• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.03a
• /
• pp.130-135
• /
• 1997

A kinematically admissible velocity field is developed for the analysis of twisting of extruded products. The twisting of extruded product is caused by the linearly increased rotational velocity from the center on the cross-section of the workpiece at the die exit. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is zero at the die entrance and is increased linearly by longitudinal distance from die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product changes with the aspect ratio of product and increases with the decreases in die length and in eccentricity of gravity center of the cross-section of workpiece at die entrance from that of the cross-section at the die exit.

• Journal of the Korean Society of Combustion
• /
• v.7 no.2
• /
• pp.1-6
• /
• 2002

Characteristics of laminar lifted flames of propane highly-diluted with nitrogen have been investigated at various temperatures of coflow air. At various fuel mole fractions, the base of laminar lifted flames has the structure of tribrachial (or triple) flame. The liftoff heights are correlated well with the stoichiometric laminar burning velocity considering initial temperature at a given coflow velocity. It shows that lifted flames are stabilized on the basis of the balance mechanism between local flow velocity and the propagation speed of tribrachial flame, regardless of the temperature of coflow and fuel mole fraction. Lifted flames exist for a jet velocity even smaller than the stoichiometric laminar burning velocity, and liftoff velocity increases more rapidly than stoichiometric laminar burning velocity as coflow temperature increases. These can be attributed to the buoyancy effect due to the density difference.

• Journal of the Korean Society of Tobacco Science
• /
• v.3 no.2
• /
• pp.109-114
• /
• 1981

This experiment was conducted with three varieties (Hicks, Burley 21, Sohyang) and cropping systems (Improved mulching, Mulching, Non mulching) of NC 2326 to analyze growth kinetics by means of growth function involving its velocity and accelerated velocity. The basic growth data were obtained by harvest method at interval of ten days from transplanting to hundred days and analyzed by , regression equation, determinant of matrix, and differentiation. The plot of total dry weight of leaves, stalk and roots per a plant vs. time forms a sigmoid curve and its function fitted logistic satisfactorily. Tobacco plant grows at an accelerated velocity. And growth velocity, symmetric about an inflection point, is proportional to biomass attained and to the difference between biomass attained and the maximum, and to the decrease according to the biomass. Of varieties and cropping systems, the most maximum velocity was 9.58g per day per plant in mulching cultivation of NC 2326 and maximum accelerated velocity was 264mg per $day^2$ per plant in Burley 21.

• Journal of Magnetics
• /
• v.18 no.2
• /
• pp.90-94
• /
• 2013

We designed a model composed of a ring type magnet, a yoke, and a sensing coil embedded in a projectile for simulating the muzzle velocity. The muzzle velocity was obtained from the master curve for the induced voltage at sensing coil and the velocity as the projectile pass through the magnetic field. The induced voltage and the projectile's velocity are fitted by the $2^{nd}$ order polynomial. The skin effect difference between projectiles which consist of aluminum-aluminum and aluminum-steel was small. The projectile will surely be burst at the pre-determined target area using the flight time and the projectile muzzle velocity calculated from the voltage induced at the sensing coil on the projectile.

• Journal of ILASS-Korea
• /
• v.3 no.1
• /
• pp.27-33
• /
• 1998

Correlations of drop size and velocity in a spray from the disintegration of liquid jet and liquid film from an internal mixing twin-fluid atomizer, were determined by phase Doppler method. The distribution pattern of Sauter mean diameter(SMD) in a spray was changed by a behavior of liquid flow. As smaller droplets became faster and slower easily by the surrounding conditions, the correlation between drop size and mean velocity was found to be varied as next 3 steps; firstly smaller droplets have a higher mean velocity at the area near atomizer, droplets have almost the same mean velocity and finally larger droplets have a higher mean velocity at the area far from an atomizer.

• International Journal of Fluid Machinery and Systems
• /
• v.8 no.4
• /
• pp.311-317
• /
• 2015

It is difficulty to calculate velocity circulation in centrifugal pump impeller outlet accurately. Velocity circulations of a double-blade pump impeller outlet were calculated with Stodola formula, Weisner formula and Stechkin formula. Simultaneously, the internal flow of impeller for the double-blade pump were measured with PIV technology and average velocity circulations at the 0.8, 1.0 and 1.2 times of design flow were obtained. All the experimental values were compared with the above calculation values at the three conditions. The results show that calculation values of velocity circulations with Weisner formula is close to the experimental values. On the basis of the above, velocity circulations of impeller outlet were corrected. The results of experimental verification show that the corrected calculation errors, whose maximum error is 3.65%, are greatly reduced than the uncorrected calculation errors. The research results could provide good references for establishment of theoretical head and multi-condition hydraulic optimization of double-blade pumps.

• Journal of Industrial Technology
• /
• v.27 no.A
• /
• pp.9-14
• /
• 2007

This study was designated to clarify the aspect of the wave propagation around the cavity. The change of traveltime and amplitude of the seismic wave was observed according to the various wave velocities of the cavity. The seismic wave detour or penetrate the cavity depending on the seismic velocity of the in-filled material. Generally, seismic wave detours toward high velocity zone around the cavity, and when the velocity of the cavity material reaches to 80 % of the base rock, the wave penetrates the cavity. The traveltime of the detouring seismic wave is not sensitive to the change of the cavity velocity, but as the velocity of the cavity increases, the fall of the amplitude was reduced. The penetrating wave showed the steeply increasing amplitude due to the reiteration of the detouring wave.

• Journal of the Korea Concrete Institute
• /
• v.11 no.4
• /
• pp.157-167
• /
• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• Journal of The Korean Astronomical Society
• /
• v.4 no.1
• /
• pp.1-8
• /
• 1971

The average velocity, 330km/sec. of the high velocity stars with respect to the galactic center is obtained from the data used by Fricke on the assumption that the rotational velocity of the Local Standard of Rest is 250km/sec. Comparing this value with the escape velocity, 380km/sec, at the solar neighborhood which is calculated from Mestel's model of the Galaxy, it is shown that most of the high velocity stars are bound to the Galaxy and that their average apogalacticon is about 40 kpc from the galactic center. And the fact that stars with radial velocities larger than 63km/sec are missing in the direction of galactic rotation of L.S.R. is interpreted as the result partly of the random distribution of the directions of motion of the high velocity stars and partly of the observational errors.

• The Journal of the Acoustical Society of Korea
• /
• v.29 no.1E
• /
• pp.11-27
• /
• 2010

Nowadays, ultrasound Doppler imaging is widely used in assessing cardiovascular functions in the human body. However, a major drawback of ultrasonic Doppler methods is that they can provide information on blood flow velocity along the ultrasound beam propagation direction only. Thus, the blood flow velocity is estimated differently depending on the angle between the ultrasound beam and the flow direction. In order to overcome this limitation, there have been many researches devoted to estimating both axial and lateral velocities. The purpose of this article is to survey various two-dimensional velocity estimation methods in the context of Doppler imaging. Some velocity vector estimation methods can also be applied to determine tissue motion as required in elastography. The discussion is mainly concerned with the case of estimating a two-dimensional in-plane velocity vector involving the axial and lateral directions.