Novel Self-Supported Natural and Synthetic Polymer Membranes for Air Humidification

Novel self-supported natural and synthetic polymer membranes of chitosan-hydroxy ethyl Cellulose-montmorillonite (CS-HEC-MMT) and polyvinyl alcohol (PVA)-polystyrene sulfonic acid (PSSA) are prepared by solution casting method followed by crosslinking. These membranes are employed for air humidification at varying temperatures between 30 degrees C and 70 degrees C and their performances are compared with commercial Nafion membranes. High hater fluxes with desired humidified-air output have been achieved for CS-HEC-MMT and PVA-PSSA hybrid membranes at air-flow rates of 1-10 slpm. Variation in the air/water mixing ratio, dew point, and relative humidity that ultimately results in desired water flux With respect to air-flow rates are also quantified for all the membranes. Water flux values for CS-HEC-MMT are less than those for Nafion (R) and PVA-PSSA membranes, but the operational Stability of CS-HEC-MMT membrane is higher than PVA-PSSA and comparable with Nafion (R) both of which can operate up to 70 degrees C at repetitive cycles of humidification.

Large deflections of simply supported beams

Large deflections of simply supported beams have been studied when the trans verse loading consists of a uniformity distributed load plus a century concentrate load under the two cases, (1) the reactions are vertical. (2) the reactions are normal to the bent beam together with frictional forces. The solutions are obtained by the use of power series expansions. This method is applicable to cases of symmetrical loading in beams.

Oxides supported carbon air-electrodes for alkaline solution power devices

Porous carbon oxygen-reducing electrodes incorporated with perovskite oxide catalysts are reported. It has been possible to fabricate high-performance oxygen-reducing electrodes by introducing La0.5Sr0.5CoO3 and La0.99Sr0.01NiO3 with the activated coconut-shell charcoal; these electrodes could sustain load currents as high as 1 A cm−2 without serious degradation. A model to explain oxygen-reducing activity of these oxides has been proposed.

Generation of rotationally dominated galaxies by mergers of pressure-supported progenitors

Through the analysis of a set of numerical simulations of major mergers between initially non-rotating, pressure-supported progenitor galaxies with a range of central mass concentrations, we have shown that: (1) it is possible to generate elliptical-like galaxies, with outside one effective radius, as a result of the conversion of orbital- into internal-angular momentum; (2) the outer regions acquire part of the angular momentum first; (3) both the baryonic and the dark matter components of the remnant galaxy acquire part of the angular momentum, the relative fractions depending on the initial concentration of the merging galaxies. For this conversion to occur the initial baryonic component must be sufficiently dense and/or the encounter should take place on an orbit with high angular momentum. Systems with these hybrid properties have recently been observed through a combination of stellar absorption lines and planetary nebulae for kinematic studies of early-type galaxies. Our results are in qualitative agreement with these observations and demonstrate that even mergers composed of non rotating, pressure-supported progenitor galaxies can produce early-type galaxies with significant rotation at large radii.

Natural frequencies of rectangular orthotropic plates with a pair of parallel edges simply supported

Solutions of the exact characteristic equations for the title problem derived earlier by an extension of Bolotin's asymptotic method are considered. These solutions, which correspond to flexural modes with frequency factor, R, greater than unity, are expressed in convenient forms for all combinations of clamped, simply supported and free conditions at the remaining pair of parallel edges. As in the case of uniform beams, the eigenvalues in the CC case are found to be equal to those of elastic modes in the FF case provided that the Kirchoff's shear condition at a free edge is replaced by the condition. The flexural modes with frequency factor less than unity are also investigated in detail by introducing a suitable modification in the procedure. When Poisson's ratios are not zero, it is shown that the frequency factor corresponding to the first symmetric mode in the free-free case is less than unity for all values of side ratio and rigidity ratios. In the case of one edge clamped and the other free it is found that modes with frequency factor less than unity exist for certain dimensions of the plate—a fact hitherto unrecognized in the literature.

Exact analysis of simply supported rhombic plates under uniform pressure

The simply supported rhombic plate under transverse load has received extensive attention from elasticians, applied mathematicians and engineers. All known solutions are based on approximate procedures. Now, an exact solution in a fast converging explicit series form is derived for this problem, by applying Stevenson's tentative approach with complex variables. Numerical values for the central deflexion and moments are obtained for various corner angles. The present solution provides a basis for assessing the accuracy of approximate methods for analysing problems of skew plates or domains.

Polymer supported metal complexes as catalysts for oxidation of thiosalts by molecular oxygen IV. Quaternised poly(4-vinyl pyridine) complexes with Cu2+ as template

Copper(II) complexes of quaternised poly(4-vinylpyridine) (PVP) of different degrees of quaternisation and copper content have been prepared by crosslinking the polymer with 1,2-dibromoethane in the presence of Cu2+ ion as template. The stability constant of the PVP---Cu(II) complexes is found to increase with the degree of crosslinking quaternisation of the resin, but the rate at which Cu2+ is adsorbed by the resin decreases. An optimum combination of both stability and rate can be achieved with a moderate degree (31%) of crosslinking. A kinetic study reveals that quaternisation increases significantly the catalytic activity of the complex for the oxidation of S2O2−3 by O2 compared with PVP----Cu(II) without quaternisation, but it deactivates the complex for the oxidation of both S3O2−6 and S4O2−6. The batch reactor oxidation kinetics at pH 2.16, where the rate is observed to be maximum, is well explained by the Langmuir—Hinshelwood model assuming the coordination of both O2 and thioanion to Cu(II) as a precursor to the oxidation reaction.

Natural frequencies of circumferentially truncated sector plates with simply supported straight edges

The classical Rayleigh-Ritz method in conjunction with suitable co-ordinate transformations is found to be effective for accurate estimation of natural frequencies of circumferentially truncated circular sector plates with simply supported straight edges. Numerical results are obtained for all the nine combinations of clamped, simply supported and free boundary conditions at the circular edges and presented in the form of graphs. The analysis confirms an earlier observation that the plate behaves like a long rectangular strip as the width of the plate in the radial direction becomes small.

Natural frequencies of circumferentially truncated sector plates with simply supported straight edges

The classical Rayleigh-Ritz method in conjunction with suitable co-ordinate transformations is found to be effective for accurate estimation of natural frequencies of circumferentially truncated circular sector plates with simply supported straight edges. Numerical results are obtained for all the nine combinations of clamped, simply supported and free boundary conditions at the circular edges and presented in the form of graphs. The analysis confirms an earlier observation that the plate behaves like a long rectangular strip as the width of the plate in the radial direction becomes small.

Carbon-Supported Pt-TiO2 as a Methanol-Tolerant Oxygen-Reduction Catalyst for DMFCs

Carbon-supported Pt-TiO2 (Pt-TiO2/C) catalysts with varying at. wt ratios of Pt to Ti, namely, 1:1, 2:1, and 3:1, are prepared by the sol-gel method. The electrocatalytic activity of the catalysts toward oxygen reduction reaction (ORR), both in the presence and absence of methanol, is evaluated for application in direct methanol fuel cells (DMFCs). The optimum at. wt ratio of Pt to Ti in Pt-TiO2/C is established by fuel cell polarization, linear sweep voltammetry, and cyclic voltammetry studies. Pt-TiO2/C heattreated at 750 degrees C with Pt and Ti in an at. wt ratio of 2:1 shows enhanced methanol tolerance, while maintaining high catalytic activity toward ORR. The DMFC with a Pt-TiO2/C cathode catalyst exhibits an enhanced peak power density of 180 mW/cm(2) in contrast to the 80 mW/cm(2) achieved from the DMFC with carbon-supported Pt catalyst while operating under identical conditions. Complementary data on the influence of TiO2 on the crystallinity of Pt, surface morphology, and particle size, surface oxidation states of individual constituents, and bulk and surface compositions are also obtained by powder X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive analysis by X-ray, and inductively coupled plasm optical emission spectrometry.

A Methanol-Tolerant Carbon-Supported Pt-Au Alloy Cathode Catalyst for Direct Methanol Fuel Cells and Its Evaluation by DFT

A Pt-Au alloy catalyst of varying compositions is prepared by codeposition of Pt and Au nanoparticles onto a carbon support to evaluate its electrocatalytic activity toward an oxygen reduction reaction (ORR) with methanol tolerance in direct methanol fuel cells. The optimum atomic weight ratio of Pt to Au in the carbon-supported Pt-Au alloy (Pt-Au/C) as established by cell polarization, linear-sweep voltammetry (LSV), and cyclic voltammetry (CV) studies is determined to be 2:1. A direct methanol fuel cell (DMFC) comprising a carbon-supported Pt-Au (2:1) alloy as the cathode catalyst delivers a peak power density of 120 mW/cm2 at 70 °C in contrast to the peak power density value of 80 mW/cm2 delivered by the DMFC with carbon-supported Pt catalyst operating under identical conditions. Density functional theory (DFT) calculations on a small model cluster reflect electron transfer from Pt to Au within the alloy to be responsible for the synergistic promotion of the oxygen-reduction reaction on a Pt-Au electrode.

Hydrothermal synthesis and structural characterization of novel alpha-Keggin unit-supported Cu(II)- and Mn(II)-bipyridine complexes from a tri-lacunary precursor

Blue [{Cu(2,2'-bipy)(2)}(2){alpha-SiW12O40}] (bipy = bipyridyl) (1) and pale yellow [Mn(2,2'-bipy)(3)](2)[alpha-SiW12O40] (2) have been synthesized hydrothermally and characterized by IR spectroscopy and single crystal X-ray structure analysis. In 1, the [alpha-SiW12O40](4-) ion acts as a bridge between the two [{Cu(2,2'-bipy)(2)](2+) moieties via coordination through the terminal oxygen atoms, while in 2, the [Mn(2,2'-bipy)(3)](2+) ion balances the charge on the polyoxo anion without forming any covalent bond. To the best of our knowledge, this is the first example of transition metal-mediated transformation of [alpha-SiW9O34](10-) to [alpha-SiW12O40](4-).

Design of rectangular reinforced concrete slabs supported on all the sides with a short discontinuous edge

Bending moment coefficients for the design of rectangular reinforced concrete panels supported on four sides with a short discontinuous edge are derived using the strip theory. The moment fields resulting from the use of proposed coefficients are examined in terms of the moment volume for possible savings in reinforcement and compared with other codified procedures. The strip coefficients averaged over the corresponding sides of the panel, besides resulting in considerable savings in reinforcement, are found to be identical with the coefficients predicted by simple yield line theory using an orthotropic layout of reinforcement.

Bending, vibration and buckling of simply supported thick orthotropic rectangular plates and laminates

This paper presents a unified exact analysis for the statics and dynamics of a class of thick laminates. A three-dimensional, linear, small deformation theory of elasticity solution is developed for the bending, vibration and buckling of simply supported thick orthotropic rectangular plates and laminates. All the nine elastic constants of orthotropy are taken into account. The solution is formally exact and leads to simple infinite series for stresses and displacements in flexure, forced vibration and "beam-column" type problems and to closed form characteristic equations for free vibration and buckling problems. For free vibration of plates, the present analysis yields a triply infinite spectrum of frequencies instead of only one doubly infinite spectrum by thin plate theory or three doubly infinite spectra by Reissner-Mindlin type analyses. Some numerical results are presented for plates and laminates. Comparison of results from thin plate, Reissner and Mindlin analyses with these yield some important conclusions regarding the validity and effects of the assumptions made in the approximate theories.

An exact analysis for vibration of simply-supported homogeneous and laminated thick rectangular plates

A three-dimensional linear, small deformation theory of elasticity solution by the direct method is developed for the free vibration of simply-supported, homogeneous, isotropic, thick rectangular plates. The solution is exact and involves determining a triply infinite sequence of eigenvalues from a doubly infinite set of closed form transcendental equations. As no restrictions are placed on the thickness variation of stresses or displacements, this formulation yields a triply infinite spectrum of frequencies, instead of only one doubly infinite spectrum by thin plate theory and three doubly infinite spectra by Mindlin's thick plate theory. Further, the present analysis yields symmetric thickness modes which neither of the approximate theories can identify. Some numerical results from the two approximate theories are compared with those from the present solution and some important conclusions regarding the effect of the assumptions made in the approximate theories are drawn. The thickness variations of stresses and displacements are also discussed. The analysis is readily extended for laminated plates of isotropic materials. Numerical results are also given for three-ply laminates, and are used to assess the accuracy of thin plate theory predictions for laminates. Extension to general lateral surface conditions and forced vibrations is indicated.