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  • Institute of Physics (IOP)  (41)
  • American Institute of Physics (AIP)  (32)
  • 1
    Electronic Resource
    Electronic Resource
    Simultaneous measurement of electron and hole escape times from biased single quantum wells (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 426-428 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Picosecond pump probe measurements on waveguides containing a single GaAs/GaAlAs quantum well have enabled us to determine for the first time both electron and hole escape times from biased quantum wells. Contributions from excitonic saturation and field screening by photogenerated carriers can be clearly identified in the nonlinear transition signal and are quantitatively modeled. Preliminary analysis suggests that thermally assisted escape is dominant at room temperature, but discrepancies are found with conventional thermionic emission models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107903
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    Paper (German National Licenses)
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  • 2
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    Structural and relaxor-like dielectric properties of unfilled tungsten bronzes Ba5−5xSm5xTi5xNb10−5xO30 (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-03-29
    Description: New unfilled tetragonal tungsten bronze (TTB) oxides, Ba 5−5x Sm 5x Ti 5x Nb 10−5x O 30 (BSTN-x), where 0.10 ≤ x ≤ 0.35, have been synthesized in this work. Their crystal structure was determined and analyzed based on Rietveld structural refinement. It is found that single TTB phase can be formed in a particular x range (i.e., 0.15 ≤ x ≤ 0.3) due to the competition interaction between tolerance factor and electronegativity difference. Furthermore, dielectric and ferroelectric results indicate that phase transitions and ferroelectric states are sensitive to x. Referring to the local chemistry, we suggest that the raise of vacancies at the A 2 -site compared with that of A 1 -site will intensely depress the normal ferroelectric phase and is in favor of relaxor ferroelectric state. Macroscopically, previous A-site size difference standpoint on fill TTB compounds cannot give a reasonable explanation about the variation of dielectric maximum temperature (T m ) for present BSTN-x compounds. Alternatively, tetragonality (c/a) is adopted which can well describe the variation of T m in whole x range. In addition, one by one correspondence between tetragonality and electrical features can be found, and the compositions involving high c/a are usually stabilized in normal ferroelectric phase. It is believed that c/a is a more appropriate parameter to illustrate the variation of ferroelectric properties for unfilled TTB system.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100) (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-03-27
    Description: The spin and orbital magnetic moments of the Fe 3 O 4 epitaxial ultrathin film synthesized by plasma assisted simultaneous oxidization on MgO(100) have been studied with X-ray magnetic circular dichroism. The ultrathin film retains a rather large total magnetic moment, i.e., (2.73 ± 0.15)  μ B /f.u., which is ∼70% of that for the bulk-like Fe 3 O 4 . A significant unquenched orbital moment up to 0.54 ± 0.05  μ B /f.u. was observed, which could come from the symmetry breaking at the Fe 3 O 4 /MgO interface. Such sizable orbital moment will add capacities to the Fe 3 O 4 -based spintronics devices in the magnetization reversal by the electric field.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 4
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    RRR and thermal conductivity of Ag and Ag-0.2 wt.%Mg alloy in Ag/Bi-2212 wires (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-12-19
    Description: Residual resistivity ratio (RRR) and thermal conductivity of metal matrix in metal/superconductor composite wires are important parameters for designing superconducting magnets. However, the resistivity of silver in reacted Ag/Bi-2212 wires has yet to be determined over temperature range from 4.2 K to 80 K because Bi-2212 filaments have a critical transition temperature T c of ∼ 80 K, and because it is unknown whether the RRR of Ag/Bi-2212 degrades with Cu diffusing from Bi-2212 filaments into silver sheathes at elevated temperatures and to what degree it varies with heat treatment. We measured the resistivity of stand-alone Ag and AgMg (Ag-0.2 wt.% Mg) wires as well as the resistivity of Ag and Ag-0.2 wt.% Mg in Ag/Bi- 2212 round wires reacted in 1 bar oxygen at 890 °C for 1, 8, 24 and 48 hours and quickly cooled to room temperature. The heat treatment was designed to reduce the critical current I c of Bi- 2212 wires to nearly zero while allowing Cu lo...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 5
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    Fourfold symmetric planar Hall effect in epitaxial La1−xSrxCoO3 thin films (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-04-07
    Description: The effect of Sr concentration on the planar Hall effect (PHE) in epitaxial magnetic phase separated La 1− x Sr x CoO 3 (0.07 ≤  x  ≤ 0.60) thin films was studied systematically. It was found that crystalline anisotropy and spin-orbital coupling are the main contributions to the unexpected fourfold symmetric PHE. The uniaxial anisotropy field was given by H uni  = 70 Oe and cubic anisotropic field H cub  = 143 Oe, respectively. The magnetic anisotropy was weakened by Sr doping, which corresponds with the disappearance of the fourfold symmetry in PHE with the increasing Sr concentration. The first principle calculations proved that the contribution of Co- d orbitals to the magnetic anisotropy strongly depends on the Sr concentration. e g − d x 2 − y 2 and e g − d 3 z 2 − r 2 orbitals play a dominant role in the magnetic anisotropy of the samples with x  = 0.125, 0.25, while the t 2 g − d x y ,   d y z ,   d x z orbitals contribute mainly to the magnetic anisotropy of the samples with x  = 0.375, 0.5, 0.625.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 6
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    The effect of strain on the domain switching of ferroelectric polycrystals (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-02-18
    Description: The effect of external strain on the non-linear electromechanical behavior of a ferroelectric poly-crystal is investigated under different applied electric fields by using a phase field model. Simulation results show that the domain switching induced by electric field under a tensile strain is much easier than that under a compressive strain, which is attributed to that a multi-domain structure can be more easily formed under the tensile strain than in the case of compressive strain when the electric field is absent. It is also found that a compressive misfit strain increases the macroscopic coercive field and remnant polarization while a tensile misfit strain decreases both of them. In addition, a compressive strain decreases the non-linear dielectric constant while a tensile strain increases it.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    Effect of hydrogen storage alloy on combustion properties of ammonium perchlorate /glycidylazide polymer -based propellant (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-12-11
    Description: Hydrogen storage alloys can serve as good potential fuels for propellant design, by improving the energy and combustion properties. The influence of hydrogen storage alloy (A30) on the combustion properties of ammonium perchlorate/glycidylazide polymer (AP/GAP)-based on propellant were studied. The results showed that A30 could increase the burning rate of propellants by 29.75% and 74.78%, compared with B30 and Al. The combustion model of AP/GAP-based propellant containing different fuel was built. Firstly, A30 reduced the high decomposition temperature and promote condensed phase reaction heat of AP. Secondly, A30 deduced the burning surface temperature. Thirdly, A30 might prove the explosive heat of propellant. Therefore, A30 could greatly improve combustion properties of AP/GAP-based propellant.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 8
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    The enhancing effect of mesogen-jacketed liquid crystalline polymer PBPCS on epoxy resin (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-12-11
    Description: The mixtures of mesogen-jacketed liquid crystalline polymers (MJLCP) and epoxy resin (E-51) have been prepared in a certain proportion. The category of the MJLCP is poly{2, 5-bis[(4-butoxyphenyl) oxycarbonyl] styrenes} (PBPCS). Methyl tetrahydro phthalic anhydride (MeTHPA) is served as a curing agent, and N, N-dimethylbenzylamine plays the role of catalyst. Then, based on the curing process, the modified materials have been acquired by casting molding. The effect of PBPCS's improvement has been researched through the mechanical properties test, dynamic thermal mechanical test and scanning electron microscope (SEM). The results indicated that PBPCS could apparently improve the mechanical properties of resin E-51. Compared with unmodified materials, the elongation at break and the tensile strength of PBPCS have been improved remarkably through modification. Both mechanical properties of the 4wt% PBPCS/E-51/MeTHPA were enhanced by 48% and 153% separately, and the characteristics of ...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 9
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    Edge Detection from High Resolution Remote Sensing Images using Two-Dimensional log Gabor Filter in Frequency Domain (2014)
    Institute of Physics (IOP)
    Details
    Publication Date: 2014-03-20
    Description: Edges are vital features to describe the structural information of images, especially high spatial resolution remote sensing images. Edge features can be used to define the boundaries between different ground objects in high spatial resolution remote sensing images. Thus edge detection is important in the remote sensing image processing. Even though many different edge detection algorithms have been proposed, it is difficult to extract the edge features from high spatial resolution remote sensing image including complex ground objects. This paper introduces a novel method to detect edges from the high spatial resolution remote sensing image based on frequency domain. Firstly, the high spatial resolution remote sensing images are Fourier transformed to obtain the magnitude spectrum image (frequency image) by FFT. Then, the frequency spectrum is analyzed by using the radius and angle sampling. Finally, two-dimensional log Gabor filter with optimal parameters is designed according ...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 10
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    The realization of ferro-ferrimagnetic transition and half-metallicity in half-Heusler CoMnGa alloy (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-11-25
    Description: We theoretically predicted that half-Heusler CoMnGa alloy to be half-metallic ferrimagnet at the equilibrium lattice parameter. With the lattice expansion, a local energy minimum occurs at a larger lattice parameter where CoMnGa alloy is in a metastable ferromagnetic state. However, a ferro-ferrimagnetic transition (Fo-Fi-T) is not observed in experiment. We found the Co-Mn antisites can induce the Fo-Fi-T by adjusting the driving force of magnetic transition and the energy barrier. The antisites are sensitive to the preparation methods and annealing temperatures. The highly ordered CoMnGa is achieved by annealing at 1073 K. The Fo-Fi-T occurs in a sample annealed at 1083 K.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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