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The selection of an underground mining method using the Fuzzy TOPSIS method: a case study in the Kamar Mahdi II fluorine mine

Javanshirgiv M., Safari M.

Mining Science

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2017

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Vol. 24

161--181

EN

The selection of the mining method is one of the most crucial decisions in the stage of designing mines. This depends on some underlying parameters such as economic, technical and efficiency properties. The parameters may be collected and examined in a wide range of methods including core drilling and developmental planning of an active mine. The process of selecting the mining method can be described as multi-criterion decision-making due to the several factors involved in the evaluation process. Through the multi-criterion decision-making, the structure of problems is analyzed. However, multi-criteria decision-making (MCDM) is often criticized because of its inability to handle uncertain and imprecise problems. Thus, the fuzzy decision-making is proposed as a powerful tool. Therefore in this paper, the fuzzy technique for order performance by similarity to ideal solution (Fuzzy TOPSIS) is used to select the best mining method among square-set stoping, cut-and-fill stoping, shrinkage stoping and sublevel stoping at the Kamar Mahdi fluorine mine based on 14 criteria such as deposit thickness, deposit dip, grade distribution, joint spacing in deposit and hanging wall as well as the cost of mining. Other criteria with the same importance for the four alternatives are neglected. Finally, the alternatives are ranked and the shrinkage stoping is proposed as the optimal mining method for this mine.

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Friction stir modification of GTA 7075-T6 Al alloy weld joints: EBSD study and microstructural evolutions

Shamanian M., Mostaan H., Safari M., Szpunar J. A.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 3

574--585

EN

As known, mechanical properties of gas tungsten arc welded 7075 Al alloys are not desirable and some techniques should be utilized in order to refine the microstructure and hence to improve the mechanical properties of weld joints. In this research work, the microstructure of gas tungsten arc welded 7075 Al alloy was modified by friction stir processing. Evaluation of the tensile strength of the welded joints showed that the tensile strength of the welded joint (228 MPa) increases up to 320 MPa after friction stir processing. In addition, electron backscattered diffractometry (EBSD) was used in order to study the microstructure and grain boundary character evolutions during arc welding and friction stir processing. It was revealed that as-cast dendritic microstructure of gas tungsten arc welded joint completely disappears during friction stir processing and very fine equiaxed grains are formed in welded joints. Analysis of EBSD data showed that friction stir processing of gas tungsten arc welded joints leads to increase of specific boundaries from 0.7% up to 7.8%. In addition, fraction of high angle boundaries increases after friction stir processing which is resulted from dynamic recrystallization occurring during friction stir processing.

3

Magneto-thermo-mechanical buckling analysis of Mindlin plate reinforced with FG-carbon nanotubes

Kolahchi R., Esmailpour M., Safari M.

Archives of Civil Engineering

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2016

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Vol. 62, nr 3

89--104

EN

A buckling analysis of temperature-dependent embedded plates reinforced by single-walled carbon nanotubes (SWCNTs) subjected to a magnetic field is investigated. The SWCNTs are distributed as uniform (UD) and three types of functionally graded nanotubes (FG), in which the material properties of the nano-composite plate are estimated based on the mixture rule. The surrounding temperature-dependent elastic medium is simulated as Pasternak foundation. Based on the orthotropic Mindlin plate theory, the governing equations are derived using Hamilton's principle. The buckling load of the structure is calculated based on an exact solution by the Navier method. The influences of elastic medium, magnetic field, temperature and distribution type, and volume fractions of SWCNT are shown on the buckling of the plate. Results indicate that CNT distribution close to the top and bottom are more efficient than that distributed near the mid-plane for increasing the stiffness of the plates.

PL

Badana jest analiza wyboczenia wbudowanych płyt zależnych od temperatury wzmacnianych jednościennymi nanorurkami węglowymi (SWCNT) poddawanych polu magnetycznemu. Nanorurki SWCNT są rozpowszechniane jako jednolite (UD), a także istnieją trzy typy rozmieszczenia FG (FGA, FGO, FGX). W celu uzyskania równoważnych właściwości materiałowych nanokompozytów dwufazowych (tj. polimer jako matryca i nanorurka węglowa jako wzmocnienie), stosuje się zasadę mieszaniny. Do modelowania matematycznego obecnej struktury stosuje ortotropową teorię płyty Mindlina. W tej teorii odkształcenie normalne i przy ścinaniu są rozpatrywane w kategoriach przemieszczenia punktu materiału na płaszczyźnie środkowej i obrotów normalnej i środkowej płaszczyzny w kierunku osi X i Y. W celu uzyskania obowiązujących równań, stosowana jest metoda energetyczna i zasada Hamiltona. Całkowita energia potencjalna płytki CNTRC to suma energii odkształcenia i pracy wykonanej przez ośrodek elastomerowy i pole magnetyczne. W przypadku energii odkształcenia, zależności przemieszczania w wyniku naprężenia są definiowane w celu uproszczenia. Ośrodek sprężysty zależny od temperatury otoczenia jest stymulowany jako podłoże Pasternaka ze stałą sprężyny i ścinania. Ponieważ ośrodek elastomerowy jest stosunkowo miękki, zakłada się, że sztywność fundamentu jest zależna od temperatury. Ponadto, w przypadku płytki poddawanej stałemu polu magnetycznemu, bierze się pod uwagę przyłożoną siłę masową oraz ocenia się elementy siły Lorentza na jednostkę płytki. Na koniec, korzystając z zasady Hamiltona i integrując wg części, uzyskuje się obowiązujące równania w zakresie wypadkowych naprężeń. Następnie, obliczając wypadkową naprężenia pod względem przemieszczenia i obrotów, uzyskuje się ostateczną formę obowiązujących równań.

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Optimal conditions for the biological removal of arsenic by a novel halophilic archaea in different conditions and its process optimization

Taran M., Safari M., Monaza A., Reza J. Z., Bakhtiyari S.

Polish Journal of Chemical Technology

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2013

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Vol. 15, nr 2

7--9

EN

Recently, concerns about arsenic have been increased due to its high acute toxicity to human and serious environmental problems. In this study, the ability of Halorcula sp. IRU1, a novel halophilic archaea isolated from Urmia lake, Iran for arsenic bioaccumulation was investigated and optimized by Taguchi experimental design. The optimum conditions for high arsenic bioaccumulation by Haloarcula sp. IRU1 could be achieved in the presence temperature 40oC, pH 8 and NaAsO2 at 90 mg/L. Under optimum conditions, the microorganism was able to perform their desired function with a 60.89 percent removal of arsenic. In conclusion, Haloarcula sp. IRU1 is resistant to arsenic and removes it in different conditions.