Comparing various machine learning approaches in modeling the dynamic viscosity of CuO/water nanofluid

Nanofluids are broadly employed in heat transfer mediums to enhance their efficiency and heat transfer capacity. Thermophysical properties of nanofluids play a crucial role in their thermal behavior. Among various properties, the dynamic viscosity is one of the most crucial ones due to its impact on fluid motion and friction. Applying appropriate models can facilitate the design of nanofluidics thermal devices. In the present study, various machine learning methods including MPR, MARS, ANN-MLP, GMDH, and M5-tree are used for modeling the dynamic viscosity of CuO/water nanofluid based on the temperature, concentration, and size of nanostructures. The input data are extracted from various experimental studies to propose a comprehensive model, applicable in wide ranges of input variables. Moreover, the relative importance of each variable is evaluated to figure out the priority of the variables and their influences on the dynamic viscosity. Finally, the accuracy of the models is compared by employing the statistical criteria such as R-squared value. The models’ outputs disclosed that employing ANN-MLP approach leads to the most precise model. R-square value and average absolute percent relative error (AAPR) value of the model by using ANN-MLP model are 0.9997 and 1.312%, respectively. According to these values, ANN-MLP is a reliable approach for predicting the dynamic viscosity of the studied nanofluid. Additionally, based on the relative importance of the input variables, it is concluded that concentration has the highest relative importance; while the influence of size is the lowest one.

     

A new pivot selection rule for the network simplex algorithm

We present a new network simplex pivot selection rule, which we call theminimum ratio pivot rule, and analyze the worst-case complexity of the resulting network simplex algorithm. We consider networks withn nodes,m arcs, integral arc capacities and integral supplies/demands of nodes. We define a {0, 1}-valued penalty for each arc of the network. The minimum ratio pivot rule is to select that eligible arc as the entering arc whose addition to the basis creates a cycle with the minimum cost-to-penalty ratio. We show that the so-defined primal network simplex algorithm solves minimum cost flow problem within O(nΔ) pivots and in O(Δ(m + n logn)) time, whereΔ is any upper bound on the sum of all arc flows in every feasible flow. For assignment and shortest path problems, our algorithm runs in O(n ²) pivots and O(nm +n ² logn) time.     

LNA (locked nucleic acid) and analogs as triplex-forming oligonucleotides

The triplex-forming abilities of some conformationally restricted nucleotide analogs are disclosed and compared herein. 2'-Amino-LNA monomers proved to be less stabilising to triplexes than LNA monomers when incorporated into a triplex-forming third strand. N2'-functionalisation of 2'-amino-LNA monomers with a glycyl unit induced the formation of exceptionally stable triplexes. Nucleotide analogs containing a C2',C3'-oxymethylene linker (E-type furanose conformation) or a C2',C4'-propylene linker (N-type furanose conformation) had no significant effect on triplex stability proving that conformational restriction per se is insufficient to stabilise triplexes.     

Template-directed oligonucleotide strand ligation, covalent intramolecular DNA circularization and catenation using click chemistry

The copper-catalyzed azide-alkyne cycloaddition reaction has been used for the template-mediated chemical ligation of two oligonucleotide strands, one with a 5'-alkyne and the other with a 3'-azide, to produce a DNA strand with an unnatural backbone at the ligation point. A template-free click-ligation reaction has been used for the intramolecular circularization of a single stranded oligonucleotide which was used as a template for the synthesis of a covalently closed DNA catenane.     

Structure, function, and stability of enzymes covalently attached to single-walled carbon nanotubes

We describe the structure, activity, and stability of enzymes covalently attached to single-walled carbon nanotubes (SWNTs). Conjugates of SWNTs with three functionally unrelated enzymes-horseradish peroxidase, subtilisin Carlsberg, and chicken egg white lysozyme-were found to be soluble in aqueous solutions. Furthermore, characterization of the secondary and tertiary structure of the immobilized proteins by circular dichroism and fluorescence spectroscopies, respectively, and determination of enzyme kinetics revealed that the enzymes retained a high fraction of their native structure and activity upon attachment to SWNTs. The SWNT-enzyme conjugates were also more stable in guanidine hydrochloride (GdnHCl) and at elevated temperatures relative to their solution counterparts. Thus, these protein conjugates represent novel preparations that possess the attributes of both soluble enzymes-high activity and low diffusional resistance-and immobilized enzymes-high stability-making them attractive choices for applications ranging from diagnostics and sensing to drug delivery.     

Strategies to design pyrazolyl urea derivatives for p38 kinase inhibition: a molecular modeling study

The p38 protein kinase is a serine–threonine mitogen activated protein kinase, which plays an important role in inflammation and arthritis. A combined study of 3D-QSAR and molecular docking has been undertaken to explore the structural insights of pyrazolyl urea p38 kinase inhibitors. The 3D-QSAR studies involved comparative molecular field analysis (CoMFA) and comparative molecular similarity indices (CoMSIA). The best CoMFA model was derived from the atom fit alignment with a cross-validated r ² (q ²) value of 0.516 and conventional r ² of 0.950, while the best CoMSIA model yielded a q ² of 0.455 and r ² of 0.979 (39 molecules in training set, 9 molecules in test set). The CoMFA and CoMSIA contour maps generated from these models provided inklings about the influence of interactive molecular fields in the space on the activity. GOLD, Sybyl (FlexX) and AutoDock docking protocols were exercised to explore the protein–inhibitor interactions. The integration of 3D-QSAR and molecular docking has proffered essential structural features of pyrazolyl urea inhibitors and also strategies to design new potent analogues with enhanced activity.     

Amperometric CO<Subscript>2</Subscript> gas sensor based on interconnected web-like nanoparticles of La<Subscript>2</Subscript>O<Subscript>3</Subscript> synthesized by ultrasonic spray pyrolysis

Thin films of La₂O₃ were deposited onto glass substrates by ultrasonic spray pyrolysis. Their structural and morphological properties were characterized by X-ray diffraction, Fourier transform Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photo-electron spectroscopy, Brunauer-Emmett-Teller and optical absorption techniques. The sensor displays superior CO₂ gas sensing performance at a low operating temperature of 498 K. The signal change on exposure to 300 ppm of CO₂ is about 75%, and the signal only drops to 91% after 30 days of operation.

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Graphical abstract Schematic diagram of the CO₂ gas sensing mechanism of an interconnected web-like La₂O₃ nanostructure in presence of 300 ppm of CO₂ gas and at an operating temperature of 498 K.

     

Phosphonium-phosphates/thiophosphates: Ionic liquids or liquid ion pairs? NMR spectroscopic classification

Structurally unique ionic liquids phosphonium-phosphate and phosphonium-thiophosphate, having both phosphorus based counter ions, in which the anionic part is represented by di-aryl phosphate or di-aryl thiophosphate and cations been tetraalkylphosphonium groups, behave differently in terms of their NMR behaviour. While phosphonium-phosphates show significant changes in its ¹H, ¹³C and ³¹P NMR chemical shifts vis. á vis. corresponding chemical shifts for a physical mixture of tetraalkylphosphonium bromide and di-aryl phosphate, phosphonium-thiophosphates behave almost similarly in terms of NMR with their synthetic precursors, hence indicating phosphate-phosphonium interaction has a significant covalent component resembling more to a liquid ion pair while thiophosphate-phosphonium interaction is principally ionic in nature. Translational diffusion behavior studied by PFGSE-NMR experiments and ionic conductivities of these ionic liquids in chloroform solution corroborated the hypothesis. The effect of variable alkyl chain length in phosphonium cation is effectively observed in the extent of ion association. Results of this study may provide insight into the solution state behavior of these ionic liquids, would help to classify those in terms of their strength of ion association and thus potential application thereof.     

Transient temperature distribution in an internally and externally insulated cylindrical shell

This paper presents the analytical solution for unsteady state temperature distribution in a cylindrical shell having thin layer of thermal insulation coating at the inner and outer surfaces. The formula has been derived assuming different initial temperatures of shell and insulation coating while the contact between them has also been assumed to be imperfect. The internal and external surfaces of the shell and coatings are exposed to the convective boundary conditions of third kind.The generalized formula obtained has been used to obtain the warming-up-period of the cylindrical wall of a Diesel engine coated internally and externally by ceramic insulation material. A plot of Temperature-time history and heat flow rates have been obtained. The problem considered has got its application in the transient thermal analysis of an adiabatic engine. Any other similar problem in metallurgical, aeronautical, furnace design, boiler design applications may be solved by the formula obtained.Nomenclature a ₁, a ₂, a ₃ thermal diffusivity of shell, inner and outer insulation coatings - A ₁(, ) to A ₆(, ) as defined in equation (4) - B _g , B _w Biot's numbers on inner and outer surfaces - C ₁, C ₂, C ₃ Specific heat of shell, inner and outer insulation coatings - F ₀ Fourier's number, F ₀ = a ₁ t/R ₂ ² - G(s) as defined in equation (4) - h _g , h _w heat transfer coefficients at inner and outer surfaces - K ₁, K ₂, K ₃ coefficient of thermal conductivity of shell, inner and outer insulation coatings - ratio defined as, - thermal activeness ratio, - L ₁ to L ₂₁ Factors defined in equation (4) - m ₂, m ₃ thermal contact resistances at interfaces, (kcal/m² hr°C)^–1 - M ₂, M ₃ dimensionless contact coefficients, M ₂ = m ₂ K ₂/₂, M ₃ = m ₃ K ₃/₃ - P factor defined in equation (7) - Q ₁, Q ₂, Q ₃, Q ₄ heat flow rates at inner, interfaces and outer surfaces - R ₁, R ₂, R ₃, R ₄ Interfaces, inner and outer radii - r radial co-ordinate - s Laplace parameter - t time - T ₁(r, t), T ₂(r, t), T ₃(r, t) temperatures in shell, inner and outer insulation coatings - T ₁₀, T ₂₀, T ₃₀ initial temperatures in shell, inner and outer insulation coatings - T _g , T _w gaseous and water side temperatures - U _m (, x) as defined in equation (4) - V _m (, x) as defined in equation (4) - W _m (, x) as defined in equation (4) - x, x ₁ dimensionless radii, x = r/R ₂ and x ₁ = R ₁/R ₂ Greek symbols ₂, ₃ thicknesses of the insulation coatings, ₂ = (R ₁ – R ₃), = (R ₄ – R ₂) - , dimensionless radii, = (r – R ₃)/₂, = (r – R ₂)/₃ - ₁₀, ₂₀, ₃₀, _g initial temperatures ₁₀ = ( T ₁₀ – T _w ); ₂₀ = (T ₂₀ – T _w ); ₃₀ = T ₃₀ – T _w ; _g = T _g – T _w ) - ₁(x, F ₀), ₂(, F ₀), ₃(, F ₀) temperature symbols defined as ₁ = ( T ₁ (r, t) – T _w ); ₂ = (T ₂ (r, t) – T _w ); ₃ = T ₃ (r, t) – T _w ) - Laplace transformation of ₁(x, F ₀), ₂(, F ₀) and ₃(, F ₀) - defined as, - defined as - defined as, - ₁, ₂, ₃ densities of shell, inner and outer insulation coatings - angle defined in equation (5) - _n factor defined in equation (7)