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Topic Review
Water Retention on Mathematical Surfaces
Water retention on mathematical surfaces is the catching of water in ponds on a surface of cells of various heights on a regular array such as a square lattice, where water is rained down on every cell in the system. The boundaries of the system are open and allow water to flow out. Water will be trapped in ponds, and eventually all ponds will fill to their maximum height, with any additional water flowing over spillways and out the boundaries of the system. The problem is to find the amount of water trapped or retained for a given surface. This has been studied extensively for two mathematical surfaces: magic squares and random surfaces. The model can also be applied to the triangular grid.
  • 477
  • 01 Nov 2022
Topic Review
Wake
In fluid dynamics, a wake may either be: 1. the region of recirculating flow immediately behind a moving or stationary blunt body, caused by viscosity, which may be accompanied by flow separation and turbulence, or 2. the wave pattern on the water surface downstream of an object in a flow, or produced by a moving object (e.g. a ship), caused by density differences of the fluids above and below the free surface and gravity (or surface tension).
  • 2.1K
  • 08 Nov 2022
Topic Review
VSOP (Planets)
The semi-analytic planetary theory VSOP (French: Variations Séculaires des Orbites Planétaires) is a mathematical model describing long-term changes (secular variation) in the orbits of the planets Mercury to Neptune. The earliest modern scientific model considered only the gravitational attraction between the Sun and each planet, with the resulting orbits being unvarying Keplerian ellipses. In reality, all the planets exert slight forces on each other, causing slow changes in the shape and orientation of these ellipses. Increasingly complex analytical models have been made of these deviations, as well as efficient and accurate numerical approximation methods. VSOP was developed and is maintained (updated with the latest data) by the scientists at the Bureau des Longitudes in Paris. The first version, VSOP82, computed only the orbital elements at any moment. An updated version, VSOP87, computed the positions of the planets directly at any moment, as well as their orbital elements with improved accuracy. At present, the difference between computational predictions and observations is so small that the model seems essentially complete in its physical principles. Such hypothetical deviations are often referred to as post-Keplerian effects.
  • 387
  • 28 Nov 2022
Topic Review
Void
Cosmic voids are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies. The cosmological evolution of the void regions differs drastically from the evolution of the Universe as a whole: there is a long stage when the curvature term dominates, which prevents the formation of galaxy clusters and massive galaxies. Hence, although even the emptiest regions of voids contain more than ~15% of the average matter density of the Universe, the voids look almost empty for an observer. Voids typically have a diameter of 10 to 100 megaparsecs (30 to 300 million light years); particularly large voids, defined by the absence of rich superclusters, are sometimes called supervoids. They were first discovered in 1978 in a pioneering study by Stephen Gregory and Laird A. Thompson at the Kitt Peak National Observatory. Voids are believed to have been formed by baryon acoustic oscillations in the Big Bang, collapses of mass followed by implosions of the compressed baryonic matter. Starting from initially small anisotropies from quantum fluctuations in the early universe, the anisotropies grew larger in scale over time. Regions of higher density collapsed more rapidly under gravity, eventually resulting in the large-scale, foam-like structure or "cosmic web" of voids and galaxy filaments seen today. Voids located in high-density environments are smaller than voids situated in low-density spaces of the universe. Voids appear to correlate with the observed temperature of the cosmic microwave background (CMB) because of the Sachs–Wolfe effect. Colder regions correlate with voids and hotter regions correlate with filaments because of gravitational redshifting. As the Sachs–Wolfe effect is only significant if the universe is dominated by radiation or dark energy, the existence of voids is significant in providing physical evidence for dark energy.
  • 2.8K
  • 18 Oct 2022
Topic Review
Virus Nanotechnology
Virus nanotechnology is the use of viruses as a source of nanoparticles for biomedical purposes. Viruses are made up of a genome and a capsid; and some viruses are enveloped. Most virus capsids measure between 20-500 nm in diameter. Because of their nanometer size dimensions, viruses have been considered as naturally occurring nanoparticles. Virus nanoparticles have been subject to the nanoscience and nanoengineering disciplines. Viruses can be regarded as prefabricated nanoparticles. Many different viruses have been studied for various applications in nanotechnology: for example, mammalian viruses are being developed as vectors for gene delivery, and bacteriophages and plant viruses have been used in drug delivery and imaging applications as well as in vaccines and immunotherapy intervention.
  • 1.3K
  • 15 Nov 2022
Biography
Vince Ebert
Vince Ebert (* 23 May 1968 in Miltenberg as Holger Ebert) is a Germany comedian, lecturer,[1] presenter, author, and recipient of a degree in physics. Vince Ebert grew up in Amorbach in Lower Franconia (Bavaria). Ebert's classmates gave him the name "Vince" when he was 14 years old because he was a fan of Vince Weber.[2] After his military service with the Signal Corps,[3] he studied physics
  • 441
  • 29 Nov 2022
Topic Review
Vigil (Spacecraft)
Vigil, formerly known as Lagrange, is a planned solar weather mission by the European Space Agency (ESA). It envisions two spacecraft to be positioned at Lagrangian points L1 and L5. Monitoring space weather includes events such as solar flares, coronal mass ejections, geomagnetic storms, solar proton events, etc. Monitoring would help predict arrival times at the Earth and any potential effect on infrastructure. The Vigil spacecraft are anticipated to launch in the mid 2020s. On 17 May 2021, ESA began soliciting design concept studies from various European industrial and scientific consortiums for the mission. A final design will be selected after approximately 18 months, in late 2022. Simultaneously, the ESA announced the No-Name Mission contest to replace the placeholder Lagrange name. The winning name, Vigil, was announced on 10 February 2022.
  • 426
  • 10 Oct 2022
Topic Review
Vat Purnima
Vat Purnima or pournima chavan or Wat Purnima (वट पूर्णिमा, vaṭapūrṇimā, also called Vat Savitri is a celebration observed by married women in the Western Indian states of Gujarat, Maharashtra, Goa and some regions of eastern Uttar Pradesh. On this Purnima or "full moon" during the three days of the month of Jyeshtha in the Hindu calendar (which falls in May-June in the Gregorian calendar) a married woman marks her love for her husband by tying a ceremonial thread around a banyan tree. The celebration is based on the legend of Savitri and Satyavan as narrated in the epic Mahabharata.
  • 285
  • 15 Nov 2022
Biography
Uschi Steigenberger
Ursula "Uschi" Steigenberger (25 April 1951 — 12 December 2018) OBE FInstP was a German condensed matter physicist and director of the ISIS neutron source. She was one of the founders of the Institute of Physics Juno Award. Steigenberger was born in Augsburg. She studied physics at the University of Würzburg, where she remained for her graduate studies. She earned a PhD in condensed matter
  • 355
  • 01 Dec 2022
Topic Review
Uniaxial Tensile Test
Tensile testing, also known as tension testing, is a fundamental materials science and engineering test in which a sample is subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength, breaking strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young's modulus, Poisson's ratio, yield strength, and strain-hardening characteristics. Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of isotropic materials. Some materials use biaxial tensile testing. The main difference between these testing machines being how load is applied on the materials.
  • 3.5K
  • 07 Nov 2022
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