39 research outputs found
Mechanical properties of Al2O3 inverse opals by means of nanoindentation
In order to understand the mechanical behaviour of Al2O3 inverse opals, nanoindentation techniques have been implemented in material layers with three different microstructures, in terms of hollow or polystyrene spheres, with Al2O3 shells of distinct wall thickness. Different indenter tip geometries as well as contact loading conditions have been used, in order to induce different stress field and fracture events to the layers. Field emission scanning electron microscopy and focused ion beam have been employed to understand accommodation of plastic deformation induced during the indentation process. Results show that materials with polystyrene spheres exhibit higher hardness and modulus under sharp indentation, and cracking resistance under spherical indentation. Furthermore, deformation is discerned to be mainly governed by the rotation of the microspheres. In the case of the inverse opals made of hollow spheres, the main deformation mechanisms activated under indentation are the rearrangement and densification of themPostprint (author's final draft
Influence of the Test Configuration and Temperature on the Mechanical Behaviour of WC-Co
In this work, the effect of the test configuration and temperature on the mechanical behaviour
of cemented carbides (WC-Co) with different carbide grain sizes (dWC) and cobalt volume fractions
(VCo), implying different binder mean free paths ( Co), was studied. The mechanical strength was
measured at 600º C with bar-shaped specimens subjected to uniaxial four-point bending (4PB) tests
and with disc specimens subjected to biaxial ball-on-three-balls (B3B) tests. The results were analysed
within the frame of theWeibull theory and compared with strength measurements performed at room
temperature under the same loading conditions. A mechanical degradation greater than 30% was
observed when the samples were tested at 600ºC due to oxidation phenomena, but higherWeibull
moduli were obtained as a result of narrower defect size distributions. A fractographic analysis was
conducted with broken specimens from each test configuration. The number of fragments (Nf) and the
macroscopic fracture surface were related to the flexural strength and fracture toughness of WC-Co.
For a given number of fragments, higher mechanical strength values were always obtained for WC-Co
grades with higher KIc. The observed differences were discussed based on a linear elastic fracture
mechanics (LEFM) model, taking into account the effect of the temperature and microstructure of the
cemented carbides on the mechanical strength.Junta de Andalucía P12-TEP-262
Quality of bladder cancer information on YouTube.
Introduction YouTube is one of the social networks most widely used as a source of information.
However, there are doubts about the scientific quality of the information available. This study aims
to characterise this by analysing videos about bladder cancer posted on YouTube.
Material and methods This was a cross-sectional descriptive study of the first 50 Spanish-language videos
published on YouTube, leaving 38 for analysis. The videos were evaluated by three urologists using two
validated questionnaires: Patient Education Materials Assessment Tool (PEMAT) and DISCERN (quality criteria for consumer health information), classifying them according to the score of the latter, in poor quality
(1–2 points) and moderate/good quality (3–5 points).
Results The median PEMAT score was 71.6% (16–5–100%) for understanding and 35.5% (0–100%) for action. According to DISCERN, 26 videos (66.7%) were of poor quality and 12 (30.8%) of moderate/good quality. We found significant differences in terms of PEMAT of understanding (p = 0.004) and action (p = 0.000).
In total, 90.9% of those involving medical staff were of low quality, which is paradoxical, but statistically significant (p = 0.01). Furthermore, 52.4% of those describing relevant information were of moderate/good
quality, and 94.1% of those not describing relevant information were of poor quality (p = 0.02).
Conclusions More than 60% of the videos published on YouTube about bladder cancer in Spanish are
of low quality. This represents an important risk of misinformation for the general public to whom most
of them are addressed.post-print729 K
Diseño, fabricación y ensayo de materiales laminados basados en el metal duro con propiedades mecánicas mejoradas
Los metales duros (WC-Co) y cermets son materiales muy usados como materiales
de herramientas. Sin embargo, los WC-Co presentan pérdidas de propiedades
mecánicas a temperaturas elevadas, mientras que la fragilidad elevada de los
segundos compromete su empleo en este tipo de aplicaciones. El uso de materiales
con función gradiente y laminados se plantean como una potencial solución. En
este trabajo se fabrican distintos tipos de diseños de laminados (WC-Co/WC-Co y
Cermet/WC-Co), que permiten alcanzar los equilibrios de comportamiento tribomecánico
y termo-mecánico deseados. En este contexto, se realiza la caracterización
macroestructural (homogeneidad e integridad estructural de las capas) y
microestructural (composición química, análisis de fases, fenómenos de difusión
en las intercaras). La caracterización mecánica incluye la resistencia a flexión y la
tenacidad de fractura, así como la resistencia al rayado. Los resultados se discuten
en el marco de la mecánica de la fractura elástica lineal, los mecanismos de aumento
de tenacidad (desvío y bifurcación de las grietas) y la presencia de un umbral de
resistencia mecánica asociado a la distribución de tensiones de compresión y tracción
en los laminados diseñados y fabricados en este trabajo.Junta de Andalucía P12-TEP-262
Improved adhesion of cathodic arc PVD AlCrSiN coating on ion-implanted WC-Co substrates
Ion implantation has been shown to improve adhesion strength of AlCrSiN coatings due to a synergic enhancement on fracture toughness and load bearing capability of the substrate that can potentially increase the in-service efficiency of coated cutting tools. In this work, AlCrSiN coatings deposited by PVD on WC-Co substrates implanted with Ti, Cr and N ion species have been processed. The mechanical properties and adhesion have been characterized by contact techniques and the residual stress of the coatings and substrates have been evaluated using FIB-DIC technique and Vickers indentation tests, respectively. An improvement of adhesion strength is obtained for treated substrates, especially for those implanted with titanium and chromium ions. This improvement is attributed to the introduction of residual stresses in the substrate, which increases its fracture toughness and enhances its load bearing capability.Work funded through The Spanish Ministry of Science, Innovation and Universities through grants PGC-2018-096855-B-C41, PGC-2018-096855-B-C42 and PGC-2018-096855-A-C4
Field Effectiveness of Drones to Identify Potential Aedes aegypti Breeding Sites in Household Environments from Tapachula, a Dengue-Endemic City in Southern Mexico
Aedes aegypti control programs require more sensitive tools in order to survey domestic and peridomestic larval habitats for dengue and other arbovirus prevention areas. As a consequence of the COVID-19 pandemic, field technicians have faced a new occupational hazard during their work activities in dengue surveillance and control. Safer strategies to monitor larval populations, in addition to minimum householder contact, are undoubtedly urgently needed. Drones can be part of the solution in urban and rural areas that are dengue-endemic. Throughout this study, the proportion of larvae breeding sites found in the roofs and backyards of houses were assessed using drone images. Concurrently, the traditional ground field technician’s surveillance was utilized to sample the same house groups. The results were analyzed in order to compare the effectiveness of both field surveillance approaches. Aerial images of 216 houses from El Vergel village in Tapachula, Chiapas, Mexico, at a height of 30 m, were obtained using a drone. Each household was sampled indoors and outdoors by vector control personnel targeting all the containers that potentially served as Aedes aegypti breeding sites. The main results were that the drone could find 1 container per 2.8 found by ground surveillance; however, containers that were inaccessible by technicians in roofs and backyards, such as plastic buckets and tubs, disposable plastic containers and flowerpots were more often detected by drones than traditional ground surveillance. This new technological approach would undoubtedly improve the surveillance of Aedes aegypti in household environments, and better vector control activities would therefore be achieved in dengue-endemic countries
Gobiernos municipales: por un desarrollo local basado en la gobernanza democrática
El presente reporte da cuenta del proceso de intervención universitaria en el municipio de Tlajomulco de Zúñiga, Jalisco, México, a través del PAP “Gobiernos Municipales: por un desarrollo local basado en la gobernanza democrática”, cuyo propósito general es:
Contribuir a la promoción de la cultura de paz, la economía social y solidaria y la promoción de los DDHH en Tlajomulco, desde la Dirección General de Cultura de Paz y Gobernanza, a través de analizar, conocer, difundir documentar y evaluar situaciones relacionadas con la construcción de espacios de paz basados en la economía social y solidaria y la difusión de los DDHH, en la construcción de una ciudad en paz y segura, que, desde una perspectiva interdisciplinar, da continuidad a los proyectos emprendidos durante el periodo anterior, referidos al rescate y apropiación social de los espacios públicos desde la perspectiva de la paz positiva, impulso a las iniciativas de emprendimiento y formación en finanzas para los jóvenes del municipio.
En el periodo de primavera 2022, se tuvieron los siguientes objetivos:
• Elaborar el diseño de un espacio público, como respuesta a una demanda de los vecinos del fraccionamiento Sendero Real, a través de las mesas de paz, que implementa el gobierno municipal de Tlajomulco de Zúñiga.
• Responder a la demanda de apoyo del sector juvenil de Tlajomulco y El Salto, expresada en los talleres de diagnóstico promovidos por el Instituto de la Juventud Tlajomulquense y del Instituto de la Juventud del Salto.
• Diseñar y aplicar una evaluación de los programas públicos de mesas de paz y chamba para todos.
La metodología aplicada implico la intervención de estudiantes de diferentes disciplinas a partir de grupos sociales específicos que presentan demandas de atención para la recuperación de sus espacios públicos y por tanto requieren de acompañamiento para el diseño de estos, el impulso al emprendimiento través de la realización de Podcast dirigidos a los jóvenes, la integración y aplicación de una propuesta de evaluación de los programas públicos “mesas de paz” y “”chamba para todos”.ITESO, A.C