Showing papers by "Polytechnic University of Turin published in 1973"
01 Dec 1973
TL;DR: In this paper, the tensile strength of isotropic rocks is measured by loading discs and rings along their diameter, and the finite element method is used to correlate tensile stress, for which tensile failure is assumed to occur in each test, with the orientation of the axes of anisotropy.
Abstract: The tensile strength of rock materials is a parameter relevant to many rock mechanics applications. Rocks are often anisotropic in nature. Therefore, it is of interest to investigate suitable experimental methods for tensile testing to be used with these rocks. An attempt is made in this paper to see if the indirect methods adopted for testing isotropic rocks can be applied. Two rock types with transversely isotropic behavior are tested by loading discs and rings along their diameter. The finite element method is used in order to correlate the tensile stress, for which tensile failure is assumed to occur in each test, with the orientation of the axes of anisotropy. It is shown that the experimental results can be appropriately explained by this method and a parameter be defined which allows one to describe the law of variation of tensile strength with the anisotropy of deformability.
82 citations
TL;DR: In this paper, the average probability of error in the presence of intersymbol interference and additive noise for multilevel pulse-amplitude-modulation (PAM) and partial-response-coded (PRC) signaling schemes is presented.
Abstract: A new method is presented to compute the average probability of error in the presence of intersymbol interference and additive noise for multilevel pulse-amplitude-modulation (PAM) and partial-response-coded (PRC) signaling schemes. The method is based upon nonclassical Gauss quadrature rules (GQR) and suffers no limitation on noise statistics, so that it applies also for non-Gaussian noise. Moreover it yields some remarkable advantages as compared with other methods, in particular, with the series expansion method that has recently received considerable attention. Expressions for the truncation error are also given and their derivation is reported in the Appendix. Finally, examples of applications are presented and comparisons with other methods are carried out.
78 citations
TL;DR: In this paper, mass transfer coefficients with gas and liquid phase controlling resistance using a concurrent flow packed column with a wide range of operating conditions and four types of packing were measured and correlated with dissipated energy values.
Abstract: Measurements were made of mass transfer coefficients with gas and liquid phase controlling resistance using a concurrent flow packed column with a wide range of operating conditions and 4 types of packing. Mass transfer coefficients were much larger than those obtainable in countercurrent towers. The results were correlated with dissipated energy values. The correlations obtained can be used to determine absorption efficiency. Experimental results show that the use of a high velocity concurrent flow column is particularly suitable when mass transfer is controlled by the liquid phase resistance with chemical reaction in the liquid. (18 refs.)
46 citations
TL;DR: Only the impulse responses of the overall channels are needed, and the computational labor is reduced to the numerical evaluation of one particular type of integral, whose computation is based upon nonclassical Gaussian quadrature rules.
Abstract: An expression for the error probability of multilevel coherent phase-shift-keyed (CPSK) systems in the presence of intersymbol, interchannel, and co-channel interferences and additive Gaussian noise is derived. An exact expression is given for the binary CPSK system, whereas upper and lower bounds are presented for the multilevel systems. The approach proposed in this paper overcomes the difficulties of the exhaustive methods and allows accurate and fast evaluation of the character error probability. Only the impulse responses of the overall channels are needed, and the computational labor is reduced to the numerical evaluation of one particular type of integral, whose computation is based upon nonclassical Gaussian quadrature rules. The model of the system is general enough to allow the choice of a rectangular or otherwise-shaped modulating pulse and a constant or shaped envelope of the modulating carrier. Phase incoherence between adjacent carriers is also assumed, and a random misalignment among the modulating bit streams can be taken into account, if necessary. Extensive numerical results are presented for 2- and 4-level systems. The presentation of the results stresses a possible utilization of them in system design problems.
46 citations
TL;DR: A technique is introduced that analyzes the time evolutions of some parameters of the speech waveform to provide a description of these evolutions when a word is pronounced and recognition is performed by parsing the descriptions.
Abstract: A technique is introduced that analyzes the time evolutions of some parameters of the speech waveform. Suitable algorithms provide a description of these evolutions when a word is pronounced. Descriptions can be seen as the phrases of a language produced by a generative grammar. Recognition is performed by parsing the descriptions. Some experimental results are reported.
26 citations
TL;DR: In this article, the recently proposed interacting boson approximation (IBA) was applied to the structure of 16 O. The T = 0, J = 0 +, 2 +, 4 +, 1 −, 3 − states below 18 MeV were calculated and compared with the known experimental levels.
23 citations
TL;DR: In this paper, a min-max approach is taken, when input and initial conditions run over given admissible sets, and methods for evaluating suitable functionals to be minimized by the optimal model are developed.
Abstract: This paper is concerned with the approximation of complex dynamical systems by simple models. A min-max approach is taken, when input and initial conditions run over given admissible sets. Methods for evaluating suitable functionals to be minimized by theoptimal model are developed. The existence of an element ofbast approximation is prooved for a large class of problems. The homogeneous case in Hilbert spaces is investigated in more detail.
22 citations
14 citations
13 citations
TL;DR: The use of nonclassical Gauss quadrature rules (GQR's) allows a theoretical study of the joint effects of phase jitter, thermal noise, and intersymbol interference on average error probability; and a maximum-precision sampling technique in the simulation of digital communication systems.
Abstract: In multilevel bandpass data transmission there is usually a difference between the phase of the carrier signal and the phase of the receiver oscillator, thereby causing imperfect demodulation. The use of nonclassical Gauss quadrature rules (GQR's) allows: 1) a theoretical study of the joint effects of phase jitter, thermal noise, and intersymbol interference on average error probability; and 2) a maximum-precision sampling technique in the simulation of digital communication systems. On this basis, the mean-square-error and zero-forcing equalizers are considered, and their performances evaluated in terms of the average error probability for multilevel pulse-amplitude-modulation (PAM) and partial-response-coded (PRC) signaling schemes.
9 citations
01 Feb 1973
TL;DR: A recursive procedure is presented which is well suited for the numerical computation of the coefficients of the Gram-Charlier series.
Abstract: The Gram-Charlier series is a known tool for approximating a probability density function when the moments or the cumulants of a random variable are known. A recursive procedure is presented which is well suited for the numerical computation of the coefficients of the series.
TL;DR: The problem is reduced to the control of the model whose output is affected by an input dependent error constrained in norm, and a min-max approach is taken, which is the solution of a set of a partial differential equation.
TL;DR: A linear dynamie system described by an approximated model leads to an uncertainty which cannot be modeled by additive noise nor by a parameter bounded variation, which leads to the minimal uncertainty.
TL;DR: Starting from input-output data of the actual system, the proposed procedure leads to determine an optimal reduced model, on which it is very easy to design a min-max control policy for the plant which guarantees a bound of the performance degradation.
TL;DR: In this article, the effect of the gyroscopic moment on the appearance of the first imaginary critical velocity was investigated and shown to have an important effect on the computation of the critical velocity.
Abstract: The effect of the gyroscopic moment on the appearance of a first imaginary critical velocity (minimum negative value of lambda) is investigated and shown to have an important effect on the computation of the first critical velocity A numerical procedure is developed which can be used for overcoming the difficulties arising when the first real and the first imaginary roots are similar in modulus As an example, a real shaft with two supports was analyzed For the computation the real shaft was subdivided into ten sections, and for two of them (representing compressor and turbine) the gyroscopic moment was taken into account The present method is especially useful when high speed computational facilities are not available
TL;DR: In this paper, a preliminary analysis of the influence of roughness on wear and friction coefficient of thermoplastic on metal pairs is presented. But the analysis is limited to a single pair.
Abstract: This work is a preliminary analysis of the influence of roughness on wear and on friction coefficient of thermoplastic on metal pairs.
TL;DR: A numerical technique used in gasdynamics is here applied to the solution of one-dimensional unsteady flows in channels in the spirit of the shallow water theory, with the explicit treatment of imbedded bores generated in the flow by coalescence of characteristics.
Abstract: A numerical technique used in gasdynamics is here applied to the solution of one-dimensional unsteady flows in channels in the spirit of the shallow water theory. Its most important feature is the explicit treatment of imbedded bores generated in the flow by coalescence of characteristics. Four numerical examples are presented to show possible applications of the method.
TL;DR: Bounded tubes can be derived from this method of approximation, in which all the possible state trajectories for the model are constrained to lie, and it is shown that the former uncertainty is always less than the latter.
TL;DR: In this article, a system of N coupled active infinite lines, excited by a set of N series impressed voltage sources and of N parallel impressed current sources, is considered, and conditions are given for the existence and the uniqueness of the response of the structure to the given excitation, within the framework of suitable distribution spaces.
Abstract: In this paper, a system of N coupled active infinite lines, excited by a set of N series impressed voltage sources and of N parallel impressed current sources, is considered. The system is assumed to be described by both a Telegraphist's and a State-space mathematical model. Conditions are given for the existence and the uniqueness of the response of the structure to the given excitation, within the framework of suitable distribution spaces.
TL;DR: In this paper, the equivalent temperature in a solar X-ray flare for λ ≈ 2 A was deduced from the measurement of the Xray flux by Explorer 37 and the simultaneous measurements of the ionospheric electron density by VLF and LF records on the Rugby-Turin link.
TL;DR: In this paper, a parametrization of the excitation spectrum of liquid helium in terms of a modified version of the Brueckner-Sawada theory is considered and found to provide a quantitative description of the available data up to k = 2.1 A-1.
TL;DR: In this article, the determinazione numerica del flusso transonico continuo attorno a profili alari and solitamente effettuata o con procedimento diretto sul piano fisico or con procedimitati indiretti sul piano odografico.
Abstract: La determinazione numerica del flusso transonico continuo attorno a profili alari e solitamente effettuata o con procedimento diretto sul piano fisico o con procedimento indiretto sul piano odografico. In questa conferenza si osserva preliminarmente che si ha sul piano odografico un problema di valori al contornocon frontiera libera. Si illustra poi un metodo iterativo diretto per la risoluzione numerica di tale problema, almeno per profili regolari.