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56-493: The acronym RHC may refer to: Relativistic heat conduction The Black Watch (Royal Highland Regiment) of Canada Radio Havana Cuba Recueil des Historiens des Croisades , a major collection of medieval primary source documents about the Crusades Receding Horizon Control, another name for Model predictive control Red Hand Commandos ,

112-464: A coordinate frame called the Cartesian frame . Similarly, the position of any point in three-dimensional space can be specified by three Cartesian coordinates , which are the signed distances from the point to three mutually perpendicular planes. More generally, n Cartesian coordinates specify the point in an n -dimensional Euclidean space for any dimension n . These coordinates are

168-521: A , b ) to the Cartesian coordinates of every point in the set. That is, if the original coordinates of a point are ( x , y ) , after the translation they will be ( x ′ , y ′ ) = ( x + a , y + b ) . {\displaystyle (x',y')=(x+a,y+b).} To rotate a figure counterclockwise around the origin by some angle θ {\displaystyle \theta }

224-659: A Loyalist paramilitary group in Northern Ireland Rosehill College , a school in South Auckland Rural health clinic C-scale of the Rockwell hardness scale The Royal Hashemite Court Royal Holloway College , University of London Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title RHC . If an internal link led you here, you may wish to change

280-449: A diagram ( 3D projection or 2D perspective drawing ) shows the x - and y -axis horizontally and vertically, respectively, then the z -axis should be shown pointing "out of the page" towards the viewer or camera. In such a 2D diagram of a 3D coordinate system, the z -axis would appear as a line or ray pointing down and to the left or down and to the right, depending on the presumed viewer or camera perspective . In any diagram or display,

336-407: A division of space into eight regions or octants , according to the signs of the coordinates of the points. The convention used for naming a specific octant is to list its signs; for example, (+ + +) or (− + −) . The generalization of the quadrant and octant to an arbitrary number of dimensions is the orthant , and a similar naming system applies. The Euclidean distance between two points of

392-436: A hyperbolic (includes a conservative term) partial differential equation , there is the possibility of phenomena such as thermal resonance and thermal shock waves . Cartesian coordinate system In geometry , a Cartesian coordinate system ( UK : / k ɑːr ˈ t iː zj ə n / , US : / k ɑːr ˈ t iː ʒ ə n / ) in a plane is a coordinate system that specifies each point uniquely by

448-433: A number line. For any point P , a line is drawn through P perpendicular to each axis, and the position where it meets the axis is interpreted as a number. The two numbers, in that chosen order, are the Cartesian coordinates of P . The reverse construction allows one to determine the point P given its coordinates. The first and second coordinates are called the abscissa and the ordinate of P , respectively; and

504-422: A pair of real numbers called coordinates , which are the signed distances to the point from two fixed perpendicular oriented lines , called coordinate lines , coordinate axes or just axes (plural of axis ) of the system. The point where the axes meet is called the origin and has (0, 0) as coordinates. The axes directions represent an orthogonal basis . The combination of origin and basis forms

560-1238: A point P can be taken as the distance from P to the plane defined by the other two axes, with the sign determined by the orientation of the corresponding axis. Each pair of axes defines a coordinate plane . These planes divide space into eight octants . The octants are: ( + x , + y , + z ) ( − x , + y , + z ) ( + x , − y , + z ) ( + x , + y , − z ) ( + x , − y , − z ) ( − x , + y , − z ) ( − x , − y , + z ) ( − x , − y , − z ) {\displaystyle {\begin{aligned}(+x,+y,+z)&&(-x,+y,+z)&&(+x,-y,+z)&&(+x,+y,-z)\\(+x,-y,-z)&&(-x,+y,-z)&&(-x,-y,+z)&&(-x,-y,-z)\end{aligned}}} The coordinates are usually written as three numbers (or algebraic formulas) surrounded by parentheses and separated by commas, as in (3, −2.5, 1) or ( t , u + v , π /2) . Thus,

616-456: A point are ( x , y ) , then its distances from the X -axis and from the Y -axis are | y | and | x |, respectively; where | · | denotes the absolute value of a number. A Cartesian coordinate system for a three-dimensional space consists of an ordered triplet of lines (the axes ) that go through a common point (the origin ), and are pair-wise perpendicular; an orientation for each axis; and

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672-401: A point are usually written in parentheses and separated by commas, as in (10, 5) or (3, 5, 7) . The origin is often labelled with the capital letter O . In analytic geometry, unknown or generic coordinates are often denoted by the letters ( x , y ) in the plane, and ( x , y , z ) in three-dimensional space. This custom comes from a convention of algebra, which uses letters near the end of

728-472: A single unit of length for all three axes. As in the two-dimensional case, each axis becomes a number line. For any point P of space, one considers a plane through P perpendicular to each coordinate axis, and interprets the point where that plane cuts the axis as a number. The Cartesian coordinates of P are those three numbers, in the chosen order. The reverse construction determines the point P given its three coordinates. Alternatively, each coordinate of

784-877: Is time , α = k /( ρ c ) is thermal diffusivity , k is thermal conductivity , ρ is density , and c is specific heat capacity . The Laplace operator , ∇ 2 {\textstyle \nabla ^{2}} , is defined in Cartesian coordinates as ∇ 2   =   ∂ 2 ∂ x 2   +   ∂ 2 ∂ y 2   +   ∂ 2 ∂ z 2 . {\displaystyle \nabla ^{2}~=~{\frac {\partial ^{2}}{\partial x^{2}}}~+~{\frac {\partial ^{2}}{\partial y^{2}}}~+~{\frac {\partial ^{2}}{\partial z^{2}}}.} This Fourier equation can be derived by substituting Fourier’s linear approximation of

840-407: Is a relaxation time , such that C 2   =   α / τ 0 . {\textstyle C^{2}~=~\alpha /\tau _{_{0}}.} This equation for the heat flux is often referred to as "Maxwell-Cattaneo equation". The most important implication of the hyperbolic equation is that by switching from a parabolic ( dissipative ) to

896-485: Is called the speed of second sound (that is related to excitations and quasiparticles , like phonons ). The equation is known as the " hyperbolic heat conduction" (HHC) equation. Mathematically, the above equation is called "telegraph equation", as it is formally equivalent to the telegrapher's equations , which can be derived from Maxwell’s equations of electrodynamics. For the HHC equation to remain compatible with

952-521: Is felt (i.e. temperature changes) at any distant point, instantaneously. The speed of propagation of heat is faster than the speed of light in vacuum, which is inadmissible within the framework of relativity. The parabolic model for heat conduction discussed above shows that the Fourier equation (and the more general Fick's law of diffusion ) is incompatible with the theory of relativity for at least one reason: it admits infinite speed of propagation of

1008-453: Is modelled by the Fourier equation , namely a parabolic partial differential equation of the kind: ∂ θ ∂ t   =   α   ∇ 2 θ , {\displaystyle {\frac {\partial \theta }{\partial t}}~=~\alpha ~\nabla ^{2}\theta ,} where θ is temperature , t

1064-514: Is obtained by projecting the point onto one axis along a direction that is parallel to the other axis (or, in general, to the hyperplane defined by all the other axes). In such an oblique coordinate system the computations of distances and angles must be modified from that in standard Cartesian systems, and many standard formulas (such as the Pythagorean formula for the distance) do not hold (see affine plane ). The Cartesian coordinates of

1120-458: Is specific entropy and σ is entropy production . This mathematical model is inconsistent with special relativity: the Green function associated to the heat equation (also known as heat kernel ) has support that extends outside the light-cone , leading to faster-than-light propagation of information. For example, consider a pulse of heat at the origin; then according to Fourier equation, it

1176-879: Is the Cartesian version of Pythagoras's theorem . In three-dimensional space, the distance between points ( x 1 , y 1 , z 1 ) {\displaystyle (x_{1},y_{1},z_{1})} and ( x 2 , y 2 , z 2 ) {\displaystyle (x_{2},y_{2},z_{2})} is d = ( x 2 − x 1 ) 2 + ( y 2 − y 1 ) 2 + ( z 2 − z 1 ) 2 , {\displaystyle d={\sqrt {(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}+(z_{2}-z_{1})^{2}}},} which can be obtained by two consecutive applications of Pythagoras' theorem. The Euclidean transformations or Euclidean motions are

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1232-454: Is the set of all real numbers. In the same way, the points in any Euclidean space of dimension n be identified with the tuples (lists) of n real numbers; that is, with the Cartesian product R n {\displaystyle \mathbb {R} ^{n}} . The concept of Cartesian coordinates generalizes to allow axes that are not perpendicular to each other, and/or different units along each axis. In that case, each coordinate

1288-501: Is usually named after the coordinate which is measured along it; so one says the x-axis , the y-axis , the t-axis , etc. Another common convention for coordinate naming is to use subscripts, as ( x 1 , x 2 , ..., x n ) for the n coordinates in an n -dimensional space, especially when n is greater than 3 or unspecified. Some authors prefer the numbering ( x 0 , x 1 , ..., x n −1 ). These notations are especially advantageous in computer programming : by storing

1344-557: The del operator, ∇, is defined in 3D as ∇   =   i   ∂ ∂ x   +   j   ∂ ∂ y   +   k   ∂ ∂ z . {\displaystyle \nabla ~=~\mathbf {i} ~{\frac {\partial }{\partial x}}~+~\mathbf {j} ~{\frac {\partial }{\partial y}}~+~\mathbf {k} ~{\frac {\partial }{\partial z}}.} It can be shown that this definition of

1400-405: The xy -plane, yz -plane, and xz -plane. In mathematics, physics, and engineering contexts, the first two axes are often defined or depicted as horizontal, with the third axis pointing up. In that case the third coordinate may be called height or altitude . The orientation is usually chosen so that the 90-degree angle from the first axis to the second axis looks counter-clockwise when seen from

1456-416: The z -coordinate is sometimes called the applicate . The words abscissa , ordinate and applicate are sometimes used to refer to coordinate axes rather than the coordinate values. The axes of a two-dimensional Cartesian system divide the plane into four infinite regions, called quadrants , each bounded by two half-axes. These are often numbered from 1st to 4th and denoted by Roman numerals : I (where

1512-457: The ( bijective ) mappings of points of the Euclidean plane to themselves which preserve distances between points. There are four types of these mappings (also called isometries): translations , rotations , reflections and glide reflections . Translating a set of points of the plane, preserving the distances and directions between them, is equivalent to adding a fixed pair of numbers (

1568-406: The Cartesian system, commonly learn the order to read the values before cementing the x -, y -, and z -axis concepts, by starting with 2D mnemonics (for example, 'Walk along the hall then up the stairs' akin to straight across the x -axis then up vertically along the y -axis). Computer graphics and image processing , however, often use a coordinate system with the y -axis oriented downwards on

1624-406: The alphabet for unknown values (such as the coordinates of points in many geometric problems), and letters near the beginning for given quantities. These conventional names are often used in other domains, such as physics and engineering, although other letters may be used. For example, in a graph showing how a pressure varies with time , the graph coordinates may be denoted p and t . Each axis

1680-407: The computer display. This convention developed in the 1960s (or earlier) from the way that images were originally stored in display buffers . For three-dimensional systems, a convention is to portray the xy -plane horizontally, with the z -axis added to represent height (positive up). Furthermore, there is a convention to orient the x -axis toward the viewer, biased either to the right or left. If

1736-903: The continuum field (in this case: heat, or temperature gradients). To overcome this contradiction, workers such as Carlo Cattaneo , Vernotte, Chester, and others proposed that Fourier equation should be upgraded from the parabolic to a hyperbolic form, where the n, the temperature field θ {\displaystyle \theta } is governed by: 1 C 2   ∂ 2 θ ∂ t 2   +   1 α   ∂ θ ∂ t   =   ∇ 2 θ . {\displaystyle {\frac {1}{C^{2}}}~{\frac {\partial ^{2}\theta }{\partial t^{2}}}~+~{\frac {1}{\alpha }}~{\frac {\partial \theta }{\partial t}}~=~\nabla ^{2}\theta .} In this equation, C

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1792-413: The coordinates both have positive signs), II (where the abscissa is negative − and the ordinate is positive +), III (where both the abscissa and the ordinate are −), and IV (abscissa +, ordinate −). When the axes are drawn according to the mathematical custom, the numbering goes counter-clockwise starting from the upper right ("north-east") quadrant. Similarly, a three-dimensional Cartesian system defines

1848-455: The coordinates of a point as an array , instead of a record , the subscript can serve to index the coordinates. In mathematical illustrations of two-dimensional Cartesian systems, the first coordinate (traditionally called the abscissa ) is measured along a horizontal axis, oriented from left to right. The second coordinate (the ordinate ) is then measured along a vertical axis, usually oriented from bottom to top. Young children learning

1904-441: The coordinates of points of the shape. For example, a circle of radius 2, centered at the origin of the plane, may be described as the set of all points whose coordinates x and y satisfy the equation x + y = 4 ; the area , the perimeter and the tangent line at any point can be computed from this equation by using integrals and derivatives , in a way that can be applied to any curve. Cartesian coordinates are

1960-518: The discovery. The French cleric Nicole Oresme used constructions similar to Cartesian coordinates well before the time of Descartes and Fermat. Both Descartes and Fermat used a single axis in their treatments and have a variable length measured in reference to this axis. The concept of using a pair of axes was introduced later, after Descartes' La Géométrie was translated into Latin in 1649 by Frans van Schooten and his students. These commentators introduced several concepts while trying to clarify

2016-449: The first axis is usually defined or depicted as horizontal and oriented to the right, and the second axis is vertical and oriented upwards. (However, in some computer graphics contexts, the ordinate axis may be oriented downwards.) The origin is often labeled O , and the two coordinates are often denoted by the letters X and Y , or x and y . The axes may then be referred to as the X -axis and Y -axis. The choices of letters come from

2072-544: The first law of thermodynamics, it is necessary to modify the definition of heat flux vector, q , to τ 0   ∂ q ∂ t   +   q   =   − k   ∇ θ , {\displaystyle \tau _{_{0}}~{\frac {\partial \mathbf {q} }{\partial t}}~+~\mathbf {q} ~=~-k~\nabla \theta ,} where τ 0 {\textstyle \tau _{_{0}}}

2128-487: The foundation of analytic geometry , and provide enlightening geometric interpretations for many other branches of mathematics, such as linear algebra , complex analysis , differential geometry , multivariate calculus , group theory and more. A familiar example is the concept of the graph of a function . Cartesian coordinates are also essential tools for most applied disciplines that deal with geometry, including astronomy , physics , engineering and many more. They are

2184-440: The heat flux vector also satisfies the second law of thermodynamics, ∇ ⋅ ( q θ )   +   ρ   ∂ s ∂ t   =   σ , {\displaystyle \nabla \cdot \left({\frac {\mathbf {q} }{\theta }}\right)~+~\rho ~{\frac {\partial s}{\partial t}}~=~\sigma ,} where s

2240-588: The heat flux vector, q , as a function of temperature gradient, q   =   − k   ∇ θ , {\displaystyle \mathbf {q} ~=~-k~\nabla \theta ,} into the first law of thermodynamics ρ   c   ∂ θ ∂ t   +   ∇ ⋅ q   =   0 , {\displaystyle \rho ~c~{\frac {\partial \theta }{\partial t}}~+~\nabla \cdot \mathbf {q} ~=~0,} where

2296-479: The ideas contained in Descartes's work. The development of the Cartesian coordinate system would play a fundamental role in the development of the calculus by Isaac Newton and Gottfried Wilhelm Leibniz . The two-coordinate description of the plane was later generalized into the concept of vector spaces . Many other coordinate systems have been developed since Descartes, such as the polar coordinates for

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2352-401: The length unit, and center at the origin), the unit square (whose diagonal has endpoints at (0, 0) and (1, 1) ), the unit hyperbola , and so on. The two axes divide the plane into four right angles , called quadrants . The quadrants may be named or numbered in various ways, but the quadrant where all coordinates are positive is usually called the first quadrant . If the coordinates of

2408-431: The line and assigning them to two distinct real numbers (most commonly zero and one). Other points can then be uniquely assigned to numbers by linear interpolation . Equivalently, one point can be assigned to a specific real number, for instance an origin point corresponding to zero, and an oriented length along the line can be chosen as a unit, with the orientation indicating the correspondence between directions along

2464-465: The line and positive or negative numbers. Each point corresponds to its signed distance from the origin (a number with an absolute value equal to the distance and a + or − sign chosen based on direction). A geometric transformation of the line can be represented by a function of a real variable , for example translation of the line corresponds to addition, and scaling the line corresponds to multiplication. Any two Cartesian coordinate systems on

2520-414: The line can be related to each-other by a linear function (function of the form x ↦ a x + b {\displaystyle x\mapsto ax+b} ) taking a specific point's coordinate in one system to its coordinate in the other system. Choosing a coordinate system for each of two different lines establishes an affine map from one line to the other taking each point on one line to

2576-411: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=RHC&oldid=928619196 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Relativistic heat conduction Heat conduction in a Newtonian context

2632-555: The most common coordinate system used in computer graphics , computer-aided geometric design and other geometry-related data processing . The adjective Cartesian refers to the French mathematician and philosopher René Descartes , who published this idea in 1637 while he was resident in the Netherlands . It was independently discovered by Pierre de Fermat , who also worked in three dimensions, although Fermat did not publish

2688-412: The orientation of the three axes, as a whole, is arbitrary. However, the orientation of the axes relative to each other should always comply with the right-hand rule , unless specifically stated otherwise. All laws of physics and math assume this right-handedness , which ensures consistency. For 3D diagrams, the names "abscissa" and "ordinate" are rarely used for x and y , respectively. When they are,

2744-429: The origin has coordinates (0, 0, 0) , and the unit points on the three axes are (1, 0, 0) , (0, 1, 0) , and (0, 0, 1) . Standard names for the coordinates in the three axes are abscissa , ordinate and applicate . The coordinates are often denoted by the letters x , y , and z . The axes may then be referred to as the x -axis, y -axis, and z -axis, respectively. Then the coordinate planes can be referred to as

2800-407: The original convention, which is to use the latter part of the alphabet to indicate unknown values. The first part of the alphabet was used to designate known values. A Euclidean plane with a chosen Cartesian coordinate system is called a Cartesian plane . In a Cartesian plane, one can define canonical representatives of certain geometric figures, such as the unit circle (with radius equal to

2856-520: The plane with Cartesian coordinates ( x 1 , y 1 ) {\displaystyle (x_{1},y_{1})} and ( x 2 , y 2 ) {\displaystyle (x_{2},y_{2})} is d = ( x 2 − x 1 ) 2 + ( y 2 − y 1 ) 2 . {\displaystyle d={\sqrt {(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}}}.} This

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2912-446: The plane, and the spherical and cylindrical coordinates for three-dimensional space. An affine line with a chosen Cartesian coordinate system is called a number line . Every point on the line has a real-number coordinate, and every real number represents some point on the line. There are two degrees of freedom in the choice of Cartesian coordinate system for a line, which can be specified by choosing two distinct points along

2968-468: The point (0, 0, 1) ; a convention that is commonly called the right-hand rule . Since Cartesian coordinates are unique and non-ambiguous, the points of a Cartesian plane can be identified with pairs of real numbers ; that is, with the Cartesian product R 2 = R × R {\displaystyle \mathbb {R} ^{2}=\mathbb {R} \times \mathbb {R} } , where R {\displaystyle \mathbb {R} }

3024-423: The point on the other line with the same coordinate. A Cartesian coordinate system in two dimensions (also called a rectangular coordinate system or an orthogonal coordinate system ) is defined by an ordered pair of perpendicular lines (axes), a single unit of length for both axes, and an orientation for each axis. The point where the axes meet is taken as the origin for both, thus turning each axis into

3080-401: The point where the axes meet is called the origin of the coordinate system. The coordinates are usually written as two numbers in parentheses, in that order, separated by a comma, as in (3, −10.5) . Thus the origin has coordinates (0, 0) , and the points on the positive half-axes, one unit away from the origin, have coordinates (1, 0) and (0, 1) . In mathematics, physics, and engineering,

3136-421: The signed distances from the point to n mutually perpendicular fixed hyperplanes . Cartesian coordinates are named for René Descartes , whose invention of them in the 17th century revolutionized mathematics by allowing the expression of problems of geometry in terms of algebra and calculus . Using the Cartesian coordinate system, geometric shapes (such as curves ) can be described by equations involving

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