Study of flow field,heat transfer,and entropy generation of nanofluid turbulent natural convection in an enclosure utilizing the computational fluid dynamics‐artificial neural network hybrid method

In this study, the turbulent natural convection of Ag‐water nanofluid in a tall, inclined enclosure has been investigated. The main objective of this study is finding the optimized angle of the enclosure with operational boundary condition in cooling from ceiling utilizing the computational fluid dynamics‐artificial neural network (CFD‐ANN) hybrid method, which has not been noticed in previous studies. To achieve this, we proposed two approaches. First, the simulations have been done with a deviation angle of 0 to 90° by using water and Ag‐water nanofluid. And second, a new prediction approach is proposed based on radial basis function artificial neural networks (RBF‐ANN) to predict the mean Nusselt number and entropy generation with the variation of Rayleigh numbers, deviation angles, and volume fractions as inputs. The results from the first approach indicate that the Rayleigh number has a considerable function in the determination of optimized angle. The results from the second approach, which used the first approach simulation results as training data set, could predict the mean Nusselt number and entropy generation with 1.4577e^?022 and 1.552e^?015 mean square error, respectively. Moreover, a new set of data for Rayleigh numbers, deviation angles, and volume fractions were used to test the performance of the prediction model, which shows promising and superior prospects for RBF‐ANN.     

Compressive quasistatic and dynamic behavior of SiC/ZrO2 aluminum-based nanocomposite

Journal of Mechanical Science and Technology - This research investigated the mechanical properties of aluminum-based nanocomposite. The spark plasma sintering method was adopted to fabricate the...     

Synthesis of mesoporous nanocrystalline zirconia with tetragonal crystallite phase by using ethylene diamine as precipitation agent

Mesoporous nanocrystalline zirconia with high surface area and pure tetragonal crystallite phase has been prepared by bifunctional ethylene diamine as both precipitating agent for ZrO(NO₃)₂ to ZrO(OH)₂ and colloidal protecting agent for the ZrO(OH)₂ nanoparticles. The effect of refluxing time and temperature on the structural properties of the zirconia were investigated. The obtained results showed that the increasing in refluxing time and temperature improved the thermal stability and increased the tetragonal content of the zirconia. The results also showed that the addition of Pluronic P123 block copolymer surfactant acted as a cosurfactant and increased the specific surface area of the zirconia.     

Crushing behaviour of composite hemispherical shells subjected to quasi-static axial compressive load

This paper examines the effects of composite constituents and geometry on the energy absorption capability of composite hemispherical shells. To examine the effects of matrix types on their energy absorption capability, glass fibre/epoxy and glass fibre/polyester hemispherical shells were fabricated. While glass fibre/epoxy and carbon fibre/epoxy hemispherical shells were fabricated to investigate the effect of fibre reinforcements. Effect of aspect ratio (R/t) was also examined and the results were presented. The results obtained showed that the energy absorption capability of the hemispherical shells significantly affected by the composite constituents as well as R/t ratio.     

Sonochemical synthesis and characterization of zinc tungstate nanoparticles and investigation of its photocatalyst application

Zinc tungstate nanoparticles were synthesized via a sonochemical method based on the reaction between zinc (II) nitrate hexahydrate and sodium tungstate dihydrate in water. The structural, morphological and optical properties of as-obtained products were characterized by techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and ultraviolet–visible spectroscopy. The samples indicated a ferromagnetic behavior, as evidenced by using vibrating sample magnetometer at room temperature. To evaluate the catalytic properties of nanocrystalline zinc tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.     

Synthesis of carbon nanotube-cadmium selenide luminescent nanocomposites using electrophoretic deposition technique

In this research, nanocomposites containing carbon nanotube (CNT)-cadmium selenide (CdSe) quantum dots (QDs) were synthesized and deposited using electrophoretic deposition technique for optical sensors and displays. The composite was first synthesized using silane grafted cadmium selenide and different concentrations of carbon nanotubes, and then deposited on the aluminum electrodes via electrophoresis method. Fourier transformation infrared confirmed the formation of CNT–CdSe nanocomposites. Microstructural investigations using scanning and transmission electron microscopy also showed the presence of the QDs on the surface of carbon nanotubes (CNTs), enhancing their surface roughness. Increasing the applied voltage from 120 to 240 V resulted in the variation of deposition yield in the range of 0.0005–0.0035 g.cm^?2. The deposition yield was first increased and then decreased in all the samples. Photoluminescence studies revealed that the deposited composite has a distinct emission peak in the range of 485–495 nm (green region) under 360 nm illumination depending on the concentration of CNTs. It can be concluded that the deposited composite may be used in field emission displays due to its high efficiency emission in the presence of CNTs.     

Nanocrystalline copper ferrite: synthesis of different shapes through a new method and its photocatalyst application

Pure CoFe₂O₄ nanostructures were prepared via auto-combustion sol–gel method in presence of different amino acids as a natural fuel. The effect of different amino acids such as leucine, asparagine, and alanine on the size, and morphology of CoFe₂O₄ nanostructures were investigated. The as-obtained CoFe₂O₄ nanostructures were analyzed by UV–Vis diffuse reflectance spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray microanalysis, and X-ray diffraction. The magnetic properties of as-prepared CoFe₂O₄ nanostructures were also investigated with vibrating sample magnetometer. In addition, methyl orange was chosen as a dye water pollution to evaluate its degradation by as-synthesize CoFe₂O₄ under ultraviolet light irradiation. Furthermore, the photocatalysis results reveal that the maximum decolorization of 82 % for methyl orange occurred with CoFe₂O₄ nanoparticles in 90 min under ultraviolet (UV) light irradiation.     

Experimental and theoretical investigation on polystyrene/n-pentane foaming process

At the present work, foaming process (bubbles nucleation and growth) of Polystyrene (PS)/n-pentane batch foaming system was studied experimentally and theoretically. Synthesized PS was characterized by rheological measurements and the foaming dynamics was studied using a designed in-situ observation apparatus. The saturation time at the lowest mass diffusivity conditions was determined to ensure that all experiments would be performed at saturation state. Dissolved content and Henry’s constant of n-pentane in PS at foaming conditions were also determined. The effects of temperature and sorption pressure as operation parameters on the foaming dynamics of PS/n-pentane system were investigated and it was found that temperature had a dramatic effect on the foaming dynamics and other parameters such solubility, diffusivity and melt strength were affected by temperature. Moreover, the bubble growth behavior of PS/n-pentane system was simulated and it was compared to the experimental results. To calculate concentration profile in the shell, mass diffusion equations were solved by implicit method with considering gas escape from the outer layer of the viscoelastic shell around the bubble. Furthermore the effect of mass diffusivity and viscosity on the bubble growth behavior was examined simultaneously and it was emphasized that the bubble growth behavior was a mass diffusion controlled phenomenon.     

Green permutation flowshop scheduling problem with sequence-dependent setup times: a case study

Increasing global energy consumption, large variations in its cost and the environmental degradation effects are good reasons for the manufacturing industries to become greener. Green shop floor scheduling is increasingly becoming a vital factor in the sustainable manufacturing. In this paper, a green permutation flowshop scheduling problem with sequence-dependent setup times is studied. Two objectives are considered including minimisation of makespan as a measure of service level and minimisation of total energy consumption as a measure of environmental sustainability. We extend a bi-objective mixed-integer linear programming model to formulate the stated problem. We develop a constructive heuristic algorithm to solve the model. The constructive heuristic algorithm includes iterated greedy (CHIG) and local search (CHLS) algorithms. We develop an efficient energy-saving method which decreases energy consumption, on average, by about 15%. To evaluate the effectiveness of the constructive heuristic algorithm, we compare it with the famous augmented ?-constraint method using various small-sized and large-sized problems. The results confirm that the heuristic algorithm obtains high-quality non-dominated solutions in comparison with the augmented ?-constraint method. Also, they show that the CHIG outperforms the CHLS. Finally, this paper follows a case-study, with in-depth analysis of the model and the constructive heuristic algorithm.     

Direct Fused Deposition Modeling 4D Printing and Programming of Thermoresponsive Shape Memory Polymers with Autonomous 2D-to-3D Shape Transformations

Herein, direct 4D printing of thermoresponsive shape memory polymers (SMPs) by the fused deposition modeling (FDM) method that enables programing of 2D objects during printing for autonomous 2D-to-3D shape transformations via simply heating is focused on. The programming process during printing is investigated through designs and experiments. The capability of programming SMPs during printing is illustrated by prestrain and bending capabilities, which are highly related to printing settings, such as nozzle temperature, print speed, layer height, infill patterns, and ratio of active parts in a bilayer structure. A nearly linear relationship for prestrain and bending parameters is experimentally revealed for different printing factors. Quantitative results are presented to be used as a guidance for designing complex 3D structures via 4D printing of 2D structures. Helix structure, twisting structure, DNA-like structures, and functional gripper are designed to demonstrate the potential of direct FDM 4D printing for creating complex 3D structures from simple 2D structures with advantages over traditional manufacturing methods. It is shown that, by removing the need for a layer-by-layer stacking process to achieve a complex 3D shape, FDM can promote sustainability via 4D printing of autonomous 2D-to-3D shape transformer structures with lower materials, time, energy, and longer service life.