230 research outputs found
Environmental and energy assessment of municipal wastewater treatment plants in Italy and Romania: A comparative study
Municipal wastewater treatment plants (MWWTPs) are essential infrastructures in any
urban context, but they may be considered as a potential source of greenhouse gas (GHG) emissions
and should be coherent with European Union (EU) policy on energy eciency. This study presents
a sustainability evaluation of four Italian and Romanian MWWTPs in terms of energy eciency
and greenhouse gas emissions using Energy Performance and Carbon Emissions Assessment and
Monitoring (ECAM) tool software. The obtained results indicated that biogas recovery improved
energy performances, while the largest contributions in terms of GHG emissions were in all cases
caused by energy consumption and methane produced during wastewater treatment. The Romanian
plants exhibited higher GHG emissions, compared to the Italian plants, mainly because of the
dierent values of national conversion factors for grid electricity (0.41 kg CO2/kWh for Italy and
1.07 kg CO2/kWh for Romania). Two scenarios aimed at enhancing the overall sustainability were
hypothesized, based on increasing the serviced population or energy eciency, achieving significant
improvements. A sustainability assessment of MWWTPs should be adopted as a useful tool to help
water utilities to introduce low-energy, low-carbon management practices as well as being useful for
policy recommendations
Water footprint assessment in North Eastern region of Romania: A case study for Iasi County, Romania
Many factors affect the water consumption pattern such as growing world population, climate changes, industrial and agricultural practices, etc. The present study provides for the first time a year-to-year analysis of water use for agricultural production, domestic water supply and industrial production from a hydrological, economical and ecological perspective in the NE region of Romania. Such an assessment can provide information to facilitate an efficient allocation of water resources to different economic and environmental demands. This assessment is also considering the general economic and social context of the Iasi county as an important area within north-eastern region of Romania. In the Iasi county, the green component takes the largest share in the total water footprint of crops because of the irrigation underdeveloped infrastructure, which makes the agricultural sector vulnerable to dry periods and floods as well. A monthly comparison between the blue water footprint and blue water availability shows that water scarcity varies greatly within the year, but also between years
Environmental performance evaluation of a drinking water treatment plant: A life cycle assessment perspective
Drinking water treatment aims to avoid or minimize some risks to human health and to provide adequate water quality by removing physical, chemical and biological contaminants. However, treatment processes require increasing efforts in terms of technology, chemicals and energy inputs, which generate increased secondary environmental impacts and added water production costs. The objective of this study is to evaluate the drinking water treatment plant (DWTP) in Iasi City (Romania) by life cycle assessment (LCA) and to identify and characterize its environmental impacts. Iasi DWTP involves the following scheme: pre-oxidation (chlorine dioxide), coagulation/flocculation, sedimentation, pH correction (calcium hydroxide), rapid sand filtration, granular activated carbon filtration and disinfection (chlorine gas). LCA was performed according to the ISO 14040 standard with the support of SimaPro 8.3. software and Eco-invent 3.3 data base. Life cycle impact assessment has been performed with Recipe 1.13. Midpoint method. The life cycle inventory included the construction and operational phases. The novelty of this study was to define two additional functional units related to removing contaminants besides the traditional 1 m3 of treated water. The main contributors to impact in most categories were: the electricity consumption (25 – 95% depending on impact category) and the ferric chloride used in coagulation/flocculation (35 – 100%, depending on impact category). Life cycle impact assessment showed that the lower the pollutant concentration, the higher the specific environmental impacts will be, which prompts for further detailed analysis of water treatment plant environmental performance in at least two directions: removal of emerging contaminants (present in very low concentrations) and a more detailed analysis on the individual performance of each treatment stage
Dislocation core field. II. Screw dislocation in iron
The dislocation core field, which comes in addition to the Volterra elastic
field, is studied for the screw dislocation in alpha-iron. This core
field, evidenced and characterized using ab initio calculations, corresponds to
a biaxial dilatation, which we modeled within the anisotropic linear
elasticity. We show that this core field needs to be considered when extracting
quantitative information from atomistic simulations, such as dislocation core
energies. Finally, we look at how dislocation properties are modified by this
core field, by studying the interaction between two dislocations composing a
dipole, as well as the interaction of a screw dislocation with a carbon atom
On the incompatibility of strains and its application to mesoscopic studies of plasticity
Structural transitions are invariably affected by lattice distortions. If the
body is to remain crack-free, the strain field cannot be arbitrary but has to
satisfy the Saint-Venant compatibility constraint. Equivalently, an
incompatibility constraint consistent with the actual dislocation network has
to be satisfied in media with dislocations. This constraint can be incorporated
into strain-based free energy functionals to study the influence of
dislocations on phase stability. We provide a systematic analysis of this
constraint in three dimensions and show how three incompatibility equations
accommodate an arbitrary dislocation density. This approach allows the internal
stress field to be calculated for an anisotropic material with spatially
inhomogeneous microstructure and distribution of dislocations by minimizing the
free energy. This is illustrated by calculating the stress field of an edge
dislocation and comparing it with that of an edge dislocation in an infinite
isotropic medium. We outline how this procedure can be utilized to study the
interaction of plasticity with polarization and magnetization.Comment: 6 pages, 2 figures; will appear in Phys. Rev.
Threshold Phenomena under Photo Excitation of Spin-crossover Materials with Cooperativity due to Elastic Interactions
Photo-induced switching from the low-spin state to the high-spin state is
studied in a model of spin-crossover materials, in which long-range
interactions are induced by elastic distortions due to different molecular
sizes the two spin states. At a threshold value of the light intensity we
observe nonequilibrium critical behavior corresponding to a mean-field spinodal
point. Finite-size scaling of the divergence of the relaxation time is revealed
by analysis of kinetic Monte Carlo simulations.Comment: 4 pages, 7 figure
Visual tool for estimating the fractal dimension of images
This work presents a new Visual Basic 6.0 application for estimating the
fractal dimension of images, based on an optimized version of the box-counting
algorithm. Following the attempt to separate the real information from noise,
we considered also the family of all band-pass filters with the same band-width
(specified as parameter). The fractal dimension can be thus represented as a
function of the pixel color code. The program was used for the study of
paintings cracks, as an additional tool which can help the critic to decide if
an artistic work is original or not. In its second version, the application was
extended for working also with csv files and three-dimensional images.Comment: A new version was accepted to Computer Physics Communications
doi:10.1016/j.cpc.2009.12.00
Realization of the mean-field universality class in spin-crossover materials
In spin-crossover materials, the volume of a molecule changes depending on
whether it is in the high-spin (HS) or low-spin (LS) state. This change causes
distortion of the lattice. Elastic interactions among these distortions play an
important role for the cooperative properties of spin-transition phenomena. We
find that the critical behavior caused by this elastic interaction belongs to
the mean-field universality class, in which the critical exponents for the
spontaneous magnetization and the susceptibility are and , respectively. Furthermore, the spin-spin correlation function is a
constant at long distances, and it does not show an exponential decay in
contrast to short-range models. The value of the correlation function at long
distances shows different size-dependences: , , and
constant for temperatures above, at, and below the critical temperature,
respectively. The model does not exhibit clusters, even near the critical
point. We also found that cluster growth is suppressed in the present model and
that there is no critical opalescence in the coexistence region. During the
relaxation process from a metastable state at the end of a hysteresis loop,
nucleation phenomena are not observed, and spatially uniform configurations are
maintained during the change of the fraction of HS and LS. These
characteristics of the mean-field model are expected to be found not only in
spin-crossover materials, but also generally in systems where elastic
distortion mediates the interaction among local states.Comment: 13 pages, 16 figure
Effects of Space Charge, Dopants, and Strain Fields on Surfaces and Grain Boundaries in YBCO Compounds
Statistical thermodynamical and kinetically-limited models are applied to
study the origin and evolution of space charges and band-bending effects at low
angle [001] tilt grain boundaries in YBaCuO and the effects of Ca
doping upon them. Atomistic simulations, using shell models of interatomic
forces, are used to calculate the energetics of various relevant point defects.
The intrinsic space charge profiles at ideal surfaces are calculated for two
limits of oxygen contents, i.e. YBaCuO and YBaCuO. At
one limit, O, the system is an insulator, while at O, a metal. This is
analogous to the intrinsic and doping cases of semiconductors. The site
selections for doping calcium and creating holes are also investigated by
calculating the heat of solution. In a continuum treatment, the volume of
formation of doping calcium at Y-sites is computed. It is then applied to study
the segregation of calcium ions to grain boundaries in the Y-123 compound. The
influences of the segregation of calcium ions on space charge profiles are
finally studied to provide one guide for understanding the improvement of
transport properties by doping calcium at grain boundaries in Y-123 compound.Comment: 13 pages, 5 figure
- …