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Topic Review
Aether Drag Hypothesis
In the 19th century, the theory of the luminiferous aether as the hypothetical medium for the propagation of light was widely discussed. An important part of this discussion was the question concerning the state of motion of Earth with respect to this medium. The aether drag hypothesis dealt with the question of whether or not the luminiferous aether is dragged by or entrained within moving matter. According to the first variant no relative motion exists between Earth and aether; according to the second one, relative motion exists and thus the speed of light should depend on the speed of this motion ("aether wind"), which should be measurable by instruments at rest on Earth's surface. Specific aether models were invented by Augustin-Jean Fresnel who in 1818 proposed that the aether is partially entrained by matter. The other one was proposed by George Stokes in 1845, in which the aether is completely entrained within or in the vicinity of matter. While Fresnel's almost stationary theory was apparently confirmed by the Fizeau experiment (1851), Stokes' theory was apparently confirmed by the Michelson–Morley experiment (1881, 1887). This contradictory situation was resolved by the works of Hendrik Antoon Lorentz (1895, 1904) whose Lorentz ether theory banished any form of aether dragging, and finally with the work of Albert Einstein (1905) whose theory of special relativity does not contain the aether as a mechanical medium at all.
  • 1.4K
  • 04 Nov 2022
Topic Review
Aeroelasticity Methods in Turbomachinery
Aeroelastic phenomena in turbomachinery are one of the most challenging problems to model using computational fluid dynamics (CFD) due to their inherent nonlinear nature, the difficulties in simulating fluid–structure interactions and the considerable computational requirements. Nonetheless, accurate modelling of self-sustained flow-induced vibrations, known as flutter, has proved to be crucial in assessing stability boundaries and extending the operative life of turbomachinery. Flutter avoidance and control is becoming more relevant in compressors and fans due to a well-established trend towards lightweight and thinner designs that enhance aerodynamic efficiency.
  • 1.5K
  • 09 Sep 2021
Topic Review
Advancing Surface Plasmon Enhanced Fluorescence based POC technologies
Point-of-care (POC) diagnostic platforms are globally employed in modern smart technologies to detect events or changes in the analyte concentration and provide qualitative and quantitative information in biosensing. Surface plasmon-coupled emission (SPCE) technology has emerged as an effective POC diagnostic tool for developing robust biosensing frameworks. The simplicity, robustness and relevance of the technology has attracted researchers in physical, chemical and biological milieu on account of its unique attributes such as high specificity, sensitivity, low background noise, highly polarized, sharply directional, excellent spectral resolution capabilities.
  • 159
  • 18 Jan 2024
Topic Review
Advances in Bioinspired Superhydrophobic Surfaces Made from Silicones
As research on superhydrophobic materials inspired by the self-cleaning and water-repellent properties of plants and animals in nature continues, the superhydrophobic preparation methods and the applications of superhydrophobic surfaces are widely reported. Silicones are preferred for the preparation of superhydrophobic materials because of their inherent hydrophobicity and strong processing ability. In the preparation of superhydrophobic materials, silicones can both form micro-/nano-structures with dehydration condensation and reduce the surface energy of the material surface because of their intrinsic hydrophobicity. The superhydrophobic layers of silicone substrates are characterized by simple and fast reactions, high-temperature resistance, UV resistance, and anti-aging. Although silicone superhydrophobic materials have the disadvantages of relatively low mechanical stability, this can be improved by the rational design of the material structure. 
  • 660
  • 27 Feb 2023
Topic Review
Advancement in UV-Visible-IR Camouflage Textiles & Camouflage Physics
Optical theory of Camouflage engineering has been invented for defence protection. This optical theory can be implemented by defence scientists to explore camouflage products and multidimensional branches of optical technologies. Advancement in ultraviolet-visible-near infrared (UV-Vis-IR) camouflage engineering has been designed for defence protection. Camouflage physics has been explained through camouflage textiles and camouflage materials. This technique of camouflage engineering can be explored to defence technology for the design and manufacturing of combat product against multidimensional combat backgrounds such as dry leaves, green leaves, tree bark-woodland combat background; water-marine combat background; sand-desertland combat background; stone-stoneland combat background; snow-snowland combat background; sky combat background; ice-iceland combat background and concrete-concreteland combat background (DGTWSICB). This is a novel addition of camouflage technology for the engineering progress of camouflage product design. Hence, camouflage engineering has been briefly reported by “Anowar Hossain’s invention of camouflage physics at PhD School, first version submitted to Nobel committee for Nobel nomination in 2023 under affiliation of RMIT University”. http://dx.doi.org/10.13140/RG.2.2.29936.23048, https://doi.org/10.5281/zenodo.8286832
  • 450
  • 06 Oct 2023
Topic Review
Advanced Telescope for High Energy Astrophysics
Advanced Telescope for High-ENergy Astrophysics (Athena) is an X-ray observatory mission selected by European Space Agency (ESA) within its Cosmic Vision program to address the Hot and Energetic Universe scientific theme. Athena will operate in the energy range of 0.2–12 keV and will offer spectroscopic and imaging capabilities exceeding those of currently operating X-ray astronomy satellites – e.g. the Chandra X-ray Observatory and XMM-Newton – by at least one order of magnitude on several parameter spaces simultaneously.
  • 397
  • 30 Sep 2022
Topic Review
Advanced Technology Large-Aperture Space Telescope
The Advanced Technology Large-Aperture Space Telescope (ATLAST) is an 8– to 16.8–meter UV-optical-NIR space telescope proposed by the Space Telescope Science Institute (STScI), the science operations center for the Hubble Space Telescope (HST). If launched, ATLAST would be a replacement and successor for the HST, with the ability to obtain spectroscopic and imaging observations of astronomical objects in the ultraviolet, optical, and infrared wavelengths, but with substantially better resolution than either HST or the planned James Webb Space Telescope (JWST). Like JWST, ATLAST would be launched to the Sun-Earth L2 Lagrange point. ATLAST is envisioned as a flagship mission of the 2025–2035 period, designed to determine whether there is life elsewhere in the galaxy. It would attempt to accomplish this by searching for "biosignatures" (such as molecular oxygen, ozone, water, and methane) in the spectra of terrestrial exoplanets. The backronym that the project currently uses, 'ATLAST', is in fact a pun. It refers to the time taken to decide on a true, visible-light, successor for the Hubble Space Telescope. However, it is expected that, as the project progresses, a new name would be chosen for the mission.
  • 1.0K
  • 25 Oct 2022
Topic Review
ADM Formalism
The ADM formalism (named for its authors Richard Arnowitt, Stanley Deser and Charles W. Misner) is a Hamiltonian formulation of general relativity that plays an important role in canonical quantum gravity and numerical relativity. It was first published in 1959. The comprehensive review of the formalism that the authors published in 1962 has been reprinted in the journal General Relativity and Gravitation, while the original papers can be found in the archives of Physical Review.
  • 857
  • 01 Nov 2022
Topic Review
ADM Energy
The ADM formalism (named for its authors Richard Arnowitt, Stanley Deser and Charles W. Misner) is a Hamiltonian formulation of general relativity that plays an important role in canonical quantum gravity and numerical relativity. It was first published in 1959. The comprehensive review of the formalism that the authors published in 1962 has been reprinted in the journal General Relativity and Gravitation, while the original papers can be found in the archives of Physical Review.
  • 688
  • 08 Nov 2022
Topic Review
Action
In physics, action is a numerical value describing how a physical system has changed over time. Action is significant because the equations of motion of the system can be derived through the principle of stationary action. In the simple case of a single particle moving with a specified velocity, the action is the momentum of the particle times the distance it moves, added up along its path, or equivalently, twice its kinetic energy times the length of time for which it has that amount of energy, added up over the period of time under consideration. For more complicated systems, all such quantities are added together. More formally, action is a mathematical functional which takes the trajectory, also called path or history, of the system as its argument and has a real number as its result. Generally, the action takes different values for different paths. Action has dimensions of energy × time or momentum × length, and its SI unit is joule-second (like the Planck constant h).
  • 2.4K
  • 25 Nov 2022
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