1,327 research outputs found
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A renaissance of audio: podcasting approaches for learning on campus and beyond
In this paper, we urge practitioners to consider the potential of podcasting for teaching, learning and assessment. Our perspective is drawn from research on IMPALA (Informal Mobile Podcasting And Learning Adaptation), which showed that there is a range of successful podcasting approaches for students on campus. After briefly surveying the background literature, we provide examples of three approaches, from three different universities: 1) helping students to prepare presentations and assessed work, 2) offering feedback from staff on students’ assessed work, and 3) assisting undergraduates to make the transition from school or college to university. Finally, we answer the important question for EDEN attendees: can podcasting approaches like these be converted for distance education? On the evidence available to date from IMPALA and other studies, we feel confident in predicting that podcasting will be integrated more and more into distance education, to the immense benefit of the long distance learner
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Conclusions from the Melville Report on the Changing Learner Experience (CLEx) Enquiry
Abstract for a short paper presented at the EDEN 2009 conference
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Balancing e-lectures with podcasts: a case study of an undergraduate engineering module
The work described in this paper is based on an engineering module that has run for six years (each academic year since 2004). The module is run online although the learners are campus-based students. This has provided an unusual opportunity to compare the same students’ experiences of on-campus and online courses. The course comprises a rich online environment including e-lectures, podcasts, video clips, website links, animations, background reading, formative quizzes, summative assignments and discussion boards. The e-lectures comprise a PowerPoint-like screen with a spoken audio track and other facilities, including a rolling transcript, video controls (for stopping, pausing and rewinding) and a search facility. Each e‑lecture is short (a maximum of ten minutes) and links to some of the learning materials (e.g. video clips and formative quizzes). The podcasts are mp3 audio files, each lasting approximately ten minutes, and are produced weekly and published through the virtual learning environment. This paper presents a pedagogical model that has been designed to develop a structure for combining these virtual learning elements and considers some of the opportunities provided by such innovative approaches for the enhancement of engineering teaching at undergraduate level. It presents research findings on student learning outcomes and provides suggestions for adopting the design for learning model presented in the paper
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Dielectric properties of epoxy nanocomposites containing TiO2, Al2O3 and ZnO fillers
The paper presents results of dielectric spectroscopy and space charge (PEA) measurements on epoxy resin filled with 10% w/w micro- and nano- sized particles of TiO2, Al3O2 and ZnO. The results appear to show that the material from which the nano-particle is made is not highly significant in influencing these results. The results support the proposition that the dielectric properties of such nano-filled composites are controlled by Stern-Gouy-Chapman layers (“interaction zones”) around the particles
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A renaissance of audio: Podcasting approaches for learning on campus and beyond
In this paper, we urge practitioners to consider the potential of podcasting for teaching, learning and assessment. Our perspective is drawn from research on IMPALA (Informal Mobile Podcasting And Learning Adaptation), which showed that there is a range of successful podcasting approaches for students on campus. After briefly surveying the background literature, we provide examples of three approaches, from three different universities: 1) helping students to prepare presentations and assessed work, 2) offering feedback from staff on students' assessed work, and 3) assisting undergraduates to make the transition from school or college to university. Finally, we would like readers to consider how podcasting approaches like these can be converted for distance education. On the evidence available to date from IMPALA and other studies, we feel confident in predicting that podcasting will be integrated more and more into distance education, to the immense benefit of the long distance learner
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"Mirror Image" space charge distribution in XLPE power cable under opposite stressing voltage polarity
The paper presents the research on space charge distribution under different polarities in full size cross-linked polyethylene power cables using the pulsed electro-acoustic technique. Under both positive and negative voltage space charge distributions possess about the same profiles but opposite polarities. Similar phenomenon had been reported previously in plaque samples and was termed as “mirror image effect”. By comparing the results among the cables treated (degassing) under different conditions, the paper concludes that the “mirror image” charge distribution is mainly attributed to bulk effect within the volume of the insulation, whilst the electron transfer by tunnelling through an electrode/insulator interface contribute to the generation of homo “mirror image” at the vicinity of the electrode
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Influence of water absorption in flexible epoxy resins on the space charge behaviour
The aim of the current work is to achieve a better understanding of the influence of water uptake in flexible epoxy resins on the space charge dynamics at high electric fields. The space charge behaviour was studied using pulsed electroacoustic (PEA) technique. The samples were prepared from Araldite CY1311, which is a bisphenol-A epoxy resin. This particular resin was chosen because its glass transition is 0°C and hence it is in a flexible state at room temperature. All samples were conditioned in containers with saturated salt solutions or de-ionised water so that various water uptake levels were obtained. It was found that the space charge dynamics was correlated with the amount of absorbed water in the samples and this is consistent with the dielectric measurements made on the same material where ion transport was identified as the main charge transport process from the observed QDC behaviour
Limitations of Kramers-Kronig transform for calculation of the DC conductance magnitude from dielectric measurements
The Kramers-Kronig (K-K) transform relates the real and imaginary parts of the complex susceptibility as a consequence of the principle of causality. It is a special case of the Hilbert transform and it is often used for estimation of the DC conductance from dielectric measurements. In this work, the practical limitations of a numerical implementation of the Kramers-Kronig transform was investigated in the case of materials that exhibit both DC conductance and quasi-DC (QDC) charge transport processes such as epoxy resins. The characteristic feature of a QDC process is that the real and imaginary parts of susceptibility (permittivity) follow fractional power law dependences with frequency with the low frequency exponent approaching -1. Dipolar relaxation in solids on the other hand has a lower frequency exponent <1. The computational procedure proposed by Jonscher for calculation of the K-K transform involves extrapolation and truncation of the data to low frequencies so that convergence of the integrals is ensured. The validity of the analysis is demonstrated by performing K-K transformation on real experimental data and on theoretical data generated using the Dissado-Hill function. It has been found that the algorithm works well for dielectric relaxation responses but it is apparent that it does not work in the case of a low frequency power law in which the low frequency exponent approaches -1, i.e. in the case of QDC responses. In this case convergence can only be guaranteed by extrapolating the low frequency power law over many decades towards zero frequency
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Electric field requirements for charge packet generation and movement in XLPE
The formation of space charge packets in XLPE (Cross-linked polyethylene) tapes from unaged cable insulation has been studied utilising the pulsed electro-acoustic (PEA) technique. The 150 m thick sheets were studied under constant applied dc field of 120 kV/mm at a temperature of 20 C for a period of 48 hours. After an inception period of about 3.5 hours, during which heterocharge accumulates at the anode and increases the local field there, a sequence of positive charge packets were observed to transit the sample starting from near the anode. Calculation of the internal field showed that the packets required a field of 140 kV/mm for their initiation. Reduction of the applied field step-wise from 120 kV/mm to 80 kV/mm indicated that the charge packet would keep moving as long as the local field at its front exceeded 100 kV/mm, but with a reducing magnitude. A return to an applied field of 120 kV/mm confirmed that the local field required to initiate a new packet was in excess of 135 kV/mm. The results are discussed in terms of current theories of charge packet formation. The first packet appears to be a moving front of field ionisation. The generation of subsequent packets is governed by the field at the anode and the balance of charge injection and extraction process, which occur there. The nature of the negative charges produced at the ionisation front is not clear, but they are unlikely to be electrons
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The role of local space charge concentrations in producing branched tree structures
Electrical trees are branched damage structures produced in polymeric insulation subject to high divergent fields. The density of branching ranges from a sparse form like a tree in winter to a dense compact form like a bush. This variation in form is significant as the bush structure occurs at higher voltages but grows slower. We present here a deterministic model for the formation of electrical trees based on damage produced by charges injected into the polymer from discharges taking place within the gas-filled tubules of the tree. A number of processes within the mechanism cause the space charge fields to fluctuate chaotically, and this is held to be responsible for the branching that is observed. Different tree shapes are found depending on whether or not injected/extracted charges reach a kinetic energy high enough for damage only at a few tree tips or everywhere around the tree periphery
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