On the stability of Hamiltonian relative equilibria with non-trivial isotropy

We consider Hamiltonian systems with symmetry, and relative equilibria with isotropy subgroup of positive dimension. The stability of such relative equilibria has been studied by Ortega and Ratiu and by Lerman and Singer. In both papers the authors give sufficient conditions for stability which require first determining a splitting of a subspace of the Lie algebra of the symmetry group, with different splittings giving different criteria. In this note we remove this splitting construction and so provide a more general and more easily computed criterion for stability. The result is also extended to apply to systems whose momentum map is not coadjoint equivariant

Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization

Context. The knowledge of abundance distributions is central to understanding the formation and evolution of galaxies. Most of the relations employed for the derivation of gas abundances have so far been derived from observations of outer disk HII regions, despite the known differences between inner and outer regions. Aims. Using integral field spectroscopy (IFS) observations we aim to perform a systematic study and comparison of two inner and outer HII regions samples. The spatial resolution of the IFS, the number of objects and the homogeneity and coherence of the observations allow a complete characterization of the main observational properties and differences of the regions. Methods. We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII regions, all of them detected and extracted from the observations of a sample of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey. Results. We find that inner HII regions show smaller equivalent widths, greater extinction and luminosities, along with greater values of [NII]{\lambda}6583/H{\alpha} and [OII]{\lambda}3727/[OIII]{\lambda}5007 emission-line ratios, indicating higher metallicites and lower ionization parameters. Inner regions have also redder colors and higher photometric and ionizing masses, although Mion/Mphot is slighty higher for the outer regions. Conclusions. This work shows important observational differences between inner and outer HII regions in star forming galaxies not previously studied in detail. These differences indicate that inner regions have more evolved stellar populations and are in a later evolution state with respect to outer regions, which goes in line with the inside-out galaxy formation paradigm.Comment: 16 page

Integrated and interactive 4D system for archaeological stratigraphy

The digitization of some of the processes carried out in an archaeological excavation is changing the way of working at the site. Today, new technologies coexist with traditional methodologies. The study of stratigraphy can combine drawings of profiles and plans, the Harris Matrix diagram, as well as digitized files that perform a complete record of the stratigraphic sequence. However, this information is usually unaggregated from the rest of the information system that makes up the archaeological record. In this paper, we present an integrated software tool and the associated methodology to record, store, visualize and analyze the 3D stratigraphy of a site. The implementation uses spatial databases to store information of a heterogeneous nature and game engines for the visualization and interaction with this information. During the excavation process, the strata are scanned using the Tof technology, which is available in many smartphones. The resulting 3D model of the stratum, once uploaded to the software system, allows us to visualize the sequence of strata incorporating the findings into their original arrangement. Some additional tools, such as the scrollbar, help to perform a temporal analysis of the site. The result is a 4D interactive stratigraphy tool, which together with the Harris Matrix, complements the archaeological record and facilitates the work to archaeologists. This methodology also allows to speed up the on-site work and the subsequent analysis, while improving the user experience with the 3D archaeological site replica.CRUE-CSICSpringer NatureSpanish GovernmentEuropean Commission TIN2017-84968-

Integrated and interactive 4D system for archaeological stratigraphy

The digitization of some of the processes carried out in an archaeological excavation is changing the way of working at the site. Today, new technologies coexist with traditional methodologies. The study of stratigraphy can combine drawings of profiles and plans, the Harris Matrix diagram, as well as digitized files that perform a complete record of the stratigraphic sequence. However, this information is usually unaggregated from the rest of the information system that makes up the archaeological record. In this paper we present an integrated software tool and the associated methodology to record, store, visualize and analyze the 3D stratigraphy of a site. The implementation uses spatial databases to store information of a heterogeneous nature and game engines for the visualization and interaction with this information. During the excavation process, the strata are scanned using the Tof technology, which is available in many smartphones. The resulting 3D model of the stratum, once uploaded to the software system, allows us to visualize the sequence of strata incorporating the findings into their original arrangement. Some additional tools, such as the scrollbar, help to perform a temporal analysis of the site. The result is a 4D interactive stratigraphy tool, which together with the Harris Matrix, complements the archaeological record and facilitates the work to archaeologists. This methodology also allows to speed up the on-site work and the subsequent analysis, while improving the user experience with the 3D archaeological site replica.Ministerio de Economía y Competitividad (Fondos FEDER). Proyecto TIN2017-84968-

Fire ignition patterns to manage prescribed fire behavior: Application to Mediterranean pine forests

Climate change and the accumulation of surface fuel are leading to global changes in the occurrence of increasingly severe fires. In light of current budgetary constraints, prescribed fire can be a very cost-efficient tool for both reducing wildfire hazards and managing fire-prone landscapes. However, despite its widespread use in some countries, social and administrative constraints arise when applied at the European or larger scales. Science-based knowledge concerning fire behavior, fuel load reduction, and tree impacts is required to support the use of prescribed fire. Spatial ignition patterns can increase or decrease the spread rate, flame length, and flame residence time according to the objectives of a prescribed fire. This work aims to analyze fire behavior using different fire ignition patterns (strip-heading fire, flanking fire, and spot-heading fire) and meteorological and fuel conditions. Seventy-seven observations or sampling units using twenty-three prescribed fires were established for fire monitoring. Non-linear models based on environmental variables were fitted for the spread rate and flame length. Our study proposes a novel way of sharing scientific knowledge in relation to the most common distances between ignition lines and ignition points used in the southern Iberian Peninsula. The spread rate and flame length can be increased in strip-heading fire, by more than 3.5-fold and more than 1.95-fold, respectively, by modifying only the distance between ignition lines. Flanking fire could lead to a decrease in the spread rate by approximately half. Although spot-heading fire can reduce the spread rate by more than 78% and flame length by more than 41%, the highest distances between points could increase the flame residence time by 39–132%. This research seeks to achieve a trade-off between fire intensity and the impacts of fire on trees, soil, and surface roots

Does intensification result in higher efficiency and sustainability? An emergy analysis of Mediterranean sheep-crop farming systems

The embodiment of resources in agricultural products depends on the way they are made, i.e., the production system. We applied emergy analysis on three contrasting sheep-crop farming systems according to different degrees of specialization, integration and intensification of production in Mediterranean Spain. We studied emergy flows, transformity values and emergy indices at the system level and per product (lamb meat; permanent crops: rainfed olive and almond; arable crops: rainfed barley, irrigated barley, alfalfa and sunflower). We found that the specialized pasture-based sheep system had the lowest intensity and efficiency and the highest sustainability, as opposite to the partially-integrated mixed system, while the fully-integrated mixed system obtained a balanced position. Lamb meat production was 1.9 and 1.3 times more intensive and efficient, respectively, in the partially-integrated mixed system than in the pasture-based sheep system, but 5.1 times less sustainable. All sheep sub-systems had comparatively lower intensity and higher sustainability than crops due to their higher capacity to use local and renewable natural resources. Our findings suggest that further support of agricultural development based on local and renewable natural resources and best practices is necessary to ensure long-term farming sustainability and social welfare

MINLP-based hybrid strategy for operating mode selection of TES-backed-up refrigeration systems

This brief deals with the satisfaction of the daily cooling demand by a hybrid system that consists of a vapour-compression refrigeration cycle and a thermal energy storage (TES) unit, based on phase change materials. The addition of the TES tank to the original refrigeration plant allows to schedule the cooling production regardless of the instantaneous demand, given that the TES tank can store cold energy and release it whenever deemed appropriate. The scheduling problem is posed as an optimization problem based on mixed-integer non-linear programming (MINLP), since it includes both discrete and continuous variables. The latter corresponds to the references on the main cooling powers involved in the problem (cooling production at the evaporator and TES charging/discharging), whereas the discrete variables define the operating mode scheduling. Therefore, in addition to the hybrid features of the physical plant, a hybrid optimal control strategy is also proposed. A receding horizon approach is applied, similar to model predictive control (MPC) strategies, while economic criteria are imposed in the objective function, as well as feasibility issues. The TES state estimation is also addressed, since its instantaneous charge ratio is not measurable. The proposed strategy is applied in simulation to a challenging cooling demand profile and the main advantages of the MINLP-based strategy over a non-linear MPC-based scheduling strategy previously developed are highlighted, regarding operating cost, ease of tuning, and ability to adapt to cooling demand variations.Comment: 22 pages, 11 figures. Postprint of the final published wor

La construcción mediática de la comunidad política: la prensa en la transición española a la democracia

El artículo analiza el comportamiento y las actitudes adoptadas por la prensa española durante el primer periodo de la transición a la democracia (noviembre de 1975-diciembre de 1978), momento en el que se realizaron los cambios políticos e institucionales más relevantes del proceso. Desde diversas perspectivas se explica el papel que jugaron los principales periódicos, así como las razones que les llevaron al consenso en los temas fundamentales de discusión pública. De esta forma, se constata cómo los medios de comunicación colaboraron de forma decisiva en la construcción de una nueva comunidad política democrática. A través de varios ejemplos de diarios, tomados uno por uno y en conjunto, se explican las especiales características de este interesante caso de colaboración entre poder político y periodismo, incluyendo algunas excepciones como la prensa de extrema derecha y los sectores nacionalistas vascos