Method for optimization of statically determined articulated structures

Se ha desarrollado un algoritrr)o de programación matemática para el dimensionamiento óptimo de estructuras articuladas isostáticas. El algoritmo propuesto se caracteriza por: a) No requerir que la función objetivo o las ecuaciones de restricción sean derivables. b) Utilizan métodos de optimización unidimensionales para pasar de una solución dada a otra mejor, c) Introducir procedimientos aleatorios para obtener información que conduce a una solución mejor. Estas características lo hacen especialmente indicado para funciones no explícitas, costosas en su evaluación y con gran cantidad de mínimos relativos. Se ilustra el método con dos ejemplos de diseño óptimo de estructuras articuladas estáticamente determinadasAn algorithm of mathematical programmation for the optimum dis'fgn of iso-static articúlate structures has been developed. The characteristics of the proposed algorithm are: a) It not requires that the objective function or the restriction equations be derivable. b) They use unidimensional methods of unidimensional optimization ío pass over from a g/Ven so/ut/on to a better one. c) To introduce contingent procedures to obtain Information which leads to a better solution. Those characteristics make it specially recommended for non-explicit functions, costly in its evaluation with a great deal of relative mínimums. The method is explained by two exampies of óptima! design of statiscally determined articulated structure

Gamma distribution function to understand anaerobic digestion kinetics: Kinetic constants are not constant

The Gamma model is a novel approach to characterise the complex degradation dynamics taking place during anaerobic digestion. This three parameters model results from combining the first-order kinetic model and the Gamma distribution function. In contrast to conventional models, where the kinetic constant is considered invariant, the Gamma model allows analysing the variability of the kinetic constant using a probability density function. The kinetic constant of mono-digestion and co-digestion batch tests of different wastes were modelled using the Gamma model and two common first-order models: one-step one-fraction model and one-step two-fraction model. The Gamma distribution function approximates three distinct probability density functions, i.e. exponential, log-normal, and delta Dirac. Specifically, (i) cattle paunch and pig manure approximated a log-normal distribution; (ii) cattle manure and microalgae approximated an exponential distribution, and (iii) primary sludge and cellulose approximated a delta Dirac distribution. The Gamma model was able to characterise two distinct waste activated sludge, one approximated to a log-normal distribution and the other to an exponential distribution. The same cellulose was tested with two different inocula; in both tests, the Gamma distribution function approximated a delta Dirac function but with a different kinetic value. The potential and consistency of Gamma model were also evident when analysing pig manure and microalgae co-digestion batch tests since (i) the mean k of the co-digestion tests were within the values of the mono-digestion tests, and (ii) the profile of the density function transitioned from log-normal to exponential distribution as the percentage of microalgae in the mixture increased

FeAl and NbAl3 intermetallic- HVOF coatings: structure and properties

Transition metal aluminides in their coating form are currently being explored in terms of resistance to oxidation and mechanical behavior. This interest in transition metal aluminides is mainly due to the fact that their high Al content makes them attractive for high-temperature applications. This is also a reason to study their resistance to wear; they may be suitable for use in applications that produce a lot of wear in aggressive environments, thus replacing established coating materials. In this study, the microstructure, microhardness, and wear and oxidation performance of FeAl and NbAl3 coatings produced by highvelocity oxy-fuel spraying are evaluated with two main aims: (i) to compare these two coating systems¿a commonly studied aluminide (FeAl) and, NbAl3, an aluminide whose deposition by thermal spraying has not been attempted to date¿and (ii) to analyze the relationship between their microstructure, composition and properties, and so clarify their wear and oxidation mechanisms. In the present study, the higher hardness of niobium aluminide coatings did not correlate with a higher wear resistance and, finally, although pesting phenomena (disintegration in oxidizing environments) were already known of in bulk niobium aluminides, here their behavior in the coating form is examined. It was shown that such accelerated oxidation was inevitable with respect to the better resistance of FeAl, but further improvements are foreseen by addition of alloying elements in that alloy

Feasibility of using low pressure cold gas spray for the spraying of thick ceramic hydroxyapatite coatings

This article deals with the production of thick ceramic hydroxyapatite coatings obtained by Low Pressure Cold Gas Spray (LPCGS) system. Several factors such as powder microstructure, surface roughness and cold gas spray system are here discussed in the build‐up process. The use of nanocrystalline powder composed by fine agglomerates and needle‐like shape microstructure allows the realignment and compaction of individual crystallites to form thick deposits. In addition, the activation of the substrate surface results convenient for the first impinging particles anchored properly. Then, layer by layer, particles can remain attached leading to coating build‐up. Additionally, the use of low shock pressure as well as constant feeding system provided by LPCGS system lead to homogeneous coatings in comparison with High Pressure Cold Gas Spray (HPCGS) system. The successful coating build‐up has been achieved not only by the use of an agglomerated feedstock powder, but also by previous surface treatment and the use of the low pressure system. The obtaining of HA components by LPCGS is promising within biomedical field. An improvement of component strength is also suggested by means of thermomechanical analysis of the powder. The performance of a post heat‐treatment leads to an increase in HA strength, as well as crystal size

Ensayo sobre la vegetación rupícola basófila de la clase Aslenietea trichornanis en la provincia corológica bética

The rupicolous calcicoles communities of the Betica biogeographical province have been studied and compiled. Some combinations and synonymy are proposed and the alliance Campanulion velutinae and the associations Teucrio-Linarietum lilacinue, Saxifragetum composh and Anthyllido-Arenarietum ahracarensis are also described.Se hace un estudio y recopilación de las comunidades vegetales rupícolas basófilas de la provincia corológica Bética. En este contexto, se proponen algunas combinaciones y sinonimias y se describe la alianza Campanuliion relutinae y las asociaciones Teucrio- Linarietum lilacinue, Saxifragetum camposii y Anthyllido-Arenarietum alfacarensis

Climate change signal in the ocean circulation of the Tyrrhenian Sea

The Tyrrhenian Sea plays an important role in the winter deep water formation in the northwestern Mediterranean through the water that enters the Ligurian Sea via the Corsica Channel. Therefore, the study of the impact of the changes on the future climate on the Tyrrhenian circulation and its consequences represents an important issue. Furthermore, the seasonally dependent Tyrrhenian circulation, which is rich in dynamical mesoscale structures, is dominated by the interplay of local climate and the basin-wide Mediterranean circulation via the water transport across its major straits, and an adequate representation of its features represents an important modeling challenge. In this work we examine with a regionally coupled atmosphere–ocean model the changes in the Tyrrhenian circulation by the end of the 21st century under the RCP8.5 emission scenario, their driving mechanisms, and their possible impact on winter convection in the NW Mediterranean. Our model successfully reproduces the main features of the Mediterranean Sea and Tyrrhenian Basin present-day circulation. We find that toward the end of the century the winter cyclonic along-slope stream around the Tyrrhenian Basin becomes weaker. This weakening increases the wind work transferred to the mesoscale structures, which become more intense than at present in winter and summer. We also find that, in the future, the northward water transport across the Corsica Channel towards the Liguro-Provençal basin becomes smaller than today. Also, water that flows through this channel presents a stronger stratification because of a generalized warming with a freshening of upper and a saltening of intermediate waters. Both factors may contribute to the interruption of deep water formation in the Gulf of Lions by the end of the century

Genome diversity of marine phages recovered from Mediterranean metagenomes: Size matters

Marine viruses play a critical role not only in the global geochemical cycles but also in the biology and evolution of their hosts. Despite their importance, viral diversity remains underexplored mostly due to sampling and cultivation challenges. Direct sequencing approaches such as viromics has provided new insights into the marine viral world. As a complementary approach, we analysed 24 microbial metagenomes ( > 0.2 μm size range) obtained from six sites in the Mediterranean Sea that vary by depth, season and filter used to retrieve the fraction. Filter-size comparison showed a significant number of viral sequences that were retained on the larger-pore filters and were different from those found in the viral fraction from the same sample, indicating that some important viral information is missing using only assembly from viromes. Besides, we were able to describe 1,323 viral genomic fragments that were more than 10Kb in length, of which 36 represented complete viral genomes including some of them retrieved from a cross-assembly from different metagenomes. Host prediction based on sequence methods revealed new phage groups belonging to marine prokaryotes like SAR11, Cyanobacteria or SAR116. We also identified the first complete virophage from deep seawater and a new endemic clade of the recently discovered Marine group II Euryarchaeota virus. Furthermore, analysis of viral distribution using metagenomes and viromes indicated that most of the new phages were found exclusively in the Mediterranean Sea and some of them, mostly the ones recovered from deep metagenomes, do not recruit in any database probably indicating higher variability and endemicity in Mediterranean bathypelagic waters. Together these data provide the first detailed picture of genomic diversity, spatial and depth variations of viral communities within the Mediterranean Sea using metagenome assemblyThis work was supported by projects MEDIMAX BFPU2013-48007-P, VIREVO CGL2016- 76273-P [AEI/FEDER, EU], (cofunded with FEDER funds) and Acciones de dinaminación REDES DE EXCELENCIA CONSOLIDER CGL2015-71523- REDC, from the Spanish Ministerio de Economía y Competitividad; and project AQUAMET PROMETEOII/2014/012 from Generalitat Valenciana. JMHM was supported with a PhD fellowship from the Spanish Ministerio de Economía y Competitividad (BES-2014-067828). MLP was supported with a Postdoctoral fellowship from the Valencian Consellería de Educació, Investigació, Cultura i Esport (APOSTD/2016/051). RGS was supported with a Predoctoral fellowship from the Valencian Consellería de Educació Investigació, Cultura i Esport (ACIF/2016/050

The effect of hot treatment on composition and microstructure of HVOF iron aluminide coatings in Na2SO4 molten salts

The paper deals with the hot corrosion performance of FeAl base intermetallic HVOF coatings in molten Na2SO4 at 850 C in an isothermal process over the span of 45 h under static conditions. The test was validated with electron microscopy and compositional analyses in the cross-section area, as well as x-ray diffraction techniques. All the coatings were characterized by Al-depleted regions, intersplat oxidation and different stoichiometric ratios of iron aluminides. The results were discussed in relation to the formation of oxide scales on the surface after exposition to corrosive media, as well as heterogeneity and defects of the sprayed coatings. The Fe40Al (at.%) powder showed quite uniform phase distribution after spraying and preserved its integrity after corrosion test; the FeCr25% ? FeAl-TiAl-Al2O3 (wt.%) and Fe46Al-6.55Si (at.%) powders exhibited interface oxidation, with localized corrosion attacks proceeding through particle boundaries and microcrack networks with no evidence of Na and S penetration. FexAly alloys are susceptible to accelerated damage and decohesion of the coating, whereas the formation of sulfides is observed at certain points

Impact of food waste composition on acidogenic co-fermentation with waste activated sludge

The impact of food waste (FW) composition on co-fermentation performance was studied to elucidate if adjusting FW composition can be used to drive the fermentation yield and profile, which is relevant for biorefinery applications. First, the impact of individual FW components (i.e., fruit, vegetables, pasta, rice, meat, fish, and cellulose) was assessed. Subsequently, the effect of mixing a protein-rich component and a carbohydrate-rich component was studied (i.e., fish/fruit and fish/cellulose, and meat/rice and meat/vegetable). All experiments were carried out in mesophilic batch assays using waste activated sludge (WAS) as main substrate, the same mixture ratio (70 % WAS +30 % FW on VS basis), and no pH control. Results showed that each FW component had a distinct effect on VFA yield and profile, with protein-rich components reaching the highest VFA yields; 502 and 442 mgCOD/gVS for WAS/Fish and WAS/Meat, respectively. A positive interaction on VFA yield was observed when mixing a protein-rich and a carbohydrate-rich component. This interaction was not proportional to the co-substrates proportion in the mixtures. On the other hand, the VFA profile was clearly driven by the components in the mixture, including both WAS and FW composition. Overall, these results indicate that predicting the VFA yield of WAS/FW co-fermentation is not just related to FW composition, but FW composition could be used to adjust the VFA profile to a certain extent

Surface and Intermediate Water Changes Triggering the Future Collapse of Deep Water Formation in the North Western Mediterranean

Deep water formation (DWF) in the North Western Mediterranean (NWMed) is a key feature of Mediterranean overturning circulation. DWF changes under global warming may have an impact on the Mediterranean biogeochemistry and marine ecosystem. Here we analyze the deep convection in the Gulf of Lions (GoL) in a changing climate using a regional climate system model with a horizontal resolution high enough to represent DWF. We find that under the RCP8.5 scenario the NWMed DWF collapses by 2040–2050, leading to a 92% shoaling in the winter mixed layer by the end of the century. The collapse is related to a strengthening of the vertical stratification in the GoL caused by changes in properties of Modified Atlantic Water and Levantine Intermediate Water, being their relative contribution to the increase of the stratification 57.8% and 42.2%, respectively. The stratification changes also alter the Mediterranean overturning circulation and the exchange with the Atlantic