Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Biaxial Tensile Test
Biaxial tensile test is a tensile testing in which the sample is stretched in two distinct directions. This technique is used to obtain the mechanical characteristics of anisotropic materials, such as composite materials, textiles, and soft biological tissues. There are three main types of biaxial tensile testing: Bursting test, based on a circular specimen clamped along the edge and inflated by air or water under pressure until the specimen bursts; Cylinder test, based on a hollow cylinder subjected to internal pressure and axial pressure or tension; Plane biaxial test, which offers the best result because of the independent force introduction in the two main directions.
  • 1.4K
  • 28 Oct 2022
Topic Review
Causal Fermion System
The theory of causal fermion systems is an approach to describe fundamental physics. It provides a unification of the weak, the strong and the electromagnetic forces with gravity at the level of classical field theory. Moreover, it gives quantum mechanics as a limiting case and has revealed close connections to quantum field theory. Therefore, it is a candidate for a unified physical theory. Instead of introducing physical objects on a preexisting spacetime manifold, the general concept is to derive spacetime as well as all the objects therein as secondary objects from the structures of an underlying causal fermion system. This concept also makes it possible to generalize notions of differential geometry to the non-smooth setting. In particular, one can describe situations when spacetime no longer has a manifold structure on the microscopic scale (like a spacetime lattice or other discrete or continuous structures on the Planck scale). As a result, the theory of causal fermion systems is a proposal for quantum geometry and an approach to quantum gravity. Causal fermion systems were introduced by Felix Finster and collaborators.
  • 463
  • 28 Oct 2022
Topic Review
Pellicle Mirror
A pellicle mirror (diminutive of pellis, a skin or film) is an ultra-thin, ultra-lightweight semi-transparent mirror employed in the light path of an optical instrument, splitting the light beam into two separate beams, both of reduced light intensity. Splitting the beam allows its use for multiple purposes simultaneously. The thinness of the mirror practically eliminates beam or image doubling due to a non-coincident weak second reflection from the nominally non-reflecting surface, a problem with mirror-type beam splitters.
  • 351
  • 28 Oct 2022
Topic Review
Stokes Boundary Layer
In fluid dynamics, the Stokes boundary layer, or oscillatory boundary layer, refers to the boundary layer close to a solid wall in oscillatory flow of a viscous fluid. Or, it refers to the similar case of an oscillating plate in a viscous fluid at rest, with the oscillation direction(s) parallel to the plate. For the case of laminar flow at low Reynolds numbers over a smooth solid wall, George Gabriel Stokes – after whom this boundary layer is called – derived an analytic solution, one of the few exact solutions for the Navier–Stokes equations. In turbulent flow, this is still named a Stokes boundary layer, but now one has to rely on experiments, numerical simulations or approximate methods in order to obtain useful information on the flow. The thickness of the oscillatory boundary layer is called the Stokes boundary-layer thickness.
  • 1.6K
  • 28 Oct 2022
Topic Review
Electromagnetically Excited Acoustic Noise and Vibration
Electromagnetically excited acoustic noise is audible sound directly produced by materials vibrating under the excitation of electromagnetic forces. Some examples of electromagnetically excited acoustic noise include the hum of transformers, the whine of some rotating electric machines, or the buzz of fluorescent lamps. The hissing of high voltage transmission lines is due to corona discharge, not magnetism. The phenomenon is also called audible magnetic noise, electromagnetic acoustic noise, or electromagnetically-induced acoustic noise, or more rarely, electrical noise, "coil noise", or "coil whine", depending on the application. The term electromagnetic noise is generally avoided as the term is used in the field of electromagnetic compatibility, dealing with radio frequencies. The term electrical noise describes electrical perturbations occurring in electronic circuits, not sound. For the latter use, the terms electromagnetic vibrations or magnetic vibrations, focusing on the structural phenomenon are less ambiguous. Acoustic noise and vibrations due to electromagnetic forces can be seen as the reciprocal of microphonics, which describes how a mechanical vibration or acoustic noise can induce an undesired electrical perturbation.
  • 1.4K
  • 28 Oct 2022
Topic Review
Perturbation
In astronomy, perturbation is the complex motion of a massive body subjected to forces other than the gravitational attraction of a single other massive body. The other forces can include a third (fourth, fifth, etc.) body, resistance, as from an atmosphere, and the off-center attraction of an oblate or otherwise misshapen body.
  • 692
  • 28 Oct 2022
Topic Review
Corium (Nuclear Reactor)
Corium, also called fuel-containing material (FCM) or lava-like fuel-containing material (LFCM), is a material that is created in the core of a nuclear reactor during a meltdown accident. It resembles natural lava in its consistency. It consists of a mixture of nuclear fuel, fission products, control rods, structural materials from the affected parts of the reactor, products of their chemical reaction with air, water and steam, and, in the event that the reactor vessel is breached, molten concrete from the floor of the reactor room.
  • 734
  • 28 Oct 2022
Topic Review
Wireless USB
Wireless USB (Universal Serial Bus) was a short-range, high-bandwidth wireless radio communication protocol created by the Wireless USB Promoter Group which intended to increase the availability of general USB-based technologies. It was unrelated to Wi-Fi, and different from the Cypress WirelessUSB offerings. It was maintained by the WiMedia Alliance which ceased operations in 2009. Wireless USB is sometimes abbreviated as "WUSB", although the USB Implementers Forum discouraged this practice and instead prefers to call the technology Certified Wireless USB to distinguish it from the competing UWB standard. Wireless USB was based on the (now defunct) WiMedia Alliance's Ultra-WideBand (UWB) common radio platform, which is capable of sending 480 Mbit/s at distances up to 3 metres (9.8 ft) and 110 Mbit/s at up to 10 metres (33 ft). It was designed to operate in the 3.1 to 10.6 GHz frequency range, although local regulatory policies may restrict the legal operating range in some countries. The standard is now obsolete, and no new hardware has been produced for many years. Support for the standard was deprecated in Linux 5.4 and removed in Linux 5.7
  • 359
  • 28 Oct 2022
Topic Review
Soil Moisture Active Passive
Soil Moisture Active Passive (SMAP) is an United States environmental research satellite launched on 31 January 2015. It was one of the first Earth observation satellites developed by NASA in response to the National Research Council’s Decadal Survey.
  • 353
  • 28 Oct 2022
Topic Review
Naturalness
In physics, naturalness is the property that the dimensionless ratios between free parameters or physical constants appearing in a physical theory should take values "of order 1" and that free parameters are not fine-tuned. That is, a natural theory would have parameter ratios with values like 2.34 rather than 234000 or 0.000234. The requirement that satisfactory theories should be "natural" in this sense is a current of thought initiated around the 1960s in particle physics. It is a criterion that arises from the seeming non-naturalness of the standard model and the broader topics of the hierarchy problem, fine-tuning, and the anthropic principle. However it does tend to suggest a possible area of weakness or future development for current theories such as the Standard Model, where some parameters vary by many orders of magnitude, and which require extensive "fine-tuning" of their current values of the models concerned. The concern is that it is not yet clear whether these seemingly exact values we currently recognize, have arisen by chance (based upon the anthropic principle or similar) or whether they arise from a more advanced theory not yet developed, in which these turn out to be expected and well-explained, because of other factors not yet part of particle physics models. The concept of naturalness is not always compatible with Occam's razor, since many instances of "natural" theories have more parameters than "fine-tuned" theories such as the Standard Model. Naturalness in physics is closely related to the issue of fine-tuning, and over the past decade many scientists argued that the principle of naturalness is a specific application of Bayesian statistics. In the history of particle physics, the naturalness principle has given correct predictions three times - in the case of electron self-energy, pion mass difference and kaon mass difference.
  • 684
  • 28 Oct 2022
  • Page
  • of
  • 131
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback