• 대한기계학회논문집
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• 제16권9호
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• pp.1796-1804
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• 1992

본 연구에서는 동심확산화염내에 생기는 매연 입자의 크기와 농도를 광산란 소멸법으로 보다 정확히 측정하여 궁극적 목적인 매연입자 제어의 기반을 조성하고자 한다.

• 한국산림과학회지
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• 제97권5호
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• pp.552-554
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• 2008

Acer palmatum was selected and its responses to elevated ozone were subsequently measured during growing periods. Ozone concentration of this study was compared to the calculated AOT40 value. A. palmatum had significantly many but small stomata size to the ozone stress. The length of stomata of A. palmatum was reduced from 5.6 to $5.0{\mu}m$ to the ozone exposure. However, the number of stomata (density) was increased from 102 to 131 in the $500{\times}500{\mu}m$ leaf area.

• 한국축산식품학회지
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• 제24권3호
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• pp.273-276
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• 2004

The objective of this study was to investigate the microstructure of folic acid-contained yogurt. Folic acids (25 and 50%) were added to milk preparation prior to pasteurization, then starter culture was added. The microstructure of yogurt containing folic acid was determined by the size of cluster of casein micelle using scanning electron microscopy and transmission electron microscopy. The cluster of casein micelle in yogurt containing folic acid were showed larger size than in control (p<0.05). In addition of 50% of folic acid, cluster of casein micelle per unit area was exhibited the highest number among tested yogurts. From these results, folic acid concentration of yogurt may be affected by mouth-feel of yogurt texture as well as the aggregation of casein micelle.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권9호
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• pp.429-433
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• 2006

PZT(80/0) powder was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The coating and drying procedure was repeated 4 times. And then the PZT(20/80) precusor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5mol/L and the number of coating was varied from 0 to 6. The porosity decreased and the grain size increased with increasing the number of coatings. The thickness of the PZT-6(6: number of coatings) films was about $60{\mu}m$. The relative dielectric constant increased and the dielectric loss decreased with increasing the number of PZT(20/80) sol coatings. The relative dielectric constant and dielectric loss of the PZT-6 thick film were 275 and 3.5%, respectively. The remanent polarization, coercive field and breakdown strength of the PZT-6 film were $19.8{\mu}C/cm^2$, 13.7kV/cm and 130kV/cm, respectively.

• 한국분말재료학회지
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• 제31권2호
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• pp.132-136
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• 2024

This study investigated the effects of revolution speed and ball size in planetary milling on the microstructure and dehydrogenation behavior of TiH₂ powder. The particle size analysis showed that the large particles present in the raw powder were effectively refined as the revolution speed increased, and when milled at 500 rpm, the median particle size was 1.47 ㎛. Milling with a mixture of balls of two or three sizes was more effective in refining the raw powder than milling with balls of a single size. A mixture of 3 mm and 5 mm diameter balls was the optimal condition for particle refinement, and the measured median particle size was 0.71 ㎛. The dependence of particle size on revolution speed and ball size was explained by changes in input energy and the number of contact points of the balls. In the milled powder, the endothermic peak measured using differential thermal analysis was observed at a relatively low temperature. This finding was interpreted as the activation of a dehydrogenation reaction, mainly due to the increase in the specific surface area and the concentration of lattice defects.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1191-1199
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• 2003

This paper describes to observe the combustion process of only one droplet cluster. In this study, liquid fuel was atomized by ultrasonic wave to form an acoustically levitated droplet cluster. In order to elucidate the detailed structure of burning process of the droplet cluster, laser tomography method was applied. Time-series planar images of fuel droplets were processed and diameter of the each droplet was calculated based on the Mie-scattering theory. Using these data, the modified droplet group combustion number was estimated in time-series. As the result, when the internal droplet group combustion occur, the modified group combustion number dose not decrease monotonically, but show a tow-staged decreasing process. In all case of combustion process, combustion reactions were measured two types that combustion speed was fast and slow. It was casued by difference of concentration degree and droplet size distribution.

• 대한기계학회논문집B
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• 제24권10호
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• pp.1359-1367
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• 2000

In-situ particle monitors(ISPMs) are widely used for monitoring contaminant particles in vacuum-based semiconductor manufacturing equipment. In the present research, the performance of a Particle Measuring Systems(PMS) Vaculaz-2 ISPM at low pressures has been studied. We generated the uniform sized methylene blue particle beams using three identical aerodynamic lenses in the center of the vacuum line, and measured the detection efficiency of the ISPM. The effects of particle size, particle concentration, mass flow rate, system pressure, and arrangement of aerodynamic lenses on the detection efficiency of the ISPM were examined. Results show that the detection efficiency of the ISPM greatly depends on the mass flow rate, and the particle Stokes number. We also found that the optimum Stokes number ranges from 0.4 to 1.9 for the experimental conditions.

• 한국분무공학회지
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• 제22권1호
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• pp.1-7
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• 2017

Recently, Performance and fuel efficiency of gasoline engines have been improved by adopting direct injection (DI) system instead of port fuel injection (PFI) system. However, injecting gasoline fuel directly into the cylinder significantly reduces the time available for mixing and evaporation. Consequently, particulate matters(PM) emissions increase. Moreover, as the emission regulations are getting more stringent, not only the mass but also the total number of PM should be reduced to satisfy the Euro VI regulations. Increasing the fuel injection pressure is one of the methods to meet this challenge. In this study, the effects of increased fuel injection pressures on combustion and emission characteristics were experimentally examined at several part load conditions in a 1.6 liter commercial gasoline direct injection engine. The main combustion durations decreased about $2{\sim}3^{\circ}$ in crank angle base by increasing the fuel injection pressure due to enhanced air-fuel mixing characteristics. The exhaust emissions and number concentration distributions of PM with particle sizes were also compared. Due to enhanced combustion characteristics, THC emissions decreased, whereas NOx emissions increased. Also, the number concentrations of PM, larger than 10 nm, also significantly decreased.

• Korean Chemical Engineering Research
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• 제43권5호
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• pp.609-615
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• 2005

$1{\mu}l$ 정도의 미량 titanium tetraisopropoxide(TTIP)를 주사기를 사용하여 1 cc 부피의 증발관에 주입하여 기화시킨 후 질소에 의해 직경 4 mm, 길이 35 cm의 관형 에어로졸반응기로 운반하여 열분해 시킴으로써 30-300 nm 크기의 $TiO_2$ 나노입자를 제조하였으며, 반응온도 및 TTIP 증기 농도가 생성된 $TiO_2$ 입자의 형상, 크기, 결정성 등에 미치는 영향을 조사하였다. 전구체 증기 농도 1 mol%에서 반응온도를 300, 500, $700^{\circ}C$로 변화시킨 결과 반응온도가 증가함에 따라 응집체를 구성하고 있는 1차 입자 크기가 감소하였고, $700^{\circ}C$에서는 입자 크기분포가 bimodal 형태를 나타내었다. 반응온도를 $700^{\circ}C$로 유지하고 전구체 증기 농도를 1, 3.5, 7 mol%로 변화시킨 결과 전구체 증기 농도 3.5 mol% 이상에서는 1 mol%에서 관찰되었던 bimodal 분포가 사라지고 응집체 내 1차 입자들의 개수가 상대적으로 많이 증가하였다. 반응온도 및 전구체 농도가 입자의 형상, 크기분포에 미치는 이와 같은 영향들을 이전의 연구결과들과 함께 비교 분석하였다.

• 한국수자원학회논문집
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• 제33권4호
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• pp.461-469
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• 2000

본 연구에서는 부유입자를 포함하는 유동을 입자크기와 입자량을 달리한 몇 가지 경우에 대하여 수치적으로 해석하고 Coleman(1981, 1986)의 실험결과와 비교하였다. 완전 난류 유동장을 해석하기 위하여 k-$\omega$난류모형을 사용하였으며, 농도장 해석을 위해서는 침강속도를 고려한 일반화된 농도방정식을 적용하였다. 유동과 입자의 상호작용은 Einstein과 Chien(1955)의 모형을 도입하여 수치계산하였다. 기존의 대부분 연구에서는 소유사의 두께를 고려하지 않은 연구를 수행하였으나, 입자량이 많아지거나 입자크기가 클 경우 이를 무시할 수 없는 것으로 밝혀졌다. 소유사의 두께와 하상에 의한 표면 거칠기 효과를 고려하여 본 연구를 수행하였는데, 여기서 농도분포를 결정짓게 되는 $\beta$값이 입자의 크기와 입자량에 관련되어 있다는 사실을 확인할 수 있었다. 기존 연구결과는 $\beta$가 1.0보다 큰 값을 가진다고 보고되었으나, 본 연구를 통해 1.0보다 작아질수 있음이 확인되었고, 이는 최근에 보고된 연구 결과와 일치되는 결과이다.