Numerical appraisal of three low Mach number algorithms for radiative–convective flows in enclosures

The present study investigates three different algorithms for the numerical simulation of non-Boussinesq convection with thermal radiative heat transfer based on a low-Mach number formulation. The solution methodology employs a fractional step approach based on the finite-volume method on arbitrary polyhedral meshes. The three algorithms compute the coupled governing equations in a segregated manner using the conservative form of momentum equations in conjunction with a variable coefficient pressure Poisson equation. The first algorithm (Algorithm A) uses conservation of mass and energy equation to compute density and temperature. The other two algorithms (Algorithm B) and (Algorithm C) calculates temperature and density from the equation of state respectively and solves a conservative form of the continuity and energy equation to obtain density and temperature respectively. The energy and mass conservation errors arising due to the use of Algorithms B and C are derived concerning various non-dimensional parameters governing the flow and heat transfer. The significance of these errors is highlighted by performing investigations over a range of Rayleigh, Prandtl, and Planck numbers for various two and three-dimensional natural convection problems with radiative heat transfer. Finally, the role of balancing of the pressure and buoyancy terms is emphasized for robust calculations of large temperature difference thermo-buoyant convection with radiative heat transfer.     

Application of Strong Arcs in m-Polar Fuzzy Graphs

Neural Processing Letters - Recently, m-polar fuzzy graph (mPF graph) becomes a growing research topic as the generalization of fuzzy graph. In this paper, at first mPF path, mPF cycle in an mPF...     

Multi-item inventory model with variable backorder and price discount under trade credit policy in stochastic demand

In this paper, a two echelon supply chain with one manufacturer and one retailer is developed for multi products. The retailer faced with the uncertain demand for all products which follows a normal distribution. The production process is assumed to be imperfect, and the defectiveness is assumed to follow a beta distribution. The manufacturer produces and delivers the products in a number of equal-sized batches to the manufacturer's warehouse, and thereby it is delivers in a number of equal batches to the retailer's warehouse. Shortages are allowed to occur, at the retailer side, and it is backordered partially. The retailer offers a price discount for backordered items to his customers. Both the lead time crashing cost and the partial backorder ratio are considered as the inverse function of lead time. Under these assumptions, there are three inventory models proposed in this paper, one with non-integrated approach, the other with an integrated approach without trade credit and finally an integrated approach with trade credit. A new iterative algorithmic procedure has been developed to minimise the total cost. Finally, numerical examples are given to illustrate the models and the sensitivity analysis is conducted over various model parameters.     

Hikami-Larkin-Nagaoka (HLN) Treatment of the Magneto-Conductivity of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> Topological Insulator

We report the magneto-conductivity analysis at different temperatures under a magnetic field of up to 5 T of a well- characterized Bi₂Te₃ crystal. Details of crystal growth and various physical properties including high linear magneto-resistance are already reported by some of us. To elaborate upon the transport properties of Bi₂Te₃ crystal, the magneto-conductivity is fitted to the known Hikami-Larkin-Nagaoka (HLN) equation and it is found that the conduction mechanism is dominated by both surface-driven weak anti-localization (WAL) and the bulk weak localization (WL) states. The value of HLN equation coefficient (α) signifying the type of localization (WL, WAL or both WL and WAL) falls within the range of ??0.5 to ??1.5. In our case, the low-field (±?0.25 T) fitting of studied crystal exhibited a value of α close to ??0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (l_φ) is found to decrease from 98.266 to 40.314 nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi₂Te₃ follows the HLN equation and quantitative analysis of the same facilitates to know the quality of studied crystal in terms of WAL to WL contributions and thus the surface to bulk conduction ratio.     

Enhanced optoelectronic,thermal, mechanical and third order nonlinear optical properties of dichlorobis(thiourea)zinc(II) crystal: an effect of Phenol red dye

For the first time the growth of dichlorobis (thiourea) zinc(II) (ZTC) monocrystal in presence of Phenol red dye of considerably good size (~13 mm?×?5 mm) has been achieved from aqueous solution using slow evaporation solution technique at room temperature. The solubility was calculated at different temperatures. The crystal structure was confirmed through X-ray diffraction analysis. The crystallinity of the dyed crystals has been enhanced revealed by Powder X-ray diffraction study. The presence of dye was inveterate by FT-IR and FT-Raman spectroscopic studies. The scanning electron microscopy analyses show that the grown crystals with dye are better than pure. Diffused reflectance was measured and optical band gap was calculated found to be enhanced from 4.5 to 4.65 eV for dyed crystals. The enhancement in the PL intensity has been observed in the dyed crystals. DSC study shows that the thermal stability has been remarkably enhanced from 163?°C (pure) to 203?°C (dyed) and various other thermal parameters are calculated. The surface study shows that the grown crystals with dye possess less dislocation than pure. Mechanical strength of the dyed crystal is found to be remarkably enhanced. Third-order nonlinear optical susceptibility (χ3) of PRZTC was found to be 2 times higher than pure. All results suggest that the properties of ZTC crystals grown in presence of dye are enhanced and can be considered as better contender in various nonlinear devices.     

Enhancement of heat transfer in a convergent/divergent channel by using carbon nanotubes in the presence of a Darcy–Forchheimer medium

This article explores the influence of thermal radiation on the flow and heat transfer of single-walled carbon nanotubes over both a convergent and divergent channel. Flow is induced due to a Darcy–Forchheimer medium. Further, the heat transfer mechanism is analyzed in the presence of a thermal radiation process. Guided by some appropriate similarity transformations, the fundamental PDEs are converted into a self-similar system of coupled non-linear ODEs. The findings are obtained with the help of the Runge–Kutta-45-based shooting method. The roles of the Reynolds number, porosity parameter, inertia coefficient parameter, Prandtl number and radiation parameter are presented graphically. Results are displayed and show that the rate of heat transfer is higher in a divergent channel as compared to a convergent channel.

     

Combining SAT Solvers with Computer Algebra Systems to Verify Combinatorial Conjectures

We present a method and an associated system, called MathCheck, that embeds the functionality of a computer algebra system (CAS) within the inner loop of a conflict-driven clause-learning SAT solver. SAT+CAS systems, à la MathCheck, can be used as an assistant by mathematicians to either find counterexamples or finitely verify open universal conjectures on any mathematical topic (e.g., graph and number theory, algebra, geometry, etc.) supported by the underlying CAS. Such a SAT+CAS system combines the efficient search routines of modern SAT solvers, with the expressive power of CAS, thus complementing both. The key insight behind the power of the SAT+CAS combination is that the CAS system can help cut down the search-space of the SAT solver, by providing learned clauses that encode theory-specific lemmas, as it searches for a counterexample to the input conjecture (just like the T in DPLL (T)). In addition, the combination enables a more efficient encoding of problems than a pure Boolean representation. In this paper, we leverage the capabilities of several different CAS, namely the SAGE, Maple, and Magma systems. As case studies, we study three long-standing open mathematical conjectures, two from graph theory regarding properties of hypercubes, and one from combinatorics about Hadamard matrices. The first conjecture states that any matching of any d-dimensional hypercube can be extended to a Hamiltonian cycle; the second states that given an edge-antipodal coloring of a hypercube there always exists a monochromatic path between two antipodal vertices; the third states that Hadamard matrices exist for all orders divisible by 4. Previous results on the graph theory conjectures have shown the conjectures true up to certain low-dimensional hypercubes, and attempts to extend them have failed until now. Using our SAT+CAS system, MathCheck, we extend these two conjectures to higher-dimensional hypercubes. Regarding Hadamard matrices, we demonstrate the advantages of SAT+CAS by constructing Williamson matrices up to order 42 (equivalently, Hadamard up to order \(4\times 42=168\)), improving the bounds up to which Williamson matrices of even order have been constructed. Prior state-of-the-art construction was only feasibly performed for odd numbers, where possible.     

Conformationally constrained PNA analogues: structural evolution toward DNA/RNA binding selectivity

Since its discovery 12 years ago, aminoethylglycyl peptide nucleic acid (aeg-PNA) has emerged as one of the successful DNA mimics for potential therapeutic and diagnostic applications. An important requisite for in vivo applications that has received inadequate attention is engineering PNA analogues for able discrimination between DNA and RNA as binding targets. Our approach toward this aim is based on structural preorganization of the backbone to hybridization-competent conformations to impart binding selectivity. This strategy has allowed us to design locked PNAs to achieve specific hybridization with DNA or RNA with aims to increase the binding strength without losing the binding specificity. This Account presents results of our rationale in design of different conformationally constrained PNA analogues, their synthesis, and evaluation of hybridization specificities.     

Study of the Effect of Nano-silica Particles on Resin-Bonded Moulding Sand Properties and Quality of Casting

The cast quality in chemical bonded sand mould system is influenced primarily by sand mould properties such as, compression strength, permeability, gas evolution, and collapsibility. Amount of resin and hardener, curing time and number of strokes influence the sand mould properties. The experiments are conducted with the above mentioned input output, as per Taguchi’s L₉ orthogonal array. Pareto analysis of variance is conducted to determine the percent contribution of inputs on output, individually. The optimal factor level is determined for each output separately. The conflicting requirements in foundry sand mould properties can be solved by multiple objective optimization. Principal component analysis is applied to determine the relative importance of individual output. Grey relational analysis is used to convert multiple objective functions to a single objective function for optimization task. Pareto analysis is utilized to determine the optimal input factor combination and their relative percent contribution towards moulding sand properties. The nano-silica particles are used as additive to enhance the moulding sand properties. The results have shown that, the nano-silica particles pose a remarkable improvement in sand mould properties and casting quality.     

Simultaneous abatement of diesel soot and NOX emissions by effective catalysts at low temperature: An overview

The diesel engine generally achieves the highest fuel, energy, and thermal efficiency due to its very high compression/expansion ratio (14:1 to 25:1). Diesel engines can have a thermal efficiency that exceeds 50%. The main problem is that they emit more pollution like fine black soot particulates (C₈H to C₁₀H) and nitrogen oxides (NO_X). These pollutants have been causing serious problems for human health and the global environment and also impacts on the engine. There are many types of catalysts investigated for simultaneous control of these two pollutants, i.e., platinum group metals (PGM; Pt, Pd, Rh, and Ir) based, spinel-type oxides, hydrotalcite, rare earth metal oxides, mixed transient metal oxides, etc. The high raw material cost of PGM catalysts has become a significant issue, so developing non-PGM catalysts are one of the promising challenges. There are no extra reductants required because soot catalytically oxidizes itself in the presence of NO_X at a faster rate than molecular oxygen and simultaneously NO_X is reduced to nitrogen. The order of oxidation potential of NO_X to oxidized soot in comparison to molecular oxygen is as follows: NO₂ > NO > O₂. To meet the very strict EPA US 2010 and Euro VI regulations of particulate matter (PM) and NO_X for heavy-duty and light-duty vehicular stringent emission, it is very important to apply the integrated catalytic systems to significantly remove PM and NO_X simultaneously. Many papers related to simultaneous control of soot and NO_X over different catalysts have been published but till now some of effective catalysts showing high conversion at low temperatures (possibly within the range typical of diesel exhaust: 150–450°C) have not been reviewed. Thus, this article provides a summary of published information regarding the effective catalysts, their preparation methods, properties, and application for simultaneous control of diesel soot and NO_X.