Some techniques are developed for constructing non-isomorphic solutions of symmetric (4t + 3,2t + 1, t) designs for suitable values of t and for (4t + 2, 8t + 2,4t + 1,2t + 1,2t) and (4t + 4, St + 6,4t + 3,2t + 2,2t + 1) designs. As an application, some non-isomorphic solutions of (19,9,4), (10,18, 9, 5, 4), and (12, 22, 11, 6, 5) designs are obtained. In [l] some other techniques were given fo...

Suppose we have a committee composed of a large number of members, and from this committee we wish to create a number of smaller subcommittees, each containing exactly the same number of members. Furthermore, in order to preserve equality and keep all committee members happy, each member must sit on exactly the same number of subcommittees and each pair of members must also sit on the same numb...

Local search is often able to solve larger problems than systematic backtracking. To apply it to a constraint satisfaction problem, the problem is often treated as an optimization problem in which the search space is the total assignments, and the number of constraint violations is to be minimized to zero. Though often successful, this approach is sometimes unsuitable for structured problems wi...

Large number of watermarks is crucial for some real watermarking applications, such as transaction tracking. The purpose of this paper is to enlarge the set of structured watermarks based on balanced incomplete block designs (BIBD). An approach is proposed to generate new structured watermarks by combining existing BIBD-based watermarks. The corresponding recognition rules for the new set of wa...

Low Density Parity Check (LDPC) Codes are the class of linear block codes which provide near capacity performance on large collection of data transmission channels while simultaneously feasible for implementable decoders. LDPC codes were first proposed by Gallger in 1967 [1] and were rarely used until their rediscovery by Mackay, Luby and others [9][10][11]. Much research is devoted to characte...

Balanced incomplete-block designs (BIBDs) with repeated blocks are studied and constructed. We continue work initiated by van Lint and Ryser in 1972 and pursued by van Lint in 1973. We concentrate on constructing (v, b, r, k, λ)-BIBDs with repeated blocks, especially those with gcd(b, r, λ) = 1 and r ≤ 20. We obtain new bounds for the multiplicity of a block in terms of the parameters of a BIBD...

Polygonal designs, a class of partially balanced incomplete block designs with regular polygons, are useful in survey sampling in terms of balanced sampling plans excluding contiguous units (BSECs) and balanced sampling plans excluding adjacent units (BSAs) when neighboring units in a population provide similar information. In this paper, the method of cyclic shifts is used and cyclic polygonal...