• Journal of Korea Society of Industrial Information Systems
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• v.24 no.5
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• pp.115-120
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• 2019

In this paper, we present the results of the performance statistical analysis of the multi-robot formation control based on receding horizon particle swarm optimization (RHPSO). The formation control problem of multi-robot system can be defined as a constrained nonlinear optimization problem when considering collision avoidance between robots. In general, the constrained nonlinear optimization problem has a problem that it takes a long time to find the optimal solution. The RHPSO algorithm was proposed to quickly find a suboptimal solution to the optimization problem of multi-robot formation control. The computational complexity of the RHPSO increases as the number of candidate solutions and generations increases. Therefore, it is important to find a suboptimal solution that can be used for real-time control with minimal candidate solutions and generations. In this paper, we compared the formation error according to the number of candidate solutions and the number of generations. Through numerical simulations under various conditions, the results are analyzed statistically and the minimum number of candidate solutions and the minimum number of generations of the RHPSO algorithm are derived within the allowable control error.

• Polymer(Korea)
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• v.25 no.5
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• pp.617-624
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• 2001

The core-shell composite latexes were synthesized by stage emulsion polymerization of methyl methacrylate (MMA) and styrene (St) with ammonium persulfate after preparing monomer pre-emulsion in the presence of anionic surfactant. However, in preparation of core-shell composite latex, several unexpected results are observed, such as, particle coagulation, low degree of polymerization, and formation of new particles during shell polymerization. To solve the disadvantages, We study the effect of initiator concentrations, surfactant concentrations, and reaction temperature on the core-shell structure of polymethyl methacrylate/polystyrene and polystyrene/polymethyl methacrylate. Particle size and particle size distribution were measured using particle size analyzer, and the morphology of the core-shell composite latex was determined using transmission electron microscope. Glass temperature was also measured using differential scanning calorimeter. To identify the core-shell structure, pH of the two composite latex solutions were measured.

• Journal of Powder Materials
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• v.6 no.3
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• pp.215-223
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• 1999

The synthesis of $Ni_5Si_2,\;Ni_2Si$ and NiSi has been investigated by mechanical alloying (MA) of Ni-27.9at%Si, Ni-33.3at%Si and Ni-50.0at%Si powder mixtures. As-received and premilled elemental powders were subjected to MA. The as-received Ni powder was spherical and the mean particle size 48.8$\mu$m, whereas the premilled Ni powder was flaky and the mean particle diameter and thickness were found to be 125 and 5$\mu$m, respectively. The mean surface area of the premilled Mi powder particle was 3.5 times as large as that of the as-received Ni powder particle. The as-received Si powder was was 10.0$\mu$m. Self-propagating high-temperature synthesis (SHS) reaction, followed by a slow reaction (a solid state diffusion), was observed to produce each Ni silicide during MA of the as-received elemental powders. In other word , the reactants and product coexisted for a long period of MA of time. Only SHS reaction was, however, observed to produce each Ni silicide during MA of the premilled elemental powders, indicating that each Ni sillicide formed rather abruptly at a short period of MA time. The mechanisms and reaction rates for the formation of the Ni silicides appeared to be influenced by the elemental powder particle size and shape as well as the heat of formation of the products $(Ni_5Si_2$longrightarrow-43.1kJ/mol.at., $Ni_2Si$$\rightarrow$-47.6kJ/mol.at.).

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3102-3107
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• 2008

This paper was focused on the particulate matter (PM) on the gasoline and bio ethanol. Bio ethanol as a clean fuel is considered one of the alternative fuels that decreased the PM emission from the vehicle. Particle formation in SI engine was depended on the fuel and engine operating condition. In this paper, Particle number concentration behaviors were analyzed by DMS500 (Differential Mobility Spectrometer) and CPC (Condensation Particle Counter) instrument which was recommended by PMP (Particle Measurement Programme). Particle emissions were measured with various engine operating variables such as air excess ratio ($\lambda$), spark timing and intake valve opening (IVO) at part load condition. In vehicle test, the number of particulate matter was analyzed with golden particle measurement system, which was consist of CVS (Constant Volume Sampler), particle number counter and particle number diluter.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.37-42
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• 2001

This paper computes the bluff-body stabilized jet and flame. This study numerically investigates the nonpremixed $C_{2}H_{4}-air$ jet for the nonreacting case and the nonpremixed $CH_{3}OH-air$ turbulent flames for the reacting case using the laminar flamelet model on modified KIVA2 code. And this study predicts $NO_{x}$ formation characteristics using Eulerian Particle Flamelet Model. In the present study, the turbulent combustion model is applied to analyze both nonreacting and reacting case. And both standard $k-{\varepsilon}$ model and modified $k-{\varepsilon}$ model are used in nonreacting case. Calculations are compared with experimental data in terms of velocity, mixture fraction, mixture fraction Root Mean Square and Temperature. The present model correctly predicts the essential features of flame structures and $NO_{x}$ formation characteristics in the bluff-body stabilized flames.

• Journal of The Korean Astronomical Society
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• v.47 no.3
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• pp.87-98
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• 2014

We develop a parallel cosmological hydrodynamic simulation code designed for the study of formation and evolution of cosmological structures. The gravitational force is calculated using the TreePM method and the hydrodynamics is implemented based on the smoothed particle hydrodynamics. The initial displacement and velocity of simulation particles are calculated according to second-order Lagrangian perturbation theory using the power spectra of dark matter and baryonic matter. The initial background temperature is given by Recfast and the temperature uctuations at the initial particle position are assigned according to the adiabatic model. We use a time-limiter scheme over the individual time steps to capture shock-fronts and to ease the time-step tension between the shock and preshock particles. We also include the astrophysical gas processes of radiative heating/cooling, star formation, metal enrichment, and supernova feedback. We test the code in several standard cases such as one-dimensional Riemann problems, Kelvin-Helmholtz, and Sedov blast wave instability. Star formation on the galactic disk is investigated to check whether the Schmidt-Kennicutt relation is properly recovered. We also study global star formation history at different simulation resolutions and compare them with observations.

• Fashion & Textile Research Journal
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• v.10 no.3
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• pp.371-376
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• 2008

Poly(ethylene-co-vinylacetate) (EVA) microspheres were prepared by thermally induced phase separation (TIPS) in toluene. The microsphere formation occurred by the nucleation and growth mechanism in metastable region. The effects of the concentration and component of the polymer and cooling rate on microsphere formation were investigated. The microsphere formation and growth were followed by the cloud point of the optical microscope measurement. The microsphere size distribution, which was obtained by particle size analyzer, became broader when the polymer concentration was higher, the content of vinyl acetate in EVA copolymer was higher, the cooling rate of EVA copolymer solution were lower. The content of disperse dye in EVA microsphere was obtained by TGA thermal analysis, the dye content of EVA15 and EVA18 were 3.5 and 2.0 wt% respectively.

• Particle and aerosol research
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• v.4 no.1
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• pp.9-20
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• 2008

The effect of light intensity on the ozone formation and the aerosol number concentration during the photochemical reactions of ambient air was investigated in an indoor smog chamber. The smog chamber consists of a housing, 64 blacklights, and a $2.5-m^3$ reaction bag made of Teflon film. The bag was filled with the unfiltered ambient air in Seoul from January 10 to March 18, 2002. In this work, the photolysis rate of $NO_2$, $k_1$ was used as an index of light intensity. Three levels of light intensity were controlled by changing the number of blacklights turned on among 64 blacklights: $0.29min^{-1}$ (50%), $0.44min^{-1}$ (75%), $0.57min^{-1}$ (100%). The ozone concentration increased rapidly within 10 minutes after irradiation irrespective of light intensity, thereafter it increased linearly during the irradiation. The ozone production rate seems to be dependent on both the light intensity and the quality of ambient air introduced into the reaction bag. The change in aerosol number concentration also depended on both the light intensity and the ambient air quality, especially aerosol size distribution. Based on the initial ambient aerosol size distributions, the photochemical potential for aerosol formation and growth is classified into two cases. One is the case showing aerosol formation and growth processes, and the other is the case showing no apparent change in particle size distribution.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1213-1220
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• 1997

Effect of particle size of alumina and amount of talc on tape casting and densification behaviors of alumina-talc system were investigated. The pseudoplastic behaviors of slurries increased with increase in amount of talc addition and decrease in alumina particle size. In case of using coarse alumina powder, densification of specimens were accelerated with increase of sintering temperature and amount of talc addition. On the contrary, fine alumina powder retarded of rearrangement of alumina particle during liquid phase sintering due to premature densification of alumina matrix region before formation of liquid phase and then densification of specimens were suppressed with increase of sintering temperature and amount of talc addition.

• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.69-75
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• 2004

In this study, various model composite latexes were synthesized using n-butyl acrylate and methyl methacrylate as comonomers by seeded multi-staged emulsion polymerization. Monodispersed model composite latex particles with size of 190 nm and polydispersity index of 1.05, which have various morphology including random copolymer particle, soft-core/hard-shell particle, hard-core/soft shell particle, and gradient-type copolymer particle, homopolymers particles were prepared. The designed morphology of model composite particles were confirmed.