• Journal of the Korea Society for Simulation
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• v.30 no.3
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• pp.31-39
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• 2021

During artillery fire, an excessive level of impulse noise propagating in the form of a storm wave is generated. Since the sound of impact from the fire affects the stability of the surrounding structures, the artillery and the structures must be separated from each other by the proper distance to avoid damages from friendly fire. However, if they have already been built within the distance, it is possible to prevent the damages by building sound barriers between them. In this study, the proper separation distance between the artillery and the structure was calculated, and the insertion losses due to various heights and shapes of the sound barrier were simulated by using the BEM(Boundary Element Method), and conclusively the optimal sound barrier was selected.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.886-891
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• 2008

This experimental investigation is concerned with the relationship between the electrical-on time of a solenoid which is located on the top of a pulse valve and air consumption of a dust collector. For the air consumption per pulse would be one of major factors affecting the operating cost of a dust collector, more attention is needed on the behaviour of a pulse valve. A pulse jet is blasted into a bag filter as the diaphragm valve opens and inflates a bag filter. This air-blast breaks up the dust layer and cleans the filter by dislodging dust cake. It is interpreted in this research that the cleaning filter is done by the impulse of a pulse jet. Hence, the magnitude and fluctuation of the dynamic pressure is measured using by a dynamic pressure sensor and the impulse is obtained by integrating dynamic pressure variation against time. Through this experimental work, conclusions are drawn implementing magnitude of averaged impulsive pressure per pulse or pressure impulse per unit volume of consumed air.

• Journal of the Korean Society of Safety
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• v.36 no.4
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• pp.71-79
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• 2021

In this study, a real-scale fuel-cell room of volume 1.36 m³ is constructed to confirm the explosion characteristics of hydrogen-air mixture gas in a hydrogen-powered house. A volume concentration of 40% is applied in the fuel-cell room as the worst-case scenario to examine the most severe accident possible, and two types of doors (made of plastic sheet and wood) are fabricated to observe their effects on the overpressure and impulse. The peak overpressure and impulse based on distance from the ignition source are experimentally observed and assessed. The maximum and minimum overpressures with a plastic-sheet door are about 20 and 6.7 kPa and those with a wooden door are about 46 and 13 kPa at distances of 1 and 5 m from the ignition source, respectively. The ranges of impulses for distances of 1-5 m from the ignition source are about 82-28 Pa·s with a plastic-sheet door and 101-28 Pa·s with a wooden door. The amount of damage to people, buildings, and property due to the peak overpressure and impulse is presented to determine the safe distance; accordingly, the safe distance to prevent harm to humans is about 5 m based on the 'injuries' class, but the structural damage was not serious.

• Journal of Navigation and Port Research
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• v.34 no.4
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• pp.271-279
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• 2010

The Mobile Harbor(MH) is a new transportation platform that can load and unload containers to and from very large container ships in the sea. This loading and unloading by crane can be performed with only very small movements of the MH in waves because MH is operated outside of the harbor. For this reason, an anti-rolling tank(ART) and an active mass driving system(AMD) were designed to reduce MH's roll motion, especially at the natural frequency of MH. In the conceptual design stage, it is difficult to confirm the design result of theses anti-rolling devices without modeling and simulation tools. Therefore, the coupled MH and anti-rolling devices' dynamic equations in waves were derived and a simulation program that can analyze the roll reduction performance in various conditions, such as sea state, wave direction, and so on, was developed. The coupled equations are constructed as an eight degrees of freedom (DOF) motion that consists of MH's six DOF dynamics and the ART's and AMD's control variables. In order to conveniently include the ART's and AMD's control dynamics in the time domain, MH's radiated wave force was described by an impulse response function derived by the damping coefficient obtained in the frequency domain, and wave exciting forces such as Froude-Krylov force and diffraction force and nonlinear buoyancy were calculated at every simulation time interval. Finally, the roll reduction performances of the designed anti-rolling devices were successfully assessed in the various loading and wave conditions by using a developed simulation program.

• The Journal of the Acoustical Society of Korea
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• v.14 no.4
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• pp.64-73
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• 1995

We developed a surface acoustic wave (SAW) computer aided design (CAD) for mobile communication using Kaier window function. The systems are composed of modules for designing apodization weighted IDT-uniform IDT, withdrawal weighted IDT-withdrawal weighted IDT, and resonator type. The design of SAW bandpass with center frequencies from 222MHz to 343MHz were simulated by the developed CAD system. Although the method proposed in this paper is formulated primarily for SAW filters, it is equally applicable to finite impulse response (FIR) digital filter design.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.6
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• pp.83-90
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• 1995

This paper analyzed the electrical field strength of porcelain suspension insulator used various testing methods in order to present the causes and countermeasure for the puncture failure by the inner minute defect. A power frequency puncture test and a step-front-of-wave flashover voltage test were conducted. The failed specimen of these samples was analyzed material characteric observed the cross-sectional picture by the scanning electron microscope, and tested the autoclave expansion for the portland cement using the metal bond agent. The porcelain made a progress the failure by the thermal expansion coefficient of the different material. The inner detecting technique on behalf of the puncture failure protection is presented such as the steep-front-of-wave flashover voltage test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.4
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• pp.87-99
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• 1993

The computer program, MFPD, which is used to backcalculate the layer moduli of asphalt concrete pavement system is modified by contemplating the depth to virtual bedrock in this study. An algorithm to estimate the depth to virtual bedrock is developed through the analysis of FWD impulse load duration and the compression wave velocity of ground. For verification of the modified MFPD, FWD is fabricated and then FWD field tests and verification tests are carried out at the test sites. Plate loading tests and surface wave propagation tests are performed at FWD test sites. Laboratory tests (Marshall stability tests, unconfined compression tests) for sampled asphalt concrete specimens are also carried out. From comparison analysis, the validity and applicability of the modified MFPD are verified.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.451-458
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• 2012

The voluntary EMG (vEMG) signal from electrically stimulated muscle is very useful for feedback control in functional electrical stimulation. However, the recorded EMG signal from surface electrodes has unwanted stimulation artifact and M-wave as well as vEMG. Here, we propose an event-synchronous adaptive digital filter for the suppression of stimulation artifact and M-wave in this application. The proposed method requires a simple experimental setup that does not require extra hardware connections to obtain the reference signals of adaptive digital filter. For evaluating the efficiency of this proposed method, the filter was tested and compared with a least square (LS) algorithm using previously measured data. We conclude that the cancellation of both primary and residual stimulation artifacts is enhanced with an event-synchronous adaptive digital filter and shows promise for clinical application to rehabilitate paretic limbs. Moreover because this algorithm is far simpler than the LS algorithm, it is portable and ready for real-time application.

• Journal of the Korean Society of Safety
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• v.4 no.1
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• pp.41-46
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• 1989

Molten salt-water explosion caused by the contact between molten salt and water is one of vapour explosions. An experimental study of the vapour explosion, which occurs when the molten mixture of Na$_2$CO$_3$-NaOH and water come in contact was performed. The pressure wave generated in each composition Of molten mixtures was measured. The results obtained are as follows： 1) The vapour explosion didn't occur for a molten salt of 100%-Na$_2$CO$_3$- 2) For a molten salt of Na$_2$CO$_3$ 80％-NaOH 20% mixture, a small vapour explosion occured initially, and a large vapour explosion, which showed the largest pressure wave among the present experiments, occurred after an induced period. 3) For molten salt of Na$_2$CO$_3$60％ - NaOH 40％ mixture and Na$_2$CO$_3$ 40％ - NaOH 60％ mixture, the vapour explosion occurred near the water surface shortly after they come in contact with water. This explosion would be caused by fragmentation of the molten salts due to impulse generated when thee molten salts and water come in contact.

• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.141-145
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• 2005

In this paper, UWB system did research about effect that interference effect with neighborhood single equipment or nearby group equipment gets In DMB service. 2.6425GHz satellite digital multimedia broadcasting service(SDMB) that electric wave interference special quality is contiguity frequency-band including interference of signal by unnecessary radiation level that is radiated in UWB system, and 3.4125GHz broadcasting relay net that is In-band frequency-band and interference effect degree that get in service did comparative analysis. SDMB system was BER $1{\times}10^{-4}$ that interference effect happens from 6.5m point and broadcasting signal reception is possible at 4m point. Also, it was BER $1{\times}10^{-4}$ that interference effect begins to happen from 5.0m point about center frequency 3.4126GHz and broadcasting signal reception is possible at 2m point. And, confirmed that UWB system of impulse method is less interference effect about 2 dB than UWB system of OFDM method, to electric wave of UWB system that is small output