Methods for the transfer function design of multiple narrow-band bandpass sigma-delta modulators

This paper presents the design analysis of novel tunable narrow-band bandpass sigma-delta modulators, which can achieve concurrent multiple noise-shaping for multi-tone input signals. Four different design methodologies based on the noise transfer functions of comb filters, slink filters, multi-notch filters and fractional delay comb filters are applied for the design of these multiple-band sigma-delta modulators. The latter approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter-based sigma-delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies. The merits and drawbacks of each technique for the various sigma-delta topologies are assessed in terms of in-band signal-to-noise ratios, accuracy of tunability and coefficient complexity for ease of implementation.

Supporting the learning and networking experiences of doctoral students

This study explores the impact of a Graduate Virtual Research Environment (GVRE) on the learning and networking experiences of research students. The GVRE was established to support and enhance research skills and employability training across a university. It provides an extensive range of resources including video reflections based on the experiences of students and staff; GVRE members are encouraged to comment and engage in discussions on these resources. Our work is framed using social theories of learning and the role of communities in the support and development of research students. In particular, we are interested in exploring the challenges involved in developing communities and networks for students whose main focus is their individual research. The GVRE was made available to over 600 students and in this research we explore its impact on the experiences of research students. In particular, we investigate four questions: (a) what impact does the students use of the GVRE have on the development of their research skills; (b) what impact does membership of the GVRE have on the networks and communities of research students; (c) how do research students view the relationships between their research skills training programme, their individual research and the GVRE; and (d) how do research students currently use social media. We use an interpretivist approach and our data sources include site statistics, responses to a questionnaire and also feedback from a focus group. Our findings indicate that networking remains an issue and students suggested approaches to facilitating this using the GVRE: (1) A clearer pathway from skills need identification to skills acquisition; (2) Rewards for activities around networking - possibly through credit on the training scheme; (3) Activities that would involve research directly. Feedback on the GVRE indicated that it is valued by research students as it facilitates the development of their research skills. In terms of marketing the GVRE to research students important factors identified were: the ease of access to the site, the overview it gives of the PhD process; and the value of the site to students around the defining moments of their studies when the students felt they needed additional advice and guidance.

Reading Maud’s remains: Tennyson, geological processes, and palaeontological reconstructions

As Tennyson's “little Hamlet ,” Maud (1855) posits a speaker who, like Hamlet, confronts the ignominious fate of dead remains. Maud's speaker contemplates such remains as bone, hair, shell, and he experiences his world as one composed of hard inorganic matter, such things as rocks, gems, flint, stone, coal, and gold. While Maud's imagery of “stones, and hard substances” has been read as signifying the speaker's desire “unnaturally to harden himself into insensibility” (Killham 231, 235), I argue that these substances benefit from being read in the context of Tennyson's wider understanding of geological processes. Along with highlighting these materials, the text's imagery focuses on processes of fossilisation, while Maud's characters appear to be in the grip of an insidious petrification. Despite the preoccupation with geological materials and processes, the poem has received little critical attention in these terms. Dennis R. Dean, for example, whose Tennyson and Geology (1985) is still the most rigorous study of the sources of Tennyson's knowledge of geology, does not detect a geological register in the poem, arguing that by the time Tennyson began to write Maud, he was “relatively at ease with the geological world” (Dean 21). I argue, however, that Maud reveals that Tennyson was anything but “at ease” with geology. While In Memoriam (1851) wrestles with religious doubt that is both initiated, and, to some extent, alleviated by geological theories, it finally affirms the transcendence of spirit over matter. Maud, conversely, gravitates towards the ground, concerning itself with the corporal remains of life and with the agents of change that operate on all matter. Influenced by his reading of geology, and particularly Charles Lyell's provocative writings on the embedding and fossilisation of organic material in strata in his Principles of Geology (1830–33) volume 2, Tennyson's poem probes the taphonomic processes that result in the incorporation of dead remains and even living flesh into the geological system.