Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Direct Methods (Electron Microscopy)
In crystallography, direct methods is a set of techniques used for structure determination using diffraction data and a priori information. It is a solution to the crystallographic phase problem, where phase information is lost during a diffraction measurement. Direct methods provides a method of estimating the phase information by establishing statistical relationships between the recorded amplitude information and phases of strong reflections.
  • 317
  • 04 Nov 2022
Topic Review
Direct Ultrafast Laser Processing
Direct ultrafast laser processing is nowadays considered the most flexible technique allowing to generate complex 3D optical functions in bulk glasses. The fact that the built-in optical element is embedded in the material brings several advantages in terms of prototype stability and lifetime, but equally in terms of complexity and number of possible applications, due to the 3D design. The generated optical functions, and in particular the single mode character of the light guiding element alongside the accessibility toward different spectral windows, depend on the refractive index contrast that can be achieved within the material transparency window and on the characteristic dimensions of the optical modification. In particular, the accessibility to the infrared and mid-infrared spectral domains, and to the relevant applications in sensing and imaging, requires increasing the cross-section of the guiding element in order to obtain the desired normalized frequency. Moreover, efficient signal extraction from the transported light requires nanometer size void-like index structures. All this demands a thorough knowledge and an optimal control of the material response within the interaction with the ultrafast laser pulse.
  • 828
  • 25 Jun 2021
Topic Review
Discrete Global Grid
A Discrete Global Grid (DGG) is a mosaic which covers the entire Earth's surface. Mathematically it is a space partitioning: it consists of a set of non-empty regions that form a partition of the Earth’s surface. In a usual grid-modeling strategy, to simplify position calculations, each region is represented by a point, abstracting the grid as a set of region-points. Each region or region-point in the grid is called a cell. When each cell of a grid is subject to a recursive partition, resulting in a "series of discrete global grids with progressively finer resolution", forming a hierarchical grid, it is named Hierarchical DGG (sometimes "DGG system"). Discrete Global Grids are used as the geometric basis for the building of geospatial data structures. Each cell is related with data objects or values, or (in the hierarchical case) may be associated with other cells. DGGs have been proposed for use in a wide range of geospatial applications, including vector and raster location representation, data fusion, and spatial databases. The most usual grids are for horizontal position representation, using a standard datum, like WGS84. In this context is commom also to use a specific DGG as foundation for geocoding standardization. In the context of a spatial index, a DGG can assign unique identifiers to each grid cell, using it for spatial indexing purposes, in geodatabases or for geocoding.
  • 615
  • 03 Nov 2022
Topic Review
Distance Measures (Cosmology)
Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe. They are often used to tie some observable quantity (such as the luminosity of a distant quasar, the redshift of a distant galaxy, or the angular size of the acoustic peaks in the cosmic microwave background (CMB) power spectrum) to another quantity that is not directly observable, but is more convenient for calculations (such as the comoving coordinates of the quasar, galaxy, etc.). The distance measures discussed here all reduce to the common notion of Euclidean distance at low redshift. In accord with our present understanding of cosmology, these measures are calculated within the context of general relativity, where the Friedmann–Lemaître–Robertson–Walker solution is used to describe the universe.
  • 3.3K
  • 19 Oct 2022
Topic Review
Domestic Refrigerators in Smart Grids
Domestic refrigeration and freezing appliances can be used for electrical load shifting from peak to off-peak demand periods, thus allowing greater penetration of renewable energy sources (RES) and significantly contributing to the reduction of CO2 emissions. The full realization of this potential can be achieved with the synergistic combination of smart grid (SG) technologies and the application of phase-change materials (PCMs). Being permanently online, these ubiquitous appliances are available for the most advanced strategies of demand-side load management (DSLM), including real-time demand response (DR) and direct load control (DLC).
  • 669
  • 27 Oct 2022
Topic Review
Dorado
Dorado, Latin for "the swordfish," is a constellation in the southern sky, first introduced by Dutch navigators in the late 16th century. Situated near the South Celestial Pole, Dorado is renowned for hosting the Large Magellanic Cloud, a satellite galaxy of our Milky Way, and several notable deep-sky objects, including the Tarantula Nebula. Its prominence in the southern hemisphere makes it a significant feature in celestial navigation and astronomical observation.
  • 254
  • 08 Mar 2024
Topic Review
Double-Blind FROG
Double-Blind FROG is a method for simultaneously measuring two unknown ultrashort laser pulses. Well established ultrafast measurement techniques like Frequency-Resolved Optical Gating (FROG) and its simplified version GRENOUILLE can only measure one unknown ultrashort laser pulse at a time. Another version of FROG, called cross-correlation FROG (XFROG), also measures only one pulse, but it involves two pulses: a known reference pulse and the unknown pulse to be measured. In modern optics experiments, ultrashort laser pulses have been used in a great variety of engineering application and scientific research, for example, biomedical engineering, material science, nonlinear spectroscopy, ultrafast chemistry, etc. Often, these experiments involve using two potentially different input laser pulses, for example, Raman spectroscopy, two-color pump-probe experiments, and non-degenerate four-wave mixing. In many situations, an output pulse is generated by a nonlinear optical process, such as harmonic generation, continuum generation, or optical parametric oscillation. In all such cases, measuring more than one pulse simultaneously is required to completely characterize the experiment and understand its results in order to eventually understand the underlying science of the process under study. Thus a measurement device capable of measuring two pulses simultaneously is highly desired.
  • 542
  • 20 Oct 2022
Topic Review
Draco
Draco, Latin for "the dragon," is a large and distinctive constellation in the northern celestial hemisphere. It is renowned for its winding shape, resembling a serpentine dragon winding around the celestial pole, and is home to several notable deep-sky objects, including the Cat's Eye Nebula and the Draco Dwarf Galaxy.
  • 298
  • 08 Mar 2024
Topic Review
Drag
In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers (or surfaces) or between a fluid and a solid surface. Unlike other resistive forces, such as dry friction, which are nearly independent of velocity, the drag force depends on velocity. Drag force is proportional to the velocity for low-speed flow and the squared velocity for high speed flow, where the distinction between low and high speed is measured by the Reynolds number. Even though the ultimate cause of drag is viscous friction, turbulent drag is independent of viscosity. Drag forces always tend to decrease fluid velocity relative to the solid object in the fluid's path.
  • 1.2K
  • 22 Nov 2022
Topic Review
Drag Polar
The drag polar or drag curve is the relationship between the lift on an aircraft and its drag, expressed in terms of the dependence of the drag coefficient on the lift coefficient. It may be described by an equation or displayed in a diagram called a polar plot.
  • 9.5K
  • 24 Oct 2022
  • Page
  • of
  • 118
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
Video Production Service
Feedback