9,924 research outputs found
Non-ergodic states induced by impurity levels in quantum spin chains
The semi-infinite XY spin chain with an impurity at the boundary has been
chosen as a prototype of interacting many-body systems to test for non-ergodic
behavior. The model is exactly solvable in analytic way in the thermodynamic
limit, where energy eigenstates and the spectrum are obtained in closed form.
In addition of a continuous band, localized states may split off from the
continuum, for some values of the impurity parameters. In the next step, after
the preparation of an arbitrary non-equilibrium state, we observe the time
evolution of the site magnetization. Relaxation properties are described by the
long-time behavior, which is estimated using the stationary phase method.
Absence of localized states defines an ergodic region in parameter space, where
the system relaxes to a homogeneous magnetization. Out of this region, impurity
levels split from the band, and localization phenomena may lead to
non-ergodicity.Comment: 10 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1703.0344
Long-term assessment of the effectiveness of coastal protection regulations in conserving natural habitats in Spain
Spain has undergone rapid socioeconomic development in the past three decades. This has been linked to massive residential and infrastructural development based on a short-term, profitable and resource-intensive consuming model. As a result, large amounts of agricultural, natural and semi-natural soils have been lost to artificial areas, especially around main cities and on the coast. In this study, we assessed the effectiveness of the Spanish Shores Act at preventing land development in two biogeographical regions and three administrative scales between 1988 and 2020 using a BACI design and remote sensing data. We also analysed the combined effect of other regulations to prevent land development on the coast. The Shores Act was effective in reducing land development although moderate to substantial land development occurred in the zones affected by the Law, especially in the Mediterranean region. Adding other sectoral regulations to the Shores Act notably and consistently reduced land development across regions. Among them, cumulative protected area (PA) regulations were most effective in reducing coastal land development. The use of satellite images, especially Sentinel 2A MSI data within a BACI design, proved a useful method for assessing the effectiveness of fine-scale objectives of environmental policies such as the Shores Act.Funding for open access charge: Universidad de Málaga / CBU
Multi-criteria analysis to determine the most appropriate fuel composition in an ammonia/diesel oil dual fuel engine
[Abstract] The possibility to employ alternative fuels is gaining special interest in the marine sector. There are several suitable candidates for traditional fossil fuels substitution. Among them, ammonia is a promising solution that allows progress on decarbonization since the ammonia molecule does not contain carbon. Hence, the present work analyzes the use of ammonia as a potential fuel for a marine engine. Particularly, a dual fuel mode ammonia/diesel oil operation is proposed. As expected, the carbon dioxide emissions are reduced as the proportion of ammonia is increased. Nevertheless, other non-desirable substances are generated such as non-reacted ammonia, NOx and N2O. Due to these opposing effects, a multi-criteria analysis is proposed to characterize the most appropriate proportion of ammonia in the fuel. The environmental damage of the different pollutants was considered. Due to the important environmental adverse effects of NOx and N2O, only a maximum 20% ammonia percentage on the fuel was obtained as the most appropriate option. A higher ammonia content leads to excessive concentrations of NOx and N2O being emitted to the environment
Possibilities of Ammonia as Both Fuel and NOᵪ Reductant in Marine Engines: A Numerical Study
[Abstract] Nowadays, the environmental impact of shipping constitutes an important challenge. In order to achieve climate neutrality as soon as possible, an important priority consists of progressing on the decarbonization of marine fuels. Free-carbon fuels, used as single fuel or in a dual-fuel mode, are gaining special interest for marine engines. A dual fuel ammonia-diesel operation is proposed in which ammonia is introduced with the intake air. According to this, the present work analyzes the possibilities of ammonia in marine diesel engines. Several ammonia-diesel proportions were analyzed, and it was found that when the proportion of ammonia is increased, important reductions of carbon dioxide, carbon monoxide, and unburnt hydrocarbons are obtained, but at the expense of increments of oxides of nitrogen (NOᵪ), which are only low when too small or too large proportions of
ammonia are employed. In order to reduce NOᵪ too, a second ammonia injection along the expansion stroke is proposed. This measure leads to important NOᵪ reductions
Interaction Effects on the Magneto-optical Response of Magnetoplasmonic Dimers
The effect that dipole-dipole interactions have on the magneto-optical (MO)
properties of magnetoplasmonic dimers is theoretically studied. The specific
plasmonic versus magnetoplasmonic nature of the dimer's metallic components and
their specific location within the dimer plays a crucial role on the
determination of these properties. We find that it is possible to generate an
induced MO activity in a purely plasmonic component, even larger than that of
the MO one, therefore dominating the overall MO spectral dependence of the
system. Adequate stacking of these components may allow obtaining, for specific
spectral regions, larger MO activities in systems with reduced amount of MO
metal and therefore with lower optical losses. Theoretical results are
contrasted and confirmed with experiments for selected structures
Proposals of a procedure to asses Pollutographs. Application to Murcia's Combined Sewer Overflows (CSOs). PĂłster
Directives 91/271/EEC and 93/481/EEC set norms regarding the management of Combined Sewer
Overflows. European Commission monitors the implementation status and implementation programmes. In
fact, during the year 2019 all the utilities should be able to quantify the pollution spilled during storm events.
And afterwards, plans have to be developed in order to reduce the impact of such events. In this paper, we
proposed a method to estimate the transported pollution during events as well as to serve as a tool for
developing plans to lessen the corresponding pollution.
The procedure is divided into three steps:
A. Periodical measurements of all relevant pollutants, e.g. total suspended solids and chemical oxygen
demand, in wet and dry weather. Such pollutant “concentrations” are correlated with the turbidity, updating
the relation among them [1].
B. Continuous measures of the turbidity. Turbidity is continously register in the sewer areas near overflow
spillways. Turbidimeters are a very convenient equipment for this purpose [2]. Actually, it is reliable, its
measures are very correlated with the total suspended solid concentration and its maintenance is easy. In this
way, combining A. and B. turbidity measures provide us a real-time estimation of the pollutant concentration.
on real time.
C. Assesment of each catchment hydrograph. Depending on the available data, this step could be based on a
design, a measured or a simulated hydrograph. In order to apply this methodology to Murcia’s Combined
Sewer System, we have used simulated hydrographs based on real measured rainfall. Murcia’s utility has
developed a calibrated SWMM model, and therefore, using the rainfall data, it is possible to estimate
hydrographs for all the relevant points of the system.
D. Estimation of each catchment pollutograph. Combining the pollutant concentration, estimated in the
previous steps, with the hydrographs, we can asses how the mass of pollutants are transported. This
information allows us to comply with EU Directives, but it will also be useful to design Murcia’s strategy to
minimize environmental impacts
Evaluating energy recovery potential in Murcia's water supply system
Murcia is the 7th most populated city in Spain. Its water supply system is extensively monitored through a
large number of pressure gauges and flow meters. Murcia’s water supply network is fed from distribution
reservoirs at enough elevation to avoid needing pumping stations for most of the city districts. Hydraulic
resources have been evaluated throughout the water supply system. Besides the pressure reducing valves,
where the assessment is quite straight forward [1], District Metered Areas (DMA) inlets have been evaluated.
In these areas despite the hydraulic resources are not as great as in pressure reducing valves locations, their
location is quite convenient. Actually, these positions are located inside the city, therefore making easy to use
the produced energy in municipal self consumption or to provide facilities to the citizens.
In order to perform such evaluation, a detailed model of the water supply network has been implemented in
EPANET parting from a GIS model. The first step of the evaluation has consisted in the optimizing and
validation of the model. Initially, the model was reviewed by comparing pressure and flow rate
measurements in the main pipes. Then, an extensive experimental campaign was designed. In that campaign
valves were switched so that each day a set of District Metered Areas (DMA) have just one metered inlet or
at the most a very short number of metered inlets, whereas having a set of pressure measurements within the
DMA. The obtained data was used to minimize errors in pressure time series, optimising roughness of the
main pipes through Levenberg/Marquardt BFGS algorithm using EPANET ToolKit through Epanet-Octave
[2]. Important roughness proposed changes tended to be located surrounding particular points, where errors
in the GIS were located (mainly wrong diameter assignement). After patching all the errors the algorithm
eased to localise, model errors were mostly below measures uncertainty, and therefore, the model was
considered validated.
Then, the hydraulic potential at the DMAs inlets has been evaluated by tracking the “instantaneous”
minimum pressure and head within each DMA, as well as the flow rate entering the DMA. So that, the
maximum head and the range of flow rates is established for the turbine.
At the moment, once that all of these potentials have been assessed, a turbine prototype is being designed
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