The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Hyung Jin Sung - One of the best experts on this subject based on the ideXlab platform.
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Cross-type optical separation of elastic oblate capsules in a uniform flow
Journal of Applied Physics, 2015Co-Authors: Cheong Bong Chang, Wei-xi Huang, Hyung Jin SungAbstract:The dynamic behavior of an elastic capsule with an initially oblate spheroidal shape during cross-type optical separation was numerically investigated. The penalty immersed boundary method was adopted for the fluid-membrane interaction, and the optical force calculation was conducted by using the ray optics method including the ray-surface intersection algorithm. The oblate elastic capsule of b/a = 0.5 with different surface Young's moduli and different initial inclination angles was considered. The oblate capsule with higher surface Young's moduli was less deformed, and was more migrated for each initial inclination angle. Unlike the oblate rigid particle, the initially inclined capsules with moderate inclination angles were similarly migrated since the oblate elastic capsule was deformed during rotation near the Laser Beam Axis. The oblate capsules can be separated according to the surface Young's modulus, except for nearly non-inclined capsules. As the fluid velocity decreased, the migration distance i...
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Optical separation of ellipsoidal particles in a uniform flow
Physics of Fluids, 2014Co-Authors: Cheong Bong Chang, Wei-xi Huang, Kyungheon Lee, Hyung Jin SungAbstract:The behavior of an ellipsoidal particle subjected to a vertical optical force by a loosely focused Laser Beam in a uniform flow was studied numerically. The fluid flow and the particle motion were separately solved and coupled using the penalty immersed boundary method, and the optical force was calculated using the dynamic ray tracing method. The optical force and optically induced torque on the ellipsoidal particle varied according to the aspect ratio and initial inclination angle. The ellipsoidal particle, whose major Axis was initially aligned with the Laser Beam Axis, was more migrated as the aspect ratio increased. The migration distance also depended on the initial inclination angle, even for a given ellipsoidal particle shape. As the Laser Beam power increased and the flow velocity decreased, the effect of the initial inclination angle increased. The ellipsoidal particles with different aspect ratios could be effectively separated if the rotation along the spanwise direction was suppressed. Moreov...
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Optical levitation of a non-spherical particle in a loosely focused Gaussian Beam
Optics express, 2012Co-Authors: Cheong Bong Chang, Wei-xi Huang, Kyungheon Lee, Hyung Jin SungAbstract:The optical force on a non-spherical particle subjected to a loosely focused Laser Beam was calculated using the dynamic ray tracing method. Ellipsoidal particles with different aspect ratios, inclination angles, and positions were modeled, and the effects of these parameters on the optical force were examined. The vertical component of the optical force parallel to the Laser Beam Axis decreased as the aspect ratio decreased, whereas the ellipsoid with a small aspect ratio and a large inclination angle experienced a large vertical optical force. The ellipsoids were pulled toward or repelled away from the Laser Beam Axis, depending on the inclination angle, and they experienced a torque near the focal point. The behavior of the ellipsoids in a viscous fluid was examined by analyzing a dynamic simulation based on the penalty immersed boundary method. As the ellipsoids levitated along the direction of the Laser Beam propagation, they moved horizontally with rotation. Except for the ellipsoid with a small aspect ratio and a zero inclination angle near the focal point, the ellipsoids rotated until the major Axis aligned with the Laser Beam Axis.
Cheong Bong Chang - One of the best experts on this subject based on the ideXlab platform.
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Cross-type optical separation of elastic oblate capsules in a uniform flow
Journal of Applied Physics, 2015Co-Authors: Cheong Bong Chang, Wei-xi Huang, Hyung Jin SungAbstract:The dynamic behavior of an elastic capsule with an initially oblate spheroidal shape during cross-type optical separation was numerically investigated. The penalty immersed boundary method was adopted for the fluid-membrane interaction, and the optical force calculation was conducted by using the ray optics method including the ray-surface intersection algorithm. The oblate elastic capsule of b/a = 0.5 with different surface Young's moduli and different initial inclination angles was considered. The oblate capsule with higher surface Young's moduli was less deformed, and was more migrated for each initial inclination angle. Unlike the oblate rigid particle, the initially inclined capsules with moderate inclination angles were similarly migrated since the oblate elastic capsule was deformed during rotation near the Laser Beam Axis. The oblate capsules can be separated according to the surface Young's modulus, except for nearly non-inclined capsules. As the fluid velocity decreased, the migration distance i...
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Optical separation of ellipsoidal particles in a uniform flow
Physics of Fluids, 2014Co-Authors: Cheong Bong Chang, Wei-xi Huang, Kyungheon Lee, Hyung Jin SungAbstract:The behavior of an ellipsoidal particle subjected to a vertical optical force by a loosely focused Laser Beam in a uniform flow was studied numerically. The fluid flow and the particle motion were separately solved and coupled using the penalty immersed boundary method, and the optical force was calculated using the dynamic ray tracing method. The optical force and optically induced torque on the ellipsoidal particle varied according to the aspect ratio and initial inclination angle. The ellipsoidal particle, whose major Axis was initially aligned with the Laser Beam Axis, was more migrated as the aspect ratio increased. The migration distance also depended on the initial inclination angle, even for a given ellipsoidal particle shape. As the Laser Beam power increased and the flow velocity decreased, the effect of the initial inclination angle increased. The ellipsoidal particles with different aspect ratios could be effectively separated if the rotation along the spanwise direction was suppressed. Moreov...
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Optical levitation of a non-spherical particle in a loosely focused Gaussian Beam
Optics express, 2012Co-Authors: Cheong Bong Chang, Wei-xi Huang, Kyungheon Lee, Hyung Jin SungAbstract:The optical force on a non-spherical particle subjected to a loosely focused Laser Beam was calculated using the dynamic ray tracing method. Ellipsoidal particles with different aspect ratios, inclination angles, and positions were modeled, and the effects of these parameters on the optical force were examined. The vertical component of the optical force parallel to the Laser Beam Axis decreased as the aspect ratio decreased, whereas the ellipsoid with a small aspect ratio and a large inclination angle experienced a large vertical optical force. The ellipsoids were pulled toward or repelled away from the Laser Beam Axis, depending on the inclination angle, and they experienced a torque near the focal point. The behavior of the ellipsoids in a viscous fluid was examined by analyzing a dynamic simulation based on the penalty immersed boundary method. As the ellipsoids levitated along the direction of the Laser Beam propagation, they moved horizontally with rotation. Except for the ellipsoid with a small aspect ratio and a zero inclination angle near the focal point, the ellipsoids rotated until the major Axis aligned with the Laser Beam Axis.
Togo Shinonaga - One of the best experts on this subject based on the ideXlab platform.
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High surface quality micro machining of monocrystalline diamond by picosecond pulsed Laser
Cirp Annals-manufacturing Technology, 2019Co-Authors: Yasuhiro Okamoto, Akira Okada, A. Kajitani, Togo ShinonagaAbstract:Abstract In micro machining of monocrystalline diamond by pulsed Laser, unique processing characteristics appeared only under a few ten picosecond pulse duration and a certain overlap rate of Laser shot. Cracks mostly propagate in parallel direction to top surface of workpiece, although the Laser Beam Axis is perpendicular to the surface. This processed area can keep diamond structure, and its surface roughness is smaller than Ra = 0.2 μm. New Laser micro machining method to keep diamond structure and small surface roughness is proposed. This method can contribute to reduce the polishing process in micro machining of diamond.
Bekir Sami Yilbas - One of the best experts on this subject based on the ideXlab platform.
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Laser repetitive pulse heating of tool surface
Optics and Laser Technology, 2011Co-Authors: Bekir Sami Yilbas, Shahzada Zaman Shuja, Shafique M A KhanAbstract:Abstract Laser heating of a cemented carbide tool is considered and the temperature field as well as phase changes in the heated region is modeled. Temperature rise, liquid layer thickness, and mushy size are predicted numerically. A control volume approach is introduced to solve the governing equations of heat transfer and phase change. Consecutive pulses with the duty cycle of 60% are accommodated in the simulations in line with the experimental conditions. An experiment is carried out to treat the cemented carbide tool surfaces using the CO2 Laser delivering consecutive pulses. The treated surfaces and their cross-sections are examined using the scanning electron microscope (SEM). It is found that the temperature gradient is high along the Laser Beam Axis resulting in cracks at the irradiated surface. The rapid solidification of the surface causes compact structures with very fine grains in the surface region of the Laser irradiated spot.
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Wedge cutting of mild steel by CO2 Laser and cut-quality assessment in relation to normal cutting
Optics and Lasers in Engineering, 2008Co-Authors: Bekir Sami Yilbas, Cihan Karatas, Ibrahim Uslan, Omer Keles, Yusuf Usta, Z. Yilbas, M. AhsanAbstract:Abstract In some applications, Laser cutting of wedge surfaces cannot be avoided in sheet metal processing and the quality of the end product defines the applicability of the Laser-cutting process in such situations. In the present study, CO 2 Laser cutting of the wedge surfaces as well as normal surfaces (normal to Laser Beam Axis) is considered and the end product quality is assessed using the international standards for thermal cutting. The cut surfaces are examined by the optical microscopy and geometric features of the cut edges such as out of flatness and dross height are measured from the micrographs. A neural network is introduced to classify the striation patterns of the cut surfaces. It is found that the dross height and out of flatness are influenced significantly by the Laser output power, particularly for wedge-cutting situation. Moreover, the cut quality improves at certain value of the Laser power intensity.
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Laser heating : an electron-kinetic theory approach and induced thermal stresses
Optics and Lasers in Engineering, 2000Co-Authors: Bekir Sami Yilbas, S.a. Gbadebo, M. SamiAbstract:Laser heating offers considerable advantages for Laser treatment of mechanical parts. The Laser heating initiates the thermal stresses and expansion of the substrate. In the present study, Laser heating of steel substrate is considered. Three-dimensional electron-kinetic theory approach is introduced when simulating the heating process. A moving Laser source is taken into account provided that the Laser scans the surface at a constant speed. Thermal stresses due to Laser heating are computed and thermal expansion along the Laser Beam Axis is predicted. It is found that the thermal stress increases considerably as the heating progresses. Moreover, the expansion of the free surface reaches a value of the order of a nanometer.
Wei-xi Huang - One of the best experts on this subject based on the ideXlab platform.
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Cross-type optical separation of elastic oblate capsules in a uniform flow
Journal of Applied Physics, 2015Co-Authors: Cheong Bong Chang, Wei-xi Huang, Hyung Jin SungAbstract:The dynamic behavior of an elastic capsule with an initially oblate spheroidal shape during cross-type optical separation was numerically investigated. The penalty immersed boundary method was adopted for the fluid-membrane interaction, and the optical force calculation was conducted by using the ray optics method including the ray-surface intersection algorithm. The oblate elastic capsule of b/a = 0.5 with different surface Young's moduli and different initial inclination angles was considered. The oblate capsule with higher surface Young's moduli was less deformed, and was more migrated for each initial inclination angle. Unlike the oblate rigid particle, the initially inclined capsules with moderate inclination angles were similarly migrated since the oblate elastic capsule was deformed during rotation near the Laser Beam Axis. The oblate capsules can be separated according to the surface Young's modulus, except for nearly non-inclined capsules. As the fluid velocity decreased, the migration distance i...
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Optical separation of ellipsoidal particles in a uniform flow
Physics of Fluids, 2014Co-Authors: Cheong Bong Chang, Wei-xi Huang, Kyungheon Lee, Hyung Jin SungAbstract:The behavior of an ellipsoidal particle subjected to a vertical optical force by a loosely focused Laser Beam in a uniform flow was studied numerically. The fluid flow and the particle motion were separately solved and coupled using the penalty immersed boundary method, and the optical force was calculated using the dynamic ray tracing method. The optical force and optically induced torque on the ellipsoidal particle varied according to the aspect ratio and initial inclination angle. The ellipsoidal particle, whose major Axis was initially aligned with the Laser Beam Axis, was more migrated as the aspect ratio increased. The migration distance also depended on the initial inclination angle, even for a given ellipsoidal particle shape. As the Laser Beam power increased and the flow velocity decreased, the effect of the initial inclination angle increased. The ellipsoidal particles with different aspect ratios could be effectively separated if the rotation along the spanwise direction was suppressed. Moreov...
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Optical levitation of a non-spherical particle in a loosely focused Gaussian Beam
Optics express, 2012Co-Authors: Cheong Bong Chang, Wei-xi Huang, Kyungheon Lee, Hyung Jin SungAbstract:The optical force on a non-spherical particle subjected to a loosely focused Laser Beam was calculated using the dynamic ray tracing method. Ellipsoidal particles with different aspect ratios, inclination angles, and positions were modeled, and the effects of these parameters on the optical force were examined. The vertical component of the optical force parallel to the Laser Beam Axis decreased as the aspect ratio decreased, whereas the ellipsoid with a small aspect ratio and a large inclination angle experienced a large vertical optical force. The ellipsoids were pulled toward or repelled away from the Laser Beam Axis, depending on the inclination angle, and they experienced a torque near the focal point. The behavior of the ellipsoids in a viscous fluid was examined by analyzing a dynamic simulation based on the penalty immersed boundary method. As the ellipsoids levitated along the direction of the Laser Beam propagation, they moved horizontally with rotation. Except for the ellipsoid with a small aspect ratio and a zero inclination angle near the focal point, the ellipsoids rotated until the major Axis aligned with the Laser Beam Axis.
