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Topic Review
Low Power Cusped Field Thruster
The cusped field thruster is a novel concept of electric propulsion devicewith the advantages of an extremely large thrust throttle ability (more than three orders of magnitude), low complexity, strong robustness and a long lifetime (more than 18,750 h). A cusped field magnetic field is formed in the channel by arranging quasi-periodic permanent magnets around the discharge channel.
  • 854
  • 28 Jul 2021
Topic Review
Wavefront shaping concepts in OCT
Optical coherence tomography (OCT) enables three-dimensional imaging with resolution on the micrometer scale. The technique relies on the time-of-flight gated detection of light scattered from a sample and has received enormous interest in applications as versatile as non-destructive testing, metrology and non-invasive medical diagnostics. However, in strongly scattering media such as biological tissue, the penetration depth and imaging resolution are limited. Combining OCT imaging with wavefront shaping approaches significantly leverages the capabilities of the technique by controlling the scattered light field through manipulation of the field incident on the sample.
  • 853
  • 24 Dec 2020
Topic Review
Solar Energy Conversion
Solar energy conversion describes technologies devoted to the transformation of solar energy to other (useful) forms of energy, including electricity, fuel, and heat. It covers light-harvesting technologies including traditional semiconductor photovoltaic devices (PVs), emerging photovoltaics, solar fuel generation via electrolysis, artificial photosynthesis, and related forms of photocatalysis directed at the generation of energy rich molecules. Fundamental electro-optical aspects in several emerging solar energy conversion technologies for generation of both electricity (photovoltaics) and solar fuels constitute an active area of current research.
  • 852
  • 19 Oct 2022
Topic Review
Liquid Crystal Waveguide Structures
Liquid crystal materials can be used to make either a core, in which light beams can be confined, or a cladding of optical waveguides.
  • 851
  • 02 Nov 2021
Topic Review
Perturbative/Non-Perturbative Quantum Field Theory
In this review, we focused on the foundations of quantum field theory, which is still believed to be the most fundamental theory, describing in principle all phenomena observed in atomic and particle physics. Unlike quantum mechanics, however, its foundations are still not cleared up. We attempted to describe how some novel approaches lead to a unified picture, in spite of the fact that several difficult open problems remain.
  • 849
  • 20 Jul 2021
Topic Review
ΔT
In precise timekeeping, ΔT (Delta T, delta-T, deltaT, or DT) is a measure of the cumulative effect of the departure of the Earth's rotation period from the fixed-length day of atomic time. Formally it is the time difference obtained by subtracting Universal Time (UT, defined by the Earth's rotation) from Terrestrial Time (TT, independent of the Earth's rotation): ΔT = TT − UT. The value of ΔT for the start of 1902 was approximately zero; for 2002 it was about 64 seconds. So the Earth's rotations over that century took about 64 seconds longer than would be required for days of atomic time. As well as this long-term drift in the length of the day there are short-term fluctuations in the length of day (Δτ) which are dealt with separately.
  • 848
  • 01 Nov 2022
Topic Review
Solar Physics
Solar physics is the branch of astrophysics that specializes in the study of the Sun. It deals with detailed measurements that are possible only for our closest star. It intersects with many disciplines of pure physics, astrophysics, and computer science, including fluid dynamics, plasma physics including magnetohydrodynamics, seismology, particle physics, atomic physics, nuclear physics, stellar evolution, space physics, spectroscopy, radiative transfer, applied optics, signal processing, computer vision, computational physics, stellar physics and solar astronomy. Because the Sun is uniquely situated for close-range observing (other stars cannot be resolved with anything like the spatial or temporal resolution that the Sun can), there is a split between the related discipline of observational astrophysics (of distant stars) and observational solar physics. The study of solar physics is also important as it provides a "physical laboratory" for the study of plasma physics.
  • 847
  • 29 Sep 2022
Topic Review
Stellar Chromospheric Variability
Chromospheric (magnetic) activity is evidence of the presence of strong and variable magnetic fields. Magnetically active chromospheres are predominantly found in cool stars with convective envelopes of spectral types F and later. Day- to year-long variability is associated with the evolution and rotational modulation of individual magnetically active regions.
  • 846
  • 12 Jan 2022
Topic Review
The TACTIC Telescope
The TACTIC (TeV Atmospheric Cherenkov Telescope with Imaging Camera) is a ground-based gamma-ray telescope in India. The telescope was set up at Mount Abu (24.6∘ N, 72.7∘ E, 1300 m above sea level)  in 1997. The operating principle of TACTIC is based on the imaging atmospheric Cherenkov technique for indirect observation of the gamma-ray sky. Since its first light in 1997, the TACTIC telescope has been employed to explore the Universe at TeV energies and several outstanding results are derived from the TACTIC data.  
  • 846
  • 28 Apr 2021
Topic Review
Fractional Calculus in Electromagnetic Theory
Fractional calculus (FC) was introduced more than 300 years ago as a generalization of classical derivative and integral definitions. It is receiving increasing attention for a growing number of applications in different sciences such as physics, biology, chemistry, engineering, finance, mechanics, optics and, in particular, for modeling physical phenomena related to non-Markovian processes, signal and image processing, dielectric relaxation, viscoelasticity, electromagnetism, control theory, pharmacokinetics, fluids, heat transfer, and so on.
  • 842
  • 27 May 2022
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