Rough set theory provides a systematic way for rule extraction, attribute reduction and knowledge classification in information systems. Some measurements are important in rough sets. For example, information entropy, knowledge dependency are useful in attribute reduction algorithms. This paper proposes the concepts of the lower and upper covering numbers to establish measurements in covering-b...

In this paper, a new algorithm for solving the single loop routing problem is presented. The purpose of the single loop routing problem(SLRP) is to find the shortest loop for an automated guided vehicle covering at least one edge of each department of a block layout. First it shown that this problem can be represented as a graph model. Then a meta-heuristic algorithm based on and colony system ...

in recent years there has been a great deal of attention paid by researchers in investigating ionic liquids (ils) mainly due to the tremendous potential that ionic liquids have in reaction and separation technology. sonic speed is an important thermodynamic property of ionic liquids (ils) and always chosen as a source to determine other properties. a database for the sonic speed of pure ils cre...

A t − α covering array is an m × n matrix, with entries from an alphabet of size α, such that for any choice of t rows, and any ordered string of t letters of the alphabet, there exists a column such that the “values” of the rows in that column match those of the string of letters. We use the Lovász Local Lemma in conjunction with a new tiling-based probability model to improve the upper bound ...

Attribute reduction (also called feature subset selection) plays an important role in rough set theory. Different from the classical attribute reduction algorithms, the methods of attribute reduction based on covering rough sets appear to be suitable for numerical data. However, it is time-consuming in dealing with the large-scale data. In this paper, we study the problem of attribute reduction...

We ask whether the notion of a homotopy class of a path on a complex algebraic variety admits a purely algebraic characterisation, and reformulate this question as a question of categoricity of the universal covering space of a complex algebraic variety in a natural countable in nitary language. We provide partial positive results towards the question. Assuming a conjecture of Shafarevich and s...

The shifting strategy, introduced by Hochbaum and Maass [10], and independently by Baker [1], is a unified framework for devising polynomial approximation schemes to NP-Hard problems. This strategy has been used to great success within the computational geometry community in a plethora of different applications; most notably covering, packing, and clustering problems [2, 5, 7, 8, 9]. In this pa...