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



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.


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.
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.


(1) See Surface tablet, Surface Book, Surface Studio and PixelSense.

(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 periodicals archive ?
But in case of membrane formation, a few zeolite crystals were formed on the support surface and it was too low to detect by XRD.
Effects of visual and support surface orientation references upon postural control in vestibular deficient subjects.
Actual events or results may differ materially as a result of risks and uncertainties facing the company, including: (a) changes in purchasing patterns or procurement rules at VA facilities, (b) changes in funding levels for the VA, (c) increased competition among suppliers to the VA and (d) changes in demand for specialty support surfaces and related products at VA facilities.
The drying effect of a low-air-loss or air-fluidized support surface may help prevent additional ulcers when excess moisture on intact skin is identified as a risk factor in these cases.
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The decline in medical sales was due primarily to lower sales of private label support surfaces.
Figure 3-4: Drivers and Limiters, Therapeutic Support Surface Market, 2011 36
The current contract provides for Span-America to sell certain lines of private-label support surfaces to Hill-Rom on a non-exclusive basis.
In addition to a talented team, Gaymar provides our Medical division with an attractive portfolio of high-performance support surface and pressure ulcer management products that target an approximately $1.
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Anodyne"), the nation's leading designer and manufacturer of specialty support surfaces and patient positioning devices serving the acute care, home care and long-term care medical markets, today announced the appointment of Abbey Daniels as the company's chief executive officer effective August 8, 2008.
Specialty Bed and Support Surface Market for Wound Management, then send an e-mail to Melina Trevino, Corporate Communications at melina.

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