Institute Plasmas e Fusao Nuclear

Lisbon, Portugal

Institute Plasmas e Fusao Nuclear

Lisbon, Portugal

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Tercas H.,Telecommunications Institute of Portugal | Tercas H.,Institute Plasmas e Fusao Nuclear | Ribeiro S.,Telecommunications Institute of Portugal | Pezzutto M.,Telecommunications Institute of Portugal | And 3 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2017

We propose a quantum thermal machine composed of two nanomechanical resonators (two membranes suspended over a trench in a substrate) placed a few μm from each other. The quantum thermodynamical cycle is powered by the Casimir interaction between the resonators and the working fluid is the polariton resulting from the mixture of the flexural (out-of-plane) vibrations. With the help of piezoelectric cells, we select and sweep the polariton frequency cyclically. We calculate the performance of the proposed quantum thermal machines and show that high efficiencies are achieved thanks to (i) the strong coupling between the resonators and (ii) the large difference between the membrane stiffnesses. Our findings can be of particular importance for applications in nanomechanical technologies where a sensitive control of temperature is needed. © 2017 American Physical Society.

Santos M.,Institute Plasmas e Fusao Nuclear | Balula S.,Institute Plasmas e Fusao Nuclear | Fortunato J.,Institute Plasmas e Fusao Nuclear | Fernandes H.,Institute Plasmas e Fusao Nuclear
Proceedings of 2016 13th International Conference on Remote Engineering and Virtual Instrumentation, REV 2016 | Year: 2016

In this paper we use a locally developed adaptive watering system as an example of a remote controlled laboratory (RCL) developed with standard open hardware and using libraries taken from the e-lab. This experiment is a particular case that could benefit from a large number of RCLs proposing different water budget strategies, allowing the studies of the best controller algorithm to save water. The water consumption log can be monitored in real-time and served to any user as a distributed remote laboratory with support of a Raspberry PI and a web connection, using an open source Arduino board and custom made shield. The ultimate goal of RCLs will be achieved when anyone can easily publish their own experiment in the WWW. © 2016 IEEE.

Oliva E.,ENSTA ParisTech | Fajardo M.,Institute Plasmas e Fusao Nuclear | Li L.,ENSTA ParisTech | Sebban S.,ENSTA ParisTech | And 2 more authors.
Optics Letters | Year: 2012

To date, plasma-based soft x-ray lasers have demonstrated experimentally 1 μJ, 1 ps (1 MW) pulses. This Letter reports extensive study using time-dependant Maxwell-Bloch code of seeding millimeter scale plasmas that store more than 100 mJ in population inversion. Direct seeding of these plasmas has to overcome very strong amplified spontaneous emission (ASE) as well as prevent wake-field amplification. Below 100 nJ injected energy, seed produces pulses with picosecond duration. To overcome this limitation, a new scheme has been studied, taking advantage of a plasma preamplifier that dramatically increases the seed energy prior to entering the main plasma amplifier leading to ASE and wake-free, fully coherent 21.6 μJ, 80 fs pulses (0.27 GW). © 2012 Optical Society of America.

Floriani E.,French National Center for Scientific Research | Vilela Mendes R.,University of Lisbon | Vilela Mendes R.,Institute Plasmas e Fusao Nuclear
Journal of Computational Physics | Year: 2013

The construction of stochastic solutions is a powerful method to obtain localized solutions in configuration or Fourier space and for parallel computation with domain decomposition. Here a stochastic solution is obtained for the magnetohydrodynamics equations. Some details are given concerning the numerical implementation of the solution which is illustrated by an example of generation of long-range magnetic fields by a velocity source. © 2013 Elsevier Inc.

Fortunato J.,Institute Plasmas e Fusao Nuclear | Lopes J.,Institute Plasmas e Fusao Nuclear | Balula S.,Institute Plasmas e Fusao Nuclear | Neto R.,Linkare T.I. Lda | Fernandes H.,Institute Plasmas e Fusao Nuclear
Proceedings of 2016 13th International Conference on Remote Engineering and Virtual Instrumentation, REV 2016 | Year: 2016

Remote Controlled Laboratories (RLCs) are expanding everywhere and there is a need for an accessible, yet robust and affordable framework to convey private experiments to the Internet based on the "Internet of Things". In this article we shall introduce a framework based on ready available open hardware and software that can be used in schools, or even at home by anyone with elementary programming skills. In a simple way we discuss how to connect a microcontroller capable of handling an experimental apparatus to the Internet based on a Raspberry Pi, and how to connect the latter using the Go-Lab framework. Moreover remote maintenance for this distributed apparatus can be provided on-line namely for update the firmware when needed. An example of an experiment provided within this technology is given showing the possibilities of this approach. © 2016 IEEE.

Mendes R.V.,University of Lisbon | Mendes R.V.,Institute Plasmas e Fusao Nuclear
Physica Scripta | Year: 2015

Non-commutative tomography is a technique originally developed and extensively used by Professors M A Man'ko and V I Man'ko in quantum mechanics. Because signal processing deals with operators that, in general, do not commute with time, the same technique has a natural extension to this domain. Here, a review is presented of the theory and some applications of non-commutative tomography for time series as well as some new results on signal processing on graphs. © 2015 The Royal Swedish Academy of Sciences.

Bertolami O.,University of Lisbon | Bertolami O.,Institute Plasmas e Fusao Nuclear | Francisco F.,Institute Plasmas e Fusao Nuclear | Francisco F.,University of Lisbon | And 4 more authors.
Space Science Reviews | Year: 2010

A methodology based on point-like sources is discussed, enabling a reliable estimate of the acceleration of the Pioneer 10 and 11 probes caused by thermal effects. A sensitivity analysis of the several parameters of the model allows for a clear indication of the possible thermal origin of the so-called Pioneer anomaly. © 2009 Springer Science+Business Media B.V.

Bertolami O.,University of Porto | Bertolami O.,Institute Plasmas e Fusao Nuclear | Carrilho P.,University of Lisbon | Paramos J.,University of Lisbon
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In this paper, we study the effects of an interaction between dark matter and dark energy through a two-scalar-field model with a potential V(χ)=e -λ P(χ), where P(χ) is a polynomial. We show that the cosmic expansion dynamics of the Universe is reproduced for a large range of the bare mass of the dark matter field and that there exist solutions with transient accelerated expansion. A modification in the exponential behavior of the potential is studied, with important physical implications, including the possibility of more realistic transient acceleration solutions. © 2012 American Physical Society.

Loarte A.,Culham Center for Fusion Energy | Loarte A.,ITER Organization | Leyland M.J.,University of York | Mier J.A.,University of Cantabria | And 7 more authors.
Nuclear Fusion | Year: 2013

The build-up of plasma parameters following the H-mode transition in JET has been analysed in view of its consequences for the alpha power evolution in the access to burning plasma conditions in ITER. JET experiments show that the build-up of plasma temperature both at the plasma core and the plasma edge occurs in timescales comparable to the energy confinement time. In contrast, the evolution of the edge and core densities differs strongly depending on the level of plasma current in the discharge and of the associated NBI penetration. For higher plasma current H-mode discharges (Ip > 2.0-2.5 MA, depending on plasma shape), with naturally higher plasma densities for which NBI penetration is poorer, the core density evolves in much longer timescales than the edge density leading to the formation of rather hollow density profiles. These hollow density profiles persist for timescales of several energy confinement times until they are usually terminated by a sawtooth. Modelling of the JET experiments with JETTO shows that the density build-up following the H-mode transition can be described with a purely diffusive model, despite the low collisionalities of high current H-mode plasmas at JET. The consequences of these JET experimental/modelling findings for the access to burning plasma conditions in the ITER QDT = 10 scenario are presented. © 2013 IAEA, Vienna.

Rodriguez-Pascual M.,CIEMAT | Scott B.D.,Max Planck Institute for Plasma Physics (Garching) | Ribeiro T.T.,Max Planck Institute for Plasma Physics (Garching) | Ribeiro T.T.,Institute Plasmas e Fusao Nuclear | And 3 more authors.
IEEE Transactions on Plasma Science | Year: 2010

The study of core turbulence represents a key line of research in fusion plasmas. By adding collisions and electromagnetic induction to the parallel dynamics of the standard six-moment toroidal model, it is possible to study the gyrofluid electromagnetic phenomena in the context of edge turbulence with the GEM code. Currently, the code describes the fluctuation free-energy conservation in a gyrofluid model by means of the polarization equation which relates the ExB flow and eddy energy to the combinations of the potential, the density, and the perpendicular temperature. To do so, supercomputers have been used only to date. In this paper, we demonstrate its feasibility as a cluster application on a production environment based on any kind of distributed memory, enhancing in this way its scope. The scalability (which grows linearly with a correlation factor of 0.99978) and the correctness of our solution with respect to the previous GEM version have been evaluated in a local cluster of 88 nodes. The fault tolerance and the Grid suitability have been demonstrated by executing our application in the EUrope Fusion for ITER Applications infrastructure by adapting the code to this paradigm and by improving its parallel Grid performance. It can be employed on its own or belonging to workflows in order to perform a wider more complex analysis of fusion reactors. © 2010 IEEE.

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