Performance analysis of hybrid/single nanofluids on augmentation of heat transport in lid-driven undulated cavity

This numerical study reveals the heat transfer performance of hybrid/single nanofluids inside a lid-driven sinusoidal trapezoidal-shaped enclosure. The right and left inclined surfaces of the trapezium have been considered as insulated, whereas the bottom sinusoidal wavy and the flat top surfaces of the enclosure as hot and cold, respectively. The governing partial differential equations of fluid's velocity and temperature have been resolved by applying the finite element method. The implications of Prandtl number (4.2-6.2), Richardson number (0.1-10.0), undulation number (0-3), nanoparticles volume fraction (0%-3%), and nanofluid/base fluid (water, water–copper (Cu), water–Cu–carbon nanotube, water–Cu–copper oxide (CuO), water–Cu–TiO₂, and water–Cu–Al₂O₃) on the velocity and temperature profiles have been studied. Simulated findings have been represented by means of streamlines, isothermal lines, and average Nusselt number of above-mentioned hybrid nanofluids for varying the governing parameters. The comparison of heat transfer rates using hybrid nanofluids and pure water has been also shown. The heat transfer rate is increased about 15% for varying Richardson number from 0.1 to 10.0. Blending of two nanoparticles suspension in base fluid has a higher heat transfer rate—approximately 5% than a mononanoparticle. Moreover, a higher average Nusselt number is obtained by 14.7% using the wavy surface than the flat surface of the enclosure. Thus, this study showed that applying hybrid nanofluid may be beneficial to obtain expected thermal performance.     

Effect of pulsed ultrasound treatment compared to continuous mode on microbiological and quality of Mirabelle plum during postharvest storage

The effects of pulsed and continuous ultrasound treatment on microbiological and physiological quality of Mirabelle plum fruit were investigated. Freshly harvested Mirabelle plum was treated with 30‐kHz pulsed and continuous ultrasound at 20 °C for 0, 15, 30, 45 and 60 min and subsequently stored at 4 °C for 10 days. The total count of bacteria, total fungi, decay index, titratable acidity (TA), total soluble solids (TSS), colour, texture, ascorbic acid content and total phenolics was measured. The results showed that pulsed and continuous ultrasonic treatment significantly (P < 0.05) reduced the number of microorganisms and improved the quality of Mirabelle plums during storage. Increasing pretreatment time enhanced the positive effects of pulsed and continuous ultrasound. Also, in terms of the total count of bacteria, total fungi, titratable acidity and total phenolics, the pulsed and continuous ultrasound did not show a significant difference (P < 0.05). However, pulsed ultrasound was better compared to continuous mode in preservation of TSS, colour, texture and ascorbic acid content of the fruit during storage. Our results demonstrated that pulsed ultrasound is an appropriate method for improving safety and maintaining the quality of Mirabelle plum fruit.     

Fermentation of table cream by Lactobacillus plantarum strains: effect on fungal growth,aflatoxin M1 and ochratoxin A

Aflatoxin M1 (AFM₁) and ochratoxin A (OTA) are two main mycotoxins in milk and dairy products. In the present work, the ability of four Lactobacillus strains (L. plantarum PTCC 1058, L. plantarum LP3, L. plantarum AF1 and L. plantarum LU5) to remove AFM1 and OTA in fermented cream was studied during 24 h fermentation. The antifungal activity of the mentioned lactobacilli against the defined fungi (Aspergillus flavus PTCC 5004, Aspergillus parasiticus PTCC 5018, Aspergillus nidulans PTCC 5014, Aspergillus ochraceus PTCC 5060) was also evaluated. The results showed that the cell counts of all strains were increased by 64–70% during fermentation. All Lactobacillus strains decreased the amount of AFM₁ significantly (P ≤ 0.05) in the range of 26–52%, which the highest AFM₁-reducing effect was related to L. plantarum LU5 (from 0.5 to 0.24 μg kg⁻¹). The mean OTA removal by Lactobacillus strains in fermented cream also ranged from 32 to 58%. Amongst Lactobacillus strains, the cell-free culture supernatants of L. plantarum LU5 showed the highest (inhibition zone of 26.7 ± 1.2 mm) and L. plantarum LP3 and L. plantarum PTCC 1058 the lowest antifungal activities. The fermented creams contained Lactobacillus strains exhibited the highest and lowest antifungal activities against A. ochraceus and A. parasiticus, respectively. L. plantarum LU5, with the inhibition zone of 27.6 ± 0.9 mm, was the most effective fungal inhibitor, while L. plantarum PTCC 1058 had the lowest antifungal activity.     

The role of geometry on the viscoelastic materials properties: tensile and stress relaxation of the yarn

The time-dependent mechanical behavior of textiles has particular importance. One of such behaviors is stress relaxation. When strain is applied constantly, there is a decreased stress with time in viscoelastic materials, which is called stress relaxation. The aim of this study is to investigate the effect of knot’s geometry (surgeon, square and eight) and the number of knots on the tensile and stress relaxation properties of the polyester yarn. Significant differences were observed for the tensile characteristics of the yarn in the presence of the knot. Generally, the knotted yarns demonstrated lower tensile stress and strain at failure. Moreover, the results revealed that the stress relaxation behavior of the yarn is affected by the number of knots and their geometry. The yarn without knot exhibited the highest stress relaxation percent while the yarn with the surgeon’s knot displayed the least stress relaxation percent. On the other hand, increasing the number of knots led to a decrease in the percentage of yarn stress relaxation.     

Effect of Al Antioxidant on the Rate of Oxidation of Carbon in MgO–C Refractory

Kinetics of air oxidation of MgO–C–Al refractory at 600°–1300°C were investigated using the software based on the modified shrinking core model (KDA). Commercial bricks containing 88.5% MgO, 10% residual carbon, and 1.5% aluminum anti-oxidant were oxidized isothermally with air. Combination of experimental data with model calculations indicated gas diffusion through solid material and pores as a major controlling step. Previously observed chemisorption process was eliminated from the rate-controlling mechanism with addition of aluminum antioxidant. Comprehensive rate equations were devised for MgO–C–Al and MgO–C oxidation reactions. Overall activation energies of Q _id (internal diffusion)=139.15 kJ/mol at T ≤800°C and Q _pd (pore diffusion)=25.48 kJ/mol at T >800°C were obtained for MgO–C–Al oxidation reactions. Corresponding values were determined to be Q _id=134.85 kJ/mol and Q _ca (chemical adsorption)=66.69 kJ/mol at T ≤800°C and Q _pd=18.95 kJ/mol and Q _ca=66.69 kJ/mol at T >800°C for MgO–C oxidation reactions. Addition of aluminum anti-oxidant indicated a reducing effect on oxidation of MgO–C bricks at 800°C≤ T ≤1250°C. Reverse behavior was observed at T ≤700°C.     

Evaluation of ZnO-Vitamin B1 Nanoparticles on Bioactivity and Physiochemical Properties of the Polycaprolactone-Based Nanocomposites

In the present study, we investigated the use of thiamine chloride hydrochloride (vitamin B₁)-modified ZnO nanoparticles (ZnO-VB₁ NPs) to reinforce polycaprolactone matrix. The stable and bioactive PCL/ZnO-VB₁ nanocomposites were fabricated with the combination of ultrasonication and solution casting methods. Transmission electron microscope results indicated that the ZnO-VB₁ NPs were uniformly dispersed in the matrix. The nanocomposites showed high hydroxyapatite formation (high bioactivity) in the simulated body fluid. The nanocomposites with 2?wt% of the modified nanoparticles were found to have highest mechanical strength. The nanocomposites with more nanofiller concentrations exhibited high wettability.