Polytechnic University of Milan

About: Polytechnic University of Milan is a education organization based out in Milan, Italy. It is known for research contribution in the topics: Computer science & Finite element method. The organization has 18231 authors who have published 58416 publications receiving 1229711 citations. The organization is also known as: PoliMi & L-NESS.

Internationalization in the information age: A new era for places, firms, and international business networks?

Abstract: The new techno-economic paradigm of the information age has brought about new structures and processes in international business (IB). In this article, we examine the changing nature of the competitive advantages of places, the competitive advantages and strategies of firms, and the governance structure of IB networks in what has also been called the third industrial revolution. These three areas of change in IB activities can be mapped respectively to the location (L), ownership (O) and internalization (I) advantages of the eclectic paradigm. We interpret these OLI factors as dynamic constructs in order to depict analytically the shifts in the IB environment and their implications for IB.

Yield criteria for amorphous glassy polymers

Abstract: Three amorphous polymers, polymethyl methacrylate, polystyrene and polycarbonate were tested in uniaxial tension, uniaxial compression, plane strain compression and simple shear, over a range of temperatures. In each test, the yield point was precisely determined via residual strain measurements after unloading. With the yield stresses determined for these four different stress states, two pressure dependent shear yield criteria, i.e, the modified Von Mises and the modified Tresca criteria, were checked and compared. It is shown that (i) in each case (material, temperature, initial ageing state), the yield locus is satisfactorily described by either one or the other of the two criteria, and (ii) each criterion can be associated with a specific deformation mode (either homogeneous or localized in shear bands). As for the temperature dependence of the yield stress sensitivity to the hydrostatic pressure, it appears to be related to the glass transition temperature (Tg) and more precisely to the α and β relaxations. Finally, the pressure dependence of the yield stress can be possibly explained as being due to two effects: (i) the influence of pressure on molecular motions leading to yielding and (ii) the influence of pressure on the microstructural state.

Graceful database schema evolution: the PRISM workbench

Abstract: Supporting graceful schema evolution represents an unsolved problem for traditional information systems that is further exacerbated in web information systems, such as Wikipedia and public scientific databases: in these projects based on multiparty cooperation the frequency of database schema changes has increased while tolerance for downtimes has nearly disappeared. As of today, schema evolution remains an error-prone and time-consuming undertaking, because the DB Administrator (DBA) lacks the methods and tools needed to manage and automate this endeavor by (i) predicting and evaluating the effects of the proposed schema changes, (ii) rewriting queries and applications to operate on the new schema, and (iii) migrating the database.Our PRISM system takes a big first step toward addressing this pressing need by providing: (i) a language of Schema Modification Operators to express concisely complex schema changes, (ii) tools that allow the DBA to evaluate the effects of such changes, (iii) optimized translation of old queries to work on the new schema version, (iv) automatic data migration, and (v) full documentation of intervened changes as needed to support data provenance, database flash back, and historical queries. PRISM solves these problems by integrating recent theoretical advances on mapping composition and invertibility, into a design that also achieves usability and scalability. Wikipedia and its 170+ schema versions provided an invaluable testbed for validating PRISM tools and their ability to support legacy queries.

Stark Effect in Perovskite/TiO2 Solar Cells: Evidence of Local Interfacial Order

Abstract: To unveil the mechanisms controlling photovoltaic conversion in high-performing perovskite-based mesostructured solar cells, we focus on the key role played by the mesoporous oxide/perovskite interface. We employ several spectroscopic techniques to design a complete scenario and corroborate our results with first principle density functional theory calculations. In particular Stark spectroscopy, a powerful tool allowing interface-sensitive analysis is employed to prove the existence of oriented permanent dipoles, consistent with the hypothesis of an ordered perovskite layer, close to the oxide surface. The existence of a structural order, promoted by specific local interactions, could be one of the decisive reasons for highly efficient carriers transport within perovskite films.

On stability and convergence of projection methods based on pressure Poisson equation

Abstract: We investigate the proper choices of spatial approximations for velocity and pressure in fractional-step projection methods. Numerical results obtained with classical finite element interpolations are presented. These tests confirm the role of the inf-sup LBB condition in non-incremental and incremental versions of the method for computing viscous incompressible flows