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.

Improved Monte Carlo inversion of surface wave data

Abstract: Inversion of surface wave data suffers from solution non-uniqueness and is hence strongly biased by the initial model. The Monte Carlo approach can handle this non-uniqueness by evidencing the local minima but it is inefficient for high dimensionality problems and makes use of subjective criteria, such as misfit thresholds, to interpret the results. If a smart sampling of the model parameter space, which exploits scale properties of the modal curves, is introduced the method becomes more efficient and with respect to traditional global search methods it avoids the subjective use of control parameters that are barely related to the physical problem. The results are interpreted drawing inference by means of a statistical test that selects an ensemble of feasible shear wave velocity models according to data quality and model parameterization. Tests on synthetic data demonstrate that the application of scale properties concentrates the sampling of model parameter space in high probability density zones and makes it poorly sensitive to the initial boundary of the model parameters. Tests on synthetic and field data, where boreholes are available, prove that the statistical test selects final results that are consistent with the true model and which are sensitive to data quality. The implemented strategies make the Monte Carlo inversion efficient for practical applications and able to effectively retrieve subsoil models even in complex and challenging situations such as velocity inversions.

Does internal finance matter for R&D? New evidence from a panel of Italian firms

Abstract: This paper investigates the relationship between finance and R&D for a panel of more than 1000 Italian manufacturing firms. While Italian firms obtain a significant share of their financing from debt, the results from a unique survey show that firms use virtually no debt to finance R&D. Because Italian firms typically do not receive external equity, the obvious source of innovation financing is internal cash flow. The sensitivity of capital investment to cash flow for small and medium-large firms is estimated, testing for the presence of informational frictions in the credit market for companies performing R&D activities. A GMM method that controls for unobserved firm-specific effects and endogenous explanatory variables is used. Cash flow plays an important role in explaining capital investment, especially for small firms. Interestingly, when the measure of firms' innovative activities is considered, significant differences are found between the sub-samples of small and medium-large firms. While small innovative firms are subject to relevant financing constraints, larger companies investing in R&D have easier access to external financing.

Tissue Engineering Approaches in the Design of Healthy and Pathological In Vitro Tissue Models.

Abstract: In the tissue engineering (TE) paradigm, engineering and life sciences tools are combined to develop bioartificial substitutes for organs and tissues, which can in turn be applied in regenerative medicine, pharmaceutical, diagnostic, and basic research to elucidate fundamental aspects of cell functions in vivo or to identify mechanisms involved in aging processes and disease onset and progression. The complex three-dimensional (3D) microenvironment in which cells are organized in vivo allows the interaction between different cell types and between cells and the extracellular matrix (ECM), the composition of which varies as a function of the tissue, the degree of maturation and health conditions. In this context, 3D in vitro models can more realistically reproduce a tissue or organ than two-dimensional (2D) models. Moreover, they can overcome the limitations of animal models and reduce the need for in vivo tests, according to the "3Rs" guiding principles for a more ethical research. The design of 3D engineered tissue models is currently in its development stage, showing high potential in overcoming the limitations of already available models. However, many issues are still opened, concerning the identification of the optimal scaffold-forming materials, cell source and biofabrication technology, and the best cell culture conditions (biochemical and physical cues) to finely replicate the native tissue and the surrounding environment. In the near future, 3D tissue engineered models are expected to become useful tools in the preliminary testing and screening of drugs and therapies and in the investigation of the molecular mechanisms underpinning disease onset and progression. In this review, the application of TE principles to the design of in vitro 3D models will be surveyed, with a focus on the strengths and weaknesses of this emerging approach. In addition, a brief overview on the development of in vitro models of healthy and pathological bone, heart, pancreas and liver will be presented.

Optimal Low-Thrust Escape Trajectories Using Gravity Assist

Abstract: Electric propulsion provides a spacecraft with continuous steering capabilities, which can be used to approach a planet with hyperbolic excess velocity that enhances the gravity assist. Low-thrust trajectories to escape from the solar system are considered in the present paper, which searches for the strategy that maximizes the spacecraft energy for assigned payload and engine operating time. The optimal conditions to escape using electric propulsion and gravity assist are presented for the cases of free-height and minimum-height  ybys. Optimal trajectories that exploit Jupiter or Venus  ybys have been computed for constant exhaust power with either constant or variable speciŽ c impulse; the procedure is also able to determine the optimal power level and to suggest when it is convenient to switch the engine on and off. The beneŽ t that system performance can receive by increasing the number of controls, i.e., by adding the possibility of coast arcs and engine throttling to the thrust direction control, is also noted.