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Topic Review
Northern Light (Spacecraft)
Northern Light was a concept mission for a robotic mission to Mars that would consist of a lander and a rover, being studied by a consortium of Canadian universities, companies and organisations. The primary contractor for the spacecraft was Thoth Technology Inc. The spacecraft would consist of four parts: an apogee kick engine to provide orbital injection for a cruise vehicle that carries the Northern Light lander and the Beaver Rover to a direct rendezvous with Mars using a Hohmann transfer orbit. Atmospheric entry would be achieved by a heat shield, parachute and airbag deployment system. The lander would transfer the rover to the Martian surface. Once deployed on the Martian surface, the lander contacts Earth directly to the 46 m parabolic antenna located at the Algonquin Radio Observatory. The Beaver Rover was proposed to have a maximum range of 1000 metres (0.62 mile) from the landing site. It would have operated under battery, utilizing tools and sensors to investigate surface rocks that may contain the presence of photosynthetic life.
  • 259
  • 03 Nov 2022
Topic Review
Magic Number
In nuclear physics, a magic number is a number of nucleons (either protons or neutrons, separately) such that they are arranged into complete shells within the atomic nucleus. As a result, atomic nuclei with a 'magic' number of protons or neutrons are much more stable than other nuclei. The seven most widely recognized magic numbers as of 2019 are 2, 8, 20, 28, 50, 82, and 126 (sequence A018226 in the OEIS). For protons, this corresponds to the elements helium, oxygen, calcium, nickel, tin, lead and the hypothetical unbihexium, although 126 is so far only known to be a magic number for neutrons. Atomic nuclei consisting of such a magic number of nucleons have a higher average binding energy per nucleon than one would expect based upon predictions such as the semi-empirical mass formula and are hence more stable against nuclear decay. The unusual stability of isotopes having magic numbers means that transuranium elements could theoretically be created with extremely large nuclei and yet not be subject to the extremely rapid radioactive decay normally associated with high atomic numbers. Large isotopes with magic numbers of nucleons are said to exist in an island of stability. Unlike the magic numbers 2–126, which are realized in spherical nuclei, theoretical calculations predict that nuclei in the island of stability are deformed. Before this was realized, higher magic numbers, such as 184, 258, 350, and 462 (sequence A033547 in the OEIS), were predicted based on simple calculations that assumed spherical shapes: these are generated by the formula [math]\displaystyle{ 2(\tbinom n1+ \tbinom n2+\tbinom n3) }[/math] (see Binomial coefficient). It is now believed that the sequence of spherical magic numbers cannot be extended in this way. Further predicted magic numbers are 114, 122, 124, and 164 for protons as well as 184, 196, 236, and 318 for neutrons. However, more modern calculations predict 228 and 308 for neutrons, along with 184 and 196.
  • 902
  • 03 Nov 2022
Topic Review
Black Holes and Quantum Mechanics
Mass and spin distributions of stellar mass black holes (BH) are important sources of information on the formation mechanism and the evolution of galaxies. The birth of a stellar-mass BH, ranging in the interval ~5–150 M⊙, is due to the spectacular phase of a massive star’s core collapse, an event involving the emission of multi-messenger signals such as neutrinos, GW’s and electromagnetic radiation in several bands.
  • 364
  • 03 Nov 2022
Topic Review
Machine-Learning-Based Methods for Acoustic Emission Testing
Acoustic emission (AE) testing has obvious limitations regarding its reproducibility: as it was said, this type of test involves the formation or progression of cracks in the material. Even when referring to specimens of the same material, of the same dimensions, and subjected to the same load cycle, they do not necessarily produce the same results. This is especially true in the case of anisotropic and heterogeneous materials. Moreover, since the signals used by precursors are of modest entity, to be able to detect possible forms of energy in the material, it is necessary to use particularly sensitive sensors. Further problems arise due to the attenuation phenomena of the acoustic stress wave that is dispersed in the material as it propagates: just as the noise due to sources independent of the possible structural defect can disturb the detection methodology. To overcome these limitations, researchers adopted alternative methodologies to improve the results of the structural damage identification procedures. The capabilities demonstrated by the technologies based on ML in detecting patterns were immediately noticed by AE researchers. To make this nondestructive testing method even more effective, all the methodologies based on ML for the recognition of the stress wave can be applied during the detection phase of the acoustic emission generated by the source. In this way, it is possible to carry out a test that is robust regarding noise and effective in detecting waves of modest entity. The most common methodologies based on ML applied in the field of AE are presented below. ML is a branch of artificial intelligence whose goal is to allow machines to automatically learn something from experience, without the need for them to be programmed in advance. Experience is a collection of data, which can be fixed and immutable, or even expand over time. Learning can be carried out through two main approaches: supervised and unsupervised.
  • 648
  • 03 Nov 2022
Topic Review
Soyuz 4
Soyuz 4 (Russian: Союз 4, Union 4) was launched on 14 January 1969, carrying cosmonaut Vladimir Shatalov on his first flight. The aim of the mission was to dock with Soyuz 5, transfer two crew members from that spacecraft, and return to Earth. The previous Soyuz flight (Soyuz 3) was also a docking attempt but failed for various reasons. The radio call sign of the crew was Amur, while Soyuz 5 was Baikal. This referred to the trans-Siberian railway project called the Baikal-Amur Mainline, which was in development at the time.
  • 354
  • 03 Nov 2022
Topic Review
Reduction Potential
Redox potential (also known as oxidation / reduction potential, ORP, pe, [math]\displaystyle{ E_{red} }[/math], or [math]\displaystyle{ E_{h} }[/math]) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respectively. Redox potential is expressed in volts (V). Each species has its own intrinsic redox potential; for example, the more positive the reduction potential (reduction potential is more often used due to general formalism in electrochemistry), the greater the species' affinity for electrons and tendency to be reduced.
  • 1.1K
  • 02 Nov 2022
Topic Review
Jiles–Atherton Model
The Jiles–Atherton model of magnetic hysteresis was introduced in 1984 by David Jiles and D. L. Atherton. This is one of the most popular models of magnetic hysteresis. Its main advantage is the fact that this model enables connection with physical parameters of the magnetic material. Jiles–Atherton model enables calculation of minor and major hysteresis loops. The original Jiles–Atherton model is suitable only for isotropic materials. However, an extension of this model presented by Ramesh et al. and corrected by Szewczyk enables the modeling of anisotropic magnetic materials.
  • 1.4K
  • 02 Nov 2022
Topic Review
List of Volcanic Features on Io
This is a list of named volcanic surface features on Jupiter's moon Io. These names have been approved for use by the International Astronomical Union. The features listed below represent a subset of the total known volcanic features on Io's surface with the majority currently not having an officially approved name. The names of volcanic features on Io use a combination of a name derived from mythological figures from around the world related to the Sun, fire, volcanoes, thunder, or smithing, places from the Greek mythological story of Io, Dante's Inferno, or from the name of a nearby feature on Io's surface and an approved descriptive term. The descriptive term used is based on the type of feature named and how it was first discovered. Volcanoes that were first observed as an active feature from observations of a volcanic plume fit under the category of "Eruptive Center" and do not use a descriptive term, though portions of these features may have also received names that do use a descriptive term, like Prometheus Patera or Masubi Fluctus. Lava flows use the descriptive term fluctus or the plural fluctūs, e.g. Acala Fluctus. Volcanic depressions use the term patera or the plural paterae, e.g. Ah Peku Patera. The term has also become the generic term for referring to these structures. Small shield volcanoes use the term tholus or the plural tholi, e.g. Inachus Tholus. Finally, channels carved by volcanic lava flows through thermal erosion use the term vallis or the plural valles. See also the list of mountains on Io and the list of regions on Io.
  • 612
  • 02 Nov 2022
Topic Review
Space and Upper Atmosphere Research Commission
Established in its modern form on 16 September 1961 by an executive order of President of Pakistan, it is headquartered in Karachi, Sindh Province of Pakistan. Part of the Strategic Plans Division (SPD) of Pakistan Armed Forces, which is currently headquartered at the Chakalala Military District under the control of the Pakistan Air Force ; the space programmes recorded number of pioneering accomplishments in space flight during the initial years of its establishment. The country's first satellite, Badr-I, was built by the SUPARCO and launched from the Xichang Satellite Launch Center, China on July 16, 1990. However, during the meantime, the space programme suffered many setbacks, difficulties, and problems that partly slowed the progress of the space programme. The bureaucratic influence and politicization further lagged the space programme and many projects were cancelled by the superior authorities. Over the years, SUPARCO expanded and it now has several installations all over the country. It has multi-lateral and bilateral international agreements. SUPARCO has been quite dormant in recent years and also have failed to make any breakthroughs. SUPARCO's science and research is mainly focused and concentrated on understanding of the Solar system, Space weather, astrophysics, astronomical observation, climatic studies, space and telemedicine, remote sensing and the Earth observation.
  • 1.2K
  • 02 Nov 2022
Topic Review
Photoelectrochemical Reduction of CO2
Photoelectrochemical reduction of CO2 is a chemical process whereby carbon dioxide is reduced to carbon monoxide or hydrocarbons by the energy of incident light. This process needs to be catalyzed either homogeneously or heterogeneously in order to proceed, and current research is aimed at developing these catalysts, most of which are semiconducting materials. Semiconducting catalysts provide favourable electron transfer kinetics. The feasibility of this chemical reaction was first theorised by Giacomo Luigi Ciamician, an Italian photochemist. Already in 1912 he stated that "By  using  suitable catalyzers,  it  should  be  possible  to  transform  the mixture  of  water  and  carbon dioxide into oxygen and methane, or to cause other endo-energetic processes." Motivation for research in this area is strong due to the current attention to atmospheric carbon dioxide as the reduction of carbon dioxide would be one route for removal and sequestration. Furthermore, the reduced species may prove to be a valuable feedstock for other processes. If the incident light utilized is solar in nature then this process also potentially represents energy routes which combine renewable energy with CO2 reduction.
  • 1.0K
  • 02 Nov 2022
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