• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.47.2-47.2
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• 2016

We introduce a magnetic field survey of the Gould Belt clouds using the James Clerk Maxwell Telescope (JCMT) POL-2: B-fields In STar-forming Region Observations (BISTRO). POL-2 with SCUBA-2 on JCMT is a unique facility, as it is the only facility world-wide that can map the magnetic field within cold dense cores and filaments on scales of ~1000 AU in nearby star-forming regions, such as Taurus and Ophiuchus. It can provide a link between the B-field measured on arc-minute scales by Planck and BLASTPOL and measurements made on arc-second scales by interferometers such as CARMA, SMA, and ALMA. BISTRO was awarded 224 hours toward 16 fields for the next 3 years and started to take data in the 2016A semester.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.79.1-79.1
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• 2017

The B-fields In STar-forming Region Observations (BISTRO) is the 3-year large program of the James Clerk Maxwell Telescope (JCMT) using SCUBA-2 and POL-2, started in 2016. We aim to study the roles of magnetic fields in star formation by observing 16 fields of nearby star forming regions, e.g., Orion and Ophiuchus molecular clouds. The angular resolution and wavelength provided by JCMT (14 arcsecond at 850 micrometer) is ideal to investigate the intermediate scales of magnetic fields (1000-10000 au) associated in cold dense cores and filaments. This year, moreover, we were awarded JCMT time for additional 16 fields (BISTRO-2), which allows us to cover broader physical properties of star forming regions. We report the current status of BISTRO and introduce BISTRO-2.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.102-109
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• 1996

Effects of frictional laws on finite element solutions in metal forming were investigated in this paper. A rigid-viscoplastic finite element formulation was given with emphasis on the frictional laws. The Coulomb friction and the constant shear friction laws were compared through finite element analyses of compression of rings and cylinders with different aspect ratios, ring-gear forging, multi-stage cold extrusion and hot strip rolling under the isothermal condition. It has been shown that two laws may yield quite different results when the aspect ratio of a process and the fractional contact region are large.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.1
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• pp.29-37
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• 1995

In many metal forming processes, it is common to use stress rings for reducing elastic deformation and failures of forming dies. But, shrink fit of dies inner diameter of die insert, machining is reuqired after shrink fit processes. The reduction of inner diameter can be predicted by the analysis of elastic-plastic finite element method. The dimension of dies before shrink fit can be determined to minimize or remove machining after shrink fit processes by deformation analysis of die. The computation of contacting stresses along die surface was analyzied by rigid plasitic finite element method, and data were interpolated by the contact search algorithm. In this paper, we propose the analysis method of forging dies after shrink fit and forming to improve dimensional accuracy of final products.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.05a
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• pp.197-205
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• 1996

A combined extrusion process studied here consists of forward and backward extrusion, and it is formed in single operation. The metal flow involved in the operation has appeared to be difficult to analyze accurately because of mixed directions of the flow. In this study, conventional two operations of a forward and a backward extrusions is transformed into one operation of mixed extrusion. A process designed by an industry expert is simulated by the rigid-plastic finite element method to investigate the metal flow and defects. In addition to the FEM simulation, experimental analysis has been carried out to confirm the design in industry, which includes material characterization, preliminary expriment, and whole experimental forming operation. The experimental results show that warm forming of extrusion is more desirable than cold working and hot forming in view of grain growth. Also two conditions of lubrication between workpiece and die has been investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.79-84
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• 2004

A light-guide is one of several important components of backlight unit in TFT-LCD. The manufacturing technology and optical system design of the light guide is very sensitive to quality and cost of the TFT-LCD module. In the present study a new manufacturing method which is called as direct surface forming(DSF) has been tested under various conditions. DSF is very similar to the well-known hot embossing except for partial contact between mold and substrate. The final V-groove pattern shows different shapes depend on the temperature of mold surface, contact time of mold and depth of V-groove.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.955-956
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• 2013

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.274-274
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.221-222
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• 2011

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.434-437
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• 2007

Cold forging technology of a gear product is being interested in the dimensional accuracy, high stiffness and reduction of stress concentration. Especially it is needed to avoid the damage due to extremely high local pressure. Therefore it is important to ensure high pressure in die design. In this study, single die insert type and splitted die insert type are considered to recognize the notch effects in the die of sprocket forming. The stress concentration has been released at the notch area by the cushion effect in the splitted die insert.