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Showing papers by "University of Trento published in 1994"


Journal ArticleDOI
TL;DR: This paper investigates the application of the mutual information criterion to evaluate a set of candidate features and to select an informative subset to be used as input data for a neural network classifier.
Abstract: This paper investigates the application of the mutual information criterion to evaluate a set of candidate features and to select an informative subset to be used as input data for a neural network classifier. Because the mutual information measures arbitrary dependencies between random variables, it is suitable for assessing the "information content" of features in complex classification tasks, where methods bases on linear relations (like the correlation) are prone to mistakes. The fact that the mutual information is independent of the coordinates chosen permits a robust estimation. Nonetheless, the use of the mutual information for tasks characterized by high input dimensionality requires suitable approximations because of the prohibitive demands on computation and samples. An algorithm is proposed that is based on a "greedy" selection of the features and that takes both the mutual information with respect to the output class and with respect to the already-selected features into account. Finally the results of a series of experiments are discussed. >

2,423 citations


Book
01 Jan 1994
TL;DR: The Dempster-Shafer Theory of Evidence is applied as a guide for the management of uncertainty in knowledge-based systems.
Abstract: Partial table of contents: DEMPSTER-SHAFER THEORY OF EVIDENCE: GENERAL ISSUES. Measures of Uncertainty in the Dempster-Shafer Theory of Evidence (G. Klir). Comparative Beliefs (S. Wong, et al.). Calculus with Linguistic Probabilities and Beliefs (M. Lamata & S. Moral). FUZZIFICATION OF DEMPSTER-SHAFER THEORY OF EVIDENCE. Rough Membership Functions (Z. Pawlak & A. Skowron). DEMPSTER-SHAFER THEORY IN DECISION MAKING AND OPTIMIZATION. Decision Analysis Using Belief Functions (T. Strat). Interval Probabilities Induced by Decision Problems (T. Whalen). DEMPSTER-SHAFER THEORY FOR THE MANAGEMENT OF UNCERTAINTY IN KNOWLEDGE-BASED SYSTEMS. Using Dempster-Shafer's Belief-Function Theory in Expert Systems (P. Shenoy). Nonmonotonic Reasoning with Belief Structures (R. Yager). Index.

792 citations


Journal ArticleDOI
TL;DR: In this article, the ambiguity of gender symbols enables us to use indirect speech and discoursively to change gender relationships in organizations, without second-sexing the female in the process.
Abstract: We “do gender” while we are at work, while we produce an organizational culture and its rules governing what is fair in the relationship between the sexes. The inner ambiguity of gender construction is expressed in the dilemma: how can we do gender without second-sexing the female? The management of cross-gendered situations (dual presence) is based on a two-stage ritual involving the ceremonial work of paying homage to the symbolic order of gender (a deep trans-psychic structure) and the remedial work of repairing the inequality inherent in gender difference. Studying the ambiguity of gender symbols enables us to use indirect speech and discoursively to change gender relationships in organizations.

382 citations


Journal ArticleDOI
TL;DR: In this paper, a semi-implicit finite difference scheme for the numerical solution of a three-dimensional shallow water model is presented and discussed, in which pressure is assumed to be hydrostatic and the velocity gradient in the momentum equations and the velocities in the vertically integrated continuity equation are discretized with the θ-method, with θ being an implicitness parameter.
Abstract: The stability analysis, the accuracy and the efficiency of a semi-implicit finite difference scheme for the numerical solution of a three-dimensional shallow water model are presented and discussed. The governing equations are the three-dimensional Reynolds equations in which pressure is assumed to be hydrostatic. The pressure gradient in the momentum equations and the velocities in the vertically integrated continuity equation are discretized with the θ-method, with θ being an implicitness parameter. It is shown that the method is stable for 1 2 ≤ θ ≤ 1, unstable for θ 1 2 and highest accuracy and efficiency is achieved when θ = 1 2 . The resulting algorithm is mass conservative and naturally allows for the simulation of flooding and drying of tidal flats.

380 citations


Journal ArticleDOI
TL;DR: This paper found that the use of a small number of nets with a sufficiently large uncorrelation in their mistakes reaches a combined performance that is significantly higher than the best obtainable from the individual nets, with a negligible effort after starting from a pool of networks produced in the development phase of an application.

323 citations


Journal ArticleDOI
TL;DR: In this article, a method was developed that yields the residual stress, the orientation distribution coefficients, the average crystallite dimension, the microstrain, and the crystal structure parameters from x-ray diffraction data in a single step procedure.
Abstract: A method is developed that yields the residual stress, the orientation distribution coefficients, the average crystallite dimension, the microstrain, and the crystal structure parameters from x‐ray diffraction data in a single‐step procedure. To this end, a general approach is introduced that combines the equations of micromechanics with the harmonic description of texture. All relationships are cast into a Rietveld‐like format, which incorporates a microstructure model derived from line‐broadening methods. In this manner, data collected over the whole x‐ray‐diffraction pattern at different tilting of the sample can be fitted directly. The associated fitting parameters are the crystal structure and microstructure, the texture coefficients, and the micromechanical properties and fields.

310 citations



Journal ArticleDOI
TL;DR: A critical analysis of the time scales necessary for true boiling, as well as for superheating above the boiling temperature, is made in order to understand the relevance of these phenomena with respect to particle emission from the Al surface.
Abstract: We have developed a numerical method to describe laser-pulse sputtering of Al in a thermal regime. The irradiation consists of a single pulse of triangular form having a duration of 30 ns. The laser light is assumed to be absorbed according to a simple exponential mechanism. Heat transport in the Al is described by the heat flow equation with boundary conditions for vaporization, with or without boiling. Vaporization rates are evaluated by the Clausius-Clapeyron law and the boiling mechanism (when boiling is assumed to be possible) is implemented as soon as the vapor pressure reaches 1 atm. A critical analysis of the time scales necessary for true boiling, as well as for superheating above the boiling temperature, is made in order to understand the relevance of these phenomena with respect to particle emission from the Al surface. Moreover, on the basis of the calculated vaporization rates, it is possible to distinguish between different gas-dynamic regimes. When the rate is less than \ensuremath{\sim}1 ML in 20 ns, the particles emerging from the surface do not achieve local thermal equilibrium, and therefore undergo free flight describable by a modified Maxwellian. When the rate is \ensuremath{\sim}1 ML in 20 ns, a Knudsen layer forms, at the boundary of which, particles achieve local thermal equilibrium and only subsequently undergo free flight. Finally, when the rate is sufficiently greater than \ensuremath{\sim}1 ML in 20 ns, the gas dynamics of the particles leaving the Knudsen layer may be described with the gas-dynamic equations, if the density is high enough, or, otherwise, by the Boltzmann equation. Numerical results concerning the effectiveness of laser sputtering in producing craters in irradiated Al, as well as the main features of the gas dynamics (including recondensation or reflection of the gas at the Al surface), are illustrated.

160 citations



Journal ArticleDOI
TL;DR: The in vitro degradation of samples of L- and D,L-lactic acid polymers, P(L)LA and P(DL)LA respectively, having different molecular weights, morphology and/or geometry, has been studied through the determination of viscometric molecular weight, mass and mechanical properties as function of the immersion time in Ringer solution.
Abstract: The in vitro degradation of samples of L- and D,L-lactic acid polymers, P(L)LA and P(DL)LA respectively, having different molecular weights, morphology and/or geometry, has been studied through the determination of viscometric molecular weight, mass and mechanical properties as function of the immersion time in Ringer solution at 37 degrees C. In particular have been compared the degradation kinetics of P(L)LA, amorphous and crystalline, and of P(L)LA and P(DL)LA having different molecular weight and sample geometry. From the molecular weight versus the degradation time data, a degradation rate has been defined, as the derivative of the function best fitting the data, normalized to the molecular weight of the polymer at each time. The behavior of the degradation rate curves, plotted against the degradation time, has been interpreted and compared with relation to the initial physical and geometrical characteristics of the PLA samples.

130 citations


Journal ArticleDOI
TL;DR: The effects of a weak random external potential on the properties of the dilute Bose gas at zero temperature is discussed and the damping of phonons is calculated also for dense superfluids.
Abstract: We discuss the effects of a weak random external potential on the properties of the dilute Bose gas at zero temperature. The results recently obtained by Huang and Meng for the depletion of the condensate and of the superfluid density are recovered. Results for the shift of the velocity of sound as well as for its damping due to collisions with the external field are presented. The damping of phonons is calculated also for dense superfluids.

Journal ArticleDOI
TL;DR: In this article, a density functional theory is used to predict the binding energy of atomic and molecular impurities (Ne, Ar, Kr, Xe, Li, Na, K, Rb, Cs and SF6) in the center of 4He clusters.
Abstract: A density functional theory is used to predict the binding energy of atomic and molecular impurities (Ne, Ar, Kr, Xe, Li, Na, K, Rb, Cs, and SF6) in the center of4He clusters, in the limit of zero temperature and for zero angular momentum states. The size dependence of the binding energy, from small clusters to the bulk liquid limit, is investigated. The behaviour of the4He density near the impurity is also studied.

Journal ArticleDOI
TL;DR: The results are in keeping with the reported coincidental nuclear staining pattern of Ki67 and MIB1, but the mean and median values of M IB1 LI are almost twice the values of Ki 67 LI, which is a reasonable substitute for the Ki67 monoclonal antibody.
Abstract: Ki67 and MIB1 monoclonal antibodies are directed against different epitopes of the same proliferation-related antigen. Whereas Ki67 works only on frozen sections, MIB1 may be used also on fixed sections. The authors immunostained a series of 40 breast carcinomas with MIB1 and Ki67 antibodies on serial frozen sections and on fixed material. The Ki67 labeling index (LI) was 12.9 +/- 8.9 and 12 (mean +/- SD and median, respectively). MIB1 LI was 21.2 +/- 11.9 and 19.5 on frozen sections and 24 +/- 15.2 and 21.5 on fixed sections (mean +/- SD and median, respectively). Ki67 LI and MIB1 LI on frozen and fixed sections were strictly correlated (P < .001). The results are in keeping with the reported coincidental nuclear staining pattern of Ki67 and MIB1, but the mean and median values of MIB1 LI are almost twice the values of Ki67 LI. The cut-off values to define high and low proliferative activity with the two antibodies are therefore different. The differences in immunolabeling may be due to better survival of the MIB1 epitope in freezing and acetone fixation or to differing accessibilities of the MIB1 and Ki67 epitopes during the cell cycle due to molecular conformational modifications. The MIB1 monoclonal antibody is a reasonable substitute for the Ki67 monoclonal antibody. The advantages of MIB1 immunostaining on paraffin sections include the feasibility of retrospective studies and of obtaining clear morphologic specimens that are optimal for use with computer-assisted image analysis systems. Our image-processing system allows automatic nuclear counting, detects positive nuclei and measures their staining intensity.

Journal ArticleDOI
TL;DR: In this paper, the problem of the formation of a free carbon phase was discussed and related to the amount of carbon in the starting gel, and an example of successful synthesis of an almost pure carbon-rich oxycarbide phase was also presented.
Abstract: Silicon-oxycarbide glasses can be synthesized from modified silica gels through a pyrolysis process in inert atmosphere. A critical analysis of the literature suggests a close relationship between oxygen content in the gel precursors and the amount of carbon atoms covalently bonded to silicon atoms in the corresponding silicon-oxycarbide phase. The problem of the formation of a free carbon phase will be discussed and related to the amount of carbon in the starting gel. An example of successful synthesis of an almost pure carbon-rich oxycarbide phase will also be presented.

Journal ArticleDOI
TL;DR: In this paper, a-C:H(N) films were implanted at room temperature with 70 keV-N+ at fluences of 6, 10 and 20 × 1016 N cm−2, and the induced structural modifications were studied by Raman spectroscopy throygh the evolution of the D and G bands.

Journal ArticleDOI
TL;DR: Simulated Annealing (SA) and Tabu Search (TS) are compared on the quadratic assignment problem in this article, and it is shown that SA can achieve a reasonable solution quality with fewer function evaluations than TS.
Abstract: Simulated Annealing (SA) and Tabu Search (TS) are compared on the Quadratic Assignment Problem. A recent work on the same benchmark suite argued that SA could achieve a reasonable solution quality with fewer function evaluations than TS. The discussion is extended by showing that the conclusions must be changed if the task is hard or a very good approximation of the optimal solution is desired, or if CPU time is the relevant parameter. In addition, a recently proposed version of TS (the Reactive Tabu Search) solves the problem of finding the proper list size with an automatic memory-based reaction mechanism.


Journal ArticleDOI
TL;DR: The role of such a kind of singularities on free and vacuum energy and also on the one-loop effective action is pointed out using $\ensuremath{\zeta}$-function regularization and heat-kernel techniques.
Abstract: Free and self-interacting scalar fields in the presence of conical singularities are analyzed in some detail. The role of such a kind of singularities on free and vacuum energy and also on the one-loop effective action is pointed out using $\ensuremath{\zeta}$-function regularization and heat-kernel techniques.

Journal ArticleDOI
TL;DR: In this paper, a simple procedure was devised for the preparation of a standard KCl powder to be used for the experimental determination of the instrumental profile in the Bragg-Brentano geometry.
Abstract: A simple procedure was devised for the preparation of a standard KCl powder to be used for the experimental determination of the instrumental profile in the Bragg–Brentano geometry. The standard was tested on several diffractometers, and narrow Bragg reflections in the range 28°–132° were recorded adopting various experimental conditions. Profiles were modeled with analytical functions, to describe the trend of width and shape of the instrumental profile as a function of the diffraction angle. Some indications were given to perform reliable profile fitting and line broadening analysis; a high resolution setup, obtained by employing narrow slits, large goniometer radius, and a monochromator in the diffracted beam, gives narrow reflections, even though the intensity of the diffracted beam is considerably reduced. The choice of these experimental conditions, which can be achieved using the majority of the commercial instruments, leads to symmetrical profiles, even at relatively low angle (2Θ=28°), which are highly recommended for reliable profile fitting and line broadening analysis.

Journal ArticleDOI
TL;DR: The absolute configuration of agelastatin A (1), the major, strongly cytotoxic alkaloid of the axinellid sponge Agelas dendromorpha from the Coral Sea, is proposed in this paper.
Abstract: The absolute configuration of agelastatin A (1), the major, strongly cytotoxic alkaloid of the axinellid sponge Agelas dendromorpha from the Coral Sea, is proposed here to be (5aS,5bS,8aS,9aR), as deduced from combined molecular-mechanics calculations and a novel application of exciton splitting to the bis[4-(dimethylamino)benzoyl] compounds (–)-9 and (–)-13, derivatives of a diamide and a hydroxyamide, respectively. The position of the conformational equilibrium of A 1 could be finely tuned by slight molecular changes. The minor analogue, agelastatin B (3), was isolated as the trimethyl derivative (–)-4.

Journal ArticleDOI
01 Mar 1994
TL;DR: In this article, the authors present the principles underlying a recently developed numerical technique for modeling transport in heterogeneous porous media and apply it to derive the concentration mean and variance, the concentration CDF, exceedance probabilities and exposure time CDF.
Abstract: This paper presents the principles underlying a recently developed numerical technique for modeling transport in heterogeneous porous media. The method is then applied to derive the concentration mean and variance, the concentration CDF, exceedance probabilities and exposure time CDF, which are required by various regulatory agencies for risk and performance assessment calculations. The dependence of the various statistics on elapsed travel time, location in space, the dimension of the detection volume, natural variability and pore-scale dispersion is investigated and discussed.

Journal ArticleDOI
TL;DR: The study shows that the amount of visceral abdominal fat is the most relevant factor for metabolic abnormalities and suggests that the effect of visceral fat is independent of body mass index.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the surface region of a polyimide can be approximated by simple analytical approximations, and these simple forms enable the recondensed quantity, Q rec, to be evaluated as the integral over time of the product of flow velocity and density.
Abstract: When solids are sputtered with sufficiently intense laser pulses, particle release takes place, and a terminating expansion then develops. The resulting gas-dynamic processes depend on whether backscattered particles are subject to recondensation or reflection. We here wish to examine the problem further with emphasis on recondensation effects , (a) We show that, under conditions of recondensation, the surface region permits simple analytical approximations, (b) These simple forms enable the recondensed quantity, Q rec , to be evaluated as the integral over time of the product of flow velocity and density. Alternatively Q rec can be deduced by numerical solution of the flow equations and in either case it is found to increase significantly with the complexity of the particles involved. Thus it ranges from a fraction ∼ 0.10 for atoms to ∼ 0.43 for large molecules. (c) Recondensation effects are particularly important when the polymer polyimide is laser sputtered, as the recondensation occurs in massive amounts beyond the bombarded spot and the patterns of recondensation show remarkable symmetry changes, (d) Closely related effects occur when targets are laser sputtered to produce films, even if formal recondensation is not involved.

Journal ArticleDOI
TL;DR: In this paper, the corrosion behavior of phosphatized zinc (Zn)-electroplated steel coated with epoxy films of different thicknesses was studied using electrochemical impedance spectroscopy (EIS).
Abstract: The corrosion behavior of phosphatized zinc (Zn)-electroplated steel coated with epoxy films of different thicknesses was studied using electrochemical impedance spectroscopy (EIS), the br...

Journal ArticleDOI
TL;DR: In this article, the physical meaning of the reactive area values of a metal under an organic coating, obtained using the breakpoint method, were reviewed, and experimental evidence indicated the area was related to coating defects and porosity, rather than to the total reactive or delaminated area.
Abstract: Experimental results and mathematical considerations were used to investigate the physical meaning and the application limits of the breakpoint method to evaluate the reactive area in organic coatings. The physical meaning of the reactive area values of a metal under an organic coating, obtained using the breakpoint method, were reviewed. Experimental evidence indicated the area was related to coating defects and porosity, rather than to the total reactive or delaminated area. Limits in applying the breakpoint method were reviewed using mathematical considerations that showed the method was not accurate when values of the coating capacitance and double-layer capacitance were too close, which was a possibility during the initial time of degradation and also when two time constants were distinguishable.

Journal ArticleDOI
TL;DR: In this article, the three-field formulation u-p-U was applied to solve dynamic equations for saturated porous media and the accuracy was determined by a comparison of the finite element results with the analytical solution given by Gajo and Mongiovi,19 for a wide range of permeability.
Abstract: The three-field formulation u–p–U is presented and is applied to solve dynamic equations for saturated porous media. In order to evaluate the accuracy and the performance of this three-field approximation, the u–U and the u–w formulations are also considered and a few one- and two-dimensional examples are solved using the three methods. Problems for which both the pore fluid and the solid grains are incompressible are also considered and are solved using the u–p-U approximation. Accuracy was determined by a comparison of the finite element results with the analytical solution given by Gajo and Mongiovi,19 for a wide range of permeability.


Journal ArticleDOI
TL;DR: Theshortening of the atrial interval after the onset of the QRS complex as found in patients during rapid atrial flutter can be explained by stretch-induced shortening of atrial refractoriness and consequent shortened of the revolution time of a functionally determined intra-atrial circuit.
Abstract: BACKGROUNDSlight variation in cycle lengths of common and rapid atrial flutter in humans is an established phenomenon, but its mechanisms have not been completely clarified. In a previous study, we demonstrated that in common atrial flutter the variations in atrial cycle length were due to atrial stretch affecting the revolution time of a reentrant circuit. In the present study, we investigate the nature of atrial cycle length variations in the rapid type of human atrial flutter.METHODS AND RESULTSAtrial interval variations of 17 episodes of rapid atrial flutter in 14 patients were investigated by measuring the sequence of atrial intervals from intraesophageal or intra-atrial leads and the onset of QRS complexes from a surface lead (V1). To study whether interval variation in flutter cycle was related to ventricular activity, a phase plot was constructed in which the flutter cycle length was plotted against the time after the previous QRS complex. This showed that the interval fluctuations were strictly c...

Journal ArticleDOI
TL;DR: Sulfix-6 and Zimmer LVC 60/30 bone cements were selected and the polymerization kinetics and resulting glass transition temperature Tg; creep behaviour in the dry or water-saturated state; and sorption and diffusion of water were studied to find out whether water sorption during the service time may not have detrimental effects on the creep resistance of the cements.

Journal ArticleDOI
TL;DR: In this article, the authors consider the effect of chemical driving forces on the diffusion flux of Ni-Ag multilayers and obtain consistent values of 0.04 ± 0.01 at 300 K, 0.15 ± 0.,02 at 400 K, and 0.24 ± 0.04 at 600 K.