Simulación de procesos de forja axisimétrica mediante el método de los elementos finitos: un modelo sencillo de rozamiento

Se presenta en este artículo un método sencillo de modelización del r.ozamiento en la simulación de procesos de forja axisimétrica mediante el Método de los Elementos Finitos (MEF). Tras una breve descripción de la formulación básica de flujo, se revisan las alternativas inás comunes para la consideración del fenómeno del rozamiento y se describe el método SMM (Stiffness Matrix Method), utilizado para tener en cuenta la fricción. Se presenta finalmente un ejemplo industrial que muestra el buen comportamiento de dicho método aplicado a la formulación de flujo.Peer Reviewe

Simulación de procesos de forja axisimétrica mediante el método de los elementos finitos: un modelo sencillo de rozamiento

Se presenta en este artículo un método sencillo de modelización del r.ozamiento en la simulación de procesos de forja axisimétrica mediante el Método de los Elementos Finitos (MEF). Tras una breve descripción de la formulación básica de flujo, se revisan las alternativas inás comunes para la consideración del fenómeno del rozamiento y se describe el método SMM (Stiffness Matrix Method), utilizado para tener en cuenta la fricción. Se presenta finalmente un ejemplo industrial que muestra el buen comportamiento de dicho método aplicado a la formulación de flujo.Peer Reviewe

Neural Improvement Heuristics for Graph Combinatorial Optimization Problems

Recent advances in graph neural network architectures and increased computation power have revolutionized the field of combinatorial optimization (CO). Among the proposed models for CO problems, Neural Improvement (NI) models have been particularly successful. However, existing NI approaches are limited in their applicability to problems where crucial information is encoded in the edges, as they only consider node features and node-wise positional encodings. To overcome this limitation, we introduce a novel NI model capable of handling graph-based problems where information is encoded in the nodes, edges, or both. The presented model serves as a fundamental component for hill-climbing-based algorithms that guide the selection of neighborhood operations for each iteration. Conducted experiments demonstrate that the proposed model can recommend neighborhood operations that outperform conventional versions for the Preference Ranking Problem with a performance in the 99th percentile. We also extend the proposal to two well-known problems: the Traveling Salesman Problem and the Graph Partitioning Problem, recommending operations in the 98th and 97th percentile, respectively

A new accounting framework for assessing forest footprint of nations

n a tele-coupled and globalized World, understanding the links between demand for wood products and land use is becoming challenging. World's economies are increasingly open and interconnected, and international trade flows of wood products are continuously growing. The increasing resource consumption of humanity is increasingly dependent on international trade. In this context, the study of forest products demand from a global-multi-regional perspective emerges as a critical issue to achieve the goal of sustainable consumption and production. In this paper, we introduce a novel accounting framework for assessing the forest footprint of nations. The method combines Multi-regional Input-Output techniques and detailed data from the Food and Agriculture Organization of the United Nations on production, consumption and bilateral trade of primary, intermediate and final wood products, advancing with respect to existing approaches with these practical distinctions for more accurate computations. The approach tracks resource flows along the global supply chain and provides detailed information on the production, transformation, international trade, and final use of 20 forest products in 223 countries, having also much wider coverage than most previous studies. We test this framework to analyse forest footprint of nations in the year 2014, showing that 22 Million hectares (Mha) of forest were harvested for the extraction of roundwood for global demand, being 9.1 Mha to satisfy the foreign demand of wood products (42% of the total forestland harvested area). Harvested forestland is concentrated in America (32%), Asia (29%) and Europe (28%), representing Africa (7%) and Oceania (4%). More than 50% of the reported forest area harvested worldwide is located in USA (15%), China (14%); Russia (11%) and Canada (8%). In terms of forest footprint, Asia shows the highest share of the total forest footprint (44%), followed by America (25%), Europe (21%), Africa (7%) and Oceania (2%). Country-wise, half is concentrated in China (24%), USA (16%), India (5%), and Russia (5%).This article was developed under Letter of Agreement between the Food and Agriculture Organization of the United Nations (FAO, UN-REDD Programme) and the Basque Centre for Climate Change (BC3). The authors thank the staff of the FAO and BC3 for their comments, discussions and suggestions on this report. We are especially grateful to Malgorzata Buszko-Briggs, Tina Vahanen and Caroline Merle (FAO Forestry Department) for their contribution to frame and coordinate the research, and to Salar Tayyib, Daniela Di Filippo, Tomasz Filipczuk (FAO Statistics Division) and Arvydas Lebedys (FAO Forestry Department) for providing datasets and for their discussions and comments on data and methodological issues. The authors also thank the support of the Spanish Ministry of Science, Innovation, and Universities, through the project MALCON, RTI 2018-099858-A-I00, the Spanish State Research Agency through María de Maeztu Excellence Unit accreditation 2018–2022 (Ref. MDM-2017-0714), funded by MCIN/AEI/10.13039/501100011033, the Basque Government BERC 2018-2021 Programme, and the EU H2020 project LOCOMOTION GA no 821105

Land cover effects on hydrologic services under a precipitation gradient

Climate change impacts on the hydrological cycle are altering the quantity, quality, and temporal distribution of riverine discharge, necessitating a more rigorous consideration of changes in land cover and land use. This study establishes relationships between different land cover combinations (e.g. percentages of forest – both native and exotic – and pastureland) and hydrological services, using hydrological indices estimated at annual and seasonal timescales in an area with a steep precipitation gradient (900–2600&thinsp;mm&thinsp;yr−1). Using discharge data from 20 catchments in the Bay of Biscay, a climate transition zone, the study applied multiple regression models to better understand how the interaction between precipitation and land cover combinations influence hydrological services. Findings showed the relationship between land cover combinations and hydrological services is highly dependent on the amount of precipitation, even in a climatically homogeneous and relatively small area. In general, in the Bay of Biscay area, the greater presence of any type of forests is associated with lower annual water resources, especially with greater percentages of exotic plantations and high annual precipitation. Where precipitation is low, forests show more potential to reduce annual and winter high flows than pasturelands, but this potential decreases as annual or seasonal precipitation increases. As annual precipitation increases, low flows increase as the percentage of exotic plantations decreases and pasturelands increase. Results obtained in this study improve understanding of the multiple effects of land cover on hydrological services, and illustrate the relevance of land planning to the management of water resources, especially under a climate change scenario.</p

Arbuscular mycorrhizal fungi (AMF) as bioprotector agents against wilt induced by Verticillium spp. in pepper.

Verticillium dahliae Kleb. is a vascular pathogen that alters water status and growth of pepper plants and causes drastic reductions in yield. Its control is difficult because it can survive in field soil for several years. The application of arbuscular mycorrhizal fungi (AMF) as bioprotector agents against V. dahliae is an alternative to the use of chemicals which, in addition, is more respectful with the environment. The establishment of the mutualistic association of plant roots and AMF involves a continuous cellular and molecular dialogue between both symbionts that includes the preactivation of plant defense responses that may enhance the resistance or tolerance of mycorrhizal plants to soil-borne pathogens. Some AMF can improve the resistance of Capsicum annuum L. against V. dahliae. This is especially relevant for pepper cultivars (i.e. cv. Piquillo) that exhibit high susceptibility to this pathogen. Compared with non-mycorrhizal plants, mycorrhizal pepper can exhibit more balanced antioxidant metabolism in leaves along the first month after pathogen inoculation, which may contribute to delay both the development of disease symptoms and the decrease of photosynthesis in Verticillium-inoculated plants with the subsequent benefit for yield. In stems, mycorrhizal pepper show earlier and higher deposition of lignin in xylem vessels than nonmycorrhizal plants, even in absence of the pathogen. Moreover, AMF can induce new isoforms of acidic chitinases and superoxide dismutase in roots. Mycorrhizal-specific induction of these enzymatic activities together with enhanced peroxidase and phenylalanine ammonia-lyase in roots may also be involved in the bioprotection of Verticillium-induced wilt in pepper by AM

The resurgence of commons and the governance of traditional commons systems at risk: The case of Enirio-Aralar

The study of commons has resurged vigorously. In this context the analysis of traditional grazing commons whose governance is subject to great challenges associated with changing socio-economic conditions and the co-existence of multiple uses is of particular interest. In this article we analyze the case of Eniriro-Aralar Community (Gipuzkoa, Basque Country), where a strong socio-ecological conflict emerged due to the multiple uses that co-exist in the area and the governance of its traditional common systems. The study shows that the subsistence of the area as a common will depend in the adaptive capacity of the community to the increasing intervention of European and regional institutions in rural planning and the satisfaction of new social demands.Esta investigación ha sido financiada mediante el proyecto del MINECO AGL2013-48361-C2-1-R

Connectivity, neutral theories and the assessment of species vulnerability to global change in temperate estuaries

One of the main adaptation strategies to global change scenarios, aiming to preserve ecosystem functioning and biodiversity, is to maximise ecosystem resilience. The resilience of a species metapopulation can be improved by facilitating connectivity between local populations, which will prevent demographic stochasticity and inbreeding. The objective of this investigation is to estimate the degree of connectivity among estuarine species along the north-eastern Iberian coast, in order to assess community vulnerability to global change scenarios. To address this objective, two connectivity proxy types have been used based upon genetic and ecological drift processes: 1) DNA markers for the bivalve cockle (Cerastoderma edule) and seagrass Zostera noltei, and 2) the decrease in the number of species shared between two sites with geographic distance; neutral biodiversity theory predicts that dispersal limitation modulates this decrease, and this has been explored in estuarine plants and macroinvertebrates. Results indicate dispersal limitation for both saltmarsh plants and seagrass beds community and Z. noltei populations; this suggests they are especially vulnerable to expected climate changes on their habitats. In contrast, unstructured spatial pattern found in macroinvertebrate communities and in C. edule genetic populations in the area suggests that estuarine soft-bottom macroinvertebrates with planktonic larval dispersal strategies may have a high resilience capacity to moderate changes within their habitats. Our findings can help environmental managers to prioritise the most vulnerable species and habitats to be restored

Zr-metal adhesion on graphenic nanostructures

3 pages, 3 figures.-- PACS nrs.: 68.35.Np, 61.46.Fg, 61.46.Df.Our high resolution transmission electronic microscopy studies of multiwall carbon nanotubes show, after the growth of zirconia nanoparticles by a hydrothermal route, the presence of surface Zr, forming an atomically thin layer. Using first-principles calculations we investigate the nature of the Zr–C interaction, which is neither ionic nor covalent, and the optimal coverage for the Zr metal in a graphene flake. This preferred coverage is in agreement with that deduced from electron energy loss spectra experiments. We show also that the amount of charge transferred to the C layer saturates as the Zr coverage increases and the Zr–C bond becomes weaker.We want to acknowledge the support by the ETORTEK (NANOMAT) program of the Basque government, the Intramural Special Project (Reference No. 2006601242), the Spanish Ministerio de Ciencia y Tecnología (MCyT) of Spain (Grant No. Fis 2007-66711-C02-C01), and the European Network of Excellence NANOQUANTA (NM4-CT-2004-500198). Y.S.P. gratefully acknowledges his DIPC grant.Peer reviewe

Pearl millet growth and biochemical alterations determined by mycorrhizal inoculation, water availability and atmospheric CO2 concentration

Pearl millet (Pennisetum glaucum L.) is an important fodder and is a potential feedstock for fuel ethanol production in dry areas. Our objectives were to assess the effect of elevated CO2 and/or reduced irrigation on biomass production and levels of sugars and proteins in leaves of pearl millet and to test whether mycorrhizal inoculation could modulate the effects of these abiotic factors on growth and metabolism. Results showed that mycorrhizal inoculation and water regime most influenced biomass of shoots and roots; however, their individual effects were dependent on the atmospheric CO2 concentration. At ambient CO2, mycorrhizal inoculation helped to alleviate effects of water deficit on pearl millet without significant decreases in biomass production, which contrasted with the low biomass of mycorrhizal plants under restricted irrigation and elevated CO2. Mycorrhizal inoculation enhanced water content in shoots, whereas reduced irrigation decreased water content in roots. The triple interaction between CO2, arbuscular mycorrhizal fungi (AMF) and water regime significantly affected the total amount of soluble sugars and determined the predominant soluble sugars in leaves. Under optimal irrigation, elevated CO2 increased the proportion of hexoses in pearl millet that was not inoculated with AMF, thus improving the quality of this plant material for bioethanol production. By contrast, elevated CO2 decreased the levels of proteins in leaves, thus limiting the quality of pearl millet as fodder and primary source for cattle feed