Experimental and numerical analysis of aerodynamic effects of repair patches on damaged airfoils

This investigation assesses the change of aerodynamic characteristics of triangular and star-shaped damaged airfoils with repair patches. Both experimental and numerical methods to determine aerodynamic coefficients are used in this study. The test model is a NACA 64₁-412 airfoil full span, which is considered by using five schematics: Clean model, damaged model, upper repaired model, lower repaired model, and fully repaired model. Repair patches are chosen based on the Aircraft battle damage repair (ABDR) manuals. Various effects of repair schemes on triangular and star-shaped damages are quantitatively and qualitatively illustrated. A novel visualization method by paint and oil is used in wind tunnel tests to study the effects of repair patches on the damaged airfoil.     

Experimental investigation of aluminum oxide nanofluid on heat pipe thermal performance

In this research, the effect of using aluminum oxide nanofluid (pure water mixed with Al₂O₃ nanoparticle with 35 nm diameter) on the thermal efficiency enhancement of a heat pipe on the different operating state was investigated.     

Micro-Cup Architecture for Printing and Coating Asymmetric 2d-Material-Based Solid-State Supercapacitors

High energy density micro-supercapacitors (MSCs) are in high demand for miniaturized electronics and microsystems. Research efforts today focus on materials development, applied in the planar interdigitated, symmetric electrode architecture. A novel “cup & core” device architecture that allows for printing of asymmetric devices without the need of accurately positioning the second finger electrode here have been introduced. The bottom electrode is either produced by laser ablation of a blade-coated graphene layer or directly screen-printed with graphene inks to create grids with high aspect ratio walls forming an array of “micro-cups”. A quasi-solid-state ionic liquid electrolyte is spray-deposited on the walls; the top electrode material -MXene inks- is then spray-coated to fill the cup structure. The architecture combines the advantages of interdigitated electrodes for facilitated ion-diffusion, which is critical for 2D-material-based energy storage systems by providing vertical interfaces with the layer-by-layer processing of the sandwich geometry. Compared to flat reference devices, volumetric capacitance of printed “micro-cups” MSC increased considerably, while the time constant decreased (by 58%). Importantly, the high energy density (3.99 µWh cm⁻²) of the “micro-cups” MSC is also superior to other reported MXene and graphene-based MSCs.     

Effect of engineered water and scale inhibitor concentration on the adsorption performance of gypsum inhibitors on multi-walled carbon nanotubes and crushed sandstone

Engineered waterflooding is an effective process for enhanced oil recovery, but it can lead to mineral scale deposition due to the incompatibility of brines. Previous studies on scale mitigation have mainly focused on high-temperature baryte and anhydrite scales, neglecting gypsum precipitation and inhibitors adsorption at low temperatures. Additionally, earlier research has used simple brines that do not reflect the actual injection and formation water in reservoirs. In this study, the impact of temperature, various brine mixtures, and thermodynamic databases on saturation ratio and scale precipitation is explored using PHREEQC (pH-REdox-EQuilibrium-C program). The study reveals that the copresence of calcium and magnesium ions improves the gypsum inhibition efficiency of scale inhibitors (SIs) at low concentrations to a maximum of 79%. However, this effect is reversed or neutral at higher SI concentrations. The study also shows that the presence of monovalent ions reduces the adsorption of SIs by multi-walled carbon nanotubes (MWCNTs). Removing sodium ions from seawater while leaving calcium and magnesium ions intact increases MWCNTs' adsorption capability to 93%. This is because monovalent cations attach to the adsorbent surface and block the active sites, whereas divalent cations act as a bridge between MWCNT and SIs. The study establishes that the behaviour of SIs regarding adsorption on MWCNT and crushed sandstone depends on various factors, including molecule size, calcium toleration of the SIs, point of zero charge, and solution pH. Understanding these factors can improve the effectiveness of SIs, reduce chemical costs, and prolong the life of oil wells.     

Effective width estimation of flanged reinforced concrete shear walls

The present study deals with introducing a novel approach toward estimating the effective width of flanged reinforced concrete shear walls (FRCSWs). Due to the paucity of studies in assessing the effective width of nonrectangular sections, this paper aims at proposing efficacious formulations for the effective width estimation of short, squat, and slender T- and U-shaped reinforced concrete (RC) shear walls subjected to the simultaneous action of the axial and lateral loading. To this end, at first, FRCSWs are simulated in the flanged shear wall numerical laboratory (FlashLab) program, which utilizes the finite element Abaqus software to analyze the walls. Thereafter, employing the developed numerical models, an extensive parametric investigation is conducted for a wide range of the key parameters. General expressions have then been developed to estimate the effective width of flanged RC shear walls invoking the evolutionary polynomial regression (EPR) analysis in conjunction with the genetic algorithm (GA). To assess the capability of the established equations in predicting the effective width of flanged sections, R-factors have been calculated for all the cases examined in this study, which ranged between 0.78 and 0.94. Furthermore, a comparison has been made among the results attained through the proposed methodology and those obtained using the conventional design codes. It was revealed that the relative error obtained employing the proposed formulations is less than that of the corresponding values of the design codes by approximately 30% on average. The superiority of the established framework stems from consideration of the following: (1) influential parameters, (2) effective width variations at different performance levels, (3) loading direction, and (4) type of the wall in the effective width calculation process.     

Structural Basis of Cyclic 1,3-Diene Forming Acyl-Coenzyme A Dehydrogenases

The biologically important, FAD-containing acyl-coenzyme A (CoA) dehydrogenases (ACAD) usually catalyze the anti-1,2-elimination of a proton and a hydride of aliphatic CoA thioesters. Here, we report on the structure and function of an ACAD from anaerobic bacteria catalyzing the unprecedented 1,4-elimination at C3 and C6 of cyclohex-1-ene-1-carboxyl-CoA (Ch1CoA) to cyclohex-1,5-diene-1-carboxyl-CoA (Ch1,5CoA) and at C3 and C4 of the latter to benzoyl-CoA. Based on high-resolution Ch1CoA dehydrogenase crystal structures, the unorthodox reactivity is explained by the presence of a catalytic aspartate base (D91) at C3, and by eliminating the catalytic glutamate base at C1. Moreover, C6 of Ch1CoA and C4 of Ch1,5CoA are positioned towards FAD-N5 to favor the biologically relevant C3,C6- over the C3,C4-dehydrogenation activity. The C1,C2-dehydrogenation activity was regained by structure-inspired amino acid exchanges. The results provide the structural rationale for the extended catalytic repertoire of ACADs and offer previously unknown biocatalytic options for the synthesis of cyclic 1,3-diene building blocks.     

Investigating the gelling behaviour of ‘waxy' paraffinic mixtures during flow shutdown

The flow of waxy or paraffinic crude oils in a pipeline could be shutdown for a variety of reasons, resulting in their cooling and subsequent gelling. Gel formation from a multicomponent wax-solvent mixture during flow shutdown was investigated experimentally and analyzed with a transient heat-transfer model based on the moving boundary problem formulation. The gelling experiments were performed with a 0.10 g/g wax-solvent mixture in a flow-loop apparatus, following the formation of a steady-state deposit layer in turbulent flow regime, at two initial wax-solvent mixture temperatures, with a constant coolant temperature, and for different shutdown times. The gel formation was found to be a fast process, which continued until the gel fully occupied the deposition tube. Gas chromatographic analyses of the deposit samples (under sheared cooling) and the gel samples (under static cooling during flow shutdown) indicated significant differences in the composition and the total wax content. The deposit samples showed an enrichment of heavier paraffins, whereas the composition of gel samples was comparable to that of the original wax-solvent mixture. The predictions from the transient model showed that a lower initial oil temperature, a lower coolant temperature, and a smaller pipe diameter would result in a faster blockage of the pipe. The predictions from the moving boundary problem formulation agreed well with the flow shutdown data, which further confirmed that the solid and gel formation from wax-solvent mixtures is modelled satisfactorily as a heat transfer process.     

Determination of elastic constants of additive manufactured Inconel 625 specimens using an ultrasonic technique

The nature of additive manufacturing (AM) processes prescribes direction-dependent properties of the final parts. The degree of material anisotropy is high     

Scalable Functionalization of Optical Fibers Using Atomically Thin Semiconductors

Atomically thin transition metal dichalcogenides are highly promising for integrated optoelectronic and photonic systems due to their exciton-driven linear and nonlinear interactions with light. Integrating them into optical fibers yields novel opportunities in optical communication, remote sensing, and all-fiber optoelectronics. However, the scalable and reproducible deposition of high-quality monolayers on optical fibers is a challenge. Here, the chemical vapor deposition of monolayer MoS₂ and WS₂ crystals on the core of microstructured exposed-core optical fibers and their interaction with the fibers’ guided modes are reported. Two distinct application possibilities of 2D-functionalized waveguides to exemplify their potential are demonstrated. First, the excitonic 2D material photoluminescence is simultaneously excited and collected with the fiber modes, opening a novel route to remote sensing. Then it is shown that third-harmonic generation is modified by the highly localized nonlinear polarization of the monolayers, yielding a new avenue to tailor nonlinear optical processes in fibers. It is anticipated that the results may lead to significant advances in optical-fiber-based technologies.