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Meteorological aspects of self-initiated upward lightning at the Säntis Tower (Switzerland)

  • Pineda, Nicolau
  • Figueras i Ventura, Jordi
  • Romero Durán, David
  • Mostajabi, A.
  • Azadifar, M.
  • Sunjerga, A.
  • Rachidi-Haeri, Farhad
  • Rubinstein, M.
  • Montanya, Joan
  • Van der Velde, Oscar Arnoud
  • Altube Vázquez, Patricia
  • Besic, Nikola
  • Grazioli, Jacopo
  • Germann, Urs
  • Williams, Earle R.
Interest in exploring the meteorological conditions favoring upward lightning from tall man-made structures has grown in recent years, largely due to the worldwide expansion of wind energy. To this end, instrumented towers existing around the world are the most suitable places to study upward lightning. In this context, an LMA network was deployed around the Säntis Mountain (northeast Switzerland) during the summer of 2017, in order to complement the long-term measurements currently held at the Säntis telecommunications tower, a lightning hot spot in central Europe. This campaign allowed, for the first time, to gather a comprehensive set of observations of self-initiated upward lightning emerging from the Tower. With the help of C-band dual-polarimetric radar data, the present work focuses on the meteorological conditions conductive to self-initiated upward lightning from the Säntis. The analysis revealed that the upward propagating positively charged leaders spread mostly horizontal above the melting level, after an initial short vertical path from the tower tip. After this initial stage, the majority of upward leaders were followed by a sequence of negative return strokes. The inception upward lightning under a stratiform cloud shield would be favored by the low height of the charge structure. From the obtained results, it turns out that a key feature favoring self-initiated upward lightning would be the proximity of the tower tip to the melting level., Peer Reviewed

Multifunctional cork – alkali-activated fly ash composites: a sustainable material to enhance buildings’ energy and acoustic performance

  • Novais, Rui M.
  • Carvalheiras, João
  • Senff, Luciano
  • Lacasta Palacio, Ana María
  • Rodríguez Cantalapiedra, Inma
  • Giró Paloma, Jessica
  • Seabra, Maria Paula
  • Labrincha Batista, João António
This work evaluates, for the first time, the possibility of producing multifunctional alkali-activated composites combining ultra-low density, low thermal conductivity, high acoustic absorption, and good moisture buffering capacity. The composites were prepared using cork as a lightweight aggregate. This novel material might promote energy savings and tackle the CO2 emissions of the building sector, while simultaneously improve the comfort for inhabitants (e.g. humidity levels regulation and sound pollution reduction). The composites apparent density (as low as 168 kg/m3) and thermal conductivity (as low as 68 mW/m K) are amongst the lowest ever reported for alkali-activated materials (AAM) composites and foams, while their sound absorption ability is comparable to the best performing AAM foams reported to date, but in addition these eco-friendly composites also show good ability to passively adjust the humidity levels inside buildings. The multifunctional properties shown by the cork – AAM composites set them apart from other conventional building materials and might contribute to the global sustainability of the construction sector., Peer Reviewed

Experimental and numerical analysis of the flow behaviour of magnesium wrought alloy AZ31 for deep drawing processes at elevated temperatures

  • Behrens, B. A.
  • Bouguecha, A.
  • Huinink, T.
  • Peshekhodov, I.
  • Matthias, T.
  • Moritz, J.
  • Schrödter, J.
In the present paper, the flow behaviour of the magnesium wrought alloy AZ31 is analysed experimentally and numerically. Especial in deep drawing processes is the knowledge of the flow behaviour important. Depending on the type and size of the hardening and softening of a material, the process parameters such as temperature and sheet thickness must be adjusted to produce a flawless part. The material behaviour of magnesium is different compared to conventional steels, because the hardening and softening effects are changing highly with increasing temperature. For this purpose, yield curves were recorded experimentally at different temperatures by means of layer compression tests. Following the yield curves were converted based on the principle of the plastic work equivalence for finite element simulations (FEA). For validation, numerical simulations of the layer compression test at elevated temperature using the converted yield curve were carried out.

Molecular dynamics simulations on interaction between dislocation and Y2O3 nanocluster in FE

  • Yashiro, Kisaragi
  • Mutsukado, Takanori
  • Tanaka, Minoru
  • Yamaguchi, Akihiro
  • Koga, Kenji
  • Segi, Takashi
  • Okuda, Takanari
For a new insight on the mechanical properties of oxide dispersion strengthened (ODS) steels from atomistic viewpoints, we have implemented molecular dynamics simulations on the interaction between Y2O3 nanocluster and dislocation in bcc Fe. There is so far no all-round interatomic potential function that can represent all the bonding state, i.e. metal, ion and covalent systems, so that we have adopted rough approximation. That is, each atom in Y2O3 is not discriminated but treated as “monatomic” pseudo-atom; and its motion is represented with the simple pairwise potential function as same as Johnson potential for Fe. The potential parameters are fitted to the energy change in the hcp infinite crystal, by using the ab-initio density functional theory(DFT) calculation for explicitly discriminated Y and O. We have set edge/screw dislocation in the centre of periodic slab cell, and approached it to the “YO” monatomic nano-cluster coherently precipitated in bcc-Fe matrix. The dislocation behavior is discussed by changing the size and periodic distance of the nano-cluster. Among the many useful results, we have obtained a conclusion that the edge dislocation is strongly trapped by YO sphere larger than the diameter of d =0 .9nm, while the screw dislocation shows various behavior, e.g. it cuts through the precipiate without remarkable resistance if the dislocation line tension is high, or it changes the slip plane leaving jogs at the position anterior to the precipiate with loose line tension

Evaluación de la sagita corneal en ojos con queratocono

  • Beltrán Arenillas, Jofre
Objectiu: Avaluar la profunditat sagital corneal en pacients amb queratocon en el meridià on es troba l’àpex del queratocon, la qual es tindrà en compte en el disseny i/o adaptació de lents de contacte a usuaris amb aquesta afectació. Mètode: Un total de 52 ulls, 27 ulls amb queratocon incipient i 25 amb queratocon avançat van ser avaluats. Es va identificar la posició de l’àpex del queratocon i es va mesurar el diàmetre corneal i la profunditat de la sagita corneal en el meridià de l’àpex. A més, es van obtenir els valors queratomètrics del radi més corbat i més pla, el Best Fit Sphere, la potència de l’àpex del queratocon i la profunditat de la càmera anterior. Es va realitzar una correlació de la profunditat de la sagita corneal en l’àpex del queratocon amb els demés paràmetres avaluats. Alguns dels paràmetres van ser recollits pel software de l’instrument Pentacam HR, mentre que altres han requerit de càlculs addicionals, basats en mesures manuals amb les eines del propi instrument realitzades en les imatges de Scheimpflug. Resultats: Es va trobar correlació estadística significativa de la profunditat de la sagita corneal en el meridià de l’àpex del queratocon amb el diàmetre corneal (p-value < 0.0001, R2 = 0.7548). No es van observar diferències en la profunditat de la sagita corneal entre queratocons incipients i avançats (p- value > 0.05). A partir del diàmetre corneal i la profunditat de la sagita corneal avaluats, es va proposar una hipotètica caixa de lents de contacte de prova per a casos de queratocon amb un rang de diàmetres de 9.79 mm fins ha 10.77 mm i amb un rang de sagites de 2411.96 m fins 3106.66 m. Conclusions: La posició més freqüent del queratocon es troba en el quadrant temporal inferior, en el meridià de 20°-40° en l’ull dret (27.50% de la mostra) i en el meridià de 120° -140° en l’ull esquerre (24.44% de la mostra). Segons l’estudi realitzat, el diàmetre en el meridià de l’àpex del queratocon és l’únic paràmetre amb suficient capacitat de predicció per a utilitzar com a guia clínic per determinar la sagita.

Powder flow within a pharmaceutical tablet press – a DEM analysis

  • Hildebrandt, Claudia
  • Gopireddy, Srikanth R.
  • Scherliess, Regina
  • Urbanetz, Nora A.
Numerical simulations in pharmaceutical industry are gaining importance as an advanced tool to elucidate the underlying physics in unit operations during tablet manufacturing. Out of different processing stages, powder flow within the tableting machine constitutes one critical step defining inter alia product safety in terms of content and content uniformity of the active pharmaceutical ingredient (API). By means of numerical simulations the Quality by Design (QbD) approach could be integrated to enhance product quality. However, the numerical simulations reported so far either evaluated the powder flow in a simplified system without considering the complex geometrical configuration within the rotary tablet press or used unrealistic micro-mechanical particle properties and sizes. This work presents a numerical approach for studying the powder flow within a force feeder to die/cavity in a rotary tablet press with actual dimensions to evaluate the final product quality. The computations were carried out using an open source discrete element method (DEM) code. The investigated system consists of a hopper, a force feeder comprising three rotating paddle wheels, and a turret with 24 dies. A poly-disperse particle size distribution was used mimicking a low dose direct compression formulation with calibrated micro-mechanical material properties. First of all, a summary of the basic metrics such particle size distribution and mass hold up in the different parts of the feeder is provided. Subsequently emphasis is given to the powder flow patterns in the force feeder that are visualized by particles’ coloring. Results reveal that (1) the powder feeding from the hopper into the feeder shows a gradient across the feeding hopper width causing an intriguing particle mixing, (2) particles are unequally refed from dosing wheel zone and (3) an intermixing between the reverse dosing and filling wheel zone can be identified. Those three visualized powder flow phenomena are supported by quantitative analysis and eventually their influence on the filled dies is being explained. In conclusion, this study helps in visualizing powder flow in a pharmaceutical tablet press disclosing astonishing particle flow phenomena that have not been reported yet.

Molecular dynamics analysis for the brownian motion of nano bubble

  • Abe, T.
  • Kawaguchi, T.
  • Saito, T.
  • Satoh, I.
The smaller bubble whose diameter is below 1 micrometer is called nanobubble or ultra-fine bubble. The size of nano bubble is so small and invisible that the diameter distribution is generally evaluated as a mean square distance(MSD) of brownian motion that is measured by Dynamic Light Scattering(DLS) method based on the Einstein-Stokes equation. The equation, however, is not clarified for the application to the bubble sizing. In our previous study, the different behavior between solid particle and bubble with the same diameter at sub-micro scale was confirmed. In this study, the Brownian motion of nano bubble as well as the solid Pt particle whose diameter are around a few nano meters were simulated with the Molecular Dynamics(MD) method. The simulation employed Lennard Jones(LJ) potential to estimate the MSD of the bubbles and particles by tracing the trajectories of the center of gravity of them and resulted that the displacement of solid particles in liquid argon was less than the predicted amount by the Einstein-Stokes equation. In order to confirm apparent viscosity caused by periodic boundary conditions, the drop velocity of the particle due to the gravity force is measured and apparent viscosity is obtained using Stokes’ low with this velocity. Considering this apparent viscosity, the diameter of the solid particle is approximated using the Einstein-Stokes equation under its diameter of 4 nm. The bubble diameter obtained by the Brownian motion is lower than the Einstein-Stokes equation

Sustainability at the Technical University of Catalonia

  • Grau Saldes, Antoni
The Technical University of Catalonia (UPC) has a large tradition of including Sustainable Development in its technical degrees. Although UPC does not offer degrees in social sciences or humanities, Education for Sustainable Development (ESD) has been closely associated with all the technological degrees and the courses offered. After having achieved the integration of Sustainability and Social Commitment” in standard Subjects as a mandatory transversal competence, we are moving forward in this direction. Actually a “Sustainability Analysis” is now required as a chapter of the final report for all the bachelor theses presented at the Barcelona School of Informatics.

Robust fault detection and isolation of wind turbines using interval observers

  • Blesa Izquierdo, Joaquim
  • Nejjari Akhi-Elarab, Fatiha
  • Rotondo, Damiano
  • Puig Cayuela, Vicenç
In order to improve reliability and safety of wind turbines, it is important to detect and isolate faults as fast as possible. In this work, an approach based on interval observers is used for robust Fault Detection and Isolation (FDI) of wind turbines. Fault detection is addressed using interval observers and unknown but bounded descriptions of the noise and modeling errors, while fault isolation is based on a row-reasoning approach. The performance of the proposed robust FDI scheme is assessed using a set of fault scenarios considered in a wind turbine benchmark., Peer Reviewed

Dos equipamientos en Morella : la escuela hogar y el instituto

  • Beltran Borràs, Júlia
La escuela hogar de Enric Miralles y Carme Pinós (1986-1995) y el instituto de Helio Piñón y Nicanor García (2001-2007) son dos obras arquitectónicas relevantes situadas en Morella, un pequeño núcleo fortificado en el interior de Castellón. En la escuela, los arquitectos tuvieron que afrontar el difícil encargo de construir fuera de las murallas que envuelven la ciudad, enfrentándose al paisaje, a la topografía de fuerte pendiente y al castillo, cuando la administración valenciana de patrimonio ya había rechazado un proyecto al considerar que no respetaba el valor histórico de la ciudad. El encargo posterior del instituto tendrá los mismos condicionantes más uno añadido, la escuela hogar ya construida en el solar vecino. Son dos edificios importantes para la ciudad que escriben una nueva etapa en su historia y para sus habitantes, y hacen revivir con sus diferencias el debate arquitectónico sobre la importancia del contexto histórico y social y el compromiso con el movimiento moderno; sobre empezar cada proyecto de nuevo y utilizar criterios de economía, de medios y recursos; sobre memoria y lógica; sobre la obra que se vive y la obra que se explica por sí misma; sobre la percepción con todos los sentidos y la importancia de la visualidad, etc. La escuela hogar obtuvo el premio de arquitectura española el año 1995, compitiendo con el edificio de Rafael Moneo de “L’illa Diagonal” y el instituto estuvo nominado a los premios FAS el año 2007. Son dos obras muy publicadas que vuelven a situar a Morella en el presente abriendo el debate entre los arquitectos, los usuarios y el público en general sobre la buena arquitectura y las relaciones que establece., Peer Reviewed

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