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Search Results: 1 - 10 of 325243 matches for " S. Davini "
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Radivoje B Pe?i?,Aleksandar Lj Davini,Dragan S Taranovi?,Danijela M Miloradovi?
Thermal Science , 2010, DOI: tsci100505069p
Abstract: A zero-dimensional, one zone model of engine cycle for steady-state regimes of engines and a simplified procedure for indicator diagrams analysis have been developed at the Laboratory for internal combustion engines, fuels and lubricants of the Faculty of Mechanical Engineering in Kragujevac. In addition to experimental research, thermodynamic modeling of working process of diesel engine with direct injection has been presented in this paper. The simplified procedure for indicator diagrams analysis has been applied, also. The basic problem, a selection of shape parameters of double Vibe function used for modeling the engine operation process, has been solved. The influence of biodiesel fuel and engine working regimes on the start of combustion, combustion duration and shape parameter of double Vibe was determined by a least square fit of experimental heat release curve.
Aspects of volumetric efficiency measurement for reciprocating engines
Pe?i? Radivoje B.,Davini? Aleksandar Lj.,Petkovi? Sne?ana D.,Taranovi? Dragan S.
Thermal Science , 2013, DOI: 10.2298/tsci120531153p
Abstract: The volumetric efficiency significantly influences engine output. Both design and dimensions of an intake and exhaust system have large impact on volumetric efficiency. Experimental equipment for measuring of airflow through the engine, which is placed in the intake system, may affect the results of measurements and distort the real picture of the impact of individual structural factors. This paper deals with the problems of experimental determination of intake airflow using orifice plates and the influence of orifice plate diameter on the results of the measurements. The problems of airflow measurements through a multi-process Otto/Diesel engine were analyzed. An original method for determining volumetric efficiency was developed based on in-cylinder pressure measurement during motored operation, and appropriate calibration of the experimental procedure was performed. Good correlation between the results of application of the original method for determination of volumetric efficiency and the results of theoretical model used in research of influence of the intake pipe length on volumetric efficiency was determined. [Acknowledgments. The paper is the result of the research within the project TR 35041 financed by the Ministry of Science and Technological Development of the Republic of Serbia]
Weak KAM Theory topics in the stationary ergodic setting
Andrea Davini,Antonio Siconolfi
Mathematics , 2009,
Abstract: We perform a qualitative analysis of the critical equation associated with a stationary ergodic Hamiltonian through a stochastic version of the metric method, where the notion of closed random stationary set, issued from stochastic geometry, plays a major role. Our purpose is to give an appropriate notion of random Aubry set, to single out characterizing conditions for the existence of exact or approximate correctors, and write down representation formulae for them. For the last task, we make use of a Lax--type formula, adapted to the stochastic environment. This material can be regarded as a first step of a long--term project to develop a random analog of Weak KAM Theory, generalizing what done in the periodic case or, more generally, when the underlying space is a compact manifold.
A metric analysis of critical Hamilton--Jacobi equations in the stationary ergodic setting
Andrea Davini,Antonio Siconolfi
Mathematics , 2009,
Abstract: We adapt the metric approach to the study of stationary ergodic Hamilton-Jacobi equations, for which a notion of admissible random (sub)solution is defined. For any level of the Hamiltonian greater than or equal to a distinguished critical value, we define an intrinsic random semidistance and prove that an asymptotic norm does exist. Taking as source region a suitable class of closed random sets, we show that the Lax formula provides admissible subsolutions. This enables us to relate the degeneracies of the critical stable norm to the existence/nonexistence of exact or approximate critical admissible solutions.
Aubry sets for weakly coupled systems of Hamilton--Jacobi equations
Andrea Davini,Maxime Zavidovique
Mathematics , 2012,
Abstract: We introduce a notion of Aubry set for weakly coupled systems of Hamilton--Jacobi equations on the torus and characterize it as the region where the obstruction to the existence of globally strict critical subsolutions concentrates. As in the case of a single equation, we prove the existence of critical subsolutions which are strict and smooth outside the Aubry set. This allows us to derive in a simple way a comparison result among critical sub and supersolutions with respect to their boundary data on the Aubry set, showing in particular that the latter is a uniqueness set for the critical system. We also highlight some rigidity phenomena taking place on the Aubry set.
On the (non) existence of viscosity solutions of multi--time Hamilton--Jacobi equations
Andrea Davini,Maxime Zavidovique
Mathematics , 2013,
Abstract: We prove that the multi--time Hamilton--Jacobi equation in general cannot be solved in the viscosity sense, in the non-convex setting, even when the Hamiltonians are in involution.
Existence and regularity of strict critical subsolutions in the stationary ergodic setting
Andrea Davini,Antonio Siconolfi
Mathematics , 2012,
Abstract: We prove that any continuous and convex stationary ergodic Hamiltonian admits critical subsolutions, which are strict outside the random Aubry set. They make up, in addition, a dense subset of all critical subsolutions with respect to a suitable metric. If the Hamiltonian is additionally assumed of Tonelli type, then there exist strict subsolutions of class $\CC^{1,1}$ in $\R^N$. The proofs are based on the use of Lax--Oleinik semigroups and their regularizing properties in the stationary ergodic environment, as well as on a generalized notion of Aubry set.
Weak KAM theoretic aspects for nonregular commuting Hamiltonians
Andrea Davini,Maxime Zavidovique
Mathematics , 2011,
Abstract: In this paper we consider the notion of commutation for a pair of continuous and convex Hamiltonians, given in terms of commutation of their Lax- Oleinik semigroups. This is equivalent to the solvability of an associated multi- time Hamilton-Jacobi equation. We examine the weak KAM theoretic aspects of the commutation property and show that the two Hamiltonians have the same weak KAM solutions and the same Aubry set, thus generalizing a result recently obtained by the second author for Tonelli Hamiltonians. We make a further step by proving that the Hamiltonians admit a common critical subsolution, strict outside their Aubry set. This subsolution can be taken of class C^{1,1} in the Tonelli case. To prove our main results in full generality, it is crucial to establish suitable differentiability properties of the critical subsolutions on the Aubry set. These latter results are new in the purely continuous case and of independent interest.
Transylvanian Review of Administrative Sciences , 2012,
Abstract: This paper completes the research of theadministrative appeal under the Serbian law. Itis preceded by two articles containing normativeanalyses of the general regime of the administrativeappeal as prescribed in the General AdministrativeProceeding Act and administrative remedies inspecial policy domains. The main part of thepaper is an empirical research concerning theef ciency of the administrative appeal. Ef ciencyis understood as a precondition for preventingappellants from seeking judicial protection andthus reducing the workload of the court. Theremaining part is dedicated to the ef ciency oftwo other administrative legal remedies, as well asto the ef ciency of the work of the Ombudsman.The purpose of the latter is to provide material for the consideration of possible amendments to theregime of the administrative appeal, which couldenhance its ef ciency.
pp <-> pi+ d process at low energy: Interplay between s-- and p-wave mechanisms
L. Canton,A. Davini,P. J. Dortmans
Physics , 1998, DOI: 10.1103/PhysRevC.58.1929
Abstract: The large variety of experimental data around the pion-production threshold are compared with a meson-exchange isobar model which includes the pion-nucleon interaction in s-- and p-waves. Theoretical results obtained with two different NN potentials (Bonn and Paris) indicate that the behavior of the excitation function at threshold is sensitive to the details of the NN correlations. The complete model presented, while developed originally to reproduce the reaction around the Delta resonance, is shown to describe well the integral (Coulomb-corrected) cross-section at threshold along with its angular distribution. At low energies the angular dependence of the analyzing power Ay0 is well reproduced also. Finally, the energy dependence of the analyzing power for theta=90 from threshold up to the Delta resonance is considered and discussed.
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