• Smart Structures and Systems
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• v.20 no.6
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• pp.709-728
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• 2017

This disquisition proposes a nonlocal strain gradient beam theory for thermo-mechanical dynamic characteristics of embedded smart shear deformable curved piezoelectric nanobeams made of porous electro-elastic functionally graded materials by using an analytical method. Electro-elastic properties of embedded curved porous FG nanobeam are assumed to be temperature-dependent and vary through the thickness direction of beam according to the power-law which is modified to approximate material properties for even distributions of porosities. It is perceived that during manufacturing of functionally graded materials (FGMs) porosities and micro-voids can be occurred inside the material. Since variation of pores along the thickness direction influences the mechanical and physical properties, so in this study thermo-mechanical vibration analysis of curve FG piezoelectric nanobeam by considering the effect of these imperfections is performed. Nonlocal strain gradient elasticity theory is utilized to consider the size effects in which the stress for not only the nonlocal stress field but also the strain gradients stress field. The governing equations and related boundary condition of embedded smart curved porous FG nanobeam subjected to thermal and electric field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is utilized to achieve the natural frequencies of porous FG curved piezoelectric nanobeam resting on Winkler and Pasternak foundation. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality parameter, electric voltage, coefficient of porosity, elastic foundation parameters, thermal effect, gradient index, strain gradient, elastic opening angle and slenderness ratio on the natural frequency of embedded curved FG porous piezoelectric nanobeam are successfully discussed. It is concluded that these parameters play important roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.847-851
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• 2011

Photovoltaic System is increasing install capacity based on environmental-friendly characteristics. It have been actively studied to improve the efficiency. In order to design highly efficient system, it is important to understand the output characteristics of solar panels. The single diode model can represent the physical characteristics of solar panel. But it needs complex process such as mutli-step measurement and numerical analysis to get the exact parameters. In this paper, The method for extracting characteristic parameters of the single diode model based on the I-V characteristic curves in the panel manufacturer's data-sheet is presented. To verify the proposed method, solar cell model constructed in simulink. Simulink model output compared with output graph in datasheet.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.8
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• pp.486-490
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• 2014

$Al_2O_3$ films on silicon carbide were fabricated by Aerosol deposition with annealing temperature at $800^{\circ}C$ and $1,000^{\circ}C$. The effect of thermal treatment on physical properties of $Al_2O_3$ thin films has been investigated by XRD (X-ray diffraction), AFM (atomic force microscope), SEM (scanning electron microscope), and AES (auger electron spectroscopy). Also electrical properties have been investigated by Keithley 4,200 semiconductor parameter analyzer to explain the interface trapped charge density ($D_{it}$), flatband voltage ($V_{FB}$) and leakage current ($I_o$). $Al_2O_3$ films become crystallized with increasing temperature by calculating full width at half maximum (FWHM) of diffraction peaks, also surface morphology is observed by topography measurement in non-contact mode AFM. $D_{it}$ was $2.26{\times}10^{-12}eV^{-1}.cm^{-2}$ at $800^{\circ}C$ annealed sample, which is the lowest value in all samples. Also the sample annealed at $800^{\circ}C$ has the lowest leakage current of $4.89{\times}10^{-13}A$.

• Journal of Astronomy and Space Sciences
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• v.4 no.1
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• pp.11-23
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• 1987

In dward nova we assume the primary star as a white dwarf and the secondary as the late type star which filled Roche lobe. Mass flow from the secondary star leads to the formation of thin accretion disk around the white dwarf. We use the $\alpha$ parameter as viscosity to maintain the disk form and propose that the outburst in dwarf nova cause the step increase of source term. With these assumptions we solve the basic equations of stellar structure using New-Raphson method. We show the physical parameters like temperature, density, pressure, opacity, surface density, height and flux to the radius of disk. Changing the value of $\alpha$, we compare several parameters when mass flow rate is constant with those of when luminosity of disk is brightest. At the same time, we obtain time-dependent variations of luminosity and mass of disk. We propose the suitable range of $\alpha$is 0.15-0.18 to the difference of luminosity. We compare several parameters of disk with those of the normal late type stars which have the same molecular weight of disk. These show the temperature and pressure of disk are similar to those of normal stars but the density of disk is lower. Maybe the outburst in dwarf nova is due to the variation of the $\alpha$ value instead of increment of mass flow from the secondary star.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.686-694
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• 2014

A power semiconductor device, usually used as a switch or rectifier, is very significant in the modern power industry. The power semiconductor, in terms of its physical properties, requires a high breakdown voltage to turn off, a low on-state resistance to reduce static loss, and a fast switching speed to reduce dynamic loss. Among those parameters, the breakdown voltage and on-state resistance rely on the doping concentration of the drift region in the power semiconductor, this effect can be more important for a higher voltage device. Although the low doping concentration in the drift region increases the breakdown voltage, the on-state resistance that is increased along with it makes the static loss characteristic deteriorate. On the other hand, although the high doping concentration in the drift region reduces on-state resistance, the breakdown voltage is decreased, which limits the scope of its applications. This addresses the fact that breakdown voltage and on-state resistance are in a trade-off relationship with a parameter of the doping concentration in the drift region. Such a trade-off relationship is a hindrance to the development of power semiconductor devices that have idealistic characteristics. In this study, a novel structure is proposed for the Insulated Gate Bipolar Transistor (IGBT) device that uses conductivity modulation, which makes it possible to increase the breakdown voltage without changing the on-state resistance through use of a P-floating layer. More specifically in the proposed IGBT structure, a P-floating layer was inserted into the drift region, which results in an alleviation of the trade-off relationship between the on-state resistance and the breakdown voltage. The increase of breakdown voltage in the proposed IGBT structure has been analyzed both theoretically and through simulations, and it is verified through measurement of actual samples.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.7
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• pp.594-599
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• 2007

[ $CulnS_2$ ] thin films were synthesized by sulfurization of Cu/In Stacked elemental layer deposited onto glass Substrates by vacuum furnace annealing at temperature $200^{\circ}C$. And structural and electrical properties were measured in order to certify optimum conditions for growth of the ternary compound semiconductor $CuInS_2$ thin films with non-stoichiometry composition. $CuInS_2$ thin film was well made at the annealed $200^{\circ}C$ of SLG/Cu/In/S stacked elemental layer which was prepared by thermal evaporator, and chemical composition of the thin film was analyzed nearly as the proportion of 1 : 1 : 2. Physical properties of the thin film were investigated at various fabrication conditions substrate temperature, annealing and temperature, annealing time by XRD, FE-SEM and Hall measurement system. The compositional deviations from the ideal chemical formula for $200^{\circ}C$ material can be conveniently described by non-molecularity$({\Delta}x=[Cu/In]-1)$ and non-stoichiometry $({\Delta}y=[{2S/(Cu+3In)}-1])$. The variation of ${\Delta}x$ would lead to the formation of equal number of donor and accepters and the films would behave like a compensated material. The ${\Delta}y$ parameter is related to the electronic defects and would determine the type of the majority charge carriers. Films with ${\Delta}y>0$ would behave as p-type material while ${\Delta}y<0$ would show n-type conductivity. At the sane time, carrier concentration, hall mobility and resistivity of the thin films was $9.10568{\times}10^{17}cm^{-3},\;312.502cm^2/V{\cdot}s\;and\;2.36{\times}10^{-2}\;{\Omega}{\cdot}cm$, respectively.

• Journal of Soil and Groundwater Environment
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• v.19 no.2
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• pp.25-37
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• 2014

The volcanic type of geothermal water is linked intimately to active or potentially active volcanoes and takes place near the plate boundaries. In contrast to the volcanic type, the geothermal water in Korea has a non-volcanic origin. Korea's geothermal water is classified into the residual magma (RM) type and deep groundwater (DG) type according to the criterion of $35^{\circ}C$. This study reviewed the relationship between the physical and chemical features of the 281 geothermal water sources in South Korea in terms of the specific capacity, water temperature, and chemical compositions of two different basements (igneous rock and metamorphic rock) as well as the geological structures. According to the spatial relationship between the geothermal holes and geological faults, the length of the major fault is considered a key parameter determining the movement to a deeper place and the temperature of geothermal water. A negligible relationship between the specific capacity (Q/s) and temperature was found for both the RM type and DG type with the greater specific capacities of the RM- and DG-igneous types than the RM- and DG-metamorphic types. No relationship was observed between Q/s and the chemical constituents ($K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$, $Zn^{2+}$, $Cl^-$, $SO_4{^{2-}}$, $HCO_3{^-}$, and $SiO_2$) in the DG-igneous and DG-metamorphic types. Furthermore, weak relationship between temperature and chemical constituents was found for both the RM type and DG type.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1363-1369
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• 2008

As game and character animation industries are growing, techniques for reproducing realistic character behaviors have been required in various fields. Therefore, intensive researches have been performed in order to find various methods for realistic character animation. The most common approaches to character animation involves tedious user input method, simulation with physical laws based on dynamics, and measurement of actors' behaviors with input devices such as motion capture system. These approaches have their own advantages, but they all have common disadvantage in character control. In order to provide users with convenient control, the realistic animation must be generated with high-level parameters, and the modification should also be made with high-level parameters. In this paper we propose techniques for developing an automated character animation tool which operates with high-level parameters, and introduce techniques for developing actual games by utilizing this tool.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.187-193
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• 2019

Regarding physical absorption mechanism for fine particles(Dust), internal pore-bridging is a major parameter in porous media. In this paper, internal bridging pore system is invented through FA-based geopolymer and incorporated PLA (Polylactic Acid) fiber with biodegradability. With various mix proportions, compressive strength over 20MPa is obtained but PLA is little dissolved in the condition of NaOH 5mole and $30^{\circ}C$ of temperature, which was found that temperature rising accelerates PLA solubility. Within 24hours, beads type PLA is completely dissolved under $90{\sim}130^{\circ}C$ and NaOH 5~12mole of alkali. In room condition, geo-polymerization is limitedly occurs so that the internal pore after PLA dissolution is thought to be effective to absorption and storage of fine particles.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.331-341
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• 2012

A modified Ignition and Growth(I&G) model which is necessary to simulate the combustion phenomena of energetic materials and an analytical model determining the unknown parameters of the reaction rate equation are proposed. The modified I&G model sustains important physical implications with overcoming some problems of previous rate equations. This rate model consist of Ignition term which represent the formation of the hotspot due to void collapse and Growth term which means the shock to detonation transition phenomena. Also, the theoretical model is used to investigate the combustion characteristics of certain energetic materials before running Hydrocode by pre-determination of unknown parameter, b, G, x, I. The analytical model provides efficient and highly accurate results rather than previous method which simulated the unconfined-rate-stick via the numerical means.