• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.235-238
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• 2009

BaMg$Al_{10}O_{17}$ (BAM) co-doped with $Eu^{2+}$ and $Mn^{2+}$ was synthesized in a solid-state reaction and their luminescence properties were investigated as functions of the concentrations of the sensitizer and activator. BAM:$Eu^{2+}$ had a broad blue emission band at 450 nm and BAM:$Mn^{2+}$ exhibited green emission at 514 nm. The energy transfer from $Eu^{2+}$ to $Mn^{2+}$ was mainly of the resonance-type via an electric dipole-quadrupole interaction. Additionally, the addition of various fluxes such as $AlF_3$ and $BaF_2$ in the synthesis improves the moist and thermal stability. This is particularly important for the phosphor in white light emitting diodes (LEDs).

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.134-138
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• 2014

Power packs can change energy to hydraulic energy generated by an engine as a tool for use with civil engineering construction equipment. This paper determines which type of power pack meets the standards of construction machinery. A power pack was formulated as a three-dimensional model by using the software CATIA. A modal analysis was conducted using ANSYS Workbench, and the resonance was checked. Next, a harmonic analysis was conducted. The analytical results show that the dynamic stability of the power pack is assured.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.470-477
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• 2002

Possibility of passive piezoelectric damping based on a new shunting parameter estimation method is studied using finite element analysis. The adopted tuning method is based electrical impedance that is found at piezoelectric device and the optimal criterion for maximizing dissipated energy at the shunt circuit. Full three dimensional finite element model is used for piezoelectric devices with cantilever plate structure and shunt electronic circuit is taken into account in the model. Electrical impedance is calculated at the piezoelectric device, which represents the structural behavior in terms of electrical field, and equivalent electrical circuit parameters for the first mode are extracted using PRAP (Piezoelectric Resonance Analysis Program). After the shunt circuit is connected to the equivalent circuit for the first mode, the shunt parameters are optimally decided based on the maximizing dissipated energy criterion. Since this tuning method is based on electrical impedance calculated at piezoelectric device, multi-mode passive piezoelectric damping can be implemented for arbitrary shaped structures.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.372-376
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• 2009

This paper describes the characteristics of piezoelectric micro power generators by the ANSYS FEA(finite element analysis). The micro power generator was designed to convert ambient vibration energy to electrical power as a ZnO piezoelectric material. To find optimal model in low vibration ambient, the shape of power generator was changed with different membrane width, thickness, length, and proof mass size. Using the ANSYS modal analysis, bending mode and stress distribution of optimal model were analyzed. Moreover, the displacement with the frequency range was analyzed by harmonic analysis. From the simulation results, the resonance frequency of optimal model is about 373 Hz and investigate the possibility of ZnO micro power generator for ambient vibration applications.

• Journal of Power Electronics
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• v.5 no.4
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• pp.247-256
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• 2005

In order to harvest power in an efficient manner from a micro piezoelectric (PZT) device for charging the battery of a remote system, a new AC/DC resonant pulse power converter is proposed. The proposed power converter has two stages in the power conversion process. The first stage includes N-type MOSFET full bridge rectifier. The second stage includes a boost converter having an N-type MOSFET and a P-type MOSFET. MOSFETs work in the $1^{st}$ or $3^{rd}$ quadrant region. A small inductor for the boost converter is assigned in order to make the size of the power converter as small as possible, which makes the on-interval of the MOSFET switch of the boost converter ultimately short. Due to this short on-interval, the parasitic junction capacitances of MOSFETs affect the performance of the power converter system. In this paper, the performance of the new converter is analytically and experimentally evaluated with consideration of the parasitic capacitance of switching devices.

• Journal of Power Electronics
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• v.10 no.6
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• pp.784-791
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• 2010

In this paper, a resonant pulse power converter (RPPC) is proposed. The proposed RPPC transfers the pulse-shape power from a DC source to a load periodically. The RPPC consists of a resonant circuit and a resonant pulse converter driven by a self-switching circuit. Depending on the magnitude difference between the input and output voltages, the operations of the RPPC are divided into 4 modes; boost mode, hybrid mode, direct mode and cut-off mode, respectively. The main switch of the RPPC turns on in the ZCS condition and off in the ZVS condition spontaneously. The operational principles of a RPPC using the self-switching technique are analyzed and verified in experiments. An example of a RPPC application is demonstrated in the area of thermoelectric energy harvesting.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.97-102
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• 2004

The Characteristics of noise and vibration by heavy-weight floor impact sound was studied. Resonance frequency increased a little in structures that use damping material in living room and bedroom, and acceleration waves length that respond became short, and displayed aspect that oscillation level decreases. Result that measure sound pressure level, structure that compare and applies damping materials with structure that apply the resilient materials from 63Hz lower part that impact energy is concentrated in energy spectrum of heavy-weight floor impact sound displayed result that sound pressure, level decreases remarkably. Therefore, according to use of damping materials, confirmed reduction effect of heavy-weight floor impact sound.

• Preventive Nutrition and Food Science
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• v.3 no.2
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• pp.203-209
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• 1998

The development of methods for the identification of irradiated foods helps enforce national and international regulations on labelling to ensure the consumer's free choice to buy irradiated or unirradiated foods. and the availabilityof such methods may assist the promotion of international trade in irradiated food products and help prevent abuse of the technology. A number of approaches to determine the physical , chemical, microbiological and biological changes that occur in foods treated with ionizing radiation have been studied. However no single method is universally applicable. Among physical measurements, the leading methods of indentification are electron spin resonance (ESR) spectroscopy and thermoluminescence(TL). ESR is an established non-destructive method for the analysis of free radicals from their traps and TL is the emission of light from irradiated mineral extracts by heating. Viscosity of carbohydrate polymers by causing chain breaks by irradiation, measuring the impedance of potatoes and detection of gases produced radiolytically are promising techniques for identification purposes. Irradiated water-containing foods show significant supercooling when monitored with a differential scanning calorimeter (DSC), which can be applied to identifying irradiated ones.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.454-457
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• 2019

Controlling the shape of Ag nanoparticles (NPs) is very difficult. In the present work, urchin Ag NPs with different sizes and pod length control have been synthesized successfully in high yield by the concentration of a reducing agent. Unique Ag NPs were observed by TEM and SEM. These nanocrystals exhibit tunable surface plasmon resonance properties from the visible to near-infrared regions. They were applied to surface-enhanced Raman scattering (SERS) substrates using rhodamine 6G (R6G), benzenethiol (BT), and 4-amino benznethiol (4-ABT) molecules. The enhanced local field effect due to the sharp pod length, size, and surface plasmon of the urchin Ag NPs resulted in enhanced SERS properties and can serve as high-sensitivity substrates for SERS measurements.

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.282-288
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• 1989

Theoretical analysis of DF-$CO_2$ transfer chemical laser is performed through simple kinetic model consisting of 30 chemical reactions. In this model, we calculate the power theoretically by solving the rate equations, which are related to the $D_2\;+\;F_2$ chain reaction and the DF-$CO_2$ resonance energy transfer, combined with both the gain processes and the stimulated emission processes. The calculated powers are verified with previously reported results in good agreements. The output energy rises linearly with the increase in pressure, and the duration time of output pulse show the inverse dependence on pressure. Through the detailed calculation of temperature and concentrations of reactants as a function of time, it is found that the deactivation processes of DF(v) can be neglected in low pressure, but they have to be considered in high pressure. From the parametric study for the variation on [$D_2]/[F_2$] and [$CO_2]/[D_2\;+\;F_2$] at several constant total pressure, the optimum lasing conditions are found to be in a range of 1/3 to 1 and 2 to 4, respectively.