Showing papers by "University of Trento published in 2001"

The Emergence of Social Enterprise

Abstract: Introduction: From Third Sector to Social Enterprise Part 1: Social Enterprises in the Fifteen EU Countries 1. Austria: Social Enterprises and New Childcare Services 2. Belgium: Social Enterprises in Community Services 3. Denmark: Co-operative Activity and Community Development 4. Finland: Labour Co-operatives as an Innovative Response to Unemployment 5. France: Social Enterprises Developing 'Proximity Services' 6. Germany: Social Enterprises and Transitional Employment 7. Greece: Social Enterprises Responding to Welfare Needs 8. Ireland: Social Enterprises and Local Development 9. Italy: From Traditional Cooperatives to Innovative Social Enterprises 10. Luxembourg: Work-Integration Social Enterprises in an Emerging Third Sector 11. Portugal: Co-operatives for Rehabilitation of People with Disabilities 12. Spain: Social Enterprises as a Response to Employment Policy Failure 13. Sweden: The Emergence of Work-Integration Social Enterprises 14. The Netherlands: Neighbourhood Development Enterprises 15. United Kingdom: A Wide Range of Social Enterprises Part 2: The Social Enterprises: A Theoretical Perspective 16. Social Enterprises as Incentive Structures: An Economic Analysis 17. The Significance of Social Capital in the Multiple Goal and Resource Structure of Social Enterprises 18. The Social Enterprise: Towards a Theoretical Socio-Economic Approach 19. Management Challenges for Social Enterprises Conclusions: Social Enterprises in Europe: A Diversity of Initiatives and Prospects

From Organizational Learning to Practice-Based Knowing

Abstract: L'A. se penche sur les biais qui jalonnent la recherche en apprentissage organisationnel. Il souligne alors l'importance de la pratique pour obtenir un savoir situe spatialement et factuellement

Rectifiability and perimeter in the Heisenberg group

Abstract: In this paper, we fully extend to the Heisenberg group endowed with its intrinsic Carnot-Caratheodory metric and perimeter the classical De Giorgi's rectifiability divergence theorems.

A new search algorithm for feature selection in hyperspectral remote sensing images

Abstract: A new suboptimal search strategy suitable for feature selection in very high-dimensional remote sensing images (e.g., those acquired by hyperspectral sensors) is proposed. Each solution of the feature selection problem is represented as a binary string that indicates which features are selected and which are disregarded. In turn, each binary string corresponds to a point of a multidimensional binary space. Given a criterion function to evaluate the effectiveness of a selected solution, the proposed strategy is based on the search for constrained local extremes of such a function in the above-defined binary space. In particular, two different algorithms are presented that explore the space of solutions in different ways. These algorithms are compared with the classical sequential forward selection and sequential forward floating selection suboptimal techniques, using hyperspectral remote sensing images (acquired by the airborne visible/infrared imaging spectrometer [AVIRIS] sensor) as a data set. Experimental results point out the effectiveness of both algorithms, which can be regarded as valid alternatives to classical methods, as they allow interesting tradeoffs between the qualities of selected feature subsets and computational cost.

Benchmark Test Calculation of a Four-Nucleon Bound State

Abstract: In the past, several efficient methods have been developed to solve the Schr\"odinger equation for four-nucleon bound states accurately. These are the Faddeev-Yakubovsky, the coupled-rearrangement-channel Gaussian-basis variational, the stochastic variational, the hyperspherical variational, the Green's function Monte Carlo, the no-core shell model, and the effective interaction hyperspherical harmonic methods. In this article we compare the energy eigenvalue results and some wave function properties using the realistic $\mathrm{AV}{8}^{\ensuremath{'}}$ NN interaction. The results of all schemes agree very well showing the high accuracy of our present ability to calculate the four-nucleon bound state.

Reactive Local Search for the Maximum Clique Problem1

Abstract: A new Reactive Local Search (\RLS ) algorithm is proposed for the solution of the Maximum-Clique problem. \RLS is based on local search complemented by a feedback (history-sensitive) scheme to determine the amount of diversification. The reaction acts on the single parameter that decides the temporary prohibition of selected moves in the neighborhood, in a manner inspired by Tabu Search. The performance obtained in computational tests appears to be significantly better with respect to all algorithms tested at the the second DIMACS implementation challenge. The worst-case complexity per iteration of the algorithm is O(max {n,m}) where n and m are the number of nodes and edges of the graph. In practice, when a vertex is moved, the number of operations tends to be proportional to its number of missing edges and therefore the iterations are particularly fast in dense graphs.

Unsupervised retraining of a maximum likelihood classifier for the analysis of multitemporal remote sensing images

Abstract: An unsupervised retraining technique for a maximum likelihood (ML) classifier is presented. The proposed technique allows the classifier's parameters, obtained by supervised learning on a specific image, to be updated in a totally unsupervised way on the basis of the distribution of a new image to be classified. This enables the classifier to provide a high accuracy for the new image even when the corresponding training set is not available.

Diffraction line profiles from polydisperse crystalline systems.

Abstract: Diffraction patterns for polydisperse systems of crystalline grains of cubic materials were calculated considering some common grain shapes: sphere, cube, tetrahedron and octahedron Analytical expressions for the Fourier transforms and corresponding column-length distributions were calculated for the various crystal shapes considering two representative examples of size-distribution functions: lognormal and Poisson Results are illustrated by means of pattern simulations for a fcc material Line-broadening anisotropy owing to the different crystal shapes is discussed The proposed approach is quite general and can be used for any given crystallite shape and different distribution functions; moreover, the Fourier transform formalism allows the introduction in the line-profile expression of other contributions to line broadening in a relatively easy and straightforward way

Surface measures in Carnot-Carathéodory spaces

Abstract: In the framework of Carnot-Caratheodory spaces we study Minkowski content and perimeter, we prove some coarea formulas, and finally we prove some variational approximations of the perimeter.

Downstream and upstream influence in river meandering. Part 2. Planimetric development

Abstract: Perturbations of channel geometry (like variations of channel curvature or channel width) in meandering rivers give rise to morphodynamic effects which display themselves through the development of large-scale perturbations of bottom topography in the form of stationary bars developing in the longitudinal direction. The latter may then drive the lateral migration of the channel by enhancing bank erosion at bar pools: through this mechanism local perturbations of channel geometry may affect the planimetric development of meandering rivers on large timescales. The problem tackled herein is whether such morphodynamic influence is invariably felt downstream as the commonly employed model of river meandering would suggest.In order to solve this problem, we derive the exact solution of the linearized form of the mathematical problem of river morphodynamics. Linear analysis had pointed out the existence of a resonance phenomenon: in a linear (hence ideal) context, resonance occurs when the meander wavenumber and the width ratio of the channel take values (λR and βR, respectively) such as to force free spatial modes of the system consisting of free bars which neither grow nor decay either in time or in space. Channels characterized by values of the width ratio β larger (smaller) than βR are called super- (sub-)resonant. The present solution, which applies to channels with constant width and arbitrary curvature distribution, shows that two distinct scenarios may occur: downstream influence is associated with sub-resonant channels and vice versa dominant upstream influence occurs in super-resonant channels. Small-amplitude waves of bottom topography are shown to migrate downstream in the former case and may migrate upstream in the latter, as resonance also defines the threshold conditions below (above) which small-amplitude alternate bar perturbations (may) migrate downstream (upstream).These results have several implications. In the present paper we examine the overdeepening phenomenon whereby abrupt variations of channel curvature, as in sequences of straight and constant curvature reaches, lead to sequences of stationary alternate bars with amplitude decaying in the longitudinal direction. We show that, along with downstream overdeepening, an upstream overdeepening scenario is predicted in the super-resonant regime.Implications of the upstream influence on planimetric development of meandering rivers are investigated in Part 2.

A knowledge level software engineering methodology for agent oriented programming

Abstract: Our goal in this paper is to introduce and motivate a methodology, called \emph{Tropos}, for building agent oriented software systems. Tropos is based on two key ideas. First, the notion of agent and all the related mentalistic notions (for instance: beliefs, goals, actions and plans) are used in all phases of software development, from the early analysis down to the actual implementation. Second, Tropos covers also the very early phases of requirements analysis, thus allowing for a deeper understanding of the environment where the software must operate, and of the kind of interactions that should occur between software and human agents. The methodology is illustrated with the help of a case study.

Expansion of a Coherent Array of Bose-Einstein Condensates

Abstract: We investigate the properties of a coherent array containing about 200 Bose-Einstein condensates produced in a far detuned 1D optical lattice. The density profile of the gas, imaged after releasing the trap, provides information about the coherence of the ground-state wave function. The measured atomic distribution is characterized by interference peaks. The time evolution of the peaks, their relative population, as well as the radial size of the expanding cloud are in good agreement with the predictions of theory. The 2D nature of the trapped condensates and the conditions required to observe the effects of coherence are also discussed.

Phase Separation in an SiCO Glass Studied by Transmission Electron Microscopy and Electron Energy‐Loss Spectroscopy

Abstract: SiCO glasses prepared from sol–gel precursors via pyrolysis in argon at temperatures ranging from 1000° to 1400°C were studied by transmission electron microscopy (TEM), in conjunction with electron energy-loss spectroscopy (EELS). EELS analysis showed that stoichiometric SiCO glass underwent phase separation, forming SiO2- and SiC-based environments. This process started at ∼1200°C. However, at temperatures >1300°C, precipitation of nanometer-sized SiC particles embedded in vitreous SiO2 was monitored by high-resolution TEM.

The use of electrochemical techniques to study the corrosion behaviour of organic coatings on steel pretreated with sol-gel zirconia films

Abstract: The two main features of a protective organic coating are its adhesion and corrosion protection. In order to improve both, chemical pretreatments have been used. The use of chromates was very popular, but recently they have been highly restricted because of their toxicity, so that chromate-free pretreatments have been developed and tested. An interesting alternative seems to be the deposition on the metallic surface of thin layers of zirconia by the sol-gel process. In this study thin films of amorphous zirconia on low carbon steel sheets have been obtained by the dip-coating technique, using two different complexing reagents. Control of the hydrolysis allowed the formation of ZrO 2 films suitable as pretreatments, promoting the adhesion of organic coatings. The behaviour of these samples was compared with steel samples pretreated in conventional phosphatation baths. The adhesion of a polyester organic coating was evaluated by the pull-off technique, by measuring the detachment of cross-scratched samples after salt fog chamber testing, or by swelling the organic coating in methyl pyrrolidone. According to the results, the samples pretreated with zirconia layers showed promising performance, in comparison with commercial chemical treatments (tricationic phosphate and iron phosphate). The organic coating adhesion on zirconia films was found to depend strongly on the process parameters, e.g. concentration of the precursors solutions and chelating agents, which determine the thickness and the amount of organic residuals of the amorphous zirconia. Electrochemical impedance spectroscopy (EIS) was also used in sodium sulphate solutions to evaluate adhesion and the corrosion behaviour of these materials. No barrier properties of the zirconia films were observed. Resistance to delamination was studied by using samples where an artificial defect was made by mechanical tools of different diameter. The information obtained by EIS was in good agreement with the data obtained by salt fog chamber tests.

Creep Viscosity and Stress Relaxation of Gel‐Derived Silicon Oxycarbide Glasses

Abstract: The temperature dependence of the viscosity and stress-relaxation kinetics of sol–gel-derived SiOC glasses that contain up to 14 at.% carbon have been characterized in the temperature range of 1000°–1400°C. The viscosity, as determined from relaxation experiments, is in good agreement with the creep viscosity and is typically two orders of magnitude higher than the viscosity of vitreous silica. However, materials suffer from partial crystallization at >1150°C, and the precipitation of β-SiC nanocrystals induces a flow-hardening behavior and results in a dynamic increase in viscosity, especially at >1200°C and for glasses with a high carbon content.

Comments on the Stress-Energy Tensor Operator in Curved Spacetime

Abstract: Hollands and Wald's technique based on *-algebras of Wick products of field operators is strightforwardly generalized to define the stress-energy tensor operator in curved globally hyperbolic spacetimes. In particular, the locality and covariance requirement is generalized to Wick products of differentiated quantum fields. The proposed stress-energy tensor operator is conserved and reduces to the classical form if field operators are replaced by classical fields satisfying the equation of motion. The definition is based on the existence of convenient counterterms given by certain local Wick products of differentiated fields. They are independent from the arbitrary length scale (and any quantum state) and they classically vanish on solutions of field equation. The averaged stress-energy tensor with respect to Hadamard quantum states can be obtained by an improved point-splitting renormalization procedure which makes use of the nonambiguous part of the Hadamard parametrix only that is completely determined by the local geometry and the parameters which appear in the Klein-Gordon operator. The averaged stress-energy tensor also coincides with that found by employing the local $\zeta$-function approach.

Overcritical rotation of a trapped Bose-Einstein condensate.

Abstract: The rotational motion of an interacting Bose-Einstein condensate confined by a harmonic trap is investigated by solving the hydrodynamic equations of superfluids, with the irrotationality constraint for the velocity field. We point out the occurrence of an overcritical branch where the system can rotate with angular velocity larger than the oscillator frequencies. We show that in the case of isotropic trapping the system exhibits a bifurcation from an axisymmetric to a triaxial configuration, as a consequence of the interatomic forces. The dynamical stability of the rotational motion with respect to the dipole and quadrupole oscillations is explicitly discussed.

Thermal vs Quantum Decoherence in Double Well Trapped Bose-Einstein Condensates

Abstract: The quantum and thermal fluctuations of the phase are investigated in a cold Bose gas confined by a double well trap. The coherence of the system is discussed in terms of the visibility of interference fringes in both momentum and coordinate space. The visibility is calculated at zero as well as at finite temperature. The thermal fluctuations are shown to affect significantly the transition from the coherent to the incoherent regime even at very low temperatures. The coherence of an array of multiple condensates is also discussed.

Composite Electrodeposition to Obtain Nanostructured Coatings

Abstract: Nanocomposite coatings are obtained by electrochemical deposition of silicon carbide nanoparticles (mean diameter 20 nm) in a nickel plating bath. The influence of nanoparticles on nickel electroplating is studied by electrochemical impedance spectroscopy at cathodic potential, and cathodic polarization diagrams are performed in the electrolyte with and without nanoparticles. We show that incorporation of 20 nm SIC particles into nickel deposits modifies the impedance and cathodic polarization diagrams in correlation with the modification of the surface morphology and crystallinity of the nickel matrix. (C) 2001 The Electrochemical Society.

Rational Criterion for Designing Opening of Slit-Check Dam

Abstract: This paper presents a theoretical approach to the problem of designing the opening in a slit-check dam. The approach is based on the conservation of the mass of water and sediments and on the energy balance under steady conditions. It leads to a relationship among opening width, sediment characteristics, mountain river geometry, and water and sediment discharge. The final relationship can be simplified to make it suitable for practical applications. Also, the problem of unsteadiness of both water and sediment is considered, as well as the possibility of treating the unsteady flow as a sequence of steady states. The results of the theory were checked in a laboratory investigation using a scale model. Different opening widths were tested under conditions of steady and unsteady supplies of water and sediment. The mean grain size of the sediment, as well as the rates of sediment and water discharge, were changed in the experiments. The results of the experiments confirm the theory quite well.

A new approach to anisotropic, bounding surface plasticity : general formulation and simulations of natural and reconstituted clay behaviour

Abstract: It is demonstrated that an efficient framework for the description of a two surface kinematic hardening/bounding surface plasticity model can be devised if the model is conceived in a normalized stress space in which the bounding surface remains of constant size. The hardening of the bounding surface is contained in the transformation laws linking ‘real’ and ‘normalized’ stresses while the geometric rules controlling kinematic hardening are considered only in terms of normalized stresses. Within the general framework thus constructed, two particular models are developed in outline. Owing to the proposed anisotropic hardening, these models are shown to have the ability to reproduce the observed characteristics of the progressive destructuration of natural cemented clays and of the plastic anisotropy of reconstituted soils. Copyright © 2001 John Wiley & Sons, Ltd.