• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.199-207
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• 2014

Although High-altitude electromagnetic pulse(HEMP) protection filter meets the requirements of pulsed current injection(PCI) acceptance test, the equipment under test which has low electromagnetic susceptibility level can be damaged during PCI verification test that is performed on operating condition of equipment. This paper proposed the HEMP effect analysis method using comparison of norms between residual current of HEMP filter and transient electromagnetic conducted susceptibility criteria of equipment, as an alternative method under the condition that performing PCI verification test is limited in HEMP hardened facilities. PCI acceptance test of HEMP filter, transient electromagnetic conducted susceptibility test, and PCI verification test are performed and test results are analyzed.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.443-446
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• 2005

This paper presents the results of the design and implementation of the airborne pulse doppler radar signal processor using high multi-DSP for the multi-function radar capability such as short-range, midium-range, and long-range depending on the mission of the vehicle. Particularly, the radar signal processor is developed using two DSP boards in parallel for the various radar signal processing algorithm. The key algorithms include LFM chirp waveform-based pulse compression, MTI clutter filter, MTD processor, adaptive CFAR, and clutter map. Especially airborne moving clutter Doppler spectrum compensation algorithm such as TACCAR is implemented for the multi-mode airborne radar system. The test results shows the good Doppler spectral separation for the clutter and the moving target in the flight test environment using helicopter

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.23-28
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• 2005

An airborne radar is an essential aviation electronic system of the helicopter to perform various missions in all-weather environments. This paper presents the results of the design and implementation of the airborne pulse doppler radar signal processor using high multi-DSP for the multi-function radar capability such as short-range, midium-range, and long-range depending on the mission of the vehicle. Particularly, the radar signal processor is developed using two DSP boards in parallel for the various radar signal processing algorithm. The key algorithms include LFM chirp waveform-based pulse compression, MTI clutter filter, MTD processor, adaptive CFAR, and clutter map. Especially airborne moving clutter Doppler spectrum compensation algorithm such as TACCAR is implemented for the multi-mode airborne radar system. The test results shows the good Doppler spectral separation for the clutter and the moving target in the flight test environment using helicopter.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.399-404
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• 2010

Test results including the variation of propellant-inlet pressure, pulsed thrust, and environment vacuum with the accompanying thermal responses are presented for the pulse-mode operation of a set of monopropellant hydrazine thrusters producing $0.95lb_f$ of nominal steady-state thrust at an inlet pressure of 350 psia. The test data are reduced into the impulse bit, specific impulse, and force centroid that are the factors typically characterizing pulse-mode performance of small rocket engines. With a scrutiny to the performance parameters, their comparison to the reference criteria of 1 lbf standard monopropellant rocket engine are successfully made.

• Nuclear Engineering and Technology
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• v.38 no.8
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• pp.785-792
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• 2006

The microwave heating system of KSTAR consists of ECH and LHCD. ECH and LHCD offer the benefits ofa reliable operation at the start of plasma formation and a non-inductive current drive durable steady state operation, respectively. LHCD uses a C-band microwave system with a frequency of 5 GHz. A pulsed power modulator with a power of 3.6 MW, $4{\mu}S$, 200 pps is required to drive the high-powered magnetron. The development of a pulse modulator with 1:4 pulse transformers is the focus of the research in this study. The peak power handling capability is 3.6 MW (45 kV, 90 A at load side with a pulse width of $4{\mu}S$). This paper describes the system overview and test results of the pulsed modulator. In particular, a simulated waveform is compared with the tested waveform.

• Journal of the Korean Geotechnical Society
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• v.26 no.3
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• pp.25-34
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• 2010

In the present paper, a numerical study was carried out to simulate ground expansion induced by an application of pulse discharge technology. Based on laboratory pulse discharge tests, the characteristics of shockwave were investigated, and then the laboratory tests were numerical1y simulated using underwater explosion model implemented in a coupled acoustic-structural finite element analysis. In addition, for clayey soils, the expansion of ground was also studied using soil properties obtained from empirical correlations with SPT N values. It was found that the calculation results well agreed with the field test results.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.486-493
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• 2015

The ultrasonic nondestructive test (NDT) was applied to deck in-service to inspect and evaluate the performance of decking materials using ultrasonic pulse velocity. First, the measuring method between direct and indirect method according to transducer arrangement was studied. Second, the ultrasonic pulse velocity of decks in-service was compared with the passage of time. Finally, the change of ultrasonic pulse velocity was evaluated to expect service life of decking materials. The results of comparison between direct and indirect method was statistically insignificant and the ratio of direct to indirect method was 1.02. 1.05 respectively. The ultrasonic pulse velocity of decks in-service was decreased as the passage of time and the linear relationship in the ultrasonic pulse velocity to passage of time was found. From the results, The ultrasonic NDT will be helpful as an efficient method of on-site management of decks in-service.

• Nuclear Engineering and Technology
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• v.17 no.1
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• pp.25-33
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• 1985

The main purpose of this work is to investigate the effects of the wall thickness, the ultrasonic frequency, and the acoustic impedance of wall material on the liquid-film thickness measurement by an ultrasonic pulse echo method. A series of liquid-film thickness measurements in a horizontal air-water stratified system was performed employing a plate-type and a tube-type test sections. Measurements were repeated changing (1) the wall thickness of the test section and (2) the transducer frequency. Also, in an effort to improve the accuracy of the measurement and to exam me the effect of acoustic impedance of wall material on the measurement by an ultrasonic technique, two different stand-off rods, one made of stainless steel and the other polyacrylate, were used in the liquid-film thickness measurement. These experimental results are discussed and compared with the actual film thicknesses.

• Journal of Digital Convergence
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• v.20 no.4
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• pp.411-418
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• 2022

The purpose of this study is to investigate the relationship between sleep time and pulse pressure in Korean adults, and the research method used data from the 7th period (2016-2018) of the National Health and Nutrition Examination Survey. Subjects were 5,707 persons aged 20 years or older, and for frequency and percentage continuous data, mean and standard deviation, cross analysis and independent t-test, and stepwise logistic regression analysis for high pulse pressure were performed. SPSS WIN 18.0 version statistical program was used. was used. As a result of the study, the prevalence of hypertension was higher in the overall population (OR=1.344, 95% CI=1.002-1.803) and in women (OR=1.624, 95% CI=1.112-2.371) when sleeping for more than 9 hours compared to less than 6 hours. high, but not significant in males (OR=1.012, 95% CI=0.631-1.550). Therefore, considering the effects of inappropriate sleep time on health, public health education and management are necessary. Further research on the relationship between sleep time and pulse pressure will be needed.

• Journal of the Korean Geotechnical Society
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• v.25 no.7
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• pp.5-10
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• 2009

The ground anchor is not usually used in soft clay and loose sand, because the pullout resistance of anchors can not be guaranteed. However, there is a method to increase the capacity of anchors using electric discharge geotechnical technologies, which are also known as pulse discharge and electric-spark technologies. The pulse-discharge anchor has a bulbed (or underreamed) bond length that is expanded by high voltage electrokinetic pulse energy. 24 anchors were installed in the weathered soil and sandy clay at the Geotechnical Experimentation Site at Sungkyunkwan University in Suwon, Korea. In this study, in order to define a relation between expansion rate of the anchor diameter and ultimate load, anchor load tests were carried out in accordance with testing procedures by AASHTO (AASHTO 1990) and FHWA (Weatheb 1998). And then several anchors were exhumed to measure the diameter of the pulse discharge anchors.