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This article is about photovoltaic electricity. Semiconductor physics explains how the absorption of light generates electrical charges. The anatomy of the photovoltaic cell makes it possible to transform these charges into current. These cells are then assembled into modules, then into panels, which are finally integrated into a complete photovoltaic system comprising, in addition to the production part, an intermediate part for adapting the energy produced to the needs of the application, which constitutes the last part, the part where the energy is consumed.
The most sensitive piping in nuclear power plants, i.e. the main primary circuit of the reactors, is in safety class 1, and is accordingly subjected to specific calculations. Some complex effects, namely heat and fatigue gradients, which can be ignored in standard piping calculations, have to be taken into account. This article is not an exhaustive summary of the regulations governing this type of calculation (ASME, RCC-M), but provides additional explanations on important points, in particular the procedure for linearizing constraints applied to heat gradients, and the calculation of the use factor for the quantification of fatigue-induced damage.
Sonochemistry involves the chemical and physical processes that take place under the action of ultrasound in solution. These processes are mainly due to cavitation, which involves the formation and implosion of gas microbubbles in liquids subjected to ultrasonic waves. As these microbubbles collapse, they release enormous amounts of energy, in the form of intense local heat, comparable to the temperature at the surface of the sun (~ 5000 K), high pressure (≤1000 atm), shock waves and acoustic microcurrents. Each cavitation bubble can be compared to a microreactor capable of initiating chemical reactions without external input of heat, reagents or catalysts. This article presents an overview of the main current applications of sonochemistry in organic chemistry.
In the current energy context, hydrogen production is a subject of debate. It appears to be a very good alternative to fossil fuels, however, its production remains for economic reasons, mainly derived from steam reforming of fossil fuels. This steam reforming technique, even if it is the most profitable, leads to gray hydrogen which at best can become blue after decarbonization. It is therefore necessary to find an alternative to produce green hydrogen at a reasonable cost (competitive with that of gray hydrogen) and among the possible technologies, water electrolysis appears at the forefront and represents a promising alternative.
Supercontinuum fiber lasers, with their high brightness and wide frequency range extending from visible to infrared, have garnered significant interest and have a major impact on fundamental science and numerous applications in metrology, spectroscopy, and imaging. This paper reviews recent advances in the development of supercontinuum fiber lasers based on specialty optical fibers, such as fluoride, chalcogenide, tellurite, and silicon-core fibers for the mid-infrared range, doped silica fibers, and hollow-core gas-filled fibers for the ultraviolet range, as well as all normal dispersion fibers for ultra-stable and coherent supercontinuum generation.
The study and analysis of vibrations (or signals) has grown considerably in recent years, due to the development of increasingly sophisticated techniques and a wide range of needs in various fields: mechanics (transport, machinery, etc.), acoustics, optics, transmissions, etc. The study and analysis of vibrations (or signals) has grown considerably in recent years, due to the development of increasingly sophisticated techniques and a wide range of needs in various fields (mechanics (transport, machinery, etc.), acoustics, optics, transmissions, etc.). Current concerns can be broadly divided into three categories. The first, which is theoretical, concerns the dynamic calculation of structures as an extension of strength of materials and continuum mechanics.
Stimulated by increasingly restrictive regulatory pressure, research activities about the replacement of toxic (organic) solvents continue to experience sustained development. Many alternatives have been proposed but the experts have to face a dual chemical and economic reality. Indeed, it is necessary to find a replacement solvent that matches both the expected properties and the cost of implementing the replacement solution. After reminding some definitions and the major trends in the field of green solvents, this article addresses some substitution strategies, before reviewing the main solutions of substitution.
Biomass burnings are becoming increasingly common and their recurrence both in France, with a record number of fires in the summer of 2022, and worldwide, with fires in Australia in 2019-2020 and in California (USA) in 2021-2022, make them a priority subject for study. Biomass fires contribute to the air quality deterioration through the emission of fine particles, the production of ozone and secondary aerosols, and accelerate climate change through the production of greenhouse gases (GHGs). All the species emitted during combustion are highly various within the smoke plume and are sources of chemical reactions during transport of the plume in the troposphere and lower stratosphere.
While often described by a single one-step reaction, combustion is actually a much more complex process. A deep understanding of this complexity requires the use of detailed kinetic models describing each reaction step, from the fuel reactant down to water and carbon dioxide. Such kinetic models, tested and validated against experimental data obtained in controlled conditions, are mandatory to develop cleaner, safer and more efficient technologies. Oxidation mechanisms of fossil fuels and biofuels are thus discussed and their specificities highlighted. The formation pathways of main pollutants (nitrogen oxides, soot precursors and unburned hydrocarbons) are also presented.
The optical properties of material media are a key to understanding the myriad applications of optics. In this article, an overview of the fundamental aspects of the interaction between light and matter is presented along several aspects: the properties of elements such as atoms, followed by the basic arrangements of molecules and solids. On this basis, the essential explanations of how light is absorbed, emitted, scattered or refracted are discussed, as well as the role of sub-wavelength structuring of material media. Three sections on emitters, detectors and spectroscopy techniques are finally accounted according to these various classes of interaction.
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