Absolute magnitude is a measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly 10 parsecs, without extinction of its light due to absorption by interstellar matter and cosmic dust. By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared among each other on a magnitude scale.
Alpha Centauri is a gravitationally bound system of the closest stars and exoplanets to our Solar System at 4.37 light-years from the Sun. The name is Latinized from α Centauri, and abbreviated Alpha Cen or α Cen. It is a triple star system consisting of α Centauri A, α Centauri B, and the closest star α Centauri C.
The Pareto distribution, named after the Italian civil engineer, economist, and sociologist Vilfredo Pareto,, is a power-law probability distribution that is used in description of social, quality control, scientific, geophysical, actuarial, and many other types of observable phenomena. Originally applied to describing the distribution of wealth in a society, fitting the trend that a large portion of wealth is held by a small fraction of the population. The Pareto principle or "80-20 rule" stating that 80% of outcomes are due to 20% of causes was named in honour of Pareto, but the concepts are distinct, and only Pareto distributions with shape value of log45 ≈ 1.16 precisely reflect it. Empirical observation has shown that this 80-20 distribution fits a wide range of cases, including natural phenomena and human activities.
A low-pass filter is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filter design. The filter is sometimes called a high-cut filter, or treble-cut filter in audio applications. A low-pass filter is the complement of a high-pass filter.
The stress–energy tensor, sometimes called the stress–energy–momentum tensor or the energy–momentum tensor, is a tensor physical quantity that describes the density and flux of energy and momentum in spacetime, generalizing the stress tensor of Newtonian physics. It is an attribute of matter, radiation, and non-gravitational force fields. This density and flux of energy and momentum are the sources of the gravitational field in the Einstein field equations of general relativity, just as mass density is the source of such a field in Newtonian gravity.
A composite material is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions.
Fractional calculus is a branch of mathematical analysis that studies the several different possibilities of defining real number powers or complex number powers of the differentiation operator D
In mathematics, a root system is a configuration of vectors in a Euclidean space satisfying certain geometrical properties. The concept is fundamental in the theory of Lie groups and Lie algebras, especially the classification and representation theory of semisimple Lie algebras. Since Lie groups and Lie algebras have become important in many parts of mathematics during the twentieth century, the apparently special nature of root systems belies the number of areas in which they are applied. Further, the classification scheme for root systems, by Dynkin diagrams, occurs in parts of mathematics with no overt connection to Lie theory. Finally, root systems are important for their own sake, as in spectral graph theory.
In the general theory of relativity, the Einstein field equations relate the geometry of spacetime to the distribution of matter within it.
An attribute grammar is a formal way to supplement a formal grammar with semantic information processing. Semantic information is stored in attributes associated with terminal and nonterminal symbols of the grammar. The values of attributes are result of attribute evaluation rules associated with productions of the grammar. Attributes allow to transfer information from anywhere in the abstract syntax tree to anywhere else, in a controlled and formal way.
In statistics, a moving average is a calculation to analyze data points by creating a series of averages of different subsets of the full data set. It is also called a moving mean (MM) or rolling mean and is a type of finite impulse response filter. Variations include: simple, cumulative, or weighted forms.
Mu Alpha Theta (ΜΑΘ) is the United States mathematics honor society for high school and two-year college students. In June 2015, it served over 108,000 student members in over 2,200 chapters in the United States and in 20 foreign countries. Its main goals are to inspire keen interest in mathematics, develop strong scholarship in the subject, and promote the enjoyment of mathematics in high school and two year college students. The name is a rough transliteration of math into Greek.
When studying and formulating Albert Einstein's theory of general relativity, various mathematical structures and techniques are used. The main tools used in this geometrical theory of gravitation are tensor fields defined on a Lorentzian manifold representing spacetime. This article is a general description of the mathematics of general relativity.
In mathematics, a differentiable manifold is a type of manifold that is locally similar enough to a vector space to allow one to apply calculus. Any manifold can be described by a collection of charts (atlas). One may then apply ideas from calculus while working within the individual charts, since each chart lies within a vector space to which the usual rules of calculus apply. If the charts are suitably compatible, then computations done in one chart are valid in any other differentiable chart.
Nonene is an alkene with the molecular formula C9H18. Many structural isomers are possible, depending on the location of the C=C double bond and the branching of the other parts of the molecule. Industrially, the most important nonenes are trimers of propene: Tripropylene. This mixture of branched nonenes is used in the alkylation of phenol to produce nonylphenol, a precursor to detergents, which are also controversial pollutants.
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline," derived from Latin roots meaning "at/alongside the kidneys," is more commonly used in the United Kingdom; in the United States, "norepinephrine," derived from Greek roots having that same meaning, is usually preferred. "Norepinephrine" is also the international nonproprietary name given to the drug. Regardless of which name is used for the substance itself, parts of the body that produce or are affected by it are referred to as noradrenergic.
An articulating screen is a built-in small electronic visual display which is not fixed, but rather can be repositioned using a hinge or pivot. The articulating screen is known under different other names such as flip-out screen, flip screen, adjustable screen, articulated screen, or hinged screen. According to the way it moves, there are four main types:
- The display moves around one axis, so that it only tilts. It is called tilting screen or tiltable screen.
- The display tilts horizontally both up and down and also vertically. This type is called double-hinged tilting screen, two-axis tilting screen, three-direction tilting screen or screen with 3-way tilt.
- The display moves around two axes which are at a right angle to each other, so that the screen both tilts and swivels. This type is called swivel screen. Other names for this type are vari-angle screen, fully articulated screen, fully articulating screen, rotating screen, multi-angle screen, variable angle screen, flip-out-and-twist screen, twist-and-tilt screen and swing-and-tilt screen.
- The display is mounted on a fully-articulating hinge that itself is attached to a tilting plate. Such display can be extended out from the back of the camera, ensuring it stays clear of the camera's left-mounted ports when flipping it out to the side. This type of articulating screen is called tilt-and-articulating screen.
- The display moves into a variety of angles; it tilts horizontally and vertically and also rotates to a certain extent while staying aligned with the lens axis. It still can not be turned all the way up, down or to the side to be seen from the front of the camera for self-portraits. This type of articulating screen is called cross-tilt screen, flexible-tilt screen or flex-tilt screen.
Tripropylene, also known as propylene trimer, is usually sold as a mixture of structural isomers of nonene. This mixture is obtained by oligomerization of propene:
The Sony α37 or Sony Alpha 37 is a single-lens reflex style digital camera that replaced the SLT-A35 in 2012. However, the Alpha 37 camera features an electronic viewfinder and a translucent mirror. The main advantage of a translucent mirror is that it needn't flip up out of the way when taking a picture in order to expose the sensor, but the camera can focus and capture images simultaneously. Also the viewfinder can be used while video recording or stills/video playback, which is useful for example in bright sunlight. The camera's 15-point autofocus system can be set to single, continuous or automatic and is arranged towards the centre. The 7 fps burst mode is available only in "speed priority" mode but can reach up to 5.5 fps burst rate in combination with any other settings. The A37 is compatible with Sony Bravia Televisions.
.xk is a temporary, unofficial country code top-level domain for the Republic of Kosovo, assigned under UN Security Council resolution 1244/99.
