surface


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surface

1. Geometry
a. the complete boundary of a solid figure
b. a continuous two-dimensional configuration
2. 
a. the uppermost level of the land or sea
b. (as modifier): surface transportation

Surface

 

a fundamental geometric concept with different meanings in different branches of geometry.

(1) A high-school geometry course considers planes, polyhedrons, and some curved surfaces. Each of the curved surfaces is defined in a special way— most often as a set of points that satisfy certain conditions. For example, the surface of a sphere is the set of points at a specified distance from a given point. The concept of a surface is merely exemplified rather than defined. Thus, a surface is said to be the boundary of a solid or the trace of a moving curve.

(2) The mathematically rigorous definition of a surface is based on the concepts of topology. The principal concept here is that of a simple surface, which may be represented as a part of a plane that is subject to continuous deformation— that is, to continuous extension, compression, or bending. More precisely, a simple surface is the image of the interior of a square under a homeomorphic, that is, a one-to-one and bicontinuous, mapping. This definition can be expressed analytically as follows. Introduce Cartesian coordinates u, v in the plane and x, y, z in space. Let S be the (open) square whose points have coordinates satisfying the inequalities 0 < u < 1 and 0 < v < 1. A simple surface is the homeomorphic image in space of the square Sʹ. The surface is given by means of formulas x = Φ (u, v), y = ψ(u, v), z = x(u, v), which are called its parametric equations. For different points (u, v) and (u ʹ, vʹ) the corresponding points (x, y, z) and (xʹ, yʹ, zʹ) must be different, and the functions Φ(u, v), ψ(u, v), and x(u, v) must be continuous. The hemisphere is an example of a simple surface. The sphere, however, is not a simple surface. Further generalization of the concept of a surface is consequently necessary. If a neighborhood of each point of a surface is a simple surface, the surface is said to be regular. From the standpoint of topological structure, surfaces as twodimensional manifolds are divided into several types, such as closed and open surfaces and orientable and nonorientable surfaces.

The surfaces investigated in differential geometry usually obey conditions associated with the possibility of using the methods of the differential calculus. These are usually smoothness conditions, such as the existence of a tangent plane or of curvature at each point of the surface. These requirements mean that the functions Φ(u, v), ψ(u, v), and x (u, v) are assumed to be once, twice, three times, or, in some problems, infinitely differentiable or even analytic. Moreover, it is required that at each point at least one of the determinants

be nonzero.

In analytic and algebraic geometry, a surface is defined as a set of points whose coordinates satisfy an equation of the form

(*) Φ(x, y, z) = 0

Thus, a given surface may or may not have a graphic geometric image. In this case, in order to preserve generality, we speak of imaginary surfaces. For example, the equation

X2 + y2 + z2 + 1 = 0

defines an imaginary sphere, although real space contains no point with coordinates satisfying this equation. If the function Φ(x, y, z) is continuous at some point and has at this point continuous partial derivatives ∂Φ/ ∂x, ∂Φ/ ∂y, ∂Φ/∂z, at least one of which does not vanish, then in the neighborhood of this point the surface defined by equation (*) will be a regular surface.

surface

[′sər·fəs]
(engineering)
The outer part (skin with a thickness of zero) of a body; can apply to structures, to micrometer-sized particles, or to extended-surface zeolites.
(mathematics)
A subset of three-space consisting of those points whose cartesian coordinates x, y, and z satisfy equations of the form x = ƒ(u, v), y = g (u, v), z = h (u, v), where ƒ, g, and h are differentiable real-valued functions of two parameters u and v which take real values and vary freely in some domain.

surface

(1) (Surface) Microsoft's hardware brand. See Surface versions.

(2) In CAD, the external geometry of an object. Surfaces are generally required for NC (numerical control) modeling rather than wireframe or solids.
References in classic literature ?
That this time would be easily measured I had no doubt, since so plain were the landmarks upon the under surface of the satellite that it would be but necessary to erect a simple instrument and mark the instant of passage of a given landmark across the instrument.
replaced it with the measured zero-bistatic ([beta] = 0) first surface reflectance at the half angle, [[rho].sub.fs](H, H).
The data is in meters above or below the reference ellipsoidal shape of Earth's sea surface. Where is the highest and lowest sea surface located in this segment of the North Atlantic Ocean?
Other tests showed [SICOR] bonds automotive paint to molded polymer parts like bumper bars so strongly that the polymer itself will break before the paint can be pulled from the surface."
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With a push of a button, the Surface Analyst quantifies the quality of the film surface.
But in the realm of new coating possibilities, Nissan's entry only scratches the surface. Materials scientists and chemists are already developing coverings that pack in more functions and complexity.
Comparison of the chemistry of the rubber side (meaning the side of the failure originating on the rubber, not necessarily that rubber is at the surface) and the metal side helps to quickly determine if the failure is cohesive (same chemistry on both sides) or adhesive (each side has chemistry related to different layers of the structure).
surface transportation capabilities ensuring the uninterrupted throughput of forces and materiel from theater Aerial Ports of Debarkation and Sea Ports of Debarkation to a designated destination.
The evolution of the indoor sports surface remains an ongoing process.
Depending on your customer's specifications, improving your castings' surface finish could be the smoothest move you've made since bellbottoms were cool.