• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.152-158
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• 2013

The purpose of this study is to investigate cooling performance of high power LEDs from 100 to 200 W class by using a jet impingement cooling module. The numerical analysis of forced convection cooling inside cooling module is carried out using a multi-purpose CFD software, FLUENT 6.3. In the experiments, the LED cooling system consists of jet impingement module, heat exchanger, water reservoir, and pump. In the present study, the cooling performance of jet impingement cooling module is investigated to determine the effect of the heat sink types on the impinging surface, the space and length of fins. Numerical and experimental studies show the reasonable agreement of LED metal PCB temperature between those results and give the optimized design parameters such as the space of fin and the length of fin. Also, the pin fin type of heat sink is found to be more efficient than the plate type heat sink in jet impingement cooling.

• Elastomers and Composites
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• v.49 no.4
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• pp.341-345
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• 2014

In this study, self-actuated photocatalyst that titanium dioxide doped by more than two transition metal was coated PU foam. The antibacterial and antifungal activity of self-actuated photocatalyst coated PU foam was characterized without light. The antibacterial property of self-actuated photocatalyst coated PU foam was shown to be reduced more than 96%, and the antifungal property was shown to be reduced more than 99.9%. The durability of self-actuated photocatalyst coated PU foam tested by Weather-O-meter showed the 7% reduction of formaldehyde decomposition from 96.5% before test to 89.8% after test. The observation of surface of PU foam coated with self-actuated photocatalyst showed that the catalyst was firmly attached to the surface of polyester fiber without separation.

• Advances in nano research
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• v.3 no.2
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• pp.97-109
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• 2015

Citrate ion is a commonly used reductant in metal colloid synthesis, undergoes strong surface interaction with silver nanocrystallites. The slow crystal growth observed as a result of the interaction between the silver surface and the citrate ion makes this reduction process unique compared to other chemical and radiolytic synthetic methods. The antimicrobial effects of silver (Ag) ion or salts are well known, but the effects of citrate coated Ag nanoparticles (CAgNPs) are scant. Herein, we have isolated biofilm causative bacteria and fungi from drinking water PVC pipe lines. Stable CAgNPs were prepared and the formation of CAgNPs was confirmed by UV-visible spectroscopic analysis and recorded the localized surface plasmon resonance of CAgNPs at 430 nm. Fourier transform infrared spectroscopic analysis revealed C=O and O-H bending vibrations due to organic capping of silver responsible for the reduction and stabilization of the CAgNPs. X-ray diffraction micrograph indicated the face centered cubic structure of the formed CAgNPs, and morphological studies including size (average size 50 nm) were carried out using transmission electron microscopy. The hydrodynamic diameter (60.7 nm) and zeta potential (-27.6 mV) were measured using the dynamic light scattering technique. The antimicrobial activity of CAgNPs was evaluated (in vitro) against the isolated fungi, Gram-negative and Gram-positive bacteria using disc diffusion method and results revealed that CAgNPs with 170ppm concentration are having significant antimicrobial effects against an array of microbes tested.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.237-241
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• 2004

Amorphous silicon (a-Si) films are used in a broad range of solar cell, flat panel display, and sensor. Because of the greater ease of deposition and lower processing temperature, thin films are widely used for thin film transistors (TFTs). However, they have lower stability under the exposure of visible light and because of their low field effect mobility ($\mu$$_{FE}$ ) , less than 1 c $m^2$/Vs, they require a driving IC in the external circuits. On the other hand, polycrystalline silicon (poly-Si) thin films have superiority in $\mu$$_{FE}$ and optical stability in comparison to a-Si film. Many researches have been done to obtain high performance poly-Si because conventional methods such as excimer laser annealing, solid phase crystallization and metal induced crystallization have several difficulties to crystallize. In this paper, a new crystallization process using a molybdenum substrate has been proposed. As we use a flexible substrate, high temperature treatment and roll-to-roll process are possible. We have used a high temperature process above 75$0^{\circ}C$ to obtain poly-Si films on molybdenum substrates by a rapid thermal annealing (RTA) of the amorphous silicon (a-Si) layers. The properties of high temperature crystallized poly-Si studied, and poly-Si has been used for the fabrication of TFT. By this method, we are able to achieve high crystal volume fraction as well as high field effect mobility.

• Resources Recycling
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• v.19 no.1
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• pp.57-65
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• 2010

Recently, we have investigated the recovery of resources from the waste material of manufacturing printed circuit board. As printed circuit board or chip has become light, small, high reliability, it is necessary to reuse and recover resources from them. Especially, the printed circuit board that has been used for important mobile electronic pans are plated with min.0.03 ${\mu}m$ to max.50 ${\mu}m$. As increasing the cost of gold, raw material, chemicals, payments and waste material, it has been accelerated the competition for reuse and recovery. But, it is insufficiency of technician and equipments for the recovery of effective resource. In this paper, as analyzing the technical trend of gold recovery and waste back board from the manufacturing process of printed circuit board, it may be effective of recycling, further more it may be contributed to develop the valuable resources.

• Analytical Science and Technology
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• v.11 no.1
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• pp.1-7
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• 1998

This study focuses on developing a controlling and analyzing software for the portable atomic emission spectrometer equipped with an electrothermal vaporizer(ETV) that can perform the in-situ trace analysis of heavy metal ions dissolved in water. The software works well for a notebook PC and it is exclusively developed for the real time analysis with a line filter and a photomultiplier light detector. The program is designed to operate under Windows 95 environment and either Korean or English can be used as a main language. The Delphi 2.0 language software is mainly used for programing. The program is designed to make a calibration curve and the system users can get the analytical data in a short time. And a final report can be generated without having difficulties. This software can be easily modified for other analytical atomic spectrometers.

• Journal of Korea Foundry Society
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• v.26 no.6
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• pp.267-271
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• 2006

Metal foam is a class of attractive materials, which exhibits unique combinations of physical, mechanical, thermal, electrical and acoustic properties. In particular, it is light and good at absorbing energy, which makes it attractive in automotive and aerospace applications weight is critical. In this paper, the Mg alloy foam was prepared by melt foaming method by addition of calcium as thickening agent, and $TiH_2$ or $CaCO_3$ powder as blowing agent. The macrostructural observation of foamed Mg showed that the pore structures of Mg alloy foam made by $CaCO_3$ as blowing agent were much better than that of foams made by $TiH_2$ as blowing agent. In addition, this paper showed the possible reason of fabrication magnesium alloy foam in proportion to blowing agent and the porosity range was about 40 to 76% as results value.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.61-62
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• 2007

HVOF thermal spray coating of micron size Co-alloy powder has been studied for the durability improvement of high velocity spindle (HVS). Optimal coating process of this system for the best surface properties is hydrogen flow rate 75 FMR, oxygen flow rate 38-42 FMR, feed rate 30 g/min at spray distance 5 inch. Friction coefficient (FC) and wear trace (WT) decrease increasing coating surface temperature from 25$^{\circ}$C to 538$^{\circ}$C due to the higher lubricant effects of the oxides at the higher temperature. At the study of adhesion of T800 coating on a light metal alloy Ti-6Al-4V (Ti64) tensile bond strength (TBS) and tensile fracture location (TFL) of Ti64/T800 are 8,740 psi and near middle of T800 coating respectively. This shows that adhesion of Ti64/T800 is higher than the cohesion strength (8,740 psi) of T800 coating. Therefore T800 coating is strongly advisable for the surface coating on HVS such as high speed air-bearing spindle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1302-1307
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• 2006

This study describes the preparation of high-performance photocatalyst and its environmental applications. We prepared visible-light response nano-particle photocatalyst exhibiting the similar photocatalytic activity with $TiO_2$, dispersed $TiO_2$ on $SiO_2$ with an active rutile type titanium oxide prepared at low temperature. The binder and stable photocatalytic $TiO_2$ sol for photocatalytic system were also prepared. Such products were evaluated by UV/Vis spectrometer, X-ray diffraction analysis, SEM, measurement of photocatalytic activities and surface area, mechanical properties of $TiO_2$-coated surfaces. The results obtained can be applied in efficient photocatalytic systems using POF and metal plate for the purification of air.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.05a
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• pp.57-61
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• 2005

In this study, the machine vision system for inspection using color recognition method have been designed and developed to automatically sort out a specified material such as Cu scraps or other non-ferrous metal scraps mixed in Fe scraps. The system consists of a CCD camera, light sources, a frame grabber, conveying devices and an air nozzled ejector, and is program-controlled by a image processing algorithm. The ejector is designed to be operated by an I/O interface communication with a hardware controller. The sorting examination results show that the efficiency of separating Cu scraps from the Fe scraps mixed with Cu scraps is around 90 % at the conveying speed of 15 m/min. and the system is proven to be excellent in terms of its efficiency. Therefore, it is expected that the system can be commercialized in shredder firms, if the high-speed automated sorting system will be realized.