• Title/Summary/Keyword: Reversal Effect

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Diffraction Efficiency Properties of Holographic Gratings by the Reversal Bleached on the Effect of Superadditivity (초부가성 효과에 의한 반전표백 홀로그래피 회절격자의 회절효율 특성)

  • Lim, Chun-Woo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.5
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    • pp.403-407
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    • 2010
  • This paper shows that the diffraction efficiency is influenced by superadditivity for the combination of the different developing agent and concentrations in the reversal bleach applied to the Slavich PFG-01 plate to be used for recording transmission holograms. The four developers based on ascorbic acid in combination with metol, phenidone, hydroquinone respectively, were studied. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC in the reversal bleach.

Exchange Coupling in NiFe/Ni Bilayer Fabricated By Electrodeposition

  • Kim, D.Y.;Jeon, S.J.;Kim, K.W.;Yoon, S.S.
    • Journal of Magnetics
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    • v.16 no.2
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    • pp.97-100
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    • 2011
  • Bilayers of soft NiFe (150 nm-420 nm) on hard Ni (150 nm) were prepared by electrodeposition. The process of magnetization reversal in the NiFe/Ni bilayers was then investigated. The hysteresis loop generated by a magnetization reversal of soft NiFe under a positive saturation state of a hard Ni layer shows a shift along the negative field axis, which is clear evidence for the exchange spring effect in the NiFe/Ni bilayers. The dependence of the coercive field $H_c$ and exchange bias field Hex on the thickness of the NiFe layer was also investigated. As the NiFe thickness increases from 150 nm to 420 nm, both $H_c$ and $H_{ex}$ decrease rapidly from $H_c$= 51.7 Oe and $H_{ex}$ = 12.2 Oe, and saturate to $H_c$ = 5.8 Oe and $H_{ex}$ = 3.5 Oe.

Residual Effects of Dietary $17\alpha-Methyltestosterone$ on Second-Year Growth, Body Composition, and Gonosomatic Indices of Blue Tilapia, Oreochromis aureus (Steindachner) (청틸라피아의 2년째 성장, 체조성 및 생식소 중량 지수에 미치는 $17\alpha-Methyltestosterone$의 잔류 효과)

  • Jo Jae-Yoon;Smitherman R. Oneal;Tave Douglas
    • Journal of Aquaculture
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    • v.8 no.4
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    • pp.271-283
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    • 1995
  • Blue tilapia, Oreochromis aureus (Steindachner) swim-up fry were fed a ration containing 0, 1, 10, or 60 ppm $17\alpha-Methyltestosterone$ (MT) for 30 days (sex reversal period). Fish that had been fed 0 ppm MT-treated feed during the sex reversal period were subsequently fed rations containing either 0 ppm MT, 10 ppm MT, or 60 ppm MT for the next 39 days (post sex reversal period) : fish that had been fed 60 ppm MT-treated feed during the sex reversal period were subsequently fed rations containing either 0 ppm MT, 10 ppm MT, or 60 ppm MT during the post sex reversal period. One group was fed 1 ppm MT-treated feed, while another group was fed 10 ppm MT-treated feed during both periods. The following growing season (10 months later), the residual effects of MT on weight gain, body composition, and gonosomatic indices (GSI) were evaluated. MT had no residual effect on growth of either sex. Groups that ate MT-treated feed were significantly (P<0.05) larger than those that received no MT during the sex reversal period, because females in the latter group lowered average weight gain. MT had a positive residual effect on body fat content in males, but had a negative effect on body moisture content. MT had a positive residual effect on body moisture content in females. MT had a significant negative effect on male and female GSI at the end of the post sex reversal period. MT consumption during the sex reversal period had a significant negative residual effect on male GSI. MT fed after sexual development (post sex reversal period) did not have a residual effect on male or female CSI.

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Investigating the Spatial Focusing Performance of Time Reversal Lamb Waves on a Plate through the Finite Element Method (유한요소법을 통한 판에서 시간반전 램파의 공간집속성능 규명)

  • Choi, Jeong-Hee;Lee, Hae-Sung;Park, Hyun-Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1120-1131
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    • 2011
  • Researches using time reversal acoustics(TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of a plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric(PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

Investigating the Spatial Focusing Performance of Time Reversal Lamb waves for Impact Localization on a Plate (판의 충격위치 추정을 위한 시간반전 램파의 공간모임성능 규명)

  • Park, Hyun-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.418-429
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    • 2011
  • Researches using time reversal acoustics (TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of the plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric (PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

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Variation of Asymmetric Hysteresis Loops with Chemical Composition of Amorphous Ferromagnetic Alloys (비정질 자성 합금의 조성에 따른 비대칭 자기 이력 곡선의 변화)

  • 신경호;민성혜;이장로
    • Journal of the Korean Magnetics Society
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    • v.5 no.4
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    • pp.261-268
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    • 1995
  • In order to investigate the origin of the asymmetric magnetization reversal effect, we studied the variation of magnetic hysteresis loops with the alloy composition in amorphous ferromagnetic alloy ribbons of ${(Fe_{1-x}Co_{x})}_{75}Si_{10}B_{15}$ system annealed at $380^{\circ}C$ for 16 hours in a zero field condition. The asymmetric magnetization reversal effect developed more strongly in amorphous ribbons having two metallic components than in ribbons having a single metallic component. The effect developed more strongly in ribbons showing a smaller value of the saturation mag¬netostriction. The development of the asymmetric magnetization reversal effect was affected by the ratio of two metallic components as well as the magnitude of the saturation magnetostriction.

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Magnetisation Reversal Dynamics in Epitaxial Fe/GaAs(001) and Fe/InAs(001) Thin Films

  • Lee, W.Y;Shin, K.H;Kim, H.J;Bland, J.A.C.
    • Journal of Magnetics
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    • v.6 no.2
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    • pp.47-52
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    • 2001
  • We present the magnetisation reversal dynamics of epitaxial Fe thin films grown on GaAs(001) and InAs(001) studied as a function of field sweep rate in the range 0.01-160 kOe/s using magneto-optic Kerr effect (MOKE). For 55 and 250 ${\AA}$ Fe/GaAs(001), we find that the hysteresis loop area A follows the scaling relation $A\propto H_{\alpha} \;with\; \alpha=0.03\sim0.05$ at low sweep rates and 0.33~0.40 at high sweep rates. For the 150${\AA}$ Fe/InAs(001) film, $\alpha$is found to be ~0.02 at low sweep rates and ~0.17 at high sweep rates. The differing values of $\alpha$ are attributed to a change of the magnetisation reversal process with increasing sweep rate. Domain wall motion dominates the magnetisation reversal at low sweep rates, but becomes less significant with increasing sweep rate. At high sweep rates, the variation of the dynamic coercivity $H_c{^*}$ is attributed to domain nucleation dominating the reversal process. The results of magnetic relaxation studies for easy-axis reversal are consistent with the sweeping of one or more walls through the entire probed region (~100$\mu m$). Domain images obtained by scanning Kerr microscopy during the easy cubic axis reversal process reveal large area domains separated by zigzag walls.

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Spatial Characteristics of Time-Reversal Pulse in Rayleigh and Ricean Fading Channels (레일레이 및 라이시안 페이딩 채널 환경 내의 시역전 펄스의 공간 특성)

  • Yoo, Hyung-Ha;Koh, Il-Suek
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.7
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    • pp.648-656
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    • 2009
  • We perform an analysis of the characteristics of the time-reversal pulse in Rayleigh or Ricean fading channel environments. We verify it by using Monte Carlo simulation. In a time-reversal system, each antenna in the time-reversal array receives signals from the transmitter and reverse the received signal in the time axis and then resend it to the original transmitter. We assume that the channel characteristics varies very slowly and the spatial separation between the antennas is not large. Hence the signals received by each antenna are correlated. In this paper, the effect of the correlation on the time-reversed pulse is examined, which includes the spatial properties of the time-reversal pulse such as the focus size, and spatial power distribution.

Analysis of Time Reversal Transmission Performance for Underwater Communications (시역전 수중 디지털 통신 성능 분석)

  • Kim, Hyeon-Su;Kwon, Yang-Soo;Lee, Il-Shin;Chung, Jae-Hak;Kim, Seong-Il
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.3
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    • pp.213-221
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    • 2009
  • The time reversal mirror (TRM) method for underwater communications has been developed to improve transmission performance with low complexity. However, digital communication parameters for TRM have not been researched deeply. This paper demonstrates that the TRM scheme obtains spatial diversity gain similar to multiple antennas, and proposes design methodologies of symbol interval, frame duration and transmission protocol for time reversal mirror transmission. Simulation results show that spatial diversity gain is achieved and the effect of ISI decreases as the number of transducer increases.

Analysis of stability on steel D&I can (Steel D&I Can의 안정성 해석)

  • Cho, S.J.;You, C.S.;Jung, S.W.;Park, H.C.;Hwang, W.;Han, K.S.
    • Proceedings of the KSME Conference
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    • 2001.11a
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    • pp.471-476
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    • 2001
  • The main object of this study is to develop a reliable FEM simulation technique for stability test using ABAQUS software and to clarify the effect of base profile of a steel D&I(drawn and ironed) can on the dome reversal pressure. For the can after body making simulation, two kind of stability test, dome buckle test and axial crush test are performed. The factors studied in the base profile on the dome reversal pressure are the base diameter, the rim radius, the dome shoulder radius, the dome radius and the dome depth. Within the limits before the occurrence of normal snap-through buckling of dome, the dome reversal pressure is improved by decreasing the base diameter, increasing the dome depth or increasing the dome shoulder depth.

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