Three‐dimensional computational comparison of mini pinned heat sinks using different nanofluids: Part one—the hydraulic‐thermal characteristics

The hydraulic‐thermal characteristics of 3D pinned heat sink designs have been numerically compared as the first part of a three‐part investigation. Five different pin geometries (circular, square, triangular, strip, and elliptic pins) and an unpinned heat sink with three types of nanofluids (Al₂O₃–H₂O, SiO₂–H₂O, and CuO–H₂O) are considered for laminar forced convection. The range of Reynolds number is from 100 to 1000, and volume fractions vary between 0% and 5%. The finite volume method is employed to solve the Navier–Stokes and energy equations by employing a SIMPLE algorithm for a computational solution. Three parameters are presented—the Nusselt number, the bottom temperature, and the hydrothermal performance of the heat sink with pressure drop data. The findings indicated that the overall hydrothermal performance of elliptic‐pinned (EP) heat sinks produces the most substantial value of 3.10 for pure water. For different nanofluids, the SiO₂–water nanofluids with EPs have the most significant hydrothermal performance. Also, this factor is enhanced with an increase in nanofluid concentration up to nearly 3.34 for 5% of SiO₂–water. Consequently, applying the elliptic‐pinned heat sinks is recommended with pure water for considering an increase in the pressure drop, with 5% of SiO₂–water nanofluids, regardless of an enlargement of pressure drop for heat‐dissipation applications.     

An investigation on machinability assessment of Al-6XN and AISI 316 alloys: an assessment study of machining

This work presents machinability assessment of AL-6XN super austenitic stainless steel alloy. Cutting forces, surface roughness, work hardening tendency and tool wear were analyzed. The assessment was conducted based on a comparison between the AL-6XN alloy and the well-known alloy in the machining field AISI 316. Finite element analysis (FEA) study was also conducted and used in this assessment. Experimental results showed maximum increase of 70% and 57% in the feed and normal forces of the AL-6XN alloy, respectively. Maximum increase in the work hardening tendency of 59% was recorded for the AL-6XN alloy while only 29% was recorded for the 316 alloy. The roughness analysis recorded an increase of 186% for the AL-6XN alloy compared to the 316 alloy. Tool wear analysis revealed the build-up edge formation, severe chipping, flank and crater wear (CW) during cutting AL-6XN alloy whereas small chipping, flank and CW were noticed during cutting 316 alloy. FEA study showed when the AL-6XN alloy machined using 65 and 94?m/min cutting speeds, the increases (compared to the 316 alloy) were: 12% and 8% in plastic strain; 20% and 20% in stresses; 48% and 100% in residual tensile stresses; 22% and 92% in residual compressive stresses, respectively.     

Textile applications of photochromic dyes. Part 4: application of commercial photochromic dyes as disperse dyes to polyester by exhaust dyeing

A series of commercial photochromic dyes was applied to polyester fabric as disperse dyes. The photocoloration properties of the dyed fabrics were investigated by applying techniques previously established in our laboratories using an independent source of ultraviolet irradiation and traditional colour measurement instrumentation. The dyed fabrics showed reversible photochromism, developing pronounced colours from weak background colours on irradiation with ultraviolet light and returning to their original state when the ultraviolet light source was removed. However, the extent of photocoloration and the depth of background colour varied significantly with the particular dye used. The dyeing procedure was optimised by maximising the degree of photocoloration, expressed as the colour difference (ΔE₁) between the colour developed after ultraviolet exposure and background colour, while minimising the background colour, expressed as the colour difference (ΔE₂) between unexposed dyed and undyed fabrics. Optimum dyeing concentrations were determined. The colour development and fading properties, fatigue resistance and storage stability of the dyed fabrics were investigated.     

A new modified differential evolution algorithm scheme-based linear frequency modulation radar signal de-noising

The main intention of this study was to investigate the development of a new optimization technique based on the differential evolution (DE) algorithm, for the purpose of linear frequency modulation radar signal de-noising. As the standard DE algorithm is a fixed length optimizer, it is not suitable for solving signal de-noising problems that call for variability. A modified crossover scheme called rand-length crossover was designed to fit the proposed variable-length DE, and the new DE algorithm is referred to as the random variable-length crossover differential evolution (rvlx-DE) algorithm. The measurement results demonstrate a highly efficient capability for target detection in terms of frequency response and peak forming that was isolated from noise distortion. The modified method showed significant improvements in performance over traditional de-noising techniques.     

Thermal and rheological properties of the supersaturated sucrose solution in the presence of different molecular weight fractions and concentrations of dextran

In our current research work, we investigated the effects of molecular weight (M _w) and the concentration of dextran presence during cane sugar manufacturing on the rheological and glass transition properties of supersaturated sucrose solution. Three dextrans of various M _w, namely 100,000 g/mol (T ₁₀₀), 500,000 g/mol (T ₅₀₀) and 2,000,000 g/mol (T ₂₀₀₀), were admixed in concentrations between 1,000 and 10,000 ppm with 65 and 75% w/w sucrose solution. The results indicated that both the apparent viscosity and dynamic modulus increased with an increase in dextran concentrations and they demonstrated strong dependence on its M _w. Glass transition temperature (T _g) of the samples was measured by differential scanning calorimetry, and their dependence on dextran M _w and concentration was analyzed by the Fox and expanded Gordon–Taylor mathematical models. It was found that the higher the M _w and concentration of the dextran, the greater the increase in T _g. The expanded Gordon–Taylor equation has proved useful in predicting the T _g of the sucrose solution in the presence of polymer.     

Carbon Nanotube (10, 0) and Silicon Nanotube (7, 0) as a Novel Material for Drug Delivery of Substituted Eugenols as Antioxidant Drugs

Silicon - The potential of CNT(10, 0) and SiNT(7, 0) and their metal doped CNT(10, 0) and SiNT(7, 0) to adsorb the NH2, OH and Ethyl eugenols are examined. The antioxidant potential of NH2-, OH-...     

New Type Anode for Calcium Ion Batteries Based on Silicon Carbide Monolayer

Silicon - A theoretical research study was conducted into the possibility of using a two-dimensional graphene-like material silicon carbide nano-sheet (2D-SiCNS) as an anode in rechargeable Ca-ion...     

Eco-friendly polyvinyl alcohol (PVA)/bamboo charcoal (BC) nanocomposites with superior mechanical and thermal properties

Carbon-based nanofillers, such as carbon nanotubes (CNTs) and graphene sheets are considered as effective nanoreinforcements due to their unique structures and material performance. However, the utilisation of such nanofillers can be hindered owing to a high level of nanotoxicity via human inhalation and high material cost for CNTs, as well as the tendency to form agglomerates of graphene sheets in polymer matrices. Bamboo charcoals (BCs) are eco-friendly and sustainable carbon-based particles, which possess good affinity with polyvinyl alcohol (PVA), one of popular water soluble biopolymers, to achieve excellent properties of PVA/BC nanocomposites. In particular, porous structures of BC particles enable polymeric molecules to easily penetrate with the strong internal bonding. In this study, fully eco-friendly PVA/BC nanocomposite films were successfully fabricated using a simple solution casting method to achieve the high dispersibility of BCs. With the inclusion of only 3 wt% BCs, tensile modulus and tensile strength of PVA/BC nanocomposite films were enhanced by 70.2 and 71.6%, respectively, when compared with those of PVA films. Better thermal stability is manifested for resulting nanocomposite films as opposed to that of pristine PVA, which is evidenced by the maximum increase of 17.8% in the decomposition temperature at the weight loss of 80%. It is anticipated that BCs can compete against conventional carbon-based nanofillers with a great potential to be developed into eco-friendly nanocomposites used for thin-film packaging application.