Hygroscopicity issues in powder and grain technology

The effect of hygroscopicity on flowability of powders and bulk solids with applications in the packaging industry is experimentally and numerically investigated. Firstly, four granular materials are tested at different water contents to study the impact of relative humidity on some hydro-mechanical properties, namely the hydraulic diffusivity on wetting, as well as the shear strength and compressibility properties of the materials. Next, a capillary model covering a wider water content range –compared to the previous tests– is applied to discrete element simulations of a granular column collapse set-up. These simulations give further insight into important aspects of grain hygroscopicity in packaging and other industrial applications (such as the kinematics of flow and flowability issues), which are outside the scope of conventional experimental testing.Postprint (published version

A new granular column collapse device to characterise flowability of bulk materials

A wide range of bulk materials with different physical properties are nowadays handled in the packaging industry using different material conveying techniques. Nevertheless, experimental methodologies to characterise flowability of granular materials in actual handling conditions are still under development. This paper presents a new fully instrumented device for flowability assessment by granular column collapse of bulk materials. The generated granular flow is monitored by load cells that register the flow heights and by a high-speed video camera that captures the bulk flow kinematics through particle image velocimetry analysis. The 3D surface morphology of the final condition is determined with a 2D laser profile scanner. Results show the effect of varying the initial column aspect ratio on flow response.Peer ReviewedPostprint (published version

A new column collapse apparatus for the characterisation of the flowability of granular materials

The packaging industry is lacking a standard methodology to characterise the granular flow of a wide range of powders and grains in actual handling conditions. We present a new fully-instrumented granular column collapse apparatus for the experimental investigation of granular flow phenomena, by a quasi-two-dimensional set-up with novel features including: a lifting gate activated by a parallelogram mechanism for material release; a reversible pneumatic circuit to impose fluidised and vacuum conditions to the initial granular column; a set of load cells to monitor the basal load distribution during flow propagation; a 3D laser line profile sensor to scan the free surface morphology of the samples at rest; and a high-speed video recording set to capture near-wall flow visualisations and relevant kinematic measures by particle image velocimetry. The selected results on dry flows of oat flakes, copper sulphate fertiliser, and talc powder samples show their distinctive flow dynamics, indicating the good flowability of fertiliser compared to the poor flowability of talc. This research has implications for the selection and design of bulk solids handling equipment, and the calibration and validation of mechanical and numerical models.Peer ReviewedPostprint (author's final draft

Diseño y desarrollo de software para experimentación virtual de física moderna

A nivel de licenciatura es común prescindir de laboratorios avanzados de física moderna debido a lo especializado del equipo y el riesgo que conlleva para el estudiante. Por otro lado el pretender entender alguna teoría solo a través de ecuaciones disminuye la atención de los estudiantes y por lo tanto su desempeño en el curso. Estas razones nos llevan a la creación de software con el cual los estudiantes experimenten virtualmente. En el experimento virtual se corroboran los conceptos físicos expuestos por el profesor en clase obteniendo una mejor asimilación de los mismos, así como la solución de problemas a través del experimento. El software usado incrementa la atención del estudiante ya que analiza de manera gráfica y animada los conceptos, esto lo hace más sencillo, según comentarios de los estudiantes en las encuestas. En este trabajo se presenta el avance del diseño y creación de software para experimentación virtual de física moderna. ABSTRACT At the undergraduate level is common without advanced modern physics laboratories due to specialized equipment and the risk involved for the student. On the other hand pretend to understand some theory only through equations reduces students' attention and therefore their performance in the course. These reasons lead to the creation of software with which students experience virtually. In the virtual experiment physical concepts presented in class by the teacher getting better assimilate them, as well as solving problems through experiments corroborate. The software used increased student attention and analyzing graphical and animated concepts way, this makes it easier, according to comments from students in the polls. In this paper we advance the design and creation of software for virtual testing of modern physics is presented

Tailings desiccation process studied in environmental chamber experiment

Case studies and numerical simulations show that the long-term stability of tailings dams largely depends on the evolution of their water content. Therefore, desiccation is one of the critical processes influencing the tailing dam's safety. In this work, the air-drying of tailings, starting from a sludge condition, is studied using a fully instrumented column experiment, performed in an environmental chamber with temperature and relative humidity control. Based on the experimental observations, a conceptual model for the desiccation process is proposed. The model consists of the combination of two mechanisms driven by evaporation: shrinkage and capillary rise. The latter is only activated after a granular structure develops (shielding skeleton), capable of sustaining the suction-induced intergranular forces. This evidence explains the tendency of real deposits to develop an unsaturated, dry tailings crust enclosing a body of mud-consistency tailings. In addition, the role of dissolved salts in the desiccation process was observed. Solutes in pore water limit the evaporation rate throughout the test by increasing osmotic suction. Moreover, salt precipitation was observed to cause an interruption of the desiccation process on two occasions during the experiment: first, by the formation of a superficial precipitation crust and later by pore clogging within a shallow layer.The authors would like to thank Cristóbal García for the knowledge provided on the Cartagena - La Unión mining region, and the research team of the Geological and Mining Institute of Spain for their collaboration in the collection of tailings samples at the San Cristóbal mine. We would also like to thank the staff of the Soil Mechanics Laboratory of the Department of Civil and Environmental Engineering, Polytechnic University of Catalonia, Spain. Finally, we would like to thank the European Commission (CORDIS) through the project FP7-PEOPLE-IRSES-2008, Marie Curie Action "GEO-engineering EXChanges between Europe and Latin-America" for the financial collaboration in this work.Peer ReviewedPostprint (author's final draft

Experimental design and analysis of a gyroelastic beam

Division of Higher Technical Education of MexicoPublished versio

Discrete element modelling of granular column collapse tests with industrial applications

Describing the behaviour of granular materials is a challenging issue for the industry. Our work concerns packaging industries where packing equipment is designed to handle a wide range of powders and bulk solids with varying physical and mechanical properties. While packaging, a variety of material conveying techniques are used ranging from air fluidisation to discharge of material through a hopper. Thereby even a small improvement in their efficiency can lead to significant benefits, both financial and environmental. Flowability of powders and bulk solids is often experimentally investigated using granular column collapse, as this test provides deep insights into the kinematics of granular flow both at particle and bulk levels [1]. Here, we consider a quasi-two-dimensional set-up with a reservoir containing the granular pile which is instantaneously released onto a channel where run-out takes place. Instead of experiments, we use discrete particle simulations allowing us to quantitatively link bulk-level observations to particle-level properties of the materials, besides enabling inverse analysis leading to indirect measures of micro-scale parameters. We present a simulation strategy aimed at controlling several particle parameters influencing the run-out: - Polydispersity in size, using different particle size distributions; and also in shape, comparing the use of spherical and non-spherical particles, namely cylinders and ellipsoids. - Mechanical properties of the contacts, comprising normal stiffness and dissipation, as well as sliding, rolling and torsion coefficients. Specifically, hygroscopic behaviour of bulk materials is inspected modifying the contact law parameters. Additionally at the bulk level, air fluidisation of the columns before release is studied through the initial packing state by changing the volume fraction of the piles. Numerical simulations are implemented with the open-source code MercuryDPMPostprint (published version

The Role of Vascular Lesions in Diabetes Across a Spectrum of Clinical Kidney Disease

Albuminuria; Diabetes; HistologyAlbuminuria; Diabetes; HistologíaAlbuminúria; Diabetis; HistologiaIntroduction The clinical-histologic correlation in diabetic nephropathy is not completely known. Methods We analyzed nephrectomy specimens from 90 patients with diabetes and diverse degrees of proteinuria and glomerular filtration rate (GFR). Results Thirty-six (40%) subjects had normoalbuminuria, 33 (37%) microalbuminuria, and 21 (23%) non-nephrotic proteinuria. Mean estimated GFR (eGFR) was 65±23 (40% 10% to 20% of the sample. Moderate hyalinosis and arteriolar sclerosis were observed in 80% to 100% of cases with normoalbuminuria, microalbuminuria, proteinuria, as well as in class I, II, or III. Conclusions Weak correspondence between analytical parameters and kidney histology was found. Thus, disease may progress undetected from the early clinical stages of the disease. Finally, vascular damage was a very common finding, which highlights the role of ischemic intrarenal disease in diabetes.This study was funded by the ERA-EDTA (European Renal Association-European Dialysis and Transplant Association). The European Nephrectomy Biobank Project (Appendix). FIS/Fondos FEDER (PI17/00257, PI16/01814, PI19/01756, PI18/01386, PI19/00588, PI19/00815, DTS18/00032, ERA-PerMed-JTC2018 (KIDNEY ATTACK AC18/00064 and PERSTIGAN AC18/00071, ISCIII-RETIC REDinREN RD016/0009), Sociedad Española de Nefrología, FRIAT, Comunidad de Madrid en Biomedicina B2017/BMD-3686 CIFRA2-CM

RED NEURONAL ARTIFICIAL PARA ORIENTACIÓN PROFESIONAL “UDPROFESSION”

El artículo presenta el desarrollo de un software para orientación profesional, a través de la implementación de redes neuronales artificiales. Inicialmente, se da una introducción sobre el tema de la orientación profesional. En segundo lugar, se describe la forma como el psicólogo lleva a cabo el proceso vocacional, destacando la manera como éste razona. Luego se justifica la selección, el diseño e implementación de redes neuronales artificiales.Posteriormente, se aborda el diseño del software, basado en aspectos, tales como: definición de entradas y salidas para la red neuronal, modelo de la red, el preprocesamiento de los datos, método de entrenamiento, entre otros. Por último, se muestra el análisis de pruebas y resultados obtenidos junto con las conclusiones

Physical activation of graphene: An effective, simple and clean procedure for obtaining microporous graphene for high-performance Li/S batteries

Graphene nanosheets are a promising scaffold to accommodate S for achieving high performanceLi/S battery. Nanosheet activation is used as a viable strategy to induce a micropore system and further improve the battery performance. Accordingly, chemical activation methods dominate despite the need of multiple stages, which slow down the process in addition to making them tiresome. Here, a three-dimensional (3D)N-doped graphene specimen was physically activated with CO2, a clean and single step process, and used for the preparation of a sulfur composite (A-3DNG/S). The A-3DNG/S composite exhibited outstanding electrochemical properties such as an excellent rate capability (1,000 mAh·g─1at 2C), high reversible capacity and cycling stability (average capacity ~ 800 mAh·g─1at 1C after 200cycles), values which exceed those measured in chemically activated graphene. Therefore, these results support the use of physical activation as a simple and efficient alternative to improve the performance of carbons as an S host for high-performance Li-S batteries