Papers by Keyword: Extinction

Abstract: Alumina nanofluid has unique thermo-physical properties which make it appreciable as thermal fluid, but its high extinction coefficient is not significant enough for making it a good solar irradiation absorber. The investigation was conducted on 0.05% v/v water-based alumina nanofluid and results showed that the nanofluid is able to attenuate approximately 50% of solar energy irradiated on the earth surface. Enhancement in absorption coefficient is found very little to increase absorptivity of basefluid using Rayleigh approach. It is found that the scattering coefficient of alumina is dominating absorption coefficient. Although high value of extinction coefficient is observed as usual, scattering is found responsible for this high extinction. The Rayleigh approach cannot explain the optical behaviour of the nanofluid and dominating scattering behaviour points toward alumina nanofluids’ weak capability as radiation absorber.

Abstract: With some theory about continuous and impulsive dynamical system, an impulsive model based on a special predator-prey system is considered. We assume that the impulsive effects occur when the density of the prey reaches a given value. For such a state-dependent impulsive system, the existence, uniqueness and orbital asymptotic stability of an order-1 periodic solution are discussed. Further, the existence of an order-2 periodic solution is also obtained, and persistence of the system is investigated.

Abstract: The nanostructure of bimetallic Au/Pd particles was fabricated to investigate their surface plasmon (SP) dynamics and local field factor. The SP dynamics was detected according to the structure, electric dipole and multipole electrical quadrupole moment. It was found that the symmetric coupling red shifts decreased obviously with the increase of the shell thickness and the nanoparticle size, and the absorption efficiencies of the nanostructure depended on the SP resonance frequency. The waves of surface plasmon Pd/Au are achieved by gradient of electrons density between interface and shell layer. The dipole couple and electrical quadrupole moment make the plasmonic anisotropy related to transition of electron energy band. The FWHM under collective plasmonic enhancement has been found to enlarge with rise of radius ratio.Moreover, the SP resonance and the local field were measured with annular limited optical distribution in terms of dipole resonance mode and resonance frequency. The resonance scattering has been changed inspite of the Au/Pd deformation and the collective plasmon enhancement. Besides, the single particle in Z direction went up with the particle dimension. The solid structures of the Au/Pd Core/shell nanoparticles were measured by TEM and EDS

Abstract: Accounting for secondary extinction (SE) of the intensities measured from a textured film by means of conventional X-ray diffractometer, a new X-ray diffraction method is described for determination of film thickness. Physically, the problem is restricted to using a reflection pair corresponding to the main component of the texture. As model sample a vacuum-deposited silver thin film is used.

Abstract: Allowing for secondary extinction (SE), a method is described for thickness measurement of thin films by x-ray absorption. The method is tested by employing Al foils and electrodeposited Cu films detached by the substrate. The thicknesses determined by the method were in fair agreement with that ones measured by the ordinary absorption method based on using incident beam intensities. Moreover, a dependence of the SE coefficient on the transmission factor of the films was experimentally shown, and thus additional light was thrown on the nature of SE.

Abstract: A method of pole density measurements is described, which uses the differences in X-ray beam polarisation of two monochromators. The method requires a single reflection at an intermediate diffraction angle. Experimental verification is provided by pole density measurements of Ag films and comparison the results obtained with the proposed method with results from the reflection-pair method [8-10].