Fundamental solution of steady oscillations equations in nonlocal thermoelastic medium with voids

Abstract

A new nonlocal theory of generalized thermoelasticity with voids based on Eringen’s nonlocal elasticity is established. The propagation of plane harmonic waves in nonlocal thermoelastic medium with voids is investigated in the context of dual-phase-lag model of generalized thermoelasticity. There exist three longitudinal waves, namely elastic (E-mode), thermal (T-mode) and volume fraction (V-mode) in addition to transverse waves which get decoupled from the rest of motion and not affected by thermal and volume fraction fields. The fundamental solution of the system of differential equations in case of steady oscillations in terms of the elementary functions has been constructed. The effect of nonlocal parameter and the effect of voids on phase velocities, attenuation coefficients and penetration depths are presented graphically.     

The Effect of Aiding/Opposing Buoyancy on Two-Dimensional Laminar Flow Across a Circular Cylinder

The effect of thermal buoyancy on the upward flow and heat transfer characteristics around a heated/cooled circular cylinder is studied. A two-dimensional finite-volume model is deployed for the analysis. The influence of aiding/opposing buoyancy is studied for the range of parameters ?0.5 ≤ Ri ≤ 0.5, 50 ≤ Re ≤ 150, and the blockage ratios of B = 0.02 and 0.25. The flow shows unsteady periodic nature in the chosen range of Reynolds numbers for the forced convective cases (Ri = 0), and the vortex shedding stops completely at some critical values of Richardson numbers.     

Mixed Convection Heat Transfer from an In-Line Row of Square Cylinders in Cross-Flow at Low Reynolds Number

This article presents a two-dimensional numerical study on the unsteady laminar mixed convection heat transfer from a row of five in-line isothermal square cylinders placed in an unconfined medium and subjected to cross-flow of a Newtonian fluid at low Reynolds number (Re = 125). The hydrodynamic and thermal transport phenomena are captured for the separation ratios (spacing to cylinder size ratio, s/d) of 0.5, 1, 1.5, 2, 3, and 4. The mixed convection heat transfer is studied for Richardson numbers (Ri) ranging from 0 to 3 with a fixed Prandtl number (Pr = 0.71). Numerical calculations are performed by using a PISO algorithm-based finite volume solver in a collocated grid system. The instantaneous vorticity fields along with the isotherm patterns are systematically presented and discussed for different separation ratios and Richardson numbers. Depending on the engineering application, the temperature difference between the surface and the free stream could vary to make buoyancy of primary importance, entailing major modification of the flow field. Additionally, the instantaneous and mean drag and lift coefficients, Strouhal numbers, and mean Nusselt numbers are determined and discussed.     

Enhanced photoactivity of visible light responsive W incorporated FeVO4 photoanode for solar water splitting

Herein, we report the preparation, characterization and investigation of previously unexplored W incorporated iron vanadate (FeVO₄) electrodes for solar light driven water oxidation in photoelectrochemical cell. The W incorporated FeVO₄ films on F-doped SnO₂ substrates have been prepared by layer-by-layer deposition of metal–organic precursor and subsequent thermal decomposition at 550 °C in air. The synthesized films with a band gap of about 2.06 eV are responsive to visible light up to wavelength of ∼600 nm, i.e. being able to harvest ∼45% of the solar spectrum. The W incorporated FeVO₄ photoanodes are active materials for photoelectrochemical water oxidation and, yield a significantly enhanced (2.5 fold higher) photocurrent in comparison to pristine FeVO₄ photoanodes. This improvement can be attributed to increased n-type conductivity by W⁶⁺ ion doping in the FeVO₄ lattice. The incident photon to current conversion efficiency achieved with developed photoanodes is as high as 6.5% at 400 nm.     

Comparative evaluation of thermal stabilities of novel sulphonic acid resins from anhydride modified polystyrene with commercial polystyrene based resins,Indion-225 and Zeo-carb 225

Non-isothermal as well as isothermal stabilities of sulphonic acid resins from polystyrene, electrophilically substituted with phthalic anhydride, pyromellitic dianhydride, trimellitic anhydride and cis-1,2,3,6 tetra-hydrophthalic anhydride have been studied and compared by d.t.a., t.g.a. and isothermal degradation of these resins at 250° ± 10°C for 72 h in air. The modified resins thus obtained exhibit better thermal stability relative to the unmodified sulphonated polystyrene. The d.t.a. and t.g.a. studies of the modified polystyrene based resins have revealed a better thermal stability compared to sulphonated polystyrene as well as commercial polystyrene divinyl benzene resins like Zeo-carb 225 and Indion 225 (available in India). Isothermal degradation of the commercial resins was studied at 250° ± 10°C for 72h in air and the analysis of the degraded product has also been carried out. Finally, attempts have been made to rationalize these observations on the basis of the structural characteristics of all the resins.     

Vinyl polymerization by carbon black,VI. Physico-chemical characteristics of poly(N-vinylcarbazole) prepared by modified and unmodified carbon black

The polymerization initiating activity of carbon black N220, unmodified as well as modified by pretreatment with various protonic and aprotonic acids has been examined in regards to N-vinylcarbazole polymerization. The physico-chemical characteristics of the polymer obtained by these catalyst systems have been investigated by I.R., X-ray, ¹H-NMR, ¹³C-NMR, gel permeation chromatography and thermal analysis measurements. Under certain conditions the resultant polymer shows some partial insolubility in methylethylketone. Contrary to the usual belief, this is not due to any stereochemical difference between the polymeric entities as observed by ¹³C-NMR spectrum analysis of the methylethylketone insoluble fraction of the polymer.     

Effect of bauxite addition on densification and mullitization behaviour of West Bengal clay

The effect of bauxite addition on the densification and mullitization of reaction sintered bauxite-clay mixture had been studied in the temperature range 1400–1500°C. The maximum bulk density (2·89 g/cc) and minimum apparent porosity (0·58%) was achieved by addition of 50 wt% bauxite. The impurities present in bauxite and clay formed liquid phase which helped in particle diffusion to aid densification. The X-ray diffraction of sample fired at 1500°C showed cristoballite phase gradually disappearing and at the same time mullite and α-Al₂O₃ phase appearing at a higher level of bauxite addition. The in situ nascent alumina formed was reactive that facilitated the formation of secondary mullite by solution precipitation mechanism. The presence of bauxite also changed the morphology of the mullite particles. Two types of mullite were distinctly observed in the SEM photographs: elongated primary mullite and equiaxed secondary mullite.     

Combined qualitative-quantitative steady-state diagnosis ofcontinuous-valued systems

This paper discusses systematic methods for diagnosis of complex engineering systems combining qualitative and quantitative analysis of analytic constraint equation system models to generate more precise and accurate candidates. Candidates generated from a qualitative steady-state partial explanation model are refined with available ordinal information on the magnitude of component parameter deviations. In addition, an incremental algorithm is implemented to efficiently process sequences of measurements. Empirical analysis demonstrates that accuracy and resolution of minimal candidate generation are improved by including ordinal information. This avoids the practical problems encountered when reasoning with pure quantitative information     

Preparation and evaluation of polyaniline and polypyrrole modified water‐dispersible conducting nanocomposites of polyacrylonitrile with silica

Water‐dispersible conducting nanocomposites were prepared by precipitating polyaniline (PANI)/polypyrrole (PPY) in an aqueous suspension of polyacrylonitrile–SiO₂ (PAN–SiO₂) via K₂CrO₄–NaAsO₂ redox polymerization. Incorporation of PANI and PPY in the composites was confirmed by the FTIR spectrum. Scanning electron microscopic analyses for the PANI–(PAN–SiO₂) and PPY–(PAN–SiO₂) composites indicated formation of lumpy aggregates with irregular sizes. TEM analyses revealed formation of spherical particles with size ranging between 80 and 150 nm for PANI–(PAN–SiO₂) nanocomposite and 75–150 nm for PPY‐(PAN‐SiO₂) nanocomposites, respectively. Thermal stabilities of the PANI–(PAN–SiO₂) and PPY–(PAN–SiO₂) nanocomposites were higher than those of the individual base polymers. Conductivity values of PANI–(PAN–SiO₂) nanocomposite (10^?3 S cm^?1) and PPY–(PAN–SiO₂) nanocomposite (10^?4 S cm^?1) were remarkably improved relative to that for PAN homopolymer (>10^?11 S cm^?1). Both of these composites produced a permanently stable aqueous suspension when the polymerization was conducted in presence of nanodimensional SiO₂ as a particulate dispersant. Copyright © 2004 Society of Chemical Industry