Showing papers by "Polytechnic University of Milan published in 1984"
Book•
01 Jan 1984TL;DR: It is necessary to consider the architecture of the distributed database as a system of principles rather than as a black-box of values.
Abstract: Distributed databases: principles and systems , Distributed databases: principles and systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
738 citations
TL;DR: The Taylor-Galerkin method is employed to derive accurate and efficient numerical schemes for the solution of time-dependent advection-diffusion problems and is successively extended to deal with nonlinear and multi-dimensional problems.
157 citations
15 Sep 1984-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, a Semiconductor Drift Chamber was produced and tested, and the performance of the test chamber was described and the signal processing to obtain the best position resolution was discussed.
Abstract: A Semiconductor Drift Chamber was produced and tested. The paper describes: 1. 1)|principle of the chamber operation; 2. 2)|the performance of the test chamber; 3. 3)|the signal processing to obtain the best position resolution.
109 citations
TL;DR: The original characteri stics of an Office Information System (OIS) in comparison with a conventional information system imply the need for new design methodol ogies and model s, which are discussed and discussed in this paper.
107 citations
TL;DR: In man the reflex pattern evoked by a painful cutaneous stimulus during locomotion is determined by the phase of the step cycle during which the stimulus is delivered, and a functional role in maintenance of postural balance during destabilizing withdrawal reactions is conceivable.
79 citations
TL;DR: For periodically time-varying matrix Riccati equations, controllability and observability (in the usual sense) are sufficient for the existence of a unique positive definite periodic solution as discussed by the authors.
Abstract: For periodically time-varying matrix Riccati equations, controllability and observability (in the usual sense) are shown to be sufficient for the existence of a unique positive definite periodic solution.
68 citations
TL;DR: In this article, it has been shown that EOPs have a physical meaning independently on intensity parametrization and that they can be used to describe the charge distribution in the molecules and to understand some electrostatic interactions between the molecules.
43 citations
TL;DR: In this paper, an analytical procedure based on the same topological approach is developed, and a comparison is made with the classical Zubov method, noting the possibility of overcoming some of the classical method's drawbacks (e.g., its nonuniform convergence).
Abstract: The paper deals with the problem of the estimation of regions of asymptotic stability for continuous, autonomous, nonlinear systems. After an outline of the main approaches available in the literature, the "trajectory reversing method" is presented as a. powerful numerical technique for low order systems. Then, an analytical procedure based on the same topological approach is developed, and a comparison is made with the classical Zubov method, noting the possibility of overcoming some of the classical method's drawbacks (e.g., its nonuniform convergence). Several examples of applications of the "trajectory reversing method" both in the numerical and analytical formulation are reported.
37 citations
TL;DR: The algorithm is based on the a priori study and exploration of the technical but not formalized language that engineers and draftsmen use to design and interpret the (analog) drawings.
36 citations
35 citations
TL;DR: An automatic pulsed laser microfluorometer with high spatial and temporal resolution, developed in the laboratories, and a dual time‐scale microprocessor‐controlled signal averager for the acquisition and processing of the signal.
Abstract: SUMMARY
The paper describes an automatic pulsed laser microfluorometer with high spatial and temporal resolution, developed in our laboratories. The instrument consists of: (i) a nitrogen-laser-pumped dye-laser for the excitation of the fluorescence, (ii) a microscope with additional optics to focus the excitation beam on the sample and to collect the fluorescence, (iii) filters or monochromators to select the output wavelength, (iv) a fast photomultiplier tube to detect the signal, and (v) a dual time-scale microprocessor-controlled signal averager for the acquisition and processing of the signal.
Examples are given that show the potential of the time-resolved fluorescence microscopy in studying, quantitatively and qualitatively, the properties of fluorescent molecules.
TL;DR: Analysis of dispersion produced by a lambda/4 multilayer dielectric mirror as a function of its construction parameters is presented, finding some cases, which seem to be of practical relevance, to prevent pulses shorter than ~50 fsec from being produced in the mode-locked laser cavity.
Abstract: Analysis of dispersion produced by a lambda/4 multilayer dielectric mirror as a function of its construction parameters is presented. The amount of dispersion can be estimated from a careful inspection of the measured reflectivity curve. In some cases, which seem to be of practical relevance, the value of dispersion is such as to prevent pulses shorter than ~50 fsec from being produced in the mode-locked laser cavity.
TL;DR: In this article, a closed-form estimate for asymptotic stability regions of second-order systems is derived in terms of quadratic functions and then it is optimized with respect to its area.
Abstract: This note gives some stability results concerning second-order systems \dot{x} = f(x) , where f(x) contains either linear and quadratic or linear and cubic terms in x . Following a Lyapunov-like approach, a closed-form estimate for asymptotic stability regions of such systems is derived in terms of quadratic functions and then it is optimized with respect to its area. Some application examples show the good results of the proposed method, in comparison to those obtained by the classical numerical approaches.
TL;DR: In this paper, a numerical method for calculating incompressible viscous flows between two concentric rotating spheres is described, where the dependent variables describing the axisymmetric flow field are the azimuthal components of the vorticity, of the velocity vector potential and of the velocities.
15 Sep 1984-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the design criteria of signal processors for semiconductor detectors in high energy physics experiments are reviewed, and several examples of processors for microstrip silicon detectors and for silicon detector telescopes are reviewed with particular emphasis on noise performance and high rate capabilities.
Abstract: Design criteria of signal processors for semiconductor detectors in high energy physics experiments are reviewed. Choice of input active devices of preamplifiers, detector-device capacitive matching, preamplifier configurations, variant and invariant signal processors are discussed. Several examples of processors for microstrip silicon detectors and for silicon detector telescopes, are reviewed with particular emphasis on noise performance and high rate capabilities.
TL;DR: In this paper, it was shown that the system is asymptotically stable if and only if the associated Lyapunov differential equation admits a periodic solution positive definite at each time instance.
TL;DR: This paper suggests implementation of a reconfigurable architecture making use of a switch organization that allows relevant reduction of added interconnection area and the complete structure, down to reconfiguration circuitry layout, is detailed.
TL;DR: In this paper, a non-linear finite element model for plain masonry structures under lateral static loads and seismic base inputs is presented, where three superimposed elasto-plastic shear elements are used in order to approximate the typical force-displacement curve for masonry.
Abstract: A non-linear finite element model for plain masonry structures under lateral static loads and seismic base inputs is presented. Three super-imposed elasto-plastic shear elements are used in order to approximate the typical force-displacement curve for masonry. Material properties are identified with respect to results of shear tests on single piers. Modelling of entire structures is then performed and the numerical results are satisfactorily checked against the experimental outputs of static and shaking table tests of simple 1 and 2 storey buildings. The out of plane behaviour of walls is accounted for by means of a simplified method.
TL;DR: It is shown that the phenotypic profiles of r - and K -selected organisms are often identical and diverge only if there are genetic constraints of a particular kind between the various evolving traits.
Book•
01 Sep 1984TL;DR: The main concern in this work is the illustration of models for natural language processing, and the discussion of their role in the development of computational studies of language.
Abstract: The main concern in this work is the illustration of models for natural language processing, and the discussion of their role in the development of computational studies of language. Topics covered include the following: competence and performance in the design of natural language systems; planning and understanding speech acts by interpersonal games; a framework for integrating syntax and semantics; knowledge representation and natural language: extending the expressive power of proposition nodes; viewing parsing as word sense discrimination: a connectionist approach; a propositional language for text representation; from topic and focus of a sentence to linking in a text; language generation by computer; understanding the Chinese language; semantic primitives or meaning postulates: mental models of propositional representations; narrative complexity based on summarization algorithms; using focus to constrain language generation; and towards an integral model of language competence.
TL;DR: In this article, the dehydration of ethyl and methyl alcohol, catalyzed by Y decationized zeolite, has been studied in order to identify the sites active in promoting the reaction.
TL;DR: In this article, the matrix Riemann-Hilbert problem arising in the time-dependent BGK model for half space problems is analyzed and a general procedure is given which leads to closed form solutions.
Abstract: The matrix Riemann-Hilbert problem arising in the time-dependent BGK model for half space problems is analyzed. The method used is similar to the one originally introduced by one of the authors for steady problems. A general procedure is given which leads to closed form solutions.
TL;DR: In this article, the authors define organizational noise as the unexpected variety which operators of the technical system have to face, and investigate two distinctive work-related phenomena: self-regulative behavior which absorbs noise and self-organization, for which noise is exploited as a source of new configurations rather then being eliminated.
Abstract: Organizational noise concerns the character and consequences of out-of-the-norm events which occur in organizations. The paper defines organizational noise as the unexpected variety which operators of the technical system have to face. The investigation of organizational noise is of twofold importance. First, it helps the analyst to understand how the work organization really functions. Second, it points out the existence of or the possibilities for implementing alternative organizational forms. New organizational forms may emerge from the organized behavior of members facing fluctuations. Two distinctive work-related phenomena are also investigated: self-regulative behavior which absorbs noise and self-organization, for which noise is exploited as a source of new configurations rather then being eliminated. Finally, some implications for methods of organizational analysis are developed.
TL;DR: In this article, a canonical solution of the matrix Riemann-Hilbert problem for sound propagation in a gas occupying a half space is presented, which is computed numerically for three particular values of the sound frequency.
Abstract: Following the procedure indicated in part I, a canonical solution of the matrix Riemann-Hilbert problem for sound propagation in a gas occupying a half space is presented. The closed form solution is computed numerically for three particular values of the sound frequency. The results compare favorably with a previously known numerical solution.
TL;DR: Curled peach leaves, naturally infected by Taphrina deformans, were studied by scanning and transmission electron microscopy, combined with cytochemistry, in order to observe the modifications induced by the pathogen in the host cells, particularly in the wall-to-wall boundary zone.
Abstract: Curled peach leaves, naturally infected by Taphrina deformans, were studied by scanning and transmission electron microscopy, combined with cytochemistry, in order to observe the modifications induced by the pathogen in the host cells, particularly in the wall-to-wall boundary zone. It was found that the asci, which are formed only on the upper leaf surface, perforate the cuticle by lysis and not only by mechanical action; hyphae growing in the intercellular spaces cause a partial dissolution of the leaf cell walls by secretion of polysaccharide-degrading enzymes including cellulase. Alteration of the host plasma membrane often accompanies cell wall degradation. It was also found that in the curled areas the palisade layer is replaced by a less differentiated tissue, while the spongy parenchyma is always well recognizable, notwithstanding cellular alteration.
TL;DR: In this paper, a new approach to quaternions and to one-index spinors in the Euclidean three-space is offered,directly derived from the vector formulation of the Euler's theorem on the general displacement of a rigid body with a fixed point.
Abstract: A new approach to quaternions and to one-index spinors in the Euclidean three-space is offered,directly derived from the vector formulation of the Euler's theorem on the general displacement of a rigid body with a fixed point. A linear and injective correspondence between quaternions and one-index spinors is introduced, leading to a spinor formulation of rotations as a natural extension of the usual quaternion automorphism and providing other kinematic relations in the spin space as well as the recovery of the usual Pauli spinor formalism.
TL;DR: In this article, a finite element model for the elastic-plastic analysis of plane frames is proposed, based on the independent modelling of the displacement and plastic strain fields; the latter is modelled both over the cross-section and along the element length as function of a finite number of parameters, which are considered as an extra set of independent variables.
Abstract: A finite element model for the elastic–plastic analysis of plane frames is proposed. The formulation is based on the independent modelling of the displacement and plastic strain fields; the latter is modelled both over the cross-section and along the element length as function of a finite number of parameters, which are considered as an extra set of independent variables, in addition to nodal displacements. Stress redistribution is allowed for over the cross-section, but not over the element length, where the distribution of stress resultants (axial forces and bending moments) is imposed consistently with the assumed displacement model; stress redistribution in terms of stress resultants becomes possible only because of the finite number of redundancies introduced when assembling. It is shown that the model can be formulated in such a way that not only compatibility and elasticity, but also equilibrium (in the sense of beam theory), are fully complied with and only the plastic portion of the constitutive relationship is approximately fulfilled, even if, in principle, to any desired level of accuracy. The model produces accurate results, including a detailed representation of the spreading of plastic zones, with a fairly limited number of elements.
TL;DR: In this article, the extinction boundary in terms of maximum depressurization rate vs initial pressure can be constructed by go/no-go testing for a given final pressure, and a good agreement was found between analytical, numerical, and experimental results.
TL;DR: The NPS seems to be quite important in the understanding of HpD tumor-specificity, since the presence of an emission band similar to the NPS one seem to be favoured in tumor cells as compared with normal cells.
TL;DR: An existence condition for the solution of an optimal control problem for a single traffic intersection is derived in this article, where the authors show that existence conditions are fairly restrictive if control is required to dissolve all intersection queues at the same time.
Abstract: An existence condition for the solution of an optimal control problem for a single traffic intersection is derived in this note The optimal control problem has been initially formulated and solved in the pioneering work of Gazis (1963, 1964) and coworkers It is shown that existence conditions are fairly restrictive if control is required to dissolve all intersection queues at the same time