Computational study on heat transfer and MHD-electrified flow of fractional Maxwell nanofluids suspended with SWCNT and MWCNT

Recent developments in fluid dynamics have been focusing on nanofluids, which preserve significant thermal conductivity properties and magnify heat transport in fluids. Classical nanofluid studies are generally confined to models described by partial differential equations of an integer order, where the memory effect and hereditary properties of materials are neglected. To overcome these downsides, the present work focuses on studying nanofluids with fractional derivatives formed by differential equations with Caputo time derivatives that provide memory effect on nanofluid characteristics. Further, heat transfer enhancement and boundary layer flow of fractional Maxwell nanofluid with single-wall and multiple walls carbon nanotubes are investigated. The Maxwell nanofluid saturates the porous medium. Also, buoyancy, magnetic, electric, and heating effects are considered. Governing continuity, momentum, and energy equations involving Caputo time-fractional derivatives reduced nondimensional forms using suitable dimensionless quantities. Numerical solutions for arising nonlinear problems are developed using finite difference approximation combined with L1 algorithm. The influence of involved physical parameters on flow and heat transfer characteristics is analyzed and depicted graphically. Our simulations found out that surface drag of Maxwell nanofluid with single-walled carbon nanotubes dominates nanofluids with multiple walls carbon nanotubes, but the reverse trend is noticed for larger Grashof number values.     

A nonlinear dynamical systems framework for structural diagnosis and prognosis

This work aims to establish a nonlinear dynamics framework for diagnosis and prognosis in structural dynamic systems. The objective is to develop an analytically sound means for extracting features, which can be used to characterize damage, from modal-based input-output data in complex hybrid structures with heterogeneous materials and many components. Although systems like this are complex in nature, the premise of the work here is that damage initiates and evolves in the same phenomenological way regardless of the physical system according to nonlinear dynamic processes. That is, bifurcations occur in healthy systems as a result of damage. By projecting a priori the equations of motion of high-dimensional structural dynamic systems onto lower dimensional center, or so-called ‘damage’, manifolds, it is demonstrated that model reduction near bifurcations might be a useful way to identify certain features in the input-output data that are helpful in identifying damage. Normal forms describing local co-dimension one and two bifurcations (e.g. transcritical, subcritical pitchfork, and asymmetric pitchfork bifurcations) are assumed to govern the initiation and evolution of damage in a low-order model. Real-world complications in damage prognosis involving spatial bifurcations, global bifurcation phenomena, and the sensitivity of damage to small changes in initial conditions are also briefly discussed.     

Characterization and optimization of color attributes chroma (C*) and lightness (L*) in offset lithography halftone print on packaging boards

The outcome of a print in production run plays a crucial role in commercial and packaging printing. In the growing packaging industry, colorfulness and saturated prints with high chroma attract the eye of the consumer. The design and layout of a packaging carton comprise of images that consist of halftones in the print process, which demand attractiveness and visibility using bright colors. In this research, an effort has been made to identify and analyze various parameters involved in offset lithography affecting color attributes of prints. This study also focused on the investigation of the best process conditions that would yield optimum color values through multiresponse factors such as chroma and lightness. A general full-factorial Design of Experiments (DOE) approach was used to evaluate the effect of prepress parameters such as screen ruling and dot shape and press parameters such ink viscosity and paper smoothness. These parameters were then optimized using a customized response surface design. From the experiment, it was observed that viscosity of the ink was a significant factor that majorly controls the color attributes. The surface smoothness of the paperboard was one of the factors influencing the improvement of color reproduction. A smoother surface makes even contact during ink transfer in the offset printing machine and hence reflects color with a higher chroma. The optimum parameters were as follows: 15 Pa s ink viscosity, 0.77 μm paper smoothness, and 200 lines per inch (lpi) screen ruling that resulted in increasing chroma (C*) in the middle and shadow tones in the halftones.     

Solid phase extraction of lead on octadecyl bonded silica membrane disk modified with Cyanex302 and determination by flame atomic absorption spectrometry

A simple, reliable and rapid method for preconcentration and determination of lead using octadecyl bonded silica membrane disk impregnated with Cyanex302 and flame atomic absorption spectrometry is presented. The influence of aqueous phase pH, type of eluent, flow rates of sample solution and eluent, volume of eluent and amount of extractant has been investigated. The break through volume is greater than 4.0 dm(3) with an enrichment factor of more than 400 and a detection limit of 1.0microg dm(-3). The method developed for determination of lead is good as six replicate determinations using 100cm(3) solution containing lead in the range 1-4900microg provides a relative standard deviation (R.S.D.) of 0.4%. The selectivity of the proposed method was confirmed from the interference studies. The developed procedure was successfully applied for the determination of lead in spiked sea water, USGS standard soil sample, sludge and industrial effluents, medicinal formulation, plant, some food products and wine.     

Evaluation of Enhanced Heat Transfer Within a Four Row Finned Tube Array of an Air Cooled Steam Condenser

Air cooled steam condensers (ACSC) consist of finned-tube arrays bundled in an A-frame structure. Inefficient performance under extreme temperature operating conditions is a common problem in ACSCs. The purpose of this study was to improve the heat transfer characteristics of an annular finned-tube system for better performance in extreme climatic conditions. Perforations were created on the surface of the annular fins to increase heat transfer coefficient (h). Mesh generation and finite volume analyses were performed using Gambit 2.4.6 and Fluent 6.3 with an RNG k–? turbulent model to calculate pressure drop (ΔP), heat flux (q), and heat transfer coefficient (h). Solid (no perforations) finned-tubes were simulated with free stream velocity ranging between 1 m/s–5 m/s and validated with the published data. Computations were performed for perforations at 30° interval starting at ±60°, ±90°, ±120°, ±150°, and ±180° from the stagnation point. Five cases with single perforation and three cases with multiple perforations were evaluated for determining the maximum q and h, as well as minimum ΔP. For the perforated case (perforations starting from 60° at interval of 30°), the fin q and h performance ratios increased by 5.96% and 7.07%, respectively. Consequently, the fin ΔP performance ratio increased by 11.87%. Thus, increased q and h is accompanied with a penalty of higher ΔP. In contrast, a single perforation location at 120° provided favorable results with a 1.70% and 2.23% increase in q and h performance ratios, respectively, while there was a relatively smaller increase (only 1.39%) of ΔP performance ratio. Perforations in the downstream region at ±120°, ±150°, and ±180° also resulted in a similar favorable outcome. Furthermore, the spacing of the fins along the arms of an A-frame ACSC was altered to decrease ΔP across the finned-tube array. Fin spacing in the A-frame structure with sparsely spaced fins in the center resulted in a 1.80% reduction in ΔP. Thus, penalty in ΔP for a perforated fin can possibly be offset by changing the fin spacing along the arms of an A-frame structure.     

Thermal performance of straight porous fin with variable thermal conductivity under magnetic field and radiation effects

The present numerical study reports the thermal performance of the straight porous fin with temperature-dependent thermal conductivity, radiation, and magnetic field effects. The heat transfer model comprising the Darcy's law for simulating flow with solid-fluid interactions in porous medium, Rosseland approximation for heat transfer through radiation, Maxwell equations for magnetic field effect and linearly varying temperature dependent thermal conductivity, results into highly nonlinear ordinary differential equation. The governing equation is solved using a finite difference scheme with suitable boundary conditions. The obtained solutions are physically interpreted by considering the impact of different nondimensional parameters on thermal performance, efficiency, and effectiveness of the system through plotted graphs. A detailed result with regard to the Nusselt number at the fin base is calculated. The results obtained are observed to be in excellent agreement with previous studies. From the study, it is observed that there is a significant effect on the thermal performance of the fin in the presence of porous constraints; also, results reveal that the nonlinear thermal conductivity parameter strengthens the thermal performance, efficiency, and effectiveness of the fin. Furthermore, the results of the study reveal that the rate of heat transfer of the fin increases with the increase in the magnetic parameter and radiation parameter.     

The effect of cation associated with Chloride and sulphate ions on the corrosion of metallic glass Fe67Co18Bl14Si1

The electrochemical corrosion behaviour of the metallic glass Fe₆₇Co₁₈B₁₄Si₁ is studied in 0.05 N solutions of alkali metal chlorides and sulphates using a potentiodynamic anodic polarization technique and weight loss measurements. An attempt is made to explain the cation effect as reflected through the changes in pH of the solution, solubilities of the salts and the rest potentials of the sample in these solutions.     

Synthesis and Characterization of Coordinatively Unsaturated Copper (II) Complexes of 1,3-Bis(2'-Pyridyl)-1,2-Diaza-2-Butene and Their Antityrosinase Activity

The coordinatively unsaturated copper (II) complexes of 1,3-bis(2'-pyridyl)-1,2-diaza-2- butene with different ancillary anions were synthesized which can bind to copper centers of tyrosinase enzyme. The compounds were found to exhibit inhibitory activities against mushroom tyrosinase and the nature and extent of inhibition is modulated according to the type of ancillary anions.     

An Introduction to Neural Networks in SCMA

Wireless Personal Communications - Sparse Code Multiple Access (SCMA) has proved to be a fascinating research in order to curtail the complications faced by the wireless communication networks....     

Three of a kind [UPS topologies, IEC standard]

With uninterruptible power supplies now used in critical applications across every industrial sector, a standard terminology to describe types and performance measures has become essential. The author outlines how the international standards community has responded to this need by introducing IEC 62040-3 which distinguishes three types of UPS topology: passive standby, line interactive, and double conversion. These three topologies are described. For low power ratings (less than 2 kVA) all three topologies, as defined by the standards, are used. For medium to high power ratings, the case for the passive standby and the line interactive is, at best, marginal, in spite of their significantly lower cost. The vast majority of sales to medium to high-power rating applications are represented by double conversion UPSs (95% from a few kVA upwards; 98% above 10 kVA). The dominance of the double-conversion topology is attributable to its almost total lack of weaknesses, combined with the capacity to meet the needs of sensitive loads at these power ratings-a consequence of UPS being connected in series with the utility power sources