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Topic Review
Grahan Mala
Grahan Mala is an astronomical treatise on the calculation of the dates and timings for the lunar and solar eclipses written by the Indian Astronomer Hemangad Thakur in the 16th century AD.
  • 879
  • 15 Dec 2023
Topic Review
Gordon Decomposition
In mathematical physics, the Gordon-decomposition (named after Walter Gordon one of the discoverers of the Klein-Gordon equation) of the Dirac current is a splitting of the charge or particle-number current into a part that arises from the motion of the center of mass of the particles and a part that arises from gradients of the spin density. It makes explicit use of the Dirac equation and so it applies only to "on-shell" solutions of the Dirac equation.
  • 706
  • 26 Oct 2022
Topic Review
Glossary of Nanotechnology
This glossary of nanotechnology is a list of definitions of terms and concepts relevant to nanotechnology, its sub-disciplines, and related fields. For more inclusive glossaries concerning related fields of science and technology, see Glossary of chemistry terms, Glossary of physics, Glossary of biology, and Glossary of engineering.
  • 597
  • 02 Nov 2022
Topic Review
Gloss Measurements
The appearance of a surface depends on four main appearance attributes, namely color, gloss, texture, and translucency. Gloss is an important attribute that people use to understand surface appearance, right after color.
  • 114
  • 03 Jan 2024
Biography
Gino Claudio Segrè
Gino Claudio Segrè (born October 4, 1938) is a Professor of Physics, Emeritus, at the University of Pennsylvania. He is the author of several books on the history of science, particularly on atomic physics. Segrè’s Faust in Copenhagen was a finalist in the Los Angeles Times Book Fair[1] and winner of the American Institute of Physics Science Writing Award.[2] Gino Segrè was born in Flore
  • 669
  • 30 Nov 2022
Topic Review
Geothrix Fermentans
Geothrix fermentans is a rod-shaped, anaerobic bacterium. It is about 0.1 µm in diameter and ranges from 2-3 µm in length. Cell arrangement occurs singly and in chains. Geothrix fermentans can normally be found in aquatic sediments such as in aquifers. As an anaerobic chemoorganotroph, this organism is best known for its ability to use electron acceptors Fe(III), as well as other high potential metals. It also uses a wide range of substrates as electron donors. Research on metal reduction by G. fermentans has contributed to understanding more about the geochemical cycling of metals in the environment.
  • 366
  • 25 Nov 2022
Biography
George Doundoulakis
George James Doundoulakis (October 19, 1921 – March 17, 2007) was a Greek American physicist and soldier who worked under British Intelligence during World War II with SOE agent Patrick Leigh Fermor, and then served with the OSS in Thessaly, Greece. He is known by his twenty-six US Patents in the fields of radar, electronics, and narrowband television. Doundoulakis is best remembered for the
  • 584
  • 11 Nov 2022
Biography
Geoffrey G. Eichholz
Geoffrey Gunther Eichholz, (June 29, 1920 – January 8, 2018) an educational leader in health physics at the Georgia Institute of Technology. Dr. Eichholz played a key role in the successful establishment of the Department of Nuclear Engineering and Health Physics. The Department has been a constant source of well-educated and well trained graduates in the field of nuclear engineering, health p
  • 430
  • 27 Dec 2022
Topic Review
GEO600
GEO600 is a gravitational wave detector located near Sarstedt in the South of Hanover, Germany. It is designed and operated by scientists from the Max Planck Institute for Gravitational Physics, Max Planck Institute of Quantum Optics and the Leibniz Universität Hannover, along with University of Glasgow, University of Birmingham and Cardiff University in the United Kingdom, and is funded by the Max Planck Society and the Science and Technology Facilities Council (STFC). GEO600 is part of a worldwide network of gravitational wave detectors. This instrument, and its sister interferometric detectors, when operational, are some of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of 10−21, about the size of a single atom compared to the distance from the Sun to the Earth. GEO600 is capable of detecting gravitational waves in the frequency range 50 Hz to 1.5 kHz. Construction on the project began in 1995.
  • 477
  • 03 Nov 2022
Topic Review
Gent (Hyperelastic Model)
The Gent hyperelastic material model is a phenomenological model of rubber elasticity that is based on the concept of limiting chain extensibility. In this model, the strain energy density function is designed such that it has a singularity when the first invariant of the left Cauchy-Green deformation tensor reaches a limiting value [math]\displaystyle{ I_m }[/math]. The strain energy density function for the Gent model is where [math]\displaystyle{ \mu }[/math] is the shear modulus and [math]\displaystyle{ J_m = I_m -3 }[/math]. In the limit where [math]\displaystyle{ I_m \rightarrow \infty }[/math], the Gent model reduces to the Neo-Hookean solid model. This can be seen by expressing the Gent model in the form A Taylor series expansion of [math]\displaystyle{ \ln\left[1 - (I_1-3)x\right] }[/math] around [math]\displaystyle{ x = 0 }[/math] and taking the limit as [math]\displaystyle{ x\rightarrow 0 }[/math] leads to which is the expression for the strain energy density of a Neo-Hookean solid. Several compressible versions of the Gent model have been designed. One such model has the form (the below strain energy function yields a non zero hydrostatic stress at no deformation, refer https://link.springer.com/article/10.1007/s10659-005-4408-x for compressible Gent models). where [math]\displaystyle{ J = \det(\boldsymbol{F}) }[/math], [math]\displaystyle{ \kappa }[/math] is the bulk modulus, and [math]\displaystyle{ \boldsymbol{F} }[/math] is the deformation gradient.
  • 971
  • 21 Nov 2022
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