Determinación del factor de distribución longitudinal de la carga en engranajes cilíndricos rectos mediante el método de los elementos finitos

El objetivo principal del presente proyecto fin de carrera es calcular el factor de distribución longitudinal de la carga en engranajes cilíndricos rectos mediante el método de los elementos finitos teniendo en cuenta la deflexión de los ejes que soportan los engranajes y la deformación torsional de las superficies de contacto y de los cuerpos de los engranajes. La inclusión en este estudio de los ejes en los modelos de elementos finitos y la consideración de la deformación torsional de las superficies de contacto y de los cuerpos de los engranajes representan un avance importante en el estudio de la capacidad de carga de las transmisiones por engranajes cilíndricos rectosEscuela Técnica Superior de Ingeniería IndustrialUniversidad Politécnica de Cartagen

Descripción del Servicio de Cirugía Menor del Centro de Salud Teruel Rural. Satisfacción de los usuarios

Objetivos: Realizar un análisis de la actividad desarrollada en el servicio de CM y conocer la opinión y la satisfacción de 20 pacientes intervenidos en un periodo trimestral de enero y febrero del año 2013 y diciembre del 2012. Material y métodos: Estudio descriptivo retrospectivo y transversal de todos los pacientes incluidos en el servicio de CM. Las variables analizadas fueron (edad, sexo, tipo de intervención, diagnóstico pre-quirúrgico, antecedentes de alergias, alteraciones de la coagulación y consentimiento informado. Se utilizaron pruebas estadísticas como: la media, DE, chi–cuadrado, ANOVA y Kruskal- Wallis, además del programa estadístico, SPSS15.0. Resultados: Se ha estudiado un total de 612 intervenciones de las cuales un 51,3% eran mujeres y 48,7 hombres. La media de edad es de 56,42 (DE=18,5). La localización anatómica más frecuente fue la cara(52,6%). Un 100% no tuvo alteraciones de la coagulación y solo 1% presentó alergias preoperatorias. El 99,3% contaban con el consentimiento informado en su historia clínica. Descripción del servicio de Cirugía menor del centro de salud Teruel Rural. En la encuesta de satisfacción, un 60% de los pacientes estaban moderadamente satisfechos, un 30% muy satisfechos y un 10% insatisfechos con la CM general. Conclusiones: El servicio de CM en el CS de Teruel Rural está muy implantado. Tiene un registro exhaustivo de todos y cada uno de los pacientes intervenidos y el grado de satisfacción de los pacientes con este servicio es muy elevado

Training-induced changes in drag-flick technique in female field hockey players

The penalty corner is one of the most important goal plays in field hockey. The drag-flick is used less by women than men in a penalty corner. The aim of this study was to describe training-induced changes in the drag-flick technique in female field hockey players. Four female players participated in the study. The VICON optoelectronic system (Oxford Metrics, Oxford, UK) measured the kinematic parameters of the drag-flick with six cameras sampling at 250 Hz, prior to and after training. Fifteen shots were captured for each subject. A Wilcoxon test assessed the differences between pre-training and post-training parameters. Two players received specific training twice a week for 8 weeks; the other two players did not train. The proposed drills improved the position of the stick at the beginning of the shot (p<0.05), the total distance of the shot (p<0.05)and the rotation radius at ball release (p<0.01). It was noted that all players had lost speed of the previous run. Further studies should include a larger sample, in order to provide more information on field hockey performance

Closed-set-based discovery of representative association rules

The output of an association rule miner is often huge in practice. This is why several concise lossless representations have been proposed, such as the “essential” or “representative” rules. A previously known algorithm for mining representative rules relies on an incorrect mathematical claim, and can be seen to miss part of its intended output; in previous work, two of the authors of the present paper have offered a complete but, often, somewhat slower alternative. Here, we extend this alternative to the case of closure-based redundancy. The empirical validation shows that, in this way, we can improve on the original time efficiency, without sacrificing completeness.Peer ReviewedPostprint (author's final draft

Environmental effects in mechanical properties of few-layer black phosphorus

We report on the mechanical properties of few-layer black phosphorus (BP) nanosheets, in high vacuum and as a function of time of exposure to atmospheric conditions. BP flakes with thicknesses ranging from 4 to 30 nm suspended over circular holes are characterized by nanoindentations using an atomic force microscope tip. From measurements in high vacuum an elastic modulus of 46 ± 10 GPa and breaking strength of 2.4 ± 1 GPa are estimated. Both magnitudes are independent of the thickness of the flakes. Our results show that the exposure to air has substantial influence in the mechanical response of flakes thinner than 6 nm but small effects on thicker flake

Improved graphene blisters by ultrahigh pressure sealing

Graphene is a very attractive material for nanomechanical devices and membrane applications. Graphene blisters based on silicon oxide micro-cavities are a simple but relevant example of nanoactuators. A drawback of this experimental set up is that gas leakage through the graphene-SiO2 interface contributes significantly to the total leak rate. Here we study the diffusion of air from pressurized graphene drumheads on SiO2 micro-cavities and propose a straightforward method to improve the already strong adhesion between graphene and the underlying SiO2 substrate, resulting in reduced leak rates. This is carried out by applying controlled and localized ultrahigh pressure (> 10 GPa) with an Atomic Force Microscopy diamond tip. With this procedure, we are able to significantly approach the graphene layer to the SiO2 surface around the drumheads, thus enhancing the interaction between them allowing us to better seal the graphene-SiO2 interface, which is reflected in up to ~ 4 times lower leakage rates. Our work opens an easy way to improve the performance of graphene as a gas membrane on a technological relevant substrate such as SiO2.Comment: pages 19, 4 figures + supplementary informatio

Fine defect engineering of graphene friction

Two-dimensional materials, in particular graphene, exhibit a low friction coefficient and good wear properties. However, the tribological properties of these materials strongly depend on faint differences at the atomic level, and the coexistence of different type of atomic defects in studied samples up to date led to experimental results difficult to reconcile. In our work, we quantified the influence of controlled induced atomic monovacancies on the frictional behaviour of graphene. Less than 0.1% of atomic vacancies induced a fivefold increase in the effective friction coefficient. We showed that friction force microscopy resolved monoatomic vacancies and provided the real-space distribution of their influence on the tribology of graphene. Two factors contributed to this increment in friction: one was related to enhanced reactivity of dangling bonds localized at the monovacancy (~1 nm2 ), that accounted for ~20% of the increase; and a more extended one (~25 nm2 ) arose from the long-range strain distribution around these defects, characteristic of graphene. These results unveil the subtle connection between friction, reactivity, and mechanical properties in two-dimensional materialsWe acknowledge financial support from Spanish MINECO (projects PID2019-106268GB-C31, PID2019-104272RB-C52, ENE2016-79282-C5-4, and MAT2017-83273-R); Comunidad de Madrid (S2018/NMT-4511, NMAT, 2D-CM); and Ramón Areces Foundation. RP, JG-H, and CG-N acknowledge support from the Spanish Ministry of Science and Innovation, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M