• Journal of the Korean Society for Precision Engineering
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• v.15 no.12
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• pp.81-88
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• 1998

Measurement and inspection of freeform surfaces are required in reverse design processes. In the case of surface measurement using a touch probe, probe radius compensation affects measuring accuracy. But current industrial practice depends upon an operator's experience to compensate for probe radius. In this paper, an on-the-machine measuring and inspection system for freeform surfaces is studied. Probe radius compensation methodology is investigated by modeling of B-spline surfaces based on digitized data. The accuracy and reliability of the developed system is verified through various kinds of numerical simulations and on-the-machine experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.911-914
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• 1995

Measurement and inspection of freeform surface are required in reverse design process. In the case of surface measurement using a touch probe, probe radius compensation affects measuring accuracy But current industrial practice depends upon an operator's experience to compensate for probe radius. In this paper, an on-the-machine measuring and inspection system for freeform surfface was developed. Probe radius compensation methodology was studied via modeling of B-spline surfaces based on digitized data. The accuracy and reliability of the measurement system was confirmed through various kinds of experiments.

• The Journal of the Korea Contents Association
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• v.14 no.10
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• pp.1-9
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• 2014

Generally, integral image used for autostereoscopic 3d display is generated for flat lens array, but flat lens array cannot provide a wide range of view for generated integral image because of narrow range of view. To make up for this flat lens array's weak point, curved lens array has been proposed, and due to technical and cost problem, approximate surface lens array composed of several flat lens array is used instead of ideal curved lens array. In this paper, we constructed an approximate surface lens array arranged for $20{\times}8$ square flat lens in 100mm radius sphere, and we could get about twice angle of view compared to flat lens array. Specially, unlike existing researches which manually generate integral image, we propose an OpenCL GPU parallel process algorithm for generating real-time integral image. As a result, we could get 12-20 frame/sec speed about various 3D volume data from $15{\times}15$ approximate surface lens array.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.5
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• pp.77-83
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• 2016

A considerable amount of researches has been performed to investigate the flow characteristics produced in the cavity system over straight wall. However, many practical applications of the cavity flows are found on curved walls, which are strongly subject to the centrifugal force effects. No work has been made on the cavity flows on the curved wall to date. In the present study, a computational fluid dynamics method has been applied to investigate the cavity flows over curved walls at Mach numbers in range of 0.4 to 0.8. The aspect ratio of the cavity was fixed at L/H=3, but the radius of curvature of the curved wall is changed in considering the real engineering practice. The results reveal that the pressure oscillations in the curved walls are stronger than those in the straight wall. It is found that the ratio of curvature of the curved wall significantly affects the unsteady flow characteristics inside the cavity.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.1-7
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• 2016

Most of the work has been done till now focused on flows over wall mounted cavities in a straight wall where the incoming flow is uniform. However, the investigation on such kind of flow over a cavity mounted on the curved walls has been seldom reported in the existing literatures. In the present study, the numerical analysis was performed to investigate the cavity flow mounted on the curved walls. The effects of wall shape, the curvature radius and the flow Mach number, were investigated for high-subsonic flows. The results show that the static pressure of cavity floor increases as the L/R increases. This effect is found to be more significant when the flow Mach number is higher. The cavity drag for the curved walls are higher as compared with that of straight wall.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.117-123
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• 2013

As fiber reinforced polymer (FRP) material is appled for a curved structure such as tunnel, FRP material must has a curved shape. Until now, the curved FRP material has been producted by hand-lay-up or filament winding work. It is impossible for mass production of the curved FRP material by these methods. Also, the quality of product by these methods is lower than that by pultrusion method. New pultrusion method and equipment had been developed for production of FRP material with steady curvature. The objective of this study is to evaluate the effect of freezing and thawing on adhesion of cement concrete with coarse-sand coated FRP in repair and reinforcement of cement-concrete structure using curved FRP material.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.455-461
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• 2010

Automated magnetic abrasive polishing which can be applied after machining of the mold on a machine tool without unloading is very effective for finishing a complicated injection mold surface. This study aims to realize one step polishing of free form surface with the same machine tool. For this purpose, magnetic flux density according to the change of curvature radii was simulated for selecting polishing conditions and experimental verification was performed with a complicated mold of aluminum alloy. As a result, it was seen by the simulation that the magnetic flux density at a gradual curvature of the mold was higher than at a steep curvature and the higher magnetic flux density produced the better surface roughness in the experimentation. The deviation for the surface roughness of the mold decreased on the whole and the uniform mold surface was obtained after the automated magnetic abrasive polishing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.259-264
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• 2012

Automatic magnetic abrasive polishing (MAP), which can be applied after machining of a mold on a machine tool without unloading, is very effective for finishing a free-form surface such as a complicated injection mold. This study aimed to improve the efficiency of MAP of a non-ferrous mold surface. The magnetic array table and control of the electromagnet polarity were applied in the MAP of a free-form surface. In this study, first, the magnetic flux density on the mold surface was simulated to determine the optimal conditions for the polarity array. Then, the MAP efficiency for polishing a non-ferrous mold surface was estimated in terms of the change in the radius of curvature and the magnetic flux density. The most improved surface roughness was observed not only in the upward tool path but also in the working area of larger magnetic flux density.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.165-170
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• 2016

Nano-scale power splitter based on curved plasmonic waveguides are designed by utilizing the multimode interference (MMI) coupler. To analyze easily the adaptive properties of plasmonic curverd multimode interference coupler(PC-MMIC), the curved form transforms equivalently into a planar form by using conformal transformation method. Also, effective dielectric method and longitudinal modal transmission-line theory are used for simulating the light propagation and optimizing the structural parameters at 3-D guiding geometry. The designed $2{\times}2$ PC-MMIC does not work well for quasi-TM mode case due to the bending structure, and it does not exist 3dB coupling property, in which the power splitting ratio is 50%:50%, for quasi-TE mode case. Further, the coupling efficiency is better when the signal is incident at channel with large curvature radius than small curvature radius.

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.168-177
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• 2024

When designing an underwater Piezoelectric Energy Harvester (PEH), Vortex Induced Vibration (VIV) is generated throughout the cantilever through a change in curvature, and the generation of VIV increases the vibration displacement of the curved cantilever PEH, which is an important factor in increasing actual power. The material of the curved PEH selected a Polyvinyline Di-Floride (PVDF) piezoelectric film, and the flow velocity is set at 0.1 m/s to 0.50 m/s for 50 mm, 130 mm, and 210 mm with various curvatures. The strain energy change of PEH by VIV was observed. The smaller the radius of curvature, the larger the VIV, and as the flow rate increased, more VIV appeared. Rapid shape transformation due to the small curvature was effective in generating VIV, and strain energy, normalized voltage, average power, etc. To increase the amount of power of the PEH, it is considered that the average power will increase as the number of curved PEHs increases as well as the steep curvature is improved.