• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.323-324
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• 2012

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.691-694
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• 1999

This paper presents a performance improvement technique of 2-D towed array shape estimation using Kalman filters. The proposed algorithm by linear model approximation corrects the position errors caused by the Kalman filter results. However, since the assumed linear model makes errors at bending parts, the spline interpolation algorithm based on curve is proposed to reduce the errors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.383.1-383
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• 2002

This research is concerned with ground experiments for satellite solar array deployment. The dynamic characteristics of the strain energy hinge is very important since it affects the shape and the speed of the solar array deployment. the rapid deployment results in overshoot and undesirable residual vibrations. The experimental results are in good agreement with theoretical results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.29-34
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• 2005

A optical head unit for nano optical probe away was developed. The optical probe array is generated by Talbot effect. The shape and thickness of microlens array(MLA) were designed to minimize the spot size at the foci of MLA. To increase the optical efficiency of the system and obtain the large tolerance for fabrication, aperture size was theoretically optimized. Then microlens illuminated aperture array(MLIAA) as an optical head unit was fabricated using a ultra violet(UV) molding process on aluminum aperture array. In this process, Al aperture array was fabricated separately using the photolithography and reactive ion etching(RIE) process. Optical properties of the generated optical probes were measured and compared at Talbot distance from the aperture array having a diameter of $1{\mu}m$ and MLIAA.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.162-165
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• 2004

On this study, we improved diaphgram for micro speaker performance using Taguchi method in discrete design space. The design of diaphgram has an effect on performance of micro speaker such as, thickness of diaphgram, shape of diaphgram, etc. Therefore this study carried to decide shape of diaphgram and thickness of diaphgram for minimizing 2nd natural frequency of diaphgram using Taguchi method. we showed improved design factors that minimized 2nd natural frequency of diaphgram. Also, 2nd natural frequency of diaphgram for micro speaker is reduced up to 37 percent maintaining twist mode shape. From the results of ANOVA, 2nd natural frequency of diaphgram for micro speaker have an effect on position of the outer curved shape and thickness of diaphgram.

• Nuclear Engineering and Technology
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• v.38 no.1
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• pp.69-80
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• 2006

Fluid-elastic instability in an air-water two-phase cross-flow has been experimentally investigated using two different arrays of straight tube bundles: normal square (NS) array and rotated square (RS) array tube bundles with the same pitch-to-diameter ratio of 1.633. Experiments have been performed over wide ranges of mass flux and void fraction. The quantitative tube vibration displacement was measured using a pair of strain gages and the detailed orbit of the tube motion was analyzed from high-speed video recordings. The present study provides the flow pattern, detailed tube vibration response, damping ratio, hydrodynamic mass, and the fluid-elastic instability for each tube bundle. Tube vibration characteristics of the RS array tube bundle in the two-phase flow condition were quite different from those of the NS array tube bundle with respect to the vortex shedding induced vibration and the shape of the oval orbit of the tube motion at the fluid-elastic instability as well as the fluid-elastic instability constant.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.194-207
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• 2021

Vortex-Induced Vibration (VIV) is a major contributor to the fatigue damage of marine risers which are often arranged in an array configuration. In addition to helical strakes and fairings, studies have been strived in searching for possible VIV suppression techniques. Inspired by giant Saguaro Cacti, flexible cylinders of different cactus-shaped cross sections were tested in a water tunnel facility, and test results showed that cactus-like body shapes reduced VIV responses of a cylinder at no cost of significant increase of drag. A series of experiments were conducted on a pair of two tandem-arranged flexible cylinders and an array of four cylinders in a square configuration to investigate the effects of wake on the dynamic responses of cylinders and the VIV mitigation effectiveness of the cactus-like body shape. Results showed that the cylinders in a square configuration, either at the upstream or downstream positions, might have larger dynamic responses than those of a single cylinder. The cactus-like body shape could mitigate VIV responses of cylinders at upstream positions in an array configuration; however, similar to helical strakes, the mitigation efficiency was reduced on downstream cylinders. Note that the cactus-like cross-sectional shape investigated was not optimized for VIV suppression. The present study indicates that the modification of the cross-sectional shape of a cylinder to a well-designed cactus-like shape may be used as an alternative technique to mitigate the VIV of marine risers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.551-554
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• 2005

This study uses a characteristic function to explain correlations between the objective function and design variables. Analysis of means and table of orthogonal array were carried out. The change of shape of diaphragm, thickness of diaphragm and voice coil weight based on the table of orthogonal array is made. Therefore this study carried to decide shape of diaphragm, voice coil weight and thickness of diaphragm for minimizing 1st natural frequency and maximizing 2nd natural frequency of diaphragm using design of experiments and characteristic function with constraints. we showed improved design factors that minimized 1st natural frequency and maximized 2nd natural frequency of diaphragm.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1497_1498
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• 2009

This paper presents the simulation of micro-lens arrays based on dry and wet etching technique. Code V (Optical Research Associates Ltd) simulation was performed to extract optimal design parameters of a Micro-Lens Array(MLA). Thickness of UV adhesive, wavelength of laser source, curvature, and shape of lens surface were chosen for the design parameters. The simulation results showed that focal length of a MLA decreased with the increase of UV adhesive thickness. And the focal length depended on shape of lens surface and length of laser source.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.644-647
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• 2003

Resulting from reproducibility and possibility of mass production. many researches to fabricate micro lens array using lithography have been developed. However, it still remains the level of fabricating compensation lens. Therefore, to realize the fabrication of lens having high numerical aperture can be the key technology of ultra slim optical system. Reflow phenomenon have been researched to make lens having high refractive power. And through those researches, the possibility to fabrication of high refractive power lens has been investigated. In this paper, we analyze the effect of many parameters in reflow process to get an aspheric shape with high repeatability. And we make possible to estimate shape error, through we give direct information about decrease in volume of photoresist.