120 research outputs found
Investigation on Pre-Ignition Combustion Events and Development of Diagnostic Solutions Based on Ion Current Signals
No full textPre-ignition combustions are extremely harmful and undesired, but the recent search for extremely efficient spark-ignition engines has implied a great increase of the in-cylinder pressure and temperature levels, forcing engine operation to conditions that may trigger this type of anomalous combustion much more frequently. For this reason, an accurate on-board diagnosis system is required to adopt protective measures, preventing engine damage. Ion current signal provides relevant information about the combustion process, and it results in a good compromise between cost, durability and information quality (signal to noise ratio levels). The GDI turbocharged engine used for this study was equipped with a production ion current sensing system, while in-cylinder pressure sensors were installed for research purposes, to better understand the pre-ignition phenomenon characteristics, and to support the development of an on-board diagnostic system solely based on ion current measurements. In this work, pre-ignition events induced by heavy knocking operation have been analysed. The focus was mainly on ion current signal real-time processing, and on the possibility to correctly and rapidly detect pre-ignition events. In a previous work, destructive effects of this kind of combustion on engine components had been described. As shown in the paper, the development and implementation of an ion current based detection algorithm results to be very effective in identifying pre-ignition combustions, and it could allow an extremely fast reaction of the engine controller that can prevent further anomalous combustions once the first event has occurred. Moreover, pre-ignition phase information extracted from the ion signal and characteristic combustion angles obtained from pressure signal analysis are well correlated, further confirming the ion signal robustness and accuracy
On the Calogero-Moser space associated with dihedral groups
No full textInternational audienceUsing the geometry of the associated Calogero-Moser space, R. Rouquier and the author have attached to any finite complex reflection group several notions (Calogero-Moser left, right or two-sided cells, Calogero-Moser cellular characters), completing the notion of Calogero-Moser families defined by Gordon. If moreover is a Coxeter group, they conjectured that these notions coincide with the analogous notions defined using the Hecke algebra by Kazhdan and Lusztig (or Lusztig in the unequal parameters case). In the present paper, we aim to investigate these conjectures whenever is a dihedral group
Turbocharger Control-Oriented Modeling: Twin-Entry Turbine Issues and Possible Solutions
No full textThe paper presents possible solutions for developing fast and reliable turbocharger models, to be used mainly for control applications. This issue is of particular interest today for SI engines since, due to the search for consistent CO2 reduction, extreme downsizing concepts require highly boosted air charge solutions to compensate for power and torque de-rating. For engines presenting at least four in-line cylinders, twin-entry turbines offer the ability of maximizing the overall energy conversion efficiency, and therefore such solutions are actually widely adopted. This work presents a critical review of the most promising (and recent) modeling approaches for automotive turbochargers, highlighting the main open issues especially in the field of turbine models, and proposing possible improvements. The main original contribution is then on solving specific issues related to the twin-entry turbine, to develop a control-oriented model able to predict the machine behavior under all possible admission conditions. The results of this study have been applied to a V8 high-performance GDI engine with twin-entry turbochargers. Experimental data are shown throughout the paper, to demonstrate the benefits of the proposed approach
Computational aspects of Calogero-Moser spaces
No full textInternational audienceWe present a series of algorithms for computing geometric and representationtheoretic invariants of Calogero-Moser spaces and rational Cherednik algebras associated with complex reflection groups. Especially, we are concerned with Calogero-Moser families (which correspond to the -fixed points of the Calogero-Moser space) and cellular characters (a proposed generalization by Rouquier and the first author of Lusztig's constructible characters based on a Galois covering of the Calogero-Moser space). To compute the former, we devised an algorithm for determining generators of the center of the rational Cherednik algebra (this algorithm has several further applications), and to compute the latter we developed an algorithmic approach to the construction of cellular characters via Gaudin operators. We have implemented all our algorithms in the Cherednik Algebra Magma Package (CHAMP) by the second author and used this to confirm open conjectures in several new cases. As an interesting application in birational geometry we are able to determine for many exceptional complex reflection groups the chamber decomposition of the movable cone of a Q-factorial terminalization (and thus the number of non-isomorphic relative minimal models) of the associated symplectic singularity
Computational aspects of Calogero-Moser spaces
No full textWe present a series of algorithms for computing geometric and
representation-theoretic invariants of Calogero-Moser spaces and rational
Cherednik algebras associated to complex reflection groups. Especially, we are
concerned with Calogero-Moser families (which correspond to the
-fixed points of the Calogero-Moser space) and cellular
characters (a proposed generalization by Rouquier and the first author of
Lusztig's constructible characters based on a Galois covering of the
Calogero-Moser space). To compute the former, we devised an algorithm for
determining generators of the center of the rational Cherednik algebra (this
algorithm has several further applications), and to compute the latter we
developed an algorithmic approach to the construction of cellular characters
via Gaudin operators. We have implemented all our algorithms in the Cherednik
Algebra Magma Package (CHAMP) by the second author and used this to confirm
open conjectures in several new cases. As an interesting application in
birational geometry we are able to determine for many exceptional complex
reflection groups the chamber decomposition of the movable cone of a
-factorial terminalization (and thus the number of non-isomorphic
relative minimal models) of the associated symplectic singularity.Comment: 42 page
Classical hydrodynamics of Calogero-Sutherland models
No full textThe Calogero Sutherland model is system of particle moving on a line and interacting with long-range
forces. In this thesis we consider the classical case where the particles may or may not possess a spin degree of freedom. We demonstrate the intimate connection between the Calogero-Sutherland system and the Benjamin Ono equation. We then directly obtain a classical hydrodynamical limit of both the spineless and spinful Calogero system. The continuum limit of the spinless system is known to exhibit solition solutions.
We show numerically that the spinful system also exhibits localized solutions with the soliton property. This
is a strong evidence that the continuum spin-Calogero model is exactly integrable.Item withdrawn by Laura Spradlin ([email protected]) on 2014-07-21T22:07:40Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
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The impact of Western beauty ideals on the lives of women and men: A sociocultural perspective
No full textAccording to a recent survey of 3,300 girls and women across 10 countries, 90 per cent of all women aged 15 to 64 worldwide want to change at least one aspect of their physical appearance, with body weight ranking the highest (Etcoff, Orbach, Scott, & D’Agostino, 2004). This finding suggests that women’s anxiety about their appearance is a global phenomenon, observed in every country studied from Saudi Arabia to the United States. Beyond body dissatisfaction, a stunning 67 per cent of all women aged 15 to 64 worldwide reported that they actually withdraw from life-engaging, life-sustaining activities due to feeling badly about their looks. These activities include giving an opinion, meeting friends, exercising, going to work, going to school, dating, and going to the doctor
Two new solvable dynamical systems of goldfish type
No full textTwo new solvable dynamical systems of goldfish type are identified, as well as their isochronous variants. The equilibrium configurations of these isochronous variants are simply related to the zeros of appropriate Laguerre and Jacobi polynomials. © 2010 The Author(s)
Appunti per lo stucco «de marmoro» a Bologna nei primi decenni del Cinquecento (con un'ipotesi su Baldassarre Peruzzi)
No full textThis article examines the diffusion of the technique of stucco made of marble powder in Bologna in the first decades of the sixteenth century through unpublished documents. The author argues that architect Baldassarre Peruzzi played a crucial role in the diffusion of this technique in Northern Italy
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