Showing papers by "Polytechnic University of Turin published in 1982"
TL;DR: In this paper, the problem of parameter estimation and of the evaluation of related uncertainty intervals is considered in the case that a probabilistic description of noise and errors is not available (of suitable), but only a bound on them is known.
Abstract: The problem of parameter estimation and of the evaluation of related uncertainty intervals is considered in the case that a probabilistic description of noise and errors is not available (of suitable), but only a bound on them is known. In the present paper only linear parametrizations and estimators are considered. Very simple and computationally feasible algorithms are derived for evaluating two different types of uncertainty intervals (Estimates Uncertainty Intervals, Parameter Uncertainty Intervals). The relationships between the EUI's and the PUI's are established, and the solution to the problem of the minimum uncertainty intervals estimator is given: the latter can be obtained by means of a simple linear programming algorithm.
351 citations
TL;DR: Markovian models are developed for the performance analysis of multiprocessor systems intercommunicating via a set of buses and are found to be surprisingly accurate for a wide range of configurations.
Abstract: Markovian models are developed for the performance analysis of multiprocessor systems intercommunicating via a set of buses. The performance index is the average number of active processors, called processing power. From processing power a variety of other performance measures can be derived as dictated by the specific processor application. Exact models are first introduced and are illustrated with a simple example. The computational complexity of the exact models is shown to increase very rapidly with system size, thus making the exact analysis impractical even for medium size systems. To overcome the complexity of computation, several approximate models are introduced. The approximate results are compared with the exact ones and found to be surprisingly accurate for a wide range of configurations. Simulation is used to validate the analytic models and to test their robustness.
120 citations
TL;DR: This paper examines the numerical integration (in the Cauchy principal value sense) of functions having (several) first order real poles and proposes an alternative algorithm for the numerical evaluation of integrals of the form.
Abstract: In this paper we examine the numerical integration (in the Cauchy principal value sense) of functions having (several) first order real poles. We give a survey of results concerning some quadrature formulas of interpolatory type proposed by Delves, Hunter, Elliott and Paget, and several other authors; along with the description we present some minor generalizations and make comments on the computational aspects. Finally, we propose an alternative algorithm for the numerical evaluation of integrals of the form
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92 citations
TL;DR: The letter describes a load-pulling method that allows an extension of the two-signal approach to applications where the output frequency spectrum is different from the input one, as in the case of power devices operating with multicarrier input signals.
Abstract: The letter describes a load-pulling method that allows an extension of the two-signal approach to applications where the output frequency spectrum is different from the input one, as in the case of power devices operating with multicarrier input signals.
87 citations
TL;DR: Markovian models are developed for the performance analysis and comparison of several single bus multiprocessor architectures, introducing simplifying assumptions that allow a compact Markovian system description.
Abstract: Markovian models are developed for the performance analysis and comparison of several single bus multiprocessor architectures. Processors are assumed to cooperate in a message passing fashion, and messages are exchanged through common memory areas. Four architectures are considered in this paper which differ in the location of the common memory modules. Contention for shared resources is modeled and the corresponding efficiency loss is studied. Numerical results are obtained for the processing power of each architecture, introducing simplifying assumptions that allow a compact Markovian system description.
75 citations
TL;DR: A bus-structured local area communications network unidirectional bus system, over which packets are broadcast, with multiple-access protocol, which allows an efficient integration of real-time traffic, such as packetized voice, with bursty data traffic.
44 citations
TL;DR: In this article, the variation with composition of the hyperfine magnetic fields of metal atoms with 2 or 3 close interstitial atoms with three non-metal nearest neighbours and paramagnetic behaviour have also been detected.
Abstract: Mossbauer spectroscopy of nitrided and carbonitrided iron powders and plates with total interstitial atom contents of between 24 and 33 at% has allowed the variation with composition of the hyperfine magnetic fields of metal atoms with 2 or 3 close interstitial atoms to be determined. Fe atoms with three non-metal nearest neighbours and paramagnetic behaviour have also been detected. Only when the content of non-metal atoms goes beyond 30 at%, do Fe atoms in e-carbonitrides display higher magnetic fields than in the corresponding e-nitrides. The lower number of electrons contributed to the iron 3d-orbitals by C atoms than by N atoms is considered the cause of the above phenomenon. The variation of other hyperfine parameters with composition is also discussed.
38 citations
01 May 1982
TL;DR: This paper deals with a class of nonlinear, time-invariant systems with memory based on the truncation of discrete-time Volterra series expansions of input-output relationships, which can be implemented by a finite-length transversal filter, a finite number of multipliers, and a summing bus.
Abstract: This paper deals with a class of nonlinear, time-invariant systems with memory - called discrete Volterra processors - based on the truncation of discrete-time Volterra series expansions of input-output relationships. These systems can be implemented by a finite-length transversal filter, a finite number of multipliers, and a summing bus, and share the interesting property of being described by a linear combination of suitable nonlinear functions of the input samples. Two examples of application are considered in some detail: (i) The design of minimum mean-square error predictors of discrete-time random processes, and (ii) The identification of discrete nonlinear systems with memory.
36 citations
TL;DR: In this article, the electrical resistivity ρ and its temperature coefficient α have been measured on amorphous ribbons prepared with different quenching rates and interpreted in terms of a theory based on the Ziman approach to the resistivity of metallic glasses.
29 citations
TL;DR: In this paper, the fracture initiation process at the notch differs according to root radius and heat treatment, and the shear lip width is linearly related to the applied J-integral at fracture.
Abstract: Charpy-V type samples either step-quenched from 1200 °C or directly quenched from the usual 870 °C temperature, fractured by a slow bend test procedure, have been fractographically examined. Their notch root radius,ρ, ranged from almost zero (fatigue precrack) up to 2.0 mm. The fracture initiation process at the notch differs according to root radius and heat treatment. Conventionally austenitized samples withρ values larger than 0.07 mm approximately (ρ
eff) always display a continuous shear lip formation along the notch surface, whereas specimens with smaller notches do not exhibit a similar feature. Moreover, shear lip width in specimens withρ >ρ
eff is linearly related to the applied J-integral at fracture. In high temperature austenitized samples similar shear lips are almost nonexistent. The above findings, as well as overall fractographic features, are combined to explain why blunt notch AISI 4340 steel specimens display a better fracture resistance if they are conventionally heat treated, whereas fatigue precracked samples show a superior fracture toughness when they are step-quenched from 1200 °C. Variations of fracture morphologies with the notch root radius and heat treating procedures are associated with a shift toward higher Charpy transition temperatures under the combined influence of decreasing root radii and coarsening of the prior austenitic grain size at high austenitizing temperatures.
27 citations
01 May 1982
TL;DR: The paper presents a new formulation of the so-called "covariance-lattice" algorithm for linear predictive analysis that makes no explicit use of the predictor coefficients but works directly on the reflection coefficients, so being better suited to fixed-point arithmetic implementation.
Abstract: The paper presents a new formulation of the so-called "covariance-lattice" algorithm for linear predictive analysis. The new method makes no explicit use of the predictor coefficients but works directly on the reflection coefficients, so being better suited to fixed-point arithmetic implementation. An example of application to speech data illustrates the above point.
TL;DR: In this article, the use of the An approximate method in solving the monokinetic neutron transport equation has been studied and it has been shown that the system of space second-order differential equations which constitute the method may be cast into a form perfectly equivalent to the PN model, for any geometry.
TL;DR: In this article, a mass transfer from FREELY-SUSPENDED PARTICLES in Stirred Tanks is described. But this is not the case in this paper.
Abstract: (1982). MASS TRANSFER FROM FREELY-SUSPENDED PARTICLES IN STIRRED TANKS† Chemical Engineering Communications: Vol. 14, No. 1-2, pp. 91-98.
TL;DR: In this article, a general magnetic loss model is presented which takes account with proper approximations of the spatial and temporal nonhomogeneities and stochastic character of the elementary dissipative mechanisms.
TL;DR: A new technique to measure the principal refractive indexes of a nematic liquid crystal using an indirect measurement of the refraction angle by determining the direction of a magnetic field which minimizes the light scattering is presented.
Abstract: A new technique to measure the principal refractive indexes of a nematic liquid crystal is presented. The method is based on an indirect measurement of the refraction angle by determining the direction of a magnetic field which minimizes the light scattering. With this technique one can perform different light scattering experiments, which require a knowledge of the refractive indexes, on the same crystal slab. The accuracy is better than ±0.15%. A discussion about the systematic error due to the distortion of the director profile near the holder edges and the relative correction is given.
TL;DR: The operating system kernel of a multiprocessor system based on 16 bit microcomputers is described, which makes available a virtual machine where processes allocated on different processors are executed in parallel, while processes which reside on the same processor are execution in a multitasking environment.
TL;DR: In this paper, a model has been developed for predicting the effect of number and size of liquid rivulets on the reaction rate in a cascade-bed reaction, and the results show that intraparticle concentration profiles are strongly affected by the distribution of the rivulests.
Abstract: The liquid in trickle-bed reactors falls in rivulets down over the catalyst particles. Heretofore, studies of the effect of fractional liquid coverage of the outer surface of the particle on reaction rate have ignored the distribution of the rivulets. A model has been developed in this paper for predicting the effect of number and size of the liquid rivulets. The system of equations has been solved numerically for a first order reaction for two types of reactions: a), one where the rate is determined by the reactant concentration in the liquid, and b), a reaction where the rate is controlled by reactant concentration in the gas phase, as in some hydrogenations.
The results show that intraparticle concentration profiles are strongly affected by the distribution and size of the rivulets. However, for both types of reactions the overall rate, as measured by an overall effectiveness factor, is not significantly affected. This result is important since it suggests that distribution and size of the liquid rivulets may be safely ignored in evaluating the effect of liquid coverage, or wetting efficiency, on the rate of reaction
Le liquide, dans les reacteurs a trois phases (“trickle beds”) tombe en film sur les particules du catalyseur. Les etudes faites jusqu'ici sur l'effet de la portion mouillee de la surface exterieure de la particule sur la vitesse de reaction n'ont pas tenu compte de la distribution des films. Dans le present travail, on a etabli un modele pour prevoir le nombre et les dimensions des films liquides. On a resolu numeriquement, pour une reaction de premier ordre, le systeme d'equations relatives a deux types de reaction: (a) une reaction dans laquelle la vitesse de reaction est determinee par la concentration du reactif dans le liquide et (b) une reaction dans laquelle la vitesse est determinee par la concentration du reactif en phase gazeuse, comme dans le cas de certaines hydrogenations.
Les resultats indiquent que la distribution et les dimensions des films affectent fortement les profils de concentration intraparticulaires; toutefois, dans le cas des deux reactions considerees, la vitesse globale, mesuree par un facteur d'efficacite globale, n'est pas affectee de maniere importante. Ce resultat a, cependant, de l'importance, car il suggere que l'on peut sans crainte ne pas tenir compte de la distribution et des dimensions des films liquides, pour evaluer l'effet de la proportion de la surface mouillee, ou efficacite du mouillage, sur la vitesse de reaction.
TL;DR: In this paper, the stime per the nucleo di Gauss-Weierstrass su gruppi di Lie compatti and se ne indicano alcune applicazioni.
Abstract: Si ottengono delle stime per il nucleo di Gauss-Weierstrass su gruppi di Lie compatti e se ne indicano alcune applicazioni.
TL;DR: In this paper, the authors examined six stopping methods of hydration of monocalcium aluminate and found that the most suitable method seems to be the following: • - an ethanol washing; this process is repeated three times; • - a further washing, with a mixture ethanol-ethyl ether; and• - a drying in stove at 40°C during six hours.
TL;DR: In this paper, correlation effects in the motion of a system of few 180° domain walls have been investigated through Barkhausen experiments and it is observed that the walls move as rigid but interacting objects during the reversal of magnetization.
Proceedings Article•
18 Aug 1982TL;DR: A novel solution based on the extraction of acoustic cues is proposed in this paper that is performed by parallel processes implementing an expert system represented by a grammar of frames.
Abstract: Efficient syllabic hypothesization in continuous speech has been so far an unsolved problem. A novel solution based on the extraction of acoustic cues is proposed in this paper. This extraction is performed by parallel processes implementing an expert system represented by a grammar of frames.
01 Jan 1982
TL;DR: In this article, a general Heisenberg system in an external field is solved by a second order cumulant-cluster approximation, and the uncompatibility between the solutions of the polarization self-consistency and minimum free energy equations is discussed.
Abstract: A general Heisenberg system in an external field is solved by a second order cumulant cluster approximation. The uncompatibility between the solutions of the polarization self consistency and minimum free energy equations is discussed. A correlated mean-field is then introduced which allows the removal of such difficulty at low temperature.
TL;DR: Which processor interconnection method makes a modular, reconfigurable system perform best in a given application?
Abstract: Which processor interconnection method makes a modular, reconfigurable system perform best in a given application? Certain tools and strategies help provide the answer.
TL;DR: In this article, the dyadic Green's functions in uniform waveguides with perfectly conducting walls are obtained, and the same forms as in the free space appear; moreover the use of the divergence theorem allow to apply the \bigtriangledown operator on the currents in the integral representations of the electromagnetic fields.
Abstract: New expressions of the dyadic Green's functions in uniform waveguides with perfectly conducting walls are obtained. Significant features of these expressions are an explicit modal evaluation of their singular part. The same forms as in the free space appear; moreover the use of the divergence theorem allow to apply the \bigtriangledown operator on the currents in the integral representations of the electromagnetic fields. Consequently the involved kernels are less singular, and this procedure can be conveniently used in some applications.
08 Mar 1982
TL;DR: In this article, a nonlinear equalizer structure is proposed and its performance is analyzed for a 4-phase PSK satellite channel, and it is shown that it can prove quite effective in terms of a tradeoff between performance improvement and hardware complexity.
Abstract: Conventional techniques attempting to compensate for the influence of linear and nonlinear distortion in digital satellite channels include optimization of channel filtering. With conventional linear filtering it has been experienced that there is still room for considerable improvement, so that it appears reasonable to investigate some forms of nonlinear filtering in an attempt to cope with those distortions. In this paper a nonlinear equalizer structure is proposed, and its performance is analyzed. It is shown, by some examples Of application to a 4-phase PSK satellite channel, that it can prove quite effective in terms of a tradeoff between performance improvement and hardware complexity.
TL;DR: A series of dental alloys were characterized with respect to chemical composition, microstructure and corrosion resistance in artificial saliva to attribute a greater corrosion resistance to the dispersion phase alloys.
TL;DR: A fabrication process for niobium-based Josephson superconductive tunnel junctions with a Pb/In alloy top electrode which showed very good mechanical and electrical properties and high oxide uniformity is described in this article.
TL;DR: In this article, the results of a monodimensional model with constant parameters for studying the thermal field on a plane surface, treated by laser beam, have been, controlled too, according to the program of the Progetto Finalizzato Laser di Potenza, sponsored by the Consiglio Nazionale delle Ricerche, that we warmly thank for the agreement to publish the result of their sponsored research.
TL;DR: In this paper, the ferromagnetic transition temperature of carefully homogeneized Ni−Fe alloys has been determined by means of Mossbauer transmission experiments down to liquid-nitrogen temperature, for Ni contents ranging between 24% and 35%.
Abstract: The ferromagnetic-transition temperatureT
c of carefully homogeneized Ni−Fe alloys has been determined by means of Mossbauer transmission experiments down to liquid-nitrogen temperature, for Ni contents ranging between 24% and 35% (atomic). The results show thatT
c decreases rapidly with decreasing Ni concentration, according to a nonlinear behaviour different from the linear one usually observed in other Ni alloys. The present data agree with the ones of other authors, but differ from other data probably obtained in less homogeneized samples.