2,770 research outputs found
Shock and rarefaction waves in a hyperbolic model of incompressible materials
No full textThe aim of the present paper is to investigate shock and rarefaction waves in a hyperbolic model of incompressible materials. To this aim, we use the so-called extended quasi-thermal-incompressible (EQTI) model, recently proposed by Gouin & Ruggeri (H. Gouin, T. Ruggeri, Internat. J. Non-Linear Mech. 47 688–693 (2012)). In particular, we use as constitutive equation a variant of the well-known Bousinnesq approximation in which the specific volume depends not only on the temperature but also on the pressure. The limit case of ideal incompressibility, namely when the thermal expansion coefficient and the compressibility factor vanish, is also considered
The explicit closure for the ultrarelativistic limit of Extended Thermodynamics of Rarefied Polyatomic Gas
Get PDFIn a recent paper the ultra-relativistic limit of a recent theory proposed by Pennisi and Ruggeri for polyatomic relativistic gas has been considered. This was important to check the general article. In particular, the explicitly expression of the characteristic velocities of the hyperbolic system were found for every value of the parameter a measuring ”how much” the gas is polyatomic. This result was achieved in terms of the components of the main field as independent variables and without writing it in terms of the physical variables. Here the closure of the field equations is considered in terms of these physical variables and their ultrarelatistic limit is obtained
The Bénard problem for quasi-thermal-incompressible materials: A linear analysis
No full textIn this paper we apply the ideas introduced with the so-called extended-quasi-thermal-incompressible (EQTI) model, recently proposed by Gouin and Ruggeri (Int. J. Non-Linear Mech. 47 (2012) 688–693) [12]. In particular, in the Oberbeck–Boussinesq approximation we consider the more realistic constitutive equation compatible with the thermodynamical stability by putting in the buoyancy term a density which depends not only by the temperature but also on the pressure. The equation for the pressure is then modified by an extra dimensionless parameter β^ which is proportional to the positive compres- sibility factor β. The 2-D linear instability of the thermal conduction solution in horizontal layers heated from below (Bénard problem) is investigated. It is shown that for any β^ : (i) the rest state pressure profile is different from the parabolic one; (ii) if convection arises, then it first arises via a stationary state and the strong principle of exchange of stability holds; for small β^ : (iii) convection certainly arises provided Ra is sufficiently large; (iv) the related critical Rayleigh number coincides -in the limit of vanishing β^ – with the classical one, and decreases as β^ increases
The Riemann problem for a hyperbolic model of incompressible fluids
No full textThe aim of the present paper is to investigate shock and rarefaction waves in a hyperbolic model of incompressible fluids. To this aim, we use the so-called extended-quasi-thermal-incompressible (EQTI) model, recently proposed by Gouin and Ruggeri (H. Gouin, T. Ruggeri, International Journal of Non-Linear Mechanics 47 (2012) 688–693). In particular, we use as constitutive equation a variant of the well-known Boussinesq approximation in which the specific volume depends not only on the temperature but also on the pressure, leading to a hyperbolic system of differential equations. The limit case of ideal incompressibility, namely when the thermal expansion coefficient and the compressibility factor vanish, is also considered. The results show that the propagation of shock waves in an EQTI fluid is characterized by small jump in specific volume and temperature, even when the jump in pressure is relevant, and rarefaction waves originating from a general Riemann problem are characterized by a very steep profile. The knowledge of the loci of the states that can be connected to a given state by a shock wave or a rarefaction wave allows also to completely solve the Riemann problem. The obtained results are confirmed by means of numerical calculations
Relativistic Eulerian rarefied gas with internal structure
No full textRecently Pennisi and Ruggeri [Ann. Phys. 377, 414 (2017)] proposed a casual hyperbolic model for a dissipative relativistic gas with internal structure. In this paper, we consider the particular case of the model when dissipation is negligible (Eulerian gas). We study in particular the energy behavior in comparison with the Synge energy which is valid for monatomic gas and we evaluate the characteristic velocities proving the hyperbolicity of the differential system. The second part of the paper is devoted to the ultra-relativistic limit of the model and we prove that there exists a critical value of the degree of freedom such that for smaller values of this quantity the ultra-relativistic limit of the energy of a gas with structure is the same as the Synge energy, while for larger degrees of freedom the energy increases with the degree of freedom itself
Asymptotic Behavior of Riemann and Riemann with Structure Problems for a 2x2 Hyperbolic Dissipative System
No full textWe present a simple 2x2 hyperbolic dissipative system that has many features
in common with systems of Extended Thermodynamics. Trough numerical
experiments we validate the Brini–Ruggeri conjecture, according to which
the Riemann and the Riemann with structure problems converge, for large time,
to a combination of shock structures (with or without sub-shocks) and rarefactions
of the equilibrium subsystem
Outcome measurement in Italy
No full textThis chapter provides an overview of outcome measurement initiatives conducted in Italian mental health services in Italy since the Reform that occurred 30 years ago, called ‘Law 180’, which radically changed the architecture of psychiatric care (De Girolamo et al., 2007). Gaining in-depth knowledge of the outcomes of people with mental disorders who receive community care has been a great challenge for both researchers and clinicians in the last 20 years, due to the lack of an agreed conceptual and methodological framework to assess outcome. Several important achievements have been fulfilled in the last decade and an agreement on the various facets of this concept has been reached. It has first been made clear that outcome measurement is not independent of ethical principles and thus should provide a wider balance of information for health policy and clinical service decisions (Thornicroft and Tansella, 1999). Then, it has been stated that for outcome measurement to be valid, reliable and useful for both programme planning and evaluation of interventions, it should be based on the principle of multiaxiality (i.e. the assessment should consider the perspectives of all those involved in the care process, including clinicians, patients, caregivers, user representatives, third-party payers, etc.) and of multidimensionality (i.e. the assessment should consider an intervention's effect on various dimensions of the patients' life, including both clinical and social aspects) (Lasalvia and Ruggeri, 2007)
Byzantine aqueducts of Constantinople outside the city
No full textThis dataset is related to the PhD research of Francesca Ruggeri, published in the thesis "Engineering the Byzantine Water Supply of Constantinople: mapping, hydrology and hydraulics of the long aqueducts outside the City" (2018) http://hdl.handle.net/1842/31521. This aims at providing additional material resulting from the GIS work presented in Chapter 5 of the thesis. Archaeological survey data were available from previous campaigns carried out by Prof. James Crow in the years 1995-2009 in Turkish Thrace. Such data were systematically reassessed and organised by the author to create a comprehensive database of the remains of the Byzantine aqueducts of Constantinople.
This dataset includes:
maps of the Byzantine aqueducts and related features, as image files [map];
map locations viewable in Google Earth/Google Maps, as .kmz files [kmz];
shapefiles of Water Supply route and features for GIS use [shp];
lists of features (bridges, tunnels, channels), as Excel files [excel].
All maps and GIS features were created in ESRI ArcMap by F Ruggeri.This dataset includes:
maps of the Byzantine aqueducts and related features, as image files [map];
map locations viewable in Google Earth/Google Maps, as .kmz files [kmz];
shapefiles of Water Supply route and features for GIS use [shp];
lists of features (bridges, tunnels, channels), as Excel files [excel].
All maps and GIS features were created in ESRI ArcMap by F Ruggeri
Mixture of Gases with Multi-Temperature: Maxwellian Iteration
No full textIn this paper a hyperbolic model is proposed for mixtures of gases which are neither viscous, nor heat-conducting (Eulerian fluids). It is built upon assumption that each constituent obeys it's own temperature. Restrictions to the structure of the model come out from basic principles of extended thermodynamics, i.e.
Galilean invariance of balance laws and entropy inequality. Hierarchy of hyperbolic subsystems is recognized, with a single-temperature model as principal subsystem and classical Euler's equations as equilibrium subsystem. Finally, in order to relate this model to classical thermodynamics, a Maxwellian iteration is performed in the case of binary mixture, giving rise to a relation between the diference of non-equilibrium temperatures of constituents and classical fields
Average temperature and Maxwellian iteration in multitemperature mixtures of fluids
No full textThis paper treats the nonequilibrium processes in mixtures of fluids under the assumption that each constituent
is characterized by its own velocity and temperature field. First we discuss the concept of the average
temperature of mixture based upon considerations that the internal energy of the mixture is the same as in the
case of a single-temperature mixture. As a consequence, it is shown that the entropy of the mixture reaches a
local maximum in equilibrium. An illustrative example of homogeneous mixtures is given to support the
theoretical considerations. Through the procedure of Maxwellian iteration a new constitutive equation for
nonequilibrium temperatures of constituents is obtained in a classical limit, together with the Fick’s law for the
diffusion flux. These results obtained for n-species are in perfect agreement with a recent classical approach of
thermodynamics of irreversible processes in multitemperature case due to Gouin and Ruggeri and generalize
our previous papers concerning the case of a binary mixture
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