Sustainability in Secondary Education in England: An Ethnographic Study

This research sets out to establish both the extent to which and the ways in which English Secondary schools have a school culture focusing upon sustainability. I visited three case study schools for six weeks each: these were carefully selected to represent a range of progress towards becoming sustainable schools. I visited two other ‘benchmark’ schools for two days each: these were chosen on the recommendations of school sustainability experts, and visiting them helped me judge the progress my case-study schools had made. I took an ethnographic approach to the research, conducting about 80 interviews with various members of my three case study schools, also consulting school documents and undertaking observations of lessons and other aspects of school life. I discovered that the case-study schools had generally made little progress on sustainability, with most school members unaware or uncertain of the basic principles of sustainability. The schools focused much more on students’ examination results and behaviour than sustainability. Leadership structures and formal student involvement in leadership at the case study schools were not conducive to sustainability. Links between campus operations and the taught curriculum were mostly absent, and where sustainability was included in lessons, it tended to be largely theoretical, with few references to its impact on the students and daily life. In the light of the case-study findings and a wide-ranging literature review, a series of recommendations are made, both for secondary schools and for national education policy. These relate, for example, to patterns of school leadership, to the Continuing Professional Development (CPD) of school leaders and teachers, to strengthening the role of sustainability in both the formal and informal curriculum, and to ensuring that students emerge better equipped for a world in which sustainability agendas will be of increasing importance.Plymouth Universit

Stability Analysis of Droop-Controlled Inverter-Based Power Grids via Timescale Separation

We consider the problem of stability analysis for distribution grids with droop-controlled inverters and dynamic distribution power lines. The inverters are modeled as voltage sources with controllable frequency and amplitude. This problem is very challenging for large networks as numerical simulations and detailed eigenvalue analysis are impactical. Motivated by the above limitations, we present in this paper a systematic and computationally efficient framework for stability analysis of inverter-based distribution grids. To design our framework, we use tools from singular perturbation and Lyapunov theories. Interestingly, we show that stability of the fast dynamics of the power grid depends only on the voltage droop gains of the inverters while, stability of the slow dynamics, depends on both voltage and frequency droop gains. Finally, by leveraging these timescale separation properties, we derive sufficient conditions on the frequency and voltage droop gains of the inverters that warrant stability of the full system. We illustrate our theoretical results through a numerical example on the IEEE 13-bus distribution grid

Microcapsules with liquid cores and solid shells for pressure release applications

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The design of a surface launch and recovery fender for DSRV "Alvin"

Submitted in partial fulfillment of the requirements of the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution and Master of Science in Ocean Engineering at the Massachusetts Institute of Technology September, 1973Surface recovery of small submersibles could be made safer for personnel and hardware with the installation on the submersible of an inflatable, pneumatic bumper which acts also as main surface buoyancy. Tne use of such a bumper in the recovery of DSRV ALVIN by her catamaran mother ship, LULU, is the subject of this study. It was determined, from first order analysis of the surge velocities of these two vessels in recovery position in a sea state 6, that any such bumper or combination of bumpers (i.e. bumper on LULU) would have to absorb 10,000 ft.-lbF., of energy. In order to protect the mechanical arm, keep the forces of collision at an acceptable level and retain present surface buoyancy, an increase in ascent and descent time must be tolerated since the uninflated vertical projected area of the forebody must increase. Large trim moments, due to the presence of the air bumper at the bow can be eliminated by use of a partially submerged bumper

A model for the initiation and propagation of electrical streamers in transformer oil and transformer oil based nanofluids

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 305-309).The widespread use of dielectric liquids for high voltage insulation and power apparatus cooling is due to their greater electrical breakdown strength and thermal conductivity than gaseous insulators, while their ability to conform to complex geometries and self-heal means that they are often of more practical use than solid insulators. Transformer oil is a particularly important dielectric liquid. The issues surrounding its electrical breakdown have been the subject of extensive research. Much of this work has focused on the formation of electrical streamers. These are low-density conductive structures that form in regions of oil that are over-stressed by electric fields on the order of 1 x 108 (V/m) or greater. Once a streamer forms it tends to elongate, growing from the point of initiation towards a grounding point. The extent of a streamer's development depends upon the nature of the electrical excitation which caused it. Sustained over-excitation can result in a streamer bridging the oil gap between its point of origin and ground. When this happens an arc will form and electrical breakdown will occur. Streamers can form due to both positive and negative excitations. Positive streamers are considered more dangerous as they form at lower electric field levels and propagate with higher velocities than negative streamers. Historically, the modeling of streamer development has proved to be a very difficult task. Much of this difficulty relates to the identification of the relevant electrodynamic processes involved. In the first section of this thesis a comprehensive analysis of the charge generation mechanisms that could play a role in streamer development is presented.(cont.) The extent of the electrodynamics associated with Fowler-Nordheim charge injection, electric field dependent ionic dissociation (the Onsager Effect) and electric field dependent molecular ionization in electrically stressed transformer oil are assessed and it is shown that molecular ionization, which results in the development of an electric field wave, is the primary mechanism responsible for streamer development. A complete three carrier liquid-phase molecular ionization based streamer model is developed and solved for a positive needle electrode excitation using the COMSOL Multiphysics finite element simulation suite. The modification of the liquid-phase molecular ionization model to account for the two-phase nature of streamer development is described and the performance of both the liquid-phase and gas/liquid two-phase models are compared with experimental results reported in the literature. The second section of this thesis focuses on the insulating characteristics of transformer oil-based nanofluids. These nanofluids, which can be manufactured from a variety of materials, have been shown to possess some unique insulating characteristics. Earlier experimental work has shown that oil-based nanofluids manufactured using conductive nanoparticles have substantially higher positive voltage breakdown levels than that of pure oil. A comprehensive electrodynamic analysis of the processes which take place in electrically stressed transformer oil-based nanofluids is presented, which illustrates how conductive nanoparticles act as electron scavengers in electrically stressed transformer oil-based nanofluids. As part of this analysis, a completely general expression for the charging dynamics of a nanoparticle in transformer oil is developed.(cont.) The solutions for the charging dynamics of a range of nanoparticle materials are presented and the implications these charging dynamics have on the development of streamers in oil-based nanofluid is explained. To confirm the validity of the electrodynamic analysis, the electric field dependent molecular ionization model for streamers in pure oil is modified for use with transformer oil-based nanofluids. This model is solved for nanofluids manufactured using conductive and insulating particles and the results that are presented confirm the paradoxical fact that nanofluids manufactured from conductive nanoparticles have superior positive electrical breakdown performance to that of pure oil. The thesis concludes by exploring the possibility of developing simplified streamer models for both transformer oil and transformer oil-based nanofluids, which are computationally efficient and can be solved quickly meaning that they can be used as practical design tools.by Francis M. O'Sullivan.Ph.D

Fabrication and testing of an infrared spectral control component for thermophotovoltaic power conversion applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 155-157).Thermophotovoltaic (TPV) power conversion is the direct conversion of thermal radiation to electricity. Conceptually, TPV power conversion is a very elegant means of energy conversion. A thermal source emits a radiative spectrum, which is incident upon a photovoltaic (PV) diode. The PV diode then converts some of the incident photons to electricity. The photons which are converted to electricity have energies greater than the electronic bandgap of the material from which the PV diode is fabricated. Unfortunately the thermal sources used in TPV systems are typically broadband, meaning that a significant amount of the emitted radiation cannot be converted to electricity because the photons are not energetic enough to produce electron-hole pairs in the PV diode. This unconvertible radiation is dissipated as heat in the PV diode and represents a very large loss in a TPV system's conversion efficiency. This thesis describes the development of a spectral control component which can be used to filter the radiation emitted from a TPV system's thermal source, such that only convertible radiation is incident upon the PV diode. The theoretical analysis of filter designs based on a Si/SiO₂ dielectric stack is described in this text. The methods and processes used to fabricate physical samples of the spectral control component are discussed. The results of the spectral analysis of the physical samples are documented and a comparison between the predicted performance of the filter designs and the measured performance of the fabricated filter samples is made.by Francis M. O'Sullivan.S.M

The link between accretion mode and environment in radio-loud active galaxies

The interactions between radio-loud AGN and their environments play an important rôle in galaxy and cluster evolution. Recent work has demonstrated fundamental differences between high- and low-excitation radio galaxies (HERGs and LERGs), and shown that they may have different relationships with their environments. In the Chandra Large Project ERA (Environments of Radio-loud AGN), we made the first systematic X-ray environmental study of the cluster environments of radio galaxies at a single epoch (z ~ 0.5), and found tentative evidence for a correlation between radio luminosity and cluster X-ray luminosity. We also found that this relationship appeared to be driven by the LERG subpopulation. We have now repeated the analysis with a low-redshift sample (z ~ 0.1), and found strong correlations between radio luminosity and environment richness and between radio luminosity and central density for the LERGs but not for the HERGs. These results are consistent with models in which the HERGs are fuelled from accretion discs maintained from local reservoirs of gas, while LERGs are fuelled more directly by gas ingested from the intracluster medium. Comparing the samples, we found that although the maximum environment richness of the HERG environments is similar in both samples, there are poorer HERG environments in the z ~ 0.1 sample than in the z ~ 0.5 sample. We have therefore tentative evidence of evolution of the HERG environments. We found no differences between the LERG subsamples for the two epochs, as would be expected if radio and cluster luminosities are related.Peer reviewedFinal Accepted Versio