• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.4
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• pp.180-184
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• 2001

The high operation frequency mainly reduces transformer volume in the power supply. A high frequency and high voltage pulse transformer is designed, fabricated, and tested. Switching frequency of the transformer is 100 kHz. Input and output voltages of the transformer are 250 V and 4 kV, respectively. Normal operation power of the transformer is 3 kW. Maximum volume of the transformer is 400 $cm^3$. The power density is thus 7.5 W/$cm^3$. The transformer will be installed in a metal box that has nominal operation temperature of 85 degree centigrade. The transformer and other high voltage components in the box will be molded with Silicon RTV(Room Temperature Vulcaniza) that has a very low thermal conductivity. Procedure of design and test results are discussed. Analytical as well as experimental results of varous paramters such as transformer loss, leakage inductance, distributed capacitance are also discussed. In addition, thermal analysis results from ANSYS code for three different operation conditions are discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.139-140
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• 2015

The purpose of this study was to evaluate existing compressive strength equation with concrete exposed to high temperature by ultrasonic pulse velocity. As the result, original compressive strength equation is proper only for compressive strength of normal concrete. Therefore, an accumulation of experimental database of concrete exposed to high temperature is necessary for proposal of new compressive strength equation.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.4
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• pp.307-311
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• 2017

Ultra short pulse laser processing with the PI (polyimide) substrate is conducted to increase flexibility and radius of curvatures. A femtosecond laser is used to perform micro machining by minimizing the heat effect in PI substrate. The laser processing according to the parameters, such as fabricated line width, depth, laser power, distance between lines, is carried out to understand the characteristics of fabricated lines. A bending test is carried out to evaluate bending shapes and the radius of curvature after bending and spreading it 1000 times. The results demonstrates that the radius of curvature decreases in deepen lines and increases with the augment of the number of the fabricated lines, and distance between lines.

• Journal of Power System Engineering
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• v.13 no.6
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• pp.57-62
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• 2009

Unsteady flows in a semi-induction system was investigated to verify their characteristics. A semi-induction system was designed and made to verify the Sow characteristics in an intake system. To attain an intact wave of an intake pulse, a single semi-intake system was adopted as a test rig. The system consists of an intake pipe and a rotary valve as a pulse generator, and a variable volume Helmholtz resonator. The variable volume Helmholtz resonator was mounted in the intake pipe to enhance a breathing capacity and engine performance. The phase and amplitude of the pulsating flow in an unsteady flow system were found to affect the charging capacity significantly. The behavior of pressure wave, their phase and amplitude were investigated in various regions. Some of the results obtained from experiments were described.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.694-700
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• 2013

The design of the exhaust manifold for the pulse converters of a 4 strokes high power medium-speed diesel engine is presented in terms of fatigue analysis. The said system undergoes thermal expansion due to high temperature of exhaust gas and is exposed to intrinsic vibration of the internal combustion engine. Moreover, the exhaust pulse generates pressure pulsating along the runner inside manifold. Under such circumstances, the design and construction of exhaust manifold must be carried out in a way to prevent early failure due to fracture. To validate the design concept, a test rig was developed to simulate the combination of thermal and vibrational movements, simultaneously. Experimental results showed that a certain sense of reliability can be achieved by considering a field factor obtained from the results of engine bench tests.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.568-572
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• 2000

This paper describes the experimental results of a transient impedance characteristics of grounding rods to a square pulse and standard lightning impulse current. The test were performed on single grounding rod($\phi$ 10mm, 1m) and triple-grounding rods( $\phi$ 10mm, 1m) of equilateral triangles with 5m spacing. For measurements of transient impedance, a pulse generator which can produce square wave of 30ns rise time and 20U Pulse duration was designed and fabricated. In the experiment, transient impedance of the grounding systems have been investigated from the recorded potential and current waveforms. The results showed that the value of the transient impedance is quite higher than the stationary resistance, and provide useful information for the value of a grounding system considered transient characteristics under a high frequency condition such as lightning stokes and ground-fault.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1482-1485
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• 2004

Electrostatic Precipitators have been used widely in industry, and play an important role in environmental protection. Electrostatic Precipitators (ESP) can be operated with a high collection efficiency and low pressure drop. Pulse energization is a technique to cope with high resistivity dust, and this results in lower power consumption. In this paper, Pulse energization ESP to use subway station air clean in subway station, design and test a pulse power supply for ESP.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.2
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• pp.131-134
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• 2008

Purpose: The objective of this study was to evaluate the clinical parameters in terms of the midazolam sedation in patients undergoing dental practice. Patients and Methods: Total 28 patients were included in this study. They received the dental practice in the daycare center and sedation was done with midazolam. The recorded variables were blood pressure, pulse rate, $SpO_2$, and patient's response. The differences between observations were analyzed with paired samples t-test. Results: The blood pressure was significantly decreased after the administration of midazolam and the systolic pressure was significantly increased at the start of operation (P<0.05). The pulse rate was significantly increased after lidocaine injection (P<0.001). The amnesic effect was shown 21 cases out of 28 cases (75%). Conclusions: The effect of midazolam on pulse rate was not significant. However, midazolam could decrease the blood pressure significantly. Therefore, the sedation with midazolam could be successfully used in the dental practice, particularly for the patients having the hypertension.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.110-115
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• 1998

An axisymmetric Navier-Stokes procedure has been developed to analyze the pulse jet flow in a ceramic filter unit for the dust dislodging process. Using Baldwin-Lomax turbulence model as a closure relationship, the SIAF(Scalar Implicit Approximate Factorization) algorithm together with the ${\delta}^k-Correction$ iterative time marching scheme is adopted to solve the unsteady compressible Navier-Stokes equations. After some validation tests, the code has been applied to solve the pulse jet flow and examine the effects of geometry and reservoir pressure condition on the pressure level inside the filter unit. To avoid dealing with the uncertainty of such factors as the cohesion of the collected dust and the adhesion of the dust to the medium and also to simplify the analysis, the filter wall is assumed to be impermeable. The results for various test cases are presented.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2186-2188
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• 1999

A high frequency and energy density pulse transformer is a critical component of a high voltage power supply in a traveling wave tube (TWT) amplifier system. In this paper, processes of design, manufacturing, and test of the transformer are discussed. Primary voltage of the transformer is 240 V. The transformer secondary have two outputs which are 4100 V (Helix) and 2050 V (Collector). Total output power is 860 W. Normal operating frequency of the transformer is 10 kHz. In high energy density pulse transformers, temperature rise is a main problem during its operation. From our study, it was found that resonant current due to leakage inductance and stray capacitance was the main cause of temperature rise. This happens because of the inherently high turn-ratio in high voltage transformers. Solutions to reduce stray components are presented.