• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.25-29
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• 2010

We have investigated the effect of surface roughness of TCO substrate on the characteristics of OLED (organic light emitting diodes) devices. In order to control the surface roughness of AZO thin films, we have processed photo-lithography and reactive ion etching. The micro-size patterned mask was used, and the etching depth was controlled by changing etching time. The surface morphology of the AZO thin film was observed by FESEM and atomic force microscopy (AFM). And then, organic materials and cathode electrode were sequentially deposited on the AZO thin films. Device structure was AZO/${\alpha}$-NPD/DPVB/$Alq_3$/LiF/Al. The DPVB was used as a blue emitting material. The electrical characteristics such as current density vs. voltage and luminescence vs. voltage of OLED devices were measured by using spectrometer. The current vs. voltage and luminance vs. voltage characteristics were systematically degraded with increasing surface roughness. Furthermore, the retention test clearly presented that the reliability of OLED devices was directly influenced with the surface roughness, which could be interpreted in terms of the concentration of the electric field on the weak and thin organic layers caused by the poor step coverage.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2003.10a
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• pp.118-118
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• 2003

In a rolling wire probe, a key component of an inspection apparatus for PDP electrode patterns, the electric performance of it is known to be strongly dependent on the surface condition of a collet pin, a needle pin, and a wire. However, the collet and needle pins rotate very rapidly in contact with each other, which results in the degradation of the surface by the heat and friction and finally the formation of black wear marks on the surface after a several hundred hours test. Once the black wear marks appear on the surface, the electric resistance of the probe increases sharply and so the integrity of the probe is severely damaged. In this experiment, TiN coating, which has excellent electric conductances and good wear-resistance, has been applied on the surface of collect and needle pins for preventing the surface damages. In order to achieve the homogeneous coating with a good adhesion property, special coating substrate stages and jigs were designed and applied during coating. TiN has been deposited using 99.999% Titanium target by a DC reactive sputtering method. According to the components and jigs, processing parameters, such as DC power, RF bias and the flow rate ratio of Ar and N$_2$ used as reactive gases, has been controlled to obtain good TiN films. Detailed problems and solutions for applying the new substrate stages and jigs will be discussed.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3325-3327
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• 1999

A microgripper driven by E-T (electro-thermal) actuators has been designed and fabricated by surface micromachining. This microgripper consists of two E-T actuators. Each actuator has two arms with different widths joined at the end to form a 'U' shape. The wider 'cold' arm has a narrow flexure at the end (anchor or electrode side) for easy bending, This actuator can be fabricated with only two masks - one for the sacrificial layer and the other for the poly-Si structure layer. An E-T actuator bends its arm due to unequal thermal expansion between the 'cold' arm and the 'hot' arm, This actuator tip moves laterally in an arcing motion towards the cold arm side when the structure is unevenly heated by the applied current. Therefore each microgripper is actuated inwards and can hold a micro object. The fabricated E-T actuator was operated in the range of $2{\sim}12V$ and $1{\sim}5mA$. and maximum tip displacement was $13.6{\mu}m$. This device may become useful in many applications because an E-T actuator can be designed and fabricated easily, and obtain large displacement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.321-322
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• 2007

In order to increase the cost effectiveness of solar cells, module production should be treated more comprehensively. Back contact cells offer distinct advantage in the interconnection of cells to modules. Thereby Mo thin film were prepared in order to clarify optimum conditions for growth of the thin film depending upon process, and then by changing a number of deposition conditions and substrate temperature conditions variously, structural and electrical characteristics were measured. For the manufacture of the Mo were vapor-deposited in the named order. Among them, Mo were vapor-deposited by using the sputtering method in consideration of their adhesive force to the substrate, and the DC power was controlled so that the composition of Mo, while the surface temperature having an effect on the quality of the thin film was changed from R.T$[^{\circ}C]$ to $200[^{\circ}C]$ at intervals of $50[^{\circ}C]$. Micro-structural studies were carried out by XRD (D/MAX-1200, Rigaku Co.) and SEM (JSM-5400, Jeol Co.). Electrical properties were measured by CMT-SR3000 Measurement System.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.155-160
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• 2005

Gravity thickening process has been widely used in WTP sludge thickening at domestic water treatment plant. The operation method of the process is very simple, however, the process requires long detention time about 24~48 hours for sludge thickening, uses polymer, and low total solids of thickened sludge to increase sludge thickening efficiency. To solve there problems, we studied about flotation process, especially, electro-flotation (EF) process in WTP sludge thickening. Electro-flotation process is simpler than dissolved-air-flotation(DAF) process because EF needs only electrode and current to generate micro-bubbles and the operation is easy. This study was performed at two batch columns to compare interface height, total solids, effluent turbidity between an electro-flotation thickening and a gravity thickening. According to the result, an electro-flotation thickening was that interface height was decreasing, total solids had high concentration, and effluent turbidity was low in comparison with a gravity thickening. Also, it will make the high efficiency of following process, such as a dehydrating process and digestive process. because of high total solids and low moisture content in the sludge.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.10
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• pp.660-666
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• 2015

Surface acoustic wave(SAW) device is used for transporting and patterning micro-scale particles such as cells. In this research, velocity of particles was investigated moved by SAW device with two types of interdigital electrode transducers(IDTs) under various conditions. SAW devices which have single IDTs and double IDTs were designed and fabricated. On the previous studies, resultant velocities of particles were predicted considering output power and power ratio between IDTs-shape. For more accurate prediction, power loss in SAW device and a power difference between two types of IDTs-shape were considered. Maximum error between the test results and predicted values was 5 % so the power loss must be considered in the velocity prediction of the particles.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.185-189
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• 2016

Among many kinds of bioaffinity sensors, the avidin-biotin system has been widely used in a variety of biological applications due to the specific and high affinity interaction of the system. In this work, gold nanorods with high surface area were explored as electrodes in order to amplify the signal response from the avidin-biotin interaction which can be further utilized for avidin-biotin biosensors. Electrochemical performance of electrodes modified with nanorods and functionalized with avidin in response to interactions with biotin at various concentrations using $[Fe(CN)_6]^{3-/4-}$ couple as the redox probe were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A very low biotin concentration of less than 1 ng/mL could be detected using the electrodes modified with nanorods.

• Biomaterials and Biomechanics in Bioengineering
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• v.2 no.2
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• pp.71-84
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• 2015

A low-profile flow sensor has been designed, fabricated, and characterized to demonstrate the feasibility for monitoring hemodynamics in cerebral aneurysm. The prototype device is composed of three micro-membranes ($500-{\mu}m$-thick polyurethane film with $6-{\mu}m$-thick layers of nitinol above and below). A novel super-hydrophilic surface treatment offers excellent hemocompatibility for the thin nitinol electrode. A computational study of the deformable mechanics optimizes the design of the flow sensor and the analysis of computational fluid dynamics estimates the flow and pressure profiles within the simulated aneurysm sac. Experimental studies demonstrate the feasibility of the device to monitor intra-aneurysmal hemodynamics in a blood vessel. The mechanical compression test shows the linear relationship between the applied force and the measured capacitance change. Analytical calculation of the resonant frequency shift due to the compression force agrees well with the experimental results. The results have the potential to address important unmet needs in wireless monitoring of intra-aneurysm hemodynamic quiescence.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.159-166
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• 2022

The assembly of the micron-sized Si/CNT/carbon composite wrapped with graphene (SCG composite) is designed and synthesized via a spray drying process. The spherical SCG composite exhibits a high discharge capacity of 1789 mAh g^-1 with an initial coulombic efficiency of 84 %. Moreover, the porous architecture of SCG composite is beneficial for enhancing cycling stability and rate capability. In practice, a blended electrode consisting of spherical SCG composite and natural graphite with a reversible capacity of ~500 mAh g^-1, shows a stable cycle performance with high cycling efficiencies (> 99.5%) during 100 cycles. These superior electrochemical performance are mainly attributed to the robust design and structural stability of the SCG composite during charge and discharge process. It appears that despite the fracture of micro-sized Si particles during repeated cycling, the electrical contact of Si particles can be maintained within the SCG composite by suppressing the direct contact of Si particles with electrolytes.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.23-28
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• 2002

This paper describes the machining characteristics of the $MoSi_2$ based composites by electric discharge drilling with various tubular electrodes, besides, Hardness characteristics and microstructures of $Nb/MoSi_2$ laminate composites were evaluated from the variation of fabricating conditions such as preparation temperature, applied pressure and pressure holding time. $MoSi_2$ -based composites has been developed in new materials for jet engine of supersonic-speed airplanes and gas turbine for high- temperature generator. Achieving this objective may require new hard materials with high strength and high temperature-resistance. However, With the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material, the tool electrode being almost non-unloaded, because there is no direct contact between the tool electrode and the workpiece. By combining a nonconducting ceramics with more conducting ceramic it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and $MoSi_2$ powder was an excellent strategy to improve hardness characteristics of monolithic $MoSi_2$. However, interfacial reaction products like (Nb, Mo)$SiO_2$ and $Nb_2Si_3$ formed at the interface of $Nb/MoSi_2$ and increased with fabricating temperature. $MoSi_2$ composites which a hole drilling was not possible by the conventional machining process, enhanced the capacity of ED-drilling by adding $NbSi_2$ relative to that of SiC or $ZrO_2$ reinforcements.