Casting Aluminum Alloys Michael V Glazoff, Vadim S Zolotorevsky, Nikolai A Belov
2007, 2010, 2010-07-07
eBook
This monograph summarizes research conducted at Moscow Institute of Steel and Alloy during many decades in part together with Alcoa Inc. The research covered areas of the structure, properties, ...thermal resistance, corrosion and fatigue of aluminum alloys in industrial manufacturing. The book features:
Emphasis on interconnection among phase equilibria, thermodynamics and microstructure of alloys
Systematic overview of all phase diagrams with Al that are important for the development of casting aluminium alloys
Diagrams ("processing windows") of important technological properties such as castability, molten metal fluidity, tendency to hot pre-solidification cracking, porosity
Mathematical models for alloy mechanical properties facilitating the down-selection of best prospect candidates for new alloy development
New principles of design of eutectic casting aluminium alloys
Examples of successful novel casting alloy development, including alloys for high-strength applications, alloys with transition metals, and novel alloys utilizing aluminium scrap
We investigate the constructive role of an external noise signal, in the form of a low-rate Poisson sequence of pulses supplied to all inputs of a spiking neural network, consisting in maintaining ...for a long time or even recovering a memory trace (engram) of the image without its direct renewal (or rewriting). In particular, this unique dynamic property is demonstrated in a single-layer spiking neural network consisting of simple integrate-and-fire neurons and memristive synaptic weights. This is carried out by preserving and even fine-tuning the conductance values of memristors in terms of dynamic plasticity, specifically spike-timing-dependent plasticity-type, driven by overlapping pre- and postsynaptic voltage spikes. It has been shown that the weights can be to a certain extent unreliable, due to such characteristics as the limited retention time of resistive state or the variation of switching voltages. Such a noise-assisted persistence of memory, on one hand, could be a prototypical mechanism in a biological nervous system and, on the other hand, brings one step closer to the possibility of building reliable spiking neural networks composed of unreliable analog elements.
Cobalt and iron(II) hexachloroclathrochelates with apical aliphatic and aromatic substituents were synthesized and characterized using cyclic voltammetry. The obtained clathrochelate-based systems ...were impregnated on the surface of carbon paper and tested as cathode electrocatalysts in water electrolysis cell with proton exchange membrane (PEM). Both the cyclic voltammograms and the current–voltage performances of membrane-electrode assemblies suggested that these cage complexes can be successfully implemented in PEM water electrolyzers and used as efficient electrocatalysts for hydrogen evolution.
Synthesis of the Co and Fe hexachloroclathrochelates and corresponding current–voltage performances of PEM water electrolysis cell. Display omitted
•Alkyl- and arylboron-capped Co and Fe hexachloroclathrochelates were synthesized.•Clathrochelate-based electrocatalysts were implemented in PEM water electrolysis.•Fe and Co clathrochelate complexes were successfully used as efficient HER catalysts.•Best performances were observed with electrocatalyst based on iron(II) cage complex.
We present the results of simulation of large-scale disturbances of the near-Earth plasma modified by high-power HF radio waves from the Sura heating facility. The numerical simulation was performed ...over the entire range of ionospheric altitudes, using an SAMI2 modified version for the input parameters corresponding to the in-situ measurements of the spatial structure of the disturbed region performed by the method of low-orbit radio tomography. The numerical simulation results conform to the radio tomography reconstruction data. The dynamics of the evolution and relaxation of large-scale temperature and plasma-density disturbances under the action of high-power HF radio waves from the Sura heater are studied on the basis of simulation data.
An axisymmetric contact problem on indentation of a rigid conical punch into an elastic transversely isotropic half-space with a functionally graded transversely isotropic coating is considered. ...Elastic moduli of the coating vary in depth according to arbitrary continuous positive functions, independent of each other. Mathematical statement of the problem is made in terms of the linear theory of elasticity. Using integral transformation technique the problem is reduced to the solution of a dual integral equation. Kernel transform of the integral equation, which is calculated numerically from a two-point boundary value problem for a system of ordinary differential equations with variable coefficients, is approximated by a product of fractional quadratic functions. Using these approximations, an approximated solution of the problem is constructed in analytical form. The solution is asymptotically exact both for small and big values of the characteristic geometrical parameter of the problem (ratio of thickness of the coating to radius of the contact area). Approximated analytical expressions relating the displacement of the punch, indentation force acting on the punch and the size of the contact area are obtained. Correlation between the contact normal stresses arising on surface of the coated half-space and on surface of the homogeneous half-space without a coating is studied. Some relations are obtained analytically using asymptotic analysis and illustrated numerically. Results on numerical simulation of an indentation of a conical punch into a hard homogeneous or functionally graded (with linearly varying elastic moduli in depth) transversely isotropic coating are provided. The materials widely used in electronics are chosen for numerical examples. Qualitative differences in process of elastic deformation of bodies with homogeneous and functionally graded coatings are illustrated.
We prove that for each positive integer
the conjugate Dirichlet kernel
is semiadditive on the interval
, that is,
for any nonnegative real numbers
and
such that
; moreover, for positive
and
with
, ...the equality is attained if and only if the condition
is satisfied. We use this property of the conjugate Dirichlet kernel to study the sum of a sine series with monotone coefficients. We also examine the properties of some nonnegative trigonometric polynomials.
This paper puts forward a method for constructing trigonometric Fourier series with
L
2
π
-unbounded partial sums that have coefficients with some preassigned properties. In particular, examples of ...trigonometric Fourier series showing that some conditions of convergence in the mean of trigonometric series cannot be sharpened are constructed.
The problem of formulating variational models for irreversible processes of media deformation is considered in this paper. For reversible processes, the introduction of variational models actually ...comes down to defining functionals with a given list of arguments of various tensor dimensions. For irreversible processes, an algorithm based on the principle of stationarity of the functional is incorrect. In this paper, to formulate a variational model of irreversible deformation processes with an expanded range of coupled effects, an approach is developed based on the idea of the introduction of the non-integrable variational forms that clearly separate dissipative processes from reversible deformation processes. The fundamental nature of the properties of symmetry and anti-symmetry of tensors of physical properties in relation to multi-indices characterizing independent arguments of bilinear forms in the variational formulation of models of thermomechanical processes has been established. For reversible processes, physical property tensors must necessarily be symmetric with respect to multi-indices. On the contrary, for irreversible thermomechanical processes, the tensors of physical properties that determine non-integrable variational forms must be antisymmetric with respect to the permutation of multi-indices. As a result, an algorithm for obtaining variational models of dissipative irreversible processes is proposed. This algorithm is based on determining the required number of dissipative channels and adding them to the known model of a reversible process. Dissipation channels are introduced as non-integrable variational forms that are linear in the variations of the arguments. The hydrodynamic models of Darcy, Navier–Stokes, and Brinkman are considered, each of which is determined by a different set of dissipation channels. As another example, a variational model of heat transfer processes is presented. The equations of heat conduction laws are obtained as compatibility equations by excluding the introduced thermal potential from the constitutive equations for temperature and heat flux. The Fourier and Maxwell–Cattaneo equations and the generalized heat conduction laws of Gaer–Krumhansl and Jeffrey are formulated.
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