• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2686-2697
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• 1994

When a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel, which causes an impulsive noise. In order to estimate the magnitudes of the noises and to effectively minimize them, the characteristics of the compression wave propagating in a tunnel must be understood. In the present paper, the experimental and analytical investigations on the attenuation and distortion of the propagating compression waves were carried out using a model tunnel. This facility is a kind of open-ended shock tube with a fast-opening gate valve instead of a general diaphragm. One-dimensional flow model employed in the present study could appropriately predict the strength of the compression wave, Mach number and flow velocity induced by the compression wave. The experimental results show that the strength of a compression wave decreases with the distance from the tunnel entrance. The decreasing rate of the wave strength and pressure gradient in the wave is strongly dependent on the strength of the initial compression wave at the tunnel entrance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.10a
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• pp.95-104
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• 2006

A floating-type wave power pump is a device which sends air into water by using wave power. The floating-type wave power pump has the new configuration composed of a curved surface reflection board, a slope, and phase plates. As a result of a water-tank experiment it turned out that the floating-type wave power pump with a curved surface reflection board and a slope raised power and efficiency in the wide wavelength waves. The result of a marine experiment was also preferable. The floating-type wave power pump sends air into the sea by using wave power, so it can be used for the improvement of marine environment. In addition, the floating body constituted of a curved surface reflection board, a slope, and phase plates, is effective as a device to utilize the energy of a wave. Therefore, it can be widely used for a wave power generation, pumping up deep seawater.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.461-464
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• 2009

The characteristics of slow wave structure employed for backward wave oscillators expected to be a high power microwave source are studied analyytically. The slow wave structure is a sinusoidally corrugated wall waveguide. The waveguide is designed and fabricated by cast aluminun. The dispersion relation and transmitted characteristics for microwaves are measured in the air. There exist literatures on high efficiency of enhanced radiation from backward wave oscillators involving plasma studied experimentally.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.481-481
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• 2007

The characteristics of slow wave structure employed for backward wave oscillator expected to be a high power microwave source are studied analytically. The slow wave structure is a sinusodially corrugated wall waveguide. The waveguide is designed and transmitted characteristics for microwave are measured in the air. There exist literatures on high efficiency of enhansed radiation from backward wave oscillators involving plasmastudied experimentally another results.

• Journal of Power Electronics
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• v.5 no.4
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• pp.257-263
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• 2005

This paper describes the development and testing results of a high density High Voltage Power Supply (HVPS) that drives microwave Traveling Wave Tubes (TWTs) of phased array transmitters for airborne EW systems. The HVPS is designed to consist of a number of modules connected in series. Among them, especially, the high-density pulse transformer module including the resonant circuit is newly designed to make the HVPS much more reliable. In addition, this paper describes the development of high voltage solid-state modulation using fast switching devices (FETs) and also represents the test results of a modulator module.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1931-1939
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• 1993

The wave propagation characteristics of laminated composites subjected to a transverse high-velocity impact of a steel ball is investigated. For this purpose, high-velocity impact experiments were conducted to obtain the strain response histories, and a finite element analysis based on the higher-order shear deformation theory in conjunction with the static contact law is used. Test materials for investigation are glass/epoxy laminated composite materials with $[0^{\circ}/45^{\circ}/0^{\circ}/-45^{\circ}]_{2s}$ and $[90^{\circ}/-45^{\circ}/90^{\circ}-45^{\circ}/90^{\circ}]_{2s}$ stacking sequences. As a result, the strain responses obtained from the experiments represented the wave propagation characteristics in the transversely impact, also the wave propagation velocities obtained from high-velocity impact experiments and wave propagation theory agree well.

• Journal of Navigation and Port Research
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• v.46 no.1
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• pp.11-17
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• 2022

The high wind wave alert has a great impact on ships and maritime service workers navigating in the vicinity of Korea. This study aims to evaluate the appropriateness of the high wind wave alert by comparing and analyzing the observation data of major marine meteorological buoys with the high wind wave alerts in the coastal sea and offshore of the West Sea, South Sea, and the East Sea announced by the Korea Meteorological Administration for the past 11 years(2010-2020). As a result of comparing the daily, monthly, and annual statistics of the high wind wave alert and marine meteorological buoy observation data for each sea area by annual, monthly, and seasonal average, the accuracy of high wind wave alerts was very low across the entire sea area. In particular, it was analyzed that the accuracy in the coastal sea of the South Sea and Jejudo was the lowest in winter. It was confirmed that the accuracy of marine weather forecasts and alerts needs to be improved when considering the effects of the high wind wave alerts on fishing vessels, passenger ships operations and tourism, and marine leisure activities.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.2
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• pp.234-242
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• 1999

Flow phenomena such as the pressure transients Inside a high-speed railway tunnel and the Impulsive waves at the exit of the tunnel are closely associated with the characteristics of the entry compression wave, which is generated by a train entering the tunnel. Tunnel entrance hood may be an effective means for alleviating the Impulsive waves and pressure transients. The objective of the current work is to explore the effects of the train nose shape and the entrance hood on the characteristics of the entry compression wave. Numerical calculations using the method of characteristics were applied to one-dimensional, unsteady, compressible flow field with respect to high-speed railway/tunnel systems. Two types of the entrance hoods and various train nose shapes were employed to reveal their influences on the entry compression wave for a wide range of train speeds. The results showed that the entry compression wave length increases as the train nose becomes longer and the train speed becomes lower. The entry compression wave length in the tunnel with hood becomes longer than that of no hood. Maximum pressure gradient in the compression wavefront reduces by the entrance hood. The results of the current work provide useful data for the design of tunnel entrance hood.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1664-1666
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• 2001

This paper presents the development of electromagnetic wave detecting equipment for diagnosis of enclosed switchboard. High voltage power equipments are very important equipment of the key industries and the private enterprise. Power line accidents are national plans because of those set off casualties lose of power equipments and communication networks. Therefore the necessity of the development of detecting for power equipment diagnosis is demand for prevention of high voltage equipment accidents. This paper is the development of electromagnetic wave detecting equipment for diagnosis of high voltage equipment. This paper establishes the diagnosis method for high voltage power equipments, that secures original technique and possesses detecting technique for electromagnetic wave. By the study we developed electromagnetic wave detector, and we applied this equipment application tests at the place constructed high voltage equipments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.178-181
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• 2001

This paper presents the development of electromagnetic wave detecting equipment for diagnosis of enclosed switchboard. High voltage power equipments are very important equipment of the key industries and the private enterprise. Power line accidents are national plans because of those set off casualties lose of power equipments and communication networks. Therefore the necessity of the development of detecting for power equipment diagnosis is demand for prevention of high voltage equipment accidents. This paper is the development of electromagnetic wave detecting equipment for diagnosis of high voltage equipment. This paper establishes the diagnosis method for high voltage power equipments, that secures original technique and possesses detecting technique for electromagnetic wave. By the study we developed electromagnetic wave detector, and we applied this equipment application tests at the place constructed high voltage equipments.