Investigation of the cutting process in sandstones with blunt PDC cutters

The forces acting on the tools when cutting rock are not only important for the design of the cutters but also because they can be utilized to characterize the rock being cut. To understand these forces, it is necessary to have a good insight into the mechanisms that govern the failure of the rock. This thesis reports on studies of the cutting process with blunt — Polycrystalline Diamond Compact (PDC) — cutters. It presents a critical review of previous analytical, experimental and numerical models for the cutting mechanisms of single cutters. Associated mining and tunnelling studies suggest that the main rock cutting mechanism is tensile failure followed by fracture propagation. The work here provides evidence that these mechanisms are not applicable when drilling sedimentary rocks under pressure with PDC cutters — where it is more likely that the mechanisms of failure is different in nature, being ductile. A cutting bit response model (Detournay and Defourny, 1992), which is based on ductile failure and considers the drilling process as a combination of a pure cutting action at the cutter face and a frictional contact at the wear flat, was selected for the present research. The model predicts that there is a linear relation between specific energy, £, and the drilling strength, S, which are two quantities with dimension of stress that are respectively defined as the horizontal and vertical force divided by the cross-sectional area of the groove traced by the cutter. The two processes, the cutting and the friction at the interface, are then studied by means of finite difference simulations with a computer programme Fast Lagrangian Analysis of Continua (FLAC). The numerical simulations are compared to the upper and lower bound plasticity solutions for this problem to determine the validity of the code. This code allows one to model large deformations and also friction at the tool/rock interface. The simulations were performed to determine: • the validity of assuming that the two processes are independent; and • to establish whether there is a linear relation between £ and S by modelling different depths of cut. An experimental programme of single cutter tests was undertaken to corroborate the numerical and analytical models. Results of cutting tests on three different sandstones using blunt PDC cutters are presented and analyzed. The experimental data support the theoretical prediction that there is a linear relation between the specific energy £ and the drilling strength S. Various quantities such as the cutting parameters (e and £), the friction coefficient (fi) and the contact strength (<r) are estimated for each of the rocks tested. The thesis also contains discussion on how these basic parameters of the drilling process are related to the geomechanical characteristics of the rocks tested. A discussion of the influence of small imperfections along the cutting edge of a “sharp” cutter on the determination of e and is also presented. The main contribution of this research therefore is the verification of the cutting model, which in turn will enable the state of wear of PDC cutters to be established form the forces measured on site.Open Acces

La Dimensión Social En La Estrategia De Desarrollo Urbano Sostenible Integrado (DUSI). El Caso De La Cuesta - Taco (San Cristóbal de La Laguna - Tenerife)

En el marco de los programas de regeneración de las áreas urbanas con problemas, impulsado por la política regional de la Unión Europea (UE), se examinan las expectativas e incertidumbres que suscita la estrategia de «Desarrollo Urbano Sostenible Integrado (DUSI) Patrimonio de Barrios (2014-2020)» en el sector de La Cuesta-Taco. La finalidad declarada de esta propuesta es mejorar y revitalizar un área urbana vulnerable de la periferia sur del municipio de San Cristóbal de La Laguna (Tenerife). Un sector que fue objeto de otra iniciativa comunitaria previa, URBAN II (2000-2006), dirigida también a resolver los problemas de degradación física y social en áreas desfavorecidas. El objetivo del presente trabajo es valorar, a partir del análisis bibliográfico y documental y con el apoyo de los testimonios de algunos informantes cualificados, la potencial capacidad de mejora que sobre la inclusión social y la participación ciudadana puede representar la citada estrategia. Los resultados, a partir del análisis de los objetivos, del diseño del programa de actuación y de los procedimientos de participación establecidos, sugieren, por un lado, que, al menos en su puesta en marcha, la estrategia DUSI no ha garantizado suficientemente la participación ciudadana y, por otro, que las medidas adoptadas para favorecer la inclusión social centran, al parecer, su atención sobre todo en la regeneración física del área.Within the framework of the regeneration programmes for urban areas with problems, driven by the regional policy of the European Union (EU), the expectations and uncertainties raised by the Integrated Sustainable Urban Development Strategies (ISUDS) Patrimonio de Barrios (2014-2020) in the area of La Cuesta-Taco are examined. The stated purpose of this proposal is to improve and revitalize a vulnerable urban area in the southern periphery of San Cristóbal de La Laguna (Tenerife). This sector was the subject of a previous community initiative, URBAN II (2000-2006), also aimed at solving the problems of physical and social degradation in disadvantaged areas. The main objective of this study is to assess, based on the bibliographical and documentary analysis and with the support of the testimonies of some qualified informants, the potential capacity of 4 improvement of the mentioned strategy on social inclusion and civic participation. The results, based on the analysis of the objectives, the design of the action programme and the established participation procedures, suggest, on the one hand, that, at least in its implementation, the ISUDS has not adequately ensured civic participation and, on the other hand, that the measures adopted to promote social inclusion seem to focus mainly on the physical regeneration of the area

Correlation between UV Index, Temperature and Humidity with Respect to Incidence and Severity of COVID 19 in Spain

Background: Various studies support the inverse correlation between solar exposure and Coronavirus SARS-CoV-2 infection. In Spain, from the Canary Islands to the northern part of the country, the global incidence of COVID-19 is different depending on latitude, which could be related to different meteorological conditions such as temperature, humidity, and ultraviolet index (UVI). The objective of the present work was to analyze the association between UVI, other relevant environmental factors such as temperature and humidity, and the incidence, severity, and mortality of COVID-19 at different latitudes in Spain. Methods: An observational prospective study was conducted, recording the numbers of new cases, hospitalizations, patients in critical units, mortality rates, and annual variations related to UVI, temperature, and humidity in five different provinces of Spain from January 2020 to February 2021. Results: Statistically significant inverse correlations (Spearman coefficients) were observed between UVI, temperature, annual changes, and the incidence of COVID-19 cases at almost all latitudes. Conclusion: Higher ultraviolet radiation levels and mean temperatures could contribute to reducing COVID-19 incidence, hospitalizations, and mortalityPartial funding for open access charge: Universidad de Málag

EL ORDENADOR COMO HERRAMIENTA INTELECTUAL

Una de las ideas más difundidas para la inserción de los ordenadores en los centros educativos y en el currículum escolar, ha sido y posiblemente siga siendo, la concepción que sobre los mismos se tiene, como instrumento de desarrollo de habilidades cognitivas en los estudiantes, en definitiva considerarlos como instrumento de desarrollo de la mente. En el artículo se presenta una investigación centrada en las posibles influencias del lenguaje de programación BASIC en dos estilos cognitivos: DIC y Al.

The Onomastics of Shakespeare\u27s Works with Classical Settings

The present invention discloses a set of dental arches comprising: an upper arch (1) formed by upper anterior (2) and posterior (3) artificial teeth and another lower arch (5) formed by lower anterior (6) and posterior (7) artificial teeth mounted in an orderly fashion on flexible bases (4) and (8) constructed of elastomeric resin in the form of an arch, having a three-dimensional movement capacity to enable adaptation to the anatomy and physiology of edentulous patients; the base material also allows the adjustment of each tooth individually, through changes of position, inclination or alignment, in a simple manner, thus producing custom prosthodontics; its use in the confection processes of removable complete and partial dentures saves time, labor and cost compared to traditional methods.US2009233255 (A1)A61C9/00A61C13/34US20070227690A61C9/00A61C13/3

Pressurometry and biomechanical study of the foot in padel

[EN] Padel is a very popular sport in countries like Spain, Argentina and Brazil, but there is a lack of scientific papers analyzing the harmfulness of their practice. Padel movements could potentially damage the foot and ankle joint. Therefore, the objective of this study was the characterization of the foot role during the execution of the most representative padel movements by techniques of pressurometry and video. The study was divided in two parts: pressurometric analysis of two movements (head-on displacement and split-step), and video recording of the foot during two games. The main conclusions of the study are the importance of forefoot zone in the padel movements, the importance of a specific shoe design for padel practice, and the importance of neuromuscular and proprioceptive training of the ankle and plantar flexors.[ES] El pádel es un deporte muy practicado en países como España, Argentina y Brasil, pero existen pocos artículos científicos que muestren la lesividad de su práctica. Los movimientos más frecuentes del pádel pueden incidir de forma lesiva en el pie y en la articulación del tobillo. Por ello, el objetivo del presente estudio fue profundizar en el análisis del rol del pie en la ejecución de los movimientos más representativos del pádel mediante técnicas de video y de presurometría. El estudio fue dividido en dos partes: análisis presurométrico de dos gestos (carrera frontal y el split-step), y filmación del pié en el trascurso de dos partidos. Las principales conclusiones obtenidas del estudio son la importancia del antepié en los movimientos analizados, la importancia de un diseño específico del calzado para el pádel, y la importancia del entrenamiento neuromuscular y propioceptivo del complejo pie-tobillo, especialmente de los flexores plantares.Priego Quesada, JI.; Olaso Melis, J.; Llana-Belloch, S.; Pérez Soriano, P.; Gonzalez Garcia, JC.; Sanchís Almenara, M. (2014). Estudio presurométrico y biomecánico del pie en el pádel. Riccafd. Revista Iberoamericana de Ciencias de la Actividad Física y el Deporte. 3(1):21-26. http://hdl.handle.net/10251/85749S21263

A molecular dynamics study of swift heavy ion irradiation of amorphous silica: the role of thermal effects

Irradiation with swift heavy ions (SHI), roughly defined as those having atomic masses larger than 15 and energies exceeding 1 MeV/amu, may lead to significant modification of the irradiated material in a nanometric region around the (straight) ion trajectory (latent tracks). In the case of amorphous silica, SHI irradiation originates nano-tracks of higher density than the virgin material (densification). As a result, the refractive index is increased with respect to that of the surroundings. Moreover, track overlapping leads to continuous amorphous layers that present a significant contrast with respect to the pristine substrate. We have recently demonstrated that SHI irradiation produces a large number of point defects, easily detectable by a number of experimental techniques (work presented in the parallel conference ICDIM). The mechanisms of energy transfer from SHI to the target material have their origin in the high electronic excitation induced in the solid. A number of phenomenological approaches have been employed to describe these mechanisms: coulomb explosion, thermal spike, non-radiative exciton decay, bond weakening. However, a detailed microscopic description is missing due to the difficulty of modeling the time evolution of the electronic excitation. In this work we have employed molecular dynamics (MD) calculations to determine whether the irradiation effects are related to the thermal phenomena described by MD (in the ps domain) or to electronic phenomena (sub-ps domain), e.g., exciton localization. We have carried out simulations of up to 100 ps with large boxes (30x30x8 nm3) using a home-modified version of MDCASK that allows us to define a central hot cylinder (ion track) from which heat flows to the surrounding cold bath (unirradiated sample). We observed that once the cylinder has cooled down, the Si and O coordination numbers are 4 and 2, respectively, as in virgin silica. On the other hand, the density of the (cold) cylinder increases with respect to that of silica and, furthermore, the silica network ring size decreases. Both effects are in agreement with the observed densification. In conclusion, purely thermal effects do not explain the generation of point defects upon irradiation, but they do account for the silica densification

Three red suns in the sky: A transiting, terrestrial planet in a triple M-dwarf system at 6.9 pc

We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of ${1.38}_{-0.12}^{+0.13}$ ${R}_{\oplus }$, an orbital period of ${5.35882}_{-0.00031}^{+0.00030}$ days, and an equilibrium temperature of ${433}_{-27}^{+28}$ K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 ${M}_{\oplus }$ on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.Accepted manuscrip

Planetary system LHS 1140 revisited with ESPRESSO and TESS

Context. LHS 1140 is an M dwarf known to host two transiting planets at orbital periods of 3.77 and 24.7 days. They were detected with HARPS and Spitzer. The external planet (LHS 1140 b) is a rocky super-Earth that is located in the middle of the habitable zone of this low-mass star. All these properties place this system at the forefront of the habitable exoplanet exploration, and it therefore constitutes a relevant case for further astrobiological studies, including atmospheric observations. Aims. We further characterize this system by improving the physical and orbital properties of the known planets, search for additional planetary-mass components in the system, and explore the possibility of co-orbitals. Methods. We collected 113 new high-precision radial velocity observations with ESPRESSO over a 1.5-yr time span with an average photon-noise precision of 1.07 m s-1. We performed an extensive analysis of the HARPS and ESPRESSO datasets and also analyzed them together with the new TESS photometry. We analyzed the Bayesian evidence of several models with different numbers of planets and orbital configurations. Results. We significantly improve our knowledge of the properties of the known planets LHS 1140 b (Pb ∼ 24.7 days) and LHS 1140 c (Pc ∼ 3.77 days). We determine new masses with a precision of 6% for LHS 1140 b (6.48 ± 0.46 Mpdbl) and 9% for LHS 1140 c (mc = 1.78 ± 0.17 Mpdbl). This reduces the uncertainties relative to previously published values by half. Although both planets have Earth-like bulk compositions, the internal structure analysis suggests that LHS 1140 b might be iron-enriched and LHS 1140 c might be a true Earth twin. In both cases, the water content is compatible to a maximum fraction of 10-12% in mass, which is equivalent to a deep ocean layer of 779 ± 650 km for the habitable-zone planet LHS 1140 b. Our results also provide evidence for a new planet candidate in the system (md = 4.8 ± 1.1Mpdbl) on a 78.9-day orbital period, which is detected through three independent methods. The analysis also allows us to discard other planets above 0.5 Mpdbl for periods shorter than 10 days and above 2 Mpdbl for periods up to one year. Finally, our co-orbital analysis discards co-orbital planets in the tadpole and horseshoe configurations of LHS 1140 b down to 1 Mpdbl with a 95% confidence level (twice better than with the previous HARPS dataset). Indications for a possible co-orbital signal in LHS 1140 c are detected in both radial velocity (alternatively explained by a high eccentricity) and photometric data (alternatively explained by systematics), however. Conclusions. The new precise measurements of the planet properties of the two transiting planets in LHS 1140 as well as the detection of the planet candidate LHS 1140 d make this system a key target for atmospheric studies of rocky worlds at different stellar irradiations.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737