Solar radio bursts as a tool for space weather forecasting
Publication date: January–February 2018Source: Comptes Rendus Physique, Volume 19, Issues 1–2Author(s): Karl-Ludwig Klein, Carolina Salas Matamoros, Pietro ZuccaAbstractThe 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 - July 5, 2018 Category: Physics Source Type: research
Foreword
Publication date: January–February 2018Source: Comptes Rendus Physique, Volume 19, Issues 1–2Author(s): Tullio Joseph Tanzi, Madhu Chandra (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Conforming discretizations of boundary element solutions to the electroencephalography forward problem
We report on the fact that several standardly used discretizations of these formulations are consistent only with an L2-framework, requiring the expansion term to be a square integrable function (i.e., in a Petrov–Galerkin scheme with expansion and testing functions). Instead, those techniques are not consistent when a more appropriate mapping in terms of fractional-order Sobolev spaces is considered. Such a mapping allows the expansion function term to be a less regular function, thus sensibly reducing the need for mesh refinements and low-precisions handling strategies that are currently required. These more favorable ...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
DEMETER observations of manmade waves that propagate in the ionosphere
Publication date: January–February 2018Source: Comptes Rendus Physique, Volume 19, Issues 1–2Author(s): Michel ParrotAbstractThis 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. ...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
The double Brewster angle effect
Publication date: January–February 2018Source: Comptes Rendus Physique, Volume 19, Issues 1–2Author(s): Laetitia Thirion-Lefevre, Régis Guinvarc'hAbstractThe 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 ...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Dossier Sommaire
Publication date: January–February 2018Source: Comptes Rendus Physique, Volume 19, Issues 1–2Author(s): (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
LED advances accelerate universal access to electric lighting
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): Peter Alstone, Arne JacobsonAbstractA rapid increase in the performance and quality of white LED light sources has changed the dynamics of electricity access in the last 10 years, reaching tens of millions of people with electric light who previously had no viable alternatives to fuel-based lighting, which is dangerous and expensive. Eliminating fuel-based lighting is a key public health, safety, social equality, and environmental opportunity that is now achievable. Technology advances in LEDs, other super-efficient appliances...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
LED-based white light
This article discusses the use of light-emitting diodes to generate white light – a research forefront in Physics and Ergonomics. We first present various technological approaches to white-light generation. After a general introduction to the human vision system, we discuss two key aspects of the quality of white light: the color of the light itself, and the color rendering of illuminated objects. We present the tools underlying modern color science, and review key color rendering metrics, from the well-known color rendering index to the latest improvements in the field.RésuméCet article présente l'utilisation des dio...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
LED lighting, ultra-low-power lighting schemes for new lighting applications
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): Marc FontoynontAbstractIn 2018, Solid-State Lighting (SSL) can totally outperform, if properly designed, most of other lighting products used for general lighting applications. This concerns various attributes such as luminous efficacy, life, spectral qualities, dimming potential, and more and more total cost of ownership. SSL can also mimic a large variety of reference light sources from candlelight to sunlight. The absence of international standards concerning LED modules remains the major difficulty for luminaire manufactur...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Editorial Board
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Dossier Sommaire
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Foreword
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): Claude Weisbuch, Erich Spitz, Aurélien David (Source: Comptes Rendus Physique)
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Historical perspective on the physics of artificial lighting
We describe the evolution of lighting technologies used throughout the ages, and how the need for improvements was such that any new technology giving better and cheaper lighting was immediately implemented. Thus, every revolution in energy sources – gas, petrol electricity – was first put to large-scale use in lighting. We describe in some detail several “ancient” techniques of scientific interest, along with their physical limitations. Electroluminescence – the phenomenon by which LEDs directly convert electricity into light – was long thought to only be of use for indicators or flat panel displays supposed t...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
Invention, development, and status of the blue light-emitting diode, the enabler of solid-state lighting
Publication date: March–April 2018Source: Comptes Rendus Physique, Volume 19, Issue 3Author(s): Daniel Feezell, Shuji NakamuraAbstractThe realization of the first high-brightness blue-light-emitting diodes (LEDs) in 1993 sparked a more than twenty-year period of intensive research to improve their efficiency. Solutions to critical challenges related to material quality, light extraction, and internal quantum efficiency have now enabled highly efficient blue LEDs that are used to generate white light in solid-state lighting systems that surpass the efficiency of conventional incandescent lighting by 15–20×. Here we dis...
Source: Comptes Rendus Physique - July 5, 2018 Category: Physics Source Type: research
