Polytechnic University of Turin

About: Polytechnic University of Turin is a education organization based out in Turin, Piemonte, Italy. It is known for research contribution in the topics: Finite element method & Nonlinear system. The organization has 11553 authors who have published 41395 publications receiving 789320 citations. The organization is also known as: POLITO & Politecnico di Torino.

Bioactive glasses: From parent 45S5 Composition to Scaffold-Assisted Tissue-Healing Therapies

Abstract: Nowadays, bioactive glasses (BGs) are mainly used to improve and support the healing process of osseous defects deriving from traumatic events, tumor removal, congenital pathologies, implant revisions, or infections. In the past, several approaches have been proposed in the replacement of extensive bone defects, each one with its own advantages and drawbacks. As a result, the need for synthetic bone grafts is still a remarkable clinical challenge since more than 1 million bone-graft surgical operations are annually performed worldwide. Moreover, recent studies show the effectiveness of BGs in the regeneration of soft tissues, too. Often, surgical criteria do not match the engineering ones and, thus, a compromise is required for getting closer to an ideal outcome in terms of good regeneration, mechanical support, and biocompatibility in contact with living tissues. The aim of the present review is providing a general overview of BGs, with particular reference to their use in clinics over the last decades and the latest synthesis/processing methods. Recent advances in the use of BGs in tissue engineering are outlined, where the use of porous scaffolds is gaining growing importance thanks to the new possibilities given by technological progress extended to both manufacturing processes and functionalization techniques.

Magnetic properties and giant magnetoresistance of melt-spun granular Cu-100-x Co-x alloys

Abstract: Room-temperature measurements of magnetization and giant magnetoresistance were performed on rapidly solidified granular ${\mathrm{Cu}}_{100\ensuremath{-}x}{\mathrm{Co}}_{x}$ systems ($x=5, 10, 15$). The magnetoresistance of melt-spun ${\mathrm{Cu}}_{100\ensuremath{-}x}{\mathrm{Co}}_{x}$ ribbons was enhanced either by suitable furnace annealings or by exploiting the dc Joule-heating technique in the attempt of precipitating smaller magnetic particles. The particle-size distribution, the particle density, and mean distance are obtained for all compositions and heat treatments through a suitable analysis of the magnetic behavior of samples. The magnetoresistance is plotted as a function of the reduced magnetization, and a significant deviation from the quadratic behavior predicted by the independent-moment approach is observed at low fields. A simple theory taking explicitly into account the correlation existing among the magnetic particles is proposed. A general expression for the magnetoresistance in granular magnetic systems is obtained, and shown to accurately fit all the experimental curves, indicating that this effect is basically determined by the ratios between two distinct correlation ranges for the magnetic-moment fluctuations and the electronic mean free path.

How far 3D shapes can be understood from 2D silhouettes

Abstract: Each 2D silhouette of a 3D unknown object O constrains O inside the volume obtained by back-projecting the silhouette from the corresponding viewpoint. A set of silhouettes specifies a boundary volume R obtained by intersecting the volumes due to each silhouette. R more or less closely approximates O, depending on the viewpoints and the object itself. This approach to the reconstruction of 3D objects is usually referred to as volume intersection. This correspondence addresses the problem of inferring the shape of the unknown object O from the reconstructed object R. For doing this, the author divides the points of the surface of R into hard points, which belong to the surface of any possible object originating R, and soft points, which may or may not belong to O. The author considers two cases: In the first case R is the closest approximation of O which can be obtained from its silhouettes, i.e., its visual hull; in the second case, R is a generic reconstructed object. In both cases the author supplies necessary and sufficient conditions for a point to be hard and gives rules for computing the hard surfaces. >

A separated-flow model for collapsible-tube oscillations

Abstract: A new model is presented to describe flow in segments of collapsible tube mounted between two rigid tubes and surrounded by a pressurized container. The new features of the model are the inclusion of (a) longitudinal wall tension and (b) energy loss in the separated flow downstream of the time-dependent constriction in a collapsing tube, in a manner which is consistent with the one-dimensional equations of motion. As well as accurately simulating steady-state collapse, the model predicts self-excited oscillations whose amplitude is large enough to be observable only if the flow in the collapsible tube becomes supercritical somewhere (fluid speed exceeding long-wave propagation speed). The dynamics of the oscillations is dominated by longitudinal movement of the point of flow separation, in response to the adverse pressure gradient associated with waves propagating backwards and forwards between the (moving) narrowest point of the constriction and the tube outlet.

Free-space optical system performance for laser beam propagation through non-Kolmogorov turbulence

Abstract: It is well know that free-space laser system performance is limited by atmospheric turbulence. Most theoretical treatments have been described for many years by Kolmogorov's power spectral density model because of its simplicity. Unfortunately, several experiments have been reported recently that show that the Kolmogorov theory is sometimes incomplete to describe atmospheric statistics properly, in particular, in portions of the troposphere and stratosphere. We present a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized amplitude factor instead of constant value 0.033. Using this new spectrum in weak turbulence, we carry out, for a horizontal path, an analysis of long-term beam spread, scintillation index, probability of fade, mean signal-to-noise ratio (SNR), and mean bit error rate (BER) as variation of the spectrum exponent. Our theoretical results show that for alpha values lower than =11/3, but not for alpha close to =3, there is a remarkable increase of scintillation and consequently a major penalty on the system performance. However, when alpha assumes a value close to =3 or for alpha values higher than =11/3, scintillation decreases, leading to an improvement on the system performance.