Free vibration of a stochastic beam-column using stochastic fem

The free vibrational characteristics of a beam-column, which is having randomly varying Young's modulus and mass density and subjected to randomly distributed axial loading is analysed. The material property fluctuations and axial loadings are considered to constitute independent one-dimensional, uni-variate, homogeneous real, spatially distributed stochastic fields. Hamilton's principle is used to formulate the problem using stochastic FEM. Vibration frequencies and mode shapes are analysed for their statistical descriptions. A numerical example is shown.

Room temperature creep in amorphous alloys: Influence of initial strain and free volume

The role of imposed strain on the room temperature time-dependent deformation behavior of bulk metallic glasses (BMGs) was systematically investigated through spherical nanoindentation creep experiments. The results show that creep occurred even at very low strains within elastic regimes and, interestingly, a precipitous increase in creep rate was found in plastic regimes, with BMG that had a higher free volume exhibiting greater creep rates. The results are discussed in terms of prevailing mechanisms of elastic/plastic deformation of amorphous alloys. (c) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Interior Medial Axis Transform computation of 3D objects bound by free-form surfaces

This paper presents an algorithm for generating the Interior Medial Axis Transform (iMAT) of 3D objects with free-form boundaries. The algorithm proposed uses the exact representation of the part and generates an approximate rational spline description of the iMAT. The algorithm generates the iMAT by a tracing technique that marches along the object's boundary. The level of approximation is controlled by the choice of the step size in the tracing procedure. Criteria based on distance and local curvature of boundary entities are used to identify the junction points and the search for these junction points is done in an efficient way. The algorithm works for multiply-connected objects as well. Results of the implementation are provided. (C) 2010 Elsevier Ltd. All rights reserved.

Homeostatic regulation of free retinol-binding protein and free thyroxine pools of plasma by their plasma carrier proteins in chicken

The mechanism underlying homeostatic regulation of the plasma levels of free retinol-binding protein and free thyroxine, the systemic distribution of which is of great importance, has been investigated. A simple method has been developed to determine the rate of dissociation of a ligand from the binding protein. Analysis of the dissociation process of retinol-binding protein from prealbumin-2 reveals that the free retinol-binding protein pool undergoes massive flux, and the prealbumin-2 participates in homeostatic regulation of the free retinol-binding protein pool. Studies on the dissociation process of thyroxine from its plasma carrier proteins show that the various plasma carrier proteins share two roles. Of the two types of protein, the thyroxine-binding globulin (the high affinity binding protein) contributes only 27% of the free thyroxine in a rapid transition process, despite its being the major binding protein. But prealbumin-2, which has lower affinity towards thyroxine, participates mainly in a rapid flux of the free thyroxine pool. Thus thyroxine-binding globulin acts predominantly as a plasma reservoir of thyroxine, and also probably in the �buffering� action on plasma free thyroxine level, in the long term, while prealbumin-2 participates mainly in the maintainance of constancy of free thyroxine levels even in the short term. The existence of these two types of binding protein facilitates compensation for the metabolic flux of the free ligand and maintenance of the thyroxine pool within a very narrow range.

Free vibration of rectangular beams of arbitrary depth

The state space approach is extended to the two dimensional elastodynamic problems. The formulation is in a form particularly amenable to consistent reduction to obtain approximate theories of any desired order. Free vibration of rectangular beams of arbitrary depth is investigated using this approach. The method does not involve the concept of the shear coefficientk. It takes into account the vertical normal stress and the transverse shear stress. The frequency values are calculated using the Timoshenko beam theory and the present analysis for different values of Poisson's ratio and they are in good agreement. Four cases of beams with different end conditions are considered.Die Zustandsraum-Technik wird auf zweidimensionale elastodynamische Probleme ausgedehnt. Die Formulierung ist besonders geeignet für die Aufstellung von Näherungstheorien beliebigen Grades. Freie Schwingungen von Rechteckbalken beliebiger Höhe wurden mit Hilfe dieser Technik untersucht. Das Verfahren umgeht den Begriff des Schubbeiwertsk. Es berücksichtigt die senkrechte Normalbeanspruchung und die Querkraft. Die Frequenzwerte werden mit Hilfe der Balkentheorie von Timoshenko und der vorliegenden Analyse berechnet, und zwar für verschiedene Werte der Querdehnzahl. Die berechneten Werte befinden sich in guter Übereinstimmung. Vier Fälle von Balken mit verschiedenen Endbedingungen werden untersucht.

Temperature dependent free energy surface of polymer folding from equilibrium and quench studies

Langevin dynamics simulation studies have been employed to calculate the temperature dependent free energy surface and folding characteristics of a 500 monomer long linear alkane (polyethylene) chain with a realistic interaction potential. Both equilibrium and temperature quench simulation studies have been carried out. Using the shape anisotropy parameter (S) of the folded molecule as the order parameter, we find a weakly first order phase transition between the high-temperature molten globule and low-temperature rodlike crystalline states separated by a small barrier of the order of k(B)T. Near the melting temperature (580 K), we observe an intriguing intermittent fluctuation with pronounced ``1/f noise characteristics'' between these two states with large difference in shape and structure. We have also studied the possibilities of different pathways of folding to states much below the melting point. At 300 K starting from the all-trans linear configuration, the chain folds stepwise into a very regular fourfold crystallite with very high shape anisotropy. Whereas, when quenched from a high temperature (900 K) random coil regime, we identify a two step transition from the random coiled state to a molten globulelike state and, further, to a anisotropic rodlike state. The trajectory reveals an interesting coupling between the two order parameters, namely, radius of gyration (R-g) and the shape anisotropy parameter (S). The rodlike final state of the quench trajectory is characterized by lower shape anisotropy parameter and significantly larger number of gauche defects as compared to the final state obtained through equilibrium simulation starting from all-trans linear chain. The quench study shows indication of a nucleationlike pathway from the molten globule to the rodlike state involving an underlying rugged energy landscape. (C) 2010 American Institute of Physics. doi:10.1063/1.3509398]

Error-free matrix symmetrizers and equivalent symmetric matrices

A symmetrizer of the matrix A is a symmetric solution X that satisfies the matrix equation XA=AprimeX. An exact matrix symmetrizer is computed by obtaining a general algorithm and superimposing a modified multiple modulus residue arithmetic on this algorithm. A procedure based on computing a symmetrizer to obtain a symmetric matrix, called here an equivalent symmetric matrix, whose eigenvalues are the same as those of a given real nonsymmetric matrix is presented.

Characterization of oxygen free radicals generated during vanadate-stimulated NADH oxidation

The oxidation of NADH and accompanying reduction of oxygen to H2O2 stimulated by polyvanadate was markedly inhibited by SOD and cytochrome c. The presence of decavanadate, the polymeric form, is necessary for obtaining the microsomal enzyme-catalyzed activity. The accompanying activity of reduction of cytochrome c was found to be SOD-insensitive and therefore does not represent superoxide formation. The reduction of cytochrome c by vanadyl sulfate was also SOD-insensitive. In the presence of H2O2 all the forms of vanadate were able to oxidize reduced cytochrome c, which was sensitive to mannitol, tris and also catalase, indicating H202-dependent generation of hydroxyl radicals. Using ESR and spin trapping technique only hydroxyl radicals, but not superoxide anion radicals, were detected during polyvanadate-dependent NADH oxidation.

Critical phenomena in polymer solutions: Scaling of the free energy

The thermodynamics of monodisperse solutions of polymers in the neighborhood of the phase separation temperature is studied by means of Wilson’s recursion relation approach, starting from an effective ϕ4 Hamiltonian derived from a continuum model of a many‐chain system in poor solvents. Details of the chain statistics are contained in the coefficients of the field variables ϕ, so that the parameter space of the Hamiltonian includes the temperature, coupling constant, molecular weight, and excluded volume interaction. The recursion relations are solved under a series of simplifying assumptions, providing the scaling forms of the relevant parameters, which are then used to determine the scaling form of the free energy. The free energy, in turn, is used to calculate the other singular thermodynamic properties of the solution. These are characteristically power laws in the reduced temperature and molecular weight, with the temperature exponents being the same as those of the 3d Ising model. The molecular weight exponents are unique to polymer solutions, and the calculated values compare well with the available experimental data.

Nonaxisymmetric unsteady motion over a rotating disk in the presence of free convection and magnetic field

The nonaxisymmetric unsteady motion produced by a buoyancy-induced cross-flow of an electrically conducting fluid over an infinite rotating disk in a vertical plane and in the presence of an applied magnetic field normal to the disk has been studied. Both constant wall and constant heat flux conditions have been considered. It has been found that if the angular velocity of the disk and the applied magnetic field squared vary inversely as a linear function of time (i.e. as (1??t*)?1, the governing Navier-Stokes equation and the energy equation admit a locally self-similar solution. The resulting set of ordinary differential equations has been solved using a shooting method with a generalized Newton's correction procedure for guessed boundary conditions. It is observed that in a certain region near the disk the buoyancy induced cross-flow dominates the primary von Karman flow. The shear stresses induced by the cross-flow are found to be more than these of the primary flow and they increase with magnetic parameter or the parameter ? characterizing the unsteadiness. The velocity profiles in the x- and y-directions for the primary flow at any two values of the unsteady parameter ? cross each other towards the edge of the boundary layer. The heat transfer increases with the Prandtl number but reduces with the magnetic parameter.

Microtensile testing of a free-standing Pt-aluminide bond coat

A finite element method (FEM)-based study has been carried out for the design of flat microtensile samples to evaluate tensile properties of Pt-aluminide (PtAl) bond coats. The critical dimensions of the sample have been determined using a two-dimensional elastic stress analysis. In the present testing scheme, the ratio of the dimensions of the holding length to the fillet radius of the sample was found important to achieve failure within the gage length. The effect of gage length and grip head length also has been examined. The simulation predictions have been experimentally verified by conducting microtensile test of an actual PtAl bond coat at room temperature. The sample design and testing scheme suggested in this study have also been found suitable for evaluation of tensile properties at high temperature. (C) 2010 Elsevier Ltd. All rights reserved.

A crosslinked ``polymer-gel'' rechargeable lithium-ion battery electrolyte from free radical polymerization using nonionic plastic crystalline electrolyte medium

A cross-linked polymer-gel soft matter electrolyte with superior electrochemical, thermal and mechanical properties obtained from free radical polymerization of vinyl monomers in a semi-solid organic nonionic plastic crystalline electrolyte for application in rechargeable lithium-ion batteries is discussed here.

Free convection about cylinders of elliptic cross section embedded in a porous medium

Numerical solutions are presented for the free convection boundary layers over cylinders of elliptic cross section embedded in a fluid-saturated porous medium. The transformed conservation equations of the nonsimilar boundary layers are solved numerically by an efficient finite-difference method. The theory was applied to a number of cylinders and the results compared very well with published analytical solutions. The results are of use in the design of underground electrical cables, power plant steam, and water distribution lines, among others.

Growth and extraction of flux free YBCO crystals

An improved flux draining technique for the extraction of grown YBCO crystals from its solvent is reported. This simple and efficient technique facilitates in-situ flux separation in the isothermal region of the furnace. Consequently, the crystals are spared from thermal shock and subsequent damage. Flux-free surfaces of these crystals were studied by optical microscopy. Transmission X-ray topographs of the crystals reveal the dislocations present in them as well as the stresses developed as a result of ferroelastic phase transition occurring during cooling.