• Title, Summary, Keyword: pulsed electric current

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Fabrication of tungsten carbide by pulsed electric current heating (펄스통전가열에 의한 텅스텐 탄화물의 제조)

  • Hong, Seong-Hyeon;Kim, Hyun-Jin
    • Particle and aerosol research
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    • v.5 no.4
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    • pp.153-158
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    • 2009
  • Tungsten carbide powder was fabricated with carbothermal reaction by pulsed electric current flowing in compact of tunsten oxide and carbon. The mixed powder of tunsten oxide and carbon was ball-milled into ultrafine powders. The mixed powder of tungsten oxide and carbon was put into carbon mold and heat-treated at $1050{\sim}1200^{\circ}C$ by pulsed electric current flowing. The formation of tungsten carbide powder could be achieved by heat treatment at $1200^{\circ}C$ for 10 minitues.

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Application of a Pulse Electric Field to Cross-flow Ultrafiltration of Protein Solution

  • Kim, Hyong-Ryul;Lee, Kisay
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.4 no.1
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    • pp.46-50
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    • 1999
  • The application of pulsed electric field was investigated in the crossflow ultrafiltration of BSA (bovine serum albumn) to economize the application time of electric current as well as to avoid inherent problems of long-term application of electric field. During the application of various cyclic patterns of pulsed electric current, the averaged filtration flowrate and the degree of concentration were maintained higher than those obtained in the absence of electric current application. The temperature increase, pH change, and BSA loss by electrodeposition were all negligible during the operation. The averaged filtration flowrate increased as the ON/OFF duration ratio of electric current was higher and as the period of ON/OFF cycle was shorter. The re-establishment of concentration polarization was dependent to the duration of current OFF state and, therefore, a longer duration of OFF state was not favorable in maintaining higher filtration flow rate. Although the averaged filtration flowrate was enhanced as the magnitude of electric current increased, the flowrate enhancement became smaller as the magnitude of current value above which the degree of electrokinetic depolarization is no further improved.

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Application Technologies of Pulsed Power with the High Voltage and Current (고전압.대전류 pulsed power의 이용기술)

  • Lee, Hyeong-Ho;Kim, Young-Bae
    • Proceedings of the KIEE Conference
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    • pp.1678-1680
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    • 1997
  • The pulsed power with the high voltage and current can be used to the fields of high speed pulses of energy in different forms such as electric current and voltage, electron beam, ion beam, x-rays, gamma rays, heat, magnetics fields, sound and shock waves. This paper is directed mainly at electrical engineers working on production and practical application of high speed pulsed power with high voltage and current.

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In Situ Observations of Sintering Process during Pulsed Current Sintering of $Al_2O_3$, ZnO and WC ALLOY

  • Kawakami, Yuji;Tamai, Fujio;Enjoji, Takashi;Shikatani, Noboru;Misawa, Tatsuya;Otsu, Masaaki;Takashima, Kazuki
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.810-811
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    • 2006
  • Pulsed Current Sintering (PCS) process possesses some problems that need to be resolved. We, therefore aims at understanding phenomena of PCS process by presenting some basic data on in situ sintering behavior of PCS. Special graphite mold equipped with thermo couple and electrodes were designed to measure the temperature, electric current and voltage inside the powder during PCS process. We apply three types of raw materials, especially for ZnO as semiconductor, $Al_2O_3$ as non-conductor and WC as good conductor. The electric current and voltage were measured for each powder during PCS process. In addition, their electric resistance properties were calculated.

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Pulsed Electric Current Sintering of Nano-crystalline Iron-base Powders

  • Li, Yuanyuan;Long, Yan;Li, Xiaoqiang;Liu, Yunzhong
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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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.

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Inactivation of Listeria monocytogenes in Brine and Saline by Alternating High-Voltage Pulsed Current

  • Lee, Mi-Hee;Han, Dong-Wook;Woo, Yeon-I.;Uzawa, Masakazu;Park, Jong-Chul
    • Journal of Microbiology and Biotechnology
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    • v.18 no.7
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    • pp.1274-1277
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    • 2008
  • The inactivating efficiency of alternating high-voltage pulsed (AHVP) current was investigated in brine (20 w/v% NaCl) and saline (0.9 w/v% NaCl) inoculated with $1\times10^7$ cells/ml of Listeria monocytogenes. AHVP current at 12 V with 1 pulse completely inactivated L. monocytogenes in brine within 3 ms, while the bacteria in saline were fully inactivated by 10-pulsed electric treatment at 12 V within the same time. Electron microscopic observation demonstrated substantial structural damage of electrically treated L. monocytogenes in brine. These results suggest that AHVP treatment would be effective for the rapid and complete inactivation of L. monocytogenes in brine or saline solution.

Effects of GTAW Pulse Condition on Penetration, Discoloration and Bending Property for Titanium Tube (GTAW 펄스 용접 조건에 따른 타이타늄 정밀관의 용입, 변색 및 굽힘특성)

  • Min, Seonghwan;An, Sungyong;Park, Jitae;Park, Youngdo;Kang, Namhyun
    • Journal of Welding and Joining
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    • v.32 no.6
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    • pp.47-55
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    • 2014
  • The purpose of the study is to produce a mechanically improved weld and minimum variation of color through comparing unpulsed and pulsed GTAW (Gas Tungsten Arc Welding) for pure titanium (CP grade7) tube. Pulsed GTAW using 60 A peak current and 20 A background current (1:9) achieved the wider window of welding conditions having part and full penetration without burn-through than the case of unpulsed GTAW. Moreover, the pulsed welding reduced a discoloration on the back bead of the weld and the size of microstructures (basket weave and serrated ${\alpha}$). That is because the pulsed welding has it's a low heat input and severe weld flow induced from electric current variation. Furthermore, the pulsed welding improved the bending property of the welded Ti tube. The enhanced bending property for the pulsed GTAW was due to the insignificant discoloration on the weld surface with maintaining the metal polish.

Pulsed Magnetron Sputtering Deposit ion of DLC Films Part I : Low-Voltage Bias-Assisted Deposition

  • Oskomov, Konstantin V.;Chun, Hui-Gon;You, Yong-Zoo;Lee, Jing-Hyuk;Kim, Kwang-Bok;Cho, Tong-Yul;Sochogov, Nikolay S.;Zakharov, Alexender N.
    • Journal of the Korean institute of surface engineering
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    • v.36 no.1
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    • pp.27-33
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    • 2003
  • Pulsed magnetron sputtering of graphite target was employed for deposition of diamond-like carbon (DLC) films. Time-resolved probe measurements of magnetron discharge plasma have been performed. It was shown that the pulsed magnetron discharge plasma density ($∼10^{17}$ $m^{-3}$ ) is close to that of vacuum arc cathode sputtering of graphite. Raman spectroscopy was sed to examine DLC films produced at low ( $U_{sub}$ / < 1 kV) pulsed bias voltages applied to the substrate. It has been shown that maximum content of diamond-like carbon in the coating (50-60%) is achieved at energy per deposited carbon atom of $E_{c}$ =100 eV. In spite of rather high percentage of $sp^3$-bonded carbon atoms and good scratch-resistance, the films showed poor adhesion because of absence of ion mixing between the film and the substrates. Electric breakdowns occurring during the deposition of the insulating DLC film also thought to decrease its adhesion.

Effect of Low Intensity Pulsed Electric Field on Ethanol Fermentation and Chemical Component Variation in a Winemaking Culture

  • Min, He-Ryeon;Jeon, Bo-Young;Seo, Ha-Na;Kim, Min-Ju;Kim, Jun-Cheol;Kim, Joon-Kuk;Park, Doo-Hyun
    • Food Science and Biotechnology
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    • v.18 no.6
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    • pp.1358-1364
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    • 2009
  • Electric polarity of working electrode and counter electrode was periodically switched at the intervals of 30 sec. Electric current generated by anodic and cathodic reaction of working electrode was reached to +30 and -12 mA in low intensity pulsed electric field (LIPEF). The yeast growth, ethanol production, and malate consumption in the initial cultivation time were more activated in the LIPEF than the conventional condition (CC). Polyphenol, total phenolic contents (TPC), and total flavonols (TF) were gradually decreased in all cultivation conditions during incubation for 2 weeks but antioxidation activity was not. TF was significantly lower in 3 and 4 V of LIPEF than CC and 2 V of LIPEF; however, the polyphenol, TPC, and antioxidation activity were a little influenced by the LIPEF. After ripening of the winemaking culture for 15 days, polyphenol, TPC, and TF were a little increased but the antioxidation activity was not.

Pulsed-Power System for Leachate Treatment Applications

  • Jang, Sung-Roc;Ryoo, Hong-Je;Ok, Seung-Bok
    • Journal of Power Electronics
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    • v.11 no.4
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    • pp.612-619
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    • 2011
  • This paper presents a water treatment system for leachate from sewage-filled ground that uses a pulsed-power modulator developed based on semiconductor switches in order to realize a long life, a high repetition rate, and a fast rising time. The specifications of the developed pulsed-power modulator are the pulsed output voltage, the output current, the pulse repetition rate (PRR), the pulse width, and an average output power of $60\;kV_{max}$, $300\;A_{max}$, 3000, $50\;{\mu}s$, and 15 kW, respectively. The pulsed-power water treatment system was introduced and analyzed using an equivalent electrical circuit model to optimize the output voltage waveform. The experimental results verify that the proposed water treatment system can be effectively used for industrial applications.