Showing papers by "Polytechnic University of Milan published in 1976"
TL;DR: A segmentation algorithm is proposed which uses dynamic programming (Viterbi algorithm with three states) and a simpler method that makes possible the estimation of the n most probable displacements is proposed.
Abstract: Various techniques are described to measure, small displacements of television images. If two successive video frames are considered, their differences are approximately a linear combination of the components of the displacement of the object. If all the points of the frame undergo the same movement, then the velocity estimation problem is solved using linear estimation. However, if some points belong to the moving object and the others to the background, the problem can be stated in the same way only if an algorithm is available to segment the image into fixed and moving areas. Afterwards, linear estimation can be applied to the moving area only. In this paper a segmentation algorithm is proposed which uses dynamic programming (Viterbi algorithm with three states). A more complex situation arises when the points belonging to the moving area are subjected to different movements. The problem can be solved once more using dynamic programming if the displacement components are quantized into (2M + 1) (2M + 1) values, and the number of states of the Viterbi algorithm is augmented to (2M + 1)^{2} . To reduce the technical difficulties of this approach, a simpler method that makes possible the estimation of the n most probable displacements is proposed. Then the image is segmented into n moving areas with different displacements and a background area using a Viterbi algorithm with n + 1 states. Experimental results show that the precision obtainable is about 0.1 pel when the displacements are up to 2-3 pels, the object had approximate dimensions of 90 \times 90 pels, and the signal-to-noise ratio was higher than 33 dB.
273 citations
TL;DR: Hierarchies of C 0 and C 1 interpolations over triangles are presented by means of a new interpretation of triangular or “area” coordinates shape functions corresponding to polynomials of arbitrary degree give rise to new families of finite elements which are computationally very efficient.
Abstract: Hierarchies of C 0 and C 1 interpolations over triangles are presented. By means of a new interpretation of triangular or “area” coordinates shape functions corresponding to polynomials of arbitrary degree are formulated. This development gives rise to new families of finite elements which are computationally very efficient. Computer programs with new, highly user oriented capabilities may be based on this development.
163 citations
TL;DR: The interplay between muscular, gravitational, inertial forces was assessed during level walking, at natural speed, related to kinematics, dynamics and energy levels of the ambulating body and to phasic muscular activity (EMG).
129 citations
TL;DR: In this article, a rational classification scheme for the physical variables and equations of whatever physical theory is then constructed, based on algebraic topology, and some examples of these schemes are given.
108 citations
TL;DR: In this paper, the mixed oxides of antimony with Sn, Fe, Co, Ni, Mn, Zn, U, Ce, and Cd were tested as catalysts in the 1-butene oxidation.
51 citations
TL;DR: In this paper, a trans square planar structure in the solid state and an epimeric equilibrium between transsquare planar structures in solution for all the new complexes are described.
36 citations
TL;DR: The lifetime of the 3d94s → 3d10 transition of Cu+ in several alkali halides has been measured as a function of temperature from L.He. to R.T. as mentioned in this paper.
36 citations
TL;DR: In this article, the authors investigated the mechanism of the oxidation of alcohols by peroxydisulphate by trapping the nucleophilic carbon-centered free-radical intermediates by protonated quinoline.
34 citations
TL;DR: The design of minimum cost networks with a given availability is discussed for different models of the cost-availability function in the links and algorithms are given for its exact or approximate evaluation.
Abstract: In order to design an available network efficiently, a parameter characterizing the network availability is needed. The global availability is suggested and algorithms are given for its exact or approximate evaluation. The design of minimum cost networks with a given availability is discussed for different models of the cost-availability function in the links. Some example network optimizations are reported.
32 citations
TL;DR: In this article, a model of elastoplastic beams and frames is considered and the plastic deformability laws (bending moments versus plastic rotations) are piecewise linearized.
Abstract: Discrete models of elastoplastic beams and frames are considered. The plastic deformability laws (bending moments versus plastic rotations) are piecewise linearized. Plastic deformations are sought as they develop along a proportional loading process. The “historical” analysis in this sense, is shown to be ameneable to the solution of a “parametric linear complementarity problem”. Recent mathematical results on this problem, due to R. W. Cottle, are used to obtain numerical solutions. Extensions are pointed out to stepwise proportional loading paths, allowing for the irreversible nature of plastic deformations.
29 citations
TL;DR: In this article, various catalysts were used to polymerize polymers with trans-1,4 or cis-1-4 structures, and the results were interpreted on the basis of a cis-addition of the monomer.
Abstract: cis,cis-1,4-Dideuterio-1,3-butadiene (1) was polymerized by various catalyst systems {Al(C2H5)3VCl3, Al(C2H5)2 ClVO(acac)2, Al(C2H5)3TiI4, Al(C2H5)2 ClCo(acac)2, (π-allyl)NiOCOCl3, (π-allyl)NiI} to polymers having a trans-1,4 or a cis-1,4 structure. Degradative oxidation of the polymers gave a mixture of racemic and meso 2,3-dideuteriosuccinic acid (2), in a ratio dependent on the particular catalyst used. The polymers obtained with the catalyst systems Al(C2H5)3VCl3 and Al(C2H5)2ClCo(acac)2 gave oxidation products with a high percentage of the racemic form of 2 (85–92%), which is indicative of a threo structure of the polymers. IR examination of the polymers obtained by the cobalt or vanadium system showed them to possess a regular structure (presence of the so-called regularity bands). The results are interpreted on the basis of a cis-addition of the monomer. The factors that determine the stereospecificity in the polymerization of 1 are discussed and possible schemes for the formation of the stereoregular polymers are examined.
cis,cis-1,4-Dideuterio-1,3-butadien (1) wurde mit Hilfe verschiedener Initiatorsysteme {Al(C2H5)3VCl3, Al(C2H5)2 ClVO(acac)2, Al(C2H5)3Til4, Al(C2H5)2 ClCo(acac)2, (π-allyl)NiOCOCl3, (π-allyl)NiI} zu Polymeren mit trans-1,4 bzw. cis-1,4 Strukturen polymerisiert. Die Polymeren ergaben beim oxidativen Abbau eine Mischung von racemischer und meso 2,3-Dideuteriobernsteinsaure (2), in einem Verhaltnis, das vom verwendeten Katalysator abhing. Die mit den Katalysatorsystemen Al(C2H5)3—VCl3 und Al(C2H5)2ClCo(acac)2 erhaltenen Polymeren ergaben Oxidationsprodukte mit einem hohen Anteil an racemischem Isomer 2 (8592%), das eine threo-Struktur der Polymeren anzeigt. Die IR-Untersuchung der mit dem Co- bzw. V-System erhaltenen Polymeren zeigte deren stereoregulare Struktur (Vorhandensein von sogenannten „regularity bands”). Die Ergebnisse werden interpretiert aufgrund einer cisAddition des Monomeren. Weiterhin werden die Faktoren, die die Stereospezifitat der Polymerisation von 1 bestimmen, diskutiert und mogliche Reaktionsschemen aufgezeigt.
TL;DR: In this paper, the authors considered the case where change underlies a nonhomogeneous Markov model and dealt with a 2-state alternating policy resulting from the superposition of failure and restoration, both showing a continuous aging with time.
Abstract: In reliability engineering and practice an important role is played by those units whose life characteristics change with time. The case is herewith considered where change underlies a nonhomogeneous Markov model. Simple repair processes then deal with a 2-state alternating policy resulting from the superposition of failure and restoration, both showing a continuous aging with time. Availability can be expressed through linear differential equations or by means of integral equations; the approaches are equivalent. A computer code is then described which calculates (i) availability, and (ii) transition densities for any continuous time dependence of failure and restoration rates. Numerical results are shown for a few examples.
TL;DR: The obtained results, as compared with the present status of the regulator theory for linear dynamical systems, allow us to point out strong similarities as well as definite differences, the latter being basically due to the essentially nonlinear nature of the systems considered herein.
Abstract: This paper deals with the problem of controlling the state of a finite automaton to some preassigned value; namely, the regulator problem. First, the simplest situation where the state of the system is currently known is briefly considered and the corresponding solution pointed out. Then, the much more difficult problem arising in the case of nontrivial output transformation is analyzed. This obviously calls for the preliminary solution of the state reconstruction problem in a partially or totally uncertain environment. The obtained results, as compared with the present status of the regulator theory for linear dynamical systems, allow us to point out strong similarities as well as definite differences, the latter being basically due to the essentially nonlinear nature of the systems considered herein.
TL;DR: In this paper, a study of several deformation bounding techniques is performed and the main previous results are outlined first with reference to general continua made of hardening materials and then a class of discrete structural models (such as some finite element discretizations) are considered and, on this basis, two categories of deformation binding techniques are described from the previous main results.
TL;DR: In this paper, the authors survey all theoretical achieveme ments of the kind above in the area of discrete periodic optimization, and contemporarily to illustrate them, by means of an elementary example.
Abstract: In dealing with periodic optimization problems, a somewhat preliminary and important question which has first to be answered is whether standard (optimal) steady-state control can be improved or not by means of a suitable cyclic operation. This question, which has been extensively considered in a lot of application-oriented works (mainly in the field of Chemical Engineering [1] – [5]) does also present a number of attractive features, from a theoretical point of view [6] – [9].Aim of this lecture is to survey all theoretical achieveme ments of the kind above in the area of Discrete Periodic Optimization, and contemporarily to illustrate them, by means of an elementary example.
TL;DR: In this article, the authors show that the equilibrium temperature in free-molecular flow can be lower than the stagnation temperature, i.e. the recovery factor smaller than one, if two distinct accommodation coefficients are assumed for the tangential and the normal translational energy of the molecules.
Abstract: The equilibrium temperature in free-molecular flow can be lower than the stagnation temperature, i.e. the recovery factor smaller than one, if two distinct accommodation coefficients are assumed for the tangential and the normal translational energy of the molecules. Moreover the equilibrium temperature turns out to be dependent on a parameter which is a function of these accommodation coefficients and therefore is related to the physical nature of the surface and of the gas. The connection of this theory with a gas-surface interaction model previously proposed by the authors is shown.
TL;DR: The reaction of allene with (Acac)Ir(η-C8H14)2 at −78°C yields new iridium(III) derivatives containing the 3,4-dimethyleneiridocyclopentane moiety as discussed by the authors.
TL;DR: In this article, a kinetic investigation of the dye-sensitized photo-oxygenation of 2-methyl-2-butene and 2,3-dimethyl-2butene, a reaction which involves singlet oxygen as intermediate species, was carried out in a gas-liquid photoreactor.
TL;DR: In this paper, it was shown that complex eigenvalues actually exist in the half-plane of a single-speed spherical shell surrounding a purely absorbing core and that the eigenvalue spectrum of the neutron transport equation in a finite body is discrete.
Abstract: If the assumption is made that the neutron speed has a positive lower bound, the eigenvalue spectrum of the neutron transport equation in a finite body is discrete1 Let λ∗ be the minimum collision rate Then it can also be shown, under rather broad assumptions, the most relevant of which is the isotropy of scattering, that the eigenvalues belonging to the half-plane Reλ > −λ∗ must be real Real eigenvalues also exist, as a rule, in the remaining half-plane Reλ ≤ −λ∗2 An old problem is: does this half-plane contain complex (ie, nonreal) eigenvalues? In this paper we study a particular one-speed problem (a thin absorbing and scattering spherical shell surrounding a purely absorbing core) and show that such complex eigenvalues actually exist
TL;DR: In this article, the adsorption properties towards oxygen and the catalytic oxidation properties of furan and n-butene-1 on a MnMoO4-based catalyst have been compared.
Abstract: In this paper the adsorption properties towards oxygen and the catalytic oxidation properties of furan and n-butene-1 on a MnMoO4-based catalyst have been compared. Different forms of adsorbed oxygen are responsible either for the oxidation of furan to maleic anhydride or of furane and n-butene-1 to carbon oxides.
TL;DR: In this paper, a series of research was conducted concerning the vibrations induced on cylinders by the vortex shedding, and the results showed that vortex shedding can induce the vibrations on cylinders of cylinders.
Abstract: This paper follows a series of researchs concerning the vibrations induced on cylinders by the vortex shedding.
TL;DR: In this paper, the 300 MHz 1H-NMR spectrum of the alkaloid Roxburghine B is completely analyzed. And the coupling constant values give evidence for the configuration, which is revised to epi-allo: H(3β), H(15α, H(20α) and C(18β).
Abstract: The 300 MHz 1H-NMR. spectrum of the alkaloid Roxburghine B is completely analysed. The coupling constant values give evidence for the configuration, which is revised to epi-allo: H(3β), H(15α), H(20α) and C(18β).
TL;DR: In this article, the possibilities of pulsed high pressure mercury capillary lamps as efficient pumping sources for dye lasers were discussed, and it was shown that a spectral efficiency as high as 24 per cent may be achieved for a typical blue lasing dye.
Abstract: This paper discusses the possibilities of pulsed high pressure mercury capillary lamps as efficient pumping sources for dye lasers. Spectral measurements show that a spectral efficiency as high as 24 per cent may be reached for a typical blue lasing dye. Laser action has been obtained with Rhodamine 6G with a repetition rate of up to 100 p.p.s., and an experimental threshold in good agreement with the theoretical one, calculated from the spectra. The life of the lamps has been tested, and no reduction of the luminous output has been observed after ∼105 pulses. Severe thermal problems have been encountered with blue lasing dyes, which we hope to solve by using watersoluble coumarins.
09 Aug 1976
TL;DR: This paper is concerned with a formal model for data structure definition: data graph grammars (DGG's).
Abstract: This paper is concerned with a formal model for data structure definition: data graph grammars (DGG's).
TL;DR: In this paper, the catalytic oxidation of lower olefins has been studied and the effect of ozonized oxygen has been examined, and the results show that the apparent activation energy decreases.
Abstract: The catalytic oxidation of lower olefins has been studied. The effect of ozonized oxygen has been examined. The results show that the apparent activation energy decreases. The industrial importance of the phenomenon is pointed out.
TL;DR: In this article, a general "energetic assumption" concerning the rate of dissipation of the energy in an impermanent network is added to the condition of statistical invariance formulated in part I. The simplest network model obeying both conditions is analyzed in some detail.
Abstract: A general “energetic assumption” concerning the rate of dissipation of the energy in an impermanent network is added to the condition of statistical invariance formulated in part I. The simplest network model obeying both conditions is analysed in some detail. Non-Newtonian viscosity, overshoot effects, gross instability effects in creep experiments (catastrophic creep behaviour) and a correct ratio (= −1/6 at small shear rates) of the secondary — to the primary normal stress difference in steady shear are predicted by this model. The result concerning the normal stress ratio at small velocity gradients is shown to apply to the general class of network fluids obeying both the condition of statistical invariance and the energetic assumption.
TL;DR: In the vicinity of structural discontinuities such as cut-outs, stiffeners and support attachments high order polynomials approximate the peak stresses occurring there better than conventional low order ones, provided only the minimal continuity requirements are enforced as discussed by the authors.
Abstract: In the vicinity of structural discontinuities such as cut-outs, stiffeners and support attachments high order polynomials approximate the peak stresses occurring there better than conventional low order ones, provided only the minimal continuity requirements are enforced.