• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.138-143
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• 2017

A performance analysis for a pulsed plasma thruster(PPT) has been conducted to predict the thrust and current change. Two models were implemented - a one-dimensional lumped circuit analysis model and the Teflon ablation model provided by Michael Keidar. The circuit model incorporating resistance and inductance models was adapted to predict the magnitude of the discharge current. Numerical simulations like current discharge rates with different voltages were reasonably well compared with experimental data. The effects of Teflon ablation on thruster characteristics were investigated.

• Journal of Magnetics
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• 제17권4호
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• pp.298-301
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• 2012

In order to know the effect of surface irregularity in the detection of local wall thinning of pipeline using pulsed eddy current (PEC), the lift-off effects on PEC signal have been investigated. Three kinds of parameters in the PEC signal, which is "peak amplitude", "time to peak amplitude" and "time to zero crossing" are analyzed to separate the lift-off effects in the PEC signal. The distance from sensor to the bottom of sample which is the total thickness of combined insulator and sample is kept constant. The magnitude of the differential peak amplitude is increased with increasing sample thickness, the time to peak amplitude is increased with increasing the sample thickness. To determine the effect of lift-off, a number of balanced transient responses combining wall thinning locations and lift-off distances were plotted.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1900-1902
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• 1997

In order to obtain various waveforms of current pulse applied at the flashlamp, we have fabricated a Pulsed Nd:YAG laser by PFN with multiple-mesh formed LC network. we have obtained various waveforms of current pulse by adjusting the values of L and C, compared these waveforms of current pulse with laser beam, and then analyzed the laser output energy. We have got relations for $E_{TH}$ and $E_L$ at each mesh which supplies energy with flashlamp and found that output of Pulsed Nd:YAG Laser for 2-mesh, 5-mesh coincided with computer's simulation, PSPICE.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.2089-2091
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• 2000

Pulsed power systems consist of a capacitor bank, an isolated high-voltage charging power-supply, high-current bus-work for charging and discharging and a control system. In such pulsed power systems, the operating-lifetime of the capacitors is closely dependent on the voltage reversal. Hence, most capacitor-discharging systems includes crowbar circuits. The crowbar circuit prevents the capacitor recharging with reverse voltage. Usually it consists of crowbar resistors and high pulse-current diode-stacks connected in series. The requirements for the diode-stacks are fast-recovery time and high-voltage and large-current ratings, which results in the high cost of the pulsed-power system. This paper presents a protection scheme of a charging and discharging system of a 500kJ capacitor bank using a low-cost crowbar circuit and safety-fuses.

• 한국전문물리치료학회지
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• 제1권1호
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• pp.61-66
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• 1994

The purpose of this study was to investigate the effect of a single treatment o voltage pulsed current (HVPC) on edema reduction. Hind limbs of 23 anesthetized were injured by dropping a 400 g weight onto the plantar aspects of the feet. On limb of each frog was randomly selected to receive 30 minutes of continuous, 12 cathodal HVPC at voltages 10 % less than motor threshold levels. Limb volumes measured by water displacement before trauma and at predetermined intervals hours posttrauma. Sources of significant differences were determined by t-test HVPC significantly (p<0.05) reduced edema formation. We hypothesize that HVP also be effective in controlling edema formation after impact injuries in humans.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.272-273
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• 2006

A new process of pulsed electric current sintering was developed. It combines compaction with activated sintering effectively and can manufacture bulky nano-crystalline materials very quickly. A nano-structured steel is obtained with high relative density and hardness by this process. The average grain size of iron matrix is 58nm and the carbide particulate size is less than 100 nm. The densification temperature of ball-milled powders is approximately $200^{\circ}C$ lower than that of blended powders. When the sintering temperature increases, the density of as-sintered specimen increases but the hardness of as-sintered specimen first increases and then decreases.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.621-622
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• 2006

In this paper, we show some experimental results of binder-free WC sintered by Pulsed Electric Current Sintering (PECS) also known as Field Assisted Sintering Technology (FAST). These binder-free WC have extremely hardness and stiffness. However, these mechanical properties are dependent on the sintering condition, e.g., maximum temperature, applied pressure, etc. We show some relationship between mechanical properties and sintering condition to improve to sinter the binder-free WC.

• International Journal of Korean Welding Society
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• 제3권1호
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• pp.29-33
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• 2003

The ferritic stainless steels are generally considered to have poor weldability compared with that of the austenitic stainless steels. However the primary advantages of ferritic stainless steels include lower material cost than the more commonly used austenitic stainless steels and a greater resistance to stress corrosion cracking. Thus, the weldability of ferritic stainless steels was investigated in this study. In concerning the weldability, Grain size measurement test, Erichsen test and Varestraint test were involved. full penetration welds were produced by autogeneous direct current straight polarity (DCSP) and pulsed currents gas tungsten arc welding (GIAW) and the effect of pulsed currents welding on the welds was compared to that of DCSP welding. The results showed that pulsed current was effective to refine grain size in the weld metal and the finest grain size was obtained at the frequency of 150Hz. In addition, the ductility of welds was lower than that of base metal. Finally, autogeneous type 444 welds were less susceptible to macro solidification cracks, but more sensitive to micro cracks; SEM/EDS analysis indicated that all the inclusions in the crack showed enrichment of Mn, Si, O and S.

• Korean Circulation Journal
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• 제53권5호
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• pp.273-293
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• 2023

Pulsed field ablation (PFA) was recently rediscovered as an emerging treatment modality for the ablation of cardiac arrhythmias. Ultra-short high voltage pulses are leading to irreversible electroporation of cardiac cells subsequently resulting in cell death. Current literature of PFA for pulmonary vein isolation (PVI) consistently reported excellent acute and long-term efficacy along with a very low adverse event rate. The undeniable benefit of the novel ablation technique is that cardiac cells are more susceptible to electrical fields whereas surrounding structures such as the pulmonary veins, the phrenic nerve or the esophagus are not, or if at all, minimally affected, which results in a favorable safety profile that is expected to be superior to the current standard of care without compromising efficacy. Nevertheless, the exact mechanisms of electroporation are not yet entirely understood on a cellular basis and pulsed electrical field protocols of different manufactures are not comparable among one another and require their own validation for each indication. Importantly, randomized controlled trials and comparative data to current standard of care modalities, such as radiofrequency- or cryoballoon ablation, are still missing. This review focuses on the "pearls" and "pitfalls" of PFA, a technology that has the potential to become the future leading energy source for PVI and beyond.

• 비파괴검사학회지
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• 제36권6호
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• pp.490-495
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• 2016

펄스와전류탐상에서 탐상 신호는 주로 센서코일에 유도되는 기전력의 시간에 따른 변화를 측정하여 사용되었는데, 최근에는 홀센서(Hall sensor)로 측정한 신호를 사용하는 경우도 많아지고 있다. 본 논문에서는 펄스와전류탐상에서 나타나는 홀센서 신호를 수치적으로 모델링하여 예측하였다. 이를 위해 두께 측정을 위한 탐촉자를 설계하고 먼저 계단입력전류를 사용한 수치해석을 수행하여 홀센서를 사용하였을 경우의 신호를 예측하였다. 또한, 코일을 센서로 사용하였을 경우의 신호도 동시에 계산하였다. 수치모델링 결과로 예측된 홀센서 신호들은 실험 연구를 통해 보고된 신호들과 유사한 형태를 가지고 있음을 확인할 수 있었다. 그리고 피검사체의 두께 변화에 따른 두 신호들의 특성을 분석하고 비교해 본 결과, 홀센서 신호에서는 코일센서 신호에 비해 두께 변화를 판별하기 위한 정보가 더 적게 제공된다는 것을 알 수 있었다. 펄스입력전류를 사용한 경우의 탐상 신호들도 계산해 본 결과, 두 신호 모두 사용된 펄스의 폭이 지난 시간에는 계단입력전류를 사용한 경우의 응답이 반대가 되어 감소하는 형태로 나타난다는 것을 확인할 수 있었다.