• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.14-22
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• 1995

This paper is concerned with the design of optimal surface heating patterns that result in focusing acoustic energy inside a subsurface target volume at a specified target time. The surface of the solid is heated by an incident laser beam which gives rise to shear and compressional waves propagating into the solid. The optimal heating design process aims to achieve the desired energy focusing at the target with minimal laser power densities and minimal system disturbance away from the target. The optimality conditions are secured via the conjugated gradient method and by the finite element method along with using the half-space Green's function matrix. Good quality energy focusing is achived with the optimal designs reflecting the high directivity of the photothermally generated shear wave patterns.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2692-2695
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• 2008

Polydiacetylene (PDA) is chemosensor materials that exhibit non-fluorescent-to-fluorescent transition as well as blue-to-red visible color change upon chemical or thermal stress. They have been studied in forms of film or microarray chip, so far. In this paper, we provide a novel technique to fabricate continuous micro-fiber PDA sensor using in-situ laser-polymerization technique and 3-D hydrodynamic focusing on a microfluidic chip. The flow of a monomer solution with diacetylene (DA) monomer is focused by a sheath flow on a 3-D microfluidic chip. The focused flow is exposed to 365 nm UV laser beam for in-situ polymerization which generates a continuous fiber containing DA monomers. Then, the fiber is exposed to 254 nm UV light to polymerize DA monomers to PDA. Preliminary results indicate that the fiber size can be controlled by the flow rates of the monomer solution and sheath flows and that a PDA sensor fiber successively responds to chemical and thermal stress.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.753-754
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• 2008

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.130-131
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• 2000

One of the more promising proposals for guiding and focusing neutral atoms involves dark hollow laser beams. When the frequency of the laser is detuned to the blue of resonance, the dipole force the atoms feel in the light confines them to the dark core where the atoms can be transported with minimal interaction with the light. The ability of the all-light atom guides to transport large number of ultracold atoms for long distances without physical walls leads to the possibility of a versatile tool for atom lithography, atom interferometry, atomic spectroscopy as well as for transporting and manipulating Bose-Einstein condensates. Furthermore since the atoms transported in all-light atom guides do not come into contact with matter, they can in principle be used to transport antimatter as well. The ability to vary the core size of the hollow beam makes the all-light atom guide potentially useful for focusing neutral atoms. The atoms could be focused as tight as the core size of the hollow beam at its waist. This new focusing scheme, called the atom funnel, would not show spherical and chromatic aberrations that conventional harmonic focusing suffers from. (omitted)

• Bulletin of the Korean Chemical Society
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• v.24 no.5
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• pp.600-604
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• 2003

The light pressure force from an optical standing wave (SW) can focus an atomic beam to submicrometer dimensions. To make the best of this technique it is necessary to find a set of optimal experimental parameters. In this paper we consider theoretically the chromium atoms focusing and demonstrate that the focusing performance depends not only on the strength of but also on the time atoms take to traverse the force field. The general conclusions drawn can easily be applied to other atoms. To analyze the problem we numerically integrate a coupled time-dependent $Schr{\"{o}}dinger$ equation over a wide range of experimental parameters. It is found that an optimal atomic beam speed-laser intensity pair does exist, which could give substantially improved focusing over the one with the experimental parameters given in the literature. It is also shown that the widely used classical particle optics approach can lead to erroneous predictions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.319-320
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.427-428
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• 2006

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.331-332
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• 2006

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2009.10a
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• pp.93-94
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• 2009

• Journal of the Korean Society for Precision Engineering
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• v.32 no.9
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• pp.773-779
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• 2015

The laser Powder Bed Fusion (PBF) system is currently recognized as a leading process. Due to the various materials employed such as thermoplastic, metal and ceramic composite powder, the application's use extends to machinery, automobiles, and medical devices. The PBF system's surface quality of prototypes and processing time are significantly affected by several parameters such as laser power, laser beam size, heat temperature and laminate thickness. In order to develop a more elaborate and rapid system, this study developed a new PBF system and sintering process. It contains a 3-axis dynamic focusing scanner system that maintains a uniform laser beam size throughout the system unlike the $f{\theta}$ lens. In this study, experiments were performed to evaluate the effects of various laser scanning parameters and fabricating parameters on the fusion process, in addition to fabricating various 3D objects using a PA-12 starting material.