Automatic adjustment method to fit T¿LOG(T/¿0) scaling for time evolution thermal depending properties of nanocristalline iron

In many forming processes the evolution of the material properties evolves with time and changes as temperature varies, forcing the use of a time-dependent thermomechanical computational model to simulate those processes. If the property under study could be described as a collectivity of microentities jumping over a certain distribution of energy barriers from one metastable state to another, then the whole behaviour of the material property follows a T·Ln(t/0) scaling. The use of T·Ln(t/0) as an integration variable could be employed to simplify the computational procedure. Also this scaling description allows to extrapolate the time evolution behaviour at times (or speeds) that are experimentally inaccessible. From this scaling it is also possible to determine the attempt period 0, needed by the computational model. All the properties described by the Arrhenius Law could be scaled by this method. In the present work the results of appling this scaling method to the hardness of a nanocrystalline iron powder with several annealing treatments are presented, and an algorithm for automatic adjustment of a T·Ln(t/0) scaling is tested.Postprint (published version

Study of the lateral pass width for conventional and ultrasonic vibrations-assisted ball burnishing on Ti-6Al-4V specimens

Ball burnishing is a technological finishing process based on plastic deformation of the objective surface by means of a hard ball gliding over it. Along with its easiness of application, possible on the same machine where machining was performed [1], burnishing is a comprehensive process able to achieve surface roughness improvements, and compressive residual stresses up to deep layers of the material [2]. Burnishing results have proved to be depending of a proper selection of parameters, which must be correctly controlled during the process. That is the case of burnishing force or the number of passes [3]. Among these parameters, the lateral pass width has proved to be influential on the surface roughness results, due to the behavior that most materials show when being plastically deformed. In effect, the applied force makes the material to flow to the borders of the burnishing imprint, giving way to a pile-up effect. This paper deals with indentation experiments on Ti-6Al-4V to deepen in the burnishing process of this material. Single burnishing imprints are geometrically characterized combining different levels of force, number of passes, and comparing the conventional process with that assisted with vibrations. An optimal lateral pass width is thus determined, and technological recommendations are made for future applications of the process.Peer ReviewedPostprint (author's final draft

Sostenibilitat en el transport: optimització del consum de combustible

La reducció del dispendi d’energia d’un vehicle es pot minimitzar mitjançant un ús adequat del sistema propulsor. El mètode desenvolupat implica l’elaboració d’un model numèric del vehicle i una descripció matemàtica de la via (perfil altimètric i traçat) per poder-lo similar en un ordinador. Amb un mètode d’optimització numèrica es pot cercar el mínim de consum d’energia i la millor relació de transmissió possible. El mètode va ser comprovat en el vehicle “Centenari” (un prototipus de vehicle de baix consum), assolint una reducció del 34% en el consum de gasolina, i permetent al vehicle recorre 1066 km amb només 1 litre de benzina.Peer Reviewe

Germinació de llavors d'espècies psammòfiles i ruderals de platja

S’ha estudiat la capacitat de germinació dels propàguls de quatre espècies (Cenchrus incertus, Tribulus terrestris, Pancratium maritimum i Xanthium strumarium), un cop se’ls ha sotmès a diferents situacions: cap tractament previ, un cop de calor amb aigua bullint i una immersió en àcid sulfúric (aquest darrer només en el cas de C. incertus). Les condicions de fotoperíode han estat 12 h llum/12 h fosc, i 24 h foscor, i la temperatura ha estat constant (25 ºC). Les llavors han estat sembrades en sorra o placa de Petri. També s’ha estudiat la capacitat de germinació de les espiguetes de Digitaria sanguinalis en funció de la profunditat d’enterrament sota unes condicions ambientals determinades (20-30 ºC i 12 h llum/12 h foscor). Els resultats més destacables han estat els següents: - Tribulus terrestris L. Les llavors de T. terrestris es mantenen latents en un 100 % després de sotmetre’s a les condicions de germinació i tractaments esmentats. - Cenchrus incertus L. El tractament de cop de calor en C. incertus manté les llavors latents en un 100 %. El tractament d’àcid sulfúric permet percentatges de germinació al voltant del 25 %, per sota dels lots no tractats, en els quals el percentatge mitjà de germinació volta el 36,37 %. - Pancratium maritimum L. El tractament de cop de calor manté el 100 % de les llavors latents. En condicions de laboratori poden mostrar una germinació mitjana superior al 86%. - Xanthium strumarium L. El tractament de cop de calor provoca un retard i una disminució del percentatge de germinació respecte les llavors no tractades. En les condicions de l’assaig s’han obtingut percentatges del 93 % d’unitats de dispersió eclosionades, amb un 48,81 % de germinacions, en aquelles llavors que no han patit cap tractament. - Digitaria sanguinalis (L.) Scop. Digitaria sanguinalis és capaç de germinar enterrada en profunditats de 0 a 10 cm, però només és capaç d’emergir quan la llavor es troba enterrada entre 0 i 2 cm

First spermatological data on the digenean genus Ityogonimus derived from the description of sperm characters of Ityogonimus ocreatus (Brachylaimidae: Ityogoniminae)

The present study describes the ultrastructural organization of the spermatozoa of the brachylaimid digenean Ityogonimus ocreatus (Ityogoniminae) by means of transmission electron microscopy (TEM). Live digeneans were collected from the digestive tract of an Iberian mole Talpa occidentalis (Eulipotyphla, Talpidae) captured accidentally during a vole pest control campaign in Priesca (Asturias, Spain). The TEM study reveals that the I. ocreatus sperm are filiform, tapered at both extremities, and have two 9+'1' trepaxonematan axonemes, external ornamentation of the plasma membrane associated with cortical microtubules, spine-like bodies, two bundles of parallel cortical microtubules and one mitochondrion overlapping the anterior part of the nucleus. The external ornamentation of the plasma membrane is located in the posterior part of the anterior region. The maximum number of parallel cortical microtubules (45) is located in the anterior part of the sperm cells. Our results are compared with the available data on the family Brachylaimidae, especially on the other Ityogoniminae studied to date (Scaphiostomum palaearcticum

Comparison of thermal performance of 3D printer liquefiers through finite element models

Open source 3D printers have experienced an intense expansion during the last years, mainly because of their accessibility and the vast availability of information thanks to user communities. This fact presents researchers with a perfect context for hardware innovation, by improving the overall printing process, also in terms of durability of the printing machine. A 3D printer liquefier must transmit heat to the thermoplastic material in order to extrude it, reaching temperatures above 200 degrees for some materials like ABS on the tip of the nozzle. The design of the heating process must comply with keeping the balance between proper heating of the material and controlling the temperature along the extruding body, so that the printer itself is not harmed for overtemperature. On the other hand, the design must guarantee that the melting front is located in an intermediate point between the nozzle tip and the entrance of the raw material, to minimize pressure drops in the system, and so decreasing the demanding energy to the feeding motors. An alternative design of the heating system, Twist3D, is proposed in this paper.Peer ReviewedPostprint (published version

Experimental analysis of manufacturing parameters’ effect on the flexural properties of wood-PLA composite parts built through FFF

This paper aims to determine the flexural stiffness and strength of a composite made of a polylactic acid reinforced with wood particles, named commercially as Timberfill, manufactured through fused filament fabrication (FFF). The influence of four factors (layer height, nozzle diameter, fill density, and printing velocity) is studied through an L27Taguchi orthogonal array. The response variables used as output results for an analysis of variance are obtained from a set of four-point bending tests. Results show that the layer height is the most influential parameter on flexural strength, followed by nozzle diameter and infill density, whereas the printing velocity has no significant influence. Ultimately, an optimal parameter set that maximizes the material’s flexural strength is found by combining a 0.2-mm layer height, 0.7-mm nozzle diameter, 75% fill density, and 35-mm/s velocity. The highest flexural resistance achieved experimentally is 47.26 MPa. The statistical results are supported with microscopic photographs of fracture sections, and validated by comparing them with previous studies performed on non-reinforced PLA material, proving that the introduction of wood fibers in PLA matrix reduces the resistance of raw PLA by hindering the cohesion between filaments and generating voids inside it. Lastly, five solid Timberfill specimens manufactured by injection molding were also tested to compare their strength with the additive manufactured samples. Results prove that treating the wood-PLA through additive manufacturing results in an improvement of its resistance and elastic properties, being the Young’s module almost 25% lower than the injected material.Preprin

First finding of Ityogonimus lorum and I. ocreatus co-infection in the Iberian mole, Talpa occidentalis

The Ityogonimus lorum-I. ocreatus co-infection is reported for the first time in the Iberian mole Talpa occidentalis in Asturias (NW Spain). Both Ityogonimus species are stenoxenous helminths of insectivores of the genus Talpa and they have often been found parasitizing the Iberian mole and also the European mole T. europaea, but a mixed infection had not been previously reported. The present study also highlights the main differential morphometric characteristics between I. lorum and I. ocreatus such as the body length, the ventral sucker diameter, the ratio between suckers and the distance between suckers

Análisis de los indicadores de estado de la vegetación y propuesta de medidas: ríos Túria y Palancia

[EN] Traditional water management and the intensive use of rivers has caused, along with undeniable benefits, a clear deterioration of river ecosystems and human impact of the channels. The issue of the new legislation is retrieve rivers ecologically, but first must analyze and diagnose the current state and then propose corrective measures. Among the avaible tools to analyze the channels is the QBR indicator representing the state of riparian vegetation. The banks of the Turia and Palancia rivers, both from the Júcar River Basin, have been analysed and later restoration measures are proposed in order to reach a good level in all water bodies.[CA] La gestió tradicional de l'aigua i l¿aprofitament intensiu dels rius ha provocat, juntament amb innegables beneficis, un clar deteriorament dels ecosistemes fluvials i una antropització dels llits. L' objectiu de les noves legislacions és recuperar ecològicament els rius però primer s'ha d'analitzar i diagnosticar l'estat actual i posteriorment proposar mesures correctores. Dins de les ferramentes que es disposa per analitzar els llits està l¿indicador QBR que representa l'estat en què es troba la vegetació de ribera. En el present treball s'analitzen les riberes dels rius Túria i Palància, ambdós de la Demarcació Hidrogràfica del Xúquer i posteriorment es proposen mesures de restauració a fi d'aconseguir un bon nivel en totes les seues masses d'aigua.[ES] La gestión tradicional del agua y el aprovechamiento intensivo de los ríos ha provocado, junto con innegables beneficios, un claro deterioro de los ecosistemas fluviales y una antropización de los cauces. El objetivo de las nuevas legislaciones es recuperar ecológicamente los ríos, pero primero se debe analizar y diagnosticar el estado actual y posteriormente proponer medidas correctoras. Dentro de las herramientas de que se dispone para analizar los cauces está el indicador QBR que representa el estado en que se encuentra la vegetación de ribera. En el presente trabajo se analizan las riberas de los ríos Turia y Palancia, ambos de la Demarcación Hidrográfica del Júcar y posteriormente se proponen medidas de restauración con el fin de alcanzar un nivel bueno en todas sus masas de agua.Fuentes Cebolla, J. (2015). Análisis de los indicadores de estado de la vegetación y propuesta de medidas: ríos Túria y Palancia. http://hdl.handle.net/10251/57024.Archivo delegad