Effect of prior cold work on mechanical properties, electrical conductivity and microstructure of aged Cu-Ti alloys

The mechanical properties, electrical conductivity and microstructure of Cu-2.7wt%Ti and Cu-5.4wt%Ti alloys have been studied in different conditions employing hardness and resistivity measurements, tensile tests and optical, scanning and transmission electron microscopy. Ageing of undeformed as well as cold worked alloys raises their hardness, strength and electrical conductivity. The hardness increased from 120 VHN for solution treated Cu-2.7Ti to 455 VHN for ST + cold worked + peak aged Cu-5.4Ti alloy. While tensile stength increased from 430 to 1450 MPa, the ductility (elongation) decreased from 36 to 1.5%. A maximum conductivity of 25% International Annealed Copper Standard (IACS) for Cu-2.7Ti and 14.5% IACS for Cu-5.4Ti is obtained with the present treatments. Peak strength was obtained when the solution treated alloys are aged at 450°C for 16 hours due to precipitation of ordered, metastable and coherent , Cu₄Ti phase having body centred tetragonal (bct) structure. While mechanical properties of Cu-Ti alloys are comparable, electrical conductivity is less than that of commercial Cu-Be-Co alloys.     

Comparison of Expedient and Optima Reinforcement Schemes for Learning Systems

Stochastic automata models have been successfully used in the past for modeling learning systems. An automaton model with a variable structure reacts to inputs from a random environment by changing the probabilities of its actions. These changes are carried out using a reinforcement scheme in such a manner that the automaton evolves to a final structure which is satisfactory in some sense. Several reinforcement schemes have been proposed in the literature for updating the structure of automata [1–4]. Most of these are expedient schemes which in the limit yield structures which are better than a device that chooses the actions with equal probabilities irrespective of the environment's response. A few schemes have also been suggested recently which in the limit lead to a continuous selection of a single optimal action as the output of the automaton, when it operates in a stationary environment and are called optimal schemes [5–7]. The question naturally arises as to which of the schemes are to be preferred in practical applications. In view of the anticipated extensive use of learning schemes in multilevel decision-making systems this question of optimality versus expediency takes on particular significance. Consequently, a comparison has to be made not merely of individual automata schemes but also of the effectiveness of such schemes in situations involving several automata (e.g. stochastic games, multilevel systems).     

Mössbauer and XRD studies on the effect of doping iron in KCaY(PO4)2

The effect of doping iron at the yttrium site in hexagonal KCaY(PO₄)₂ is studied for various concentrations ofx (0≤x≤1), of iron using Mössbauer and X-ray diffraction methods. For low iron concentrations, very little changes in structure are seen but atx≈0·1, onset of new peaks in the XRD pattern is observed. The Mössbauer study of the doped samples reveals that iron has a solubility of up to 2·5% in the parent phase with any excess iron precipitating out to form a new and unknown phase. From a detailed analysis of the X-ray diffraction pattern (corresponding tox=1) of the latter phase, it is found that this phase is rhombohedral with the possible space groupR3.     

Common coupling and pointer variables,with application to a Linux case study

Both common coupling and pointer variables can exert a deleterious effect on the quality of software. The situation is exacerbated when global variables are assigned to pointer variables, that is, when an alias to a global variable is created. When this occurs, the number of global variables increases, and it becomes considerably harder to compute quality metrics correctly. However, unless aliasing is taken into account, variables may incorrectly appear to be unreferenced (neither defined nor used), or to be used without being defined. These ideas are illustrated by means of a case study of common coupling in the Linux kernel.

Sparsity Enforcing Edge Detection Method for Blurred and Noisy Fourier data

We present a new method for estimating the edges in a piecewise smooth function from blurred and noisy Fourier data. The proposed method is constructed by combining the so called concentration factor edge detection method, which uses a finite number of Fourier coefficients to approximate the jump function of a piecewise smooth function, with compressed sensing ideas. Due to the global nature of the concentration factor method, Gibbs oscillations feature prominently near the jump discontinuities. This can cause the misidentification of edges when simple thresholding techniques are used. In fact, the true jump function is sparse, i.e. zero almost everywhere with non-zero values only at the edge locations. Hence we adopt an idea from compressed sensing and propose a method that uses a regularized deconvolution to remove the artifacts. Our new method is fast, in the sense that it only needs the solution of a single l ₁ minimization. Numerical examples demonstrate the accuracy and robustness of the method in the presence of noise and blur.     

Compliant cryptologic protocols

Literally, the word compliance suggests conformity in fulfilling official requirements. This paper presents the results of the analysis and design of a class of protocols called compliant cryptologic protocols (CCPs). The paper presents a notion for compliance in cryptosystems that is conducive as a cryptologic goal. CCPs are employed in security systems used by at least two mutually mistrusting sets of entities. The individuals in the sets of entities only trust the design of the security system and any trusted third party the security system may include. Such a security system can be thought of as a broker between the mistrusting sets of entities. Published online: 15 November 2002     

On the relationship between the electronic density of states and the superconducting critical temperature of disordered V3Si

The available data on the effect of neutron and α-particle irradiation on the superconducting properties and the low-temperature specific heat capacity of single- and polycrystalline V₃Si were analyzed in a unified manner. It was found that the electron-phonon renormalization parameter λ does not vary simply proportionally to the bare density of electron states at the Fermi level as had been earlier conjectured by Dynes and Varma, nor does it vary in exactly the same manner as found by Fradin and Williamson to hold for a variety of vanadium-based A15 structure compounds and pseudobinary alloys. When the behavior of V₃Si is compared with that of Nb₃Sn, Nb₃Al, and Nb₃Ge, it is seen that the response to disorder of parameters of importance in the superconductivity of these compounds does not follow any simple, universal behavior.