• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2006년도 춘계학술발표대회 논문집
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• pp.123-128
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• 2006

We constructed a micro-patterning system that build patterns on a photoresist coated wafer using laser direct writing system. Confocal microscope system was adapted for real-time auto-focusing of the laser writing lens to generate lines of uniform width.

• 설비공학논문집
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• 제11권1호
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• pp.10-17
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• 1999

The present work presents condensation heat transfer and pressure drop data for the flow of R-12 in flat extruded aluminum tubes with small hydraulic diameters. The tube outside dimensions are $18mm(width){\times}1.7mm(height)$. Three types of internal geometry with the same outside dimensions are tested : sample 1 (7 tube holes), sample 2 (13 tube holes) and sample 3 (7 tube holes, micro-fin). The overall heat transfer coefficient is obtained for air-to-refrigerant heat transfer, and the Wilson plot method is used to determine the heat transfer coefficient for refrigerant flow. The sample 2 and sample 3 show significantly higher performance than sample 1. The heat transfer rates for the sample 2 and sample 3 are 9% and 12% higher, respectively, than sample 1. The friction factors for the sample 2 and sample 3 are 11.9% and 2.4% higher, respectively, than sample 1.

• 한국생산제조학회지
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• 제20권3호
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• pp.322-328
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• 2011

This paper presents inverse kinematics and workspace analysis of a planar three degree-of-freedom (DOF) parallel manipulator. Furthermore, optimization problem of the manipulator is presented. The manipulator adopts PRR (Prismatic-Revolute-Revolute) mechanism and the prismatic actuators are fixed to the base. This leads to a reduction of the inertia of the moving links and hence enables it to move with high speed. The actuators are linear electric motors. First, the mechanism based on the geometry of the manipulator is introduced. Second, a workspace analysis is performed. Finally, design optimization is carried out to have large workspace. The proposed approach can be applied to the design optimization of various three DOF parallel manipulators in order to maximize their workspace. The performance of mechanism is improved and satisfies the requirements of workspace to align micro-components.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.879-884
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• 2007

Flywheel energy storage systems have advantages over other types of energy storage devices in such aspects as unlimited charge/discharge cycles and environmental friendliness. In this paper we propose a millimeter scale flywheel energy storage device. The flywheel is supported by a pair of passive magnetic bearings and rotated by a toroidally wound electric motor/generator. The geometry of the bearings is optimized for the maximum dynamic performance.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.211-214
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• 2003

This paper presents the microscopic observation results from the picture frame test using five-harness satin weave fabric composite. Aligned and misaligned specimens are observed to verify the exact tow deformation pattern such as tow interval and change in tow amplitude. To observe the micro-deformation of the fabric structure, appropriate specimens from picture frame test are sectioned and observed under the microscope. From the observation results, it is found that a picture frame test with a misaligned fibre orientation angle shows large differences in deformation between tensile and compressive tow directions.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.205-211
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• 2000

Friction control is highly desirable for optimization of tribological systems. In this work, the effect of geometric structure of the solid surface on friction is investigated using a Scanning Electron Microscope equipped with a tribotester. Silicon and silicon oxide specimens were used and undulations on the surface were fabricated by mechanical and chemical methods. It is shown that the friction coefficient depends on the relative dimensions of the ball and the width of undualation. By optimizing the geometry of the undulation, friction reduction may be achieved.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2763-2768
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• 2007

Recently, as the semiconductor production technology develops, there has been growing interest in the cooling system using micro fluid pump. Among the various types of micro fluid pump, the valve-less diffuser/nozzle has been extensively studied in recent years. However, the flat-walled diffuser/nozzle flow has not been clearly looked into due to its non-linear characteristics. In this paper, the flow characteristics of the flat-walled diffuser/nozzle have been analyzed using similitude model and simulations. Similitude models are designed so that the flow pattern is same as that of 1/10 scale flow by using high viscous fluid as working fluid. The results are compared to the simulations. It is shown that the flow characteristics of 2D simulation are different from 3D simulations at high Re region, and the measured pump efficiency is highly dependent on the pressure difference as well as the channel geometry. From these results, the desirable conditions for the efficient pump is discussed.

• ETRI Journal
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• 제40권2호
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• pp.275-282
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• 2018

Flash reduction of graphene oxide is an efficient method for producing high quality reduced graphene oxide under room temperature ambient conditions without the use of hazardous reducing agents (such as hydrazine and hydrogen iodide). The entire process is fast, low-cost, and suitable for large-scale fabrication, which makes it an attractive process for industrial manufacturing. Herein, we present a simple fabrication method for a flexible in-plane graphene micro-supercapacitor using flash light irradiation. All carbon-based, monolithic supercapacitors with in-plane geometry can be fabricated with simple flash irradiation, which occurs in only a few milliseconds. The thinness of the fabricated device makes it highly flexible and thus useful for a variety of applications, including portable and wearable electronics. The rapid flash reduction process creates a porous graphene structure with high surface area and good electrical conductivity, which ultimately results in high specific capacitance ($36.90mF\;cm^{-2}$) and good cyclic stability up to 8,000 cycles.

• 한국정밀공학회지
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• 제25권9호
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• pp.95-102
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• 2008

A miniature metal bellows is used to minimize the excessive flow of the cryogenic gas in Joule-Thomson micro cryocooler. It is made of metal alloy and its geometry is axisymmetric. The bellows is filled with high pressure gas. It contracts or expands in the axial direction for a wide change of temperature, because the pressure and volume inside the bellows must be satisfied with state equation of the gas. Therefore, in order to design the bellows in Joule-Thomson micro-cryocooler, it is important to evaluate deformation of the bellows under internal pressure exactly. Considering geometric nonlinearity, deformations analysis of the bellows were obtained by a commercial finite element code ANSYS, The bellows was modeled by 3-node axisymmetric shell elements with reduced integration. Experiments were also performed to prove the validity of proposed numerical analysis. The results by numerical analysis and experiments were shown in good agreements.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1754-1761
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• 2003

The atomic force microscopy (AFM) based lithographic technique has been used directly to machine material surface and fabricate nano components in MEMS (micro electro mechanical system). In this paper, three-dimensional molecular dynamics (MD) simulations have been conducted to evaluate the characteristic of deformation process at atomistic scale for nano-lithography process. Effects of specific combinations of crystal orientations and cutting directions on the nature of atomistic deformation were investigated. The interatomic force between diamond tool and workpiece of copper material was assumed to be derived from the Morse potential function. The variation of tool geometry and cutting depth was also evaluated and the effect on machinability was investigated. The result of the simulation shows that crystal plane and cutting direction significantly influenced the variation of the cutting forces and the nature of deformation ahead of the tool as well as the surface deformation of the machined surface.