Papers by Keyword: Scattering

Abstract: During selective laser sintering (SLS) process, the laser transmission in the polymer powder bed and solid polymer is different. The laser interaction with the powder bed splits into absorption, reflection and scattering three parts. The photon scattering between the polymer particles leads laser repeated absorption by particles, changes the photon’s traveling directions, and further influences the temperature distribution at the scanning laser area. New distribution and attenuation coefficients need to be introduced for correcting the results. For better simulating the photons travel ways, we introduce the modified Monte-Carlo method and Mie-Scattering theory to predict laser distribution in the polymer powder bed, by considering the scattering phenomenon. This paper analyses how the initial porosity influences the maximum temperature, laser attenuation rate and porosity change rate. The results show that lower porosity promoting the laser scattering phenomenon, decreasing the maximum temperature and the powder porosity change rate.

Abstract: The project presents the use of laser and magnetic nanoparticles like iron oxide (Fe₃O₄) in heavy metal detection in water. In this method, metal Nanomagnets particles result in a magnetic reagent for the rapid removal of heavy metals from solutions or water of magnitude to concentration 0.25wt%. This can be done by measuring the magneto-optical parameters (as a hysteric loop) of the solution as an indication of the change in concentrations of the detected heavy metal. The samples used in this work using the Tigris River water that supported from al-Wathba lab. water projects of the Baghdad water directorate at Baghdad-Iraq. Putting here a study of the effect of graphene and metal oxide such as cobalt and nickel which doped the ferrofluid (iron oxide) /polymer/water (Tigris river water) composite on the magneto-optical properties. The graphene adding had the best result in low threshold magnetic field which was 67mGauss, give the motive to use it in fast sensing and detecting of heavy metal in Tigris river water.

Abstract: The influence of optical characteristics of semitransparent thermal barrier coatings (TBC) on thermal regulation of heat-stressed elements of power plants is studied. There was used the developed by the authors methodology of physical and mathematical simulation of thermoradiational (in the range 1-2 μm) and conductive heat transmission in ceramic thermal insulation of chamber combustion inner walls of a diesel engine. The paper discusses temporal temperature regimes in model two-layer TBC-coatings in the form of a selectively scattering and absorbing (in the near infrared range) ceramic heat-insulating layer, deposited on the bonding sublayer (with boundary reflection) of the internal surface of the combustion chamber of Low Heat Rejection diesel. Spectrophotometric measurements of the optical parameters have ensured estimates of optical and thermal fields of the investigated ceramics, the structural composition of which was determined on the basis of ZrO₂+8%Y₂O₃. For typical values of radiant-convective flux up to 1-2 MW/m² (effecting on heat-stressed elements of heat-insulated combustion chamber of a diesel engine in pulse-periodic regime) optical and structural parameters TBC-coatings that ensure control and superintendence of the ceramic layer surface temperature and its temperature gradient were proposed.

Abstract: Light scattering caused by pores detrimentally affects the optical transparency of transparent ceramics. Herein, Mie theory has been used to calculate the cross-section of pore scattering in transparent ceramics, and the influence of wavelength, pore size distribution and refractive index has been discussed in detail. For wavelength between 200 nm and 2000 nm, the scattering cross-section decreases with increasing wavelength, which means that pore scattering is more detrimental to short-wavelength transparency. With ZOLD function simulating the pore size distribution inside the ceramic, it has been found that the scattering is strongest when the most-probable diameter d_m equals the incident light wavelength λ. And FWHM (full width at half maximum) parameter a also affects the scattering cross-section. a between 0.003 and 0.7 is necessary for obtaining high optical transparency in visible wavelength range. The method presented in this work is available for the estimation of scattering effect in different kinds of materials, which may be useful for future design of high-transparency ceramics.

Abstract: During operation of coal mines, polluted air is emitted from the ventilation shafts, it contains large amount of carbon and rock dust with various physical and mechanical composition. Dust contains freshly formed silicon dioxide and other components of the mineral product that are hazardous to human health, which are scattered in the surface layer of the atmosphere. Mainly fine dust comes from the mine workings, and the release of the total dust mass by 80 – 96 % is due to the operation of the loading and unloading complex. It is established that the level of dustiness decreases mainly due to the settling in the mine workings of the coarsely dispersed dust fraction. The environment receives mainly fine dust with a high content of fine particles, which can be intensively dispersed outside the sanitary protection zone of the mine. A mathematical model is obtained in the form of a differential equation of mass transfer, which takes into account the physic and mechanical composition of the dust emission from the ventilation shaft of the coal mine as a factor of ecological hazard. The obtained results determine the directions of effective struggle against dust emissions of coal mines.

Abstract: We have investigated a possibility of photon propagation into the human tissue model (skin, fat, and skeletal muscle) by Monte Carlo method using Matlab program. There were some parameters of each tissue layer effecting on the light packet, for instance the absorption coefficient, scattering coefficient, anisotropy factor and thickness. It was found that the photon distribution on the surface of the human tissue and photon penetration into the human tissue under the propagation of 100,000 photons were - 0.8580 cm to + 0.7030 cm (served as two detection points) and 0.7220 cm respectively. Therefore, the simulation result gave the photon penetration depth of 0.2220 cm at the skeletal muscle. These numbers could be primarily used as a standard for design and construction of the tissue diagnostic instrument.

Abstract: This paper describes the reception, researching and electrodynamics investigations of recently obtained materials. These materials demonstrated the losses dielectric behavior and represent a wide interest as radio markers with controlled distortion. The investigated samples can be used as a coating for rotating machine elements for radio diagnostics. The considered materials performed by epoxy warp with high dispersity metal powder content established the required properties for iron 60 % and nickel 60 %. Primary materials parameters are taken in the natural experiment and electrodynamics properties are studied based on a mathematical model. The presented results can be extended to seminatural experiment setup in future. This paper does not contain the formulation of electrodynamic problem.

Abstract: Light scattering of the upper polymer have a great influence on welding quality. Light scattering of high density polyethylene (HDPE) and low density polyethylene (LDPE) are assessed by constructing experiment and numerical computation method. Firstly, the beam quality of semiconductor laser is analyzed, power flux distribution of the laser beam in a defocused plane is measured by knife edge method; Afterwards, the power flux distributions of the laser beam after passing through HDPE/LDPE are measured by line scanning method; Lastly, with the combination of the mathematical model which is used to calculate scattering coefficient and standard deviation of scattering, scattering related parameters and the laser power flux distribution at the welding interface are obtained by writing a program in MATLAB. The results show that the light scattering coefficient of high density polyethylene is up to 0.988, the light scattering coefficient of low density polyethylene is 0.92; Higher crystalline polyethylene leads to more obvious light scattering; the laser beam power flux distribution at the weld interface affected by scattering is determined, which lays a solid foundation on numerical simulation in laser transmission welding.

Abstract: Dye sensitized solar cells based on TiO₂ nanorod suffers from low dye loading and poor light scattering ability, both of which obstacle the improvement of energy conversion efficiency. In this paper, we have successfully synthesized TiO₂ rutile nanostructures with tunable morphology on FTO substrates with a one-step hydrothermal synthesis by changing the Ti concentration in the precursor solution. Three different photoanodes, namely, nanorod layer, nanorod layer with flower-like clusters and nanorod layer with densely packed spheres, are obtained without using any surfactants. The photoanode of nanorod layer with densely packed spheres exhibits improved dye loading and enhanced light reflection from 600-800 nm. DSSCs based on such a photoanode exhibits an energy conversion efficiency of 4.08%, achieving a nearly three-fold enhancement compared with dye sensitized solar cells based on TiO₂ nanorod array.

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.