Comments on "nonlinear H-infinity output feedback control with integrator for polynomial discrete-time systems'

[EN] This note points out that controllers resulting from Corollaries 3.1 and 3.2 and Theorem 3.1 in Saat and Nguang (Int. J. Robust Nonlinear Control 2013; 10.1002/rnc.3130) do not improve over the open-loop performance.The research in this area has been supported by the Spanish Government (MINECO) under research project DPI2011-27845-C02-01.Sala, A.; Pitarch Pérez, JL. (2015). Comments on "nonlinear H-infinity output feedback control with integrator for polynomial discrete-time systems'. International Journal of Robust and Nonlinear Control. 25(15):2869-2870. https://doi.org/10.1002/rnc.3237S28692870251

Influence of the microstructure on the thermal shock behavior of cemented carbides

The influence of single and repetitive sudden changes of temperature on the mechanical integrity of cemented carbides was investigated as a function of their microstructure. Thermal shock resistance was assessed by testing the residual flexural strength of hardmetal beams after being subjected to thermal shock by water quenching. Results indicate that hard cemented carbides tend to exhibit a superior resistance to the nucleation of thermal shock damage but a lower resistance to the propagation of this damage mechanism than tough grades, and vice versa. These trends are in agreement with those expected from the evaluation of the thermal shock Hasselman’s parameters. The evidenced strength loss after thermal shock may be related to the subcritical growth of intrinsic flaws driven by localized microcracking surrounding them. Results also point out on Ni-base hardmetals to exhibit a slightly higher resistance to abrupt changes of temperature than Co-base ones.Peer ReviewedPostprint (author's final draft

Desarrollo de una plataforma para el análisis de Twitter

[ES] Vivimos en una época donde el flujo de datos ha aumentado exponencialmente, sobre todo con la llegada de las redes sociales las cuales han permitido que prácticamente toda la población mundial pueda compartir información u opiniones. Esta inmensa cantidad de datos dificulta contrastar la información más relevante haciendo paradójicamente, que estos pierdan visibilidad. Así pues, surge la necesidad de aplicar un filtro para que cada persona pueda ver la información que realmente le interese sin necesidad de indagar más de lo necesario. En el caso que nos ocupa, Twitter, no es una excepción. Esta red social dispone de millones de usuarios activos y como es obvio, se publica muchísima información por segundo. En este proyecto, se aborda la posibilidad de que el usuario visualice de una manera gráfica y rápida qué datos se están publicando sobre algún tema en específico. En concreto, el objetivo principal de este trabajo es la de contrastar la información recogida de Twitter y mostrarla de tal forma que el usuario emplee el tiempo justo en cubrir sus necesidades sobre algún tema de su interés y que esta experiencia le resulte más gratificante posible.[EN] We live in a time where the flow of data has increased exponentially, especially with the arrival of social networks, which have allowed practically the entire world population to share information or opinions. This immense amount of data makes it difficult to contrast the most relevant information, paradoxically causing them to lose visibility. Therefore, the need to apply a filter appears in order to let people see information that interests them without having to search more than necessary. In the present case, Twitter is not an exception. This social network has millions of active users and a lot of information is published per second. In this project, the possibility is addressed for the user to visualize in a graphic as a fast way what data is being published on a specific topic, concretely, the main objective of this task is to contrast the information collected from Twitter and display it in a way that the user employs only the necessary time to meet his needs on a topic of interest and make this experience as rewarding as possible.[CA] Vivim en una època on el flux de dades ha augmentat exponencialment, sobretot amb l'arribada de les xarxes socials les quals han permès que pràcticament tota la població mundial puga compartir informació o opinions. Aquesta immensa quantitat de dades dificulta contrastar la informació més rellevant fent paradoxalment, que aquestes perden visibilitat. Així doncs, sorgeix la necessitat d'aplicar un filtre perquè cada persona puga veure la informació que realment li interessa sense necessitat de indagar més del necessari. En el cas que ens ocupa, Twitter, no és una excepció. Aquesta xarxa social disposa de milions d'usuaris actius i com és obvi, es publica moltíssima informació per segon. En aquest projecte, s'aborda la possibilitat que l'usuari visualitze d'una manera gràfica i ràpida quines dades s'estan publicant sobre algun tema específic. En concret, l’objectiu principal d'aquest treball és la de contrastar la informació recollida de Twitter i mostrar-la de tal manera que l'usuari faça servir el temps just en cobrir les seves necessitats sobre algun tema del seu interès i que aquesta experiencia li resulte el més gratificant possible.Pitarch Miravete, JL. (2021). Desarrollo de una plataforma para el análisis de Twitter. Universitat Politècnica de València. http://hdl.handle.net/10251/172708TFG

Mechanics and mechanisms of fatigue in a WC-Ni hardmetal and a comparative study with respect to WC-Co hardmetals

There is a major interest in replacing cobalt binder in hardmetals (cemented carbides) aiming for materials with similar or even improved properties at a lower price. Nickel is one of the materials most commonly used as a binder alternative to cobalt in these metal-ceramic composites. However, knowledge on mechanical properties and particularly on fatigue behavior of Ni-base cemented carbides is relatively scarce. In this study, the fatigue mechanics and mechanisms of a fine grained WC-Ni grade is assessed. In doing so, fatigue crack growth (FCG) behavior and fatigue limit are determined, and the attained results are compared to corresponding fracture toughness and flexural strength. An analysis of the results within a fatigue mechanics framework permits to validate FCG threshold as the effective fracture toughness under cyclic loading. Experimentally determined data are then used to analyze the fatigue susceptibility of the studied material. It is found that the fatigue sensitivity of the WC-Ni hardmetal investigated is close to that previously reported for Co-base cemented carbides with alike binder mean free path. Additionally, fracture modes under stable and unstable crack growth conditions are inspected. It is evidenced that stable crack growth under cyclic loading within the nickel binder exhibit faceted, crystallographic features. This microscopic failure mode is rationalized on the basis of the comparable sizes of the cyclic plastic zone ahead of the crack tip and the characteristic microstructure length scale where fatigue degradation phenomena take place in hardmetals, i.e. the binder mean free path. (C) 2014 Elsevier Ltd. All rights reserved.Peer ReviewedPostprint (author’s final draft

Implementation of an effective time-saving two-stage methodology for microstructural characterization of cemented carbides

Linear intercept on scanning electron microscopy micrographs is the most commonly used measurement method to determine carbide grain size and contiguity in WC–Co cemented carbides (hardmetals). However, it involves manual time-consuming measurements and is critically dependent on the quality of the micrographs as well as on the identification and definition of grain boundaries. In this study a two-stage methodology for microstructural characterization of hardmetals is presented. First, a digital semi-automatic image analysis procedure for grain size determination of the carbide phase is presented. It involves an experimental assessment of grain size on processed images corresponding to a series of WC–Co and WC–Ni cemented carbide grades with different microstructural characteristics. Obtained results are then compared to the values obtained by means of the linear intercept technique. A good correlation between the mean grain sizes determined following both measurement techniques was attained. Based on experimental findings, a series of empirical relations were found to correlate grain size distributions obtained following both methods. Second, an empirical relation for estimating carbide contiguity in WC–Co cemented carbides is proposed. This relation considers simultaneously the influence of the binder content and the experimentally determined mean grain size on contiguity. The proposed equation for contiguity estimation is based on extensive data collection from open literature. An excellent agreement was attained between contiguity values estimated from such equation and those obtained using the linear intercept technique. This validates the two-stage procedure as an effective time-saving methodology for microstructural characterization of WC–Co cemented carbides.Peer ReviewedPostprint (author's final draft

Residual strength of WC-Co cemented carbides after being subjected to abrupt temperature changes

Thermal shock and thermal fatigue are recognized as common failure modes for WC - Co cemented carbides (hardmetals) in several applications in volving service temperature changes. However, information on microstructure - performance for these materials when subjected to abrupt changes in temper ature is rather limited. In this investigation, the thermal shock resistance of two WC - Co cemented carbides is studied on the basis of their residual strength after being subjected to temperature changes. The materials studied correspond to grades with dif ferent grain size (medium and ultrafine) but similar binder content. Thermal shock variables include two temperature difference ranges (400ºC and 550ºC) as well as number of abrupt changes (1, 3 and 10). Residual strength results were related to parameters extracted from Hasselman’s theory . It is found that medium - sized hardmetal exhibits a higher strength loss in the first quenching cycle but a greater damage tolerance to repeated thermal shocks than the ultrafine - sized. The assessed residual strength tren ds are in agreement with those expected from evaluation of Hasselman’s parameters for quantifying resistance to either crack initiation or crack propagation induced by thermal shockPostprint (published version

Optimization Alternatives for Robust Model-based Design of Synthetic Biological Circuits

[EN] Synthetic biology is reaching the situation where tuning devices by hand is no longer possible due to the complexity of the biological circuits being designed. Thus, mathematical models need to be used in order, not only to predict the behavior of the designed synthetic devices; but to help on the selection of the biological parts, i.e., guidelines for the experimental implementation. However, since uncertainties are inherent to biology, the desired dynamics for the circuit usually requires a trade-off among several goals. Hence, a multi-objective optimization design (MOOD) naturally arises to get a suitable parametrization (or range) of the required kinetic parameters to build a biological device with some desired properties. Biologists have classically addressed this problem by evaluating a set of random Monte Carlo simulations with parameters between an operation range. In this paper, We propose solving the MOOD by means of dynamic programming using both a global multi-objective evolutionary algorithm (MOLA) and a local gradient-based nonlinear programming (NLP) solver. The performance of both alternatives is then checked in the design of a well-known biological circuit: a genetic incoherent feed-forward loop showing adaptive behavior. (C) 2016, IFAC (International Federation of Antomatic Control) Hosting by Elsevier Ltd. All rights reserved.The research leading to these results has received funding from the European Union (FP7/2007-2013 under grant agreement no604068), the Spanish Government (FEDER-CICYT DPI2011-524 28112-C04-01, DPI2014-55276-C5-1-R, DPI2015-70975-P) and the National Council of Scientific and Technologic Development of Brazil (BJT-304804/2014-2). Yadira Boada thanks also grant FPI/2013-3242 of the Universitat Politecnica de ValenciaBoada-Acosta, YF.; Pitarch Pérez, JL.; Vignoni, A.; Reynoso Meza, G.; Picó, J. (2016). Optimization Alternatives for Robust Model-based Design of Synthetic Biological Circuits. IFAC-PapersOnLine. 49(7):821-826. https://doi.org/10.1016/j.ifacol.2016.07.291S82182649

Strength degradation of cemented carbides due to thermal shock

Despite the recognition of thermal shock and thermal fatigue as common failure modes in cemented carbide applications, the information on the influence of the microstructure on the resistance of hardmetals to abrupt temperature changes is rather scarce. In this paper, the strength behaviour of cemented carbides after severe thermal shock damage is investigated. In doing so, cemented carbides were subjected to thermal shock at two temperature ranges (¿T of 400ºC and 550ºC) and their retained strength evaluated as a measure of their thermal shock resistance. Residual strength results are then related to crack initiation (R) and propagation (R’’’’) Hasselman parameters. Results indicate that the finer the microstructure, the better the resistance to the nucleation of thermal shock damage of hardmetals. This strength trend is in accordance with higher R and lower R’’’’ parameters for the studied materials.Peer ReviewedPostprint (author's final draft

Intrinsic hardness of constitutive phases in WC-Co composites: Nanoindentation testing, statistical analysis, WC crystal orientation effects and flow stress for the constrained metallic binder

The intrinsic hardness of the constitutive phases in WC-Co composites is investigated by combining experimental and statistical analysis nanoindentation techniques. It is done on the basis of considering the cemented carbide material as effectively heterogeneous at the microstructure scale, i.e. consisting of three phases defined by either different chemical nature (carbides and binder) or distinct carbide crystal orientation (i.e. with surface normal perpendicular to either basal or prismatic planes). As main outcome, experimentally measured and statistically significant intrinsic hardness values for the defined phases (WC and constrained metallic binder) are analyzed and determined. Besides the evidence of crystal anisotropy for the WC phase, they permit to identify and account the expected strengthening of the plastic-constrained metallic binder, a critical input parameter for hardness and toughness modelling as well as for microstructural design optimization of ceramic composites reinforced by ductile metallic ligaments. (C) 2015 Elsevier Ltd. All rights reserved.Postprint (published version

Identification of ABA-Mediated Genetic and Metabolic Responses to Soil Flooding in Tomato (Solanum lycopersicum L. Mill)

[EN] Soil flooding is a compound abiotic stress that alters soil properties and limits atmospheric gas diffusion (O-2 and CO2) to the roots. The involvement of abscisic acid (ABA) in the regulation of soil flooding-specific genetic and metabolic responses has been scarcely studied despite its key importance as regulator in other abiotic stress conditions. To attain this objective, wild type and ABA-deficient tomatoes were subjected to short-term (24 h) soil waterlogging. After this period, gas exchange parameters were reduced in the wild type but not in ABA-deficient plants that always had higher E and g(s). Transcript and metabolite alterations were more intense in waterlogged tissues, with genotype-specific variations. Waterlogging reduced the ABA levels in the roots while inducing PYR/PYL/RCAR ABA receptors and ABA-dependent transcription factor transcripts, of which induction was less pronounced in the ABA-deficient genotype. Ethylene/O-2-dependent genetic responses (ERFVIIs, plant anoxia survival responses, and genes involved in the N-degron pathway) were induced in hypoxic tissues independently of the genotype. Interestingly, genes encoding a nitrate reductase and a phytoglobin involved in NO biosynthesis and scavenging and ERFVII stability were induced in waterlogged tissues, but to a lower extent in ABA-deficient tomato. At the metabolic level, flooding-induced accumulation of Ala was enhanced in ABA-deficient lines following a differential accumulation of Glu and Asp in both hypoxic and aerated tissues, supporting their involvement as sources of oxalacetate to feed the tricarboxylic acid cycle in waterlogged tissues and constituting a potential advantage upon long periods of soil waterlogging. The promoter analysis of upregulated genes indicated that the production of oxalacetate from Asp via Asp oxidase, energy processes such as acetyl-CoA, ATP, and starch biosynthesis, and the lignification process were likely subjected to ABA regulation. Taken together, these data indicate that ABA depletion in waterlogged tissues acts as a positive signal, inducing several specific genetic and metabolic responses to soil flooding.This work was supported by the Spanish Ministerio de Economia y Competitividad, Universitat Jaume I and Generalitat Valenciana/Fondo Europeo de Desarrollo Regional (FEDER), co-funded through grant nos. AGL2016-76574-R, UJI-B201623, UJI-B2016-24, IDIFEDER/2018/010, and UJI-B2019-24 to AG-C, VA, and MG-G, respectively. CD was supported by UJI PICD program. MG-G and JM were supported by Ramon y Cajal contracts from Spanish Ministerio de Economia y Competitividad (RYC-2016-19325 and RYC-201723645, respectively). JR was supported by a Juan de la CiervaFormacion contract from the Spanish Ministerio de Economia y Competitividad (FJCI-2016-28601).De Ollas, C.; González-Guzmán, M.; Pitarch, Z.; Matus, JT.; Candela, H.; Rambla Nebot, JL.; Granell Richart, A.... (2021). Identification of ABA-Mediated Genetic and Metabolic Responses to Soil Flooding in Tomato (Solanum lycopersicum L. Mill). Frontiers in Plant Science. 12:1-20. https://doi.org/10.3389/fpls.2021.613059S1201