828 research outputs found
High energy neutrino telescopes
No full textA review of the potential of Neutrino Telescopes to contribute to Astrophysics and Elementary Particle Physics is presented. The status of the four neutrino telescopes presently under construction is reviewed. An inexpensive modular design of how to reach an 1 km2 telescope with an energy threshold of a few GeV is proposed. © 1996 Kluwer Academic Publishers
Vortex-induced vibration of flexible cylinders in time-varying flows
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 221-226).This thesis investigates two aspects of Vortex-Induced Vibrations (VIV) on long flexible cylinders. The work is split into a minor and major part. The minor part addresses the effect of Reynolds number on flexible cylinder VIV. The major contribution addresses the prediction of VIV under unsteady current excitation or time-varying flows. The study on the effect of Reynolds number makes extensive use of a recent set of experiments performed by MARINTEK on behalf of SHELL Exploration and Production Co. Three 38[gamma] long cylinders of different diameters were towed through the ocean basin over a wide range of Reynolds numbers in both uniform and sheared flows. The experimental data showed that the response amplitudes and dimensionless response frequency are strongly influenced by the Reynolds number. Both of these Reynolds effects should be of interest to riser designers that traditionally rely on experimental data obtained at much lower Reynolds numbers. In this thesis, I propose a dimensionless parameter, [gamma], that governs whether lock-in under unsteady flow conditions is possible and show that it is useful for determining a priori whether the response under unsteady conditions will be similar to the response under steady flows. The unsteady flow parameter, [gamma], describes the change in flow speed per cycle of cylinder vibration and is defined as: ... The experimental data necessary to support this work is taken from a set of experiments performed at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University (SJTU), where a 4[gamma] long flexible cylinder was towed through an ocean basin under carefully selected amounts of acceleration/deceleration. Analysis of the experimental data showed that the response can typically be divided into three regimes based on the [gamma] value: For very quickly accelerating flows ([gamma] > 0.1) the cylinder cannot react quickly enough and at most a couple of cycles of small amplitude vibration will be observed. For moderately accelerating flows (0.02 < [gamma] < 0.1), the cylinder will typically start vibrating and can build up a significant response. However, most of the time, the flow will have exited the required synchronization region before the cylinder manages to reach the large amplitudes observed in steady flows. For very slowly accelerating flows ([gamma] < 0.02), the flow is changing considerably slower than the cylinder's reaction time and thus, the cylinder has more than enough time to build up its response. Under these conditions, the observed response is qualitatively similar to the response of flexible cylinders in steady flows. The [gamma] dependence that was identified in the SJTU data is not limited to that specific situation but instead, is a general property of low mass ratio cylinders vibrating in unsteady flows. This is shown by demonstrating how the unsteady flow parameter, [gamma], can be used to analyze unsteady response data from the aforementioned SHELL tests where the riser models were considerably longer than the SJTU model. This thesis shows how a single ramp test -- where the towing speed is continuously varied in a control manner -- may be used to obtain the same information as 10 constant speed tests covering the range of speeds. This can and will significantly reduce the number of runs necessary to completely characterize the VIV response of flexible cylinders and will translate into large cost savings in the future. The thesis closes by describing the differences observed in the VIV response at high mode numbers depending on whether the time-varying flow was accelerating or decelerating. In both situations a 'hysteresis' effect is noted, where the cylinder is found to 'lag behind' preferring to vibrate in the previously excited mode as a result of cylinder lock-in. In accelerating flows, this means that the cylinder will typically be responding one mode lower than it would have in a steady flow. In decelerating flows, the same 'lag' or 'hysteresis' will cause the cylinder to respond one (or more) mode number(s) higher than it would have in a steady flow.by Themistocles L. Resvanis.Ph. D
Tests of. mu. -e universality for weak neutral currents at PEP
No full textTwo techniques are proposed to test the universality of the ..mu../minus/e weak neutral current interaction of large Q/sup 2/. Both techniques require large statistics and some degree of longitudinal e/sup +/,e/sup minus/ polarization but are otherwise feasible at PEP
Co-designing Speakers Corner
No full text“What might a twenty-first century Speakers’ Corner look like and how should the design process ensure that local people can contribute?”
The paper considers this question through describing a three year collaboration between MA Creative Practice for Narrative Environments (MACPfNE) at CSM, and the Speakers’ Corner Trust (SCT). SCT is a charity promoting public debate and active citizenship to revitalise civil society in the UK. It pursues its aims by forming local Committees which ‘own’ and steer the establishment of Speakers’ Corners as platforms for public engagement. MACPfNE is an innovative course that encourages multidisciplinary collaboration and the use of narrative as a tool to develop user focused environments.
Working closely with SCT, MACPfNE staff and students developed a methodology whereby communities co-create their own physical manifestation of Speakers’ Corner to suit needs and environment. The methodology and its theoretical foundation were developed through a series of live projects, including: a generic mobile Speakers’ Corner prototype, tested at the Global Forum for Freedom of Expression in Oslo; the co-design with local school children, followed by implementation of London’s second Speakers’ Corner in a community park in North London; and a pilot project to co-design Speakers’ Corner in every school playground
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