Joseph A. O'Sullivan

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An information–theoretic analysis of information hiding is presented in this paper, forming the theoretical basis for design of information–hiding systems. Information hiding is an emerging research area which encompasses applications such as copyright protection for digital media, watermarking, fingerprinting, and steganography. In these applications,(More)
The electrocardiogram (ECG) is an emerging biometric modality that has seen about 13 years of development in peer-reviewed literature, and as such deserves a systematic review and discussion of the associated methods and findings. In this paper, we review most of the techniques that have been applied to the use of the electrocardiogram for biometric(More)
Abs,stract-A new approach to high-resolution radar imaging is presented. The starting point is a model of the radar echo signal based on the physics governing radar reflections. This model has been used several times in the past for describing radar targets that are rough compared to the wavelength of the transmitted radiation. Without specifying precisely(More)
In this paper, we present the results of an analysis of the electrocardiogram (ECG) as a biométrie using a novel short-time frequency method with robust feature selection. Our proposed method incorporates heartbeats from multiple days and fuses information. Single lead ECG signals from a comparatively large sample of 269 subjects that were sampled(More)
Wireless sensor networks often face the critical challenge of sustaining long-term operation on limited battery energy. Coverage maintenance protocols can effectively prolong network lifetime by maintaining sufficient sensing coverage over a region using a small number of active nodes while scheduling the others to sleep. We present a novel distributed(More)
Biological and machine pattern recognition systems face a common challenge: Given sensory data about an unknown pattern, classify the pattern by searching for the best match within a library of representations stored in memory. In many cases, the number of patterns to be discriminated and the richness of the raw data force recognition systems to internally(More)
A family of alternating minimization algorithms for finding maximum-likelihood estimates of attenuation functions in transmission X-ray tomography is described. The model from which the algorithms are derived includes polyenergetic photon spectra, background events, and nonideal point spread functions. The maximum-likelihood image reconstruction problem is(More)
This paper discusses a new roughness penalty for use in estimation problems including image estimation problems. It is one of a new class of penalty functions for use in estimation and image regularization that has recently been proposed. These functions penalize the discrepancy between an image and a shifted version of itself; here the discrepancy measure(More)