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Mildly degenerate Kirchhoff equations with weak dissipation: Global existence and time decay
No full textSUMMARY We consider the hyperbolic-parabolic singular perturbation problem for a degenerate quasilinear Kirchhoff equation with weak dissipation. This means that the coefficient of the dissipative term tends to zero when t → +∞. We prove that the hyperbolic problem has a unique global solution for suitable values of the parameters. We also prove that the solution decays to zero, as t → +∞, with the same rate of the solution of the limit problem of parabolic type
Integrated visual nanometric three dimensional positioning and inspection in the automated assembly of AFM probe arrays
Get PDFSUMMARY This paper presents the design of a monocular three dimensional artificial vision system attached to a 20x microscope lens for precision and microsystems applications. Possible uses in assembly include: positioner calibration, sensor-based part handling, positioning, and inspection in the nanometric range. The developed image acquisition method – along one direction (in steps of 100 nm), the depth-from-focus algorithm and subpixel interpolation (of 5 acquisitions for concurrent localization and inspection), allow to overcome the physical optics limitation achieving a resolution under 200 nm. The vision strategy and algorithms, described in the paper, have been validated by handling an AFM probe array by a micropositioner
3D Printing: testine inkjet sotto la lente
No full textRIASSUNTO Tramite un sistema di visione con telecamera ad alta velocità vengono filmate le gocce emesse da una comune testina inkjet (a getto di inchiostro), fissata su un apposito carrello. Le immagini acquisite sono elaborate ed analizzate per rilevare le caratteristiche fisiche delle gocce (es. morfologia, velocità), al fine di controllare il funzionamento della testina. L’obiettivo finale del lavoro è di acquisire le informazioni necessarie per sviluppare ed ottimizzare un’applicazione di prototipazione rapida basata sulla tecnica 3DPrinting (3DP). SUMMARY Using a vision system with high-speed camera, the images of drops emitted by a common inkjet cartridge are grabbed. They are then processed and analyzed for physical characteristics of the droplets (e.g., morphology, speed) in order to control the cartridge operation. The ultimate goal of this work is to gather the information needed to develop and optimize an application based on rapid prototyping technique 3DPrinting (3DP)
Monitoring a virtualized network infrastructure -- An IaaS perspective
No full textSUMMARY Infrastructure as a Service (IaaS) providers keep extending with new features the computing infrastructures they offer on a pay per use basis. In this paper we explore reasons and opportunities to include networking within such features, meeting the demand of users that need composite computing architectures similar to Grid
Orbit Determination with the two-body Integrals
No full textWe investigate a method to compute a finite set of preliminary orbits for solar system bodies using the first integrals of the Kepler problem. This method is thought for the applications to the modern sets of astrometric observations, where often the information contained in the observations allows only to compute, by interpolation, two angular positions of the observed body and their time derivatives at a given epoch; we call this set of data attributable. Given two attributables of the same body at two different epochs we can use the energy and angular momentum integrals of the two-body problem to write a system of polynomial equations for the topocentric distance and the radial velocity at the two epochs. We define two different algorithms for the computation of the solutions, based on different ways to perform elimination of variables and obtain a univariate polynomial. Moreover we use the redundancy of the data to test the hypothesis that two attributables belong to the same body (linkage problem). It is also possible to compute a covariance matrix, describing the uncertainty of the preliminary orbits which results from the observation error statistics. The performance of this method has been investigated by using a large set of simulated observations of the Pan-STARRS project
Low-Temperature Liquid-phase Infiltration of Sintered microparts by Gold Eutectic Alloys/Infiltrazione a bassa temperatura in fase liquida di microparti sinterizzate mediante leghe eutettiche di oro
No full textThe flexibility of powder-based RP (or SFF) techniques and the densification method proposed in this paper would open a whole
new range of applications both in the macro and micro scale where thermal constraints exist. This work starts from a simple
idea, the infiltration of sintered skeletons made of pure gold spherical powder ranging between 5 and 40 μm in size, by binary gold eutectics based on silicon, germanium and tin, with a melting point as low as 278°C.
The variable space was investigated in a preliminary manner.
Experiments have shown that high densification rate, good surface finish and improved mechanical properties can be achieved with this process
Tunneling control and localization for Bose-Einstein condensates in a frequency modulated optical lattice
No full textThe similarity between matter waves in periodic potential and solid-state
physics processes has triggered the interest in quantum simulation using
Bose-Fermi ultracold gases in optical lattices. The present work evidences the
similarity between electrons moving under the application of oscillating
electromagnetic fields and matter waves experiencing an optical lattice
modulated by a frequency difference, equivalent to a spatially shaken periodic
potential. We demonstrate that the tunneling properties of a Bose-Einstein
condensate in shaken periodic potentials can be precisely controlled. We take
additional crucial steps towards future applications of this method by proving
that the strong shaking of the optical lattice preserves the coherence of the
matter wavefunction and that the shaking parameters can be changed
adiabatically, even in the presence of interactions. We induce reversibly the
quantum phase transition to the Mott insulator in a driven periodic potential
An approach to Mobile Grid platforms for the development and support of complex ubiquitous applications
No full textSeveral complex and time-critical applications require the existence of novel distributed, heterogeneous and dynamic platforms composed of a variety of fixed and mobile processing nodes and networks. Such platforms, that can be called Pervasive Mobile Grids, aim to merge the features of Pervasive Computing and High-performance Grid Computing onto a new emerging paradigm. In this Chapter we study a methodology for designing high-performance distributed computations, able to exploit the heterogeneity and dynamicity of Pervasive Grids, by expressing Adaptivity and Context Awareness directly at the application level. We describe a programming model approach, and we compare it with other existing research works in the field of Pervasive Mobile Computing, discussing the rationales of the requirements and the features of a novel programming model for the target platforms and applications. In order to exemplify the proposed methodology we introduce our evaluation framework ASSISTANT, and we provide some interesting future directions in this research field
Toward the synthesis of fine chemicals from lactose: preparation of d-xylo and l-lyxo-aldohexos-5-ulose derivatives
No full textSUMMARY The transformation of (5R)-2,6-di-O-benzyl-5-C-methoxy-β-d-galactopyranosyl-(1→4)-2,3:5,6-di-O-isopropylidene-aldehydo-d-glucose dimethyl acetal (8) into partially protected derivatives of d-xylo- and l-lyxo-aldohexos-5-ulose has been reported, applying appropriate epimerisation methods to its 3′-O- and 4′-O-protected alcoholic derivatives
La città degli espressionisti: scenografie cinematografiche
Get PDFRIASSUNTO Il saggio introduce un serrato confronto tra le immagini di città definite dal movimento espressionista e quelle presenti nei film dell’epoca, con la duplice consapevolezza da un lato che per gli architetti espressionisti la realtà privilegiata e immediatamente disponibile nella quale sperimentare la propria arte siano state le scenografie, dall’altro che per l’industria cinematografica del tempo fosse ancora difficoltoso effettuare riprese in esterno, per cui il set divenne un laboratorio obbligato ed un incentivo per l’invenzione architettonica. Le scenografie si prestavano alla sperimentazione di una nuova espressività e a verifiche formali o spaziali senza limiti e vincoli. Dall’esame di sei case-studies si evidenziano qui specificamente quali elementi - sia nelle scenografie, sia nell’atmosfera urbana presentata dai film ritenuti vicini al movimento d’avanguardia - siano direttamente riconducibili alla temperie culturale espressionista. Si offre inoltre una sintetica elencazione dei più importanti film ad ambientazione urbana girati da artisti tedeschi negli anni Venti-Trenta. SUMMARY The essay compares the images of the city defined by the Expressionist movement and the city images in the films of the time. Expressionist architects discovered that film-set design gave them a chance to experiment with their artistic skills. At the same time, film studios could not shoot outdoors easily and so were forced to rely on constructed sets. All this worked out as an incentive for architectural invention. Sets became an apt proving ground for the new expressiveness of the architects as well as a way to experiment with the use of space without limits and constraints. This essay examines the cases of 6 films whose elements are specifically and directly attributable to the Expressionist culture. Here the case of the city encompasses both set design and the urban atmosphere in films linked with the avant-garde movements. The essay also provides a filmography of the most important films with urban settings shot by German artists in the 1920s and 1930s