• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.36-44
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• 2000

The flow at the impeller exit is important to validate engineering design and numerical analysis of pumps. We installed axisymmetric collector instead of the volute casing, so there is no interaction between the impeller and casing. A hot-film probe and a high response pressure transducer are used to investigate the flow at impeller exit and vaneless diffuser region for design and off design flow rate. For a single suction centrifugal pump of low specific speed, the flow field such as velocity, flow angle, and total pressure are measured by traversing the probe across the vaneless diffuser. These data can be used for performance prediction, design, and numerical analysis of pumps.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.555-556
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• 2006

An experimental performance test has been carried out to improve a new blade with higher performance. Most of blades of the fan are designed to be a seamless and simple type, and the flow momentum can generally be evaluated to be comparatively low. Because some portions of the blowing winds can easily be passed through the seamless sharp edge of the blade, and several results studied on these problems have been reported: on the simple blade with edge-line seam, on the simple blade with guide seam. However the results do not show the remarkable increasement of performance of the blades. In this experimental performance test of the blades the design techniques of the blades with double seams (stem seam and edge seam) and comparison tests have been focused. As a first step the comparisons of velocity distributions and flow-rates depending upon the blade are presented in this paper.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.109-120
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• 2008

An innovative method of changing a centrifugal low specific speed pump performance and pressure fluctuation by applying outlet flaps to impeller exit has been investigated. The outlet blade edge section corresponds to the trailing edge of wing on the circular-cascade, which dominates the pump performance and pressure fluctuation. Computational fluid dynamics (CFD) analysis of the entire impeller and volute casing and an experimental investigation are conducted. The pressure fluctuation and the vibration of the shaft are measured simultaneously. Kurtosis is applied as a dimensionless parameter with which the unevenness of velocity distribution at impeller outlet is indicated. The influence of the flaps on the pressure fluctuation is explained by the kurtosis. This paper presents a theoretical method of predicting the pump performance related to the attachment of a flap at impeller outlet.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.4
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• pp.350-354
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• 2002

In this paper, we designed an autopilot of the unmanned piloted vehicle to guide to the specific position, and analyzed robustness of the designed autopilot. We divide an aircraft velocity into the three case which are low, cruising and high speed, and designed autopilot gains are gain scheduled. We generated the turbulence for the operational altitudes and proved robustness of the designed autopilot for the turbulence using simulation.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.51.1-51.1
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• 2012

We observed low-z quasar PG1426+015 (z=0.086), using the near-IR high resolution echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. Using an Adoptive Optics system, the full width at half maximum of the point spread function was about 0.3 arcsec, which can effectively separate the quasar spectra from the host galaxy spectra. We also maximize the total exposure time up to several hours per target, and develop data reduction methods to increase the signal-to-noise ratios. This poster presents the data reduction processes and sample spectra from the quasar and its host galaxy. These spectral lines will be used to study the physical mechanism of quasars, and the velocity dispersions of the stars in the bugle of the host galaxy.

• Journal of computational fluids engineering
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• v.6 no.3
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• pp.1-9
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• 2001

Mixed convection in a horizontal annulus is considered, and the effect of a forced flow on the natural convective flow is investigated. The inner cylinder is hotter than the outer cylinder, and the outer cylinder is rotating with constant angular velocity with its axis at the center of the annulus. The unsteady streamfunction-vorticity equation is solved with a finite difference method. For the fluid with Pr=0.7, there appear flows with two eddies, one eddy, or no eddy according the Rayleigh and Reynolds numbers. The rotation of the outer cylinder reduces the heat transfer rate at the wall of the annulus. The oscillatory multicellular flow of a low Prandtl number fluid with Pr=0.01 can be effectively suppressed by the forced flow.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.65-68
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• 2004

A new multifunctional sandwich composite was investigated in this paper. The honeycomb core of this composite was filled with viscoelastic material in order to obtain an improved impact performance. The fillings in the honeycomb cells was hoped to provide the act of energy dissipation in this combined material system. Low-velocity drop-weight test was set up to the specimens with various stacked carbon/epoxy laminate facesheets, $[0/90]_{4s},\;[0/45/-45/90]_{2s}$. Load and energy history were checked and compared for the both groups of specimens, with and without rubber fillings. Further, the damaged faces were inspected visually by ultrasonic C-scan.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.161-164
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• 2002

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Tensile test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. EFPI was less sensible to the damage signals compared with the optical fiber vibration sensor. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1083-1094
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• 2003

This study represents an assessment of the phase-Doppler technique to the measurements of dense droplet laden jet. High-pressure injection fuel sprays have been investigated to evaluate the use of the Phase-Doppler anemometry (PDA) technique. The critical issue is the stability of the phase-Doppler anemometry technique for dense droplet laden jet such as Diesel fuel spray in order to insure the results from the drop size and velocity measurements are repeatable, consistent, and physically realistic because the validation rate of experimental data is very low due to the thick optical density. The effect of shift frequency is minor, however, the photomultiplier tube (PMT) voltage setting is very sensitive to the data acquisition and noise in dense droplet laden jet. The optimum PMT voltage and shift frequency should be chosen so that the data such as volume flux and drop diameter do not change rapidly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1795-1805
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• 2002

A position controller which can achieve a specified dynamic performance irrespective of the different operating position of the pneumatic cylinder is proposed. The position controller developed in this paper is composed of a nonlinear compensator and a disturbance observer. The nonlinear compensator which feeds back position, velocity and acceleration is derived from the nonlinear dominating equations of the position control system to compensate for variation of dynamic characteristics of a pneumatic cylinder according to the change of the operating position. The disturbance observer including a simplified linear model is designed to reduce the effect of model discrepancy in the low frequency range which cannot be suppressed by the nonlinear compensator. The results of the experiments show that the position control performance maintains a designed performance regardless of the variations of an operating position of the pneumatic cylinder.