• Title/Summary/Keyword: Space charge effect

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On a New Evolutionary Algorithm for Network Optimization Problems (네트워크 문제를 위한 새로운 진화 알고리즘에 대하여)

  • Soak, Sang-Moon
    • Journal of the Korean Operations Research and Management Science Society
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    • v.32 no.2
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    • pp.109-121
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    • 2007
  • This paper focuses on algorithms based on the evolution, which is applied to various optimization problems. Especially, among these algorithms based on the evolution, we investigate the simple genetic algorithm based on Darwin's evolution, the Lamarckian algorithm based on Lamark's evolution and the Baldwin algorithm based on the Baldwin effect and also Investigate the difference among them in the biological and engineering aspects. Finally, through this comparison, we suggest a new algorithm to find more various solutions changing the genotype or phenotype search space and show the performance of the proposed method. Conclusively, the proposed method showed superior performance to the previous method which was applied to the constrained minimum spanning tree problem and known as the best algorithm.

Organic Bistable Switching Memory Devices with MeH-PPV and Graphene Oxide Composite

  • Senthilkumar, V.;Kim, Yong Soo
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.5
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    • pp.290-292
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    • 2015
  • We have reported about bipolar resistive switching effect on Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]:Graphene oxide composite films, which are sandwiched between aluminum and indium tin oxide electrodes. In this case, I-V sweep curve showed a hysteretic behavior, which varied according to the polarity of the applied voltage bias. The device exhibited excellent switching characteristics, with the ON/OFF ratio being approximately two orders in magnitude. The device had good endurance (105 cycles without degradation) and long retention time (5 × 103 s) at room temperature. The bistable switching behavior varied according to the trapping and de-trapping of charges on GO sites; the carrier transport was described using the space-charge-limited current (SCLC) model.

Numerical Analysis of the Incident ion Energy and Angle Distribution in the DC Magnetron Sputtering for the Variation of Gas Pressure

  • Hur, Min Young;Oh, Sehun;Kim, Ho Jun;Lee, Hae June
    • Applied Science and Convergence Technology
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    • v.27 no.1
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    • pp.19-22
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    • 2018
  • The ion energy and angle distributions (IEADs) in the DC magnetron sputtering systems are investigated for the variation of gas pressure using particle-in-cell simulation. Even for the condition of collisionless ion sheath at low pressure, it is possible to change the IEAD significantly with the change of gas pressure. The bombarding ions to the target with low energy and large incident angle are observed at low pressure when the sheath voltage drop is low. It is because the electron transport is hindered by the magnetic field at low pressure because of few collisions per electron gyromotion while the ions are not magnetized. Therefore, the space charge effect is the most dominant factor for the determination of IEADs in low-pressure magnetron sputtering discharges.

pH Effects at Doped Si Semiconductor Interfaces (Doping된 Si 반도체 세계에서 pH 효과)

  • 천장호;라극환
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.12
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    • pp.1859-1864
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    • 1990
  • The effect of H+ and OH- ion concentrations at doped Si semiconductor/pH buffer solution interfaces were investigated in terms of cyclic current-voltage characteristics. The effects of space charge on oppositely doped Si semiconductors, i.e., p-and n-Si semiconductors, can be effectively applied to study the pH effects and the slow surface states at the interfaces. The adsorptions of H+ and OH- inons on the doped Si semiconductor surfaces are physical adsorption rather than chemical adsorption. Adsorptive processes and charging effects of the slow surface states can be explained as the potential barrier variations and the related current-voltage characteristics at the interfaces. Under forward bias, the charged slow surface states on the p-and n-si semiconductor surface are donor and acceptor slow surface states, respectively. The effects of minority carriers on the slow surface states can be neglected at the doped Si semiconductor interfaces.

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Studies on the Time Dependent Electrical Conductivity of Rutile Single Crystal (Rutile 단결정의 전기전도도 시간의존성 연구)

  • 김병국;박순자
    • Journal of the Korean Ceramic Society
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    • v.26 no.1
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    • pp.1-6
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    • 1989
  • The phenomena that the electrical conductivity of rutile single crystal changes with time were investigated along the a and c crystallographic axes, at 85$0^{\circ}C$ and Po2 in the range of 1~10-18.5atm. The D.C. conductivity decreased with and saturated some value after ca. 100 hours. But the A.C. conductivity showed no time dependence in the whole Po2 range. These experimental results suggest that the time dependence of D.C. conductivity of rutile single crystal is due to space charge polarization effect; the electrode was Pt which is complete electronic conductor, while the sample was TiO2 which is mixed conductor.

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Numerical Analysis of the Incident Ion Energy and Angle Distribution in the DC Magnetron Sputtering for the Variation of Gas Pressure

  • Hur, Min Young;Oh, Sehun;Kim, Ho Jun;Lee, Hae June
    • Applied Science and Convergence Technology
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    • v.27 no.2
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    • pp.26-29
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    • 2018
  • The ion energy and angle distributions (IEADs) in the DC magnetron sputtering systems are investigated for the variation of gas pressure using particle-in-cell simulation. Even for the condition of collisionless ion sheath at low pressure, it is possible to change the IEAD significantly with the change of gas pressure. The bombarding ions to the target with low energy and large incident angle are observed at low pressure when the sheath voltage drop is low. It is because the electron transport is hindered by the magnetic field at low pressure because of few collisions per electron gyromotion while the ions are not magnetized. Therefore, the space charge effect is the most dominant factor for the determination of IEADs in low-pressure magnetron sputtering discharges.

Treeing Phenomena in the Home-made Solid Organic Insulating Materials (국산유기절연재료의 Treeing현상)

  • 성영권;이헌용;이계호;유기한
    • 전기의세계
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    • v.26 no.2
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    • pp.57-65
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    • 1977
  • In roder to investigate the influence of treeing on electric breakdown of solid organic insulator the initiation and growing mechanism of tree itself, and the correlation between corona discharge and treeing phenomena in solid orgainc insulating materials, several experiments were carried out by means of needle test on polymethyl-methacrylate. The obtained results showed that the existence of voids in specimen had important effects on initiation voltage of trees and, when the direct voltage was applied, the initiation voltage of trees increased by space charge effect. And also the stagnation phenomena due to the transfer of vacancy cluster or polymekr cage in specimen might beconsidered in process of growth of trees, and corona discharge seemed to be the pre-phenomena of treeing because trees were normally initiated by internal discharge in voids.

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Effect of Space Charge on the Properties of Pyroelectricity of PVDF Films (PVDF 필름의 초전특성에 공간전하가 미치는 영향)

  • 류강식;류부형;김경환;김봉흡
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.37 no.3
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    • pp.163-170
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    • 1988
  • In order to investigate the mechanism of pyroelectricity on polyvinylidene fluoride film, the observations were carried out on the characteristics of infrared spectra, thermally stimulated current and pyroelectric current. As the results obtained from the study, it was concluded that the origin for thermally stimulated current exhibited above room temperature can be attributed to hole injected from anode during poling process. Futhermore it is clarified also that the origin of pyroelectricity observed on the specimen concerned is to spontaneous polarization of CF dipole attached to molecular chain segment, however, the fraction of spontaneous polarization is largely influenced by the amount of hole injected from anode.

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The crystallinity and electrical characteristics of low density polyetylene thin film (저밀도 폴리에틸렌 필림의 결정화도 및 전기적 특성)

  • 윤중락;권정열;이헌용
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.11a
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    • pp.164-168
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    • 1996
  • The relation between crystallinity and thermal history in low density polyethylene thin films and their effect on electric conduction phenomena and dielectric breakdown was studied. The low density polythylene thin films obtained by the solution growth method heat-treated at 140[$^{\circ}C$] for 2 h and subsequently cooling to various ways. The degree of crystallinity was estimated by the X-ray diffraction measurement for the specimen of slowly cooling, ICE quenching and liquid nitrogen quenching. The result shows that the crystallinity decreases become faster as the cooling speed increased, and that conduction phenomenon is governed by the space charge limited current in high field. It was found that the dielectric breakdown field increases with an increase in cooling speed and test number in self-healing breakdown method.

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Effect of Space Charge on the PD Pattern or Dielectric barrier Discharge at AC Voltage (교류전압에서 PD 패턴(또는 유전체장벽 효과)에 미치는 공간전하의 영향)

  • 황보승;이동영
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 1998.11a
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    • pp.101-107
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    • 1998
  • 본 논문에서는 최근 국내·외적으로 활발하게 연구되고 있는 고분자 절연재료에 있어서 공간 전하가 전기적 특성에 미치는 영향에 대한 연구로서, 기존에는 보고되지 않았던 새로운 측정시스템과 분석 방법을 제시하였다. 그리고, 이러한 측정시스템을 이용하여 교류전압 하에서 PD 발생시에 절연체 표면에 축적되는 공간전하의 직접적인 관측을 통하여 공간전하와 PD와의 연관성에 대한 규명을 실시하였다. 실험결과로부터 PD 패턴은 방전에 의해 절연체 내부보다는 표면에 축적되는 동적 공간전하와 매우 밀접한 관계를 가지고 있는 것을 알 수 있었으며, 또한 PD 발생시 공기층 전압은 이러한 동적 공간전하에 의해 지배됨을 확인할 수 있었다. 그리고, 일정전계 이상에서는 공간전하의 축적에 의한 영향으로 PD 크기와 공기층 전압은 더 이상 증가하지 않았다는 것을 확인할 수 있었다. 이러한 실험결과는 유전체장벽방전을 이용한 NOx, SOx 등의 공해물질의 분해에 있어서, 현재까지는 분해시스템에 전달되는 전력은 인가전압의 주파수와 크기에 비례하는 것으로 생각해 왔으나, 본 실험결과를 통하여 일정전계 이상에서는 전압상승에 의한 분해 효율의 향상을 기대하기 힘들다는 것을 나타낸다.

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