Which could be the role of Hybrid Fibre Coax in Next Generation Access networks?

Next generation access networks (NGAN) will support a renewed communication structure where opportunities lie in the provision of ubiquitous broadband connectivity, a wide variety of new applications, appealing contents and a general support to the sustainable growth of diverse sectors. From their deployment it is expected a wealth of innovations, jobs creation and a new wave of economic growth. In this paper we discuss which could be the role of Hybrid Fibre Coax (HFC) in the Next Generation Access Network (NGAN) roadmap. Thus, we propose a simplified model for making approximate cost calculations for HFC deployment based on the geographic and sociodemographic characteristics of Spain. Considering the latest evolution of HFC based on DOCSIS 3.0 from integrated (I-CMTS) towards modular (M-CMTS), the results from the model are compared with the most competitive NGAN for ultrabroadband speeds: Fibre to the Home (FTTH) based on Gigabitcapable Passive Optical Networks (GPON

Gravitational lensing by wave dark matter halos

Wave Dark Matter (WaveDM) has recently gained attention as a viable candidate to account for the dark matter content of the Universe. In this paper we explore the extent to which dark matter halos in this model, and under what conditions, are able to reproduce strong lensing systems. First, we analytically explore the lensing properties of the model -- finding that a pure WaveDM density profile, a soliton profile, produces a weaker lensing effect than other similar cored profiles. Then we analyze models with a soliton embedded in an NFW profile, as has been found in numerical simulations of structure formation. We use a benchmark model with a boson mass of $m_a=10^{-22}{\rm eV}$, for which we see that there is a bi-modality in the contribution of the external NFW part of the profile, and actually some of the free parameters associated with it are not well constrained. We find that for configurations with boson masses $10^{-23}$ -- $10^{-22}{\rm eV}$, a range of masses preferred by dwarf galaxy kinematics, the soliton profile alone can fit the data but its size is incompatible with the luminous extent of the lens galaxies. Likewise, boson masses of the order of $10^{-21}{\rm eV}$, which would be consistent with Lyman-$\alpha$ constraints and consist of more compact soliton configurations, necessarily require the NFW part in order to reproduce the observed Einstein radii. We then conclude that lens systems impose a conservative lower bound $m_a > 10^{-24}$ and that the NFW envelope around the soliton must be present to satisfy the observational requirements.Comment: 26 pages, 7 figures, Publishe

Teleological structure of scientific and mathematical education

One of the main educational objectives in the current Spanish curricula is to develop mathematical and scientific competences, understood as the set of skills and abilities needed to apply Mathematics and Science in situations where are required. This is therefore closely related, on one hand, to the functionality of the knowledge, in the sense of its usefulness in problem solving and in mathematical and science modeling problems. And, on the other hand, is related to the understanding of disciplinary knowledge, a cognitive phenomenon that enables and gives competence to the individual to elaborate contextualized and accurate answers. These answers involve the use of mathematical and scientific knowledge in some of the categories of their phenomenological and epistemological dimensions. For this reason, in this work we carry out a theoretical and reflexive analysis that tries to determine which aspects of the Mathematics and Science Education should be promoted in order to optimize the formative dimension of an individual in these disciplines. This dimension, frequently forgotten in learning and teaching processes, turns out to be, in conjunction with the functional and instrumental dimensions, necessary to acquire the appropriate knowledge in Mathematics and Science that will enable future citizens to permanently adapt to the environment and eventually transform it positively. The results of the analysis show the components of this dimension that should be prioritized in the Science and Mathematics Education: the intellectual autonomy, understood as the ability to think for ourselves and to put in use our abilities and skills to generate information to solve real life problems and to make the right decisions; the moral autonomy, defined as the capacity to face with real life problems with ethical implications; and the social autonomy, understood as the aptitude to make decisions using social abilities and skills.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.“Criterios e instrumentos de evaluación de unidades de enseñanza y aprendizaje” (PPIT.UMA.B1.2017/16) financiado por la Universidad de Málaga en la convocatoria de 2017-2018

Raising the Efficiency Limit of the GaAs-based Intermediate Band Solar Cell Through the Implementation of a Mololithic Tandem with an AlGaAs top Cell.

The high efficiency limit of the intermediate band solar cell (IBSC) corresponds to the case of using as intermediate band (IB) host material a semiconductor with gap in the range of 2 eV. Traditional photovoltaic materials, such as Si and GaAs, are not appropriate to produce IB devices because their gaps are too narrow. To overcome this problem, we propose the implementation of a multi-junction device consisting of an IBSC combined with a single gap cell. We calculate the efficiency limits using the detailed balance model and conclude that they are very high (> 60% under maximum concentration) for any fundamental bandgap from 0.7 to 3.6 eV in the IBSC inserted in the tandem. In particular, the two-terminal tandem of a GaAs-based IBSC current matched to an optimized AlGaAs top cell has an efficiency limit as high as 64%

Silica final lenses under HiPER laser fusion reactor operation conditions

We have studied the thermo-mechanical response and atomistic degradation of final lenses in HiPER project. Final silica lenses are squares of 75 × 75 cm2 with a thickness of 5 cm. There are two scenarios where lenses are located at 8 m from the centre: •HiPER 4a, bunches of 100 shots (maximum 5 DT shots <48 MJ at ≈0.1 Hz). No blanket in chamber geometry. •HiPER 4b, continuous mode with shots ≈50 MJ at 10 Hz to generate 0.5 GW. Liquid metal blanket in chamber design

An overview on armor research for the laser fusion project HiPER

During the current preparatory phase of the European laser fusion project HiPER, an intensive effort has being placed to identify an armour material able to protect the internal walls of the chamber against the high thermal loads and high fluxes of x-rays and ions produced during the fusion explosions. This poster addresses the different threats and limitations of a poly-crystalline Tungsten armour. The analysis is carried out under the conditions of an experimental chamber hypothetically constructed to demonstrate laser fusion in a repetitive mode, subjected to a few thousand 48MJ shock ignition shots during its entire lifetime. If compared to the literature, an extrapolation of the thermomechanical and atomistic effects obtained from the simulations of the experimental chamber to the conditions of a Demo reactor (working 24/7 at hundreds of MW) or a future power plant (producing GW) suggests that “standard” tungsten will not be a suitable armour. Thus, new materials based on nano-structured W and C are being investigated as possible candidates. The research programme launched by the HiPER material team is introduced

Sostenibilidad de recursos energéticos fosiles y minerales: Uso racional de abastecmiento y cosumo

Esta primera parte referente a la “Garantía del Suministro Energético” sirve como introducción al informe realizado por este Grupo de Trabajo sobre “Sostenibilidad de los Recursos Energéticos Fósiles y Minerales: Uso Racional en el Abastecimiento y Consumo”. Queremos, en primer lugar, agradecer al Congreso del Medio Ambiente la oportunidad de poder debatir este tema de trascendencia capital para la economía global y, de forma especial, a José Sierra, Consejero de la Comisión Nacional de Energía su contribución desinteresada e imprescindible para el desarrollo de este trabajo

Integrating the RTO in the MPC: an adaptive gradient-based approach

Model Predictive Control (MPC) is the most used advanced control technique in process industries, since it ensures stability, constraints satisfaction and convergence to the setpoint. The optimal setpoint is calculated by the Real Time Optimizer (RTO), minimizing the economic objective taking into account the operational limits of the plant. Since RTO employs complex stationary nonlinear models to perform the optimization and a larger sampling time than the controller, the economic setpoints calculated by the RTO may be inconsistent for the MPC layer and the economic performance of the overall controller may be worse than expected. The aim of this work is to propose an MPC controller that explicitly integrates the RTO into the MPC control layer. The proposed strategy is based on the MPC for tracking; the optimization problem to be solved only requires one evaluation of the gradient of the economic cost function at each sampling time. Based on this gradient, a second order approximation of the economic function is obtained and used in the MPC optimization problem resulting in a convex optimization problem. Recursive feasibility and convergence to the optimal equilibrium point is ensured

Modelling and Characterization of Multiple Level Intermediate Band Solar Cell

Intermediate band solar cells (IBSCs) are a new kind of devices capable of surpassing the Shockley Queisser efficiency limit for conventional solar cells. This novel technology requires the use of a new type of material named intermediate band (IB) material which makes a better use of the solar spectrum thanks to the existence of a collection of electronic levels within the band gap of the semiconductor. Quantum Dots (QDs) remain as a feasible technology to implement IB materials. InAs/GaAs QD-IBSCs were manufactured in order to test the validity of the concept, although their real size and shape are far from the optimum. This causes extra electron levels to appear within the nanostructure confining potential, degrading the performance of the device. In this paper, the effect of these extra levels will be studied through a multiple level IBSC model based on the detailed balance, but modified so a term accounting for the non-radioactive recombination (NRR) is also included. The model is completed with constant fitting parameters so the concentration JL-VOC curves (which do not incorporate series resistance effects) can be fitted. Several QD-IBSCs where manufactured, measured and fitted with this model, rendering relevant information about the recombination nature of the QD-IBSC

EMTP model of a bidirectional cascaded multilevel solid state transformer for distribution system studies

This paper presents a time-domain model of a MV/LV bidirectional solid state transformer (SST). A multilevel converter configuration of the SST MV side is obtained by cascading a single-phase cell made of the series connection of an H bridge and a dual active bridge (dc-dc converter); the aim is to configure a realistic SST design suitable for MV levels. A three-phase four-wire converter has been used for the LV side, allowing the connection of both load/generation. The SST model, including the corresponding controllers, has been built and encapsulated as a custom-made model in the ATP version of the EMTP for application in distribution system studies. Several case studies have been carried out in order to evaluate the behavior of the proposed SST design under different operating conditions and check its impact on power qualityPostprint (published version