• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.77-86
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• 2012

We have carried out a series of numerical experiments to study the effect of average particle size on the mechanical properties of granite-derived weathered soils. A distinct-element method was adopted to study the changes in macro-scale mechanical properties with particle size and maximum-to-minimum particle size ratio. The numerical soil specimen with cohesion values of 0.25 MPa and internal friction angle of 29 degrees was prepared for reference. While keeping the porosity values constant, we varied particle size and size distribution to study how cohesion and internal friction angle changes. The experimental results show that the values of cohesion apparently decrease with increasing particle size. Changes in the values of internal friction angles are small, but there is a trend of increase in internal friction angle as the average particle size increases. This study demonstrates a possibility that the results of numerical experiments of this type may be used for rapid estimation of mechanical properties of granite-derived weathered soils. For example, when mechanical properties obtained through in situ tests and particle size data obtained through lab analysis are available for a site, it is expected that the mechanical properties of weathered granite soils with varying degrees of weathering (thus, varying particle size) may be estimated rapidly only with particle size data for that site.

• Transactions on Electrical and Electronic Materials
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• v.4 no.1
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• pp.29-33
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• 2003

Europium doped yttrium oxide submicron-sized particles were prepared by ultrasonic aerosol pyrolysis. To examine the size effect of submicron-sized-particle, the photoluminescence of the particles was investigated. The particle size was controlled by pH, reaction temperature, molar concentration of yttrium in precursor solution. The PL intensity of submicron-sized particles was decreased with particles size. When the particle size is above about 150 times of Bohr radius of Y$_2$O$_3$, the optical property of the particles shows the bulk characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.946-949
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• 2002

Particulate contamination is known to be a significant cause of failures of removable storage media. In this work, The effect of particles on the surface damage of removable hard disk media was investigated. The particles of different materials and size were introduced to the head-disk interface using a particle injection system. It was found that the particles of particulate size and property serious damaged the media. This study showed that cleaning pad is effective for reducing particle contamination, except for the particles of specific size and property. As a means to removed the particles of specific size, the concept of using a stepped taper at the leading edge of the slider is proposed.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.145-148
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• 2011

The thermal behavior of lithiated Si anodes has been investigated using differential scanning calorimetry (DSC). In particular, the effect of Si particle size on the thermal stability of a fully lithiated Si electrode was investigated. For DSC measurements, a lithiated Si anode was heated in a hermetically sealed high-pressure pan with a polyvinylidene fluoride (PVDF) binder and a 1 M $LiPF_6$ solution in an ethylene carbonate (EC)-diethyl carbonate (DEC) mixture. The thermal evolution around $140^{\circ}C$ increases with lithiation and with decreasing particle size; this phenomenon is attributed to the thermal decomposition of the solid electrolyte interface (SEI) film. Exothermic peaks, following a broad peak at around $140^{\circ}C$, shift to a lower temperature with a decrease in particle size, indicating that the thermal stability of the lithiated Si electrode strongly depends on the Si particle size.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.5
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• pp.384-393
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• 1998

A mixed powder of electrolyte and matrix support materials with a proper proportion was used for the fabrication of an electrolyte matrix sheet. The purpose of this study is to reduce the large change in MCFC cell thickness occurring in the initial start-up period when separate sheets of electrolyte and support are used. A focus was put on how small the carbonate particles could be made. The particle size of the carbonate powder was controlled by ball milling and the distribution was measured using a particle size analyser. The thickness change was reduced to 20% by this approach, which could be compared to 27% observed in a conventional cell. The thickness changes of electrolyte matrix have linear relation sizes of carbonate powders.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.2
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• pp.113-123
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• 1990

To study deleterious effects of contaminants contained in lubricating systems, the effects of fine alumina particle concentration and size on the critical failure load, friction and wear characteristic were examined on boundary lubrication condition using the four ball machine. The following conclusions are deduced: The abrasive is found to cause a transition from mild wear to severe wear at less severe conditions than with clean oil. In mild wear region the friction and wear increase with particle size and concentration, but in severe wear region do not exhibit any definite trend. In relation to film thinckness there is a threshold of particle size beyond which the failure load no longer decreases with particle size.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1330-1337
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• 1994

This study is to predict the lateral dispersion of the particles with time in a vertical pipe. Particle is released downward and located in the center of a pipe through which stationary, homogeneous turbulent air is flowing. We assume that gas turbulence velocities have a Gaussian probability density distribution and the presence of particle is not to alter turbulent structures. Particle trajectory is computed by numerically integrating the particle Lagrangian equation of motion, with a random sampling to determine the fluctuating air velocity experienced by each particle, which considered inertia effect and crossing-trajectories effect. The result shows characterestics of particle dispersion according to flow field condition and droplet size by using the parameters and scales, which expressed characterestics of flow field and particle. Predictions agree reasonably with experimental data.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.155-161
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• 2001

In this study, we analyzed the $NO_X$ removal efficiency and particle size distribution by the pulsed corona discharge process and investigated the effect of several process variables. The NO removal efficiencies and the particle characteristics were measured and analyzed as the function of initial concentrations of NO, $H_2O$, and $NH_3$, applied voltage, pulse frequency and residence time. As the frequency of applied voltage increases, or as the applied voltage increases or as the residence time increases, the NO removal efficiency increases. The change of initial $NH_3$ and $H_2O$ concentrations do not affect the NO removal efficiency significantly. The particle concentration and size increases with the increases of initial NO concentration, residence time and applied voltage.

• Korean Journal of Materials Research
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• v.17 no.1
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• pp.50-55
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• 2007

Ultra-fine Copper powder for a conductive paste in electric-electronic field have been synthesized by chemical reduction of aqueous $CuSO_4$ with hydrazine hydrate $(N_2H_4{\cdot}H_2O)$ as a reductor. The effect of reaction conditions such as dispersant and reaction temperature on the particle size and shape for the prepared Cu powders was investigated by means of XRD, SEM, TEM and TGA. Experiments showed that type of dispersant and reaction temperature were affected on the particle size and morphology of the copper powder. When the carboxymethyl cellulose (CMC) was added as a dispersant the relative mono-dispersed and spherical Cu powder was obtained. Cu powders with particle size of approximately 140nm and narrow particle size distribution were obtained from 0.3M $CuSO_4$ with adding of 0.03M CMC and 40ml $N_2H_4{\cdot}H_2O$ at a reaction temperature of $70^{\circ}C$.

• Journal of Biosystems Engineering
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• v.26 no.5
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• pp.475-480
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• 2001

Sensing soil organic matter is crucial for precision farming and environment friendly agriculture. Near infra-red(NIR) was utilized to measure the soil organic matter. Multivariate calibration methods, including stepwise multiple linear regression(MLR), principal components recession(PCR) and partial least squares regression(PLS), were applied to soil spectral reflectance data to predict the organic matter content. The effect of soil particle size and water content was studied. The range of soil organic matter contents was from 0.5 to 11%. Near infrared (NIR) region from 700 to 2,500nm was applied. For uniform soil particle size, result had good correlation (R$\^$2/ = 0.984, standard error of prediction= 0.596). The effect of soil particle size could be eliminated with 1st order derivative of the NIR signal. However. moist soil had a little lower correlation. R$\^$2/ was 0.95 and standard error of prediction was 0.94% using the PLS method. The results showed the possibility of soil organic matter measurement using NIR reflectance on the field.