• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.30-37
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• 2007

In this paper, Water Entry Point Selection Algorithm(WEPSA) for selecting an optimal Water Entry Point of anti-submarine missiles which maximizes Detection Probability about a given target was investigated. WEPSA is a method which decides the position of an optimal Water Entry Point with calculating the target Detection Probability of a torpedo in the whole domain which centered by the target, performing the Monte-Carlo Simulations which include errors for the target informations and for weapon delivery. We can decide an optimal Water Entry Point of anti-submarine missiles which maximizes Detection Probability about a given target with WEPSA, if we get target informations about target range, target bearing, target speed and target course from Combat Systems.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.3
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• pp.394-403
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• 2008

The effects of water injection (WI) and urea injection for NOx on a 4-cylinder Direct Injection (DI) diesel engine were investigated experimentally. For water injection, it was installed at the intake pipe and the water quantity was controlled at the intake manifold and Manifold Air Flow (MAF) temperatures while the urea injection was located at the exhaust pipe and the urea quantity was controlled by NOx quantity and MAF. The effects of WI system, urea-SCR system and the combined system were investigated with and without exhaust gas recirculation (EGR). Several experiments were performed to characterize the urea-SCR system, using engine operating points of varying raw NOx emissions. The results of the Stoichiometric Urea Flow (SUF) and NOx map were obtained. In addition, NOx results were illustrated according to the engine speed and load. It is concluded that the NOx reduction effects of the combined system without the EGR were better than those with the EGR-based engine.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.2
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• pp.51-61
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• 2001

A numerical study has been conducted to characterize the transient pressure in a simple water supply pipe system with an air chamber by utilizing a commercial code that employs the method of characteristics. Some results produced for validation in the study agree quite well with the previously reported. Several parameters are than varied. Among them are the valve closure time, the wave speed, the static pressure, the polytropic exponent, the air chamber volume, the diameter and the shape of orifice in the air chamber, etc, while the water temperature and velocity are kept constant at $20^\circ{C}$ and 0.8m/s, respectively. Results reported in this parametric study may be useful to understand the unsteady behavior of the system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.33-34
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• 2020

Unit-water content is an element directly related to durability and unit-water content of concrete used at construction site has a great effect on the durability of construction structure. Many methods are being discussed for more convenient and accurate measurements of unit-water content. Therefore, an experimental study was conducted on the prediction of unit-water content using ultrasonic equipment. Depending on the amount of cement in cement paste, the speed of ultrasonic waves varies and the experiment will be carried out using the same reception sensitivity in the future.

• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.61-67
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• 2024

In this study, the behavior of water droplets on a solid-infused surface was evaluated by quantifying a water droplet's contact angle, sliding angle, and terminal velocity. The contact angle hysteresis and sliding angle of water on the solid-infused surface were measured to be lower than those of the hydrophobic PTFE surface. It led to the enhancement of the initiation of the water droplet's movement. When the capillary number was lower than Ca < 0.004, the terminal velocity of the water droplet on the solid-infused surface was higher than the PTFE surface due to the low contact line resistance. However, the transition of the droplet morphology from a hemispherical shape to a streamlined teardrop shape beyond Ca > 0.004 lost the effect of reducing frictional resistance on the solid-infused surface.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.293-300
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• 2013

This study used a water tank and wave maker to generate conditions similar to the real ocean environment. Given that the waves were properly generated in the water tank, a precise analysis indicated the quantitative value of the wave force acting on a body. A high-speed camera and wave-level gauge were used to measure the temporal wave motion and period. A series of artificial water waves were successfully generated using three different wave periods and amplitudes. Each of the waves captured by a high-speed camera was sinusoidal and did not maintain its shape properly without a wave absorber, but it was substantially improved and well shaped when the wave absorber was installed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.243-250
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• 2014

Fiber-optic cables towed by underwater vehicles have an important role in enhancing the mission capability of a mother ship. In general, fiber optic cables are unwound in water for securing unwinding stability and preventing unwinding-related problems. Therefore, in this study, the numerically simulated result is verified against the experimental result in water, and the cable-unwinding motion is predicted based on the increase in unwinding velocity. The experimental apparatus is composed of a water tank and a winder, and a high-speed camera is used for photographing the cable-unwinding motion. The numerical result defined in the Cartesian coordinate system is solved using a transient-state unwinding equation of motion. The numerical result agrees well with the experimental result, and it can predict cable-unwinding behaviors in according to an increase in the unwinding velocity.

• Journal of the korean society of oceanography
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• v.35 no.3
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• pp.129-152
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• 2000

The Cheju Current (CC), defined here as a mean eastward flow in the Cheju Strait, mostly carries water of high temperature and salinity originating from the Kuroshio in winter and spring, the Cheju Warm Current Water (CWCW). The strong core of the eastward component of the CC is found close to Cheju Island (Cheju-Do, hereafter) in winter and spring with a peak speed of about 17.0 cm/s. The eastward flow weakens towards the northern Cheju Strait, and a weak westward flow occurs occasionally close to the southern coast of Korea. The volume transport ranges from 0.37 to 0.45 Sv(1 Sv=10$^6$ m$^3$/s) in winter and spring. Seasonal thermocline and harocline are formed in summer and eroded in November. The occurrence of the CWCW is confined in the southern Cheju Strait close to Cheju-Do below the seasonal thermocline in summer and fall, and cold water occupies the lower layer north of the CWCW which is thought to be brought into the area from the area west of Cheju-Do along with the CWCW. Stratification acts to increase both the speed of the CC with a peak speed of greater than 30 cm/s and the vertical shear of the along-strait currents. The strong core of the CC detached from the coast of Cheju-Do and shifted to the north during the stratified seasons. The volume transport in summer and fall ranges 0.510.66 Sv, which is about 1.5 times larger than that in winter and spring. An annual cycle of the cross-strait sea level difference shows its maximum in summer and fall and minimum in winter and spring, whose tendency is consistent with the annual variability of the CC and its transport estimated from the ADCP measurements. Moored current measurements west of Cheju-Do indicate the clockwise turning of the CC, and the moored current measurements in the Cheju Strait for 1530 days show the low-frequency variability of the along-strait flow with a period of about 37 days.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.773-777
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• 1999

Scale-up experiments for hydrolysis of beef tallow, fat, and palm kernel with lipase derived from Candida cylindracea were carried out in 1-1, 100-1, and 10,000-1 reactors. The optimum agitation speed for the hydrolysis of the 1-1 reactor was investigated and found to be 350rpm, and this was a basis for the scale-up of agitation speed. The hydrolysis system in this work was the oil-water system in which the hydrolysis seems to process a heterogeneous reaction. An emulsion condition was the most important factor for determining the reaction rate of hydrolysis. Therefore, the scale-up of agitation speed was performed by using the power n = 1/3 in an equation of the rules of thumb method. The geometrical similarity for scaling-up turned out to be unsatisfactory in this study. Thus, the working volume per one agitator was used for the scale-up. In the case of scale-up from a 1-1 reactor to a 100-1 reactor, the hydrolysis of palm kernel was very much scaled-up by initiating the rules of thumb method. However, the hydrolysis of fat and beef tallow in a 100-1 reactor was a little higher than that of the 1-1 reactor because of the difference of geometrical similarity. The scale-up of hydrolysis from the 100-1 reactor to the 10,000-1 reactor was improved compared to that of the 1-1 to 100-1 reactor. The present results indicated that the scale-up of hydrolysis in the oil-water system by the rules of thumb method was more satisfactory under the condition of geometrical similarity. Even in the case where geometrical similarity was not satisfactory, the working volume per one agitator could be used for the scale-up of a heterogeneous enzyme reaction.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.5
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• pp.379-384
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• 2013

For effective ship management in VTS(Vessel Traffic Service), it needs to assess the external force acting on ship. Big data in maritime traffic can be roughly categorized into two groups. One is the traffic information including ship's particulars. The other is the external force information e.g., wind, sea wave, tidal current. This paper proposes the method to assess the external force acting on ship using big data in maritime traffic. To approach Big data in maritime traffic, we propose the Waterway External Force Code(WEF code) which consist of wind, wave, tidal and current information, Speed Over the Water(SOW) of each ship, weather information. As a results, the external force acting a navigating ship is estimated.