Polytechnic University of Catalonia

About: Polytechnic University of Catalonia is a education organization based out in Barcelona, Spain. It is known for research contribution in the topics: Finite element method & Population. The organization has 16006 authors who have published 45325 publications receiving 949306 citations. The organization is also known as: UPC - BarcelonaTECH & Technical University of Catalonia.

Noise focusing and the emergence of coherent activity in neuronal cultures

Abstract: Neuronal networks can spontaneously exhibit periodic bursts of collective activity. High-resolution calcium imaging and computer modelling of in vitro cultures now reveal that this behaviour is a consequence of noise focusing—an implosive concentration of spontaneous activity due to the interplay between network topology and intrinsic neuronal dynamics.

Rare-earth-free propulsion motors for electric vehicles: A technology review

Abstract: Several factors including fossil fuels scarcity, prices volatility, greenhouse gas emissions or current pollution levels in metropolitan areas are forcing the development of greener transportation systems based on more efficient electric and hybrid vehicles. Most of the current hybrid electric vehicles use electric motors containing powerful rare-earth permanent magnets. However, both private companies and estates are aware of possible future shortages, price uncertainty and geographical concentration of some critical rare-earth elements needed to manufacture such magnets. Therefore, there is a growing interest in developing electric motors for vehicular propulsion systems without rare-earth permanent magnets. In this paper this problematic is addressed and the state-of-the-art of the electric motor technologies for vehicular propulsion systems is reviewed, where the features required, design considerations and restrictions are addressed.

On the Evolution of Stars that Form Electron-Degenerate Cores Processed by Carbon Burning. III. The Inward Propagation of a Carbon-Burning Flame and Other Properties of a 9 M☉ Model Star

Abstract: A 9 M☉ stellar model of Population I composition is evolved from the hydrogen-burning main sequence to the thermally pulsing "super" asymptotic giant branch stage, where it has an electron-degenerate core composed of an inner oxygen-neon (ONe) part of mass ~1.066 M☉ and an outer carbon-oxygen (CO) layer of mass ~0.05 M☉ and is experiencing thermal pulses driven by helium-burning thermonuclear flashes. The carbon-burning phase of the 9 M☉ model is in many respects similar to, but differs importantly from that of a 10 M☉ model studied earlier. In both cases, carbon is ignited off center, and a series of carbon flashes accompanied by a convective shell occur. In contrast to the 10 M☉ model, the 9 M☉ model experiences the second dredge-up phenomenon (the penetration of the base of the hydrogen-rich convective envelope inward into helium- and carbon-rich material) near the beginning rather than near the end of the carbon-burning phase. The first carbon-burning flash causes helium burning to shut down and the release of gravothermal energy (compressional and thermal energy) between the helium-carbon discontinuity and the base of the convective envelope plays a dominant role in the dredge-up event. Beginning with the third carbon-burning shell flash, the "flame front," defined as being coincident with the base of the convective shell, propagates inward with a speed close to theoretical predictions that relate flame speed to local thermodynamic, opacity, and energy-generation rate characteristics. Ahead of the inward moving front, most of the nuclear energy released in a "precursor flame" goes into heating and expanding matter. As the precursor flame moves toward the center, its radial thickness decreases and, to follow the progress of the front with standard techniques, both the spatial grid size and the time step must be continually decreased. Following the front gives one the opportunity to ponder Zeno's paradox, which is averted because the thickness of the precursor flame remains finite. On reaching the center, the carbon-burning flame reverses direction and continues moving outward until it is within ~0.03 M☉ of the helium-burning shell. After carbon burning is completed,12C remains at a finite abundance throughout the electron-degenerate core of mass ~1.116 M☉ and is more abundant than 20Ne in the outer ~0.05 M☉ of this core. Over most of the ONe interior of both the 9 and 10 M☉ models,23Na is more abundant than 24Mg, but the maximum 12C abundance in the 9 M☉ model ONe interior (X[12C] ~ 0.048) is significantly larger than in the 10 M☉ model (X[12C] ~ 0.012). For an ONe white dwarf that accretes enough matter to reach the Chandrasekhar limiting mass, this may make the difference between total explosive disruption (large 12C abundance) and collapse to neutron-star dimensions (small 12C abundance). The abundances in the CO part of the core have relevance for understanding the abundances in the ejecta of classical novae produced by massive ONe white dwarfs in close binaries. In the outer ~0.014 M☉ of the CO part of the core, the abundances of all neon isotopes are much less than solar, and 25Mg and the neutron-rich isotopes made during the formation of 25Mg are at a total abundance equal to the initial abundance of CNO elements in the model. As in the 10 M☉ case, thermal pulses occasioned by helium shell flashes begin after hydrogen is reignited and the carbon-burning luminosity drops below ~100 L☉. The time between pulses is ~400 yr, roughly twice as large as in the 10 M☉ model. After the ejection of the hydrogen-rich envelope as a planetary nebula, the remnant of the 9 M☉ model is expected to evolve into a white dwarf of mass ~1.15 M☉, the outer ~0.08 M☉ of which is composed of carbon and oxygen.

Surface Faceting and Reconstruction of Ceria Nanoparticles.

Abstract: The surface atomic arrangement of metal oxides determines their physical and chemical properties, and the ability to control and optimize structural parameters is of crucial importance for many applications, in particular in heterogeneous catalysis and photocatalysis. Whereas the structures of macroscopic single crystals can be determined with established methods, for nanoparticles (NPs), this is a challenging task. Herein, we describe the use of CO as a probe molecule to determine the structure of the surfaces exposed by rod-shaped ceria NPs. After calibrating the CO stretching frequencies using results obtained for different ceria single-crystal surfaces, we found that the rod-shaped NPs actually restructure and expose {111} nanofacets. This finding has important consequences for understanding the controversial surface chemistry of these catalytically highly active ceria NPs and paves the way for the predictive, rational design of catalytic materials at the nanoscale.