• Journal of Magnetics
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• v.17 no.1
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• pp.1-5
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• 2012

The coercivity of a single 27 nm-spherical barium ferrite (S-BaFe) particle was simulated using three models: 1) Gibbs free energy (GFE), 2) Landau-Lifshitz-Gilbert (LLG), and 3) Stoner-Wohlfarth (S-W). Spherically and hexagonally shaped particles were used in the GFE and LLG simulations to investigate coercivity with the different shape anisotropies. The effect of shape was not included in the S-W model. It was found that the models using a spherical shape resulted in a coercivity higher than the models using the hexagonal shape with both shapes having the same diameter. The coercivity estimated with the S-W model was approximately the same as that for the spherical-shape models, which indicates that spherical shape has no significant effect on the particle's coercivity at nanoscale.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.930-934
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• 2002

Nanosized $WO_3$ powders were synthesized by the sol-precipitation process using $WCl_{6}$ as the starting material, ethanol as a solvent and $NH_4$OH solution as a precipitant, followed by a washing-drying treatment and calcination. The effects on the powder crystallinity and microstructure of calcination temperature were investigated with XRD and FE-SEM. The $WO_3$ powders calcined at $500^{\circ}C$ and $700^{\circ}C$ showed good crystallinity and their mean particle size was 30nm and 70nm, respectively. These powders were used for the preparation of pastes which were printed as thick films on alumina substrates with comb-type Pt electrodes. The particle size strongly influenced the $NO_2$ gas sensing property of the thick films. A significant reduction in the $NO_2$ sensitivity was observed for the film prepared from larger particle size, having thus a larger grain size. For the film having a smaller grain size, on the other hand, the higher $NO_2$ sensitivity was observed and the sensitivity increased with $NO_2$ concentration.

• Journal of Powder Materials
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• v.12 no.3
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• pp.201-207
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• 2005

Nickel powders were synthesized by the hydrazine reduction of nickel chloride solution containing ammonia in DEA solutions. The size distribution of nickel powders were investigated as a function of ammonia concentration, hydrazine concentration and the mixed composition ratio of diethanolammine (DEA) and triethanolammine (TEA). Nickel powders with the size in submicron range were obtained at $185^{\circ}C$ for 45 minutes by hydrazine reduction of nickel chloride solution in DEA solutions. The hydrazine concentrations showed significant effects on the particle size and shape distribution of nickel powders under $NH_3/Ni^{2+}$ molar ratio of 2.0 condition. As the mixed volume ratio of TEA and DEA increased, nickel powders with relatively larger particle size and low agglomeration were obtained. Nickel powders with particle size in the ranged from 0.4 to $0.9\;{\mu}m$ were obtained at the 50 $vol.%$ of TEA.

• Journal of the Korean Magnetics Society
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• v.27 no.1
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• pp.23-29
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• 2017

In this study, the influences of magnetization reversal and magnetic interaction on the coercivity of Sr-ferrite particles with different sizes were investigated through various magnetic measurements. The shape of the initial magnetization curve and the magnetic field dependence of the coercive force indicate that the magnetization reversal changes from domain nucleation to wall pinning as the particle size decreases. On the other hand, the Henkel plot, interaction field factor and ${\Delta}M(H)$ obtained from the DCD and IRM curves show that the strength of the dipolar interaction is increased with increasing the particle size. Therefore, it can be concluded that coercivity is closely related to magnetic interaction as well as magnetization reversal mechanism.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.5
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• pp.93-102
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• 1996

Laser-induced plume and laser-target interaction during pulsed laser deposition are demonstrated for a lead zirconate titanate (PZT). A KrF excimer laser (wavelength 248nm) was used and the laser was pulsed at 20Hz, with nominal pulse width of 20ns. The laser fluence was~$16J/cm^2,$ with 100mJ per pulse. The laser-induced plasma plume for nanosecond laser irradiation on PZT target has been investigated by optical emission spectra using an optical multichannel analyzer(OMA) and by direct observation of the plume using an ICCD high speed photography. OMA analysis showed two distinct ionic species with different expansion velocities of fast or slow according to their ionization states. The ion velocity of the front surface of the developing plume was about $10^7$cm/sec and corresponding kinetic energy was about 100eV. ICCD photograph showed another kind of even slower moving particles ejected from the target. These particles considered expelled molten parts of the target. SEM morphologies of the laser irradiated targets showed drastic melting and material removal by the laser pulse, and also showed the evidence of the molten particle ejection. The physics of the plasma(plume) formation and particle ejection has been discussed.

• Journal of Information Display
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• v.3 no.3
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• pp.17-23
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• 2002

In this work we report methods of formation of three-dimensional structures of particles in a liquid crystal host. We found that, under the appropriate conditions, the particles are captured and dragged by the moving isotropic/nematic front during the phase transition process. This movement of the particles can be enhanced significantly or suppressed drastically with the influence of an electric field and/or with changing the conditions of the phase transition, such as the rate of cooling. As a result, a wide variety of particle structures can be obtained ranging from a fine-grained cellular structure to stripes of varying periods to a course-grained "root" structures. Changing the properties of the materials, such as the size and density of the particles and the surface anchoring of the liquid crystal at the particle surface, can also be used to control the morphology of the three-dimensional particle network and adjust the physical properties of the resulting dispersions. These particle structures may be used to affect the performance of LCD's much as polymers have been used in the past.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.146-147
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• 2007

We present full 3-D simulation of dielectrophoretic (DEP) deflection of particle trajectory in micro channel and compare the simulation results with experimental results. In simulation, the particle 3-D movements along x, y and z-axis are simulated precisely, and the streamlines of particles movements and the change of particle height are investigated experimentally. Therefore, the deflection performance is investigated on the designed and fabricated deflection microchip.

• Computers and Concrete
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• v.7 no.2
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• pp.103-118
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• 2010

Penetration of a fragment-like projectile into Fiber Reinforced Concrete (FRC) was simulated using finite element (FE) and particle formulations. Extreme deformations and failure of the material during the penetration event were modeled with multiple approaches to evaluate how well each represented the actual physics of the penetration process and compared to experimental data. A Fragment Simulating Projectile(FSP) normally impacting a flat, square plate of FRC was modeled using two target thicknesses to examine the different levels of damage. The thinner plate was perforated by the FSP, while the thicker plate captured the FSP and only allowed penetration part way through the thickness. Full three dimensional simulations were performed, so the capability was present for non-symmetric FRC behavior and possible projectile rotation in all directions. These calculations assessed the ability of the finite element and particle formulations to calculate penetration response while assessing criteria necessary to perform the computations. The numerical code EPIC contains the element and particle formulations, as well as the explicit methodology and constitutive models, needed to perform these simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.5955-5977
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• 2018

Performance of the interpolation algorithm used in the technique of bi-dimensional empirical mode decomposition directly affects its popularization and application, so that the researchers pay more attention to the algorithm reasonable, accurate and fast. However, it has been a lack of an adaptive interpolation algorithm that is relatively satisfactory for the bi-dimensional empirical mode decomposition (BEMD) and is derived from the image characteristics. In view of this, this paper proposes an image interpolation algorithm based on the particle swarm and fractal. Its procedure includes: to analyze the given image by using the fractal brown function, to pick up the feature quantity from the image, and then to operate the adaptive image interpolation in terms of the obtained feature quantity. All parameters involved in the interpolation process are determined by using the particle swarm optimization algorithm. The presented interpolation algorithm can solve those problems of low efficiency and poor precision in the interpolation operation of bi-dimensional empirical mode decomposition and can also result in accurate and reliable bi-dimensional intrinsic modal functions with higher speed in the decomposition of the image. It lays the foundation for the further popularization and application of the bi-dimensional empirical mode decomposition algorithm.

• Advances in materials Research
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• v.2 no.3
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• pp.141-153
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• 2013

Nanocrystalline Barium niobate ($BaNbO_3$) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that $BaNbO_3$ posses a cubic structure with lattice constant $a=4.071{\AA}$. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of $1425^{\circ}C$ for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered $BaNbO_3$ at 5MHz sample is found to be 32.92 and $8.09{\times}10^{-4}$ respectively, at room temperature. The temperature coefficient of dielectric constant was $-179pp/^{\circ}C$. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.