Inhomogeneous flow model of natural convection,entropy generation,and heatlines visualization in wavy I-shaped enclosure with rectangular heater

The present investigation is on examination of the natural convection and entropy generation considering the heatlines visualization of nanofluid I-shaped enclosure with two corrugated walls considering inner rectangular heater of three different heights. The influence of Brownian motion along with thermophoresis had been implemented using Inhomogeneous two-phase model of nanofluid. The governing equations were solved numerically using COMSOL software. Influence of Rayleigh number $$, Buoyancy ratio number $$, Lewis number $$, heater length $$. The results indicate that the influence of Lewis number on heat transfer bettering is stronger at high Rayleigh number $$ while its impact is negligible at a lower value of Rayleigh number (conduction mode). In addition, the total entropy generation gets its highest value at Lewis number $$. Bejan number, fluid flow strength and heat rate increase as the rectangular heater height increases. Also, higher heat transfer augmentation is taken when the heater height is $$ while increasing the heater height to $$ leads to more total entropy generation. The impact of heater height on total entropy generation is highly affected by Rayleigh number as increasing the heater height from $$ into $$, total entropy generation increases by $$ at $$ while it increases by $$ at $$.     

Experimental and numerical modelling of the three-dimensional incompressible flow behaviour in the near wake of circular cylinders

An experimental investigation was carried out to study the structure of the flow field around three-dimensional circular cylinders. The study of the flow field around an obstacle was performed in a wind tunnel using a particle image velocimetry (PIV) system. The flow of a fluid around an obstacle with a different velocity to the oncoming flow was examined. The results showed the dependence of the flow structure around the obstacle on its Reynolds number, and the spacing between a pair of obstacles. Detailed quantitative information of turbulence parameters in the vicinity of the obstacle was attained. Extensive wind tunnel experimental results are presented and compared with numerical simulation. A three-dimensional numerical model with Reynolds stress model (RSM) turbulence and a non-uniform grid system were used to examine the effects of a single cylinder and two cylinders in tandem on the flow. The principal objective was to analyse three-dimensional flow past a single cylinder and two circular cylinders placed in tandem by combining the application of a PIV experimental technique and an RSM turbulence model.For the case of two cylinders in tandem, the flow patterns are characterized in the gap region as a function of the distance between the cylinders. A good level of agreement was found between the experimental results of flow and numerical simulation.     

Antibacterial effect of dental cements evaluated using agar diffusion test

Purpose: Secondary caries can occur around the restoration, fixed prosthesis, and orthodontic band margins because of cariogenic bacteria. Long-lasting antibacterial effectiveness of dental cements used contemporarily can reduce this phenomenon. The purpose of this study was to examine the antibacterial activities of nine dental cements (BisCem^®, Super-Bond C&B, Rely X^TM, Panavia^TM F 2.0, Variolink^® II, Unitek^TM Multi Cure, Multilink^® Automix, Clearfil^TM Esthetic Cement, Transbond^TM LR) using agar diffusion test. Materials and methods: The test materials were inserted into the wells of Muller Hinton agar plates inoculated with Streptococcus mutans and Streptococcus salivarious. The diameters of the inhibition zones produced around the materials were measured after 24 h of incubation. Two-Way ANOVA, the Kruskal-Wallis, and the Mann–Whitney U tests at a significance level of p < 0.05 were analyzed for the results. Results: Unitek Multi Cure cement exhibited a significant difference from the control group against both S. mutans and S. salivarious (p < 0.05). While the zone of inhibition of Unitek Multi Cure cement was shorter (8.50 ± 1.77) than the control group (12.63 ± 1.30), Unitek Multi Cure had antibacterial effect against S. mutans and S. salivarious (p < 0.05). S. mutans displayed a significantly lower resistance to Unitek Multi Cure, BisCem, and Superbond C&B than S. salivarious (p < 0.05). Conclusion: Conventional glass ionomer cement, Unitek Multi Cure, exhibited greatest in vitro antibacterial activity against both S. mutans and S. salivarious. Formation of dental caries had been suppressed by the fluoride-releasing GICs.     

Extracting the Optical Parameters of the Fabricated (Al/Bare Borosilicate Crown Glass,BK-7/Ag) Multiple Layers

Significant effort has been devoted in this work to convert bare glass substrate with high transmittance, into reflective layers to know its suitability for modern applications. The glass substrate has been carefully chosen for its durability, high permeability, and ability to withstand any external stresses as a result of the accumulation of layers that reduce its permeability to convert it with the thin films coated on it into reflective materials. In parallel, the thin layer to be coated on the substrate is selected from films that can withstand external influences and their great optical properties, not to mention that they are cheap and can produce highly reflective surfaces. The optical measurements (transmittance and reflectance spectra) have been performed in the UV, Vis and NIR regions of the spectrum, that is, in the range between 300 and 1200 nm. Such measurements have been made for the bare glass substrate, the glass substrate with the Al (top side), and the glass substrate with Ag on it (bottom side), and then the optical measurements have been made for the three layers. The corresponding optical parameters of each layer have been calculated and ultimately a reflective layer with high electrical conductivity and excellent optical properties has been obtained that can be adapted for different application purposes.

     

The electrochemical investigation of salts partition with ion exchange membranes

The regenaration of acid and base from the solutions containing metallic salts was achieved by salt splitting method (SSM) using not only anion-exchange membranes (AEM) but also cation-exchange membrane (CEM). In these experiments, while the ion exchange membrane was anion-exchange membrane, acid solutions were used as an anolyte and different salts of potassium were used as a catholyte. In addition to these experiments, while the ion exchange membrane was cation-exchange membrane, base solutions were used as a catholyte and different salts of potassium were used as an anolyte. The effects of current density, initial concentrations of anolyte and catholyte solutions, the type of salt solution and the type of the ion-exchange membranes on the recovery ratio of bases and acids were investigated. The results of the experiments were investigated with the Statistical Package for Social Sciences (SPSS) program. The obtained results show that this technique can be used not only for recovering the acid and base wastes of industry but also for removing the impurities in order to obtain pure acids and bases in laboratory conditions.     

The peripheral dose outside the applicator in electron beams of Oncor linear accelerator

In this study, the peripheral dose outside the applicator was measured using electron beams produced by an Oncor linear accelerator and compared with the data of the treatment planning system (TPS). The dose profiles have been measured, by using a water-equivalent slab phantom and a parallel plate ionisation chamber, at 6, 9 and 15 MeV energy levels in 5×5, 10×10, 15×15, 20×20 and 25×25 cm(2) applicators and at 0, 10 and 20° gantry angles; and at the surface, 0.2, 0.5, 1 cm and d(max) depth for each electron energy level. The peripheral dose has been determined with these profiles by normalisation at the field central beam axis (CAX). It has been noticed that, using a 10×10 cm(2) applicator, there is a 1.4 % dose peak on the surface 6 cm away from the field edge where the field CAX is at 100 %, at a gantry angle of 0° with 6 and 9 MeV electron beams; also for the 15 MeV electron beam there is a 2.3 % dose peak. It has been discovered that the peak dose approaches a minimum depending on the increase in depth and reaches 2.5-4 % depending on the growth of the field dimension. At gantry angles of 10 and 20°, 6 and 9 MeV electron beams created small peaks and a maximum dose could be reached at 0.2 and 1 cm depth. Electron beam of 15 MeV did not peak at depths of 0.2 and 1 cm at gantry angles of 10 and 20°. The measured peripheral dose outside the applicators has been compared with the data from a TPS's computer using the Pencil Beam algorithm; it has been stated that dose calculations can be made as far as 3 cm outside the field. In conclusion, the TPS is not sufficient to measure the peripheral dose outside the applicators, and this dose can only be determined by direct measurement.     

Extent of decortication and quality of flour, couscous and porridge made from different sorghum cultivars

Sorghum grain was decorticated to remove 10%, 20%, 30% and 40% of the kernel for the purpose of improving flour colour, couscous colour and yield, and porridge texture. Flour lightness increased while yellow colour decreased with increased extent of decortication. Processing of the flours into couscous caused a considerable drop in lightness and increased yellow colour in couscous at all levels of decortication. As decortication level increased, couscous colour became lighter. Yellow colour progressively increased up to 30% kernel removal and dropped at 40%. Couscous yield, as measured by the proportion of particles of 1–2 mm size, also increased up to 30% kernel removal. This improvement in yield was attributed to decreased proportion of bran as indicated by ash content. However, the yield dropped at 40% kernel removal due to formation of large chunks of agglomerated flour particles. Thick porridge became harder as decortication level increased and this was strongly associated with the concomitant increase in starch concentration. Overall, this study defined the decortication levels necessary to improve the couscous colour and yield, and texture of porridge made from different sorghum cultivars.     

Production of bacterial cellulose fibers in the presence of effective microorganism

In this study, effective microorganism (EM) was added into fermentation medium in static culture to enhance bacterial cellulose (BC) production by Acetobacter xylinum 23769 strain. According to SEM micrographs, BC pellicles from BC-Baikal EM1 show a smaller diameter and a relatively narrow diameter distribution compared to BC pellicles from Hestrin–Schramm (HS) medium. The BC-HS absorbed 90.5 times its dry weight of water. The water holding capacity increased to 132.5 for BC-Baikal EM1 medium compared to BC-HS. From the FT-IR spectra, BC samples exhibited a similar pattern. The crystalline indices of Baikal EM1-altered BC (66%) were lower than Baikal EM1-free BC (71%).