• Tribology and Lubricants
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• v.6 no.2
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• pp.94-98
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• 1990

The size and concentration of wear debris in lubricating oil often reveal the operating condition of the rotating machinery. To evaluate the possible application of light attenuation measurement for the estimation of wear debris concentration in the lubricating oil, the light transmittance through the lubricating oil cell contaminated with various concentrations of diatomire particles was measured, the attenuation coefficient was estimated from the transmittance measurement and the coefficients were compared with those obtained from the scattering theory. The comparision showed good agreements between them. It is also noted that the experimentally determined attenuation coefficient showed almost linear relation with particle weight coucentrations for the concentrations within the range of 2000 ppm. For the case of 0 ppm weight concentration of diatomire particles in the lubricating oil cell, the thickness of the cell required to give $100 \muW$ light attenuation is 7.75 mm. This result indicates that the light attenuation method will be one of the possible candidates of machine failure diagnostic sensors for the estimation of wear debris concentration in the lubricating oil.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.501-508
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• 1987

Experimental studies of particle (TiO$\_$2/) deposition from the laminar hot gas particle flow (about 1565K) onto the cold wall surface (about 1215K-1530K) were carried out by the 'real time' laser light reflectivity method (LLRM) and the photographs of scanning electron microscope(SEM). The LLRM was used for the measurement of thermophoretic deposition rates of small particles (d$\_$p/<3.mu.m), and the photographs of SEM were used for determining what factors control the collection of particles having diameters ranging from 0.2 to 30 microns. Two phenomena are primarily responsible for transport of the particles across the laminar boundary layers and deposition: (1) particle thermophoresis (i.e. particles migration down a temperature gradient), and (2) particle inertial impaction, the former effect being especially larger factor of the particle deposition in its size over the range of 0.2 to 1 microns. And also, this study indicates that thermophoresis can be important for particles as large as 15 microns. Beyond d$\_$p/=16.mu.m, this effect diminishes and the inertial impaction is taken into account as a dominant mechanism of particle deposition. The results of present experiments found to be in close agreement with existing theories.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.04a
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• pp.361-362
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• 2008

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.10a
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• pp.290-291
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• 2008

• Journal of Magnetics
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• v.19 no.4
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• pp.323-326
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• 2014

Superparamagnetic maghemite nanoparticles were prepared by chemical co-precipitation, followed by a temperate oxidation stage, and investigated using FE-SEM, XRD, TGA, VSM, and M$\ddot{o}$ssbauer spectroscopy. Through SEM image and XRD analysis, its average particle size was found to be 13.9 nm. While VSM magnetic measurement showed typical superparamagnetic behavior at room temperature, M$\ddot{o}$ssbauer spectroscopic investigation revealed that non-vanishing magnetic hyperfine structure were retained. Cation distribution estimated from M$\ddot{o}$ssbauer spectroscopy confirmed the formation of maghemite nanophase in the sample.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.434-435
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• 2002

에어로졸 입자의 크기 분포를 측정하는: 방법은 여러 가지가 있다. 이중 광학 입자계수기(Optical Particle Counter)는 직경 0.3-25$\mu\textrm{m}$의 입자의 산란광의 강도를 측정하여 입자의 크기별 개수를 측정하는 기기로 청정지역의 대기 중 부유하는 입자의 측정에 널리 사용되고 있다 (전영신 등, 1999). 본 연구에서는 기상청 기상연구소에서 측정한 광i부 입자계수기(HYAC/ROYCO 5230)의 측정자료를 이용하여 2001년도 1년간 서울의 대기 에어로졸의 특성과 경향을 분석하였다. 측정결과는 대기환경월보(환경부, 2001) (중략)

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.670-675
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• 2010

Inorganic-organic hybrid material such as vinyl-nano sized silica ball was synthesized by acrylo-alkoxysilane and nano silica ball with different particle size. And then they were formulated into acrylic-melamine clearcoat. This material is fully characterized with various analytical methods and applied for strength measurement. The glossy effect, matting effect and anti-scratching properties of materials were investigated for further growth and maintenance. When the particle size of nano silica ball is 20~30 nm, the glossy retain effect was increased by 7% compared to bare acrylic-melamine clearcoat. When a commercially available silica Aerosil 200 (Hydrophilic fumed silica, average particle size 12 nm, Degussa) react with vinyl alkoxysilane vinyl-fumed silica complex form. The vinyl-fumed silica along with clearcoat increases only 2% increase at glossy retain. Nano-scratch test results also support the glossy retain effect of vinyl nano-sized silica ball in clearcoat.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.453-458
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• 2020

In this study, ethylene-propylene-diene monomer (EPDM) rubbers reinforced with various particle size of carbon black were prepared and tested. We followed recently published CSA/ANSI CHMC2 standard "the test methods for evaluating material compatibility in compressed hydrogen applications-polyemr". Measurement of change in hardness, tensile strength and volume were performed after exposure to maximum operating pressure, 87.5 MPa, for 168 hours (1 week). Once EPDM was exposed to high-pressure hydrogen, the samples experience volume increase and degradation of the physical properties. Also, after the dissolved hydrogen was fully eliminated from the specimens, the hardness and the tensile properties were not recovered. The rubber reinforced with smaller sizes of carbon black particles showed less volume expansion and decrease of physical properties. As a result, smaller particle size of carbon black filler led to more resistance to high-pressure hydrogen.

• Journal of Powder Materials
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• v.23 no.2
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• pp.136-142
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• 2016

As precursors of cathode materials for lithium ion batteries, $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$ powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of $NH_4OH$ in air or nitrogen ambient. Calcination of the precursors with $Li_2CO_3$ for 8 h at $1,000^{\circ}C$ in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as $Ni_{1/3}Co_{1/3}Mn_{1/3}(OH)_2$. Regardless of the atmosphere, the final powders exhibit the XRD patterns of $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.59-64
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• 2011

Degree of unsaturation in fatty acid molecules plays an important role in the formation of vesicles. Vesicle formation from C18 fatty acids with different amount of double bonds such as oleic acid, linoleic acid and linolenic acid with the incorporation of 1,2-dipalmitoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DPPE-PEG2000) have been examined by TEM. Critical vesicular concentrations (CVC) of the vesicle suspension are determined by turbidity and surface tension methods. The CVC of fatty acids increases when the amount of unsaturation in the alkyl chain increases. On the other hand, stability of vesicle suspension has been examined by using particle size and zeta potential at $30^{\circ}C$. There was a dramatic decrease in particle size measurement from mono-unsaturation to tri-unsaturation which could be due to the effect of fluidity in the membrane bilayer caused by different degree of unsaturation. The values of zeta potential for vesicles that were formed without the incorporation of DPPE-PEG2000 were in the range of -70 mV to -100 mV. It has been observed that the incorporation of DPPEPEG2000 to the vesicle reduces the magnitude of zeta potential. However, this phenomenon does not obviously seen in fatty acid vesicles formed by linoleate-linoleic acid and linolenate-linolenic acid. We therefore conclude that the addition of DPPE-PEG2000 does not effectively improve the stability of the linoleate-linoleic acid and linolenatelinolenic acid vesicle at pH 9.0 after the evaluation of their particle size and zeta potential over a period of 30 days. Although the vesicles formed were not stable for more than 10 days, they have displayed the potential in encapsulating the active ingredients such as vitamin E and calcein. The results show that the loading efficiencies of vitamin E are of encouraging value.