• Journal of Welding and Joining
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• v.14 no.2
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• pp.65-70
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• 1996

Detonation velocity of domestic expolsives was measured using the Dautriche method. The variables employed in this study were the thickness of explosive and the amount of salt added in the ammonium nitrate(AN) explosive. As the results of this study, it was shown that the detonation velocity increases with an increase of explosive thickness but decreases with an increase of salt content. It was further demonstrated that the detonation velocity decreases rather rapidly when the salt content increases over 20 percent. In addition, the accuracy of Dautriche method was evaluated as a preliminary study and its result showed that this method is quite reliable with an experimental error of less than 10 pct.

• Korean Journal of Hydrosciences
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• v.3
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• pp.45-59
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• 1992

The flow characteristics varying with rate of the radius of curvature to width (Rc/B) in open channel bends are investigated with a simplified numerical model. Secondary flow velocity and transverise bed slope are formulated from the equations of momentum and force balance analysis, respectively. The conservation equations of mass and streamwise momentum are simplified by depth integration and its solution could be obtained from the explicit finite difference method. Three sets of computer simulation are executed. The rates of Rc/B adopted in simulations are 2.7, 5.4 and 8.1. The terms analyzed in this paper secondary flow velocity, streamwise velocity, the path of maximum steamwise velocity, deviation angle, and mass-shift velocity.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.81-89
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• 1998

Numerical calculation tools for forging of gear-like components based on kinematically admissible velocity fields for upper bound method applicable to various deformation features of workpiece in forging processes were suggested. Each one of them deals with unidirectional flow of metal on dies, such as external involute spur gear. square spline, internal serrations. A complex calculation tool of gear-like component forging process was built up by combining these kinematically velocity fields. In this paper the workpiece with 110th external and internal teeth is divided into two parts. The deformation of each part is analyzed simultaneously using numerical calculation tool from combined kinematically admissible velocity field. The experimental set-up was installed in a 200 ton hydraulic press. As a result, each kinematically admissible velocity field could be combined with others and the calculated solution are useful to predict the capacity of forging equipment.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.318-326
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• 2008

Recently, a new seismic probe, called "MudFork", has been developed and can be utilized for accurate and easy measurements of shear wave velocities of soft soils. To expand its use to estimate undrained shear strength and density, correlations between those and shear wave velocity were being attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a soft ground site near Incheon, Korea. Also, undisturbed samples were obtained and shear wave velocities of the samples were measured as well as undrained shear strength, using triaxial compression test and bender elements. A simple linear relationship between shear strength and shear wave velocity was obtained, and a tentative relationship between density and shear wave velocity was also defined.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.656-665
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• 2010

Shear modulus has been recognized as one of the important soil properties in dynamic analysis of ground and can be calculated from in situ measurement of shear wave velocity. Field seismic tests are the most accurate but expensive methods to investigate dynamic ground characteristics. Due to that reason, empirical equations for estimating the shear wave velocity are widely used rather than conducting in-situ tests. The most common equations are based on the N value obtained in conjuctions with a standard penetration test. In this paper, the field datas of standard penetration test and suspension PS logging measured in 126 sites of Korea were summarized and the correlation equations between N value and shear wave velocity are suggested.

• Journal of Environmental Science International
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• v.14 no.2
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• pp.209-214
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• 2005

Draft is defined as an unwanted local cooling of the human body caused by air movement. It is a serious problem in many ventilated or air conditioned buildings. Often draft complaints occur although measured velocities in the occupied zone maybe lower than prescribed in existing standards. Purpose of this study is to clarify the evaluation of thermal comfort based on temperature and air velocity in winter. Experiments were performed in an environmental chamber in winter. Indoor temperature and air velocity was artificially controlled. The experiments were performed to evaluate temperature conditions and air velocity conditions by physiological and psychological responses of human. According to physiological responses and psychological responses, it was clear that the optimum air velocity is about 0.15 m/s and 0.30 m/s.

• Journal of Environmental Science International
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• v.6 no.1
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• pp.25-31
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• 1997

The variations of gas hold-up, overall volumetric oxygen mass transfer coefficients and liquid circulation velocity in an internal loop reactor were investigated to manifest scale-up effect. The relationship between superficial gas velocity and gas hold-up were found as Ugr = 0.045 $\varepsilon$r in the pilot-scale and Ugr = 0.056 $\varepsilon$r in the bench-scale reactor. The overall volumetric oxygen mass tractsfer coefficient, KLa was slightly increased in the pilot-scale than in the bench-scale reactor. Flow regime was changed from the bubble flow to the churn-turbulent flow when the superficial gas velocity reached to 3.5 - 4 cm/sec in the pilot-scale.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.619-622
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• 2005

This study concerns the new strength equation of concrete by ultrasonic pulse velocity test. There are not only few estimate strength equations of concrete by ultrasonic pulse velocity test, but also many problems to apply them because of time,. cost, easiness, structural damage, reliability and so on. For this study, there performed a series of test and proposed equations as follows; Linear: ${\Large f}_{ck}=-193.15+60.97Vp\;r^2=77.9\%$ Quadratic : ${\Large f}_{ck}=276.85-189.64Vp+33.22Vp^2\;r^2=80.3\%$ here, $f_{ck}$ : Estimated compressive strength of concrete by MPa Vp : Ultrasonic Pulse Velocity of concrete by km/sec

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.330-333
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• 2006

In this paper experimental tests were performed to evaluate velocities of the acoustic waves through prestressed concrete beam and source locations using AE technique. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made 18 locations. The velocities of AE signals are evaluated using the time differences of arrival times and the distances between the AE source loactions and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000m/sec and the velocity decreased with the increase of the trevalling times due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the accuracy of source location is increased when the velocity of each AE sensor used rather than the average velocity.

• Journal of Ocean Engineering and Technology
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• v.16 no.5
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• pp.41-48
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• 2002

Numerical experiments are conducted using a three-dimensional baroclinic equation model and a Lagrangian method for clarifying the effect of th settling velocity on the suspended solids diffusion caused by the dredging and the reclamination works. Diffusion characteristics of the neutral particles and the weighting particles is experimented by the Lagrangian particles trajectory model, The results show that the diffusion characteristics of the suspended solids is effected by the settling velocity classified by the particles size in the density layered semi-closed bay. To estimate exactly the diffusion characteristics of the suspended solids and the contaminant with weight the three-dimensional baroclinic equation model and the three-dimensional Lagrangian particles trajectory model considering the settling velocity of the particle in the density layered semi-closed bay must be used.