University of Tabriz

About: University of Tabriz is a education organization based out in Tabriz, Iran. It is known for research contribution in the topics: Population & Nanocomposite. The organization has 12141 authors who have published 20976 publications receiving 313982 citations.

Characterization of hot pressed SiC whisker reinforced TiB2 based composites

Abstract: TiB2–SiC ceramic composites, with different contents of SiC whiskers (SiCw), as a ceramic sinter-additive, were prepared by the hot pressing process at 1850 °C for 2 h under a pressure of 20 MPa. For comparison, a monolithic TiB2 ceramic was also fabricated under the identical temperature, pressure, atmosphere, and holding time by the hot pressing process. The effects of fabrication process and SiC whiskers on microstructural features, phase evolution and mechanical properties were investigated. Hardness measurements revealed an initial increase in hardness for TiB2–SiC compared to TiB2. Also the improvement of the fracture toughness was attributed to the toughening and strengthening effects of SiC whiskers such as crack deflection. The results showed that promoted densification of TiB2–SiC ceramic composites is due to addition of SiC whiskers and reduction of oxide impurities by reacting with SiC whiskers and removing them from the surface layer of TiB2 particles. The reaction between TiB2 particles and SiC whiskers led to in-situ formation of TiC phase in the matrix as well. In general, it is concluded that the sinterability of TiB2-based composites was remarkably improved by introducing SiC whiskers compared to the single phase TiB2 ceramic.

Photocatalytic ozonation of phenazopyridine using TiO2 nanoparticles coated on ceramic plates: mechanistic studies, degradation intermediates and ecotoxicological assessments

Abstract: Removal of phenazopyridine (PhP), an analgesic drug, from water with different oxidation processes including photocatalysis, ozonation and photocatalytic ozonation was studied. The experiments were conducted using a semi-batch reactor where TiO2 nanoparticles were immobilized on ceramic plates irradiated by UV-A light in the proximity of oxygen and/or ozone. The surface morphology, topography and roughness of the bare and TiO2-coated ceramic plates were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Comparing the processes of photocatalysis, ozonation and photocatalytic ozonation revealed that using photocatalytic ozonation led to the highest efficiency (85% at 35 min) in PhP removal. The influence of pH, PhP initial concentration and ozone gas flow rate on the removal of PhP was investigated in both individual and combined processes. The presence of synergy was investigated under various operational parameters. The mechanism of photocatalytic ozonation process was investigated in the presence of various reactive oxygen species (ROS) scavengers. The main intermediate products of PhP produced in ozonation and photocatalytic ozonation processes were verified by the GC–MS technique. The chronic phytotoxicity of PhP and its intermediate compounds formed in ozonation and photocatalytic ozonation was evaluated using aquatic species Spirodela polyrrhiza (S. polyrrhiza). It was found that the photocatalytic ozonation process, in contrast to the single ozonation process, can efficiently reduce the phytotoxicity of the PhP from aqueous solutions.

Esterification reaction using solid heterogeneous acid catalysts under solvent-less condition

Abstract: The preparation of di-2-ethylhexylphthalate (DOP) via esterification reaction of phthalic anhydride by 2-ethylhexanol in the presence of solid acidic catalysts has been investigated. The used catalysts were natural zeolite, synthetic zeolites (ZEOKAR-2, ASHNCH-3), heteropolyacid H4Si(W3O10)4 and sulfated ZrO2. The reactions were carried out under solvent-less conditions. It was observed that sulfated ZrO2 has higher reactivity and efficiency among the investigated catalysts. In the next part of the work, important plasticizers and ester base oils have prepared through esterification reaction of anhydrides and acids by alcohols in the presence of sulfated zirconia.

System of fractional differential algebraic equations with applications

Abstract: One of the important classes of coupled systems of algebraic, differential and fractional differential equations (CSADFDEs) is fractional differential algebraic equations (FDAEs). The main difference of such systems with other class of CSADFDEs is that their singularity remains constant in an interval. However, complete classifying and analyzing of these systems relay mainly to the concept of the index which we introduce in this paper. For a system of linear differential algebraic equations (DAEs) with constant coefficients, we observe that the solvability depends on the regularity of the corresponding pencils. However, we show that in general, similar properties of DAEs do not hold for FDAEs. In this paper, we introduce some practical applications of systems of FDAEs in physics such as a simple pendulum in a Newtonian fluid and electrical circuit containing a new practical element namely fractors. We obtain the index of introduced systems and discuss the solvability of these systems. We numerically solve the FDAEs of a pendulum in a fluid with three different fractional derivatives (Liouville–Caputo’s definition, Caputo–Fabrizio’s definition and with a definition with Mittag–Leffler kernel) and compare the effect of different fractional derivatives in this modeling. Finally, we solved some existing examples in research and showed the effectiveness and efficiency of the proposed numerical method.

Long-term monthly average temperature forecasting in some climate types of Iran, using the models SARIMA, SVR, and SVR-FA

Abstract: Temporal changes of the global surface temperature have been used as a prominent indicator of global climate change; therefore, making dependable forecasts underlies the foundation of sound environmental policies. In this research, the accuracy of the Seasonal Autoregressive Integrated Moving Average (SARIMA) Stochastic model has been compared with the Support Vector Regression (SVR) and its merged type with Firefly optimization algorithm (SVR-FA) as a meta-innovative model, in long-term forecasting of average monthly temperature. For this, 5 stations from different climates of Iran (according to the Extended De Martonne method) were selected, including Abadan, Anzali, Isfahan, Mashhad, and Tabriz. The data were collected during 1951–2011, for training (75%) and testing (25%). After selecting the best models, the average monthly temperature has been forecasted for the period 2012–2017. The results showed that the models had better performances in Extra-Arid and Warm (Abadan) and after that Extra-Arid and Cold (Isfahan) climate, in long-term forecasting. The weakest performances of the models were reported in Semi-Arid and Cold climate, including Mashhad and Tabriz. Also, despite the use of the non-linear SVR model and its meta-innovative type, SVR-FA, the results showed that, in the climates of Iran, the linear and classical SARIMA model still offers a more appropriate performance in temperature long-term forecasting. So that it could forecast the average monthly temperature of Abadan with root mean square error (RMSE) = 1.027 °C, and Isfahan with RMSE = 1.197 °C for the 6 years ahead. The SVR and SVR-FA models also had good performances. The results of this checking also report the effectiveness of the merging SVR model with the Firefly optimization algorithm in temperature forecasting in Iran’s climates, so, compared with the SVR model, it is suggested to use SVR-FA for temperature forecasting.