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991.
On the basis of the extended Huygens-Fresnel principle and the unified theory of coherence and polarization of light we determine the changes in various polarization properties of stochastic beams propagating through the turbulent clear-water ocean. The ocean-induced fluctuations in the refractive index are described via the recently developed power spectrum which takes into account both temperature and salinity variations. Numerical examples of changes in the spectral density, the degree of polarization and in the polarization ellipse are given for electromagnetic Gaussian Schell-model beams. We demonstrate, in particular, how polarization of the propagating beam is affected by statistical properties of the source and by several parameters of oceanic turbulence. We find that propagation of light beams in the oceanic turbulence resembles that in the atmospheric turbulence qualitatively, however evolution and asymptotic saturation of polarization in the oceanic turbulence occurs at much shorter distances. 相似文献
992.
Ramón Herrera Eugenio San Martin 《The European Physical Journal C - Particles and Fields》2011,71(7):1701
Warm-intermediate inflationary universe models in the context of braneworld cosmologies are studied. This study is done in
the weak and strong dissipative regimes. We find that the scalar potentials and dissipation coefficients in terms of the scalar
field evolve as type-power-law and powers of logarithms, respectively. General conditions required for these models to be
realizable are derived and discussed. We also study the scalar and tensor perturbations for each regime. We use recent astronomical
observations to constrain the parameters appearing in the braneworld models. 相似文献
993.
Andreas Schwenke Philipp Wagener Stefan Nolte Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2011,104(1):77-82
The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied
during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary
liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed
nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser
wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease
of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental
wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without
plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by
Mie-scattering of dispersed nanoparticle clusters. 相似文献
994.
Lance Nielsen 《Mathematical Physics, Analysis and Geometry》2011,14(4):279-294
In this paper we investigate the relation between weak convergence of a sequence \(\left\{ \mu_{n}\right\} \) of probability measures on a Polish space S converging weakly to the probability measure μ and continuous, norm-bounded functions into a Banach space X. We show that, given a norm-bounded continuous function f:S→X, it follows that \(\lim_{n\to\infty}\int_{S}f\, d\mu_{n}=\int_{S}f\, d\mu\)—the limit one has for bounded and continuous real (or complex)—valued functions on S. This result is then applied to the stability theory of Feynman’s operational calculus where it is shown that the theory can be significantly improved over previous results. 相似文献
995.
Zhan-Shuo Hu Fei-Yi Hung Shoou-Jinn Chang Kuan-Jen Chen Yi-Wei Tseng Bohr-Ran Huang Bo-Cheng Lin Wei-Yang Chou Jay Chang 《Journal of nanoparticle research》2011,13(10):4757-4763
The photo-current of n-ZnO/p-Si heterojunction photodiodes was improved by embedding Ag nanoparticles in the interface (ZnO/nano-PAg/p-Si), and the ratio between photo- and dark-current increased by about three orders more than that of a n-ZnO/p-Si specimen. The improvement in the photo-current resulted from the light scattering of embedded Ag nanoparticles. The I–V curve of n-ZnO/p-Si degraded after thermal treatment (A-ZnO/p-Si) because the silicon robbed the oxygen from ZnO to form amorphous silicon dioxide and left an oxygen vacancy. Notably,
the properties of ZnO/nano-PAg/p-Si were better in the time-dependent photoresponse under 10 V bias. Ag nanoparticles (15–20 nm) scattered the UV light randomly
and increased the probability for the absorption of ZnO to enhance the properties of the photodiode. 相似文献
996.
A green method, using pulsed spark-discharge (PSD) to synthesize gold nanoparticles (AuNPs) in ethanol, is studied in this
article. Unlike conventional methods for metal nanoparticles synthesis, the PSD method does not require the addition of chemical
surfactants and stabilizers. The size of PSD–AuNPs is examined by transmission electron microscopy, with a range 5–50 nm.
The chemical compounds, crystal structure, and surface plasmon resonance of PSD–AuNPs are studied using energy dispersive
X-ray spectroscopy, X-ray diffraction, and UV–Visible spectroscopy, respectively. Zeta potential analysis shows that a negative
charge (−40 mV) on the surface of the PSD–AuNPs may be contributing to the stability of the suspension. During the gold electrodes
discharge in the ethanol, under an intensive electric field and thermal energy, bulk metallic gold and ethanol may produce
AuNPs and varieties of chemical derivatives, which are also studied by GC/MS and FTIR to investigate the suspension mechanism.
The analysis results show that there is an oxidation reaction of ethanol occurring during the PSD process to produce ethanol
derivatives, such as acetaldehyde, acetic acid, and ethyl acetate, which may modify the surface of AuNPs by coordination of
oxygen atoms. However, only acetic acid can form a negative charge by the deprotonation of the carboxylic group of surface
in ethanol, resulting in the creation of a repulsion force between the particles to form the stable colloid system. The experimental
results indicate that PSD is an alternative green process to synthesize gold nanoparticles suspension in ethanol. Moreover,
with a gold rod consumption rate of 15 mg/L, concentrations of gold nanoparticles ~9 ppm have been observed; therefore, the
net production rate is around 60%. 相似文献
997.
Wen-ting Xu Hai-ling Tu Da-li Liu Ran Teng Qing-hua Xiao Qing Chang 《Journal of nanoparticle research》2011,13(12):7095-7098
An innovative fabrication technique for the nanometer-sized SiGe/Si heterostructure was developed in this study. Ge was induced
in Si substrate by two-step ion implantation. The spherical SiGe nanoclusters are self-assembled in the Si substrate by subsequent
rapid thermal annealing at 1,100 °C. The diameter of the spherical SiGe nanoclusters is 5–7 nm. Visible photoluminescence
from this nanometer-sized SiGe/Si heterostructure at room temperature was investigated. We found three peak energies of visible
luminescence spectra at 1.97, 2.13, and 2.16 eV, respectively. The luminescence intensity depends on the number of the nanoclusters
and will be decreased because of the micro-defects around the heterostructure, which is discussed in detail. 相似文献
998.
Khaled Habib 《Optical Review》2011,18(4):324-330
A critical (steady state) value of the thermal expansion coefficients of different coatings was determined by a nondestructive
technique (NDT) known as laser shearography. The behavior of organic coatings, i.e., ACE premium-grey enamel, a yellow acrylic
lacquer, and a gold nail polish on a metallic alloy, i.e., a carbon steel, was investigated over a temperature range of 20–60
°C. The value of the thermal expansion coefficients of coatings was derived from the slope of the plot of the thermal deformation
(strain) versus the applied temperature. The integrity of the coatings with respect to time was assessed by comparison the
measured coefficients of thermal expansion (CTE) to the critical (steady state) or asymptotic value of CTE. By shearography,
measurement of coating properties could be performed independent of parameters such as UV exposure, humidity, presence of
chemical species, and other parameters which may normally interfere with conventional methods of the assessing of the integrity
of coatings. Therefore, one may measure CTE of coatings, regardless of the history of the coating, in order to assess the
integrity of coatings. Also, the obtained shearography data were found to be in a reasonable trend with the data of electrochemical
impedance spectroscopy (EIS) in 3%NaCl solution. 相似文献
999.
Gold,silver, and palladium nanoparticle/nano-agglomerate generation,collection, and characterization
Sunita R. Boddu Veera R. Gutti Tushar K. Ghosh Robert V. Tompson Sudarshan K. Loyalka 《Journal of nanoparticle research》2011,13(12):6591-6601
Generation, collection, and characterization of gold, silver, and palladium nanoparticles and nano-agglomerates (collectively
“nanoparticles”) have been explored. The nanoparticles were generated with a spark aerosol generator (Palas GFG-1000). They
were collected using a deposition cell under diffusion and thermophoresis. The shapes and sizes of the deposited particles
were measured using transmission electron microscopy (TEM). TEM images showed that the particles were in the range of 8–100 nm
in diameter, and their shapes varied from nearly spherical to highly non-spherical. Thermophoresis enhanced the deposition
of nanoparticles (over the diffusive or the isothermal deposition) in all cases. Further, the size distributions of the nanoparticles
generated in the gas phase (aerosol) were measured using a scanning mobility particle sizer (SMPS 3080, TSI) spectrometer.
The SMPS results show that an increase in the spark frequency of the generator shifted the size distributions of the nanoparticles
to larger diameters, and the total particle mass production rate increased linearly with increase in the spark frequency.
The computational fluid dynamics code Fluent (Ansys) was used to model the flow in the deposition cell, and the computed results
conform to the observations. 相似文献
1000.
Guadalupe Valverde-Aguilar Jorge A. García-Macedo Víctor M. Rentería-Tapia Raúl W. Gómez Manuel Quintana-García 《Journal of nanoparticle research》2011,13(10):4613-4622
Hexagonal mesostructured films containing silver ions were obtained by sol–gel method. Brij 58 was used to produce channels
into the film, which house these ions. The films were exposure to UV radiation to produced silver metallic nanoparticles.
The presence of the metallic nanoparticles was determined by infrared spectroscopy and optical absorption. Besides, these
nanoparticles and core–shell structures of silver–silver oxide nanoparticles were identified by high-resolution transmission
electronic microscopy. From these measurements, the obtained size range for silver nanoparticles was 6.1 nm. The absorption
spectrum located at 440 nm was modelled and well fitted with the Gans theory considering refractive index higher than the
one coming from host matrix. This index is explained because the silver oxide shell modifies the local surrounding medium
of the metallic nanoparticles. 相似文献