A matrix is simple if it is a (0,1)-matrix and there are no repeated columns. Given a (0,1)-matrix F , we say a matrix A has F as a configuration, denoted F ≺ A, if there is a submatrix of A which is a row and column permutation of F . Let |A| denote the number of columns of A. Let F be a family of matrices. We define the extremal function forb(m,F) = max{|A| : A is an m−rowed simple matrix and...

An extended visual cryptography scheme, (? Qual ; ? Forb ; m)-EVCS for short, with pixel \expansion" m, for an access structure (? Qual ; ? Forb) on a set of n participants, is a technique to encode n innocent looking images in such a way that when we stack together the transparencies associated to participants in any set X 2 ? Qual we get the secret message with no trace of the original images...

Let P be a configuration, i.e., a finite poset with top element. Let Forb(P ) be the class of bounded distributive lattices L whose Priestley space P(L) contains no copy of P . We show that the following are equivalent: Forb(P ) is first-order definable, i.e., there is a set of first-order sentences in the language of bounded lattice theory whose satisfaction characterizes membership in Forb(P ...

this research was conducted to investigate the relationships between soil(organic matter, potassium, phosphorous, sodium, fine gravel, soil texture, ec, lime,gypsum, nitrogen) and environmental (elevation, slope) factors with distribution ofvegetation types in rangelands of sabzdasht, located in bafgh, yazd province at 2012. forthis purpose, four vegetation types were selected as follows: artem...

Experimental trampling trials using a standardized methodology were undertaken in 10 replicate blocks in three vegetation types in an urban reserve in the subtropics of Australia. In each block different intensities of trampling (controls, 10, 25, 50, 100, 150, 200, 250, 300, 400 and 500 passes) were applied, and vegetation parameters were measured pre-trampling, immediately after trampling and...