Heat transfer through an electrical coil

A theoretical "basis is laid down for determining the radial conductivity for electrical coils of cylindrical construction made from electrical grade, round copper wire covered with a thin layer of plastic insulation, both with and without paper interleaving between the windings. A novel technique is used to give the radial conductivity of a coil in the form of equations which are functions of the thermal conductance of the insulation on the wire, the conductivity of the air, the maximum compression of the insulation under load, the relationship between the thermal conductance of paper and the applied load, and general dimensions. The technique approximates the lines of heat flow through the coil by a system of lines that can be analysed by one-dimensional heat transfer theory. Methods are described for determining the properties of the constituents of the coil that are required for the calculation of the conductivity, and the results of experiments are given that show that the accuracy of the theoretical prediction of the conductivity is better than + -15% of that obtained by direct test upon the coil. The analysis for the radial conductivity of non-interleaved coils is extended to cover axial conductivity but no experimental verification is given. The use of the two conductivities, axial and radial, in obtaining the temperature distribution by numerical analysis is shown and the limitations of the analysis is discussed. Finally a computer programme is provided for calculating the conductivity of paper interleaved coils

Writing US identities in the wars without frontlines: literary perspectives on the Persian Gulf and Iraq wars

For many cultural commentators, the Persian Gulf War (1990-1991) signalled a new era in which technological advances transformed warfare into what Jean Baudrillard refers to as a virtual experience epitomised by “surgical strikes” and “smart-bombs”. In contrast, the Iraq War (2003-2009) was hailed by many as a return to a more conventional form of combat in which soldiers fought their enemy in face-to-face interactions. This thesis argues that such an analysis of the conflicts overlooks the complexity of the war experience for many Gulf and Iraq War combatants. It therefore seeks to construct a reading of the literary responses to these conflicts, including novels, memoirs, and poetry, as well as alternative forms of narrative, which acknowledges the complexity of each war. Whilst it is important to recognise the ways in which Gulf War combatants experienced virtual war and Iraq War soldiers experienced guerrilla warfare, it is equally important to acknowledge the ways in which these conflicts resisted popular perceptions of them, and how this incongruence affected the combatants

Development of early mathematical skills with a tablet intervention: a randomized control trial in Malawi

Evaluation of educational interventions is necessary prior to wide-scale rollout. Yet very few rigorous studies have been conducted on the effectiveness of tablet-based interventions, especially in the early years and in developing countries. This study reports a randomized control trial to evaluate the effectiveness of a tablet intervention for supporting the development of early mathematical skills in primary school children in Malawi. A total sample of 318 children, spanning Standards 1–3, attending a medium-sized urban primary school, were randomized to one of three groups: maths tablet intervention, non-maths tablet control, and standard face-to-face practice. Children were pre-tested using tablets at the start of the school year on two tests of mathematical knowledge and a range of basic skills related to scholastic progression. Class teachers then delivered the intervention over an 8-weeks period, for the equivalent of 30-min per day. Technical support was provided from the local Voluntary Service Overseas (VSO). Children were then post-tested on the same assessments as given at pre-test. A final sample of 283 children, from Standards 1–3, present at both pre- and post-test, was analyzed to investigate the effectiveness of the maths tablet intervention. Significant effects of the maths tablet intervention over and above standard face-to-face practice or using tablets without the maths software were found in Standards 2 and 3. In Standard 3 the greater learning gains shown by the maths tablet intervention group compared to both of the control groups on the tablet-based assessments transferred to paper and pencil format, illustrating generalization of knowledge gained. Thus, tablet technology can effectively support early years mathematical skills in developing countries if the software is carefully designed to engage the child in the learning process and the content is grounded in a solid well-constructed curriculum appropriate for the child’s developmental stage

Secondary Benefits to Attentional Processing Through Intervention with an Interactive Maths App

Previous research has shown that a specific interactive app, designed to support the development of early mathematical skills and delivered on hand-held tablets, is effective at raising mathematical attainment in young children in low-and high-income countries. In the countries where this app has been deployed, teachers have consistently reported improved concentration skills in children who have received intervention with this app. To investigate the legitimacy of these claims, we conducted secondary data analyses of children’s performance on core cognitive tasks to examine if additional benefits are observed in children who received intervention with the interactive maths app compared to those that did not. We drew on data from a three-arm randomised control trial conducted in a primary school in Malawi (Pitchford, 2015). In addition to assessing mathematical skills, children’s visual attention, short-term memory, and manual processing speed were examined at baseline, before the introduction of the maths app intervention, and at endline, after the intervention had been implemented for 8 weeks. A group of 318 children (73-161 months) attending Standards 1-3 of a Malawian primary school were randomised to receive either the new maths app (treatment group), a non-maths app that required similar interactions to engage with the software as with the maths app (placebo group), or standard teacher-led mathematical practice (control group). Before and after the 8-week intervention period children were assessed on mathematics and core cognitive skills. Results showed the maths app intervention supported significant and independent gains in mathematics and visual attention. Increases in visual attention were attributable only to interactions with the maths app. No significant benefits to attention were found from using the tablet device with non-maths software or standard class-based mathematical practice. These results suggest that high-quality interactive, educational apps can significantly improve attentional processing in addition to the scholastic skills targeted by the intervention

Orbiting passive microwave sensor simulation applied to soil moisture estimation

A sensor/scene simulation program was developed and used to determine the effects of scene heterogeneity, resolution, frequency, look angle, and surface and temperature relations on the performance of a spaceborne passive microwave system designed to estimate soil water information. The ground scene is based on classified LANDSAT images which provide realistic ground classes, as well as geometries. It was determined that the average sensitivity of antenna temperature to soil moisture improves as the antenna footprint size increased. Also, the precision (or variability) of the sensitivity changes as a function of resolution

Holdouts in Sovereign Debt Restructuring: A Theory of Negotiation in a Weak Contractual Environment

Why is it difficult to restructure sovereign debt in a timely manner? In this paper we present a theory of the sovereign debt restructuring process in which delay arises as individual creditors hold-up a set- tlement in order to extract greater payments from the sovereign. We then use the theory to analyze recent policy proposals aimed at ensuring equal repayment of creditor claims. Strikingly, we show that such collective action policies may increase delay by encouraging free-riding on negotiation costs, even while preventing hold-up and reducing total negotiation costs. A calibrated version of the model can account for observed delays, and finds that free riding is quantitatively relevant: whereas in sim- ple low-cost debt restructuring operations collective mechanisms will reduce delay by more than 60%, in high-cost complicated restructurings the adoption of such mechanisms results in a doubling of delay.