• Preventive Nutrition and Food Science
• /
• v.16 no.2
• /
• pp.174-178
• /
• 2011

The cell permeability and cytotoxic effects of different-sized zinc oxide (ZnO) particles were investigated using a human colorectal adenocarcinoma cell line called Caco-2. Morphological observation by scanning electron microscopy revealed that three zinc oxides with different mean particle sizes (ZnO-1, 20 nm; ZnO-2, 90~200 nm; ZnO-3, $1\sim5\;{\mu}m$) tended to aggregate, particularly in the case of ZnO-1. When cytotoxicities of all three sizes of zinc oxide particles were measured at concentration ranges of $1\sim1000\;{\mu}g$/mL, significant decreases in cell viability were observed at concentrations of $50\;{\mu}g$/mL and higher. Among the three zinc oxides, ZnO-1 showed the lowest viability at $50\;{\mu}g$/mL in Caco-2 cells, followed by ZnO-2 and ZnO-3. The permeate concentration of ZnO-1 from the apical to the basolateral side in the Caco-2 model system after four hours was about three-fold higher than that of either ZnO-2 or ZnO-3. These results demonstrated that ZnO-1, with a 20 nm mean particle size, had poorer viability and better permeability in Caco-2 cells than ZnO-2 and ZnO-3.

• 연구논문집
• /
• s.28
• /
• pp.39-47
• /
• 1998

Industrial electrostatic precipitation is a very complex process, which involves multiple-way interaction between the electric field, the fluid flow, and the particulate motion. This paper describes a strongly coupled calculation procedure for the rigorous computation of particle dynamics during electrostatic precipitation. The turbulent gas flow and the particle motion under electrostatic forces are calculated by using the commercial computational fluid dynamics (CFD) package FLUENT linked to a finite-volume solver for the electric field and ion charge. Particle charge is determined from both local electrical conditions and the cell residence time which the particle has experienced through its path. Particle charge density and the particle velocity are averaged in a control volume to use Lagrangian information of the particle motion in calculating the gas and electric fields. The turbulent particulate transport and the effects of particulate space charge on the electrical current flow are investigated. The calculated results for poly-dispersed particles are compared with those for mono-dispersed particles, and significant differences are demonstrated.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.10a
• /
• pp.128-130
• /
• 2008

One of methods to increase the efficiency of a dye-sensitized solar cell(DSC) is the effective usage of the incident light. It can be controlled by using a light scattering layer. The light scattering effect makes that the optical path length of incident light to DSC increases. And then, the photocurrent and the efficiency is increased because of the increase of dye adsorption and the abundant amount of the light. In this study, we apply the light scattering layer to DSC by using two $TiO_2$ pastes that have different particle sizes. As a result, the photocurrent increases and the total efficiency is also increases in the case of using large-sized $TiO_2$ particle as the light scattering layer.

• 한국가시화정보학회:학술대회논문집
• /
• 2005.12a
• /
• pp.85-88
• /
• 2005

Experimental study has been conducted to evaluate characteristics of particle laden flows at the ratio of channel diameter to particle diameter (B = 14.9, 21.6 and 55). Particle velocities and radial concentrations are obtained using a microscope Nd:YAG laser and cooled CCD camera. Results show that there are relative velocities between the fluid and the particles at B = 14.9. It is also observed that the particles are accumulated at r=$0.5\∼0.82R$, with R being tile tube radius, and particle migration occurs at small Reynolds number, by comparing with the results obtained in macro scale. This gives optimal factors for designing microfluidic channels for cell or Particle separation, particle focusing, and so on.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.47.2-47.2
• /
• 2016

The protons and helium ions in the solar wind are observed to possess anisotropic temperature profiles. The anisotropy appears to be limited by various marginal instability conditions. One of the efficient methods to investigate the global dynamics and distribution of various temperature anisotropies in the large-scale solar wind models may be that based upon the macroscopic quasi-linear approach. The present paper investigates the proton and helium ion anisotropy instabilities on the basis of comparison between the quasi-linear theory versus particle-in-cell simulation. It is found that the overall dynamical development of the particle temperatures is quite accurately reproduced by the macroscopic quasi-linear scheme. The wave energy development in time, however, shows somewhat less restrictive comparisons, indicating that while the quasi-linear method is acceptable for the particle dynamics, the wave analysis probably requires higher-order physics, such as wave-wave coupling or nonlinear wave-particle interaction. We carried out comparative studies of proton firehose instability, aperiodic ordinary mode instability, and helium ion anisotropy instability. It was found that the agreement between QL theory and PIC simulation is rather good. It means that the quasilinear approximation enjoys only a limited range of validity, especially for the wave dynamics and for the relatively high-beta regime.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.2
• /
• pp.169-173
• /
• 2009

We studied driving characteristics according to the ratio of mass and charging (m/q) value for charged toner particles with black and yellow color in charged particle type display panel. After biasing rectangle pulse to the transparency electrodes of putted panel with toner particles, its response time and contrast ratio are simultaneously measured using a laser as a optical source, photodiode as a detector and reflective system. As a results, contrast ratio is largest at the shortest response time region which is different to the particle because of m/q. We proposed relational equation for response time, m/q, cell gap and biasing voltage. It has not been studied and reported to analyze the relationship of response time, biasing voltage, lumping phenomena, cell gap, and contrast ratio for toner particle type display.

• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.1
• /
• pp.64-70
• /
• 2018

In this study, the kg-class Ni-Al alloy fabrication process at low temperature was developed from the physical mixture of Ni and Al powders. The AlCl3 as an activator was used to reduce the temperature of alloy synthesis below the melting temperature of Ni and Al elements (<$500^{\circ}C$). Mixed phase of Ni3Al intermetallic and Ni-Al solid-solution were identified in the XRD pattern analysis. Furthermore, from the analysis of SEM and particle size analyzer, we found that the particle size of synthesized alloy powders was not changed compared to the initial size of Ni particle after the formation of alloy powder at $500^{\circ}C$. In the creep test, the anode (which was fabricated by the prepared Ni-Al alloy powders in this study) displayed the enhanced creep resistance compared to the conventional anode.

• Korean Journal of Materials Research
• /
• v.24 no.2
• /
• pp.98-104
• /
• 2014

Vacuum kinetic spray(VKS) is a relatively advanced process for fabricating thin/thick and dense ceramic coatings via submicron-sized particle impact at room temperature. However, unfortunately, the particle velocity, which is an important value for investigating the deposition mechanism, has not been clarified yet. Thus, in this research, VKS average particle velocities were derived by numerical analysis method(CFD: computational fluid dynamics) connected with an experimental approach(SCM: slit cell method). When the process gas or powder particles are accelerated by a compressive force generated by gas pressure in kinetic spraying, a tensile force generated by the vacuum in the VKS system accelerates the process gas. As a result, the gas is able to reach supersonic speed even though only 0.6MPa gas pressure is used in VKS. In addition, small size powders can be accelerated up to supersonic velocity by means of the drag-force of the low pressure process gas flow. Furthermore, in this process, the increase of gas flow makes the drag-force stronger and gas distribution more homogenized in the pipe, by which the total particle average velocity becomes higher and the difference between max. and min. particle velocity decreases. Consequently, the control of particle size and gas flow rate are important factors in making the velocity of particles high enough for successful deposition in the VKS system.

• Korean journal of food and cookery science
• /
• v.22 no.4 s.94
• /
• pp.419-427
• /
• 2006

The purpose of this study is to promote the substitution of rice flour for wheat flour in making bread and thus the consumption of rice by examining the effect of particle size of rice flour on leavening rice bread. For this purpose, several experiments were carried out. With regard to particle size distribution, 59.45% of wheat flour had passed 200 mesh and 3 kinds of rice flour milled to penetrate into 20, 35, and 45 mesh (S1, S2 and S3) had passed 21.88%, 33.1% and 36.38% of those for 200 mesh, respectively. To leaven the rice flour dough to bread, 25% of vital gluten was needed. To determine the optimal water quantity for rice bread dough, the hardness of wheat and rice flour dough was measured by rheometer. The appropriate water quantity for S1, S2 and S3 was set at 285 ml , 295 ml and 335${\sim}$340m1, respectively. The loaf volume index of the wheat flour bread was 6.24, while that of and rice flour bread S1, S2 and S3 was 5.38, 5.50 and 5.75, respectively. These results indicated that the loaf volume index of rice flour bread is lower than that of wheat flour bread, but that the volume of rice flour bread was increased with fuel particle size of rice flour. Scanning electron microscopy (SEM), image of the wheat bread tissue at a magnification of 35 times showed long, large, oval-shaped, air cells and thin cell membrane, as well as small air cells, whereas the images of rice flour showed angular, circular, air cells and rough and thick cell membrane. The size and number of air cells in the rice bread were larger in S2 and S3 with fuel particle flours than in S1. In particular, the bread made with S3 contained many air cells that were as large as those in the wheat bread were. In addition, when the inner cell wall was magnified 1500 times, almost no small air cell was observed in C and S3, whereas many fine air cells were observed in the cell wall of S1 and S2.

• Nuclear Engineering and Technology
• /
• v.52 no.3
• /
• pp.568-574
• /
• 2020

The feasibility of the particle-in-cell (PIC) method is assessed to simulate the non-collective phenomena like non-collective Thomson scattering (TS). The non-collective TS in the laser-plasma interaction, which is related to the single-particle behavior, is simulated through a 2D relativistic PIC code (XOOPIC). For this simulation, a non-collective TS is emitted from a 50-50 DT plasma with electron density and temperature of n_e = 3.00 × 10¹³ cm^-3 and T_e = 1000 eV, typical for the edge plasma at ITER measured by ETS system, respectively. The wavelength, intensity, and FWHM of the laser applied in the ETS system are λ_i,0 = 1.064 × 10^-4 cm, I_i = 2.24 × 10¹⁷ erg=s·㎠, and 12.00 ns, respectively. The electron density and temperature predicted by the PIC simulation, obtained from the TS scattered wave, are n_e,TS = 2.91 × 10¹³ cm^-3 and T_e,TS = 1089 eV, respectively, which are in accordance with the input values of the simulated plasma. The obtained results indicate that the ambiguities rising due to the contradiction between the PIC statistical collective mechanism caused by the super-particle concept and the non-collective nature of TS are resolved. The ability and validity to use PIC method to study the non-collective regimes are verified.