A notion of a Frobenius manifold with a nice real structure was introduced by Hertling. It is called CDV structure (Cecotti-Dubrovin-Vafa structure). In this paper, we introduce a “positivity condition” on CDV structures and show that any Frobenius manifold of rank two with real spectrum can be equipped with a positive CDV structure. We extend naturally the symmetries of Frobenius structures gi...

In this paper we generalize the method of sweeping, which may be used for both object representation and object visualization, to objects in E 4. The generalized sweeping method involves a trajectory in E 4 , and a three-dimensional cross-section orthogonal to the trajectory. Three alternatives are considered for specifying the relationship between the trajectory and the cross-section, namely t...

A declarative constraint-violation checker and message generator can ease both administrator constraint specification and user adjudication. A prototype implementation of “sanity checks” in the context of an ensemble of automated information extractors illustrates its usefulness.

In this paper we investigate the minimum code distance of QC LDPC codes [1], [2], [3]. These codes form an important subclass of LDPC codes [4], [5]. These codes also are a subclass of protograph-based LDPC codes [6]. QC LDPC codes can be easily stored as their parity-check matrices can be easily described. Besides such codes have efficient encoding [7] and decoding [8] algorithms. All of these...

An algebraic group ring method for constructing codes with no short cycles in the check matrix is derived. It is shown that the matrix of a group ring element has no short cycles if and only if the collection of group differences of this element has no repeats. When applied to elements in the group ring with small support this gives a general method for constructing and analysing low density pa...

Corresponding Author: Jehad Q. Odeh Alnihoud Department of Compute Science, Al al-Bayt University, Mafraq, Jordan Email: [email protected] Abstract: In this research, we propose a new approach to increase the capacity and enhance the reliability of hiding voice data in Arabic text. Using Kashida to hide bits in Arabic text is one of the most promising approaches in steganography. Unfortunately,...

We study a modification method for constructing lowdensity parity-check (LDPC) codes for solid burst erasures. Our proposed modification method is based on a column permutation technique for a parity-check matrix of the original LDPC codes. It can change the burst erasure correction capabilities without degradation in the performance over random erasure channels. We show by simulation results t...

Gallager introduced LDPC codes in 1962, presenting a construction method to randomly allocate bits in a sparse parity-check matrix subject to constraints on the row and column weights. Since then improvements have been made to Gallager’s construction method and some analytic constructions for LDPC codes have recently been presented. However, analytically constructed LDPC codes comprise only a v...

In this letter, we propose an appealing class of nonbinary quasi-cyclic low-density parity-check (QC-LDPC) cycle codes. The parity-check matrix is carefully designed such that the corresponding generator matrix has some nice properties: 1) systematic, 2) quasi-cyclic, and 3) sparse, which allows a parallel encoding with low complexity. Simulation results show that the performance of the propose...