• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1993.10a
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• pp.4-11
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• 1993

Composite propellant combustion is studied experimentally with systematic variation of particle sizes and mix ratios of coarse and fine APs. Considering the different modes of oxidizer-fuel flames in heterogeneous systems, the complex flame model is described to identify what combustion mechanisms are important under what conditions. The effects of AP particle size, ratio of coarse to fine AP, and pressure on burning rates are discussed in terms of qualitative theory of flame microstructure.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.562-567
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• 2007

To precipitate the complex gels of the pH 6, 7, 8, 9 included in a flux and an aluminum hydroxides gel, an aqueous solution of a mixture of $Na_2CO_3\;and\;Na_2PO_4{\cdot}12H_2O$ was added with stirring in an aqueous solution of a mixture of $Al_2(SO_4){_3}{\cdot}18H_2O,\;Na_2SO_4\;and\;K_2SO_4$, and then the complex gels were aged in 20 h at $90^{\circ}C$. As the hydrolysis pH changed, it had an effect on the physical properties such as the crystal structure, crystal morphology and a phase transition temperature of the AlO(OH) gel, and also on the crystal structure, crystal morphology, particle size and particle size distribution of the ${\alpha}-Al_2O_3$ platelets prepared by molten-salt precipitation. Also, in this study, the complex gels were crystallized at $1,200^{\circ}C$ and thereafter dried at $110^{\circ}C$, and then it was investigated to effect of the hydrolysis pH on the crystal structure, morphology and particle size distribution of the ${\alpha}-Al_2O_3$ platelets crystals using XRD, DTA, SEM and particle size analyzer.

• Particle and aerosol research
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• v.13 no.4
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• pp.173-182
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• 2017

An Eulerian-Lagrangin approach is used to compute particle dispersion from a power plant chimney. For air flow, three-dimensional incompressible filtered Navier-Stokes equations are solved with a subgrid-scale model by integrating the Newton's equation, while the dispersed phase is solved in a Lagrangian framework. The velocity ratios between crossflow and a jet of 0.455 and 0.727 are considered. Flow fields and particle distribution of both cases are evaluated and compared. When the velocity ratio is 0.455, it demonstrates a Kelvin-Helmholtz vortex structure above the chimney caused by the interaction between crossflow and a jet, whereas the other case shows flow structures at the top of the chimney collapsed by fast crossflow. Also, complex wake structures cause different particle distributions behind the chimney. The case with the velocity ratio of 0.727 demonstrates strong particle concentration at the vortical region, whereas the case with the velocity ratio of 0.455 shows more dispersive particle distribution. The simulation result shows similar tendency to the experimental result.

• Journal of Radiation Protection and Research
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• v.12 no.2
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• pp.28-36
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• 1987

Gaussian plume model is used to assess environmental dose for abnormal radioactive release in nuclear facility, but there has a problem to use it for complex terrain. In this report, MATTEW and WIND04 Codes which had been verified were used to calculate wind field in the complex terrain. Under the base of these codes principle, wind fields were obtained from the calculation of the finite difference approximation for advection-diffusion equations which satisfy the mass-conservative law. Particle concentrations and external doses were calculated by using PIC model which approximate the particle to radioactive cloud, and atmospheric diffusion of the particles from the random walk method. The results show that the adjusted wind fields and the distributions of the exposure dose vary with the topography of the complex terrain.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.48.3-49
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• 2017

Interplanetary space of the solar system contains a large number of dust particles, referred to as Interplanetary Dust Particles (IDPs) cloud complex. They are observable through meteors and zodiacal lights. The relative contribution of possible sources to the IDPs cloud complex was an controversial topic, however, recent research (Yang & Ishiguro, 2015 and references therein) suggested a dominance of cometary origin. In this study, we numerically investigated the orbital evolution of cometary dust particles, with special concerns on different evolutionary tracks and its consequences according to initial orbits, size and particle shape. The effect of dust particle density and initial size-frequency distribution (SFD) were not decisive in total cloud complex mass and mass supply rate, when these physical quantities are confined by observed zodiacal light brightness and dust particle SFD at 1 au. We noticed that, if we assume the existence of fluffy aggregates discovered in the Earth's stratosphere and the coma of 67P/Churyumov-Gerasimenko, the required mass supply rate decreases significantly. We also found out that close encounters with planets (mostly Jupiter) are the dominating factor of the orbital evolution of dust particles, as the result, the lifetime of cometary dust particles are shorter than Poynting-Robertson lifetime (around 250 thousand years). As another consequence of severe close encounters, only a small fraction of cometary dust particles can be transferred into the orbit < 1 au. This effect is significant for large size particles of ${\beta}$ < 0.01. The exceptional cases are dust particles ejected from 2P/Encke and active asteroids. Because they rarely encounter with Jupiter, most dust particles ejected from those objects are governed by Poynting-Robertson effect and well transferred into the orbits of small semimajor axis. In consideration of the above effects, we directly estimated probability of mutual collisions between dust particles and concluded that mutual collisions in the IDPs cloud complex is mostly ignorable, except for the case of large sized particles from active asteroids.

• Journal of Pharmaceutical Investigation
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• v.39 no.5
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• pp.339-343
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• 2009

Recently, co-delivery of drug and gene has been attempted for higher therapeutic effects of anticancer agents. In this study, cationic liposomes were prepared using 1,2-dioleoyl-3-trimethylammoniopropane (DOTAP) as a cationic lipid to investigate the effect of drug loading on the physicochemical characteristics of cationic liposomes/DNA complexes. The complex formation between cationic liposomes and negatively charged plasmid DNA was confirmed and the protection from DNase was observed. Particle size of complexes was reduced not by drug loading, but by the increased ratio of cationic lipid to plasmid DNA. Meanwhile, zeta potential of complex was increased by the addition of cationic liposomes to complexes and the effect of drug loading on the zeta potential was not much higher than on particle size. Gel retardation of complexes was indicated when the complexation weight ratios of cationic lipid to plasmid DNA were higher than 24:1 for drug free complexes and 20:1 for drug loaded ones, respectively. Agarose gel retardation showed the similar complexation between plasmid DNA and drug free liposomes or drug loaded liposomes. Both complexes protected plasmid DNA from DNase independent of complexation temperature. From the results, drug loading may affect not the complex formation of cationic liposomes and plasmid DNA, but the particle size of complex.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.421-426
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• 2005

Fuzzy logic, neural network, fuzzy-neural network play an important as the key technology of linguistic modeling for intelligent control and decision making in complex systems. The fuzzy-neural network (FNN) learning represents one of the most effective algorithms to build such linguistic models. This paper proposes particle swarm optimization algorithm based optimal learning fuzzy-neural network (PSOA-FNN). The proposed learning scheme is the fuzzy-neural network structure which can handle linguistic knowledge as tuning membership function of fuzzy logic by particle swarm optimization algorithm. The learning algorithm of the PSOA-FNN is composed of two phases. The first phase is to find the initial membership functions of the fuzzy neural network model. In the second phase, particle swarm optimization algorithm is used for tuning of membership functions of the proposed model.

• Textile Coloration and Finishing
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• v.15 no.6
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• pp.8-17
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• 2003

In order to investigate the possibility of PVA particle as toner, PVA/PVAc particle was manufactured. Fine spherical PVAc particle with emulsifier SDS(sodium Dodecyl Sulfate) and initiator V-50(2,2'- azo bis(2-amidinopropane) dihydrochloride) was manufactured by emulsion polymerization. And then, the PVAc was carried with surface saponification. PVA/PVAc skin core structured particle was obtained under optimum saponification condition. PVA skin side in manufactured PVA/PVAc particles was dyed with 1:2 metal complex type C. I. Acid Yellow 235 and then the dyed PVA particles were observed with a optical microscope. Under given polymerization condition such as SDS concentration, $1.62\times{10}^{-2} \;mol/lH_2O$, V-50 concetration, $3.7\times{10}^{-3}\;mol/lH_2O$ and temperature $50^\circ{C}$ , the high molecular weight of PVAc with Pn 13,900 and PVA with Pn 3,400 was produced. The particle distribution of obtained PVAc microspheres was appeared highly at 60 and $100\mu{m}$, respectively.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.2
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• pp.67-83
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• 2002

The coupled model (SMART) of dynamic meteorology model and particle dispersion model was developed. The numerical experiment on the relationship between change of land use and diffusion behavior in complex terrain was carried out using this model. It tried to investigate the change of particle diffusion behavior and local weather under the condition in which land-land breeze and sea breeze and mountain breeze intermingled. The numerical experiment results are as follows; 1) The more complicated local circulation field of the interaction of sea breeze, mountain breeze and Land -land breeze is formed. Then, the region circulation in which the urbanization is specific by location of the region is strengthened and is weakened. 2) Though in the region with dominant sea breeze, Land-land breeze does not appear directly, the progress of the sea wind to the inland is affected. 3) In the prediction of the air diffusion, emission high quality and accurate information of the emission site are important. That is to say, the dispersion predicting result which emission high quality and small error of the site perfectly vary for Land - land breeze in the effect may be brought about.

• Particle and aerosol research
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• v.4 no.2
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• pp.51-67
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• 2008

In this study, we devoted to kinetic measurement of the catalytic oxidation of iron-containing flame soot particles and better understanding the role of catalytic particles on carbon oxidation in particular at low temperature, targeting on autothermal regeneration of diesel particulate filter by diesel exhaust gas. Carbon-based Fe-containing particles generated by spraying ferrocene-doped diesel fuel in an oxy-hydrogen flame are tested and compared with a commercial carbon black powder for thermogravimetric analysis (TGA), secondary ion mass spectrometry (SIMS), Fourier-transform infrared spectroscopy (FTIR), Induced coupled plasma-Atomic emission spectroscopy (ICP-AES), and High-resolution transmission electron microscopy (HR-TEM). As a result, we found that a small amount of the ferrocene addition led to significant reductions in a on-set temperature and an activation energy of the carbon oxidation as well. An oxygenated surface complex forming at the particle surface could be thought as active species that would be readily consumed in particular at low temperature.