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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).
  • 532
  • 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).
  • 532
  • 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.
  • 531
  • 08 Oct 2022
Biography
Neil Gershenfeld
Neil A. Gershenfeld (born 1959 or 1960)[1] is an United States professor at MIT and the director of MIT's Center for Bits and Atoms, a sister lab to the MIT Media Lab. His research studies are predominantly focused in interdisciplinary studies involving physics and computer science, in such fields as quantum computing, nanotechnology, and personal fabrication. Gershenfeld attended Swarthmore Col
  • 530
  • 30 Nov 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”. 
  • 529
  • 10 Feb 2023
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. 
  • 529
  • 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.
  • 528
  • 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
Biography
David Carroll
David Carroll (born January 13, 1963) is a U.S. physicist, materials scientist and nanotechnologist, Fellow of the American Physical Society, and director of the Center for Nanotechnology and Molecular Materials at Wake Forest University.[1] He has contributed to the field of nanoscience and nanotechnology through his work in nanoengineered cancer therapeutics, nanocomposite-based display and li
  • 527
  • 29 Dec 2022
Topic Review
High-Precision Trace Hydrogen Sensing
Despite its growing importance in the energy generation and storage industry, the detection of hydrogen in trace concentrations remains challenging, as established optical absorption methods are ineffective in probing homonuclear diatomics. Besides indirect detection approaches using, e.g., chemically sensitized microdevices, Raman scattering has shown promise as an alternative direct method of unambiguous hydrogen chemical fingerprinting. 
  • 526
  • 13 Jun 2023
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