electronic Materials
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• 제5권3호
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• pp.89-92
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• 2004

For improving solar efficiencies, down conversion of high-energy photons to visible lights is discussed. The losses due to thermalization of charge carriers generated by the absorption of high-energy photons, can largely be reduced in a solar cell if more than one electron-hole pair can be generated per incident photon. The solar cell was constructed of dye-sensitized anatase-based TiO$_2$, approximately 30nm particle size, 6$\mu\textrm{m}$thickness, and 6${\times}$6$\textrm{mm}^2$ active area, Pt counter electrode and I$_3$$\^$-/I$_2$$\^$-/ electrolyte. After correction for losses due to light reflection and absorption by the conducting glass, the conversion of photons to electric current is practically quantitative in the plateau region of the curves. The incident photon to current conversion efficiency(IPCE) of N3 used as a dye in this work is about 80% at around 590nm and 610nm which is the emission spectrum of Eu doped LGF. The Eu doped LGF powder was prepared by conventional ceramic process, and used as a down converter for DSC after spin coated on the slide glass and fired.

• Progress in Superconductivity
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• 제10권2호
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• pp.99-102
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• 2009

We report our development of the fabrication process of sub-micron scale $Al-AlO_x-Al$ tunnel junction by using electron-beam lithography and double-angle shadow evaporation technique. We used double-layer resist to construct a suspended bridge structure, and double-angle electron-beam evaporation to form a sub-micron scale overlapped junction. We adopted an e-beam insensitive resist as a bottom sacrificing layer. Tunnel barrier was formed by oxidation of the bottom aluminum layer between the bottom and top electrode deposition, which was done in a separate load-lock chamber. The junction resistance is designed and controlled to be 50 $\Omega$ to match the impedance of the transmission line. The junctions will be used in the broadband shot noise thermometry experiment, which will serve as a link between the electrical unit and the thermodynamic unit.

• 한국결정성장학회지
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• 제8권2호
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• pp.221-226
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• 1998

$RuO_2$ 하부전극 상에 형성된 $(Ba, Sr)TiO_3$[BST] 박막의 물성을 향상시키기 위하여 비정질 BST층(30, 70nm)을 $RuO_2$와 BST사이에 증착하여 2중 BST구조를 형성시켰다. 비정질 BST층의 도입을 통해, BST박막의 평균 입도가 증가하고, 표면 거칠기가 감소하여 전체 BST 박막의 미세구조와 표면 mophology가 단일 BST박막에 비해 상당한 변화가 발생함을 확인하였다. 30nm의 비정질측이 적용된 BST박막의 경우, 하부기판의 영향으로부터 비교적 자유로운 미세구조를 갖는 BST 박막이 형성되었다. 2중 BST 박막의 경우 유전상수는 340, 누설전류는 $6.85{\times}10^{-7}A/{\textrm}{cm}^2$로서 비정질층을 갖지 않는 단일 BST 박막에 비하여(유전상수: 152, 누설전류: $1.25{\times}10^{-5}A/{\textrm}{cm}^2$)놀라운 전기적 특성의 향상이 이루어짐을 확인하였다.