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Sample records for flux tube delocalization

  1. Flux tubes at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cea, Paolo [INFN, Sezione di Bari,Via G. Amendola 173, I-70126 Bari (Italy); Dipartimento di Fisica dell’Università di Bari,Via G. Amendola 173, I-70126 Bari (Italy); Cosmai, Leonardo [INFN, Sezione di Bari,Via G. Amendola 173, I-70126 Bari (Italy); Cuteri, Francesca; Papa, Alessandro [Dipartimento di Fisica, Università della Calabria & INFN-Cosenza,Ponte Bucci, cubo 31C, I-87036 Rende (Cosenza) (Italy)

    2016-06-07

    The chromoelectric field generated by a static quark-antiquark pair, with its peculiar tube-like shape, can be nicely described, at zero temperature, within the dual superconductor scenario for the QCD confining vacuum. In this work we investigate, by lattice Monte Carlo simulations of the SU(3) pure gauge theory, the fate of chromoelectric flux tubes across the deconfinement transition. We find that, if the distance between the static sources is kept fixed at about 0.76 fm ≃1.6/√σ and the temperature is increased towards and above the deconfinement temperature T{sub c}, the amplitude of the field inside the flux tube gets smaller, while the shape of the flux tube does not vary appreciably across deconfinement. This scenario with flux-tube “evaporation” above T{sub c} has no correspondence in ordinary (type-II) superconductivity, where instead the transition to the phase with normal conductivity is characterized by a divergent fattening of flux tubes as the transition temperature is approached from below. We present also some evidence about the existence of flux-tube structures in the magnetic sector of the theory in the deconfined phase.

  2. Physics of magnetic flux tubes

    CERN Document Server

    Ryutova, Margarita

    2015-01-01

    This book is the first account of the physics of magnetic flux tubes from their fundamental properties to collective phenomena in an ensembles of flux tubes. The physics of magnetic flux tubes is absolutely vital for understanding fundamental physical processes in the solar atmosphere shaped and governed by magnetic fields. High-resolution and high cadence observations from recent space and  ground-based instruments taken simultaneously at different heights and temperatures not only show the ubiquity of filamentary structure formation but also allow to study how various events are interconnected by system of magnetic flux tubes. The book covers both theory and observations. Theoretical models presented in analytical and phenomenological forms are tailored for practical applications. These are welded with state-of-the-art observations from early decisive ones to the most recent data that open a new phase-space for exploring the Sun and sun-like stars. Concept of magnetic flux tubes is central to various magn...

  3. Profile modifications in laser-driven temperature fronts using flux-limiters and delocalization models

    Science.gov (United States)

    Colombant, Denis; Manheimer, Wallace; Busquet, Michel

    2004-11-01

    A simple steady-state model using flux-limiters by Day et al [1] showed that temperature profiles could formally be double-valued. Stability of temperature profiles in laser-driven temperature fronts using delocalization models was also discussed by Prasad and Kershaw [2]. We have observed steepening of the front and flattening of the maximum temperature in laser-driven implosions [3]. Following the simple model first proposed in [1], we solve for a two-boundary value steady-state heat flow problem for various non-local heat transport models. For the more complicated models [4,5], we obtain the steady-state solution as the asymptotic limit of the time-dependent solution. Solutions will be shown and compared for these various models. 1.M.Day, B.Merriman, F.Najmabadi and R.W.Conn, Contrib. Plasma Phys. 36, 419 (1996) 2.M.K.Prasad and D.S.Kershaw, Phys. Fluids B3, 3087 (1991) 3.D.Colombant, W.Manheimer and M.Busquet, Bull. Amer. Phys. Soc. 48, 326 (2003) 4.E.M.Epperlein and R.W.Short, Phys. Fluids B3, 3092 (1991) 5.W.Manheimer and D.Colombant, Phys. Plasmas 11, 260 (2004)

  4. Flux Tube Dynamics in the Dual Superconductor

    International Nuclear Information System (INIS)

    Lampert, M.; Svetitsky, B.

    1999-01-01

    We have studied plasma oscillations in a flux tube created in a dual superconductor. The theory contains an Abelian gauge field coupled magnetically to a Higgs field that confines electric charge via the dual Meissner effect. Starting from a static flux tube configuration, with electric charges at either end, we release a fluid of electric charges in the system that accelerate and screen the electric field. The weakening of the electric field allows the flux tube to collapse, and the inertia of the charges forces it open again. We investigate both Type I and Type II superconductors, with plasma frequencies both above and below the threshold for radiation into the Higgs vacuum. (The parameters appropriate to QCD are in the Type II regime; the plasma frequency depends on the mass taken for the fluid constituents.) The coupling of the plasma oscillations to the Higgs field making up the flux tube is the main new feature in our work

  5. Observation of a Coulomb flux tube

    Science.gov (United States)

    Greensite, Jeff; Chung, Kristian

    2018-03-01

    In Coulomb gauge there is a longitudinal color electric field associated with a static quark-antiquark pair. We have measured the spatial distribution of this field, and find that it falls off exponentially with transverse distance from a line joining the two quarks. In other words there is a Coulomb flux tube, with a width that is somewhat smaller than that of the minimal energy flux tube associated with the asymptotic string tension. A confinement criterion for gauge theories with matter fields is also proposed.

  6. Models of Flux Tubes from Constrained Relaxation

    Indian Academy of Sciences (India)

    tribpo

    J. Astrophys. Astr. (2000) 21, 299 302. Models of Flux Tubes from Constrained Relaxation. Α. Mangalam* & V. Krishan†, Indian Institute of Astrophysics, Koramangala,. Bangalore 560 034, India. *e mail: mangalam @ iiap. ernet. in. † e mail: vinod@iiap.ernet.in. Abstract. We study the relaxation of a compressible plasma to ...

  7. Identification of radio emission from the Io flux tube

    International Nuclear Information System (INIS)

    Riddle, A.C.

    1983-01-01

    Many theories and observations suggest that Jovian decametric radio emission is generated in flux tubes that pass close to Io's orbit. However, comparison of theory and observation is hindered by lack of knowledge as to which specific flux tube is responsible for a particular emission. In this note, emission from the instantaneous Io flux tube is identified. This makes possible a mapping of emissions onto the causative flux tubes for a significant range of Jovian longitudes (240 0 --360 0 )

  8. THE TOPOLOGY OF CANONICAL FLUX TUBES IN FLARED JET GEOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Lavine, Eric Sander; You, Setthivoine, E-mail: Slavine2@uw.edu, E-mail: syou@aa.washington.edu [University of Washington, 4000 15th Street, NE Aeronautics and Astronautics 211 Guggenheim Hall, Box 352400, Seattle, WA 98195 (United States)

    2017-01-20

    Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). We outline here a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of the species’ canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. A flared, current-carrying magnetic flux tube in an ion-electron plasma with finite ion momentum is thus equivalent to either a pair of electron and ion flow flux tubes, a pair of electron and ion canonical momentum flux tubes, or a pair of electron and ion canonical vorticity flux tubes. We examine the morphology of all these flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, axisymmetric magnetic geometry. Calculations of gauge-invariant relative canonical helicities track the evolution of magnetic, cross, and kinetic helicities in the system, and show that ion flow fields can unwind to compensate for an increasing magnetic twist. The results demonstrate that including a species’ finite momentum can result in a very long collimated canonical vorticity flux tube even if the magnetic flux tube is flared. With finite momentum, particle density gradients must be normal to canonical vorticities, not to magnetic fields, so observations of collimated astrophysical jets could be images of canonical vorticity flux tubes instead of magnetic flux tubes.

  9. Dynamical Processes in Flux Tubes and their Role in ...

    Indian Academy of Sciences (India)

    We model the dynamical interaction between magnetic flux tubes and granules in the solar photosphere which leads to the excitation of transverse (kink) and longitudinal (sausage) tube waves. The investigation is motivated by the interpretation of network oscillations in terms of flux tube waves. The calculations show that ...

  10. Simulations of fully deformed oscillating flux tubes

    Science.gov (United States)

    Karampelas, K.; Van Doorsselaere, T.

    2018-02-01

    Context. In recent years, a number of numerical studies have been focusing on the significance of the Kelvin-Helmholtz instability in the dynamics of oscillating coronal loops. This process enhances the transfer of energy into smaller scales, and has been connected with heating of coronal loops, when dissipation mechanisms, such as resistivity, are considered. However, the turbulent layer is expected near the outer regions of the loops. Therefore, the effects of wave heating are expected to be confined to the loop's external layers, leaving their denser inner parts without a heating mechanism. Aim. In the current work we aim to study the spatial evolution of wave heating effects from a footpoint driven standing kink wave in a coronal loop. Methods: Using the MPI-AMRVAC code, we performed ideal, three dimensional magnetohydrodynamic simulations of footpoint driven transverse oscillations of a cold, straight coronal flux tube, embedded in a hotter environment. We have also constructed forward models for our simulation using the FoMo code. Results: The developed transverse wave induced Kelvin-Helmholtz (TWIKH) rolls expand throughout the tube cross-section, and cover it entirely. This turbulence significantly alters the initial density profile, leading to a fully deformed cross section. As a consequence, the resistive and viscous heating rate both increase over the entire loop cross section. The resistive heating rate takes its maximum values near the footpoints, while the viscous heating rate at the apex. Conclusions: We conclude that even a monoperiodic driver can spread wave heating over the whole loop cross section, potentially providing a heating source in the inner loop region. Despite the loop's fully deformed structure, forward modelling still shows the structure appearing as a loop. A movie attached to Fig. 1 is available at http://https://www.aanda.org

  11. Force-free thin flux tubes: Basic equations and stability

    International Nuclear Information System (INIS)

    Zhugzhda, Y.D.

    1996-01-01

    The thin flux tube approximation is considered for a straight, symmetrical, force-free, rigidly rotating flux tube. The derived set of equations describes tube, body sausage, and Alfveacute charn wave modes and is valid for any values of Β. The linear waves and instabilities of force-free flux tubes are considered. The comparison of approximate and exact solutions for an untwisted, nonrotating flux tube is performed. It is shown that the approximate and exact dispersion equations coincides, except the 20% discrepancy of sausage frequencies. An effective cross section is proposed to introduce the removal of this discrepancy. It makes the derived approximation correct for the force-free thin flux tube dynamics, except the detailed structure of radial eigenfunction. The dispersion of Alfveacute charn torsional waves in a force-free tubes appears. The valve effect of one directional propagation of waves in rotating twisted tube is revealed. The current and rotational sausage instabilities of a force-free, thin flux tube are considered. copyright 1996 American Institute of Physics

  12. Supersymmetric quantum mechanics of the flux tube

    Science.gov (United States)

    Belitsky, A. V.

    2016-12-01

    The Operator Product Expansion approach to scattering amplitudes in maximally supersymmetric gauge theory operates in terms of pentagon transitions for excitations propagating on a color flux tube. These obey a set of axioms which allow one to determine them to all orders in 't Hooft coupling and confront against explicit calculations. One of the simplifying features of the formalism is the factorizability of multiparticle transitions in terms of single-particle ones. In this paper we extend an earlier consideration of a sector populated by one kind of excitations to the case of a system with fermionic as well as bosonic degrees of freedom to address the origin of the factorization. While the purely bosonic case was analyzed within an integrable noncompact open-spin chain model, the current case is solved in the framework of a supersymmetric sl (2 | 1) magnet. We find the eigenfunctions for the multiparticle system making use of the R-matrix approach. Constructing resulting pentagon transitions, we prove their factorized form. The discussion corresponds to leading order of perturbation theory.

  13. Magnetic flux tube models in superstring theory

    CERN Document Server

    Russo, Jorge G

    1996-01-01

    Superstring models describing curved 4-dimensional magnetic flux tube backgrounds are exactly solvable in terms of free fields. We consider the simplest model of this type (corresponding to `Kaluza-Klein' Melvin background). Its 2d action has a flat but topologically non-trivial 10-dimensional target space (there is a mixing of angular coordinate of the 2-plane with an internal compact coordinate). We demonstrate that this theory has broken supersymmetry but is perturbatively stable if the radius R of the internal coordinate is larger than R_0=\\sqrt{2\\a'}. In the Green-Schwarz formulation the supersymmetry breaking is a consequence of the presence of a flat but non-trivial connection in the fermionic terms in the action. For R R/2\\a' there appear instabilities corresponding to tachyonic winding states. The torus partition function Z(q,R) is finite for R > R_0 (and vanishes for qR=2n, n=integer). At the special points qR=2n (2n+1) the model is equivalent to the free superstring theory compactified on a circle...

  14. Lifetime of electric flux tubes near the QCD phase transition

    International Nuclear Information System (INIS)

    Faroughy, Cyrus; Shuryak, Edward

    2010-01-01

    Electric flux tubes are a well-known attribute of the quantum chromodynamic (QCD) vacuum in which they manifest confinement of electric color charges. Recently, experimental results appeared which suggest that not only do those objects persist at temperatures T≅T c near the QCD phase transitions, but their decay is suppressed and the resulting clusters in Au-Au collisions are larger than in pp collisions (i.e., in vacuum). This correlates well with recent theoretical scenarios that view the QCD matter in the T≅T c region as a dual-magnetic plasma dominated by color-magnetic monopoles. In this view, the flux tubes are stabilized by dual-magnetic currents and are described by dual magnetohydrodynamics (DMHD). In this article, we calculate classically the dissipative effects in the flux tube. Such effects are associated with rescattering and finite conductivity of the matter. We derive the DMHD solution in the presence of dissipation and then estimate the lifetime of the electric flux tubes. The conclusion of this study is that a classical treatment leads to too short of a lifetime for the flux tubes.

  15. CURRENT BUILDUP IN EMERGING SERPENTINE FLUX TUBES

    International Nuclear Information System (INIS)

    Pariat, E.; Masson, S.; Aulanier, G.

    2009-01-01

    The increase of magnetic flux in the solar atmosphere during active-region formation involves the transport of the magnetic field from the solar convection zone through the lowest layers of the solar atmosphere, through which the plasma β changes from >1 to <1 with altitude. The crossing of this magnetic transition zone requires the magnetic field to adopt a serpentine shape also known as the sea-serpent topology. In the frame of the resistive flux-emergence model, the rising of the magnetic flux is believed to be dynamically driven by a succession of magnetic reconnections which are commonly observed in emerging flux regions as Ellerman bombs. Using a data-driven, three-dimensional (3D) magnetohydrodynamic numerical simulation of flux emergence occurring in active region 10191 on 2002 November 16-17, we study the development of 3D electric current sheets. We show that these currents buildup along the 3D serpentine magnetic-field structure as a result of photospheric diverging horizontal line-tied motions that emulate the observed photospheric evolution. We observe that reconnection can not only develop following a pinching evolution of the serpentine field line, as usually assumed in two-dimensional geometry, but can also result from 3D shearing deformation of the magnetic structure. In addition, we report for the first time on the observation in the UV domain with the Transition Region and Coronal Explorer (TRACE) of extremely transient loop-like features, appearing within the emerging flux domain, which link several Ellermam bombs with one another. We argue that these loop transients can be explained as a consequence of the currents that build up along the serpentine magnetic field.

  16. Formation and dynamics of a solar eruptive flux tube

    Science.gov (United States)

    Inoue, Satoshi; Kusano, Kanya; Büchner, Jörg; Skála, Jan

    2018-01-01

    Solar eruptions are well-known drivers of extreme space weather, which can greatly disturb the Earth's magnetosphere and ionosphere. The triggering process and initial dynamics of these eruptions are still an area of intense study. Here we perform a magnetohydrodynamic simulation taking into account the observed photospheric magnetic field to reveal the dynamics of a solar eruption in a real magnetic environment. In our simulation, we confirmed that tether-cutting reconnection occurring locally above the polarity inversion line creates a twisted flux tube, which is lifted into a toroidal unstable area where it loses equilibrium, destroying the force-free state, and driving the eruption. Consequently, a more highly twisted flux tube is built up during this initial phase, which can be further accelerated even when it returns to a stable area. We suggest that a nonlinear positive feedback process between the flux tube evolution and reconnection is the key to ensure this extra acceleration.

  17. Critical heat flux in tubes and tight hexagonal rod lattices

    International Nuclear Information System (INIS)

    Erbacher, F.J.; Cheng Xu; Zeggel, W.

    1994-01-01

    The critical heat flux (CHF) in small-diameter tubes and in tight hexagonal 7-rod and 37-rod bundles was investigated in the KRISTA test facility, using Freon 12 as the working fluid. The measurements in tubes showed that the influence of the tube diameter on CHF cannot be described as suggested by earlier publications with sufficient accuracy. CHF in bundles is lower than in tubes under comparable conditions. The influence of spacers (grid spacers, wire wraps) on CHF was found to be governed by local steam qualities. A comparison of the test results with some CHF prediction methods showed that the look-up table method reproduces the test results in circular tubes most accurately. Combined with CHF look-up tables, subchannel analysis and Ahmad's fluid-to-fluid scaling law, Freon experiments have proven to be a suitable tool for CHF prediction in water-cooled rod bundles. (orig.) [de

  18. Multi-flux-tube system in the dual Ginzburg-Landau theory

    International Nuclear Information System (INIS)

    Ichie, H.; Suganuma, H.; Toki, H.

    1996-01-01

    We study the multi-flux-tube system in terms of the dual Ginzburg-Landau theory. We consider two periodic cases, where the directions of all the flux tubes are the same in one case and alternating in the other case for neighboring flux tubes. We formulate the multi-flux-tube system by regarding it as the system of two flux tubes penetrating through a two-dimensional spherical surface. We find the multi-flux-tube configuration becomes uniform above some critical flux-tube number density ρ c =1.3 endash 1.7 fm -2 . On the other hand, the inhomogeneity of the color electric distribution appears when the flux-tube density is smaller than ρ c . We study the inhomogeneity on the color electric distribution in relation with the flux-tube number density, and discuss the quark-gluon plasma formation process in ultrarelativistic heavy-ion collisions. copyright 1996 The American Physical Society

  19. Guided flows in coronal magnetic flux tubes

    Science.gov (United States)

    Petralia, A.; Reale, F.; Testa, P.

    2018-01-01

    Context. There is evidence that coronal plasma flows break down into fragments and become laminar. Aims: We investigate this effect by modelling flows confined along magnetic channels. Methods: We consider a full magnetohydrodynamic (MHD) model of a solar atmosphere box with a dipole magnetic field. We compare the propagation of a cylindrical flow perfectly aligned with the field to that of another flow with a slight misalignment. We assume a flow speed of 200 km s-1 and an ambient magnetic field of 30 G. Results: We find that although the aligned flow maintains its cylindrical symmetry while it travels along the magnetic tube, the misaligned one is rapidly squashed on one side, becoming laminar and eventually fragmented because of the interaction and back-reaction of the magnetic field. This model could explain an observation made by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory of erupted fragments that fall back onto the solar surface as thin and elongated strands and end up in a hedge-like configuration. Conclusions: The initial alignment of plasma flow plays an important role in determining the possible laminar structure and fragmentation of flows while they travel along magnetic channels. Movies are available in electronic form at http://www.aanda.org

  20. Dynamical Processes in Flux Tubes and their Role in ...

    Indian Academy of Sciences (India)

    tribpo

    tubes and granules in the solar photosphere which leads to the excitation of transverse (kink) and longitudinal ... the energy flux in transverse waves is calculated and the implications for chromospheric heating are ... highly dynamical state, due to the buffeting effect of random convective motions. (e.g., Müller 1983; Muller et ...

  1. Vertical motions in an intense magnetic flux tube. Pt. 5

    International Nuclear Information System (INIS)

    Webb, A.R.; Roberts, B.

    1980-01-01

    It is of interest to examine the effect of radiative relaxation on the propagation of waves in an intense magnetic flux tube embedded in a stratified atmosphere. The radiative energy loss (assuming Newton's law of cooling) leads to a decrease in the vertical phase-velocity of the waves, and to a damping of the amplitude for those waves with frequencies greater than the adiabatic value (ωsub(upsilon)) of the tube cut-off frequency. The cut-off frequency is generalized to include the effects of radiative relaxation, and allows the waves to be classified as mainly progressive or mainly damped. The phase-shift between velocity oscillations at two different levels and the phase-difference between temperature and velocity perturbations are compared with the available observations. Radiative dissipation of waves propagating along an intense flux tube may be the cause of the high temperature (and excess brightness) observed in the network. (orig.)

  2. RESONANT ABSORPTION OF AXISYMMETRIC MODES IN TWISTED MAGNETIC FLUX TUBES

    Energy Technology Data Exchange (ETDEWEB)

    Giagkiozis, I.; Verth, G. [Solar Plasma Physics Research Centre, School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Hicks Building, Sheffield, S3 7RH (United Kingdom); Goossens, M.; Doorsselaere, T. Van [Centre for mathematical Plasma Astrophysics, Mathematics Department, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium); Fedun, V. [Department of Automatic Control and Systems Engineering, University of Sheffield, Mappin Street, Amy Johnson Building, Sheffield, S1 3JD (United Kingdom)

    2016-06-01

    It has been shown recently that magnetic twist and axisymmetric MHD modes are ubiquitous in the solar atmosphere, and therefore the study of resonant absorption for these modes has become a pressing issue because it can have important consequences for heating magnetic flux tubes in the solar atmosphere and the observed damping. In this investigation, for the first time, we calculate the damping rate for axisymmetric MHD waves in weakly twisted magnetic flux tubes. Our aim is to investigate the impact of resonant damping of these modes for solar atmospheric conditions. This analytical study is based on an idealized configuration of a straight magnetic flux tube with a weak magnetic twist inside as well as outside the tube. By implementing the conservation laws derived by Sakurai et al. and the analytic solutions for weakly twisted flux tubes obtained recently by Giagkiozis et al. we derive a dispersion relation for resonantly damped axisymmetric modes in the spectrum of the Alfvén continuum. We also obtain an insightful analytical expression for the damping rate in the long wavelength limit. Furthermore, it is shown that both the longitudinal magnetic field and the density, which are allowed to vary continuously in the inhomogeneous layer, have a significant impact on the damping time. Given the conditions in the solar atmosphere, resonantly damped axisymmetric modes are highly likely to be ubiquitous and play an important role in energy dissipation. We also suggest that, given the character of these waves, it is likely that they have already been observed in the guise of Alfvén waves.

  3. Neutron flux measurements in C-9 capsule pressure tube

    International Nuclear Information System (INIS)

    Barbos, D.; Roth, C. S.; Gugiu, D.; Preda, M.

    2001-01-01

    C-9 capsule is a fuel testing facility in which the testing consists of a daily cycle ranging between the limits 100% power to 50% power. C-9 in-pile section with sample holder an instrumentation are introduced in G-9 and G-10 experimental channels. The experimental fuel channel has a maximum value when the in-pile section (pressure tube) is in G-9 channel and minimum value in G-10 channel. In this paper the main goals are determination or measurements of: - axial thermal neutron flux distribution in C-9 pressure tube both in G-9 and G-10 channel; - ratio of maximum neutron flux value in G-9 and the same value in G-9 channel and the same value in G-10 channel; - neutron flux-spectrum. On the basis of axial neutron flux distribution measurements, the experimental fuel element in sample holder position in set. Both axial neutron flux distribution of thermal neutrons and neutron flux-spectrum were performed using multi- foil activation technique. Activation rates were obtained by absolute measurements of the induced activity using gamma spectroscopy methods. To determine the axial thermal neutron flux distribution in G-9 and G-10, Cu 100% wire was irradiated at the reactor power of 2 MW. Ratio between the two maximum values, in G-9 and G-10 channels, is 2.55. Multi-foil activation method was used for neutron flux spectrum measurements. The neutron spectra and flux were obtained from reaction rate measurements by means of SAND 2 code. To obtain gamma-ray spectra, a HPGe detector connected to a multichannel analyzer was used. The spectrometer is absolute efficiency calibrated. The foils were irradiated at 2 MW reactor power in previously determined maximum flux position resulted from wire measurements. This reaction rates were normalized for 10 MW reactor power. Neutron self shielding corrections for the activation foils were applied. The self-shielding corrections are computed using Monte Carlo simulation methods. The measured integral flux is 1.1·10 14 n/cm 2 s

  4. Dynamic and Stagnating Plasma Flow Leading to Magnetic-Flux-Tube Collimation

    International Nuclear Information System (INIS)

    You, S.; Yun, G.S.; Bellan, P.M.

    2005-01-01

    Highly collimated, plasma-filled magnetic-flux tubes are frequently observed on galactic, stellar, and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic-flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic-flux tube and the stagnation of the resulting flow causes this flux tube to become collimated

  5. Inlet effect induced ''upstream'' critical heat flux in smooth tubes

    International Nuclear Information System (INIS)

    Kitto, J.B. Jr.

    1986-01-01

    An unusual form of ''upstream'' critical heat flux (CHF) has been observed and directly linked to the inlet flow pattern during an experimental study of high pressure (17 - 20 MPa) water flowing through a vertical 38.1 mm ID smooth bore tube with uniform axial and nonuniform circumferential heating. These upstream CHF data were characterized by temperature excursions which initially occurred at a relatively fixed axial location in the middle of the test section while the outlet and inlet heated lengths experienced no change. A rifled tube inlet flow conditioner could be substituted for a smooth tube section to generate the desired swirling inlet flow pattern. The upstream CHF data were found to match data from a uniformly heated smooth bore tube when the comparison was made using the peak local heat flux. The mechanism proposed to account for the upstream CHF observations involves the destructive interference between the decaying swirl flow and the secondary circumferential liquid flow field resulting from the one-sided heating

  6. Application of the Critical Heat Flux Look-Up Table to Large Diameter Tubes

    Directory of Open Access Journals (Sweden)

    M. El Nakla

    2013-01-01

    Full Text Available The critical heat flux look-up table was applied to a large diameter tube, namely 67 mm inside diameter tube, to predict the occurrence of the phenomenon for both vertical and horizontal uniformly heated tubes. Water was considered as coolant. For the vertical tube, a diameter correction factor was directly applied to the 1995 critical heat flux look-up table. To predict the occurrence of critical heat flux in horizontal tube, an extra correction factor to account for flow stratification was applied. Both derived tables were used to predict the effect of high heat flux and tube blockage on critical heat flux occurrence in boiler tubes. Moreover, the horizontal tube look-up table was used to predict the safety limits of the operation of boiler for 50% allowable heat flux.

  7. Vertical motions in an intense magnetic flux tube

    International Nuclear Information System (INIS)

    Roberts, B.; Webb, A.R.

    1978-01-01

    The recent discovery of localised intense magnetic fields in the solar photosphere is one of the major surprises of the past few years. Here the theoretical nature of small amplitude motions in such an intense magnetic flux tube, within which the field strength may reach 2 kG is considered. A systematic derivation of the governing 'expansion' equations is given for a vertical slender tube, taking into account the dependence upon height of the buoyancy, compressibility and magnetic forces. Several special cases (e.g. the isothermal atmosphere) are considered as well as a more realistic, non-isothermal, solar atmosphere. The expansion procedure is shown to give good results in the special case of a uniform basic-state (in which gravity is negligible) and for which a more exact treatment is possible. (Auth.)

  8. Further comparisons of critical heat flux correlations for vertical tubes

    International Nuclear Information System (INIS)

    Govan, A.H.

    1986-11-01

    An earlier report by Govan (1984, AERE-R11298), described a data-bank of critical heat flux measurements in vertical upflow in tubes, and compared the predictions of the Harwell Annular Flow Model with two previously reported correlations. In this report two further correlations, those of Biasi [1967, Studies on burnout, Part 3] and Zuber [1961, Int. Devel. Heat Transfer, Part 2, PB230-236]/ Griffith,[1977, Nucl. Safety vol 18, no3] have been tested. These two correlations are used extensively in reactor design. Overall comparisons are given between all the correlations tested so far. (author)

  9. Vertical motions in an intense magnetic flux tube. Pt. 4

    International Nuclear Information System (INIS)

    Webb, A.R.; Roberts, B.

    1980-01-01

    Radiative damping of waves is important in the upper photosphere. It is thus of interest to examine the effect of radiative relaxation on the propagation of waves in an intense magnetic flux tube embedded in a uniform atmosphere. Assuming Newton's law of cooling, it is shown that the radiative energy loss leads to wave damping. Both the damping per wavelength and the damping per period reach maximum value when the sound and radiative timescales are comparable. The stronger the magnetic field, the greater is the damping. (orig.)

  10. Pair production at the edge of the QED flux tube

    Energy Technology Data Exchange (ETDEWEB)

    Berényi, Dániel, E-mail: berenyi.daniel@wigner.mta.hu [Loránd Eötvös University, H-1117, Budapest (Hungary); Wigner RCP, Institute for Particle and Nuclear Physics, P.O. Box 49, Budapest 1525 (Hungary); Varró, Sándor [Wigner RCP, Institute for Solid State Physics and Optics, P.O. Box 49, Budapest 1525 (Hungary); Skokov, Vladimir V. [Department of Physics, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI 49008, United Sates (United States); Lévai, Péter [Wigner RCP, Institute for Particle and Nuclear Physics, P.O. Box 49, Budapest 1525 (Hungary)

    2015-10-07

    We investigate the process of Abelian pair production in the presence of strong inhomogeneous and time-dependent external electric fields. The spatial dependence of the external field is motivated by a non-Abelian color flux tube in heavy-ion collisions. We show that the inhomogeneity significantly increases the particle yield compared to that in the commonly used models with a constant and homogeneous field. Moreover our results indicate that in contrast to the latter, most of the particles are produced at the interface of the field profile in accordance with Heisenberg's prediction.

  11. Maximum allowable heat flux for a submerged horizontal tube bundle

    International Nuclear Information System (INIS)

    McEligot, D.M.

    1995-01-01

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or open-quotes criticalclose quotes) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. In general, we are considering boiling after the pool reaches its saturation temperature rather than sub-cooled pool boiling which should occur during early stages of transient operation. A combination of literature review and simple approximate analysis has been used. To date our main conclusion is that estimates of q inch chf are highly uncertain for this configuration

  12. Preliminary Study of Magnetic Flux Leakage on Tube Inspection

    International Nuclear Information System (INIS)

    Noorhazleena Azaman; Ilham Mukriz Zainal Abidin; Nurul Ain Ahmad Latif

    2015-01-01

    Magnetic Flux Leakage (MFL) is an advanced NDT technique which has the inspection capability in wall loss detection and measurement of sharp defects such as pitting, grooving and circumferential cracks in ferromagnetic samples. The working principle of MFL involves the induction of magnetic field in the part to be tested and the response or signal produced is analysed to determine the presence and characteristics of defects. In this paper, simulation and experimental work on wall loss detection in steel tube using MFL were carried out. The simulation was performed using Comsol software and followed by experimental work using MFL system for validation. The results from the simulation and experiment indicates that variation of the groove defect affect the magnetisation and the output of the MFL signal is related to change of flux caused by the detection of wall loss. (author)

  13. Influence of test tube material on subcooled flow boiling critical heat flux in short vertical tube

    International Nuclear Information System (INIS)

    Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki

    2007-01-01

    The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3 m/s), the inlet subcoolings (ΔT sub,in =48.6 to 154.7 K), the inlet pressure (P in =735.2 to 969.0 kPa) and the increasing heat input (Q 0 exp(t/τ), τ=10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tube of inner diameter (d=6 mm), heated length (L=66 mm) and L/d=11 with the inner surface of rough finished (Surface roughness, Ra=3.18 μm), the Cupro Nickel (Cu-Ni 30%) test tube of d=6 mm, L=60 mm and L/d=10 with Ra=0.18 μm and the Platinum (Pt) test tubes of d=3 and 6 mm, L=66.5 and 69.6 mm, and L/d=22.2 and 11.6 respectively with Ra=0.45 μm are used in this work. The CHF data for the SUS304, Cu-Ni 30% and Pt test tubes were compared with SUS304 ones for the wide ranges of d and L/d previously obtained and the values calculated by the authors' published steady state CHF correlations against outlet and inlet subcoolings. The influence of the test tube material on CHF is investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux is discussed. (author)

  14. Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube

    International Nuclear Information System (INIS)

    Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

    2006-01-01

    The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u = 4.0 to 13.3 m/s), the inlet subcooling (ΔT sub,in = 48.6 to 154.7 K), the inlet pressure (P in = 735.2 to 969.0 kPa) and the increasing heat input (Q 0 exp(t/t), t = 10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tubes of inner diameters (d = 6 mm), heated lengths (L = 66 mm) and L/d = 11 with the inner surface of rough finished (Surface roughness, R a = 3.18 μm), the Cupro Nickel (Cu-Ni 30%) test tubes of d = 6 mm, L = 60 mm and L/d = 10 with R a = 0.18 μm and the Platinum (Pt) test tubes of d = 3 and 6 mm, L = 66.5 and 69.6 mm, and L/d 22.2 and 11.6 respectively with R a = 0.45 μm are used in this work. The CHF data for the SUS304, Cu-Ni 30% and Pt test tubes were compared with SUS304 ones for the wide ranges of d and L/d previously obtained and the values calculated by the authors' published steady state CHF correlations against outlet and inlet subcooling. The influence of the test tube material on CHF is investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux is discussed. (authors)

  15. Hexagonal tube behaviour in fuel assemblies under neutron flux in a French fast neutron reactor core

    International Nuclear Information System (INIS)

    Bernard, A.; Ammann, P.

    This paper presents what is obtained in the field of the interpretation by calculation of the post irradiation examination of hexagonal tubes, and in the field of prevision by calculation of the behaviour of hexagonal tubes under fast flux [fr

  16. Flux tubes in U(1) - Do they attract or repel each other?

    International Nuclear Information System (INIS)

    Zach, M.; Faber, M.; Skala, P.

    1998-01-01

    The dually transformed path integral of four-dimensional U(1) lattice gauge theory is used for a numerical investigation of multiply charged systems and the interaction between flux tubes. For this aim, it is convenient to implement periodically closed flux tubes (torelons) in the dual formulation. We calculate the free energy as well as the total electro-magnetic energy of doubly charged flux tubes as a function of the coupling β. The main results are that the string tension scales proportionally to the charge (contrary to the Coulomb potential) and in the range 0.9<β<1.0 we find a clear signal for attraction between flux tubes. (orig.)

  17. Magnetic flux tubes and transport of heat in the convection zone of the sun

    International Nuclear Information System (INIS)

    Spruit, H.C.

    1977-01-01

    This thesis consists of five papers dealing with transport of heat in the solar convection zone on the one hand, and with the structure of magnetic flux tubes in the top of the convection zone on the other hand. These subjects are interrelated. For example, the heat flow in the convection zone is disturbed by the presence of magnetic flux tubes, while exchange of heat between a flux tube and the convection zone is important for the energy balance of such a tube. A major part of this thesis deals with the structure of small magnetic flux tubes. Such small tubes (diameters less than about 2'') carry most of the flux appearing at the solar surface. An attempt is made to construct models of the surface layers of such small tubes in sufficient detail to make a comparison with observations possible. Underlying these model calculations is the assumption that the magnetic elements at the solar surface are flux tubes in a roughly static equilibrium. The structure of such tubes is governed by their pressure equilibrium, exchange of heat with the surroundings, and transport of heat by some modified form of convection along the tube. The tube models calculated are compared with observations

  18. Flux tube gyrokinetic simulations of the edge pedestal

    Science.gov (United States)

    Parker, Scott; Wan, Weigang; Chen, Yang

    2011-10-01

    The linear instabilities of DIII-D H-mode pedestal are studied with gyrokinetic micro-turbulence simulations. The simulation code GEM is an electromagnetic δf code with global tokamak geometry in the form of Miller equilibrium. Local flux tube simulations are carried out for multiple positions of two DIII-D profiles: shot #98889 and shot #131997. Near the top of the pedestal, the instability is clearly ITG. The dominant instability of the pedestal appears at the steep gradient region, and it is identified as a low frequency mode mostly driven by electron temperature gradient. The mode propagates along the electron diamagnetic direction for low n and may propagate along the ion direction for high n. At some positions near the steep gradient region, an ion instability is found which shows some characteristics of kinetic ballooning mode (KBM). These results will be compared to the results of E. Wang et al. and D. Fulton et al. in the same session. We thank R. Groebner and P. Snyder for providing experimental profiles and helpful discussions.

  19. Sunspots and the physics of magnetic flux tubes. II. Aerodynamic drag

    International Nuclear Information System (INIS)

    Parker, E.N.

    1979-01-01

    The aerodynamic drag on a slender flux tube stretched vertically across a convective cell may push the flux tube into the updrafts or into the downdrafts, depending on the density stratification of the convecting fluid and the asymmetry of the fluid motions. The drag is approximately proportional to the local kinetic energy density, so the density stratification weights the drag in favor of the upper layers where the density is low, tending to push the vertical tube into the downdrafts. If, however, the horizontal motions in the convective cell are concentrated toward the bottom of the cell, they may dominate over the upper layers, pushing the tube into the updrafts. In the simple, idealized circumstance of a vertical tube extending across a fluid of uniform density in a convective cell that is symmetric about its midplane, the net aerodynamic drag vanishes in lowest order. The higher order contributions, including the deflection of the tube, then provide a nonvanishing force pushing the tube into a stable equilibrium midway between the updraft and the downdraft.It is pointed out that in the strongly stratified convective zone of the Sun, a downdraft herds flux tubes together into a cluster, while an updraft disperses them. To account for the observed strong cohesion of the cluster of flux tubes that make up a sunspot, we propose a downdraft of the order 2 km s - 1 through the cluster of seprate tubes beneath the sunspot

  20. Intermittent energy bursts and recurrent topological change of a twisting magnetic flux tube

    International Nuclear Information System (INIS)

    Amo, Hiroyoshi; Sato, Tetsuya; Kageyama, Akira.

    1994-09-01

    When continuously twisted, a magnetic flux tube suffers a large kink distortion in the middle part of the tube, like a knot-of-tension instability of a bundle of twisted rubber strings, and reconnection is triggered starting with the twisted field lines and quickly proceeding to the untwisted field lines at the twist-untwist boundary, whereby a giant burst-like energy release takes place. Subsequently, bursts occur intermittently and reconnection advances deeper into the untwisted region. Then, a companion pair of the linked twist-untwist flux tubes reconnect with each other to return to the original axisymmetric tube. The process is thus repeatable. (author)

  1. Effects of MHD slow shocks propagating along magnetic flux tubes in a dipole magnetic field

    Directory of Open Access Journals (Sweden)

    N. V. Erkaev

    2002-01-01

    Full Text Available Variations of the plasma pressure in a magnetic flux tube can produce MHD waves evolving into shocks. In the case of a low plasma beta, plasma pressure pulses in the magnetic flux tube generate MHD slow shocks propagating along the tube. For converging magnetic field lines, such as in a dipole magnetic field, the cross section of the magnetic flux tube decreases enormously with increasing magnetic field strength. In such a case, the propagation of MHD waves along magnetic flux tubes is rather different from that in the case of uniform magnetic fields. In this paper, the propagation of MHD slow shocks is studied numerically using the ideal MHD equations in an approximation suitable for a thin magnetic flux tube with a low plasma beta. The results obtained in the numerical study show that the jumps in the plasma parameters at the MHD slow shock increase greatly while the shock is propagating in the narrowing magnetic flux tube. The results are applied to the case of the interaction between Jupiter and its satellite Io, the latter being considered as a source of plasma pressure pulses.

  2. Sunspots and the physics of magnetic flux tubes in the sun

    International Nuclear Information System (INIS)

    Ballegooijen, A.A. van.

    1982-01-01

    This thesis refers to the sub-surface structure of the solar magnetic field. Following an introductory chapter, chapter II presents an analysis of spectroscopic observations of a sunspot at infrared wavelengths and models of the temperature stratification in the sunspot atmosphere are derived. The main subject of this thesis concerns the structure of the magnetic field deep down below the stellar surface, near the base of the convective envelope. In Chapter III the stability of toroidal flux tubes to wave-like perturbations is discussed, assuming that the tubes are neutrally buoyant. A model is proposed in which the toroidal flux tubes are neutrally buoyant and located in a stably stratified layer just below the base of the convective zone. On the basis of some simple assumptions for the temperature stratification in this storage layer the author considers in Chapter IV the properties of the vertical flux tubes in the convective zone. The adiabatic flux model cannot satisfactorily be applied to the simplified model of the storage layer, so that the problem of magnetic flux storage is reconsidered in Chapter V. A new model of the temperature stratification at the interface of convective zone and radiative interior of the sun is described. Finally, in Chapter VI, the stability of toroidal flux tubes in a differentially rotating star are discussed. It is demonstrated that for realistic values of the magnetic field strength, rotation has a strong effect on the stability of the toroidal flux tubes. (C.F.)

  3. Exploring the Flux Tube Paradigm in Solar-like Convection Zones

    Science.gov (United States)

    Weber, Maria A.; Nelson, Nicholas; Browning, Matthew

    2017-08-01

    In the solar context, important insight into the flux emergence process has been obtained by assuming the magnetism giving rise to sunspots consists partly of idealized flux tubes. Global-scale dynamo models are only now beginning to capture some aspects of flux emergence. In certain regimes, these simulations self-consistently generate magnetic flux structures that rise buoyantly through the computational domain. How similar are these dynamo-generated, rising flux structures to traditional flux tube models? The work we present here is a step toward addressing this question. We utilize the thin flux tube (TFT) approximation to simply model the evolution of flux tubes in a global, three-dimensional geometry. The TFTs are embedded in convective flows taken from a global dynamo simulation of a rapidly rotating Sun within which buoyant flux structures arise naturally from wreaths of magnetism. The initial conditions of the TFTs are informed by rising flux structures identified in the dynamo simulation. We compare the trajectories of the dynamo-generated flux loops with those computed through the TFT approach. We also assess the nature of the relevant forces acting on both sets of flux structures, such as buoyancy, the Coriolis force, and external forces imparted by the surrounding convection. To achieve the fast <15 day rise of the buoyant flux structures, we must suppress the large retrograde flow established inside the TFTs which occurs due to a strong conservation of angular momentum as they move outward. This tendency is common in flux tube models in solar-like convection zones, but is not present to the same degree in the dynamo-generated flux loops. We discuss the mechanisms that may be responsible for suppressing the axial flow inside the flux tube, and consider the implications this has regarding the role of the Coriolis force in explaining sunspot latitudes and the observed Joy’s Law trend of active regions. Our work aims to provide constraints, and possible

  4. Heat tranfer decrease during water boiling in a tube for the heat flux step distribution by the tube length

    International Nuclear Information System (INIS)

    Remizov, O.V.; Sergeev, V.V.; Yurkov, Yu.I.

    1983-01-01

    The effect of the heat flux distribution along the circular tube length on supercritical convective heat transfer at parameters typical for steam generators heated by liquid metal is studied. The effect of conditions in a under- and a supercritical zones of a vertical tube with independently heated lower and upper sections on supercritical convective heat transfer is studied on a water circulation loop at 9.8-17.7 MPa pressure and 330-1000 kg/m 2 s mass velocities. The experimental heat fluxes varied within the following limits: at the upper section from 0 to 474 kW/m 2 , at the lower section from 190 to 590 kW/m 2 . Analysis of the obtained data shows that when heat flux changes in the supercritical zone rewetting of the heated surface and simultaneous existence of two critical zones are observed. The effect of heat flux in the supercritical zone on convective heat transfer is ambiguous: the heat flux growth up to 60-100 kW/m 2 leads to increasing minimum values of the heat transfer factor in the supercritical zone, and a further heat flux growth - to their reduction. The conclusion is made that the value of heat flux in the undercritical zone affects convective heat transfer in the supercritical zone mainly through changing the value of critical vapour content

  5. A twisted flux-tube model for solar prominences. I. General properties

    International Nuclear Information System (INIS)

    Priest, E.R.; Hood, A.W.; Anzer, U.

    1989-01-01

    It is proposed that a solar prominence consists of cool plasma supported in a large-scale curved and twisted magnetic flux tube. As long as the flux tube is untwisted, its curvature is concave toward the solar surface, and so it cannot support dense plasma against gravity. However, when it is twisted sufficiently, individual field lines may acquire a convex curvature near their summits and so provide support. Cool plasma then naturally tends to accumulate in such field line dips either by injection from below or by thermal condensation. As the tube is twisted up further or reconnection takes place below the prominence, one finds a transition from normal to inverse polarity. When the flux tube becomes too long or is twisted too much, it loses stability and its true magnetic geometry as an erupting prominence is revealed more clearly. 56 refs

  6. Numerical simulation of heat fluxes in a two-temperature plasma at shock tube walls

    International Nuclear Information System (INIS)

    Kuznetsov, E A; Poniaev, S A

    2015-01-01

    Numerical simulation of a two-temperature three-component Xenon plasma flow is presented. A solver based on the OpenFOAM CFD software package is developed. The heat flux at the shock tube end wall is calculated and compared with experimental data. It is shown that the heat flux due to electrons can be as high as 14% of the total heat flux. (paper)

  7. Numerical simulation of heat fluxes in a two-temperature plasma at shock tube walls

    Science.gov (United States)

    Kuznetsov, E. A.; Poniaev, S. A.

    2015-12-01

    Numerical simulation of a two-temperature three-component Xenon plasma flow is presented. A solver based on the OpenFOAM CFD software package is developed. The heat flux at the shock tube end wall is calculated and compared with experimental data. It is shown that the heat flux due to electrons can be as high as 14% of the total heat flux.

  8. Dry-out heat fluxes of falling film and low-mass flux upward-flow in heated tubes

    International Nuclear Information System (INIS)

    Koizumi, Yasuo; Ueda, Tatsuhiro; Matsuo, Teruyuki; Miyota, Yukio

    1998-01-01

    Dry-out heat fluxes were investigated experimentally for a film flow falling down on the inner surface of vertical heated-tubes and for a low mass flux forced-upward flow in the tubes using R 113. This work followed the study on those for a two-phase natural circulation system. For the falling film boiling, flow state observation tests were also performed, where dry-patches appearing and disappearing repeatedly were observed near the exit end of the heated section at the dry-out heat flux conditions. Relation between the dry-out heat flux and the liquid film flow rate is analyzed. The dry-out heat fluxes of the low mass flux upflow are expressed well by the correlation proposed in the previous work. The relation for the falling film boiling shows a similar trend to that for the upflow boiling, however, the dry-out heat fluxes of the falling film are much lower, approximately one third, than those of the upward flow. (author)

  9. Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube; Transfert thermique et flux critique dans un ecoulement helicoidal en tube chauffe asymetriquement

    Energy Technology Data Exchange (ETDEWEB)

    Boscary, J [CEA Centre d` Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Direction des Sciences de la Matiere; [Association Euratom-CEA, Centre d` Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    1997-03-01

    The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author) 197 refs.

  10. Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow; Transfert thermique et flux critique dans un ecoulement helicoidal en tube chauffe asymetriquement

    Energy Technology Data Exchange (ETDEWEB)

    Boscary, J

    1995-10-01

    The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs.

  11. Dynamos driven by poloidal flows in untwisted, curved and flat Riemannian diffusive flux tubes

    International Nuclear Information System (INIS)

    De Andrade, L.C.G.

    2010-01-01

    Recently Vishik anti-fast dynamo theorem has been tested against non-stretching flux tubes (Phys. Plasmas, 15 (2008)). In this paper, another anti dynamo theorem, called Cowling's theorem, which states that axisymmetric magnetic fields cannot support dynamo action, is carefully tested against thick tubular and curved Riemannian untwisted flows, as well as thin flux tubes in diffusive and diffusion less media. In the non-diffusive media Cowling's theorem is not violated in thin Riemann-flat untwisted flux tubes, where the Frenet curvature is negative. Nevertheless the diffusion action in the thin flux tube leads to a dynamo action driven by poloidal flows as shown by Love and Gubbins (Geophysical Res., 23 (1996) 857) in the context of geo dynamos. Actually it is shown that a slow dynamo action is obtained. In this case the Frenet and Riemann curvature still vanishes. In the case of magnetic filaments in diffusive media dynamo action is obtained when the Frenet scalar curvature is negative. Since the Riemann curvature tensor can be expressed in terms of the Frenet curvature of the magnetic flux tube axis, this result can be analogous to a recent result obtained by Chicone, Latushkin and Smith, which states that geodesic curvature in compact Riemannian manifolds can drive dynamo action in the manifold. It is also shown that in the absence of diffusion, magnetic energy does not grow but magnetic toroidal magnetic field can be generated by the poloidal field, what is called a plasma dynamo.

  12. Dynamics of local isolated magnetic flux tubes in a fast-rotating stellar atmosphere

    International Nuclear Information System (INIS)

    Chou, W.; Tajima, C.T.; Shibata, K.

    1998-01-01

    Dynamics of magnetic flux tubes in the fast rotating stellar atmosphere is studied. We focus on the effects and signatures of the instability of the flux tube emergence influenced by the Coriolis force. We present the result from a linear stability analysis and discuss its possible signatures in the course of the evolution of G-type and M-type stars. We present a three dimensional magnetohydrodynamical simulation of local isolated magnetic flux tubes under a magnetic buoyancy instability in co-rotating Cartesian coordinates. We find that the combination of the buoyancy instability and the Coriolis effect gives rise to a mechanism, to twist the emerging magnetic flux tube into a helical structure. The tilt angle, east-west asymmetry and magnetic helicity of the Twisted flux tubes in the simulations are studied in detail. The linear and nonlinear analyses provide hints as to what kind of pattern of large spots in young M-type main-sequence stars might be observed. We find that young and old G-type stars may have different distributions of spots while M-type stars may always have low latitudes spots. The size of stellar spots may decrease when a star becomes older, due to the decreasing of magnetic field. A qualitative comparison with solar observations is also presented

  13. Benchmark of WIMS-IST against MCNP for CANDU pressure tube fast fluxes

    International Nuclear Information System (INIS)

    Donders, R.E.; Douglas, S.R.

    2002-01-01

    Pressure tube fast-flux data in CANDU are currently calculated using the multi-group neutron transport code WIMS-IST. In this study, the WIMS-IST fast flux calculations are benchmarked against MCNP calculations (a Monte Carlo particle transport code), over the range of fuel burnup and coolant density in CANDU. The comparison shows good agreement between WIMS and MCNP, with WIMS fast fluxes being 1.5% to 4% lower than the MCNP values. The difference is smallest for fresh fuel, and increases with burnup. The fast flux gradient across the pressure tube (factor of 1.23 from inner edge to outer edge) is accurately calculated by WIMS. When reporting fast fluxes in pressure tubes, these are generally given as >1.000 MeV fluxes. For WIMS, this requires an extra conversion step, since the WIMS ENDF/B libraries do not have a group boundary at 1 MeV. The conversion step is based on a fictitious isotope ONEMEV in the WIMS nuclear data library. The conversion factor in WIMS was found to be about one percent too high. When providing >1 MeV fluxes from WIMS, this partially compensates for the slight under prediction of the fast flux. Pressure tube >1 MeV fluxes from WIMS are therefore 0.5% to 3% lower than MCNP values. To obtain accurate fast flux data, neutron transport calculations must be performed on a critical cell. For this study, all calculations were performed with radial albedo boundary conditions giving a critical cell. This required the use of an albedo version of MCNP, developed at AECL. (author)

  14. Calculation of fast neutron flux in reactor pressure tubes and experimental facilities

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, P. C. [Canadian General Electric (Canada)

    1968-07-15

    The computer program EPITHET was used to calculate the fast neutron flux (>1 MeV) in several reactor pressure tubes and experimental facilities in order to compare the fast neutron flux in the different cases and to provide a self-consistent set of flux values which may be used to relate creep strain to fast neutron flux . The facilities considered are shown below together with the calculated fast neutron flux (>1 MeV). Fast flux 10{sup 13} n/cm{sup 2}s: NPD 1.14, Douglas Point 2.66, Pickering 2.89, Gentilly 2.35, SGHWR 3.65, NRU U-1 and U-2 3.25'' pressure tube - 19 element fuel 3.05, NRU U-1 and U-2 4.07'' pressure tube - 28 element fuel 3.18, NRU U-1 and U-2 4.07'' pressure tube - 18 element fuel 2.90, NRX X-5 0.88, PRTR Mk I fuel 2.81, PRTR HPD fuel 3.52, WR-1 2.73, Mk IV creep machine (NRX) 0.85, Mk VI creep machine (NRU) 2.04, Biaxial creep insert (NRU U-49) 2.61.

  15. High heat flux tests at divertor relevant conditions on water-cooled swirl tube targets

    International Nuclear Information System (INIS)

    Schlosser, J.; Boscary, J.

    1994-01-01

    High heat flux experiments were performed to provide a technology for heat flux removal under NET/ITER relevant conditions. The water-cooled rectangular test sections were made of hardened copper with a stainless steel twisted tape installed inside a circular channel and one-side heated. The tests aimed to investigate the heat transfer and the critical heat flux in the subcooled boiling regime. A CHF data base of 63 values was established. Test results have shown the thermalhydraulic ability of swirl tubes to sustain an incident heat flux up to a 30 MW.m -2 range. (author) 10 refs.; 7 figs

  16. Dynamical fragmentation of flux tubes in the Friedberg-Lee model

    International Nuclear Information System (INIS)

    Loh, S.; Greiner, C.; Mosel, U.; Thoma, M.H.

    1997-01-01

    We present two novel dynamical features of flux tubes in the Friedberg-Lee model. First the fusion of two (anti-)parallel flux tubes, where we extract a string-string interaction potential which has a qualitative similarity to the nucleon-nucleon potential in the Friedberg-Lee model obtained by Koepf et al. Furthermore we show the dynamical breakup of flux tubes via qq-particle production and the disintegration into mesons. We find, as a shortcoming of the present realization of the model, that the full dynamical transport approach presented in a previous publication fails to provide the disintegration mechanism in the semiclassical limit. Therefore, in addition, we present here a molecular dynamical approach for the motion of the quarks and show, as a first application, the space-time development of the quarks and their mean-fields for Lund-type string fragmentation processes. (orig.)

  17. Critical heat flux measurements in small-diameter tubes using R12 as model fluid

    International Nuclear Information System (INIS)

    Mueller-Menzel, T.

    1987-01-01

    Results of critical heat flux measurements are reported for vertical upflow of Refrigerant 12 at high mass fluxes and high pressures in small diameter tubes. The data are transformed into water data using a scaling law, which is verified by means of a new analysis. An error estimation includes the error of the scaling law. Special phenomena ('limiting quality', 'upstream boiling crisis') are explained by theoretical models. The applicability of existing correlations is checked and a new CHF-table for small diameter tubes is presented. With 41 figs., 12 tabs [de

  18. Studies on the instrumentation of a beam-tube medium flux reactor

    International Nuclear Information System (INIS)

    Axmann, A.; Pollet, J.L.; Queudot, J.

    1979-01-01

    In the years 1977/78, the ad hoc commitee for medium-flux reactor development of the Federal Ministry for Research and Technology developed constructional concepts for a medium-flux reactor to be utilized by beam tube experiments. The HMI has elaborated contributions for discussions of the subject of instrumentation, in particular for experiments in solid state physics. These contributions are contained in the report. (orig./RW) [de

  19. The flow distribution in the parallel tubes of the cavity receiver under variable heat flux

    International Nuclear Information System (INIS)

    Hao, Yun; Wang, Yueshe; Hu, Tian

    2016-01-01

    Highlights: • An experimental loop is built to find the flow distribution in the parallel tubes. • With the concentration of heat flux, two-phase flow makes distribution more uneven. • The total flow rate is chosen appropriately for a wider heat flux distribution. • A suitable system pressure is essential for the optimization of flow distribution. - Abstract: As an optical component of tower solar thermal power station, the heliostat mirror reflects sunlight to one point of the heated surface in the solar cavity receiver, called as one-point focusing system. The radiation heat flux concentrated in the cavity receiver is always non-uniform temporally and spatially, which may lead to extremely local over-heat on the receiver evaporation panels. In this paper, an electrical heated evaporating experimental loop, including five parallel vertical tubes, is set up to evaluate the hydrodynamic characteristics of evaporation panels in a solar cavity receiver under various non-uniform heat flux. The influence of the heat flux concentration ratio, total flow rate, and system pressure on the flow distribution of parallel tubes is discussed. It is found that the flow distribution becomes significantly worse with the increase of heat flux and concentration ratio; and as the system pressure decreased, the flow distribution is improved. It is extremely important to obtain these interesting findings for the safe and stable operation of solar cavity receiver, and can also provide valuable references for the design and optimization of operating parameters solar tower power station system.

  20. A review on critical heat flux in horizontal tubes

    International Nuclear Information System (INIS)

    Baburajan, P.K.; Gaikwad, Avinash; Prabhu, S.V.

    2015-01-01

    Coolant channels of PHWR during accident similar to loss of coolant accident (LOCA) may experience different flow transients with low pressure and low flow conditions. In the advanced PHWRs it is desired to have small amount of positive quality at the exit of the coolant channel to increase the thermal efficiency. Investigation on pressure drop and heat transfer coefficient under subcooled boiling condition is important in the design and operation of the PHWRs. Understanding of thermal hydraulic phenomena associated with horizontal flow is also important in the safety and accident management in these reactors. A detailed experimental investigation on the important thermal hydraulic phenomena of horizontal tubes under low pressure and low flow conditions is carried out. The phenomena covered in this work are measurement of diabatic single phase and subcooled boiling pressure drop and local heat transfer coefficients, steady state CHF, effect of upstream flow restrictions on flow transients and CHF, CHF under oscillatory flow and flow decreasing transients. A detailed literature review is carried out on CHF in horizontal channels to take stock of the works being carried out along with current state of the art and to justify the motivation for the experimental study. This paper presents the review of available literature on horizontal CHF with the results of the experimental work. (author)

  1. Design and use of the ORNL HFIR [High Flux Isotope Reactor] pneumatic tube irradiation systems

    International Nuclear Information System (INIS)

    Dyer, F.F.; Emery, J.F.; Robinson, L.; Teasley, N.A.

    1987-01-01

    A second pneumatic tube that was recently installed in the High Flux Isotope Reactor for neutron activation analysis is described. Although not yet tested, the system is expected to have a thermal neutron flux of about 1.5 x 10 14 cm -2 s -1 . A delayed neutron counter is an integral part of the pneumatic tube, and all of the hardware is present to enable automated use of the counter. The system is operated with a Gould programmable controller that is programmed with an IBM personal computer. Automation of any mode of operation, including the delayed neutron counter, will only require a nominal amount of software development. Except for the lack of a hot cell, the irradiation facility has all of the advantageous features of an older pneumatic tube that has been in operation for 17 years. The design of the system and some applications and methods of operation are described

  2. Correlation of critical heat flux data for uniform tubes

    Energy Technology Data Exchange (ETDEWEB)

    Jafri, T.; Dougherty, T.J.; Yang, B.W. [Columbia Univ., New York, NY (United States)

    1995-09-01

    A data base of more than 10,000 critical heat flux (CHF) data points has been compiled and analyzed. Two regimes of CHF are observed which will be referred to as the high CHF regime and the low CHF regime. In the high CHF regime, for pressures less than 110 bar, CHF (q{sub c}) is a determined by local conditions and is adequately represented by q{sub c} = (1.2/D{sup 1/2}) exp[-{gamma}(GX{sub t}){sup 1/2}] where the parameter {gamma} is an increasing function of pressure only, X{sub t} the true mass fraction of steam, and all units are metric but the heat flux is in MWm{sup -2}. A simple kinetic model has been developed to estimate X{sub t} as a function of G, X, X{sub i}, and X{sub O}, where X{sub i} is the inlet quality and X{sub O} represents the quality at the Onset of Significant Vaporization (OSV) which is estimated from the Saha-Zuber (S-Z) correlation. The model is based on a rate equation for vaporization suggested by, and consistent with, the S-Z correlation and contains no adjustable parameters. When X{sub i}X{sub O}, X{sub t} depends on X{sub i}, a nonlocal variable, and, in this case, CHF, although determined by local conditions, obeys a nonlocal correlation. This model appears to be satisfactory for pressures less than 110 bar, where the S-Z correlation is known to be reliable. Above 110 bar the method of calculating X{sub O}, and consequently X{sub t}, appears to fail, so this approach can not be applied to high pressure CHF data. Above 35 bar, the bulk of the available data lies in the high CHF regime while, at pressures less than 35 bar, almost all of the available data lie in the low CHF regime and appear to be nonlocal.

  3. Duality of the magnetic flux tube and electric current descriptions magnetospheric plasma and energy flow

    International Nuclear Information System (INIS)

    Atkinson, G.

    1981-01-01

    The duality between electric current and magnetic flux tubes is outlined for the magnetosphere. Magnetic flux tubes are regarded as fluid elements subjected to various stresses. Current closure then becomes the dual of stress balance, and Poynting vector energy flow a dual of J x E dissipation. The stresses acting on a flux tube are magnetic stresses, which correspond to currents at a distance, and plasma stresses, which correspond to local currents. The duality between current and stress is traced for ionospheric ion drag forces, solar wind stresses at the magnetopause, inertial effects, and the effects of energetic plasma on flux tubes. The stress balance and dual current systems are outlined for idealized magnetospheres of increasing complexity. For a simple magnetosphere with no convective flow, the balance stresses are solar wind pressure and neutral sheet plasma pressure. The corresponding current systems are the Chapman-Ferraro magnetopause currents and the magetotail current system. The introduction of convective flow introduces further stresses: ionospheric ion drag. Alfven layer shielding, and an imbalance in day-night magnetic stresses due to transport of flux tubes to the nightside by the solar wind. These stresses balance, and hence the corresponding additional currents (the ionospheric Pedersen current and the electrojets, the partial ring current, and two other current systems from the magnetopause and tail) must form a closed current system and do so by the region I and II field-aligned currents of Iijima and Potemra. The energy flow in the above models is described in terms of both Poynting vectors and the above current systems. Temporal variations examined are (1) an increase in dayside merging and/or nightside reconnection, (2) an increase in the energy density of plasma in the plasma sheet, (3) an increase in ionospheric conductivity, and (4) an increase in solar wind pressure

  4. Critical heat flux for downward-facing pool boiling on CANDU calandria tube surface

    Energy Technology Data Exchange (ETDEWEB)

    Behdadi, Azin, E-mail: behdada@mcmaster.ca; Talebi, Farshad; Luxat, John

    2017-04-15

    Highlights: • Pressure tube-calandria tube contact may challenge fuel channel integrity in CANDU. • Critical heat flux variation is predicted on the outer surface of CANDU calandria tube. • A two-phase boundary layer flow driven by buoyancy is modeled on the surface. • Different slip ratios and flow regimes are considered inside the boundary layer. • Subcooling effects are added to the model using wall heat flux partitioning. - Abstract: One accident scenario in CANDU reactors that can challenge the integrity of the primary pressure boundary is a loss of coolant accident, referred to as critical break LOCA, in which the pressure tube (PT) can undergo thermal creep strain deformation and contact its calandria tube (CT). In such case, rapid redistribution of stored heat from PT to CT, leads to a large spike in heat flux to the moderator which can cause bubble accumulation and dryout on the CT surface. A challenge to fuel channel integrity is posed if critical heat flux occurs on the surface of the CT and results in sustained film boiling. If the post-dryout temperature becomes sufficiently high then continued creep strain of the PT and CT may lead to fuel channel failure. In this study, a mechanistic model is developed to predict the critical heat flux variations along the downward facing outer surface of CT. The hydrodynamic model considers a liquid macrolayer beneath an elongated vapor slug on the surface. Local dryout is postulated to occur whenever the fresh liquid supply to the macrolayer is not sufficient to compensate for the liquid depletion. A boundary layer analysis is performed, treating the two phase motion as an external buoyancy driven flow. The model shows good agreement with the available experimental data and has been modified to take into account the effect of subcooling.

  5. Surprisingly low frequency attenuation effects in long tubes when measuring turbulent fluxes at tall towers

    DEFF Research Database (Denmark)

    Ibrom, Andreas; Brændholt, Andreas; Pilegaard, Kim

    2016-01-01

    The eddy covariance technique relies on the fast and accurate measurement of gas concentration fluctuations. While for some gasses robust and compact sensors are available, measurement of, e.g., non CO2 greenhouse gas fluxes is often performed with sensitive equipment that cannot be run on a tower...... without massively disturbing the wind field. To measure CO and N2O fluxes, we installed an eddy covariance system at a 125 m mast, where the gas analyser was kept in a laboratory close to the tower and the sampling was performed using a 150 m long tube with a gas intake at 96 m height. We investigated...... by reducing both the water vapour dilution correction and the cross sensitivity effects on the N2O and CO flux measurements. Here we present the set-up of the concentration step change experiment and its results and compare them with recently developed theories for the behaviour of gases in turbulent tube...

  6. Numerical prediction of dryout heat flux in vertical uniformly heated round tubes

    International Nuclear Information System (INIS)

    Okawa, Tomio; Kotani, Akio; Kataoka, Isao; Naito, Masanori

    2003-01-01

    Dryout heat fluxes in vertical uniformly heated round tubes were predicted using a film flow model. The correlations adopted in the present analysis were summarized as follows: (1) Entrainment rate and deposition rate were evaluated by the correlations whose validity was confirmed in wide range of thermal-hydraulic conditions. (2) In addition to the droplet entrainment due to interfacial shear force, the entrainment resulting from the boiling in liquid film was considered. (3) The vapor quality at the onset of annular flow was evaluated by the correlation based on the measurement of minimum droplet flowrate. (4) It was postulated that the droplet flowrate at the starting point of annular flow was to be approximated by that in equilibrium state. (5) The onset of critical heat flux condition was determined by the complete disappearance of liquid film. Though several assumptions were used in the present model, all the correlations adopted here were based on experimental data or considerations of the physical processes in annular flow. The resulting model required no parameters that should be adjusted from the measured data of critical heat flux. A number of experimental data of critical heat flux in forced flow of water in vertical uniformly heated round tubes were used to test the basic performance of the model. The comparisons between the calculated and measured critical heat fluxes showed that the predicted results by the present model agree with the experimental data fairly well if the flow pattern at burnout is considered annular flow. The predictive capability was not deteriorated even in the cases of small diameter tube, short length tube as well as low vapor quality at the onset of critical heat flux condition. (author)

  7. Correlation between the critical heat flux and the fractal surface roughness of zirconium alloy tubes

    International Nuclear Information System (INIS)

    Fong, R.W.L.; McRae, G.A.; Coleman, C.E.; Nitheanandan, T.; Sanderson, D.B.

    1999-10-01

    In CANDU fuel channels, Zircaloy calandria tubes isolate the hot pressure tubes from the cool heavy water moderator. The heavy-water moderator provides a backup heat sink during some postulated loss-of-coolant accidents. The decay heat from the fuel is transferred to the moderator to ensure fuel channel integrity during emergencies. Moderator temperature requirements are specified to ensure that the transfer of decay heat does not exceed the critical heat flux (CHF) on the outside surface of the calandria tube. An enhanced CHF provides increases in safety margin. Pool boiling experiments indicate the CHF is enhanced with glass-peening of the outside surface of the calandria tubes. The objective of this study was to evaluate the surface characteristics of glass-peened tubes and relate these characteristics to CHF. The micro-topologies of the tube surfaces were analysed using stereo-pair micrographs obtained from scanning electron microscopy (SEM) and photogrammetry techniques. A linear relationship correlated the CHF as a function of the 'fractal' surface roughness of the tubes. (author)

  8. ON THE ANISOTROPY IN EXPANSION OF MAGNETIC FLUX TUBES IN THE SOLAR CORONA

    Energy Technology Data Exchange (ETDEWEB)

    Malanushenko, A. [Department of Physics, Montana State University, Bozeman, MT (United States); Schrijver, C. J. [Lockheed Martin Advanced Technology Center, Palo Alto, CA (United States)

    2013-10-01

    Most one-dimensional hydrodynamic models of plasma confined to magnetic flux tubes assume circular tube cross sections. We use potential field models to show that flux tubes in circumstances relevant to the solar corona do not, in general, maintain the same cross-sectional shape through their length and therefore the assumption of a circular cross section is rarely true. We support our hypothesis with mathematical reasoning and numerical experiments. We demonstrate that lifting this assumption in favor of realistic, non-circular loops makes the apparent expansion of magnetic flux tubes consistent with that of observed coronal loops. We propose that in a bundle of ribbon-like loops, those that are viewed along the wide direction would stand out against those that are viewed across the wide direction due to the difference in their column depths. That result would impose a bias toward selecting loops that appear not to be expanding, seen projected in the plane of sky. An implication of this selection bias is that the preferentially selected non-circular loops would appear to have increased pressure scale heights even if they are resolved by current instruments.

  9. Critical heat flux of subcooled flow boiling in a narrow tube

    International Nuclear Information System (INIS)

    Inasaka, Fujio; Nariai, Hideki; Shimura, Toshiya.

    1986-01-01

    The critical heat flux (CHF) of subcooled flow boiling in a narrow tube was investigated experimentally using water as a coolant. Experiments were conducted at nearly ambient pressure under the following conditions: tube inside diameter: 1 ∼ 3 mm, tube length: 10 ∼ 100 mm, and water mass velocity: 7000 - 20000 kg/(m 2 · s). The critical heat flux increases the shorter the tube length and the smaller the tube inside diameter, at the same water mass velocity and exit quality. Experimental data were compared with empirical correlations, such as the Griffel and Knoebel correlations for subcooled boiling at low pressure, the Tong correlation for subcooled boiling at high pressure, and the Katto correlation. The existence of two parameter regions was confirmed. The first is the low CHF region in which experimental data can be predicted well by Griffel and Knoebel correlations, and the second is the high CHF region in which experimental data are higher than the predictions by the above two correlations. (author)

  10. Heat transfer and critical heat flux in a spiral flow in an asymmetrical heated tube

    International Nuclear Information System (INIS)

    Boscary, J.; Association Euratom-CEA, Centre d'Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance

    1997-03-01

    The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author)

  11. Heat transfer and critical heat flux in a asymmetrically heated tube helicoidal flow

    International Nuclear Information System (INIS)

    Boscary, J.

    1995-10-01

    The design of plasma facing components is crucial for plasma performance in next fusion reactors. These elements will be submitted to very high heat flux. They will be actively water-cooled by swirl tubes in the subcooled boiling regime. High heat flux experiments were conducted in order to analyse the heat transfer and to evaluate the critical heat flux. Water-cooled mock-ups were one-side heated by an electron beam gun for different thermal-hydraulic conditions. The critical heat flux was detected by an original method based on the isotherm modification on the heated surface. The wall heat transfer law including forced convection and subcooled boiling regimes was established. Numerical calculations of the material heat transfer conduction allowed the non-homogeneous distribution of the wall temperature and of the wall heat flux to be evaluated. The critical heat flux value was defined as the wall maximum heat flux. A critical heat flux model based on the liquid sublayer dryout under a vapor blanket was established. A good agreement with test results was found. (author). 198 refs., 126 figs., 21 tabs

  12. Field-aligned current density versus electric potential characteristics for magnetospheric flux tubes

    International Nuclear Information System (INIS)

    Lemaire, J.; Scherer, M.

    1983-01-01

    The field-aligned current density (Jsub(tot)) is a non-linear function of the applied potential difference (phi) between the ionosphere and the magnetosphere. This nonlinear function has been calculated for plasma boundary conditions typical in a dayside cusp magnetic flux tube. The J-characteristic of such a flux tube changes when the temperatures of the warm magnetospheric electrons and of the cold ionospheric electrons are modified; it changes also when the relative density of the warm plasma is modified; the presence of trapped secondary electrons changes also the J-characteristic. The partial currents contributed by the warm and cold electrons, and by warm and cold ions are illustrated. The dynamic characteristic of an electric circuit depends on the static characteristic of each component of the sytem: i.e. the resistive ionosphere, the return current region, and the region of particle precipitation whose field-aligned current/voltage characteristics have been studied in this article

  13. Fluctuations of the baryonic flux-tube junction from effective string theory

    International Nuclear Information System (INIS)

    Pfeuffer, Melanie; Bali, Gunnar S.; Panero, Marco

    2009-01-01

    In quenched QCD, where the dynamic creation of quark-antiquark pairs out of the vacuum is neglected, a confined baryonic system composed of three static quarks exhibits stringlike behavior at large interquark separation, with the formation of flux tubes characterized by the geometry of the so-called Y ansatz. We study the fluctuations of the junction of the three flux tubes, assuming the dynamics to be governed by an effective bosonic string model. We show that the asymptotic behavior of the effective width of the junction grows logarithmically with the distance between the sources, with the coefficient depending on the number of joining strings, on the dimension of spacetime and on the string tension.

  14. Experimental study and technique for calculation of critical heat fluxes in helium boiling in tubes

    International Nuclear Information System (INIS)

    Arkhipov, V.V.; Kvasnyuk, S.V.; Deev, V.I.; Andreev, V.K.

    1979-01-01

    Studied is the effect of regime parameters on critical heat loads in helium boiling in a vertical tube in the range of mass rates of 80 2 xc) and pressures of 100<=p<=200 kPa for the vapor content range corresponding to the heat exchange crisis of the first kind. The method for calculating critical heat fluxes describing experimental data with the error less than +-15% is proposed. The critical heat loads in helium boiling in tubes reduce with the growth of pressure and vapor content in the regime parameter ranges under investigation. Both positive and negative effects of the mass rate on the critical heat flux are observed. The calculation method proposed satisfactorily describes the experimental data

  15. N+ρ decay of baryons in a flux-tube-breaking mechanism

    International Nuclear Information System (INIS)

    Stassart, P.; Stancu, F.

    1990-01-01

    A flux-tube-breaking mechanism motivated by QCD is extended to the analysis of the decay of nonstrange resonances into N+ρ. A proper threshold behavior is obtained by taking into account the instability of the ρ meson. The only parameter of the model has previously been fixed to adjust the decay of Δ into N+π. We find a good agreement with the few available data and make predictions for many other resonances where data are needed

  16. Application of tube critical heat flux tables to annuli and rod bundles

    International Nuclear Information System (INIS)

    Ulrych, G.

    1985-01-01

    The purpose of this paper is to show that tables for the critical heat flux (CHF) in tubes have a much wider range of applicability than only to tubes. With the proper choice of a characteristic length replacing the tube diameter as a parameter the validity of the tables can be expanded to more complex geometries. The paper describes how the tables must be applied to annuli or rod bundles. The data base for comparisons is mainly taken from the open literature. For rod bundles the proposed methodology was checked for very different geometries including rod bundles from very tight hexagonal to extremely open square bundle arrays. It is concluded that the tables give reasonable results for a wide range of hydraulic diameters

  17. Magnetic swirls and associated fast magnetoacoustic kink waves in a solar chromospheric flux tube

    Science.gov (United States)

    Murawski, K.; Kayshap, P.; Srivastava, A. K.; Pascoe, D. J.; Jelínek, P.; Kuźma, B.; Fedun, V.

    2018-02-01

    We perform numerical simulations of impulsively generated magnetic swirls in an isolated flux tube that is rooted in the solar photosphere. These swirls are triggered by an initial pulse in a horizontal component of the velocity. The initial pulse is launched either (a) centrally, within the localized magnetic flux tube or (b) off-central, in the ambient medium. The evolution and dynamics of the flux tube are described by three-dimensional, ideal magnetohydrodynamic equations. These equations are numerically solved to reveal that in case (a) dipole-like swirls associated with the fast magnetoacoustic kink and m = 1 Alfvén waves are generated. In case (b), the fast magnetoacoustic kink and m = 0 Alfvén modes are excited. In both these cases, the excited fast magnetoacoustic kink and Alfvén waves consist of a similar flow pattern and magnetic shells are also generated with clockwise and counter-clockwise rotating plasma within them, which can be the proxy of dipole-shaped chromospheric swirls. The complex dynamics of vortices and wave perturbations reveals the channelling of sufficient amount of energy to fulfil energy losses in the chromosphere (˜104 W m-1) and in the corona (˜102 W m-1). Some of these numerical findings are reminiscent of signatures in recent observational data.

  18. A comparison of critical heat flux in tubes and bilaterally heated annuli

    Energy Technology Data Exchange (ETDEWEB)

    Doerffer, S.; Groeneveld, D.C.; Cheng, S.C. [Univ. of Ottawa (Canada)

    1995-09-01

    This paper examines the critical heat flux (CHF) behaviour for annular flow in bilaterally heated annuli and compares it to that in tubes and unilaterally heated annuli. It was found that the differences in CHF between bilaterally and unilaterally heated annuli or tubes strongly depend on pressure and quality. the CHF in bilaterally heated annuli can be predicted by tube CHF prediction methods for the simultaneous CHF occurrence at both surfaces, and the following flow conditions: pressure 7-10 MPa, mass flux 0.5-4.0 Mg/m{sup 2}s and critical quality 0.23-0.9. The effect on CHF of the outer-to-inner surface heat flux ratio, was also examined. The prediction of CHF for bilaterally heated annuli was based on the droplet-diffusion model proposed by Kirillov and Smogalev. While their model refers only to CHF occurrence at the inner surface, we extended it to cases where CHF occurs at the outer surface, and simultaneously at both surfaces, thus covering all cases of CHF occurrence in bilaterally heated annuli. From the annuli CHF data of Becker and Letzter, we derived empirical functions required by the model. the proposed equations provide good accuracy for the CHF data used in this study. Moreover, the equations can predict conditions at which CHF occurs simultaneously at both surfaces. Also, this method can be used for cases with only one heated surface.

  19. Closed flux tubes in D=2+1SU(N) gauge theories: dynamics and effective string description

    International Nuclear Information System (INIS)

    Athenodorou, Andreas; Teper, Michael

    2016-01-01

    We extend our earlier calculations of the spectrum of closed flux tubes in SU(N) gauge theories in 2+1 dimensions, with a focus on questions raised by recent theoretical progress on the effective string action of long flux tubes and the world-sheet action for flux tubes of moderate lengths. Our new calculations in SU(4) and SU(8) provide evidence that the leading O(1/l"γ) non-universal correction to the flux tube ground state energy does indeed have a power γ≥7. We perform a study in SU(2), where we can traverse the length at which the Nambu-Goto ground state becomes tachyonic, to obtain an all-N view of the spectrum. Our comparison of the k=2 flux tube excitation energies in SU(4) and SU(6) suggests that the massive world sheet excitation associated with the k=2 binding has a scale that knows about the group and hence the theory in the bulk, and we comment on the potential implications of world sheet massive modes for the bulk spectrum. We provide a quantitative analysis of the surprising (near-)orthogonality of flux tubes carrying flux in different SU(N) representations, which implies that their screening by gluons is highly suppressed even at small N.

  20. Closed flux tubes in D=2+1SU(N) gauge theories: dynamics and effective string description

    Energy Technology Data Exchange (ETDEWEB)

    Athenodorou, Andreas [Department of Physics, University of Cyprus,POB 20537, 1678 Nicosia (Cyprus); Computation-based Science and Technology Research Center, The Cyprus Institute,20 Kavafi Str., Nicosia 2121 (Cyprus); Teper, Michael [Rudolf Peierls Centre for Theoretical Physics, University of Oxford,1 Keble Road, Oxford OX1 3NP (United Kingdom)

    2016-10-18

    We extend our earlier calculations of the spectrum of closed flux tubes in SU(N) gauge theories in 2+1 dimensions, with a focus on questions raised by recent theoretical progress on the effective string action of long flux tubes and the world-sheet action for flux tubes of moderate lengths. Our new calculations in SU(4) and SU(8) provide evidence that the leading O(1/l{sup γ}) non-universal correction to the flux tube ground state energy does indeed have a power γ≥7. We perform a study in SU(2), where we can traverse the length at which the Nambu-Goto ground state becomes tachyonic, to obtain an all-N view of the spectrum. Our comparison of the k=2 flux tube excitation energies in SU(4) and SU(6) suggests that the massive world sheet excitation associated with the k=2 binding has a scale that knows about the group and hence the theory in the bulk, and we comment on the potential implications of world sheet massive modes for the bulk spectrum. We provide a quantitative analysis of the surprising (near-)orthogonality of flux tubes carrying flux in different SU(N) representations, which implies that their screening by gluons is highly suppressed even at small N.

  1. Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube

    Energy Technology Data Exchange (ETDEWEB)

    Requerey, Iker S.; Cobo, B. Ruiz [Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain); Iniesta, J. C. Del Toro; Suárez, D. Orozco [Instituto de Astrofísica de Andalucía (CSIC), Apdo. de Correos 3004, E-18080 Granada (Spain); Rodríguez, J. Blanco [Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; Noort, M. van [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Schmidt, W. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Pillet, V. Martínez [National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States); Knölker, M., E-mail: iker@iac.es [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)

    2017-03-01

    We study the dynamics and topology of an emerging magnetic flux concentration using high spatial resolution spectropolarimetric data acquired with the Imaging Magnetograph eXperiment on board the sunrise balloon-borne solar observatory. We obtain the full vector magnetic field and the line of sight (LOS) velocity through inversions of the Fe i line at 525.02 nm with the SPINOR code. The derived vector magnetic field is used to trace magnetic field lines. Two magnetic flux concentrations with different polarities and LOS velocities are found to be connected by a group of arch-shaped magnetic field lines. The positive polarity footpoint is weaker (1100 G) and displays an upflow, while the negative polarity footpoint is stronger (2200 G) and shows a downflow. This configuration is naturally interpreted as a siphon flow along an arched magnetic flux tube.

  2. Switching process between bistable positons of multiquantum flux tubes in a thin-film type I superconductor

    International Nuclear Information System (INIS)

    Parisi, J.; Huebener, R.P.; Muhlemeier, B.

    1983-01-01

    A superconducting memory device based on a bistable vortex position represents an interesting storage medium for future Josephson computers. In order to study the operational mode of such a single-flux quantum memory cell, we use as a model system multiquantum flux tubes in a thin-film type I superconductor (Pb). By employing high-resolution stroboscopic magnetooptical flux detection, we are able to globally visualize both spatial and temporal behavior of rapidly switching individual flux tubes. All experimental results agree reasonably well with theoretical model considerations of the energy balance during the elementary switching process

  3. Sunspots and the physics of magnetic flux tubes. III - Aerodynamic lift

    Science.gov (United States)

    Parker, E. N.

    1979-01-01

    The aerodynamic lift exerted on a magnetic flux tube by the asymmetric flow around the two sides of the tube is calculated as part of an investigation of the physics of solar flux tubes. The general hydrodynamic forces on a rigid circular cylinder in a nonuniform flow of an ideal fluid are derived from the first derivatives of the velocity field. Aerodynamic lift in a radial nonuniform flow is found to act in the direction of the flow, toward the region of increased flow velocity, while in a shear flow, lift is perpendicular to the free stream and directed toward increasing flow velocity. For a general, three dimensional, large-scale stationary incompressible equilibrium flow, an expression is also derived relating the lift per unit length to the dynamical pressure, cylinder radius and the gradient of the free-stream velocity. Evidence from an asymmetric airfoil in a uniform flow indicates that lift is enhanced in a real fluid in the presence of turbulence.

  4. A study on the critical heat flux for annuli and round tubes under low pressure conditions

    International Nuclear Information System (INIS)

    Park, Jae Wook

    1997-02-01

    This study aims to reveal the characteristics of the critical heat flux (CHF) of internally heated concentric annuli and vertical round tubes in low-pressure and low-flow (LPLF) conditions. Although many efforts have been devote to the subject of the CHF during the last forty years, the information on the CHF phenomenon for LPLF conditions is still very limited. The applicable ranges of the CHF correlations for annuli and round tubes are concentrate on the operating conditions of nuclear power plant (NPP), namely high-pressure and high-flow (HPHF) conditions. these facts promoted to collect the reliable CHF data for LPLF conditions for both annuli and round tubes. The critical heat flux data for vertical flow boiling of water in annuli and round tubes at low pressures and low mass fluxes show the following trends: The observed CHF mechanism for annuli was changed in the order of flooding, churn-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. The observed parametric trends for annuli are consistent with the previous understanding except that the CHF for downward flow is considerably lower (up to 40%) than that for upward flow. The critical quality is much lower than that for round tubes at the same inlet conditions. The observed parametric trends for round tubes are generally consistent with the previous understanding except for system pressure an tube diameter effect. For the system pressure effect, it is observed that the pressure effect is complicated but not so large, whereas the existing CHF correlations do not present the parametric trend exactly. For tube diameter effect, the decreasing trends of CHF with respect to tube diameter was the general understanding so far, but in this region the CHF show a increasing trend of tube diameter. The prediction and the parametric trend analyses are performed by two view points, I.e., for fixed inlet conditions and for local

  5. External glass peening of zircaloy calandria tubes to increase the critical heat flux

    International Nuclear Information System (INIS)

    Fong, R.W.L.; Coleman, C.E.; Nitheanandan, T.; Kroeger, V.D.; Moyer, R.G.; Sanderson, D.B.; Root, J.H.; Rogge, R.B.

    1997-12-01

    Glass-peening the outside surfaces of Zircaloy calandria tubes increases the nucleation sites available for boiling heat transfer and has been demonstrated to enhance the critical heat flux (CHF) in pool-boiling experiments. The objective of this study is to optimise the heat-transfer enhancement by glass peening while ensuring that the microstructure of the peened tube is acceptable for reactor use. Pool-boiling tests were done using small Zircaloy tubes with as-received ('smooth') surfaces and variously peened surfaces, to evaluate two peening parameters, glass-bead size and the coverage of peened surface. Our results showed that the maximum enhancement of CHF (by 60% compared with as-received tubes) was obtained using a glass-bead size of 90-125 μm with a coverage of 100%. The CHF enhancement was found to be insensitive to glass-bead size over a wide range (from 60-90 μm to 125-180 μm). Using a fixed glass-bead size of 125-180 μm to evaluate the influence of peening coverage, the maximum effect on the CHF response was obtained with a coverage of 1 00%. The microstructures of the peened tubes were evaluated using light microscopy, X-ray and neutron diffraction, and mechanical tests. After peening, the microstructure in the subsurface layer (-30 μm) consisted of deformed α-Zr grains, and the crystallographic texture of the grains changed slightly. After stress-relieving at 500 degrees C for 1 h, some recrystallisation had occurred and the residual strains remaining in the tube were low. The tensile and burst properties of glass-peened and stress-relieved tubes were similar to those of as-received tubes. The microstructures introduced by peening and stress relieving were judged to have little effect on creep and growth behaviour. Since there are no deleterious consequences of the glass-peening treatment, the peened and stress-relieved tubes are found to be acceptable for reactor use. (author)

  6. Sabots, Obturator and Gas-In-Launch Tube Techniques for Heat Flux Models in Ballistic Ranges

    Science.gov (United States)

    Bogdanoff, David W.; Wilder, Michael C.

    2013-01-01

    For thermal protection system (heat shield) design for space vehicle entry into earth and other planetary atmospheres, it is essential to know the augmentation of the heat flux due to vehicle surface roughness. At the NASA Ames Hypervelocity Free Flight Aerodynamic Facility (HFFAF) ballistic range, a campaign of heat flux studies on rough models, using infrared camera techniques, has been initiated. Several phenomena can interfere with obtaining good heat flux data when using this measuring technique. These include leakage of the hot drive gas in the gun barrel through joints in the sabot (model carrier) to create spurious thermal imprints on the model forebody, deposition of sabot material on the model forebody, thereby changing the thermal properties of the model surface and unknown in-barrel heating of the model. This report presents developments in launch techniques to greatly reduce or eliminate these problems. The techniques include the use of obturator cups behind the launch package, enclosed versus open front sabot designs and the use of hydrogen gas in the launch tube. Attention also had to be paid to the problem of the obturator drafting behind the model and impacting the model. Of the techniques presented, the obturator cups and hydrogen in the launch tube were successful when properly implemented

  7. Particle propagation, wave growth and energy dissipation in a flaring flux tube

    Science.gov (United States)

    White, S. M.; Melrose, D. B.; Dulk, G. A.

    1986-01-01

    Wave amplification by downgoing particles in a common flare model is investigated. The flare is assumed to occur at the top of a coronal magnetic flux loop, and results in the heating of plasma in the flaring region. The hot electrons propagate down the legs of the flux tube towards increasing magnetic field. It is simple to demonstrate that the velocity distributions which result in this model are unstable to both beam instabilities and cyclotron maser action. An explanation is presented for the propagation effects on the distribution, and the properties of the resulting amplified waves are explored, concentrating on cyclotron maser action, which has properties (emission in the z mode below the local gyrofrequency) quite different from maser action by other distributions considered in the context of solar flares. The z mode waves will be damped in the coronal plasma surrounding the flaring flux tube and lead to heating there. This process may be important in the overall energy budget of the flare. The downgoing maser is compared with the loss cone maser, which is more likely to produce observable bursts.

  8. An Analytical Model for Prediction of Magnetic Flux Leakage from Surface Defects in Ferromagnetic Tubes

    Directory of Open Access Journals (Sweden)

    Suresh V.

    2016-02-01

    Full Text Available In this paper, an analytical model is proposed to predict magnetic flux leakage (MFL signals from the surface defects in ferromagnetic tubes. The analytical expression consists of elliptic integrals of first kind based on the magnetic dipole model. The radial (Bz component of leakage fields is computed from the cylindrical holes in ferromagnetic tubes. The effectiveness of the model has been studied by analyzing MFL signals as a function of the defect parameters and lift-off. The model predicted results are verified with experimental results and a good agreement is observed between the analytical and the experimental results. This analytical expression could be used for quick prediction of MFL signals and also input data for defect reconstructions in inverse MFL problem.

  9. TIME-DEPENDENT TURBULENT HEATING OF OPEN FLUX TUBES IN THE CHROMOSPHERE, CORONA, AND SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Woolsey, L. N.; Cranmer, S. R., E-mail: lwoolsey@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)

    2015-10-01

    We investigate several key questions of plasma heating in open-field regions of the corona that connect to the solar wind. We present results for a model of Alfvén-wave-driven turbulence for three typical open magnetic field structures: a polar coronal hole, an open flux tube neighboring an equatorial streamer, and an open flux tube near a strong-field active region. We compare time-steady, one-dimensional turbulent heating models against fully time-dependent three-dimensional reduced-magnetohydrodynamic modeling of BRAID. We find that the time-steady results agree well with time-averaged results from BRAID. The time dependence allows us to investigate the variability of the magnetic fluctuations and of the heating in the corona. The high-frequency tail of the power spectrum of fluctuations forms a power law whose exponent varies with height, and we discuss the possible physical explanation for this behavior. The variability in the heating rate is bursty and nanoflare-like in nature, and we analyze the amount of energy lost via dissipative heating in transient events throughout the simulation. The average energy in these events is 10{sup 21.91} erg, within the “picoflare” range, and many events reach classical “nanoflare” energies. We also estimated the multithermal distribution of temperatures that would result from the heating-rate variability, and found good agreement with observed widths of coronal differential emission measure distributions. The results of the modeling presented in this paper provide compelling evidence that turbulent heating in the solar atmosphere by Alfvén waves accelerates the solar wind in open flux tubes.

  10. Observing long colour flux tubes in SU(2) lattice gauge theory

    CERN Document Server

    Bali, G S; Schlichter, C; Bali, G S; Schilling, K; Schlichter, C

    1995-01-01

    We present results of a high statistics study of the chromo field distribution between static quarks in SU(2) gauge theory on lattices of volumes 16^4, 32^4, and 48^3*64, with physical extent ranging from 1.3 fm up to 2.7 fm at beta=2.5, beta=2.635, and beta=2.74. We establish string formation over physical distances as large as 2 fm. The results are tested against Michael's sum rules. A detailed investigation of the transverse action and energy flux tube profiles is provided. As a by-product, we obtain the static lattice potential in unpreceded accuracy.

  11. Study on tube critical heat flux data treatment with artificial neural networks

    International Nuclear Information System (INIS)

    Han Lang; Shan Jianqiang

    2005-01-01

    Prediction of the Critical Heat Flux (CHF) are analyzed by Artificial Neural Networks (ANN) to a CHF database for upward flow of water in uniformly heated vertical round tubes. The analysis is performed with three viewpoints hypothesis, i.e. for fixed inlet condition, fixed exit condition and local condition. Half of 6941 from CHF database data is trained through ANN, the trained ANN predicts the total CHF data better than any other conventional correlations, showing RMS error of 6.6%, 10.39% and 21.39%, respectively. (author)

  12. Sunspots and the physics of magnetic flux tubes. III. Aerodynamic lift

    International Nuclear Information System (INIS)

    Parker, E.N.

    1979-01-01

    The aerodynamic lift on a rigid circular cylinder of radius a in a nonuniform free stream is calculated to first order in the derivatives of the free-stream velocity, u(r). The lift per unit length, is of the order of the dynamical pressure 1/2rhou 2 times (a 2 /u 2 ) vertical-bardelu 2 vertical-bar. The results have application to the motion of flux tubes in the Sun. Illustrative examples are provided in subsequent papers of this series

  13. MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR

    International Nuclear Information System (INIS)

    Martínez-Sykora, Juan; Cheung, Mark C. M.; Moreno-Insertis, Fernando

    2015-01-01

    We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street

  14. MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-Sykora, Juan; Cheung, Mark C. M. [Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States); Moreno-Insertis, Fernando [Instituto de Astrofísica de Canarias, E-38200 La Laguna (Tenerife) (Spain)

    2015-11-20

    We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street.

  15. Formation of field-twisting flux tubes on the magnetopause and solar wind particle entry into the magnetosphere

    International Nuclear Information System (INIS)

    Sato, T.; Shimada, T.; Tanaka, M.; Hayashi, T.; Watanabe, K.

    1986-01-01

    A global interaction between the solar wind with a southward interplanetary magnetic field (IMF) and the magnetosphere is studied using a semi-global simulation model. A magnetic flux tube in which field lines are twisted is created as a result of repeated reconnection between the IMF and the outermost earth-rooted magnetic field near the equatorial plane and propagates to higher latitudes. When crossing the polar cusp, the flux tube penetrates into the magnetosphere reiterating reconnection with the earth-rooted higher latitude magnetic field, whereby solar wind particles are freely brought inside the magnetosphere. The flux tube structure has similarities in many aspects to the flux transfer events (FTEs) observed near the dayside magnetopause

  16. NUMERICAL SIMULATIONS OF PLASMA DYNAMICS IN THE VICINITY OF A RETRACTING FLUX TUBE

    Energy Technology Data Exchange (ETDEWEB)

    Scott, Roger B.; Longcope, Dana W.; McKenzie, David E. [Montana State University P.O. Box 173840 Bozeman, MT 59717-3840 (United States)

    2016-11-01

    In a previous paper, we presented an analytical, zero- β model for supra-arcade downflows in which a retracting flux tube deforms the surrounding magnetic field, constricting the flow of plasma along affected field lines and, in some cases, forcing the plasma to exhibit collimated shocks. Here we present a numerical simulation based on the same model construction—a retracting flux tube is treated as a rigid boundary around which the plasma is forced to flow and the magnetic field and plasma evolve according to the governing equations of magnetohydrodynamics. We find that the collimated shocks described in our previous study are recovered for plasma β in the range of 0 ≤ β ≲ 1, while for 1 ≲ β the behavior is similar to the simpler hydrodynamic case, with classical bow shocks forming when the acoustic Mach number approaches or exceeds unity. Furthermore, we find that while the plasma β is important for identifying the various types of behaviors, more important still is the Alfvén Mach number, which, if large, implies that the bulk kinetic energy of the fluid exceeds the internal energy of the magnetic field, thereby leading to the formation of unconfined, fast-mode magnetosonic shocks, even in the limit of small β .

  17. Soft photon production in the boost-invariant color-flux tube model

    International Nuclear Information System (INIS)

    Czyz, W.; Florkowski, W.

    1993-07-01

    Starting from the classical expressions for emission of radiation we calculate soft photon production in the boost-invariant color-flux tube model. In the center-of-mass system of the initial tube we find that for large energies (√s ∼ 20 GeV) the production of photons with frequencies: 20 MeV < ω < 50 MeV, and emitted perpendicularly to the collision axis is strongly enhanced; it exceeds considerably production of photons given by the Low limit. For the emission more collinear with the collision axis and for decreasing ω the effect becomes weaker and, eventually, in the limit ω = 0 we recover precisely the Low formula. We also find that for smaller energies (√s ∼ 5 GeV) the emission of photons is well reproduced by the Low formula. Generally speaking, the observed enhancement is related to the existence of a large, i.e. extended in time, region of photon emission. This, in turn, results from the time dilution accompanying the space-time evolution of tubes. Strong time dilution effects follow from the boost-invariance of our model and, for large s, considerably enhance radiation of soft photons. By the same token, this enhancement decreases with decreasing s, because dilation decreases. (author). 21 refs, 7 figs

  18. Soft photon production in the boost-invariant color-flux tube model

    Energy Technology Data Exchange (ETDEWEB)

    Czyz, W. [Uniwersytet Jagiellonski, Cracow (Poland). Inst. Fizyki]|[Institute of Nuclear Physics, Cracow (Poland); Florkowski, W. [Institute of Nuclear Physics, Cracow (Poland)

    1993-07-01

    Starting from the classical expressions for emission of radiation we calculate soft photon production in the boost-invariant color-flux tube model. In the center-of-mass system of the initial tube we find that for large energies ({radical}s {approx} 20 GeV) the production of photons with frequencies: 20 MeV < {omega} < 50 MeV, and emitted perpendicularly to the collision axis is strongly enhanced; it exceeds considerably production of photons given by the Low limit. For the emission more collinear with the collision axis and for decreasing {omega} the effect becomes weaker and, eventually, in the limit {omega} = 0 we recover precisely the Low formula. We also find that for smaller energies ({radical}s {approx} 5 GeV) the emission of photons is well reproduced by the Low formula. Generally speaking, the observed enhancement is related to the existence of a large, i.e. extended in time, region of photon emission. This, in turn, results from the time dilution accompanying the space-time evolution of tubes. Strong time dilution effects follow from the boost-invariance of our model and, for large s, considerably enhance radiation of soft photons. By the same token, this enhancement decreases with decreasing s, because dilation decreases. (author). 21 refs, 7 figs.

  19. Closed flux tubes and their string description in D=3 1 SU(N) gauge theories

    International Nuclear Information System (INIS)

    Athenodorou, Andreas; Bringoltz, Barak; Teper, Michael

    2010-08-01

    We calculate the energy spectrum of a confining flux tube that is closed around a spatial torus, as a function of its length l. We do so for various SU(N) gauge theories in 3+1 dimensions, and for various values of spin, parity and longitudinal momentum. We are able to present usefully accurate results for about 20 of the lightest such states, for a range of l that begins close to the (finite volume) deconfining phase transition at l√σ ∝ 1.6, and extends up to l√σ∝6 (where σ is the string tension). We find that most of these low-lying states are well described by the spectrum of the Nambu-Goto free string theory in flat space-time. Remarkably, this is so not only at the larger values of l, where the gap between the ground state energy and the low-lying excitations becomes small compared to the mass gap, but also down to much shorter lengths where these excitation energies become large compared to √σ, the flux-tube no longer 'looks' anything like a thin string, and an expansion of the effective string action in powers of 1/l no longer converges. All this is for flux in the fundamental representation. We also calculate the k=2 (anti)symmetric ground states and these show larger corrections at small l. So far all this closely resembles our earlier findings in 2+1 dimensions. However, and in contrast to the situation in D=2+1, we also find that there are some states, with J P =0 - quantum numbers, that show large deviations from the Nambu-Goto spectrum. We investigate the possibility that (some of) these states may encode the massive modes associated with the internal structure of the flux tube, and we discuss how the precocious free string behaviour of most states constrains the effective string action, on which much interesting theoretical progress has recently been made. (orig.)

  20. Non-Abelian flux tubes in N=1 SQCD: Supersizing world-sheet supersymmetry

    International Nuclear Information System (INIS)

    Shifman, M.; Yung, A.

    2005-01-01

    We consider non-Abelian 1/2 Bogomol'nyi-Prasad-Sommerfield (BPS) flux tubes (strings) in a deformed N=2 supersymmetric gauge theory, with mass terms μ 1,2 of the adjoint fields breaking N=2 down to N=1. The main feature of the non-Abelian strings is the occurrence of orientational moduli associated with the possibility of rotations of their color fluxes inside a global SU(N) group. The bulk four-dimensional theory has four supercharges; half-criticality of the non-Abelian strings would imply then N=1 supersymmetry on the world sheet, i.e. two supercharges. In fact, superalgebra of the reduced moduli space has four supercharges. Internal dynamics of the orientational moduli are described by a two-dimensional CP(N-1) model on the string world sheet. We focus mainly on the SU(2) case, i.e. CP(1) world-sheet theory. We show that non-Abelian BPS strings exist for all values of μ 1,2 . The low-energy theory of moduli is indeed CP(1), with four supercharges, in a wide region of breaking parameters μ 1,2 . Only in the limit of very large μ 1,2 , above some critical value does the N=2 world-sheet supersymmetry break down to N=1. We observe 'supersymmetry emergence' for the flux-tube junction (confined monopole): The kink-monopole is half-critical considered from the standpoint of the world-sheet CP(1) model (i.e. two supercharges conserved), while in the bulk N=1 theory there is no monopole central charge at all

  1. Condensation heat transfer and pressure drop of R-410A in a 7.0 mm O.D. microfin tube at low mass fluxes

    Science.gov (United States)

    Kim, Nae-Hyun

    2016-12-01

    R-410A condensation heat transfer and pressure drop data are provided for a 7.0 mm O.D. microfin tube at low mass fluxes (50-250 kg/m2 s). The heat transfer coefficient of the microfin tube shows a minimum behavior with the mass flux. At a low mass flux, where flow pattern is stratified, condensation induced by surface tension by microfins overwhelms condensation induced by shear, and the heat transfer coefficient decreases as mass flux increases. At a high mass flux, where flow pattern is annular, condensation induced by shear governs the heat transfer, and the heat transfer coefficient increases as mass flux increases. The pressure drop of the microfin tube is larger than that of the smooth tube at the annular flow regime. On the contrary, the pressure drop of the smooth tube is larger than that of the microfin tube at the stratified flow regime.

  2. Assembly and Delivery of Rabbit Capsules for Irradiation of Silicon Carbide Cladding Tube Specimens in the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Koyanagi, Takaaki [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    Neutron irradiation of silicon carbide (SiC)-based fuel cladding under a high radial heat flux presents a critical challenge for SiC cladding concepts in light water reactors (LWRs). Fission heating in the fuel provides a high heat flux through the cladding, which, combined with the degraded thermal conductivity of SiC under irradiation, results in a large temperature gradient through the thickness of the cladding. The strong temperature dependence of swelling in SiC creates a complex stress profile in SiCbased cladding tubes as a result of differential swelling. The Nuclear Science User Facilities (NSUF) Program within the US Department of Energy Office of Nuclear Energy is supporting research efforts to improve the scientific understanding of the effects of irradiation on SiC cladding tubes. Ultimately, the results of this project will provide experimental validation of multi-physics models for SiC-based fuel cladding during LWR operation. The first objective of this project is to irradiate tube specimens using a previously developed design that allows for irradiation testing of miniature SiC tube specimens subjected to a high radial heat flux. The previous “rabbit” capsule design uses the gamma heating in the core of the High Flux Isotope Reactor (HFIR) to drive a high heat flux through the cladding tube specimens. A compressible aluminum foil allows for a constant thermal contact conductance between the cladding tubes and the rabbit housing despite swelling of the SiC tubes. To allow separation of the effects of irradiation from those due to differential swelling under a high heat flux, a new design was developed under the NSUF program. This design allows for irradiation of similar SiC cladding tube specimens without a high radial heat flux. This report briefly describes the irradiation experiment design concepts, summarizes the irradiation test matrix, and reports on the successful delivery of six rabbit capsules to the HFIR. Rabbits of both low and high

  3. Flow boiling heat transfer of R134a and R404A in a microfin tube at low mass fluxes and low heat fluxes

    Science.gov (United States)

    Spindler, Klaus; Müller-Steinhagen, Hans

    2009-05-01

    An experimental investigation of flow boiling heat transfer in a commercially available microfin tube with 9.52 mm outer diameter has been carried out. The microfin tube is made of copper with a total fin number of 55 and a helix angle of 15°. The fin height is 0.24 mm and the inner tube diameter at fin root is 8.95 mm. The test tube is 1 m long and is electrically heated. The experiments have been performed at saturation temperatures between 0 and -20°C. The mass flux was varied between 25 and 150 kg/m2s, the heat flux from 15,000 W/m2 down to 1,000 W/m2. All measurements have been performed at constant inlet vapour quality ranging from 0.1 to 0.7. The measured heat transfer coefficients range from 1,300 to 15,700 W/m2K for R134a and from 912 to 11,451 W/m2K for R404A. The mean heat transfer coefficient of R134a is in average 1.5 times higher than for R404A. The mean heat transfer coefficient has been compared with the correlations by Koyama et al. and by Kandlikar. The deviations are within ±30% and ±15%, respectively. The influence of the mass flux on the heat transfer is most significant between 25 and 62.5 kg/m2s, where the flow pattern changes from stratified wavy flow to almost annular flow. This flow pattern transition is shifted to lower mass fluxes for the microfin tube compared to the smooth tube.

  4. Evaluation of subcooled critical heat flux correlations for tubes with and without internal twisted tapes

    International Nuclear Information System (INIS)

    Inasaka, F.; Nariai, H.

    1996-01-01

    Eleven correlations and models for critical heat flux (CHF) of subcooled flow boiling in water were evaluated. Both a direct substitution method (DSM) and a heat balance condition method (HBM) were compared in the evaluations. The HBM was recommended as a better prediction method in the present study. For straight tubes under uniform heating conditions, the correlations of the Gunther, Knoebel, modified Tong, W-2, and Tong-75, and also the Celata and Weisman-Pei models were confirmed to give reasonably good predictions. Among them, the Celata model was the best with respect to accuracy. For swirl flow under uniform heating conditions, Tong-75-I (involving modification of the water velocity parameter) and Nariai-Inasaka correlations were confirmed to give reasonably good predictions, even though their predictions were too low for the CHF under non-uniform heating conditions. (orig.)

  5. Meson emissions from quark-gluon plasma through formation and fission of chromoelectric flux tubes

    International Nuclear Information System (INIS)

    Matsui, T.; Banerjee, B.; Glendenning, N.K.

    1983-06-01

    In the present work we study a facet of the plasma evolution, the formation and radiation of mesons at the surface of hog plasma. The surface meson radiation would play two important roles. First, it may carry some information about the pre-freezeout stage of the plasma evolution. Second, it causes a pressure decrease at the surface that works against the expansion. In the extreme, the plasma may extinct very rapidly by the surface meson radiation without collective expansion. It is very unclear how the incident quark degrees of freedom is converted into mesonic degrees of freedom and how the color confinement works in such a process. We have studied the problem by fully employing the chromoelectric flux tube model. We found that their parametrization is quite unsatisfactory and is actually incompatible with a dynamical description of color confinement. We briefly recapitulate our treatments and findings

  6. Upstream magnetospheric ion flux tube within a magnetic cloud: Wind/STICS

    Science.gov (United States)

    Posner, Arik; Liemohn, Michael W.; Zurbuchen, Thomas H.

    2003-03-01

    We present a case study of a remarkable upstream O+ and N+ ion outflow event. We present observational evidence for spatially structured outflow of these Low Charge State Heavy Ions (LCSHIs) of magnetospheric origin along a small reconnected field line region within the framework of a magnetic cloud of an ICME. From the particles' in situ 3D distribution function we conclude that in this case the interaction of the outflow with the bow shock is small. We conclude further that the gyrophases of outflowing ions at the reconnection point are randomly distributed. This leads to the formation of a flux tube with a specific geometry. In particular, the outflow reveals spatial dispersion and non-gyrotropy. This result has implications for the size of the dayside reconnection site.

  7. Two regimes of flux scaling in axially homogeneous turbulent convection in vertical tube

    Science.gov (United States)

    Pawar, Shashikant S.; Arakeri, Jaywant H.

    2016-08-01

    From experiments of axially homogeneous turbulent convection in a vertical tube using heat (Prandtl number Pr≃6 ) and brine (Pr≃600 ) we show that at sufficiently high Rayleigh numbers (Rag), the Nusselt number Nug˜(RagPr)1/2, which corresponds to the so-called ultimate regime scaling. In heat experiments below certain Rag,however,there is transition to a new regime, Nug˜(RagPr)0.3. This transition also seems to exist in earlier reported data for Pr=1 and Pr≃600 , at different Rag. However, the transition occurs at a single Grashof number, Grgc≃1.6 ×105 , and unified flux scalings for Pr≥1 , Nug/Pr˜Grg0.3, and Nug/Pr˜Grg1/2 can be given for the two regimes.

  8. Limited Streamer Tubes for the BaBar Instrumented Flux Return Upgrade

    International Nuclear Information System (INIS)

    Lu, C.

    2005-01-01

    Starting from the very beginning of their operation the efficiency of the RPC chambers in the BaBar Instrumented Flux Return (IFR) has suffered serious degradation. After intensive investigation, various remediation efforts had been carried out, but without success. As a result the BaBar collaboration decided to replace the dying barrel RPC chambers about two years ago. To study the feasibility of using the Limited Streamer Tube (LST) as the replacement of RPC we carried out an R and D program that has resulted in BaBar's deciding to replace the barrel RPC's with LST's. In this report we summarize the major detector R and D results, and leave other issues of the IFR system upgrade to the future publications

  9. Dynamo generation of magnetic fields in three-dimensional space: Solar cycle main flux tube formation and reversals

    International Nuclear Information System (INIS)

    Yoshimura, H.

    1983-01-01

    Dynamo processes as a magnetic field generation mechanism in astrophysics can be described essentially by movement and deformation of magnetic field lines due to plasma fluid motions. A basic element of the processes is a kinematic problem. As an important prototype of these processes, we investigate the case of the solar magnetic cycle. To follow the movement and deformation, we solve magnetohydrodynamic (MHD) equations by a numerical method with a prescribed velocity field. A simple combination of differential rotation and global convection, given by a linear analysis of fluid dynamics in a rotating sphere, can perpetually create and reverse great magnetic flux tubes encircling the Sun. We call them the main flux tubes of the solar cycle. They are progenitors of small-scale flux ropes of the solar activity. This shows that magnetic field generation by fluid motions is, in fact, possible and that MHD equations have a new type of oscillatory solution. The solar cycle can be identified with one of such oscillatory solutions. This means that we can follow detailed stages of the field generation and reversal processes of the dynamo by continuously observing the Sun. It is proposed that the magnetic flux tube formation by streaming plasma flows exemplified here could be a universal mechanism of flux tube formation in astrophysics

  10. Stochastic delocalization of finite populations

    International Nuclear Information System (INIS)

    Geyrhofer, Lukas; Hallatschek, Oskar

    2013-01-01

    The localization of populations of replicating bacteria, viruses or autocatalytic chemicals arises in various contexts, such as ecology, evolution, medicine or chemistry. Several deterministic mathematical models have been used to characterize the conditions under which localized states can form, and how they break down due to convective driving forces. It has been repeatedly found that populations remain localized unless the bias exceeds a critical threshold value, and that close to the transition the population is characterized by a diverging length scale. These results, however, have been obtained upon ignoring number fluctuations (‘genetic drift’), which are inevitable given the discreteness of the replicating entities. Here, we study the localization/delocalization of a finite population in the presence of genetic drift. The population is modeled by a linear chain of subpopulations, or demes, which exchange migrants at a constant rate. Individuals in one particular deme, called ‘oasis’, receive a growth rate benefit, and the total population is regulated to have constant size N. In this ecological setting, we find that any finite population delocalizes on sufficiently long time scales. Depending on parameters, however, populations may remain localized for a very long time. The typical waiting time to delocalization increases exponentially with both population size and distance to the critical wind speed of the deterministic approximation. We augment these simulation results by a mathematical analysis that treats the reproduction and migration of individuals as branching random walks subject to global constraints. For a particular constraint, different from a fixed population size constraint, this model yields a solvable first moment equation. We find that this solvable model approximates very well the fixed population size model for large populations, but starts to deviate as population sizes are small. Nevertheless, the qualitative behavior of the

  11. Critical heat flux and transition boiling characteristics for a sodium-heated steam generator tube for LMFBR applications

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, S.; Holmes, D.H.

    1977-04-01

    An experimental program was conducted to characterize critical heat flux (CHF) in a sodium-heated steam generator tube model at a proposed PLBR steam generator design pressure of 7.2 MPa. Water was circulated vertically upward in the tube and the heating sodium was flowing counter-current downward. The experimental ranges were: mass flux, 110 to 1490 kg/s.m/sup 2/ (0.08 to 1.10 10/sup 6/ lbm/h.ft/sup 2/); critical heat flux, 0.16 to 1.86 MW/m/sup 2/ (0.05 to 0.59 10/sup 6/ Btu/h.ft/sup 2/); and critical quality, 0.48 to 1.0. The CHF phenomenon for the experimental conditions is determined to be dryout as opposed to departure from nucleate boiling (DNB). The data are divided into high- and low-mass flux regions.

  12. On the look-up tables for the critical heat flux in tubes (history and problems)

    International Nuclear Information System (INIS)

    Kirillov, P.L.; Smogalev, I.P.

    1995-01-01

    The complication of critical heat flux (CHF) problem for boiling in channels is caused by the large number of variable factors and the variety of two-phase flows. The existence of several hundreds of correlations for the prediction of CHF demonstrates the unsatisfactory state of this problem. The phenomenological CHF models can provide only the qualitative predictions of CHF primarily in annular-dispersed flow. The CHF look-up tables covered the results of numerous experiments received more recognition in the last 15 years. These tables are based on the statistical averaging of CHF values for each range of pressure, mass flux and quality. The CHF values for regions, where no experimental data is available, are obtained by extrapolation. The correction of these tables to account for the diameter effect is a complicated problem. There are ranges of conditions where the simple correlations cannot produce the reliable results. Therefore, diameter effect on CHF needs additional study. The modification of look-up table data for CHF in tubes to predict CHF in rod bundles must include a method which to take into account the nonuniformity of quality in a rod bundle cross section

  13. On the area expansion of magnetic flux tubes in solar active regions

    Energy Technology Data Exchange (ETDEWEB)

    Dudík, Jaroslav [DAMTP, CMS, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Dzifčáková, Elena [Astronomical Institute of the Academy of Sciences of the Czech Republic, Fričova 298, 251 65 Ondřejov (Czech Republic); Cirtain, Jonathan W., E-mail: J.Dudik@damtp.cam.ac.uk, E-mail: elena@asu.cas.cz [NASA Marshall Space Flight Center, VP 62, Huntsville, AL 35812 (United States)

    2014-11-20

    We calculated the three-dimensional (3D) distribution of the area expansion factors in a potential magnetic field, extrapolated from the high-resolution Hinode/SOT magnetogram of the quiescent active region NOAA 11482. Retaining only closed loops within the computational box, we show that the distribution of area expansion factors show significant structure. Loop-like structures characterized by locally lower values of the expansion factor are embedded in a smooth background. These loop-like flux tubes have squashed cross-sections and expand with height. The distribution of the expansion factors show an overall increase with height, allowing an active region core characterized by low values of the expansion factor to be distinguished. The area expansion factors obtained from extrapolation of the Solar Optical Telescope magnetogram are compared to those obtained from an approximation of the observed magnetogram by a series of 134 submerged charges. This approximation retains the general flux distribution in the observed magnetogram, but removes the small-scale structure in both the approximated magnetogram and the 3D distribution of the area expansion factors. We argue that the structuring of the expansion factor can be a significant ingredient in producing the observed structuring of the solar corona. However, due to the potential approximation used, these results may not be applicable to loops exhibiting twist or to active regions producing significant flares.

  14. Optimized numerical annular flow dryout model using the drift-flux model in tube geometry

    International Nuclear Information System (INIS)

    Chun, Ji Han; Lee, Un Chul

    2008-01-01

    Many experimental analyses for annular film dryouts, which is one of the Critical Heat Flux (CHF) mechanisms, have been performed because of their importance. Numerical approaches must also be developed in order to assess the results from experiments and to perform pre-tests before experiments. Various thermal-hydraulic codes, such as RELAP, COBRATF, MARS, etc., have been used in the assessment of the results of dryout experiments and in experimental pre-tests. These thermal-hydraulic codes are general tools intended for the analysis of various phenomena that could appear in nuclear power plants, and many models applying these codes are unnecessarily complex for the focused analysis of dryout phenomena alone. In this study, a numerical model was developed for annular film dryout using the drift-flux model from uniform heated tube geometry. Several candidates of models that strongly affect dryout, such as the entrainment model, deposition model, and the criterion for the dryout point model, were tested as candidates for inclusion in an optimized annular film dryout model. The optimized model was developed by adopting the best combination of these candidate models, as determined through comparison with experimental data. This optimized model showed reasonable results, which were better than those of MARS code

  15. On the look-up tables for the critical heat flux in tubes (history and problems)

    Energy Technology Data Exchange (ETDEWEB)

    Kirillov, P.L.; Smogalev, I.P. [Institute of Physics and Power Engineering, Kaluga (Russian Federation)

    1995-09-01

    The complication of critical heat flux (CHF) problem for boiling in channels is caused by the large number of variable factors and the variety of two-phase flows. The existence of several hundreds of correlations for the prediction of CHF demonstrates the unsatisfactory state of this problem. The phenomenological CHF models can provide only the qualitative predictions of CHF primarily in annular-dispersed flow. The CHF look-up tables covered the results of numerous experiments received more recognition in the last 15 years. These tables are based on the statistical averaging of CHF values for each range of pressure, mass flux and quality. The CHF values for regions, where no experimental data is available, are obtained by extrapolation. The correction of these tables to account for the diameter effect is a complicated problem. There are ranges of conditions where the simple correlations cannot produce the reliable results. Therefore, diameter effect on CHF needs additional study. The modification of look-up table data for CHF in tubes to predict CHF in rod bundles must include a method which to take into account the nonuniformity of quality in a rod bundle cross section.

  16. Heat transfer augmentation in a tube using nanofluids under constant heat flux boundary condition: A review

    International Nuclear Information System (INIS)

    Singh, Vinay; Gupta, Munish

    2016-01-01

    Highlights: • Reviews heat transfer augmentation of nanofluids in a tube with constant heat flux. • Recent advances in hybrid nanofluids are reviewed. • Identifies and compares significant results. • Scope of future research in this area is discussed. - Abstract: In the last few decades, research on nanofluids has increased rapidly. Traditional heat transfer fluids with order of nanometer sized particles (1–100 nm) suspended in them are termed as nanofluids. Nanofluids have been proved as better heat transfer fluids despite of various contradictions in results by different research groups. The aim of this article is to review and summarize the recent experimental and theoretical studies on convective heat transfer in heat exchangers using constant heat flux boundary condition. The use of different types of nanoparticles with different base fluids by different research groups has been presented and compared. Further an overview of experimental results about heat transfer abilities of hybrid nanofluids from available literature sources is also presented. Finally, the challenges and future directions in which research can be further progress are discussed.

  17. Critical heat flux data in a vertical tube at low and medium pressures

    Energy Technology Data Exchange (ETDEWEB)

    Teyssedou, A [Institut de Genie Nucleaire, Ecole Polytechnique, C.P. 6079, succ. Centre-ville, Montreal, Quebec H3C 3A7 (Canada); Olekhnowitch, A [Institut de Genie Nucleaire, Ecole Polytechnique, C.P. 6079, succ. Centre-ville, Montreal, Quebec H3C 3A7 (Canada); Tapucu, A [Institut de Genie Nucleaire, Ecole Polytechnique, C.P. 6079, succ. Centre-ville, Montreal, Quebec H3C 3A7 (Canada); Champagne, P [Institut de Genie Nucleaire, Ecole Polytechnique, C.P. 6079, succ. Centre-ville, Montreal, Quebec H3C 3A7 (Canada); Groeneveld, D [Chalk River Laboratories, AECL Research, Chalk River (Canada)

    1994-09-01

    AECL Research and Ecole Polytechnique have been cooperating on the validation of the critical heat flux (CHF) look-up table (D.C. Groeneveld et al., Heat Transfer Eng. 7(1-2) (1986) 46-62). For low and medium pressures the values in the table have been obtained by extrapolation and curve fitting; therefore, errors could be expected. To reduce these possible extrapolation errors, CHF experiments are being carried out in water cooled 8mm internal diameter (ID) tubes, at conditions where the data are scarce. This paper presents some of the experimental CHF data obtained for vertical up flow in an 8mm ID test section, for a wide range of exit qualities (5-70%) and the exit pressure ranging from 5 to 30bar. The experiments were carried out for heated lengths of 0.75, 1, 1.4 and 1.8m. In general, the collected data show parametric trends similar to those described in the open literature. However, it was observed that for low pressure conditions CHF depends on the heated length; this dependence begins to disappear for exit pressure of about 30bar. The CHF data have also been compared with predictions of well-known correlations (L. Biasi et al., Energia Nucl. 14(9) (1967) 530-536; R. Bowring, Br. Report AEEW-R789, Winfrith, UK, 1972; Y. Khatto and H. Ohno, Int. J. Heat Mass Transfer 27 (1984) 1641-1648) and those of the look-up table given by Groeneveld et al. For low pressures and low mass fluxes the look-up table seems to yield better predictions of the CHF than the correlations. However, for medium pressures and mass fluxes the correlations perform better than the look-up table; among those tested, Katto and Ohno's correlation gives the best results. ((orig.))

  18. Simulation of the space-time evolution of color-flux tubes (guidelines to the TERMITE program)

    International Nuclear Information System (INIS)

    Dyrek, A.

    1990-08-01

    We give the description of the computer program which simulates boost-invariant evolution of color-flux tubes in high-energy processes. The program provides a graphic demonstration of space-time trajectories of created particles and can also be used as Monte-Carlo generator of events. (author)

  19. Width and string tension of the flux tube in SU(2) lattice gauge theory at high temperature

    Science.gov (United States)

    Chagdaa, S.; Galsandorj, E.; Laermann, E.; Purev, B.

    2018-02-01

    We study the profiles of the flux tube between a static quark and an antiquark in quenched SU(2) lattice gauge theory at temperatures around the deconfinement phase transition. The physical width of the flux tube and the string tension have been determined from the transverse profiles and the q\\bar{q} potential, respectively. Exploiting the computational power of a GPU accelerator in our flux tube investigation, we achieve much higher statistics through which we can increase the signal to noise ratio of our observables in the simulation. This has allowed the investigation of larger lattices as well as larger separations between the quarks than in our previous work. The improved accuracy gives us better results for the width and the string tension. The physical width of the flux tube increases with the temperature up to around T c while keeping its increasing dependence on the q\\bar{q} separation. The string tension results are compared for two different sizes of the lattice. As the lattice becomes larger and finer together with the improved precision, the temperature dependent string tension tends to have a smaller value than the previous one.

  20. Flux tubes and the type-I/type-II transition in a superconductor coupled to a superfluid

    International Nuclear Information System (INIS)

    Alford, Mark G.; Good, Gerald

    2008-01-01

    We analyze magnetic-flux tubes at zero temperature in a superconductor that is coupled to a superfluid via both density and gradient ('entrainment') interactions. The example we have in mind is high-density nuclear matter, which is a proton superconductor and a neutron superfluid, but our treatment is general and simple, modeling the interactions as a Ginzburg-Landau effective theory with four-fermion couplings, including only s-wave pairing. We numerically solve the field equations for flux tubes with an arbitrary number of flux quanta and compare their energies. This allows us to map the type-I/type-II transition in the superconductor, which occurs at the conventional κ≡λ/ξ=1/√(2) if the condensates are uncoupled. We find that a density coupling between the condensates raises the critical κ and, for a sufficiently high neutron density, resolves the type-I/type-II transition line into an infinite number of bands corresponding to 'type-II(n)' phases, in which n, the number of quanta in the favored flux tube, steps from 1 to infinity. For lower neutron density, the coupling creates spinodal regions around the type-I/type-II boundary, in which metastable flux configurations are possible. We find that a gradient coupling between the condensates lowers the critical κ and creates spinodal regions. These exotic phenomena may not occur in nuclear matter, which is thought to be deep in the type-II region but might be observed in condensed-matter systems

  1. Irradiation of Wrought FeCrAl Tubes in the High Flux Isotope Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Linton, Kory D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Field, Kevin G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    The Advanced Fuels Campaign within the Nuclear Technology Research and Development program of the Department of Energy Office of Nuclear Energy is seeking to improve the accident tolerance of light water reactors. Alumina-forming ferritic alloys (e.g., FeCrAl) are one of the leading candidate materials for fuel cladding to replace traditional zirconium alloys because of the superior oxidation resistance of FeCrAl. However, there are still some unresolved questions regarding irradiation effects on the microstructure and mechanical properties of FeCrAl at end-of-life dose levels. In particular, there are concerns related to irradiation-induced embrittlement of FeCrAl alloys due to secondary phase formation. To address this issue, Oak Ridge National Laboratory has developed a new experimental design to irradiate shortened cladding tube specimens with representative 17×17 array pressurized water reactor diameter and thickness in the High Flux Isotope Reactor (HFIR) under relevant temperatures (300–350°C). Post-irradiation examination will include studies of dimensional change, microstructural changes, and mechanical performance. This report briefly summarizes the capsule design concept and the irradiation test matrix for six rabbit capsules. Each rabbit contains two FeCrAl alloy tube specimens. The specimens include Generation I and Generation II FeCrAl alloys with varying processing conditions, Cr concentrations, and minor alloying elements. The rabbits were successfully assembled, welded, evaluated, and delivered to the HFIR along with a complete quality assurance fabrication package. Pictures of the rabbit assembly process and detailed dimensional inspection of select specimens are included in this report. The rabbits were inserted into HFIR starting in cycle 472 (May 2017).

  2. THE BEHAVIOR OF TRANSVERSE WAVES IN NONUNIFORM SOLAR FLUX TUBES. I. COMPARISON OF IDEAL AND RESISTIVE RESULTS

    International Nuclear Information System (INIS)

    Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Goossens, Marcel

    2013-01-01

    Magnetohydrodynamic (MHD) waves are ubiquitously observed in the solar atmosphere. Kink waves are a type of transverse MHD waves in magnetic flux tubes that are damped due to resonant absorption. The theoretical study of kink MHD waves in solar flux tubes is usually based on the simplification that the transverse variation of density is confined to a nonuniform layer much thinner than the radius of the tube, i.e., the so-called thin boundary approximation. Here, we develop a general analytic method to compute the dispersion relation and the eigenfunctions of ideal MHD waves in pressureless flux tubes with transversely nonuniform layers of arbitrary thickness. Results for kink waves are produced and compared with fully numerical resistive MHD eigenvalue computations in the limit of small resistivity. We find that the frequency and resonant damping rate are the same in both ideal and resistive cases. The actual results for thick nonuniform layers deviate from the behavior predicted in the thin boundary approximation and strongly depend on the shape of the nonuniform layer. The eigenfunctions in ideal MHD are very different from those in resistive MHD. The ideal eigenfunctions display a global character regardless of the thickness of the nonuniform layer, while the resistive eigenfunctions are localized around the resonance and are indistinguishable from those of ordinary resistive Alfvén modes. Consequently, the spatial distribution of wave energy in the ideal and resistive cases is dramatically different. This poses a fundamental theoretical problem with clear observational consequences

  3. Magnetic trapping of energetic particles on open dayside boundary layer flux tubes

    International Nuclear Information System (INIS)

    Cowley, S.W.H.; Lewis, Z.V.

    1990-01-01

    Both simple as well as detailed empirical magnetic models of the Earth's dayside magnetosphere suggest that field lines near the magnetopause boundary in the noon quadrant (∼ 09:00 to ∼ 15:00 M.L.T.) possess an unusual property due to the compressive effect of the impinging solar wind flow, namely that the equatorial region represents a local maximum in the magnetic field strength, and not a minimum as elsewhere in the magnetosphere. In this region the field lines can therefore support two distinct particle populations, those which bounce across the equator between mirror points on either side, and those which are trapped about the off-equatorial field strength minima and are confined to one side of the equator. When these field lines become magnetically open due to the occurrence of magnetic reconnection at the equatorial magnetopause, the former particles will rapidly escape into the magnetosheath by field-aligned flow, while the latter population may be sustained within the boundary layer over many bounce periods, as the flux tubes contract and move tailward. Consequently, trapped distributions of energetic particles may commonly occur on open field lines in the dayside boundary layer in the noon quadrant, particularly at high latitudes. The existence of such particles is thus not an infallible indicator of the presence of closed magnetic field lines in this region. At earlier and later local times, however, the boundary layer field lines revert to possessing a minimum in the field strength at the equator. (author)

  4. Dynamics of nonlinear resonant slow MHD waves in twisted flux tubes

    Directory of Open Access Journals (Sweden)

    R. Erdélyi

    2002-01-01

    Full Text Available Nonlinear resonant magnetohydrodynamic (MHD waves are studied in weakly dissipative isotropic plasmas in cylindrical geometry. This geometry is suitable and is needed when one intends to study resonant MHD waves in magnetic flux tubes (e.g. for sunspots, coronal loops, solar plumes, solar wind, the magnetosphere, etc. The resonant behaviour of slow MHD waves is confined in a narrow dissipative layer. Using the method of simplified matched asymptotic expansions inside and outside of the narrow dissipative layer, we generalise the so-called connection formulae obtained in linear MHD for the Eulerian perturbation of the total pressure and for the normal component of the velocity. These connection formulae for resonant MHD waves across the dissipative layer play a similar role as the well-known Rankine-Hugoniot relations connecting solutions at both sides of MHD shock waves. The key results are the nonlinear connection formulae found in dissipative cylindrical MHD which are an important extension of their counterparts obtained in linear ideal MHD (Sakurai et al., 1991, linear dissipative MHD (Goossens et al., 1995; Erdélyi, 1997 and in nonlinear dissipative MHD derived in slab geometry (Ruderman et al., 1997. These generalised connection formulae enable us to connect solutions obtained at both sides of the dissipative layer without solving the MHD equations in the dissipative layer possibly saving a considerable amount of CPU-time when solving the full nonlinear resonant MHD problem.

  5. Critical heat flux experiments in a circular tube with heavy water and light water. (AWBA Development Program)

    International Nuclear Information System (INIS)

    Williams, C.L.; Beus, S.G.

    1980-05-01

    Experiments were performed to establish the critical heat flux (CHF) characteristics of heavy water and light water. Testing was performed with the up-flow of heavy and of light water within a 0.3744 inch inside diameter circular tube with 72.3 inches of heated length. Comparisons were made between heavy water and light water critical heat flux levels for the same local equilibrium quality at CHF, operating pressure, and nominal mass velocity. Results showed that heavy water CHF values were, on the average, 8 percent below the light water CHF values

  6. Lava tube shatter rings and their correlation with lava flux increases at Kīlauea Volcano, Hawai‘i

    Science.gov (United States)

    Orr, T.R.

    2011-01-01

    Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava tubes. They are typified by an upraised rim of blocky rubble and a central depression. Prior to this study, shatter rings had not been observed forming, and, thus, were interpreted in many ways. This paper describes the process of formation for shatter rings observed at Kīlauea Volcano during November 2005–July 2006. During this period, tilt data, time-lapse images, and field observations showed that episodic tilt changes at the nearby Pu‘u ‘Ō‘ō cone, the shallow magmatic source reservoir, were directly related to fluctuations in the level of lava in the active lava tube, with periods of deflation at Pu‘u ‘Ō‘ō correlating with increases in the level of the lava stream surface. Increases in lava level are interpreted as increases in lava flux, and were coincident with lava breakouts from shatter rings constructed over the lava tube. The repetitive behavior of the lava flux changes, inferred from the nearly continuous tilt oscillations, suggests that shatter rings form from the repeated rise and fall of a portion of a lava tube roof. The locations of shatter rings along the active lava tube suggest that they form where there is an abrupt decrease in flow velocity through the tube, e.g., large increase in tube width, abrupt decrease in tube slope, and (or) sudden change in tube direction. To conserve volume, this necessitates an abrupt increase in lava stream depth and causes over-pressurization of the tube. More than a hundred shatter rings have been identified on volcanoes on Hawai‘i and Maui, and dozens have been reported from basaltic lava fields in Iceland, Australia, Italy, Samoa, and the mainland United States. A quick study of other basaltic lava fields worldwide, using freely available satellite imagery, suggests that they might be even more common than previously thought. If so, this confirms that episodic

  7. Sunspots and the physics of magnetic flux tubes. IV. Aerodynamic lift on a thin cylinder in convective flows

    International Nuclear Information System (INIS)

    Tsinganos, K.C.

    1979-01-01

    The aerodynamic lift exerted on a long circular cylinder immersed in a convective flow pattern in an ideal fluid is calculated to establish the equilibrium position of the cylinder. The calculations establish the surprising result that the cylinder is pushed out of the upwellings and the downdrafts of the convective cell, into a location midway between them.The implications for the intense magnetic flux tubes in the convection beneath the surface of the Sun are considered

  8. Sunspots and the physics of magnetic flux tubes. IV - Aerodynamic lift on a thin cylinder in convective flows

    Science.gov (United States)

    Tsinganos, K. C.

    1979-01-01

    The aerodynamic lift exerted on a long circular cylinder immersed in a convective flow pattern in an ideal fluid is calculated to establish the equilibrium position of the cylinder. The calculations establish the surprising result that the cylinder is pushed out the upwellings and the downdrafts of the convective cell, into a location midway between them. The implications for the intense magnetic flux tubes in the convection beneath the surface of the sun are considered.

  9. Chromospheric polarimetry through multiline observations of the 850-nm spectral region - II. A magnetic flux tube scenario

    Science.gov (United States)

    Quintero Noda, C.; Kato, Y.; Katsukawa, Y.; Oba, T.; de la Cruz Rodríguez, J.; Carlsson, M.; Shimizu, T.; Orozco Suárez, D.; Ruiz Cobo, B.; Kubo, M.; Anan, T.; Ichimoto, K.; Suematsu, Y.

    2017-11-01

    In this publication, we continue the work started in Quintero Noda et al., examining this time a numerical simulation of a magnetic flux tube concentration. Our goal is to study if the physical phenomena that take place in it, in particular, the magnetic pumping, leaves a specific imprint on the examined spectral lines. We find that the profiles from the interior of the flux tube are periodically doppler shifted following an oscillation pattern that is also reflected in the amplitude of the circular polarization signals. In addition, we analyse the properties of the Stokes profiles at the edges of the flux tube discovering the presence of linear polarization signals for the Ca II lines, although they are weak with an amplitude around 0.5 per cent of the continuum intensity. Finally, we compute the response functions to perturbations in the longitudinal field, and we estimate the field strength using the weak-field approximation. Our results indicate that the height of formation of the spectral lines changes during the magnetic pumping process, which makes the interpretation of the inferred magnetic field strength and its evolution more difficult. These results complement those from previous works, demonstrating the capabilities and limitations of the 850-nm spectrum for chromospheric Zeeman polarimetry in a very dynamic and complex atmosphere.

  10. Color superconductivity, ZN flux tubes and monopole confinement in deformed N=2* super Yang-Mills theories

    International Nuclear Information System (INIS)

    Kneipp, Marco A.C.

    2003-11-01

    We study the ZN flux tubes and monopole confinement in deformed N=2* super Yang-Mills theories. In order to do that we consider an N=4 super Yang-Mills theory with an arbitrary gauge group G and add some N=2, N=1 and N=0 deformation terms. We analyze some possible vacuum solutions and phases of the theory, depending on the deformation terms which are added. In the Coulomb phase for the N=2* theory, G is broken to U(1)r and the theory has monopole solutions. Then, by adding some deformation terms, the theory passes to the Higgs or color superconducting phase, in which G is broken to its center CG. In this phase we construct the ZN flux tubes Ansatz and obtain the BPS string tension. We show that the monopole magnetic fluxes are linear integer combinations of the string fluxes and therefore the monopoles can become confined. Then, we obtain a bound for the threshold length of the string-breaking. We also show the possible formation of a confining system with 3 different monopoles for the SU(3) gauge group. Finally we show that the BPS string tensions of the theory satisfy the Casimir scaling law. (author)

  11. Three-dimensional calculations of neutron streaming in the beam tubes of the ORNL HFIR [High Flux Isotope Reactor] Reactor

    International Nuclear Information System (INIS)

    Childs, R.L.; Rhoades, W.A.; Williams, L.R.

    1988-01-01

    The streaming of neutrons through the beam tubes in High Flux Isotope Reactor at Oak Ridge National Laboratory has resulted in a reduction of the fracture toughness of the reactor vessel. As a result, an evaluation of vessel integrity was undertaken in order to determine if the reactor can be operated again. As a part of this evaluation, three-dimensional neutron transport calculations were performed to obtain fluxes at points of interest in the wall of the vessel. By comparing the calculated and measured activation of dosimetry specimens from the vessel surveillance program, it was determined that the calculated flux shape was satisfactory to transpose the surveillance data to the locations in the vessel. A bias factor was applied to correct for the average C/E ratio of 0.69. 8 refs., 7 figs., 3 tabs

  12. Boiling transition and the possibility of spontaneous nucleation under high subcooling and high mass flux density flow in a tube

    International Nuclear Information System (INIS)

    Fukuyama, Y.; Kuriyama, T.; Hirata, M.

    1986-01-01

    Boiling transition and inverted annular heat transfer for R-113 have been investigated experimentally in a horizontal tube of 1.2 X 10/sup -3/ meter inner diameter with heating length over inner diameter ratio of 50. Experiments cover a high mass flux density range, a high local subcooling range and a wide local pressure range. Heat transfer characteristics were obtained by using heat flux control steady-state apparatus. Film boiling treated here is limited to the case of inverted annular heat transfer with very thin vapor film, on the order of 10/sup -6/ meter. Moreover, film boiling region is always limited to a certain downstream part, since the system has a pressure gradient along the flow direction. Discussions are presented on the parametric trends of boiling heat transfer characteristic curves and characteristic points. The possible existence is suggested of a spontaneous nucleation control surface boiling phenomena. And boiling transition heat flux and inverted annular heat transfer were correlated

  13. Measurement of the neutron flux distributions, epithermal index, Westcott thermal neutron flux in the irradiation capsules of hydraulic conveyer (Hyd) and pneumatic tubes (Pn) facilities of the KUR

    International Nuclear Information System (INIS)

    Chatani, Hiroshi

    2001-05-01

    The reactions of Au(n, γ) 198 Au and Ti(n, p) 47 or 48 Sc were used for the measurements of the thermal and epithermal (thermal + epithermal) and the fast neutron flux distributions, respectively. In the case of Hyd (Hydraulic conveyer), the thermal + epithermal and fast neutron flux distributions in the horizontal direction in the capsule are especially flat; the distortion of the fluxes are 0.6% and 5.4%, respectively. However, these neutron fluxes in the vertical direction are low at the top and high at the bottom of the capsule. These differences between the top and bottom are 14% for both distributions. On the other hand, in polyethylene capsules of Pn-1, 2, 3 (Pneumatic tubes Nos. 1, 2, 3), in contrast with Hyd, these neutron flux distributions in the horizontal direction have gradients of 8 - 18% per 2.5 cm diameter, and those on the vertical axis have a distortion of approximately 5%. The strength of the epithermal dE/E component relative to the neutron density including both thermal and epithermal neutrons, i.e., the epithermal index, for the hydraulic conveyer (Hyd) and pneumatic tube No.2 (Pn-2), in which the irradiation experiments can be achieved, are determined by the multiple foil activation method using the reactions of Au(n, γ) 198 Au and Co(n, γ) 60(m+g) Co. The epithermal index observed in an aluminum capsule of Hyd is 0.034-0.04, and the Westcott thermal neutron flux is 1.2x10 14 cm -2 sec -1 at approximately 1 cm above the bottom. The epithermal index in a Pn-2 polyethylene capsule was measured by not only the multiple foil activation method but also the Cd-ratio method in which the Au(n, γ) 198 Au reaction in a cadmium cover is also used. The epithermal index is 0.045 - 0.055, and the thermal neutron flux is 1.8x10 13 cm -2 sec -1 . (J.P.N.)

  14. Critical heat flux of R134A and R245FA in a 2.2 mm circular tube

    Energy Technology Data Exchange (ETDEWEB)

    Tibirica, Cristiano Bigonha; Ribatski, Gherhardt [Universidade de Sao Paulo (EESC/USP), Sao Carlos, SP (Brazil). Escola de Engenharia. Dept. de Engenharia Mecanica], E-mails: bigonha@sc.usp.br, ribatski@sc.usp.br; Szczukiewicz, Sylwia; Thome, John Richard [Ecole Polytechnique Federale de Lausanne (LTCM/EPFL) (Switzerland). Lab. of Heat and Mass Transfer], Emails: sylwia.szczukiewicz@epfl.ch, john.thome@epfl.ch

    2010-07-01

    Critical heat flux (CHF) during flow boiling is generally related to a drastic decrease in the heat transfer coefficient and it is the maximum operational heat flux that can be achieved under safe operation. Due to such a fact, this topic has attracted great attention of the academic society dealing with boiling heat transfer and also in the industrial sector involved with the dissipation of high heat flux densities. In the specific case of high heat flux densities, micro-channel flow boiling is a promising technique for pursuing this objective. The boundary where microscale effects start in flow boiling is still an open issue in the literature and a 3 mm internal diameter (ID) threshold value, as suggested by Kandlikar and Grande (2003) is frequently adopted to characterize this point. Considering the needs for a better understanding of the micro/macro transition, this paper presents new experimental critical heat flux results in saturated flow boiling conditions for a macro/micro-scale tube. The data were obtained in a horizontal 2.20 mm ID stainless steel tube with heating lengths of 361 and 154 mm, R134a and R245fa as working fluids, mass velocities ranging from 100 to 1500 kg/m{sup 2s}, critical heat fluxes from 25 to 300 kW/m2, exit saturation temperatures of 25, 31 and 35 degree C, and critical vapor qualities ranging from 0.55 to 1. The experimental results show that critical heat flux increases with increasing mass velocity and inlet subcooling but decreases with increasing saturation temperature and heated length. The data also indicated a higher CHF for R245fa when compared with R134a at similar conditions. The experimental data were compared against the following CHF predictive methods: Katto and Ohno (1984), Shah (1987), Zhang et al. (2006) and Ong and Thome(2010). Katto and Ohno (1984) and Ong and Thome (2010) best predicted the database with a mean average error smaller than 15%. Both correlations include low and high pressure fluids in their

  15. Critical heat flux of water in vertical round tubes at low-pressure and low-flow conditions

    International Nuclear Information System (INIS)

    Park, Jae-Wook; Kim, Hong-Chae; Beak, Won-Pil; Chang, Soon Heung

    1997-01-01

    A series of critical heat flux (CHF) tests have been performed to provide a reliable set of CHF data for water flow in vertical round tubes at low pressure and low flow (LPLF) conditions. The range of experimental conditions is as follows: diameter 8, 10 mm; heated length 0.5, 1 m; pressure 2-9 bar, mass flux 50-200 kg/m 2 s; inlet subcooling 350, 450 kJ/kg. The observed parametric trends are generally consistent with the previous understanding except for the effects of system pressure and tube diameter. The pressure effect is small but very complicated; existing CHF correlations do not represent this parametric trend properly. CHF increases with the increase in diameter at fixed exit conditions, contrary to the general understanding. The artificial neural networks are applied to the round tube CHF data base at LPLF (P = 110-1100 kPa, G = 0-500 kg/m 2 s) conditions. The trained backpropagation networks (BPNs) predict CHF better than any other CHF correlations. Parametric trends of CHF based on the BPN for fixed inlet conditions generally agree well with our experimental results. (author)

  16. Effect of Magnetic Twist on Nonlinear Transverse Kink Oscillations of Line-tied Magnetic Flux Tubes

    Science.gov (United States)

    Terradas, J.; Magyar, N.; Van Doorsselaere, T.

    2018-01-01

    Magnetic twist is thought to play an important role in many structures of the solar atmosphere. One of the effects of twist is to modify the properties of the eigenmodes of magnetic tubes. In the linear regime standing kink solutions are characterized by a change in polarization of the transverse displacement along the twisted tube. In the nonlinear regime, magnetic twist affects the development of shear instabilities that appear at the tube boundary when it is oscillating laterally. These Kelvin–Helmholtz instabilities (KHI) are produced either by the jump in the azimuthal component of the velocity at the edge of the sharp boundary between the internal and external part of the tube or by the continuous small length scales produced by phase mixing when there is a smooth inhomogeneous layer. In this work the effect of twist is consistently investigated by solving the time-dependent problem including the process of energy transfer to the inhomogeneous layer. It is found that twist always delays the appearance of the shear instability, but for tubes with thin inhomogeneous layers the effect is relatively small for moderate values of twist. On the contrary, for tubes with thick layers, the effect of twist is much stronger. This can have some important implications regarding observations of transverse kink modes and the KHI itself.

  17. Radiant and convective heat transfer for flow of a transparent gas in a short tube with prescribed sinusoidal wall heat flux

    International Nuclear Information System (INIS)

    de Lemos, M.J.S.

    1982-01-01

    The present analysis accounts for radiant and convective heat transfer for a transparent fluid flowing in a short tube with prescribed wall heat flux. The heat flux distribution used was of sine shape with maximum at the middle of the tube. Such a solution is the approximate one for axial power in a nuclear reactor. The solutions for the tube wall and gas bulk temperatures were obtained by successive substitutions for the wall and gas balance energy equations. The results show a decrease of 30% for the maximum wall temperature using black surface (e = 1). In this same case, the increasing in the gas temperature shows a decrease of 58%

  18. Delocalization transition for the Google matrix.

    Science.gov (United States)

    Giraud, Olivier; Georgeot, Bertrand; Shepelyansky, Dima L

    2009-08-01

    We study the localization properties of eigenvectors of the Google matrix, generated both from the world wide web and from the Albert-Barabási model of networks. We establish the emergence of a delocalization phase for the PageRank vector when network parameters are changed. For networks with localized PageRank, eigenvalues of the matrix in the complex plane with a modulus above a certain threshold correspond to localized eigenfunctions while eigenvalues below this threshold are associated with delocalized relaxation modes. We argue that, for networks with delocalized PageRank, the efficiency of information retrieval by Google-type search is strongly affected since the PageRank values have no clear hierarchical structure in this case.

  19. Mechanism of subcooled water flow boiling critical heat flux in a circular tube at high liquid Reynolds number

    International Nuclear Information System (INIS)

    Hata, K.; Fukuda, K.; Masuzaki, S.

    2014-01-01

    The subcooled boiling heat transfer and the steady state critical heat flux (CHF) in a vertical circular tube for the flow velocities (u=3.95 to 30.80 m/s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter (d=6 mm) and heated length (L=59.5 mm) is used in this work. The outer surface temperatures of the SUS304 test tube with heating are observed by an infrared thermal imaging camera and a video camera. The subcooled boiling heat transfers for SUS304 test tube are compared with the values calculated by other workers' correlations for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated into details based on the experimental data. Nucleate boiling surface superheats at the CHF are close to the lower limit of the heterogeneous spontaneous nucleation temperature and the homogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled flow boiling CHF on the SUS304 circular tube is discussed at high liquid Reynolds number. On the other hand, theoretical equations for k-ε turbulence model in a circular tube of a 3 mm in diameter and a 526 mm long are numerically solved for heating of water on heated section of a 3 mm in diameter and a 67 mm long with various thicknesses of conductive sub-layer by using PHOENICS code under the same conditions as the experimental ones previously obtained considering the temperature dependence of thermo-physical properties concerned. The Platinum (Pt) test tube of inner diameter (d=3 mm) and heated length (L=66.5 mm) was used in this experiment. The thicknesses of conductive sub-layer from non-boiling regime to CHF are clarified. The thicknesses of conductive sub-layer at the CHF point are evaluated for various flow velocities. The experimental values of the CHF are also compared with the corresponding

  20. Measurement of mass flux in two-phase flow using combinations of Pitot tubes and gamma densitometers

    International Nuclear Information System (INIS)

    Hau, K.F.F.L.; Banerjee, S.

    1981-01-01

    New experimental data indicate that mass flux in cocurrent gas-liquid flows may be determined by the use of Pitot tubes in conjunction with a local mixture density measurement technique. The data were taken over a wide range of flow regimes in a horizontal pipe and included separated patterns such as stratified and annular flows. Local mixture densities were obtained by a computer-assisted algebraic reconstruction technique that used chordal average densities measured by traversing gamma beam attenuation. The results extend the applicability of this mass flux measurement technique well beyond the relatively homogeneous, high-pressure, steam-water flow situations originally studied by S. Banerjee and D.M. Nguyen. 13 refs

  1. Sunspots and the physics of magnetic flux tubes. VI - Convective propulsion. VII - Heat flow in a convective downdraft

    Science.gov (United States)

    Parker, E. N.

    1979-01-01

    The effect of negative aerodynamic drag in an ideal fluid subject to convective instability is considered. It is shown that a cylinder moving in such a fluid is propelled forward in its motion by the convective forces and that the characteristic acceleration time is comparable to the onset time of convective motions in the fluid. It is suggested that convective propulsion plays an important role in the dynamics of flux tubes extending through the surface of the sun. The suppression of the upward heat flow in a Boussinesq convective cell with free upper and lower boundaries by a downdraft is then analyzed. Application to the solar convection zone indicates that downdrafts of 1 to 2 km/s at depths of 1000 to 4000 km beneath the visible surface of the sun are sufficient to reduce the upward heat flux to a small fraction of the ambient value.

  2. The role of the velocity gradient in laminar convective heat transfer through a tube with a uniform wall heat flux

    International Nuclear Information System (INIS)

    Wang Liangbi; Zhang Qiang; Li Xiaoxia

    2009-01-01

    This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy conservation equation of convective heat transfer is used to explain convective heat transfer there are two points that are difficult for teachers to explain and for undergraduates to understand: thermal diffusivity is placed before the Laplacian operator of temperature; on the wall surface (the fluid side) the velocity is zero, a diffusion equation of temperature is gained from energy conservation equation, however, temperature cannot be transported. Consequently, the real physical meaning of thermal diffusivity is not clearly reflected in the energy conservation equation, and whether heat transfer occurs through a diffusion process or a convection process on the wall surface is not clear. Through a simple convective heat transfer case: laminar convective heat transfer in a tube with a uniform wall heat flux on the tube wall, this paper explains these points more clearly. The results declare that it is easier for teachers to explain and for undergraduates to understand these points when a description of heat transfer in terms of the heat flux is used. In this description, thermal diffusivity is placed before the Laplacian operator of the heat flux; the role of the velocity gradient in convective heat transfer appears, on the wall surface, the fact whether heat transfer occurs through a diffusion process or a convection process can be explained and understood easily. The results are not only essential for teachers to improve the efficiency of university-level physics education regarding heat transfer, but they also enrich the theories for understanding heat transfer

  3. Prediction of strongly-heated gas flows in a vertical tube using explicit algebraic stress/heat-flux models

    International Nuclear Information System (INIS)

    Baek, Seong Gu; Park, Seung O.

    2003-01-01

    This paper provides the assessment of prediction performance of explicit algebraic stress and heat-flux models under conditions of mixed convective gas flows in a strongly-heated vertical tube. Two explicit algebraic stress models and four algebraic heat-flux models are selected for assessment. Eight combinations of explicit algebraic stress and heat-flux models are used in predicting the flows experimentally studied by Shehata and McEligot (IJHMT 41(1998) p.4333) in which property variation was significant. Among the various model combinations, the Wallin and Johansson (JFM 403(2000) p. 89) explicit algebraic stress model-Abe, Kondo, and Nagano (IJHFF 17(1996) p. 228) algebraic heat-flux model combination is found to perform best. We also found that the dimensionless wall distance y + should be calculated based on the local property rather than the property at the wall for property-variation flows. When the buoyancy or the property variation effects are so strong that the flow may relaminarize, the choice of the basic platform two-equation model is a most important factor in improving the predictions

  4. Magnetic Flux Rope Shredding By a Hyperbolic Flux Tube: The Detrimental Effects of Magnetic Topology on Solar Eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Chintzoglou, Georgios [Lockheed Martin Solar and Astrophysics Laboratory, 3176 Porter Drive, Palo Alto, CA 94304 (United States); Vourlidas, Angelos [The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723 (United States); Savcheva, Antonia; Tassev, Svetlin [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Beltran, Samuel Tun; Stenborg, Guillermo, E-mail: gchintzo@lmsal.com [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2017-07-10

    We present the analysis of an unusual failed eruption captured in high cadence and in many wavelengths during the observing campaign in support of the Very high Angular resolution Ultraviolet Telescope ( VAULT2.0 ) sounding rocket launch. The refurbished VAULT2.0 is a Ly α ( λ 1216 Å) spectroheliograph launched on 2014 September 30. The campaign targeted active region NOAA AR 12172 and was closely coordinated with the Hinode and IRIS missions and several ground-based observatories (NSO/IBIS, SOLIS, and BBSO). A filament eruption accompanied by a low-level flaring event (at the GOES C-class level) occurred around the VAULT2.0 launch. No coronal mass ejection was observed. The eruption and its source region, however, were recorded by the campaign instruments in many atmospheric heights ranging from the photosphere to the corona in high cadence and spatial resolution. This is a rare occasion that enabled us to perform a comprehensive investigation on a failed eruption. We find that a rising Magnetic Flux Rope (MFR)-like structure was destroyed during its interaction with the ambient magnetic field, creating downflows of cool plasma and diffuse hot coronal structures reminiscent of “cusps.” We employ magnetofrictional simulations to show that the magnetic topology of the ambient field is responsible for the destruction of the MFR. Our unique observations suggest that the magnetic topology of the corona is a key ingredient for a successful eruption.

  5. Magnetic Flux Rope Shredding By a Hyperbolic Flux Tube: The Detrimental Effects of Magnetic Topology on Solar Eruptions

    International Nuclear Information System (INIS)

    Chintzoglou, Georgios; Vourlidas, Angelos; Savcheva, Antonia; Tassev, Svetlin; Beltran, Samuel Tun; Stenborg, Guillermo

    2017-01-01

    We present the analysis of an unusual failed eruption captured in high cadence and in many wavelengths during the observing campaign in support of the Very high Angular resolution Ultraviolet Telescope ( VAULT2.0 ) sounding rocket launch. The refurbished VAULT2.0 is a Ly α ( λ 1216 Å) spectroheliograph launched on 2014 September 30. The campaign targeted active region NOAA AR 12172 and was closely coordinated with the Hinode and IRIS missions and several ground-based observatories (NSO/IBIS, SOLIS, and BBSO). A filament eruption accompanied by a low-level flaring event (at the GOES C-class level) occurred around the VAULT2.0 launch. No coronal mass ejection was observed. The eruption and its source region, however, were recorded by the campaign instruments in many atmospheric heights ranging from the photosphere to the corona in high cadence and spatial resolution. This is a rare occasion that enabled us to perform a comprehensive investigation on a failed eruption. We find that a rising Magnetic Flux Rope (MFR)-like structure was destroyed during its interaction with the ambient magnetic field, creating downflows of cool plasma and diffuse hot coronal structures reminiscent of “cusps.” We employ magnetofrictional simulations to show that the magnetic topology of the ambient field is responsible for the destruction of the MFR. Our unique observations suggest that the magnetic topology of the corona is a key ingredient for a successful eruption.

  6. Closed flux tubes and their string description in D=3+1 SU(N) gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Athenodorou, Andreas [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Bringoltz, Barak [Washington Univ., Seattle, WA (United States). Dept. of Physics; Teper, Michael [Oxford Univ. (United Kingdom). Centre for Theoretical Physics

    2010-08-15

    We calculate the energy spectrum of a confining flux tube that is closed around a spatial torus, as a function of its length l. We do so for various SU(N) gauge theories in 3+1 dimensions, and for various values of spin, parity and longitudinal momentum. We are able to present usefully accurate results for about 20 of the lightest such states, for a range of l that begins close to the (finite volume) deconfining phase transition at l{radical}{sigma} {proportional_to} 1.6, and extends up to l{radical}{sigma}{proportional_to}6 (where {sigma} is the string tension). We find that most of these low-lying states are well described by the spectrum of the Nambu-Goto free string theory in flat space-time. Remarkably, this is so not only at the larger values of l, where the gap between the ground state energy and the low-lying excitations becomes small compared to the mass gap, but also down to much shorter lengths where these excitation energies become large compared to {radical}{sigma}, the flux-tube no longer 'looks' anything like a thin string, and an expansion of the effective string action in powers of 1/l no longer converges. All this is for flux in the fundamental representation. We also calculate the k=2 (anti)symmetric ground states and these show larger corrections at small l. So far all this closely resembles our earlier findings in 2+1 dimensions. However, and in contrast to the situation in D=2+1, we also find that there are some states, with J{sup P}=0{sup -} quantum numbers, that show large deviations from the Nambu-Goto spectrum. We investigate the possibility that (some of) these states may encode the massive modes associated with the internal structure of the flux tube, and we discuss how the precocious free string behaviour of most states constrains the effective string action, on which much interesting theoretical progress has recently been made. (orig.)

  7. Experimental design and analysis for irradiation of SiC/SiC composite tubes under a prototypic high heat flux

    Science.gov (United States)

    Petrie, Christian M.; Koyanagi, Takaaki; McDuffee, Joel L.; Deck, Christian P.; Katoh, Yutai; Terrani, Kurt A.

    2017-08-01

    The purpose of this work is to design an irradiation vehicle for testing silicon carbide (SiC) fiber-reinforced SiC matrix composite cladding materials under conditions representative of a light water reactor in order to validate thermo-mechanical models of stress states in these materials due to irradiation swelling and differential thermal expansion. The design allows for a constant tube outer surface temperature in the range of 300-350 °C under a representative high heat flux (∼0.66 MW/m2) during one cycle of irradiation in an un-instrumented ;rabbit; capsule in the High Flux Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding tubes, due to irradiation swelling, without changing the thermal resistance of the gap between the cladding and irradiation capsule. Finite-element analyses of the capsule were performed, and the models used to calculate thermal contact resistance were validated by out-of-pile testing and post-irradiation examination of the foils and passive SiC thermometry. Six irradiated cladding tubes (both monoliths and composites) were irradiated and subsequently disassembled in a hot cell. The calculated temperatures of passive SiC thermometry inside the capsules showed good agreement with temperatures measured post-irradiation, with two calculated temperatures falling within 10 °C of experimental measurements. The success of this design could lead to new opportunities for irradiation applications with materials that suffer from irradiation swelling, creep, or other dimensional changes that can affect the specimen temperature during irradiation.

  8. Experimental design and analysis for irradiation of SiC/SiC composite tubes under a prototypic high heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Petrie, Christian M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Koyanagi, Takaaki [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McDuffee, Joel L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Deck, Christian P. [General Atomics, San Diego, CA (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Terrani, Kurt A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-04

    The purpose of this work is to design an irradiation vehicle for testing silicon carbide (SiC) fiber-reinforced SiC matrix composite cladding materials under conditions representative of a light water reactor in order to validate thermo-mechanical models of stress states in these materials due to irradiation swelling and differential thermal expansion. The design allows for a constant tube outer surface temperature in the range of 300–350 °C under a representative high heat flux (~0.66 MW/m2) during one cycle of irradiation in an un-instrumented “rabbit” capsule in the High Flux Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding tubes, due to irradiation swelling, without changing the thermal resistance of the gap between the cladding and irradiation capsule. Finite-element analyses of the capsule were performed, and the models used to calculate thermal contact resistance were validated by out-of-pile testing and post-irradiation examination of the foils and passive SiC thermometry. Six irradiated cladding tubes (both monoliths and composites) were irradiated and subsequently disassembled in a hot cell. The calculated temperatures of passive SiC thermometry inside the capsules showed good agreement with temperatures measured post-irradiation, with two calculated temperatures falling within 10 °C of experimental measurements. Furthermore, the success of this design could lead to new opportunities for irradiation applications with materials that suffer from irradiation swelling, creep, or other dimensional changes that can affect the specimen temperature during irradiation.

  9. Thermohydraulics in rod bundles and critical heat flux in transient conditions in a tube

    International Nuclear Information System (INIS)

    Courtaud, M.; Roumy, R.

    1975-01-01

    After the determination of the scaling factor of Stevens's similitude for the pressure range of pressurized water vectors by comparison of critical heat flux data in from and in water, some examples of studies performed with freon are shown. The efficiency of the mixing vanes of spacer grids has been determined on the mixing phenomenon in single phase on critical heat flux. A calculation performed with the code FLICA using subchannel analysis on freon data transposed in water is in good agreement with the experiment. The influence of the number of spacer grids has been also shown. Critical heat fluxes have been determined in water at 140 bar in steady state and transient conditions on two tubular test sections. During the transient tests the flow rate was reduced by half in 0.5 seconds and the reincreased heat flux and inlet temperature remaining constant. These tests have shown the validity of the method which consists in using a critical heat flux correlation determined in steady state conditions applied with local transient conditions of enthalpy and mass velocity computed with the FLICA code [fr

  10. Thermodynamic optimization of a coiled tube heat exchanger under constant wall heat flux condition

    International Nuclear Information System (INIS)

    Satapathy, Ashok K.

    2009-01-01

    In this paper the second law analysis of thermodynamic irreversibilities in a coiled tube heat exchanger has been carried out for both laminar and turbulent flow conditions. The expression for the scaled non-dimensional entropy generation rate for such a system is derived in terms of four dimensionless parameters: Prandtl number, heat exchanger duty parameter, Dean number and coil to tube diameter ratio. It has been observed that for a particular value of Prandtl number, Dean number and duty parameter, there exists an optimum diameter ratio where the entropy generation rate is minimum. It is also found that with increase in Dean number or Reynolds number, the optimum value of the diameter ratio decreases for a particular value of Prandtl number and heat exchanger duty parameter.

  11. Why fast solar wind originates from slowly expanding coronal flux tubes

    International Nuclear Information System (INIS)

    Wang, Y.M.; Sheeley, N.R. Jr.

    1991-01-01

    Empirical studies indicate that the solar wind speed at earth is inversely correlated with the divergence rate of the coronal magnetic field. It is shown that this result is consistent with simple wind acceleration models involving Alfven waves, provided that the wave energy flux at the coronal base is taken to be roughly constant within open field regions. 9 refs

  12. Critical heat flux of water in vertical tubes with an upper plenum and a closed bottom

    International Nuclear Information System (INIS)

    Kim, Hong Chae; Baek, Won Pil; Chang, Soon Heung

    2000-01-01

    An experimental study is conducted for vertical round tubes with an upper plenum and a closed bottom to investigate CHF behavior and CHF onset location under the counter-current condition. The measured CHF values are well predicted by general Wallis type flooding correlations. A 1-D steady state analytical flooding model for thermosyphon by El-Genk and Saber was assessed with the data and the liquid film thickness at the liquid entrance was calculated. The CHF onset position becomes different with L/D and D, and liquid entrance geometry affects only CHF values not CHF onset positions

  13. Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube

    Energy Technology Data Exchange (ETDEWEB)

    Nigmatulin, R.I.

    1995-09-01

    The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered.

  14. Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube

    International Nuclear Information System (INIS)

    Nigmatulin, R.I.

    1995-01-01

    The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered

  15. An investigation of critical heat fluxes in vertical tubes internally cooled by Freon-12. Part I - Critical heat flux experiments with axially uniform and non-uniform heating and comparisons of data with selected correlations

    International Nuclear Information System (INIS)

    Green, W.J.; Stevens, J.R.

    1981-08-01

    Experiments have been performed using vertical heated tubes, cooled internally by Freon-12, to determine critical heat fluxes (CHFs) for both a uniformly heated section and an exit region with a separately controlled power supply. Heated lengths of the main separately were 2870 mm (8.48 and 16.76 mm tube bores) and 3700 mm (for 21.34 mm tube bore); heated length of the exit section was 230 mm. Coolant pressures, exit qualities and mass fluxes were in the range 0.9 to 1.3 MPa, 0.19 to 0.86, and 380 to 2800 kg m -2 s -1 , respectively. The data have been compared with published empirical correlations specifically formulated to predict CHFs in Freon-cooled, vertical tubes; relevant published CHF data have also been compared with these correlations. These comparisons show that, even over the ranges of conditions for which the correlations were developed, predicted values are only accurate to within +-20 per cent. Moreover, as mass fluxes increase above 3500 kg m -2 s -1 , the modified Groeneveld correlation becomes increasingly inadequate, and the Bertoletti and modified Bertoletti correlations under-predict CHF values by increasing amounts. At mass fluxes below 750 kg m -2 s -1 the Bertoletti correlations exhibit increasing inaccuracy with a decrease in mass flux. For non-uniform heating, the correlations are at variance with the experimental data

  16. Closed flux tubes and their string description in D=2+1 SU(N) gauge theories

    International Nuclear Information System (INIS)

    Athenodorou, Andreas; Bringoltz, Barak; Teper, Michael

    2011-08-01

    We carry out lattice calculations of the spectrum of confining flux tubes that wind around a spatial torus of variable length l, in 2+1 dimensions. We compare the energies of the lowest ∝30 states to the free string Nambu-Goto model and to recent results on the universal properties of effective string actions. Our most useful calculations are in SU(6) at a small lattice spacing, which we check is very close to the N→ ∞ continuum limit. We find that the energies, E n (l), are remarkably close to the predictions of the free string Nambu-Goto model, even well below the critical length at which the expansion of the Nambu-Goto energy in powers of 1/l 2 diverges and the series needs to be resummed. Our analysis of the ground state supports the universality of the O(1/l) and the O(1/l 3 ) corrections to σl, and we find that the deviations from Nambu-Goto at small l prefer a leading correction that is O(1/l 7 ), consistent with theoretical expectations. We find that the low-lying states that contain a single phonon excitation are also consistent with the leading O(1/l 7 ) correction dominating down to the smallest values of l. By contrast our analysis of the other light excited states clearly shows that for these states the corrections at smaller l resum to a much smaller effective power. Finally, and in contrast to our recent calculations in D=3+1, we find no evidence for the presence of any non-stringy states that could indicate the excitation of massive flux tube modes. (orig.)

  17. Closed flux tubes and their string description in D=2+1 SU(N) gauge theories

    Energy Technology Data Exchange (ETDEWEB)

    Athenodorou, Andreas [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Bringoltz, Barak [The Israeli Institute for Advanced Research (IIAR), Rehovot (Israel); Teper, Michael [Oxford Univ. (United Kingdom). Rudolf Peierls Centre for Theoretical Physics

    2011-08-15

    We carry out lattice calculations of the spectrum of confining flux tubes that wind around a spatial torus of variable length l, in 2+1 dimensions. We compare the energies of the lowest {proportional_to}30 states to the free string Nambu-Goto model and to recent results on the universal properties of effective string actions. Our most useful calculations are in SU(6) at a small lattice spacing, which we check is very close to the N{yields} {infinity} continuum limit. We find that the energies, E{sub n}(l), are remarkably close to the predictions of the free string Nambu-Goto model, even well below the critical length at which the expansion of the Nambu-Goto energy in powers of 1/l{sup 2} diverges and the series needs to be resummed. Our analysis of the ground state supports the universality of the O(1/l) and the O(1/l{sup 3}) corrections to {sigma}l, and we find that the deviations from Nambu-Goto at small l prefer a leading correction that is O(1/l{sup 7}), consistent with theoretical expectations. We find that the low-lying states that contain a single phonon excitation are also consistent with the leading O(1/l{sup 7}) correction dominating down to the smallest values of l. By contrast our analysis of the other light excited states clearly shows that for these states the corrections at smaller l resum to a much smaller effective power. Finally, and in contrast to our recent calculations in D=3+1, we find no evidence for the presence of any non-stringy states that could indicate the excitation of massive flux tube modes. (orig.)

  18. [Delocalizing the mind. Peirce, James, Wittgenstein, Descombes].

    Science.gov (United States)

    Chauviré, Christiane

    2010-01-01

    The cognitive sciences have breathed fresh air into the old problem of localizing mental functions, which was often laughed off. Regarding the most philosophical form of the question on the localization of the mind, authors such as Peirce, James, Wittgenstein, and most recently Descombes have imagined delocalizing the mind in order to spread the conviction that the idea itself of a location of the mental is meaningless and to criticize the localisationism of today's cognitive scientists.

  19. Critical heat flux in bottom heated two-phase thermosyphon. Improvement in critical heat flux due to concentric tube; Katan shuchu kanetsugata niso netsu syphon no genkai netsu ryusoku. Nijukan ni yoru genkai netsu ryusoku no kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Monde, M.; Mitsutake, Y. [Saga University, Saga (Japan). Faculty of Science and Engineering

    2000-02-25

    An experiment has been carried out to elucidate the critical heat flux (CHF) of an open two-phase thermosyphon with a bottom heated chamber in which heat is absorbed by evaporation of liquid. Another objective is to enhance the CHF using a concentric-tube by which counter-current flow of vapor and liquid in the throat of the chamber can be controlled well. The CHF data are measured for the saturated liquid of R 113 at a different pressure and different configuration of concentric tubes. The CHF data without the inner tube are in good agreement with the existing correlation and analytical result. The CHF increases by as much as several times of the CHF without the inner tube with an increase in the inner tube diameter up to a certain diameter of the inner tube and then decreases continuously as the inner tube diameter approaches the outer tube diameter. The optimum diameter of inner tube exists at which the CHF is maximum. (author)

  20. High-energy x-ray detection of G359.89–0.08 (SGR A–E): magnetic flux tube emission powered by cosmic rays?

    DEFF Research Database (Denmark)

    Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.

    2014-01-01

    of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A–E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps Te...

  1. Heat transfer to sub- and supercritical water flowing upward in a vertical tube at low mass fluxes: numerical analysis and experimental validation

    NARCIS (Netherlands)

    Odu, Samuel Obarinu; Koster, P.; van der Ham, Aloysius G.J.; van der Hoef, Martin Anton; Kersten, Sascha R.A.

    2016-01-01

    Heat transfer to supercritical water (SCW) flowing upward in a vertical heated tube at low mass fluxes (G ≤ 20 kg/m2 s) has been numerically investigated in COMSOL Multiphysics and validated with experimental data. The turbulence models, essential to describing local turbulence, in COMSOL have been

  2. Electron delocalization in α-nitrogen

    International Nuclear Information System (INIS)

    Storchak, V.; Brewer, J.H.; Morris, G.D.; British Columbia Univ., Vancouver, BC

    1995-06-01

    A new technique has been developed for measuring electron drift mobility in crystals on a microscopic scale through its effect on muonium (Mu = μ + + e - ) atom formation via transport of electrons to thermalized positive muons (μ + ). Electron transport mechanisms are shown to be fundamentally different in the α and β phases of solid nitrogen, giving of about 5 orders of magnitude difference in electron mobilities. Contrary to previously reported results of macroscopic time-of-flight measurements, excess electrons appear to be delocalized in α-N 2 . (author). 22 refs., 3 figs

  3. Effects of Oxidation and fractal surface roughness on the wettability and critical heat flux of glass-peened zirconium alloy tubes

    International Nuclear Information System (INIS)

    Fong, R.W.L.; Nitheanandan, T.; Bullock, C.D.; Slater, L.F.; McRae, G.A.

    2003-05-01

    Glass-bead peening the outside surfaces of zirconium alloy tubes has been shown to increase the Critical Heat Flux (CHF) in pool boiling of water. The CHF is found to correlate with the fractal roughness of the metal tube surfaces. In this study on the effect of oxidation on glass-peened surfaces, test measurements for CHF, surface wettability and roughness have been evaluated using various glass-peened and oxidized zirconium alloy tubes. The results show that oxidation changes the solid-liquid contact angle (i.e., decreases wettability of the metal-oxide surface), but does not change the fractal surface roughness, appreciably. Thus, oxidation of the glass-peened surfaces of zirconium alloy tubes is not expected to degrade the CHF enhancement obtained by glass-bead peening. (author)

  4. Flux

    DEFF Research Database (Denmark)

    Ravn, Ib

    . FLUX betegner en flyden eller strømmen, dvs. dynamik. Forstår man livet som proces og udvikling i stedet for som ting og mekanik, får man et andet billede af det gode liv end det, som den velkendte vestlige mekanicisme lægger op til. Dynamisk forstået indebærer det gode liv den bedst mulige...... kanalisering af den flux eller energi, der strømmer igennem os og giver sig til kende i vore daglige aktiviteter. Skal vores tanker, handlinger, arbejde, samvær og politiske liv organiseres efter stramme og faste regelsæt, uden slinger i valsen? Eller skal de tværtimod forløbe ganske uhindret af regler og bånd...

  5. Does chaos assist localization or delocalization?

    Science.gov (United States)

    Tan, Jintao; Lu, Gengbiao; Luo, Yunrong; Hai, Wenhua

    2014-12-01

    We aim at a long-standing contradiction between chaos-assisted tunneling and chaos-related localization study quantum transport of a single particle held in an amplitude-modulated and tilted optical lattice. We find some near-resonant regions crossing chaotic and regular regions in the parameter space, and demonstrate that chaos can heighten velocity of delocalization in the chaos-resonance overlapping regions, while chaos may aid localization in the other chaotic regions. The degree of localization enhances with increasing the distance between parameter points and near-resonant regions. The results could be useful for experimentally manipulating chaos-assisted transport of single particles in optical or solid-state lattices.

  6. Adaptation of a Freon-12 critical heat flux correlation to correlate water data from uniformly heated vertical tubes. Part I: Based on critical heat flux data for water at pressures of 3 to 14 MPa

    International Nuclear Information System (INIS)

    Green, W.J.

    1981-12-01

    Comparisons have been made between experimental critical heat flux (CHF) data for upflow of water in uniformly heated vertical tubes and values calculated from an empirical CHF correlation developed from Freon-12 data. When this correlation is re-evaluated to account for vapour Prandtl number effects, very good agreement is obtained between experimental data and calculated values over a wide range of coolant conditions. Comparison of values calculated from the revised correlation with 2063 sets of CHF data obtained from experiments with water in vertical, uniformly heated tubes shows a mean ratio of the calculated to experimental CHF of 0.82 and an r.m.s. error of 5.8 per cent for the following coolant conditions: (1) local pressure of 3.4 to 12 MPa; (2) mass flux greater than approx. 300 kg s -1 m -2 , and (3) thermal equilibrium value of exit quality greater than 0.1

  7. Measurement of mass flux in high temperature high pressure steam-water two-phase flow using a combination of Pitot tubes and a gamma densitometer

    International Nuclear Information System (INIS)

    Chan, A.M.C.; Bzovey, D.

    1990-01-01

    The design and calibration of a two-phase mass-flux measurement device making use of a Pitot-tube rake and a gamma densitometer are described. Five Pitot tubes and three chordal void-fraction measurements are used. Similar devices have been reported previously. The present device is designed for easy operation and simple data interpretation for both axisymmetric and non-axisymmetric flows under high pressure transient two-phase flow conditions. The device was calibrated using a vertical two-phase flow loop as well as a model-scale pump loop in horizontal orientation. Good agreement between the measured two-phase mass fluxes and the single-phase values was obtained in both cases. (orig.)

  8. Inverted V's and/or discrete arcs: a three-dimensional phenomenon at boundaries between magnetic flux tubes

    International Nuclear Information System (INIS)

    Atkinson, G.

    1982-01-01

    If discrete arcs and inverted V's are associated with current sheets and the U shaped electric potential structure, then existing two-dimensional models are probably inadequate. The rapid east-west electric-field associated flow in the arms of the U shaped potential structure requires that there must be a substantial inflow to the outflow from each arm somewhere along the system since arcs and inverted V's have a limited east-west extent. Thus strong north-south polarization currents occur as the plasma enters and leaves the arms of the U. It is hypothesized that these currents, determine the north-south thickness. Three representative three-dimensional models are considered in which the current sheets are either tangential or rotational discontinuities modified by the U shaped potential structure. Thicknesses of the order of a few tens of kilometers are obtained. The occurence and type of discontinuity expected at various locations in the magnetosphere are considered. Discontinuities and hence inverted V's and/or arcs are expected at the interface between open and closed field lines, which explains quiet time polar cap sun-aligned arcs, and at interfaces between plasmas which have merged or been injected on the dayside or reconnected on the nightside in different impulsive events. The last two account for arcs occurring near the throat at active times and for parallel arcs within the oval. The occurrence of long parallel arcs within the oval is encouraged by the convective flow pattern and by the differences in precipitation from flux tubes with differential histories

  9. Experimental study of heat exchange coefficients, critical heat flux and charge losses, using water-steam mixtures in turbulent flow in a vertical tube

    International Nuclear Information System (INIS)

    Perroud, P.; De La Harpe, A.; Rebiere, J.

    1960-12-01

    Two stainless steel tubes were used (with diameters of 5 and 10 mm, lengths 400 and 600 mm respectively), heated electrically (50 Hz). The mixture flows from top to bottom. The work was carried out mainly on mixtures of high concentration (x > 0.1), at pressures between 50 and 60 kg/cm 2 , flowing as a liquid film on the walls of the tube with droplets suspended in the central current of steam. By analysis of the heat transfer laws the exchange mechanisms were established, and the conditions under which the critical heat flux may be exceeded without danger of actual burnout were determined. In this way high output concentrations (x s > 0.9) may be obtained. An attempt has been made to find out to what extent existing correlation formulae can be used to account for the phenomena observed. It is shown that those dealing with exchange coefficients can only be applied in a first approximation in cases where exchange by convection is preponderant, and only below the critical flux. The formulae proposed by WAPD and CISE do not give a satisfactory estimation of the critical heat flux, and the essential reasons for this inadequacy are explained. Lastly, the Martinelli and Nelson method may be used to an approximation of 30 per cent for the calculation of charge losses. (author) [fr

  10. Combination of helical ferritic-steel inserts and flux-tube-expansion divertor for the heat control in tokamak DEMO reactor

    International Nuclear Information System (INIS)

    Takizuka, T.; Tokunaga, S.; Hoshino, K.; Shimizu, K.; Asakura, N.

    2015-01-01

    Edge localized modes (ELMs) in the H-mode operation of tokamak reactors may be suppressed/mitigated by the resonant magnetic perturbation (RMP), but RMP coils are considered incompatible with DEMO reactors under the strong neutron flux. We propose an innovative concept of the RMP without installing coils but inserting ferritic steels of the helical configuration. Helically perturbed field is naturally formed in the axisymmetric toroidal field through the helical ferritic steel inserts (FSIs). When ELMs are avoided, large stationary heat load on divertor plates can be reduced by adopting a flux-tube-expansion (FTE) divertor like an X divertor. Separatrix shape and divertor-plate inclination are similar to those of a simple long-leg divertor configuration. Combination of the helical FSIs and the FTE divertor is a suitable method for the heat control to avoid transient ELM heat pulse and to reduce stationary divertor heat load in a tokamak DEMO reactor

  11. Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold

    Energy Technology Data Exchange (ETDEWEB)

    Peeters, A. G.; Rath, F.; Buchholz, R.; Grosshauser, S. R.; Strintzi, D.; Weikl, A. [Physics Department, University of Bayreuth, Universitätsstrasse 30, Bayreuth (Germany); Camenen, Y. [Aix Marseille Univ, CNRS, PIIM, UMR 7345, Marseille (France); Candy, J. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States); Casson, F. J. [CCFE, Culham Science Centre, Abingdon OX14 3DB, Oxon (United Kingdom); Hornsby, W. A. [Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2 85748 Garching (Germany)

    2016-08-15

    It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transport is mediated by avalanche structures which propagate through the marginally stable regions.

  12. Propagation of Torsional Alfvén Waves from the Photosphere to the Corona: Reflection, Transmission, and Heating in Expanding Flux Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Ballester, José Luis, E-mail: roberto.soler@uib.es [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2017-05-01

    It has been proposed that Alfvén waves play an important role in the energy propagation through the solar atmospheric plasma and its heating. Here we theoretically investigate the propagation of torsional Alfvén waves in magnetic flux tubes expanding from the photosphere up to the low corona and explore the reflection, transmission, and dissipation of wave energy. We use a realistic variation of the plasma properties and the magnetic field strength with height. Dissipation by ion–neutral collisions in the chromosphere is included using a multifluid partially ionized plasma model. Considering the stationary state, we assume that the waves are driven below the photosphere and propagate to the corona, while they are partially reflected and damped in the chromosphere and transition region. The results reveal the existence of three different propagation regimes depending on the wave frequency: low frequencies are reflected back to the photosphere, intermediate frequencies are transmitted to the corona, and high frequencies are completely damped in the chromosphere. The frequency of maximum transmissivity depends on the magnetic field expansion rate and the atmospheric model, but is typically in the range of 0.04–0.3 Hz. Magnetic field expansion favors the transmission of waves to the corona and lowers the reflectivity of the chromosphere and transition region compared to the case with a straight field. As a consequence, the chromospheric heating due to ion–neutral dissipation systematically decreases when the expansion rate of the magnetic flux tube increases.

  13. An intermetallic powder-in-tube approach to increased flux-pinning in Nb3Sn by internal oxidation of Zr

    Science.gov (United States)

    Motowidlo, L. R.; Lee, P. J.; Tarantini, C.; Balachandran, S.; Ghosh, A. K.; Larbalestier, D. C.

    2018-01-01

    We report on the development of multifilamentary Nb3Sn superconductors by a versatile powder-in-tube technique (PIT) that demonstrates a simple pathway to a strand with a higher density of flux-pinning sites that has the potential to increase critical current density beyond present levels. The approach uses internal oxidation of Zr-alloyed Nb tubes to produce Zr oxide particles within the Nb3Sn layer that act as a dispersion of artificial pinning centres (APCs). In this design, SnO2 powder is mixed with Cu5Sn4 powder within the PIT core that supplies the Sn for the A15 reaction with Nb1Zr filament tubes. Initial results show an average grain size of ˜38 nm in the A15 layer, compared to the 90-130 nm of typical APC-free high-J c strands made by conventional PIT or Internal Sn processing. There is a shift in the peak of the pinning force curve from H/H irr of ˜0.2 to ˜0.3 and the pinning force curves can be deconvoluted into grain boundary and point-pinning components, the point-pinning contribution dominating for the APC Nb-1wt%Zr strands.

  14. AN EXPERIMENTAL STUDY FOR HEAT TRANSFER ENHANCEMENT BY LAMINAR FORCED CONVECTION FROM HORIZONTAL AND INCLINED TUBE HEATED WITH CONSTANT HEAT FLUX, USING TWO TYPES OF POROUS MEDIA

    Directory of Open Access Journals (Sweden)

    Thamir K. Jassem

    2015-02-01

    Full Text Available An experimental forced laminar study was presented in this research for an air flowing through a circular channel for different angles ( ,30o,45o,60o, the channel was heated at constant heat flux , the channel also was packed with steel and glass spheres respectively . The tests were done for three values of Peclets number (2111.71,3945.42,4575.47 with changing the heat flux for each case and five times for each number.The results showed that the dimensionless temperature distribution  will decrease with increasing the dimensionless channel length for all cases with changing Peclet number, heat flux and inclination angles, and its lowest value will be for glass spheres at highest flux, while at lower flux for , and the decreasing in dimensionless temperature was closed for both types of packed at other inclination angles.The study declared that the local Nusselt number decreases with increasing the dimensionless length of the channel for both packeds and for different applied heat flux, also through this study it was declared that the average Nusselt increases as Peclet number increases for both packed. Its value for the glass spheres is greater than the steel spheres with percentage (98.3% at small Peclet, and percentage (97.2% at large Peclet number for the horizontal tube, and (98.3% at small Peclet number and (97.8% at large Peclet number at  .Through this study its was found that average Nusselt number increases along the channel as the heat flux increases, because the bulk temperature will increase as the flow proceeds toward the end of the channel , so the heat transfer coefficient will increase.  It was declared from this study that in the case of the steel packed the heat transfer will occur mainly by conduction, while in the case of glass packed the heat transfer will occur mainly by laminar forced convection, where the lowest Nusselt number (Nu=3.8 was found when the pipe is horizontal and lowest heat flux and lowest Peclet number.  

  15. A Comparison between a Minijet Model and a Glasma Flux Tube Model for Central Au-Au Collisions at √(ovr sNN)=200 GeV

    International Nuclear Information System (INIS)

    Longacre, R.S.

    2011-01-01

    In this paper we compare two models with central Au-Au collisions at √(ovr s NN )=200 GeV. The first model is a minijet model which assumes that around ∼50 minijets are produced in back-to-back pairs and have an altered fragmentation functions. It is also assumed that the fragments are transparent and escape the collision zone and are detected. The second model is a glasma flux tube model which leads to flux tubes on the surface of a radial expanding fireball driven by interacting flux tubes near the center of the fireball through plasma instabilities. This internal fireball becomes an opaque hydro fluid which pushes the surface flux tubes outward. Around ∼12 surface flux tubes remain and fragment with ∼1/2 the produced particles escaping the collision zone and are detected. Both models can reproduce two particle angular correlations in the different p t1 p t2 bins. We also compare the two models for three additional effects: meson baryon ratios; the long range nearside correlation called the ridge; and the so-called mach cone effect when applied to three particle angular correlations.

  16. The Funnel Geometry of Open Flux Tubes in the Low Solar Corona Constrained by O VI and Ne VIII Outflow

    Science.gov (United States)

    Byhring, Hanne S.; Esser, Ruth; Lie-Svendsen, Oystein

    2008-01-01

    Model calculations show that observed outflow velocities of order 7-10 km/s of C IV and O VI ions, and 15-20 km/s of Ne VIII ions, are not only consistent with models of the solar wind from coronas holes, but also place unique constraints on the degree of flow tube expansion as well as the location of the expansion in the transition region/lower corona.

  17. The Role of the Velocity Gradient in Laminar Convective Heat Transfer through a Tube with a Uniform Wall Heat Flux

    Science.gov (United States)

    Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia

    2009-01-01

    This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…

  18. Spin delocalization phase transition in a correlated electrons model

    International Nuclear Information System (INIS)

    Huerta, L.

    1990-11-01

    In a simplified one-site model for correlated electrons systems we show the existence of a phase transition corresponding to spin delocalization. The system becomes a solvable model and zero-dimensional functional techniques are used. (author). 7 refs, 3 figs

  19. Evaluation of subcooled critical heat flux correlations using the PU-BTPFL CHF database for vertical upflow of water in a uniformly heated round tube

    International Nuclear Information System (INIS)

    Hall, D.D.; Mudawar, I.

    1997-01-01

    A simple methodology for assessing the predictive ability of critical heat flux (CHF) correlations applicable to subcooled flow boiling in a uniformly heated vertical tube is developed. Popular correlations published in handbooks and review articles as well as the most recent correlations are analyzed with the PU-BTPFL CHF database, which contains 29,718 CHF data points. This database is the largest collection of CHF data (vertical upflow of water in a uniformly heated round tube) ever cited in the world literature. The parametric ranges of the CHF database are diameters from 0.3 to 45 mm, length-to-diameter ratios from 2 to 2484, mass velocities from 0.01 x 10 3 to 138 x 10 3 kg/m 2 ·s, pressures from 1 to 223 bars, inlet subcoolings from 0 to 347 C, inlet qualities from -2.63 to 0.00, outlet subcoolings from 0 to 305 C, outlet qualities from -2.13 to 1.00, and CHFs from 0.05 x 10 6 to 276 x 10 6 W/m 2 . The database contains 4,357 data points having a subcooled outlet condition at CHF. A correlation published elsewhere is the most accurate in both low- and high-mass velocity regions, having been developed with a larger database than most correlations. In general, CHF correlations developed from data covering a limited range of flow conditions cannot be extended to other flow conditions without much uncertainty

  20. Heating and reconnection of the emerging magnetic flux-tubes and the role of the interchange instability

    International Nuclear Information System (INIS)

    Uchida, Y.; Sakurai, T.

    1977-01-01

    In this paper it is proposed that the basic behaviors of newly-emerged magnetic regions (NEMR) as seen in EUV and soft X-rays from space are interpreted by the interchange instability of the magnetic field of NEMR in the global situation surrounding it. It is shown that the situation with the NEMR is unstable against the interchange instability, and a continual relaxation to the lower energy state, or a continual invasion of the magnetic flux of the NEMR to the ambient region in the form of fine bundles or thin sheets, will take place in a short time scale of tau 1 approximately L/Vsub(A) following the change in the boundary condition at the photosphere. The second and the final relaxation is shown to be the enhanced Joule dissipation in a time scale of hours to several days occurring in the thin current sheets on the interface of this intermingled structure which is distributed in a large volume. This hypothesis may provide an explanation for the heating of NEMR to an X-ray emitting temperature, which is otherwise rather difficult to explain. The observed fast reconnection without appreciable flares (except for some smaller brightenings) is another aspect which can be explained in the present hypothesis. Namely, since the situation with the NEMR is unstable for the interchange from the beginning, the stressed configuration is relaxed before storing appreciable energy in the form of magnetic stress and therefore without a drastic release of a large amount of stored stress energy in the form of a flare. (Auth.)

  1. Experimental study of heat exchange coefficients, critical heat flux and charge losses, using water-steam mixtures in turbulent flow in a vertical tube; Etude experimentale des coefficients d'echanges thermiques, des flux de chaleur critiques et des pertes de charge avec des melanges eau-vapeur en ecoulement turbulent dans un tube vertical

    Energy Technology Data Exchange (ETDEWEB)

    Perroud, P; De La Harpe, A; Rebiere, J [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1960-12-15

    Two stainless steel tubes were used (with diameters of 5 and 10 mm, lengths 400 and 600 mm respectively), heated electrically (50 Hz). The mixture flows from top to bottom. The work was carried out mainly on mixtures of high concentration (x > 0.1), at pressures between 50 and 60 kg/cm{sup 2}, flowing as a liquid film on the walls of the tube with droplets suspended in the central current of steam. By analysis of the heat transfer laws the exchange mechanisms were established, and the conditions under which the critical heat flux may be exceeded without danger of actual burnout were determined. In this way high output concentrations (x{sub s} > 0.9) may be obtained. An attempt has been made to find out to what extent existing correlation formulae can be used to account for the phenomena observed. It is shown that those dealing with exchange coefficients can only be applied in a first approximation in cases where exchange by convection is preponderant, and only below the critical flux. The formulae proposed by WAPD and CISE do not give a satisfactory estimation of the critical heat flux, and the essential reasons for this inadequacy are explained. Lastly, the Martinelli and Nelson method may be used to an approximation of 30 per cent for the calculation of charge losses. (author) [French] On a utilise deux tubes en acier inox (avec des diametres de 5 et 10 mm, et des longueurs respectives 400 et 600 mm) chauffes electriquement (50 Hz). Le melange s'ecoule de haut en bas. Les etudes ont porte plus specialement sur des melanges de titres eleves (x > 0,1) a des pressions comprises entre 60 et 90 kg/cm{sup 2} dont l'ecoulement se fait avec film liquide annulaire et gouttelettes en suspension dans le coeur de vapeur. Par l'analyse des lois de transfert de chaleur, on a precise les mecanismes d'echanges et l'on a d'autre part determine dans quelles conditions le flux de chaleur critique peut etre depasse sans danger de 'burnout' proprement dit. On peut ainsi obtenir des

  2. Delocalized Claudin-1 promotes metastasis of human osteosarcoma cells

    Energy Technology Data Exchange (ETDEWEB)

    Jian, Yuekui; Chen, Changqiong; Li, Bo; Tian, Xiaobin, E-mail: drtxb_guiyang@sina.com

    2015-10-23

    Tight junction proteins (TJPs) including Claudins, Occludin and tight junction associated protein Zonula occludens-1 (ZO-1), are the most apical component of junctional complex that mediates cell–cell adhesion in epithelial and endothelial cells. In human malignancies, TJPs are often deregulated and affect cellular behaviors of tumor cells. In this study, we investigated alternations of TJPs and related biological characteristics in human osteosarcoma (OS). Claudin1 was increased in the metastatic OS cells (KRIB and KHOS) compared with the normal osteoblast cells (hFOB1.19) or primary tumor cells (HOS and U2OS), whereas no significant difference was found in Occludin and ZO-1. Immunohistochemistry, immunofluorescence and Western blotting revealed that Claudin1 was initially localized at cell junctions of normal osteoblasts, but substantially delocalized to the nucleus of metastatic OS cells. Phenotypically, inhibition of the nucleus Claudin1 expression compromised the metastatic potential of KRIB and KHOS cells. Moreover, we found that protein kinase C (PKC) but not PKA phosphorylation influenced Claudin1 expression and cellular functions, as PKC inhibitor (Go 6983 and Staurosporine) or genetic silencing of PKC reduced Claudin1 expression and decreased the motility of KRIB and KHOS cells. Taken together, our study implied that delocalization of claudin-1 induced by PKC phosphorylation contributes to metastatic capacity of OS cells. - Highlights: • Claudin1 is increased during the malignant transformation of human OS. • Delocalization of Claudin1 in metastatic OS cells. • Silencing nuclear Claudin1 expression inhibits cell invasion of OS. • Deregulated Claudin1 is regulated by PKC.

  3. Exciton localization-delocalization transition in an extended dendrimer

    Energy Technology Data Exchange (ETDEWEB)

    Pouthier, Vincent, E-mail: vincent.pouthier@univ-fcomte.fr [Institut UTINAM, Université de Franche-Comté, CNRS UMR 6213, 25030 Besançon Cedex (France)

    2013-12-21

    Exciton-mediated quantum state transfer between the periphery and the core of an extended dendrimer is investigated numerically. By mapping the dynamics onto that of a linear chain, it is shown that a localization-delocalization transition arises for a critical value of the generation number G{sub c} ≈ 5. This transition originates in the quantum interferences experienced by the excitonic wave due to the multiple scatterings that arise each time the wave tunnels from one generation to another. These results suggest that only small-size dendrimers could be used for designing an efficient quantum communication protocol.

  4. Exciton localization-delocalization transition in an extended dendrimer

    International Nuclear Information System (INIS)

    Pouthier, Vincent

    2013-01-01

    Exciton-mediated quantum state transfer between the periphery and the core of an extended dendrimer is investigated numerically. By mapping the dynamics onto that of a linear chain, it is shown that a localization-delocalization transition arises for a critical value of the generation number G c ≈ 5. This transition originates in the quantum interferences experienced by the excitonic wave due to the multiple scatterings that arise each time the wave tunnels from one generation to another. These results suggest that only small-size dendrimers could be used for designing an efficient quantum communication protocol

  5. INTERNATIONAL EXPANSION OF SERVICE COMPANIES USING THE STRATEGY OF DELOCALIZATION

    Directory of Open Access Journals (Sweden)

    Lucretia Mariana CONSTANTINESCU

    2014-06-01

    Full Text Available The elimination of the constraints related to distance, service demand increase and service accessibility, from the perspective of their commercial capacity, have encouraged service companies to invest abroad, with the desire to identify new clients and to use their specific competitive advantages, and, for this reason, in this work, we shall present new delocalization models that could be used by the companies of the dematerialized economy to transfer some activities outside of their country of origin through the realization of a commercial presence (foreign direct investment - FDI and their integration with the other entities of the network, in order to exploit the comparative advantages of the different locations.

  6. An utilization of liquid sublayer dryout mechanism in predicting critical heat flux under low pressure and low velocity conditions in round tubes

    International Nuclear Information System (INIS)

    Lee, Kwang-Won; Baik, Se-Jin; Ro, Tae-Sun

    2000-01-01

    From a theoretical assessment of extensive critical heat flux (CHF) data under low pressure and low velocity (LPLV) conditions, it was found out that lots of CHF data would not be well predicted by a normal annular film dryout (AFD) mechanism, although their flow patterns were identified as annular-mist flow. To predict these CHF data, a liquid sublayer dryout (LSD) mechanism has been newly utilized in developing the mechanistic CHF model based on each identified CHF mechanism. This mechanism postulates that the CHF occurrence is caused by dryout of the thin liquid sublayer resulting from the annular film separation or breaking down due to nucleate boiling in annular film or hydrodynamic fluctuation. In principle, this mechanism well supports the experimental evidence of residual film flow rate at the CHF location, which can not be explained by the AFD mechanism. For a comparative assessment of each mechanism, the CHF model based on the LSD mechanism is developed together with that based on the AFD mechanism. The validation of these models is performed on the 1406 CHF data points ranging over P=0.1-2 MPa, G=4-499 kg m -2 s -1 , L/D=4-402. This model validation shows that 1055 and 231 CHF data are predicted within ±30 error bound by the LSD mechanism and the AFD mechanism, respectively. However, some CHF data whose critical qualities are <0.4 or whose tube length-to-diameter ratios are <70 are considerably overestimated by the CHF model based on the LSD mechanism. These overestimations seem to be caused by an inadequate CHF mechanism classification and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities as well as a new bubble detachment model for LPLV conditions, are needed to improve the model accuracy.

  7. Heat transfer in smooth tubes, between parallel plates, along a semi-infinite plate, in annular spaces and along tube bundles for exponential distribution of the heat flux in forced, laminar or turbulent flow; Transfert de chaleur dans des tubes lisses, entre des plaques planes paralleles, le long d'une plaque plane, dans des espaces annulaires et le long de faisceaux tubulaires pour une repartition exponentielle du flux de chaleur en ecoulement force, laminaire ou turbulent

    Energy Technology Data Exchange (ETDEWEB)

    Graber, H [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

    1969-04-01

    By introducing an additional parameter F{sub 0}, the processes known hitherto for calculating heat transfer are extended to the heat flux distributions following an exponential law q{sub w} = exp(mx) which give a heat transfer coefficient, independent of position for laminar and turbulent flow with a linear pressure drop. For laminar flow along a semi-infinite plate, the heat flux distribution in accordance with the law qw = x{sup m} leads to the Nusselt number, regardless of the position. Nu is then determined by the thickness of the thermal boundary layer. For the annular space, the equations for explicit calculation of the temperature field will be given, as well as the Nusselt number in laminar flow and constant heat flux. In turbulent flow, the laws of distribution of eddy diffusivity for momentum in a tube, established by H. Reichardt, adapted for the annular space and the tube bundle, give the velocity field and the coefficient of friction and thus permit solution of the heat transfer equations. The results of the numerical calculation are given in the tables and diagrams for an extended range of the various parameters and compared with the experimental results. A simple process to determine the lower limit of the thermal entry length will be described. (author) [French] Par l'introduction d'un parametre supplementaire F{sub 0}, les procedes connus jusqu'a present pour le calcul du transfert de chaleur sont etendus aux repartitions exponentielles q{sub w} = exp(mx) du flux de chaleur qui indiquent un coefficient de transfert de chaleur independant de l'endroit pour l'ecoulement laminaire ou turbulent avec chute de pression lineaire. Pour l'ecoulement laminaire le long d'une plaque plane, la repartition du flux de chaleur selon la loi q{sub w} = x{sup m} conduit au nombre de Nusselt independant de l'endroit. Nu est alors determine par l'epaisseur de la couche limite thermique. Pour l'espace annulaire, seront indiquees les equations pour le calcul explicite du

  8. Heat transfer in smooth tubes, between parallel plates, along a semi-infinite plate, in annular spaces and along tube bundles for exponential distribution of the heat flux in forced, laminar or turbulent flow; Transfert de chaleur dans des tubes lisses, entre des plaques planes paralleles, le long d'une plaque plane, dans des espaces annulaires et le long de faisceaux tubulaires pour une repartition exponentielle du flux de chaleur en ecoulement force, laminaire ou turbulent

    Energy Technology Data Exchange (ETDEWEB)

    Graber, H. [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

    1969-04-01

    By introducing an additional parameter F{sub 0}, the processes known hitherto for calculating heat transfer are extended to the heat flux distributions following an exponential law q{sub w} = exp(mx) which give a heat transfer coefficient, independent of position for laminar and turbulent flow with a linear pressure drop. For laminar flow along a semi-infinite plate, the heat flux distribution in accordance with the law qw = x{sup m} leads to the Nusselt number, regardless of the position. Nu is then determined by the thickness of the thermal boundary layer. For the annular space, the equations for explicit calculation of the temperature field will be given, as well as the Nusselt number in laminar flow and constant heat flux. In turbulent flow, the laws of distribution of eddy diffusivity for momentum in a tube, established by H. Reichardt, adapted for the annular space and the tube bundle, give the velocity field and the coefficient of friction and thus permit solution of the heat transfer equations. The results of the numerical calculation are given in the tables and diagrams for an extended range of the various parameters and compared with the experimental results. A simple process to determine the lower limit of the thermal entry length will be described. (author) [French] Par l'introduction d'un parametre supplementaire F{sub 0}, les procedes connus jusqu'a present pour le calcul du transfert de chaleur sont etendus aux repartitions exponentielles q{sub w} = exp(mx) du flux de chaleur qui indiquent un coefficient de transfert de chaleur independant de l'endroit pour l'ecoulement laminaire ou turbulent avec chute de pression lineaire. Pour l'ecoulement laminaire le long d'une plaque plane, la repartition du flux de chaleur selon la loi q{sub w} = x{sup m} conduit au nombre de Nusselt independant de l'endroit. Nu est alors determine par l'epaisseur de la couche limite thermique. Pour l'espace annulaire, seront

  9. The order parameter of glass transition: Spontaneously delocalized nanoscale solitary wave with transverse ripplon-like soft wave

    Directory of Open Access Journals (Sweden)

    Jia Lin Wu

    2013-06-01

    Full Text Available In macromolecular self-avoiding random walk, movement of each chain-particle accompanies an instantaneous spin system with de Gennes n = 0 that provides extra energy, extra vacancy volume and relaxation time needed for chain-particles co-movement. Using these additional and instantaneous spin systems not only directly yields the same Brownian motion mode in glass transition (GT and reptation-tube model, but also proves that the entangled chain length corresponding to the Reynolds number in hydrodynamics and the inherent diffusion - delocalization mode of entangled chains, from frozen glass state to melt liquid state, is a chain-size solitary wave with transverse ripplon-like soft wave. Thus, the order parameter of GT is found. The various currently available GT theories, such as Static Replica, Random First-Order Transition, Potential Energy Landscape, Mode-Coupling and Nanoscale Heterogeneity, can be unified using the additional and instantaneous spin system. GT served as an inspiration and continues to serve as the paradigm in the universal random delocalization transitions from disorder to more disorder until turbulence.

  10. Universal Properties of Many-Body Delocalization Transitions

    Directory of Open Access Journals (Sweden)

    Andrew C. Potter

    2015-09-01

    Full Text Available We study the dynamical melting of “hot” one-dimensional many-body localized systems. As disorder is weakened below a critical value, these nonthermal quantum glasses melt via a continuous dynamical phase transition into classical thermal liquids. By accounting for collective resonant tunneling processes, we derive and numerically solve an effective model for such quantum-to-classical transitions and compute their universal critical properties. Notably, the classical thermal liquid exhibits a broad regime of anomalously slow subdiffusive equilibration dynamics and energy transport. The subdiffusive regime is characterized by a continuously evolving dynamical critical exponent that diverges with a universal power at the transition. Our approach elucidates the universal long-distance, low-energy scaling structure of many-body delocalization transitions in one dimension, in a way that is transparently connected to the underlying microscopic physics. We discuss experimentally testable signatures of the predicted scaling properties.

  11. Coherent delocalization: views of entanglement in different scenarios

    International Nuclear Information System (INIS)

    De J León-Montiel, R; Vallés, A; Torres, J P; Moya-Cessa, H M

    2015-01-01

    The concept of entanglement was originally introduced to explain correlations existing between two spatially separated systems, that cannot be described using classical ideas. Interestingly, in recent years, it has been shown that similar correlations can be observed when considering different degrees of freedom of a single system, even a classical one. Surprisingly, it has also been suggested that entanglement might be playing a relevant role in certain biological processes, such as the functioning of pigment-proteins that constitute light-harvesting complexes of photosynthetic bacteria. The aim of this work is to show that the presence of entanglement in all of these different scenarios should not be unexpected, once it is realized that the very same mathematical structure can describe all of them. We show this by considering three different, realistic cases in which the only condition for entanglement to exist is that a single excitation is coherently delocalized between the different subsystems that compose the system of interest. (letter)

  12. Influence of the heat flux and of the gas on heat transfer and friction coefficients in a smooth cylindrical tube; Influence du flux de chaleur et de la nature du gaz sur les coefficients d'echange et le frottement dans un tube cylindrique lisse

    Energy Technology Data Exchange (ETDEWEB)

    Delpont, J P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1962-12-15

    The stainless steel tube used for the experiments is heated by means of d.c current; its inside diameter is 40 mm; its length is about 5.80 meters. Special core has been taken (heated rocket) to avoid heat loss and to provide very accurate measurements. The cooling gases tested are air and carbon dioxide at a pressure of 2.6 to 19 psi; the Reynolds number ranges from 70,000 to 10{sup 6}, the wall temperature and the heat flux reach respectively 430 deg C and 16 watts/cm{sup 2}. The Reynolds number Re{sub m}, Stanton number M{sub m} and friction coefficient f are computed by evaluating the physical properties of the gases at the mean temperature T{sub m}. For a given Reynolds number, a decrease of M{sub m} and of f is observed hen the heat flux increases, this decrease reaches 10 per cent in the experiments described. A formulation is proposed to express this effect in terms of a heat flow parameter (T{sub m} - T{sub m}) / T{sub p} used as a corrective factor (T{sub p} = wall temperature). The correlation formulae are: M{sub m} = 0.0168 Re{sub m}{sup -0.18} P{sub m}{sup -0.6} (1 - 0.4 [(T{sub p} - T{sub m}) / T{sub p}]) for air f = f{sub 0} (1 0.25 [(T{sub p} - T{sub m}) / T{sub p}]) for air M{sub m} = 0.0171 Re{sub m}{sup -0.18} P{sub m}{sup -0.6} (1 - 0.2 [(T{sub p} - T{sub m}) / T{sub p}]) for carbon dioxide f = f{sub 0} (1 - 0.20 [(T{sub p} - T{sub m}) / T{sub p}]) for carbon dioxide where f{sub 0} = the friction coefficient for isotherm flow. (author) [French] Le tube utilite a un diametre interieur de 40 mm; sa longueur est de 5,80 m environ; il est en acier inoxydable et chauffe par un courant continu. Des precautions particulieres (enceinte chauffante exterieure) ont ete prises pour eviter tout echange de chaleur avec le milieu exterieur et permettre des mesures extremement precises. Les gaz de refroidissement experimentes sont l'air et le gaz corbonique sous une pression de 1,8 a 13 hpz; les nombres de Reynolds vont de 70 000 a 10{sup 6}, la temperature de

  13. Symmetry-enhanced supertransfer of delocalized quantum states

    International Nuclear Information System (INIS)

    Lloyd, Seth; Mohseni, Masoud

    2010-01-01

    Coherent hopping of excitation relies on quantum coherence over physically extended states. In this work, we consider simple models to examine the effect of symmetries of delocalized multi-excitation states on the dynamical timescales, including hopping rates, radiative decay and environmental interactions. While the decoherence (pure dephasing) rate of an extended state over N sites is comparable to that of a non-extended state, superradiance leads to a factor of N enhancement in decay and absorption rates. In addition to superradiance, we illustrate how the multi-excitonic states exhibit 'supertransfer' in the far-field regime-hopping from a symmetrized state over N sites to a symmetrized state over M sites at a rate proportional to MN. We argue that such symmetries could play an operational role in physical systems based on the competition between symmetry-enhanced interactions and localized inhomogeneities and environmental interactions that destroy symmetry. As an example, we propose that supertransfer and coherent hopping play a role in recent observations of anomalously long diffusion lengths in nano-engineered assembly of light-harvesting complexes.

  14. Many-body delocalization with random vector potentials

    Science.gov (United States)

    Cheng, Chen; Mondaini, Rubem

    In this talk we present the ergodic properties of excited states in a model of interacting fermions in quasi-one dimensional chains subjected to a random vector potential. In the non-interacting limit, we show that arbitrarily small values of this complex off-diagonal disorder triggers localization for the whole spectrum; the divergence of the localization length in the single particle basis is characterized by a critical exponent ν which depends on the energy density being investigated. However, when short-ranged interactions are included, the localization is lost and the system is ergodic regardless of the magnitude of disorder in finite chains. Our numerical results suggest a delocalization scheme for arbitrary small values of interactions. This finding indicates that the standard scenario of the many-body localization cannot be obtained in a model with random gauge fields. This research is financially supported by the National Natural Science Foundation of China (NSFC) (Grant Nos. U1530401 and 11674021). RM also acknowledges support from NSFC (Grant No. 11650110441).

  15. ND and NB systems in quark delocalization color screening model

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lifang [Nanjing College of Information Technology, Department of Quality-Oriented Education, Nanjing (China); Huang, Hongxia; Ping, Jialun [Nanjing Normal University, Department of Physics, Nanjing (China)

    2017-02-15

    The ND and NB systems with I = 0 and 1, J{sup P} = (1)/(2){sup ±}, (3)/(2){sup ±}, and (5)/(2){sup ±} are investigated within the framework of the quark delocalization color screening model. The results show that all the positive-parity states are unbound. By coupling to the ND* channel, the state ND with I = 0, J{sup P} = (1)/(2){sup -} can form a bound state, which can be invoked to explain the observed Σ(2800) state. The mass of the ND* with I = 0, J{sup P} = (3)/(2){sup -} is close to that of the reported Λ{sub c}(2940){sup +}, which indicates that Λ{sub c}(2940){sup +} can be explained as a ND* molecular state in QDCSM. Besides, the ΔD* with I = 1, J{sup P} = (5)/(2){sup -} is also a possible resonance state. The results of the bottom case of the NB system are similar to those of the ND system. Searching for these states will be a challenging subject of experiments. (orig.)

  16. How do electron localization functions describe π-electron delocalization?

    Science.gov (United States)

    Steinmann, Stephan N; Mo, Yirong; Corminboeuf, Clemence

    2011-12-14

    Scalar fields provide an intuitive picture of chemical bonding. In particular, the electron localization function (ELF) has proven to be highly valuable in interpreting a broad range of bonding patterns. The discrimination between enhanced or reduced electron (de)localization within cyclic π-conjugated systems remains, however, challenging for ELF. In order to clearly distinguish between the local properties of ten highly and weakly π-(de)localized prototype systems, we compare the ELFs of both the canonical wave functions and electron-localized states (diabatic) with those of two closely related scalar fields: the electron localizability indicator (ELI-D) and the localized orbital locator (LOL). The simplest LOL function distinguishes enhanced from weak π-(de)localization in an insightful and reliable manner. LOL offers the finest contrast between annulenes with 4n/4n + 2 π electrons and their inorganic analogues as well as between hyperconjugated cyclopentadiene derivatives. LOL(π) also gives an appealing and intuitive picture of the π-bond. In contrast, the most popular ELF fails to capture subtle contrasting local electronic properties and suffers from the arbitrariness of the σ/π dissection. The orbital separation of the most recent ELI-D is clear-cut but the interpretations sometime less straightforward in the present context.

  17. Communication: Spectroscopic consequences of proton delocalization in OCHCO+

    Science.gov (United States)

    Fortenberry, Ryan C.; Yu, Qi; Mancini, John S.; Bowman, Joel M.; Lee, Timothy J.; Crawford, T. Daniel; Klemperer, William F.; Francisco, Joseph S.

    2015-08-01

    Even though quartic force fields (QFFs) and highly accurate coupled cluster computations describe the OCHCO+ cation at equilibrium as a complex between carbon monoxide and the formyl cation, two notable and typical interstellar and atmospheric molecules, the prediction from the present study is that the equilibrium C∞v structure is less relevant to observables than the saddle-point D∞h structure. This is the conclusion from diffusion Monte Carlo and vibrational self-consistent field/virtual state configuration interaction calculations utilizing a semi-global potential energy surface. These calculations demonstrate that the proton "rattle" motion (ν6) has centrosymmetric delocalization of the proton over the D∞h barrier lying only 393.6 cm-1 above the double-well OCHCO+ C∞v minima. As a result, this molecule will likely appear D∞h, and the rotational spectrum will be significantly dimmer than the computed equilibrium 2.975 D center-of-mass dipole moment indicates. However, the proton transfer fundamental, determined to be at roughly 300 cm-1, has a very strong intensity. This prediction as well as those of other fundamentals should provide useful guides for laboratory detection of this cation. Finally, it is shown that the two highest energy QFF-determined modes are actually in good agreement with their vibrational configuration interaction counterparts. These high-level quantum chemical methods provide novel insights into this fascinating and potentially common interstellar molecule.

  18. Communication: Spectroscopic consequences of proton delocalization in OCHCO+

    International Nuclear Information System (INIS)

    Fortenberry, Ryan C.; Yu, Qi; Mancini, John S.; Bowman, Joel M.; Lee, Timothy J.; Crawford, T. Daniel; Klemperer, William F.; Francisco, Joseph S.

    2015-01-01

    Even though quartic force fields (QFFs) and highly accurate coupled cluster computations describe the OCHCO + cation at equilibrium as a complex between carbon monoxide and the formyl cation, two notable and typical interstellar and atmospheric molecules, the prediction from the present study is that the equilibrium C ∞v structure is less relevant to observables than the saddle-point D ∞h structure. This is the conclusion from diffusion Monte Carlo and vibrational self-consistent field/virtual state configuration interaction calculations utilizing a semi-global potential energy surface. These calculations demonstrate that the proton “rattle” motion (ν 6 ) has centrosymmetric delocalization of the proton over the D ∞h barrier lying only 393.6 cm −1 above the double-well OCHCO + C ∞v minima. As a result, this molecule will likely appear D ∞h , and the rotational spectrum will be significantly dimmer than the computed equilibrium 2.975 D center-of-mass dipole moment indicates. However, the proton transfer fundamental, determined to be at roughly 300 cm −1 , has a very strong intensity. This prediction as well as those of other fundamentals should provide useful guides for laboratory detection of this cation. Finally, it is shown that the two highest energy QFF-determined modes are actually in good agreement with their vibrational configuration interaction counterparts. These high-level quantum chemical methods provide novel insights into this fascinating and potentially common interstellar molecule

  19. Delocalization of brane gravity by a bulk black hole

    International Nuclear Information System (INIS)

    Seahra, Sanjeev S; Clarkson, Chris; Maartens, Roy

    2005-01-01

    We investigate the analogue of the Randall-Sundrum braneworld in the case when the bulk contains a black hole. Instead of the static vacuum Minkowski brane of the RS model, we have an Einstein static vacuum brane. We find that the presence of the bulk black hole has a dramatic effect on the gravity that is felt by brane observers. In the RS model, the 5D graviton has a stable localized zero mode that reproduces 4D gravity on the brane at low energies. With a bulk black hole, there is no such solution-gravity is delocalized by the 5D horizon. However, the brane does support a discrete spectrum of metastable massive bound states, or quasinormal modes, as was recently shown to be the case in the RS scenario. These states should dominate the high frequency component of the bulk gravity wave spectrum on a cosmological brane. We expect our results to generalize to any bulk spacetime containing a Killing horizon. (letter to the editor)

  20. Classification of delocalization power of global unitary operations in terms of LOCC one-piece relocalization

    Directory of Open Access Journals (Sweden)

    Akihito Soeda

    2010-06-01

    Full Text Available We study how two pieces of localized quantum information can be delocalized across a composite Hilbert space when a global unitary operation is applied. We classify the delocalization power of global unitary operations on quantum information by investigating the possibility of relocalizing one piece of the quantum information without using any global quantum resource. We show that one-piece relocalization is possible if and only if the global unitary operation is local unitary equivalent of a controlled-unitary operation. The delocalization power turns out to reveal different aspect of the non-local properties of global unitary operations characterized by their entangling power.

  1. Flux transformers made of commercial high critical temperature superconducting wires.

    Science.gov (United States)

    Dyvorne, H; Scola, J; Fermon, C; Jacquinot, J F; Pannetier-Lecoeur, M

    2008-02-01

    We have designed flux transformers made of commercial BiSCCO tapes closed by soldering with normal metal. The magnetic field transfer function of the flux transformer was calculated as a function of the resistance of the soldered contacts. The performances of different kinds of wires were investigated for signal delocalization and gradiometry. We also estimated the noise introduced by the resistance and showed that the flux transformer can be used efficiently for weak magnetic field detection down to 1 Hz.

  2. Physics of magnetic flux ropes

    Science.gov (United States)

    Russell, C. T.; Priest, E. R.; Lee, L. C.

    The present work encompasses papers on the structure, waves, and instabilities of magnetic flux ropes (MFRs), photospheric flux tubes (PFTs), the structure and heating of coronal loops, solar prominences, coronal mass ejections and magnetic clouds, flux ropes in planetary ionospheres, the magnetopause, magnetospheric field-aligned currents and flux tubes, and the magnetotail. Attention is given to the equilibrium of MFRs, resistive instability, magnetic reconnection and turbulence in current sheets, dynamical effects and energy transport in intense flux tubes, waves in solar PFTs, twisted flux ropes in the solar corona, an electrodynamical model of solar flares, filament cooling and condensation in a sheared magnetic field, the magnetopause, the generation of twisted MFRs during magnetic reconnection, ionospheric flux ropes above the South Pole, substorms and MFR structures, evidence for flux ropes in the earth magnetotail, and MFRs in 3D MHD simulations.

  3. Role of coherence and delocalization in photo-induced electron transfer at organic interfaces

    Science.gov (United States)

    Abramavicius, V.; Pranculis, V.; Melianas, A.; Inganäs, O.; Gulbinas, V.; Abramavicius, D.

    2016-09-01

    Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrödinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

  4. Mobility of delocalized charge carriers in an ideal homopolar glass as a function of temperature

    International Nuclear Information System (INIS)

    Iskra, V.D.

    1986-01-01

    The relationship between temperature and the mobility of delocalized charge carriers for an intrinsic random field of a homopolar glass is investigated through application of a method of scattering amplitude calculation based on employing short-lived potential factorization

  5. Multiconfiguration Pair-Density Functional Theory Is Free From Delocalization Error.

    Science.gov (United States)

    Bao, Junwei Lucas; Wang, Ying; He, Xiao; Gagliardi, Laura; Truhlar, Donald G

    2017-11-16

    Delocalization error has been singled out by Yang and co-workers as the dominant error in Kohn-Sham density functional theory (KS-DFT) with conventional approximate functionals. In this Letter, by computing the vertical first ionization energy for well separated He clusters, we show that multiconfiguration pair-density functional theory (MC-PDFT) is free from delocalization error. To put MC-PDFT in perspective, we also compare it with some Kohn-Sham density functionals, including both traditional and modern functionals. Whereas large delocalization errors are almost universal in KS-DFT (the only exception being the very recent corrected functionals of Yang and co-workers), delocalization error is removed by MC-PDFT, which bodes well for its future as a step forward from KS-DFT.

  6. Many-body localization-delocalization transition in the quantum Sherrington-Kirkpatrick model

    Science.gov (United States)

    Mukherjee, Sudip; Nag, Sabyasachi; Garg, Arti

    2018-04-01

    We analyze the many-body localization- (MBL) to-delocalization transition in the Sherrington-Kirkpatrick (SK) model of Ising spin glass in the presence of a transverse field Γ . Based on energy-resolved analysis, which is of relevance for a closed quantum system, we show that the quantum SK model has many-body mobility edges separating the MBL phase, which is nonergodic and nonthermal, from the delocalized phase, which is ergodic and thermal. The range of the delocalized regime increases with an increase in the strength of Γ , and eventually for Γ larger than ΓCP the entire many-body spectrum is delocalized. We show that the Renyi entropy is almost independent of the system size in the MBL phase while the delocalized phase shows extensive Renyi entropy. We further obtain the spin-glass transition curve in the energy density ɛ -Γ plane from the collapse of the eigenstate spin susceptibility. We demonstrate that in most of the parameter regime, the spin-glass transition occurs close to the MBL transition, indicating that the spin-glass phase is nonergodic and nonthermal while the paramagnetic phase is delocalized and thermal.

  7. Drive-induced delocalization in the Aubry-André model

    Science.gov (United States)

    Ray, S.; Ghosh, A.; Sinha, S.

    2018-01-01

    Motivated by the recent experiment by Bordia et al. [Nat. Phys. 13, 460 (2017), 10.1038/nphys4020], we study the single particle delocalization phenomena of the Aubry-André (AA) model subjected to periodic drives. In two distinct cases we construct an equivalent classical description to illustrate that the drive-induced delocalization phenomena stems from an instability and the onset of chaos in the underlying dynamics. In the first case we analyze the delocalization and the thermalization in a time modulated AA potential with respect to driving frequency and demonstrate that there exists a threshold value of the amplitude of the drive. In the next example, we show that the periodic modulation of the phase of the hopping amplitude induced by a gauge field leads to an unusual effect on delocalization with a nonmonotonic dependence on the driving frequency. Within a window of such a driving frequency a delocalized Floquet band with a mobility edge appears, exhibiting multifractality in the spectrum as well as in the Floquet eigenfunctions. Finally, we explore the effect of interaction and discuss how the results of the present analysis can be tested experimentally.

  8. Tube plug

    International Nuclear Information System (INIS)

    Zafred, P. R.

    1985-01-01

    The tube plug comprises a one piece mechanical plug having one open end and one closed end which is capable of being inserted in a heat exchange tube and internally expanded into contact with the inside surface of the heat exchange tube for preventing flow of a coolant through the heat exchange tube. The tube plug also comprises a groove extending around the outside circumference thereof which has an elastomeric material disposed in the groove for enhancing the seal between the tube plug and the tube

  9. Effect of Tube Pitch on Pool Boiling Heat Transfer of Vertical Tube Bundle

    International Nuclear Information System (INIS)

    Kang, Myeong Gie

    2016-01-01

    Summarizing the previous results it can be stated that heat transfer coefficients are highly dependent on the tube pitch and the heat flux of the relevant tube. The published results are mostly about the horizontal tubes. However, there are many heat exchangers consisting of vertical tubes like AP600. Therefore, the focus of the present study is an identification of the effects of a tube pitch as well as the heat flux of a relevant tube on the heat transfer of a tube bundle installed vertically. When the heat flux is increased many bubbles are generating due to the increase of the nucleation sites. The bubbles become coalescing with the nearby bubbles and generates big bunches of bubbles on the tube surface. This prevents the access of the liquid to the surface and deteriorates heat transfer. The bubble coalescence is competing with the mechanisms enhancing heat transfer. The pitch was varied from 28.5 mm to 95 mm and the heat flux of the nearby tube was changed from 0 to 90kW/m"2. The enhancement of the heat transfer is clearly observed when the heat flux of the nearby tube becomes larger and the heat flux of the upper tube is less than 40kW/m"2. The effect of the tube pitch on heat transfer is negligible as the value of DP/ is increased more than 4.

  10. Effect of pressure on f-electron delocalization and oxidation in actinide dioxides

    Energy Technology Data Exchange (ETDEWEB)

    Petit, L., E-mail: leon.petit@stfc.ac.uk [Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Szotek, Z.; Temmerman, W.M. [Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Stocks, G.M. [Materials Science and Technology Division and Center for Defect Physics, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Svane, A. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

    2014-08-01

    Using first principles calculations, we have investigated f-electron delocalization and oxidation in the actinide dioxides under pressure. Whilst UO{sub 2} is found on the verge of an insulator to metal transition at the equilibrium volume, increasingly larger pressures are required to delocalize f-electrons in NpO{sub 2}, PuO{sub 2}, and AmO{sub 2}, respectively 49, 112, and 191 GPa. Compared to this broad range of pressures, the experimentally observed structural transitions, in all four dioxides, occur between 30 and 40 GPa, which leads us to conclude that the associated volume collapse is not due to f-electron delocalization. In contrast, oxidation of the dioxides is found to be linked to the degree of f-electron localization, but it emerges that for naturally occurring pressures (<10 GPa), higher oxides only exist for UO{sub 2}.

  11. Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer

    KAUST Repository

    Steyrleuthner, Robert

    2016-12-20

    We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear spins using electron nuclear double resonance spectroscopy. An extrapolation of the corresponding oligomer spectra reveals that charges tend to delocalize over 4.0-4.8 nm with delocalization strongly dependent on molecular order and crystallinity of the PBTTT polymer thin films. Density functional theory calculations of hyperfine couplings confirm that long-range corrected functionals appropriately describe the change in coupling strength with increasing oligomer size and agree well with the experimentally measured polymer limit. Our discussion presents general guidelines illustrating the various pitfalls and opportunities when deducing polaron localization lengths from hyperfine coupling spectra of conjugated polymers.

  12. On the mobility of delocalized and self-trapped positronium states in ionic crystals

    CERN Document Server

    Bondarev, I V

    2003-01-01

    The temperature dependence of the diffusivity is studied for delocalized and self-trapped positronium (Ps) atoms in ionic crystals. Detailed calculations taking into account low-temperature and inelastic scattering corrections and a Ps scattering form-factor have been performed for delocalized Ps. Low-temperature and inelastic corrections to the delocalized Ps diffusivity are shown to be essential below several tens of K, while the form-factor contribution is negligibly small up to thousand K. The mobility of self-trapped Ps is analyzed within the framework of a small polaron approach. The hopping contribution to the self-trapped Ps diffusivity is shown to be adiabatic in its physical nature. The tunnel contribution is in general not small and may turn out to be dominating even at very high temperatures. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  13. Gastrostomy Tube (G-Tube)

    Science.gov (United States)

    ... any of these problems: a dislodged tube a blocked or clogged tube any signs of infection (including redness, swelling, or warmth at the tube site; discharge that's yellow, green, or foul-smelling; fever) excessive bleeding or drainage from the tube site severe abdominal pain lasting ...

  14. An application of liquid sublayer dryout mechanism to the prediction of critical heat flux under low pressure and low velocity conditions in round tubes

    International Nuclear Information System (INIS)

    Lee, Kwang-Won; Yang, Jae-Young; Baik, Se-Jin

    1997-01-01

    Based on several experimental evidences for nucleate boiling in annular film and the existence of residual liquid film flow rate at the critical heat flux (CHF) location, the liquid sublayer dryout (LSD) mechanism under annular film is firstly introduced to evaluate the CHF data at low pressure and low velocity (LPLV) conditions, which would not be predicted by a normal annular film dryout (AFD) model. In this study, the CHF occurrence due to annular film separation or breaking down is phenomenologically modelled by applying the LSD mechanism to this situation. In this LSD mechanism, the liquid sublayer thickness, the incoming liquid velocity to the liquid sublayer, and the axial distance from the onset of annular flow to the CHF location are used as the phenomena-controlling parameters. From the model validation on the 1406 CHF data points ranging over P = 0.1 - 2 MPa, G = 4 - 499 kg/m 2 s, L/D = 4 - 402, most of CHF data (more than 1000 points) are predicted within ±30% error bounds by the LSD mechanism. However, some calculation results that critical qualities are less than 0.4 are considerably overestimated by this mechanism. These overpredictions seem to be caused by inadequate CHF mechanism classification criteria and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities and a new bubble detachment model for LPLV conditions are needed to improve the model accuracy. (author)

  15. Entropy Generation during Turbulent Flow of Zirconia-water and Other Nanofluids in a Square Cross Section Tube with a Constant Heat Flux

    Directory of Open Access Journals (Sweden)

    Hooman Yarmand

    2014-11-01

    Full Text Available The entropy generation based on the second law of thermodynamics is investigated for turbulent forced convection flow of ZrO2-water nanofluid through a square pipe with constant wall heat flux. Effects of different particle concentrations, inlet conditions and particle sizes on entropy generation of ZrO2-water nanofluid are studied. Contributions from frictional and thermal entropy generations are investigated, and the optimal working condition is analyzed. The results show that the optimal volume concentration of nanoparticles to minimize the entropy generation increases when the Reynolds number decreases. It was also found that the thermal entropy generation increases with the increase of nanoparticle size whereas the frictional entropy generation decreases. Finally, the entropy generation of ZrO2-water was compared with that from other nanofluids (including Al2O3, SiO2 and CuO nanoparticles in water. The results showed that the SiO2 provided the highest entropy generation.

  16. Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer

    KAUST Repository

    Steyrleuthner, Robert; Zhang, Yuexing; Zhang, Lei; Kraffert, Felix; Cherniawski, Benjamin P.; Bittl, Robert; Briseno, Alejandro L.; Bredas, Jean-Luc; Behrends, Jan

    2016-01-01

    We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear

  17. Understanding the effects of electronic polarization and delocalization on charge-transport levels in oligoacene systems

    KAUST Repository

    Sutton, Christopher; Tummala, Naga Rajesh; Kemper, Travis; Aziz, Saadullah G.; Sears, John; Coropceanu, Veaceslav; Bredas, Jean-Luc

    2017-01-01

    Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.

  18. Is there a delocalization transition in a two-dimensional model for quantum percolation

    International Nuclear Information System (INIS)

    Dasgupta, I.; Saha, T.; Mookerjee, A.; Chakrabarti, B.K.

    1992-01-01

    In this paper, the authors estimate the transmittance of the quantum percolation model of Eggarter and Kirkpatrick on the square lattice of various sizes using the vector recursion method. The authors note from finite size scaling that there is no delocalization transition for any degree of disorder in two dimensions

  19. Exciton delocalization incorporated drift-diffusion model for bulk-heterojunction organic solar cells

    Science.gov (United States)

    Wang, Zi Shuai; Sha, Wei E. I.; Choy, Wallace C. H.

    2016-12-01

    Modeling the charge-generation process is highly important to understand device physics and optimize power conversion efficiency of bulk-heterojunction organic solar cells (OSCs). Free carriers are generated by both ultrafast exciton delocalization and slow exciton diffusion and dissociation at the heterojunction interface. In this work, we developed a systematic numerical simulation to describe the charge-generation process by a modified drift-diffusion model. The transport, recombination, and collection of free carriers are incorporated to fully capture the device response. The theoretical results match well with the state-of-the-art high-performance organic solar cells. It is demonstrated that the increase of exciton delocalization ratio reduces the energy loss in the exciton diffusion-dissociation process, and thus, significantly improves the device efficiency, especially for the short-circuit current. By changing the exciton delocalization ratio, OSC performances are comprehensively investigated under the conditions of short-circuit and open-circuit. Particularly, bulk recombination dependent fill factor saturation is unveiled and understood. As a fundamental electrical analysis of the delocalization mechanism, our work is important to understand and optimize the high-performance OSCs.

  20. Understanding the effects of electronic polarization and delocalization on charge-transport levels in oligoacene systems

    KAUST Repository

    Sutton, Christopher

    2017-06-13

    Electronic polarization and charge delocalization are important aspects that affect the charge-transport levels in organic materials. Here, using a quantum mechanical/ embedded-charge (QM/EC) approach based on a combination of the long-range corrected omega B97X-D exchange-correlation functional (QM) and charge model 5 (CM5) point-charge model (EC), we evaluate the vertical detachment energies and polarization energies of various sizes of crystalline and amorphous anionic oligoacene clusters. Our results indicate that QM/EC calculations yield vertical detachment energies and polarization energies that compare well with the experimental values obtained from ultraviolet photoemission spectroscopy measurements. In order to understand the effect of charge delocalization on the transport levels, we considered crystalline naphthalene systems with QM regions including one or five-molecules. The results for these systems show that the delocalization and polarization effects are additive; therefore, allowing for electron delocalization by increasing the size of the QM region leads to the additional stabilization of the transport levels. Published by AIP Publishing.

  1. Controlling the delocalization-localization transition of light via electromagnetically induced transparency

    International Nuclear Information System (INIS)

    Cheng Jing; Huang Guoxiang

    2011-01-01

    We propose a scheme to realize a transition from delocalization to localization of light waves via electromagnetically induced transparency. The system we suggested is a resonant cold atomic ensemble having N configuration, with a control field consisting of two pairs of laser beams with different cross angles, which produce an electromagnetically induced quasiperiodic waveguide (EIQPW) for the propagation of a signal field. By appropriately tuning the incommensurate rate or relative modulation strength between the two pairs of control-field components, the signal field can exhibit the delocalization-localization transition as it transports inside the atomic ensemble. The delocalization-localization transition point is determined and the propagation property of the signal field is studied in detail. Our work provides a way of realizing wave localization via atomic coherence, which is quite different from the conventional, off-resonant mechanism-based Aubry-Andre model, and the great controllability of the EIQPW also allows an easy manipulation of the delocalization-localization transition.

  2. Probing Intermolecular Electron Delocalization in Dimer Radical Anions by Vibrational Spectroscopy

    International Nuclear Information System (INIS)

    Mani, Tomoyasu; Brookhaven National Laboratory; Grills, David C.

    2017-01-01

    Delocalization of charges is one of the factors controlling charge transport in conjugated molecules. It is considered to play an important role in the performance of a wide range of molecular technologies, including organic solar cells and organic electronics. Dimerization reactions are well-suited as a model to investigate intermolecular spatial delocalization of charges. And while dimerization reactions of radical cations are well investigated, studies on radical anions are still scarce. Upon dimerization of radical anions with neutral counterparts, an electron is considered to delocalize over the two molecules. By using time-resolved infrared (TRIR) detection coupled with pulse radiolysis, we show that radical anions of 4-n-hexyl-4'-cyanobiphenyl (6CB) undergo such dimerization reactions, with an electron equally delocalized over the two molecules. We have recently demonstrated that nitrile ν(C≡N) vibrations respond to the degree of electron localization of nitrile-substituted anions: we can quantify the changes in the electronic charges from the neutral to the anion states in the nitriles by monitoring the ν(C≡N) IR shifts. In the first part of this article, we show that the sensitivity of the ν(C≡N) IR shifts does not depend on solvent polarity. In the second part, we describe how probing the shifts of the nitrile IR vibrational band unambiguously confirms the formation of dimer radical anions, with K dim = 3 × 10 4 M –1 . IR findings are corroborated by electronic absorption spectroscopy and electronic structure calculations. We find that the presence of a hexyl chain and the formation of π–π interactions are both crucial for dimerization of radical anions of 6CB with neutral 6CB. Our study provides clear evidence of spatial delocalization of electrons over two molecular fragments.

  3. Halogen Bonding from Dispersion-Corrected Density-Functional Theory: The Role of Delocalization Error.

    Science.gov (United States)

    Otero-de-la-Roza, A; Johnson, Erin R; DiLabio, Gino A

    2014-12-09

    Halogen bonds are formed when a Lewis base interacts with a halogen atom in a different molecule, which acts as an electron acceptor. Due to its charge transfer component, halogen bonding is difficult to model using many common density-functional approximations because they spuriously overstabilize halogen-bonded dimers. It has been suggested that dispersion-corrected density functionals are inadequate to describe halogen bonding. In this work, we show that the exchange-hole dipole moment (XDM) dispersion correction coupled with functionals that minimize delocalization error (for instance, BH&HLYP, but also other half-and-half functionals) accurately model halogen-bonded interactions, with average errors similar to other noncovalent dimers with less charge-transfer effects. The performance of XDM is evaluated for three previously proposed benchmarks (XB18 and XB51 by Kozuch and Martin, and the set proposed by Bauzá et al.) spanning a range of binding energies up to ∼50 kcal/mol. The good performance of BH&HLYP-XDM is comparable to M06-2X, and extends to the "extreme" cases in the Bauzá set. This set contains anionic electron donors where charge transfer occurs even at infinite separation, as well as other charge transfer dimers belonging to the pnictogen and chalcogen bonding classes. We also show that functional delocalization error results in an overly delocalized electron density and exact-exchange hole. We propose intermolecular Bader delocalization indices as an indicator of both the donor-acceptor character of an intermolecular interaction and the delocalization error coming from the underlying functional.

  4. Delocalization of Relativistic Dirac Particles in Disordered One-Dimensional Systems and Its Implementation with Cold Atoms

    International Nuclear Information System (INIS)

    Zhu Shiliang; Zhang Danwei; Wang, Z. D.

    2009-01-01

    We study theoretically the localization of relativistic particles in disordered one-dimensional chains. It is found that the relativistic particles tend to delocalization in comparison with the nonrelativistic particles with the same disorder strength. More intriguingly, we reveal that the massless Dirac particles are entirely delocalized for any energy due to the inherent chiral symmetry, leading to a well-known result that particles are always localized in one-dimensional systems for arbitrary weak disorders to break down. Furthermore, we propose a feasible scheme to detect the delocalization feature of the Dirac particles with cold atoms in a light-induced gauge field.

  5. Role of transport band edge variation on delocalized charge transport in high-mobility crystalline organic semiconductors

    Science.gov (United States)

    Kadashchuk, Andrey; Tong, Fei; Janneck, Robby; Fishchuk, Ivan I.; Mityashin, Alexander; Pavlica, Egon; Köhler, Anna; Heremans, Paul; Rolin, Cedric; Bratina, Gvido; Genoe, Jan

    2017-09-01

    We demonstrate that the degree of charge delocalization has a strong impact on polarization energy and thereby on the position of the transport band edge in organic semiconductors. This gives rise to long-range potential fluctuations, which govern the electronic transport through delocalized states in organic crystalline layers. This concept is employed to formulate an analytic model that explains a negative field dependence coupled with a positive temperature dependence of the charge mobility observed by a lateral time-of-flight technique in a high-mobility crystalline organic layer. This has important implications for the further understanding of the charge transport via delocalized states in organic semiconductors.

  6. Fundamental Studies of Charge Migration and Delocalization Relevant to Solar Energy Conversion

    Energy Technology Data Exchange (ETDEWEB)

    Michael J. Therien

    2012-06-01

    This program aimed to understand the molecular-level principles by which complex chemical systems carry out photochemical charge separation, transport, and storage, and how these insights could impact the design of practical solar energy conversion and storage devices. Towards these goals, this program focused on: (1) carrying out fundamental mechanistic and transient dynamical studies of proton-coupled electron-transfer (PCET) reactions; (2) characterizing and interrogating via electron paramagnetic resonance (EPR) spectroscopic methods novel conjugated materials that feature large charge delocalization lengths; and (3) exploring excitation delocalization and migration, as well as polaron transport properties of meso-scale assemblies that are capable of segregating light-harvesting antennae, nanoscale wire-like conduction elements, and distinct oxidizing and reducing environments.

  7. Creating cat states in one-dimensional quantum walks using delocalized initial states

    International Nuclear Information System (INIS)

    Zhang, Wei-Wei; Gao, Fei; Goyal, Sandeep K; Sanders, Barry C; Simon, Christoph

    2016-01-01

    Cat states are coherent quantum superpositions of macroscopically distinct states and are useful for understanding the boundary between the classical and the quantum world. Due to their macroscopic nature, cat states are difficult to prepare in physical systems. We propose a method to create cat states in one-dimensional quantum walks using delocalized initial states of the walker. Since the quantum walks can be performed on any quantum system, our proposal enables a platform-independent realization of the cat states. We further show that the linear dispersion relation of the effective quantum walk Hamiltonian, which governs the dynamics of the delocalized states, is responsible for the formation of the cat states. We analyze the robustness of these states against environmental interactions and present methods to control and manipulate the cat states in the photonic implementation of quantum walks. (paper)

  8. Delocalization of Coherent Triplet Excitons in Linear Rigid Rod Conjugated Oligomers.

    Science.gov (United States)

    Hintze, Christian; Korf, Patrick; Degen, Frank; Schütze, Friederike; Mecking, Stefan; Steiner, Ulrich E; Drescher, Malte

    2017-02-02

    In this work, the triplet state delocalization in a series of monodisperse oligo(p-phenyleneethynylene)s (OPEs) is studied by pulsed electron paramagnetic resonance (EPR) and pulsed electron nuclear double resonance (ENDOR) determining zero-field splitting, optical spin polarization, and proton hyperfine couplings. Neither the zero-field splitting parameters nor the optical spin polarization change significantly with OPE chain length, in contrast to the hyperfine coupling constants, which showed a systematic decrease with chain length n according to a 2/(1 + n) decay law. The results provide striking evidence for the Frenkel-type nature of the triplet excitons exhibiting full coherent delocalization in the OPEs under investigation with up to five OPE repeat units and with a spin density distribution described by a nodeless particle in the box wave function. The same model is successfully applied to recently published data on π-conjugated porphyrin oligomers.

  9. Selecting core-hole localization or delocalization in CS2 by photofragmentation dynamics.

    Science.gov (United States)

    Guillemin, R; Decleva, P; Stener, M; Bomme, C; Marin, T; Journel, L; Marchenko, T; Kushawaha, R K; Jänkälä, K; Trcera, N; Bowen, K P; Lindle, D W; Piancastelli, M N; Simon, M

    2015-01-21

    Electronic core levels in molecules are highly localized around one atomic site. However, in single-photon ionization of symmetric molecules, the question of core-hole localization versus delocalization over two equivalent atoms has long been debated as the answer lies at the heart of quantum mechanics. Here, using a joint experimental and theoretical study of core-ionized carbon disulfide (CS2), we demonstrate that it is possible to experimentally select distinct molecular-fragmentation pathways in which the core hole can be considered as either localized on one sulfur atom or delocalized between two indistinguishable sulfur atoms. This feat is accomplished by measuring photoelectron angular distributions within the frame of the molecule, directly probing entanglement or disentanglement of quantum pathways as a function of how the molecule dissociates.

  10. Localization and delocalization of a one-dimensional system coupled with the environment

    Science.gov (United States)

    Zhu, Hong-Jun; Xiong, Shi-Jie

    2010-03-01

    We investigate several models of a one-dimensional chain coupling with surrounding atoms to elucidate disorder-induced delocalization in quantum wires, a peculiar behaviour against common wisdom. We show that the localization length is enhanced by disorder of side sites in the case of strong disorder, but in the case of weak disorder there is a plateau in this dependence. The above behaviour is the conjunct influence of the coupling to the surrounding atoms and the antiresonant effect. We also discuss different effects and their physical origin of different types of disorder in such systems. The numerical results show that coupling with the surrounding atoms can induce either the localization or delocalization effect depending on the values of parameters.

  11. Delocalization of charge and current in a chiral quasiparticle wave packet

    Science.gov (United States)

    Sarkar, Subhajit

    2018-03-01

    A chiral quasiparticle wave packet (c-QPWP) is defined as a conventional superposition of chiral quasiparticle states corresponding to an interacting electron system in two dimensions (2D) in the presence of Rashba spin-orbit coupling (RSOC). I investigate its internal structure via studying the charge and the current densities within the first-order perturbation in the electron-electron interaction. It is found that the c-QPWP contains a localized charge which is less than the magnitude of the bare charge and the remaining charge resides at the system boundary. The amount of charge delocalized turns out to be inversely proportional to the degenerate Fermi velocity v0(=√{α2+2 μ /m }) when RSOC (with strength α ) is weak, and therefore externally tunable. For strong RSOC, the magnitudes of both the delocalized charge and the current further strongly depend on the direction of propagation of the wave packet. Both the charge and the current densities consist of an anisotropic r-2 tail away from the center of the wave packet. Possible implications of such delocalizations in real systems corresponding to 2D semiconductor heterostructure are also discussed within the context of particle injection experiments.

  12. Quantum transport through disordered 1D wires: Conductance via localized and delocalized electrons

    International Nuclear Information System (INIS)

    Gopar, Víctor A.

    2014-01-01

    Coherent electronic transport through disordered systems, like quantum wires, is a topic of fundamental and practical interest. In particular, the exponential localization of electron wave functions-Anderson localization-due to the presence of disorder has been widely studied. In fact, Anderson localization, is not an phenomenon exclusive to electrons but it has been observed in microwave and acoustic experiments, photonic materials, cold atoms, etc. Nowadays, many properties of electronic transport of quantum wires have been successfully described within a scaling approach to Anderson localization. On the other hand, anomalous localization or delocalization is, in relation to the Anderson problem, a less studied phenomenon. Although one can find signatures of anomalous localization in very different systems in nature. In the problem of electronic transport, a source of delocalization may come from symmetries present in the system and particular disorder configurations, like the so-called Lévy-type disorder. We have developed a theoretical model to describe the statistical properties of transport when electron wave functions are delocalized. In particular, we show that only two physical parameters determine the complete conductance distribution

  13. Boiling heat transfer on horizontal tube bundles

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    Nucleate boiling heat transfer characteristics for a tube in a bundle differ from that for a single tube in a pool and this difference is known as 'tube bundle effect.' There exist two bundle effects, positive and negative. The positive bundle effect enhances heat transfer due to convective flow induced by rising bubbles generated from the lower tubes, while the negative bundle effect deteriorates heat transfer due to vapor blanketing caused by accumulation of bubbles. Staggered tube bundles tested and found that the upper tubes in bundles have higher heat transfer coefficients than the lower tubes. The effects of various parameters such as pressure, tube geometry and oil contamination on heat transfer have been examined. Some workers attempted to clarify the mechanism of occurrence of 'bundle effect' by testing tube arrangements of small scale. All reported only enhancement in heat transfer but results showed the symptom of heat transfer deterioration at higher heat fluxes. As mentioned above, it has not been clarified so far even whether the 'tube bundle effect' should serve as enhancement or deterioration of heat transfer in nucleate boiling. In this study, experiments are performed in detail by using bundles of small scale, and effects of heat flux distribution, pressure and tube location are clarified. Furthermore, some consideration on the mechanisms of occurrence of 'tube bundle effect' is made and a method for prediction of heat transfer rate is proposed

  14. SURFACE ALFVEN WAVES IN SOLAR FLUX TUBES

    Energy Technology Data Exchange (ETDEWEB)

    Goossens, M.; Andries, J.; Soler, R.; Van Doorsselaere, T. [Centre for Plasma Astrophysics, Department of Mathematics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Arregui, I.; Terradas, J., E-mail: marcel.goossens@wis.kuleuven.be [Solar Physics Group, Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2012-07-10

    Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. Alfven waves and magneto-sonic waves are particular classes of MHD waves. These wave modes are clearly different and have pure properties in uniform plasmas of infinite extent only. Due to plasma non-uniformity, MHD waves have mixed properties and cannot be classified as pure Alfven or magneto-sonic waves. However, vorticity is a quantity unequivocally related to Alfven waves as compression is for magneto-sonic waves. Here, we investigate MHD waves superimposed on a one-dimensional non-uniform straight cylinder with constant magnetic field. For a piecewise constant density profile, we find that the fundamental radial modes of the non-axisymmetric waves have the same properties as surface Alfven waves at a true discontinuity in density. Contrary to the classic Alfven waves in a uniform plasma of infinite extent, vorticity is zero everywhere except at the cylinder boundary. If the discontinuity in density is replaced with a continuous variation of density, vorticity is spread out over the whole interval with non-uniform density. The fundamental radial modes of the non-axisymmetric waves do not need compression to exist unlike the radial overtones. In thin magnetic cylinders, the fundamental radial modes of the non-axisymmetric waves with phase velocities between the internal and the external Alfven velocities can be considered as surface Alfven waves. On the contrary, the radial overtones can be related to fast-like magneto-sonic modes.

  15. How thick are chromoelectric flux tubes

    International Nuclear Information System (INIS)

    Luescher, M.; Muenster, G.; Weisz, P.

    1980-07-01

    We analyse the space dependence of the expectation value of the chromoelectric energy density in the presence of a static quark anti-quark pair by means of the strong coupling expansion on a lattice and by the relativistic string model. Both methods indicate that the transversal width of the field energy distribution increases without bound, when the quark anti-qark separation goes to infinity. (orig.)

  16. Feeding Tubes

    Science.gov (United States)

    ... feeding therapies have been exhausted. Please review product brand and method of placement carefully with your physician ... Total Parenteral Nutrition. Resources: Oley Foundation Feeding Tube Awareness Foundation Children’s Medical Nutrition Alliance APFED’s Educational Webinar ...

  17. The degree of π electron delocalization and the formation of 3D-extensible sandwich structures.

    Science.gov (United States)

    Wang, Xiang; Wang, Qiang; Yuan, Caixia; Zhao, Xue-Feng; Li, Jia-Jia; Li, Debao; Wu, Yan-Bo; Wang, Xiaotai

    2016-04-28

    DFT B3LYP/6-31G(d) calculations were performed to examine the feasibility of graphene-like C42H18 and starbenzene C6(BeH)6 (SBz) polymers as ligands of 3D-extensible sandwich compounds (3D-ESCs) with uninterrupted sandwich arrays. The results revealed that sandwich compounds with three or more C42H18 ligands were not feasible. The possible reason may be the localization of π electrons on certain C6 hexagons due to π-metal interactions, which makes the whole ligand lose its electronic structure basis (higher degree of π electron delocalization) to maintain the planar structure. For comparison, with the aid of benzene (Bz) molecules, the SBz polymers can be feasible ligands for designing 3D-ESCs because the C-Be interactions in individual SBz are largely ionic, which will deter the π electrons on one C6 ring from connecting to those on neighbouring C6 rings. This means that high degree of π electron delocalization is not necessary for maintaining the planarity of SBz polymers. Such a locally delocalized π electron structure is desirable for the ligands of 3D-ESCs. Remarkably, the formation of a sandwich compound with SBz is thermodynamically more favourable than that found for bis(Bz)chromium. The assembly of 3D-ESCs is largely exothermic, which will facilitate future experimental synthesis. The different variation trends on the HOMO-LUMO gaps in different directions (relative to the sandwich axes) suggest that they can be developed to form directional conductors or semiconductors, which may be useful in the production of electronic devices.

  18. Steam generator tube extraction

    International Nuclear Information System (INIS)

    Delorme, H.

    1985-05-01

    To enable tube examination on steam generators in service, Framatome has now developed a process for removing sections of steam generator tubes. Tube sections can be removed without being damaged for treating the tube section expanded in the tube sheet

  19. Ferromagnetism carried by highly delocalized hybrid states in Sc-doped ZnO thin films

    KAUST Repository

    Benali Kanoun, Mohammed

    2012-05-29

    We present first-principles results for Sc-doped ZnOthin films. Neighboring Sc atoms in the surface and/or subsurface layers are found to be coupled ferromagnetically, where only two of the possible configurations induce spin polarization. In the first configuration, the polarization is carried by the Sc d states as expected for transition metaldoping. However, there is a second configuration which is energetically favorable. It is governed by polarized hybrid states of the Zns, O p, and Sc d orbitals. Such highly delocalized states can be an important ingredient for understanding the magnetism of dopedZnOthin films.

  20. Manifestation of Strongly Delocalized Atomic States in the 5s Photoionization of Xenon

    International Nuclear Information System (INIS)

    Schmoranzer, H.; Lauer, S.; Vollweiler, F.; Reichardt, G.; Schartner, K.; Mentzel, G.; Wilhelmi, O.; Sukhorukov, V.L.; Lagutin, B.M.; Petrov, I.D.

    1997-01-01

    The photoionization (PI) of the Xe atom was investigated in the vicinity of the 5s -shell threshold by photon-induced fluorescence spectroscopy. The highest resolution so far attained of 2meV enabled us to observe a new series of resonance structures in the 5s -PI cross section closely above threshold. Calculations of the partial 5s - and 5p -PI cross sections were performed taking into account many-electron correlations. These structures were related with strongly delocalized f -resonances which affect the 5s -PI cross section due to their mixing with p -resonances. copyright 1997 The American Physical Society

  1. Improving the calandria tubes for CANDU reactors

    International Nuclear Information System (INIS)

    Coleman, C.E.; Fong, R.W.L.; Doubt, G.L.

    1997-01-01

    CANDU calandria tubes are made from annealed Zircaloy-2 sheet formed into a cylinder and welded along its length to make the tube. The current calandria tubes have given exemplary service for many years. With more stringent regulations and the need to accommodate warm cooling water in tropical countries, we started a development program to increase the margins for failure during postulated accidents. These improvements involve increasing the tube strength and optimising the heat-transfer from an excessively hot fuel channel to the cool moderator. If the postulated accident involves a pressure tube break, it would be desirable if the calandria tube withstood the full pressure of the heat-transport system. The weakest link in current calandria tubes is the weld. Thickening the weld can increase the strength by 20% while seamless tubes can be 45% stronger than current tubes. The latter tubes can hold full system pressure for many hours without failure. If during the postulated accident the fuel and pressure tube become excessively hot but do not touch the calandria tube, the radiant heat loss must be maximised. Current calandria tubes have an absorptivity (emissivity) of about 0.2. To protect the fuel and the fuel channel we have devised a finish to the inside surface of the calandria tube that increases the emissivity to 0.7. If during the postulated accident the hot pressure tube touches the cool calandria tube, the contact conductance and the critical heat flux must be optimised to ensure nucleate boiling of the moderator at the outside surface of the calandria tube and therefore efficient exploitation of the moderator as a heat sink. In laboratory tests small ridges on the inside surface and roughening of the outside surface have been shown to increase the margins against failure and increase the possible moderator temperatures thus providing the opportunity to decrease the cost of the moderator heat-exchange system and remove restrictions on reactor operation in

  2. Dark states and delocalization: Competing effects of quantum coherence on the efficiency of light harvesting systems.

    Science.gov (United States)

    Hu, Zixuan; Engel, Gregory S; Alharbi, Fahhad H; Kais, Sabre

    2018-02-14

    Natural light harvesting systems exploit electronic coupling of identical chromophores to generate efficient and robust excitation transfer and conversion. Dark states created by strong coupling between chromophores in the antenna structure can significantly reduce radiative recombination and enhance energy conversion efficiency. Increasing the number of the chromophores increases the number of dark states and the associated enhanced energy conversion efficiency yet also delocalizes excitations away from the trapping center and reduces the energy conversion rate. Therefore, a competition between dark state protection and delocalization must be considered when designing the optimal size of a light harvesting system. In this study, we explore the two competing mechanisms in a chain-structured antenna and show that dark state protection is the dominant mechanism, with an intriguing dependence on the parity of the number of chromophores. This dependence is linked to the exciton distribution among eigenstates, which is strongly affected by the coupling strength between chromophores and the temperature. Combining these findings, we propose that increasing the coupling strength between the chromophores can significantly increase the power output of the light harvesting system.

  3. Ear Tubes

    Science.gov (United States)

    ... of the ear drum or eustachian tube, Down Syndrome, cleft palate, and barotrauma (injury to the middle ear caused by a reduction of air pressure, ... specialist) may be warranted if you or your child has experienced repeated ... fluid in the middle ear, barotrauma, or have an anatomic abnormality that ...

  4. Theoretical studies of π-electron delocalization and localization on intramolecular proton transfer in the ground state

    Science.gov (United States)

    Peng, Hongliang; Huang, Pengru; Yi, Pinggui; Xu, Fen; Sun, Lixian

    2018-02-01

    Proton transfer processes of 15 benzimidazole compounds are studied by density functional theory methods, and natural orbital energy index (NOEI) is introduced. Here, NOEI and nucleus independent chemical shift (NICS) are applied to estimate the π-electron localization and delocalization, respectively. Proton transfer potential energy surfaces are calculated to explore these processes, and the results show that the changes of the π-electron delocalization of the phenyl (pyridyl) is the main factors for the stability of keto form. There is high correlation between the π-electron delocalization and the proton transfer barrier. When the π-electron localization is considered, the regression increases the correlation coefficient, increasing from 0.9663 to 0.9864. NOEI index is sensitive to π-electron localization; it is a beneficial and useful complement to NICS.

  5. σ-Bond Electron Delocalization in Oligosilanes as Function of Substitution Pattern, Chain Length, and Spatial Orientation

    Directory of Open Access Journals (Sweden)

    Johann Hlina

    2016-08-01

    Full Text Available Polysilanes are known to exhibit the interesting property of σ-bond electron delocalization. By employing optical spectroscopy (UV-vis, it is possible to judge the degree of delocalization and also differentiate parts of the molecules which are conjugated or not. The current study compares oligosilanes of similar chain length but different substitution pattern. The size of the substituents determines the spatial orientation of the main chain and also controls the conformational flexibility. The chemical nature of the substituents affects the orbital energies of the molecules and thus the positions of the absorption bands.

  6. Electron tube

    Science.gov (United States)

    Suyama, Motohiro [Hamamatsu, JP; Fukasawa, Atsuhito [Hamamatsu, JP; Arisaka, Katsushi [Los Angeles, CA; Wang, Hanguo [North Hills, CA

    2011-12-20

    An electron tube of the present invention includes: a vacuum vessel including a face plate portion made of synthetic silica and having a surface on which a photoelectric surface is provided, a stem portion arranged facing the photoelectric surface and made of synthetic silica, and a side tube portion having one end connected to the face plate portion and the other end connected to the stem portion and made of synthetic silica; a projection portion arranged in the vacuum vessel, extending from the stem portion toward the photoelectric surface, and made of synthetic silica; and an electron detector arranged on the projection portion, for detecting electrons from the photoelectric surface, and made of silicon.

  7. Chest tube insertion

    Science.gov (United States)

    Chest drainage tube insertion; Insertion of tube into chest; Tube thoracostomy; Pericardial drain ... Be careful there are no kinks in your tube. The drainage system should always sit upright and be placed ...

  8. TEMPERATURE GRADIENTS IN THE SOLAR ATMOSPHERE AND THE ORIGIN OF CUTOFF FREQUENCY FOR TORSIONAL TUBE WAVES

    International Nuclear Information System (INIS)

    Routh, S.; Musielak, Z. E.; Hammer, R.

    2010-01-01

    Fundamental modes supported by a thin magnetic flux tube embedded in the solar atmosphere are typically classified as longitudinal, transverse, and torsional waves. If the tube is isothermal, then the propagation of longitudinal and transverse tube waves is restricted to frequencies that are higher than the corresponding global cutoff frequency for each wave. However, no such global cutoff frequency exists for torsional tube waves, which means that a thin and isothermal flux tube supports torsional tube waves of any frequency. In this paper, we consider a thin and non-isothermal magnetic flux tube and demonstrate that temperature gradients inside this tube are responsible for the origin of a cutoff frequency for torsional tube waves. The cutoff frequency is used to determine conditions for the wave propagation in the solar atmosphere, and the obtained results are compared to the recent observational data that support the existence of torsional tube waves in the Sun.

  9. Statistical and stochastic aspects of the delocalization problem in quantum mechanics

    International Nuclear Information System (INIS)

    Claverie, P.; Diner, S.

    1976-01-01

    The space-time behaviour of electrons in atoms and molecules is reviewed. The wave conception of the electron is criticized and the poverty of the non-reductionist attitude is underlined. Further, the two main interpretations of quantum mechanics are recalled: the Copenhagen and the Statistical Interpretations. The meaning and the successes of the Statistical Interpretation are explained and it is shown that it does not solve all problems because quantum mechanics is irreducible to a classical statistical theory. The fluctuation of the particle number and its relationship to loge theory, delocalization and correlation is studied. Finally, different stochastic models for microphysics are reviewed. The markovian Fenyes-Nelson process allows an interpretation of the original heuristic considerations of Schroedinger. Non-markov processes with Schroedinger time evolution are shown to be equivalent to the base state analysis of Feynmann but they are unsatisfactory from a probabilistic point of view. Stochastic electrodynamics is presented as the most satisfactory conception nowadays

  10. Theory of Excitonic Delocalization for Robust Vibronic Dynamics in LH2.

    Science.gov (United States)

    Caycedo-Soler, Felipe; Lim, James; Oviedo-Casado, Santiago; van Hulst, Niek F; Huelga, Susana F; Plenio, Martin B

    2018-06-11

    Nonlinear spectroscopy has revealed long-lasting oscillations in the optical response of a variety of photosynthetic complexes. Different theoretical models that involve the coherent coupling of electronic (excitonic) or electronic-vibrational (vibronic) degrees of freedom have been put forward to explain these observations. The ensuing debate concerning the relevance of either mechanism may have obscured their complementarity. To illustrate this balance, we quantify how the excitonic delocalization in the LH2 unit of Rhodopseudomonas acidophila purple bacterium leads to correlations of excitonic energy fluctuations, relevant coherent vibronic coupling, and importantly, a decrease in the excitonic dephasing rates. Combining these effects, we identify a feasible origin for the long-lasting oscillations observed in fluorescent traces from time-delayed two-pulse single-molecule experiments performed on this photosynthetic complex and use this approach to discuss the role of this complementarity in other photosynthetic systems.

  11. Towards a Density Functional Theory Exchange-Correlation Functional able to describe localization/delocalization

    Science.gov (United States)

    Mattsson, Ann E.; Wills, John M.

    2013-03-01

    The inability to computationally describe the physics governing the properties of actinides and their alloys is the poster child of failure of existing Density Functional Theory exchange-correlation functionals. The intricate competition between localization and delocalization of the electrons, present in these materials, exposes the limitations of functionals only designed to properly describe one or the other situation. We will discuss the manifestation of this competition in real materials and propositions on how to construct a functional able to accurately describe properties of these materials. I addition we will discuss both the importance of using the Dirac equation to describe the relativistic effects in these materials, and the connection to the physics of transition metal oxides. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Radiant absorption characteristics of corrugated curved tubes

    Directory of Open Access Journals (Sweden)

    Đorđević Milan Lj.

    2017-01-01

    Full Text Available The utilization of modern paraboloidal concentrators for conversion of solar radiation into heat energy requires the development and implementation of compact and efficient heat absorbers. Accurate estimation of geometry influence on absorption characteristics of receiver tubes is an important step in this process. This paper deals with absorption characteristics of heat absorber made of spirally coiled tubes with transverse circular corrugations. Detailed 3-D surface-to-surface Hemicube method was applied to compare radiation performances of corrugated and smooth curved tubes. The numerical results were obtained by varying the tube curvature ratio and incident radiant heat flux intensity. The details of absorption efficiency of corrugated tubes and the effect of curvature on absorption properties for both corrugated and smooth tubes were presented. The results may have significance to further analysis of highly efficient heat absorbers exposed to concentrated radiant heating. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 42006

  13. Source Terms for HFIR Beam Tube Shielding Analyses, and a Complete Shielding Analysis of the HB-3 Tube

    International Nuclear Information System (INIS)

    Bucholz, J.A.

    2000-01-01

    The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory is in the midst of a massive upgrade program to enhance experimental facilities. The reactor presently has four horizontal experimental beam tubes, all of which will be replaced or redesigned. The HB-2 beam tube will be enlarged to support more guide tubes, while the HB-4 beam tube will soon include a cold neutron source

  14. Source Terms for HFIR Beam Tube Shielding Analyses, and a Complete Shielding Analysis of the HB-3 Tube

    Energy Technology Data Exchange (ETDEWEB)

    Bucholz, J.A.

    2000-07-01

    The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory is in the midst of a massive upgrade program to enhance experimental facilities. The reactor presently has four horizontal experimental beam tubes, all of which will be replaced or redesigned. The HB-2 beam tube will be enlarged to support more guide tubes, while the HB-4 beam tube will soon include a cold neutron source.

  15. Studies in boiling heat transfer in two phase flow through tube arrays: nucleate boiling heat transfer coefficient and maximum heat flux as a function of velocity and quality of Freon-113

    International Nuclear Information System (INIS)

    Rahmani, R.

    1983-01-01

    The nucleate boiling heat-transfer coefficient and the maximum heat flux were studied experimentally as functions of velocity, quality and heater diameter for single-phase flow, and two-phase flow of Freon-113 (trichlorotrifluorethane). Results show: (1) peak heat flux: over 300 measured peak heat flux data from two 0.875-in. and four 0.625-in.-diameter heaters indicated that: (a) for pool boiling, single-phase and two-phase forced convection boiling the only parameter (among hysteresis, rate of power increase, aging, presence and proximity of unheated rods) that has a statistically significant effect on the peak heat flux is the velocity. (b) In the velocity range (0 0 position or the point of impact of the incident fluid) and the top (180 0 position) of the test element, respectively

  16. Neutron flux measurement by mobile detectors

    International Nuclear Information System (INIS)

    Verchain, M.

    1987-01-01

    Various incore instrumentation systems and their technological evolution are first reviewed. Then, for 1300 MWe PWR nuclear power plant, temperature and neutron flux measurement are described. Mobile fission chambers, with their large measuring range and accurate location allow a good knowledge of the core. Other incore measures are possible because of flux detector thimble tubes inserted in the reactor core [fr

  17. Physics of magnetic flux ropes. Geophysical Monograph, No. 58

    International Nuclear Information System (INIS)

    Russell, C.T.; Priest, E.R.; Lee, L.C.

    1990-01-01

    The present work encompasses papers on the structure, waves, and instabilities of magnetic flux ropes (MFRs), photospheric flux tubes (PFTs), the structure and heating of coronal loops, solar prominences, coronal mass ejections and magnetic clouds, flux ropes in planetary ionospheres, the magnetopause, magnetospheric field-aligned currents and flux tubes, and the magnetotail. Attention is given to the equilibrium of MFRs, resistive instability, magnetic reconnection and turbulence in current sheets, dynamical effects and energy transport in intense flux tubes, waves in solar PFTs, twisted flux ropes in the solar corona, an electrodynamical model of solar flares, filament cooling and condensation in a sheared magnetic field, the magnetopause, the generation of twisted MFRs during magnetic reconnection, ionospheric flux ropes above the South Pole, substorms and MFR structures, evidence for flux ropes in the earth magnetotail, and MFRs in 3D MHD simulations

  18. Intuitive Understanding of sigma Delocalization in Loose and sigma Localization in Tight Helical Conformations of an Oligosilane Chain

    Czech Academy of Sciences Publication Activity Database

    Jovanovic, M.; Antic, D.; Rooklin, D.; Bande, A.; Michl, Josef

    2017-01-01

    Roč. 12, č. 11 (2017), s. 1250-1263 ISSN 1861-4728 Institutional support: RVO:61388963 Keywords : electron delocalization * electron localization * electronic states * oligosilanes * sigma conjugation Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 4.083, year: 2016

  19. Effect of Molecular Packing and Charge Delocalization on the Nonradiative Recombination of Charge-Transfer States in Organic Solar Cells

    KAUST Repository

    Chen, Xiankai

    2016-09-05

    In organic solar cells, a major source of energy loss is attributed to nonradiative recombination from the interfacial charge transfer states to the ground state. By taking pentacene–C60 complexes as model donor–acceptor systems, a comprehensive theoretical understanding of how molecular packing and charge delocalization impact these nonradiative recombination rates at donor–acceptor interfaces is provided.

  20. photomultiplier tubes

    CERN Multimedia

    photomultiplier tubes. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  1. photomultiplier tube

    CERN Multimedia

    photomultiplier tubes. A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

  2. Intra-molecular Charge Transfer and Electron Delocalization in Non-fullerene Organic Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qinghe [Department of Chemistry, Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Guangdong 515063, P. R. China; Zhao, Donglin [Department of Chemistry, The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States; Goldey, Matthew B. [Institute for Molecular Engineering, The University of Chicago, 5747 South Ellis Avenue, Chicago, Illinois 60637, United States; Filatov, Alexander S. [Department of Chemistry, The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States; Sharapov, Valerii [Department of Chemistry, The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States; Colón, Yamil J. [Institute for Molecular Engineering, Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States; Institute for Molecular Engineering, The University of Chicago, 5747 South Ellis Avenue, Chicago, Illinois 60637, United States; Cai, Zhengxu [Department of Chemistry, The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States; Chen, Wei [Institute for Molecular Engineering, Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States; Institute for Molecular Engineering, The University of Chicago, 5747 South Ellis Avenue, Chicago, Illinois 60637, United States; de Pablo, Juan [Institute for Molecular Engineering, Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States; Institute for Molecular Engineering, The University of Chicago, 5747 South Ellis Avenue, Chicago, Illinois 60637, United States; Galli, Giulia [Institute for Molecular Engineering, Materials Science Division, Argonne National Laboratory, 9700 Cass Avenue, Lemont, Illinois 60439, United States; Institute for Molecular Engineering, The University of Chicago, 5747 South Ellis Avenue, Chicago, Illinois 60637, United States; Yu, Luping [Department of Chemistry, The James Franck Institute, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, United States

    2018-03-02

    Two types of electron acceptors were synthesized by coupling two kinds of electron-rich cores with four equivalent perylene diimides (PDIs) at the a position. With fully aromatic cores, TPB and TPSe have pi-orbitals spread continuously over the whole aromatic conjugated backbone, unlike TPC and TPSi, which contain isolated PDI units due to the use of a tetrahedron carbon or silicon linker. Density functional theory calculations of the projected density of states showed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) for TPB are localized in separate regions of space. Further, the LUMO of TPB shows a greater contribution from the orbitals belonging to the connective core of the molecules than that of TPC. Overall, the properties of the HOMO and LUMO point at increased intra-molecular delocalization of negative charge carriers for TPB and TPSe than for TPC and TPSi and hence at a more facile intra-molecular charge transfer for the former. The film absorption and emission spectra showed evidences for the inter -molecular electron delocalization in TPB and TPSe, which is consistent with the network structure revealed by X-ray diffraction studies on single crystals of TPB. These features benefit the formation of charge transfer states and/or facilitate charge transport. Thus, higher electron mobility and higher charge dissociation probabilities under J(sc) condition were observed in blend films of TPB:PTB7-Th and TPSe:PTB7-Th than those in TPC:PTB7Th and TPSi:PTB7-Th blend films. As a result, the J(sc) and fill factor values of 15.02 mA/cm(2), 0.58 and 14.36 mA/cm(2), 0.55 for TPB- and TPSe-based solar cell are observed, whereas those for TPC and TPSi are 11.55 mA/cm2, 0.47 and 10.35 mA/cm(2), 0.42, respectively.

  3. Horizontal beam tubes in FRM-II

    International Nuclear Information System (INIS)

    Coors, D.; Vanvor, D.

    2001-01-01

    The new research reactor in Garching FRM-II is equipped with 10 leak tight horizontal beam tubes (BT1 - BT10), each of them consisting of a beam tube structure taking an insert with neutron channels. The design of all beam tube structures is similar whereas the inserts are adapted to the special requirements of the using of each beam tube. Inside the reflector tank the beam tube structures are shaped by the inner cones which are made of Al-alloy with circular and rectangular cross sections. They are located in the region of maximum neutron flux (exception BT10), they are directly connected to the flanges of the reflector tank, their lengths are about 1.5 m (exception BT10) and their axes are directed tagentially to the core centre thus contributing to a low γ-noise at the experiments. (orig.)

  4. Physics of Magnetic Flux Ropes

    CERN Document Server

    Priest, E R; Lee, L C

    1990-01-01

    The American Geophysical Union Chapman Conference on the Physics of Magnetic Flux Ropes was held at the Hamilton Princess Hotel, Hamilton, Bermuda on March 27–31, 1989. Topics discussed ranged from solar flux ropes, such as photospheric flux tubes, coronal loops and prominences, to flux ropes in the solar wind, in planetary ionospheres, at the Earth's magnetopause, in the geomagnetic tail and deep in the Earth's magnetosphere. Papers presented at that conference form the nucleus of this book, but the book is more than just a proceedings of the conference. We have solicited articles from all interested in this topic. Thus, there is some material in the book not discussed at the conference. Even in the case of papers presented at the conference, there is generally a much more detailed and rigorous presentation than was possible in the time allowed by the oral and poster presentations.

  5. Exploring Fragility: Industrial Delocalization, Occupational and Environmental Risks, and Non-Governmental Organizations

    Directory of Open Access Journals (Sweden)

    Raquel Maria Rigotto

    2009-03-01

    Full Text Available What is the role of non-governmental organizations – NGOs – in the process of industrial delocalization and socio-spatial redistribution of occupational and environmental risks? In an attempt to contribute to this debate, this study approaches the issue in a very specific socio-historical context, marked by recent accelerated industrialization in a small town in Northeast Brazil. Based on semi-structured interviews with leaders of four local NGOs, the way they perceive and value the risks introduced into the area and relations between industrialization and local development are analyzed. Findings show a strong adherence to the industrial plan by workers’ trade unions, whilst other NGOs are highly critical with regard thereto, but undertake no social or political activity regarding the issues they identify. This phenomenon is discussed in terms of the modus operandi of ideology and its strategies for symbolic construction, enabling a comprehensive reinterpretation of how capital also benefits, in its mobility, from local society’s fragility in organizing and protecting quality of life and public health.

  6. Delocalized organic pollutant destruction through a self-sustaining supercritical water oxidation process

    International Nuclear Information System (INIS)

    Lavric, E.D.; Weyten, H.; Ruyck, J. de; Plesu, V.; Lavric, V.

    2005-01-01

    Supercritical water oxidation (SCWO) is a recent development aiming at the destruction of organic pollutants present with low concentrations in waste waters. The present paper focuses on the process simulation of SCWO with emphasis on the proper modelling of supercritical thermodynamic conditions and on the possibility to make the SCWO process self-sufficient from the energetic viewpoint. Self-sufficiency may be of interest to encourage more delocalization of waste water treatment. The process of SCWO for dilute waste water (no more than 5 wt.%) is modelled through the ASPEN Plus copyright process simulator. Studies were made to search for energetic self-sufficiency conditions using various technologies for power production from the heat of reaction, like supercritical water expansion in a turbine, use of a closed Brayton cycle (CBC) and use of an organic Rankine cycle (ORC). The results obtained showed that the process is energetically self-sufficient using either a small supercritical turbine, or an ORC. In less restrictive conditions regarding the component efficiencies, the CBC, in theory, also leads to self-sufficiency, but from the analysis, it appears that this solution is less realistic

  7. Detecting a pronounced delocalized state in third-harmonic generation phenomenon; a quantum chaos approach

    Science.gov (United States)

    Behnia, S.; Ziaei, J.; Khodavirdizadeh, M.

    2018-06-01

    Nonlinear optics (NLO) deserves special attention in new optical devices, making it possible to generate coherent light more efficiently. Among the various NLO phenomena the third-harmonic generation (THG) is at the core of the effective operating mechanism of broadband wavelength conversion, in all-optical devices. Here, we aim to understand how the third-order susceptibility and the electric field may be effectively effect on the localization properties of the light in the THG process when included in a two-mode cavity coherently perturbed by a classical field. We address a stable-unstable transition due to the combination effect of the aforementioned factors. We report a reliable evidence confirming the appearance of chaos in THG under suitable conditions. By tracing the signatures of adjacent-spectral-spacing-ratio (ASSR) distribution and participation ratio, we also find a critical point (ɛc ,κc) =(3 . 1 , 0 . 35) for which a pronounced delocalized response is seen. This study may have profound findings for practical devices, and ushers in new opportunities for practical exploitation of the electric field and the third-order susceptibility effect in nonlinear optical devices.

  8. Charge-Transfer States in Organic Solar Cells: Understanding the Impact of Polarization, Delocalization, and Disorder

    KAUST Repository

    Zheng, Zilong

    2017-05-08

    We investigate the impact of electronic polarization, charge delocalization, and energetic disorder on the charge-transfer (CT) states formed at a planar C60/pentacene interface. The ability to examine large complexes containing up to seven pentacene molecules and three C60 molecules allows us to take explicitly into account the electronic polarization effects. These complexes are extracted from a bilayer architecture modeled by molecular dynamics simulations and evaluated by means of electronic-structure calculations based on long-range-separated functionals (ωB97XD and BNL) with optimized range-separation parameters. The energies of the lowest charge-transfer states derived for the large complexes are in very good agreement with the experimentally reported values. The average singlet-triplet energy splittings of the lowest CT states are calculated not to exceed 10 meV. The rates of geminate recombination as well as of dissociation of the triplet excitons are also evaluated. In line with experiment, our results indicate that the pentacene triplet excitons generated through singlet fission can dissociate into separated charges on a picosecond time scale, despite the fact that their energy in C60/pentacene heterojunctions is slightly lower than the energies of the lowest CT triplet states.

  9. Burnout in a channel with non-uniform circumferential heat flux

    International Nuclear Information System (INIS)

    Lee, D.H.

    1966-03-01

    Burnout experiments are reported for uniform flux and circumferential flux tilt (maximum/average flux about 1.25) with tubes and annuli, all the experiments having uniform axial heating. These show similar results, the burnout power with flux tilt being within 10% of that with uniform flux. For the same mean exit steam quality, the local maximum flux is higher than the predicted burnout value and generally a better prediction is obtained using the average flux. (author)

  10. Eustachian tube patency

    Science.gov (United States)

    Eustachian tube patency refers to how much the eustachian tube is open. The eustachian tube runs between the middle ear and the throat. It controls the pressure behind the eardrum and middle ear space. This helps keep ...

  11. Feeding tube - infants

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/007235.htm Feeding tube - infants To use the sharing features on this page, please enable JavaScript. A feeding tube is a small, soft, plastic tube placed ...

  12. Electron charge and spin delocalization revealed in the optically probed longitudinal and transverse spin dynamics in n -GaAs

    Science.gov (United States)

    Belykh, V. V.; Kavokin, K. V.; Yakovlev, D. R.; Bayer, M.

    2017-12-01

    The evolution of the electron spin dynamics as consequence of carrier delocalization in n -type GaAs is investigated by the recently developed extended pump-probe Kerr/Faraday rotation spectroscopy. We find that isolated electrons localized on donors demonstrate a prominent difference between the longitudinal and transverse spin relaxation rates in a magnetic field, which is almost absent in the metallic phase. The inhomogeneous transverse dephasing time T2* of the spin ensemble strongly increases upon electron delocalization as a result of motional narrowing that can be induced by increasing either the donor concentration or the temperature. An unexpected relation between T2* and the longitudinal spin relaxation time T1 is found, namely, that their product is about constant, as explained by the magnetic field effect on the spin diffusion. We observe a two-stage longitudinal spin relaxation, which suggests the establishment of spin temperature in the system of exchange-coupled donor-bound electrons.

  13. Characteristics of the JRR-3M neutron guide tubes

    International Nuclear Information System (INIS)

    Suzuki, Masatoshi; Ichikawa, Hiroki; Kawabata, Yuji.

    1993-01-01

    Large scale neutron guide tubes have been installed in the upgraded JRR-3 (Japan Research Reactor No.3, JRR-3M). The total length of the guide tubes is 232m. The neutron fluxes and spectra were measured at the end of the neutron guide tubes. The neutron fluxes of thermal neutron guide tubes with characteristic wavelength of 2A are 1.2 x 10 8 n/cm 2 · s. The neutron fluxes of cold guide tubes are 1.4 x 10 8 n/cm 2 · s with characteristic wavelength of 4A and 2.0 x 10 8 n/cm 2 · s with 6A when the cold neutron source is operated. The neutron spectra measured by time-of-flight method agree well with their designed ones. (author)

  14. Observation of suppressed Auger mechanism in type-I quantum well structures with delocalized electron-hole wavefunctions

    Energy Technology Data Exchange (ETDEWEB)

    Hassani Nia, Iman; Fathipour, Vala; Mohseni, Hooman, E-mail: hmohseni@ece.northwestern.edu [Bio-Inspired Sensors and Optoelectronics Laboratory (BISOL), Department of Electrical Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-08-15

    We report the first observation of non-threshold Auger mechanism for a quantum well structure with Type-I band alignment. Excitation-dependent photoluminescence measurements were used to extract the Auger recombination coefficients from 77 K up to room temperature. The results verify the role of interface mediated momentum exchange as well as suppression of Auger recombination for delocalized electron-hole wavefunctions.

  15. Tube holding system

    International Nuclear Information System (INIS)

    Cunningham, R.C.

    1978-01-01

    A tube holding rig is described for the lateral support of tubes arranged in tight parcels in a heat exchanger. This tube holding rig includes not less than two tube supporting assemblies, with a space between them, located crosswise with respect to the tubes, each supporting assembly comprising a first set of parallel components in contact with the tubes, whilst a second set of components is also in contact with the tubes. These two sets of parts together define apertures through which the tubes pass [fr

  16. Elucidating the role of surface passivating ligand structural parameters in hole wave function delocalization in semiconductor cluster molecules.

    Science.gov (United States)

    Teunis, Meghan B; Nagaraju, Mulpuri; Dutta, Poulami; Pu, Jingzhi; Muhoberac, Barry B; Sardar, Rajesh; Agarwal, Mangilal

    2017-09-28

    This article describes the mechanisms underlying electronic interactions between surface passivating ligands and (CdSe) 34 semiconductor cluster molecules (SCMs) that facilitate band-gap engineering through the delocalization of hole wave functions without altering their inorganic core. We show here both experimentally and through density functional theory calculations that the expansion of the hole wave function beyond the SCM boundary into the ligand monolayer depends not only on the pre-binding energetic alignment of interfacial orbitals between the SCM and surface passivating ligands but is also strongly influenced by definable ligand structural parameters such as the extent of their π-conjugation [π-delocalization energy; pyrene (Py), anthracene (Anth), naphthalene (Naph), and phenyl (Ph)], binding mode [dithiocarbamate (DTC, -NH-CS 2 - ), carboxylate (-COO - ), and amine (-NH 2 )], and binding head group [-SH, -SeH, and -TeH]. We observe an unprecedentedly large ∼650 meV red-shift in the lowest energy optical absorption band of (CdSe) 34 SCMs upon passivating their surface with Py-DTC ligands and the trend is found to be Ph- wave function delocalization rather than carrier trapping and/or phonon-mediated relaxation. Taken together, knowledge of how ligands electronically interact with the SCM surface is crucial to semiconductor nanomaterial research in general because it allows the tuning of electronic properties of nanomaterials for better charge separation and enhanced charge transfer, which in turn will increase optoelectronic device and photocatalytic efficiencies.

  17. Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization.

    Science.gov (United States)

    Lin, Qisheng; Miller, Gordon J

    2018-01-16

    complexity can be realized by small amounts of Li replacing Zn atoms in the parent binary compounds CaZn 2 , CaZn 3 , and CaZn 5 ; their phase formation and bonding schemes can be rationalized by Fermi surface-Brillouin zone interactions between nearly free-electron states. "Cation-rich", electron-poor polar intermetallics have emerged using rare earth metals as the electropositive ("cationic") component together metal/metalloid clusters that mimic the backbones of aromatic hydrocarbon molecules, which give evidence of extensive electronic delocalization and multicenter bonding. Thus, we can identify three distinct, valence electron-poor, polar intermetallic systems that have yielded unprecedented phases adopting novel structures containing complex clusters and intriguing bonding characteristics. In this Account, we summarize our recent specific progress in the developments of novel Au-rich BaAl 4 -type related structures, shown in the "gold-rich grid", lithiation-modulated Ca-Li-Zn phases stabilized by different bonding characteristics, and rare earth-rich polar intermetallics containing unprecedented hydrocarbon-like planar Co-Ge metal clusters and pronounced delocalized multicenter bonding. We will focus mainly on novel structural motifs, bonding analyses, and the role of valence electrons for phase stability.

  18. Numerical investigation of heat transfer in annulus laminar flow of multi tubes-in-tube helical coil

    Science.gov (United States)

    Nada, S. A.; Elattar, H. F.; Fouda, A.; Refaey, H. A.

    2018-03-01

    In the present study, a CFD analysis using ANSYS-FLUENT 14.5 CFD package is used to investigate the characteristics of heat transfer of laminar flow in annulus formed by multi tubes in tube helically coiled heat exchanger. The numerical results are validated by comparison with previous experimental data and fair agreements were existed. The influences of the design and operation parameters such as heat flux, Reynolds numbers and annulus geometry on the heat transfer characteristics are investigated. Different annulus of different numbers of inner tubes, specifically 1, 2, 3, 4 and 5 tubes, are tested. The Results showed that for all the studied annulus, the heat flux has no effect on the Nusselt number and compactness parameter. The annulus formed by using five inner tubes showed the best heat transfer performance and compactness parameter. Correlation of predicting Nusselt number in terms of Reynolds number and number of inner tubes are presented.

  19. Tubes, Mono Jets, Squeeze Out and CME

    Energy Technology Data Exchange (ETDEWEB)

    Longacre, R. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-10-23

    Glasma Flux Tubes, Mono Jets with squeeze out flow around them plus the Chiral Magnetic Effect(CME) are physical phenomenon that generate two particle correlation with respect to the reaction plane in mid-central 20% to 30% Au-Au collision √sNN = 200.0 GeV measured at RHIC.

  20. Bender/Coiler for Tubing

    Science.gov (United States)

    Stoltzfus, J. M.

    1983-01-01

    Easy-to-use tool makes coils of tubing. Tubing to be bend clamped with stop post. Die positioned snugly against tubing. Operator turns handle to slide die along tubing, pushing tubing into spiral groove on mandrel.

  1. Burnout in the horizontal tubes of a furnace waterwall panel

    Energy Technology Data Exchange (ETDEWEB)

    B.Y. Kamenetskii [All-Russia Research Institute of Nuclear Power Engineering (OAO VNIIAM), Moscow (Russian Federation)

    2009-07-01

    An experimental study of heat transfer that occurs in tubes nonuniformly heated over the perimeter at low velocities of subcooled water flowing in them is presented. Experiments with unsteady supply of heat made it possible to determine heat fluxes under burnout conditions. Unusually low values of critical heat fluxes were obtained under such conditions.

  2. Burnout in the horizontal tubes of a furnace waterwall panel

    Science.gov (United States)

    Kamenetskii, B. Ya.

    2009-08-01

    An experimental study of heat transfer that occurs in tubes nonuniformly heated over the perimeter at low velocities of subcooled water flowing in them is presented. Experiments with unsteady supply of heat made it possible to determine heat fluxes under burnout conditions. Unusually low values of critical heat fluxes were obtained under such conditions.

  3. Ideal flux field dielectric concentrators.

    Science.gov (United States)

    García-Botella, Angel

    2011-10-01

    The concept of the vector flux field was first introduced as a photometrical theory and later developed in the field of nonimaging optics; it has provided new perspectives in the design of concentrators, overcoming standard ray tracing techniques. The flux field method has shown that reflective concentrators with the geometry of the field lines achieve the theoretical limit of concentration. In this paper we study the role of surfaces orthogonal to the field vector J. For rotationally symmetric systems J is orthogonal to its curl, and then a family of surfaces orthogonal to the lines of J exists, which can be called the family of surfaces of constant pseudopotential. Using the concept of the flux tube, it is possible to demonstrate that refractive concentrators with the shape of these pseudopotential surfaces achieve the theoretical limit of concentration.

  4. Vortex line topology during vortex tube reconnection

    Science.gov (United States)

    McGavin, P.; Pontin, D. I.

    2018-05-01

    This paper addresses reconnection of vortex tubes, with particular focus on the topology of the vortex lines (field lines of the vorticity). This analysis of vortex line topology reveals key features of the reconnection process, such as the generation of many small flux rings, formed when reconnection occurs in multiple locations in the vortex sheet between the tubes. Consideration of three-dimensional reconnection principles leads to a robust measurement of the reconnection rate, even once instabilities break the symmetry. It also allows us to identify internal reconnection of vortex lines within the individual vortex tubes. Finally, the introduction of a third vortex tube is shown to render the vortex reconnection process fully three-dimensional, leading to a fundamental change in the topological structure of the process. An additional interesting feature is the generation of vorticity null points.

  5. Splitting of inviscid fluxes for real gases

    Science.gov (United States)

    Liou, Meng-Sing; Van Leer, Bram; Shuen, Jian-Shun

    1990-01-01

    Flux-vector and flux-difference splittings for the inviscid terms of the compressible flow equations are derived under the assumption of a general equation of state for a real gas in equilibrium. No necessary assumptions, approximations for auxiliary quantities are introduced. The formulas derived include several particular cases known for ideal gases and readily apply to curvilinear coordinates. Applications of the formulas in a TVD algorithm to one-dimensional shock-tube and nozzle problems show their quality and robustness.

  6. v-Src causes delocalization of Mklp1, Aurora B, and INCENP from the spindle midzone during cytokinesis failure

    Energy Technology Data Exchange (ETDEWEB)

    Soeda, Shuhei [Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675 (Japan); Nakayama, Yuji, E-mail: nakayama@mb.kyoto-phu.ac.jp [Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675 (Japan); Department of Biochemistry and Molecular Biology, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414 (Japan); Honda, Takuya; Aoki, Azumi; Tamura, Naoki; Abe, Kohei; Fukumoto, Yasunori [Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675 (Japan); Yamaguchi, Naoto, E-mail: nyama@faculty.chiba-u.jp [Department of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Inohana 1-8-1, Chuo-ku, Chiba 260-8675 (Japan)

    2013-06-10

    Src-family tyrosine kinases are aberrantly activated in cancers, and this activation is associated with malignant tumor progression. v-Src, encoded by the v-src transforming gene of the Rous sarcoma virus, is a mutant variant of the cellular proto-oncogene c-Src. Although investigations with temperature sensitive mutants of v-Src have shown that v-Src induces many oncogenic processes, the effects on cell division are unknown. Here, we show that v-Src inhibits cellular proliferation of HCT116, HeLa S3 and NIH3T3 cells. Flow cytometry analysis indicated that inducible expression of v-Src results in an accumulation of 4N cells. Time-lapse analysis revealed that binucleation is induced through the inhibition of cytokinesis, a final step of cell division. The localization of Mklp1, which is essential for cytokinesis, to the spindle midzone is inhibited in v-Src-expressing cells. Intriguingly, Aurora B, which regulates Mklp1 localization at the midzone, is delocalized from the spindle midzone and the midbody but not from the metaphase chromosomes upon v-Src expression. Mklp2, which is responsible for the relocation of Aurora B from the metaphase chromosomes to the spindle midzone, is also lost from the spindle midzone. These results suggest that v-Src inhibits cytokinesis through the delocalization of Mklp1 and Aurora B from the spindle midzone, resulting in binucleation. -- Highlights: • v-Src inhibits cell proliferation of HCT116, HeLa S3 and NIH3T3 cells. • v-Src induces binucleation together with cytokinesis failure. • v-Src causes delocalization of Mklp1, Aurora B and INCENP from the spindle midzone.

  7. Effect of electron (de)localization and pairing in the electrochemistry of polyoxometalates: study of Wells-Dawson molybdotungstophosphate derivatives.

    Science.gov (United States)

    Parent, Loïc; Aparicio, Pablo A; de Oliveira, Pedro; Teillout, Anne-Lucie; Poblet, Josep M; López, Xavier; Mbomekallé, Israël M

    2014-06-16

    Polyoxometalates (POMs) are inorganic entities featuring extensive and sometimes unusual redox properties. In this work, several experimental techniques as well as density functional theory (DFT) calculations have been applied to identify and assess the relevance of factors influencing the redox potentials of POMs. First, the position of the Mo substituent atom in the Wells-Dawson structure, α1- or α2-P2W17Mo, determines the potential of the first 1e(-) reduction wave. For P2W(18-x)Mox systems containing more than one Mo atom, reduction takes place at successively more positive potentials. We attribute this fact to the higher electron delocalization when some Mo oxidizing atoms are connected. After having analyzed the experimental and theoretical data for the monosubstituted α1- and α2-P2W17Mo anions, some relevant facts arise that may help to rationalize the redox behavior of POMs in general. Three aspects concern the stability of systems: (i) the favorable electron delocalization, (ii) the unfavorable e(-)-e(-) electrostatic repulsion, and (iii) the favorable electron pairing. They explain trends such as the second reduction wave occurring at more positive potentials in α1- than in α2-P2W17Mo, and also the third electron reduction taking place at a less negative potential in the case of α2, reversing the observed behavior for the first and the second waves. In P2W17V derivatives, the nature of the first "d" electron is more localized because of the stronger oxidant character of V(V). Thus, the reduction potentials as well as the computed reduction energies (REs) for the second reduction of either isomer are closer to each other than in Mo-substituted POMs. This may be explained by the lack of electron delocalization in monoreduced P2W17V(IV) systems.

  8. Experimental study of heat transfer for parallel flow in tube bundles with constant heat flux and for medium Prandtl numbers; Etude experimentale du transfert de chaleur dans des faisceaux tubulaires en ecoulement parallele pour une densite de flux thermique constante dans le domaine des nombres de Prandtl moyens

    Energy Technology Data Exchange (ETDEWEB)

    Rieger, M [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires

    1968-06-01

    The heat transfer parameters were determined experimentally in electrically heated tube bundles for turbulent flow parallel to the axis. The tubes were arranged in a pattern of equilateral triangles. The ratios of the distance between the axes of the tubes to their external diameter were 1.60 and 1.25 in the two test sections studied. The experiments were carried out with distilled water and with a mixture of 60 per cent ethylene glycol and 40 per cent water. The values obtained for the Prandtl numbers in this way fell within the range from 2.3 to 18. The Reynolds numbers were varied between 10{sup 4} and 2.10{sup 5}. The relation between the mean heat transfer coefficients and the friction factor in the tube bundles was found from the experiments as: Nu = [Re Pr {zeta}/8]/[1+{radical}({zeta}/8) 8.8 (Pr-1.3) Pr{sup -0.22}]. The experimentally determined mean Nusselt numbers were also given by the following function: Nu = (0.0122 + 0.00245 p/d) Re{sup 0.86} Pr{sup 0.4}, with a maximum deviation of {+-}4 per cent. For certain local Nusselt numbers, deviations of up to 20 per cent with respect to the relations given were observed. (author) [French] Dans des faisceaux tubulaires a chauffage electrique parcourus par un ecoulement turbulent parallele a l'axe, on a determine experimentalement les parametres du transfert de chaleur. Les centres des sections droites des tubes etaient des sommets de triangles equilateraux. Les rapports de la distance a l'axe des tubes et leur diametre exterieur dans les deux veines de mesure etudiees etaient de 1.60 et 1.25. Des essais furent effectues avec de l'eau distillee ainsi qu'avec un melange de 60 pour cent de glycol ethylenique et 40 pour cent d'eau. Les valeurs des nombres de Prandtl obtenues ainsi etaient situees entre 2.3 a 18. On a fait varier les nombres de Reynolds entre 10{sup 4} et 2.10{sup 5}. La relation entre les nombres caracteristiques de transfert de chaleur moyens et la perte de charge dans les faisceaux tabulaires

  9. On the role of delocalization in benzene: Theoretical and experimental investigation of the effects of strained ring fusion

    Energy Technology Data Exchange (ETDEWEB)

    Faust, Rudiger [Univ. of California, Berkeley, CA (United States)

    1993-04-01

    When an important compound`s discovery dates back as far as 1825, one would imagine that every facet of its chemical and physical properties has been illuminated in the meantime. Benzene, however, has not ceased to challenge the chemist`s notion of structure and bonding since its first isolation by Michael Faraday. This report is divided into the following six chapters: 1. Aromaticity -- Criteria, manifestations, structural limitations; 2. The role of delocalization in benzene; 3. The thermochemical properties of benzocyclobutadienologs; 4. Ab initio study of benzenes fused to four-membered rings; 5. Non-planar polycyclic aromatic hydrocarbons; and 6. Experimental details and input decks. 210 Refs.

  10. Molecular-weight dependence of interchain polaron delocalization and exciton bandwidth in high-mobility conjugated polymers

    DEFF Research Database (Denmark)

    Chang, J.F.; Clark, J.; Zhao, N.

    2006-01-01

    delocalization with increasing conjugation length and crystalline quality. From comparative studies of field-effect transistor characteristics, film morphology, and optical properties our study provides a microscopic understanding of the factors which limit the charge transport in P3HT to field-effect mobilities......Interchain interactions have a profound effect on the optical as well as charge transport properties of conjugated polymer thin films. In contrast to oligomeric model systems in solution-deposited polymer thin films the study of such effects is complicated by the complex microstructure. We present...

  11. Heat transfer in laminar flow for a finned double - tube

    International Nuclear Information System (INIS)

    Colle, S.

    1977-01-01

    An analitical study of the steady-state heat transfer in laminar flow in finned double-tube heat exchangers is presented. The fins are plane, straight and continous, equally spaced and are fixed over the external surface of the inner tube. A constant peripheral temperature distribution is assumed to apply over the inner tube surface and each fin, and a constant peripheral heat flux is assumed to apply over the outer tube surface, while the overall heat flux is suposed to be uniform in the longitudinal direction of the duct. The prediction of the thermal performance of the finned double-tube is made by means of the relationship between the Nusselt number, the boundary conditions and the geometric characteristcs of the duct. (author) [pt

  12. Nucleate boiling heat transfer on horizontal tubes in bundles

    International Nuclear Information System (INIS)

    Fujital, Y.; Ohta, H.; Hidaka, S.; Nishikawa, K.

    1986-01-01

    In order to clarify the heat transfer mechanisms of the flooded type horizontal tube bundle evaporator, heat transfer characteristics of tube bundles of experimental scale which consist both of smooth and enhanced tubes were investigated in detail. The experiments of saturated nucleate boiling were performed by using Freon 113 under pressures 0.1 to 1 MPa, and the effects of various parameters, for example, bundle arrangement, heat flux, pressure on the characteristics of an individual tube are clarified. Experimental data is reproduced well by a proposed heat transfer model in which convective heat transfer coefficients due to rising bubbles are estimated as a function of their volumetric flow rate

  13. Fracture analysis of HFIR beam tube caused by radiation embrittlement

    International Nuclear Information System (INIS)

    Chang, S.J.

    1994-01-01

    With an attempt to estimate the neutron beam tube embrittlement condition for the Oak Ridge High Flux Isotope Reactor (HFIR), fracture mechanics calculations are carried out in this paper. The analysis provides some numerical result on how the tube has been structurally weakened. In this calculation, a lateral impact force is assumed. Numerical result is obtained on how much the critical crack size should be reduced if the beam tube has been subjected to an extended period of irradiation. It is also calculated that buckling strength of the tube is increased, not decreased, with irradiation

  14. X-ray tubes

    International Nuclear Information System (INIS)

    Young, R.W.

    1979-01-01

    A form of x-ray tube is described which provides satisfactory focussing of the electron beam when the beam extends for several feet from gun to target. Such a tube can be used for computerised tomographic scanning. (UK)

  15. Pressure tube type reactors

    International Nuclear Information System (INIS)

    Komada, Masaoki.

    1981-01-01

    Purpose: To increase the safety of pressure tube type reactors by providing an additional ECCS system to an ordinary ECCS system and injecting heavy water in the reactor core tank into pressure tubes upon fractures of the tubes. Constitution: Upon fractures of pressure tubes, reduction of the pressure in the fractured tubes to the atmospheric pressure in confirmed and the electromagnetic valve is operated to completely isolate the pressure tubes from the fractured portion. Then, the heavy water in the reactor core tank flows into and spontaneously recycles through the pressure tubes to cool the fuels in the tube to prevent their meltdown. By additionally providing the separate ECCS system to the ordinary ECCS system, fuels can be cooled upon loss of coolant accidents to improve the safety of the reactors. (Moriyama, K.)

  16. Gastrostomy feeding tube - bolus

    Science.gov (United States)

    Feeding - gastrostomy tube - bolus; G-tube - bolus; Gastrostomy button - bolus; Bard Button - bolus; MIC-KEY - bolus ... KEY, 3 to 8 weeks after surgery. These feedings will help your child grow strong and healthy. ...

  17. Feeding tube insertion - gastrostomy

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002937.htm Feeding tube insertion - gastrostomy To use the sharing features on this page, please enable JavaScript. A gastrostomy feeding tube insertion is the placement of a feeding ...

  18. Neural Tube Defects

    Science.gov (United States)

    Neural tube defects are birth defects of the brain, spine, or spinal cord. They happen in the ... that she is pregnant. The two most common neural tube defects are spina bifida and anencephaly. In ...

  19. Evidence for side-chain π-delocalization in a planar substituted benzene: an experimental and theoretical charge density study on 2,5-dimethoxybenzaldehyde thiosemicarbazone.

    Science.gov (United States)

    Farrugia, Louis J; Khalaji, Aliakbar Dehno

    2011-11-17

    The charge density in 2,5-dimethoxybenzaldehyde thiosemicarbazone (1) has been studied experimentally using Mo-K(α) X-ray diffraction at 100 K, and by theory using DFT calculations at the B3LYP/6-311++G(2d,2p) level. The quantum theory of atoms in molecules (QTAIM) was used to investigate the extent of π-delocalization in the thioamide side-chain, which is virtually coplanar with the benzene ring. The experimental and theoretical ellipticity profiles along the bond paths were in excellent agreement, and showed that some of the formal single bonds in the side-chain have significant π-bond character. This view was supported by the magnitudes of the topological bond orders and by the delocalization indices δ(Ω(A), Ω(B)). An orbital decomposition of δ(Ω(A), Ω(B)) demonstrated that there was significant π-character in all the interchain non-H chemical bonds. On the other hand, the source function referenced at the interchain bond critical points could not provide any evidence for π-delocalization, showing instead only limited σ-delocalization between nearest neighbors. Overall, the topological evidence and the atomic graphs of the oxygen atoms did not provide convincing evidence for π-delocalization involving the methoxy substituents.

  20. Diameter effect on critical heat flux

    International Nuclear Information System (INIS)

    Tanase, A.; Cheng, S.C.; Groeneveld, D.C.; Shan, J.Q.

    2009-01-01

    The critical heat flux look-up table (CHF LUT) is widely used to predict CHF for various applications, including design and safety analysis of nuclear reactors. Using the CHF LUT for round tubes having inside diameters different from the reference 8 mm involves conversion of CHF to 8 mm. Different authors [Becker, K.M., 1965. An Analytical and Experimental Study of Burnout Conditions in Vertical Round Ducts, Aktiebolaget Atomenergie Report AE 177, Sweden; Boltenko, E.A., et al., 1989. Effect of tube diameter on CHF at various two phase flow regimes, Report IPE-1989; Biasi, L., Clerici, G.C., Garriba, S., Sala, R., Tozzi, A., 1967. Studies on Burnout, Part 3, Energia Nucleare, vol. 14, pp. 530-536; Groeneveld, D.C., Cheng, S.C., Doan, T., 1986. AECL-UO critical heat flux look-up table. Heat Transfer Eng., 7, 46-62; Groeneveld et al., 1996; Hall, D.D., Mudawar, I., 2000. Critical heat flux for water flow in tubes - II subcooled CHF correlations. Int. J. Heat Mass Transfer, 43, 2605-2640; Wong, W.C., 1996. Effect of tube diameter on critical heat flux, MaSC dissertation, Ottawa Carleton Institute for Mechanical and Aeronautical Engineering, University of Ottawa] have proposed several types of correlations or factors to describe the diameter effect on CHF. The present work describes the derivation of new diameter correction factor and compares it with several existing prediction methods

  1. Anderson localized state as a predissipative state: irreversible emission of thermalized quanta from a dynamically delocalized state.

    Science.gov (United States)

    Yamada, Hiroaki; Ikeda, Kensuke S

    2002-04-01

    It was shown that localization in one-dimensional disordered (quantum) electronic system is destroyed against coherent harmonic perturbations and the delocalized electron exhibits an unlimited diffusive motion [Yamada and Ikeda, Phys. Rev. E 59, 5214 (1999)]. The appearance of diffusion implies that the system has potential for irreversibility and dissipation. In the present paper, we investigate dissipative property of the dynamically delocalized state, and we show that an irreversible quasistationary energy flow indeed appears in the form of a "heat" flow when we couple the system with another dynamical degree of freedom. In the concrete we numerically investigate dissipative properties of a one-dimensional tight-binding electronic system perturbed by time-dependent harmonic forces, by coupling it with a quantum harmonic oscillator or a quantum anharmonic oscillator. It is demonstrated that if the on-site potential is spatially irregular an irreversible energy transfer from the scattered electron to the test oscillator occurs. Moreover, the test oscillator promptly approaches a thermalized state characterized by a well-defined time-dependent temperature. On the contrary, such a relaxation process cannot be observed at all for periodic potential systems. Our system is one of the minimal quantum systems in which a distinct nonequilibrium statistical behavior is self-induced.

  2. A novel investigation of heat transfer characteristics in rifled tubes

    Science.gov (United States)

    Jegan, C. Dhayananth; Azhagesan, N.

    2018-05-01

    The experimental investigation of heat transfer of water flowing in a rifled tube was explored at different pressures and at various operating conditions in a rifled tube heat exchanger. The specifications for the inner and outer diameters of the inner tube are 25.8 and 50.6 mm, respectively. The working fluids used in shell side and tube side are cold and hot water. The rifled tube was made of the stainless steel with 4 ribs, 50.6 mm outer diameter, 0.775 mm rib height, 58o helix angle and the length 1500 mm. The effect of pressure, wall heat flux and friction factor were discussed. The results confirm that even at low pressures the rifled tubes has an obvious enhancement in heat transfer compared with smooth tube. Results depicts that the Nusselt number increases with Reynolds number and the friction factor decreases with increase in Reynolds number and the heat transfer rate is higher for the rifled tube when compared to smooth tube, because of strong swirl flow due to centrifugal action. It also confirms that, the friction factor obtained from the rifled tube is significantly higher than that of smooth tube.

  3. 21 CFR 868.5800 - Tracheostomy tube and tube cuff.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tracheostomy tube and tube cuff. 868.5800 Section... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5800 Tracheostomy tube and tube cuff. (a) Identification. A tracheostomy tube and tube cuff is a device intended to be placed into a...

  4. Delocalization and occupancy effects of 5f orbitals in plutonium intermetallics using L3-edge resonant X-ray emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Booth, C. H.; Medling, S. A.; Jiang, Yu; Bauer, E. D.; Tobash, P. H.; Mitchell, J. N.; Veirs, D. K.; Wall, M. A.; Allen, P. G.; Kas, J. J.; Sokaras, D.; Nordlund, D.; Weng, T. -C.

    2014-06-24

    Although actinide (An) L3 -edge X-ray absorption near-edge structure (XANES) spectroscopy has been very effective in determining An oxidation states in insulating, ionically bonded materials, such as in certain coordination compounds and mineral systems, the technique fails in systems featuring more delocalized 5f orbitals, especially in metals. Recently, actinide L3-edge resonant X-ray emission spec- troscopy (RXES) has been shown to be an effective alternative. This technique is further demonstrated here using a parameterized partial unoccupied density of states method to quantify both occupancy and delocalization of the 5f orbital in ?-Pu, ?-Pu, PuCoGa5 , PuCoIn5 , and PuSb2. These new results, supported by FEFF calculations, highlight the effects of strong correlations on RXES spectra and the technique?s ability to differentiate between f-orbital occupation and delocalization.

  5. Heat exchanger tube tool

    International Nuclear Information System (INIS)

    Gugel, G.

    1976-01-01

    Certain types of heat-exchangers have tubes opening through a tube sheet to a manifold having an access opening offset from alignment with the tube ends. A tool for inserting a device, such as for inspection or repair, is provided for use in such instances. The tool is formed by a flexible guide tube insertable through the access opening and having an inner end provided with a connector for connection with the opening of the tube in which the device is to be inserted, and an outer end which remains outside of the chamber, the guide tube having adequate length for this arrangement. A flexible transport hose for internally transporting the device slides inside of the guide tube. This hose is long enough to slide through the guide tube, into the heat-exchanger tube, and through the latter to the extent required for the use of the device. The guide tube must be bent to reach the end of the heat-exchanger tube and the latter may be constructed with a bend, the hose carrying anit-friction elements at interspaced locations along its length to make it possible for the hose to negotiate such bends while sliding to the location where the use of the device is required

  6. Critical flux determination by flux-stepping

    DEFF Research Database (Denmark)

    Beier, Søren; Jonsson, Gunnar Eigil

    2010-01-01

    In membrane filtration related scientific literature, often step-by-step determined critical fluxes are reported. Using a dynamic microfiltration device, it is shown that critical fluxes determined from two different flux-stepping methods are dependent upon operational parameters such as step...... length, step height, and.flux start level. Filtrating 8 kg/m(3) yeast cell suspensions by a vibrating 0.45 x 10(-6) m pore size microfiltration hollow fiber module, critical fluxes from 5.6 x 10(-6) to 1.2 x 10(-5) m/s have been measured using various step lengths from 300 to 1200 seconds. Thus......, such values are more or less useless in itself as critical flux predictors, and constant flux verification experiments have to be conducted to check if the determined critical fluxes call predict sustainable flux regimes. However, it is shown that using the step-by-step predicted critical fluxes as start...

  7. Intercostal drainage tube or intracardiac drainage tube?

    Directory of Open Access Journals (Sweden)

    N Anitha

    2016-01-01

    Full Text Available Although insertion of chest drain tubes is a common medical practice, there are risks associated with this procedure, especially when inexperienced physicians perform it. Wrong insertion of the tube has been known to cause morbidity and occasional mortality. We report a case where the left ventricle was accidentally punctured leading to near-exsanguination. This report is to highlight the need for experienced physicians to supervise the procedure and train the younger physician in the safe performance of the procedure.

  8. Intercostal drainage tube or intracardiac drainage tube?

    Science.gov (United States)

    Anitha, N; Kamath, S Ganesh; Khymdeit, Edison; Prabhu, Manjunath

    2016-01-01

    Although insertion of chest drain tubes is a common medical practice, there are risks associated with this procedure, especially when inexperienced physicians perform it. Wrong insertion of the tube has been known to cause morbidity and occasional mortality. We report a case where the left ventricle was accidentally punctured leading to near-exsanguination. This report is to highlight the need for experienced physicians to supervise the procedure and train the younger physician in the safe performance of the procedure.

  9. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... YouTube Videos » NEI YouTube Videos: Amblyopia Listen NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration ... Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: ...

  10. Effect of heated length on the Critical Heat Flux of subcooled flow boiling. 2. Effective heated length under axially nonuniform heating condition

    International Nuclear Information System (INIS)

    Kinoshita, Hidetaka; Yoshida, Takuya; Nariai, Hideki; Inasaka, Fujio

    1998-01-01

    Effect of heated length on the Critical Heat Flux (CHF) of subcooled flow boiling with water was experimentally investigated by using direct current heated tube made of stainless steel a part of whose wall thickness was axially cut for realizing nonuniform heat flux condition. The higher enhancement of the CHF was derived for shorter tube length. The effective heated length was determined for the tube under axially nonuniform heat flux condition. When the lower heat flux part below the Net Vapor Generation (NVG) heat flux exists at the middle of tube length, then the effective heated length becomes the tube length downstream the lower heat flux parts. However, when the lower heat flux part is above the NVG, then the effective heated length is full tube length. (author)

  11. Pediatric cuffed endotracheal tubes

    Directory of Open Access Journals (Sweden)

    Neerja Bhardwaj

    2013-01-01

    Full Text Available Endotracheal intubation in children is usually performed utilizing uncuffed endotracheal tubes for conduct of anesthesia as well as for prolonged ventilation in critical care units. However, uncuffed tubes may require multiple changes to avoid excessive air leak, with subsequent environmental pollution making the technique uneconomical. In addition, monitoring of ventilatory parameters, exhaled volumes, and end-expiratory gases may be unreliable. All these problems can be avoided by use of cuffed endotracheal tubes. Besides, cuffed endotracheal tubes may be of advantage in special situations like laparoscopic surgery and in surgical conditions at risk of aspiration. Magnetic resonance imaging (MRI scans in children have found the narrowest portion of larynx at rima glottides. Cuffed endotracheal tubes, therefore, will form a complete seal with low cuff pressure of <15 cm H 2 O without any increase in airway complications. Till recently, the use of cuffed endotracheal tubes was limited by variations in the tube design marketed by different manufacturers. The introduction of a new cuffed endotracheal tube in the market with improved tracheal sealing characteristics may encourage increased safe use of these tubes in clinical practice. A literature search using search words "cuffed endotracheal tube" and "children" from 1980 to January 2012 in PUBMED was conducted. Based on the search, the advantages and potential benefits of cuffed ETT are reviewed in this article.

  12. MAPLE research reactor beam-tube performance

    International Nuclear Information System (INIS)

    Lee, A.G.; Lidstone, R.F.; Gillespie, G.E.

    1989-05-01

    Atomic Energy of Canada Limited (AECL) has been developing the MAPLE (Multipurpose Applied Physics Lattice Experimental) reactor concept as a medium-flux neutron source to meet contemporary research reactor applications. This paper gives a brief description of the MAPLE reactor and presents some results of computer simulations used to analyze the neutronic performance. The computer simulations were performed to identify how the MAPLE reactor may be adapted to beam-tube applications such as neutron radiography

  13. Thermal isomerizations of ketenimines to nitriles: evaluations of sigma-Dot (sigma(*)) constants for spin-delocalizations

    Science.gov (United States)

    Kim; Zhu; Lee

    2000-05-19

    Rate constants (k(Y)) of the isomerizations of 11 diphenyl N-(substituted benzyl) ketenimines were measured at 40, 50, 60, and 70 degrees C. Activation parameters DeltaH()(Y) and DeltaS()(Y) were obtained using the Eyring equation. The relative rates (k(Y)/k(H)) were fitted into Hammett single correlations (log k(Y)/k(H) = rhosigma and log k(Y)/k(H) = rho(*)sigma(*)). The single correlations have been compared with Hammett dual correlations (log k(Y)/k(H) = rhosigma + rho(*)sigma(*) ). Separate treatments of para and meta substituents yielded even better correlations. Para substituents control the rates through spin-delocalizations and inductive effects. The former outweighs the latter when the latter exerts a modest but distinct influence on the rates. On the other hand, inductive effects are the "major" or the sole interactions triggered by meta substituents.

  14. Lunar Lava Tube Sensing

    Science.gov (United States)

    York, Cheryl Lynn; Walden, Bryce; Billings, Thomas L.; Reeder, P. Douglas

    1992-01-01

    Large (greater than 300 m diameter) lava tube caverns appear to exist on the Moon and could provide substantial safety and cost benefits for lunar bases. Over 40 m of basalt and regolith constitute the lava tube roof and would protect both construction and operations. Constant temperatures of -20 C reduce thermal stress on structures and machines. Base designs need not incorporate heavy shielding, so lightweight materials can be used and construction can be expedited. Identification and characterization of lava tube caverns can be incorporated into current precursor lunar mission plans. Some searches can even be done from Earth. Specific recommendations for lunar lava tube search and exploration are (1) an Earth-based radar interferometer, (2) an Earth-penetrating radar (EPR) orbiter, (3) kinetic penetrators for lunar lava tube confirmation, (4) a 'Moon Bat' hovering rocket vehicle, and (5) the use of other proposed landers and orbiters to help find lunar lava tubes.

  15. Categorising YouTube

    DEFF Research Database (Denmark)

    Simonsen, Thomas Mosebo

    2011-01-01

    This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC) of YouTube. The article investigates the construction of navigation processes on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube......’s technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a user-driven bottom-up folksonomy and a hierarchical browsing system that emphasises a culture of competition...... and which favours the already popular content of YouTube. With this taxonomic approach, the UGC videos are registered and analysed in terms of empirically based observations. The article identifies various UGC categories and their principal characteristics. Furthermore, general tendencies of the UGC within...

  16. Steam generator tube performance

    International Nuclear Information System (INIS)

    Tatone, O.S.; Pathania, R.S.

    1983-08-01

    A review of the performance of steam generator tubes in 110 water-cooled nuclear power reactors showed that tubes were plugged at 46 (42 percent) of the reactors. The number of tubes removed from service increased from 1900 (0.14 percent) in 1980 to 4692 (0.30 percent) in 1981. The leading causes of tube failures were stress corrosion cracking from the primary side, stress corrosion cracking (or intergranular attack) from the secondary side and pitting corrosion. The lowest incidence of corrosion-induced defects from the secondary side occurred in reactors that used all-volatile treatment since start-up. At one reactor a large number of degraded tubes were repaired by sleeving which is expected to become an important method of tube repair in the future

  17. Rectangular drift tube characteristics

    International Nuclear Information System (INIS)

    Denisov, D.S.; Musienko, Yu.V.

    1985-01-01

    Results on the study of the characteristics of a 50 x 100 mm aluminium drift tube are presented. The tube was filled with argon-methane and argon-isobutane mixtures. With 16 per cent methane concentration the largest deviation from a linear relation between the drift time and the drift path over 50 mm is less than 2 mm. The tube filled with argon-isobutane mixture is capable of operating in a limited streamer mode

  18. Modelling of pressure tube Quench using PDETWO

    International Nuclear Information System (INIS)

    Parlatan, Y.; Lei, Q.M.; Kwee, M.

    2004-01-01

    Transient two-dimensional heat conduction calculations have been carried out to determine the time-dependent temperature distribution in an overheated pressure tube during quenching with water. The purpose of the calculations is to provide input for evaluation of thermal (secondary) stresses in the pressure tube due to quench. The quench phenomenon in pressure tubes could occur in several hypothetical accident scenarios, including incidents involving intermittent buoyancy-induced flow during outages. In these scenarios, there will be two (radial and axial) or three dimensional temperature gradients, resulting in thermal stresses in the pressure tube, as the water front reaches and starts to cool down the hot pressure tube. The transient, two-dimensional heat conduction equation in the pressure tube during quench is solved using a FORTRAN package called PDETWO, available in the open literature for solving time-dependent coupled systems of non-linear partial differential equations over a two-dimensional rectangular region. This routine is based on finite difference solution of coupled, non-linear partial differential equations. Temperature gradient in the circumferential gradient is neglected for conservatism and convenience. The advancing water front is not modelled explicitly, and assumed to be at a uniform temperature and moving at a constant velocity inferred from experimental data. For outer surface and both ends of the pressure tube in the axial direction, a zero-heat flux boundary condition is assumed, while for the inner surface a moving water-quench front is assumed by appropriately varying the fluid temperature and the heat transfer coefficient. The pressure tube is assumed to be at a uniform temperature of 400 o C initially, to represent conditions expected during an intermittent buoyancy-influenced flow scenario. The results confirm the expectations that axial temperature gradients and associated heat fluxes are small in comparison with those in the

  19. Categorising YouTube

    OpenAIRE

    Simonsen, Thomas Mosebo

    2011-01-01

    This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC) of YouTube. The article investigates the construction of navigation processes on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube’s technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a...

  20. Pressure tube reactor

    International Nuclear Information System (INIS)

    Susuki, Akira; Murata, Shigeto; Minato, Akihiko.

    1993-01-01

    In a pressure tube reactor, a reactor core is constituted by arranging more than two units of a minimum unit combination of a moderator sealing pipe containing a calandria tube having moderators there between and a calandria tube and moderators. The upper header and a lower header of the calandria tank containing moderators are communicated by way of the moderator sealing tube. Further, a gravitationally dropping mechanism is disposed for injecting neutron absorbing liquid to a calandria gas injection portion. A ratio between a moderator volume and a fuel volume is defined as a function of the inner diameter of the moderator sealing tube, the outer diameter of the calandria tube and the diameter of fuel pellets, and has no influence to intervals of a pressure tube lattice. The interval of the pressure tube lattice is enlarged without increasing the size of the pressure tube, to improve production efficiency of the reactor and set a coolant void coefficient more negative, thereby enabling to improve self controllability and safety. Further, the reactor scram can be conducted by injecting neutron absorbing liquid. (N.H.)

  1. Heated Tube Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Heated Tube Facility at NASA GRC investigates cooling issues by simulating conditions characteristic of rocket engine thrust chambers and high speed airbreathing...

  2. Steam generator tube performance

    International Nuclear Information System (INIS)

    Tatone, O.S.; Pathania, R.S.

    1984-10-01

    A review of the performance of steam generator tubes in 116 water-cooled nuclear power reactors showed that tubes were plugged at 54 (46 percent) of the reactors. The number of tubes removed from service decreased from 4 692 (0.30 percent) in 1981 to 3 222 (0.20 percent) in 1982. The leading causes of tube failures were stress corrosion cracking from the primary side, stress corrosion cracking (or intergranular attack) from the secondary side and pitting corrosion. The lowest incidence of corrosion-induced defects from the secondary side occurred in reactors that have used only volatile treatment, with or without condensate demineralization

  3. Steam generator tube performance

    International Nuclear Information System (INIS)

    Tatone, O.S.; Tapping, R.L.; Stipan, L.

    1992-03-01

    A survey of steam generator operating experience for 1986 has been carried out for 184 pressurized water and pressurized heavy-water reactors, and 1 water-cooled, graphite-moderated reactor. Tubes were plugged at 75 of the reactors (40.5%). In 1986, 3737 tubes were plugged (0.14% of those in service) and 3148 tubes were repaired by sleeving. A small number of reactors accounted for the bulk of the plugged tubes, a phenomenon consistent with previous years. For 1986, the available tubesheet sludge data for 38 reactors has been compiled into tabular form, and sludge/deposit data will be incorporated into all future surveys

  4. Temperature dependent spectroscopic studies of the electron delocalization dynamics of excited Ce ions in the wide band gap insulator, Lu2SiO5

    NARCIS (Netherlands)

    Van der Kolk, E.; Basun, S.A.; Imbusch, G.F.; Yen, W.M.

    2003-01-01

    Electron delocalization processes of optically excited states of Ce3+ impurities in Lu2SiO5 were investigated by means of a temperature and spectrally resolved photoconductivity study. By monitoring separately the strength of the photocurrent resulting from excitation into each of the Ce3+?5d

  5. Correlation between abnormal deuterium flux and heat flow in a D/Pd system

    International Nuclear Information System (INIS)

    Li Xingzhong; Liu Bin; Tian Jian; Wei Qingming; Zhou Rui; Yu Zhiwu

    2003-01-01

    Deuterium flux through the thin wall of a palladium tube has been studied by monitoring gas pressure and temperature. A high-precision calorimeter (Calvet) was used to detect heat flow when the heater was shut down and the palladium tube was cooling down slowly. At certain temperatures an abnormal deuterium flux appeared. This deuterium flux reached a peak when the temperature of the palladium was decreasing. This abnormal deuterium flux differs from the monotonic feature of a normal diffusive flux and is accompanied by a heat flow

  6. Steam generator tube failures

    International Nuclear Information System (INIS)

    MacDonald, P.E.; Shah, V.N.; Ward, L.W.; Ellison, P.G.

    1996-04-01

    A review and summary of the available information on steam generator tubing failures and the impact of these failures on plant safety is presented. The following topics are covered: pressurized water reactor (PWR), Canadian deuterium uranium (CANDU) reactor, and Russian water moderated, water cooled energy reactor (VVER) steam generator degradation, PWR steam generator tube ruptures, the thermal-hydraulic response of a PWR plant with a faulted steam generator, the risk significance of steam generator tube rupture accidents, tubing inspection requirements and fitness-for-service criteria in various countries, and defect detection reliability and sizing accuracy. A significant number of steam generator tubes are defective and are removed from service or repaired each year. This wide spread damage has been caused by many diverse degradation mechanisms, some of which are difficult to detect and predict. In addition, spontaneous tube ruptures have occurred at the rate of about one every 2 years over the last 20 years, and incipient tube ruptures (tube failures usually identified with leak detection monitors just before rupture) have been occurring at the rate of about one per year. These ruptures have caused complex plant transients which have not always been easy for the reactor operators to control. Our analysis shows that if more than 15 tubes rupture during a main steam line break, the system response could lead to core melting. Although spontaneous and induced steam generator tube ruptures are small contributors to the total core damage frequency calculated in probabilistic risk assessments, they are risk significant because the radionuclides are likely to bypass the reactor containment building. The frequency of steam generator tube ruptures can be significantly reduced through appropriate and timely inspections and repairs or removal from service

  7. Method for shaping polyethylene tubing

    Science.gov (United States)

    Kramer, R. C.

    1981-01-01

    Method forms polyethylene plastic tubing into configurations previously only possible with metal tubing. By using polyethylene in place of copper or stain less steel tubing inlow pressure systems, fabrication costs are significantly reduced. Polyethylene tubing can be used whenever low pressure tubing is needed in oil operations, aircraft and space applications, powerplants, and testing laboratories.

  8. Pyrotechnic Tubing Connector

    Science.gov (United States)

    Graves, Thomas J.; Yang, Robert A.

    1988-01-01

    Tool forms mechanical seal at joint without levers or hydraulic apparatus. Proposed tool intended for use in outer space used on Earth by heavily garbed workers to join tubing in difficult environments. Called Pyrotool, used with Lokring (or equivalent) fittings. Piston slides in cylinder when pushed by gas from detonating pyrotechnic charge. Impulse of piston compresses fittings, sealing around butting ends of tubes.

  9. Subcooled Pool Boiling from Two Tubes of 6 Degree Included Angle in Vertical Alignment

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)

    2015-05-15

    One of the major issues in the design of a heat exchanger is the heat transfer in a tube bundle. The passive condensation heat exchanger (PCHX) adopted in APR+ has U-type tube. The PCHX is submerged in the passive condensation cooling tank (PCCT). The heat exchanging tubes are in vertical alignment and inclined at 3 degrees to prevent water hammer as shown in Fig. 1. For the cases, the upper tube is affected by the lower tube. Therefore, the results for a single tube are not applicable to the design of the PCHX. However, the passive heat exchangers are submerged in the subcooled water under atmospheric pressure. The water temperature in the PCCT rises according to the PAFS actuation and reaches the saturation temperature after more than 2.5 hours. Since this period is very important to maintain reactor integrity, the exact evaluation of heat transfer on the tube bundle is indispensable. Although an experimental study on both subcooled and saturated pool boiling of water was performed to obtain local heat transfer coefficients on a 3 degree inclined tube at atmospheric pressure by Kang, no previous results were treating the bundle effect in the subcooled liquid. The heat transfer on the upper tube is enhanced compared with the single tube. The enhancement of the heat transfer on the upper tube is estimated by the bundle effect ( h{sub r} ). It is defined as the ratio of the heat transfer coefficient ( h{sub b} ) for an upper tube in a bundle with lower tubes activated to that for the same tube activated alone in the bundle. The upper tube within a tube bundle can significantly increase nucleated boiling heat transfer compared to the lower tubes at moderate heat fluxes. Summarizing the published results, it is still necessary to identify effects of liquid subcooling on inclined tubes for application to the PCHX design. Therefore, the present study is aimed to study the variations of pool boiling heat transfer on a tube bundle having a 6 degree included angle in

  10. Properties of Flux Tubes and the Relation with Solar Irradiance ...

    Indian Academy of Sciences (India)

    tribpo

    with variations on time-scales of minutes up to the length of the solar cycle. Most prominent is a .... Frutiger et al. 1999). To bypass the difficulties arising from such multi dimensional or multi component ... The fractional coverage of the solar ...

  11. A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

    Energy Technology Data Exchange (ETDEWEB)

    You, Setthivoine [Univ. of Washington, Seattle, WA (United States)

    2017-12-20

    Understanding the interaction between plasma flows and magnetic fields remains a fundamental problem in plasma physics, with important applications to astrophysics, fusion energy, and advanced space propulsion. For example, flows are of primary importance in astrophysical jets even if it is not fully understood how jets become so long without becoming unstable. Theories for the origin of magnetic fields in the cosmos rely on flowing charged fluids that should generate magnetic fields, yet this remains to be demonstrated experimentally. Fusion energy reactors can be made smaller with flows that improve stability and confinement. Advanced space propulsion could be more efficient with collimated and stable plasma flows through magnetic nozzles but must eventually detach from the nozzle. In all these cases, there appears to be a spontaneous emergence of flowing and/or magnetic structures, suggesting a form of self-organization in plasmas. Beyond satisfying simple intellectual curiosity, understanding plasma self-organization could enable the development of methods to control plasma structures for fusion energy, space propulsion, and other applications. The research project has therefore built a theory and an experiment to investigate the interaction between magnetic fields and plasma flows. The theory is called canonical field theory for short, and the experiment is called Mochi after a rice cake filled with surprising, yet delicious fillings.

  12. Molybdenum Tube Characterization report

    Energy Technology Data Exchange (ETDEWEB)

    Beaux II, Miles Frank [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Usov, Igor Olegovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-02-07

    Chemical vapor deposition (CVD) techniques have been utilized to produce free-standing molybdenum tubes with the end goal of nuclear fuel clad applications. In order to produce tubes with properties desirable for this application, deposition rates were lowered requiring long deposition durations on the order of 50 hours. Standard CVD methods as well as fluidized-bed CVD (FBCVD) methods were applied towards these objectives. Characterization of the tubes produced in this manner revealed material suitable for fuel clad applications, but lacking necessary uniformity across the length of the tubes. The production of freestanding Mo tubes that possess the desired properties across their entire length represents an engineering challenge that can be overcome in a next iteration of the deposition system.

  13. Effects of Dihedral Angle on Pool Boiling Heat Transfer from Two Tubes in Vertical Alignment

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Myeong-Gie [Andong National University, Andong (Korea, Republic of)

    2014-10-15

    One of the major issues in pool boiling heat transfer is a tube arrangement. The upper tube is affected by the lower tube and the enhancement of the heat transfer on the upper tube is estimated by the bundle effect ( h{sub r} ). It is defined as the ratio of the heat transfer coefficient ( h{sub b} ) for an upper tube in a bundle with lower tubes activated to that for the same tube activated alone in the bundle. Since heat transfer is related with the conditions of a tube surface, bundle geometries, and a liquid type, lots of studies have been carried out for the combinations of those parameters. The most effective parameter must be the tube pitch. Many researchers have been investigated its effect on heat transfer enhancement for the tube bundles and the tandem tubes. The heat transfer on the upper tube of the tubes is enhanced compared with the single tube. The upper tube within a tube bundle can significantly increase nucleate boiling heat transfer compared to the lower tubes at moderate heat fluxes. At high heat fluxes these influences disappear and the data merge onto the pool boiling curve of a single tube. It was explained that the major influential factor is the convective effects due to the fluid velocity and the rising bubbles. They used microstructure-R134a or FC-3184 combinations and identified that the increase in the heat flux of the lower tube decreased the superheat ( ∆T{sub sat} ) of the upper tube. The passive condensers adopted in SWR1000 and APR+ has U-type tubes. Those tubes are slightly inclined from the horizontal to prevent the occurrence of the water hammer. Since the pitch between the upper and lower tubes is varying along the tube length, the results for the fixed pitch are not applicable to the analysis of these condensers. Although there are lots of studies introducing results for the effects of inclination angle on pool boiling heat transfer, no results are treating the angle between two tubes. Therefore, the present study is aimed

  14. CHF prediction in rod bundles using round tube data

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Wallen F.; Veloso, Maria A.F.; Pereira, Cláubia; Costa, Antonella L., E-mail: wallenfds@yahoo.com.br, E-mail: mdora@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear

    2017-07-01

    The present work concerns the use of 1995 CHF table for uniformly heated round tubes, developed jointly by Canadian and Russian researchers, for the prediction of critical heat fluxes in rod bundles geometries. Comparisons between measured and calculated critical heat fluxes indicate that this table could be applied to rod bundles provided that a suitable correction factor is employed. The tolerance limits associated with the departure from nucleate boiling ratio (DNBR) are evaluated by using statistical analysis. (author)

  15. A model for correlating burnout in round tubes

    International Nuclear Information System (INIS)

    Kirby, G.J.

    1966-09-01

    A model is presented which represents the film flow rate in the climbing film regime of boiling two phase flow. By calculating the dryout point burnout heat fluxes for round tubes both uniformly and non-uniformly heated axially have been predicted with accuracies as good as the best empirical correlations. The model is used to investigate the effect of varying flux profile as well as the other system describing parameters. (author)

  16. Ferromagnetic material inspection for feedwater heater and condenser tubes

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    In recent years, special ferritic stainless steels, such as AL29-4C/sup TM/, Sea-Cure/sup TM/, E-Brite/sup TM/, 439, and similar alloys have been introduced as tube material in condensers, feedwater heaters, moisture separator/reheaters, and other heat exchangers. In addition, carbon steel tubes are widely used in feedwater heaters and heat exchangers in chemical plants. The main problem with the in-service inspection of these ferritic alloys and carbon steel tubes lies in their highly ferromagnetic properties. These properties severely limit the application of the standard eddy current techniques. The effort was undertaken under EPRI sponsorship to develop a reliable technique for in-service inspection of ferromagnetic tubes. The new method combines the measurement of magnetic flux leakage generated around the defects with measurement of total flux in the tube wall. The heart of the inspection system is a special ID probe that magnetizes the tube and generates signals for any tube defect. A permanent record of inspection is provided with a strip-chart or magnetic tape recorder. The laboratory and field evaluation of this new system demonstrated its very good sensitivity to small defects, its reliability, and its ruggedness. Defects as small as 10% external wall loss in heavy wall carbon steel tube were detected. Tubes in the power plant were inspected at a rate of 300-500 tubes per eight-hour shift. The other advantages of this newly developed technique are its simplicity, low cost of instrumentation, easy data interpretation, and full portability

  17. Primary study for boron neutron capture therapy uses the RSG-GAS beam tube facility

    International Nuclear Information System (INIS)

    Suroso

    2000-01-01

    The minimum epithermal neutron flux as one of the prerequisite of Boron Neutron Capture Therapy (BNCT) is 1.0 x 10 9 n/(cm 2 s) RSG-GAS have 6 beam tube facilities for neutron source, which is one of the beam tube S-2 has a possibility to utilization for BNCT facility. The totally flux neutron measurement in the front of S-2 beam tube is 1.8 x 10 7 n/(cm 2 s). The neutron flux measurement was less than for BNCT minimum prerequisite. Concerning to the flux neutron production in the reactor, which is reach to 2.5 x 10 14 n/(cm 2 s), there for the S-2 beam tube could be used beside collimator modification

  18. Sensitive technique for detecting outer defect on tube with remote field eddy current testing

    International Nuclear Information System (INIS)

    Kobayashi, Noriyasu; Nagai, Satoshi; Ochiai, Makoto; Jimbo, Noboru; Komai, Masafumi

    2008-01-01

    In the remote field eddy current testing, we proposed the method of enhancing the magnetic flux density in the vicinity of an exciter coil by controlling the magnetic flux direction for increasing the sensitivity of detecting outer defects on a tube and used the flux guide made of a magnetic material for the method. The optimum structural shape of the flux guide was designed by the magnetic field analysis. On the experiment with the application of the flux guide, the magnetic flux density increased by 59% and the artificial defect detection signal became clear. We confirmed the proposed method was effective in a high sensitivity. (author)

  19. Generalized drift-flux correlation

    International Nuclear Information System (INIS)

    Takeuchi, K.; Young, M.Y.; Hochreiter, L.E.

    1991-01-01

    A one-dimensional drift-flux model with five conservation equations is frequently employed in major computer codes, such as TRAC-PD2, and in simulator codes. In this method, the relative velocity between liquid and vapor phases, or slip ratio, is given by correlations, rather than by direct solution of the phasic momentum equations, as in the case of the two-fluid model used in TRAC-PF1. The correlations for churn-turbulent bubbly flow and slug flow regimes were given in terms of drift velocities by Zuber and Findlay. For the annular flow regime, the drift velocity correlations were developed by Ishii et al., using interphasic force balances. Another approach is to define the drift velocity so that flooding and liquid hold-up conditions are properly simulated, as reported here. The generalized correlation is used to reanalyze the MB-2 test data for two-phase flow in a large-diameter pipe. The results are applied to the generalized drift flux velocity, whose relationship to the other correlations is discussed. Finally, the generalized drift flux correlation is implemented in TRAC-PD2. Flow reversal from countercurrent to cocurrent flow is computed in small-diameter U-shaped tubes and is compared with the flooding curve

  20. Automation in tube finishing bay

    International Nuclear Information System (INIS)

    Bhatnagar, Prateek; Satyadev, B.; Raghuraman, S.; Syama Sundara Rao, B.

    1997-01-01

    Automation concept in tube finishing bay, introduced after the final pass annealing of PHWR tubes resulted in integration of number of sub-systems in synchronisation with each other to produce final cut fuel tubes of specified length, tube finish etc. The tube finishing bay which was physically segregated into four distinct areas: 1. tube spreader and stacking area, 2. I.D. sand blasting area, 3. end conditioning, wad blowing, end capping and O.D. wet grinding area, 4. tube inspection, tube cutting and stacking area has been studied

  1. Magnetic-flux pump

    Science.gov (United States)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

  2. Radon flux measurement methodologies

    International Nuclear Information System (INIS)

    Nielson, K.K.; Rogers, V.C.

    1984-01-01

    Five methods for measuring radon fluxes are evaluated: the accumulator can, a small charcoal sampler, a large-area charcoal sampler, the ''Big Louie'' charcoal sampler, and the charcoal tent sampler. An experimental comparison of the five flux measurement techniques was also conducted. Excellent agreement was obtained between the measured radon fluxes and fluxes predicted from radium and emanation measurements

  3. Neutron flux enhancement in the NRAD reactor

    International Nuclear Information System (INIS)

    Weeks, A.A.; Heidel, C.C.; Imel, G.R.

    1988-01-01

    In 1987 a series of experiments were conducted at the NRAD reactor facility at Argonne National Laboratory - West (ANL-W) to investigate the possibility of increasing the thermal neutron content at the end of the reactor's east beam tube through the use of hydrogenous flux traps. It was desired to increase the thermal flux for a series of experiments to be performed in the east radiography cell, in which the enhanced flux was required in a relatively small volume. Hence, it was feasible to attempt to focus the cross section of the beam to a smaller area. Two flux traps were constructed from unborated polypropylene and tested to determine their effectiveness. Both traps were open to the entire cross-sectional area of the neutron beam (as it emerges from the wall and enters the beam room). The sides then converged such that at the end of the trap the beam would be 'focused' to a greater intensity. The differences in the two flux traps were primarily in length, and hence angle to the beam as the inlet and outlet cross-sectional areas were held constant. The experiments have contributed to the design of a flux trap in which a thermal flux of nearly 10 9 was obtained, with an enhancement of 6.61

  4. Critical heat flux and exit film flow rate in a flow boiling system

    International Nuclear Information System (INIS)

    Ueda, Tatsuhiro; Isayama, Yasushi

    1981-01-01

    The critical heat flux in a flowing boiling system is an important problem in the evaporating tubes with high thermal load such as nuclear reactors and boilers, and gives the practical design limit. When the heat flux in uniformly heated evaporating tubes is gradually raised, the tube exit quality increases, and soon, the critical heat flux condition arises, and the wall temperature near tube exit rises rapidly. In the region of low exit quality, the critical heat flux condition is caused by the transition from nucleating boiling, and in the region of high exit quality, it is caused by dry-out. But the demarcation of both regions is not clear. In this study, for the purpose of obtaining the knowledge concerning the critical heat flux condition in a flowing boiling system, the relation between the critical heat flux and exit liquid film flow rate was examined. For the experiment, a uniformly heated vertical tube supplying R 113 liquid was used, and the measurement in the range of higher heating flux and mass velocity than the experiment by Ueda and Kin was carried out. The experimental setup and experimental method, the critical heat flux and exit quality, the liquid film flow rate at heating zone exit, and the relation between the critical heat flux and the liquid film flow rate at exit are described. (Kako, I.)

  5. Contribution to the heat transfer analysis of substitute refrigerants in evaporator tubes with smooth or enhanced tube surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kattan, N

    1997-12-31

    The substitution of CFC refrigerants in refrigeration systems, heat pumps and organic Rankine cycles for heat recovery, requests a good knowledge of heat transfer properties of substitute fluids. A new test facility has been built at the Laboratory for Industrial Energy Systems (LENI) to contribute to this international effort. It consists of two sets of concentric tubes allowing either annular or inside tube convective boiling with a counter current water flow heating to be studied. A new data base including heat transfer coefficients and pressure drop measurements for four new refrigerants (R123, R134A, R402A and R404A) and three older refrigerants (R11, R12 and R502) has been collected. Flow boiling measurements covered a broad range of mass velocities, vapor qualities and heat fluxes. Some of the tests included plain tubes and others enhanced surface tubes (microfilms from Wieland) in horizontal and vertical orientations. An improved Wilson plot technique, that covers both the transition and turbulent flow regimes of the water flowing in the annular channel for the inside tube boiling tests, is proposed to overcome the severe limitations of conventional Wilson plots, to improve accuracy and to facilitate data processing. Mean flow boiling heat transfer coefficients were measured for R12 and R134A evaporating inside a horizontal plain tube and for R11 and R123 evaporating inside a horizontal plain tube. Local flow boiling heat transfer coefficients were measured for : R134A, R123, R404A and R502 evaporating inside a horizontal plain tube, for R134A and R123 evaporating inside a horizontal microfin tube and for R134 evaporating inside a vertical microfin tube. In addition microfin heat transfer augmentation relative to plain tube test data was investigated. The measured heat transfer coefficients were compared to different existing inside tube flow boiling correlations. (author) figs., tabs., refs.

  6. Burnout heat flux in natural flow boiling

    International Nuclear Information System (INIS)

    Helal, M.M.; Darwish, M.A.; Mahmoud, S.I.

    1978-01-01

    Twenty runs of experiments were conducted to determine the critical heat flux for natural flow boiling with water flowing upwards through annuli of centrally heated stainless steel tube. The test section has concentric heated tube of 14mm diameter and heated lengthes of 15 and 25 cm. The outside surface of the annulus was formed by various glass tubes of 17.25, 20 and 25.9mm diameter. System pressure is atmospheric. Inlet subcooling varied from 18 to 5 0 C. Obtained critical heat flux varied from 24.46 to 62.9 watts/cm 2 . A number of parameters having dominant influence on the critical heat flux and hydrodynamic instability (flow and pressure oscillations) preceeding the burnout have been studied. These parameters are mass flow rate, mass velocity, throttling, channel geometry (diameters ratio, length to diameter ratio, and test section length), and inlet subcooling. Flow regimes before and at the moments of burnout were observed, discussed, and compared with the existing physical model of burnout

  7. Helically coiled tube heat exchanger

    International Nuclear Information System (INIS)

    Harris, A.M.

    1981-01-01

    In a heat exchanger such as a steam generator for a nuclear reactor, two or more bundles of helically coiled tubes are arranged in series with the tubes in each bundle integrally continuing through the tube bundles arranged in series therewith. Pitch values for the tubing in any pair of tube bundles, taken transverse to the path of the reactor coolant flow about the tubes, are selected as a ratio of two unequal integers to permit efficient operation of each tube bundle while maintaining the various tube bundles of the heat exchanger within a compact envelope. Preferably, the helix angle and tube pitch parallel to the path of coolant flow are constant for all tubes in a single bundle so that the tubes are of approximately the same length within each bundle

  8. Steam generator tube performance

    International Nuclear Information System (INIS)

    Tatone, O.S.; Pathania, R.S.

    1982-04-01

    The performance of steam generator tubes in water-cooled nuclear power reactors has been reviewed for 1980. Tube defects occurred at 38% of the 97 reactors surveyed. This is a marginal improvement over 1979 when defects occurred at 41% of the reactors. The number of failed tubes was also lower, 0.14% of the tubes in service in 1980 compared with 0.20% of those in service in 1979. Analysis of the causes of these failures indicates that stress corrosion cracking was the leading failure mechanism. Reactors that used all-volatile treatment of secondary water, with or without full-flow condensate demineralization since start-up showed the lowest incidence of corrosion-related defects

  9. X-ray tube

    International Nuclear Information System (INIS)

    Webley, R.S.

    1975-01-01

    The object of the invention described is to provide an X-ray tube providing a scanned X-ray output which does not require a scanned electron beam. This is obtained by an X-ray tube including an anode which is rotatable about an axis, and a source of a beam of energy, for example an electron beam, arranged to impinge on a surface of the anode to generate X-radiation substantially at the region of incidence on the anode surface. The anode is rotatable about the axis to move the region of incidence over the surface. The anode is so shaped that the rotation causes the region of incidence to move in a predetermined manner relative to fixed parts of the tube so that the generated X-radiation is scanned in a predetermined manner relative to the tube. (UK)

  10. Fuel assembly guide tube

    International Nuclear Information System (INIS)

    Jabsen, F.S.

    1979-01-01

    This invention is directed toward a nuclear fuel assembly guide tube arrangement which restrains spacer grid movement due to coolant flow and which offers secondary means for supporting a fuel assembly during handling and transfer operations

  11. Bull Moose Tube Company

    Science.gov (United States)

    The EPA is providing notice of a proposed Administrative Penalty Assessment against the Bull Moose Tube Company, a business located at 1819 Clarkson Road, Chesterfield, MO, 63017, for alleged violations at the facility located at 406 East Industrial Drive,

  12. Tracheostomy tube - eating

    Science.gov (United States)

    Trach - eating ... take your first bites. Certain factors may make eating or swallowing harder, such as: Changes in the ... easier to swallow. Suction the tracheostomy tube before eating. This will keep you from coughing while eating, ...

  13. Nitrile-functionalized ruthenium nanoparticles: charge delocalization through Ru − N ≡ C interface

    International Nuclear Information System (INIS)

    Zhang, Fengqi; Huang, Lin; Zou, Jiasui; Yan, Jinwu; Zhu, Jiaying; Kang, Xiongwu; Chen, Shaowei

    2017-01-01

    Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) were stabilized by the self-assembly of nitrile molecules onto the ruthenium colloid surface by virtue of the formation of Ru−N≡C interfacial bonding linkages. Thermogravimetric analysis showed that there were about 63 nitrile ligands per nanoparticle, corresponding to an average molecular footprint of 22.4 Å 2 . Proton nuclear magnetic resonance (NMR) studies suggested an end-on configuration of the nitrile moiety on the metal core surface. Meanwhile, infrared measurements showed that the C≡N stretch red-shifted from 2246 to 1944 cm −1 upon adsorption on the nanoparticle surfaces, as confirmed by 15 N isotopic labeling. This apparent red-shift suggests extensive intraparticle charge delocalization, which was further manifested by photoluminescence measurements of 1-cyanopyrene-functionalized ruthenium nanoparticles that exhibited a red shift of 40 nm of the emission maximum, in comparison to that of free monomers. The results further highlight the significance of metal−organic contacts in the manipulation of the dynamics of intraparticle charge transfer and the nanoparticle optical and electronic properties.

  14. Localized vs. delocalized character of charge carriers in LaAlO3/SrTiO3 heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Kejin; Schlappa, Justine; Strocov, Vladimir; Frison, Ruggero; Patthey, Luc; Schmitt, Thorsten [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Radovic, Milan [Laboratory for Synchrotron and Neutron Spectroscopy, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Mesot, Joel [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Laboratory for Synchrotron and Neutron Spectroscopy, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    2011-07-01

    Oxide heterostructures have been attracting great attention due to extraordinary phenomena occurring at the interface and their potential application for device design. A particularly fascinating system is the two-dimensional conductive interface between the band insulators LaAlO{sub 3} (LAO) and SrTiO{sub 3} (STO), which can be even driven to magnetic and superconducting phases at low temperatures. Resonant inelastic X-ray scattering at Ti L-edges is particularly suitable to address the electronic structure of its interface since the Ti{sup 3+} states clearly display strong dd excitations while Ti{sup 4+} states exhibit only elastic emission in the low energy loss regime. Our studies on LAO/STO superlattices prepared by pulsed laser deposition unambiguously reveal the presence of both localized and delocalized Ti 3d carriers generated during the building of the LAO/STO interfaces. Systematic studies on samples before and after annealing under O{sub 2} atmosphere and high temperature show that the dual character carriers can be either induced by electron transfer due to the polar-discontinuity or by oxygen vacancies defects. Oxygen vacancies and electronic reconstruction are equivalent in balancing the built-up electric potential.

  15. Localized holes and delocalized electrons in photoexcited inorganic perovskites: Watching each atomic actor by picosecond X-ray absorption spectroscopy

    Directory of Open Access Journals (Sweden)

    Fabio G. Santomauro

    2017-07-01

    Full Text Available We report on an element-selective study of the fate of charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr3 perovskite nanocrystals in toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing the Br K-edge, the Pb L3-edge, and the Cs L2-edge, we find that holes in the valence band are localized at Br atoms, forming small polarons, while electrons appear as delocalized in the conduction band. No signature of either electronic or structural changes is observed at the Cs L2-edge. The results at the Br and Pb edges suggest the existence of a weakly localized exciton, while the absence of signatures at the Cs edge indicates that the Cs+ cation plays no role in the charge transport, at least beyond 80 ps. This first, time-resolved element-specific study of perovskites helps understand the rather modest charge carrier mobilities in these materials.

  16. Nitrile-functionalized ruthenium nanoparticles: charge delocalization through Ru − N ≡ C interface

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fengqi; Huang, Lin; Zou, Jiasui [South China University of Technology, New Energy Research Institute, School of Environment and Energy, Guangzhou Higher Education Mega Centre (China); Yan, Jinwu; Zhu, Jiaying [South China University of Technology, School of Bioscience and Bioengineering, Guangzhou Higher Education Mega Centre (China); Kang, Xiongwu, E-mail: esxkang@scut.edu.cn; Chen, Shaowei, E-mail: shaowei@ucsc.edu [South China University of Technology, New Energy Research Institute, School of Environment and Energy, Guangzhou Higher Education Mega Centre (China)

    2017-03-15

    Ruthenium nanoparticles (2.06 ± 0.46 nm in diameter) were stabilized by the self-assembly of nitrile molecules onto the ruthenium colloid surface by virtue of the formation of Ru−N≡C interfacial bonding linkages. Thermogravimetric analysis showed that there were about 63 nitrile ligands per nanoparticle, corresponding to an average molecular footprint of 22.4 Å{sup 2}. Proton nuclear magnetic resonance (NMR) studies suggested an end-on configuration of the nitrile moiety on the metal core surface. Meanwhile, infrared measurements showed that the C≡N stretch red-shifted from 2246 to 1944 cm{sup −1} upon adsorption on the nanoparticle surfaces, as confirmed by {sup 15}N isotopic labeling. This apparent red-shift suggests extensive intraparticle charge delocalization, which was further manifested by photoluminescence measurements of 1-cyanopyrene-functionalized ruthenium nanoparticles that exhibited a red shift of 40 nm of the emission maximum, in comparison to that of free monomers. The results further highlight the significance of metal−organic contacts in the manipulation of the dynamics of intraparticle charge transfer and the nanoparticle optical and electronic properties.

  17. Streak tube development

    International Nuclear Information System (INIS)

    Hinrichs, C.K.; Estrella, R.M.

    1979-01-01

    A research program for the development of a high-speed, high-resolution streak image tube is described. This is one task in the development of a streak camera system with digital electronic readout, whose primary application is for diagnostics in underground nuclear testing. This program is concerned with the development of a high-resolution streak image tube compatible with x-ray input and electronic digital output. The tube must be capable of time resolution down to 100 psec and spatial resolution to provide greater than 1000 resolution elements across the cathode (much greater than presently available). Another objective is to develop the capability to make design changes in tube configurations to meet different experimental requirements. A demountable prototype streak tube was constructed, mounted on an optical bench, and placed in a vacuum system. Initial measurements of the tube resolution with an undeflected image show a resolution of 32 line pairs per millimeter over a cathode diameter of one inch, which is consistent with the predictions of the computer simulations. With the initial set of unoptmized deflection plates, the resolution pattern appeared to remain unchanged for static deflections of +- 1/2-inch, a total streak length of one inch, also consistent with the computer simulations. A passively mode-locked frequency-doubled dye laser is being developed as an ultraviolet pulsed light source to measure dynamic tube resolution during streaking. A sweep circuit to provide the deflection voltage in the prototype tube has been designed and constructed and provides a relatively linear ramp voltage with ramp durations adjustable between 10 and 1000 nsec

  18. Researching YouTube

    OpenAIRE

    Arthurs, Jane; Drakopoulou, Sophia; Gandini, Alessandro

    2018-01-01

    ‘Researching YouTube’ introduces the special issue of Convergence which arose out of an international academic conference on YouTube that was held in London at Middlesex University in September 2016. The conference aimed to generate a robust overview of YouTube’s changing character and significance after its first ten years of development by creating a productive dialogue between speakers from different disciplines and cultures, and between YouTube-specific research and wider debates in media...

  19. Tubing crimping pliers

    Science.gov (United States)

    Lindholm, G.T.

    1981-02-27

    The disclosure relates to pliers and more particularly to pliers for crimping two or more pieces of copper tubing together prior to their being permanently joined by brazing, soldering or the like. A die containing spring-loaded pins rotates within a cammed ring in the head of the pliers. As the die rotates, the pins force a crimp on tubing held within the pliers.

  20. Radiation transport calculations for the ANS [Advanced Neutron Source] beam tubes

    International Nuclear Information System (INIS)

    Engle, W.W. Jr.; Lillie, R.A.; Slater, C.O.

    1988-01-01

    The Advanced Neutron Source facility (ANS) will incorporate a large number of both radial and no-line-of-sight (NLS) beam tubes to provide very large thermal neutron fluxes to experimental facilities. The purpose of this work was to obtain comparisons for the ANS single- and split-core designs of the thermal and damage neutron and gamma-ray scalar fluxes in these beams tubes. For experimental locations far from the reactor cores, angular flux data are required; however, for close-in experimental locations, the scalar fluxes within each beam tube provide a credible estimate of the various signal to noise ratios. In this paper, the coupled two- and three-dimensional radiation transport calculations employed to estimate the scalar neutron and gamma-ray fluxes will be described and the results from these calculations will be discussed. 6 refs., 2 figs

  1. Pressure tube reactor

    International Nuclear Information System (INIS)

    Seki, Osamu; Kumasaka, Katsuyuki.

    1988-01-01

    Purpose: To remove the heat of reactor core using a great amount of moderators at the periphery of the reactor core as coolants. Constitution: Heat of a reactor core is removed by disposing a spontaneous recycling cooling device for cooling moderators in a moderator tank, without using additional power driven equipments. That is, a spontaneous recycling cooling device for cooling the moderators in the moderator tank is disposed. Further, the gap between the inner wall of a pressure tube guide pipe disposed through the vertical direction of a moderator tank and the outer wall of a pressure tube inserted through the guide pipe is made smaller than the rupture distortion caused by the thermal expansion upon overheating of the pressure tube and greater than the minimum gap required for heat shiels between the pressure tube and the pressure tube guide pipe during usual operation. In this way, even if such an accident as can not using a coolant cooling device comprising power driven equipment should occur in the pressure tube type reactor, the rise in the temperature of the reactor core can be retarded to obtain a margin with time. (Kamimura, M.)

  2. Tube spacer grid for a heat-exchanger tube bundle

    International Nuclear Information System (INIS)

    Scheidl, H.

    1976-01-01

    A tube spacer grid for a heat-exchanger tube bundle is formed by an annular grid frame having a groove formed in its inner surface in which the interspaced grid bars have their ends positioned and held in interspaced relationship by short sections of tubes passed through holes axially formed in the grid frame so that the tubes are positioned between the ends of the grid bars in the grooves. The tube sections may be cut from the same tubes used to form the tube bundle. 5 claims, 3 drawing figures

  3. Dryout in sodium-heated helically-coiled steam generator tubes

    International Nuclear Information System (INIS)

    Tomita, Y.; Kosugi, T.; Kubota, J.; Nakajima, K.; Tsuchiya, T.

    1984-01-01

    Experimental research on the dryout phenomenon in sodium heated, helically coiled steam generator tubes was carried out. The fluctuation of the tube wall temperature caused by dryout was measured with thermocouples installed in the center of the tube wall. Empirical correlations of dryout quality were developed as functions of critical heat flux, water mass velocity and saturation pressure. These correlations confirmed that the design criterion of the MONJU steam generator was reasonable. (author)

  4. Impact of electron delocalization on the nature of the charge-transfer states in model pentacene/C60 Interfaces: A density functional theory study

    KAUST Repository

    Yang, Bing

    2014-12-04

    Electronic delocalization effects have been proposed to play a key role in photocurrent generation in organic photovoltaic devices. Here, we study the role of charge delocalization on the nature of the charge-transfer (CT) states in the case of model complexes consisting of several pentacene molecules and one fullerene (C60) molecule, which are representative of donor/acceptor heterojunctions. The energies of the CT states are examined by means of time-dependent density functional theory (TD-DFT) using the long-range-corrected functional, ωB97X, with an optimized range-separation parameter, ω. We provide a general description of how the nature of the CT states is impacted by molecular packing (i.e., interfacial donor/acceptor orientations), system size, and intermolecular interactions, features of importance in the understanding of the charge-separation mechanism.

  5. Charge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT

    KAUST Repository

    Zhang, Yuexing

    2016-04-25

    We investigate theoretically charge delocalization in radical-cations, i.e., positive polarons, formed on oligomer chains of poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT. We use non-empirically tuned range-separated density functionals (TRS-DFT), including LC-ωPBE, LC-BLYP, and ωB97XD. We consider the evolution with oligomer length of the molecular geometric and electronic structures, optical absorption features, and spin densities. The TRS-DFT results indicate that a positive polaron can delocalize ideally over some 10 thiophene rings when the backbone is non-planar and up to 14 rings for a backbone forced to be completely planar. Interestingly, up to six polarons can co-exist side-by-side in a hexamer (which contains 24 thiophene rings), which is consistent with the highest degrees of doping (oxidation) experimentally achievable in polythiophene derivatives.

  6. Charge Delocalization in Oligomers of Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT

    KAUST Repository

    Zhang, Yuexing; Steyrleuthner, Robert; Bredas, Jean-Luc

    2016-01-01

    We investigate theoretically charge delocalization in radical-cations, i.e., positive polarons, formed on oligomer chains of poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene), PBTTT. We use non-empirically tuned range-separated density functionals (TRS-DFT), including LC-ωPBE, LC-BLYP, and ωB97XD. We consider the evolution with oligomer length of the molecular geometric and electronic structures, optical absorption features, and spin densities. The TRS-DFT results indicate that a positive polaron can delocalize ideally over some 10 thiophene rings when the backbone is non-planar and up to 14 rings for a backbone forced to be completely planar. Interestingly, up to six polarons can co-exist side-by-side in a hexamer (which contains 24 thiophene rings), which is consistent with the highest degrees of doping (oxidation) experimentally achievable in polythiophene derivatives.

  7. Numerical Simulation of Liquid Nitrogen Chilldown of a Vertical Tube

    Science.gov (United States)

    Darr, Samuel; Hu, Hong; Schaeffer, Reid; Chung, Jacob; Hartwig, Jason; Majumdar, Alok

    2015-01-01

    This paper presents the results of a one-dimensional numerical simulation of the transient chilldown of a vertical stainless steel tube with liquid nitrogen. The direction of flow is downward (with gravity) through the tube. Heat transfer correlations for film, transition, and nucleate boiling, as well as critical heat flux, rewetting temperature, and the temperature at the onset of nucleate boiling were used to model the convection to the tube wall. Chilldown curves from the simulations were compared with data from 55 recent liquid nitrogen chilldown experiments. With these new correlations the simulation is able to predict the time to rewetting temperature and time to onset of nucleate boiling to within 25% for mass fluxes ranging from 61.2 to 1150 kg/(sq m s), inlet pressures from 175 to 817 kPa, and subcooled inlet temperatures from 0 to 14 K below the saturation temperature.

  8. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... search for current job openings visit HHS USAJobs Home >> NEI YouTube Videos >> NEI YouTube Videos: Amblyopia Listen NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia Animations Blindness Cataract ...

  9. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... search for current job openings visit HHS USAJobs Home » NEI YouTube Videos » NEI YouTube Videos: Amblyopia Listen NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia Animations Blindness Cataract ...

  10. Refrigerant charge, pressure drop, and condensation heat transfer in flattened tubes

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, M J; Newell, T A; Chato, J C [University of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering; Infante Ferreira, C A [Delft University of Technology (Netherlands). Laboratory for Refrigeration and Indoor Climate Control

    2003-06-01

    Horizontal smooth and microfinned copper tubes with an approximate diameter of 9 mm were successively flattened in order to determine changes in flow field characteristics as a round tube is altered into a flattened tube profile. Refrigerants R134a and R410A were investigated over a mass flux range from 75 to 400 kg m{sup -2} s{sup -}2{sup 1} and a quality range from approximately 10-80%. For a given refrigerant mass flow rate, the results show that a significant reduction in refrigerant charge is possible. Pressure drop results show increases of pressure drop at a given mass flux and quality as a tube profile is flattened. Heat transfer results indicate enhancement of the condensation heat transfer coefficient as a tube is flattened. Flattened tubes with an 18{sup o} helix angle displayed the highest heat transfer coefficients. Smooth tubes and axial microfin tubes displayed similar levels of heat transfer enhancement. Heat transfer enhancement is dependent on the mass flux, quality and tube profile. (author)

  11. Treatment of delocalized electron transfer in periodic and embedded cluster DFT calculations: The case of Cu on ZnO (10(1)0).

    Science.gov (United States)

    Hellström, Matti; Spångberg, Daniel; Hermansson, Kersti

    2015-12-15

    We assess the consequences of the interface model-embedded-cluster or periodic-slab model-on the ability of DFT calculations to describe charge transfer (CT) in a particularly challenging case where periodic-slab calculations indicate a delocalized charge-transfer state. Our example is Cu atom adsorption on ZnO(10(1)0), and in fact the periodic slab calculations indicate three types of CT depending on the adsorption site: full CT, partial CT, and no CT. Interestingly, when full CT occurs in the periodic calculations, the calculated Cu atom adsorption energy depends on the underlying ZnO substrate supercell size, since when the electron enters the ZnO it delocalizes over as many atoms as possible. In the embedded-cluster calculations, the electron transferred to the ZnO delocalizes over the entire cluster region, and as a result the calculated Cu atom adsorption energy does not agree with the value obtained using a large periodic supercell, but instead to the adsorption energy obtained for a periodic supercell of roughly the same size as the embedded cluster. Different density functionals (of GGA and hybrid types) and basis sets (local atom-centered and plane-waves) were assessed, and we show that embedded clusters can be used to model Cu adsorption on ZnO(10(1)0), as long as care is taken to account for the effects of CT. © 2015 Wiley Periodicals, Inc.

  12. Magnetic Exchange Couplings from Semilocal Functionals Evaluated Nonself-Consistently on Hybrid Densities: Insights on Relative Importance of Exchange, Correlation, and Delocalization.

    Science.gov (United States)

    Phillips, Jordan J; Peralta, Juan E

    2012-09-11

    Semilocal functionals generally yield poor magnetic exchange couplings for transition-metal complexes, typically overpredicting in magnitude the experimental values. Here we show that semilocal functionals evaluated nonself-consistently on densities from hybrid functionals can yield magnetic exchange couplings that are greatly improved with respect to their self-consistent semilocal values. Furthermore, when semilocal functionals are evaluated nonself-consistently on densities from a "half-and-half" hybrid, their errors with respect to experimental values can actually be lower than those from self-consistent calculations with standard hybrid functionals such as PBEh or TPSSh. This illustrates that despite their notoriously poor performance for exchange couplings, for many systems semilocal functionals are capable of delivering accurate relative energies for magnetic states provided that their electron delocalization error is corrected. However, while self-consistent calculations with hybrids uniformly improve results for all complexes, evaluating nonself-consistently with semilocal functionals does not give a balanced improvement for both ferro- and antiferromagnetically coupled complexes, indicating that there is more at play with the overestimation problem than simply the delocalization error. Additionally, we show that for some systems the conventional wisdom of choice of exchange functional mattering more than correlation does not hold. This combined with results from the nonself-consistent calculations provide insight on clarifying the relative roles of exchange, correlation, and delocalization in calculating magnetic exchange coupling parameters in Kohn-Sham Density Functional Theory.

  13. Hideout in steam generator tube deposits

    International Nuclear Information System (INIS)

    Balakrishnan, P.V.; Franklin, K.J.; Turner, C.W.

    1998-05-01

    Hideout in deposits on steam generator tubes was studied using tubes coated with magnetite. Hideout from sodium chloride solutions at 279 degrees C was followed using an on-line high-temperature conductivity probe, as well as by chemical analysis of solution samples from the autoclave in which the studies were done. Significant hideout was observed only at a heat flux greater than 200 kW/m 2 , corresponding to a temperature drop greater than 2 degrees C across the deposits. The concentration factor resulting from the hideout increased highly non-linearly with the heat flux (varying as high as the fourth power of the heat flux). The decrease in the apparent concentration factor with increasing deposit thickness suggested that the pores in the deposit were occupied by a mixture of steam and water, which is consistent with the conclusion from the thermal conductivity measurements on deposits in a separate study. Analyses of the deposits after the hideout tests showed no evidence of any hidden-out solute species, probably due to the concentrations being very near the detection limits and to their escape from the deposit as the tests were being ended. This study showed that hideout in deposits may concentrate solutes in the steam generator bulk water by a factor as high as 2 x 10 3 . Corrosion was evident under the deposit in some tests, with some chromium enrichment on the surface of the tube. Chromium enrichment usually indicates an acidic environment, but the mobility required of chromium to become incorporated into the thick magnetite deposit may indicate corrosion under an alkaline environment. An alkaline environment could result from preferential accumulation of sodium in the solution in the deposit during the hideout process. (author)

  14. Inviscid flux-splitting algorithms for real gases with non-equilibrium chemistry

    Science.gov (United States)

    Shuen, Jian-Shun; Liou, Meng-Sing; Van Leer, Bram

    1990-01-01

    Formulations of inviscid flux splitting algorithms for chemical nonequilibrium gases are presented. A chemical system for air dissociation and recombination is described. Numerical results for one-dimensional shock tube and nozzle flows of air in chemical nonequilibrium are examined.

  15. Flux trapping during field reversal in a field reversed theta pinch

    International Nuclear Information System (INIS)

    Milroy, R.D.; Hoffman, A.L.; Slough, J.T.; Harding, D.G.

    1983-01-01

    In this paper we present new results from both numerical and experimental studies of the formation of the conducting sheath near the tube wall and its effectiveness in trapping bias flux during field reversal

  16. Tube plug removal machine

    International Nuclear Information System (INIS)

    Hawkins, P.J.

    1987-01-01

    In a nuclear steam generator wherein some faulty tubes have been isolated by mechanical plugging, to remove a selected plug without damaging the associated tube, a plug removal machine is used. The machine drills into a plug portion with a tap drill bit having a drill portion a tap portion and a threaded portion, engaging that plug portion with the threaded portion after the drilled hole has been threaded by the tap portion thereof, and removing a portion of the plug in the tube with a counterbore drill bit mounted concentrically about the tap drill bit. A trip pin and trip spline disengage the tap drill bit from the motor. The counterbore drill bit is thereafter self-centered with respect to the tube and plug about the now stationary tap drill bit. After a portion of the plug has been removed by the counterbore drill bit, pulling on the top drill bit by grippers on slots will remove the remaining plug portion from the tube. (author)

  17. Categorising YouTube

    Directory of Open Access Journals (Sweden)

    Thomas Mosebo Simonsen

    2011-09-01

    Full Text Available This article provides a genre analytical approach to creating a typology of the User Generated Content (UGC of YouTube. The article investigates the construction of navigationprocesses on the YouTube website. It suggests a pragmatic genre approach that is expanded through a focus on YouTube’s technological affordances. Through an analysis of the different pragmatic contexts of YouTube, it is argued that a taxonomic understanding of YouTube must be analysed in regards to the vacillation of a user-driven bottom-up folksonomy and a hierarchical browsing system that emphasises a culture of competition and which favours the already popular content of YouTube. With this taxonomic approach, the UGC videos are registered and analysed in terms of empirically based observations. The article identifies various UGC categories and their principal characteristics. Furthermore, general tendencies of the UGC within the interacting relationship of new and old genres are discussed. It is argued that the utility of a conventional categorical system is primarily of analytical and theoretical interest rather than as a practical instrument.

  18. Measuring of tube expansion

    International Nuclear Information System (INIS)

    Vogeleer, J. P.

    1985-01-01

    The expansion of the primary tubes or sleeves of the steam generator of a nuclear reactor plant are measured while the tubes or sleeves are being expanded. A primary tube or sleeve is expanded by high pressure of water which flows through a channel in an expander body. The water is supplied through an elongated conductor and is introduced through a connector on the shank connected to the conductor at its outer end. A wire extends through the mandrel and through the conductor to the end of the connector. At its inner end the wire is connected to a tapered pin which is subject to counteracting forces produced by the pressure of the water. The force on the side where the wire is connected to the conductor is smaller than on the opposite side. The tapered pin is moved in the direction of the higher force and extrudes the wire outwardly of the conductor. The tapered surface of the tapered pin engages transverse captive plungers which are maintained in engagement with the expanding tube or sleeve as they are moved outwardly by the tapered pin. The wire and the connector extend out of the generator and, at its outer end, the wire is connected to an indicator which measures the extent to which the wire is moved by the tapered pin, thus measuring the expansion of the tube or sleeve as it progresses

  19. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  20. Theoretical and experimental study of bent fully aperiodic large-pitch fibers for enhancing the high-order modes delocalization

    Science.gov (United States)

    du Jeu, Rémi; Dauliat, Romain; Darwich, Dia; Auguste, Jean-Louis; Benoît, Aurélien; Leconte, Baptiste; Malleville, Marie-Alicia; Jamier, Raphaël.; Schuster, Kay; Roy, Philippe

    2018-02-01

    The power scaling of fiber lasers and amplifiers has triggered an extensive development of large-mode area fibers among which the most promising are the distributed mode filtering fibers and the large-pitch fibers. These structures enable for an effective higher-order modes delocalization and subsequently a singlemode emission. An interesting alternative consists in using the fully-aperiodic large-pitch fibers, into which the standard air-silica photonic crystal cladding is replaced by an aperiodic pattern made of solid low-index inclusions cladding. However, in such a structure, the core and the background cladding material surrounding it must have rigorously the same refractive index. Current synthesis processes and measurement techniques offer respectively a maximum resolution of 5×10-4 and 1×10-4 while the indexmatching must be as precise as 1×10-5 . Lately a gain material with a refractive index 1.5×10-4 higher than that of the background cladding material was fabricated, thus re-confining the first higher-order modes in the core. A numerical study is carried out on the benefit of bending such fully-aperiodic fiber to counteract this phenomenon. Optimized bending axis and radius have been determined. Experiments are done in a laser cavity operating at 1030 nm using an 88cm-long 51μm core diameter ytterbium-doped fiber. Results demonstrate an improvement of the M2 from 1.7 when the fiber is kept straight to 1.2 when it is bent with a 100 to 60 cm bend radius. These primary results are promising for future power scaling.

  1. Effect of protonation, composition and isomerism on the redox properties and electron (de)localization of classical polyoxometalates

    Science.gov (United States)

    López, Xavier

    2017-10-01

    This publication reviews some relevant features related with the redox activity of two inorganic compounds: [XM12O40]q- (Keggin structure) and [X2M18O62]q- (Wells-Dawson structure). These are two well-known specimens of the vast Polyoxometalate (POM) family, which has been the subject of extensive experimental and theoretical research owing to their unmatched properties. In particular, their redox activity focus a great deal of attention from scientists due to their prospective related applications. POMs are habitually seen as `electron sponges' since many of them accept several electrons without losing their chemical identity. This makes them excellent models to study mechanisms of electrochemical nature. Their redox properties depend on: (i) the type and number of transition metal atoms in the structure, (ii) the basicity of the first reduced species and, occasionally, of the fully oxidized species; (iii) the size of the molecule, (iv) the overall negative charge of the POM, and (v) the size of the central heteroatom. In the last years, important collaboration between the experimental and theoretical areas has been usual on the development of POM science. In the present chapter three of these synergies are highlighted: the influence of the internal heteroatom upon the redox potentials of Keggin anions; the dependence of the redox waves of Fe-substituted Wells-Dawson compounds with pH; and the role of electron delocalization and pairing in mixed-metal Mo/W Wells-Dawson compounds in their ability to accept electrons. In these three cases, a complete understanding of the problem would not have been possible without the mutual benefit of experimental and computational data.

  2. Advanced evacuated tube collectors

    Science.gov (United States)

    Schertz, W. W.; Hull, J. R.; Winston, R.; Ogallagher, J.

    1985-04-01

    The essence of the design concept for these new collectors is the integration of moderate levels of nonimaging concentration inside the evacuated tube itself. This permanently protects the reflection surfaces and allows the use of highly reflecting front surface mirrors with reflectances greater than 95%. Previous fabrication and long term testing of a proof-of-concept prototype has established the technical success of the concept. Present work is directed toward the development of a manufacturable unit that will be suitable for the widest possible range of applications. Design alternatives include scaling up the original prototype's tube diameter from 5 cm to 10 cm, using an internal shaped metal concentrating reflector, using a variety of profile shapes to minimize so-called gap losses and accommodate both single ended and double-ended flow geometries, and allowing the use of heat pipes for the absorber tube.

  3. Square through tube

    International Nuclear Information System (INIS)

    Akita, Junji; Honma, Toei.

    1975-01-01

    Object: To provide a square through tube involving thermal movement in pipelines such as water supply pump driving turbine exhaust pipe (square-shaped), which is wide in freedom with respect to shape and dimension thereof for efficient installation at site. Structure: In a through tube to be airtightly retained for purpose of decontamination in an atomic power plant, comprising a seal rubber plate, a band and a bolt and a nut for securing said plate, the seal rubber plate being worked into the desired shape so that it may be placed in intimate contact with the concrete floor surface by utilization of elasticity of rubber, thereby providing airtightness at a corner portion of the square tube. (Kamimura, M.)

  4. SG tube identification

    International Nuclear Information System (INIS)

    Hoogstraten, P. van

    1994-01-01

    A ''Tracker'' system is described which is designed to identify any tube in a reactor steam generator quickly and safely. Occupational radiation doses to maintenance workers are reduced by using a Tracker and emergency down times are shortened. The system employs a television camera and light source in a stainless steel box with a large window. Both the camera and spotlight can be panned and tilted to reach any point on the tubesheet and are remotely controlled. An operator at a safe working distance can identify any tube visible on a real time video by comparison with the tubesheet pattern stored earlier in the computer memory. The identified tube can then be spotlighted and dealt with quickly by a maintenance worker inside the channel head. (UK)

  5. First Research Coordination Meeting on Prediction of Axial and Radial Creep in HWR Pressure Tubes. Presentations

    International Nuclear Information System (INIS)

    2013-01-01

    Pressure tube deformation is a critical aging issue in operating Heavy Water Reactors (HWRs). According to the service year, horizontal pressure tubes have three kinds of deformation: diametral creep leading to the flow bypass and the penalty to critical heat flux for fuel rods, longitudinal creep leading to the interference of feeder pipes and/or with fuelling machine, and sagging leading to the interference with in-core components and potential contact between the pressure tube and calandria tube. The CRP scope includes the establishment of a database for pressure tube deformation, microstructure characterization of pressure tube materials collected from HWRs currently operating in Member States and development of a prediction model for pressure tube deformation

  6. Emergence of localized states in narrow GaAs/AlGaAs nanowire quantum well tubes.

    Science.gov (United States)

    Shi, Teng; Jackson, Howard E; Smith, Leigh M; Jiang, Nian; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Zheng, Changlin; Etheridge, Joanne

    2015-03-11

    We use low-temperature photoluminescence, photoluminescence excitation, and photoluminescence imaging spectroscopy to explore the optical and electronic properties of GaAs/AlGaAs quantum well tube (QWT) heterostructured nanowires (NWs). We find that GaAs QWTs with widths >5 nm have electronic states which are delocalized and continuous along the length of the NW. As the NW QWT width decreases from 5 to 1.5 nm, only a single electron state is bound to the well, and no optical excitations to a confined excited state are present. Simultaneously, narrow emission lines (fwhm points along the length of the NW. We find that these quantum-dot-like states broaden at higher temperatures and quench at temperatures above 80 K. The lifetimes of these localized states are observed to vary from dot to dot from 160 to 400 ps. The presence of delocalized states and then localized states as the QWTs become more confined suggests both opportunities and challenges for possible incorporation into quantum-confined device structures.

  7. PRODUCTION OF URANIUM TUBING

    Science.gov (United States)

    Creutz, E.C.

    1958-04-15

    The manufacture of thin-walled uranium tubing by the hot-piercing techique is described. Uranium billets are preheated to a temperature above 780 d C. The heated billet is fed to a station where it is engaged on its external surface by three convex-surfaced rotating rollers which are set at an angle to the axis of the billet to produce a surface friction force in one direction to force the billet over a piercing mandrel. While being formed around the mandrel and before losing the desired shape, the tube thus formed is cooled by a water spray.

  8. Guide tube sleeve

    International Nuclear Information System (INIS)

    Attix, D.J.

    1983-01-01

    The invention increases the operating capacity of a nuclear reactor by causing a modification in the flow pattern of the coolant which enhances the coolant's effectiveness. The apparatus provides a thin-walled tubular sleeve closely surrounding but not attached to the exterior surface of a guide tube in a fuel assembly. The wall of the sleeve has tabs projecting outwardly into adjacent flow channels. The sleeve is attached to the wall of a cellular void through which passes the guide tube associated with said sleeve. The tabs increase the flow of water in the channel and thus increase the heat transfer

  9. Pressure tube type research reactor

    International Nuclear Information System (INIS)

    Ueda, Hiroshi.

    1976-01-01

    Object: To prevent excessive heat generation due to radiation of a pressure tube vessel. Structure: A pressure tube encasing therein a core comprises a dual construction comprising inner and outer tubes coaxially disposed. High speed cooling water is passed through the inner tube for cooling. In addition, in the outer periphery of said outer tube there is provided a forced cooling tube disposed coaxially thereto, into which cooling fluid, for example, such as moderator or reflector is forcibly passed. This forced cooling tube has its outer periphery surrounded by the vessel into which moderator or reflector is fed. By the provision of the dual construction of the pressure tube and the forced cooling tube, the vessel may be prevented from heat generation. (Ikeda, J.)

  10. Double wall steam generator tubing

    International Nuclear Information System (INIS)

    Padden, T.R.; Uber, C.F.

    1983-01-01

    Double-walled steam generator tubing for the steam generators of a liquid metal cooled fast breeder reactor prevents sliding between the surfaces due to a mechanical interlock. Forces resulting from differential thermal expansion between the outer tube and the inner tube are insufficient in magnitude to cause shearing of base metal. The interlock is formed by jointly drawing the tubing, with the inside wall of the outer tube being already formed with grooves. The drawing causes the outer wall of the inner tube to form corrugations locking with the grooves. (author)

  11. Delocalization in polymer models

    CERN Document Server

    Jitomirskaya, S Yu; Stolz, G

    2003-01-01

    A polymer model is a one-dimensional Schroedinger operator composed of two finite building blocks. If the two associated transfer matrices commute, the corresponding energy is called critical. Such critical energies appear in physical models, an example being the widely studied random dimer model. Although the random models are known to have pure-point spectrum with exponentially localized eigenstates for almost every configuration of the polymers, the spreading of an initially localized wave packet is here proven to be at least diffusive for every configuration.

  12. Tube-dwelling invertebrates

    NARCIS (Netherlands)

    Hölker, Franz; Vanni, Michael J.; Kuiper, Jan J.; Meile, Christof; Grossart, Hans Peter; Stief, Peter; Adrian, Rita; Lorke, Andreas; Dellwig, Olaf; Brand, Andreas; Hupfer, Michael; Mooij, Wolf M.; Nützmann, Gunnar; Lewandowski, Jörg

    2015-01-01

    There is ample evidence that tube-dwelling invertebrates such as chironomids significantly alter multiple important ecosystem functions, particularly in shallow lakes. Chironomids pump large water volumes, and associated suspended and dissolved substances, through the sediment and thereby compete

  13. Cladding tube manufacturing technology

    International Nuclear Information System (INIS)

    Hahn, R.; Jeong, Y. H.; Baek, B. J.; Kim, K. H.; Kim, S. J.; Choi, B. K.; Kim, J. M.

    1999-04-01

    This report gives an overview of the manufacturing routine of PWR cladding tubes. The routine essentially consists of a series of deformation and annealing processes which are necessary to transform the ingot geometry to tube dimensions. By changing shape, microstructure and structure-related properties are altered simultaneously. First, a short overview of the basics of that part of deformation geometry is given which is related to tube reducing operations. Then those processes of the manufacturing routine which change the microstructure are depicted, and the influence of certain process parameters on microstructure and material properties are shown. The influence of the resulting microstructure on material properties is not discussed in detail, since it is described in my previous report A lloy Development for High Burnup Cladding . Because of their paramount importance still up to now, and because manufacturing data and their influence on properties for other alloys are not so well established or published, the descriptions are mostly related to Zry4 tube manufacturing, and are only in short for other alloys. (author). 9 refs., 46 figs

  14. Thoughts on accelerator tubes

    International Nuclear Information System (INIS)

    Larson, J.D.

    1978-01-01

    A brief, subjective review is given of mechanisms that may be limiting electrostatic accelerator tubes to present levels of performance. Suggestions are made for attacking these limitations with the purpose of stimulating the thinking of designers and users of electrostatic accelerators

  15. Tracheostomy tube - speaking

    Science.gov (United States)

    ... with others. However, you can learn how to speak with a tracheostomy tube. It just takes practice. There ... If it is hard to speak with a trach in place, special devices can help you learn to create sounds. One-way valves, called speaking valves, are placed ...

  16. Thoughts of accelerator tubes

    International Nuclear Information System (INIS)

    Larson, J.D.

    1977-01-01

    A brief, subjective review is given of mechanisms that may be limiting electrostatic accelerator tubes to present levels of performance. Suggestions are made for attacking these limitations with the purpose of stimulating the thinking of designers and users of electrostatic accelerators

  17. Cladding tube manufacturing technology

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, R. [Kraftwerk Union AG, Mulheim (Germany); Jeong, Y.H.; Baek, B.J.; Kim, K.H.; Kim, S.J.; Choi, B.K.; Kim, J.M. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1999-04-01

    This report gives an overview of the manufacturing routine of PWR cladding tubes. The routine essentially consists of a series of deformation and annealing processes which are necessary to transform the ingot geometry to tube dimensions. By changing shape, microstructure and structure-related properties are altered simultaneously. First, a short overview of the basics of that part of deformation geometry is given which is related to tube reducing operations. Then those processes of the manufacturing routine which change the microstructure are depicted, and the influence of certain process parameters on microstructure and material properties are shown. The influence of the resulting microstructure on material properties is not discussed in detail, since it is described in my previous report 'Alloy Development for High Burnup Cladding.' Because of their paramount importance still up to now, and because manufacturing data and their influence on properties for other alloys are not so well established or published, the descriptions are mostly related to Zry4 tube manufacturing, and are only in short for other alloys. (author). 9 refs., 46 figs.

  18. A comparison of the CHF between tubes and annuli under PWR thermal-hydraulic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Herer, C. [RRAMATOME EP/TC, Paris (France); Souyri, A. [EdF DER/RNE/TTA, Chatou (France); Garnier, J. [CEA DRN/DTP/STR/LETC, Grenoble (France)

    1995-09-01

    Critical Heat Flux (CHF) tests were carried out in three tubes with inside diameters of 8, 13, and 19.2 mm and in two annuli with an inner tube of 9.5 mm and an outer tube of 13 or 19.2 mm. All axial heat flux distributions in the test sections were uniform. The coolant fluid was Refrigerant 12 (Freon-12) under PWR thermal-hydraulic conditions (equivalent water conditions - Pressure: 7 to 20 MPa, Mass Velocity: 1000 to 6000 kg/m2/s, Local Quality: -75% to +45%). The effect of tube diameter is correlated for qualities under 15%. The change from the tube to the annulus configuration is correctly taken into account by the equivalent hydraulic diameter. Useful information is also provided concerning the effect of a cold wall in an annulus.

  19. Modeling the quenching of a calandria tube following a critical break LOCA in a CANDU reactor

    International Nuclear Information System (INIS)

    Jiang, J.T.; Luxat, J.C.

    2008-01-01

    Following a postulated critical large break LOCA a pressure tube (PT) can experience creep deformation and balloon uniformly into contact with the calandria tube (CT). The resultant heat flux to CT is high as stored heat is transferred out of the hot PT. This heat flux can cause dryout on the outer surface of the CT and establish film boiling. This paper presents a model of buoyancy-driven natural convection film boiling on the outside of a horizontal tube with diameter relevant to a CANDU CT (approximately 130mm). The model has been developed to analyze the variation of steady state vapor film thickness as a function of sub-cooling temperature, wall superheat and incident heat flux. The CT outer surface heat flux and effective film boiling heat transfer coefficient from the model are in good agreement with available experimental data. (author)

  20. Modeling the quenching of a calandria tube following a critical break LOCA in a CANDU reactor

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J.T.; Luxat, J.C. [McMaster Univ., Dept. of Engineering Physics, Hamilton, Ontario (Canada)

    2008-07-01

    Following a postulated critical large break LOCA a pressure tube (PT) can experience creep deformation and balloon uniformly into contact with the calandria tube (CT). The resultant heat flux to CT is high as stored heat is transferred out of the hot PT. This heat flux can cause dryout on the outer surface of the CT and establish film boiling. This paper presents a model of buoyancy-driven natural convection film boiling on the outside of a horizontal tube with diameter relevant to a CANDU CT (approximately 130mm). The model has been developed to analyze the variation of steady state vapor film thickness as a function of sub-cooling temperature, wall superheat and incident heat flux. The CT outer surface heat flux and effective film boiling heat transfer coefficient from the model are in good agreement with available experimental data. (author)

  1. Cosmic muon flux measurements at the Kimballton Underground Research Facility

    International Nuclear Information System (INIS)

    Kalousis, L N; Guarnaccia, E; Link, J M; Mariani, C; Pelkey, R

    2014-01-01

    In this article, the results from a series of muon flux measurements conducted at the Kimballton Underground Research Facility (KURF), Virginia, United States, are presented. The detector employed for these investigations, is made of plastic scintillator bars readout by wavelength shifting fibers and multianode photomultiplier tubes. Data was taken at several locations inside KURF, spanning rock overburden values from ∼ 200 to 1450 m.w.e. From the extracted muon rates an empirical formula was devised, that estimates the muon flux inside the mine as a function of the overburden. The results are in good agreement with muon flux calculations based on analytical models and MUSIC

  2. Equipment for thermal neutron flux measurements in reactor R2

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, E; Nilsson, T; Claeson, S

    1960-04-15

    For most of the thermal neutron flux measurements in reactor R2 cobalt wires will be used. The loading and removal of these wires from the reactor core will be performed by means of a long aluminium tube and electromagnets. After irradiation the wires will be scanned in a semi-automatic device.

  3. Experimental Study of Flow Boiling Heat Transfer in a Horizontal Microfin Tube

    OpenAIRE

    Yu, Jian; Koyama, Shigeru; Momoki, Satoru

    1995-01-01

    An experimental study on flow boiling heat transfer in a horizontal microfin tube is conducted with pure refrigerants HFC134a, HCFC123 and HCFC22 using a water-heated double-tube type test section. The test microfin tube is a copper tube having the following dimensions: 8.37mm mean inside diameter, 0.168mm fin height, 60fin number and 18 degree of helix angle. The local heat transfer coefficients for both counter and parallel flows are measured in a range of heat flux of 1 to 93W/m^2, mass ve...

  4. Performance of pressure tubes in CANDU reactors

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, D.; Griffiths, M.; Bickel, G.; Buyers, A.; Coleman, C.; Nordin, H.; St Lawrence, S. [Canadian Nuclear Laboratories, Chalk River, Ontario (Canada)

    2016-06-15

    The pressure tubes in CANDU reactors typically operate for times up to about 30 years prior to refurbishment. The in-reactor performance of Zr-2.5Nb pressure tubes has been evaluated by sampling and periodic inspection. This paper describes the behavior and discusses the factors controlling the behaviour of these components. The Zr–2.5Nb pressure tubes are nominally extruded at 815{sup o}C, cold worked nominally 27%, and stress relieved at 400 {sup o}C for 24 hours, resulting in a structure consisting of elongated grains of hexagonal close-packed alpha-Zr, partially surrounded by a thin network of filaments of body-centred-cubic beta-Zr. These beta-Zr filaments are meta-stable and contain about 20% Nb after extrusion. The stress-relief treatment results in partial decomposition of the beta-Zr filaments with the formation of hexagonal close-packed alpha-phase particles that are low in Nb, surrounded by a Nb-enriched beta-Zr matrix. The material properties of pressure tubes are determined by variations in alpha-phase texture, alpha-phase grain structure, network dislocation density, beta-phase decomposition, and impurity concentration that are a function of manufacturing variables. The pressure tubes operate at temperatures between 250 {sup o}C and 310 {sup o}C with coolant pressures up to about 11 MPa in fast neutron fluxes up to 4 x 10{sup 17} n·m{sup -2}·s{sup -1} (E > 1 MeV) and the properties are modified by these conditions. The properties of the pressure tubes in an operating reactor are therefore a function of both manufacturing and operating condition variables. The ultimate tensile strength, fracture toughness, and delayed hydride-cracking properties (velocity (V) and threshold stress intensity factor (K{sub IH})) change with irradiation, but all reach a nearly limiting value at a fluence of less than 10{sup 25} n·m{sup -2} (E > 1 MeV). At this point the ultimate tensile strength is raised about 200 MPa, toughness is reduced by about 50%, V increases

  5. Neutron flux enhancement in the NRAD reactor

    International Nuclear Information System (INIS)

    Weeks, A.A.; Heidel, C.C.; Imel, G.R.

    1988-01-01

    In 1987 a series of experiments were conducted at the NRAD reactor facility at Argonne National Laboratory - West (ANL-W) to investigate the possibility of increasing the thermal neutron content at the end of the reactor's east beam tube through the use of hydrogenous flux traps. It was desired to increase the thermal flux for a series of experiments to be performed in the east radiography cell, in which the enhanced flux was required in a relatively small volume. Hence, it was feasible to attempt to focus the cross section of the beam to a smaller area. Two flux traps were constructed from unborated polypropylene and tested to determine their effectiveness. Both traps were open to the entire cross-sectional area of the neutron beam (as it emerges from the wall and enters the beam room). The sides then converged such that at the end of the trap the beam would be 'focused' to a greater intensity. The differences in the two flux traps were primarily in length, and hence angle to the beam as the inlet and outlet cross-sectional areas were held constant. It should be noted that merely placing a slab of polypropylene in the beam will not yield significant multiplication as neutrons are primarily scattered away

  6. Drift tubes of Linac 2

    CERN Multimedia

    Photographic Service

    1977-01-01

    Being redied for installation, those at the right are for tank 1, those on the left for tank 2. Contrary to Linac 1, which had drift-tubes supported on stems, here the tubes are suspended, for better mechanical stability.

  7. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: Amblyopia ... *PDF files require the free Adobe® Reader® software for viewing. This website is maintained by the ...

  8. Tubing For Sampling Hydrazine Vapor

    Science.gov (United States)

    Travis, Josh; Taffe, Patricia S.; Rose-Pehrsson, Susan L.; Wyatt, Jeffrey R.

    1993-01-01

    Report evaluates flexible tubing used for transporting such hypergolic vapors as those of hydrazines for quantitative analysis. Describes experiments in which variety of tubing materials, chosen for their known compatibility with hydrazine, flexibility, and resistance to heat.

  9. Prospects for stronger calandria tubes

    International Nuclear Information System (INIS)

    Ells, C.E.; Coleman, C.E.; Hosbons, R.R.; Ibrahim, E.F.; Doubt, G.L.

    1990-12-01

    The CANDU calandria tubes, made of seam welded and annealed Zircaloy-2, have given exemplary service in-reactor. Although not designed as a system pressure containment, calandria tubes may remain intact even in the face of pressure tube rupture. One such incident at Pickering Unit 2 demonstrated the economic advantage of such an outcome, and a case can be made for increasing the probability that other calandria tubes would perform in a similar fashion. Various methods of obtaining stronger calandria tubes are available, and reviewed here. When the tubes are internally pressurized, the weld is the weak section of the tube. Increasing the oxygen concentration in the starting sheet, and thickening the weld, are promising routes to a stronger tube

  10. Expansion lyre-shaped tube

    International Nuclear Information System (INIS)

    Andro, Jean.

    1973-01-01

    The invention relates the expansion lyre-shaped tube portions formed in dudgeoned tubular bundles between two bottom plates. An expansion lyre comprises at least two sets of tubes of unequal lengths coplanar and symmetrical with respect to the main tube axis, with connecting portions between the tubes forming said sets. The invention applies to apparatus such as heat exchangers, heaters, superheaters or breeders [fr

  11. Experimental investigation of the reverse heat transfer of R134a flow through non-adiabatic coiled capillary tubes

    Energy Technology Data Exchange (ETDEWEB)

    Zareh, Masoud; Heidari, Mohammad Ghorbani [Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2016-07-15

    This research represents an experimental investigation of the metastable flow and re-condensation phenomenon through non-adiabatic lateral helical capillary tubes and suction tube heat exchanger. The results show that mass flux ratio has a vital role: It affects metastable flow and also reverse heat transfer phenomenon through non-adiabatic helical capillary tube. Therefore, by increasing of the mass flux ratio, the rate of heat transfer between them decreases. In contrast to the strong rate condition of heat transfer between them, reverse heat transfer or re-condensation maybe happen. Moreover, experimental results show that for R134 flow with mass flux ratio more than 57.84, metastable flow exists in non-adiabatic capillary tube with 0.9144 mm inner diameter, 30 mm coil diameter, 6.18 m length, 4 mm inner diameter of compressor suction tube.

  12. Chest tube insertion - series (image)

    Science.gov (United States)

    Chest tubes are inserted to drain blood, fluid, or air and allow full expansion of the lungs. The tube is placed in the pleural space. The area where the tube will be inserted is numbed (local anesthesia). The patient may also be sedated. The chest ...

  13. Tube Length and Water Flow

    Directory of Open Access Journals (Sweden)

    Ben Ruktantichoke

    2011-06-01

    Full Text Available In this study water flowed through a straight horizontal plastic tube placed at the bottom of a large tank of water. The effect of changing the length of tubing on the velocity of flow was investigated. It was found that the Hagen-Poiseuille Equation is valid when the effect of water entering the tube is accounted for.

  14. Tubing cutter for tight spaces

    Science.gov (United States)

    Girala, A. S.

    1980-01-01

    Cutter requires few short swings of handle to rotate its cutting edge full 360 around tube. It will cut tubing installed in confined space that prevents free movement of conventional cutter. Cutter is snapped onto tube and held in place by spring-loaded clamp. Screw ratchet advances cutting wheel.

  15. Interplay of spin-dependent delocalization and magnetic anisotropy in the ground and excited states of [Gd2@C78]- and [Gd2@C80]-

    Science.gov (United States)

    Mansikkamäki, Akseli; Popov, Alexey A.; Deng, Qingming; Iwahara, Naoya; Chibotaru, Liviu F.

    2017-09-01

    The magnetic properties and electronic structure of the ground and excited states of two recently characterized endohedral metallo-fullerenes, [Gd2@C78]- (1) and [Gd2@C80]- (2), have been studied by theoretical methods. The systems can be considered as [Gd2]5+ dimers encapsulated in a fullerene cage with the fifteen unpaired electrons ferromagnetically coupled into an S = 15/2 high-spin configuration in the ground state. The microscopic mechanisms governing the Gd-Gd interactions leading to the ferromagnetic ground state are examined by a combination of density functional and ab initio calculations and the full energy spectrum of the ground and lowest excited states is constructed by means of ab initio model Hamiltonians. The ground state is characterized by strong electron delocalization bordering on a σ type one-electron covalent bond and minor zero-field splitting (ZFS) that is successfully described as a second order spin-orbit coupling effect. We have shown that the observed ferromagnetic interaction originates from Hund's rule coupling and not from the conventional double exchange mechanism. The calculated ZFS parameters of 1 and 2 in their optimized geometries are in qualitative agreement with experimental EPR results. The higher excited states display less electron delocalization, but at the same time they possess unquenched first-order angular momentum. This leads to strong spin-orbit coupling and highly anisotropic energy spectrum. The analysis of the excited states presented here constitutes the first detailed study of the effects of spin-dependent delocalization in the presence of first order orbital angular momentum and the obtained results can be applied to other mixed valence lanthanide systems.

  16. Effect of axial heat flux distribution on CHF

    Energy Technology Data Exchange (ETDEWEB)

    Park, Cheol

    2000-10-01

    Previous investigations for the effect of axial heat flux distributions on CHF and the prediction methods are reviewed and summarized. A total of 856 CHF data in a tube with a non-uniform axial heat flux distribution has been compiled from the articles and analyzed using the 1995 Groeneveld look-up table. The results showed that two representative correction factors, K5 of the look-up table and Tongs F factor, can be applied to describe the axial heat flux distribution effect on CHF. However, they overpredict slightly the measured CHF, depending on the quality and flux peak shape. Hence, a corrected K5 factor, which accounts for the axial heat flux distribution effect is suggested to correct these trends. It predicted the CHF power for the compiled data with an average error of 1.5% and a standard deviation of 10.3%, and also provides a reasonable prediction of CHF locations.

  17. Heat Exchanger Tube to Tube Sheet Joints Corrosion Behavior

    Directory of Open Access Journals (Sweden)

    M. Iancu

    2013-03-01

    Full Text Available Paper presents the studies made by the authors above the tube to tube sheet fittings of heat exchanger with fixed covers from hydrofining oil reforming unit. Tube fittings are critical zones for heat exchangers failures. On a device made from material tube and tube sheet at real joints dimensions were establish axial compression force and traction force at which tube is extracted from expanded joint. Were used two shapes joints with two types of fittings surfaces, one with smooth hole of tube sheet and other in which on boring surface we made a groove. From extracted expanded tube zones were made samples for corrosion tests in order to establish the corrosion rate, corrosion potential and corrosion current in working mediums such as hydrofining oil and industrial water at different temperatures. The corrosion rate values and the temperature influence are important to evaluate joints durability and also the results obtained shows that the boring tube sheet shape with a groove on hole tube shape presents a better corrosion behavior then the shape with smooth hole tube sheet.

  18. Heat transfer behaviors in round tube with conical ring inserts

    International Nuclear Information System (INIS)

    Promvonge, P.

    2008-01-01

    To increase convection heat transfer in a uniform heat flux tube by a passive method, several conical rings used as turbulators are mounted over the test tube. The effects of the conical ring turbulator inserts on the heat transfer rate and friction factor are experimentally investigated in the present work. Conical rings with three different diameter ratios of the ring to tube diameter (d/D = 0.5, 0.6, 0.7) are introduced in the tests, and for each ratio, the rings are placed with three different arrangements (converging conical ring, referred to as CR array, diverging conical ring, DR array and converging-diverging conical ring, CDR array). In the experiment, cold air at ambient condition for Reynolds numbers in a range of 6000-26,000 is passed through the uniform heat flux circular tube. It is found that the ring to tube diameter ratio and the ring arrays provide a significant effect on the thermal performance of the test tube. The experimental results demonstrate that the use of conical ring inserts leads to a higher heat transfer rate than that of the plain surface tube, and the DR array yields a better heat transfer than the others. The results are also correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and diameter ratio. An augmentation of up to 197%, 333%, and 237% in Nusselt number is obtained in the turbulent flow for the CR, DR and CDR arrays, respectively, although the effect of using the conical ring causes a substantial increase in friction factor

  19. State-dependent electron delocalization dynamics at the solute-solvent interface: soft-x-ray absorption spectroscopy and ab initio calculations.

    Science.gov (United States)

    Bokarev, Sergey I; Dantz, Marcus; Suljoti, Edlira; Kühn, Oliver; Aziz, Emad F

    2013-08-23

    Nonradiative decay channels in the L-edge fluorescence yield spectra from transition-metal-aqueous solutions give rise to spectral distortions with respect to x-ray transmission spectra. Their origin is unraveled here using partial and inverse partial fluorescence yields on the microjet combined with multireference ab initio electronic structure calculations. Comparing Fe2+, Fe3+, and Co2+ systems we demonstrate and quantify unequivocally the state-dependent electron delocalization within the manifold of d orbitals as one origin of this observation.

  20. Optical density of states in ultradilute GaAsN alloy: Coexistence of free excitons and impurity band of localized and delocalized states

    Energy Technology Data Exchange (ETDEWEB)

    Bhuyan, Sumi; Pal, Bipul; Bansal, Bhavtosh, E-mail: bhavtosh@iiserkol.ac.in [Indian Institute of Science Education and Research Kolkata, Mohanpur Campus, Nadia 741252, West Bengal (India); Das, Sanat K.; Dhar, Sunanda [Department of Electronic Science, University of Calcutta, 92 A.P.C. Road, Kolkata 700009 (India)

    2014-07-14

    Optically active states in liquid phase epitaxy-grown ultra-dilute GaAsN are studied. The feature-rich low temperature photoluminescence spectrum has contributions from excitonic band states of the GaAsN alloy, and two types of defect states—localized and extended. The degree of delocalization for extended states both within the conduction and defect bands, characterized by the electron temperature, is found to be similar. The degree of localization in the defect band is analyzed by the strength of the phonon replicas. Stronger emission from these localized states is attributed to their giant oscillator strength.

  1. YouTube Physics

    Science.gov (United States)

    Riendeau, Diane

    2012-09-01

    To date, this column has presented videos to show in class, Don Mathieson from Tulsa Community College suggested that YouTube could be used in another fashion. In Don's experience, his students are not always prepared for the mathematic rigor of his course. Even at the high school level, math can be a barrier for physics students. Walid Shihabi, a colleague of Don's, decided to compile a list of YouTube videos that his students could watch to relearn basic mathematics. I thought this sounded like a fantastic idea and a great service to the students. Walid graciously agreed to share his list and I have reproduced a large portion of it below.

  2. Neutron image intensifier tubes

    International Nuclear Information System (INIS)

    Verat, M.; Rougeot, H.; Driard, B.

    1983-01-01

    The most frequently used techniques in neutron radiography employ a neutron converter consisting of either a scintillator or a thin metal sheet. The radiation created by the neutrons exposes a photographic film that is in contact with the converter: in the direct method, the film is exposed during the time that the object is irradiated with neutrons; in the transfer method, the film is exposed after the irradiation of the object with neutrons. In industrial non-destructive testing, when many identical objects have to be checked, these techniques have several disadvantages. Non-destructive testing systems without these disadvantages can be constructed around neutron-image intensifier tubes. A description and the operating characteristics of neutron-image intensifier tubes are given. (Auth.)

  3. Tube coupling device

    Science.gov (United States)

    Myers, William N. (Inventor); Hein, Leopold A. (Inventor)

    1987-01-01

    A first annular ring of a tube coupling device has a keyed opening sized to fit around the nut region of a male coupling, and a second annular ring has a keyed opening sized to fit around the nut of a female coupling. Each ring has mating ratchet teeth and these rings are biased together, thereby engaging these teeth and preventing rotation of these rings. This in turn prevents the rotation of the male nut region with respect to the female nut. For tube-to-bulkhead locking, one facet of one ring is notched, and a pin is pressed into an opening in the bulkhead. This pin is sized to fit within one of the notches in the ring, thereby preventing rotation of this ring with respect to the bulkhead.

  4. PEG Tube Placement

    Directory of Open Access Journals (Sweden)

    Saptarshi Biswas

    2014-01-01

    Full Text Available Percutaneous endoscopic gastrostomy (PEG has been used for providing enteral access to patients who require long-term enteral nutrition for years. Although generally considered safe, PEG tube placement can be associated with many immediate and delayed complications. Buried bumper syndrome (BBS is one of the uncommon and late complications of percutaneous endoscopic gastrostomy (PEG placement. It occurs when the internal bumper of the PEG tube erodes into the gastric wall and lodges itself between the gastric wall and skin. This can lead to a variety of additional complications such as wound infection, peritonitis, and necrotizing fasciitis. We present here a case of buried bumper syndrome which caused extensive necrosis of the anterior abdominal wall.

  5. Compact neutron flux monitor

    International Nuclear Information System (INIS)

    Madhavi, V.; Phatak, P.R.; Bahadur, C.; Bayala, A.K.; Jakati, R.K.; Sathian, V.

    2003-01-01

    Full text: A compact size neutron flux monitor has been developed incorporating standard boards developed for smart radiation monitors. The sensitivity of the monitors is 0.4cps/nV. It has been tested up to 2075 nV flux with standard neutron sources. It shows convincing results even in high flux areas like 6m away from the accelerator in RMC (Parel) for 106/107 nV. These monitors have a focal and remote display, alarm function with potential free contacts for centralized control and additional provision of connectivity via RS485/Ethernet. This paper describes the construction, working and results of the above flux monitor

  6. Quantitative experiments on thermal hydraulic characteristics of an annular tube with twisted fins

    International Nuclear Information System (INIS)

    Ezato, Koichiro; Dairaku, Masayuki; Taniguchi, Masaki; Sato, Kazuyoshi; Suzuki, Satoshi; Akiba, Masato

    2003-11-01

    Thermal hydraulic experiments measuring critical heat flux (CHF) and pressure drop of an annular tube with twisted fins, ''annular swirl tube'', has been performed to examine its applicability to the ITER divertor cooling structure. The annular swirl tube consists of two concentric circular tubes, the outer and inner tubes. The outer tube with outer and inner diameters (OD and ID) of 21 mm and 15 mm is made of Cu-alloy that is CuCrZr and oe of candidate materials of the ITER divertor cooling tube. The inner tube with OD of 11 mm and ID of 9 mm is made of stainless steal. It has an external swirl fin with twist ratio (y) of three to enhance its heat transfer performance. In this tube, cooling water flows inside of the inner tube first, and then returns into an annulus between the outer and inner tubes with a swirl flow at an end-return of the cooling tube. The CHF experiments show that no degradation of CHF of the annular swirl tube in comparison with the conventional swirl tube whose dimensions are similar to those of the outer tube of the annular swirl tube. A minimum axial velocity of 7.1 m/s is required to remove the incident heat flux of 28MW/m 2 , the ITER design value. Applicability of the JAERI's correlation for the heat transfer to the annular swirl tube is also demonstrated by comparing the experimental results with those of the numerical analysis. The friction factor correlation for the annular flow with the twisted fins is also proposed for the hydrodynamic design of the ITER vertical target. The least pressure drop at the end-return is obtained by using the hemispherical end-plug. Its radius is the same as that of ID of the outer cooling tube. These results show that thermal-hydraulic performance of the annular swirl tube is promising in application to the cooling structure for the ITER vertical target. (author)

  7. Recurrent inspection of tubes

    International Nuclear Information System (INIS)

    Andersson, S.

    1984-01-01

    Recommendations concerning the selection of areas for the inspection of tubes have been outlined. The aim is to focus the control on the regions which are important for the safety and where damage is supposed to take place. The number of zones will depend on the risk factors as judged by experts. The localizing will be based upon probable damaging mechanisms. A certain number of areas should be chosen at random. (G.B.)

  8. Cathode ray tube screens

    International Nuclear Information System (INIS)

    Cockayne, B.; Robbins, D.J.; Glasper, J.L.

    1982-01-01

    An improved cathode ray tube screen is described which consists of a single- or a poly-crystalline slice of a material such as yttrium aluminium garnet in which dopants such as Tb 3 + , Eu 3 + , Ce 3 + or Tm 3 + are ion implanted to different depths or in different areas of the screen. Annealing the screen removes lattice damage caused by the ion implanting and assists the diffusion of the dopant into the crystal. (U.K.)

  9. Cathode ray tube

    International Nuclear Information System (INIS)

    1979-01-01

    A cathode ray tube comprises two electron lens means in combination to crossover the electron beam at a second crossover between the two electron lens means with one of the two lens means having a variable voltage applied thereto to control the location of the beam crossover in order to focus the beam onto a display screen at any location away from the screen center. (Auth.)

  10. Fabrication of seamless calandria tubes

    International Nuclear Information System (INIS)

    Saibaba, N.; Phanibabu, C.; Bhaskara Rao, C.V.; Kalidas, R.; Ganguly, C.

    2002-01-01

    Full text: Calandria tube is a large diameter, thin walled zircaloy-4 tube and is an important structural component of PHWR type of reactors. These tubes are lifetime components and remain during the full life of the reactor. Calandria tubes are classified as extremely thin walled tubes with a diameter to wall thickness ratio of around 96. Such thin walled tubes are conventionally produced by seam welded route comprising of extrusion of slabs followed by a series of hot and rolling passes, shaping into O-shape and eventual welding. An alternative and superior method of fabricating the calandria tubes, the seamless route, has been developed, which involves hot extrusion of mother blanks followed by three successive cold pilger reductions. Eccentricity correction of the extruded blanks is carried out on a special purpose grinding equipment to bring the wall thickness variation within permissible limits. Predominant wall thickness reductions are given during cold pilgering to ensure high Q-factor values. The texture in the finished tubes could be closely, controlled with an average f r value of 0.65. Pilgering parameters and tube guiding system have been specially designed to facilities rolling of thin walled tubes. Seamless calandria tubes have distinct advantages over welded tubes. In addition to the absence of weld, they are dimensionally more stable, lighter in weight and possess uniform grains with superior grain size. The cycle time from billet to finished product is substantially reduced and the product is amenable to high level of quality assurance. The most significant feature of the seamless route is its material recovery over welded route. Residual stresses measured in the tubes indicate that these are negligible and uniform along the length of the tube. In view of their superior quality, the first charge of seamless calandria tubes will be rolled into the first 500 MWe Pressurised Heavy Water Reactor at Tarapur

  11. Pressure distribution over tube surfaces of tube bundle subjected to two phase cross flow

    International Nuclear Information System (INIS)

    Sim, Woo Gun

    2013-01-01

    Two phase vapor liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two phase flow, it is essential to obtain detailed information about the characteristics of a two phase flow. The characteristics of a two phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid dynamic force acting on the cylinder owing to the pressure distribution. A two phase flow was pre mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two phase cross flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results

  12. Chemical potential and reaction electronic flux in symmetry controlled reactions.

    Science.gov (United States)

    Vogt-Geisse, Stefan; Toro-Labbé, Alejandro

    2016-07-15

    In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  13. CRL X-ray tube

    International Nuclear Information System (INIS)

    Kolchevsky, N.N.; Petrov, P.V.

    2015-01-01

    A novel types of X-ray tubes with refractive lenses are proposed. CRL-R X-ray tube consists of Compound Refractive Lens- CRL and Reflection X-ray tube. CRL acts as X-ray window. CRL-T X-ray consists of CRL and Transmission X-ray tube. CRL acts as target for electron beam. CRL refractive lens acts as filter, collimator, waveguide and focusing lens. Properties and construction of the CRL X-ray tube are discussed. (authors)

  14. Heat flux limiting sleeves

    Science.gov (United States)

    Harris, William G.

    1985-01-01

    A heat limiting tubular sleeve extending over only a portion of a tube having a generally uniform outside diameter, the sleeve being open on both ends, having one end thereof larger in diameter than the other end thereof and having a wall thickness which decreases in the same direction as the diameter of the sleeve decreases so that the heat transfer through the sleeve and tube is less adjacent the large diameter end of the sleeve than adjacent the other end thereof.

  15. Influence of boiler load on water tubes burnout

    Energy Technology Data Exchange (ETDEWEB)

    Said, S.A.M.; Habib, M.A.; Badr, H.M.; Mansour, R. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Mechanical Engineering

    2009-07-01

    The influence of boiler loads on water tube burnout was investigated. The in-service boiler had 2 burners at different levels located in the front of the burner's wall. Homogenous-flow and separated-flow models were designed to simulate the water circulation and combustion processes inside the boiler tubes. Heat flux calculations were derived by solving the conservation of mass, momentum, and energy equations and species concentration as well as by solving turbulence, reaction rate, and radiation model equations. Results of the study showed that heat flux during full loads ranged from close to 0 to 270 kW/m2. The right side screen wall of the burner exhibited higher heat flux values in the middle region of the wall where large areas were subjected to heat flux close to a maximum of 270 kW/m2. Results also included reductions in heat flux values at partial loads. Maximum values were reduced from 270 kW/m2 ato 230 kW/m2 at 75 per cent capacity and 200 kW/m2 at 60 per cent capacity. The rate of steam generation increased from 0.1 kg/s to 0.153 kg/s when the distance from the burner wall increased from 2 meters to 12 meters. 10 refs., 10 figs.

  16. Microdischarges in DC accelerator tubes

    International Nuclear Information System (INIS)

    Eastham, D.A.; Thorn, R.

    1978-07-01

    Voltage tests on the Daresbury ceramic/titanium accelerator tube have shown that microdischarges play an important role in the conditioning process. It has been found that the voltage onset for microdischarges in a tube is dependent on the surface contamination of the electrodes and the tube geometry (in particular the tube length). This geometrical effect can be related to the trajectories of secondary ions emitted from the electrode surfaces. Sensitive diagnostic techniques have been developed to study the mass and energy distribution of ions emitted along the axis of the tube during these predischarges. The energy distribution of protons (and H - ions) can be related to the origins of the discharges in the tube. Detailed results are presented for a particular tube geometry. (author)

  17. Falling film evaporation on a tube bundle with plain and enhanced tubes

    International Nuclear Information System (INIS)

    Habert, M.

    2009-04-01

    The complexities of two-phase flow and evaporation on a tube bundle present important problems in the design of heat exchangers and the understanding of the physical phenomena taking place. The development of structured surfaces to enhance boiling heat transfer and thus reduce the size of evaporators adds another level of complexity to the modeling of such heat exchangers. Horizontal falling film evaporators have the potential to be widely used in large refrigeration systems and heat pumps, in the petrochemical industry and for sea water desalination units, but there is a need to improve the understanding of falling film evaporation mechanisms to provide accurate thermal design methods. The characterization of the effect of enhanced surfaces on the boiling phenomena occurring in falling film evaporators is thus expected to increase and optimize the performance of a tube bundle. In this work, the existing LTCM falling film facility was modified and instrumented to perform falling film evaporation measurements on single tube row and a small tube bundle. Four types of tubes were tested including: a plain tube, an enhanced condensing tube (Gewa-C+LW) and two enhanced boiling tubes (Turbo-EDE2 and Gewa-B4) to extend the existing database. The current investigation includes results for two refrigerants, R134a and R236fa, at a saturation temperature of T sat = 5 °C, liquid film Reynolds numbers ranging from 0 to 3000, at heat fluxes between 20 and 60 kW/m² in pool boiling and falling film configurations. Measurements of the local heat transfer coefficient were obtained and utilized to improve the current prediction methods. Finally, the understanding of the physical phenomena governing the falling film evaporation of liquid refrigerants has been improved. Furthermore, a method for predicting the onset of dry patch formation has been developed and a local heat transfer prediction method for falling film evaporation based on a large experimental database has been proposed

  18. Design basis for creep of zirconium alloy components in a fast neutron flux

    International Nuclear Information System (INIS)

    Ross-Ross, P.A.; Fidleris, V.

    1975-01-01

    The chalk River Nuclear Laboratory's experience with the creep of zirconium alloys in a neutron flux is described. Fast neutron flux changes the creep behaviour of zirconium alloys and new design criteria for in-reactor applications are needed. From experimental results empirical relations describing the effects of neutron flux, stress, temperature, time and anisotropy on creep rate were established. The relations are applied to the design of pressure tubes. (author)

  19. Design basis for creep of zirconium alloy components in a fast neutron flux

    International Nuclear Information System (INIS)

    Ross-Ross, P.A.; Fidleris, V.

    1974-01-01

    The Chalk River Nuclear Laboratory's experience with the creep of zirconium alloys in a neutron flux is described. Fast neutron flux changes the creep behavior of zirconium alloys and new design criteria for in-reactor applications are needed. From experimental results empirical relations describing the effects of neutron flux, stress, temperature, time, and anisotropy on creep rate were established. The relations are applied to the design of pressure tubes. (author)

  20. Ultrasonic inspection of tube to tube plate welds

    International Nuclear Information System (INIS)

    Telford, D.W.; Peat, T.S.

    1985-01-01

    To monitor the deterioration of a weld between a tube and tube plate which has been repaired by a repair sleeve inside the tube and brazed at one end to the tube, ultrasound from a crystal at the end of a rod is launched, in the form of Lamb-type waves, into the tube through the braze and allowed to travel along the tube to the weld and be reflected back along the tube. The technique may also be used for the type of heat exchanger in which, during construction, the tubes are welded to the tube plate via external sleeves in which case the ultrasound is used in a similar manner to inspect the sleeve/tube plate weld. an electromagnetic transducer may be used to generate the ultrasound. The ultrasonic head comprising the crystal and an acoustic baffle is mounted on a Perspex (RTM) rod which may be rotated by a stepping motor. Echo signals from the region of deterioration may be isolated by use of a time gate in the receiver. The device primarily detects circumferentially orientated cracks, and may be used in heat exchangers in nuclear power plants. (author)

  1. Liquid-Nitrogen Test for Blocked Tubes

    Science.gov (United States)

    Wagner, W. R.

    1984-01-01

    Nondestructive test identifies obstructed tube in array of parallel tubes. Trickle of liquid nitrogen allowed to flow through tube array until array accumulates substantial formation of frost from moisture in air. Flow stopped and warm air introduced into inlet manifold to heat tubes in array. Tubes still frosted after others defrosted identified as obstructed tubes. Applications include inspection of flow systems having parallel legs.

  2. Primary cosmic ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Stanev, Todor

    2001-05-01

    We discuss the primary cosmic ray flux from the point of view of particle interactions and production of atmospheric neutrinos. The overall normalization of the cosmic ray flux and its time variations and site dependence are major ingredients of the atmospheric neutrino predictions and the basis for the derivation of the neutrino oscillation parameters.

  3. Flux cutting in superconductors

    International Nuclear Information System (INIS)

    Campbell, A M

    2011-01-01

    This paper describes experiments and theories of flux cutting in superconductors. The use of the flux line picture in free space is discussed. In superconductors cutting can either be by means of flux at an angle to other layers of flux, as in longitudinal current experiments, or due to shearing of the vortex lattice as in grain boundaries in YBCO. Experiments on longitudinal currents can be interpreted in terms of flux rings penetrating axial lines. More physical models of flux cutting are discussed but all predict much larger flux cutting forces than are observed. Also, cutting is occurring at angles between vortices of about one millidegree which is hard to explain. The double critical state model and its developments are discussed in relation to experiments on crossed and rotating fields. A new experiment suggested by Clem gives more direct information. It shows that an elliptical yield surface of the critical state works well, but none of the theoretical proposals for determining the direction of E are universally applicable. It appears that, as soon as any flux flow takes place, cutting also occurs. The conclusion is that new theories are required. (perspective)

  4. Heat flux microsensor measurements

    Science.gov (United States)

    Terrell, J. P.; Hager, J. M.; Onishi, S.; Diller, T. E.

    1992-01-01

    A thin-film heat flux sensor has been fabricated on a stainless steel substrate. The thermocouple elements of the heat flux sensor were nickel and nichrome, and the temperature resistance sensor was platinum. The completed heat flux microsensor was calibrated at the AEDC radiation facility. The gage output was linear with heat flux with no apparent temperature effect on sensitivity. The gage was used for heat flux measurements at the NASA Langley Vitiated Air Test Facility. Vitiated air was expanded to Mach 3.0 and hydrogen fuel was injected. Measurements were made on the wall of a diverging duct downstream of the injector during all stages of the hydrogen combustion tests. Because the wall and the gage were not actively cooled, the wall temperature reached over 1000 C (1900 F) during the most severe test.

  5. Theoretical investigation of the relative stability of Na{sup +}He{sub n} (n = 2–24) clusters: Many-body versus delocalization effects

    Energy Technology Data Exchange (ETDEWEB)

    Issaoui, Noureddine, E-mail: issaoui-noureddine@yahoo.fr; Abdessalem, Kawther; Ghalla, Houcine [Faculty of Sciences, Quantum Physics Laboratory, University of Monastir, Monastir 5079 (Tunisia); Yaghmour, Saud Jamil [Faculty of Science, King Abdul-Aziz University, Jeddah (Saudi Arabia); Calvo, Florent [University of Grenoble Alpes, LIPHY, F-38000 Grenoble, France and CNRS, LIPHY, F-38000 Grenoble (France); Oujia, Brahim [Faculty of Sciences, Quantum Physics Laboratory, University of Monastir, Monastir 5079 (Tunisia); Faculty of Science, King Abdul-Aziz University, Jeddah (Saudi Arabia)

    2014-11-07

    The solvation of the Na{sup +} ion in helium clusters has been studied theoretically using optimization methods. A many-body empirical potential was developed to account for Na{sup +}–He and polarization interactions, and the most stable structures of Na{sup +}He{sub n} clusters were determined using the basin-hopping method. Vibrational delocalization was accounted for using zero-point energy corrections at the harmonic or anharmonic levels, the latter being evaluated from quantum Monte Carlo simulations for spinless particles. From the static perspective, many-body effects are found to play a minor role, and the structures obtained reflect homogeneous covering up to n = 10, followed by polyicosahedral packing above this size, the cluster obtained at n = 12 appearing particularly stable. The cationic impurity binds the closest helium atoms sufficiently to negate vibrational delocalization at small sizes. However, this snowball effect is obliterated earlier than shell completion, the nuclear wavefunctions of {sup 4}He{sub n}Na{sup +} with n = 5–7, and n > 10 already exhibiting multiple inherent structures. The decrease in the snowball size due to many-body effects is consistent with recent mass spectrometry measurements.

  6. An investigation on thermal and friction effect produced by friction welding of SA 213 tube to SA 387 tube plate

    Directory of Open Access Journals (Sweden)

    S. Pandia Rajan

    2016-03-01

    Full Text Available The present study investigates the effect of thermal and friction produced in the tube to tube plate during the friction welding process by using a Tungsten carbide external tool. In this process, the fictional welding of SA 213 tube and SA 387 tube plate was done by using an external tool. Modeling of tool and wok piece is done by using Solid works and to study the thermal and frictional effect by using Ansys. In this research work, joining of SA 213 tube to SA 387 tube plate was done by using two different techniques such as with hole [WH] and without hole [WOH]. The stress value of with hole and without hole such as 18,782 MPa and 10,486 MPa respectively and the ultimate heat flux generated with hole and without hole such as 0.80475 W/mm2 and 1.1344 W/mm2 respectively were observed.

  7. Heat transfer and flow pattern during two-phase flow boiling of R-134a in horizontal smooth and microfin tubes

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Minghuei; Lin, Tsunkuo; Tseng, Chyuanchyi [National Sun Yat Sen Univ., Taiwan (China). Dept. of Mechanical Engineering

    2002-09-01

    Flow pattern and heat transfer during evaporation in a 10.7 mm diameter smooth tube and a micro-fin tube are presented. The tubes were tested in the ranges of mass flux between 163 and 408 kg m{sup -2}s{sup -1} and heat flux between 2200 and 56 000 W m{sup -2}. The evaporation temperature was 6{sup o}C. Flow maps for both the tubes are plotted in the coordinates of mass flux and vapor quality. The relations of flow pattern and local heat transfer coefficient are discussed. The heat transfer coefficients for intermittent and annular flows in both the smooth tube and the micro-fin tube are shown to agree well with Gungor and Winterton's correlation with modified constants. (author)

  8. Tubing misconnections: normalization of deviance.

    Science.gov (United States)

    Simmons, Debora; Symes, Lene; Guenter, Peggi; Graves, Krisanne

    2011-06-01

    Accidental connection of an enteral system to an intravenous (IV) system frequently results in the death of the patient. Misconnections are commonly attributed to the presence of universal connectors found in the majority of patient care tubing systems. Universal connectors allow for tubing misconnections between physiologically incompatible systems. The purpose of this review of case studies of tubing misconnections and of current expert recommendations for safe tubing connections was to answer the following questions: In tubing connections that have the potential for misconnections between enteral and IV tubing, what are the threats to safety? What are patient outcomes following misconnections between enteral and IV tubing? What are the current recommendations for preventing misconnections between enteral and IV tubing? Following an extensive literature search and guided by 2 models of threats and errors, the authors analyzed case studies and expert opinions to identify technical, organizational, and human errors; patient-related threats; patient outcomes; and recommendations. A total of 116 case studies were found in 34 publications. Each involved misconnections of tubes carrying feedings, intended for enteral routes, to IV lines. Overwhelmingly, the recommendations were for redesign to eliminate universal connectors and prevent misconnections. Other recommendations were made, but the analysis indicates they would not prevent all misconnections. This review of the published case studies and current expert recommendations supports a redesign of connectors to ensure incompatibility between enteral and IV systems. Despite the cumulative evidence, little progress has been made to safeguard patients from tubing misconnections.

  9. Modelling of oxidation and hydriding behaviour of Zircaloy-2 pressure tubes in PHWR

    International Nuclear Information System (INIS)

    Sah, D.N.; Sunil Kumar; Khan, K.B.

    2002-01-01

    A computer model named DOCTOR (Deuteriding of Coolant Tubes during Operation of Reactor) has been developed for predicting the axial profile of oxide thickness and hydrogen (Deuterium) concentration in PHWR pressure tubes. This model is applicable to single channel or full core analysis. The main source of hydrogen is considered to be oxidation of pressure tube on the i.d. surface by high temperature coolant water. Three stages of oxidation is considered namely, pre- transition, post transition and accelerated. Oxidation rate is considered to be dependent on channel power, axial power/flux distribution, coolant temperature and pre-existing oxide thickness at the location. The kinetics parameters for oxidation model are derived from the actual measurement of oxide thickness on a number of pressure tubes examined in PIE Division. The input data required for the model are: channel power, channel power factor, axial flux distribution, coolant inlet temperature, critical oxide thickness, hydrogen pick up fraction, initial hydrogen in the material and time of operation (efpy). The model calculates the oxide layer thickness on the inside surface of the pressure tube along the length. The amount of hydrogen picked up by the pressure tube is calculated from the oxide thickness using hydrogen pick up fraction determined from the PIE data. The pressure tube length is divided into a number of axial segments for calculation. The temperature and fast neutron flux assumed to be constant in a given segment. The axial temperature profile calculated from the axial power profile in the channel is used for calculating the oxidation rate at various locations in the pressure tube. The model has been validated with PIE data of hydrogen equivalent measurement on a number of irradiated Zircaloy-2 pressure tubes of various PHWRs. The performance of the model in predicting the axial profile of hydrogen in the pressure tubes has been found to be good. (author)

  10. TEM examination of irradiated zircaloy-2 pressure tube material

    International Nuclear Information System (INIS)

    Srivastava, D.; Tewari, R.; Dey, G.K.; Sharma, B.P.; Sah, D.N.; Banerjee, Suparna; Sahoo, K.C.

    2005-09-01

    In the present work, microstructure of the zircaloy-2 pressure tube material irradiated in the Indian Pressurized Heavy Water RAPP-1. Reactor (PHWR) has been examined for the first time using transmission electron microscope (TEM). The samples were obtained from a zircaloy-2 pressure tube, which had been in operation in the high flux region of Rajasthan Atomic Power Station Unit -1, for a period for 6.77 effective full power years (EFPYs) and expected to have a cumulative radiation damage of about 3 dpa. In this study irradiated microstructure has been characterized and compared it with the microstructure of the unirradiated pressure tube samples. The effect of irradiation on the hydriding behaviour is also studied. (author)

  11. Flux nucleation in the current-induced resistive state of a constricted type I superconductor

    International Nuclear Information System (INIS)

    Selig, K.P.; Huebener, R.P.

    1981-01-01

    The current-induced resistive state in a constricted type I superconductor is characterized by a train of flux tubes traversing the sample perpendicular to the direction of the applied current following its nucleation at the sample edge. The temporal structure of the nucleation process can be investigated by attempting to synchronize this process with small periodic current pulses superimposed on the direct bias current. The resistive dc voltage is then to be measured as a function of the pulse parameters such as frequency and width. We have performed such experiments at 4.2 K on constricted Pb films of 6--8 μm thickness and 100 μm width. Simultaneously with the electrical measurements the dynamic behavior of the flux tubes was directly observed using a stroboscopic magnetooptical method for magnetic flux detection. Our electrical measurements clearly show how the size of the nucleated flux tubes varies with the direct bias current and the nucleation frequency. The positive wall energy in the Pb films results in a lower limit for this size as expected. The influence of the preceding flux tubes still existing within the constriction upon the flux nucleation process is revealed in detail. All observations can be understood from a consideration of the energy balance during the flux nucleation process

  12. X-ray topography with scintillators coupled to image intensifiers or camera tubes

    International Nuclear Information System (INIS)

    Beauvais, Yves; Mathiot, Alain.

    1978-01-01

    The possibility of imaging topographic figures in real time by using a thin scintillator coupled to either a high-gain image intensifier or a camera tube is investigated. The camera tube must have a high gain because of the low photon fluxes that are encountered in practice, and because of the relatively low quantum yield of thin phosphors. With conventional X-ray generators, the resolution is photon-noise limited. With more powerful generators like synchrotrons, real-time imaging appears possible, and the resolution is limited by the modulation transfer function of the image tube. Higher resolution can be reached by increasing the magnification between the screen and the image tube. When doing so, the input field is reduced and thinner phosphor screens must be used, resulting in a lower yield. Each time the magnification is doubled, the minimum required photon flux is multiplier by about 8, so that the advantages of increasing the magnification are rapidly limited, so far as real-time imaging is concerned. Because image tube resolution is mainly limited by the modulation transfer function of the phosphor for image intensifiers, and by that of the target for camera tubes, improvement of photocathode resolution can be obtained by magnifying electron optics. A zooming electron optic would permit the field and the resolution of the tube to be adapted to the observed subject. Unfortunately such tubes do not exist at present for this type of application, and in the required size

  13. Sealed ion accelerator tubes (survey)

    International Nuclear Information System (INIS)

    Voitsik, L.R.

    1985-01-01

    The first publications on developing commercial models of small-scale sealed accelerator tubes in which neutrons are generated appeared in the foreign press in 1954 to 1957; they were very brief and were advertising-oriented. The tubes were designed for neutron logging of oil wells instead of ampule neutron sources (Po + Be, Ra + Be). Later, instruments of this type began to be called neutron tubes from the resulting neutron radiation that they gave off. In Soviet Union a neutron tube was developed in 1958 in connection with the development of the pulsed neutron-neutron method of studying the geological profile of oil wells. At that time the tube developed was intended, in the view of its inventors, to replace standard isotope sources with constant neutron yield. A fairly detailed survey of neutron tubes was made in the studies. 8 refs., 8 figs

  14. Steam generator tube integrity program

    International Nuclear Information System (INIS)

    Dierks, D.R.; Shack, W.J.; Muscara, J.

    1996-01-01

    A new research program on steam generator tubing degradation is being sponsored by the U.S. Nuclear Regulatory Commission (NRC) at Argonne National Laboratory. This program is intended to support a performance-based steam generator tube integrity rule. Critical areas addressed by the program include evaluation of the processes used for the in-service inspection of steam generator tubes and recommendations for improving the reliability and accuracy of inspections; validation and improvement of correlations for evaluating integrity and leakage of degraded steam generator tubes, and validation and improvement of correlations and models for predicting degradation in steam generator tubes as aging occurs. The studies will focus on mill-annealed Alloy 600 tubing, however, tests will also be performed on replacement materials such as thermally-treated Alloy 600 or 690. An overview of the technical work planned for the program is given

  15. Free compression tube. Applications

    Science.gov (United States)

    Rusu, Ioan

    2012-11-01

    During the flight of vehicles, their propulsion energy must overcome gravity, to ensure the displacement of air masses on vehicle trajectory, to cover both energy losses from the friction between a solid surface and the air and also the kinetic energy of reflected air masses due to the impact with the flying vehicle. The flight optimization by increasing speed and reducing fuel consumption has directed research in the aerodynamics field. The flying vehicles shapes obtained through studies in the wind tunnel provide the optimization of the impact with the air masses and the airflow along the vehicle. By energy balance studies for vehicles in flight, the author Ioan Rusu directed his research in reducing the energy lost at vehicle impact with air masses. In this respect as compared to classical solutions for building flight vehicles aerodynamic surfaces which reduce the impact and friction with air masses, Ioan Rusu has invented a device which he named free compression tube for rockets, registered with the State Office for Inventions and Trademarks of Romania, OSIM, deposit f 2011 0352. Mounted in front of flight vehicles it eliminates significantly the impact and friction of air masses with the vehicle solid. The air masses come into contact with the air inside the free compression tube and the air-solid friction is eliminated and replaced by air to air friction.

  16. Tube leak detector

    International Nuclear Information System (INIS)

    Morita, Bunji; Takamura, Koichi; Matsuda, Shigehiro; Kiyosawa, Shun-ichi; Asami, Toru; Yamada, Hiroshi; Naruse, Shin-ichi.

    1995-01-01

    The device of the present invention detects occurrence of leakage in a steam generator, a steam heating tube, or a heat exchanger of a nuclear power plant. Namely, an vibration sensor is disposed at the rear end of a rod-like supersonic resonance member. A node portion for the vibrations of the resonance member is held by a holding member and attached to a wall surface of a can such as a boiler. With such a constitution, the resonance member is resonated by supersonic waves generated upon leakage of the tube. The vibrations are measured by the vibration sensor at the rear end. Presence of leakage is detected by utilizing one or more of resonance frequencies. Since the device adopts a resonance phenomenon, a conduction efficiency of the vibrations is high, thereby enabling to detect leakage at high sensitivity. In addition, the supersonic wave resonance member has its top end directly protruded into a pressure vessel such as a boiler by using a metal or a ceramic which is excellent in heat and pressure resistance. Accordingly, the sound of leak can be detected efficiently. (I.S.)

  17. Shock tube Multiphase Experiments

    Science.gov (United States)

    Middlebrooks, John; Allen, Roy; Paudel, Manoj; Young, Calvin; Musick, Ben; McFarland, Jacob

    2017-11-01

    Shock driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching practical applications in engineering and science. The instability is present in high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase interface is impulsively accelerated by the passage of a shockwave. It is similar in development to the Richtmyer-Meshkov (RM) instability however, particle-to-gas coupling is the driving mechanism of the SDMI. As particle effects such as lag and phase change become more prominent, the SDMI's development begins to significantly deviate from the RM instability. We have developed an experiment for studying the SDMI in our shock tube facility. In our experiments, a multiphase interface is created using a laminar jet and flowed into the shock tube where it is accelerated by the passage of a planar shockwave. The interface development is captured using CCD cameras synchronized with planar laser illumination. This talk will give an overview of new experiments conducted to examine the development of a shocked cylindrical multiphase interface. The effects of Atwood number, particle size, and a second acceleration (reshock) of the interface will be discussed.

  18. Pressure tube reactors

    International Nuclear Information System (INIS)

    Natori, Hisahide.

    1981-01-01

    Purpose: To improve the electrical power generation efficiency in a pressure tube reactor in which coolants and moderators are separated by feedwater heating with heat generated in heavy water and by decreasing the amount of steams to be extracted from the turbine. Constitution: A heat exchanger and a heavy water cooler are additionally provided to a conventional pressure tube reactor. The heat exchanger is disposed at the pre-stage of a low pressure feedwater heater series. High temperature heavy water heated in the core is passed through the primary side of the exchanger, while feedwater is passed through the secondary side. The cooler is disposed on the downstream of the heat exchanger in the flowing direction of the heavy water, in which heavy water from the heat exchanger is passed through the primary side and the auxiliary equipment cooling water is sent to the secondary side thereof. Accordingly, since extraction of heating steams is no more necessary, the steam can be used for the rotation of the turbine, and the electrical power generation efficiency can be improved. (Seki, T.)

  19. Analysis of coolant flow in central tube of WWER-440 fuel assemblies

    International Nuclear Information System (INIS)

    Zsiros, G.; Toth, S.; Attila Aszodi, A.

    2011-01-01

    Three dimensional computational fluid dynamics model has been built to investigate the coolant flow in the central tube of the WWER-440 fuel assemblies. The model was verified based on measured data of the Kurchatov Institute. With the model calculations were performed for two fuel assemblies used in PAKS NPP. One of them has symmetrical and another has inclined pin power profile. Ratios of the outlet mass fluxes of the central tube to the inlet mass fluxes of the rod bundle were determined. Heat up ratios of the tube and rod bundle flows were calculated too. Sensitivity of the results on the assembly power distribution, inlet temperature and mass flow rate was investigated. The results of these simulations can be used as boundary conditions of central tube in studies of coolant mixing in fuel assembly heads. (Authors)

  20. Measurements of electrically exploded tubes

    International Nuclear Information System (INIS)

    Shearer, J.W.; Hartman, C.W.; Munger, R.H.; Gullickson, R.L.; Trimble, D.O.; Cheng, D.Y.

    1975-01-01

    The dynamics of electrically exploded tubes were investigated, principally by means of current measurements and flash x-ray pictures. The pinch effect was observed on the tube motion. Pileup of the imploding tube metal was seen on axis. An approximate analytical model can be roughly fitted to the data, but a more complete fit can be obtained with detailed numerical codes. Application of the results to the planning of future gas-embedded Z-pinch experiments is discussed. (U.S.)

  1. Failure analysis of boiler tube

    International Nuclear Information System (INIS)

    Mehmood, K.; Siddiqui, A.R.

    2007-01-01

    Boiler tubes are energy conversion components where heat energy is used to convert water into high pressure superheated steam, which is then delivered to a turbine for electric power generation in thermal power plants or to run plant and machineries in a process or manufacturing industry. It was reported that one of the tubes of a fire-tube boiler used in a local industry had leakage after the formation of pits at the external surface of the tube. The inner side of the fire tube was working with hot flue gasses with a pressure of 10 Kg/cm/sup 2/ and temperature 225 degree C. The outside of the tube was surrounded by feed water. The purpose of this study was to determine the cause of pits developed at the external surface of the failed boiler tube sample. In the present work boiler tube samples of steel grade ASTM AI61/ASTM A192 were analyzed using metallographic analysis, chemical analysis, and mechanical testing. It was concluded that the appearance of defects on the boiler tube sample indicates cavitation type corrosion failure. Cavitation damage superficially resembled pitting, but surface appeared considerably rougher and had many closely spaced pits. (author)

  2. Radiation-resistant camera tube

    International Nuclear Information System (INIS)

    Kuwahata, Takao; Manabe, Sohei; Makishima, Yasuhiro

    1982-01-01

    It was a long time ago that Toshiba launched on manufacturing black-and-white radiation-resistant camera tubes employing nonbrowning face-plate glass for ITV cameras used in nuclear power plants. Now in compliance with the increasing demand in nuclear power field, the Company is at grips with the development of radiation-resistant single color-camera tubes incorporating a color-stripe filter for color ITV cameras used under radiation environment. Herein represented are the results of experiments on characteristics of materials for single color-camera tubes and prospects for commercialization of the tubes. (author)

  3. YouTube and 'psychiatry'.

    Science.gov (United States)

    Gordon, Robert; Miller, John; Collins, Noel

    2015-12-01

    YouTube is a video-sharing website that is increasingly used to share and disseminate health-related information, particularly among younger people. There are reports that social media sites, such as YouTube, are being used to communicate an anti-psychiatry message but this has never been confirmed in any published analysis of YouTube clip content. This descriptive study revealed that the representation of 'psychiatry' during summer 2012 was predominantly negative. A subsequent smaller re-analysis suggests that the negative portrayal of 'psychiatry' on YouTube is a stable phenomenon. The significance of this and how it could be addressed are discussed.

  4. Bacterial Biofilms in Jones Tubes.

    Science.gov (United States)

    Ahn, Eric S; Hauck, Matthew J; Kirk Harris, Jonathan; Robertson, Charles E; Dailey, Roger A

    To investigate the presence and microbiology of bacterial biofilms on Jones tubes (JTs) by direct visualization with scanning electron microscopy and polymerase chain reaction (PCR) of representative JTs, and to correlate these findings with inflammation and/or infection related to the JT. In this study, prospective case series were performed. JTs were recovered from consecutive patients presenting to clinic for routine cleaning or recurrent irritation/infection. Four tubes were processed for scanning electron microscopy alone to visualize evidence of biofilms. Two tubes underwent PCR alone for bacterial quantification. One tube was divided in half and sent for scanning electron microscopy and PCR. Symptoms related to the JTs were recorded at the time of recovery. Seven tubes were obtained. Five underwent SEM, and 3 out of 5 showed evidence of biofilms (60%). Two of the 3 biofilms demonstrated cocci and the third revealed rods. Three tubes underwent PCR. The predominant bacteria identified were Pseudomonadales (39%), Pseudomonas (16%), and Staphylococcus (14%). Three of the 7 patients (43%) reported irritation and discharge at presentation. Two symptomatic patients, whose tubes were imaged only, revealed biofilms. The third symptomatic patient's tube underwent PCR only, showing predominantly Staphylococcus (56%) and Haemophilus (36%) species. Two of the 4 asymptomatic patients also showed biofilms. All symptomatic patients improved rapidly after tube exchange and steroid antibiotic drops. Bacterial biofilms were variably present on JTs, and did not always correlate with patients' symptoms. Nevertheless, routine JT cleaning is recommended to treat and possibly prevent inflammation caused by biofilms.

  5. Grooved tube plug rolls in

    International Nuclear Information System (INIS)

    Krausser, P.

    1991-01-01

    The removable plugs used to date by the Power Generation Group (KWU) of Siemens to seal defective steam generator tubes have a good track record. Their sealing principle is based on the elastic tensioning of three seal disks against the inside wall of the tube. Now a further removable plug is available -a roll-in plug with a metal-coated surface. It is particularly suitable for use in the roller-expanded zone of the tubes at the tube sheet. The plugs can be used in both Siemens-KWU steam generators and in steam generators manufactured in compliance with the guidelines of the ASME Code. (author)

  6. Learning from YouTube [Video Book

    Science.gov (United States)

    Juhasz, Alexandra

    2011-01-01

    YouTube is a mess. YouTube is for amateurs. YouTube dissolves the real. YouTube is host to inconceivable combos. YouTube is best for corporate-made community. YouTube is badly baked. These are a few of the things Media Studies professor Alexandra Juhasz (and her class) learned about YouTube when she set out to investigate what actually happens…

  7. Continuous magnetic flux pump

    Science.gov (United States)

    Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

    1966-01-01

    A method and means for altering the intensity of a magnetic field by transposing flux from one location to the location desired fro the magnetic field are examined. The device described includes a pair of communicating cavities formed in a block of superconducting material, is dimensioned to be insertable into one of the cavities and to substantially fill the cavity. Magnetic flux is first trapped in the cavities by establishing a magnetic field while the superconducting material is above the critical temperature at which it goes superconducting. Thereafter, the temperature of the material is reduced below the critical value, and then the exciting magnetic field may be removed. By varying the ratios of the areas of the two cavities, it is possible to produce a field having much greater flux density in the second, smaller cavity, into which the flux transposed.

  8. Flux in Tallinn

    Index Scriptorium Estoniae

    2004-01-01

    Rahvusvahelise elektroonilise kunsti sümpoosioni ISEA2004 klubiõhtu "Flux in Tallinn" klubis Bon Bon. Eestit esindasid Ropotator, Ars Intel Inc., Urmas Puhkan, Joel Tammik, Taavi Tulev (pseud. Wochtzchee). Klubiõhtu koordinaator Andres Lõo

  9. Flux shunts for undulators

    International Nuclear Information System (INIS)

    Hoyer, E.; Chin, J.; Hassenzahl, W.V.

    1993-05-01

    Undulators for high-performance applications in synchrotron-radiation sources and periodic magnetic structures for free-electron lasers have stringent requirements on the curvature of the electron's average trajectory. Undulators using the permanent magnet hybrid configuration often have fields in their central region that produce a curved trajectory caused by local, ambient magnetic fields such as those of the earth. The 4.6 m long Advanced Light Source (ALS) undulators use flux shunts to reduce this effect. These flux shunts are magnetic linkages of very high permeability material connecting the two steel beams that support the magnetic structures. The shunts reduce the scalar potential difference between the supporting beams and carry substantial flux that would normally appear in the undulator gap. Magnetic design, mechanical configuration of the flux shunts and magnetic measurements of their effect on the ALS undulators are described

  10. Critical heat flux on micro-structured zircaloy surfaces for flow boiling of water at low pressures

    International Nuclear Information System (INIS)

    Haas, C.; Miassoedov, A.; Schulenberg, T.; Wetzel, T.

    2012-01-01

    The influence of surface structure on critical heat flux for flow boiling of water was investigated for Zircaloy tubes in a vertical annular test section. The objectives were to find suitable surface modification processes for Zircaloy tubes and to test their critical heat flux performance in comparison to the smooth tube. Surface structures with micro-channels, porous layer, oxidized layer, and elevations in micro- and nano-scale were produced on a section of a Zircaloy cladding tube. These modified tubes were tested in an internally heated vertical annulus with a heated length of 326 mm and an inner and outer diameter of 9.5 and 18 mm. The experiments were performed with mass fluxes of 250 and 400 kg/(m 2 s), outlet pressures between 120 and 300 kPa, and constant inlet subcooling enthalpy of 167 kJ/kg. Only a small influence of modified surface structures on critical heat flux was observed for the pressure of 120 kPa in the present test section geometry. However, with increasing pressure the critical heat flux could increase up to 29% using the surface structured tubes with micro-channels, porous and oxidized layers. Capillary effects and increased nucleation site density are assumed to improve the critical heat flux performance. (authors)

  11. Neutron flux monitor

    International Nuclear Information System (INIS)

    Oda, Naotaka.

    1993-01-01

    The device of the present invention greatly saves an analog processing section such as an analog filter and an analog processing circuit. That is, the device of the present invention comprises (1) a neutron flux detection means for detecting neutron fluxed in the reactor, (2) a digital filter means for dividing signals corresponding to the detected neutron fluxes into predetermined frequency band regions, (3) a calculation processing means for applying a calculation processing corresponding to the frequency band regions to the neutron flux detection signals divided by the digital filter means. With such a constitution, since the neutron detection signals are processed by the digital filter means, the accuracy is improved and the change for the property of the filter is facilitated. Further, when a neutron flux level is obtained, a calculation processing corresponding to the frequency band region can be conducted without the analog processing circuit. Accordingly, maintenance and accuracy are improved by greatly decreasing the number of parts. Further, since problems inherent to the analog circuit are solved, neutron fluxes are monitored at high reliability. (I.S.)

  12. Neutron flux monitoring device

    International Nuclear Information System (INIS)

    Shimazu, Yoichiro.

    1995-01-01

    In a neutron flux monitoring device, there are disposed a neutron flux measuring means for outputting signals in accordance with the intensity of neutron fluxes, a calculation means for calculating a self power density spectrum at a frequency band suitable to an object to be measured based on the output of the neutron flux measuring means, an alarm set value generation means for outputting an alarm set value as a comparative reference, and an alarm judging means for comparing the alarm set value with the outputted value of the calculation means to judge requirement of generating an alarm and generate an alarm in accordance with the result of the judgement. Namely, the time-series of neutron flux signals is put to fourier transformation for a predetermined period of time by the calculation means, and from each of square sums for real number component and imaginary number component for each of the frequencies, a self power density spectrum in the frequency band suitable to the object to be measured is calculated. Then, when the set reference value is exceeded, an alarm is generated. This can reliably prevent generation of erroneous alarm due to neutron flux noises and can accurately generate an alarm at an appropriate time. (N.H.)

  13. Techniques for measurement of heat flux in furnace waterwalls of boilers and prediction of heat flux – A review

    International Nuclear Information System (INIS)

    Sankar, G.; Chandrasekhara Rao, A.; Seshadri, P.S.; Balasubramanian, K.R.

    2016-01-01

    Highlights: • Heat flux measurement techniques applicable to boiler water wall are elaborated. • Applications involving heat flux measurement in boiler water wall are discussed. • Appropriate technique for usage in high ash Indian coal fired boilers is required. • Usage of chordal thermocouple is suggested for large scale heat flux measurements. - Abstract: Computation of metal temperatures in a furnace waterwall of a boiler is necessary for the proper selection of tube material and thickness. An adequate knowledge of the heat flux distribution in the furnace walls is a prerequisite for the computation of metal temperatures. Hence, the measurement of heat flux in a boiler waterwall is necessary to arrive at an optimum furnace design, especially for high ash Indian coal fired boilers. Also, a thoroughly validated furnace model will result in a considerable reduction of the quantum of experimentation to be carried out. In view of the above mentioned scenario, this paper reviews the research work carried out by various researchers by experimentation and numerical simulation in the below mentioned areas: (i) furnace modeling and heat flux prediction, (ii) heat flux measurement techniques and (iii) applications of heat flux measurements.

  14. Tube to tube excursive instability - sensitivities and transients

    International Nuclear Information System (INIS)

    Brown, M.; Layland, M.W.

    1980-01-01

    A simple basic analysis of excursive instability in a boiler tube shows how it depends upon operating conditions and physical properties. A detailed mathematical model of an AGR boiler is used to conduct a steady state parameter sensitivity survey. It is possible from this basis to anticipate the effects of changes in operating conditions and changes in design parameters upon tube to tube stability. Dynamic responses of tubes operating near the stability threshold are examined using a mathematical model. Simulated excursions are triggered by imparting small abrupt pressure changes on the boiler inlet pressure. The influences of the magnitude of the pressure change, waterside friction factor and gas side coupling between tubes are examined. (author)

  15. Jose Cabrera (Zorita) tube examination

    International Nuclear Information System (INIS)

    Kuchirka, P.J.

    1986-01-01

    Jose Cabrera (Zorita) tube examination procedures are discussed. This plant continues to use phosphate water chemistry (sodium/phosphate ratio = 2.1). Three hot leg tube segments were pulled from the Jose Cabera (Zorita) plant in 1985. One tube had a field EC indication on the OD at the first tube support plate and the other two had field EC indications on their ID about 3 inches above the bottom of the tube sheet. All three tubes were initially sent to Battelle for preliminary NDE and decontamination. Segments of two tubes were sent to Westinghouse for destructive examination. The results of the laboratory eddy current and radiographic examinations are given. The results of the visual examinations are also given. The tube with OD indications was destructively examined and shallow intergranular pitting and intergranular attack, up to 2 mils deep, were found on the OD in the tube sheet region. Local areas of IGA, up to 5 mils deep, were found on the OD within the tube support plate region. A summary of this information together with supporting micrographs is given. It was hypothesized that a caustic crevice environment was the cause of this mild degradation. Shallow areas of thinning or wastage, up to 3 mils, were found just above the top of the tube sheet in the sludge pile region. Even more shallow wastage was found at the edges of support plate locations. This wastage is believed to be the remnant of early plant chemistry when a higher sodium/phosphate ratio and higher phosphate concentration were allowed

  16. Tube for irradiation equipment

    International Nuclear Information System (INIS)

    Goehrich, K.; Vogt, H.

    1979-01-01

    This patent describes a tube for irradiation equipment for limiting an emergent beam, with a baseplate, possessing a central aperture, intended for attaching to the equipment, as well as four carrier plates, each of which possesses a limiting edge and a sliding edge located at right angles thereto. The carrier plates are located parallel to the baseplate, the limiting edge of each carrier plate resting against the sliding edge of the adjacent carrier plate and each of the two mutually opposite pairs of carrier plates being displaceable, parallel to the direction of its sliding edges and symmetrically to the center of the transmission aperture, for the purpose of continuously varying the transmission aperture defined by the limiting edges, during which displacement each of the displaced carrier plates carries with it the carrier plate, resting against the limiting edge of the former plate, parallel to the direction of the limiting edge of the latter plate. 8 claims

  17. Primary Fallopian Tube Carcinoma

    Directory of Open Access Journals (Sweden)

    Prasad K Shetty

    2011-01-01

    Full Text Available Primary Fallopian Tube Carcinoma (PFTC is rare and accounts for about 0.3% of all gynecologic cancers. Less than 1500 cases have been reported in the literature. It arises in postmenopausal women and typically presents with abdominal pelvic pain, vaginal bleeding and watery discharge. However, a correct diagnosis is rarely achieved preoperative, and in many cases, the diagnosis is made after incidental surgery for unrelated conditions commonly being ovarian carcinoma . Compared with ovarian carcinoma, PFTC more often presents at early stages, but it has a worse prognosis. PFTC is usually managed in the same manner as ovarian cancer. We report a case of Left PFTC that presented as Left ovarian mass, and we briefly review the literature.

  18. Pressure tube reactor

    International Nuclear Information System (INIS)

    Matsumoto, Tomoyuki; Fujino, Michihira.

    1980-01-01

    Purpose: To equalize heavy water flow distribution by providing a nozzle for externally injecting heavy water from a vibration preventive plate to the upper portion to feed the heavy water in a pressure tube reactor and swallowing up heavy water in a calandria tank to supply the heavy water to the reactor core above the vibration preventive plate. Constitution: A moderator injection nozzle is mounted on the inner wall of a calandria tank. Heavy water is externally injected above the vibration preventive plate, and heavy water in the calandria tank is swallowed up to supply the heavy water to the core reactor above the vibration preventive plate. Therefore, the heavy water flow distribution can be equalized over the entire reactor core, and the distribution of neutron absorber dissolved in the heavy water is equalized. (Yoshihara, H.)

  19. A New Resonance Tube

    Science.gov (United States)

    Bates, Alan

    2017-12-01

    The measurement of the speed of sound in air with the resonance tube is a popular experiment that often yields accurate results. One approach is to hold a vibrating tuning fork over an air column that is partially immersed in water. The column is raised and lowered in the water until the generated standing wave produces resonance: this occurs at the point where sound is perceived to have maximum loudness, or at the point where the amplitude of the standing wave has maximum value, namely an antinode. An antinode coincides with the position of the tuning fork, beyond the end of the air column, which consequently introduces an end correction. One way to minimize this end correction is to measure the distance between consecutive antinodes.

  20. Research for rolling effects on flow pattern of gas-water flow in horizontal tubes

    International Nuclear Information System (INIS)

    Luan Feng; Yan Changqi

    2007-01-01

    The flow pattern transition of two-phase flow is caused by the inertial force resulted from rolling and incline of horizontal tubes under rolling state. an experimental study on the flow patterns of gas-water flow was carried out in horizontal tubes under rolling state, which rolling period is 15 second and rolling angle is 10 degrees, and a pattern flow picture is shown. It was found that there are two flow patterns in one rolling period under some gas flux and water flux. (authors)

  1. A model of the fluid temperature field in a turbulent flow parallel to heated tube bundle

    International Nuclear Information System (INIS)

    Carvalho Tofani, P. de.

    1986-01-01

    Basic understanding of thermal-hydraulic phenomena is essential to achieving reactor fuel assembly performance analysis. In this paper, a dimensionless parameter - a normalized fluid temperature - is defined and applied to fluid temperature measurements at particular positions at the exit plane of a bank of nine heated tubes, under different transverse heat flux shapes. This parameter presents an asymptotic trend to equilibrium values, which depend upon considered positions and flux shapes; when increasing the bulk Reynolds Number. Proposed correlations underlie the present approach to predict the fluid temperature field within the tube bundle. (Author) [pt

  2. Vaporization inside a mini microfin tube: experimental results and modeling

    Science.gov (United States)

    Diani, A.; Rossetto, L.

    2015-11-01

    This paper proposes a comparison among the common R134a and the extremely low GWP refrigerant R1234yf during vaporization inside a mini microfin tube. This microfin tube has an internal diameter of 2.4 mm, it has 40 fins, with a fin height of 0.12 mm. Due to the high heat transfer coefficients shown by this tube, this technology can lead to a refrigerant charge reduction. Tests were run in the Heat Transfer in Micro Geometries Lab of the Dipartimento di Ingegneria Industriale of the Università di Padova. Mass velocities range between 375 and 940 kg m-2 s-1, heat fluxes from 10 to 50 kW m-2, vapour qualities from 0.10 to 0.99, at a saturation temperature of 30°C. The comparison among the two fluids is proposed at the same operating conditions, in order to highlight the heat transfer and pressure drop differences among the two refrigerants. In addition, two correlations are proposed to estimate the heat transfer coefficient and frictional pressure drop during refrigerant flow boiling inside mini microfin tubes. These correlations well predict the experimental values, and thus they can be used as a useful tool to design evaporators based on these mini microfin tubes.

  3. Numerical simulation of triple concentric-tube heat exchangers

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Valladares, O. [Centro de Investigacion en Energia (CIE), Universidad Nacional Autonoma de Mexico (UNAM), Privada Xochicalco S/N, Temixco, 62580, Morelos (Mexico)

    2004-10-01

    A detailed one-dimensional steady and transient numerical simulation of the thermal and fluid-dynamic behaviour of triple concentric-tube heat exchangers has been developed. The governing equations (continuity, momentum and energy) inside the inner tube and the annulus (inner and outer), together with the energy equations in the inner, intermediate and outermost tube wall and insulation, are solved iteratively in a segregated manner. The discretized governing equations in the zones with fluid flow are coupled using an implicit step by step method. This formulation requires the use of empirical information for the evaluation of convective heat transfer, shear stress and void fraction. An implicit central difference numerical scheme and a line-by-line solver was used in the inner and intermediate tube walls and the outermost tube wall with insulation. All the flow variables (enthalpies, temperatures, pressures, mass fractions, velocities, heat fluxes, etc.) together with the thermophysical properties are evaluated at each point of the grid in which the domain is discretized. Different numerical aspects and comparisons with results obtained from the technical literature are presented in order to verify and validate the model. (authors)

  4. Condensation Analysis of Steam/Air Mixtures in Horizontal Tubes

    International Nuclear Information System (INIS)

    Lee, Kwon Yeong; Bae, Sung Won; Kim, Moo Hwan

    2008-01-01

    Perhaps the most common flow configuration in which a convective condensation occurs is a flow in a horizontal circular tube. This configuration is encountered in air-conditioning and refrigeration condensers as well as condensers in Rankine power cycles. Although a convective condensation is also sometimes contrived to occur in a co-current vertical downward flow, a horizontal flow is often preferred because the flow can be repeatedly passed through the heat exchanger core in a serpentine fashion without trapping liquid or vapor in the return bends. Many researchers have investigated a in-tube condensation for horizontal heat exchangers. However, almost all of them obtained tube section-averaged data without a noncondensable gas. Recently, Wu and Vierow have experimentally studied the condensation of steam in a horizontal heat exchanger with air present. In order to measure the condenser tube inner surface temperatures and to calculate the local heat fluxes, they developed an innovative thermocouple design that allowed for nonintrusive measurements. Here we developed a theoretical model using the heat and mass analogy to analyze a steam condensation with a noncondensable gas in horizontal tubes

  5. Laced permanent magnet quadrupole drift tube magnets

    International Nuclear Information System (INIS)

    Feinberg, B.; Behrsing, G.U.; Halbach, K.; Marks, J.S.; Morrison, M.E.; Nelson, D.H.

    1988-10-01

    A laced permanent magnet quadrupole drift tube magnet has been constructed for a proof-of-principle test. The magnet is a conventional tape-wound quadrupole electromagnet, using iron pole- pieces, with the addition of permanent magnet material (neodymium iron) between the poles to reduce the effects of saturation. The iron is preloaded with magnetic flux generated by the permanent magnet material, resulting in an asymmetrical saturation curve. Since the polarity of the quadrupole magnets in a drift tube linac is not reversed we can take advantage of this asymmetrical saturation to provide greater focusing strength. The magnet configuration has been optimized and the vanadium permendur poles needed in a conventional quadrupole have been replaced with iron poles. The use of permanent magnet material has allowed us to increase the focusing strength of the magnet by about 20% over that of a conventional tape-wound quadrupole. Comparisons will be made between this magnet and the conventional tape-wound quadrupole. 3 refs., 5 figs

  6. Neutron accelerator tube having improved ionization section

    International Nuclear Information System (INIS)

    Givens, W.W.

    1982-01-01

    A neutron accelerator tube is described having a target section, an ionization section, and a replenisher section for supplying accelerator gas to the ionization section. The ionization section is located between the target and the replenisher section and includes an ionization chamber adapted to receive accelerator gas from the replenisher section. The ionization section further includes spaced cathodes having opposed active surfaces exposed to the interior of the ionization chamber. An anode is located intermediate the cathodes whereby in response to an applied positive voltage, electrons created by field emission are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons. The active surface of at least one of the cathodes is formulated of a material having a secondary electron emission factor of at least one cathode member located in the tube adjacent to th replenisher section may have a protuberant portion extending axially into the ionization chamber. The other cathode spaced from the first cathode member in the direction of the target has an aperture therein along the axis of the protuberant portion. An annular magnet extends around the exterior of the ionization chamber and envelops the anode member. Means are provided to establish a high permeability magnetic flux path extending outwardly from the opposed poles from the magnet to the active surfaces of the cathode members

  7. Neutron accelerator tube having improved ionization section

    International Nuclear Information System (INIS)

    Givens, W.W.

    1981-01-01

    A neutron accelerator tube having a target section, an ionization section, and a replenisher section for supplying accelerator gas to the ionization section. The ionization section is located between the target and the replenisher section and includes an ionization chamber adapted to receive accelerator gas from the replenisher section. The ionization section further includes spaced cathodes having opposed active surfaces exposed to the interior of the ionization chamber. An anode is located intermediate the cathodes whereby in response to an applied positive voltage, electrons created by field emmission are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons. The active surface of at least one of the cathodes is formulated of a material having a secondary electron emission factor of at least 2. One cathode member located in the tube adjacent to the replenisher section may have a protuberant portion extending axially into the ioization chamber. The other cathode spaced from the first cathode member in the direction of the target has an aperture therein along the axis of the protuberant portion. An annular magnet extends around the exterior of the ionization chamber and envelops the anode member. Means are provided to establish a high permeability magnetic flux path extending outwardly from the opposed poles from the magnet to the active surfaces of the cathode members

  8. The effect of diameter on vertical and horizontal flow boiling crisis in a tube cooled by Freon-12

    International Nuclear Information System (INIS)

    Merilo, M.; Ahmad, S.Y.

    1979-03-01

    The influence of test section orientation and diameter on flow boiling crisis occurring in tubes has been studied experimentally using Freon-12 as a coolant. At low mass flux the critical heat flux (CHF) was lower in horizontal flow than in vertical. As either the liquid or vapour velocity, or both, were increased the vertical and horizontal CHF results converged. Above a mass flux of 4 Mg.m -2 .s -1 the results were essentially identical. The effect of tube diameter on boiling crisis in general depends crucially on the parameters which are maintained constant when the comparison is made. (author)

  9. Evaporation heat transfer characteristics inside the U-bend of the smooth and the microfin tube using alternative refrigerant

    Energy Technology Data Exchange (ETDEWEB)

    Cho, K N [Sung Kyun Kwan University, Seoul (Korea, Republic of); Kim, B G [Sung Kyun Kwan University Graduate School, Seoul (Korea, Republic of)

    1997-09-01

    The present work experimentally investigated the effects of mass flux, heat flux, inlet quality on the heat transfer performance inside the U-bend of smooth and microfin tube using R-22 and R-407C refrigerants. The parameters were 200 and 400 kg/m{sup 2} s for mass flux, 6 and 12 kw/m{sup 2} for heat flux, 0.1 and 0.2 for inlet quality under the pressure of 0.65 MPa. The apparatus consisted of the test section of four straight sections and three U-bends, preheater, condenser, refrigerant pump, mass flow meter etc. The average heat transfer coefficient at the downstream straight section after U-bend was affected by U-bend due to the centrifugal force and mixing of two-phase flow in the U-bend. The average heat transfer coefficient at the U-bend was 4{approx}33 % higher than that at the straight section. The average heat transfer coefficients were affected in the order of mass flux, heat flux and inlet quality. The average heat transfer coefficients in the microfin tube were lager by 19{approx}49 % and 33{approx}69 % than that in the smooth tube at the straight section and at the U-bend separately. The average heat transfer coefficients for R-407C were larger by 33{approx}41 % and 17{approx}29% than that for R-22 in the smooth tube and the microfin tube separately. (author). 24 refs., 9 figs.

  10. Flow boiling heat transfer of carbon dioxide inside a small-sized microfin tube

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Chaobin; Haraguchi, Nobori; Hihara, Eiji [Department of Human and Engineered Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa-shi, Chiba 277-8563 (Japan)

    2010-06-15

    This study investigated the flow boiling heat transfer of carbon dioxide inside a small-sized microfin tube (mean inner diameter: 2.0 mm; helix angle: 6.3 ) at a saturation temperature of 15 C, and heat and mass flux ranges of 4.5-18 kW m{sup -2} and 360-720 kg m{sup -2} s{sup -1}, respectively. Although, experimental results indicated that heat flux has a significant effect on the heat transfer coefficient, the coefficient does not always increase with mass flux, as in the case of conventional refrigerants such as HFCs or HCFCs. Under certain conditions, the heat transfer coefficient at a high mass flux was lower than that at a lower mass flux, indicating that convective heat transfer had a suppression effect on nucleate boiling. The heat transfer coefficients in the microfin tubes were 1.9{proportional_to}2.3 times the values in smooth tubes of the same diameter under the same experimental conditions, and the dryout quality was much higher, ranging from 0.9 to 0.95. The experimental results indicated that using microfin tubes may considerably increase the overall heat transfer performance. (author)

  11. Molecular Level Design Principle behind Optimal Sizes of Photosynthetic LH2 Complex: Taming Disorder through Cooperation of Hydrogen Bonding and Quantum Delocalization.

    Science.gov (United States)

    Jang, Seogjoo; Rivera, Eva; Montemayor, Daniel

    2015-03-19

    The light harvesting 2 (LH2) antenna complex from purple photosynthetic bacteria is an efficient natural excitation energy carrier with well-known symmetric structure, but the molecular level design principle governing its structure-function relationship is unknown. Our all-atomistic simulations of nonnatural analogues of LH2 as well as those of a natural LH2 suggest that nonnatural sizes of LH2-like complexes could be built. However, stable and consistent hydrogen bonding (HB) between bacteriochlorophyll and the protein is shown to be possible only near naturally occurring sizes, leading to significantly smaller disorder than for nonnatural ones. Extensive quantum calculations of intercomplex exciton transfer dynamics, sampled for a large set of disorder, reveal that taming the negative effect of disorder through a reliable HB as well as quantum delocalization of the exciton is a critical mechanism that makes LH2 highly functional, which also explains why the natural sizes of LH2 are indeed optimal.

  12. Temperature-induced delocalization of charge carriers and semiconductor to metal-like phase in SrFeO{sub 3-δ}

    Energy Technology Data Exchange (ETDEWEB)

    Manimuthu, P.; Venkateswaran, C. [University of Madras, Department of Nuclear Physics, Guindy Campus, Chennai (India); Murugaraj, R. [Anna University, Department of Physics, MIT Campus, Chennai (India)

    2015-04-01

    Perovskite SrFeO{sub 3-δ}, a Ruddlesden-Popper class of system exhibits interesting electronic and magnetic properties. Influence of oxygen vacancies on the electrical response of nanocrystalline SrFeO{sub 2.91} as a function of temperature is investigated using impedance spectroscopy technique. A change observed in the Nyquist plot at 383 K has been analyzed in terms of localized and delocalized e{sub g} electrons. An unusual and interesting temperature-induced semiconductor to metal-like transition is observed in the frequency-dependent real part of dielectric permittivity. Dependence of frequency on the real and imaginary parts of impedance with respect to temperature supports the presence of semiconductor to metal-like transition in SrFeO{sub 2.91}. (orig.)

  13. Improper tube fixation causing a leaky cuff

    Directory of Open Access Journals (Sweden)

    Gupta Babita

    2010-01-01

    Full Text Available Leaking endotracheal tube cuffs are common problems in intensive care units. We report a case wherein the inflation tube was damaged by the adhesive plaster used for tube fixation and resulted in leaking endotracheal tube cuff. We also give some suggestions regarding the tube fixation and some remedial measures for damaged inflation system.

  14. Characterization of tube support alloys

    International Nuclear Information System (INIS)

    Vaia, A.R.

    1985-01-01

    The involvement and relationship of carbon steel corrosion products in the tube denting phenomenon promoted an intensive research effort to: 1) understand, reproduce, and arrest the denting process, and 2) evaluate alternative tube support materials to provide additional corrosion resistance. The paper summarizes a corrosion testing program for the verification of type 405 stainless steel under acid or all volatile treatment conditions

  15. Radioisotope study of Eustachian tube

    International Nuclear Information System (INIS)

    De Rossi, G.; Campioni, P.; Vaccaro, A.

    1988-01-01

    Radioisotope studies of Eustachian tube are suggested in the preoperative phase of tympanoplasty, in order to assess tubal drainage and secretion. The use of gamma camera fitted to a computer allowed the AA, to calculate some semi-quantitative parameters for an exact assessment of the radioactivity transit from the tympanic cass up to the pharyngeal cavity, throughout the Eustachian tube. (orig.) [de

  16. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... Amblyopia Listen NEI YouTube Videos YouTube Videos Home Age-Related Macular Degeneration Amblyopia Animations Blindness Cataract Convergence ... is maintained by the NEI Office of Science Communications, Public Liaison, and Education. Technical questions about this ...

  17. Tubing Cutter is Activated Hydraulically

    Science.gov (United States)

    Mcsmith, D. G.; Richardson, J. I.

    1983-01-01

    Hydraulically-actuated tubing cutter severs tubing when operator squeezes handle grip. "Gooseneck" extension enables cutter to be used in areas where accessiblity is limited. Cutter has potential as flight-line tool and is useful in automobile and fire rescue work.

  18. Flaming on YouTube

    NARCIS (Netherlands)

    Moor, Peter J.; Heuvelman, A.; Verleur, R.

    2010-01-01

    In this explorative study, flaming on YouTube was studied using surveys of YouTube users. Flaming is defined as displaying hostility by insulting, swearing or using otherwise offensive language. Three general conclusions were drawn. First, although many users said that they themselves do not flame,

  19. NEI You Tube Videos: Amblyopia

    Medline Plus

    Full Text Available ... Amaurosis Low Vision Refractive Errors Retinopathy of Prematurity Science Spanish Videos Webinars NEI YouTube Videos: Amblyopia Embedded video for NEI YouTube Videos: Amblyopia NEI Home Contact Us A-Z Site Map NEI on Social Media Information in Spanish (Información en español) Website, ...

  20. Flowmeter with silicon flow tube

    NARCIS (Netherlands)

    Lammerink, Theodorus S.J.; Dijkstra, Marcel; Haneveld, J.; Lötters, Joost Conrad

    2009-01-01

    A flowmeter comprising a system chip with a silicon substrate provided on a carrier, in an opening whereof at least one silicon flow tube is provided for transporting a medium whose flow rate is to be measured, said tube having two ends that issue via a wall of the opening into channels coated with