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Topic Review
Muon Radiography with Nuclear Emulsion Detectors
The paper presents the test experiment to investigate one of UNESCO’s world heritage objects, an archaeological site in the Naryn-Kala citadel (Derbent, Republic of Dagestan, RF) hidden under the ground surface. The function of the site could be revealed by the muon radiography studies. Several nuclear emulsion detectors were exposed for two months inside the site at a depth about 10 m from the modern surface. The use of nuclear emulsions as probing radiation detectors combined with the potential of modern image analysis methods provides for a uniquely high resolution capacity of recording instrumentation and 3D reconstruction of the internal structure of the investigated object. Here we present short descrption of muon radiography method, the test experiment, data analysis details and the first results.
  • 1.9K
  • 30 Oct 2020
Topic Review
Carbon-Burning Process
The carbon-burning process or carbon fusion is a set of nuclear fusion reactions that take place in the cores of massive stars (at least 8 [math]\displaystyle{ \begin{smallmatrix}M \odot\end{smallmatrix} }[/math] at birth) that combines carbon into other elements. It requires high temperatures (> 5×108 K or 50 keV) and densities (> 3×109 kg/m3). These figures for temperature and density are only a guide. More massive stars burn their nuclear fuel more quickly, since they have to offset greater gravitational forces to stay in (approximate) hydrostatic equilibrium. That generally means higher temperatures, although lower densities, than for less massive stars. To get the right figures for a particular mass, and a particular stage of evolution, it is necessary to use a numerical stellar model computed with computer algorithms. Such models are continually being refined based on nuclear physics experiments (which measure nuclear reaction rates) and astronomical observations (which include direct observation of mass loss, detection of nuclear products from spectrum observations after convection zones develop from the surface to fusion-burning regions – known as dredge-up events – and so bring nuclear products to the surface, and many other observations relevant to models).
  • 1.9K
  • 17 Nov 2022
Topic Review
Bohr–van Leeuwen Theorem
The Bohr–van Leeuwen theorem states that when statistical mechanics and classical mechanics are applied consistently, the thermal average of the magnetization is always zero. This makes magnetism in solids solely a quantum mechanical effect and means that classical physics cannot account for diamagnetism.
  • 1.9K
  • 21 Oct 2022
Biography
Boris Stoyanov
Boris Stoyanov is a theoretical physicist working on Membrane Theory, Supergravity and Superstring Theory. He is the Principal and Permanent Member of SUGRA INSTITUTE, Executive Director of BRANE HEPLAB and the Giordano Bruno Professor of Membrane Theory at DARK MODULI INSTITUTE. Boris Stoyanov is a relatively young theoretical physicist dealing with the exclusive theories of supergravity, super
  • 1.9K
  • 01 Sep 2022
Topic Review
Reconnaissance Satellite
A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The first generation type (i.e., Corona and Zenit) took photographs, then ejected canisters of photographic film which would descend back down into Earth's atmosphere. Corona capsules were retrieved in mid-air as they floated down on parachutes. Later, spacecraft had digital imaging systems and downloaded the images via encrypted radio links. In the United States, most information available is on programs that existed up to 1972, as this information has been declassified due to its age. Some information about programs prior to that time is still classified, and a small amount of information is available on subsequent missions. A few up-to-date reconnaissance satellite images have been declassified on occasion, or leaked, as in the case of KH-11 photographs which were sent to Jane's Defence Weekly in 1984.
  • 1.8K
  • 03 Nov 2022
Topic Review
Progress of 2D Semiconductor-based photocatalysts
A complete view of basic principles and mechanisms with regard to improving the structure stability, physical and chemical properties of the low dimensional semiconductor-based photocatalysts is presented here. Various 2D semiconductor-based photocatalysts show a high electrochemical property and photocatalytic performance due to their ultrathin character, high specific surface area with more activity sites, tunable bandgap to absorb sunlight and versatile options in structural assembly with other nanosheets. At present, most photocatalysts still need rare or expensive noble metals to improve the photocatalytic activity, which inhibits their commercial-scale application extremely. Thus, developing less costly, earth-abundant semiconductor-based photocatalysts with the efficient conversion of sunlight energy remains the primary challenge. A concise overview of different types of 2D semiconductor-mediated photocatalysts is given to figure out the advantages and disadvantages for mentioned semiconductor-based photocatalysis, including the structural property and stability, synthesize method, electrochemical property, and optical properties for H2/O2 production half-reaction along with overall water splitting.
  • 1.8K
  • 21 Oct 2020
Topic Review
Gyrotrons
Gyrotrons are among the most powerful sources of coherent radiation that operate in CW and long pulse regimes in the sub-THz and the THz frequency ranges of the electromagnetic spectrum, i.e. between 0.3 THz and 3.0 THz (corresponding to wavelengths from 1.0 to 0.1 mm). This region, which spans between the frequency bands occupied by various electronic and photonic devices, respectively, is habitually called a THz power gap. The underlying mechanism of the operation of the gyrotron involves a formation of bunches of electrons gyrating in a helical electron beam and their synchronous interaction with a fast (i.e. having a superluminal phase velocity) electromagnetic wave, producing a bremsstrahlung radiation. In contrast to the slow-wave tubes, which utilize tiny structures with dimensions comparable to the wavelength of the radiation, the gyrotrons have a simpler resonant system (cavity resonator) with dimensions that are much greater than the wavelength. This allows much more powerful electron beams to be used and thus higher output powers to be achieved. Although in comparison with the classical microwave tubes the gyrotrons are characterized by greater volume and weight due to the presence of bulky parts (such as superconducting magnets and massive collectors where the energy of the spent electron beam is dissipated) they are much more compact and can easily be embedded in a sophisticated laboratory equipment (e.g. spectrometers, technological systems, etc.) than other devices such as free-electron lasers (FEL) and radiation sources based on electron accelerators. Nowadays, the gyrotrons are used as powerful sources of coherent radiation in the wide fields of high-power sub-THz and THz science and technologies [1][2][3].
  • 1.8K
  • 29 Oct 2020
Topic Review
MEMS Acoustic Emission Sensors
Micro-electro-mechanical-systems (MEMS) acoustic emission (AE) sensors are designed to detect active defects in materials with the transduction mechanisms of piezoresistivity, capacitance or piezoelectricity. The majority of MEMS AE sensors are designed as resonators to improve the signal-to-noise ratio. The fundamental design variables of MEMS AE sensors include resonant frequency, bandwidth/quality factor and sensitivity. Micromachining methods have the flexibility to tune the sensor frequency to a particular range, which is important, as the frequency of AE signal depends on defect modes, constitutive properties and structural composition.
  • 1.8K
  • 22 Dec 2020
Topic Review
Stellar Aberration (Derivation from Lorentz Transformation)
Stellar aberration is an astronomical phenomenon "which produces an apparent motion of celestial objects". It can be proven mathematically that stellar aberration is due to the change of the astronomer's inertial frame of reference. The formula is derived with the use of Lorentz transformation of the star's coordinates. As the astronomer John Herschel has already explained in 1844, the stellar aberration does not depend on the relative velocity of the star towards Earth. Otherwise eclipsing binary stars would appear to be separated, in stark contrast to observation: both stars are rotating with high speed —and ever changing and different velocity vectors— around each other, but they appear as one spot all the time.
  • 1.8K
  • 27 Oct 2022
Topic Review
Piezoelectric Transducers Energy Conversion Network
Conversion between mechanical energy and electrical energy is critically important in industrial applications. Piezoelectric materials are unique for their ability in electric–mechanical transduction by applications of piezoelectric transducers that are usually spherical, cylindrical, or schistose. This topic review presents the most recent development of a piezoelectric transducers energy conversion network.
  • 1.8K
  • 31 Oct 2020
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