• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_2
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• pp.1037-1045
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• 2022

In this study, nanoscale Al₂O3 ceramic particles were used due its exceptionally high hardness characteristics, chemical stability, and wear resistance properties. These nanoparticles will be used to investigate the optimal process conditions for the electro co-deposition of the Ni-Al₂O₃ composite coatings. A Watts bath electrolytic solution of a controlled composition along with a fixed agitation speed was used for this study. Whereas the current density, the pH value, temperature and concentration of the nano Al₂O₃ particles of the electrolyte were designated as the manipulative variables. The experimental design method was based on the orthogonal array to find the optimum processing parameters for the electro co-deposition of Ni-Al₂O₃ composite coatings. The result of confirmation experimental based on the optimal processing condition through the analysis of variance ; EDX analysis found that the ratio of alumina increased to 8.65 wt.% and subsequently the overall hardness increased to 983 Hv. Specially, alumina were evenly distributed on Nickel matrix and particles were embedded more firmly and finely in Nickel matrix.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.1
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• pp.44-49
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• 2017

Titanium has been used in various fields due to its good corrosion and erosion resistance, and superior mechanical properties. The process for selective electro-deposition on a titanium surface using laser beam is proposed in this paper. The process consists of laser irradiation, electro-deposition, and ultrasonic cleaning. Laser irradiation can change the surface morphology of titanium. Through laser irradiation, the surface cleaning effect and a rough surface can be achieved. The surface roughness of titanium was measured according to the laser beam conditions. The characteristics of selective electro-deposition on titanium surface according to surface roughness are investigated by various analytical methods such as SEM, and EDS.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.62-74
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• 1994

This paper addresses on the model synthesis and performance analysis of an engine mount featuring electro-rheological(ER) fluids which undergo a phase change when subjected to electric fields. A novel type of ER fluid-filled engine mount is devised and its hydraulic model is constructed. An equivalent mechanical model is subsequently obtained from the governing equation of the hydraulic model. The model parameters associated with the ER fluids are distilled from experimental investigations on the Bingham properties of the fluids. The distilled data are then incorporated into the governing model to undertake feasible work through computer simulations,. It is shown that the proposed engine mount has an inherent capability of controlling both the damping force and the resonance frequency. Other superior performance characteristics accrued from the proposed methodology are also evaluated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.84-90
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• 2001

The electro-reheoligical(ER) effect refers to the abrupt change in viscosity in certain suspensions on application of an electric field. This paper presents experimental results on material properties of an ER fluids subjected to electrical fatigues. As a first step, two types of EF fluids are made of arabic gum and methyl cellulose(MC) choosing 25% of parti-cle weight-concentration. Following the construction of test mechanism for electrical durability of ER fluid, the dynamic yield shear stress and current density of the ER fluids are experimentally distilled as a function of electric field. The yield shear stress of operated ER fluids are distilled and compared with those of unused ER fluids.

• Advances in nano research
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• v.5 no.4
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• pp.313-336
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• 2017

This article investigates vibration behavior of magneto-electro-elastic functionally graded (MEE-FG) nanobeams embedded in two-parameter elastic foundation using a third-order parabolic shear deformation beam theory. Material properties of MEE-FG nanobeam are supposed to be variable throughout the thickness based on power-law model. Based on Eringen's nonlocal elasticity theory which captures the small size effects and using the Hamilton's principle, the nonlocal governing equations of motions are derived and then solved analytically. Then the influences of elastic foundation, magnetic potential, external electric voltage, nonlocal parameter, power-law index and slenderness ratio on the frequencies of the embedded MEE-FG nanobeams are studied.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.198-198
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• 2012

Graphene has been the subject of intense study in recent years owing to its good optoelectronic properties, possibility for stretchable electronics, and so on. Especially, many research groups have studied about graphene nanostructures with various sizes and shapes. Graphene needs to be fabricated into useful devices with controllable electrical properties for its successful device applications. However, this been far from satisfaction owing to a lack of reliable pattern transfer techniques. Photolithography, nanowire etching, and electron beam lithography methods are commonly used for construction of graphene patterns, but those techniques have limitations for getting controllable GNRs. We have developed a novel nanoscale pattern transfer technique based on an electro-hydrodynamic lithography providing highly scalable versatile pattern transfer technique viable for industrial applications. This technique was exploited to fabricate nanoscale patterned graphene structures in a predetermined shape on a substrate. FE-SEM, AFM, and Raman microscopy were used to characterize the patterned graphene structures. This technique may present a very reliable high resolution pattern transfer technique suitable for graphene device applications and can be extended to other inorganic materials.

• Advances in nano research
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• v.15 no.5
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• pp.423-439
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• 2023

The aim of this paper is to investigate the free vibration behavior of the micro sandwich beam composing of five layers such as functionally graded (FG) porous core, nanocomposite reinforced by carbon nanotubes (CNTs) and piezomagnetic/piezoelectric layers subjected to magneto electrical potential resting on silica aerogel foundation. The effect of foundation has been taken into account using Vlasov model in addition to rigid base assumption. For this purpose, an iterative technique is applied. The material properties of the FG porous core and FG nanocomposite layers are considered to vary throughout the thickness direction of the beams. Based on the Timoshenko beam theory and Hamilton's principle, the governing equations of motion for the micro sandwich beam are obtained. The Navier's type solution is utilized to obtain analytical solutions to simply supported micro sandwich beam. Results are verified with corresponding literatures. In the following, a study is carried out to find the effects of the porosity coefficient, porous distribution, volume fraction of CNT, the thickness of silica aerogel foundation, temperature and moisture, geometric parameters, electric and magnetic potentials on the vibration of the micro sandwich beam. The results are helpful for the design and applications of micro magneto electro mechanical systems.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1220-1222
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• 2004

We developed a new device structure using anisotropic phase separation from liquid crystal (LC) and polymer composite materials using UV intensity variation and polymer wetting properties. In the device, the LC molecules are isolated in pixels where LCs are surrounded by the inter-pixel vertical polymer walls and the horizontal polymer films on the upper substrate. These devices show very good mechanical stability against external pressure. The electro-optic characteristics and the mechanical stability of the devices are discussed in view of the flexible display applications.

• Composites Research
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• v.20 no.3
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• pp.50-54
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• 2007

The Ionic Polymer Metal Composite (IPMC), an electro-active polymer, has many advantages including bending actuation, low weight, low power consumption, and flexibility. These advantages coincide with the requirements of a bio-related application. Thus, IPMC is promising materials for bio-mimetic actuator and sensor applications. Before applying IPMC to actual application, basic mechanical properties of IPMC should be studied in order to utilize IPMC for practical uses. Therefore, IPMCs are fabricated to investigate the mechanical characteristics. Nafion is used as a base ionic polymer. Mason samples cast with various thicknesses are used to test the thickness effects of IPMC. Subsequently, IPMC is fabricated using the chemical reduction method. The deformation, blocking force and frequency response of the IPMC actuator are important properties. In this present study, the performances of the IPMC actuators, including the deformation, blocking force and natural frequency, are then obtained according to only the input voltage and IPMC dimensions. Finally, the empirical performance model and the equivalent stiffness model of the IPMC actuator are established using experiments results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.1
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• pp.1-5
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• 2007

The structural and morphological properties of planar, nonpolar (11-20) a-plane GaN layers grown by hydride vapor phase epitaxy on (1-102) r-plan sapphire substrates are characterized. We report on the effect of low temperature ($500/550/600/660^{\circ}C$) AIN buffer layers on the structural properties of HVPE grown a-GaN kayers. and for the comparison, low temperature GaN and InGaN buffer layers are also tried for the growth of a-plane GaN layers. The structural geometry of a-GaN layers is severely affected on the growth condition of low temperature buffer layers. The most planar a-GaN could be obtained with $GaCl_3$ pretreatment at the growth temperature of $820^{\circ}C$.