Showing papers by "Polytechnic University of Turin published in 1977"

The Riemannian structure on the states of quantum-like systems

Abstract: A riemannian metric is introduced in the manifold representing the states of a generic physical system, under suitable assumptions of regularity on the “generalized transition probability” defined in [1]. From the mean values of the observables it is then possible to construct gradients and brackets, and in the special case of a system admitting a quantum-mechanical description the latter are shown to be related to the familiar commutators via a skew-symmetric tensor field which is part of the intrinsic geometry of the projective Hilbert space of physical states.

Segregation phenomenon in spouted beds

Abstract: Preliminary experiments with spouted beds of binary mixtures of particles have shown that segregation according to size or density clearly occurs, with heavier particles going to the upper inside part of the annulus. Segregation tendency becomes less pronounced with increasing gas flow rate. During continuous operation, the concentration of coarse particles in the discharge stream was found to be initially lower than in the feed but it increased within a short time (10–50 min) to the feed concentration. However, the proportion of coarse particles in the bed solids (x) always remained higher than in the solids leaving the bed (y). A state of equilibrium was found to exist between these two concentrations, described by the following equation: y = xn The exponent n turned out to be a function of gas velocity and particle size of the individual components of the mixture, but, not of their proportions, nor of feed rate. An empirical correlation for n is proposed. Des experiences preliminaires qu'on a effectuees sur des melanges binaires de particules, en employant des lits soumis au giclage, ont indique qu'il s'y faisait une segregation selon les dimensions ou la densite des particules: les plus lourdes sont allees a la partie superieure a l'interieur du tore; la tendance la segregation est devenue moins prononcee lorsqu'on a augmente le debit du gaz. On a constate qu'en regime permanent la concentration des grosses particules dans le flux de decharge etait d'abord moindre que celle de l'alimentation, mais qu'en peu de temps (10 a 50 minutes) elle devenait egale a cette derniere. Toutefois, la proportion de grosses particules dans les matieres solides (x) du lit est demeuree toujours plus elevee que dans le cas des matiere solides (y) qui quittaient le lit; on a observe qu'il existait un etat d'equilibre entre les deux concentrations mentionnees, lequel est decrit par l'equation suivante: y =xn L'exposant n s'est avere une fonction de la vitesse du gaz et des dimensions des particules des composants individuels du melange, mais non pas de leurs proportions ni de la vitesse de l'alimentation. On propose une correlation empirique pour n.

Canonical approach to the quantum problem of the motion of a particle in a viscous medium

Abstract: (ricevnto il 4 Marzo 1977) The problem of the quantum treatment of dissipative phenomena is still an open one and many different approaches have been proposed, that never could lead to com- pletely satisfying results. A simple way which can be followed consists in starting from a classical problem and then quantizing it via the usual correspondence principle and the canonical for- malism. Limiting us to the case of a particle of mass ~ in a viscous medium whose friction coefficient is ? (a constant), the classical problem of motion is governed by Langevin's equation (1) mF + m~ =f(t)--VV(r), where r is the particle position,

Measurement of Static AM-PM Conversion in Frequency Multipliers

Abstract: The generation of very narrow spectral lines in the far-infrared by frequency synthesis from VHF precision sources requires very stringent specifications on the spectral purity of the source and on the phase noise introduced by the synthesizer. The dc measurements of the AM-PM conversion in different multiplier stages are presented in this paper: stages employing transistors, varactors and step-recovery diodes are examined. The results show that a few degrees per dB of input level variation are typical for the AM-PM conversion reported to the input in a simple, carefully built and well tuned multiplier stage employing any of the mentioned solid state devices. This value is shown to be unlikely to degrade more than the expected n2 factor the spectral purity of a signal with AM noise as low with respect to PM noise as it is in the output of a good quartz crystal controlled oscillator; however, such a conversion could become a source of phase noise, with degradation of the spectral purity, for a signal with a slightly worse AM noise.

On the Refractive Indexes of Nematic Liquid Crystal

Abstract: A new theory of the optical properties of a nematic liquid crystal is developed. Each molecule is assumed to be spherical, but anisotropic with respect to its electric polarisability. The local field is evaluated through a generalization of the procedure employed by one of the authors (1976) in connection with the dielectric properties of simpler liquids. The agreement between theoretical and experimental refractive indexes of MBBA is found to be higher for this theory than for previous theories developed in the framework of the Lorentz-field approximation (Vuks, Neugebauer).

Loss contributions from correlations among irreversible movements of bloch walls

Abstract: Theories on excess losses based on calculations of eddy currents due to the continuous and uniform motion of domain walls can only partly explain loss anomalies in G. O. FeSi. Furthermore, they completely fail to account for excess losses and non-linearity effects observed in many materials, where domain size is small compared to sample thickness. In the present work total losses are calculated considering also the contribution from irreversible movements of Bloch walls. The local magnetization is treated as a random function of time, characterized by a periodic and a non periodic component. Computation of losses is performed by convenient integration of the power spectrum of the voltage induced by the local magnetization variations. When the correlation among irreversible wall movements is taken into account, it is found that this provides a contribution to losses per cycle, which increases proportionally to the square root of the magnetizing frequency. Agreement is found with experimental behavior of losses in amorphous ferromagnets.

Maintenance strategies for PCM circuit switching

Abstract: During all the system design phase of an SPC switching system, a considerable effort is devoted to maintenance, both from a hardware and software point of view. The maintenance phases include fault detection, fault analysis (e.g., identification of the faulty security block within the switching system), fault isolation, fault reporting, fault localization, fault clearance, and restoration to service with the eventual requalification and reinitialization of the repaired security block. The paper mainly discusses fault detection and fault analysis strategies with specific reference to PCM digital switching systems. Different means leading to fault detection are presented with reference to central control, network access devices (scanners, drivers, markers), and digital switching network (duplicated or not duplicated). These means include automatic on-line tests (monitoring and routining), on-demand on-line tests, and alarm handling. Fault analysis can be accomplished by means of a deductive or a statistical method. As the latter seems more attractive, three basic methods of statistical fault analysis are presented. They use, respectively, two counters (operation and fault counter) per security block; one fault counter per security block; one "historical" fault stack, in which all the identities of security blocks involved in faulty operations are stored. The above fault analysis strategies are compared mainly in terms of core memory occupancy, processor time, and software complexity.

Highly selective RC-active filters using mucroer polynomials

Abstract: The complete design of a highly selective bandpass RC-active filter is presented, where special attention is payed to the choice of the approximating function. By using multiple critical route equiripple (mucroer) polynomials, a substantial reduction in maximum Q-factor and variance of the attenuation is obtained. This fact allows the use of biquadratic building blocks with only one operational amplifier (o.a.) in a cascade connection, without the need of multiple-loop feedback techniques. Furthermore, a much smoother group delay is achieved. The price payed for all these advantages is a slight increase in the number of 2ndorder sections to be cascaded. In the realisation, the real-integrator multiple-feedback (r.i.m.f.) section has been employed for its low-cost, easy-tuning, and high-Q capabilities. In the paper, the design and tuning procedure of this block are reported, together with the corresponding experimental results. Finally, a compensation technique of the Q-factor variability with the temperature is described and the experimental curves arc shown

Maximally flat approximation of lowpass RC active filters with multiple real pole

Abstract: A new maximally flat approximation criterion is proposed to realise lowpass RC active filters with a reduced number of amplifiers with respect to the classical Butterworth polynomials. This improvement is obtained by adding a multiple real pole and reducing the number of the complex pole pairs. The cascade connection of 3rd-order blocks allows the realisation of filters with fewer sections (fewer o.a.s) with respect to the commonly used cascade connections of 2nd-order blocks.

A theory of electric polarization in liquids: IV. Discussion of the approximations☆

Abstract: The main approximations used in the theory of dielectric liquids previously developed by the author (1976) are discussed They are shown to be widely justifiable in the framework of the Yvon-Kirkwood model, treating the polarisability as a molecular constant, independent of the thermodynamical state of the liquid

Syntax-directed recognition of spoken words in real-time

Abstract: A real-time recognizer of isolated words spoken in the italian language is presented. Each distinct level of recognition (segmentation, phonemic classification and lexical recognition) is controlled by the rules of appropriate grammars whose symbols are fuzzy linguistic variables. The recognition strategy depends on the lexical redundancy of the protocol and is based on a classification of speech units into broad phonetic classes, eventually followed by a classification into more detailed classes if some ambiguities still remain. The recognition steps are shown in detail through some examples.

Mucroer polynomials in passive-filter design

Abstract: The application of MUCROER (multiple critical root equal ripple) polynomials to the synthesis of LC lowpass ladder filters is investigated. Through an example, it is shown that MUCROER polynomials do not allow as great a tolerance to the components as Chebyshev polynomials do.

Complete Radiation Pattern of Parabolic Reflectors, Including the Effects of a Loaded Rim

Abstract: This paper deals with the calculation of the complete radiation pattern of a parabolic reflector antenna by using the induced currents method and the geometrical theory of diffraction in different regions, extended in particular to the case of a loaded rim. A package of computer programs is presented and a set of results, showing the possibility of improved radiation performances, is given.

Photoélectrochimiephotoelectrochemical processes on anodic layers

Abstract: Properties of anodic layers formed on various stainless steels and other iron base alloys were studied by means of photopotential and photocurrent measurements. The tests were carried out in boratebuffer solutions and in sulphate solutions with pH ranging from 2 to 11. The study has been extended to layers formed by thermal oxidation in air. The results obtained at pH 8.7 indicated that the various materials can be grossly classified into two groups according to their photoelectrochemical behaviour : those behaving like Fe and those behaving like Ni. The first group comprises Fe-Cr alloys, Fe-Ni alloys below 40 % Ni, and all the examined stainless steels. To the second group belong Fe-Ni alloys with more than 40 % Ni. For Fe-Ni alloys with Ni> 40 % a difference of the semiconducting properties has been established between anodic and thermal oxides. A difference of behaviour was also observed between AISI 3xx type and AISI 4xx type steels in the electrode potential range 500-1100 mV (NHE) when the pH is below 4. Tests were also made in order to investigate the influence of anodic current density on the characteristics of anodic layers during their formation

Pion double charge exchange in heavy nuclei

Abstract: In view of the forthcoming operation of the 0micron spectrometer at the CERN synchrocyelotron it seems to us tha t the t ime is ripe for an analysis of the nuclear physics experiments already planned, e.g. pion backward scattering and pion doublecharge exchange (DCX) (1). Theoretical aspects of pion scattering have been discussed in detail by several authors (2). Recent measurements (a) at low energy (30~