117,414 research outputs found
Germ hypoellipticity and loss of derivatives
No full textWe prove hypoellipticity in the sense of germs for the operator
where
even though it fails to be hypoelliptic in the strong sense. The primary tool is an a priori estimate.</p
SISTEMA PER LA GENERAZIONE DI MOTI DI SWIRL PER MOTORI ALTERNATIVI DOTATI DI DUE INIETTORI PER CILINDRO
No full textSISTEMA PER LA GENERAZIONE DI MOTI DI SWIRL PER MOTORI ALTERNATIVI DOTATI DI DUE INIETTORI PER CILINDR
Large HSDI CR diesel engines multiple injections and multiple swirls concept
No full textAll future power developments should consider as primary tasks the achievement of the required emission levels and CO2-values, while still providing optimum torque-to-rpm curves, the lowest SFC (Specific Fuel Consumption) over the widest range possible, good power-to-weight and affordable costs. One method to achieve these objectives is the downsizing. To achieve the levels of engine performance that are required, a significant increase in the rated speed and in the boost pressure is mandatory. In this case, the result is an increase in the flow rate through the intake and exhaust ports and valves. Considering the impact of these changes, the port layout of the system is reanalyzed. Another physical limit to the maximum speed depends on the CR (Common Rail) injector dynamic performances. These performances decrease with size for inertia problems and they depend on the amount of effort involved in their development. Automotive engines in the range of 10 to 100 HP per cylinder are the most common. For this reason, these injectors are the most advanced and costeffective. Furthermore, their small size and inertia is favorable to the best dynamic performance. The larger number of nozzles improves combustion performance. In fact the better surface to volume ratio or the spray improves heat transfer. For this reason, multiple injection systems can be used in the modern HSDI (High Speed Direct Injection) CR large diesels. This solution was commonplace before WWII, but has been progressively abandoned with the introduction of mechanical high-pressure injection systems and the bowl combustion chamber. In this paper, a dual combustion chamber per cylinder engine is considered. The primary purpose of this study is to examine the best port layout on a modern diesel combustion system and to introduce a new promising concept. The study included flow measurements of intake flow and CFD simulations of the flow field during intake. This design enables the formation of two homogenous swirls centered onto the injectors, with excellent flow coefficient. The design also allows an increase in volumetric efficiency combined with a reduction in flow losses. © 2006-2015 Asian Research Publishing Network (ARPN)
La ragione referendaria e i suoi giudici
No full textIl saggio analizza la giurisprudenza costituzionale in tema di ammissibilità del referendum abrogativo, evidenziandone la creatività e le contraddizioni dovute all'innesto della ragionevolezza in un sindacato astratto ed oggettivo. Queste decisioni hanno portato alla marginalizzazione dell'istituto referendario. Per invertire simile tendenza, l’articolo propone di adeguare le tecniche decisore della Corte costituzionale alla creatività argomentativa dimostrata da questa giurisprudenza
Characterization of magnetic IrMn/NiFe nanostructures
No full textIt is now largely demonstrated that magnetic systems structured on a nanometric length scale may exhibit peculiar magnetic properties, generally indicated as disordered magnetism effects, originating from the concomitant presence of topological disorder and competing magnetic interactions, as a consequence of the lack of structural periodicity. It is to be expected that this complex mix of magnetic effects play a relevant role also in the behavior of exchange coupled antiferromagnetic (AFM)/ferromagnetic (FM) systems, where the torque action exerted by the interfacial AFM spins on the FM ones brings about the insurgence of an unidirectional exchange anisotropy for the FM magnetization, and then the exchange bias (EB) effect.
In this work the EB properties of the IrMn/NiFe system in form of continuous film and of arrays of square dots with different size (1000, 500 and 300 nm), produced by e-beam lithography and dc-sputtering deposition, have been investigated. The stacking of the final samples was Si (substrate)/Cu[5 nm]/IrMn[10 nm]/NiFe[5 nm] (in square brackets the nominal thickness of each layer is reported). Structural investigations by TEM of the continuous IrMn/NiFe film indicate that the bulk of the AFM layer consists of nanograins with mean size ~ 10 nm, whereas the NiFe phase appears amorphous. In particular, the TEM analysis reveals the existence of a structurally disordered IrMn region (2-3 nm thick) at the interface between the FM phase and the bulk of the AFM layer. This finding, namely the evidence of structural disorder, strongly supports the spin-glass like magnetic character of the interfacial IrMn region, deduced by SQUID measurements on the continuous film, Figure 3. The existence of a low temperature frozen collective regime of the interfacial AFM spins and its break up above a critical temperature, that we have schematically settled at T = 100 K, determine the thermal evolution of the EB properties. In fact, below 100 K, the exchange coupling between IrMn and NiFe is ruled by magnetically correlated, frozen AFM spins, subjected to a strong effective local anisotropy, which results in high Hex (exchange field) and HC (coercivity) values. Above 100 K, the AFM/FM coupling is governed by a fraction of interfacial AFM spins, magnetically polarized by the AFM nanograins. Hence, Hex and HC decrease more and more with rising T, reflecting the progressive thermal instability of the AFM nanograins, assumed as essentially non-interacting. The spatial confinement, namely the passage from the continuous film to the dot structure, affects the exchange coupling mechanism when the dot size enters the sub-micron regime [1].
This research work has been carried out in the framework of the project FIRB 2010 “Tailoring the magnetic anisotropy of nanostructures for enhancing the magnetic stability of magnetoresistive devices”-NANOREST
References
1. F. Spizzo, E. Bonfiglioli, M. Tamisari, A. Gerardino, G. Barucca, A. Notargiacomo , F. Chinni, L. Del Bianco, “Magnetic exchange coupling in IrMn/NiFe nanostructures: from the continuous film to dot arrays”, Physical Review B, 91, pp.064410 1-9, 2015
Computational analysis with Turbokiva code on multivalves spark ignition engine performance
No full textn.d
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Shroud of Turin between history and science: an ongoing debate
No full textThe Shroud of Turin has passed through centuries of history, has travelled and has experienced events, which have only partially been recorded in documentary sources. Popular-cultural tradition has now accepted it as being the Shroud of the historical Christ. Nevertheless, public opinion has always been divided between those who believe in its authenticity and those who do not. Since the seventies there have been various wide-ranging study campaigns devoted to unravelling the mystery. Today the Shroud has become once more the centre of attention for the scientific world on the occasion of its last exposition. This paper aims to present a chronology of the investigative phases conducted so far and to put forward a new proposal in the field of image analysis and artistic diagnosis
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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