ISTRAŽIVANJE OPERACIJA MINIRANJA KORISTEĆI METODU ODLUČIVANJA

Blasting is one of the most important operations in the mining projects. Inappropriate blasting pattern may lead to unwanted events such as poor fragmentation, back break, fly rock etc. and affect the whole operation physically and economically. In fact selecting of the most suitable pattern among previously performed patterns can be considered as a Multi Attribute Decision MakingMiniranje je jedna od najvažnijih operacija pri projektiranju u rudarstvu. Nedovoljno dobar uzorak može pridonijeti nastanku neželjenih događaja kao što su fragmentizacija, pucanje, \u27fly rock\u27 itd. te utjecati na razvoj cijele operacije fizički i ekonomski. U principu, odabir najboljeg uzorka može se smatrati važnom odlukom

Circular simple shear extrusion as an alternative for simple shear extrusion technique for producing bulk nanostructured materials

© 2018 The Authors. Published by Elsevier B.V. Recently, simple shear extrusion is introduced to fabricate ultrafine-grained materials. It was designed for billets with square cross-sections and was investigated well previously. This study aims to introduce an alternative design of simple shear extrusion process with a circular cross-section, which is named circular simple shear extrusion. The deformation behavior during the new process is investigated by finite element analysis using ABAQUS/Explicit software package. The load of the process and the strain distribution on the processed-sample are studied by a set of simulations. The results show that, in comparison to conventional simple shear extrusion, the circular simple shear extrusion process needs lower extrusion pressures. Also, the accumulated strains are closer to theoretical ones. The amount of friction force in the process with circular cross-section is lower in comparison with the square one which leads to both, the longer service life of the circular simple shear extrusion dies and the lower cost of production. Hence, this new geometry has a strong potential in terms of industrial applications.Shiraz University (grant number 96-GR-ENG-15)

Improvement of Hydrogenation and Dehydrogenation Kinetics of As-Cast AZ91 Magnesium Alloy via Twin Parallel Channel Angular Extrusion Processing

Copyright: © 2022 by the authors. In the current study, Twin Parallel Channel Angular Extrusion (TPCAE) as a developed SPD processing technique is used to improve the hydrogen storage properties of AZ91 cast alloy. The processing is conducted at different temperatures, ranging from 340 °C down to 200 °C. The hydrogen absorption and desorption tests are conducted kinetically at three different temperatures, using a Sievert-type apparatus. Remarkable improvement in the absorption kinetic is achieved as a result of the TPCAE processing. A maximum absorption capacity of 6.1 wt.% within a time span of 2000 s is achieved for the sample with three passes of processing complemented at 250 °C. Also, the kinetic of dehydrogenation is improved significantly and complete desorption at 350 °C is achieved for all the processed samples within a time span of maximum 2500 s. By calculating the activation energy of hydrogenation and evaluating the microstructure changes, it is found that implementing sufficient thermomechanical work level along with applying the last pass of the process at lower temperature results in a reduction of the activation energy and improvement of the hydrogenation kinetic.Shiraz University, grant number 99-GR-ENG 15

Effects of Gravitational Microlensing on P-Cygni Profiles of Type Ia Supernovae

A brief description of the deformed spectra of microlensed SNe Ia is presented. We show that microlensing amplification can have significant effects on line profiles. The resonance-scattering code SYNOW is used to compute the intensity profile in the rest frame of the supernova. The observed (microlensed) spectral lines are predicted assuming a simple stellar-size deflector, and are compared to unlensed cases to show the effects microlensing by solar-size deflectors can have on spectral lines. We limit our work to spherically symmetric deflectors.Comment: 18 pages, 9 figures, references added, submitted to Ap

Role of strain reversal in microstructure and texture of pure al during non-monotonic simple shear straining

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Dyestuff is one of the most widely released pollutants into the environment. Many approaches have been considered to deal with the dye removal from polluted water such as adsorption, ultrafiltration, osmosis, solvent extraction and photocatalytic degradation. The photocatalytic degradation process is one of the most beneficial, economical and environmentally friendly ways to degrade the organic pollutants from wastewater. In this study, an efficient ferrite-based photocatalyst, AgFeO2/rGO/TiO2 was successfully developed using simple deposition and reflux method. Physical, chemical and structural properties were analyzed by using XRD, FTIR Raman and PL spectroscopy. The efficiency of photocatalyst was investigated for the decolorization of methyl blue (MB) dye and activity was measured through UV-vis spectroscopy. The effect of parameters like pH, concentrations of MB dye, and loading of silver ferrite (AgFeO2) was investigated. The study depicted that the properties of TiO2 were improved due to addition of silver ferrite and reduced graphene oxide (rGO). The 2.5% AgFeO2/rGO/TiO2 exhibited the highest efficiency and completely degraded the 50 ppm of MB dye in 30 min. The parametric study revealed that dye decolorization is faster in a neutral solution than in basic and acidic medium. The higher performance of the photocatalyst was attributed to the reduced charge recombination and improved optical properties. Thus, AgFeO2/rGO/TiO2 can be a potential composite for photocatalytic dye degradation and other photocatalytic applications under UV-Visible light irradiations

On the Production of Severely Deformed Workpieces in Large Scales: A Step Towards Industrialization

© 2019, The Author(s). Improvement of the functional properties of aluminium and its alloys by grain refinement is an effective way to increase their applications. The capability of severe plastic deformation methods to produce ultrafine-grained materials has been well established. However, their industrial application is limited because of the required additional equipment and limitation of the product size. Due to the direct extrusion characteristic of the simple shear extrusion (SSE) method and consequently the minimal additional tools and expenses, SSE is a good candidate for commercialization. The aim of this research is to scale up the SSE products to facilitate their potential use in practical applications. To overcome the limitation on the length of the plunger and reduce the load of the SSE process, a design is proposed in the current research. Microstructural investigations and mechanical tests of commercial pure aluminium (AA1050) workpieces confirm the effectiveness of the proposed design on the grain refinement and its capability to reduce the processing load