Local reference frameIn theoretical physics, a local reference frame (local frame) refers to a coordinate system or frame of reference that is only expected to function over a small region or a restricted region of space or spacetime. The term is most often used in the context of the application of local inertial frames to small regions of a gravitational field.
Cyrillic alphabetsNumerous Cyrillic alphabets are based on the Cyrillic script. The early Cyrillic alphabet was developed in the 9th century AD and replaced the earlier Glagolitic script developed by the Byzantine theologians Cyril and Methodius. It is the basis of alphabets used in various languages, past and present, Slavic origin, and non-Slavic languages influenced by Russian. As of 2011, around 252 million people in Eurasia use it as the official alphabet for their national languages. About half of them are in Russia.
Alphabet ukrainienLalphabet ukrainien (en Українська азбука, Oukraïns’ka azbouka ou абетка, abetka) est l'alphabet utilisé pour écrire la langue ukrainienne. C’est une variante de l’alphabet cyrillique créé à la fin du premier millénaire. L’alphabet ukrainien, qui est bicaméral, comprend les lettres suivantes : L’ukrainien est parfois transcrit avec l’alphabet latin – c’est ce qui s’appelle la romanisation – pour en faciliter la lecture aux personnes ne sachant pas lire l’alphabet cyrillique.
Coordonnées cartésiennesUn système de coordonnées cartésiennes permet de déterminer la position d'un point dans un espace affine (droite, plan, espace de dimension 3, etc.) muni d'un repère cartésien. Le mot cartésien vient du mathématicien et philosophe français René Descartes. Il existe d'autres systèmes de coordonnées permettant de repérer un point dans le plan ou dans l'espace. Sur une droite affine , un repère est la donnée de : une origine , c'est-à-dire un point distingué de ; un vecteur de la droite vectorielle directrice .
Fire safetyFire safety is the set of practices intended to reduce destruction caused by fire. Fire safety measures include those that are intended to prevent the ignition of an uncontrolled fire and those that are used to limit the spread and impact of a fire. Fire safety measures include those that are planned during the construction of a building or implemented in structures that are already standing and those that are taught or provided to occupants of the building. Threats to fire safety are commonly referred to as fire hazards.
Relativistic angular momentumIn physics, relativistic angular momentum refers to the mathematical formalisms and physical concepts that define angular momentum in special relativity (SR) and general relativity (GR). The relativistic quantity is subtly different from the three-dimensional quantity in classical mechanics. Angular momentum is an important dynamical quantity derived from position and momentum. It is a measure of an object's rotational motion and resistance to changes in its rotation.
Triangle du feuLe triangle du feu est un modèle simple pour comprendre les éléments nécessaires pour la plupart des combustions et incendies. Le concept de « triangle du feu » est voisin du concept de « tétraèdre du feu » : le triangle mobilise trois éléments et correspond à la combustion sans flammes le tétraèdre mobilise quatre éléments et correspond à la combustion avec flammes. La réaction chimique de la combustion ne peut se produire que si l'on réunit au minimum trois éléments : un combustible, un comburant (dioxygène), et une énergie d'activation, chacun en quantité suffisante.
Preferred frameIn theoretical physics, a preferred frame or privileged frame is usually a special hypothetical frame of reference in which the laws of physics might appear to be identifiably different (simpler) from those in other frames. In theories that apply the principle of relativity to inertial motion, physics is the same in all inertial frames, and is even the same in all frames under the principle of general relativity.
Écologie du feuvignette|300x300px| Old fire dans les montagnes de San Bernardino (image prise depuis la Station spatiale internationale ) L'écologie du feu est une discipline scientifique qui s'intéresse aux processus naturels impliquant le feu dans un écosystème et aux effets écologiques, aux interactions entre le feu et les composants abiotiques et biotiques d'un écosystème, et au rôle en tant que processus écosystémique.
Exact trigonometric valuesIn mathematics, the values of the trigonometric functions can be expressed approximately, as in , or exactly, as in . While trigonometric tables contain many approximate values, the exact values for certain angles can be expressed by a combination of arithmetic operations and square roots. The trigonometric functions of angles that are multiples of 15°, 18°, or 22.5° have simple algebraic values. These values are listed in the following table for angles from 0° to 90°.
Projectile motionProjectile motion is a form of motion experienced by an object or particle (a projectile) that is projected in a gravitational field, such as from Earth's surface, and moves along a curved path under the action of gravity only. In the particular case of projectile motion on Earth, most calculations assume the effects of air resistance are passive and negligible. The curved path of objects in projectile motion was shown by Galileo to be a parabola, but may also be a straight line in the special case when it is thrown directly upward or downward.
Fire worshipWorship or deification of fire (also pyrodulia, pyrolatry or pyrolatria) is known from various religions. Fire has been an important part of human culture since the Lower Paleolithic. Religious or animist notions connected to fire are assumed to reach back to such early prehuman times. In Indo-European languages, there were two concepts regarding fire: that of an animate type called *h1n̥gwnís (cf. Sanskrit agni, English ignite from Latin ignis, Polish ogień and Russian ogon), and an inanimate type *péh2wr̥ (cf.
