3,162 research outputs found
Quench characteristics of a stabilizer-free 2G HTS conductor
No full textThe prospect of medium/high field superconducting magnets using second generation (2G) HTS tapes is approaching reality with continued enhancement in the performance of these conductors. While the cryogenic stability and quench propagation are fundamental issues for the design and safe operation of superconducting magnets, there is insufficient understanding and experimental data for 2G HTS conductors, in particular for the high field scenario at low temperature (<77 K) where the current sharing regime is much larger than in low temperature superconductors. The present work includes a systematic characterization of the relevant thermal-electrical properties used for both qualitative discussion and numerical analysis. Direct measurements of one dimensional adiabatic quench initiation and propagation of a stabilizer-free 2G conductor have been carried out with spatial-temporal recording of temperature and voltage following the deposition of varying local heat pulses to the conductor at different temperatures between 30 K and 77 K carrying different transport currents. The minimum quench energy, and the heat generation in the minimum propagation zone (MPZ) have been obtained as a function of temperature and transport current. The results show quench features unique to HTS such as an increasing MPZ with transport current and higher quench energies at lower temperatures. The experimental results are discussed in the context of current sharing over a large temperature range
Quench characteristics of bi2212 solenoid insert coils in background field up to 20 T
No full textThe use of wind and react bi2212 wire for high field ( >;20 T) insert coils has been demonstrated to be a promising technology. While cryogenic stability and quench propagation are fundamental issues for the design and safe operation of superconducting magnets there is little data for the high field application. The present work shows data from systematic quench measurements at 4.2 K on two 6-layer 300 mm high bi2212 solenoid coils at different currents I between 50% and 95% of Ic in different background fields of 15, 18 and 20 T from a wide bore compact NbTi-Nb3Sn magnet developed by Oxford Instruments. The quench was induced by localized heat pulses (20–100 ms) and recorded with temporal-spatial resolved voltage taps and thermometers. By precise control of the power delivered in the heat pulse, the minimum quench energy MQE and the time constant for the quasi-stationary minimum propagation zone MPZ was obtained for each test condition. MQE was found to follow a scaling law of Ic2/I4 in three different coils. The MPZ exhibited the expected anisotropy, extending predominately in the tangential direction and confined in a single winding layer. The propagation was also predominantly along the winding layer with a relatively slow velocity less than 50 cm/s, with an even lower radial propagation velocity of 3 mm/s. In the present study, the interplay between the HTS coils and with the LTS background field were also measured and the results are highly relevant to the design of 20 T plus high field magnets with integrated LTS and HTS coils. The results were analysed in the context of a wide current temperature range for current sharing in the bi2212 wire and the T3 dependence of heat capacity at low temperatures
Correspondence to Mary Ann Smith From William H. Borders and C.M. Lowe, March 22, 1961
No full textCorrespondence from William H. Borders and C.M. Lowe to Mary Ann Smith notifying her of a meeting for the Atlanta Student Adult Liaison. 1 page
Three-component velocity measurements in a momentum-conserving, axisymmetric, turbulent jet
No full textExperiments have been performed on a momentum conserving axisymmetric turbulent jet, the turbulence characteristics of which are well known [1]. Simultaneous three-component velocity measurements are acquired with high spatial and temporal resolution, using a new triple-sensor hotwire probe. Velocity and directional calibrations are performed using a dedicated automatic calibration system. Two experiments are performed; one for capturing the average velocity field in a 3D volume, and one for investigating the turbulence spectra in specific points in space. In the first experiment, measurements are performed in 9 equidistant cross-planes, from 10- to 50-diameters downstream of the nozzle using a computer-controlled traversing system. The spatial resolution is as low as 1 mm and the sampling rate was 10 kHz. In the second experiment, long velocity time histories are acquired with 50 kHz sampling rate to perform power spectral density computations for each velocity component. Preliminary results of velocity capture confirm the general characteristics of the turbulent jet. The power spectra at different positions indicate that the turbulent fluctuations are not isotropic at lower frequencies
A General History of the Congregation of the Mission Beginning after the Death of Blessed Vincent de Paul
No full textThis work is the earliest known history of the Congregation of the Mission and dates from about 1730. Vincentian historian John E. Rybolt, C.M., building on the initiative of Stafford Poole, C.M., completed this English translation from the original French. The author, Claude-Joseph Lacour, C.M. (1672-1731), drew from already published materials and his own recollections. While the story he tells may seem familiar, Lacour included materials that are unknown anywhere else and delivers a first-hand account of the Congregation’s rapid growth in those early days. The text is essential reading for anyone wishing to better understand Vincent de Paul’s society of apostolic life of priests and brothers following his death.https://via.library.depaul.edu/vincentian_ebooks/1044/thumbnail.jp
Turbulent separation in lower curved wall channels
No full textTurbulent boundary layer separation in channels with a lower curved wall is studied using direct numerical simulations (DNS). Turbulence dynamics are studied through classical statistical tools such as the turbulent kinetic energy budget for varying lower curved wall dimensions. The geometry features are expected to have a significant effect on the fluid flow structures and the characteristic scales of separation. The separation bubble behind the bump is studied in terms of its size, turbulent kinetic energy production mechanisms and transfer and scale-by-scale energy budget. New innovative data-analysis techniques will be used based on the generalisation of the Kolmogorov equation to anisotropic and spatially non-homogeneous flow configurations
Turbulence modulation in particle laden homogeneous shear flow: Exact Regularized Point Particle method
No full textThis contribution presents a first evaluation of a new approach, dubbed the Exact Regularized Point Particle (ERPP) method [Gualtieri et al., Exact regularized point particle method for multi-phase flows in the two-way coupling regime, arXiv preprint arXiv:1405.6969], designed to model the modulation of turbulence by hundred thousands of small inertial particles. The approach overcomes some intrinsic difficulties which arise in some circumstances in available approaches like, e.g., the Particle In Cell (PIC) method introduced by Crowe and coworkers since 1977. Numerical results concerning a homogeneous shear flow at moderate values of the Reynolds number laden with hundred thousand of small inertial particles are discussed documenting the turbulence modification in the so-called two-way coupling regime, in a range of control parameters unaccessible to the available approaches
The great household in late medieval England
No full textIn the later medieval centuries, a whole range of important social, political, and artistic activities took place against the backdrop of the great English households. In this lively book, C. M. Woolgar explores the fascinating details of life in a great house. Based on extensive investigation of household accounts and related primary documents, Woolgar vividly illuminates the operations of great households. He also delineates the major changes that transformed the economy and geography of both lay and clerical households between 1200 and 1500.In this portrait of aristocratic and gentry life in medieval England, Woolgar describes the roles of family members, the situations of servants, the uses of space within the household, food and drink for daily consumption and for special occasions, furnishing, clothing, arrangements for travel, household animals, cleanliness and hygiene, entertainment, the practices of religion, and intellectual life. The author also analyzes the qualitative and social evolution of great households as definitions of magnificence and conventions of etiquette became increasingly elaborate
Turbulence modulation in particle laden pipe flow: Exact regularized point particle method
No full textMany technological applications are characterized by turbulent bounded flows with dispersed particles. For high mass load (particle/fluid mass ratio) a significant inter-phase momentum exchange occurs (two-way coupling regime), inducing a significant alteration of the turbulent field which, in turn, modifies the dynamics of the suspended phase. Aim of the present study is exploring the potentially of recently developed momentum coupling method, dubbed the Exact Regularized Point Particle (ERPP) method, in reproducing via Direct Numerical Simulation (DNS) the detailed dynamics of a particles laden turbulent pipe flow. The comparison with available experimental and numerical data confirms the ability of the new approach in reproducing the relevant dynamics also in parameter ranges which are unaccessible to standard techniques
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