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

Conclusions from the Melville Report on the Changing Learner Experience (CLEx) Enquiry

Abstract for a short paper presented at the EDEN 2009 conference

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

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

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

"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

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

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

The effect of water absorption on the dielectric properties of epoxy nanocomposites

In this research, the influence of water absorption on the dielectric properties of epoxy resin and epoxy micro-composites and nano-composites filled with silica has been studied. Nanocomposites were found to absorb significantly more water than unfilled epoxy. However, the microcomposite absorbed less water than unfilled epoxy: corresponding to reduced proportion of the epoxy in this composite. The glass transition temperatures of all the samples were measured by both differential scanning calorimetry and dielectric spectroscopy. The Tg decreased as the water absorption increased and, in all cases, corresponded to a drop of approximately 20K as the humidity was increased from 0% to 100%. This implied that for all the samples, the amount of water in the resin component of the composites was almost identical. It was concluded that the extra water found in the nanocomposites was located around the surface of the nanoparticles. This was confirmed by measuring the water uptake, and the swelling and density change, as a function of humidity as water was absorbed. The water shell model, originally proposed by Lewis and developed by Tanaka, has been further developed to explain low frequency dielectric spectroscopy results in which percolation of charge carriers through overlapping water shells was shown to occur. This has been discussed in terms of a percolation model. At 100% relative humidity, water is believed to surround the nanoparticles to a depth of approximately 5 monolayers. A second layer of water is proposed that is dispersed by sufficiently concentrated to be conductive; this may extend for approximately 25 nm. If all the water had existed in a single layer surrounding a nanoparticle, this layer would have been approximately 3 to 4 nm thick at 100%. This "characteristic thickness" of water surrounding a given size of nanoparticle appeared to be independent of the concentration of nanoparticles but approximately proportional to water uptake. Filler particles that have surfaces that are functionalized to be hydrophobic considerably reduce the amount of water absorbed in nanocomposites under the same conditions of humidity. Comments are made on the possible effect on electrical aging