• International Journal of Fluid Machinery and Systems
• /
• v.4 no.4
• /
• pp.375-386
• /
• 2011

The turbo-type blood pump studied in this paper has an impeller that is magnetically suspended in a double volute casing. The impeller rotates with minimal fluctuations caused by fluid and magnetic forces. In order to improve stability of the rotating impeller and to facilitate long-term use, a careful investigation of the pressure fluctuations and of the fluid force acting on the impeller is necessary. For this purpose, two models of the pump with different volute cross-sectional area are designed and studied with computational fluid dynamics software. The results show that the fluid force varies with the flow rate and shape of the volute, that the fluctuations of fluid force decrease with increasing flow rate and that the vibratory movement of the impeller is more efficiently suppressed in a narrow volute.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.10
• /
• pp.1271-1278
• /
• 2004

In order to measure non-intrusively velocity profile in liquid metal flow, a modified electromagnetic flowmeter was designed, which was based on electromagnetic tomography technique. Under the assumption that flow is fully-developed, axisymmetric and rectilinear, the velocity profile was reconstructed after the flowmeter equation, the first kind of Fredholm integration equation, was linearized. In reconstruction process Tikhonov regularization method with regularization parameter was used. The reconstructed velocity profile had the nearly same as turbulent flow profile which was approximately represented as log law. In addition, flowmeter output fur a fixed magnet rotation angle was linearly proportional to flow rate. When magnet rotation angle was 54$^{\circ}$, axisymmetric weight function was nearly uniform so that the flowmeter gives a constant signal for any fully-developed, axisymmetric and rectilinear profile with a constant flow rate.

• Proceedings of the IEEK Conference
• /
• 2000.09a
• /
• pp.901-904
• /
• 2000

A direct authentication from gray-scale image, instead of the conventional multi-step preprocessing, is proposed using Gabor filter-based features from the gray-scale fingerprint around core point. The core point is located as a reference point for the translation invariant matching. And its principal symmetry axis is detected for the rotation invariant matching from its neighboring region centered at the core point. And then fingerprint is divided into non-overlapping blocks with respect to the core point and features are directly extracted form the blocked gray level fingerprint using Gabor filter. The proposed fingerprint authentication is based on the Euclidean distance between the corresponding Gabor features of the input and the template fingerprints. Experiments are conducted on 300${\times}$300 fingerprints obtained from a CMOS sensor with 500 dpi resolution, and the proposed method could lower the False Reject Rate(FRR) to 18.2% under False Acceptance Rate(FAR) of 0%.

• Journal of the Korean Ceramic Society
• /
• v.32 no.2
• /
• pp.270-278
• /
• 1995

Nd : YAl3(BO3)4 (NYAB) single crystal has been developed for green laser. In this experiment, we found K2O/3MoO3/0.5B2O3 to be a suitable flux for NYAB crystal growth, and grew NYAB crystal by TSSG method using this flux. By varying the cooling rate of solution, seed orientation, and rotation speed, the effects of these growth conditions on the crystal quality and its morphology were examined. Suitable growth conditiions were a cooling rate slower than 2.4$^{\circ}C$/day, the rotation speed of 25~30 rpm, and the <001> seed orienttion. The phases of grown crystal, coexisting and volatile materials were investigated by X-ray diffraction. In addition, the possiblity of laser action was examined by UV analysis.

• Journal of the Korean Mathematical Society
• /
• v.43 no.2
• /
• pp.413-424
• /
• 2006

Let $\Gamma$ be a bounded rotation (BR) curve without cusps in the complex plane $\mathbb{C}$ and let G := int $\Gamma$. We prove that the rate of convergence of the interpolating polynomials based on the zeros of the Faber polynomials $F_n\;for\;\bar G$ to the function of the reflexive Smirnov-Orlicz class $E_M (G)$ is equivalent to the best approximating polynomial rate in $E_M (G)$.

• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.323-326
• /
• 2006

Numerical solutions for spin-up problem of a thermally stratified fluid in a cylinder with an insulating sidewall and time-dependent rotation rate are presented. Detailed results are given for aspect ratio of O(1), fixed Ekman number $10-^{4}$, Rossby number 0.05 and Prandtl number O(1). Angular velocity of a cylinder wall changes with following formula, $\Omega_f=\Omega_i+\Delta\Omega[1-\exp(-t/t_c)]$. Here, this $t_c$, value, which is very significant in present study, represents that how fast/slow the angular velocity of the cylinder wall reaches final angular velocity. The normalized azimuthal velocity and meridional flow plots for several tc value which cover ranges of the stratification parameter S(1 ~ 10) are presented. The role of viscous-diffusion and Coriolis term in present study is examined by diagnostic analysis of the azimuthal velocity equation.

• The Bulletin of The Korean Astronomical Society
• /
• v.35 no.1
• /
• pp.66.1-66.1
• /
• 2010

Using two-dimensional numerical hydrodynamic simulations, we investigate the star formation rate (SFR) in turbulent, multiphase, galactic gaseous disks. Our simulation domain is axisymmetric, and local in the radial direction and global in the vertical direction. Our models include galactic rotation, vertical density stratification, self-gravity, radiative heating and cooling, and thermal conduction, but do not include spiral-arm features. Turbulence in our models is driven by momentum feedback from supernova explosion events occurring in localized dense regions formed by thermal and gravitational instabilities. Self-consistent radiative heating, representing enhanced/reduced FUV photons from the star formation, is also taken into account. By controlling three parameters (the gas surface density, the stellar disk density, and the angular rotation rate) that characterize local galactic disks, we explore how the SFR depends on the background environmental state. We also discuss the relation between the SFR and the gas surface density found in our numerical models in comparison with observations.

• Proceedings of the IEEK Conference
• /
• 2003.07e
• /
• pp.2032-2035
• /
• 2003

This paper focused on the possibility of face recognition using Flexible let Point Setting method in Gabor Filter Based Face Recognition. Gabor Filter is very sensible to the Texture variation. Therefore, any little change in the face expression or rotation of posture make recognition rate down significantly. A suggested solution for this problem is the Flexible Jet Point Setting. A significant effect of this method is that the number of Jet Point has been reduced from over 150 to under 30 even though the change of recognition rate between two methods is neglectable, Furthermore a set of feature values which results from a set of Gabor filtering became insensible to face variation such as expression, rotation, and light effect. Retinex Algorithm which has been developed by NASA are used as pre-processing.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.2
• /
• pp.98-104
• /
• 2012

In this paper, precision processing is carried out for the pre hardened steel(HRC 54), which is one of injection mould materials. Processing characteristics are estimated according to the number of tool cutting blade and roundness is observed by the 3-Dimensional measuring machine. The surface roughness affected by the wire electric discharge machining are measured. Cutting component force of STAVOX is the highest in condition of 2F processing because load per a blade of cutting tool is high. Especially, the difference in Fz is over 20N by cutting load. The slower spindle rotation speed and tool feed rate are, the better cutting component force is. The roundness of hole processed in condition of 4F is good because feed rate is able to be fast. When rotation speed is increased, the surface roughness is decreased. The surface roughness acquired in condition of 2F processing is higher about 50% than 4F processing.

• Journal of the Optical Society of Korea
• /
• v.3 no.2
• /
• pp.80-85
• /
• 1999

We propose and demonstrate a new scheme for suppression of output distortion in an open-loop gyroscope employing an erbium-doped fiber amplifier/source (FAS). In addition to the main modulation for the rotation rate measurement, a small auxiliary modulation at a different frequency is used to extract an error signal, which is necessary for keeping the quasi-dc component of the feedback signal power at a constant level for varying rotation rate. By active tracking of the optimum modulation condition using this two-frequency modulation scheme, we obtain stable gyro output with suppressed distortion as well as stable FAS characteristics. We also calculate the distortion in the gyro response due to the feedback effect, from which we estimate the FAS gyro output distortion due to the residual ac feedback effect when the dc feedback effect is removed by the proposed scheme. The measured residual deviation agrees reasonably with the estimation.