Encontrado(s) 2242200 resultado(s)
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Encontrada(s) 224220 página(s)
Measurement of the 235U(n,f) cross section relative to the 6Li(n,t) and 10B(n,a) standards from thermal to 170 keV neutron energy range at n_TOF
- Amaducci, Simone
- Cosentino, Luigi
- Barbagallo, Massimo
- Calviño Tavares, Francisco
- Casanovas Hoste, Adrià
- Tarifeño Saldivia, Ariel Esteban
- Cortés Rossell, Guillem Pere
The 235U(n,f) cross section was measured in a wide energy range at n_TOF relative to 6Li(n,t) and 10B(n,alpha), with high resolution and in a wide energy range, with a setup based on a stack of six samples and six silicon detectors placed in the neutron beam. This allowed us to make a direct comparison of the reaction yields under the same experimental conditions, and taking into account the forward/backward emission asymmetry. A hint of an anomaly in the 10÷30 keV neutron energy range had been previously observed in other experiments, indicating a cross section systematically lower by several percent relative to major evaluations. The present results indicate that the evaluated cross section in the 9÷18 keV neutron energy range is indeed overestimated, both in the recent updates of ENDF/B-VIII.0 and of the IAEA reference data. Furthermore, these new high-resolution data confirm the existence of resonance-like structures in the keV neutron energy region. The new, high accuracy results here reported may lead to a reduction of the uncertainty in the 1÷100 keV neutron energy region. Finally, the present data provide additional confidence on the recently re-evaluated cross section integral between 7.8 and 11 eV.
An approximate expression to estimate signal-to-noise improvement in cylindrical near-field measurements
- Romeu Robert, Jordi
- Jofre Roca, Lluís
- Cardama Aznar, Ángel
A very simple approximate expression for the process gain (PG) for the cylindrical case is derived. The different approximations and assumptions required to obtain this expression are shown. This expression might be useful for most practical cylindrical near-field measurements, providing a very simple mean to assess the near-field dynamic range requirements to obtain a desired far-field signal-to-noise ratio (SNR)., Peer Reviewed
Ver en: http://hdl.handle.net/2117/1706
- Blázquez Fernández, Carlos
This project presents the fundamental aspects of the RFID (Radio-frequency identifica-tion) technology used to establish wireless communications. The project focuses on thepassive mode of RFID, where the receiver does not have any power supply, which allowsits miniaturization and low cost.On the other hand, two articles from different authors are analyzed. The first consists onthe design of a very low power passive receiver through various techniques of optimizationin the hardware’s manufacture.In the second, a drone is used as an intermediate element between the transmitter and thereceiver to extend up to 10 times the typical range of passive RFID. The study focuses onthe treatment of the RF signal to considerably eliminate the interferences and to preciselylocalize the receiver., Outgoing
- Roqueiro, Nestor
- Claumann, Carlos
- Guillamon Grabolosa, Antoni
- Fossas Colet, Enric
We explore the identification of neuronal voltage traces by artificial neural networks based on wavelets (Wavenet). More precisely, we apply a modification in the representation of dynamical systems by Wavenet which decreases the number of used functions; this approach combines localized and global scope functions (unlike Wavenet, which uses localized functions only). As a proof-of-concept, we focus on the identification of voltage traces obtained by simulation of a paradigmatic neuron model, the Morris-Lecar model. We show that, after training our artificial network with biologically plausible input currents, the network is able to identify the neuron's behaviour with high accuracy, thus obtaining a black box that can be then used for predictive goals. Interestingly, the interval of input currents used for training, ranging from stimuli for which the neuron is quiescent to stimuli that elicit spikes, shows the ability of our network to identify abrupt changes in the bifurcation diagram, from almost linear input-output relationships to highly nonlinear ones. These findings open new avenues to investigate the identification of other neuron models and to provide heuristic models for real neurons by stimulating them in closed-loop experiments, that is, using the dynamic-clamp, a well-known electrophysiology technique., Peer Reviewed
- Cermak, Martin
- Hapla, Vaclav
- Horak, David
This contribution is focused on a description of implementation details for solver related to the slope stability benchmarks in 3D. Such problems are formulated by the standard elastoplastic models containing the Mohr-Coulomb yield criterion and by the limit analysis of collapse states. The implicit Euler method and higher order ﬁnite elements are used for discretization. The discretized problem is solved by non-smooth Newton-like methods in combination with incremental methods of limit load analysis. In this standard approach, we propose several innovative techniques. Firstly, we use recently developed sub-diﬀerential based constitutive solution schemes. Such an approach is suitable for non-smooth yield criteria, and leads better return-mapping algorithms. For example, a priori decision criteria for each return-type or simpliﬁed construction of consistent tangent operators are applied. The parallel codes are developed in MATLAB using Parallel Computing Toolbox. For parallel implementation of linear systems, we use the TFETI domain decomposition method. It is a non-overlapping method where the Lagrange multipliers are used to enforce continuity on the subdomain interfaces and satisfaction of the Dirichlet boundary conditions.
Evaluating silver-plated nylon (Ag/PA66) e-textiles for bioelectrical impedance analysis (BIA) application
- Logothetis, Irini
- Gil Galí, Ignacio
- Vatansever, Derman
- Dabnichki, Peter
- Pirogova, Elena
Bioelectrical Impedance Analysis (BIA) is an established method for assessing integrity of biotissue. Adapting BIA as a diagnostic tool to monitor electrophysiological activity gives rise to evidence-based objective diagnostic approaches as opposed to visual assessment currently performed by practitioners in wound healing management. Advancements in the telecommunication and textile industries have made the Internet of Wearable Things (IoWT), the future of telemedicine. E-textile electrodes give us the ability for long-term monitoring applications; however, they are associated with electrode polarization impedance (Zp) contributing to the electrode-skin impedance (Zes). By studying the design of e-textile electrodes, we can reduce Zp and characterise it relative to changes in skin properties, such as skin temperature and perspiration. In this study, we examined the effects of selected textile substrates on changes in Zp of e-textile electrodes, and characterized Zp in a climatic chamber with temperature and relative humidity settings emulating skin temperature and perspiration. An air permeability test was also conducted to account for the physiological comfort of the e-textile electrodes. Our results demonstrate that a polyester non-woven felt substrate is ideal for use in e-textile electrodes. By understanding and quantifying the relationship between Zp, skin temperature and perspiration, this insight can be incorporated into the calibration process of BIA systems for accurate long-term monitoring resulting in an objective assessment of changes in tissue integrity., Peer Reviewed
Experimental and numerical investigations of concrete behaviour at meso-level during quasi-static splitting tension
- Suchorzewski, J.
- Tejchman, J.
The paper describes experimental and numerical results of quasi-static splitting tensile tests on concrete specimens at meso-scale level. The loading strip was made of plywood or steel. Fracture in concrete was detected at the aggregate level by means of three nondestructive methods: 3D x-ray micro-computed tomography, 2D scanning electron microscope and manual 2D digital microscope. The discrete element method was used to directly simulate experiments at the meso-scale. Concrete was modelled as a random heterogeneous 4-phase material composed of aggregate particles, cement matrix, interfacial transitional zones and macro-voids based on micro-tomographic images. Two-dimensional calculations with real concrete microstructure were carried out. A satisfactory agreement between numerical and experimental results was achieved. The evolution of contact normal forces, coordination number, broken contacts, grain rotations and crack displacements was also investigated. In addition, each energy component was calculated and analyzed at a different stress-displacement stage.
- Mier Torrecilla, Mónica de
- Idelsohn Barg, Sergio Rodolfo
- Oñate Ibáñez de Navarra, Eugenio
In this monograph we have focused on understanding the basic physical principles of multi-fluid flows and the difficulties that arise in their numerical simulation. We have extended the Particle Finite Element Method to problems involving several different fluids with the aim of exploiting the fact that Lagrangian methods are specially well suited for tracking any kind of interfaces. We have developed a numerical scheme able to deal with large jumps in the physical properties (density and viscosity), include surface tension, and accurately represent all types of discontinuities in the flow variables at the interface. The scheme is based on decoupling the nodes position, velocity and pressure variables through the Picard linearization and a pressure segregation method which takes into account the interface conditions. The interface has been defined to be aligned with the moving mesh, so that it remains sharp along time. Furthermore, pressure degrees of freedom have been duplicated at the interface nodes to represent the discontinuity of this variable due to surface tension and variable viscosity, and the mesh has been refined in the vicinity of the interface to improve the accuracy of the computations. We have applied the resulting scheme to several academic and geological problems,such as the two-fluid sloshing, extrusion of viscous fluids, bubble rise and breakup,mixing of magmatic liquids and negatively buoyant jets.
- Sousa Lamas, Antonio
- Camiola, V.D.
- Romano, V.
In a previous paper  we have studied the coexistence of coupled 2DEG and 3DEG in the proximity of a silicon-oxide interface in a MOSFET devising a hydrodynamical model obtained by taking the moment of the kinetic transport equation and by resorting to the maximum entropy principle for the closure relations. Here we classify the model from the point of view of PDEs by showing that it is hyperbolic in the relevant physical region of density, energy, velocity and energy fluxes in each subband and bulk electrons.