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
Stress Measures
The most commonly used measure of stress is the Cauchy stress tensor, often called simply the stress tensor or "true stress". However, several other measures of stress can be defined. Some such stress measures that are widely used in continuum mechanics, particularly in the computational context, are: The Kirchhoff stress (τ). The Nominal stress (N). The first Piola-Kirchhoff stress (P). This stress tensor is the transpose of the nominal stress (P=NT). The second Piola-Kirchhoff stress or PK2 stress (S). The Biot stress (T).
  • 531
  • 06 Dec 2022
Topic Review
Ray Tracing
In physics, ray tracing is a method for calculating the path of waves or particles through a system with regions of varying propagation velocity, absorption characteristics, and reflecting surfaces. Under these circumstances, wavefronts may bend, change direction, or reflect off surfaces, complicating analysis. Ray tracing solves the problem by repeatedly advancing idealized narrow beams called rays through the medium by discrete amounts. Simple problems can be analyzed by propagating a few rays using simple mathematics. More detailed analysis can be performed by using a computer to propagate many rays. When applied to problems of electromagnetic radiation, ray tracing often relies on approximate solutions to Maxwell's equations that are valid as long as the light waves propagate through and around objects whose dimensions are much greater than the light's wavelength. Ray theory does not describe phenomena such as interference and diffraction, which require wave theory (involving the phase of the wave).
  • 531
  • 03 Nov 2022
Topic Review
Horror Vacui
In physics, horror vacui, or plenism (/ˈpliːnɪzəm/), commonly stated as "nature abhors a vacuum", is a postulate attributed to Aristotle, who articulated a belief, later criticized by the atomism of Epicurus and Lucretius, that nature contains no vacuums because the denser surrounding material continuum would immediately fill the rarity of an incipient void. He also argued against the void in a more abstract sense (as "separable"), for example, that by definition a void, itself, is nothing, and following Plato, nothing cannot rightly be said to exist. Furthermore, insofar as it would be featureless, it could neither be encountered by the senses, nor could its supposition lend additional explanatory power. Hero of Alexandria challenged the theory in the first century CE, but his attempts to create an artificial vacuum failed. The theory was debated in the context of 17th-century fluid mechanics, by Thomas Hobbes and Robert Boyle, among others, and through the early 18th century by Sir Isaac Newton and Gottfried Leibniz.
  • 530
  • 08 Oct 2022
Topic Review
Metasurface Photodetectors
Photodetectors are the essential building blocks of a wide range of optical systems. Typical photodetectors only convert the intensity of light electrical output signals, leaving other electromagnetic parameters, such as the frequencies, phases, and polarization states unresolved. 
  • 528
  • 26 Jan 2022
Topic Review
Current Status of The Celestial Reference Frame
The International Celestial Reference Frame (ICRF) is based on the currently accepted International Celestial Reference System (ICRS) and forms the basis for all positional astronomy in the radio domain. The first three generations of this frame have been built from high precision Very Long Baseline Interferometry (VLBI) astrometric measurements of positions of extragalactic radio sources (quasars and other radio-loud Active Galactic Nuclei, AGN), with each successive realization of the ICRF becoming more precise. VLBI angular position accuracy has now improved to near the 100 micro-arcsecond (μas) level. Catalogues of positions of extragalactic radio sources with the highest precision, such as the ICRF, are crucial to many applications, such as determining the Earth’s orientation in space, providing calibrator sources for astronomy, studying the motion of tectonic plates, and in spacecraft navigation. The ICRF also contributes towards the realization of a Global Geodetic Reference Frame (GGRF) for sustainable development, a resolution adopted by the United Nations in 2015.
  • 527
  • 28 Jul 2022
Topic Review
Marchywka Effect
The Marchywka effect refers to electrochemical cleaning of diamond using an electric field induced with remote electrodes.
  • 527
  • 25 Oct 2022
Topic Review
Label-Free Multiphoton Microscopy
Label-free microscopy methods rely on photophysical processes to generate signals through specific interactions with biological molecules and offer great potential for basic research and clinical applications.
  • 527
  • 28 Apr 2021
Topic Review
Kounotori Integrated Tether Experiment
Kounotori 6 (こうのとり6号機), also known as HTV-6, is the sixth flight of the H-II Transfer Vehicle, an uncrewed cargo spacecraft launched to resupply the International Space Station. It was launched at 13:26:47 UTC on 9 December 2016 aboard H-IIB launch vehicle from Tanegashima Space Center.
  • 527
  • 27 Oct 2022
Topic Review
All-d-Metal Heusler Alloys
A promising strategy, resulting in novel compounds with better mechanical properties and substantial magnetocaloric effects, is favoring the d–d hybridization with transition-metal elements to replace p–d hybridization. The term given to these materials is “all-d-metal”. 
  • 525
  • 10 Feb 2023
Topic Review
The Advanced Applications of 2D Materials in SERS
Surface-enhanced Raman scattering (SERS) as a label-free, non-contact, highly sensitive, and powerful technique has been widely applied in determining bio- and chemical molecules with fingerprint recognitions. 2-dimensional (2D) materials with layered structures, tunable optical properties, good chemical/physical stabilities, and strong charge–transfer interaction with molecules have attracted researchers’ interests. Two-D materials with a large and flat surface area, as well as good biocompatibility have been considered promising candidates in SERS and widely applied in chemical and bio-applications. It is well known that the noble metallic nanostructures with localized surface plasmon effects dominate the SERS performance. The combination of noble metallic nanostructure with 2D materials is becoming a new and attractive research domain. The SERS substrates combined with 2D materials, such as 2D graphene/metallic NPs, 2D materials@metallic core-shell structures, and metallic structure/2D materials/metallic structure are intensely studied.
  • 524
  • 25 Nov 2022
  • Page
  • of
  • 118
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
Video Production Service
Feedback