• 대한화학회지
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• 제39권5호
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• pp.399-407
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• 1995

회토류와 악티늄족 원소의 현장분석을 목적으로 휴대용 극미량 분석용 원자 분광계인 Electrothermal-Hollow Cathode Glow Discharge Spectrometry(Et-HCGDS)가 제작되었다.본 분광계의 기본 구조는 전기열과 글로우 방전에 기초를 두고 있으며 본 분광계가 미량의 원소분석에도 유용함을 실험적으로 살펴보았다. 본 연구는 새로이 제작된 Et-HCGDS라는 글로우방전 시스템을 사용하여 공기의 저온 플라스마를 만들고 여기서 얻은 공기의 방출 스펙스럼에 관하여 연구하였다. 본 연구를 통하여 Et-HCGDS를 사용할시에 공기가 흐름가스로 유용하며 이 경우 대기의 분석도 쉽게 이루어질 수 있음을 알았다. 글로우 방전을 이용하여 관찰한 공기의 방출 스펙트럼의 분석을 통하여 볼 때 거의 질소에 의한 방출이 전 자외선과 가시광선 영역에서 골고루 나타남을 살펴보았다. 공기를 흐름가스로 사용할 시에도 여러파장 영역에서 미량 분석이 가능함을 알았다. 이 결과는 앞으로 Et-HCGDS를 사용하여 현장에서 공기만을 사용하여 분석을 수행할 경우에 필요한 기초 자료로 활용될 수 있으리라 본다. 본 연구에서 수행한 공기 방출 스펙트럼의 분석은 대기 분석 및 물질 분석에도 중요한 기초자료로 쓰이게 되리라 기대하며 이와 더불어 방출을 이용한 분광분석에서 공기로 인한 간섭 스펙트럼등을 이해하는 경우에도 중요한 참고자료로 활용되리라 본다.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1808-1815
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• 2001

The characteristics of a pulsed plasma jet originating from an electrothermal capillary discharge have been investigate using laser-induced fluorescence (LIF) measurement. Previous emission measurements of a 3.1 kJ plasma jet show trial upstream of the Mach disk the temperature and electron number density are about 14,000 K and and 10$\^$17/ cm$\^$-3/, while downstream of the Mach dick tole values are about 25,000 K and 10$\^$18/ cm$\^$-3/, respectively. However, these values are barred on line-of-sight integrated measurements that may be misleading. Hence, LIF is being used to provide both spatially and temporally resolved measurements. Our recent work has been directed at using planar laser-induced fluorescence (PLIF) imaging of atomic copper in the plasma jet flow field. Copper is a good candidate for PLIF studies because it is present throughout the plasma and has electronic transitions that provide an excellent pump-detect strategy. Our PLIF results to date show that emission measurements may give a misleading picture of the flow field, as there appeals to be a large amount of relatively low temperature copper outside the barrel shock. which may lead to errors in temperature inferred from emission spectroscopy. In this paper, the copper LIF image is presented and at the moment, relative density of atomic copper, which is distributed in the upstream of the pulsed plasma jet, is discussed qualitatively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2648-2651
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• 2008

In AC electrowetting, it has been reported that there is a flow inside droplets. The flow characteristics such as flow rate, direction and the pattern of streamline are altered according to the frequency range of applied voltage. However, the mechanism of the flow has not been explained yet. This work is concentrated on investigation of the flow mechanism when high-frequency voltage is applied to droplets. We propose that this phenomenon arises from the electro-thermal flow. A numerical analysis is performed for the needle-electrode-plane geometry in which the Coulombic force term is included in the Navier-Stokes equation. According to our analysis, electrical charge is generated due to conductivity gradient which is originated from the nonuniform Joule heating of fluid medium. The result of the analysis is compared with experimental result.

• 분석과학
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• 제15권6호
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• pp.514-520
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• 2002

효율적인 시료의 분석을 위하여 개선된 전열증기화 속빈음극관 글로우 방전 우너자방출분광 장치를 제작하여 그에 대한 기초 연구를 수행하였다. 본 시스템은 개선된 속빈음극관 글로우 방잔에 개선된 전열증기화법을 이용한 샘플주입방법을 응용하였으며, ${\mu}{\ell}$단위의 적은 양으로도 분석가능하도록 순수한 텅스템 재질로 된 나선형 코일을 제작하여 증기화 효율을 최대한 높일수 있도록 하여 글로우 방전으로 최대한 많은 양이 주입될 수 있도록 개선하였다. 최적화된 분석조건을 위한 방전조건으로 시료운반기체 사용량과 방전 전력을 측정하였으며, 그 전에 글로우 방전셀의 냉각장치 및 내부의 구조적인 문제 여부에 따른 방출세기에 미치는 영향과 측정 정밀도를 관찰하였다. 방출되어 발생된 빛은 광전송용 광파이버에 의하여 효율적으로 검출기에 운반되도록 구성 제작하였으며, 마지막으로 본 연구결과에 의한 직선성을 관찰하였다.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1691-1698
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• 2001

In recent years, significant progress has been made in modeling turbulence behavior in plasma and its effect on transport. It has also been made in diagnostics for turbulence measurement; however, there is still a large gap between theoretical model and experimental measurements. Visualization of turbulence can improve the connection to theory and validation of the theoretical model. One method to visualize the flow structures in plasma is a laser Schlieren imaging technique. We have recently applied this technique and investigated the characteristics of a highly underexpanded pulsed plasma jet originating from an electrothermal capillary source. Measurements include temporally resolved laser Schlieren imaging of a precursor blast wave. Analysis on the trajectory of the precursor blast wave shows that it does not follow the scaling expected for a strong shock resulting from the instantaneous deposition of energy at a point. However, the shock velocity does scale as the square root of the deposited energy, in accordance with the point deposition approximation.

• 한국가시화정보학회지
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• 제17권1호
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• pp.69-77
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• 2019

This paper introduces microfluidic manipulation of microorganism by opto-electrokinetic technique, named rapid electrokinetic patterning (REP). REP is a hybrid method that utilizes the simultaneous application of a uniform electric field and a focused laser to manipulate various kinds and types of colloidal particles. Using the technique in preliminary experiments, we have successfully aggregated, translated, and trapped not only spherical polystyrene, latex, and magnetic particles but also ellipsoidal glass particles. Extending the manipulation target to cells, we attempted to manipulate saccharomyces cerevisiae (S. cerevisiae), the most commonly used microorganism for food fermentation and biomass production. As a result, S. cerevisiae were assembled and dynamically trapped by REP at arbitrary location on an electrode surface. It firmly establishes the usefulness of REP technique for development of a high-performance on-chip bioassay system.

• 한국전산유체공학회지
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• 제14권1호
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• pp.70-77
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• 2009

In this study, time-dependent numerical analysis was carried out to investigate the plasma jet impingement on a flat plate, and a compressible form of two-dimensional inviscid gas dynamics equations were solved using the flux corrected transport algorithm. The mathematical modeling of Joule heating in the polycarbonate capillary bore and the mass ablation from the bore wall was incorporated in the numerical analysis and the series of computation was performed for three cases depending on the distance of the opposing plate from the capillary exit. The computational results reveal that the presence of the opposing plate does not affect the flow conditions inside the capillary when compared to the case of open-air plasma discharge. In the exterior region, the flow structure shows the typical supersonic underexpanded jet which consists of the strong Mach disk in front of the opposing plate and the barrel shock at the side of the jet. It is found that the shock evolution becomes more quasi-steady when the plate distance decreases. Also, the effects of the distance between the capillary bore exit and the opposing plate on the flow conditions along the opposing plate are investigated and the pressure variation on the plate shows more complicated interaction between the plasma discharge and the opposing plate when the location of plate becomes closer to the capillary exit.