1,722 research outputs found
Adopting a circular economy: Current practices and future perspectives
All scientists, researchers, and citizens are involved in achieving sustainable goals. Their current actions contribute to writing a story for future generations, and interesting perspectives can be narrated based only on a great sense of social responsibility. The literature gives a great deal of attention to the models of a Circular Economy (CE). This topic is multidisciplinary and different sectors are involved in its development. This Special Issue aims to underline the relevance of the CE models in the scientific field and its applications in real contexts in order to achieve sustainability goals
Estimating Central Bank preferences in a small open economy: Sweden 1995-2009
Interest Rate rules are often estimated as simple reaction functions linking the policy interest rate to variables such as (forecasted) inflation and the output gap; however, the coefficients estimated with this approach are convolutions of structural and preference parameters. I propose an approach to estimate Central Bank preferences starting from the Central Bank's optimization problem within a small open economy. When we consider open economies in a regime of Inflation Targeting, the issue of the role of the exchange rate in the Monetary Policy rule becomes relevant. The empirical analysis is conducted on Sweden, to verify whether the recent stabilization of the Krona/Euro exchange rate was due to âFear of Floatingâ; the results show that the exchange rate might not have played a role in monetary policy, suggesting that the stabilization probably occurred as a result of increased economic integration and business cycle convergence.Interest Rate Rules, Inflation Targeting, Central Bank Preferences, Fear of Floating.
A multicriteria analysis of photovoltaic systems: Energetic, environmental, and economic assessments
The development of photovoltaic (PV) energy has led to rising efficiencies, better reliability, and falling prices. A multicriteria analysis (MCA) of PV systems is proposed in this paper in order to evaluate the sustainability of alternative projects. The investigations are presented using multiple indicators: Energy Payback Time (EPBT), Energy Return on Investment (EROI), Greenhouse Gas per kilowatt-hour (GHG/kWh), Greenhouse Gas Payback Time (GPBT), Greenhouse Gas Return on Investment (GROI), Net Present Value (NPV), Discounted Payback Time (DPBT), and Discounted Aggregate Cost Benefit (D(B/C) A). PV energy is a relevant player in global electricity market and can have a key-role in sustainable growth
Consistent and transferrable coarse-grained model for semidilute polymer solutions in good solvent
We present a coarse-grained model for linear polymers with a tunable number
of effective atoms (blobs) per chain interacting by intra- and inter-molecular
potentials obtained at zero density. We show how this model is able to
accurately reproduce the universal properties of the underlying solution of
athermal linear chains at various levels of coarse-graining and in a range of
chain densities which can be widened by increasing the spatial resolution of
the multiblob representation, i.e., the number of blobs per chain. The present
model is unique in its ability to quantitatively predict thermodynamic and
large scale structural properties of polymer solutions deep in the semidilute
regime with a very limited computational effort, overcoming most of the
problems related to the simulations of semidilute polymer solutions in good
solvent conditions.Comment: 19 pages, 15 figures, 3 table
Future trajectories of renewable energy consumption in the European Union
Renewable energy sources (RESs) are able to reduce the European Union (EU)âs dependence
on foreign energy imports, also meeting sustainable objectives to tackle climate change and to enhance
economic opportunities. Energy management requires a quantitative analysis and the European
Commission follows the performance of each Member State (MS) in order to define the corrective
measures towards 2020 targets. Starting from historical data reported in the Eurostat database and
through a mathematical model, this work proposes future trajectories towards 2020 of the share of
energy from renewables (REs) in terms of gross final energy consumption (GFEC). Furthermore,
a quantitative analysis based on two indicesâ(i) the share of REs in GFEC, and (ii) gross final
renewable energy consumption (GFREC) per capitaâpermits a comparison among 28 MSs. The share
of REs in GFEC in EU 28 varies from 19.4% to 21.8% in future trajectories towards 2020. Sweden and
Finland occupy the top part of the ranking, while six MSs (Belgium, France, Ireland, Luxembourg,
The Netherlands, and the United Kingdom) are not able to reach the 2020 targets
Depletion effects in colloid-polymer solutions
The surface tension, the adsorption, and the depletion thickness of polymers
close to a single nonadsorbing colloidal sphere are computed by means of Monte
Carlo simulations. We consider polymers under good-solvent conditions and in
the thermal crossover region between good-solvent and behavior. In the
dilute regime we consider a wide range of values of , from (planar
surface) up to -50, while in the semidilute regime, for
( is the polymer concentration and is
its value at overlap), we only consider and 2. The results are
compared with the available theoretical predictions, verifying the existing
scaling arguments. Field-theoretical results, both in the dilute and in the
semidilute regime, are in good agreement with the numerical estimates for
polymers under good-solvent conditions.Comment: 26 pages, 12 figure
Integral-equation analysis of single-site coarse-grained models for polymer-colloid mixtures
We discuss the reliability of integral-equation methods based on several
commonly used closure relations in determining the phase diagram of
coarse-grained models of soft-matter systems characterized by mutually
interacting soft and hard-core particles. Specifically, we consider a set of
potentials appropriate to describe a system of hard-sphere colloids and linear
homopolymers in good solvent, and investigate the behavior when the soft
particles are smaller than the colloids, which is the regime of validity of the
coarse-grained models. Using computer-simulation results as a benchmark, we
find that the hypernetted-chain approximation provides accurate estimates of
thermodynamics and structure in the colloid-gas phase in which the density of
colloids is small. On the other hand, all closures considered appear to be
unable to describe the behavior of the mixture in the colloid-liquid phase, as
they cease to converge at polymer densities significantly smaller than those at
the binodal. As a consequence, integral equations appear to be unable to
predict a quantitatively correct phase diagram.Comment: 16 pages, 11 figures, 3 table
Coarse-graining polymer solutions: a critical appraisal of single- and multi-site models
We critically discuss and review the general ideas behind single- and
multi-site coarse-grained (CG) models as applied to macromolecular solutions in
the dilute and semi-dilute regime. We first consider single-site models with
zero-density and density-dependent pair potentials. We highlight advantages and
limitations of each option in reproducing the thermodynamic behavior and the
large-scale structure of the underlying reference model. As a case study we
consider solutions of linear homopolymers in a solvent of variable quality.
Secondly, we extend the discussion to multi-component systems presenting, as a
test case, results for mixtures of colloids and polymers. Specifically, we
found the CG model with zero-density potentials to be unable to predict
fluid-fluid demixing in a reasonable range of densities for mixtures of
colloids and polymers of equal size. For larger colloids, the polymer volume
fractions at which phase separation occurs are largely overestimated. CG models
with density-dependent potentials are somewhat less accurate than models with
zero-density potentials in reproducing the thermodynamics of the system and,
although they presents a phase separation, they significantly underestimate the
polymer volume fractions along the binodal. Finally, we discuss a general
multi-site strategy, which is thermodynamically consistent and fully
transferable with the number of sites, and that allows us to overcome most of
the limitations discussed for single-site models.Comment: 23 pages, 9 figures, 4 table
Spatio-temporal spectral analysis of a forced cylinder wake
The wake of a circular cylinder performing rotary oscillations is studied
using hydrodynamic tunnel experiments at . Two-dimensional particle
image velocimetry on the mid-plane perpendicular to the axis of cylinder is
used to characterize the spatial development of the flow and its stability
properties. The lock-in phenomenon that determines the boundaries between
regions of the forcing parameter space were the wake is globally unstable or
convectively unstable is scrutinized using the experimental data. A novel
method based on the analysis of power density spectra of the flow allows us to
give a detailed description of the forced wake, shedding light on the energy
distribution in the different frequency components and in particular on a
cascade-like mechanism evidenced for a high amplitude of the forcing
oscillation. In addition, a calculation of the drag from the velocity field is
performed, allowing us to relate the resulting force on the body to the wake
properties.Comment: 8 pages, 8 figure
Centrifugal instability of Stokes layers in crossflow: the case of a forced cylinder wake
The wake flow around a circular cylinder at performing
rotatory oscillations has been thoroughly discussed in the literature, mostly
focusing on the modifications to the natural B\'enard-von K\'arm\'an vortex
street that result from the forced shedding modes locked to the rotatory
oscillation frequency. The usual experimental and theoretical frameworks at
these Reynolds numbers are quasi-two-dimensional, since the secondary
instabilities bringing a three-dimensional structure to the cylinder wake flow
occur only at higher Reynolds numbers. In the present paper we show that a
three-dimensional structure can appear below the usual three-dimensionalization
threshold, when forcing with frequencies lower than the natural vortex shedding
frequency, at high amplitudes, as a result of a previously unreported
mechanism: a pulsed centrifugal instability of the oscillating Stokes layer at
the wall of the cylinder. The present numerical investigation lets us in this
way propose a physical explanation for the turbulence-like features reported in
the recent experimental study of D'Adamo et al. (2011).Comment: 18 pages, 13 figures. To appear in Proc. Roy. Soc. A. For
supplementary video material, see http://vimeo.com/12315202
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