Improving the dynamic performance of continuous-flow mixing of pseudoplastic fluids possessing yield stress using Maxblend impeller

The strategic approach of this article is to characterize the continuous-flow mixing of pseudoplastic fluids possessing yield stress in a stirred reactor with the Maxblend impeller. Dynamic experiments were carried out through the frequency-modulated random binary input of a brine solution to determine the extent of non-ideal flows. Mixing quality was determined on the basis of the extent of channeling and fully mixed volume. The effects of important parameters such as impeller speed (25–500 rpm), absence of baffles, fluid rheology (0.5–1.5%), fluid flow rate (3.20–14.17 L min⁻¹), and the locations of inlet/outlet on the dynamic performance of the continuous-flow mixing vessel were explored. The performance of the Maxblend impeller was then compared to the performances of various types of impellers such as close-clearance (an anchor), axial-flow (a Lightnin A320), and radial-flow (a Scaba 6SRGT) impellers. It was found when the channeling approached zero and the fully mixed volume approached the total fluid volume in the vessel, the power drawn by the A320 impeller and the Scaba impeller were about 2.9 and 4.3 times greater than that of the Maxblend impeller. Thus, the Maxblend impeller was able to drastically improve the performance of continuous-flow mixing with huge power savings. The mixing quality was further improved by optimizing the impeller speed, decreasing the fluid flow rate, decreasing the fluid concentration, and using bottom inlet- top outlet configuration. The flow non-ideality of the mixing system increased in the absence of the baffles. Thus, better mixing quality and more energy savings can be achieved by employing the findings of this study.     

Volatile Organic Compounds Emitted by Fungal Associates of Conifer Bark Beetles and their Potential in Bark Beetle Control

Conifer bark beetles attack and kill mature spruce and pine trees, especially during hot and dry conditions. These beetles are closely associated with ophiostomatoid fungi of the Ascomycetes, including the genera Ophiostoma, Grosmannia, and Endoconidiophora, which enhance beetle success by improving nutrition and modifying their substrate, but also have negative impacts on beetles by attracting predators and parasites. A survey of the literature and our own data revealed that ophiostomatoid fungi emit a variety of volatile organic compounds under laboratory conditions including fusel alcohols, terpenoids, aromatic compounds, and aliphatic alcohols. Many of these compounds already have been shown to elicit behavioral responses from bark beetles, functioning as attractants or repellents, often as synergists to compounds currently used in bark beetle control. Thus, these compounds could serve as valuable new agents for bark beetle management. However, bark beetle associations with fungi are very complex. Beetle behavior varies with the species of fungus, the stage of the beetle life cycle, the host tree quality, and probably with changes in the emission rate of fungal volatiles. Additional research on bark beetles and their symbiotic associates is necessary before the basic significance of ophiostomatoid fungal volatiles can be understood and their applied potential realized.     

Characterization of the continuous-flow mixing of non-Newtonian fluids using the ratio of residence time to batch mixing time

Continuous-flow mixing of pseudoplastic fluids possessing yield stress is a complex phenomenon exhibiting non-ideal flows within the stirred vessels. Electrical resistance tomography (ERT), a non-intrusive technique, was employed to measure the mixing time in the batch mode while dynamic tests were performed to study the mixing system in the continuous mode. This study attempts to explore the effects of the operating conditions and design parameters on the ratio of the residence time (τ) to the mixing time (θ) for the continuous-flow mixing of non-Newtonian fluids. To achieve these objectives, the effects of impeller types (four axial-flow impellers: A310, A315, 3AH, and 3AM; and three radial-flow impellers: RSB, RT, and Scaba), impeller speed (290–754 rpm), fluid rheology (0.5–1.5%, w/v), impeller off-bottom clearance (H/2.7–H/2.1, where H is the fluid height in the vessel), locations of inlet and outlet (configurations: top inlet-bottom outlet and bottom inlet-top outlet), pumping directions of an axial-flow impeller (up-pumping and down-pumping), fluid height in the vessel (T/1.06–T/0.83, where T is the tank diameter), residence time (257–328 s), and jet velocity (0.317–1.66 ms⁻¹) on the ratio of τ to θ were investigated. The results showed that the extent of the non-ideal flows (channeling and dead volume) in the continuous-flow mixing approached zero when the value of τ/θ varied from 8.2 to 24.5 depending on the operating conditions and design parameters. Thus, to design an efficient continuous-flow mixing system for non-Newtonian fluids, the ratio of the residence time to the mixing time should be at least 8.2 or higher.     

Prediction of inter-laminar stresses in composite honeycomb sandwich panels under mechanical loading using Variational Asymptotic Method

This work focuses on the formulation of an asymptotically correct theory for symmetric composite honeycomb sandwich plate structures. In these panels, transverse stresses tremendously influence design. The conventional 2-D finite elements cannot predict the thickness-wise distributions of transverse shear or normal stresses and 3-D displacements. Unfortunately, the use of the more accurate three-dimensional finite elements is computationally prohibitive. The development of the present theory is based on the Variational Asymptotic Method (VAM). Its unique features are the identification and utilization of additional small parameters associated with the anisotropy and non-homogeneity of composite sandwich plate structures. These parameters are ratios of smallness of the thickness of both facial layers to that of the core and smallness of 3-D stiffness coefficients of the core to that of the face sheets. Finally, anisotropy in the core and face sheets is addressed by the small parameters within the 3-D stiffness matrices. Numerical results are illustrated for several sample problems. The 3-D responses recovered using VAM-based model are obtained in a much more computationally efficient manner than, and are in agreement with, those of available 3-D elasticity solutions and 3-D FE solutions of MSC NASTRAN.     

Stealth assessment strategy in distributed systems using optimal deep learning with game based learning

The Journal of Supercomputing - Game-based learning (GBL) is familiar in several respects, as it can embed problem-solving challenges in an interactive virtual environment to improve...     

Heat Transfer Efficiency of Aluminum Substrates With Embedded Semi-Active Thermal Control Device

This article presents the work carried out in evaluating the efficiency of embedded heat pipes in simulated satellite substrates subjected to localized heat sources. The experimental setup that comprises either an aluminum plate or an aluminum honeycomb sandwich panel with an electrical heating element was designed. Various experiments were conducted on the substrates with and without embedded heat pipes at various heating power inputs. Case studies with adjoined and inclined substrates, employing either one or two embedded heat pipes having different insertion lengths, were performed. With the help of COMSOL Multiphysics 3.5a software, an equivalent three-dimensional finite-element model of the experimental setup was created and analyzed under the same real-time conditions. Based on the experimental results, design guidelines are proposed for optimized heat management within a satellite substrate using embedded heat pipes.     

Synthesis,characterization, optical and electrical properties of thermally stable polyazomethines derived from 4,4′-oxydianiline

Three soluble, thermally stable azomethine polymers were synthesized by the oxidative polycondensation of azomethine bisphenols using NaOCl as an oxidant in aqueous alkaline medium. The azomethine bisphenol monomers, 4,4′-oxybis[N-(2-hydroxy-3-methoxybenzilidine)aniline], 4,4′-oxybis[N-(2-hydroxy-5-bromobenzilidine)aniline] and 4,4′-oxybis[N-(2-hydroxynaphthalidine) aniline] were synthesized by the condensation of 4,4′-oxydianiline with three aromatic aldehydes. The structures of the monomers and polymers were confirmed by Fourier Transform infrared spectroscopy, UV–visible, ¹H-NMR and ¹³C-NMR spectroscopic techniques. Morphology of the synthesized polymers was characterized using scanning electron microscope. The thermal stability of the polymers is evidenced by high carbines residue obtained in TGA. Fluorescence spectra showed that the emission maxima centred in the region 420–460 nm for all the compounds with large stokes shift values (?λ_ST). Electrical conductivity of iodine-doped polymers was measured by four-point probe technique. The synthesized polymers have shown good electrical conductivity on iodine doping, and it increases with the increase in iodine vapour contact time. The self-extinguishing property of the synthesized polymers was studied by the calculation of the limiting oxygen index values with van Krevelen’s equation.     

Facial Expression Recognition Using Enhanced Convolution Neural Network with Attention Mechanism

Facial Expression Recognition (FER) has been an interesting area of research in places where there is human-computer interaction. Human psychology, emotions and behaviors can be analyzed in FER. Classifiers used in FER have been perfect on normal faces but have been found to be constrained in occluded faces. Recently, Deep Learning Techniques (DLT) have gained popularity in applications of real-world problems including recognition of human emotions. The human face reflects emotional states and human intentions. An expression is the most natural and powerful way of communicating non-verbally. Systems which form communications between the two are termed Human Machine Interaction (HMI) systems. FER can improve HMI systems as human expressions convey useful information to an observer. This paper proposes a FER scheme called EECNN (Enhanced Convolution Neural Network with Attention mechanism) to recognize seven types of human emotions with satisfying results in its experiments. Proposed EECNN achieved 89.8% accuracy in classifying the images.     

Experimental study on the thermal performance of a KNO2-KNO3 mixture in a trapezoidal solar pond

Journal of Mechanical Science and Technology - Salt gradient solar ponds (SGSPs) are thermal devices used for storing solar energy for low-temperature applications. The thermal performance analysis...     

Investigation of aggregation induced emission in 4-hydroxy-3-methoxybenzaldehyde azine and polyazine towards application in (opto) electronics: synthesis,characterization, photophysical and electrical properties

An azine monomer 4-hydroxy-3-methoxybenzaldehyde azine was synthesized by refluxing with ethanolic solution of vanillin with hydrazine hydrate. It was then converted into polyazine by oxidative polymerization. The structure of azine and polyazine was characterized by FT-IR, UV–visible, ¹H-NMR and ¹³C-NMR. Spectral results suggest the formation of polymer, through C–C and C–O–C coupling of the phenylene and oxyphenylene. The relationship between the structures and photophysical properties of azine and polyazine was studied. Both azine and polyazine show, aggregation induced emission with increase in concentration in DMSO solution. The single crystal structure of azine suggesting the various inter and intra molecular interactions rigidify the conformation and locked the intramolecular rotations of the phenyl rings in the molecule. The inhibition of intramolecular rotation, J- aggregation and increase of conjugation impart the fluorescence in aggregated state. Additionally, the electronic properties namely orbital energies and resulting energy gap calculated theoretically by density functional theory (DFT).