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

Weighted Contrastive Divergence

Learning algorithms for energy based Boltzmann architectures that rely on gradient descent are in general computationally prohibitive, typically due to the exponential number of terms involved in computing the partition function. In this way one has to resort to approximation schemes for the evaluation of the gradient. This is the case of Restricted Boltzmann Machines (RBM) and its learning algorithm Contrastive Divergence (CD). It is well-known that CD has a number of shortcomings, and its approximation to the gradient has several drawbacks. Overcoming these defects has been the basis of much research and new algorithms have been devised, such as persistent CD. In this manuscript we propose a new algorithm that we call Weighted CD (WCD), built from small modifications of the negative phase in standard CD. However small these modifications may be, experimental work reported in this paper suggest that WCD provides a significant improvement over standard CD and persistent CD at a small additional computational cost

FULL POPULATION TESTING FOR VALIDATION OF HUMAN RESTRAINT SYSTEMS ON COMMERCIAL AND NON COMMERCIAL ERGOMETERS

Human missions to Mars is one of the main objectives for scientific space international community and major goals on physiological and biomechanical space research is reduction of muscle atrophy (Fitts, 2000; Zange, 1997). MARES (Muscular Atrophy Research and Exercise System) system is an ergometer to be flown and installed in the International Space Station in the year 2007. This system will allow neuromuscular and gravitational physiology research on orbit. MARES consists of a control electronics that drives a motor, to which a subject .is connected by means of a restraining system named HRS (Human Restraint System). This ergometer can be programmed to work in 14 different modes (Isometric, Isotonic, Isokinetic, Spring, Friction, Additional Moment of Inertia/Mass, Pseudogravitational, Position Control, Velocity Control, Torque/Force Control, Power Control, Physical Elements, Extended Torque/Force Control, Quick Release). All of this modes are available for 11 movements, corresponding to main body joints and movements

Fair weather induced charges and currents on tall wind turbines and experiments with kites

Earth’s atmospheric potential rapidly increases up to few tens of kilovolts below 200 m altitude. This potential drop will induce charge to tall objects at ground by virtue of electrostatic induction. In this work we investigate the induced electric charges in fair weather to a 1.5 MW and 5 MW wind turbines. The effect of rotation is included and the current calculated result in currents of few micro-amps. The production of point discharge and corona is investigated and some experiments are conducted by means of instrumented kites.Preprin

Diseño de sistema servidor de monitorización de máquinas eléctricas con acceso a datos por la nube

En el presente documento se recoge el diseño e implementación de un sistema de toma de medidas de consumo de equipos eléctricos de forma remota con monitorización y acceso a datos a través de la nube basado en Raspberry Pi usando el protocolo MQTT y la implementación de una aplicación Android para demostrar su funcionalidad. Se adjunta también un estudio económico de desarrollo del proyecto así como un estudio de aplicación del mismo a casos reales.This document provides the design and the implementation of an electrical equipment consumption measurement system remotely with cloud-based monitoring and data access using a Raspberry Pi and the MQTT protocol and the subsequent implementation of an Android application to demonstrate its functionality. Attached to it there is also a budget of project development as well as its study of application to real cases.Romero-Ortells Labrada, F. (2017). Diseño de sistema servidor de monitorización de máquinas eléctricas con acceso a datos por la nube. http://hdl.handle.net/10251/90067TFG

Nonuniform traffic distribution model in reverse link of multilaterate/multiservie WCDMA/based systems

This paper focuses on the modeling of the reverse link of a wideband code division multiple access system in a nonhomogeneous environment with a single cell. Multiple traffic spatial and service nonuniformities are considered in the analytical model, and then, expressions for required transmitted power and the associated outage probability and block error rate are derived. Special attention is also paid to the effect caused by different transmission bit rates and the spatial location of the traffic nonuniformities. From the presented expressions, it is possible to set appropriate load thresholds to control the desired error rate. Although the model considers a single cell, results in terms of maximum allowable load can also be applicable in multicell scenarios.Peer Reviewe

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

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