• 한국레이저가공학회지
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• 제17권1호
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• pp.1-6
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• 2014

Indium tin oxide (ITO) is an important transparent conducting oxide (TCO). ITO films have been widely used as transparent electrodes in optoelectronic devices such as organic light-emitting devices (OLED) because of their high electrical conductivity and high transmission in the visible wavelength. Finding ways to control ITO micromachining depth is important role in the fabrication and assembly of display field. This study presented the depth control of ITO patterns on glass substrate using a femtosecond laser and slit. In the proposed approach, a gaussian beam was transformed into a quasi-flat top beam by slit. In addition, pattern of square type shaped by slit were fabricated on the surfaces of ITO films using femtosecond laser pulse irradiation, under 1030nm, single pulse. Using femtosecond laser and slit, we selectively controlled forming depth and removed the ITO thin films with thickness 145nm on glass substrates. In particular, we studied the effect of pulse number on the ablation of ITO. Clean removal of the ITO layer was observed when the 6 pulse number at $2.8TW/cm^2$. Furthermore, the morphologies and fabricated depth were characterized using a optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS).

• Journal of Magnetics
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• 제21권2호
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• pp.266-272
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• 2016

Transcranial magnetic stimulation devices has been used mainly for diagnostic purposes by measuring the functions of the nervous system rather than for treatment purposes, and has a problem of considerable energy fluctuations per repeated pulse. The majority of strokes are caused by ischemia and result in brain tissue damage, leading to problems of the central nervous system including hemiparesis, dysfunction of language and consciousness, and dysfunction of perception. Control is difficult and the size is large due to the difficulty of digitalizing the energy stored in a capacitor, and there are many heavy devices. In addition, there are many constraints when it is used for a range of purposes such as head and neck diagnosis, treatment and rehabilitation of nerve palsy, muscle strengthening, treatment of urinary incontinence etc. Output stabilization and minimization of the energy variation rate are required as the level of the transcranial magnetic stimulation device is dramatically improved and the demand for therapeutic purposes increases. This study developed a compact, low cost transcranial magnetic stimulation device with minimal energy variation of a high repeated pulse and output stabilization using a real time capacitor charge discharge voltage. Ischemia was induced in male SD rats by closing off the common carotid artery for 5 minutes, after which the blood was re-perfused. In the cerebrum, the number of PARP reactive cells after 24 hours significantly decreased (p < 0.05) in the TMS group compared to the GI group. As a result, TMS showed the greatest effect on necrosis-related PARP immuno-reactive cells 24 hours after ischemia, indicating necrosis inhibition, blocking of neural cell death, and protection of neural cells.

• 대한화학회지
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• 제32권2호
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• pp.130-134
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• 1988

수은방울전극에서 바로 시안이온을 시차펄스음극벗김 전압전류 법으로 측정한 결과 검출한계를 낮출수가 있었다. 가장 알맞는 실험조건은 다음과 같다. : 0.1M KCl-0.01M 인산염 지지전해질, pH 7, 석출전위 0.00V, 그리고 석출시간 3분이었다. 이 조건에서 검출한계는 $3{\times}10^{-7}M$ (8ppb) $CN^-$이다.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.74-78
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• 2008

High-speed tool steels are extensively used in tooling industries for manufacturing cutting tools, forming tools, and rolls. Electrical discharge machining (EDM) has been found to be an effective process for machining these extremely hard and difficult-to-cut materials. Extensive research has been conducted to identify the optimum machining parameters for EDM with different tool steels. This paper presents a fundamental study of the surface characteristics of SKH-51 tool steel machined by micro-EDM, with particular focus on obtaining a better surface finish. An RC pulse generator was used to obtain a better surface finish as it produces fine discharge craters. The main operating parameters studied were the gap voltage and the capacitance while the resistance and other gap control parameters were kept constant. A negative tungsten electrode was used in this study. The micro-EDM performance was analyzed by atomic force microscopy to determine the average surface roughness and the distance between the highest peak and lowest valley. The topography of the machined surface was observed using a scanning electron microscope and a digital optical microscope.

• 한국방사선학회논문지
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• 제5권4호
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• pp.161-169
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• 2011

본 연구는 입체적 분포를 형성한 시각신경계에 대하여 MRI 시스템의 경사자기장으로써 하나의 스캔 대상단면을 3차원 형태의 여러 방향으로 향하게 하는 다중사위 스캔각도의 변화에 관하여 실험하였고 기존의 단순각도 사방향 검사방법과 비교 고찰 하였다. 입체적 분포를 이루는 뇌의 시각신경계에 대하여 MR 시스템의 경사자기장으로써 국내 정상 성인을 대상으로 시각신경의 사위영상화를 위한 기존의 사위(시상-관상단면) 스캔방법과 다중사위(시상-관상-횡단면) 스캔각도의 변화를 실험하였다. 그 결과 다중각도를 이용한 사위스캔 방법이 기존의 스캔방법에 비해 더 넓은 영역의 해부학적 정보를 나타내는 것을 영상으로 확인하였다. 또한 시각신경을 명료하게 나타내기 위해서는 영상단면두께와 펄스시퀀스의 선택도 고려되어야할 것으로 확인 되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.818-819
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• 2015

PAL-XFEL 장치에 사용 할 고전압 펄스 모듈레이터 출력파워는 수 ${\mu}s$ 범위의 짧은 고전압(400 kV), 대전류(500 A) 펄스를 요구한다. 이러한 펄스파워를 얻기 위해서 PFN(Pulse Forming Network)에 에너지를 축적하고, 플라즈마 스위치인 싸이라트론을 통하여 에너지를 신속하게 클라이스트론 쪽으로 전달한다. 클라이스트론은 모듈레이터에서 공급하는 펄스 전원을 이용하여 RF를 증폭하는 대출력 고주파 증폭장치이다. 고전압 펄스 모듈레이터 제어기는 고속펄스 신호처리 모듈(Fast Pulse Signal Conditioning Module), PLC(Programmable Logic Controller)로 구성되어 있다. 고전압 펄스 모듈레이터에 사용하는 대용량 싸이라트론은 고전력을 스위칭 할 때 발생하는 스위칭 노이즈는 매우 크다. 이러한 노이즈는 모듈레이터의 출력 시그널인 빔 전압, 빔 전류, EOLC(End of Line Clipper) 전류, DC high voltage에 섞여 있으면서 신호 왜곡 및 제어장치의 고장을 유발시킨다. 이처럼 노이즈가 많이 포함되어 있는 아닐로그 신호를 깨끗한 신호(a clean signal)로 바꾸어주는 노이즈 필터링 장치인 고속펄스 신호처리 모듈을 제작하여 실험한 결과를 알아보고 모듈레이터 인터록 시스템인 PLC에서 Dynamic Interlock의 응답시간을 빠르게 하기위한 회로 수정에 대한 결과에 관하여 기술하고자 한다.

• 한국분말재료학회지
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• 제12권3호
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• pp.167-173
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• 2005

Production of weakly agglomerated nanopowders with the characteristic size of about 10 nm and a narrow particle size distribution is still a topical problem especially if the matter is an acceptable output (>50 g/hour), a high purity of the final product, and a low (energy consumption. The available experience and literature data show that the most promising approach to production of such powders is the evaporation-condensation method, which has a set of means for heating of the target. From this viewpoint the use of pulsed electron accelerators for production of nanopowders is preferable since they allow a relatively simple adjustment of the energy, the pulse length, and the pulse repetition rate. The use of a pulsed electron accelerator provides the following opportunities: a high-purity product; only the target and the working gas will interact and their purity can be controlled; evaporation products will be removed from the irradiation zone between pulses; as a result, the electron energy will be used more efficiently; adjustment of the particle size distribution and the characteristic size of particles by changing the pulse energy and the irradiated area. Considering the obtained results, we developed a design and made an installation for production of nanopowders, which is based on a hollow-cathode pulsed gas-filled diode. The use of a hollow-cathode gas-filled diode allows producing and utilizing an electron beam in a single chamber. The emission modulation in the hollow cathode will allow forming an electron beam 5 to 100 ms long. This will ensure an exact selection of the beam energy. By now we have completed the design work, manufactured units, equipped the installation, and began putting the installation into operation. A small amount of nanopowders has been produced.

• 전기학회논문지
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• 제59권4호
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• pp.762-767
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• 2010

This paper describes characteristic of a light triggered thyristor investigated by experiment to adopt it into a main switch of a pulsed power unit. Triggering principle of the light triggered thyristor are referred with its structure and equivalent circuit. Operational principle and simulation result of a capacitive pulsed power circuit are explained. A variety of triggering conditions of triggering circuit and characteristics on turn-on, turn-off, voltage dividing in series operation, overvoltage protection function of the light triggered thyristor are investigated by experiments. Experimental result of 40 kJ pulsed power unit using the light triggered thyristor is presented.

• 전기학회논문지
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• 제62권7호
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• pp.937-942
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• 2013

Equivalent series impedance of high-voltage pulsed power capacitor is one of the important electrical characteristics both for users and for capacitor manufacturers because it may have serious effects on the performance of pulse forming circuits. In this paper, definition of equivalent series impedance and factors which generate equivalent series impedance are reviewed. Theoretical analysis for the calculation of equivalent series impedance based on differential measurement method is described and calculation program has been developed. In order to acquire data which are necessary to calculate equivalent series impedance from discharging current waveform, charging-dischargig controller has been manufactured. Measurement results of equivalent series impedance for high voltage pulsed power capacitor have been given.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1389_1390
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• 2009

펄스파워 전원장치에서 전류펄스 파형을 성형하기 위해 인덕터를 이용한다. 이 인덕터는 고주파용이므로 철심(core)이 없는 공심이어야 하며, 또한 표피효과(skin effect)로 인한 저항손실의 영향을 줄일 수 있는 구조로 제작되어야 한다. 표피효과를 줄이기 위해서, 인덕터는 권선의 동판을 3장 겹쳐서 나선형으로 감은 젤리롤(jelly roll)형으로 제작하였고, 실험을 통하여 인덕턴스값과 저항값을 측정한 결과를 소개 하고자 한다.