• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.81-88
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• 2010

Small size polymer electrolyte membrane fuel cell (PEMFC) stacks were prepared using carbon composite and graphite bipolar plates and their performances were evaluated on reactant gas and operating time. In comparison to single cell and stack, it was identified that home-made bipolar plate was well-designed to maximize stack performance as high as that of single cell. During long-term operation, the performances of stacks using two different kinds of bipolar plates were compared. The decrease of performance in both stacks was accelerated with increasing load current. It was observed from stack test that the stack performance using carbon composite bipolar plate was very similar to that using graphite bipolar plate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.245-245
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• 2009

l-D nanostructured materials have much more attention because of their outstanding properties and wide applicability in device fabrication. Copper oxide(CuO) has been realized as a p-type metal oxide semiconductor with narrow band gap of 1.2 -1.5eV. Copper oxide nanostructures can be synthesized by various growth method such as oxidation reaction, thermal evaporation thermal decomposition, sol-gel. and Mostly CuO nanowire prepared on the Cu substrate such as Copper foil, grid, plate. In this study, CuO NWs were grown by thermal oxidation (at various temperatures in air (1 atm)) of Cu metal deposited on CuO (20nm)/$SiO_2$(250nm)/Si. A 20nm-thick CuO layer was used as an adhesion layer between Cu metal and $SiO_2$

• Advances in nano research
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• v.9 no.4
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• pp.237-250
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• 2020

An accurate plate theory for assessing sandwich structures is of interest in order to provide precise results. Hence, this paper develops Layer-Wise (LW) theory for reaching precise results in terms of buckling and vibration behavior of Functionally Graded Carbon Nanotube-Reinforced Composite (FG-CNTRC) annular nanoplates. Furthermore, for simulating the structure much more realistic, its edges are elastically restrained against in-plane and transverse displacement. The nano structure is integrated with piezoelectric layers. Four distributions of Single-Walled Carbon Nanotubes (SWCNTs) along the thickness direction of the core layer are investigated. The Differential Quadrature Method (DQM) is utilized to solve the motion equations of nano structure subjected to the electric field. The influence of various parameters is depicted on both critical buckling load and frequency of the structure. The accuracy of solution procedure is demonstrated by comparing results with classical edge conditions. The results ascertain that the effects of different distributions of CNTs and their volume fraction are significant on the behavior of the system. Furthermore, the amount of in-plane and transverse spring coefficients plays an important role in the buckling and vibration behavior of the nano-structure and optimization of nano-structure design.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.513-520
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• 2011

The NIL processes have been studied to implement low cost, high throughput and high resolution application. A RNIL(roller NIL) is an alternative approach to flat nanoimprint lithography. RNIL process is necessary to transfer patterns on flexible substrates. Compared with flat NIL, RNIL has the advantages of better uniformity, less pressing force, and the ability to repeat the patterning process continuously on a large substrate. This paper studies the design, construction and verification of a thermal RNIL system. The proposed RNIL system can easily adopt the flat shaped hot plate which is one of the most important technologies for NIL. The NIL system can be used to transfer patterns from a flexible stamp to a flexible substrate, from a flexible stamp to a Si substrate, and from a roller stamp to a flexible substrate, etc. Patterning on flexible substrates is one of the key technologies to produce bendable displays, solar cells and other applications.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.51-56
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• 2019

LuAG:Ce(Lu₃Al₅O₁₂:Ce³⁺) nano phosphor were synthesized by applying the coprecipitation method. It is used to increase the color rendering of phosphor ceramic plate for high power LEDs and laser lighting. Internal quantum efficiency and absorption of LuAG:Ce nano phosphor are 51.5 % and 64.4 %, respectively, which is higher than the previously studied nano phosphors. The maximum absorption wavelength of this phosphor is 450 nm blue light, and the emission wavelength is 510 nm. The emission wavelength shifted to longer wavelength when the concentration of Ce increased in the heat treatment of the reducing atmosphere. Thermal quenching of LuAG nano phosphor was 70 % at 200 ℃, it was explained by their significant quenching of all raman scattering modes, implying the restriction of electron-phonon couplings caused by their defects.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.61-68
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• 2019

Only the power is converted from AC to DC, in accordance with IEC 60587 based test method, in order to develop the LSR(Liquid Silicone Rubber) insulator material for HVDC, the experiment of Inclined Plate Tracking and Erosion Resistance was conducted. A contaminant (2.5 mS/cm: ammonium chloride) was applied at a rate of 0.3 ml/min and a voltage of ${\pm}3.5kV$, and was evaluated on the basis of 60 mA/2s. The samples were prepared by dispersing LSR/Nano silica_25wt% Composites in LSR. The erosion phenomena of surface discharge and tracking due to DC polarity and negative polarity were measured by image, leakage current maximum and thermal camera. The thermal imaging camera measured the surface temperature generated by the joule heat of the leakage current due to the drying discharge and the conductive current. After the measurement, the tracking and erosion mechanisms were evaluated for erosion weight, erosion depth and erosion length. Positive and negative polarity of LSR/Nano Silica_25wt% composite Tracking and erosion results show that positive polarity is more severe than negative polarity.

• Current Photovoltaic Research
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• v.11 no.2
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• pp.54-57
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• 2023

Recently, requirements for improving the convenience of constructing BIPV (Building Integrated Photo Voltaic) modules had increased. To solve this problem, we fabricated shingled PV modules integrated with bent steel plates for building integrated photovoltaics. These PV modules could be constructed directly on the roof without the installation structure. We found optimal lamination conditions with supporting structures to fabricate a module on a bent steel plate. Moreover, we applied a shingled design to PV modules integrated with bent steel plates to achieve a high electrical output power. The shingled module with bent steel plates shows 142.80 W of solar-to-power conversion in 0.785 m² area.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.144-144
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• 2013

Non-thermal atmospheric pressure plasmas have recently garnered much attention due to their unique physical and chemical properties that are sometimes significantly different from those of low pressure plasmas. It can offer many possible application areas including nano and bio/medical areas. Many different types of plasma sources have been developed for specific needs, which can be one of the important merits of the atmospheric pressure plasmas since characteristics of the produced plasma depend significantly on operating parameters such as driving frequency, supply gas type, driving voltage waveform, gas flow rate, gas composition, geometrical factor etc. Among many source configurations, parallel plate type geometry is one of the simplest configurations so that it can offer many insights for understanding basic underlying physics. Traditionally, the parallel plate type set up has been studied actively for understanding low pressure plasma physics along with extensive employment in industries for the same reason. By considering that understanding basic physics, in conjunction with plasma-surface interactions especially for nano & bio materials, should be pursued in parallel with applications, we investigated atmospheric pressure discharge characteristics in a parallel plate type capacitive discharge source with two parallel copper electrodes of 60 mm in diameter and several millimeters in gap distance. In this presentation, some plasma characteristics by varying many operating variables such as inter-electrode distance, gas pressure, gas composition, driving frequency etc will be discussed. The results may be utilized for plasma control for widening application flexibility.

• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.431-448
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• 2012

In this paper, the first-order shear deformation theory (FSDT) (Mindlin) for continuum incorporating surface energy is exploited to study the static behavior of ultra-thin functionally graded (FG) plates. The size-dependent mechanical response is very important while the plate thickness reduces to micro/nano scales. Bulk stresses on the surfaces are required to satisfy the surface balance conditions involving surface stresses. Unlike the classical continuum plate models, the bulk transverse normal stress is preserved here. By incorporating the surface energies into the principle of minimum potential energy, a series of continuum governing differential equations which include intrinsic length scales are derived. The modifications over the classical continuum stiffness are also obtained. To illustrate the application of the theory, simply supported micro/nano scaled rectangular films subjected to a transverse mechanical load are investigated. Numerical examples are presented to present the effects of surface energies on the behavior of functionally graded (FG) film, whose effective elastic moduli of its bulk material are represented by the simple power law. The proposed model is then used for a comparison between the continuum analysis of FG ultra-thin plates with and without incorporating surface effects. Also, the transverse shear strain effect is studied by a comparison between the FG plate behavior based on Kirchhoff and Mindlin assumptions. In our analysis the residual surface tension under unstrained conditions and the surface Lame constants are expected to be the same for the upper and lower surfaces of the FG plate. The proposed model is verified by previous work.

• Structural Engineering and Mechanics
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• v.84 no.5
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• pp.685-697
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• 2022

Nanotechnology has become one of the interesting technique used in material science and engineering. However, it is low used in civil engineering structures. The purpose of the present study is to investigate the static behavior of concrete plates reinforced with silica-nanoparticles. Due to agglomeration effect of silica-nanoparticles in concrete, Voigt's model is used for obtaining the equivalent nano-composite properties. Furthermore, the plate is simulated mathematically with higher order shear deformation theory. For a large use of this study, the concrete plate is assumed resting on a Pasternak elastic foundation, including a shear layer, and Winkler spring interconnected with a Kerr foundation. Using the principle of virtual work, the equilibrium equations are derived and by the mean of Hamilton's principle the energy equations are obtained. Finally, based on Navier's technique, closed-form solutions of simply supported plates have been obtained. Numerical results are presented considering the effect of different parameters such as volume percent of SiO₂ nanoparticles, mechanical loads, geometrical parameters, soil medium, on the static behavior of the plate. The most findings of this work indicate that the use of an optimum amount of SiO₂ nanoparticles on concretes increases better mechanical behavior. In addition, the elastic foundation has a significant impact on the bending of concrete slabs.