• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.171.2-171.2
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• 2015

Nowadays, trivalent rare-earth ($RE^{3+}$) ions activated metal oxides have been proved to be excellent host materials due to their various applications. Facile wet-chemical technique have been considered as the best synthetic route due its intensive interest in the preparation of nanostructures. Europium ion doped lanthanum hydroxide ($La(OH)_3:Eu^{3+}$) phosphors were synthesized by the facile wet chemical method using the hexamethylenetetramine (HMTA) as a mediated surfactant. The thermal behavior for the $La(OH)_3:Eu^{3+}$ phosphors was investigated by thermogravimetric and differential thermal analysis method. The morphological studies were measured by scanning electron microscope and transmission electron microscope measurements, indicating three-dimensional (3D) flower-like $La(OH)_3:Eu^{3+}$ nanorod bundles. After subsequent annealing process, the lanthanum oxide ($La_2O_3:Eu^{3+}$) phosphor exhibited similar kind of morphology. The synthesized $La(OH)_3:Eu^{3+}$ and $La_2O_3:Eu^{3+}$ samples were characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. Furthermore, photoluminescence and cathodoluminescence properties were studied in details.

• Journal of Pharmaceutical Investigation
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• v.32 no.3
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• pp.173-179
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• 2002

Solid dispersions of ipriflavone with PVP were prepared by a spray-drying method in order to improve the bioavailability. They were measured with scanning electron microscopy, differential scanning calorimetry, x-ray powder diffraction, and Fourier transform infrared spectroscopy to evaluate the physicochemical interaction between ipriflavone and PVP and study the correlation between these physicochemical characteristics and bioavailability. Ipriflavone exhibited crystallinity, whereas PVP was almost amorphous. The area of the endotherm $({\Delta}H)$ of freezer milled ipriflavone, freezer milled ipriflavone physically mixed with freezer milled PVP, and physically mixed ipriflavone with PVP was almost the same, whereas ${\Delta}H$ of the solid dispersed ipriflavone with PVP was much smaller than that of the other preparation types. Also, the crystallinity and the crystal size of ipriflavone in the solid dispersed ipriflavone with PVP were much smaller than those of the other preparation types. From the in vivo test, the AUC of the solid dispersed ipriflavone with PVP was approximately 10 times higher than that of the physically mixed ipriflavone with PVP. The solid dispersion using the spray-drying method with a water-soluble polymer, PVP, may be effective for the improvement of the bioavailability.

• Journal of the Korea Society of Computer and Information
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• v.4 no.2
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• pp.141-146
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• 1999

In this paper, picture set filter is proposed for preserving compression ratio and video qualify. This filter controls the compression ratio of each frame depending on the correlation to the reference frame by selectively eliminating less important high-resolution areas. Consequently, video quality can be preserved and bit rate can be controlled adaptively. In the simulation, to test the performance of the proposed coding method, comparisons with the full search block matching algorithm and the differential image coding algorithm are made. In the former case, video quality, compression ratio and encoding time is improved. In the latter case, video quality is degraded, but compression ratio and encoding time is improved. Consequently. the proposed method shows a reasonably good performance over existing ones.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1087-1107
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• 2016

A method of damage detection based on the moving harmonic excitation and continuous wavelet transforms is presented. The applied excitation is used as a moving actuator and its frequency and speed parameters can be adjusted for an amplified response. The continuous wavelet transforms, CWT, is used for cracks detection based on the resulting amplified signal. It is demonstrated that this identification procedure is largely better than the classical ones based on eigenfrequencies or on the eigenmodes wavelet transformed. For vibration responses, free and forced vibration analyses of multi-cracked beams are investigated based on both analytical and numerical methodological approaches. Cracks are modeled through rotational springs whose compliances are evaluated using linear elastic fracture mechanics. Based on the obtained forced responses, multi-cracks positions are accurately identified and the CWT identification can be highly improved by adjusting the frequency and the speed excitation parameters.

• Journal of Magnetics
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• v.6 no.1
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• pp.23-26
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• 2001

Nano-crystalline hexaferrite $BaFe_{12}O_{19}$(BaM) thin films have been prepared by the sol-gel method. A solution of Ba-nitrate and Fe-nitrates was dissolved in solvent with the stoichiometric ratio Ba/Fe=1/10. Films were spin-coated onto $SiO_2$Si substrates, dried and then heated in air at various temperatures. In films prepared at a drying temperature $T_d=250^{\circ}C$ and a crystallizing temperature 650${\circ}C$, single-phase BaM was obtained. High coercivities were obtained in these nano-crystalline thin films, 4~5.5 kOe for hexaferrite. Polycrystalline BaM/$SiO_2$/Si(100) thin films were characterized by Rutherford backscattering (RBS), thermogravimetry (TGA), differential thermal analysis (DTA), x-ray diffraction (XRD), and vibrating sample magnetometry (VSM), as well as Fourier transform infrared spectroscopy (FTIR). The perpendicular coercivity $H_{C\bot}$ and in-plane coercivity $H_{CII}$ after annealing at 650${\circ}C$ for 2 hours were 4766 Oe and 4480 Oe, respectively, at room temperature, under a maximum applied field of 10 kOe.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.1
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• pp.46-58
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• 2011

A steady-state analysis and a simple dynamic model as simplified methods are developed, and results of energy consumption loads are compared with results obtained using computer to evaluate the analytical solution. Before obtaining simplified model a mathematical model is formulated for the effect of wall mass on the thermal performance of four different houses having various wall construction. This analytical study was motivated by the experimental work of Burch et al. An analytical solution of one-dimensional, linear, partial differential equation for wall temperature profiles and room air temperatures is obtained using the Laplace transform method. Typical Meteorological Year data are processed to yield hourly average monthly values. This study is conducted using weather data from four different locations in the United States: Albuquerque, New mexico; Miami, Florida; Santa Maria, California; and Washington D.C. for both winter and summer conditions. The steady state analysis that does not include the effect of thermal mass can provide an accurate estimate of energy consumption in most cases except for houses #2 and #4 in mild weather areas. This result shows that there is an effect of mass on the thermal performance of heavily constructed house in mild weather conditions. The simple dynamic model is applicable for high cycling rates and accurate values of inside wall temperature and ambient air temperature.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.15-24
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• 1996

This paper presents a new method for visual servoing to control the pose(position and orientation) of the robotic manipulators for grasping the 3-D moving object whose initial pose and moving informations are unknown by using the stereo camera. The stereo camera is mounted on the end-effector of robotic manipulator. In order to track the current pose of robotic manipulator to the desired pose, we use the image Jacobian, which is described by the differential transform, relating the change in image feature point to the change in the object's pose with respect to the camera. In this paper the simple PD controller is adopted for the robotic manipulator to track the desired pose. Finally, the effectiveness of the proposed method is confirmed by some computer simulations.

• Journal of applied mathematics & informatics
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• v.42 no.3
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• pp.607-623
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• 2024

This article studies the effects of heat generation/absorption and thermal radiation on the unsteady magnetohydrodynamic (MHD) Casson fluid flow past a vertical plate through rotating porous medium with constant temperature and mass diffusion. It is assumed that the plate temperature and concentration level are raised uniformly. For finding the exact solution, a set of non-dimensional partial differential equations is solved analytically using the Laplace transform technique. The influence of various non-dimensional parameters on the velocity are discussed, including the effects of the magnetic parameter M, heat generation/absorption Q, thermal radiation parameter R, Prandtl number Pr, Schmidt number Sc, permeability of porous medium parameter, Casson fluid parameter γ, on velocity, temperature, and concentration profiles, which are discussed through several figures. It is found that velocity, temperature, and concentration profiles in the case of heat generation parameter Q, Casson fluid parameter γ, thermal Grashof number Gr, mass Grashof number Gc, Permeability Porous medium parameter K, and time t have retarding effects. It is also seen that the magnetic field M, Thermal Radiation parameter R, Prandtl field Pr, Schmidt number Sc have reverse effects on it.

• Journal of Ceramic Processing Research
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• v.21 no.1
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• pp.5-13
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• 2020

(K0.5Na0.5)NbO3-based ceramic powders for lead-free piezoelectric applications are usually prepared by solid state synthesis. This generally involves wet ball milling in an organic liquid such as ethanol, which is a drawback for industrial production. In the present work, a method for the preparation of NaNbO3 nanopowders is modified to produce a simple method of preparing (K0.5Na0.5)NbO3 nanopowders by an aqueous route. K2CO3, Na2CO3 and NH4[NbO(C2O4)2].xH2O are mixed in water and dried to form a gel, which is then calcined at temperatures between 400 ~ 650 ℃ for 1 h. The uncalcined gel and calcination products are analysed using Thermogravimetric Analysis/Differential Thermal Analysis, X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy and Raman Scattering. A single phase tetragonal (K0.5Na0.5)NbO3 nanopowder with a particle size of ~ 30 nm can be produced after calcination at 650 ℃ for 1 h.

• Advances in nano research
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• v.16 no.6
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• pp.623-638
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• 2024

This study investigates the thermal post-buckling behavior of concrete eccentric annular sector plates reinforced with graphene oxide powders (GOPs). Employing the minimum total potential energy principle, the plates' stability and response under thermal loads are analyzed. The Haber-Schaim foundation model is utilized to account for the support conditions, while the transform differential quadrature method (TDQM) is applied to solve the governing differential equations efficiently. The integration of GOPs significantly enhances the mechanical properties and stability of the plates, making them suitable for advanced engineering applications. Numerical results demonstrate the critical thermal loads and post-buckling paths, providing valuable insights into the design and optimization of such reinforced structures. This study presents a machine learning algorithm designed to predict complex engineering phenomena using datasets derived from presented mathematical modeling. By leveraging advanced data analytics and machine learning techniques, the algorithm effectively captures and learns intricate patterns from the mathematical models, providing accurate and efficient predictions. The methodology involves generating comprehensive datasets from mathematical simulations, which are then used to train the machine learning model. The trained model is capable of predicting various engineering outcomes, such as stress, strain, and thermal responses, with high precision. This approach significantly reduces the computational time and resources required for traditional simulations, enabling rapid and reliable analysis. This comprehensive approach offers a robust framework for predicting the thermal post-buckling behavior of reinforced concrete plates, contributing to the development of resilient and efficient structural components in civil engineering.