• Title/Summary/Keyword: Charge density wave

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THE EFFECT OF DUST PARTICLES ON ION ACOUSTIC SOLITARY WAVES IN A DUSTY PLASMA

  • Choi, Cheong-Rim;Lee, Dae-Young;Kim, Yong-Gi
    • Journal of Astronomy and Space Sciences
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    • v.21 no.3
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    • pp.201-208
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    • 2004
  • In this paper we have examined the effect of dust charge density on nonlinear ion acoustic solitary wave which propagates obliquely with respect to the external magnetic field in a dusty plasma. For the dusty charge density below a critical value, the Sagdeev potential $\Psi1(n)$ has a singular point in the region n < 1, where n is the ion number density divided by its equilibrium number density. If there exists a dust charge density over the critical value, the Sagdeev potential becomes a finite function in the region n < 1, which means that there may exist the rarefactive ion acoustic solitary wave. By expanding the Sagdeev potential in the small amplitude limit up to on4 near n=1, we find the solution of ion acoustic solitary wave. Therefore we suggest that the dust charge density plays an important role in generating the rarefactive solitary wave.

The piezoelectricity of trabecular bone in cancellous bone wave propagation

  • Yoon, Young June;Chung, Jae Pil
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.14 no.1
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    • pp.104-107
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    • 2021
  • The orientation of trabeculae and porosity determine the wave propagation in cancellous bone. Wave propagation, as well as charge density and piezoelectricity, stimulate bone remodeling. Also, Charged ions in the fluid affect wave propagation in cancellous bone. But the trabecular struts' piezoelectricity does not change the waveform of cancellous bone. However, the underlying mechanism is unknown yet why trabecula struts' piezoelectricity does not change wave propagation through cancellous bone. Thus, we derived the governing equation indicating that trabecular struts' piezoelectric properties show that those do not affect wave propagation in cancellous bone.

Factors Affecting the Magnitude of the Metal-Insulator Transition Temperature in AMo4O6 (A=K, Sn)

  • Jung, Dong-Woon;Choi, Kwang-Sik;Kim, Sung-Jin
    • Bulletin of the Korean Chemical Society
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    • v.25 no.7
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    • pp.959-964
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    • 2004
  • A low-dimensional metal frequently exhibits a metal-insulator transition through a charge-density-wave (CDW) or a spin-density-wave (SDW) which accompany it's structural changes. The transition temperature is thought to be determined by the amount of energy produced during the transition process and the softness of the original structure. $AMo_4O_6$ (A=K, Sn) are known to be quasi-one dimensional metals which exhibit metalinsulator transitions. The difference of the transition temperatures between $KMo_4O_6$ and $SnMo_4O_6$ (A=K, Sn) is examined by investigating their electronic and structural properties. Fermi surface nesting area and the lattice softness are the governing factors to determine the metal-insulator transition temperature in $AMo_4O_6$ compounds.

Research on Changes in Short Circuit Current of C-Si Solar Cell by Charge Density Waves (전하밀도파 이론으로 결정질 태양전지의 입사각에 따른 단락전류밀도 변화 연구)

  • Seo, Il Won;Koo, Je Huan;Yun, Myoung Soo;Jo, Tae Hoon;Lee, Won Young;Cho, Guang Sup;Kwon, Gi Chung
    • Journal of the Korean Vacuum Society
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    • v.22 no.4
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    • pp.218-224
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    • 2013
  • We measure solar currents transformed from quantum efficiency as a function of incident angles of solar lights. According to conventional models for solar cells, solar currents can be induced when electrons are separated into electrons and holes in the presence of incident solar lights. On the contrary, solar currents can be possible at the time when pinned charge density waves go beyond the pinning potential barrier under the influence of incident solar beams suggested by some authors. In this experiment, measured solar currents and our theory are in good correspondence to confirm the angle dependence of solar lights.

High brightness property of Power Electroluminescent Device using ZnS:Cu (ZnS:Cu를 이용한 후막 전계발광소자의 고휘도 특성)

  • Lee, Jong-Chan;Park, Dae-Hui
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.5
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    • pp.349-353
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    • 1999
  • In this paper, to fabricate the AC power electroluminescent device (PELD) with high brightness, new structure that constructed single emissive layer between electrodes was proposed. Dielectric and phosphor material structure that constructed single emissive layer between electrodes was proposed. Dielectric and phosphor material were BaTiO3 and ZnS:Cu respectively. Fabricated AC power EL devices were estimated by optical and electrical properties of EL spectrum, brightness, CIE coordinate system, transferred charge density and EL emission wave in time domain. With above results, we found that brightness of newly proposed AC powder EL power EL device was 2754 cd/m2 at 100V, 400 Hz and compared with conventional device structure.

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A Study on the Atomic and Electronic Structures of DNA-nucleobases-adsorbed Graphene Through First-principles LCAO Method (제일원리 LCAO 방법을 이용한 DNA Nucleobase 흡착된 그라핀의 원자 및 전자구조 연구)

  • Lee, Eun-Cheol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.6
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    • pp.510-514
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    • 2011
  • Based on first-principles LCAO method, we study the electronic and atomic structures of DNA nucleobases adenine (A), thymine (T), guanine (G), and cytosine (C) adsorbed on graphene surfaces. The ${\pi}-{\pi}$ stacking interactions between graphene and nucleobases lead to the bilayer geometries similar to the Bernal stacked graphite. Through the density of states and charge density analyses, it is found that nucleobases are physisorbed on graphene by dispersive interactions with negligible charge exchange. Our calculations reproduce the atomic structures obtained in previous plane wave calculations accurately with much less computation, and well describe the delocalized ${\pi}-{\pi}$ interactions in graphene-nucleobases system, indicating that the LCAO method is very efficient for investigating graphene-bio systems.

Measurement of Electron-neutral Collision Frequency Using Wave-cutoff Method

  • Yu, Gwang-Ho;Na, Byeong-Geun;Kim, Dae-Ung;Lee, Yun-Seong;Park, Gi-Jeong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.234-234
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    • 2011
  • Electron-neutral collision frequency is one of the important parameters in the plasma physics and in industrial plasma engineering. We can understand the momentum, energy, and charge transport properties of the plasma using electron-neutral collision frequency.[1] The wave-cutoff method is a diagnostic method for the electron density measurement, but the cutoff peak value depends on gas pressure. The wave-cutoff signal becomes unclear as increasing gas pressure. The reason of pressure dependence is that the electron-neutral collision disturbs electron motion so that microwave can propagate through plasma at plasma frequency.[2] Using the pressure dependence of wave-cutoff method we can find the electron-neutral collision frequency. At first we tried to confirm this method using well known gas such as Ar. The cutoff signal decrease as increasing gas pressure (the simulation result). The wave-cutoff signal is unclear at a gas pressure of 500 mTorr. (electron density $1.0{\times}10^{10}/cm^3$, electron temperature 1.7 eV, electron -neutral collision frequency~1 GHz). In this condition, the electron-neutral collision frequency is closed to the wave-cutoff frequency.

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A Study on the Electromagnetic Properties due to Circuit Patters in the Printed Circuit Hoard using Computer Simulation (컴퓨터 시뮬레이션을 이용한 PCB기판에서의 회로패턴에 따른 전자기적 특성에 관한 연구)

  • 이찬오;이성일;김용주;박광현;이준웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.11a
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    • pp.265-269
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    • 1996
  • In this paper, electric field interference was analyzed in the Printed Circuit Board to restrain the elcctromagnetic wave using Boundary Element Method and Finite Element Method. First, charge density distribution was simulated using Boundary Element Method and the characteristic impedance was caculated to restrain the reflex wave, and mutual capacitance was caculated in the multi-strip line PCB. Finally, electric field was simulated in the variable patterns using Finite Element Method. As a result, the optimal structure and characteristics of strip line was obtained and the imformations about the optimal design pattern could be obtained with the analysing the feild distribution.

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Effect of the Photosensitizer on the Photo refractive Effect Using a Low $T_g$ Sol-Gel Glass

  • Choi, Dong-Hoon;Jun, Woong-Gi;Oh, Kwang-Yong;Yoon, Han-Na;Kim, Jae-Hong
    • Macromolecular Research
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    • v.11 no.4
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    • pp.250-255
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    • 2003
  • We prepared the photorefractive sol-gel glass based on organic-inorganic hybrid materials containing a charge transporting molecule, second-order nonlinear optical (NLO) chromophore, photosensitizer, and plasticizer. Carbazole and 2-{ 4-[(2-hydroxy-ethyl)-methyl-amino]-benzylidene}-malononitrile were reacted with isocyanato-triethoxy silane and the functionalized silanes were employed to fabricate the efficient photorefractive media induding 2,4,7-trinitrot1uorenone (TNF) to form a charge transfer complex. The prepared sol-gel glass samples showed a large net gain coefficient and high diffraction efficiency at a certain composition. As the concentration of photosensitizer increased, the photorefractive properties were enhanced due to an increment of charge carrier density. Dynamic behavior of the diffraction efficiency was also investigated with the concentration of the photosensitizer.