324,538 research outputs found
Il pedagogista e i differenti ruoli professionali
No full textL'educazione appare oggi più che mai una sfida difficile, un compito delicato che richiede preparazione e consapevolezza. Ne deriva l'importanza di sottolineare come essa non possa essere pensata come fatto naturale, scontato ed immediato. Il capitolo si propone di approfondire alcuni aspetti inerenti la figura professionale dell'educatore e del pedagogista e delle dinamiche correlate a tali ruoli
Varicocele treatment in pediatric age: report of different techniques
No full textThe author analyze the results of different surgical tecniques in patients treated for idiopathic varicocel
Solving a collection of free coexistence-like problems in stability
No full textThe problem of the stability of the origin for the sytem (∗) x ̈+xf(x)=0, y ̈+yw(x)=0, f(0)>0, f∈C1, w∈C0, is said to be related to coexistence if (∗) has a first integral of the form y ̇s(x,x ̇)−ys ̇(x,x ̇). In this case the author says that (f,w,s) is coexistence-like. In this paper the author assumes that s is given by s(x,x ̇)=x ̇(1+αx), α∈R, and determines and constructs all the maps f such that the origin is a stable equilibrium for the system in (∗) with w(x)=(f(x)+xf′(x)+αx(4f(x)+xf′(x)))/(1+αx)
Canonical kernel representations for behaviors over finite Abelian groups
No full textIn this paper the problem of constructing canonical kernel representations for systems whose alphabet set is an Abelian group is addressed. In standard linear system theory, there exist two important canonical kernel representations: minimal and row reduced kernel representations. In this paper we propose an extension of such canonical kernel representations to the group case. This topic has applications in the theory of convolutional codes over groups where kernel representations correspond to syndrome formers which are essential in decoding
Stability analysis and synthesis for scalar linear systems with a quantized feedback
No full textIt is well known that a linear system controlled by a quantized feedback may exhibit the wild dynamic behavior which is typical of a nonlinear system. In the classical literature devoted to control with quantized feedback, the flow of information in the feedback was not considered as a critical parameter. Consequently, in that case, it was natural in the control synthesis to simply choose the quantized feedback approximating the one provided by the classical methods, and to model the quantization error as an additive white noise. On the other hand, if the flow of information has to be limited, for instance, because of the use of a transmission channel with limited capacity, some specific considerations are in order. The aim of this paper is to obtain a detailed analysis of linear scalar systems with a stabilizing quantized feedback control. First, a general framework based on a sort of Lyapunov approach encompassing known stabilization techniques is proposed. In this case, a rather complete analysis can be obtained through a nice geometric characterization of asymptotically stable closed-loop maps. In particular, a general tradeoff relation between the number of quantization intervals, quantifying the information flow, and the convergence time is established. Then, an alternative stabilization method, based on the chaotic behavior of piecewise affine maps is proposed. Finally, the performances of all these methods are compared
System theoretic propertiesof convolutional codes over rings
No full textConvolutional codes over rings are particularly suitable for representing codes over phase-modulation signals. In order to develop a complete structural analysis of this class of codes, it is necessary to study rational matrices over rings, which constitutes the generator matrices (encoders) for such convolutional codes. Noncatastrophic, minimal, systematic, and basic generator matrices are introduced and characterized by using a canonical form for polynomial matrices over rings. Finally, some classes of convolutional codes, defined according to the generator matrix they admit, are introduced and analyzed from a system-theoretic point of view
Minimal and systematic convolutional codes over finite abelian groups
No full textConvolutional codes over Abelian groups provide an effective theoretical framework for the analysis of some classes of TCM codes. The encoder synthesis for this class of codes is not as simple as in the binary case, since minimal encoders in the group case might be necessarily nonlinear. In this contribution an algorithmic method testing whether a convolutional code over an Abelian group admits a systematic or a minimal homomorphic encoder is provided. This test consists in verifying whether a subgroup splits in a group. Through this method, the class of codes admitting systematic encoders and the class of codes admitting minimal encoders can be compared. Finally this test is applied to some examples of practical relevance
Classification problems for shifts on modules over a principalideal domain
No full textIn this paper we study symbolic dynamics over alphabets which are modules over a principal ideal domain, considering topological shifts which are also submodules. Our main result is the classification, up to algebraic and topological conjugacy, of the torsion-free, transitive, finite memory shifts
Difference equations, shift operators and systems over Noetherian factorial domains
No full textAbstractIn this paper we study a class of operators which act on spaces of sequences taking value on a module over a Noetherian factorial domain. These operators are obtained as linear combinations of the operators that shift the sequences forward and backward. For this reason they are called shift operators. The properties of this class of operators are effectively applied to study difference equations and dynamical systems over rings
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