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In this research, the lateral buckling analysis and layup optimization of the laminated composite of web and flanges tapered thin-walled I-beams based on maximizing lateral-torsional stability strength and minimizing mass/cost of ...
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In this research, the lateral buckling analysis and layup optimization of the laminated composite of web and flanges tapered thin-walled I-beams based on maximizing lateral-torsional stability strength and minimizing mass/cost of the structure are investigated. The classical lamination theory and Vlasov's model for thin-walled cross-section are adopted to establish the total potential energy for thin-walled symmetric balanced laminated beams with varying I-section. By implementing the Ritz method, an explicit formulation for the lateral-torsional buckling load of a double-tapered beam subjected to transverse loading is then derived in terms of the load height parameter and stiffness quantities. Subsequently, the optimal arrangements of layer sequences are obtained using the non-dominated sorting genetic algorithm (NSGA-II) and properly defined objective function. The critical factors of fitness function as lateral buckling strength and the mass of the structure with critical limitations as ply angle, number of layers for the web and flanges, and the thickness of all section walls are considered in this study. Finally, the optimal layer arrangement for the web and flanges are separately determined and discussed. The results show that the presented optimization procedure and layups patterns lead to increasing the lateral-torsional buckling capacity about 52% compared to the conventional angle-ply and unidirectional layups for the web and flanges, respectively.
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Fabrication of 0.74(Bi0.5Na0.5)TiO3-0.26SrTiO(3) (abbreviated as BNST26) ceramics via both conventional furnace sintering (CFS) and microwave sintering (MWS) was investigated in this work. MWS at 1100 degrees C for 5 min resulted ...
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Fabrication of 0.74(Bi0.5Na0.5)TiO3-0.26SrTiO(3) (abbreviated as BNST26) ceramics via both conventional furnace sintering (CFS) and microwave sintering (MWS) was investigated in this work. MWS at 1100 degrees C for 5 min resulted in ceramic with density comparable to that of ceramic fabricated via CFS at 1175 degrees C for 2 h. Average grain sizes of 3.2 mu m and 2.4 mu m were calculated for the ceramics prepared by CFS and MWS, respectively, which was attributed to the lower temperature and shorter sintering time for MWS compared with CFS. In order to investigate the effect of sintering method on the electrical properties of the prepared ceramics, the polarization hysteresis, bipolar and unipolar strain curves, and temperature dependence of permittivity were explored. The results revealed that the remanent polarization (P-r) and coercive field (E-c) of the ceramic prepared by MWS at 1100 degrees C for 5 min were comparable to those of the ceramic under CFS at 1175 degrees C for 2 h. However, the maximum polarization (P-max) of the CFS ceramic was higher than that of the MWS ceramic. In the case of electric field-induced strain, there was no considerable difference between the MWS and CFS ceramics, and normalized strain d(33)* = 501 pm/V was obtained for the MWS ceramic at 1100 degrees C, indicating the effectiveness of MWS for fabrication of BNT-based piezoceramics at lower temperature and shorter time versus CFS.
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In this work, a novel water-soluble Salen type Cu(II) Schiff base complex functionalized silica-coated magnetite nanoparticles [Fe3O4@SiO2/Schiff base of Cu(II)] was synthesized and characterized. First, an immobilized water-solub...
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In this work, a novel water-soluble Salen type Cu(II) Schiff base complex functionalized silica-coated magnetite nanoparticles [Fe3O4@SiO2/Schiff base of Cu(II)] was synthesized and characterized. First, an immobilized water-soluble Schiff base was synthesized from the condensation reaction between 3-amino propyl triethoxy silane (APTES) functionalized silica-coated magnetite nanoparticles and a water-soluble aldehyde (sodium salicylaldehyde-5-sulfonate monohydrate). After that, functionalized Schiff base was converted to functionalized Cu(II) Schiff base complex as the result of reaction with Cu(II) acetate tetrahydrate. The structural and magnetic properties of the prepared compounds were identified by FT-IR, XRD, SEM, EDX, TEM, VSM, and TGA. The catalytic activity of the novel nanocatalyst was investigated for the preparation of 2-amino-4H-chromene derivatives through an one-pot, three-component reaction of dimedone, aromatic aldehydes, and malononitrile, in the presence of catalytic amounts of the Fe3O4@SiO2/Schiff base of Cu(II) nanocatalyst in water and at room temperature. The 2-amino-4H-chromene derivatives were obtained in good to excellent yields. Furthermore, because of the solubility of metal Schiff base complexes in water, the nanocatalyst dispersed in water easily without using ultrasonic or shaker.
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In this study, fluorescence in situ hybridization (FISH) and PCR-amplified fragments of the 16SrDNA gene were used to determine prokaryotes diversity in Urmia Salt Lake. Prokaryote cell population in Urmia lake range from 3.1 +/- ...
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In this study, fluorescence in situ hybridization (FISH) and PCR-amplified fragments of the 16SrDNA gene were used to determine prokaryotes diversity in Urmia Salt Lake. Prokaryote cell population in Urmia lake range from 3.1 +/- 0.3 x 10(6), 2 +/- 0.2 x 10(8), 4 +/- 0.3 x 10(8), and 1.8 +/- 0.2 x 10(8) cells ml(-1) for water, soil, sediment, and salt samples by DAPI (4, 6-diamidino-2-phenylindole) direct count, respectively. The proportion of bacteria and archaea in the samples determinable by FISH ranged between 36.1 and 55% and 48.5 and 55.5%, respectively. According to the DGGE method, some bands were selected and separated from the gel, then amplified and sequenced. The results of sequences were related to two phyla Proteobacteria (16.6%) and Bacteroidetes (83.3%), which belonged to four genera Salinibacter, Mangroviflexus, Pseudomonas, and Cesiri-bacter, and the archaeal sequences were related to Euryarchaeota phyla and three genera Halonotius, Haloquadraturn, and Halorubrum. According to our results, it seems that prokaryotic populations in this hypersaline environment are more diverse than expected, and bacteria are so abundant and diverse and form the metabolically active part of the microbial population inhabiting this extreme environment. Molecular dependent and independent approaches revealed a different aspect of this environment microbiota.
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In this paper, the elastic, elastoplastic, and thermal residual stresses due to autofrettage in a thick-walled spherical structure have been investigated. A steady-state radial temperature gradient has been applied throughout the ...
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In this paper, the elastic, elastoplastic, and thermal residual stresses due to autofrettage in a thick-walled spherical structure have been investigated. A steady-state radial temperature gradient has been applied throughout the thickness of the shell structure made of elastic-perfect-plastic constitutive material. This temperature gradient is assumed to be in both directions from inward to outward and vice versa. To calculate the equivalent stress and initial yield point, the Von Mises yield criterion (failure criterion) is used, and all relations are derived analytically. Then, the differences between the elastic-plastic behavior and the residual stresses in the thick-walled structure, caused by loading in two states of the temperature gradient, are investigated. Finally, the conditions for the occurrence of reverse yielding and its relation with the thickness and temperature gradient are carefully studied.
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The present work focuses on the development of a new electrochemical platform based on CoMn2O4-rGO/1-ethyl-3-methylimidazolium chloride modified carbon paste electrode (CoMn2O4-rGO/IL/CPE) for electrochemical determination of peth...
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The present work focuses on the development of a new electrochemical platform based on CoMn2O4-rGO/1-ethyl-3-methylimidazolium chloride modified carbon paste electrode (CoMn2O4-rGO/IL/CPE) for electrochemical determination of pethidine in the presence of biological species. For the first time, the electrooxidation mechanism of pethidine in presences of morphine and olanzapine is investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) technologies. The as-synthesized CoMn2O4-rGO nanocomposites are characterized by physicochemical measurements such as X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Field emission scanning electron microscopy (FE-SEM), and Fourier transform infrared (FTIR). The obtained results illustrated synergistic interactions between rGO and CoMn2O4 structures. Also, to investigate the electrode charge-transfer resistances, electrochemical features of the resulting nanocomposites are studied via electrochemical impedance spectroscopy (EIS) analysis. Based on the result, three segmented linear ranges are observed over the range 0.08-900 mu M and detection limit of 0.024 mu M. Over the 10.0-40.0 mu M ranges of pethidine in phosphate buffer solution (PBS-pH 7.0), suitable diffusion coefficient of 5.67 x 10(-7) cm(2) s(-1) is evaluated by chronoamperometry technique (CHA). Finally, the CoMn2O4-rGO/IL/CPE with high sensitivity, selectivity and repeatability is successfully used for determination of pethidine in real sample and drug formulation.
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In this paper, the thermo-elasto-plastic behavior of a thick walled cylindrical shell made of a Functionally Graded Material (FGM) is analyzed by Successive Approximation Method (SAM). The FGM ingredients include Aluminum and Sili...
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In this paper, the thermo-elasto-plastic behavior of a thick walled cylindrical shell made of a Functionally Graded Material (FGM) is analyzed by Successive Approximation Method (SAM). The FGM ingredients include Aluminum and Silicon Carbide in which the effective material properties are estimated using the Modified Rule of Mixture. The shell is subjected to a combination of internal pressure and temperature gradient. After application of equilibrium equations for derivation of governing equations, the Differential Quadrature Method (DQM) is used for numerical solution. It is assumed that the two ends of the cylinder are closed and the plane strain conditions are established. The distribution of elastoplastic stresses and strains along the cylinder's thickness is presented in terms of characteristics of material composition and thermo-mechanical loadings such as volume fraction, in-homogeneous index, internal pressure and thermal loadings. Trueness and accuracy of the present problem is justified through comparison with available results in literature. The results show that by enhancement of ceramic particles percentage in the outer layers of cylinder's wall, amount of plastic strains is reduced at that layers, but at the same time, the amount of plastic strains and range of plastic region, increases at inner layers of thickness.
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Let G be a n-vertex simple graph. Suppose A(G) and L(G) = increment (G) - A(G) are adjacency and Laplacian matrix of G, respec-tively, where increment (G) is degree matrix of G. EE(G) = & sigma;ni=1 e & lambda;i and LEE(G) = & sigma;ni=1 e & mu;i are calle...
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Let G be a n-vertex simple graph. Suppose A(G) and L(G) = increment (G) - A(G) are adjacency and Laplacian matrix of G, respec-tively, where increment (G) is degree matrix of G. EE(G) = & sigma;ni=1 e & lambda;i and LEE(G) = & sigma;ni=1 e & mu;i are called Estrada and Laplacian Estrada in-dex of G, where & lambda;i and & mu;i, 1 < i < n, denote the eigenvalues of A(G) and L(G). In this paper, some new upper and lower bounds for EE(G) and LEE(G) are given. Moreover, some relations be-tween EE(G) and LEE(G), and the number of spanning trees are established.
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Satisfactory discrimination between the neutron and gamma components in a mixed neutron-gamma field is one of the most important objectives of neutron dosimetry. One of the common techniques for estimat ing gamma and neutron dose ...
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Satisfactory discrimination between the neutron and gamma components in a mixed neutron-gamma field is one of the most important objectives of neutron dosimetry. One of the common techniques for estimat ing gamma and neutron dose components in mixed neutron-gamma fields is the two peak method. This method has been applied us ing do simeters such as LiF:Mg,Ti, but in the present work, a (LiF)-Li-6:Mg,Cu,P dosimeter has been used, whose thermoluminescence sensitivity is much higher than the LiF:Mg,Ti dosimeter, and therefore, if appro priate results are achieved, it can drastically reduce the dose estimation threshold. Applicability of (LiF)-Li-6:Mg,Cu,P for estimation of the gamma dose using the two peak method in a mixed thermal neutron-gamma radiation field was studied. The ratio of the area underneath the high tem perature thermoluminescence glow peak to dosimetry peak of this phosphor in an Am-Be neutron field is 0.127, while this ratio in a pure gamma ray field of Cs-137 is 0.039. The calibration curves were obtained by separately irradiating (LiF)-Li-6:Mg,Cu,P chips with known gamma and neu tron doses. Results show that (LiF)-Li-6:Mg,Cu,P can be used to estimate the contributions of neu tron and gamma doses in a mixed neutron-gamma field by using the two peak method.
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In the present study, a finite element method was carried out on the single point incremental forming process of explosive-welded Al/Cu bimetal. The effect of process parameters, such as the tool diameter, vertical pitch, sheet th...
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In the present study, a finite element method was carried out on the single point incremental forming process of explosive-welded Al/Cu bimetal. The effect of process parameters, such as the tool diameter, vertical pitch, sheet thickness, pyramid angle, and process strategies, were investigated on the forming forces, dimensional accuracy, and thickness distribution of a truncated pyramid with FEM approaches. The results obtained from the simulation were validated by experiments. The findings indicated that by increasing the tool radius and vertical pitch size, the forming force increases and the wall thickness decreases. The finite element prediction for forming force, thickness distribution, and process strategies shown good agreement with experiments.
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