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Autoregressions with constant parameters are special cases of a general iterative process which, in this paper, is given explicit form. No restriction is imposed to the process of variation of the random variable which is permitted to suffer both continuous variations and/or discrete jumps. As a consequence, the general autoregression assumes the same form of the iterative solution of an appropriate integral (master) equation. The procedure which leads to this conclusion is simple but not so direct and requires a special expedient that in this paper is discussed in detail. [ABSTRACT FROM AUTHOR]

Examples of multiexponential decay of indole are reported. Problems connected with the minimization procedure are also outlined. [ABSTRACT FROM AUTHOR]

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We study propagation of an electron wave in a double-quantum-well structure formed by alternate layers of GaAlAs and GaAs. In such a structure, electron states parallel to the layers are described by 2D plane waves and in the perpendicular direction by the bound states of the confining potential. We show that an electron, initially introduced in one well, will execute oscillations between the two wells of the structure. Although the frequency of oscillations depends primarily on the distance separating the wells and the confining potential, it is shown in this paper that the frequency also depends on the effective mass of the electron, if it is different within and outside the well. Expressions are derived for the frequency of oscillations, taking into account the difference in the effective mass of the electron. [ABSTRACT FROM AUTHOR]

This paper surveys the early history of solid-state physics, particularly the period 1949-58, and the seminal role of Fausto Fumi in establishing the first school of modern solid-state physics in Italy. [ABSTRACT FROM AUTHOR]

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In this paper we discuss some points concerning the design of an on-chip electronic refrigerator based on low-resistance tunnel junctions. We describe our Nb/AlO/Cu (SIN) and Nb/AlO/Cu/Al (SINS') junctions and we report on the measurements of their I-V characteristics between 10 K and 0.3 K, showing that the junctions of the first type are suitable for the refrigerator fabrication. [ABSTRACT FROM AUTHOR]

The paper presents the X-ray diffractometry analysis of thin-layer structures made by exploiting the combination of two diffraction geometries-the Bragg one and the Laue one. For this purpose a three-crystal setting was applied. Since the structural parameters of thin layers vary primarily along the surface normal, directing the diffraction vector along this normal, one can succeed in the assessment of the quality in whole, but not in the extraction of different components of lattice damage. The paper shows that, in order to evaluate the contributions, the application of the Laue geometry is promising; it substantially facilitates the study of relaxation, the determination of compositionally dependent properties and the evaluation of macro- as well as micro-strain components. The objects under study were GaAs/Si and SiGe/Si heterostructures as well as (CaF+CdF)/Si superlattices. [ABSTRACT FROM AUTHOR]

The first paper in this series investigated, from the mathematical point of view, several aspects of the thermodynamic fluid theories (of divergence type). The object of this second paper is to present a simple example of such a theory. Here the Grad moment method is applied to a classical Boltzmann equation to obtain a determined system of the quasi-linear, first-order partial differential equations for the evaluation of the usual hydrodynamic variables and the stress deviator. As demonstrated already by Loose and Hess ( Phys. Rev. A, 37, 2099 (1988)), these equations provide valuable information about the shear-rate dependence of the viscosity coefficients and on other non-Newtonian properties of the pressure tensor. Accidentally, for the above-mentioned choice of independent gas-state variables, the truncation scheme of Grad not only leads to a symmetric hyperbolic system of differential equations, but also is in complete agreement with the variational approach to Maxwell's equations of transfer. Thus the proposed method enables one to obtain the supplementary balance law, interpreted as the equation of balance of entropy, satisfied by a certain function h of the original variables. This function, which in the present case can be calculated explicitly, is referred to as the specific entropy (per unit mass). The resulting non-linear expression for h is investigated with a view to a deeper understanding of a status of the extended Gibbs relation. Due to the existence of this relation, one easily arrives at the natural definitions of temperature, pressure, and thermodynamic potentials for gaseous systems «not infinitesimally near to equilibrium». [ABSTRACT FROM AUTHOR]

Some of the available, phenomenological studies on the dissipative fluid theories have involved extending the set of independent dynamical variables. In the favourite case of a chemically inert fluid, one can propose to enlarge the usual hydrodynamic space both by introducing eight components of the stress deviator and the heat flux and by treating them as the fundamental variables on the same footing as the mass density and the specific internal energy. A candidate theory of this kind is based upon the quasi-linear, first-order partial differential equations for the evaluation of all variables. In this paper, the differential field equations are studied with a view to a deeper understanding of non-equilibrium thermodynamics for dissipative fluids. A characteristic feature of the endeavour is that not only it is now possible to have the differential field equations consistent with a supplementary balance law, interpreted as the equation of balance of entropy, but also possible to clarify the meaning of temperature and pressure beyond local equilibrium and to obtain the theory of thermodynamic potentials for systems «not infinitesimally near to equilibrium». These results are achieved via the use of the critical-point theory, as formulated by Morse, in the context of the well-known extremum property of entropy. Mathematically, the supplementary balance law is derived by exploiting the calculus of «vertical» differential forms, and the differential field equations are defined intrinsically, i.e. without making any explicit reference to a particular coordinate system. Finally, the paper discusses some problems concerning the structure of an expression for the entropy flux. [ABSTRACT FROM AUTHOR]

The internal friction (loss tangent) of solids is normally measured, as a function of temperature, with a torsion pendulum operating in free decay. Curves of the internal friction and the oscillation frequency, against temperature, are obtained at various moments of inertia, to extract the parameters characteristic of the relaxation process (relaxation time and strength). In all these experiments only the temperature is considered as an independent variable and the moment of inertia of the pendulum is mainly used to shift the internal friction peaks in the temperature scale. It is pointed out in the paper that the moment of inertia is also an independent variable which can be used to determine, with high accuracy, if the measured peak is of the Debye type or not. A new torsion pendulum, with continuously variable moment of inertia is presented, which allows measurements of the partial derivative of the internal friction and the oscillation frequency with respect to the moment of inertia, at constant temperature. Finally, some measurements of the Snoek relaxation in Nb-O alloys are presented, to show the applicability of the concepts developed in the paper. [ABSTRACT FROM AUTHOR]

In a previous paper, Kliros et al. presented a model calculation of the Hall conductivity as a function of the Landau level broadening Γ for finite temperatures. In this paper, the effect of Landau-level broadening on the structure of the Hall conductivity is investigated. The experimental data regarding the Si-MOSFET and GaAs-heterostructure experiments are reproduced including a functional dependence of Γ on the magnetic field. The influence of the effective g-factor is considered as well. [ABSTRACT FROM AUTHOR]

Our earlier foundation paper for the new science of Theoretical Conchology presented a general theory explaining seashell growth trajectories in terms of optimal, energy-efficient, tensile «clockspring» curves satisfying Hamilton's «least-action» principle. Meanwhile, working in isolation and publishing in Japanese, after the tradition of Wasan, Takashi Okamoto presented precise measurements and uncannily accurate 3D curveguesses which provide a fine description of several bizarre, and previously little understood, «free-coiling» heteromorphic ammonites. One of these, Nipponites mirabilis, is so bizarre and wild that it provides the first good test of our new general theory. We are able to demonstrate that, merely by choosing the two fundamental constants of differential geometry to be complex numbers, our standard «clockspring' curves adequately describe and explain these geometries though one small improvement is possible. Even more surprising, considering the sheer wildness of the geometries, is the fact that Okamoto's guessed 3D «spheroidal» shapes agree with our correct, more general, «Lissajous» counterparts to several significant figures ... a remarkable feat of precise measurement and intuition, on Okamoto's part, perhaps in its own way comparable to the achievements of Tycho Brahae and Johannes Keppler. [ABSTRACT FROM AUTHOR]

Multiterm calculations of energy distributions and transport coefficients of electrons in real and model gases acted upon by d.c. electric fields have recently been done by the authors with a new theory, developed to overcome known limitations of the conventional approach. In all of our previous calculations, gas temperature has always been neglected, for analytical and numerical simplicity. In this paper it is shown how this unphysical limitation can be removed. The real impact of a gas temperature different from zero is also studied by specific calculations of transport coefficients and energy distributions in Ar and Hg at very low values of the field. [ABSTRACT FROM AUTHOR]

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