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In plane geometry, the einstein problem asks about the existence of a single prototile that by itself forms an aperiodic set of prototiles; that is, a shape that can tessellate space but only in a nonperiodic way. Such a shape is called an einstein, a word play on ein Stein, German for "one stone". [2]
Potential energy surface for silver depositing on an aluminium–palladium–manganese (Al–Pd–Mn) quasicrystal surface. Similar to Fig. 6 in Ref. [1] A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic.
Transformation problem: The transformation problem is the problem specific to Marxist economics, and not to economics in general, of finding a general rule by which to transform the values of commodities based on socially necessary labour time into the competitive prices of the marketplace. The essential difficulty is how to reconcile profit in ...
An aperiodic tiling is a non-periodic tiling with the additional property that it does not contain arbitrarily large periodic regions or patches. A set of tile-types (or prototiles) is aperiodic if copies of these tiles can form only non-periodic tilings. The Penrose tilings are a well-known example of aperiodic tilings. [1] [2]
In economics, a non-renewable resource is defined as goods whose greater consumption today implies less consumption tomorrow. [27] David Ricardo in his early works analysed the pricing of exhaustible resources, and argued that the price of a mineral resource should increase over time. He argued that the spot price is always determined by the ...
The economics and policy area focuses on the human aspects of environmental problems. Traditional areas of environmental and natural resource economics include welfare theory, land/location use, pollution control, resource extraction, and non-market valuation, and also resource exhaustibility, [ 5 ] sustainability , environmental management ...
An example of such a tiling is shown in the adjacent diagram (see the image description for more information). A tiling that cannot be constructed from a single primitive cell is called nonperiodic. If a given set of tiles allows only nonperiodic tilings, then this set of tiles is called aperiodic . [ 3 ]
Nonmetallic material, or in nontechnical terms a nonmetal, refers to materials which are not metals. Depending upon context it is used in slightly different ways. In everyday life it would be a generic term for those materials such as plastics, wood or ceramics which are not typical metals such as the iron alloys used in bridges.