• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.194-197
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• 2005

Pulse-mode performance evaluation is made for a set of monopropellant hydrazine thrusters producing $0.95 lb_{f}$ of nominal steady-state thrust at an inlet pressure of 350 psia. With a brief description on the hot-firing test matrix, a typical data obtained from pulse-mode firing is given directly showing the variational behavior of propellant supply pressure, vacuum condition, and thrust, in addition to the thermal response of the thruster. The performance features are successfully compared to the reference criteria of 1-lbf standard monopropellant rocket engine.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.719-720
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• 2004

A multi-megawatt long pulse ion source (LPIS) of neutral beam injector was developed for the KSTAR. Beam extraction experiments of the LPIS were carried out at the neutral beam test stand (NBTS). Design requirements for the ion source were 120 kV/65 A deuterium beam and a 300 s pulse length. A maximum ion density of $9.1310^{11}$ $cm^{-3}$ was measured by using electric probes, and an optimum arc efficiency of 0.46 A/kW was estimated with ion saturation current of the probes, arc power, and total beam area. An arcing problem, caused by the structural defect of decelerating grid supporter, in the third gap was solved by the blocking of backstream ion particles, originated from the plasma in the neutralizer duct, through the unnecessary spaces on the side of grid supporter. A maximum drain power of 1.5 MW (i.e. 70 kV/21 A) with hydrogen was measured for a pulse duration of 0.5 s. Optimum beam perveance was ranged from 0.75 to 0.85. An improved design of accelerator for the effective control of beam particle trajectory should provide higher beam perveance.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.5
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• pp.703-711
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• 2013

In this paper, we have proposed high power generator with Induction Voltage Adder of three cells. IVA which has n cells can generate n-th times high power pulse, is a more stable system than Marx generator in the view of breakdown. We applied amorphous metal magnetic cores as an energy storing material for IVA rather than ferrite cores because of their higher magnetic flux swing to make it more compact system and the loss of it was also considered in the design. For driving the IVA, we design Blumlein pulse generators which are filled with pure water for high dielectric constant and high breakdown field strength, and triggered by single Marx generator. We have presented the PSPICE simulation and its test result.

• Korean Journal of Clinical Laboratory Science
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• v.47 no.1
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• pp.28-34
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• 2015

Pulse wave velocity (PWV) is used to non-invasively estimate the severity of arteriosclerosis by measuring arterial stiffness. Increased arterial stiffness measured by PWV stands for progressive arteriosclerosis and is caused by atherosclerotic risk factors. This study is focused on how brachial-ankle pulse wave velocity (baPWV) is related to the leading risk factors for arteriosclerosis or atherosclerosis. Subjects were 114, 69 males and 45 females who are in 60's and had baPWV test for acute stroke. The results are as follows: the group with increased arterial stiffness showed significant increase in HbA1c, total cholesterol, BSBP (brachial artery systolic blood pressure), BDBP (brachial artery diastolic blood pressure), CSBP (central artery systolic blood pressure), CDBP (central artery diastolic blood pressure), augmentation index (AIx) and diabetes mellitus. Correlation analysis between baPWV and atherosclerotic risk factor showed significant relationship in age, HbA1c, LDL cholesterol, BSBP, BDBP, CSBP, CDBP and augmentation index. baPWV was independently related to age and BSBP in multiple linear regression analysis. The group with increased arterial stiffness was independently related to BDBP in multiple logistic regression analysis. This study might be meaningful in evaluating the relationship between arterial stiffness and atherosclerotic risk factor in a new way, and be helped to make various studies for cardiovascular disease.

• Journal of Adhesion and Interface
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• v.7 no.4
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• pp.10-12
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• 2006

The successful use of adhesively bonded parts depends on the defect-free bond of the components. Therefore it is necessary to detect relevant faults and defects in an early state of the production. A 100% test should be pursued, but especially at complicated structures the detection of defects is not easy. Possible testing methods, which show a high potential for the NDT of adhesively bonded parts, are thermography based NDT methods. At present mainly two different procedures of active thermography are being used: Pulse and Lock-In Thermography. With pulse thermography the examined material is warmed up with a short energy pulse (light, eddy current or ultrasonic pulse) and the heat response is recorded after a certain time. The result is an infrared image which indicates material defects in different depths. This paper presents a variety of images showing the capability of Lock-In Thermography to image subsurface defects. Several examples of adhesives joints qualify the ultrasonic Lock-In-Thermography for the in-process quality control for adhesive bonded components.

• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.731-740
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• 2011

An acoustic velocity profiler is developed, which is able to be used for open-channel flow measurement. It measures flow velocity based Doppler effect on acoustic signals, which is estimated by using pulse repetition frequency technique. Laboratory and field tests were made to verify velocity measuring performance of the developed device. It is confirmed that the acoustic velocity profiler can normally measure vertical velocity profile in the range above 0.1 m from the bottom and has equivalent performance to commercial acoustic velocity measuring devices.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2163-2170
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• 2012

A signal receiving system can measure and analyze frequency, pulse modulation, scan modulation, frequency modulation on pulse, phase modulation on pulse of RF signal. A signal receiving system should be verified under simulated RF signal environment prior to verification on operation in fields. This paper describes an effective method to generate simulated RF signals with considering operational scenario. The simulated RF signal generator can be effectively used to evaluate the performance of the signal receiver and reduce the test cost of the signal receiver.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1864-1866
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• 1996

Grounding is the art of making an electrical connection to the earth. In order to protect man, electrical and/or electric equipments from the lightning strokes, all the energy of lightning strokes must be diverted via a safe path to earth. It is essential to the transient grounding resistance against lightning strokes. In this paper, measurements and analyses of grounding surge impedance have been investigated. For measurements of grounding surge impedance the pulse generator was designed and fabricated. The pulse generator has rise time of 22.4 ns and pulse duration of $8\;{\mu}s$. The transient grounding resistance has been measuring by injecting low power and step current between the earthing system under test and a remote reference earth and measuring the potential rise caused by this current. As a result, the transient grounding resistance against lightning surge in the short time domain is much higher than steady state grounding resistance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2189-2195
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• 2007

In this paper, we propose a newly developed selective reset waveform of a ac PDP using the wide erase pulse technique with the control of address bias voltage. Although it is generally understood that the wide pulse erasing methode shows the narrow driving margin in an opposite discharge type ac PDP, we could obtain a moderate driving margin in a 3-electrode surface discharge type ac PDP. The obtained driving margin shows a strong dependency on the sustain voltage and the address bias voltage. The lower the sustain and the address bias voltage, the wider the driving margin. The pulse width of the proposed waveform is only $10{\mu}s$, which gives additional time to the sustain period, hence increases the brightness. The brightness and contrast ratio increase about 20% together comparing to the conventional ramp type selective reset waveform with the driving scheme of 10 subfield ADS method. The driving margin was measured with the line by line addressed pattern on the white test panel of 2inch diagonal size and the discharge gas was Ne+Xe4%, 400torr.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1762-1764
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• 2016

A pulse radar signal is characterized by periodic pulses and noise components between them. In this Letter, we present a test statistic for detecting the presence of a pulse radar which exploits the inherent characteristics of a pulse radar signal by the ratio of maximum power to minimum power from the received signal and compares its sensing performance with that of the energy detector by computer simulation in a variety of situations.