Analysis of the Process Parameter Influence in Laser Cladding of 316L Stainless Steel

Laser Cladding is one of the leading processes within Additive Manufacturing technologies, which has concentrated a considerable amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in the laser cladding processing of single and compound volumes (solid forms) made from AISI 316L stainless steel powders and using a coaxial nozzle for their deposition. Process speed, applied laser power and powder flow are considered to be the main variables affecting the laser cladding in single clads, whereas overlap percentage and overlapping strategy also become relevant when dealing with multiple clads. By setting appropriate values for each process parameter, the main goal of this paper is to develop a processing window in which a good metallurgical bond between the delivered powder and the substrate is obtained, trying simultaneously to maintain processing times at their lowest value possible. Conventional metallography techniques were performed on the cross sections of the laser tracks to measure the effective dimensions of clads, height and width, as well as the resulting dilution value. Besides the influence of the overlap between contiguous clads and layers, physical defects such as porosity and cracks were also evaluated. Optimum process parameters to maximize productivity were defined as 13 mm/s, 2500 W, 30% of overlap and a 25 g/min powder feed rat

Acciones de acogida del proyecto mentor de la EUITI

Desde el curso académico 2008/2009 el Proyecto Mentor de la Escuela Universitaria de Ingeniería Técnica Industrial (EUITI) de la UPM [1] participa en distintas acciones de acogida de los alumnos de nuevo ingreso propio del centro. Estas actividades son el primer contacto de los mentores con los alumnos de nuevo ingreso y además son reforzadas por el apoyo y experiencia de los tutores y mentores del curso anterior, favoreciendo la interrelación de alumnos de distintos cursos y especialidades. Para la correcta realización de estas actividades, los alumnos mentores reciben un intensivo programa de formación que incluye aspectos psicosociales propios de la mentoría [2]. La presente comunicación tiene el propósito de describir dichas acciones así como presentar y valorar los resultados obtenidos a través de la encuest

Sensibilización a hongos anemófilos en trabajadores del Archivo y Biblioteca de la Universidad de La Habana

Introducción: En Cuba no se conoce la prevalencia de sensibilización a hongos anemófilos en trabajadores(as) de archivos y bibliotecas. Objetivo: Determinar la frecuencia de sensibilización a aeroalérgenos micóticos y la prevalencia de enfermedades alérgicas en trabajadores(as) del Archivo y la Biblioteca de la Universidad de La Habana. Métodos: Estudio observacional, y transversal, que incluyó 53 trabajadores(as). Se les realizó historia clínica y pruebas cutáneas por punción (PCP) con extractos de hongos anemófilos. Se analizó: edad, sexo, resultados de PCP, tamaño del habón y área de trabajo. Se empleó X2 para comparar frecuencias de sensibilización y t de student para el tamaño del habón, con significación estadística si p < 0,05. Resultados: El 64 % de los trabajadores(as) del archivo y el 33 % de la biblioteca estuvieron al menos sensibilizados a un hongo. La especie Aspergillus níger predominó con el mayor porcentaje de sensibilización (20,4 %). La rinitis alérgica fue la enfermedad más frecuente en estos trabajadores(as), 23 casos (43,3 %). La combinación de asma y rinitis se encontró en 9 trabajadores(as). En el 32,1 % de los casos (9) con enfermedad alérgica respiratoria se encontró positividad, al menos a un hongo anemófilo. Los mayores tamaños del habón se encontraron en los trabajadores(as) del archivo, especialmente para Alternaria alternata (3,46 mm) y Penicillium notatum (3,43 mm). Conclusiones: Existe elevada prevalencia de sensibilización a hongos anemófilos en los trabajadores(as) investigados. Son necesarios más estudios que investiguen la sensibilización a estas y otras especies fúngicas en este entorno laboral

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites

The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions. The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence were evaluated in terms of the independent contribution of the starch matrix and the wood microparticles to the hardness value. The influence of drying time on the density and weight uptake of the injection-molded composites was highlighted. The results revealed the role of the mechanism of water evaporation, showing that the dependence of water uptake and temperature was greater for the starch–wood composites than for the pure starch sample. Experiments performed during the drying process at 70°C indicated that the wood in the starch composites did not prevent water loss from the samples.Peer reviewe