• 대한기계학회논문집B
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• 제25권4호
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• pp.496-506
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• 2001

The effect of corona discharge on soot emission was experimentally investigated. Size and number concentrations of soot aggregates were measured and compared for various voltages. Regardless of the polarity of the applied voltage, the flame length decreased and the tip of flame spreaded with increasing voltage. For the experimental conditions selected, the flame was blown off toward the ground electrode by corona ionic wind. When the negative applied voltage was greater than 3kV(for electrode spacing = 3.5cm), soot particles in inception or growth region were affected by the corona discharge, resulting in the reduction of number concentration. The results show that the ionic wind favored soot oxidation and increased flame temperature. Number concentration and primary particle size greatly increased, when the corona electrodes were located the region of soot nucleation or growth(close to burner mouth).

• Korea-Australia Rheology Journal
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• 제17권2호
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• pp.35-40
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• 2005

Nanofluid is a novel heat transfer fluid prepared by dispersing nanometer-sized solid particles in traditional heat transfer fluid to increase thermal conductivity and heat transfer performance. In this research we have considered the rheological properties of nanofluids made of CuO particles of 10-30nm in length and ethylene glycol in conjunction with the thermal conductivity enhancement. When examined using TEM, individual CuO particles have the shape of prolate spheroid of the aspect ratio of 3 and most of the particles are under aggregated states even after sonication for a prolonged period. From the rheological property it has been found that the volume fraction at the dilute limit is 0.002, which is much smaller than the value based on the shape and size of individual particles due to aggregation of particles. At the semi-dilute regime, the zero shear viscosity follows the Doi-Edwards theory on rodlike particles. The thermal conductivity measurement shows that substantial enhancement in thermal conductivity with respect to particle concentration is attainable only when particle concentration is below the dilute limit.

• 천문학회지
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• 제34권4호
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• pp.231-235
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• 2001

Cosmic-ray acceleration, although physically important in many astrophysical contexts, is difficult to incorporate into numerical models,. because it involves microphysics that is generally far from thermodynamic equilibrium, and also because the length and time scales for that physics typically range over many orders of magnitude, reflecting the huge range of particle rigidities that must be represented. The most common accelerator models are stochastic in nature and involve nonequilibrium plasma properties that are also often poorly understood. Still, nature clearly finds a way to produce simple, robust and almost scale-free energy distributions for the cosmic-rays. Their importance has inspired a number of approaches to examining the production and transport of cosmic-ray particles in numerical simulations. I offer here a brief comparison of some of the methods that have been introduced.

• 한국전기전자재료학회논문지
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• 제16권1호
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• pp.70-76
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• 2003

For the development of superconducting power apparatus, it is necessary to establish the dielectric technology in coolant like L$N_2$. Therefore in this paper we conducted experiment of surface flashover that could occur in the windings of HTS transformer which will be developed in the pancake coil type. First, we distinguished two types of surface flashover by electrode alignment, such as parallel and vertical, and then compared with each characteristics of surface flashover. The flashover voltage was more affected by thickness of spacer than by surface length when the thickness of spacer is over 1 mm. And the surface flashover with metallic particle attached on the spacer was tested, it was affected by the particle position. The more close to the electrodes, the worse the characteristics. Also the experiment was conducted when the electrode was immersed in liquid nitrogen(L$N_2$) partially. The surface flashover characteristics of spacer was, when immersed partially in 50%, rapidly decreased.

• Journal of Forest and Environmental Science
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• 제23권2호
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• pp.73-78
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• 2007

Ultrasonic deinkings of white ledger were carried out to confirm whether the ink removal efficiency and pulp qualities can be improved by the ultrasonic deinking. The effects of conventional pulping and ultrasonic treatment of white ledger on the ink particle size distribution and ink removal coefficient were compared. The physical properties of paper, energy consumption and effluent qualities were measured. The ultrasonic treatment of white ledger resulted in the ink particle size distribution suitable for flotation. The ink removal efficiency, brightness, breaking length and effluent quality were improved by the ultrasonic deinking. It is expected that the competitiveness of ultrasonic deinking system can be improved by the optimization of treatment condition.

• 대한기계학회논문집
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• 제13권4호
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• pp.703-707
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• 1989

본 연구에서는 반무한체에 대하여 활성화 에너지가 매우 큰 경우의 점근법을 적용하여 이 두 변수의 시간에 따른 변화가 점화지연시간에 미치는 영향을 해석적으로 알아보고 참고문헌(1)의 실험치와 비교하고자 한다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.238-239
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• 2006

Nozzle geometry influences gas dynamics making sprayed particle behavior one of the most important parameters in cold spray process. Gas flows at the entrance convergent section of the nozzle takes place at relatively high temperature and are subsonic. Thus, this region is a very suitable environment for heating spray particle. In this study, numerical simulation and experiments were conducted to investigate the effect of nozzle contour, entrance geometry of nozzle and powder injection position at nozzle on the cold spray process. The process changes were observed through numerical simulation studies and the results were used to find a correlation with coating properties.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.645-647
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• 1993

Surface breakdown characteristics are investigated under metallic-particle contaminated conditions in $SF_6$ gas. The main results show that a rib increases breakdown voltage by a corona stabilization effect and the elongation of discharge path. The breakdown voltage at higher pressures than 4 atm may be estimated on the basis of mean breakdown field strength($E_{BD}$) and discharge length(L) which depend on gas pressure and surface shape.

• Ocean Systems Engineering
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• 제12권3호
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• pp.285-300
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• 2022

This paper adopts the Smoothed Particle Hydrodynamics (SPH) open-source code SPHinXsys to study the solitary wave interaction with coastal structures. The convergence properties of the model in terms of particle size and smoothing length are tested based on the example of solitary wave propagation in a flat-bottom wave flume. After that, the solitary wave interactions with a suspended submerged flat plate and deck with girders are studied. The wave profile and velocity field near the surface of the structures, as well as the wave forces exerted onto the structures are analyzed.

• 한국초지조사료학회지
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• 제5권1호
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• pp.73-78
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• 1985

본(本) 연구(硏究)는 Sorghum-Sudan hybrid를 생육시기별(生育時期別)로 절단(切斷)길이를 달리하여 silage를 제조하였을 때 이들이 silage의 품질(品質)에 미치는 영향을 구명(究明)하고저 실시되었다. 출수기(出穗期), 유숙기(乳熟期), 호숙기(糊熟期), 황숙기(黃熟期)에 예취(刈取)하여 각(各) 생육시기별(生育時期別)로 절단(切斷)길이를 1.0, 2.5 4.0cm로 하여 silage를 제조한 후 silage의 일반성분(一般成分), 유기산함량(有機酸含量), pH 및 Ammonia 태(態) N를 분석(分析)하여 silage의 품질(品質)을 평가(評價)하고, 주요성분간(主要成分間)의 상호관계(相互關係)를 분석(分析)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 생육(生育)이 진행(進行)됨에 따라 수분함량(水分含量)은 감소되어 건물함량(乾物含量)이 증가(增加)되었다. 조단백질함량(粗蛋白質含量)은 출수기(出穗期)에 12.55%에서 생육(生育)이 진행(進行)됨에 따라 감소하였고, 조섬유(粗纖維)는 증가(增加)하는 현상이었다. 2. Silage의 수분함량(水分含量)은 생육(生育)이 진행(進行)됨에 따라 현저히 감소되었다 (P<0.01). 3. Silage의 pH는 2.5cm로 절단(切斷)한 것이 가장 낮게 나타났으나 유의차(有意差)는 없었고 황숙기(黃熟期)가 3.53으로 가장 낮았으며 호숙기(糊熟期)가 4.59로 가장 높았다 (P<0.01). 4. Total-N에 대(對)한 Ammonia 태(態) N의 비율은 출수기(出穗期)가 16.3%로 가장 많고 호숙기(糊熟期)는 9.2%로 가장 적었다. 5. 유기산함양(有機酸含量)은 절단(切斷)길이별(別)로는 일정치 않으나 황숙기(黃熟期)가 유산(乳酸)은 많고 낙산(酪酸)이 없어 가장 양질(良質)의 silage를 만들 수 있는 것으로 나타났다. 6. pH와 유산(乳酸)(r=-0.719), 총산(總酸)(r=-0.716)간(間)과 낙산(酪酸)과 Flieg's score(r=-0.872) 간(間)에는 부(負)의 상관(相觀)이 있었고(P<0.01), 유산(乳酸)과 총산(總酸)(r=0.990), 수분(水分)과 ammonia 태(態) N(r=0 767)간(間)에는 정(正)의 상관(相關)이 있었다(P<0.01).