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- David W Sims, Emily J Southall, +15 authors Julian D Metcalfe
- Nature
- 2008

Many free-ranging predators have to make foraging decisions with little, if any, knowledge of present resource distribution and availability. The optimal search strategy they should use to maximize encounter rates with prey in heterogeneous natural environments remains a largely unresolved issue in ecology. Lévy walks are specialized random walks giving… (More)

- C. Tjhai, M. Tomlinson, R. Horan, M. Ahmed, M. Ambroze
- 2008

This paper presents a more efficient algorithm to count codewords of given weights in self-dual double-circulant and formally self-dual quadratic double-circulant codes over GF(2). A method of deducing the modular congruence of the weight distributions of the binary quadratic double-circulant codes is proposed. This method is based on that proposed by… (More)

- C. Tjhai, M. Tomlinson, R. Horan, M. Ahmed, M. Ambroze
- 2006 IEEE Information Theory Workshop - ITW '06…
- 2006

An efficient algorithm to count all codewords of given weight and a method to deduce the modular congruence of the weight distributions of the binary quadratic double-circulant codes are presented. Using this algorithm, we give the weight distribution of the quadratic double-circulant code of length 168 and that of the extended quadratic-residue code of the… (More)

- R. Horan, Cen Tjhai, Martin Tomlinson, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2005

We show how to construct an algorithm to search for binary idempotents which may be used to construct binary LDPC codes. The algorithm, which allows control of the key properties of sparseness, code rate and minimum distance, is constructed in the Mattson-Solomon domain. Some of the new codes, found by using this technique, are displayed.

- Victoria J Wearmouth, Matthew J McHugh, +5 authors David W Sims
- Proceedings. Biological sciences
- 2014

The decisions animals make about how long to wait between activities can determine the success of diverse behaviours such as foraging, group formation or risk avoidance. Remarkably, for diverse animal species, including humans, spontaneous patterns of waiting times show random 'burstiness' that appears scale-invariant across a broad set of scales. However,… (More)

- Cen Tjhai, Martin Tomlinson, R. Horan, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2005

— Based on the ideas of cyclotomic cosets, idempotents and Mattson-Solomon polynomials, we present a new method to construct GF(2 m), where m > 0 cyclic low-density parity-check codes. The construction method produces the dual code idempotent which is used to define the parity-check matrix of the low-density parity-check code. An interesting feature of this… (More)

In this paper we propose a new high capacity, low energy requirement, and robust spread spectrum watermark approach for still images. This approach uses an orthogonalisation scheme to generate a set of binary spread spectrum carriers that are able to minimize the interference of the original image on the watermark information detection, so that, more than… (More)

- Cen Tjhai, Martin Tomlinson, Marcel Ambroze, Mohammed Zaki Ahmed
- ArXiv
- 2008

The Hamming weight enumerator function of the formally self-dual even, binary extended quadratic residue code of prime p = 8m + 1 is given by Gleason's theorem for singly-even code. Using this theorem, the Hamming weight distribution of the extended quadratic residue is completely determined once the number of codewords of Hamming weight j Aj, for 0 ≤ j ≤… (More)

- Ke Zhang, Martin Tomlinson, Mohammed Zaki Ahmed, Marcel Ambroze, Miguel R. D. Rodrigues
- IET Communications
- 2014

- Martin Tomlinson, Mubarak Jibril, Cen Tjhai, Sergey Bezzateev, Markus Grassl, Mohammed Zaki Ahmed
- IEEE Transactions on Information Theory
- 2013

We present an efficient construction of extended length Goppa codes. Using this construction, we obtain 78 new nonbinary codes with better minimum distance than the previously known codes with the same length and dimension. The construction is based on the observation that certain Goppa codes can be seen as BCH codes.