• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.811-816
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• 2011

We develop a plastic object lens for blu-ray disc playing pick-up module as morethan 0.85 numerical aperture in this research. We design plastic object lens for blu-ray disc playing pick-up module's each factor's in balanced and made our designed lens by injection molding. Furthermore, by correction designing in mold-core, we optimization our lens efficiency as world grade; wave front aberration $0.028{\lambda}$. RMS, light axis differential 0.3967arcmin. We can manufacture localized blu-ray disc's pick-up lens's component and by this fact we obtain international competitiveness. The result of this research will be very helpful to develop a single objective lens for 3 different wavelength of laser diodes in playing and recording pick-up module.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1703-1711
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• 2000

Microstructural morphology of molded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) has been studied as a function of epoxy fraction. Injection-moulding of a thin composite plaque at a temperature below the melting point of the LCP fibrils by suing the extruded LCP/PA6 pellets produced multi-layered structures: 1) the surface skin layer with thickness of 65-120 ym exhibiting a transverse orientation, 2) the sub-skin layer with an orientation perpendicular to the surface skin, i.e. in the flow direction, 3) the core layer with arc-curved flow patterns. Similar microstructural orientations were observed in the respective layers for the composite plaques with different fractions of epoxy.

• Design & Manufacturing
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• v.2 no.1
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• pp.21-26
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• 2008

In this research, jar die of cosmetic products which is difficult to produce variously was developed and can be obtain the productivity improvement by flexibility with two system which can control the die temperature. Flow analysis of jar was performed to find out the curvature radius of parts. In order to reduce thickness of jar, cycle time, deformation, uniform curvature of internal jar was maintained by rapid cooling. In external of dies, cooling channel, injection molding condition, die temperature control system were researched to make dies low temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.594-600
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• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat a conductive workpiece by means of high-frequency electric current caused by electromagnetic induction. Because the induction heating is a convenient and efficient way of indirect heating, it has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers an experimental investigation on the rapid heating using the induction heating and rapid cooling using a vortex tube in order to eliminate an excessive cycle time increase. Experiments are performed in the case of a steel cup mold core with various heating and cooling conditions. Temperature is measured during heating and cooling time, from which appropriate mold heating and cooling conditions can be obtained.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.18-26
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• 2001

OSKA engine was developed to remove the dense core of injection sprays. The engine uses impinging spray on a small pip, which spray after impinging is broken into smaller drops and disperses into fee space in chamber. In this paper the pip size is analyzed to give more dispersion of spray and fuel vapor. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form, and the droplet wall interaction is modelled as a function of the velocity normal to impaction lands. The droplet distributions, vapor fractions and gas flows are analyzed for various injection pressure cases. Numerical results indicate that the land diameter of 5.6mm has the best performance of spray dynamics and vaporization in the test sizes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.74-77
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• 2009

Demands for high quality and productivity of precision mechanical parts are increasing greatly nowadays due to the rapid growth of information technologies and convergence industries. Therefore, core technologies for fabrication of precision mechanical parts are the fundamental issues, which are the precision machining, micro powder injection molding technologies, MR polishing, micro polymer processes, micro actuation modules and so on. These technologies are directly related to the mass production of high functional devices and machineries. Therefore, this study investigates the fabrication technologies of micro precision molds for advanced devices for possible commercialization in a near future.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.131-137
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• 2014

A 120 GHz voltage controlled oscillator (VCO) with a divider chain including an injection locked frequency divider (ILFD) and six static frequency dividers is demonstrated using 65-nm CMOS technology. The VCO is designed based on the LC cross-coupled push-push structure and operates around 120 GHz. The 60 GHz ILFD at the first stage of the frequency divider chain is based on a similar topology as the core of the VCO to ensure the frequency alignment between the two circuit blocks. The static divider chain is composed of D-flip flops, providing a 64 division ratio. The entire circuit consumes a DC power of 68.5 mW with the chip size of $1385{\times}835{\mu}m^2$.

• Design & Manufacturing
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• v.11 no.2
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• pp.9-14
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• 2017

The design and manufacturing tehcnology of IC sockets beyond 0.3mm pitch were presented. We compared the developed IC socket with the conventional one especially on the core metal-insulation part. Advanced machining techniques were employed to provide high precision. Our wire electrodischarge machining and high speed machining centers were able to maintain the micro-scale precision. We performed an injection molding analysis using a commercial analysis tool to predict the performance of the developed IC socket. We found that the solidification of the plastic resin and the high level of the clamping force are responsible for the defects such as incomplete filling and short shot. From these results, we modified the IC socket and successfully remove the defects. We were also able to find out that the new design socket needs less maintenance cost.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.374-374
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• 2010

Charge transfer mechanism of poly(4,4'-aminotriphenylene hexafluoroisopropylidenediphthalimide) (TP6F PI) which exhibits bistable ON and OFF switching has been studied using photoemission electron spectroscopy (PES) and near-edge x-ray absorption fine structure (NEXAFS). Here, we demonstrate novel set-up in which holes are injected by photoemission process instead of direct charge carrier injection via metal electrode. The accumulated charges on the PI surface in the OFF state abruptly flow across the PI film when the bias voltage of a back electrode reaches a specific value, indicating that the film is changed to the ON state. Core level and x-ray absorption spectra probed at charge injection region via photoemission process do not show any evidences implying structural modification of TP6F PI during the phase change. Whereas, in valence band spectra, the highest occupied molecular orbital (HOMO) is shifted toward Fermi level, responsible for improved hole-mobility of TP6F PI of ON state.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.10
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• pp.675-683
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• 2017

In this study, a theoretical analysis was performed to the flow of refilling stage in a safety injection tank, which is the core cooling system of nuclear power plant in an emergency. A theoretical model was proposed with a nonlinear governing equation defining on the flow of the refilling process of the coolant. Utilizing the Taylor-series expansion, the $1^{st}$ - order approximation flow equation was obtained, along with its analytic solution of closed type, which could predict accurately the variations of free surface height and flow rate of the coolant. The availability of theoretical result was confirmed by comparing with previous experimental results.