• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.786-791
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• 2013

A high voltage pulse generator based on the Blumlein pulse forming line (PFL) was fabricated to produce a voltage pulse whose peak value is ~300 kV and pulse duration is ~50 ns. Three cylindrical electrodes, such as inner, middle, and outer electrodes, are concentrically placed to make a compact PFL. To increase the pulse duration of the output pulse without any change of the size of the generator, the middle electrode is replaced by a helical strip electrode. To determine the radius of the helical electrode, the impedance of the helical Blumlein PFL is calculated using an approximate formula where the dispersive property of the helical Blumlein PFL is not considered. The dependence of the impedance on the frequency is computed by a commercial program. The number of turns in the helical electrode is decided to provide a demanded pulse duration. The experimental result shows that the helical Blumlein PFL is capable of making a high voltage pulse of ~50 ns pulse duration.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.809-815
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• 1998

This study has been performed to investigate MRR(metal removal rate) surface roughness with various pulse-on duration using the copper and graphite electrode according to the electrode size on the heat treated STD 11 which is extensively used for metallic molding steel in the EDM. The results obtained are as follow ;a)MRR increases a lot when pulse-on duration is 100 $\mu{s}$ or less but MRR has little difference with pulse-on duration of 100 $\mu{s}$ or more b) According to the increase of Pulse-on duration the large the electrode size the more MRR c) Safe discharge is needed to make maximum of MRR and the metallic organization must be complicated for discharge induction. d) Actual machining time is longer than theoretical machining time at the short pulse-on duration because of skin effect of current. e) Graphite electrode needs the larger electric discharge energy than copper electrode to remove remained chips completely.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.10
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• pp.458-463
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• 2006

The purpose of this work is to investigate the fundamental properties of the gradual muscle force potentiation. We investigated the dependence of force potentiation on both the pulse-amplitude and the pulse-duration with different ramp-up time. The experimental results showed that the force increment ratio (FIR) during constant electrical stimulation decreased with pulse-amplitude and also with pulse-duration. The FIR was greater with short ramp-up time in both the pulse-amplitude and pulse-width modulation. The feasible mechanism might be that the myosin light chain phosphorylation induces the force potentiation and it occurs only in the fast type muscle fibers which are recruited first. These observations indicate that muscle potentiation must be understood well for the accurate control of muscle force.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2155-2156
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• 2006

The purpose of this work is to investigate the fundamental properties of the gradual muscle force potentiation for the prediction of muscle force and body movement from the stimulation input with musculo-skeletal model. We investigated the dependence of force potentiation on both the pulse-amplitude and the pulse-duration. The experimental result showed that the force increment ratio during electrical stimulation decreased with pulse-amplitude. The force increment ratio decreased with short pulse-duration and was maintained to be constant with pulse-duration longer than $500{\mu}s$. A new model of the muscle potentiation based on these results is desired in the future.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.53-59
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• 1997

This study has been performed to inmvestigate MRR(metal removal rate), REW(relative electrode wear), surface roughness, heat transumutation layer and microhardness distribution in cross-section of the machined surface with various pulse-on duration and peak pulse current, using the copper and graphite electrode on the heat treated STD11 which is extensively used for metallic molding steel with the EDM. The results obtained are as follows; a) There exists critical pulse-on duration(If Ip equals 5A, .tau. on is 50 .mu. s) which shows the the maximum MRR in accordance with peak oulse current and the MRR decreases when the pulse-on duration exceeds the critical pulse-on during because of the abnormal electric discharge. b) Safe discharge is needed to make maximum of MRR and the metalic organization must be complicated for discharge induction. c) Graphite has much more benefits than copper electrode when rapid machining is done without electrode wear. d) The most external surface has the highest microhardness because of car- burizing from heat analysis of the dielectric fluid and the lower layar of the white covered layer has lower microhar dness than base matal because of softening.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.513-518
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• 2001

[ $Al_[2}O_{3}$ ] ceramics are generally used as components in processing equipment, devices or machinery. But it's difficult to machining as being machanical because $Al_[2}O_{3}$ ceramics are brittle materials. This study described a basic study of the input parameters effect on the dimension of the microhole at the $Al_[2}O_{3}$ ceramics using Nd:YAG laser. Major input parameters are peak power, pulse frequency and pulse duration in the laser microhole machining of $Al_[2}O_{3}$ ceramics. We will get a smaller microhole and diameter rate by an appropriate peak power, pulse duration.

• Journal of Biomedical Engineering Research
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• v.36 no.5
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• pp.191-197
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• 2015

Laser acupuncture is defined as the stimulation of traditional acupuncture points with low-intensity, nonthermal laser irradiation. Possible advantages in using laser acupuncture are the noninvasive, painless and low risks of infection treatment. The purpose of this study is to assess the effect of laser acupuncture on the quality and waveform of arterial pulses. Ten acupuncture points were stimulated repeatedly three times in 30 individuals by laser with emission in the near infrared spectral region (808 nm) using an out power and power density of 45 mW and $143W/cm^2$. The analysis of pulse quality and waveform was performed based on the measurement of arterial pressure of the left and right wrist, using a 3-dimensional blood pressure pulse analyzer. Excess-like pulse quality of subjects before laser acupuncture changed significantly to balanced pulse quality after 10, 20, and 30 minutes of laser acupuncture; coefficient of deficient or excess, $C_{DE}$, decreased significantly from 0.68 before acupuncture to 0.61, 0.55, and 0.55 after 10, 20, 30 minutes of laser acupuncture ($$p{\leq_-}0.006$$), respectively. Other pulse qualities, floating or sinking, slow or rapid, choppy or slippery did not change significantly by laser acupuncture (p > 0.05). Pulse waveform analysis showed that amplitude of main peak (systolic function or aortic compliance, $h_1$) of left and right artery pulse waves decreased significantly after 10, 20, and 30 minutes of laser acupuncture (p < 0.05). Other parameters, duration of one cardiac cycle (T), duration of rapid systolic ejection ($T_1$), duration of the systolic phase ($T_4$), and duration of the diastolic phase ($T_5$) of left and right artery pulses did not change significantly after laser acupuncture (p > 0.05).

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.329-333
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• 2001

The pulsed poser system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNox/DeSOx power system, ozon generator, etc. A pulse energy efficiency for load depends on the rising time, peak value, pulse duration and impedance matching, etc. The pulse generator generally required for short pusle duration and high peak value was forced to consider its volume and economy. In this study, developing a compact pulse generator that applied for cascading method to be made of two pulse transformers, we compared cascading voltage with non cascading one by applying the pulse energy to load. Adopting cascading technique to pulse transformer, we found that average cascading voltage was about 60[%] of theoretical value. Maximum cascading ratio was calculated at 60 times compared with non cascading voltage.

• International Journal of Aerospace System Engineering
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• v.2 no.1
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• pp.58-61
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• 2015

Under the background of combustion instability in solid rocket motor, to study the relationship between pressure oscillations and dynamic process of propellant flames, it is necessary to simulate an oscillation environment with certain frequency, amplitude and duration. This paper presents an experimental installation of pressure oscillation based on pulse-driving technique, with which pressure oscillations features under different pulse-driving conditions were compared and analyzed. For the pulse-driver applied in this paper, a pressure oscillation with 0.15s-0.5s duration, 179Hz-210Hz first order frequency, 0.04MPa-0.35MPa amplitude is simulated. The test results show that an oscillation with higher frequency and lager amplitude can be obtained when pulse-driver is installed on the top of the installation cavity, while on the side, an oscillation with a longer duration and approximate cavity natural frequency can be simulated.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1475-1484
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• 2003

The EDM processing characteristics of one of the nickel-based heat resistant alloys, Hastelloy- X, were investigated under the various EDM conditions and analyzed in terms of surface integrity. This alloy is commonly used as a material for the hot gas path component of gas turbines and it is difficult to machine by conventional machining methods. The primary EDM parameter which was varied in this study were the pulse-on time. Since the pulse-on time is one of the main factors that determines the intensity of the electrical discharge energy, it was expected that the machining ratio and the surface integrity of the specimens would be proportionally dependent on the pulse-on duration. However, experimental results showed that MRR (material removal rate) and EWR (electrode wear rate) behaved nonlinearly with respect to the pulse duration, whereas the morphological and metallurgical features showed rather a constant trend of change by the pulse duration. In addition the heat treating process affected the recast layer and HAZ to be recrystallized but softening occurred in recast layer only. A metallurgical evaluation of the microstructure for the altered material zone was also conducted.