LED lighting efficacy: Status and directions
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): Paul Morgan Pattison, Monica Hansen, Jeffrey Y. TsaoAbstractA monumental shift from conventional lighting technologies (incandescent, fluorescent, high intensity discharge) to LED lighting is currently transpiring. The primary driver for this shift has been energy efficiency and associated cost savings. LED lighting is now more efficacious than any of the conventional lighting technologies with room to still improve. Near term, phosphor-converted LED packages have the potential for efficacy improvement between 160 lm/W (now) t...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Dislocations hétéro-interfaciales vis perçant une plaquette mince
Publication date: Available online 26 April 2018Source: Comptes Rendus PhysiqueAuthor(s): Salem Neily, Hajer Ghabri, Sami Youssef, Roland BonnetRésuméEn microscopie électronique à transmission et haute résolution, l'échantillon est transparent aux électrons et son épaisseur est souvent inférieure à environ 10 nm. Lorsqu'il contient un défaut linéaire comme une dislocation vis, l'image obtenue peut montrer des perturbations plus ou moins importantes due à la relaxation élastique au voisinage des deux surfaces libres. Par conséquent, l'interprétation théorique d'une image doit inclure cette relaxation dans l...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Many-body localization: An introduction and selected topics
We present a basic introduction to the topic of many-body localization, using the simple example of a quantum spin chain that allows us to illustrate several of the properties of this phase. We then briefly review the current experimental research efforts probing this physics. The largest part of this review is a selection of more specialized questions, some of which are currently under active investigation. We conclude by summarizing the connections between many-body localization and quantum simulations.RésuméQue se passe-t-il dans un système quantique isolé lorsque celui-ci présente du désordre et des interactions ...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Temps de cohérence d'un condensat de Bose–Einstein dans un gaz isolé harmoniquement piégé
Publication date: Available online 7 May 2018Source: Comptes Rendus PhysiqueAuthor(s): Yvan Castin, Alice SinatraRésuméNous étudions la dynamique de phase à l'équilibre d'un condensat dans un gaz de bosons en interaction faible harmoniquement piégé et isolé de l'environnement. Nous trouvons qu'au bout d'un temps long devant le temps de collision typique entre les quasi-particules de Bogolioubov, la variance du déphasage du condensat comporte en général un terme balistique quadratique en temps et un terme diffusif affine en temps. Nous donnons des expressions analytiques des coefficients correspondants, à la lim...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Driven dissipative dynamics and topology of quantum impurity systems
We present different recent applications of this method: (i) how topological properties of the spin such as the Berry curvature and the Chern number can be measured dynamically, and how dissipation affects the topology and the measurement protocol, (ii) how quantum spin chains can experience synchronization dynamics via coupling with a common bath. In the second part of this review, we discuss quantum engineering of spin–boson and related models in circuit quantum electrodynamics (cQED), quantum electrical circuits, and cold-atoms architectures. In different realizations, the Ohmic environment can be represented by a lon...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Driven dissipative dynamics and topology of quantum impurity systems
We present different recent applications of this method: (i) how topological properties of the spin such as the Berry curvature and the Chern number can be measured dynamically, and how dissipation affects the topology and the measurement protocol, (ii) how quantum spin chains can experience synchronization dynamics via coupling with a common bath. In the second part of this review, we discuss quantum engineering of spin–boson and related models in circuit quantum electrodynamics (cQED), quantum electrical circuits, and cold-atoms architectures. In different realizations, the Ohmic environment can be represented by a lon...
Source: Comptes Rendus Physique - May 28, 2018 Category: Physics Source Type: research
Temps de coh érence d'un condensat de Bose–Einstein dans un gaz isolé harmoniquement piégé
Publication date: Available online 7 May 2018 Source:Comptes Rendus Physique Author(s): Yvan Castin, Alice Sinatra We study the condensate phase dynamics in a low-temperature equilibrium gas of weakly interacting bosons, harmonically trapped and isolated from the environment. We find that at long times, much longer than the collision time between Bogoliubov quasi-particles, the variance of the phase accumulated by the condensate grows with a ballistic term quadratic in time and a diffusive term affine in time. We give the corresponding analytical expressions in the limit of a large system, in the collisionless regime a...
Source: Comptes Rendus Physique - May 8, 2018 Category: Physics Source Type: research
Many-body localization: An introduction and selected topics
We present a basic introduction to the topic of many-body localization, using the simple example of a quantum spin chain that allows us to illustrate several of the properties of this phase. We then briefly review the current experimental research efforts probing this physics. The largest part of this review is a selection of more specialized questions, some of which are currently under active investigation. We conclude by summarizing the connections between many-body localization and quantum simulations. (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - April 28, 2018 Category: Physics Source Type: research
Dislocations h étéro-interfaciales vis perçant une plaquette mince
Publication date: Available online 26 April 2018 Source:Comptes Rendus Physique Author(s): Salem Neily, Hajer Ghabri, Sami Youssef, Roland Bonnet A specimen observed in high-resolution transmission electron microscopy is electron transparent and its thickness is often less than about 10 nm. When it contains a linear defect like a screw dislocation, the obtained image can exhibit more or less important perturbations due to elastic relaxation nearby both free surfaces. Therefore, the theoretical interpretation of an image should include this relaxation in the calculation model. In the present work, it is evaluated for ...
Source: Comptes Rendus Physique - April 27, 2018 Category: Physics Source Type: research
Drone-borne GPR design: Propagation issues
The objective is to see if a solution can be found in the near future. (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - April 14, 2018 Category: Physics Source Type: research
RFID: A key technology for Humanity
Publication date: January–February 2018 Source:Comptes Rendus Physique, Volume 19, Issues 1–2 Author(s): Yvan Duroc, Smail Tedjini The RFID (Radio Frequency IDentification) technology is a well-known wireless application for traceability, logistics, and access control. It became ubiquitous in industry and our daily life (ticketing, payment, passports, car keys, etc.). RFID is nowadays a standardized technology; its inherent advantages, which are unitary, identification, wireless communication, and low cost of tags, provide it with decisive practical benefits that drive new developments in terms of concepts and appl...
Source: Comptes Rendus Physique - April 14, 2018 Category: Physics Source Type: research
From quantum physics to digital communication: Single sideband continuous phase modulation
Publication date: January–February 2018 Source:Comptes Rendus Physique, Volume 19, Issues 1–2 Author(s): Haïfa Farès, D. Christian Glattli, Yves Louët, Jacques Palicot, Christophe Moy, Preden Roulleau In the present paper, we propose a new frequency-shift keying continuous phase modulation (FSK–CPM) scheme having, by essence, the interesting feature of single-sideband (SSB) spectrum providing a very compact frequency occupation. First, the original principle, inspired from quantum physics (levitons), is presented. Besides, we address the problem of low-complexity coherent detection of this new waveform, ba...
Source: Comptes Rendus Physique - April 14, 2018 Category: Physics Source Type: research
The double Brewster angle effect
Publication date: January–February 2018 Source:Comptes Rendus Physique, Volume 19, Issues 1–2 Author(s): Laetitia Thirion-Lefevre, Régis Guinvarc'h The Double Brewster angle effect (DBE) is an extension of the Brewster angle to double reflection on two orthogonal dielectric surfaces. It results from the combination of two pseudo-Brewster angles occurring in complementary incidence angles domains. It can be observed for a large range of incidence angles provided that double bounces mechanism is present. As a consequence of this effect, we show that the reflection coefficient at VV polarization can be at least 10 dB...
Source: Comptes Rendus Physique - April 14, 2018 Category: Physics Source Type: research
Solar radio bursts as a tool for space weather forecasting
Publication date: January–February 2018 Source:Comptes Rendus Physique, Volume 19, Issues 1–2 Author(s): Karl-Ludwig Klein, Carolina Salas Matamoros, Pietro Zucca The solar corona and its activity induce disturbances that may affect the space environment of the Earth. Noticeable disturbances come from coronal mass ejections (CMEs), which are large-scale ejections of plasma and magnetic fields from the solar corona, and solar energetic particles (SEPs). These particles are accelerated during the explosive variation of the coronal magnetic field or at the shock wave driven by a fast CME. In this contribution, it is ...
Source: Comptes Rendus Physique - April 14, 2018 Category: Physics Source Type: research
DEMETER observations of manmade waves that propagate in the ionosphere
Publication date: January–February 2018 Source:Comptes Rendus Physique, Volume 19, Issues 1–2 Author(s): Michel Parrot This paper is a review of manmade waves observed by the ionospheric satellite DEMETER. It concerns waves emitted by the ground-based VLF and ELF transmitters, by broadcasting stations, by the power line harmonic radiation, by industrial noise, and by active experiments. Examples are shown including, for the first time, the record of a wave coming from an ELF transmitter. These waves propagate upwards in the magnetosphere and they can be observed in the magnetically conjugated region of emission. Dep...
Source: Comptes Rendus Physique - April 14, 2018 Category: Physics Source Type: research
