3,908 research outputs found

    Nonlinear viscous hydrodynamics in various dimensions using AdS/CFT

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    We compute coefficients of two-derivative terms in the hydrodynamic energy momentum tensor of a viscous fluid which has an AdS_D dual with D between 3 and 7. For the case of D=3 we obtain an exact AdS_3 black hole solution, valid to all orders in a derivative expansion, dual to a perfect fluid in 1+1 dimensions.Comment: 20 pages; typos corrected, references adde

    The benefits of residential fieldwork for school science : insights from a five-year initiative for inner-city students in the UK

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    International audienceThere is considerable international interest in the value of residential fieldwork for school students. In the UK, pressures on curriculum time, rising costs and heightened concern over students' safety are curtailing residential experiences. Collaboration between several key providers across the UK created an extensive programme of residential courses for 11-14 year olds in London schools from 2004-2008. Some 33,000 students from 849 schools took part. This paper draws on the evaluation of the programme that gathered questionnaire, interview and observational data from 2706 participating students, 70 teachers and 869 parents / carers from 46 schools mainly in deprived areas of the city. Our findings revealed that students' collaborative skills improved and interpersonal relationships were strengthened and taken back to school. Gains were strongest in social and affective domains; behavioural improvements occurred for some students. Individual cognitive gains were revealed more convincingly during face-to-face interviews than through survey items. Students from socially deprived backgrounds benefitted from exposure to learning environments which promoted authentic practical inquiry. Over the five year programme, combined physical adventure and real-world experiences proved to be popular with students and their teachers. Opportunities for learning and doing science in ways not often accessible in urban school environments were opened up. Further programmes, building upon the provision of mixed curriculum-adventure course design, have been implemented across the UK as a result of the London experience. The popularity and apparent success of these combination courses suggest that providers need to consider the value of developing similar programmes in the future

    What contribution can residential field courses make to the education of 11-14 year-olds?

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    In this article we evaluate the effects that residential field courses had for 428 KS3 (11-14 year-old) students from 10 London schools in 2004. Teachers and students reported that levels of motivation and participation were very high, particularly where activities were adventure-based rather than purely academic. Many students surpassed their own expectations of achievement during the courses, and both students and teachers felt that the general levels of trust in others and the self-confidence shown by the students on the courses were higher than in school. Teachers were very impressed overall by the development of teamwork skills amongst the students and the vast majority of students maintained or built positive relationships with each other, with teachers and with centre staff. However, although students generally recognised that they had used or learnt new subject-specific skills, few teachers had planned how to monitor the effectiveness of the learning opportunities or how to follow them up in the longer term

    Development of a time domain reflectometry sensor for cone penetration testing

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    An essential component for evaluating the performance of a mine site after its closure includes the tracking of water movement through mine waste such as tailings and overburden. A critical element of this evaluation is the measurement of the volume of water stored in the closure landform. The objective of this project was to design a time domain reflectometry (TDR) device that could be used to measure the volumetric water content of a soil profile to depths of 10 to 20 m. Upon completion of this project, the device will be integrated onto ConeTec’s cone penetration testing (CPT) shaft for initially monitoring Syncrude Canada Limited’s northeastern Alberta oil sands mine site. The objective of this project will be achieved through at least two phases of research and development; this thesis concentrates on the first phase. In this phase, research focused on prototype development through laboratory testing to determine appropriate TDR probe geometries and configurations that could be integrated onto a CPT shaft. Considerations also had to be made for protecting the integrity of the probe during field use and mitigating the effects of highly electrically conductive soils common in reclaimed mine sites. A number of different prototype designs were initially investigated in this research, leading to the development of a refined prototype for advanced testing. Testing for the project was carried out first in solutions of known dielectric constants and salinities, and then proceeded to soils with a range of known water contents and salinities. Good quality electrical connections were found to be crucial for generating waveforms that were easy to interpret; bad connections resulted in poor results in a number of cases. Decreased probe sensitivity was observed in response to increased rod embedment within the probe variants. A far greater decrease in sensitivity was seen in the results of the fully sheathed rods, although the sheathing was effective for extending the range of the probe in electrically conductive testing conditions. Despite poor results that were seen in some of the tests, overall the results were promising. In particular, results from the push-test showed that the probe was able to monitor changes in water content with depth

    The IRAS 1.2 Jy Survey: Redshift Data

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    We present the redshift data for a survey of galaxies selected from the data base of the Infrared Astronomical Satellite (IRAS). This survey extends the 1.936 Jy sample of Strauss et al. (1992) from a flux limit of 1.936 Jy at 60 microns to 1.2 Jy. The survey extension consists of 3920 sources in the flux interval 1.2 - 1.936 Jy, of which 2663 are galaxies with measured redshifts. Fourteen objects (0.52%) do not have redshifts. The survey covers 87.6% of the sky. The data for the complete 1.2 Jy survey (the data presented here in addition to that of Strauss \etal 1992) may be obtained in a machine-readable form from the National Space Science Data Center and from the anonymous ftp site given above.Comment: uuencoded postscript file. Figures, data tables, and machine readable data files can be obtained via anonymous ftp to (192.16.204.30) ftp://eku.ias.edu/pub/fisher/12jy/12jy.tar.Z (a compressed tar file)

    Method for Turbocharging Single Cylinder Four Stroke Engines

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    This paper presents a feasibility study of a method for turbocharging single cylinder, four-stroke internal combustion engines. Turbocharging is not conventionally used with single cylinder engines because of the timing mismatch between when the turbo is powered, during the exhaust stroke, and when it can deliver air to the cylinder, during the intake stroke. The proposed solution involves an air capacitor on the intake side of the engine between the turbocharger and intake valves. The capacitor acts as a buffer and would be implemented as a new style of intake manifold with a larger volume than traditional systems. In order for the air capacitor to be practical, it needs to be sized large enough to maintain the turbocharger pressure during the intake stroke, cause minimal turbo lag, and significantly increase the density of the intake air. By creating multiple flow models of air through the turbocharged engine system, we found that the optimal size air capacitor is between four and five times the engine capacity. For a capacitor sized for a one-liter engine, the lag time was found to be approximately two seconds, which would be acceptable for slowly accelerating applications such as tractors, or steady state applications such as generators. The density increase that can be achieved in the capacitor, compared to air at standard ambient temperature and pressure, was found to vary between fifty percent for adiabatic compression and no heat transfer from the capacitor, to eighty percent for perfect heat transfer. These increases in density are proportional to, to first order, the anticipated power increases that could be realized with a turbocharger and air capacitor system applied to a single cylinder, four-stroke engine.Massachusetts Institute of Technology. Department of Mechanical Engineerin
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