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61.
Based on the extended Huygens–Fresnel integral, analytical formulas for the cross-spectral density, mean-squared beam width
and angular spread of a partially coherent elegant Hermite–Gaussian (HG) beam in turbulent atmosphere are derived. The evolution
properties of the average intensity, spreading and directionality of a partially coherent elegant HG beam in turbulent atmosphere
are studied numerically. It is found that the partially coherent elegant HG beam with smaller initial coherence width, larger
beam order and longer wavelength is less affected by the atmospheric turbulence. Compared to the partially coherent standard
HG beam, the partially coherent elegant HG beam is less affected by turbulence under the same condition. Furthermore, it is
found that there exist equivalent partially coherent standard and elegant HG beams, equivalent fully coherent standard and
elegant HG beams, and an equivalent Gaussian–Schell-model beam may have the same directionality as a fully coherent Gaussian
beam whether in free space or in turbulent atmosphere. Our results can be utilized in short and long atmospheric optical communication
systems. 相似文献
62.
?. Arpali S. A. Arpali Y. Baykal H. T. Eyyubo?lu 《Applied physics. B, Lasers and optics》2011,103(1):237-244
The intensity fluctuation of a partially coherent laser beam array is examined. For this purpose, the on-axis scintillation
index at the receiver plane is analytically formulated via the extended Huygens–Fresnel diffraction integral in conditions
of weak atmospheric turbulence. The effects of the propagation length, number of beamlets, radial distance, source size, wavelength
of operation and coherence level on the scintillation index are investigated for a horizontal propagation path. It is found
that, regardless of the number of beamlets, the scintillation index always rises with an increasing propagation length. If
laser beam arrays become less coherent, the scintillation index begins to fall with growing source sizes. Given the same level
of partial coherence, slightly less scintillations will occur when the radial distance of the beamlets from the origin is
increased. At partial coherence levels, lower scintillations are observed for larger numbers of beamlets. Both for fully and
partially coherent laser beam arrays, scintillations will drop on increasing wavelengths. 相似文献
63.
A generalized optical beam expression is developed that presents the majority of the existing optical source fields such as Bessel, Laguerre–Gaussian, dark hollow, bottle, super Gaussian, Lorentz, super-Lorentz, flat-topped, Hermite–sinusoidal-Gaussian, sinusoidal-Gaussian, annular, Gauss–Legendre, vortex, also their higher order modes with their truncated, elegant and elliptical versions. Source intensity profiles derived from the generalized optical source beam fields are checked to match the intensity profiles of many individual known beam types. Source intensities for several interesting beam combinations are presented. Our generalized optical source beam field expression can be used to examine both the source characteristics and the propagation properties of many different optical beams in a single formulation. 相似文献
64.
Aslihan Baykal Dihan Zhang Jakob Knelles Isabel T. Alt Bernd Plietker 《化学:亚洲杂志》2019,14(17):3003-3010
The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) is an active catalyst in C?H‐amination but also in proton‐transfer catalysis. Herein, we describe the successful use of this complex as a proton‐transfer catalyst in the cyclocondensation reaction between azides and ketones to the corresponding 1,2,3‐triazoles. Cross‐experiments indicate that the proton‐transfer catalysis is significantly faster than the nitrene‐transfer catalysis, which would lead to the C?H amination product. An example of a successful sequential Dimroth triazole–indoline synthesis to the corresponding triazole‐substituted indolines is presented. 相似文献
65.
Zn-doped nickel ferrite nanoparticles (Zn0.6Ni0.4Fe2O4) have been prepared via a surfactant, polyethylene glycol assisted hydrothermal route. X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), and vibrating scanning magnetometry (VSM) were used for the structural, morphological, and magnetic characterizations of the product, respectively. TEM analysis revealed that the nanoparticles have a narrow size distribution, with average particle size of 15±1 nm, which agrees well with the XRD based estimate of 14±2 nm. The absence of saturation and remanent magnetization, and coercivity in the high temperature region of the M-H curve and non-zero magnetic moments indicate superparamagnetism of the nanoparticles with a canted spin structure. The appearance of a peak on the temperature-dependent zero-field cooling magnetization curve at ∼190 K indicates the blocking temperature of the sample. 相似文献
66.
The propagation of arbitrary laser beams in free space is examined. For this purpose, starting with an incident field of arbitrary field distribution, the intensity at the receiver plane is formulated via Huygens Fresnel diffraction integral. Arbitrary source field profile is produced by decomposing the source into incremental areas (pixels). The received field through the propagation in free space is found by superposing the contributions from all source incremental areas. The proposed method enables us to evaluate the received intensity originating from any type of source field. Using the arbitrary beam excitation, intensity of various laser beams such as cos-Gaussian, cosh-Gaussian, general type beams are checked to be consistent with the already existing results in literature, and the received intensity distributions are obtained for some original arbitrary beam field profiles. Our received intensity formulation for the arbitrary source field profiles presented in this paper can find application in optics communication links, reflection from rough surfaces, optical cryptography and optical imaging systems. 相似文献
67.
Propagation of circular and elliptical anomalous hollow beams in a turbulent atmosphere is investigated in detail. Based on the extended Huygens–Fresnel integral, analytical formulae for the average irradiance of circular and elliptical anomalous hollow beams propagating in a turbulent atmosphere are derived. The irradiance and spreading properties of circular and elliptical anomalous hollow beams in a turbulent atmosphere and in free space are studied numerically. It is found that circular and elliptical anomalous hollow beams at short propagation distance in turbulent atmosphere have similar propagation properties to those of free space, while at long propagation distance, circular and elliptical anomalous hollow beams eventually become circular Gaussian beams in a turbulent atmosphere, which is much different from their propagation properties in free space. The conversion from an anomalous hollow beam to a circular Gaussian beam becomes quicker and the beam spot spreads more rapidly for a larger structure constant, a shorter wavelength and a smaller waist size of the initial beam. 相似文献
68.
We calculate the bi-invariant metric of FIO(2), the inhomogeneous invariance quantum group of the fermion algebra. We find that this metric is identical to that of the bi-invariant metric of GL(2, R) + × SU (1, 1). However, the quantum group manifold is restricted to a region of the GL(2, R) manifold. 相似文献
69.
Abdülhadi Baykal Yüksel Köseoğlu Mehmet Şenel 《Central European Journal of Chemistry》2007,5(1):169-176
Heating hydrous manganese (II) hydroxide gel at 85 °C for 12 hours produces Mn3O4 nanoparticles. They were characterized by X-ray powder diffraction (XRD) and infrared spectroscopy (FTIR). The particle size
estimated from the SEM and X-ray peak broadening is approximately 32 nm, showing them to be nanocrystalline. EPR measurements
confirm a typical Mn2+signal with a highly resolved hyperfine structure.
相似文献
70.
Nermin Kasapoglu Bahar Birsöz Abdülhadi Baykal Yüksel Köseoglu Muhammet S. Toprak 《Central European Journal of Chemistry》2007,5(2):570-580
A series of Ni doped cobalt ferrite compounds with the formula Ni
χ
Co1−χ
Fe2O4 where x=0, 0.2, 0.4, 0.6, 0.8, and 1.0 were prepared using a hydrothermal method and subsequently sintered/annealed at 600
°C for 3 h. The influence of the Ni content on the lattice parameter, a, stretching vibration and the magnetization of specimens were subsequently studied. XRD and FTIR were used to investigate
structure and composition variations. All samples were found to have a cubic spinel structure. SEM was used to study morphological
variations. The results indicate that the average particle sizes are between 30–35 nm with a narrow size distribution along
with nanocrystals forming of regular octahedrons. A decrease in the peak to peak line width and increase in resonance field
with increasing Ni content were observed from ESR measurements. Based on ESR results, a core-shell type of formation was proposed
where the core is made up of undoped CoFe2O4 and the shell is Ni2+ doped CoFe2O4.
相似文献