Building a Better Bijection between Classes of Compositions

A bijective proof is given for the following theorem: The number of compositions of n into parts congruent to a (mod b) equals the number of compositions of n + b - a into parts congruent to b (mod a) that are greater than or equal to b. The bijection is then shown to preserve palindromicity

A Bijection between Two Classes of Restricted Compositions

Two proofs, one using generating functions, the other bijective, are given for the following theorem: The number of compositions of n into parts congruent to 1 (mod k) equals the number of compositions of n + k − 1 into parts greater than k − 1. This bijection is then proven to hold for palindromic compositions. A more general theorem is presented in conclusion

Construction of a Full Row-Rank Matrix System for Multiple Scanning Directions in Computed Tomography

A full row-rank system matrix generated by scans along two directions in discrete tomography was recently studied. In this paper, we generalize the result to multiple directions. Let Ax = h be a reduced binary linear system generated by scans along three directions. Using geometry, it is shown in this paper that the linearly dependent rows of the system matrix A can be explicitly identified and a full row-rank matrix can be obtained after the removal of those rows. The results could be extended to any number of multiple directions. Therefore, certain software packages requiring a full row-rank system matrix can be adopted to reconstruct an image. Meanwhile, the cost of computation is reduced by using a full row-rank matrix