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21.
We present a method for the fabrication of PVTri-BaFe12O19 nanocomposites by in-situ polymerization of PVTri in the presence of synthesized BaFe12O19 nanoparticles. Nanoparticles, polymer and nanocomposite were analyzed by XRD, FTIR, TGA, TEM, NMR, GPC and conductivity techniques for structural and physicochemical characteristics. Crystallographic analysis revealed the phase as hexaferrite and X-ray line profile fitting yielded a crystallite size of 17±5 nm. Conjugation of PVTri to nanoparticle surface was assessed to be via carbonyl groups on the polymer. TG analysis revealed that 45 wt% of nanocomposite is inorganic phase (BaFe12O19). It was found out that the ac conductivity of nanocomposite under a certain frequency increases with temperature. 相似文献
22.
Acta Mathematica Hungarica - 相似文献
23.
The propagation of phase-locked and non-phase-locked laser array beams of radial and rectangular symmetries in a turbulent
atmosphere are investigated based on the extended Huygens–Fresnel integral. The beamlet used in our paper for constructing
the laser array beams is of elliptical Gaussian mode. Analytical formulae for the average irradiance of phase-locked and non-phase-locked
radial and rectangular laser array beams are derived through vector integration and tensor operation. The irradiance properties
of these laser array beams in a turbulent atmosphere are studied numerically. It is found that both phase-locked and non-phase-locked
radial and rectangular laser array beams eventually become circular Gaussian beams in a turbulent atmosphere, which is much
different from their propagation properties in free space. The propagation properties are closely related to the parameters
of laser array beams and the structure constant of the turbulent atmosphere.
PACS 42.25.Bs; 41.85.Ew; 42.68.Ay 相似文献
24.
Yahya Baykal 《Optics Communications》2007,269(1):30-38
The receiver intensity profile of an off-axis-Gaussian beam travelling in random medium is formulated. By examining the related exponential terms of this intensity expression, the rules governing the receiver plane displacements are deduced. Off-axis-Gaussian beam is characterized by introducing into a Gaussian beam, complex displacement parameters that exhibit transverse source coordinate dependent attenuation and phase shifts. Our results are applied to turbulent horizontal links. Intensity plots describing the dependence on the source and propagation parameters both on the source and the receiver planes are provided. Even though the normalized intensities of the off-axis-Gaussian beam having the same source sizes but differing displacements in x- and y-directions may look the same on the source plane, they will differentiate after propagation. The views from the progress of an off-axis-Gaussian beam along the turbulent link length show that a source displaced beam will act according to rules set by related exponential terms. An asymmetrical (ellipsoidal) off-axis-Gaussian beam will initially be converted into symmetric (circular) shape at the intermediate link lengths, then it will start to expand in the other direction, thus reverting to an ellipsoid shape whose major axis is now along the transverse coordinate opposite to that of the source plane. 相似文献
25.
26.
The on-axis scintillation index for a circular dark hollow beam (DHB) propagating in a weak turbulent atmosphere is formulated,
and the scintillation properties of a DHB are investigated in detail. The scintillation index for a DHB reduces to the scintillation
index for a Gaussian beam, an annular beam and a flat-topped beam under certain conditions. It is found that the scintillation
index of a DHB is closely related to the beam parameters and can be lower than that of a Gaussian beam, an annular beam and
a flat-topped beam in a weak turbulent atmosphere at smaller waist sizes and longer propagation lengths.
PACS 42.25.Bs; 42.68.Ay 相似文献
27.
28.
Heru Kuswanto Franois Goutaland Abdennacer Yahya Aziz Boukenter Youcef Ouerdane 《Journal of Non》2001,280(1-3):277-280
The effects of heat-treatment and ultraviolet (UV) light at 325 nm on virgin and hydrogen loaded germanosilicate optical fibers have been investigated by using laser spectroscopy technique. The luminescence band around 650 nm is sensitive to heat treatment. The hydrogen reloading of the hydrogen loaded fibers subsequent to heat treatment showed a new emission band around 570 nm. The irradiated fibers have an emission band around 383 nm which was not detected in hydrogen loaded fibers. 相似文献
29.
30.
Ashish Kumar Yahya E. Jad Ayman El-Faham Beatriz G. de la Torre Fernando Albericio 《Tetrahedron letters》2017,58(30):2986-2988
Herein, we report the use of γ-valerolactone (GVL) and N-formylmorpholine (NFM) as DMF substitutes in polystyrene based SPPS. The solubility of selected amino acids and coupling reagents were studied in GVL and NFM, followed by their use in the successful synthesis of Aib-enkephalin pentapeptide (H-Tyr-Aib-Aib-Phe-Leu-NH2) and Aib-ACP decapeptide (H-Val-Gln-Aib-Aib-Ile-Asp-Tyr-Ile-Asn-Gly-NH2). 相似文献