4,971 research outputs found
A mesoscopic approach to diffusion phenomena in mixtures
The mesosocpic concept is applied to the theory of mixtures. The aim is to
investigate the diffusion phenomenon from a mesoscopic point of view. The
domain of the field quantities is extended by the set of mesoscopic variables,
here the velocities of the components. Balance equations on this enlarged space
are the equations of motion for the mesoscopic fields. Moreover, local
distribution functions of the velocities are introduced as a statistical
element, and an equation of motion for this distribution function is derived.
From this equation of motion differential equations for the diffusion fluxes,
and also for higher order fluxes are obtained. These equations are of balance
type, as it is postulated in Extended Thermodynamics. The resulting evolution
equation for the diffusion flux generalizes the Fick's law
Energy chirp measurements by means of an RF deflector: a case study the gamma beam source LINAC at ELI-NP
RF Deflector (RFD) based measurements are widely used in highâbrightness electron LINAC around the world in order to measure the ultraâshort electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light InfrastructureâNuclear Physics (ELIâNP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen
Overparenting hurts me: how does it affect offspring psychological outcomes?
This review focuses on a peculiar typology of parenting characterized by overprotection, overinvolvement, overcontrol and an excess of entanglement; academic literature refers to this parenting style with the term overparenting or helicopter parenting. An in-depth description of overparenting constitutes the first part of this review. The second part of this review reports empirical evidence regarding the effects of overparenting on offspring psychological outcomes with particular regard to internalizing and externalizing disorders, coping strategies and dysfunctional personality traits. Depression and anxiety symptoms are frequently exhibited in offspring exposed to overparenting, as well as negative affectivity and maladaptive coping. Furthermore, adolescents and adults with overparenting parents seem to have an increased likelihood of exhibiting narcissistic pathological traits
Path integrals and degrees of freedom in many-body systems and relativistic field theories
The identification of physical degrees of freedom is sometimes obscured in
the path integral formalism, and this makes it difficult to impose some
constraints or to do some approximations. I review a number of cases where the
difficulty is overcame by deriving the path integral from the operator form of
the partition function after such identification has been made.Comment: 15 pages, volume in honor of prof.Yu.A.Simono
Towards an optical potential for rare-earths through coupled channels
The coupled-channel theory is a natural way of treating nonelastic channels,
in particular those arising from collective excitations, defined by nuclear
deformations. Proper treatment of such excitations is often essential to the
accurate description of reaction experimental data. Previous works have applied
different models to specific nuclei with the purpose of determining
angular-integrated cross sections. In this work, we present an extensive study
of the effects of collective couplings and nuclear deformations on integrated
cross sections as well as on angular distributions in a consistent manner for
neutron-induced reactions on nuclei in the rare-earth region. This specific
subset of the nuclide chart was chosen precisely because of a clear static
deformation pattern. We analyze the convergence of the coupled-channel
calculations regarding the number of states being explicitly coupled. Inspired
by the work done by Dietrich \emph{et al.}, a model for deforming the spherical
Koning-Delaroche optical potential as function of quadrupole and hexadecupole
deformations is also proposed. We demonstrate that the obtained results of
calculations for total, elastic and inelastic cross sections, as well as
elastic and inelastic angular distributions correspond to a remarkably good
agreement with experimental data for scattering energies above around a few
MeV.Comment: 7 pages, 6 figures. Submitted to the proceedings of the XXXVI
Reuni\~ao de Trabalho de F\'{\i}sica Nuclear no Brasil (XXXVI Brazilian
Workshop on Nuclear Physics), held in Maresias, S\~ao Paulo, Brazil in
September 2013, which should be published on AIP Conference Proceeding
Series. arXiv admin note: substantial text overlap with arXiv:1311.1115,
arXiv:1311.042
Role of the mean curvature in the geometry of magnetic confinement configurations
Examples are presented of how the geometric notion of the mean curvature is
used for general magnetic field configurations and magnetic surfaces. It is
shown that the mean magnetic curvature is related to the variation of the
absolute value of the magnetic field along its lines. Magnetic surfaces of
constant mean curvature are optimum for plasma confinement in multimirror open
confinement systems and rippled tori.Comment: PDFLaTeX, 10 pages, 5 figure
Simbol-X Background Minimization: Mirror Spacecraft Passive Shielding Trade-Off Study
The present work shows a quantitative trade-off analysis of the Simbol-X
Mirror Spacecraft (MSC) passive shielding, in the phase space of the various
parameters: mass budget, dimension, geometry, and composition. A simplified
physical (and geometrical) model of the sky screen, implemented by means of a
GEANT4 simulation, has been developed to perform a performance-driven mass
optimization and evaluate the residual background level on Simbol-X focal
plane.Comment: 3 pages, 6 figures, to appear in the proceedings of the second
Simbol-X International Symposium "Simbol-X - Focusing on the Hard X-ray
Universe", AIP Conf. Proc. Series, P. Ferrando and J. Rodriguez ed
Modelling burned area in Africa
The simulation of current and projected wildfires is essential for predicting crucial aspects of vegetation patterns, biogeochemical cycling as well as pyrogenic emissions across the African continent. This study uses a data-driven approach to parameterize two burned area models applicable to dynamic vegetation models (DVMs) and Earth system models (ESMs). We restricted our analysis to variables for which either projections based on climate scenarios are available, or that are calculated by DVMs, and we consider a spatial scale of one degree as the scale typical for DVMs and ESMs. By using the African continent here as an example, an analogue approach could in principle be adopted for other regions, for global scale dynamic burned area modelling. <br><br> We used 9 years of data (2000â2008) for the variables: precipitation over the last dry season, the last wet season and averaged over the last 2 years, a fire-danger index (the Nesterov index), population density, and annual proportion of area burned derived from the MODIS MCD45A1 product. Two further variables, tree and herb cover were only available for 2001 as a remote sensing product. Since the effect of fires on vegetation depends strongly on burning conditions, the timing of wildfires is of high interest too, and we were able to relate the seasonal occurrence of wildfires to the daily Nesterov index. <br><br> We parameterized two generalized linear models (GLMs), one with the full variable set (model VC) and one considering only climate variables (model C). All introduced variables resulted in an increase in model performance. Model VC correctly predicts the spatial distribution and extent of fire prone areas though the total variability is underrepresented. Model VC has a much lower performance in both aspects (correlation coefficient of predicted and observed ratio of burned area: 0.71 for model VC and 0.58 for model C). We expect the remaining variability to be attributed to additional variables which are not available at a global scale and thus not incorporated in this study as well as its coarse resolution. An application of the models using climate hindcasts and projections ranging from 1980 to 2060 resulted in a strong decrease of burned area of ca. 20â25%. Since wildfires are an integral part of land use practices in Africa, their occurrence is an indicator of areas favourable for food production. In absence of other compensating land use changes, their projected decrease can hence be interpreted as a indicator for future loss of such areas
Numerical study of the scaling properties of SU(2) lattice gauge theory in Palumbo non-compact regularization
In the framework of a non-compact lattice regularization of nonabelian gauge
theories we look, in the SU(2) case, for the scaling window through the
analysis of the ratio of two masses of hadronic states. In the two-dimensional
parameter space of the theory we find the region where the ratio is constant,
and equal to the one in the Wilson regularization. In the scaling region we
calculate the lattice spacing, finding it at least 20% larger than in the
Wilson case; therefore the simulated physical volume is larger.Comment: 24 pages, 7 figure
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