Laser cleaning of materials’ surfaces implies the removal of deposited pollutants without affecting the material. Nanosecond Nd:YAG pulsed laser, operating at 1064 nm and 532nm, was utilized. Different laser intensities and number of pulses were used on metallic and non-metallic surfaces under O2 and Ar environments to remove metal oxide and crust. Cleaning efficiency was studied by optical microscope. The results indicated the superiority of 1064 nm over the 532 nm wavelength without any detectable damage to materials’ surfaces. Marble cleaned in Oxygen gas environment was better than in Ar gas.
The real and imaginary part of complex dielectric constant for InAs(001) by adsorption of oxsagen atoms has been calculated, using numerical analysis method (non-linear least square fitting). As a result a mathematical model built-up and the final result show a fairly good agreement with other genuine published works.
The pumping station became widely used in many fields. Free surface vortices at intakes of pumps are not favorable. It may cause noise, excessive vibration, damage to the pumping structure, reduction in efficiency and flow for hydro-turbines, etc. One of the important problems encountered during the pump intake design is the depth of submergence and other design parameters to avoid strong free-surface vortices formation. This study aims to compute the critical submergence depth with some geometrical and hydraulic limitations by using Computational Fluid Dynamic (CFD) package. The mathematical model was validated with a laboratory model that had been conducted. The model of three intake pipes was investigated under five d
... Show MoreThe features of plasmonic surface frequency sensor technology, such as the small number of sensor samples required, electromagnetic interference, and high sensitivity, have been found to be highly important.. In this paper, a simulation program was created in Matlab_b2018 by adopting Fresnel equations for calculating the reflectivity of the electromagnetic wave between different media. A surface plasmon resonance sensor based on electromagnetic wavelengths within the range (100 nm to 1000 nm) has been proposed. The transfer matrix was used for a system consisting of four different media. The first medium is a semicircular BK7 glass prism, the second medium is a gold layer (40 nm thick), then a bismuth layer of variable thickne
... Show MoreHedging is a linguistic phenomenon used to convey interpersonal messages in spoken interaction. It is a communicative strategy which enables speakers to soften the force of utterances or moderate the assertive force of utterances. It is resulted from different features such as uncertainty, doubt, tentativeness, ambiguity, neutrality, mitigation, and subjectivity. Hedging is used widely in TV debates to make utterances more acceptable to the interlocutors. Hedges are expressions used to communicate the speaker's weak commitment to information conveyed. The utterances in debates are often hedged because in an unhedged form might sound threatening to the addressees, and, therefore, be likely to be rejected.
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... Show MoreArabic prose poem and the antithesis of contrast: poetry _ prose and West _ East
In this work we investigate and calculate theoretically the variation in a number of optoelectronic properties of AlGaAs/GaAs quantum wire laser, with emphasis on the effect of wire radius on the confinement factor, density of states and gain factor have been calculated. It is found that there exist a critical wire radius (rc) under which the confinement of carriers are very weak. Whereas, above rc the confinement factor and hence the gain increase with increasing the wire radius.
This work presents the characteristics of plasma produced by fundamental wavelength (1064 nm) Q- switched Nd:YAG laser on Ag:Ni alloy in distilled water were investigated at different laser energies by optical emission spectroscopy technique. The size of produced nanoparticles from Ag:Ni target in distilled water were studied, by x-ray diffraction, UV-visible absorbance and atomic force microscopy, at different laser energies. Spectroscopic measurements show that electron temperature and electron density increase with increasing laser energy. It was found from AFM measurements that the produced nanoparticle size decrease from 97.13 nm to 71.20 nm, while XRD shows that the crestalline size decrease from 15.5 nm to 9 nm with increasing pul
... Show MoreThe objective of this paper was to study the laser spot welding process of low carbon steel sheet. The investigations were based on analytical and finite element analyses. The analytical analysis was focused on a consistent set of equations representing interaction of the laser beam with materials. The numerical analysis based on 3-D finite element analysis of heat flow during laser spot welding taken into account the temperature dependence of the physical properties and latent heat of transformations using ANSYS code V.10.0 to simulate the laser welding process. The effect of laser operating parameters on the results of the temperature profile were studied in addition to the effect on thermal stresses and dimensions of the laser w
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