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Sample records for flux tube approximation

  1. Flux tube spectra from approximate integrability at low energies

    NASA Astrophysics Data System (ADS)

    Dubovsky, S.; Flauger, R.; Gorbenko, V.

    2015-03-01

    We provide a detailed introduction to a method we recently proposed for calculating the spectrum of excitations of effective strings such as QCD flux tubes. The method relies on the approximate integrability of the low-energy effective theory describing the flux tube excitations and is based on the thermodynamic Bethe ansatz. The approximate integrability is a consequence of the Lorentz symmetry of QCD. For excited states, the convergence of the thermodynamic Bethe ansatz technique is significantly better than that of the traditional perturbative approach. We apply the new technique to the lattice spectra for fundamental flux tubes in gluodynamics in D = 3 + 1 and D = 2 + 1, and to k-strings in gluodynamics in D = 2 + 1. We identify a massive pseudoscalar resonance on the worldsheet of the confining strings in SU(3) gluodynamics in D = 3 + 1, and massive scalar resonances on the worldsheet of k = 2.3 strings in SU(6) gluodynamics in D = 2 + 1.

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

    SciTech Connect

    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.

  3. Flux Tube Model

    NASA Astrophysics Data System (ADS)

    Steiner, O.

    2011-05-01

    This Fortran code computes magnetohydrostatic flux tubes and sheets according to the method of Steiner, Pneuman, & Stenflo (1986) A&A 170, 126-137. The code has many parameters contained in one input file that are easily modified. Extensive documentation is provided in README files.

  4. First Reconnected Flux Tubes

    NASA Astrophysics Data System (ADS)

    Andersson, L.; Lapenta, G.; Newman, D. L.; Markidis, S.; Spanswick, E. L.; Baker, J. B.; Clausen, L. B.; Larson, D. E.; Ergun, R. E.; Frey, H. U.; Singer, H. J.; Angelopoulos, V.; Bonnell, J. W.; McFadden, J. P.; Glassmeier, K.; Wolfgang, B.

    2011-12-01

    THEMIS observations from the magnetic equator (the equatorial plane) in the near-earth tail reveal a great amount of information regarding the plasma environment in the vicinity of the first reconnected flux tubes (a subgroup of dipolarization fronts). Two sequential observations of dipolarization fronts are analyzed in detail using three of the THEMIS spacecraft. Particle acceleration to high energies (>50 keV) is observed together with a void region interpreted as a region to which the full electron distribution has incomplete access. Whistler waves, which are observed, could be driven by one of the two electron populations located in the wake of the first reconnected flux tubes. The detailed observations are compared with 2D and 3D implicit kinetic simulation of reconnection events. This presentation focuses on the similarity between observation and simulation. One key aspect of this presentation is a demonstration of how different the signature is when observing at vs off the magnetic equator, since most observations in the literature (unlike the observations presented here) are from off the equator. For this event, additional spacecraft and ground observations have been analyzed, which demonstrate that a reconfiguration of the magnetosphere is taking place. However, the focus of this presentation is on the small scale (<~10 di), rather than the large scale (~20 Re).

  5. Charm production in flux tubes

    NASA Astrophysics Data System (ADS)

    Aguiar, C. E.; Kodama, T.; Nazareth, R. A. M. S.; Pech, G.

    1996-01-01

    We argue that the nonperturbative Schwinger mechanism may play an important role in the hadronic production of charm. We present a flux tube model which assumes that the colliding hadrons become color charged because of gluon exchange, and that a single nonelementary flux tube is built up as they recede. The strong chromoelectric field inside this tube creates quark pairs (including charmed ones) and the ensuing color screening breaks the tube into excited hadronic clusters. In their turn these clusters, or ``fireballs,'' decay statistically into the final hadrons. The model is able to account for the soft production of charmed, strange, and lighter hadrons within a unified framework.

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

    NASA Astrophysics Data System (ADS)

    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 Alfvén 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 Alfvén 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.

  7. Equilibrium model of thin magnetic flux tubes. [solar atmosphere

    NASA Technical Reports Server (NTRS)

    Bodo, G.; Ferrari, A.; Massaglia, S.; Kalkofen, W.; Rosner, R.

    1984-01-01

    The existence of a physically realizable domain in which approximations that lead to a self consistent solution for flux tube stratification in the solar atmosphere, without ad hoc hypotheses, is proved. The transfer equation is solved assuming that no energy transport other than radiative is present. Convective motions inside the tube are assumed to be suppressed by magnetic forces. Only one parameter, the plasma beta at tau = 0, must be specified, and this can be estimated from observations of spatially resolved flux tubes.

  8. Pentaquark in the flux tube model

    SciTech Connect

    Iwasaki, M.; Takagi, F.

    2008-03-01

    We propose a model for pentaquarks in an excited state in the flux tube picture. The pentaquark is assumed to be composed of two diquarks and an antiquark connected by a color flux tube with a junction. If the pentaquark is rotating rapidly, it is polarized into two clusters: one is a diquark and the other is an antiquark plus another diquark. Excited energy of this quasilinear system is calculated with the use of the WKB approximation. It is predicted that there exist quasistable excited pentaquarks: 1690 MeV(3/2{sup +}), 2000 MeV(5/2{sup -}), 2250 MeV(7/2{sup +}) etc., which decay mainly through three-body modes.

  9. Pentaquark in the flux tube model

    NASA Astrophysics Data System (ADS)

    Iwasaki, M.; Takagi, F.

    2008-03-01

    We propose a model for pentaquarks in an excited state in the flux tube picture. The pentaquark is assumed to be composed of two diquarks and an antiquark connected by a color flux tube with a junction. If the pentaquark is rotating rapidly, it is polarized into two clusters: one is a diquark and the other is an antiquark plus another diquark. Excited energy of this quasilinear system is calculated with the use of the WKB approximation. It is predicted that there exist quasistable excited pentaquarks: 1690MeV(3/2+), 2000MeV(5/2-), 2250MeV(7/2+) etc., which decay mainly through three-body modes.

  10. Chromoelectric flux tubes in QCD

    SciTech Connect

    Cardaci, Mario Salvatore; Cea, Paolo; Cosmai, Leonardo; Falcone, Rossella; Papa, Alessandro

    2011-01-01

    We analyze the distribution of the chromoelectric field generated by a static quark-antiquark pair in the SU(3) vacuum and revisit previous results for SU(2). We find that the transverse profile of the flux tube resembles the dual version of the Abrikosov vortex field distribution. We give an estimate of the London penetration length of the chromoelectric field in the confined vacuum. We also speculate on the value of the ratio between the penetration lengths for SU(2) and SU(3) gauge theories.

  11. Investigating the Dynamics of Canonical Flux Tubes

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; Sears, Jason; Intrator, Thomas; You, Setthivoine

    2016-10-01

    Canonical flux tubes are flux tubes of the circulation of a species' canonical momentum. They provide a convenient generalization of magnetic flux tubes to regimes beyond magnetohydrodynamics (MHD). We hypothesize that hierarchies of instabilities which couple disparate scales could transfer magnetic pitch into helical flows and vice versa while conserving the total canonical helicity. This work first explores the possibility of a sausage instability existing on top of a kink as mechanism for coupling scales, then presents the evolution of canonical helicity in a gyrating kinked flux rope. Analytical and numerical stability spaces derived for magnetic flux tubes with core and skin currents indicate that, as a flux tube lengthens and collimates, it may become kink unstable with a sausage instability developing on top of the kink. A new analysis of 3D magnetic field and ion flow data on gyrating kinked magnetic flux ropes from the Reconnection Scaling Experiment tracks the evolution of canonical flux tubes and their helicity. These results and methodology are being developed as part of the Mochi experiment specifically designed to observe the dynamics of canonical flux tubes. This work is supported by DOE Grant DE-SC0010340 and the DOE Office of Science Graduate Student Research Program and prepared in part by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-697161.

  12. Investigating the Dynamics of Canonical Flux Tubes

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; Carroll, Evan; Kamikawa, Yu; Lavine, Eric; Vereen, Keon; You, Setthivoine

    2013-10-01

    Canonical flux tubes are defined by tracing areas of constant magnetic and fluid vorticity flux. This poster will present the theory for canonical flux tubes and current progress in the construction of an experiment designed to observe their evolution. In the zero flow limit, canonical flux tubes are magnetic flux tubes, but in full form, present the distinct advantage of reconciling two-fluid plasma dynamics with familiar concepts of helicity, twists and linkages. The experiment and the DCON code will be used to investigate a new MHD stability criterion for sausage and kink modes in screw pinches that has been generalized to magnetic flux tubes with skin and core currents. Camera images and a 3D array of ˙ B probes will measure tube aspect-ratio and ratio of current-to-magnetic flux, respectively, to trace these flux tube parameters in a stability space. The experiment's triple electrode planar gun is designed to generate azimuthal and axial flows. These diagnostics together with a 3D vector tomographic reconstruction of ion Doppler spectroscopy will be used to verify the theory of canonical helicity transport. This work was sponsored in part by the US DOE Grant DE-SC0010340.

  13. Effective string description of confining flux tubes

    NASA Astrophysics Data System (ADS)

    Brandt, Bastian B.; Meineri, Marco

    2016-08-01

    We review the current knowledge about the theoretical foundations of the effective string theory for confining flux tubes and the comparison of the predictions to pure gauge lattice data. A concise presentation of the effective string theory is provided, incorporating recent developments. We summarize the predictions for the spectrum and the profile/width of the flux tube and their comparison to lattice data. The review closes with a short summary of open questions for future research.

  14. Dynamics of flux tubes in accretion disks

    NASA Technical Reports Server (NTRS)

    Vishniac, E. T.; Duncan, R. C.

    1994-01-01

    The study of magnetized plasmas in astrophysics is complicated by a number of factors, not the least of which is that in considering magnetic fields in stars or accretion disks, we are considering plasmas with densities well above those we can study in the laboratory. In particular, whereas laboratory plasmas are dominated by the confining magnetic field pressure, stars, and probably accretion disks, have magnetic fields whose beta (ratio of gas pressure to magnetic field pressure) is much greater than 1. Observations of the Sun suggest that under such circumstances the magnetic field breaks apart into discrete flux tubes with a small filling factor. On the other hand, theoretical treatments of MHD turbulence in high-beta plasmas tend to assume that the field is more or less homogeneously distributed throughout the plasma. Here we consider a simple model for the distribution of magnetic flux tubes in a turbulent medium. We discuss the mechanism by which small inhomogeneities evolve into discrete flux tubes and the size and distribution of such flux tubes. We then apply the model to accretion disks. We find that the fibrilation of the magnetic field does not enhance magnetic buoyancy. We also note that the evolution of an initially diffuse field in a turbulent medium, e.g., any uniform field in a shearing flow, will initially show exponential growth as the flux tubes form. This growth saturates when the flux tube formation is complete and cannot be used as the basis for a self-sustaining dynamo effect. Since the typical state of the magnetic field is a collection of intense flux tubes, this effect is of limited interest. However, it may be important early in the evolution of the galactic magnetic field, and it will play a large role in numerical simulations. Finally, we note that the formation of flux tubes is an essential ingredient in any successful dynamo model for stars or accretion disks.

  15. Wave function properties of a single and a system of magnetic flux tube(s) oscillations

    NASA Astrophysics Data System (ADS)

    Esmaeili, Shahriar; Nasiri, Mojtaba; Dadashi, Neda; Safari, Hossein

    2016-10-01

    In this study, the properties of wave functions of the MHD oscillations for a single and a system of straight flux tubes are investigated. Magnetic flux tubes with a straight magnetic field and longitudinal density stratification were considered in zero-β approximation. A single three-dimensional wave equation (eigenvalue problem) is solved for longitudinal component of the perturbed magnetic field using the finite element method. Wave functions (eigenfunction of wave equation) of the MHD oscillations are categorized into sausage, kink, helical kink, and fluting modes. Exact recognition of the wave functions and the frequencies of oscillations can be used in coronal seismology and also helps to the future high-resolution instruments that would be designed for studying the properties of the solar loop oscillations in details. The properties of collective oscillations of nonidentical and identical system of flux tubes and their interactions are studied. The ratios of frequencies, the oscillation frequencies of a system of flux tubes to their equivalent monolithic tube (ω sys/ω mono), are obtained between 0.748 and 0.841 for a system of nonidentical tubes, whereas the related ratios of frequencies for a system of identical flux tubes are fluctuated around 0.761.

  16. Siphon flows in isolated magnetic flux tubes. 3: The equilibrium path of the flux tube arch

    NASA Technical Reports Server (NTRS)

    Thomas, John H.; Montesinis, Benjamin

    1989-01-01

    The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for flux tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.

  17. Siphon flows in isolated magnetic flux tubes. 3: The equilibrium path of the flux tube arch

    NASA Astrophysics Data System (ADS)

    Thomas, John H.; Montesinis, Benjamin

    1989-09-01

    The arched equilibrium path of a thin magnetic flux tube in a plane-stratified, nonmagnetic atmosphere is calculated for cases in which the flux tube contains a steady siphon flow. The large scale mechanical equilibrium of the flux tube involves a balance among the magnetic buoyancy force, the net magnetic tension force due to the curvature of the flux tube axis, and the inertial (centrifugal) force due to the siphon flow along curved streamlines. The ends of the flux tube are assumed to be pinned down by some other external force. Both isothermal and adiabatic siphon flows are considered for flux tubes in an isothermal external atmosphere. For the isothermal case, in the absence of a siphon flow the equilibrium path reduces to the static arch calculated by Parker (1975, 1979). The presence of a siphon flow causes the flux tube arch to bend more sharply, so that magnetic tension can overcome the additional straightening effect of the inertial force, and reduces the maximum width of the arch. The curvature of the arch increases as the siphon flow speed increases. For a critical siphon flow, with supercritical flow in the downstream leg, the arch is asymmetric, with greater curvature in the downstream leg of the arch. Adiabatic flow have qualitatively similar effects, except that adiabatic cooling reduces the buoyancy of the flux tube and thus leads to significantly wider arches. In some cases the cooling is strong enough to create negative buoyancy along sections of the flux tube, requiring upward curvature of the flux tube path along these sections and sometimes leading to unusual equilibrium paths of periodic, sinusoidal form.

  18. MHD waves on solar magnetic flux tubes - Tutorial review

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1990-01-01

    Some of the highly simplified models that have been developed for solar magnetic flux tubes, which are intense photospheric-level fields confined by external gas pressure but able to vary rapidly with height, are presently discussed with emphasis on the torsional Alfven mode's propagation, reflection, and non-WKB properties. The 'sausage' and 'kink' modes described by the thin flux-tube approximation are noted. Attention is also given to the surface waves and resonance absorption of X-ray-emitting loops, as well as to the results of recent work on the resonant instabilities that occur in the presence of bulk flows.

  19. MHD waves on solar magnetic flux tubes - Tutorial review

    NASA Astrophysics Data System (ADS)

    Hollweg, Joseph V.

    Some of the highly simplified models that have been developed for solar magnetic flux tubes, which are intense photospheric-level fields confined by external gas pressure but able to vary rapidly with height, are presently discussed with emphasis on the torsional Alfven mode's propagation, reflection, and non-WKB properties. The 'sausage' and 'kink' modes described by the thin flux-tube approximation are noted. Attention is also given to the surface waves and resonance absorption of X-ray-emitting loops, as well as to the results of recent work on the resonant instabilities that occur in the presence of bulk flows.

  20. Diamagnetic force on a flux tube

    NASA Technical Reports Server (NTRS)

    Yeh, T.

    1983-01-01

    The diamagnetic force on a straight flux tube is elucidated. The case when the flux tube has a circular cross section is considered, and the result is generalized to the case of noncircular cross section. The result shows that when the external magnetic field is uniform, the diamagnetic force is simply equal to the vector multiplication of the internal conduction current and the external magnetic field. It is independent of the size and shape of the cross section of the flux tube. This is analogous to the Kutta-Joukowski theorem that the aerodynamic lift force is proportional to the vector multiplication of the unperturbed flow velocity and the circulation around the airfoil. When the external magnetic field is nonuniform, the diamagnetic force has an additional contribution which is proportional to the gradient of magnetic pressure and to the volume of the flux tube. The constant of proportionality, which is shown to be equal to two for a circular cross section, indicates the enhancement of the nonuniformity of the external magnetic field in the vicinity of the periphery by the polarization current.

  1. Color magnetic flux tubes in dense QCD

    SciTech Connect

    Eto, Minoru; Nitta, Muneto

    2009-12-15

    QCD is expected to be in the color-flavor locking phase in high baryon density, which exhibits color superconductivity. The most fundamental topological objects in the color superconductor are non-Abelian vortices which are topologically stable color magnetic flux tubes. We present numerical solutions of the color magnetic flux tube for diverse choices of the coupling constants based on the Ginzburg-Landau Lagrangian. We also analytically study its asymptotic profiles and find that they are different from the case of usual superconductors. We propose the width of color magnetic fluxes and find that it is larger than naive expectation of the Compton wavelength of the massive gluon when the gluon mass is larger than the scalar mass.

  2. ON THE DISPERSION AND SCATTERING OF MAGNETOHYDRODYNAMIC WAVES BY LONGITUDINALLY STRATIFIED FLUX TUBES

    SciTech Connect

    Andries, J.; Cally, P. S. E-mail: paul.cally@monash.edu

    2011-12-20

    We provide a fairly general analytic theory for the dispersion and scattering of magnetohydrodynamic waves by longitudinally stratified flux tubes. The theory provides a common framework for, and synthesis of, many previous studies of flux tube oscillations that were carried out under various simplifying assumptions. The present theory focuses on making only a minimal number of assumptions. As a result it thus provides an analytical treatment of several generalizations of existing tube oscillation models. The most important practical cases are inclusion of plasma pressure and possibly buoyancy effects in models of straight non-diverging tubes as applied in coronal seismology, and relaxation of the 'thin tube' approximation in oscillation models of diverging tubes as applied both in the context of p-mode scattering and coronal seismology. In particular, it illustrates the unifying theoretical framework underlying both the description of waves scattered by flux tubes and the dispersion of waves carried along flux tubes.

  3. Dynamics of Quarks in a 2D Flux Tube

    SciTech Connect

    Koshelkin, Andrey V.; Wong, Cheuk-Yin

    2015-01-01

    On the basis of a compactification of the (3+1) into (1+1) dimensional space-time [1], the quark states inside the 2D flux tube are studied for the case of a linear transverse confining potential. The derived states are classified by both the projections of the orbital momentum and the spin along the tube direction. The spectrum of the fermion states is evaluated. It is found that the energy eigenvalues of the quarks appear to be approximately related to the square root of the eigenvalues of the two-dimensional harmonic oscillator.

  4. The Topology of Canonical Flux Tubes in Flared Jet Geometry

    NASA Astrophysics Data System (ADS)

    Sander Lavine, Eric; You, Setthivoine

    2017-01-01

    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.

  5. MAGNETIC FLUX TUBE INTERCHANGE AT THE HELIOPAUSE

    SciTech Connect

    Florinski, V.

    2015-11-01

    The magnetic field measured by Voyager 1 prior to its heliocliff encounter on 2012.65 showed an unexpectedly complex transition from the primarily azimuthal inner-heliosheath field to the draped interstellar field tilted by some 20° to the nominal azimuthal direction. Most prominent were two regions of enhanced magnetic field strength depleted in energetic charged particles of heliospheric origin. These regions were interpreted as magnetic flux tubes connected to the outer heliosheath that provided a path for the particles to escape. Despite large increases in strength, the field’s direction did not change appreciably at the boundaries of these flux tubes. Rather, the field’s direction changed gradually over several months prior to the heliocliff crossing. It is shown theoretically that the heliopause, as a pressure equilibrium layer, can become unstable to interchange of magnetic fields between the inner and the outer heliosheaths. The curvature of magnetic field lines and the anti-sunward gradient in plasma kinetic pressure provide conditions favorable for an interchange. Magnetic shear between the heliosheath and the interstellar fields reduces the growth rates, but does not fully stabilize the heliopause against perturbations propagating in the latitudinal direction. The instability could create a transition layer permeated by magnetic flux tubes, oriented parallel to each other and alternately connected to the heliosheath or the interstellar regions.

  6. Approximate Design Method for Single Stage Pulse Tube Refrigerators

    NASA Astrophysics Data System (ADS)

    Pfotenhauer, J. M.; Gan, Z. H.; Radebaugh, R.

    2008-03-01

    An approximate design method is presented for the design of a single stage Stirling type pulse tube refrigerator. The design method begins from a defined cooling power, operating temperature, average and dynamic pressure, and frequency. Using a combination of phasor analysis, approximate correlations derived from extensive use of REGEN3.2, a few `rules of thumb,' and available models for inertance tubes, a process is presented to define appropriate geometries for the regenerator, pulse tube and inertance tube components. In addition, specifications for the acoustic power and phase between the pressure and flow required from the compressor are defined. The process enables an appreciation of the primary physical parameters operating within the pulse tube refrigerator, but relies on approximate values for the combined loss mechanisms. The defined geometries can provide both a useful starting point, and a sanity check, for more sophisticated design methodologies.

  7. Flux tubes in the QCD vacuum

    NASA Astrophysics Data System (ADS)

    Cea, Paolo; Cosmai, Leonardo; Cuteri, Francesca; Papa, Alessandro

    2017-06-01

    The hypothesis that the QCD vacuum can be modeled as a dual superconductor is a powerful tool to describe the distribution of the color field generated by a quark-antiquark static pair and, as such, can provide useful clues for the understanding of confinement. In this work we investigate, by lattice Monte Carlo simulations of the S U (3 ) pure gauge theory and of (2 +1 )-flavor QCD with physical mass settings, some properties of the chromoelectric flux tube at zero temperature and their dependence on the physical distance between the static sources. We draw some conclusions about the validity domain of the dual superconductor picture.

  8. Interaction of twisted curved flux tubes

    NASA Astrophysics Data System (ADS)

    Selwa, Malgorzata; Parnell, Clare; Priest, Eric

    Most solar eruptions are initiated from sigmoidal structures. We perform 3D MHD numerical experiments of the interaction of force-free dipolar flux tubes. The magnetic configuration is initialized as either a potential or a force-free dipole with a constant density. Next we perturb the dipoles by twisting or rotating them leading to reconnection in a resistive MHD regime. We compare the connectivity, energetics and topological features in both models, vary the contact angle of the dipoles and check if the initial configuration (sigmoidal or not) affects flares and eruption initiation leading to faster and stronger reconnection.

  9. Dynamic phenomena in coronal flux tubes

    NASA Technical Reports Server (NTRS)

    Mariska, J. T.; Boris, J. P.

    1981-01-01

    The study of stellar atmospheres and the determination of specific physical mechanisms, geometries, and magnetic structures by which coronae are maintained is examined. Ultraviolet and soft X-ray components observed in the radiative output of cool stars and the Sun require counterentropic temperature gradients for their explanation. The existence of a hot corona is recognized as a result of mechanical or fluid dynamic effects and the importance of the magnetic field in the heating is accepted. Magnetohydrodynamic energy release associated with the emergence of magnetic flux through the chromosphere and its dynamic readjustment in the corona are major counterentropic phenomena which are considered as primary candidates for corona heating. Systematic plows in coronal flux tubes result from asymmetric heating and systematic flows can exist without substantial chromospheric pressure differences.

  10. Method for limiting heat flux in double-wall tubes

    DOEpatents

    Hwang, Jaw-Yeu

    1982-01-01

    A method of limiting the heat flux in a portion of double-wall tubes including heat treating the tubes so that the walls separate when subjected to high heat flux and supplying an inert gas mixture to the gap at the interface of the double-wall tubes.

  11. A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

    NASA Astrophysics Data System (ADS)

    You, Setthivoine; von der Linden, Jens; Vereen, Keon; Carroll, Evan; Kamikawa, Yu; Lavine, Eric Sander

    2013-10-01

    A new research program aims to simulate a magnetically driven jet launched by an accretion disk in a laboratory experiment. The experiment replaces an accretion disk that would rotate at impractical speeds in the laboratory with three concentric annular electrodes, independently biased by two sets of pulsed power supplies to generate magnetized plasma shear flows. With three electrodes, the radial electric field can be set up to approximate the rotation profile of an accretion disk. The primary diagnostics include arrays of magnetic probes to measure 3D magnetic fields and arrays of lines-of-sight to measure 3D ion flows from vector tomography of ion Doppler spectral lines. The symmetry of fast gas puff sources is fine-tuned with a fast ion gauge to remove any anchoring effects of discrete gas holes on the azimuthal rotation of the plasma jet. The aim is to understand how magnetically driven astrophysical jets become long and collimated, how they become unstable or turbulent, and investigate the physics from a canonical flux tube point-of-view. A canonical flux tube is a fundamental tube of magnetic flux with helical flows. This work is supported by the US DOE Grant DE-SC0010340

  12. Coulomb flux tube on the lattice

    NASA Astrophysics Data System (ADS)

    Chung, Kristian; Greensite, Jeff

    2017-08-01

    In Coulomb gauge a longitudinal electric field is generated instantaneously with the creation of a static quark-antiquark pair. The field due to the quarks is a sum of two contributions, one from the quark and one from the antiquark, and there is no obvious reason that this sum should fall off exponentially with distance from the sources. We show here, however, from numerical simulations in pure SU(2) lattice gauge theory, that the color Coulomb electric field does in fact fall off exponentially with transverse distance away from a line joining static quark-antiquark sources, indicating the existence of a color Coulomb flux tube, and the absence of long-range Coulomb dipole fields.

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

    SciTech Connect

    McEligot, D.M.

    1995-08-14

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or {open_quotes}critical{close_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.

  14. Equilibrium structure of solar magnetic flux tubes: Energy transport with multistream radiative transfer

    NASA Technical Reports Server (NTRS)

    Hasan, S. S.; Kalkofen, W.

    1994-01-01

    We examine the equilibrium structure of vertical intense magnetic flux tubes on the Sun. Assuming cylindrical geometry, we solve the magnetohydrostatic equations in the thin flux-tube approximation, allowing for energy transport by radiation and convection. The radiative transfer equation is solved in the six-stream approximation, assuming gray opacity and local thermodynamic equilibrium. This constitutes a significant improvement over a previous study, in which the transfer was solved using the multidimensional generalization of the Eddington approximation. Convection in the flux tube is treated using mixing-length theory, with an additional parameter alpha, characterizing the suppression of convective energy transport in the tube by the strong magnetic field. The equations are solved using the method of partial linearization. We present results for tubes with different values of the magnetic field strength and radius at a fixed depth in the atmosphere. In general, we find that, at equal geometric heights, the temperature on the tube axis, compared to the ambient medium, is higher in the photosphere and lower in the convection zone, with the difference becoming larger for thicker tubes. At equal optical depths the tubes are generally hotter than their surroundings. The results are comparatively insensitive to alpha but depend upon whether radiative and convective energy transport operate simultaneously or in separate layers. A comparison of our results with semiempirical models shows that the temperature and intensity contrast are in broad agreement. However, the field strengths of the flux-tube models are somewhat lower than the values inferred from observations.

  15. Equilibrium structure of solar magnetic flux tubes: Energy transport with multistream radiative transfer

    NASA Technical Reports Server (NTRS)

    Hasan, S. S.; Kalkofen, W.

    1994-01-01

    We examine the equilibrium structure of vertical intense magnetic flux tubes on the Sun. Assuming cylindrical geometry, we solve the magnetohydrostatic equations in the thin flux-tube approximation, allowing for energy transport by radiation and convection. The radiative transfer equation is solved in the six-stream approximation, assuming gray opacity and local thermodynamic equilibrium. This constitutes a significant improvement over a previous study, in which the transfer was solved using the multidimensional generalization of the Eddington approximation. Convection in the flux tube is treated using mixing-length theory, with an additional parameter alpha, characterizing the suppression of convective energy transport in the tube by the strong magnetic field. The equations are solved using the method of partial linearization. We present results for tubes with different values of the magnetic field strength and radius at a fixed depth in the atmosphere. In general, we find that, at equal geometric heights, the temperature on the tube axis, compared to the ambient medium, is higher in the photosphere and lower in the convection zone, with the difference becoming larger for thicker tubes. At equal optical depths the tubes are generally hotter than their surroundings. The results are comparatively insensitive to alpha but depend upon whether radiative and convective energy transport operate simultaneously or in separate layers. A comparison of our results with semiempirical models shows that the temperature and intensity contrast are in broad agreement. However, the field strengths of the flux-tube models are somewhat lower than the values inferred from observations.

  16. Siphon flows in isolated magnetic flux tubes. II - Adiabatic flows

    NASA Technical Reports Server (NTRS)

    Montesinos, Benjamin; Thomas, John H.

    1989-01-01

    This paper extends the study of steady siphon flows in isolated magnetic flux tubes surrounded by field-free gas to the case of adiabatic flows. The basic equations governing steady adiabatic siphon flows in a thin, isolated magnetic flux tube are summarized, and qualitative features of adiabatic flows in elevated, arched flux tubes are discussed. The equations are then cast in nondimensional form and the results of numerical computations of adiabatic siphon flows in arched flux tubes are presented along with comparisons between isothermal and adiabatic flows. The effects of making the interior of the flux tube hotter or colder than the surrounding atmosphere at the upstream footpoint of the arch is considered. In this case, is it found that the adiabatic flows are qualitatively similar to the isothermal flows, with adiabatic cooling producing quantitative differences. Critical flows can produce a bulge point in the rising part of the arch and a concentration of magnetic flux above the bulge point.

  17. Incompressible magnetohydrodynamic modes in the thin magnetically twisted flux tube

    NASA Astrophysics Data System (ADS)

    Cheremnykh, O. K.; Fedun, V.; Kryshtal, A. N.; Verth, G.

    2017-08-01

    Context. Observations have shown that twisted magnetic fields naturally occur, and indeed are omnipresent in the Sun's atmosphere. It is therefore of great theoretical interest in solar atmospheric waves research to investigate the types of magnetohydrodynamic (MHD) wave modes that can propagate along twisted magnetic flux tubes. Aims: Within the framework of ideal MHD, the main aim of this work is to investigate small amplitude incompressible wave modes of twisted magnetic flux tubes with m ≥ 1. The axial magnetic field strength inside and outside the tube will be allowed to vary, to ensure the results will not be restricted to only cold plasma equilibria conditions. Methods: The dispersion equation for these incompressible linear MHD wave modes was derived analytically by implementing the long wavelength approximation. Results: It is shown, in the long wavelength limit, that both the frequency and radial velocity profile of the m = 1 kink mode are completely unaffected by the choice of internal background magnetic twist. However, fluting modes with m ≥ 2 are sensitive to the particular radial profile of magnetic twist chosen. Furthermore, due to background twist, a low frequency cut-off is introduced for fluting modes that is not present for kink modes. From an observational point of view, although magnetic twist does not affect the propagation of long wavelength kink modes, for fluting modes it will either work for or against the propagation, depending on the direction of wave travel relative to the sign of the background twist.

  18. The Topology of Canonical Flux Tubes in Flared Jet Geometry

    NASA Astrophysics Data System (ADS)

    Lavine, Eric Sander; You, Setthivoine

    2016-10-01

    Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by MHD. We outline here a more fundamental approach based on flux tubes of canonical vorticity. 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. We examine the morphology of these canonical flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, dipole magnetic field. Calculations of gauge-invariant relative canonical helicity track the evolution of magnetic, cross, and kinetic helicities in the system and show that ion flow fields can unwind to compensate for increasing magnetic twist. The results demonstrate that including a species' finite momentum can result in long, collimated canonical vorticity flux tubes even when 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. This work is supported by DOE Grant DE-SC0010340.

  19. Supersymmetric quantum mechanics of the flux tube

    NASA Astrophysics Data System (ADS)

    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.

  20. Benchmarking gyrokinetic simulations in a toroidal flux-tube

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Parker, S. E.; Wan, W.; Bravenec, R.

    2013-09-01

    A flux-tube model is implemented in the global turbulence code GEM [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 839 (2007)] in order to facilitate benchmarking with Eulerian codes. The global GEM assumes the magnetic equilibrium to be completely given. The initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, etc.) to be equal to the values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. This implementation shows disagreement with Eulerian codes in linear simulations. An alternative flux-tube model based on a complete local equilibrium solution of the Grad-Shafranov equation [J. Candy, Plasma Phys. Controlled Fusion 51, 105009 (2009)] is then implemented. This results in better agreement between Eulerian codes and the particle-in-cell (PIC) method. The PIC algorithm based on the v||-formalism [J. Reynders, Ph.D. dissertation, Princeton University, 1992] and the gyrokinetic ion/fluid electron hybrid model with kinetic electron closure [Y. Chan and S. E. Parker, Phys. Plasmas 18, 055703 (2011)] are also implemented in the flux-tube geometry and compared with the direct method for both the ion temperature gradient driven modes and the kinetic ballooning modes.

  1. Benchmarking gyrokinetic simulations in a toroidal flux-tube

    SciTech Connect

    Chen, Y.; Parker, S. E.; Wan, W.; Bravenec, R.

    2013-09-15

    A flux-tube model is implemented in the global turbulence code GEM [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 839 (2007)] in order to facilitate benchmarking with Eulerian codes. The global GEM assumes the magnetic equilibrium to be completely given. The initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, etc.) to be equal to the values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. This implementation shows disagreement with Eulerian codes in linear simulations. An alternative flux-tube model based on a complete local equilibrium solution of the Grad-Shafranov equation [J. Candy, Plasma Phys. Controlled Fusion 51, 105009 (2009)] is then implemented. This results in better agreement between Eulerian codes and the particle-in-cell (PIC) method. The PIC algorithm based on the v{sub ||}-formalism [J. Reynders, Ph.D. dissertation, Princeton University, 1992] and the gyrokinetic ion/fluid electron hybrid model with kinetic electron closure [Y. Chan and S. E. Parker, Phys. Plasmas 18, 055703 (2011)] are also implemented in the flux-tube geometry and compared with the direct method for both the ion temperature gradient driven modes and the kinetic ballooning modes.

  2. Structure of sunspot penumbrae - Fallen magnetic flux tubes

    NASA Technical Reports Server (NTRS)

    Wentzel, Donat G.

    1992-01-01

    A model is presented of a sunspot penumbra involving magnetic flux tubes that have fallen into the photosphere and float there. An upwelling at the inner end of a fallen tube continuously provides additional gas. This gas flows along and lengthens the tube and is observable as the Evershed flow. Fallen flux tubes may appear as bright streaks near the upwelling, but they become dark filaments further out. The model is corroborated by recent optical high-resolution magnetic data regarding the penumbral filaments, by the 12-micron magnetic measurements relevant to the height of the temperature minimum, and by photographs of the umbra/penumbra boundary.

  3. TWISTED MAGNETIC FLUX TUBES IN THE SOLAR WIND

    SciTech Connect

    Zaqarashvili, Teimuraz V.; Vörös, Zoltán; Narita, Yasuhito; Bruno, Roberto

    2014-03-01

    Magnetic flux tubes in the solar wind can be twisted as they are transported from the solar surface, where the tubes are twisted due to photospheric motions. It is suggested that the twisted magnetic tubes can be detected as the variation of total (thermal+magnetic) pressure during their passage through the observing satellite. We show that the total pressure of several observed twisted tubes resembles the theoretically expected profile. The twist of the isolated magnetic tube may explain the observed abrupt changes of magnetic field direction at tube walls. We have also found some evidence that the flux tube walls can be associated with local heating of the plasma and elevated proton and electron temperatures. For the tubes aligned with the Parker spiral, the twist angle can be estimated from the change of magnetic field direction. Stability analysis of twisted tubes shows that the critical twist angle of the tube with a homogeneous twist is 70°, but the angle can further decrease due to the motion of the tube with respect to the solar wind stream. The tubes with a stronger twist are unstable to the kink instability, therefore they probably cannot reach 1 AU.

  4. Colour flux-tubes in static pentaquark and tetraquark systems

    NASA Astrophysics Data System (ADS)

    Bicudo, Pedro; Cardoso, Nuno; Cardoso, Marco

    2012-04-01

    The colour fields created by the static tetraquark and pentaquark systems are computed in quenched SU(3) lattice QCD, with gauge invariant lattice operators, in a 243×48 lattice at β=6.2. We generate our quenched configurations with GPUs, and detail the respective benchmarks in different SU(N) groups. While at smaller distances the Coulomb potential is expected to dominate, at larger distances it is expected that fundamental flux tubes, similar to the flux-tube between a quark and an antiquark, emerge and confine the quarks. In order to minimize the potential the fundamental flux tubes should connect at 120° angles. We compute the square of the colour fields utilizing plaquettes, and locate the static sources with generalized Wilson loops and with APE smearing. The tetraquark system is well described by a double-Y-shaped flux-tube, with two Steiner points, but when quark-antiquark pairs are close enough the two junctions collapse and we have an X-shaped flux-tube, with one Steiner point. The pentaquark system is well described by a three-Y-shaped flux-tube where the three flux junctions are Steiner points.

  5. OBSERVATION OF FLUX-TUBE CROSSINGS IN THE SOLAR WIND

    SciTech Connect

    Arnold, L.; Li, G.; Li, X.; Yan, Y.

    2013-03-20

    Current sheets are ubiquitous in the solar wind. They are a major source of the solar wind MHD turbulence intermittency. They may result from nonlinear interactions of the solar wind MHD turbulence or are the boundaries of flux tubes that originate from the solar surface. Some current sheets appear in pairs and are the boundaries of transient structures such as magnetic holes and reconnection exhausts or the edges of pulsed Alfven waves. For an individual current sheet, discerning whether it is a flux-tube boundary or due to nonlinear interactions or the boundary of a transient structure is difficult. In this work, using data from the Wind spacecraft, we identify two three-current-sheet events. Detailed examination of these two events suggests that they are best explained by the flux-tube-crossing scenario. Our study provides convincing evidence supporting the scenario that the solar wind consists of flux tubes where distinct plasmas reside.

  6. Sunspots and the physics of magnetic flux tubes. V - Mutual hydrodynamic forces between neighboring tubes

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1979-01-01

    The mutual hydrodynamic forces between parallel cylinders in a moving fluid are illustrated through several formal examples. Parallel tubes in a uniform flow are attracted or repelled depending on whether they are side by side or one ahead of the other, respectively. A pulsating or undulating tube attracts all other neighboring tubes toward itself. These hydrodynamic effects suggest that the separate flux tubes beneath the sunspots exert significant attractive forces on each other.

  7. J/ ψ-dissociation by a color electric flux tube

    NASA Astrophysics Data System (ADS)

    Loh, S.; Greiner, C.; Mosel, U.

    1997-02-01

    We address the question of how a c - c¯state (a J/ ψ) can be dissociated by the strong color electric fields when moving through a color electric flux tube. The color electric flux tube and the dissociation of the heavy quarkonia state are both described within the Friedberg-Lee color dielectric model. We speculate on the importance of such an effect with respect to the observed J/ ψ-suppression in ultrarelativistic heavy ion collisions.

  8. Flux tube analysis of L-band ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Mannucci, A. J.; Butala, M. D.; Pi, X.; Valladares, C. E.

    2013-06-01

    This manuscript presents magnetic flux tube analysis of L-band signal scintillation in the nighttime equatorial and low-latitude ionosphere. Residues of the scintillation index S4 estimated from the L-band signals received from Geostationary Earth Orbit (GEO) satellites are employed in the analysis. The S4 estimates have been shown to be associated with simultaneous GPS VTEC variations derived from JPL's GIPSY-GIM package. We have applied the wavelet decomposition technique simultaneously on the S4 time series in a flux tube over the equatorial and low-latitude regions. The technique decomposes the S4 signal to identify the dominant mode of variabilities and the temporal variations of scintillation-producing irregularities in the context of a flux tube. Statistically significant regions of the wavelet power spectra considered in our study have mainly shown that (a) dominant plasma irregularities associated with S4 variabilities in a flux tube have periods of about 4 to 15 minutes (horizontal irregularity scales of about 24 to 90 km). These periods match short period gravity waves, (b) scintillation-producing irregularities are anisotropic along the flux tube and in the east-west direction, and (c) the occurrences of scintillation-producing irregularities along the flux tube indicate that the entire flux tube became unstable. However, plasma instability occurrences were not simultaneous in most cases along the flux tube, there were time delays of various orders. Understanding the attributes of L-band scintillation-producing irregularities could be important for developing measures to mitigate L-band signal degradation.

  9. Improved approximate formulas for flux from cylindrical and rectangular sources

    SciTech Connect

    Wallace, O.J.; Bokharee, S.A.

    1993-03-01

    This report provides two new approximate formulas for the flux at detector points outside the radial and axial extensions of a homogeneous cylindrical source and improved approximate formulas for the flux at points opposite rectangular surface sources. These formulas extend the range of geometries for which analytic approximations may be used by shield design engineers to make rapid scoping studies and check more extensive calculations for reasonableness. These formulas can be used to support skeptical, independent evaluations and are also valuable teaching tools for introducing shield designers to complex shield analyses.

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

    NASA Astrophysics Data System (ADS)

    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

  11. Stability of cool flux tubes in the solar chromosphere. II - Non-linear dynamical behaviour

    NASA Astrophysics Data System (ADS)

    Hassan, S. S.; Kneer, F.

    1990-06-01

    A single vertical cool flux tube in the solar chromosphere is focused upon for stability studies. The analysis of a previous study by Hasan and Kneer (1986) is extended to the nonlinear regime with a view to examining the consequences of having self-exciting mechanisms of oscillations above the photosphere. In particular, the possibility of whether the motions driven by the convective instability caused by the presence of CO could extract sufficient energy from the radiation field near the Tmin region of empirical models and deposit it in higher layers to produce chromospheric heating is investigated. The time evolution of this instability is followed by solving the MHD equations in the thin flux tube approximation. The analysis includes energy exchange with the radiation field. The simulations of a flux tube with a transmitting upper boundary show that the average energy flux in the oscillations is inadequate for chromospheric heating.

  12. Boiling inside tubes: Critical heat flux for upward flow in uniformly heated vertical tubes

    NASA Astrophysics Data System (ADS)

    1986-11-01

    ESDU 85041 recommended a procedure for estimating the heat flux at different locations along a heated tube through which a boiling liquid is flowing, assuming that the wall is wetted by the liquid. The purpose of this Data Item (ESDU 86032) is to enable the reader to check, in the case of flow up a uniformly heated vertical tube, that the heat flux does not exceed the critical value above which the liquid would not wet the wall. This point marks the onset of dryout accompanied by an increase in resistance to heat transfer and the possible onset of corrosion and overheating of the tube. The open literature contains many experimental values of the critical heat flux (CHF) in flow up electrically heated vertical tubes, mostly with water or R.12. These results have been used to check various procedures for predicting CHF with flow up vertical tubes. The recommended procedure is given in detail and illustrated in an example.

  13. Comparison of the Radiative Two-Flux and Diffusion Approximations

    NASA Technical Reports Server (NTRS)

    Spuckler, Charles M.

    2006-01-01

    Approximate solutions are sometimes used to determine the heat transfer and temperatures in a semitransparent material in which conduction and thermal radiation are acting. A comparison of the Milne-Eddington two-flux approximation and the diffusion approximation for combined conduction and radiation heat transfer in a ceramic material was preformed to determine the accuracy of the diffusion solution. A plane gray semitransparent layer without a substrate and a non-gray semitransparent plane layer on an opaque substrate were considered. For the plane gray layer the material is semitransparent for all wavelengths and the scattering and absorption coefficients do not vary with wavelength. For the non-gray plane layer the material is semitransparent with constant absorption and scattering coefficients up to a specified wavelength. At higher wavelengths the non-gray plane layer is assumed to be opaque. The layers are heated on one side and cooled on the other by diffuse radiation and convection. The scattering and absorption coefficients were varied. The error in the diffusion approximation compared to the Milne-Eddington two flux approximation was obtained as a function of scattering coefficient and absorption coefficient. The percent difference in interface temperatures and heat flux through the layer obtained using the Milne-Eddington two-flux and diffusion approximations are presented as a function of scattering coefficient and absorption coefficient. The largest errors occur for high scattering and low absorption except for the back surface temperature of the plane gray layer where the error is also larger at low scattering and low absorption. It is shown that the accuracy of the diffusion approximation can be improved for some scattering and absorption conditions if a reflectance obtained from a Kubelka-Munk type two flux theory is used instead of a reflection obtained from the Fresnel equation. The Kubelka-Munk reflectance accounts for surface reflection and

  14. Pseudocompressible approximation and statistical turbulence modeling: application to shock tube flows.

    PubMed

    Soulard, Olivier; Griffond, Jérôme; Souffland, Denis

    2012-02-01

    In this work, a pseudocompressible approximation relevant for turbulent mixing flows encountered in shock tubes is derived. The asymptotic analysis used for this purpose puts forward the role played by four dimensionless numbers on the flow compressibility, namely, the turbulent, deformation, stratification, and buoyancy force Mach numbers. The existence of rapid distortion and diffusion-dissipation regimes is also accounted for in the analysis. Some consequences of the derived pseudocompressible approximation on statistical turbulence models are discussed. In particular, the evolutions of the density variance and flux are examined, as well as the turbulent transport of energy. The different aspects of this study are assessed by performing a direct numerical simulation of a shock tube flow configuration.

  15. Empty Flux Tubes and Plasmasphere Refilling as Seen by IMAGE

    NASA Technical Reports Server (NTRS)

    Adrian, M. L.; Gallagher, D. L.; Sandel, B. R.; Green, J. L.; Reinish, B.; Goldstein, J.; Huegrich, T.

    2002-01-01

    When a plasmaspheric flux tube is empty, what plasma is actually missing? When a flux tube refills, where does the plasma accumulate first? How long does it take to refill a flux tube to a level that is essentially saturated? Owing to the observational difficulties of measuring the distribution of plasmaspheric plasma along a flux tube, these questions have remained unanswered over many decades of study since discovery of the plasmasphere. They are important questions, because of the role that plasmaspheric plasma plays in collisional losses of higher energy populations, in modifying instabilities for wave-particle interactions, and in influencing the transport of energy through plasma waves. The Extreme Ultraviolet Imager and the Radio Plasma Imager on the IMAGE Mission are providing new, critical observations of the dynamic outer plasmasphere where convective erosion and refilling dominate. Latitudinal density profiles along a single L-shell from BPI confirm earlier indications of a mid-latitude transition between the altitude organized structure of the ionosphere and L-shell organized plasmasphere. Emptied flux tubes often mean empty only above about 1 Re in altitude or below plus or minus 40 degrees in magnetic latitude. Refilling to nearly saturated levels is found to take much less than that previously found necessary to complete the process. The observations behind these conclusions and the new light brought to plasmaspheric refilling will be discussed.

  16. CURRENT BUILDUP IN EMERGING SERPENTINE FLUX TUBES

    SciTech Connect

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

    2009-08-20

    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 {beta} 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.

  17. Energy propagation by transverse waves in multiple flux tube systems using filling factors

    SciTech Connect

    Van Doorsselaere, T.; Gijsen, S. E.; Andries, J.; Verth, G. E-mail: stief.gijsen@wis.kuleuven.be E-mail: g.verth@sheffield.ac.uk

    2014-11-01

    In the last few years, it has been found that transverse waves are present at all times in coronal loops or spicules. Their energy has been estimated with an expression derived for bulk Alfvén waves in homogeneous media, with correspondingly uniform wave energy density and flux. The kink mode, however, is localized in space with the energy density and flux dependent on the position in the cross-sectional plane. The more relevant quantities for the kink mode are the integrals of the energy density and flux over the cross-sectional plane. The present paper provides an approximation to the energy propagated by kink modes in an ensemble of flux tubes by means of combining the analysis of single flux tube kink oscillations with a filling factor for the tube cross-sectional area. This finally allows one to compare the expressions for energy flux of Alfvén waves with an ensemble of kink waves. We find that the correction factor for the energy in kink waves, compared to the bulk Alfvén waves, is between f and 2f, where f is the density filling factor of the ensemble of flux tubes.

  18. Temporal features of the refilling of a plasmaspheric flux tube

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Schunk, R. W.; Thiemann, H.

    1986-01-01

    The refilling of plasmaspheric flux tubes was studied by assuming that the protonosphere provides an ionospheric boundary where the H(+) density can be assumed; the supersonic flow in the flux tube is driven by the depletion of the plasma from the flux tube, while the base density and pressure in the protonosphere remain constant. The time-dependent continuity and momentum equations for the H(+) ions were solved. The electron gas was assumed to obey the Boltzmann law, and the proton gas was assumed to be isothermal. In agreement with the postulate of Banks et al. (1971), it was found that an important feature of the refilling is the formation of a shock pair at the equator; as the shocks propagate toward the ionosphere, the refilling occurs. Depending on the density at the ionospheric boundaries, a fair agreement was found between the refilling rates obtained for L = 6.6 and those from the GEOS 2 observations.

  19. A Flux Tube Solar Dynamo Model Based on the Competing Role of Buoyancy and Downflows

    NASA Astrophysics Data System (ADS)

    Li, L. H.; Sofia, S.; Belvedere, G.

    2005-08-01

    A magnetic flux tube can be considered both as a separate body and as a confined field. As a field, it is affected by both differential rotation (Ω-effect) and cyclonic convection (α-effect). As a body, the tube experiences not only a buoyant force, but also a dynamic pressure due to downflows above the tube. These two competing dynamic effects are incorporated into the α-Ω dynamo equations through the total magnetic turbulent diffusivity, leading to a flux tube dynamo operating in the convection zone. We analyze and solve the extended dynamo equations in the linear approximation by adopting the observed solar internal rotation and assuming a downflow effect derived from numerical simulations of a solar convection zone. The model reproduces the 22 yr cycle period; the extended butterfly diagram with the confinement of strong activity to low heliographic latitudes |Φ|<=35deg the evidence that at low latitudes the radial field is in an approximately π phase lag compared to the toroidal field at the same latitude; the evidence that the poleward branch is in a π/2 phase lag with respect to the equatorward branch; and the evidence that most of the magnetic flux is present in an intermittent form, concentrated into strong flux tubes.

  20. Magnetic field characters of returning flux tubes in Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Lai, Hairong; Russell, Christopher; Jia, Yingdong; Wei, Hanying

    2016-04-01

    Deep in the Saturnian magnetosphere, water-group neutrals are ionized after being released from the plume of Enceladus at 4 RS. This forms a plasma disk from 2.5 to 8 RS around Saturn and the typical source rate is 12~250 kg/s. Such plasma addition must be shed to the solar wind ultimately to maintain the plasma density in the magnetosphere in long term average. In this plasma transfer process, the magnetic flux also convects outward. To conserve the total magnetic flux imposed on the magnetosphere by the planet's internal dynamo, the magnetic flux has to return to the inner magnetosphere. Flux tubes are found to be the major form of such return. Determining such flux tubes is essential in understanding the breathing of Saturn magnetosphere. We investigated 10 years of Cassini magnetometer data to identify over six hundred flux-returning events between 4 and 18 in L. Statistical properties are presented, to constrain the origin, transport and evolution of these flux tubes.

  1. Signature of the Fragmentation of a Color Flux Tube

    DOE PAGES

    Wong, Cheuk-Yin

    2015-10-07

    The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of the local conservation of momentum and charge, the production of amore » $q$-$$\\bar q$$ pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced pions however can be signalled by the their rapidity difference $$\\Delta y$$ falling within the window of $$|\\Delta y | < 1/(dN_\\pi/dy)$$, on account of the space-time-rapidity ordering of produced pions in a flux tube fragmentation. Therefore, the local conservation of momentum will lead to a suppression of azimuthal two-pion correlation $$dN/(d\\Delta \\phi\\, d\\Delta y)$$ on the near side at $$(\\Delta \\phi, \\Delta y) \\sim 0$$, but an enhanced azimuthal correlation on the back-to-back, away side at $$(\\Delta \\phi$$$\\sim$$$ \\pi,\\Delta y$$$\\sim$$0). Similarly, in a flux tube fragmentation, the local conservation of charge will forbid the production of like charge pions within $$|\\Delta y | < 1/(dN_\\pi/dy)$$, but there is no such prohibition for $$|\\Delta y| >1/(dN_\\pi/dy)$$. These properties may be used as the signature for the fragmentation of a color flux tube.« less

  2. Signature of the Fragmentation of a Color Flux Tube

    SciTech Connect

    Wong, Cheuk-Yin

    2015-10-07

    The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of the local conservation of momentum and charge, the production of a $q$-$\\bar q$ pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced pions however can be signalled by the their rapidity difference $\\Delta y$ falling within the window of $|\\Delta y | < 1/(dN_\\pi/dy)$, on account of the space-time-rapidity ordering of produced pions in a flux tube fragmentation. Therefore, the local conservation of momentum will lead to a suppression of azimuthal two-pion correlation $dN/(d\\Delta \\phi\\, d\\Delta y)$ on the near side at $(\\Delta \\phi, \\Delta y) \\sim 0$, but an enhanced azimuthal correlation on the back-to-back, away side at $(\\Delta \\phi$$\\sim$$ \\pi,\\Delta y$$\\sim$0). Similarly, in a flux tube fragmentation, the local conservation of charge will forbid the production of like charge pions within $|\\Delta y | < 1/(dN_\\pi/dy)$, but there is no such prohibition for $|\\Delta y| >1/(dN_\\pi/dy)$. These properties may be used as the signature for the fragmentation of a color flux tube.

  3. Regge trajectories of exotic hadrons in the flux tube model

    NASA Astrophysics Data System (ADS)

    Nandan, Hemwati; Ranjan, Akhilesh

    2016-02-01

    We have investigated the Regge trajectories of exotic hadrons by considering different possible pentaquark configurations with finite quark mass in the flux tube model. Significant deviation is observed in the linear behavior of the Regge trajectories for pentaquark systems in view of the universal value of the Regge slope parameter for hadrons. The modified Regge trajectories are also compared with the available experimental and lattice data. It is observed that the nonlinear Regge trajectories of such pentaquark systems can be well described by the relativistic corrections in view of the current quark masses and the high rotational speed of the quarks at the end of flux tube structure.

  4. Dissipationless Damping of Compressive MHD Modes in Twisted Flux Tubes

    NASA Astrophysics Data System (ADS)

    Giagkiozis, I.; Fedun, V.; Verth, G.; Goossens, M. L.; Van Doorsselaere, T.

    2015-12-01

    Axisymmetric modes in straight magentic flux tubes exhibit a cutoff in the long wavelength limit and no damping is predicted. However, as soon as weak magnetic twist is introduced inside as well as outside the magnetic flux tube the cutoff recedes. Furthermore, when density variations are also incomporated within the modelresonant absorption appears. In this work we explore analytically the expected damping times for waves within the Alfven continuum for different solar atmospheric conditions. Based on the results in this work we offer insight on recent observations of sausage wave damping in the chromosphere.

  5. Explosive instability and erupting flux tubes in a magnetized plasma

    PubMed Central

    Cowley, S. C.; Cowley, B.; Henneberg, S. A.; Wilson, H. R.

    2015-01-01

    The eruption of multiple flux tubes in a magnetized plasma is proposed as a mechanism for explosive release of energy in plasmas. A significant fraction of the linearly stable isolated flux tubes are shown to be metastable in a box model magnetized atmosphere in which ends of the field lines are embedded in conducting walls. The energy released by destabilizing such field lines can be a large proportion of the gravitational energy stored in the system. This energy can be released in a fast dynamical time. PMID:26339193

  6. The Color Flux Tube as an Effective String

    NASA Astrophysics Data System (ADS)

    Pepe, Michele

    2011-05-01

    We investigate the low-energy regime of the confining string connecting color sources in Yang-Mills theory. First, we present results of the Monte Carlo measurement of the width of the flux tube between two static quarks in the fundamental representation both at zero and at finite temperature. Then we consider the confining flux tube connecting color sources in larger representations of the gauge group. For stable strings—the k-strings—we study the Luscher term; for unstable strings we investigate their decay as the distance between the static sources is increased.

  7. Estimation of the flux tube diameters outside sunspots using Hinode observations. Preliminary results

    NASA Astrophysics Data System (ADS)

    Botygina, O. O.; Gordovskyy, M. Yu.; Lozitsky, V. G.

    2016-09-01

    Indirect estimations of diameters of the smallest flux tubes outside sunspots are made using SOT/Hinode observations of Fe I 6301.5 and 6302.5 lines. These estimations are based on the comparison of measured effective magnetic field strength B_{eff} in named lines. It is shown that B_{eff}(6301.5)/B_{eff}(6302.5)≈ 1.3 in the range B_{eff}=40-300 G, and B_{eff} (6301.5)/B_{eff}(6302.5)≈.0 for B_{eff}≤10-20 G. The first case corresponds to the two-component magnetic field with kG flux tubes and weak background field, whereas the second one corresponds to background field without flux tubes. Assuming that the field range B_{eff}=10-40 G corresponds to the case with only one flux tube in each pixel, the flux tube diameters should be 15-30 km. Possible influence of the brightness contrast and the Zeeman saturation could change this estimation by approximately 20%.

  8. Flux limiters. [for shock tube flow computation

    NASA Technical Reports Server (NTRS)

    Sweby, P. K.

    1985-01-01

    It is well known that first order accurate difference schemes for the numerical solution of conservation laws produce results which suffer from excessive numerical diffusion, classical second order schemes, although giving better resolution, suffer from spurious oscillations. Recently much effect has been put into achieving high resolution without these oscillations, using a variety of techniques. Here one class of such methods, that of flux limiting, is outlined together with the TVD constraint used to ensure oscillation free solutions. Brief numerical comparisons of different limiting functions are also presented.

  9. Sunspots and the physics of magnetic flux tubes. I - The general nature of the sunspot. II - Aerodynamic drag

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1979-01-01

    Analysis of the dynamical stability of a large flux tube suggests that the field of a sunspot must divide into many separate tubes within the first 1000 km below the surface. Buoyancy of the Wilson depression at the visible surface and probably also a downdraft beneath the sunspot hold the separate tubes in a loose cluster. Convective generation of Alfven waves, which are emitted preferentially downward, cools the tubes. Aerodynamic drag on a slender flux tube stretched vertically across a convective cell is also studied. Since the drag is approximately proportional to the local kinetic energy density, the density stratification weights the drag in favor of the upper layers. Horizontal motions concentrated in the bottom of the convective cell may reverse this density effect. A downdraft of about two km/sec through the flux tubes beneath the sunspot is hypothesized.

  10. Lagrange mesh, relativistic flux tube, and rotating string.

    PubMed

    Buisseret, Fabien; Semay, Claude

    2005-02-01

    The Lagrange mesh method is a very accurate and simple procedure to compute eigenvalues and eigenfunctions of nonrelativistic and semirelativistic Hamiltonians. We show here that it can be used successfully to solve the equations of both the relativistic flux tube model and the rotating string model, in the symmetric case. Verifications of the convergence of the method are given.

  11. Reconnection Between Twisted Flux Tubes - Implications for Coronal Heating

    NASA Astrophysics Data System (ADS)

    Knizhnik, K. J.; Antiochos, S. K.; DeVore, C. R.; Klimchuk, J. A.; Wyper, P. F.

    2015-12-01

    The nature of the heating of the Sun's corona has been a long-standing unanswered problem in solar physics. Beginning with the work of Parker (1972), many authors have argued that the corona is continuously heated through numerous small-scale reconnection events known as nanoflares. In these nanoflare models, stressing of magnetic flux tubes by photospheric motions causes the field to become misaligned, producing current sheets in the corona. These current sheets then reconnect, converting the free energy stored in the magnetic field into heat. In this work, we use the Adaptively Refined MHD Solver (ARMS) to perform 3D MHD simulations that dynamically resolve regions of strong current to study the reconnection between twisted flux tubes in a plane-parallel Parker configuration. We investigate the energetics of the process, and show that the flux tubes accumulate stress gradually before undergoing impulsive reconnection. We study the motion of the individual field lines during reconnection, and demonstrate that the connectivity of the configuration becomes extremely complex, with multiple current sheets being formed, which could lead to enhanced heating. In addition, we show that there is considerable interaction between the twisted flux tubes and the surrounding untwisted field, which contributes further to the formation of current sheets. The implications for observations will be discussed. This work was funded by a NASA Earth and Space Science Fellowship, and by the NASA TR&T Program.

  12. Statistical Flux Tube Properties of 3D Magnetic Carpet Fields

    NASA Astrophysics Data System (ADS)

    Close, R. M.; Parnell, C. E.; Mackay, D. H.; Priest, E. R.

    2003-02-01

    The quiet-Sun photosphere consists of numerous magnetic flux fragments of both polarities that evolve with granular and supergranular flow fields. These concentrations give rise to a web of intermingled magnetic flux tubes which characterise the coronal magnetic field. Here, the nature of these flux tubes is studied. The photosphere is taken to be the source plane and each photospheric fragment is represented by a series of point sources. By analysing the potential field produced by these sources, it is found that the distribution of flux tube lengths obtained by (i) integrating forward from positive sources and (ii) tracing back from negative sources is highly dependent on the total flux imbalance within the region of interest. It is established that the relation between the footpoint separation of a flux tube and its height cannot be assumed to be linear. Where there is a significant imbalance of flux within a region, it is found that fragments of the dominant polarity will have noticeably more connections, on average, than the minority polarity fragments. Despite this difference, the flux from a single fragment of either polarity is typically divided such that (i) 60-70% connects to one opposite-polarity fragment, (ii) 25-30% goes to a further 1 to 2 opposite-polarity fragments, and (iii) any remaining flux may connect to as many as another 50 or more other opposite-polarity fragments. This is true regardless of any flux imbalance within the region. It is found that fragments connect preferentially to their nearest neighbours, with, on average, around 60-70% of flux closing down within 10 Mm of a typical fragment. Only 50% of the flux in a quiet region extends higher than 2.5 Mm above the solar surface and 5-10% extends higher than 25 Mm. The fragments that contribute to the field above this height cover a range of sizes, with even the smallest of fragments contributing to the field at heights of over 50 Mm.

  13. Modeling the Subsurface Evolution of Active-Region Flux Tubes

    NASA Astrophysics Data System (ADS)

    Fan, Y.

    2009-12-01

    I present results from a set of 3-D spherical-shell MHD simulations of the buoyant rise of active region flux tubes in the solar interior that put new constraints on the initial twist of the subsurface tubes in order for them to emerge with tilt angles consistent with the observed Joy's law for the mean tilt of solar active regions. Due to asymmetric stretching of the Ω-shaped tube by the Coriolis force, a field strength asymmetry develops with the leading side having a greater field strength and thus being more cohesive compared to the following side. Furthermore, the magnetic flux in the leading leg shows more coherent values of local twist α ≡ JB / B2, whereas the values in the following leg show large fluctuations and are of mixed signs.

  14. Doppler displacements in kink MHD waves in solar flux tubes

    NASA Astrophysics Data System (ADS)

    Goossens, Marcel; Van Doorsselaere, Tom; Terradas, Jaume; Verth, Gary; Soler, Roberto

    Doppler displacements in kink MHD waves in solar flux tubes Presenting author: M. Goossens Co-authors: R. Soler, J. Terradas, T. Van Doorsselaere, G. Verth The standard interpretation of the transverse MHD waves observed in the solar atmosphere is that they are non-axisymmetric kink m=1) waves on magnetic flux tubes. This interpretation is based on the fact that axisymmetric and non-axisymmetric fluting waves do not displace the axis of the loop and the loop as a whole while kink waves indeed do so. A uniform transverse motion produces a Doppler displacement that is constant across the magnetic flux tube. A recent development is the observation of Doppler displacements that vary across the loop. The aim of the present contribution is to show that spatial variations of the Doppler displacements across the loop can be caused by kink waves. The motion associated with a kink wave is purely transverse only when the flux tube is uniform and sufficiently thin. Only in that case do the radial and azimuthal components of displacement have the same amplitude and is the azimuthal component a quarter of a period ahead of the radial component. This results in a unidirectional or transverse displacement. When the flux tube is non-uniform and has a non-zero radius the conditions for the generation of a purely transverse motion are not any longer met. In that case the motion in a kink wave is the sum of a transverse motion and a non-axisymmetric rotational motion that depends on the azimuthal angle. It can produce complicated variations of the Doppler displacement across the loop. I shall discuss the various cases of possible Doppler displacenents that can occur depending on the relative sizes of the amplitudes of the radial and azimuthal components of the displacement in the kink wave and on the orientation of the line of sight.

  15. MULTIPLE SCATTERING OF WAVES BY A PAIR OF GRAVITATIONALLY STRATIFIED FLUX TUBES

    SciTech Connect

    Hanasoge, Shravan M.; Cally, Paul S.

    2009-05-20

    We study the near-field coupling of a pair of flux tubes embedded in a gravitationally stratified environment. The mutual induction of the near-field jackets of the two flux tubes can considerably alter the scattering properties of the system, resulting in sizable changes in the magnitudes of scattering coefficients and bizarre trends in the phases. The dominant length scale governing the induction zone turns out to be approximately half the horizontal wavelength of the incident mode, a result that fits in quite pleasantly with extant theories of scattering. Higher-{beta} flux tubes are more strongly coupled than weaker ones, a consequence of the greater role that the near-field jacket modes play in such tubes. We also comment on the importance of incorporating the effects of multiple scattering when studying the effects of mode absorption in plage and interpreting related scattering measurements. That the near field plays such an important role in the scattering process lends encouragement to the eventual goal of observationally resolving subwavelength features of flux tubes using techniques of helioseismology.

  16. The delta-Eddington approximation for radiative flux transfer

    NASA Technical Reports Server (NTRS)

    Joseph, J. H.; Wiscombe, W. J.; Weinman, J. A.

    1976-01-01

    Simple approximations, like the Eddington, are often incapable of coping with the highly asymmetric phase functions typical of particulate scattering. A simple yet accurate method called the delta-Eddington approximation is proposed for determining monochromatic radiative fluxes in an absorbing-scattering atmosphere. In this method, the governing phase function is approximated by a Dirac delta function forward scatter peak and a two-term expansion of the phase function. The fraction of scattering into the truncated forward peak is taken proportional to the square of the phase function asymmetry factor, which distinguishes the delta-Eddington approximation from others of similar nature. The transmission, reflection, and absorption predicted by the delta-Eddington approximation are compared with doubling method calculations for realistic ranges of optical depth, single-scattering albedo, surface albedo, sun angle and asymmetry factor. The approximation is shown to provide an accurate and analytically simple parameterization of radiation to replace the empirism currently encountered in many general circulation and climate models.

  17. Evidence of Twisted Flux-Tube Emergence in Active Regions

    NASA Astrophysics Data System (ADS)

    Poisson, M.; Mandrini, C. H.; Démoulin, P.; López Fuentes, M.

    2015-03-01

    Elongated magnetic polarities are observed during the emergence phase of bipolar active regions (ARs). These extended features, called magnetic tongues, are interpreted as a consequence of the azimuthal component of the magnetic flux in the toroidal flux-tubes that form ARs. We develop a new systematic and user-independent method to identify AR tongues. Our method is based on determining and analyzing the evolution of the AR main polarity inversion line (PIL). The effect of the tongues is quantified by measuring the acute angle [ τ] between the orientation of the PIL and the direction orthogonal to the AR main bipolar axis. We apply a simple model to simulate the emergence of a bipolar AR. This model lets us interpret the effect of magnetic tongues on parameters that characterize ARs ( e.g. the PIL inclination and the tilt angles, and their evolution). In this idealized kinematic emergence model, τ is a monotonically increasing function of the twist and has the same sign as the magnetic helicity. We systematically apply our procedure to a set of bipolar ARs (41 ARs) that were observed emerging in line-of-sight magnetograms over eight years. For most of the cases studied, the tongues only have a small influence on the AR tilt angle since tongues have a much lower magnetic flux than the more concentrated main polarities. From the observed evolution of τ, corrected for the temporal evolution of the tilt angle and its final value when the AR is fully emerged, we estimate the average number of turns in the subphotospherically emerging flux-rope. These values for the 41 observed ARs are below unity, except for one. This indicates that subphotospheric flux-ropes typically have a low amount of twist, i.e. highly twisted flux-tubes are rare. Our results demonstrate that the evolution of the PIL is a robust indicator of the presence of tongues and constrains the amount of twist in emerging flux-tubes.

  18. Achieving Zero Current for Polar Wind Outflow on Open Flux Tubes Subjected to Large Photoelectron Fluxes

    NASA Technical Reports Server (NTRS)

    Wilson, G. R.; Khazanov, G.; Horwitz, J. L.

    1997-01-01

    In this study we investigate how the condition of zero current on open flux tubes with polar wind outflow, subjected to large photoelectron fluxes, can be achieved. We employ a steady state collisionless semikinetic model to determine the density profiles of O(+), H(+), thermal electrons and photoelectrons coming from the ionosphere along with H(+), ions and electrons coming from the magnetosphere. The model solution attains a potential distribution which both satisfies the condition of charge neutrality and zero current. For the range of parameters considered in this study we find that a 45-60 volt discontinuous potential drop may develop to reflect most of the photoelectrons back toward the ionosphere. This develops because the downward flux of electrons from the magnetosphere to the ionosphere on typical open flux tubes (e.g. the polar rain) appears to be insufficient to balance the photoelectron flux from the ionosphere.

  19. Low thermal flux glass-fiber tubing for cryogenic service.

    NASA Technical Reports Server (NTRS)

    Hall, C. A.; Pharo, T. J., Jr.; Phillips, J. M.

    1972-01-01

    Study of thin metallic liners which provide leak-free service in cryogenic propulsion plumbing systems and are overwrapped with a glass-fiber composite that provides strength and protection from handling damage. The composite tube is lightweight, strong, and has a very low thermal flux. The resultant reduced boiloff of stored cryogenic propellants yields a substantial weight savings for long-term missions (seven days or greater). Twelve styles of tubing ranging from 1/2 to 5 in. in diameter were fabricated and tested with excellent results for most of the concepts at operating temperatures from +70 to -423 F and operating pressures up to 3000 psi.

  20. Pair creation in an electric flux tube and chiral anomaly

    SciTech Connect

    Iwazaki, Aiichi

    2009-11-15

    Using the chiral anomaly, we discuss the pair creation of massless fermions under the effect of a magnetic field B-vector when an electric flux tube E-vector parallel to B-vector is switched on. The tube is axially symmetric and infinitely long. For the constraint B>>E, we can analytically obtain the spatial and temporal behaviors of the number density of the fermions, the azimuthal magnetic field generated by the fermions, and so on. We find that the lifetime t{sub c} of the electric field becomes shorter as the width of the tube becomes narrower. Applying it to the plasma in high-energy heavy-ion collisions, we find that the color electric field decays quickly such that t{sub c}{approx_equal}Q{sub s}{sup -1}, in which Q{sub s} is the saturation momentum.

  1. From QCD Flux Tubes to Gravitational S-matrix and Back

    NASA Astrophysics Data System (ADS)

    Gorbenko, Victor

    We study the effective field theory of long relativistic strings such as confining flux tubes in QCD. Our main focus is on the scattering matrix of massless exci- tations propagating on the string’s worldsheet. The Lorentz invariance of QCD manifests itself in certain soft theorems satisfied by the amplitudes. We find that critical dimension appears as a condition that allows this scattering to be inte- grable and consequently flux tubes in four-dimensional QCD do not fall into this category. In case of the critical dimension equal to 26, however, we are able to find a full integrable S-matrix that exhibits many features expected from gravi- tational models. Moreover, it gives rise to a family of not necessarily integrable two-dimensional theories that inherit very peculiar UV-properties. We discuss im- plication of this construction for the hierarchy problem. We then return to the QCD flux tubes and find that integrability-inspired techniques can be applied to them in an approximate way that allows us to calculate their spectrum in the regime inaccessible for standard perturbation theory. In particular, analysis of the lattice data allows us to identify the first massive particle present on the world sheet of the QCD flux tube.

  2. A Multiple Flux-tube Solar Wind Model

    NASA Astrophysics Data System (ADS)

    Pinto, Rui F.; Rouillard, Alexis P.

    2017-04-01

    We present a new model, MULTI-VP, which computes the three-dimensional structure of the solar wind and includes the chromosphere, the transition region, and the corona and low heliosphere. MULTI-VP calculates a large ensemble of wind profiles flowing along open magnetic field lines that sample the entire three-dimensional atmosphere or, alternatively, a given region of interest. The radial domain starts from the photosphere and typically extends to about 30 {R}ȯ . The elementary uni-dimensional wind solutions are based on a mature numerical scheme that was adapted in order to accept any flux-tube geometry. We discuss here the first results obtained with this model. We use Potential Field Source-surface extrapolations of magnetograms from the Wilcox Solar Observatory to determine the structure of the background magnetic field. Our results support the hypothesis that the geometry of the magnetic flux-tubes in the lower corona controls the distribution of slow and fast wind flows. The inverse correlation between density and speed far away from the Sun is a global effect resulting from small readjustments of the flux-tube cross-sections in the high corona (necessary to achieve global pressure balance and a uniform open flux distribution). In comparison to current global MHD models, MULTI-VP performs much faster and does not suffer from spurious cross-field diffusion effects. We show that MULTI-VP has the capability to predict correctly the dynamical and thermal properties of the background solar wind (wind speed, density, temperature, magnetic field amplitude, and other derived quantities) and to approach real-time operation requirements.

  3. The equilibrium structure of thin magnetic flux tubes. II. [in sun and late stars

    NASA Technical Reports Server (NTRS)

    Kalkofen, W.; Rosner, R.; Ferrari, A.; Massaglia, S.

    1986-01-01

    The thermal structure of the medium inside thin, vertical magnetic flux tubes embedded in a given external atmosphere is investigated, assuming cylindrical symmetry and a depth-independent plasma beta. The variation with tube radius of the temperature on the tube axis is computed and the temperature on the tube wall is estimated. The temperature variation across the flux tube is found to be due to the depth variation of the intensity and to the density stratification of the atmosphere. Since the temperature difference between the axis and the wall is small in thin flux tubes (of the order of 10 percent), the horizontal temperature gradient may often be neglected and the temperature in a tube of given radius may be described by a single function of depth. Thus, a more detailed numerical treatment of the radiative transfer within thin flux tubes can be substantially simplified by neglecting horizontal temperature differences within the flux tube proper.

  4. A multiscale two-point flux-approximation method

    SciTech Connect

    Møyner, Olav Lie, Knut-Andreas

    2014-10-15

    A large number of multiscale finite-volume methods have been developed over the past decade to compute conservative approximations to multiphase flow problems in heterogeneous porous media. In particular, several iterative and algebraic multiscale frameworks that seek to reduce the fine-scale residual towards machine precision have been presented. Common for all such methods is that they rely on a compatible primal–dual coarse partition, which makes it challenging to extend them to stratigraphic and unstructured grids. Herein, we propose a general idea for how one can formulate multiscale finite-volume methods using only a primal coarse partition. To this end, we use two key ingredients that are computed numerically: (i) elementary functions that correspond to flow solutions used in transmissibility upscaling, and (ii) partition-of-unity functions used to combine elementary functions into basis functions. We exemplify the idea by deriving a multiscale two-point flux-approximation (MsTPFA) method, which is robust with regards to strong heterogeneities in the permeability field and can easily handle general grids with unstructured fine- and coarse-scale connections. The method can easily be adapted to arbitrary levels of coarsening, and can be used both as a standalone solver and as a preconditioner. Several numerical experiments are presented to demonstrate that the MsTPFA method can be used to solve elliptic pressure problems on a wide variety of geological models in a robust and efficient manner.

  5. Propagation of nonlinear, radiatively damped longitudinal waves along magnetic flux tubes in the solar atmosphere

    NASA Technical Reports Server (NTRS)

    Herbold, G.; Ulmschneider, P.; Spruit, H. C.; Rosner, R.

    1985-01-01

    For solar magnetic flux tubes three types of waves are compared: longitudinal MHD tube waves, acoustic tube waves propagating in the same tube geometry but with rigid walls and ordinary acoustic waves in plane geometry. It is found that the effect of the distensibility of the tube is small and that longitudinal waves are essentially acoustic tube waves. Due to the tube geometry there is considerable difference between longitudinal waves or acoustic tube waves and ordinary acoustic waves. Longitudinal waves as well as acoustic tube waves show a smaller amplitude growth, larger shock formation heights, smaller mean chromospheric temperature but a steeper dependence of the temperature gradient on wave period.

  6. Investigating the Dynamics of Canonical Flux Tubes in Jet Geometry

    NASA Astrophysics Data System (ADS)

    Lavine, Eric; You, Setthivoine

    2014-10-01

    Highly collimated plasma jets are frequently observed at galactic, stellar, and laboratory scales. Some models suppose these jets are magnetohydrodynamically-driven magnetic flux tubes filled with flowing plasma, but they do not agree on a collimation process. Some evidence supporting a universal MHD pumping mechanism has been obtained from planar electrode experiments with aspect ratios of ~10:1 however, these jets are subject to kink instabilities beyond a certain length and are unable to replicate the remarkable aspect ratios (10-1000:1) seen in astrophysical systems. Other models suppose these jets are flowing Z-pinch plasmas and experiments that use stabilizing shear flows have achieved aspect ratios of ~30:1, but are line tied at both ends. Can both collimation and stabilization mechanisms work together to produce long jets without kink instabilities and only one end tied to the central object? This question is evaluated from the point of view of canonical flux tubes and canonical helicity transport, indicating that jets can become long and collimated due to a combination of strong helical shear flows and conversion of magnetic helicity into kinetic helicity. The MOCHI LabJet experiment is designed to study this in the laboratory. Supported by US DoE Early Career Grant DE-SC0010340.

  7. Dynamic Flux Tubes Form Reservoirs of Stability in Neuronal Circuits

    NASA Astrophysics Data System (ADS)

    Monteforte, Michael; Wolf, Fred

    2012-10-01

    Neurons in cerebral cortical circuits interact by sending and receiving electrical impulses called spikes. The ongoing spiking activity of cortical circuits is fundamental to many cognitive functions including sensory processing, working memory, and decision making. London et al. [Sensitivity to Perturbations In Vivo Implies High Noise and Suggests Rate Coding in Cortex, Nature (London)NATUAS0028-0836 466, 123 (2010).10.1038/nature09086] recently argued that even a single additional spike can cause a cascade of extra spikes that rapidly decorrelate the microstate of the network. Here, we show theoretically in a minimal model of cortical neuronal circuits that single-spike perturbations trigger only a very weak rate response. Nevertheless, single-spike perturbations are found to rapidly decorrelate the microstate of the network, although the dynamics is stable with respect to small perturbations. The coexistence of stable and unstable dynamics results from a system of exponentially separating dynamic flux tubes around stable trajectories in the network’s phase space. The radius of these flux tubes appears to decrease algebraically with neuron number N and connectivity K, which implies that the entropy of the circuit’s repertoire of state sequences scales as Nln⁡(KN).

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

    SciTech Connect

    Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

    2006-07-01

    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 ({delta}T{sub sub,in} = 48.6 to 154.7 K), the inlet pressure (P{sub in} = 735.2 to 969.0 kPa) and the increasing heat input (Q{sub 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{sub a} = 3.18 {mu}m), the Cupro Nickel (Cu-Ni 30%) test tubes of d = 6 mm, L = 60 mm and L/d = 10 with R{sub a} = 0.18 {mu}m 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{sub a} = 0.45 {mu}m 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)

  9. NUMERICAL SIMULATIONS OF MULTIPLE SCATTERING OF THE f-MODE BY FLUX TUBES

    SciTech Connect

    Felipe, T.; Crouch, A.; Birch, A.

    2013-09-20

    We use numerical simulations to study the absorption and phase shift of surface-gravity waves caused by groups of magnetic flux tubes. The dependence of the scattering coefficients on the distance between the tubes and their positions is analyzed for several cases with two or three flux tubes embedded in a quiet Sun atmosphere. The results are compared with those obtained neglecting completely or partially multiple scattering effects. We show that multiple scattering has a significant impact on the absorption measurements and tends to reduce the phase shift. We also consider more general cases of ensembles of randomly distributed flux tubes, and we have evaluated the effects on the scattering measurements of changing the number of tubes included in the bundle and the average distance between flux tubes. We find that for the longest wavelength incoming waves, multiple scattering enhances the absorption, and its efficiency increases with the number of flux tubes and the reduction of the distance between them.

  10. Dynamics of Magnetic Flux Tubes in an Advective Flow around a Black Hole

    NASA Astrophysics Data System (ADS)

    Deb, Arnab; Chakrabarti, Sandip Kumar; Giri, Kinsuk

    2016-07-01

    Magnetic fields cannibalized by an accretion flow would very soon have a dominant toroidal component. Without changing the topology, we study the movements of these flux tubes inside a geometrically thick advective disk which undergo centrifugal pressure supported shocks. We also consider the effects of the flux tubes on the flow. We use a finite element method (Total Variation Diminishing) for this purpose and specifically focussed whether the flux tubes contribute to changes in outflow properties in terms of its collimation and outflow rates. It is seen that depending upon the cross sectional radius of the flux tubes (which control the drag force), these field lines may move towards the central object or oscillate vertically before eventually escaping out of the funnel wall (pressure zero surface). These interesting results obtained with and without flux tubes point to the role the flux tubes play in collimation of jets and outflows.

  11. KELVIN-HELMHOLTZ INSTABILITY IN CORONAL MAGNETIC FLUX TUBES DUE TO AZIMUTHAL SHEAR FLOWS

    SciTech Connect

    Soler, R.; Terradas, J.; Oliver, R.; Ballester, J. L.; Goossens, M.

    2010-04-01

    Transverse oscillations of coronal loops are often observed and have been theoretically interpreted as kink magnetohydrodynamic (MHD) modes. Numerical simulations by Terradas et al. suggest that shear flows generated at the loop boundary during kink oscillations could give rise to a Kelvin-Helmholtz instability (KHI). Here, we investigate the linear stage of the KHI in a cylindrical magnetic flux tube in the presence of azimuthal shear motions. We consider the basic, linearized MHD equations in the beta = 0 approximation and apply them to a straight and homogeneous cylindrical flux tube model embedded in a coronal environment. Azimuthal shear flows with a sharp jump of the velocity at the cylinder boundary are included in the model. We obtain an analytical expression for the dispersion relation of the unstable MHD modes supported by the configuration, and compute analytical approximations of the critical velocity shear and the KHI growth rate in the thin tube limit. A parametric study of the KHI growth rates is performed by numerically solving the full dispersion relation. We find that fluting-like modes can develop a KHI in timescales comparable to the period of kink oscillations of the flux tube. The KHI growth rates increase with the value of the azimuthal wavenumber and decrease with the longitudinal wavenumber. However, the presence of a small azimuthal component of the magnetic field can suppress the KHI. Azimuthal motions related to kink oscillations of untwisted coronal loops may trigger a KHI, but this phenomenon has not been observed to date. We propose that the azimuthal component of the magnetic field is responsible for suppressing the KHI in a stable coronal loop. The required twist is small enough to prevent the development of the pinch instability.

  12. Nonlinear fast sausage waves in homogeneous magnetic flux tubes

    NASA Astrophysics Data System (ADS)

    Mikhalyaev, Badma B.; Ruderman, Michael S.

    2015-12-01

    > We consider fast sausage waves in straight homogeneous magnetic tubes. The plasma motion is described by the ideal magnetohydrodynamic equations in the cold plasma approximation. We derive the nonlinear Schrödinger equation describing the nonlinear evolution of an envelope of a carrier wave. The coefficients of this equation are expressed in terms Bessel and modified Bessel functions. They are calculated numerically for various values of parameters. In particular, we show that the criterion for the onset of the modulational or Benjamin-Fair instability is satisfied. The implication of the obtained results for solar physics is discussed.

  13. A magnetohydrodynamic simulation of the formation of magnetic flux tubes at the earth's dayside magnetopause

    NASA Technical Reports Server (NTRS)

    Ogino, Tatsuki; Walker, Raymond J.; Ashour-Abdalla, Maha

    1989-01-01

    Dayside magnetic reconnection was studied by using a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. Two different mechanisms were found for the formation of magnetic flux tubes at the dayside magnetopause, which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large B(y) component. When the B(y) component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection.

  14. A magnetohydrodynamic simulation of the formation of magnetic flux tubes at the Earth's dayside magnetopause

    SciTech Connect

    Ogino, Tatsuki ); Walker, R.J.; Ashour-Abdalla, Maha )

    1989-02-01

    The authors have studied dayside magnetic reconnection by using a three-dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. They found two different mechanisms for the formation of magnetic flux tubes at the dayside magnetopause which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large B{sub y} component. When the B{sub y} component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection.

  15. Flux tube train model for local turbulence simulation of toroidal plasmas

    SciTech Connect

    Watanabe, T.-H.; Sugama, H.; Ishizawa, A.; Nunami, M.

    2015-02-15

    A new simulation method for local turbulence in toroidal plasmas is developed by extending the conventional idea of the flux tube model. In the new approach, a train of flux tubes is employed, where flux tube simulation boxes are serially connected at each end along a field line so as to preserve a symmetry of the local gyrokinetic equations for image modes in an axisymmetric torus. Validity of the flux tube train model is confirmed against the toroidal ion temperature gradient turbulence for a case with a long parallel correlation of fluctuations, demonstrating numerical advantages over the conventional method in the time step size and the symmetry-preserving property.

  16. Plasma dynamics on current-carrying magnetic flux tubes

    NASA Technical Reports Server (NTRS)

    Swift, Daniel W.

    1992-01-01

    A 1D numerical simulation is used to investigate the evolution of a plasma in a current-carrying magnetic flux tube of variable cross section. A large potential difference, parallel to the magnetic field, is applied across the domain. The result is that density minimum tends to deepen, primarily in the cathode end, and the entire potential drop becomes concentrated across the region of density minimum. The evolution of the simulation shows some sensitivity to particle boundary conditions, but the simulations inevitably evolve into a final state with a nearly stationary double layer near the cathode end. The simulation results are at sufficient variance with observations that it appears unlikely that auroral electrons can be explained by a simple process of acceleration through a field-aligned potential drop.

  17. Radiative Heating and the Buoyant Rise of Magnetic Flux Tubes in the Solar interior

    NASA Astrophysics Data System (ADS)

    Fan, Y.; Fisher, G. H.

    1996-06-01

    We study the effect of radiative heating on the evolution of thin magnetic flux tubes in the solar interior and on the eruption of magnetic flux loops to the surface. Magnetic flux tubes experience radiative heating because (1) the mean temperature gradient in the lower convection zone and the overshoot region deviates substantially from that of radiative equilibrium, and hence there is a non-zero divergence of radiative heat flux; and (2) the magnetic pressure of the flux tube causes a small change of the thermodynamic properties within the tube relative to the surrounding field-free fluid, resulting in an additional divergence of radiative heat flux. Our calculations show that the former constitutes the dominant source of radiative heating experienced by the flux tube. In the overshoot region, the radiative heating is found to cause a quasi-static rising of the toroidal flux tubes with an upward drift velocity ˜ 10-3|δ| cm s-1, where δ ≡ ∇e - ∇ad < 0 describes the subadiabaticity in the overshoot layer. The upward drift velocity does not depend sensitively on the field strength of the flux tubes. Thus in order to store toroidal flux tubes in the overshoot region for a period comparable to the length of the solar cycle, the magnitude of the subadiabaticity δ(< 0) in the overshoot region must be as large as ˜ 3 × 10-4. We discuss the possibilities for increasing the magnitude of δ and for reducing the rate of radiative heating of the flux tubes in the overshoot region. Using numerical simulations we study the formation of ‘Ω’-shaped emerging loops from toroidal flux tubes in the overshoot region as a result of radiative heating. The initial toroidal tube is assumed to be non-uniform in its thermodynamic properties along the tube and lies at varying depths beneath the base of the convection zone. The tube is initially in a state of neutral buoyancy with the internal density of the tube plasma equal to the local external density. We find from our

  18. AN ESTIMATE OF THE DETECTABILITY OF RISING FLUX TUBES

    SciTech Connect

    Birch, A. C.; Braun, D. C.; Fan, Y.

    2010-11-10

    The physics of the formation of magnetic active regions (ARs) is one of the most important problems in solar physics. One main class of theories suggests that ARs are the result of magnetic flux that rises from the tachocline. Time-distance helioseismology, which is based on measurements of wave propagation, promises to allow the study of the subsurface behavior of this magnetic flux. Here, we use a model for a buoyant magnetic flux concentration together with the ray approximation to show that the dominant effect on the wave propagation is expected to be from the roughly 100 m s{sup -1} retrograde flow associated with the rising flux. Using a B-spline-based method for carrying out inversions of wave travel times for flows in spherical geometry, we show that at 3 days before emergence the detection of this retrograde flow at a depth of 30 Mm should be possible with a signal-to-noise level of about 8 with a sample of 150 emerging ARs.

  19. Approximation to the Probability Density at the Output of a Photmultiplier Tube

    NASA Technical Reports Server (NTRS)

    Stokey, R. J.; Lee, P. J.

    1983-01-01

    The probability density of the integrated output of a photomultiplier tube (PMT) is approximated by the Gaussian, Rayleigh, and Gamma probability densities. The accuracy of the approximations depends on the signal energy alpha: the Gamma distribution is accurate for all alpha, the Raleigh distribution is accurate for small alpha (approximate or less than 1 photon) and the Gaussian distribution is accurate for large alpha (approximate or greater than 10 photons).

  20. Refilling of geosynchronous flux tubes as observed at the equator by GEOS 2

    SciTech Connect

    Sojka, J.J.; Wrenn, G.L.

    1985-07-01

    During periods of extended quiet geomagnetic activity the geosynchronous satellite orbit lies inside the plasmasphere. Five such periods were observed by the GEOS 2 satellite. During the initial 48 hours of such periods the equatorial plasma flux tube density increases at 30 to 50 per cu cm/day. However, on reaching approximately 100 per cu cm the refilling rate decreases, and refilling is limited. Only when the density reaches approximately 100 per cu cm do the plasma characteristics and fluctuations appear to be plasmaspheric and the flow predominantly corotational. The hot outer zone of the plasmasphere is highly structured in density and temperature when viewed from a corotating satellite. This region also has a relatively dense population of warm subkilovolt electrons. These warm electrons whose density is approximately 1 percent to 50 percent of the cold plasma may be the heat source for the hot outer zone ions. 36 references.

  1. Riemannian geometry of twisted magnetic flux tubes in almost helical plasma flows

    SciTech Connect

    Garcia de Andrade, L.C.

    2006-02-15

    Riemannian geometry of curves applied recently by Ricca [Fluid Dyn. Res 36, 319 (2005)] in the case of inflectional disequilibrium of twisted magnetic flux tubes is used here to compute the magnetic helicity force-free field case. Here the application of Lorentz force-free to the magnetic flux tube in tokamaks allows one to obtain an equation that generalizes the cylindrical tokamak equation by a term that contains the curvature of the magnetic flux tube. Another example of the use of the magnetic flux tube is done by taking the electron magnetohydrodynamics (MHD) fluid model (EMHD) of plasma physics that allows one to compute the velocity of the fluid in helical and almost helical flows in terms of the Frenet torsion of thin magnetic flux tubes. The cases of straight and curved twisted tubes are examined. Second-order effects on the Frenet torsion arise on the poloidal component of the magnetic field, while curvature effects appear in the toroidal component. The magnetic fields are computed in terms of the penetration depth used in superconductors. The ratio between poloidal and toroidal components of the magnetic field depends on the torsion and curvature of the magnetic flux tube. It is shown that the rotation of the almost helical plasma flow contributes to the twist of the magnetic flux tube through the total Frenet torsion along the tube.

  2. Magnetohydrostatic Equilibrium. II. Three-dimensional Multiple Open Magnetic Flux Tubes in the Stratified Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Gent, F. A.; Fedun, V.; Erdélyi, R.

    2014-07-01

    A system of multiple open magnetic flux tubes spanning the solar photosphere and lower corona is modeled analytically, within a realistic stratified atmosphere subject to solar gravity. This extends results for a single magnetic flux tube in magnetohydrostatic equilibrium, described in Gent et al. Self-similar magnetic flux tubes are combined to form magnetic structures, which are consistent with high-resolution observations. The observational evidence supports the existence of strands of open flux tubes and loops persisting in a relatively steady state. Self-similar magnetic flux tubes, for which an analytic solution to the plasma density and pressure distribution is possible, are combined. We calculate the appropriate balancing forces, applying to the equations of momentum and energy conservation to preserve equilibrium. Multiplex flux tube configurations are observed to remain relatively stable for up to a day or more, and it is our aim to apply our model as the background condition for numerical studies of energy transport mechanisms from the solar surface to the corona. We apply magnetic field strength, plasma density, pressure, and temperature distributions consistent with observational and theoretical estimates for the lower solar atmosphere. Although each flux tube is identical in construction apart from the location of the radial axis, combinations can be applied to generate a non-axisymmetric magnetic field with multiple non-uniform flux tubes. This is a considerable step forward in modeling the realistic magnetized three-dimensional equilibria of the solar atmosphere.

  3. Magnetohydrostatic equilibrium. II. Three-dimensional multiple open magnetic flux tubes in the stratified solar atmosphere

    SciTech Connect

    Gent, F. A.; Erdélyi, R.; Fedun, V.

    2014-07-01

    A system of multiple open magnetic flux tubes spanning the solar photosphere and lower corona is modeled analytically, within a realistic stratified atmosphere subject to solar gravity. This extends results for a single magnetic flux tube in magnetohydrostatic equilibrium, described in Gent et al. Self-similar magnetic flux tubes are combined to form magnetic structures, which are consistent with high-resolution observations. The observational evidence supports the existence of strands of open flux tubes and loops persisting in a relatively steady state. Self-similar magnetic flux tubes, for which an analytic solution to the plasma density and pressure distribution is possible, are combined. We calculate the appropriate balancing forces, applying to the equations of momentum and energy conservation to preserve equilibrium. Multiplex flux tube configurations are observed to remain relatively stable for up to a day or more, and it is our aim to apply our model as the background condition for numerical studies of energy transport mechanisms from the solar surface to the corona. We apply magnetic field strength, plasma density, pressure, and temperature distributions consistent with observational and theoretical estimates for the lower solar atmosphere. Although each flux tube is identical in construction apart from the location of the radial axis, combinations can be applied to generate a non-axisymmetric magnetic field with multiple non-uniform flux tubes. This is a considerable step forward in modeling the realistic magnetized three-dimensional equilibria of the solar atmosphere.

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

    SciTech Connect

    Dudík, Jaroslav; Dzifčáková, Elena; Cirtain, Jonathan W. E-mail: elena@asu.cas.cz

    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.

  5. New analytical approximations for the liquid rise in a capillary tube

    NASA Astrophysics Data System (ADS)

    González-Santander, J. L.; Martín, G.

    2015-04-01

    We present the ordinary differential equation (ODE) that governs the motion of a liquid rising in a capillary tube in such a way that we can easily derive the principal analytical approximations given in the literature. From this presentation, the numerical solution of the liquid rise over time could be computed very quickly and easily. Furthermore, we derive other analytical approximations not given in the literature, providing a mathematical justification for the cases in which such approximations are good. Some of the approximations found fit the experimental data better than the analytical approximations given in the literature.

  6. Sausage Instabilities on top of Kinking Lengthening Current-Carrying Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; You, Setthivoine

    2015-11-01

    Observations indicate that the dynamics of magnetic flux tubes in our cosmos and terrestrial experiments involve fast topological change beyond MHD reconnection. Recent experiments suggest that hierarchies of instabilities coupling disparate plasma scales could be responsible for this fast topological change by accessing two-fluid and kinetic scales. This study will explore the possibility of sausage instabilities developing on top of a kink instability in lengthening current-carrying magnetic flux tubes. Current driven flux tubes evolve over a wide range of aspect ratios k and current to magnetic flux ratios λ . An analytical stability criterion and numerical investigations, based on applying Newcomb's variational approach to idealized magnetic flux tubes with core and skin currents, indicate a dependence of the stability boundaries on current profiles and overlapping kink and sausage unstable regions in the k - λ trajectory of the flux tubes. A triple electrode planar plasma gun (Mochi.LabJet) is designed to generate flux tubes with discrete core and skin currents. Measurements from a fast-framing camera and a high resolution magnetic probe are being assembled into stability maps of the k - λ space of flux tubes. This work was sponsored in part by the US DOE Grant DE-SC0010340.

  7. Low thermal flux glass-fiber tubing for cryogenic service

    NASA Technical Reports Server (NTRS)

    Hall, C. A.; Spond, D. E.

    1977-01-01

    This paper describes analytical techniques, fabrication development, and test results for composite tubing that has many applications in aerospace and commercial cryogenic installations. Metal liner fabrication is discussed in detail with attention given to resistance-welded liners, fusion-welded liners, chem-milled tubing liners, joining tube liners and end fittings, heat treatment and leak checks. Composite overwrapping, a second method of tubing fabrication, is also discussed. Test programs and analytical correlation are considered along with composite tubing advantages such as minimum weight, thermal efficiency and safety and reliability.

  8. Low thermal flux glass-fiber tubing for cryogenic service

    NASA Technical Reports Server (NTRS)

    Hall, C. A.; Spond, D. E.

    1977-01-01

    This paper describes analytical techniques, fabrication development, and test results for composite tubing that has many applications in aerospace and commercial cryogenic installations. Metal liner fabrication is discussed in detail with attention given to resistance-welded liners, fusion-welded liners, chem-milled tubing liners, joining tube liners and end fittings, heat treatment and leak checks. Composite overwrapping, a second method of tubing fabrication, is also discussed. Test programs and analytical correlation are considered along with composite tubing advantages such as minimum weight, thermal efficiency and safety and reliability.

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

    SciTech Connect

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

    2013-11-10

    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.

  10. HOW MUCH DOES A MAGNETIC FLUX TUBE EMERGE INTO THE SOLAR ATMOSPHERE?

    SciTech Connect

    Magara, T.

    2012-03-20

    The emergence process of the magnetic field into the solar atmosphere plays an essential role in determining the configuration of the magnetic field and its activity on the Sun. This paper focuses on how much the magnetic flux contained by a flux tube emerges into the solar atmosphere, which is the key to understanding the physical mechanism of solar eruptions. By comparing a kinematic model of an emerging flux tube to a series of magnetohydrodynamic simulations, we derive the characteristics of the emergence process, showing how the process depends on the pre-emerged state of the magnetic field such as the radius of a flux tube, field strength, field-line twist, and wavelength of undulation assumed by the flux tube. We also discuss the relationship between magnetic configurations and their stability on the Sun.

  11. CONDITIONS FOR TRANSVERSE WAVES PROPAGATION ALONG THIN MAGNETIC FLUX TUBES ON THE SUN

    SciTech Connect

    Lopin, Igor; Nagorny, Ivan

    2013-09-10

    The propagation of kink waves in the thin gravity stratified flux tubes with a generalized magnetic field distribution model is considered in cylindrical geometry. The new kink wave equations for both wave variables are obtained. It is shown that the inclusion of the radial component of an unperturbed tube magnetic field sufficiently transforms the conditions for the propagation of transverse waves. It is demonstrated that, for the models of isothermal and polytropic atmosphere in the tube and its environment, the propagation of kink waves along thin magnetic flux tubes is cutoff-free.

  12. The nonlinear gyro-kinetic flux tube code GKW

    NASA Astrophysics Data System (ADS)

    Peeters, A. G.; Camenen, Y.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P.; Strintzi, D.; Szepesi, G.

    2009-12-01

    A new nonlinear gyro-kinetic flux tube code (GKW) for the simulation of micro instabilities and turbulence in magnetic confinement plasmas is presented in this paper. The code incorporates all physics effects that can be expected from a state of the art gyro-kinetic simulation code in the local limit: kinetic electrons, electromagnetic effects, collisions, full general geometry with a coupling to a MHD equilibrium code, and E×B shearing. In addition the physics of plasma rotation has been implemented through a formulation of the gyro-kinetic equation in the co-moving system. The gyro-kinetic model is five-dimensional and requires a massive parallel approach. GKW has been parallelised using MPI and scales well up to 8192+ cores. The paper presents the set of equations solved, the numerical methods, the code structure, and the essential benchmarks. Program summaryProgram title: GKW Catalogue identifier: AEES_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEES_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL v3 No. of lines in distributed program, including test data, etc.: 29 998 No. of bytes in distributed program, including test data, etc.: 206 943 Distribution format: tar.gz Programming language: Fortran 95 Computer: Not computer specific Operating system: Any for which a Fortran 95 compiler is available Has the code been vectorised or parallelised?: Yes. The program can efficiently utilise 8192+ processors, depending on problem and available computer. 128 processors is reasonable for a typical nonlinear kinetic run on the latest x86-64 machines. RAM:˜128 MB-1 GB for a linear run; 25 GB for typical nonlinear kinetic run (30 million grid points) Classification: 19.8, 19.9, 19.11 External routines: None required, although the functionality of the program is somewhat limited without a MPI implementation (preferably MPI-2) and the FFTW3 library. Nature of problem: Five

  13. Evidence from lattice data for a new particle on the worldsheet of the QCD flux tube.

    PubMed

    Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor

    2013-08-09

    We propose a new approach for the calculation of the spectrum of excitations of QCD flux tubes. It relies on the fact that the worldsheet theory is integrable at low energies. With this approach, energy levels can be calculated for much shorter flux tubes than was previously possible, allowing for a quantitative comparison with existing lattice data. The improved theoretical control makes it manifest that existing lattice data provides strong evidence for a new pseudoscalar particle localized on the QCD flux tube--the worldsheet axion.

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

    NASA Astrophysics Data System (ADS)

    You, Setthivoine

    2006-10-01

    This talk presents experimental observations, first reported by You, Yun, Bellan in PRL (art. 045002, 2005), strongly supporting the ``MHD pump-collimation'' model proposed by Bellan in Phys. Plasmas (vol. 10, p.1999, 2003). Collimated, plasma-filled, magnetic flux tubes are observed over a tremendous range of scales. In laboratory plasmas, on the surface of the Sun, or jetting out of galactic cores, these flux tubes are extremely collimated, with cross-sections that do not vary much along the length of the tube even in the absence of external magnetic fields or any significant ambient medium pressure. Furthermore, these flux tubes are not in static equilibrium but exhibit strong plasma flows on a rapid time-scale compared to their overall motion within their surroundings. The Caltech experiment simulates magnetically-driven astrophysical jets at the laboratory scale by imposing boundary conditions analogous to astrophysical jet boundary conditions and with plasma dimensionless numbers comparable to numerical MHD simulations. Observations show a distinct sequence of events. The initial flux tubes flare out into the large vacuum, because the magnetic field weakens away from the source. As electrical current flows, the flux tubes become denser and more collimated while sucking plasma from gas sources at the system boundary, effectively acting like a magnetohydrodynamic pump. These flux tubes then merge together into a single column which jets out into the vacuum. The jet continues the same pumping process, to become even denser and more collimated, until either the electrical current or the supply of particles stop. The strong plasma flow convects frozen-in magnetic flux to regions of weaker magnetic field at the end of the tube, and as the flow stagnates there, magnetic flux piles up, pinching the tube into a collimated filament.

  15. Pool boiling of distilled water over tube bundle with variable heat flux

    NASA Astrophysics Data System (ADS)

    Swain, Abhilas; Mohanty, Rajiva Lochan; Das, Mihir Kumar

    2017-02-01

    The experimental investigation of saturated pool boiling heat transfer of distilled water over plain tube bundle, under uniform and varying heat flux condition along the height are presented in this article. Experiments are carried out under various heat flux configurations applied to rows of tube bundles and pitch distance to diameter ratios of 1.25, 1.6 and 1.95. The wall superheats and pool boiling heat transfer coefficients over individual rows are determined. The pool boiling heat transfer coefficients for variable heat flux and uniform heat flux conditions are compared. The results indicate that the bundle effect is found to exist for uniform as well as variable heat flux under all operating conditions in the present investigation. The variable heat flux resulted in range of wall superheat being highest for decreasing heat flux from bottom to top and lowest for increasing heat flux from bottom to top.

  16. Pool boiling of distilled water over tube bundle with variable heat flux

    NASA Astrophysics Data System (ADS)

    Swain, Abhilas; Mohanty, Rajiva Lochan; Das, Mihir Kumar

    2017-08-01

    The experimental investigation of saturated pool boiling heat transfer of distilled water over plain tube bundle, under uniform and varying heat flux condition along the height are presented in this article. Experiments are carried out under various heat flux configurations applied to rows of tube bundles and pitch distance to diameter ratios of 1.25, 1.6 and 1.95. The wall superheats and pool boiling heat transfer coefficients over individual rows are determined. The pool boiling heat transfer coefficients for variable heat flux and uniform heat flux conditions are compared. The results indicate that the bundle effect is found to exist for uniform as well as variable heat flux under all operating conditions in the present investigation. The variable heat flux resulted in range of wall superheat being highest for decreasing heat flux from bottom to top and lowest for increasing heat flux from bottom to top.

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

    NASA Astrophysics Data System (ADS)

    Athenodorou, Andreas; Teper, Michael

    2016-10-01

    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.

  18. Auroral evidence of flux tube blockage near noon at Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Radioti, Aikaterini; Grodent, Denis; Gérard, Jean-Claude; Southwood, David; Chané, Emmanuel; Bonfond, Bertrand; Pryor, Wayne

    2016-04-01

    We discuss plasma circulation in Saturn's magnetosphere on the basis of auroral observations. Auroral enhancements in the dawn region are suggested to be related to intense field-aligned currents generated by hot tenuous plasma carried inward in fast moving flux tubes as they return from tail reconnection site to the dayside. Here we demonstrate that the rotation of the auroral emission in the dawn sector is occasionally (in half of the auroral sequences examined) slowed down and blocked near noon for a couple of hours. When the blockage is prominent and persistent, we observe auroral evidence of dayside magnetopause reconnection and openign of flux. A possible interpretation for our observations could be that depleted flux tubes at large radial distances, which rotate around Saturn are blocked in the prenoon sector between the heavy Vasyliunas cycle flux tubes on one side, and the magnetopause on the other side. These depleted flux tubes have to move above or below the current sheet to pass this blockage. The blockage of the field lines close to midday will bend them and trigger reconnection, which opens the flux tubes and allows for solar wind material to enter the magnetosphere. Secondly, we suggest that the circulation pattern of depleted flux tubes close to noon in Saturn's magnetosphere alternates between a 'blocked' and 'unblocked' state, depending on the solar wind dynamic pressure and the internal processes.

  19. Ionospheric Joule heating and Poynting flux in quasi-static approximation

    NASA Astrophysics Data System (ADS)

    VanhamäKi, H.; Yoshikawa, A.; Amm, O.; Fujii, R.

    2012-08-01

    Energy flow is an important aspect of magnetosphere-ionosphere coupling. Electromagnetic energy is transported as Poynting flux from the magnetosphere to the ionosphere, where it is dissipated as Joule heating. Recently Richmond derived an "Equipotential Boundary Poynting Flux (EBPF) theorem", that the Poynting flux within a flux tube whose boundary is an equipotential curve is dissipated inside the ionospheric foot point of the flux tube. In this article we study Richmond's EBPF theorem more closely by considering the curl-free and divergence-free parts as well as the Hall and Pedersen parts of the ionospheric current system separately. Our main findings are that i) divergence-free currents are on average dissipationless, ii) the curl-free Pedersen current is responsible for the whole ionospheric Joule heating and iii) pointwise match between vertical Poynting flux and ionospheric Joule heating is broken by gradients of Hall and Pedersen conductances. Results i) and ii) hold when integrated over the whole ionosphere or any area bounded by an equipotential curve. The present study is limited to quasi-static phenomena. The more general topic of electrodynamic Joule heating and Poynting flux, including inductive effects, will be addressed in a future study.

  20. New constraint on effective field theories of the QCD flux tube

    NASA Astrophysics Data System (ADS)

    Baker, M.

    2016-03-01

    Effective magnetic S U (N ) gauge theory with classical ZN flux tubes of intrinsic width 1/M is an effective field theory of the long-distance quark-antiquark interaction in S U (N ) Yang-Mills theory. Long-wavelength fluctuations of the ZN vortices of this theory lead to an effective string theory. In this paper, we clarify the connection between effective field theory and effective string theory, and we propose a new constraint on these vortices. We first examine the impact of string fluctuations on the classical dual superconductor description of confinement. At interquark distances R ˜1/M , the classical action for a straight flux tube determines the heavy quark potentials. At distances R ≫1/M , fluctuations of the flux tube axis x ˜ give rise to an effective string theory with an action Seff(x ˜), the classical action for a curved flux tube, evaluated in the limit 1/M →0 . This action is equal to the Nambu-Goto action. These conclusions are independent of the details of the ZN flux tube. Further, we assume the QCD flux tube satisfies the additional constraint, ∫0∞r d r T/θθ(r ) r2=0 , where T/θθ(r ) r2 is the value of the θ θ component of the stress tensor at a distance r from the axis of an infinite flux tube. Under this constraint, the string tension σ equals the force on a quark in the chromoelectric field E → of an infinite straight flux tube, and the Nambu-Goto action can be represented in terms of the chromodynamic fields of effective magnetic S U (N ) gauge theory, yielding a field theory interpretation of effective string theory.

  1. Long-lived auroral structures and atmospheric losses through auroral flux tubes on Mars

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Woch, J.; Barabash, S.; Lundin, R.

    2009-04-01

    The ASPERA-3 observations of electron and ion fluxes over the regions dominated by crustal magnetic fields show the existence of long-lived and active aurora-type magnetic flux tubes with a width of 20-150 km. The activity manifests itself by large electron energy fluxes (≥10-4 W/m2) and strong distortions in the upper (350-400 km) ionosphere. In some events the peaked electron energy distributions typical for Earth aurora are so pronounced that they are present in velocity distribution functions. A significant depletion of such auroral flux tubes is accompanied by the appearance of oxygen beams and a heating of the ions of ionospheric origin. Auroral activity was observed on several subsequent orbits of the Mars Express spacecraft during more than two weeks implying a stable existence of aurora on Mars. Atmospheric loss driven by energy deposition in the auroral flux tubes is estimated as ˜1023 s-1.

  2. An approximate algorithm for the flux from a rectangular volume source

    SciTech Connect

    Wallace, O.J.

    1994-11-09

    An exact semi-analytic formula for the flux from a rectangular surface source with a slab shield has been derived and the required function table has been calculated. This formula is the basis for an algorithm which gives a good approximation for the flux from a rectangular volume source. No other hand calculation method for this source geometry is available in the literature.

  3. Sausage instabilities on top of kinking lengthening current-carrying magnetic flux tubes

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; You, Setthivoine

    2017-05-01

    We theoretically explore the possibility of sausage instabilities developing on top of a kink instability in lengthening current-carrying magnetic flux tubes. Observations indicate that the dynamics of magnetic flux tubes in our cosmos and terrestrial experiments can involve topological changes faster than time scales predicted by resistive magnetohydrodynamics. Recent laboratory experiments suggest that hierarchies of instabilities, such as kink and Rayleigh-Taylor, could be responsible for initiating fast topological changes by locally accessing two-fluid and kinetic regimes. Sausage instabilities can also provide this coupling mechanism between disparate scales. Flux tube experiments can be classified by the flux tube's evolution in a configuration space described by a normalized inverse aspect-ratio k ¯ and current-to-magnetic flux ratio λ ¯ . A lengthening current-carrying magnetic flux tube traverses this k ¯ - λ ¯ space and crosses stability boundaries. We derive a single general criterion for the onset of the sausage and kink instabilities in idealized magnetic flux tubes with core and skin currents. The criterion indicates a dependence of the stability boundaries on current profiles and shows overlapping kink and sausage unstable regions in the k ¯ - λ ¯ space with two free parameters. Numerical investigation of the stability criterion reduces the number of free parameters to a single one that describes the current profile and confirms the overlapping sausage and kink unstable regions in k ¯ - λ ¯ space. A lengthening, ideal current-carrying magnetic flux tube can therefore become sausage unstable after it becomes kink unstable.

  4. Signatures of Flux Tube Fragmentation and Strangeness Correlations in pp Collisions

    NASA Astrophysics Data System (ADS)

    Wong, Cheuk-Yin

    2017-01-01

    In the fragmentation of a color flux tube in high-energy pp collisions or e +-e‑ annihilations, the production of pairs along a color flux tube precedes the fragmentation of the tube. The local conservation laws in the production of these pairs will lead to the correlations of adjacently produced hadrons. As a consequence, the fragmentation of a flux tube will yield a many-hadron correlation in the form of a chain of hadrons ordered in rapidity, with adjacent hadrons correlated in charges, flavor contents, and azimuthal angles. It will also lead to a two-hadron angular correlation between two hadrons with opposite charges or strangeness that is suppressed at Δϕ ~ 0 but enhanced at Δϕ ~ π, within a rapidity window Δy~1/(dN/dy).

  5. Flux Transfer Events Simultaneously Observed by Polar and Cluster: Flux Rope in the Subsolar Region and Flux Tube Addition to the Polar Cusp

    NASA Technical Reports Server (NTRS)

    Le, G.; Zheng, Y.; Russell, C. T.; Pfaff, R. F.; Lin, N.; Slavin, J. A.; Parks, G.; Wilber, M.; Petrinec, S. M.; Lucek, E. A.; Reme, H.

    2007-01-01

    The phenomenon called flux transfer events (FTEs) is widely accepted as the manifestation of time-dependent reconnection. In this paper, we present observational evidence of a flux transfer event observed simultaneously at low-latitude by Polar and at high-latitude by Cluster. This event occurs on March 21, 2002, when both Cluster and Polar are located near local noon but with a large latitudinal separation. During the event, Cluster is moving outbound from the polar cusp to the magnetosheath, and Polar is in the magnetosheath near the equatorial magnetopause. The observations show that a flux transfer event occurs between the equator and the northern cusp. Polar and Cluster observe the FTE s two open flux tubes: Polar encounters the southward moving flux tube near the equator; and Cluster the northward moving flux tube at high latitude. The low latitude FTE appears to be a flux rope with helical magnetic field lines as it has a strong core field and the magnetic field component in the boundary normal direction exhibits a strong bi-polar variation. Unlike the low-latitude FTE, the high-latitude FTE observed by Cluster does not exhibit the characteristic bi-polar perturbation in the magnetic field. But the plasma data clearly reveal its open flux tube configuration. It shows that the magnetic field lines have straightened inside the FTE and become more aligned to the neighboring flux tubes as it moves to the cusp. Enhanced electrostatic fluctuations have been observed within the FTE core, both at low- and high-latitudes. This event provides a unique opportunity to understand high-latitude FTE signatures and the nature of time-varying reconnection.

  6. Evidence from Lattice Data for a New Particle on the Worldsheet of the QCD Flux Tube

    NASA Astrophysics Data System (ADS)

    Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor

    2013-08-01

    We propose a new approach for the calculation of the spectrum of excitations of QCD flux tubes. It relies on the fact that the worldsheet theory is integrable at low energies. With this approach, energy levels can be calculated for much shorter flux tubes than was previously possible, allowing for a quantitative comparison with existing lattice data. The improved theoretical control makes it manifest that existing lattice data provides strong evidence for a new pseudoscalar particle localized on the QCD flux tube—the worldsheet axion.

  7. The model of self-sustained propagation of a magnetic reconnection along the flux tube

    NASA Astrophysics Data System (ADS)

    Dumin, Yurii

    This work represents a further development of our earlier ideas about heating the solar corona in the transition region from the "induction" to "drift" freezing of the magnetic field in plasma [1, 2]. The new detailed study of this process in the magnetic tube filled with a weakly-ionized plasma of the lower solar atmosphere shows that ignition of the magnetic reconnection develops most efficiently at the spot of approximate equality between the gyro-and collisional frequencies of charged particles. Next, due to the heat release and its propagation along the magnetic flux tube, the spot of most efficient reconnection moves upwards, thereby producing a self-sustained propagation of the reconnection along the field lines. The temperature increases sharply with height just due to decrease in plasma density, stratified by the gravitational field. This phenomenon may be efficiently applied to model the solar microflares, which are believed now to be an important ingredient of the solar atmosphere heating. References: 1. Yu.V. Dumin. Can Heating of the Solar Corona Be Related to a Transition from the In-duction to Drift Mechanism of the Magnetic Field Freezing in Plasma? Advances in Space Research, v.30, p.565 (2002). 2. Yu.V. Dumin. On the Physical Nature of the Magnetic-Field Freezing-in Effect in Collision-less Cosmic Plasmas. Solar System Research, v.32, p.323 (1998).

  8. NUMERICAL EXPERIMENTS ON THE TWO-STEP EMERGENCE OF TWISTED MAGNETIC FLUX TUBES IN THE SUN

    SciTech Connect

    Toriumi, S.; Yokoyama, T.

    2011-07-10

    We present the new results of the two-dimensional numerical experiments on the cross-sectional evolution of a twisted magnetic flux tube rising from the deeper solar convection zone (-20,000 km) to the corona through the surface. The initial depth is 10 times deeper than most of the previous calculations focusing on the flux emergence from the uppermost convection zone. We find that the evolution is illustrated by the following two-step process. The initial tube rises due to its buoyancy, subject to aerodynamic drag due to the external flow. Because of the azimuthal component of the magnetic field, the tube maintains its coherency and does not deform to become a vortex roll pair. When the flux tube approaches the photosphere and expands sufficiently, the plasma on the rising tube accumulates to suppress the tube's emergence. Therefore, the flux decelerates and extends horizontally beneath the surface. This new finding owes to our large-scale simulation, which simultaneously calculates the dynamics within the interior as well as above the surface. As the magnetic pressure gradient increases around the surface, magnetic buoyancy instability is triggered locally and, as a result, the flux rises further into the solar corona. We also find that the deceleration occurs at a higher altitude than assumed in our previous experiment using magnetic flux sheets. By conducting parametric studies, we investigate the conditions for the two-step emergence of the rising flux tube: field strength {approx}> 1.5 x 10{sup 4} G and the twist {approx}> 5.0 x 10{sup -4} km{sup -1} at -20,000 km depth.

  9. Flux tubes embedded into reconnection outflows in the solar wind

    NASA Astrophysics Data System (ADS)

    Voros, Z.; Zaqarashvili, T.; Sasunov, Y.; Narita, Y.

    2015-12-01

    Reconnection exhausts in the solar wind are usually interpreted in terms of a quasi-stationary Petschek-type reconnection model. Accordingly, within a region of magnetic field reversal, the wedge-shaped, Alfvenic accelerated plasma outflow is bounded by layers containing (anti-) correlated components of speed and magnetic field fluctuations. However, time-dependent impulsive reconnection can generate flux ropes embedded into accelerated outflows. Reconnection associated moving flux ropes or plasmoids are frequently observed in the Earth's magnetotail, while similar observations are missing in the solar wind. We present the first observations of small-scale magnetic flux ropes associated with reconnection exhausts in the solar wind, using the data from the WIND probe. We argue that the interaction of moving flux ropes with the background plasma can generate turbulence leading finally to the local heating of the solar wind.

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

    SciTech Connect

    Chou, W.; Tajima, C.T.; Matsumoto, R. |; 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.

  11. Benchmarking Particle-in-Cell drift wave simulations with Eulerian simulations in a flux-tube

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Parker, Scott; Wan, Weigang; Bravenec, Ronald; Wang, Eric; Candy, Jeff

    2012-10-01

    We present the implementation of a flux-tube option in the global turbulence code GEM.footnotetextY. Chen and S. E. Parker, J. Comp. Phys. 220, 839 (2007) This is necessary for benchmarking purposes because of the immense complexity involved in comparing global simulations. The global GEM assumes the magnetic equilibrium to be completely given. Our initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, T, ∇T, the Jacobian etc.) to be equal to their values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. We found good agreement between GEM and GYRO/GS2 for the mode frequency/growth rate in the case of adiabatic electrons, but a difference of ˜15% in the growth rates when kinetic electrons are included. Our goal is to understand the origin of this moderate disagreement. An alternative local geometry model based on a local solution of the Grad-Shafranov equationfootnotetextJ. Candy, Plasma Phys. Control. Fusion 51, 105009 (2009) has been implemented and new benchmarking results from this model will be presented.

  12. The stretching of magnetic flux tubes in the convective overshoot region

    NASA Technical Reports Server (NTRS)

    Fisher, George H.; Mcclymont, Alexander N.; Chou, Dean-Yi

    1991-01-01

    The present study examines the fate of a magnetic flux tube initially lying at the bottom of the solar convective overshoot region. Stretching of the flux tube, e.g., by differential rotation, reduces its density, causing it to rise quasi-statically (a process referred to as vertical flux drift) until it reaches the top of the overshoot region and enters the buoyantly unstable convection region, from which a portion of it may ultimately protrude to form an active region on the surface. It is suggested that vertical flux drift and flux destabilization are inevitable consequences of field amplification, and it is surmised that these phenomena should be considered in self-consistent models of solar and stellar dynamos operating in the overshoot region.

  13. The stretching of magnetic flux tubes in the convective overshoot region

    NASA Technical Reports Server (NTRS)

    Fisher, George H.; Mcclymont, Alexander N.; Chou, Dean-Yi

    1991-01-01

    The present study examines the fate of a magnetic flux tube initially lying at the bottom of the solar convective overshoot region. Stretching of the flux tube, e.g., by differential rotation, reduces its density, causing it to rise quasi-statically (a process referred to as vertical flux drift) until it reaches the top of the overshoot region and enters the buoyantly unstable convection region, from which a portion of it may ultimately protrude to form an active region on the surface. It is suggested that vertical flux drift and flux destabilization are inevitable consequences of field amplification, and it is surmised that these phenomena should be considered in self-consistent models of solar and stellar dynamos operating in the overshoot region.

  14. Heat flux solutions of the 13-moment approximation transport equations in a multispecies gas

    SciTech Connect

    Jian Wu; Taieb, C.

    1993-09-01

    The authors study steady state heat flux equations by means of the 13-moment approximation for situations applicable to aeronomy and space plasmas. They compare their results with Fourier`s law applied to similar problems, to test validity conditions for it. They look at the flux of oxygen and hydrogen ions in the high-latitude ionosphere, and compare calculations with observations from EISCAT radar measurements. These plasma components are observed to have strongly non-Maxwellian distributions.

  15. Approximate Analytic Solutions for the Primary Auroral Electron Flux and Related Quantities.

    DTIC Science & Technology

    1981-03-03

    Preliminary Remarks 18 8.2 Unidirectional- Monoenergetic Incident Flux 19 8.3 Isotropic-Maxwellian Incident Flux 20 8.4 Isotropic- Monoenergetic Incident...PSEUDOPARTICLES To APPROXIMATE THE SUMS 25 51 Contents 11. COMPARISONS 28 11. 1 Preliminary Remarks 28 11. 2 Comparisons for Isotropic - Monoenerget ie...the Analytic, Range, and Rees Models for 10, 5, and 2 KeV Isotrqpic- Monoenergetic Sources Each Containing 1 erg/cm s 30 6. Incident Maxwellian Energy

  16. Numerical approximation of head and flux covariances in three dimensions using mixed finite elements

    NASA Astrophysics Data System (ADS)

    James, Andrew I.; Graham, Wendy D.

    A numerical method is developed for accurately approximating head and flux covariances and cross-covariances in finite two- and three-dimensional domains using the mixed finite element method. The method is useful for determining head and flux covariances for non-stationary flow fields, for example those induced by injection or extraction wells, impermeable subsurface barriers, or non-stationary hydraulic conductivity fields. Because the numerical approximations to the flux covariances are obtained directly from the solution to the coupled problem rather than having to differentiate head covariances, the approximations are in general more accurate than those obtained from conventional finite difference or finite element methods. Results for uniform flow example problems are consistent with results from previously published finite domain analyses and demonstrate that head variances and covariances are quite sensitive to boundary conditions and the size of the bounded domain. Flux variances and covariances are less sensitive to boundary conditions and domain size. Results comparing approximations from lower-order Raviart-Thomas-Nedelec and higher order Brezzi-Douglas-Marini [9] finite element spaces indicate that higher order element space improve the estimate of the flux covariances, but do not significantly affect the estimate of the head covariances.

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

    NASA Astrophysics Data System (ADS)

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

    1997-02-01

    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 q overlineq- 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 wuarks and their mean-fields for Lund-type string fragmentation processes.

  18. Numerical simulations of magnetic Kelvin-Helmholtz instability at a twisted solar flux tube

    NASA Astrophysics Data System (ADS)

    Murawski, K.; Chmielewski, P.; Zaqarashvili, T. V.; Khomenko, E.

    2016-07-01

    The paper aims to study the response of a solar small-scale and weak magnetic flux tube to photospheric twisting motions. We numerically solve three-dimensional ideal magnetohydrodynamic equations to describe the evolution of the perturbation within the initially static flux tube, excited by twists in the azimuthal component of the velocity. These twists produce rotation of the magnetic field lines. Perturbation of magnetic field lines propagates upwardly, driving vertical and azimuthal flow as well as plasma compressions and rarefactions in the form of eddies. We conclude that these eddies result from the sheared azimuthal flow which seeds Kelvin-Helmholtz instability (KHI) between the flux tube and the ambient medium. Numerically obtained properties of the KHI confirm the analytical predictions for the occurrence of the instability.

  19. Dynamics of multiple flux tubes in sawtoothing KSTAR plasmas heated by electron cyclotron waves: I. Experimental analysis of the tube structure

    NASA Astrophysics Data System (ADS)

    Choe, G. H.; Yun, G. S.; Nam, Y.; Lee, W.; Park, H. K.; Bierwage, A.; Domier, C. W.; Luhmann, N. C., Jr.; Jeong, J. H.; Bae, Y. S.; the KSTAR Team

    2015-01-01

    Multiple (two or more) flux tubes are commonly observed inside and/or near the q = 1 flux surface in KSTAR tokamak plasmas with localized electron cyclotron resonance heating and current drive (ECH/CD). Detailed 2D and quasi-3D images of the flux tubes obtained by an advanced imaging diagnostic system showed that the flux tubes are m/n = 1/1 field-aligned structures co-rotating around the magnetic axis. The flux tubes typically merge together and become like the internal kink mode of the usual sawtooth, which then collapses like a usual sawtooth crash. A systematic scan of ECH/CD beam position showed a strong correlation with the number of flux tubes. In the presence of multiple flux tubes close to the q = 1 surface, the radially outward heat transport was enhanced, which explains naturally temporal changes of electron temperature. We emphasize that the multiple flux tubes are a universal feature distinct from the internal kink instability and play a critical role in the control of sawteeth using ECH/CD.

  20. Axisymmetric and non-axisymmetric modulated MHD waves in magnetic flux tubes

    NASA Astrophysics Data System (ADS)

    Chargeishvili, B. B.; Japaridze, D. R.

    2016-02-01

    Nonlinear modulated both axisymmetric and non-axisymmetric MHD wave propagation in magnetic flux tubes is studied. In the cylindrical coordinates, ordinary differential equation with cubic nonlinearity is derived. In both cases of symmetry, the equation has solitary solutions. Modulation stability of the solutions is studied. The results of the study show that the propagation of axisymmetric soliton causes rising of plasma temperature in peripheral regions of a magnetic flux tube. In the non-axisymmetric case, it gives also temperature rising effect. Results of theoretical study are examined on idealized model of chromospheric spicule.

  1. Measurements and computations of mass flow and momentum flux through short tubes in rarefied gases

    NASA Astrophysics Data System (ADS)

    Lilly, T. C.; Gimelshein, S. F.; Ketsdever, A. D.; Markelov, G. N.

    2006-09-01

    Gas flows through orifices and short tubes have been extensively studied from the 1960s through the 1980s for both fundamental and practical reasons. These flows are a basic and often important element of various modern gas driven instruments. Recent advances in micro- and nanoscale technologies have paved the way for a generation of miniaturized devices in various application areas, from clinical analyses to biochemical detection to aerospace propulsion. The latter is the main area of interest of this study, where rarefied gas flow into a vacuum through short tubes with thickness-to-diameter ratios varying from 0.015 to 1.2 is investigated both experimentally and numerically with kinetic and continuum approaches. Helium and nitrogen gases are used in the range of Reynolds numbers from 0.02 to 770 (based on the tube diameter), corresponding to Knudsen numbers from 40 down to about 0.001. Propulsion properties of relatively thin and thick tubes are examined. Good agreement between experimental and numerical results is observed for mass flow rate and momentum flux, the latter being corrected for the experimental facility background pressure. For thick-to-thin tube ratios of mass flow and momentum flux versus pressure, a minimum is observed at a Knudsen number of about 0.5. A short tube propulsion efficiency is shown to be much higher than that of a thin orifice. The effect of surface specularity on a thicker tube specific impulse was found to be relatively small.

  2. The Role of Twisted Magnetic Flux Tubes in Topological Space Weather Forecasting

    NASA Astrophysics Data System (ADS)

    Nightingale, R. W.

    2008-12-01

    More and more twisted magnetic flux tubes are being identified in the solar active regions of solar cycle 23 utilizing imagery from high resolution satellite instrumentation, such as TRACE, Hinode, and SOHO/MDI. The twisted flux tubes carry energy and helicity via the Poynting Flux from below the photosphere up into the corona, where much of it is stored in the non-potentiality of the fields, many times visible in the form of sigmoidal and anti-sigmoidal shapes, until dissipation occurs mostly following eruptive events. The twisted flux tubes are easily observed and measured in TRACE whitelight in cross section as sunspots at the photosphere, which rotate about their umbral centers. The first results presented at the 2007 Fall AGU from a statistical study on the number of rotating sunspots showed that almost all of the measurable sunspots during the solar maximum year of 2000 were rotating. Here we extend the study to include halo coronal mass ejections (CMEs) observed by SOHO/LASCO, of which 80% are associated with rotating sunspots and twisted magnetic flux tubes in 2000. Many of the CMEs, consisting of very energetic particles normally captured within a magnetic cloud of twisted flux tubes, accelerate out into the heliosphere where the Earth and its magnetic fields can encounter them, causing large geomagnetic events, such as geomagnetic storms, Solar Particle Events (SPEs), and other space weather effects. The amount of twist, or helicity, and its directionality may play important roles in solar eruptions and in the CME's interaction with the magnetosphere. Within the next year the Solar Dynamics Observatory (SDO) will launch and the HMI and AIA instruments will be available to observe the rotating sunspots and twisted magnetic flux tubes in greater detail than is currently being done to improve our understanding of these processes. Examples of such events and topological features will be shown and discussed with respect to the role that twisted magnetic flux

  3. Length and time for development of laminar flow in tubes following a step increase of volume flux

    NASA Astrophysics Data System (ADS)

    Chaudhury, Rafeed A.; Herrmann, Marcus; Frakes, David H.; Adrian, Ronald J.

    2015-01-01

    Laminar flows starting up from rest in round tubes are relevant to numerous industrial and biomedical applications. The two most common types are flows driven by an abruptly imposed constant pressure gradient or by an abruptly imposed constant volume flux. Analytical solutions are available for transient, fully developed flows, wherein streamwise development over the entrance length is absent (Szymanski in J de Mathématiques Pures et Appliquées 11:67-107, 1932; Andersson and Tiseth in Chem Eng Commun 112(1):121-133, 1992, respectively). They represent the transient responses of flows in tubes that are very long compared with the entrance length, a condition that is seldom satisfied in biomedical tube networks. This study establishes the entrance (development) length and development time of starting laminar flow in a round tube of finite length driven by a piston pump that produces a step change from zero flow to a constant volume flux for Reynolds numbers between 500 and 3,000. The flows are examined experimentally, using stereographic particle image velocimetry and computationally using computational fluid dynamics, and are then compared with the known analytical solutions for fully developed flow conditions in infinitely long tubes. Results show that step function volume flux start-up flows reach steady state and fully developed flow five times more quickly than those driven by a step function pressure gradient, a 500 % change when compared with existing estimates. Based on these results, we present new, simple guidelines for achieving experimental flows that are fully developed in space and time in realistic (finite) tube geometries. To a first approximation, the time to achieve steady spatially developing flow is nearly equal to the time needed to achieve steady, fully developed flow. Conversely, the entrance length needed to achieve fully developed transient flow is approximately equal to the length needed to achieve fully developed steady flow. Beyond this

  4. The Emergence of Kinked Flux Tubes as the Source of Delta-Spots on the Photosphere

    NASA Astrophysics Data System (ADS)

    Knizhnik, Kalman; Linton, Mark; Norton, Aimee Ann

    2017-08-01

    It has been observationally well established that the magnetic configurations most favorable to producing energetic flaring events reside in so called delta-spots. These delta-spots are a subclass of sunspots, and are classified as sunspots which have umbrae (dark regions in the interior of sunspots) with opposite magnetic polarities that share a common penumbra. They are characterized by strong rotation and an extremely compact magnetic configuration, and are observed to follow an inverse-Hale law. It has been shown that over 90% of X-class flares that occurred during solar cycles 22 and 23 originated in delta-spots (Guo, Lin & Deng, 2014). Understanding the origin of delta-spots, therefore, is a crucial step towards the ultimate goal of space weather forecasting. In this work, we argue that delta-spots arise during the emergence of kinked flux tubes into the corona, and that their unique properties are due to the emergence of knots present in the kink mode of twisted flux tubes. We present numerical simulations that study the emergence of both kink-stable and unstable flux tubes into the solar corona, and demonstrate quantitatively that their photospheric signatures are dramatically different, with the latter flux tubes demonstrating strong coherent rotation and a very tight flux distribution on the photosphere. We show that the coronal magnetic field resulting from the emergence of a kinked flux tube contains significantly more free energy than the unkinked case, potentially leading to more energetic flares. We discuss the implications of our simulations for observations.

  5. Building 3D data sets of flux tube dynamics

    NASA Astrophysics Data System (ADS)

    Loseth, B.; Intrator, T. P.; Sears, J.

    2010-11-01

    Magnetic Reconnection occurs when oppositely directed magnetic fields are advected towards each other as plasma flow. The magnetic fields diffuse through a small region where the frozen flux condition of ideal magnetohydrodynamics (MHD) breaks down and the field lines lose their identity and reconnect to other fields. The reconnection process is important in the confinement of fusion plasmas as well as long-standing solar-physics issues in solar flares, geomagnetic storms, and black hole accretion discs. The Reconnection Scaling Experiment (RSX) uses plasma guns to create one, two, or more parallel flux ropes in a cylindrical chamber with an axial magnetic guide field. The plasma channels twist helically and merge or bounce depending on the attractive force due to the parallel currents and the repulsive force associated with axial and azimuthal magnetic field line bending. The dynamics of merging and bouncing may lead to a new understanding of the statistical mechanics of magnetic fields and provide a means of visualizing three-dimensional MHD turbulence. An update of the RSX vessel including an adjustable magnetic probe array is currently under way and will allow for the building of 3D data sets of these dynamics.

  6. Simulation of magnetic flux leakage: Application to tube inspection

    NASA Astrophysics Data System (ADS)

    Prémel, Denis; Fnaeich, E. A.; Djafa, S.; Pichon, L.; Trillon, A.; Bisiaux, B.

    2012-05-01

    The detection of flaws in steel pipes using Magnetic Flux Leakage (MFL) consists in detecting magnetic flux leaks outside the pipe, either with a magnetic sensor or with an induction coil, while the pipe is rotating. In the Vallourec group, many NDT units use MFL for testing ferromagnetic pipes. In order to improve the performances of flaw detection, CEA LIST and the Vallourec Research Aulnoye (VRA) group are collaborating on MFL modelling. The aim is to be able to perform parametric studies thanks to a fast 3D numerical model dedicated to MFL systems. A simplified 2D geometry has already been derived for the development of first simulation tools. When considering the B-H curve of ferromagnetic materials, the non-linear magnetostatic problem can be solved with the generalized boundary element method (BEMG), which comes to the evaluation of two equivalent scalar potentials: the surface charge density and the volume charge density. When applying the Galerkin method for the discretization of integral equations, the particularity of this numerical model lies in the implementation of high order basis functions for the interpolation of the scalar unknowns. This paper presents some first numerical results for the numerical validation of the semi-analytical model.

  7. Magnetic Reconnection in a Solar Eruption -Formation of the Flux Tube and its Eruption-

    NASA Astrophysics Data System (ADS)

    Inoue, Satoshi; Büchner, Jörg

    2016-07-01

    A solar eruption is one of a dramatic phenomenon observed in the solar corona. The flux tube, which is a bundle of highly twisted lines, is widely believed as a driver source of the eruption. Although the magnetic reconnection is a key process of the formation of the flux tube as well as the eruptive process, these dynamics are still open to be solved. In order to clarify these dynamics, we first perform a magnetohydrodynamic (MHD) simulation using a force-free field extrapolated from the photospheric magnetic field. Our simulation successfully produced the typical eruptive processes in which the twisted flux tube slowly ascends in the beginning of the eruption; afterwards, it shows the fast ascending. We found that the reconnection is a key process to break the force-free field initially constructed, and highly twisted flux tube formation during the slow rising phase and even after the fast eruption. Next we compare with Büchner + Skala simulations and compressively discuss the play of the reconnection in the solar eruption.

  8. Plasma dynamics on current-carrying magnetic flux tubes. II - Low potential simulation

    NASA Technical Reports Server (NTRS)

    Swift, Daniel W.

    1992-01-01

    The evolution of plasma in a current-carrying magnetic flux tube of variable cross section is investigated using a one-dimensional numerical simulation. The flux tube is narrow at the two ends and broad in the middle. The middle part of the flux tube is loaded with a hot, magnetically trapped population, and the two ends have a more dense, gravitationally bound population. A potential difference larger than the gravitational potential but less than the energy of the hot population is applied across the domain. The general result is that the potential change becomes distributed along the anode half of the domain, with negligible potential change on the cathode half. The potential is supported by the mirror force of magnetically trapped particles. The simulations show a steady depletion of plasma on the anode side of the flux tube. The current steadily decreases on a time scale of an ion transit time. The results may provide an explanation for the observed plasma depletions on auroral field lines carrying upward currents.

  9. Detection of Cracks at Welds in Steel Tubing Using Flux Focusing Electromagnetic Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Simpson, John; Namkung, Min

    1994-01-01

    The inspection of weldments in critical pressure vessel joints is a major concern in the nuclear power industry. Corrosive environments can speed the fatigue process and access to the critical area is often limited. Eddy current techniques have begun to be used to help overcome these obstacles [1]. As direct contact and couplants are not required, remote areas can be inspected by simply snaking an eddy current coil into the intake tube of the vessel. The drawback of the eddy current method has been the high sensitivity to small changes in the conductivity and permeability of the test piece which are known to vary at weldments [1]. The flaw detection mechanism of the flux focusing electromagnetic probe can help alleviate these difficulties and provide a unique capability for detecting longitudinal fatigue cracks in critical tube structures. The Flux Focusing Electromagnetic Flaw Detector, originally invented for the detection of fatigue and corrosion damage in aluminum plates [2-3], has been adapted for use in testing steel tubing for longitudinal fatigue cracks. The modified design allows for the probe to be placed axisymmetrically into the tubing, inducing eddy currents in the tube wall. The pickup coil of the probe is fixed slightly below the primary windings and is rotated 90 so that its axis is normal to the tube wall. The magnetic flux of the primary coil is focused through the use of ferromagnetic material so that in the absence of fatigue damage there will be no flux linkage with the pickup coil. The presence of a longitudinal fatigue crack will cause the eddy currents induced in the tube wall to flow around the flaw and directly under the pickup coil. The magnetic field associated with these currents will then link the pickup coil and an unambiguous increase in the output voltage of the probe will be measured. The use of the flux focusing electromagnetic probe is especially suited for the detection of flaws originating at or near tube welds. The probe is

  10. Detection of Cracks at Welds in Steel Tubing Using Flux Focusing Electromagnetic Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Simpson, John; Namkung, Min

    1994-01-01

    The inspection of weldments in critical pressure vessel joints is a major concern in the nuclear power industry. Corrosive environments can speed the fatigue process and access to the critical area is often limited. Eddy current techniques have begun to be used to help overcome these obstacles [1]. As direct contact and couplants are not required, remote areas can be inspected by simply snaking an eddy current coil into the intake tube of the vessel. The drawback of the eddy current method has been the high sensitivity to small changes in the conductivity and permeability of the test piece which are known to vary at weldments [1]. The flaw detection mechanism of the flux focusing electromagnetic probe can help alleviate these difficulties and provide a unique capability for detecting longitudinal fatigue cracks in critical tube structures. The Flux Focusing Electromagnetic Flaw Detector, originally invented for the detection of fatigue and corrosion damage in aluminum plates [2-3], has been adapted for use in testing steel tubing for longitudinal fatigue cracks. The modified design allows for the probe to be placed axisymmetrically into the tubing, inducing eddy currents in the tube wall. The pickup coil of the probe is fixed slightly below the primary windings and is rotated 90 so that its axis is normal to the tube wall. The magnetic flux of the primary coil is focused through the use of ferromagnetic material so that in the absence of fatigue damage there will be no flux linkage with the pickup coil. The presence of a longitudinal fatigue crack will cause the eddy currents induced in the tube wall to flow around the flaw and directly under the pickup coil. The magnetic field associated with these currents will then link the pickup coil and an unambiguous increase in the output voltage of the probe will be measured. The use of the flux focusing electromagnetic probe is especially suited for the detection of flaws originating at or near tube welds. The probe is

  11. Numerical simulation of filling a magnetic flux tube with a cold plasma: Anomalous plasma effects

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Leung, W. C.

    1995-01-01

    Large-scale models of plasmaspheric refilling have revealed that during the early stage of the refilling counterstreaming ion beams are a common feature. However, the instability of such ion beams and its effect on refilling remain unexplored. In order to learn the basic effects of ion beam instabilities on refilling, we have performed numerical simulations of the refilling of an artificial magnetic flux tube. (The shape and size of the tube are assumed so that the essential features of the refilling problem are kept in the simulation and at the same time the small scale processes driven by the ion beams are sufficiently resolved.) We have also studied the effect of commonly found equatorially trapped warm and/or hot plasma on the filling of a flux tube with a cold plasma. Three types of simulation runs have been performed.

  12. Flux-tube geometry and solar wind speed during an activity cycle

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Brun, A. S.; Rouillard, A. P.

    2016-07-01

    Context. The solar wind speed at 1 AU shows cyclic variations in latitude and in time which reflect the evolution of the global background magnetic field during the activity cycle. It is commonly accepted that the terminal (asymptotic) wind speed in a given magnetic flux-tube is generally anti-correlated with its total expansion ratio, which motivated the definition of widely used semi-empirical scaling laws relating one to the other. In practice, such scaling laws require ad hoc corrections (especially for the slow wind in the vicinities of streamer/coronal hole boundaries) and empirical fits to in situ spacecraft data. A predictive law based solely on physical principles is still missing. Aims: We test whether the flux-tube expansion is the controlling factor of the wind speed at all phases of the cycle and at all latitudes (close to and far from streamer boundaries) using a very large sample of wind-carrying open magnetic flux-tubes. We furthermore search for additional physical parameters based on the geometry of the coronal magnetic field which have an influence on the terminal wind flow speed. Methods: We use numerical magneto-hydrodynamical simulations of the corona and wind coupled to a dynamo model to determine the properties of the coronal magnetic field and of the wind velocity (as a function of time and latitude) during a whole 11-yr activity cycle. These simulations provide a large statistical ensemble of open flux-tubes which we analyse conjointly in order to identify relations of dependence between the wind speed and geometrical parameters of the flux-tubes which are valid globally (for all latitudes and moments of the cycle). Results: Our study confirms that the terminal (asymptotic) speed of the solar wind depends very strongly on the geometry of the open magnetic flux-tubes through which it flows. The total flux-tube expansion is more clearly anti-correlated with the wind speed for fast rather than for slow wind flows, and effectively controls the

  13. 3D Laboratory Measurements of Forces, Flows, and Collimation in Arched Flux Tubes

    NASA Astrophysics Data System (ADS)

    Haw, Magnus; Bellan, Paul

    2016-10-01

    Fully 3D, vector MHD force measurements from an arched, current carrying flux tube (flux rope) are presented. The experiment consists of two arched plasma-filled flux ropes each powered by a capacitor bank. The two loops are partially overlapped, as in a Venn diagram, and collide and reconnect during their evolution. B-field data is taken on the lower plasma arch using a 54 channel B-dot probe. 3D volumetric data is acquired by placing the probe at 2700 locations and taking 5 plasma shots at each location. The resulting data set gives high resolution (2cm, 10ns) volumetric B-field data with high reproducibility (deviation of 3% between shots). Taking the curl of the measured 3D B-field gives current densities (J) in good agreement with measured capacitor bank current. The JxB forces calculated from the data have a strong axial component at the base of the current channel and are shown to scale linearly with axial gradients in current density. Assuming force balance in the flux tube minor radius direction, we infer near-Alfvenic axial flows from the footpoint regions which are consistent with the measured axial forces. Flux tube collimation is observed in conjunction with these axial flows. These dynamic processes are relevant to the stability and dynamics of coronal loops. Supported provided by NSF, AFOSR.

  14. Quasi-steady multiple flux tubes induced by localized current perturbation in toroidal plasma

    NASA Astrophysics Data System (ADS)

    Yun, Gunsu

    2015-11-01

    Quasi-steady helical modes with dual, triple, or more flux tubes are easily produced by localized current drive in the core of sawtoothing plasma on the KSTAR tokamak. Individual flux tubes have m / n = 1 / 1 helicity, co-rotate around the magnetic axis, and later merge into a single m = 1 mode. The merged mode eventually crashes with rapid collapse of the core pressure and the next cycle repeats the same pattern, exhibiting sawtooth-like oscillations in the core pressure. The generation mechanism of multiple flux tubes (MFTs) has been studied in two different approaches to understand the observed trend that the number of flux tubes increases as the current drive location moves away from the magnetic axis up to about the magnetic surface of the safety factor q = 1 at the mode collapse: (1) nonlinear reduced MHD simulation with a localized current source modeling the time-varying interaction between the current source and flux tubes and (2) linear MHD simulation with a prescribed q profile with a radially localized current blip. Both studies show that MFTs can be produced only in plasmas with nearly flat q profile close to unity, suggesting the collapse of the m = 1 mode (i.e., sawtooth crash) is complete. Recent observation of long-lived MFTs induced by localized current drive in non-sawtoothing plasma suggests that q profile evolution toward lower- m instability is required for the merging and crash of MFTs. Work supported by the National Research Foundation of Korea, US D.O.E., and Japan Society for the Promotion of Science.

  15. Correlation of critical heat flux data for uniform tubes

    SciTech Connect

    Jafri, T.; Dougherty, T.J.; Yang, B.W.

    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.

  16. MULTI-SCALE MODELING AND APPROXIMATION ASSISTED OPTIMIZATION OF BARE TUBE HEAT EXCHANGERS

    SciTech Connect

    Bacellar, Daniel; Ling, Jiazhen; Aute, Vikrant; Radermacher, Reinhard; Abdelaziz, Omar

    2014-01-01

    Air-to-refrigerant heat exchangers are very common in air-conditioning, heat pump and refrigeration applications. In these heat exchangers, there is a great benefit in terms of size, weight, refrigerant charge and heat transfer coefficient, by moving from conventional channel sizes (~ 9mm) to smaller channel sizes (< 5mm). This work investigates new designs for air-to-refrigerant heat exchangers with tube outer diameter ranging from 0.5 to 2.0mm. The goal of this research is to develop and optimize the design of these heat exchangers and compare their performance with existing state of the art designs. The air-side performance of various tube bundle configurations are analyzed using a Parallel Parameterized CFD (PPCFD) technique. PPCFD allows for fast-parametric CFD analyses of various geometries with topology change. Approximation techniques drastically reduce the number of CFD evaluations required during optimization. Maximum Entropy Design method is used for sampling and Kriging method is used for metamodeling. Metamodels are developed for the air-side heat transfer coefficients and pressure drop as a function of tube-bundle dimensions and air velocity. The metamodels are then integrated with an air-to-refrigerant heat exchanger design code. This integration allows a multi-scale analysis of air-side performance heat exchangers including air-to-refrigerant heat transfer and phase change. Overall optimization is carried out using a multi-objective genetic algorithm. The optimal designs found can exhibit 50 percent size reduction, 75 percent decrease in air side pressure drop and doubled air heat transfer coefficients compared to a high performance compact micro channel heat exchanger with same capacity and flow rates.

  17. Numerical simulations of three-dimensional magnetic swirls in a solar flux-tube

    NASA Astrophysics Data System (ADS)

    Chmielewski, Piotr; Murawski, Krzysztof; Solov'ev, Alexandr A.

    2014-07-01

    We aim to numerically study evolution of Alfvén waves that accompany short-lasting swirl events in a solar magnetic flux-tube that can be a simple model of a magnetic pore or a sunspot. With the use of the FLASH code we numerically solve three-dimensional ideal magnetohydrodynamic equations to simulate twists which are implemented at the top of the photosphere in magnetic field lines of the flux-tube. Our numerical results exhibit swirl events and Alfvén waves with associated clockwise and counterclockwise rotation of magnetic lines, with the largest values of vorticity at the bottom of the chromosphere, and a certain amount of energy flux.

  18. Potassium flux in the pollen tubes was essential in plant sexual reproduction.

    PubMed

    Wu, Ju-You; Jin, Cong; Zhang, Shao-Ling

    2011-06-01

    Potassium channels are controlling K (+) transport across plasma membrane and thus playing a central role in all aspects of osmolarity as well as numerous other functions in plants including in sexual reproduction. We have used whole-cell and single-channel patch-clamp recording techniques investigated the regulation of intracellular free Ca ( 2+) -activated outward K (+) channels in Pyrus pyrifolia pollen tube protoplasts. We have also showed the channels could be inhibited by heme and activated carbon monoxide (CO). In the presence of oxygen and NADPH, hemoxygenases catalyzes heme degradation, producing biliverdin, iron and CO. Considered the oxygen concentration approaching zero in the ovary, the heme will inhibit the K (+) outward flux from the intracellular of pollen tube, increasing the pollen tubes osmolarity, inducing pollen tube burst. Here we discuss the putative role of K (+) channels in plant sexual reproduction.

  19. Numerical Simulations of Torsional Alfvén Waves in Axisymmetric Solar Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Wójcik, D.; Murawski, K.; Musielak, Z. E.; Konkol, P.; Mignone, A.

    2017-02-01

    We numerically investigate Alfvén waves propagating along an axisymmetric and non-isothermal solar flux tube embedded in the solar atmosphere. The tube magnetic field is current-free and diverges with height, and the waves are excited by a periodic driver along the tube magnetic field lines. The main results are that the two wave variables, the velocity and magnetic field perturbations in the azimuthal direction, behave differently as a result of gradients of the physical parameters along the tube. To explain these differences in the wave behavior, the time evolution of the wave variables and the resulting cutoff period for each wave variable are calculated and used to determine regions in the solar chromosphere where strong wave reflection may occur.

  20. Habitability of planets on eccentric orbits: Limits of the mean flux approximation

    NASA Astrophysics Data System (ADS)

    Bolmont, Emeline; Libert, Anne-Sophie; Leconte, Jeremy; Selsis, Franck

    2016-06-01

    Unlike the Earth, which has a small orbital eccentricity, some exoplanets discovered in the insolation habitable zone (HZ) have high orbital eccentricities (e.g., up to an eccentricity of ~0.97 for HD 20782 b). This raises the question of whether these planets have surface conditions favorable to liquid water. In order to assess the habitability of an eccentric planet, the mean flux approximation is often used. It states that a planet on an eccentric orbit is called habitable if it receives on average a flux compatible with the presence of surface liquid water. However, because the planets experience important insolation variations over one orbit and even spend some time outside the HZ for high eccentricities, the question of their habitability might not be as straightforward. We performed a set of simulations using the global climate model LMDZ to explore the limits of the mean flux approximation when varying the luminosity of the host star and the eccentricity of the planet. We computed the climate of tidally locked ocean covered planets with orbital eccentricity from 0 to 0.9 receiving a mean flux equal to Earth's. These planets are found around stars of luminosity ranging from 1 L⊙ to 10-4L⊙. We use a definition of habitability based on the presence of surface liquid water, and find that most of the planets considered can sustain surface liquid water on the dayside with an ice cap on the nightside. However, for high eccentricity and high luminosity, planets cannot sustain surface liquid water during the whole orbital period. They completely freeze at apoastron and when approaching periastron an ocean appears around the substellar point. We conclude that the higher the eccentricity and the higher the luminosity of the star, the less reliable the mean flux approximation.

  1. THE RISE OF ACTIVE REGION FLUX TUBES IN THE TURBULENT SOLAR CONVECTIVE ENVELOPE

    SciTech Connect

    Weber, Maria A.; Fan Yuhong; Miesch, Mark S.

    2011-11-01

    We use a thin flux tube model in a rotating spherical shell of turbulent convective flows to study how active region scale flux tubes rise buoyantly from the bottom of the convection zone to near the solar surface. We investigate toroidal flux tubes at the base of the convection zone with field strengths ranging from 15 kG to 100 kG at initial latitudes ranging from 1{sup 0} to 40{sup 0} with a total flux of 10{sup 22} Mx. We find that the dynamic evolution of the flux tube changes from convection dominated to magnetic buoyancy dominated as the initial field strength increases from 15 kG to 100 kG. At 100 kG, the development of {Omega}-shaped rising loops is mainly controlled by the growth of the magnetic buoyancy instability. However, at low field strengths of 15 kG, the development of rising {Omega}-shaped loops is largely controlled by convective flows, and properties of the emerging loops are significantly changed compared to previous results in the absence of convection. With convection, rise times are drastically reduced (from years to a few months), loops are able to emerge at low latitudes, and tilt angles of emerging loops are consistent with Joy's law for initial field strengths of {approx}>40 kG. We also examine other asymmetries that develop between the leading and following legs of the emerging loops. Taking all the results together, we find that mid-range field strengths of {approx}40-50 kG produce emerging loops that best match the observed properties of solar active regions.

  2. The optimization of fin-tube heat exchanger with longitudinal vortex generators using response surface approximation and genetic algorithm

    NASA Astrophysics Data System (ADS)

    Wu, Xuehong; Liu, DanDan; Zhao, Min; Lu, YanLi; Song, Xiaoyong

    2016-09-01

    Delta winglet works better than other vortex generators in improving the performance of fin-tube heat exchangers. In this paper, Response Surface Approximation is used to study the effects of the fin pitch, the ratio of the longitudinal tube pitch to transverse tube pitch, the ratio of both sides V 1 , V h of delta winglets and the attack angle of delta winglets on the performance of fin-tube heat exchanger. Firstly, Twenty-nine numerical group experiments including five times repeated experiments at the central point are conducted. Then, the analyses of variable (ANOVA) and regression are performed to verify the accuracy of the polynomial coefficients. Finally, the optimization of the fin-tube heat exchanger using the Genetic Algorithm is conducted and the best performance of j/f (1/3) is found to be 0.07945, which is consistent with the numerical result.

  3. Fast Solar Wind from Slowly Expanding Magnetic Flux Tubes (P54)

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.; Dwivedi, B. N.

    2006-11-01

    aks.astro.itbhu@gmail.com We present an empirical model of the fast solar wind, emanating from radially oriented slowly expanding magnetic flux tubes. We consider a single-fluid, steady state model in which the flow is driven by thermal and non-thermal pressure gradients. We apply a non-Alfvénic energy correction at the coronal base and find that specific relations correlate solar wind speed and non-thermal energy flux with the aerial expansion factor. The results are compared with the previously reported ones.

  4. Signature of collision of magnetic flux tubes in the quiet solar photosphere

    NASA Astrophysics Data System (ADS)

    Andic, Aleksandra

    2011-08-01

    Collision of the magnetic flux tubes in the Quiet Sun was proposed as one of the possible sources for the heating of the solar atmosphere (Furusawa and Sakai, 2000). The solar photosphere was observed using the New Solar Telescope ad Big Bear Solar Observatory. In TiO spectral line at 705.68 nm we approached resolution of 0.1''. The horizontal plasma wave was observed spreading from the larger bright point. Shorty after this wave an increase in the oscillatory power appeared at the same location as the observed bright point. This behavior matches some of the results from the simulation of the collision of the two flux tubes with a weak current.

  5. Event-by-event study of space-time dynamics in flux-tube fragmentation

    NASA Astrophysics Data System (ADS)

    Wong, Cheuk-Yin

    2017-07-01

    In the semi-classical description of the flux-tube fragmentation process for hadron production and hadronization in high-energy {e}+{e}- annihilations and pp collisions, the rapidity-space-time ordering and the local conservation laws of charge, flavor, and momentum provide a set of powerful tools that may allow the reconstruction of the space-time dynamics of quarks and mesons in exclusive measurements of produced hadrons, on an event-by-event basis. We propose procedures to reconstruct the space-time dynamics from event-by-event exclusive hadron data to exhibit explicitly the ordered chain of hadrons produced in a flux tube fragmentation. As a supplementary tool, we infer the average space-time coordinates of the q-\\bar{q} pair production vertices from the {π }- rapidity distribution data obtained by the NA61/SHINE Collaboration in pp collisions at \\sqrt{s}=6.3 to 17.3 GeV.

  6. Laboratory Measurement of 3D Magnetic Reconnection of Arched Flux Tubes

    NASA Astrophysics Data System (ADS)

    Haw, Magnus; Bellan, Paul M.

    2015-11-01

    An experiment has been constructed to collide two arched magnetic flux tubes at different angles with fully 3D, non-symmetric geometry. The configuration is designed to mimic sheared solar arcades and evaluate the importance of magnetic reconnection in such systems. Time resolved (1MHz) 3D magnetic measurements are taken with a multi-channel 3D magnetic probe. Preliminary analysis shows good agreement between calculated current density and external current diagnostics. Additional simultaneous diagnostics include voltage probes, fast camera imaging, and a 12-channel spectrometer. The spectrometer measures temperature, density, velocity, while the camera provides a view of global plasma behavior. Fast camera images indicate that the topology of the flux tubes evolves such that two equally sized, overlapping loops reconnect to form a small underlying loop and a large overarching loop.

  7. Spectral line radiation from solar small-scale flux tubes. II

    NASA Astrophysics Data System (ADS)

    Hasan, S. S.; Kneer, F.; Kalkofen, W.

    1998-04-01

    We examine spectral line radiation from small-scale magnetic flux tubes in the solar atmosphere. This is a continuation of work by Kneer et al. (1996). The main difference with the previous investigation is in the choice of the external atmosphere. Earlier we adopted an atmosphere resembling the empirical quiet Sun model for the ambient medium. In the present study, we iteratively adjust the temperature structure of the external atmosphere to fit the Stokes I and V profiles and the average continuum intensities with those obtained from observations. Our models are hotter in the uppermost photospheric layers and cooler in the deeper layers than the quiet Sun model and agree well with semi-empirical flux tube models.

  8. Distortions of Magnetic Flux Tubes in the Presence of Electric Currents

    NASA Astrophysics Data System (ADS)

    Malanushenko, Anna; Rempel, Matthias; Cheung, Mark

    2016-05-01

    Solar coronal loops possess several peculiar properties, which have been a subject of intensive research for a long time. These in particular include the lack of apparent expansion of coronal loops and the increased pressure scale height in loops compared to the diffuse background. Previously, Malanushenko & Schrijver (2013) proposed that these could be explained by the fact that magnetic flux tubes expand with height in a highly anisotropic manner. They used potential field models to demonstrate that flux tubes that have circular cross section at the photosphere, in the corona turn into a highly elongates structures, more resembling thick ribbons. Such ribbons, viewed along the expanding edge, would appear as thin, crisp structures of a constant cross-section with an increased pressure scale height, and when viewed along the non-expanding side, would appear as faint, wide and underdense features. This may also introduce a selection bias,when a set of loops is collected for a further study, towards those viewed along the expanding edge.However, some of the past studies have indicated that strong electric currents flowing in a given flux tube may result in the tube maintaining a relatively constant cross-sectional shape along its length. Given that Malanushenko & Schrijver (2013) focused on a potential, or current-free, field model of an active region, the extend to which their analysis could be applied to the real solar fields, was unclear.In the present study, we use a magnetic field created by MURaM, a highly realistic state-of-the-art radiative MHD code (Vogler et al, 2005; Rempel et al, 2009b). MURaM was shown to reproduce a wide variety of observed features of the solar corona (e.g., Hansteen et al, 2010; Cheung et al. 2007, 2008; Rempel 2009a,b). We analyze the distortions of magnetic flux tubes in a MURaM simulation of an active region corona. We quantify such distortions and correlate them with a number of relevant parameters of flux tubes, with a

  9. ORIGIN OF MACROSPICULE AND JET IN POLAR CORONA BY A SMALL-SCALE KINKED FLUX TUBE

    SciTech Connect

    Kayshap, P.; Srivastava, Abhishek K.; Murawski, K.; Tripathi, Durgesh E-mail: aks@aries.res.in E-mail: durgesh@iucaa.ernet.in

    2013-06-10

    We report an observation of a small-scale flux tube that undergoes kinking and triggers the macrospicule and a jet on 2010 November 11 in the north polar corona. The small-scale flux tube emerged well before the triggering of the macrospicule and as time progresses the two opposite halves of this omega-shaped flux tube bent transversely and approach each other. After {approx}2 minutes, the two approaching halves of the kinked flux tube touch each other and an internal reconnection as well as an energy release takes place at the adjoining location and a macrospicule was launched which goes up to a height of 12 Mm. Plasma begins to move horizontally as well as vertically upward along with the onset of the macrospicule and thereafter converts into a large-scale jet in which the core denser plasma reaches up to {approx}40 Mm in the solar atmosphere with a projected speed of {approx}95 km s{sup -1}. The fainter and decelerating plasma chunks of this jet were also seen up to {approx}60 Mm. We perform a two-dimensional numerical simulation by considering the VAL-C initial atmospheric conditions to understand the physical scenario of the observed macrospicule and associated jet. The simulation results show that reconnection-generated velocity pulse in the lower solar atmosphere steepens into slow shock and the cool plasma is driven behind it in the form of macrospicule. The horizontal surface waves also appeared with shock fronts at different heights, which most likely drove and spread the large-scale jet associated with the macrospicule.

  10. Propagation of Long-Wavelength Nonlinear Slow Sausage Waves in Stratified Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Barbulescu, M.; Erdélyi, R.

    2016-05-01

    The propagation of nonlinear, long-wavelength, slow sausage waves in an expanding magnetic flux tube, embedded in a non-magnetic stratified environment, is discussed. The governing equation for surface waves, which is akin to the Leibovich-Roberts equation, is derived using the method of multiple scales. The solitary wave solution of the equation is obtained numerically. The results obtained are illustrative of a solitary wave whose properties are highly dependent on the degree of stratification.

  11. Dilation of force-free magnetic flux tubes. [solar magnetic field profiles

    NASA Technical Reports Server (NTRS)

    Frankenthal, S.

    1977-01-01

    A general study is presented of the mapping functions which relate the magnetic-field profiles across a force-free rope in segments subjected to various external pressures. The results reveal that if the external pressure falls below a certain critical level (dependent on the flux-current relation which defines the tube), the magnetic profile consists of an invariant core sheathed in a layer permeated by an azimuthal magnetic field.

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

    SciTech Connect

    Doerffer, S.; Groeneveld, D.C.; Cheng, S.C.

    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.

  13. Horizontal radiative fluxes in clouds and accuracy of the independent pixel approximation at absorbing wavelengths

    NASA Astrophysics Data System (ADS)

    Marshak, A.; Oreopoulos, L.; Davis, A. B.; Wiscombe, W. J.; Cahalan, R. F.

    For absorbing wavelengths, we discuss the effect of horizontal solar radiative fluxes in clouds on the accuracy of a conventional plane-parallel radiative transfer calculation for a single pixel, known as the Independent Pixel Approximation (IPA). Vertically integrated horizontal fluxes can be represented as a sum of three components: the IPA accuracies for reflectance, transmittance and absorptance. We show that IPA accuracy for reflectance always improves with more absorption, while the IPA accuracy for transmittance is less sensitive to the changes in absorption: with respect to the non-absorbing case, it may first deteriorate for weak absorption and then improve again for strongly absorbing wavelengths. IPA accuracy for absorptance always deteriorates with more absorption.

  14. Scaling in situ cosmogenic nuclide production rates using analytical approximations to atmospheric cosmic-ray fluxes

    NASA Astrophysics Data System (ADS)

    Lifton, Nathaniel; Sato, Tatsuhiko; Dunai, Tibor J.

    2014-01-01

    Several models have been proposed for scaling in situ cosmogenic nuclide production rates from the relatively few sites where they have been measured to other sites of interest. Two main types of models are recognized: (1) those based on data from nuclear disintegrations in photographic emulsions combined with various neutron detectors, and (2) those based largely on neutron monitor data. However, stubborn discrepancies between these model types have led to frequent confusion when calculating surface exposure ages from production rates derived from the models. To help resolve these discrepancies and identify the sources of potential biases in each model, we have developed a new scaling model based on analytical approximations to modeled fluxes of the main atmospheric cosmic-ray particles responsible for in situ cosmogenic nuclide production. Both the analytical formulations and the Monte Carlo model fluxes on which they are based agree well with measured atmospheric fluxes of neutrons, protons, and muons, indicating they can serve as a robust estimate of the atmospheric cosmic-ray flux based on first principles. We are also using updated records for quantifying temporal and spatial variability in geomagnetic and solar modulation effects on the fluxes. A key advantage of this new model (herein termed LSD) over previous Monte Carlo models of cosmogenic nuclide production is that it allows for faster estimation of scaling factors based on time-varying geomagnetic and solar inputs. Comparing scaling predictions derived from the LSD model with those of previously published models suggest potential sources of bias in the latter can be largely attributed to two factors: different energy responses of the secondary neutron detectors used in developing the models, and different geomagnetic parameterizations. Given that the LSD model generates flux spectra for each cosmic-ray particle of interest, it is also relatively straightforward to generate nuclide-specific scaling

  15. Habitability of planets on eccentric orbits: limits of the mean flux approximation

    NASA Astrophysics Data System (ADS)

    Bolmont, Emeline; Libert, Anne-Sophie; Leconte, Jérémy; Selsis, Franck; Turbet, Martin; Forget, François

    2016-04-01

    A few of the planets found in the insolation habitable zone (region in which a planet with an atmosphere can sustain surface liquid water, Kasting et al. 1993) are on eccentric orbits, such as GJ 667Cc (eccentricity of < 0.3, Anglada-Escude et al. 2012) or HD 16175 b (eccentricity of 0.6, Peek et al. 2009). This raises the question of the potential habitability of planets that only spend a fraction of their orbit in the habitable zone. Usually for a planet of semi-major axis a and eccentricity e, the averaged flux over one orbit received by the planet is considered. This averaged flux corresponds to the flux received by a planet on a circular orbit of radius r = a(1 -e2)1/4. If this orbital distance is within the habitable zone, the planet is said "habitable". However, for a hot star, for which the habitable zone is far from the star, the climate can be degraded when the planet is temporarily outside the habitable zone. We investigate here the limits of validity of the mean flux approximation used to assess the potential habitability of eccentric planets. For this study, we consider ocean planets in synchronized rotation and planets with a rotation period of 24 hr. We investigate the influence of the type of host star and the eccentricity of the orbit on the climate of a planet. We do so by scaling the duration of its orbital period and its apastron and periastron distance to ensure that it receives in average the same incoming flux as Earth's. We performed sets of 3D simulations using the Global Climate Model LMDz (Wordsworth et al. 2011, Forget et al. 2013, Leconte et al. 2013). The atmosphere is composed of N2, CO2 and H2O (gas, liquid, solid) in Earth-like proportions. First, we do not take into account the spectral difference between a low luminosity star and a Sun-like star. Second, the dependence of the albedo of ice and snow on the spectra of the host star is taken into account. This influences the positive ice-albedo feedback and can lead to a different

  16. Habitability of planets on eccentric orbits: limits of the mean flux approximation??

    NASA Astrophysics Data System (ADS)

    Bolmont, Emeline; Libert, Anne-Sophie; Leconte, Jeremy; Selsis, Franck

    2015-07-01

    A few of the planets found in the insolation habitable zone (as defined by Kasting et al. 1993) are on eccentric orbits, such as HD 136118 b (eccentricity of ˜0.3, Wittenmyer et al. 2009). This raises the question of the potential habitability of planets that only spend a fraction of their orbit in the habitable zone. Usually for a planet of semi-major axis a and eccentricity e, the averaged flux over one orbit received by the planet is considered. This averaged flux corresponds to the flux received by a planet on a circular orbit of radius r = a(1-eˆ2)ˆ1/4. If this orbital distance is within the habitable zone, the planet is considered "habitable". However, for a hot star, for which the habitable zone is far from the star, the climate can be degraded when the planet is temporarily outside the habitable zone. The influence of the orbital eccentricity of a planet on its climate has already been studied for Earth-like conditions (same star, same rotation period), with Global Climate Models (GCM) such as in Williams & Pollard 2002 and Linsenmeier et al. 2014. Spiegel 2010 and Dressing et al. 2010 have also studied the effect of eccentricity for more diverse conditions with energy-balanced models. We performed a set of simulations using the Global Climate Model LMDz (Wordsworth et al. 2011, Forget et al. 2013, Leconte et al. 2013). We computed the climate of aqua planets receiving a mean flux equal to Earth's, around stars of luminosity ranging from 1 Lsun to 10-4 Lsun and of orbital eccentricity from 0 to 0.9. We show the limits of the mean flux approximation, depending on the previous parameters and also the thermal inertia of oceans.

  17. PROPAGATION AND DISPERSION OF SAUSAGE WAVE TRAINS IN MAGNETIC FLUX TUBES

    SciTech Connect

    Oliver, R.; Terradas, J.; Ruderman, M. S.

    2015-06-10

    A localized perturbation of a magnetic flux tube produces wave trains that disperse as they propagate along the tube, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. We find that the propagating wave train undergoes stronger attenuation for longer axisymmetric (or shorter transverse) perturbations, while the internal to external density ratio has a smaller effect on the attenuation. Moreover, for parameter values typical of coronal loops axisymmetric (transverse) wave trains travel at a speed 0.75–1 (1.2) times the Alfvén speed of the magnetic tube. In both cases, the wave train passage at a fixed position of the magnetic tube gives rise to oscillations with periods of the order of seconds, with axisymmetric disturbances causing more oscillations than transverse ones. To test the detectability of propagating transverse or axisymmetric wave packets in magnetic tubes of the solar atmosphere (e.g., coronal loops, spicules, or prominence threads) a forward modeling of the perturbations must be carried out.

  18. Propagation and Dispersion of Sausage Wave Trains in Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Oliver, R.; Ruderman, M. S.; Terradas, J.

    2015-06-01

    A localized perturbation of a magnetic flux tube produces wave trains that disperse as they propagate along the tube, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. We find that the propagating wave train undergoes stronger attenuation for longer axisymmetric (or shorter transverse) perturbations, while the internal to external density ratio has a smaller effect on the attenuation. Moreover, for parameter values typical of coronal loops axisymmetric (transverse) wave trains travel at a speed 0.75-1 (1.2) times the Alfvén speed of the magnetic tube. In both cases, the wave train passage at a fixed position of the magnetic tube gives rise to oscillations with periods of the order of seconds, with axisymmetric disturbances causing more oscillations than transverse ones. To test the detectability of propagating transverse or axisymmetric wave packets in magnetic tubes of the solar atmosphere (e.g., coronal loops, spicules, or prominence threads) a forward modeling of the perturbations must be carried out.

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

    NASA Astrophysics Data System (ADS)

    Requerey, Iker S.; Ruiz Cobo, B.; Del Toro Iniesta, J. C.; Orozco Suárez, D.; Blanco Rodríguez, J.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; van Noort, M.; Schmidt, W.; Martínez Pillet, V.; Knölker, M.

    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.

  20. The motion of magnetic flux tube at the dayside magnetopause under the influence of solar wind flow

    SciTech Connect

    Liu, Z.X.; Hu, Y.D.; Li, F. ); Pu, Z.Y. )

    1990-05-01

    The authors propose that flux transfer events (FTEs) at the dayside magnetopause are formed by fluid vortices in the flow field. According to the view of vortex-induced reconnection a FTE tube is a magnetic fluid vortex tube (MF vortex tube). The motion of a FTE tube can be represented by that of a MF vortex in the formation region located in the dayside magnetopause region. This study deals with the internal and external influences governing the motion of MF vortex tubes. The equations of motion of a vortex tube are established and solved. It is found that a FTE tube moves frm low latitude to high latitude with a certain speed. However, the motional path is not a straight line but oscillates about the northward direction for the northern hemisphere. The motional velocity, amplitude and period of the oscillation depend on the flow field and magnetic field in the magnetosheath and magnetosphere as well as the size of the FTE tube.

  1. The sensitivity of latent heat flux to the air humidity approximations used in ocean circulation models

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Niiler, Pearn P.

    1990-01-01

    In deriving the surface latent heat flux with the bulk formula for the thermal forcing of some ocean circulation models, two approximations are commonly made to bypass the use of atmospheric humidity in the formula. The first assumes a constant relative humidity, and the second supposes that the sea-air humidity difference varies linearly with the saturation humidity at sea surface temperature. Using climatological fields derived from the Marine Deck and long time series from ocean weather stations, the errors introduced by these two assumptions are examined. It is shown that the errors reach above 100 W/sq m over western boundary currents and 50 W/sq m over the tropical ocean. The two approximations also introduce erroneous seasonal and spatial variabilities with magnitudes over 50 percent of the observed variabilities.

  2. Forced Convection Boiling and Critical Heat Flux of Ethanol in Electrically Heated Tube Tests

    NASA Technical Reports Server (NTRS)

    Meyer, Michael L.; Linne, Diane L.; Rousar, Donald C.

    1998-01-01

    Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.

  3. Auroral electron precipitation and flux tube erosion in Titan’s upper atmosphere

    NASA Astrophysics Data System (ADS)

    Snowden, D.; Yelle, R. V.; Galand, M.; Coates, A. J.; Wellbrock, A.; Jones, G. H.; Lavvas, P.

    2013-09-01

    Cassini dasta shows that Titan’s atmosphere strongly depletes the electron content in Saturn’s flux tubes, producing features known as electron bite-outs, which indicate that the flux of auroral electrons decreases over time. To understand this process we have developed a time-dependent two-stream model, which uses field line geometries and drift paths calculated by a three-dimensional multi-fluid model of Titan’s plasma interaction. The boundary conditions of the model account for the time-dependent reduction or increase in electron flux along Saturn’s magnetic field lines because of the loss or production of electrons in Titan’s atmosphere. The modification of the auroral electron flux depends on the electron bounce period in Saturn’s outer magnetosphere; therefore, we also calculate electron bounce periods along several Kronian field lines accounting for both the magnetic mirroring force and the field-aligned electric potential in Saturn’s plasma sheet. We use the time-dependent two-stream model to calculate how the reduction in the auroral electron flux affects electron impact ionization and energy deposition rates in Titan’s upper atmosphere. We find that the flux of higher energy (>50 eV) electrons entering Titan’s atmosphere is strongly reduced over time, resulting in smaller ionization and energy deposition rates below ∼1300 km altitude. Finally, we show that sample spectrograms produced from our calculations are consistent with CAPS-ELS data.

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

    NASA Astrophysics Data System (ADS)

    Ibrom, Andreas; Brændholt, Andreas; Pilegaard, Kim

    2016-04-01

    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 the frequency attenuation and the time lag of the N2O and CO concentration measurements with a concentration step experiment. The results showed surprisingly high cut-off frequencies (close to 2 Hz) and small low-pass filter induced time lags (< 0.3 s), which were similar for CO and N2O. The results indicate that the concentration signal was hardly biased during the ca 10 s travel through the tube. Due to the larger turbulence time scales at large measurement heights the low-pass correction was for the majority of the measurements < 5%. For water vapour the tube attenuation was massive, which had, however, a positive effect 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 flows.

  5. GENERATION OF MAGNETOHYDRODYNAMIC WAVES IN LOW SOLAR ATMOSPHERIC FLUX TUBES BY PHOTOSPHERIC MOTIONS

    SciTech Connect

    Mumford, S. J.; Fedun, V.; Erdélyi, R.

    2015-01-20

    Recent ground- and space-based observations reveal the presence of small-scale motions between convection cells in the solar photosphere. In these regions, small-scale magnetic flux tubes are generated via the interaction of granulation motion and the background magnetic field. This paper studies the effects of these motions on magnetohydrodynamic (MHD) wave excitation from broadband photospheric drivers. Numerical experiments of linear MHD wave propagation in a magnetic flux tube embedded in a realistic gravitationally stratified solar atmosphere between the photosphere and the low choromosphere (above β = 1) are performed. Horizontal and vertical velocity field drivers mimic granular buffeting and solar global oscillations. A uniform torsional driver as well as Archimedean and logarithmic spiral drivers mimic observed torsional motions in the solar photosphere. The results are analyzed using a novel method for extracting the parallel, perpendicular, and azimuthal components of the perturbations, which caters to both the linear and non-linear cases. Employing this method yields the identification of the wave modes excited in the numerical simulations and enables a comparison of excited modes via velocity perturbations and wave energy flux. The wave energy flux distribution is calculated to enable the quantification of the relative strengths of excited modes. The torsional drivers primarily excite Alfvén modes (≈60% of the total flux) with small contributions from the slow kink mode, and, for the logarithmic spiral driver, small amounts of slow sausage mode. The horizontal and vertical drivers primarily excite slow kink or fast sausage modes, respectively, with small variations dependent upon flux surface radius.

  6. Generation of Magnetohydrodynamic Waves in Low Solar Atmospheric Flux Tubes by Photospheric Motions

    NASA Astrophysics Data System (ADS)

    Mumford, S. J.; Fedun, V.; Erdélyi, R.

    2015-01-01

    Recent ground- and space-based observations reveal the presence of small-scale motions between convection cells in the solar photosphere. In these regions, small-scale magnetic flux tubes are generated via the interaction of granulation motion and the background magnetic field. This paper studies the effects of these motions on magnetohydrodynamic (MHD) wave excitation from broadband photospheric drivers. Numerical experiments of linear MHD wave propagation in a magnetic flux tube embedded in a realistic gravitationally stratified solar atmosphere between the photosphere and the low choromosphere (above β = 1) are performed. Horizontal and vertical velocity field drivers mimic granular buffeting and solar global oscillations. A uniform torsional driver as well as Archimedean and logarithmic spiral drivers mimic observed torsional motions in the solar photosphere. The results are analyzed using a novel method for extracting the parallel, perpendicular, and azimuthal components of the perturbations, which caters to both the linear and non-linear cases. Employing this method yields the identification of the wave modes excited in the numerical simulations and enables a comparison of excited modes via velocity perturbations and wave energy flux. The wave energy flux distribution is calculated to enable the quantification of the relative strengths of excited modes. The torsional drivers primarily excite Alfvén modes (≈60% of the total flux) with small contributions from the slow kink mode, and, for the logarithmic spiral driver, small amounts of slow sausage mode. The horizontal and vertical drivers primarily excite slow kink or fast sausage modes, respectively, with small variations dependent upon flux surface radius.

  7. The deformation of flux tubes in the solar wind with applications to the structure of magnetic clouds and CMEs

    NASA Technical Reports Server (NTRS)

    Cargill, Peter J.; Chen, James; Spicer, D. S.; Zalesak, S. T.

    1994-01-01

    Two dimensional magnetohydrodynamic simulations of the distortion of a magnetic flux tube, accelerated through ambient solar wind plasma, are presented. Vortices form on the trailing edge of the flux tube, and couple strongly to its interior. If the flux tube azimuthal field is weak, it deforms into an elongated banana-like shape after a few Alfven transit times. A significant azimuthal field component inhibits this distortion. In the case of magnetic clouds in the solar wind, it is suggested that the shape observed at 1 AU was determined by distortion of the cloud in the inner heliosphere. Distortion of the cloud beyond 1 AU takes many days. It is estimated that effective drag coefficients slightly greater than unity are appropriate for modeling flux tube propagation. Synthetic magnetic field profiles as would be seen by a spacecraft traversing the cloud are presented.

  8. Simulation of a Collision between Shock Waves and a Magnetic Flux Tube: Excitation of Surface Alfvén Waves and Body Alfvén Waves

    NASA Astrophysics Data System (ADS)

    Sakai, J. I.; Kawata, T.; Yoshida, K.; Furusawa, K.; Cramer, N. F.

    2000-07-01

    To explain the observed dynamics of the small-scale magnetic flux tubes in the quiet photospheric network, Furusawa & Sakai presented simulation results on the collision of two flux tubes. They found that shock waves appear during the collision of two magnetic flux tubes, when two magnetic flux tubes with weak electric current collide with each other. The shock waves so generated can subsequently collide with another flux tube, and we investigate here the interaction process of the shock with the flux tube. It is found that during the collision of a shock wave with a magnetic flux tube with weak electric current, surface Alfvén waves can be generated and propagate along the flux tube. However, when the shock wave collides with a magnetic flux tube with strong current, body Alfvén waves can be generated and propagate along the flux tube. It is also shown that, when we take into account the effect of a background density inhomogeneity due to gravity, there occurs a strong upward plasma jet along the flux tube, as well as surface Alfvén waves. The energy conversion rate from the shock wave energy to the upward MHD waves, as well as upward plasma flows, is about 40% and thus is very efficient. We apply our results to the problem of solar coronal heating.

  9. THE EMERGENCE OF A TWISTED FLUX TUBE INTO THE SOLAR ATMOSPHERE: SUNSPOT ROTATIONS AND THE FORMATION OF A CORONAL FLUX ROPE

    SciTech Connect

    Fan, Y.

    2009-06-01

    We present a three-dimensional simulation of the dynamic emergence of a twisted magnetic flux tube from the top layer of the solar convection zone into the solar atmosphere and corona. It is found that after a brief initial stage of flux emergence during which the two polarities of the bipolar region become separated and the tubes intersecting the photosphere become vertical, significant rotational motion sets in within each polarity. The rotational motions of the two polarities are found to twist up the inner field lines of the emerged fields such that they change their orientation into an inverse configuration (i.e., pointing from the negative polarity to the positive polarity over the neutral line). As a result, a flux rope with sigmoid-shaped, dipped core fields forms in the corona, and the center of the flux rope rises in the corona with increasing velocity as the twisting of the flux rope footpoints continues. The rotational motion in the two polarities is a result of propagation of nonlinear torsional Alfven waves along the flux tube, which transports significant twist from the tube's interior portion toward its expanded coronal portion. This is a basic process whereby twisted flux ropes are developed in the corona with increasing twist and magnetic energy, leading up to solar eruptions.

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

    NASA Technical Reports Server (NTRS)

    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.

  11. The dynamic evolution of active-region-scale magnetic flux tubes in the turbulent solar convective envelope

    NASA Astrophysics Data System (ADS)

    Weber, Maria Ann

    2014-12-01

    The Sun exhibits cyclic properties of its large-scale magnetic field on the order of sigma22 years, with a ˜11 year frequency of sunspot occurrence. These sunspots, or active regions, are the centers of magnetically driven phenomena such as flares and coronal mass ejections. Volatile solar magnetic events directed toward the Earth pose a threat to human activities and our increasingly technological society. As such, the origin and nature of solar magnetic flux emergence is a topic of global concern. Sunspots are observable manifestations of solar magnetic fields, thus providing a photospheric link to the deep-seated dynamo mechanism. However, the manner by which bundles of magnetic field, or flux tubes, traverse the convection zone to eventual emergence at the solar surface is not well understood. To provide a connection between dynamo-generated magnetic fields and sunspots, I have performed simulations of magnetic flux emergence through the bulk of a turbulent, solar convective envelope by employing a thin flux tube model subject to interaction with flows taken from a hydrodynamic convection simulation computed through the Anelastic Spherical Harmonic (ASH) code. The convective velocity field interacts with the flux tube through the drag force it experiences as it traverses through the convecting medium. Through performing these simulations, much insight has been gained about the influence of turbulent solar-like convection on the flux emergence process and resulting active region properties. I find that the dynamic evolution of flux tubes change from convection dominated to magnetic buoyancy dominated as the initial field strength of the flux tubes increases from 15 kG to 100 kG. Additionally, active-region-scale flux tubes of 40 kG and greater exhibit properties similar to those of active regions on the Sun, such as: tilt angles, rotation rates, and morphological asymmetries. The joint effect of the Coriolis force and helical motions present in convective

  12. Flux rope, hyperbolic flux tube, and late extreme ultraviolet phases in a non-eruptive circular-ribbon flare

    NASA Astrophysics Data System (ADS)

    Masson, Sophie; Pariat, Étienne; Valori, Gherardo; Deng, Na; Liu, Chang; Wang, Haimin; Reid, Hamish

    2017-08-01

    Context. The dynamics of ultraviolet (UV) emissions during solar flares provides constraints on the physical mechanisms involved in the trigger and the evolution of flares. In particular it provides some information on the location of the reconnection sites and the associated magnetic fluxes. In this respect, confined flares are far less understood than eruptive flares generating coronal mass ejections. Aims: We present a detailed study of a confined circular flare dynamics associated with three UV late phases in order to understand more precisely which topological elements are present and how they constrain the dynamics of the flare. Methods: We perform a non-linear force-free field extrapolation of the confined flare observed with the Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) instruments on board Solar Dynamics Observatory (SDO). From the 3D magnetic field we compute the squashing factor and we analyse its distribution. Conjointly, we analyse the AIA extreme ultraviolet (EUV) light curves and images in order to identify the post-flare loops, and their temporal and thermal evolution. By combining the two analyses we are able to propose a detailed scenario that explains the dynamics of the flare. Results: Our topological analysis shows that in addition to a null-point topology with the fan separatrix, the spine lines and its surrounding quasi-separatix layer (QSL) halo (typical for a circular flare), a flux rope and its hyperbolic flux tube (HFT) are enclosed below the null. By comparing the magnetic field topology and the EUV post-flare loops we obtain an almost perfect match between the footpoints of the separatrices and the EUV 1600 Å ribbons and between the HFT field line footpoints and bright spots observed inside the circular ribbons. We show, for the first time in a confined flare, that magnetic reconnection occurred initially at the HFT below the flux rope. Reconnection at the null point between the flux rope and the

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

    NASA Technical Reports Server (NTRS)

    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

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

    NASA Technical Reports Server (NTRS)

    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.

  15. Alfven waves in the solar atmosphere. III - Nonlinear waves on open flux tubes

    NASA Technical Reports Server (NTRS)

    Hollweg, J. V.; Jackson, S.; Galloway, D.

    1982-01-01

    Consideration is given the nonlinear propagation of Alfven waves on solar magnetic flux tubes, where the tubes are taken to be vertical, axisymmetric and initially untwisted and the Alfven waves are time-dependent axisymmetric twists. The propagation of the waves into the chromosphere and corona is investigated through the numerical solution of a set of nonlinear, time-dependent equations coupling the Alfven waves into motions that are parallel to the initial magnetic field. It is concluded that Alfven waves can steepen into fast shocks in the chromosphere, pass through the transition region to produce high-velocity pulses, and then enter the corona, which they heat. The transition region pulses have amplitudes of about 60 km/sec, and durations of a few tens of seconds. In addition, the Alfven waves exhibit a tendency to drive upward flows, with many of the properties of spicules.

  16. Linear MHD Wave Propagation in Time-Dependent Flux Tube. II. Finite Plasma Beta

    NASA Astrophysics Data System (ADS)

    Williamson, A.; Erdélyi, R.

    2014-04-01

    The propagation of magnetohydrodynamic (MHD) waves is an area that has been thoroughly studied for idealised static and steady state magnetised plasma systems applied to numerous solar structures. By applying the generalisation of a temporally varying background density to an open magnetic flux tube, mimicking the observed slow evolution of such waveguides in the solar atmosphere, further investigations into the propagation of both fast and slow MHD waves can take place. The assumption of a zero-beta plasma (no gas pressure) was applied in Williamson and Erdélyi ( Solar Phys. 2013, doi:10.1007/s11207-013-0366-9, Paper I) is now relaxed for further analysis here. Firstly, the introduction of a finite thermal pressure to the magnetic flux tube equilibrium modifies the existence of fast MHD waves which are directly comparable to their counterparts found in Paper I. Further, as a direct consequence of the non-zero kinetic plasma pressure, a slow MHD wave now exists, and is investigated. Analysis of the slow wave shows that, similar to the fast MHD wave, wave amplitude amplification takes place in time and height. The evolution of the wave amplitude is determined here analytically. We conclude that for a temporally slowly decreasing background density both propagating magnetosonic wave modes are amplified for over-dense magnetic flux tubes. This information can be very practical and useful for future solar magneto-seismology applications in the study of the amplitude and frequency properties of MHD waveguides, e.g. for diagnostic purposes, present in the solar atmosphere.

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

    SciTech Connect

    Woolsey, L. N.; Cranmer, S. R.

    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.

  18. A thermal mixing model of crossflow in tube bundles for use with the porous body approximation

    SciTech Connect

    Ashcroft, J.; Kaminski, D.A.

    1996-06-01

    Diffusive thermal mixing in a heated tube bundle with a cooling fluid in crossflow was analyzed numerically. From the results of detailed two-dimensional models, which calculated the diffusion of heat downstream of one heated tube in an otherwise adiabatic flow field, a diffusion model appropriate for use with the porous body method was developed. The model accounts for both molecular and turbulent diffusion of heat by determining the effective thermal conductivity in the porous region. The model was developed for triangular shaped staggered tube bundles with pitch to diameter ratios between 1.10 and 2.00 and for Reynolds numbers between 1,000 and 20,000. The tubes are treated as nonconducting. Air and water were considered as working fluids. The effective thermal conductivity was found to be linearly dependent on the tube Reynolds number and fluid Prandtl number, and dependent on the bundle geometry. The porous body thermal mixing model was then compared against numerical models for flows with multiple heated tubes with very good agreement.

  19. Observations on Characterization of Defects in Coiled Tubing From Magnetic-Flux-Leakage Data

    SciTech Connect

    Timothy R. McJunkin; Karen S. Miller; Charles R. Tolle

    2006-04-01

    This paper presents observations on the sizing of automatically detected artificial flaws in coiled tubing samples using magnetic-flux-leakage data. Sixty-six artificial flaws of various shapes and types, ranging from 0.30 mm deep pits to slots with length of 9.5 mm, in 44.45 mm outer diameter pipe were analyzed. The detection algorithm and the information automatically extracted from the data are described. Observations on the capabilities and limitations for determining the size and shape of the flaws are discussed.

  20. Dynamics of monopoles and flux tubes in two-flavor dynamical QCD

    SciTech Connect

    Bornyakov, V.G.; Ichie, H.; Koma, Y.; Mori, Y.; Nakamura, Y.; Suzuki, T.; Pleiter, D.; Schierholz, G.; Streuer, T.; Stueben, H.

    2004-10-01

    We investigate the confining properties of the QCD vacuum with N{sub f}=2 flavors of dynamical quarks, and compare the results with the properties of the quenched theory. We use nonperturbatively O(a) improved Wilson fermions to keep cutoff effects small. We focus on color magnetic monopoles. Among the quantities we study are the monopole density and the monopole screening length, the static potential and the profile of the color electric flux tube. We furthermore derive the low-energy effective monopole action. Marked differences between the quenched and dynamical vacuum are found.

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

    SciTech Connect

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

    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.

  2. Stresses and deformations in cross-ply composite tubes subjected to a uniform temperature change: Elasticity and Approximate Solutions

    NASA Technical Reports Server (NTRS)

    Hyer, M. W.; Cooper, D. E.; Cohen, D.

    1985-01-01

    The effects of a uniform temperature change on the stresses and deformations of composite tubes are investigated. The accuracy of an approximate solution based on the principle of complementary virtual work is determined. Interest centers on tube response away from the ends and so a planar elasticity approach is used. For the approximate solution a piecewise linear variation of stresses with the radial coordinate is assumed. The results from the approximate solution are compared with the elasticity solution. The stress predictions agree well, particularly peak interlaminar stresses. Surprisingly, the axial deformations also agree well. This, despite the fact that the deformations predicted by the approximate solution do not satisfy the interface displacement continuity conditions required by the elasticity solution. The study shows that the axial thermal expansion coefficient of tubes with a specific number of axial and circumferential layers depends on the stacking sequence. This is in contrast to classical lamination theory which predicts the expansion to be independent of the stacking arrangement. As expected, the sign and magnitude of the peak interlaminar stresses depends on stacking sequence.

  3. Nonlinear Torsional and Compressional Waves in a Magnetic Flux Tube with Electric Current near the Quiet Solar Photospheric Network

    NASA Astrophysics Data System (ADS)

    Sakai, J. I.; Minamizuka, R.; Kawata, T.; Cramer, N. F.

    2001-04-01

    Recent high-resolution observations from photospheric magnetograms made with the SOHO/Michelson Doppler Imager instrument and the Swedish Vacuum Solar Telescope on La Palma showed that magnetic flux tubes in the quiet photospheric network of the solar photosphere are highly dynamic objects with small-scale substructures. We investigate nonlinear waves propagating along a magnetic flux tube in weakly ionized plasmas with high plasma beta (β~=1) by using three-dimensional neutral MHD equations. Recently Sakai et al. investigated nonlinear wave propagation along a magnetic flux tube with a weak current for the two cases of uniform density along the flux tube and density inhomogeneity due to solar gravity. They showed that shear Alfvén waves are excited by localized, predominantly rotational perturbations and that excited waves with a strong upflow of wave energy can propagate only upward along the flux tube when density inhomogeneity due to gravity is taken into account. In this paper we extend this work by investigating nonlinear torsional and compressional waves in a magnetic flux tube with a strong electric current, i.e., a twisted magnetic field, near the quiet solar photospheric network. If gravity is neglected, the torsional waves are found to propagate in a direction such as to decrease the twist of the magnetic field, while the compressional waves propagate symmetrically. We have found that solar gravity results in the important effect that wave energies excited by both torsional and compressional disturbances can be transferred upward in both untwisted and highly twisted flux tubes and eventually contribute to coronal heating.

  4. Magnetic-flux-driven topological quantum phase transition and manipulation of perfect edge states in graphene tube.

    PubMed

    Lin, S; Zhang, G; Li, C; Song, Z

    2016-08-24

    We study the tight-binding model for a graphene tube with perimeter N threaded by a magnetic field. We show exactly that this model has different nontrivial topological phases as the flux changes. The winding number, as an indicator of topological quantum phase transition (QPT) fixes at N/3 if N/3 equals to its integer part [N/3], otherwise it jumps between [N/3] and [N/3] + 1 periodically as the flux varies a flux quantum. For an open tube with zigzag boundary condition, exact edge states are obtained. There exist two perfect midgap edge states, in which the particle is completely located at the boundary, even for a tube with finite length. The threading flux can be employed to control the quantum states: transferring the perfect edge state from one end to the other, or generating maximal entanglement between them.

  5. Magnetic-flux-driven topological quantum phase transition and manipulation of perfect edge states in graphene tube

    PubMed Central

    Lin, S.; Zhang, G.; Li, C.; Song, Z.

    2016-01-01

    We study the tight-binding model for a graphene tube with perimeter N threaded by a magnetic field. We show exactly that this model has different nontrivial topological phases as the flux changes. The winding number, as an indicator of topological quantum phase transition (QPT) fixes at N/3 if N/3 equals to its integer part [N/3], otherwise it jumps between [N/3] and [N/3] + 1 periodically as the flux varies a flux quantum. For an open tube with zigzag boundary condition, exact edge states are obtained. There exist two perfect midgap edge states, in which the particle is completely located at the boundary, even for a tube with finite length. The threading flux can be employed to control the quantum states: transferring the perfect edge state from one end to the other, or generating maximal entanglement between them. PMID:27554930

  6. A comparison of methods to estimate organ doses in CT when utilizing approximations to the tube current modulation function

    PubMed Central

    Khatonabadi, Maryam; Zhang, Di; Mathieu, Kelsey; Kim, Hyun J.; Lu, Peiyun; Cody, Dianna; DeMarco, John J.; Cagnon, Chris H.; McNitt-Gray, Michael F.

    2012-01-01

    Purpose: Most methods to estimate patient dose from computed tomography (CT) exams have been developed based on fixed tube current scans. However, in current clinical practice, many CT exams are performed using tube current modulation (TCM). Detailed information about the TCM function is difficult to obtain and therefore not easily integrated into patient dose estimate methods. The purpose of this study was to investigate the accuracy of organ dose estimates obtained using methods that approximate the TCM function using more readily available data compared to estimates obtained using the detailed description of the TCM function. Methods: Twenty adult female models generated from actual patient thoracic CT exams and 20 pediatric female models generated from whole body PET/CT exams were obtained with IRB (Institutional Review Board) approval. Detailed TCM function for each patient was obtained from projection data. Monte Carlo based models of each scanner and patient model were developed that incorporated the detailed TCM function for each patient model. Lungs and glandular breast tissue were identified in each patient model so that organ doses could be estimated from simulations. Three sets of simulations were performed: one using the original detailed TCM function (x, y, and z modulations), one using an approximation to the TCM function (only the z-axis or longitudinal modulation extracted from the image data), and the third was a fixed tube current simulation using a single tube current value which was equal to the average tube current over the entire exam. Differences from the reference (detailed TCM) method were calculated based on organ dose estimates. Pearson's correlation coefficients were calculated between methods after testing for normality. Equivalence test was performed to compare the equivalence limit between each method (longitudinal approximated TCM and fixed tube current method) and the detailed TCM method. Minimum equivalence limit was reported for

  7. In situ measurements of the plasma bulk velocity near the Io flux tube

    NASA Technical Reports Server (NTRS)

    Barnett, A.

    1985-01-01

    The flow around the Io flux tube was studied by analyzing the eleven spectra taken by the Voyager 1 Plasma Science (PLS) experiment in its vicinity. The bulk plasma parameters were determined using a procedure that uses the full response function of the instrument and the data in all four PLS sensors. The mass density of the plasma in the vicinity of Io is found to be 22,500 + or - 2,500 amu/cu cm and its electron density is found to be 1500 + or - 200/cu cm. The Alfven speed was determined using three independent methods; the values obtained are consistent and taken together yield V sub A = 300 + or - 50 km/sec, corresponding to an Alfven Mach number of 0.19 + or - 0.02. For the flow pattern, good agreement was found with the model of Neubauer (1980), and it was concluded that the plasma flows around the flux tube with a pattern similar to the flow of an incompressible fluid around a long cylinder obstacle of radius 1.26 + or - 0.1 R sub Io.

  8. Plasmaspheric filament: an isolated magnetic flux tube filled with dense plasmas

    NASA Astrophysics Data System (ADS)

    Murakami, Go; Yoshikawa, Ichiro; Yoshioka, Kazuo; Yamazaki, Atsushi; Kagitani, Masato; Taguchi, Makoto; Kikuchi, Masayuki; Kameda, Shingo; Nakamura, Masato

    2013-01-01

    Abstract<p label="1">The Telescope of Extreme Ultraviolet (TEX) onboard Japan's lunar orbiter KAGUYA provided the first sequential images of the Earth's plasmasphere from the "side" (meridian) view. The TEX instrument obtained the global distribution of the terrestrial helium ions (He+) by detecting resonantly scattered emission at 30.4 nm. One of the most striking features of the plasmasphere found by TEX is an arc-shaped structure of enhanced brightness, which we call a "plasmaspheric filament". In the TEX image on 2 June 2008, the filament structure was clearly aligned to the dipole magnetic field line of L = 3.7 at 7.3 magnetic local time. Our analysis suggests that the filament represents an isolated <span class="hlt">flux</span> <span class="hlt">tube</span> filled with four times higher He+ density than its neighbors. We found four events of plasmaspheric filament in the images obtained between March and June 2008, and in all four events, the geomagnetic activity was quite low. The plasmaspheric filament in the TEX image is the first evidence that a "finger" structure seen in the IMAGE-EUV image is the projection of an isolated <span class="hlt">flux</span> <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...831...94S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...831...94S"><span>Numerical Simulations of Plasma Dynamics in the Vicinity of a Retracting <span class="hlt">Flux</span> <span class="hlt">Tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scott, Roger B.; Longcope, Dana W.; McKenzie, David E.</p> <p>2016-11-01</p> <p>In a previous paper, we presented an analytical, zero-β model for supra-arcade downflows in which a retracting <span class="hlt">flux</span> <span class="hlt">tube</span> 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 <span class="hlt">flux</span> <span class="hlt">tube</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1360021-event-event-study-space-time-dynamics-flux-tube-fragmentation','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1360021-event-event-study-space-time-dynamics-flux-tube-fragmentation"><span>Event-by-Event Study of Space-Time Dynamics in <span class="hlt">Flux-Tube</span> Fragmentation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wong, Cheuk-Yin</p> <p>2017-05-25</p> <p>In the semi-classical description of the <span class="hlt">flux-tube</span> fragmentation process for hadron production and hadronization in high-energymore » $e^+e^-$ annihilations and $pp$ collisions, the rapidity-space-time ordering and the local conservation laws of charge, flavor, and momentum provide a set of powerful tools that may allow the reconstruction of the space-time dynamics of quarks and mesons in exclusive measurements of produced hadrons, on an event-by-event basis. We propose procedures to reconstruct the space-time dynamics from event-by-event exclusive hadron data to exhibit explicitly the ordered chain of hadrons produced in a <span class="hlt">flux</span> <span class="hlt">tube</span> fragmentation. As a supplementary tool, we infer the average space-time coordinates of the $q$-$$\\bar q$$ pair production vertices from the $$\\pi^-$$ rapidity distribution data obtained by the NA61/SHINE Collaboration in $pp$ collisions at $$\\sqrt{s}$$ = 6.3 to 17.3 GeV.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..DPPTP6069P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..DPPTP6069P"><span>A Low Cost Photo-Electric Detector for an Arched <span class="hlt">Flux</span> <span class="hlt">Tube</span> Experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perkins, Rory; Bellan, Paul</p> <p>2008-11-01</p> <p>A low cost EUV detector is being developed for use in a laboratory experiment where two plasma-filled <span class="hlt">flux</span> <span class="hlt">tubes</span> merge in either a co-helicity or counter-helicity arrangement (J.F. Hansen, S.K.P. Tripathi, and P.M. Bellan, Phys. Plasma 2, 3177(2004)). The detector utilizes the photo-electric effect to measure EUV radiation from 10 to 120 nm (S.J. Zweben, R.J. Taylor, Plasma Physics, Vol. 23, No. 4(1981)). The detector geometry is coaxial. A cylindrical collimator capped in wire mesh was placed around the magnesium disk to collimate the field of view and reduce capacitive pick-up. Magnets placed outside the collimator deflect incoming charged particles. The detector was tested in a vacuum chamber with a flash lamp located 50 cm from the detector. A current-to-voltage amplifier with a 1 microsecond rise-time read the detector's output on the test chamber. The detector output on the main experimental chamber was sent directly into 50 ohms with no amplification and produced signals above 200 mV, well above the observed noise. The rise-time for this configuration is well below 1 microsecond. An array of such detectors is currently being designed to image the <span class="hlt">flux</span> <span class="hlt">tubes</span> in this EUV range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Ap%26SS.361..355A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Ap%26SS.361..355A"><span>Particle acceleration in three-dimensional reconnection of <span class="hlt">flux-tube</span> disconnection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akbari, Z.; Hosseinpour, M.; Mohammadi, M. A.</p> <p>2016-11-01</p> <p>"<span class="hlt">Flux-tube</span> disconnection" is a type of steady-state three-dimensional magnetic reconnection with O-point at the origin of the resistive diffusion region. Magnetic reconnection is accepted as a potential mechanism for particle acceleration in astrophysical and space plasmas, especially in solar flares. By using the static magnetic and electric fields for <span class="hlt">flux-tube</span> disconnection, features of test particle acceleration with input parameters for the solar corona are investigated. We show that a proton injected close to origin of the diffusion region can be accelerated to a very high kinetic energy along the magnetic field lines. The efficient acceleration takes place at the radial point where the electric drift velocity has its maximum magnitude. However, a proton injected at radial distances far away from the origin is not accelerated efficiently and even may be trapped in the field lines. The final kinetic energy of the particle depends significantly on the amplitude of the electric field rather than the amplitude of magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21452697','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21452697"><span>FULLY RESOLVED QUIET-SUN MAGNETIC <span class="hlt">FLUX</span> <span class="hlt">TUBE</span> OBSERVED WITH THE SUNRISE/IMAX INSTRUMENT</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lagg, A.; Solanki, S. K.; Riethmueller, T. L.; Schuessler, M.; Hirzberger, J.; Feller, A.; Borrero, J. M.; Barthol, P.; Gandorfer, A.; MartInez Pillet, V.; Bonet, J. A.; Del Toro Iniesta, J. C.; Domingo, V.; Knoelker, M.; Title, A. M.</p> <p>2010-11-10</p> <p>Until today, the small size of magnetic elements in quiet-Sun areas has required the application of indirect methods, such as the line-ratio technique or multi-component inversions, to infer their physical properties. A consistent match to the observed Stokes profiles could only be obtained by introducing a magnetic filling factor that specifies the fraction of the observed pixel filled with magnetic field. Here, we investigate the properties of a small magnetic patch in the quiet Sun observed with the IMaX magnetograph on board the balloon-borne telescope SUNRISE with unprecedented spatial resolution and low instrumental stray light. We apply an inversion technique based on the numerical solution of the radiative transfer equation to retrieve the temperature stratification and the field strength in the magnetic patch. The observations can be well reproduced with a one-component, fully magnetized atmosphere with a field strength exceeding 1 kG and a significantly enhanced temperature in the mid to upper photosphere with respect to its surroundings, consistent with semi-empirical <span class="hlt">flux</span> <span class="hlt">tube</span> models for plage regions. We therefore conclude that, within the framework of a simple atmospheric model, the IMaX measurements resolve the observed quiet-Sun <span class="hlt">flux</span> <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22356484','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22356484"><span>Propagation and dispersion of transverse wave trains in magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Oliver, R.; Terradas, J.; Ruderman, M. S.</p> <p>2014-07-01</p> <p>The dispersion of small-amplitude, impulsively excited wave trains propagating along a magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> is investigated. The initial disturbance is a localized transverse displacement of the <span class="hlt">tube</span> that excites a fast kink wave packet. The spatial and temporal evolution of the perturbed variables (density, plasma displacement, velocity, ...) is given by an analytical expression containing an integral that is computed numerically. We find that the dispersion of fast kink wave trains is more important for shorter initial disturbances (i.e., more concentrated in the longitudinal direction) and for larger density ratios (i.e., for larger contrasts of the <span class="hlt">tube</span> density with respect to the environment density). This type of excitation generates a wave train whose signature at a fixed position along a coronal loop is a short event (duration ≅ 20 s) in which the velocity and density oscillate very rapidly with typical periods of the order of a few seconds. The oscillatory period is not constant but gradually declines during the course of this event. Peak values of the velocity are of the order of 10 km s{sup –1} and are accompanied by maximum density variations of the order of 10%-15% the unperturbed loop density.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10168361','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10168361"><span>Columbia University flow instability experimental program: Volume 7. Single <span class="hlt">tube</span> tests, critical heat <span class="hlt">flux</span> test program</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dougherty, T.; Maciuca, C.; McAssey, E.V. Jr.; Reddy, D.G.; Yang, B.W.</p> <p>1992-09-01</p> <p>This report deals with critical heat <span class="hlt">flux</span> (CHF) measurements in vertical down flow of water at low pressures in a round Inconel <span class="hlt">tube</span>, 96 inches long and 0.62 inch inside diameter. A total of 28 CHF points were obtained. These data were found to correlate linearly with the single variable q, defined as the heat <span class="hlt">flux</span> required to raise the enthalpy from the inlet value to the saturation value. These results were compared to the published results of Swedish investigators for vertical upflow of water at low pressures in round <span class="hlt">tubes</span> of similar diameters and various lengths. The parameter q depends on the inlet enthalpy and is a nonlocal variable, thus this correlation is nonlocal unless the coefficients depend upon <span class="hlt">tube</span> length in a particular prescribed manner. For the low pressure Swedish data, the coefficients are practically independent of length and hence the correlation is nonlocal. In the present investigation only one length was employed, so it is not possible to determine whether the correlation for these data is local or nonlocal, although there is reason to believe that it is local. The same correlation was applied to a large data base (thousands of CHF points) compiled from the published data of a number of groups and found to apply, with reasonable accuracy over a wide range of conditions, yielding sometimes local and sometimes nonlocal correlations. The basic philosophy of data analysis here was not to generate a single correlation which would reproduce all data, but to search for correlations which apply adequately over some range and which might have some mechanistic significance. The tentative conclusion is that at least two mechanisms appear operative, leading to two types of correlations, one local, the other nonlocal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APS..DPPPP8068T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APS..DPPPP8068T"><span>The 3D Structure of <span class="hlt">Flux</span> <span class="hlt">Tubes</span> That Admit Flute Instability in the Scrape-Off-Layer (SOL) of Tokamaks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takahashi, Hironori</p> <p>2014-10-01</p> <p>A severe reduction in size down to an ion gyro-radius scale, commonly known as ``squeezing,'' in a lateral dimension of the cross section of a <span class="hlt">flux</span> <span class="hlt">tube</span> is traditionally thought to inhibit the occurrence of the flute instability in the Scrape-off-Layer of a diverted tokamak by isolating the main volume of the <span class="hlt">flux</span> <span class="hlt">tube</span> from its ends at electrically conducting target plates. A study reported here in the 3D <span class="hlt">flux</span> <span class="hlt">tube</span> structure reveals the absence of squeezing for a <span class="hlt">flux</span> <span class="hlt">tube</span> that is sufficiently large in its toroidal extent (small toroidal harmonic number n) and located in a layer of low field-line shear around the ``sweet spot'' (about mid-way between the primary and secondary separatrices). The low-shear layer does not hence inhibit the flute instability through the squeezing mechanism, and may thus restore the flute instability, among the most virulent in the magnetized plasma, to the ranks of candidate electrostatic instabilities thought to underlie the turbulence in the SOL in tokamaks. Variations along the <span class="hlt">flux</span> <span class="hlt">tube</span> of geometrical characteristics including the cross section will be calculated to develop criteria for the absence of squeezing. Supported in part by the US DOE under DE-AC02-09CH11466.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27869864','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27869864"><span>Photomultiplier <span class="hlt">tube</span> calibration based on Na lidar observation and its effect on heat <span class="hlt">flux</span> bias.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Alan Z; Guo, Yafang</p> <p>2016-11-20</p> <p>Na lidar can measure vertical wind and temperature at high temporal and vertical resolutions, enough to resolve gravity wave perturbations. Heat <span class="hlt">flux</span> due to dissipating gravity waves is an important quantity that can be derived from such perturbations. When lidar signals are high, a photomultiplier <span class="hlt">tube</span> (PMT) used to count incoming photons may suffer from the saturation effect, and its output count is not linearly related to incoming photon counts. Corrections to this effect can be measured in a laboratory setting but may have large errors at high count rates. We show that the errors in the PMT correction can cause significant bias in the heat <span class="hlt">flux</span> calculation due to the inherent correlation between wind and temperature errors. Using the measurements made by Na lidar at the Andes Lidar Observatory with Hamamatsu PMTs, we developed a calibration procedure to remove such PMT correction errors from laboratory measurements. By applying the revised PMT correction curve we demonstrated that the heat <span class="hlt">flux</span> bias can be removed through this procedure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...791..129H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...791..129H"><span>The Scattering of f- and p-modes from Ensembles of Thin Magnetic <span class="hlt">Flux</span> <span class="hlt">Tubes</span>: An Analytical Approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hanson, Chris S.; Cally, Paul S.</p> <p>2014-08-01</p> <p>Motivated by the observational results of Braun, we extend the model of Hanson & Cally to address the effect of multiple scattering of f and p modes by an ensemble of thin vertical magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> in the surface layers of the Sun. As in the observational Hankel analysis, we measure the scatter and phase shift from an incident cylindrical wave in a coordinate system roughly centered in the core of the ensemble. It is demonstrated that although thin <span class="hlt">flux</span> <span class="hlt">tubes</span> are unable to interact with high-order fluting modes individually, they can indirectly absorb energy from these waves through the scatters of kink and sausage components. It is also shown how the distribution of absorption and phase shift across the azimuthal order m depends strongly on the <span class="hlt">tube</span> position as well as on the individual <span class="hlt">tube</span> characteristics. This is the first analytical study into an ensembles multiple-scattering regime that is embedded within a stratified atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22365268','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22365268"><span>The scattering of f- and p-modes from ensembles of thin magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span>: an analytical approach</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hanson, Chris S.; Cally, Paul S.</p> <p>2014-08-20</p> <p>Motivated by the observational results of Braun, we extend the model of Hanson and Cally to address the effect of multiple scattering of f and p modes by an ensemble of thin vertical magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> in the surface layers of the Sun. As in the observational Hankel analysis, we measure the scatter and phase shift from an incident cylindrical wave in a coordinate system roughly centered in the core of the ensemble. It is demonstrated that although thin <span class="hlt">flux</span> <span class="hlt">tubes</span> are unable to interact with high-order fluting modes individually, they can indirectly absorb energy from these waves through the scatters of kink and sausage components. It is also shown how the distribution of absorption and phase shift across the azimuthal order m depends strongly on the <span class="hlt">tube</span> position as well as on the individual <span class="hlt">tube</span> characteristics. This is the first analytical study into an ensembles multiple-scattering regime that is embedded within a stratified atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/891238','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/891238"><span>Limited Streamer <span class="hlt">Tube</span> System for Detecting Contamination in the Gas Used in the BaBar Instrumented <span class="hlt">Flux</span> Return</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Huntley, L.I.; /Franklin - Marshall Coll.</p> <p>2006-08-30</p> <p>The Resistive Plate Chambers (RPCs) initially installed in the Instrumented <span class="hlt">Flux</span> Return (IFR) of the BABAR particle detector have proven unreliable and inefficient for detecting muons and neutral hadrons. In the summer of 2004, the BABAR Collaboration began replacing the RPCs with Limited Streamer <span class="hlt">Tubes</span> (LSTs). LST operation requires a mixture of very pure gases and an operating voltage of 5500 V to achieve maximum efficiency. In the past, the gas supplies obtained by the BABAR Collaboration have contained contaminants that caused the efficiency of the IFR LSTs to drop from <span class="hlt">approximately</span> 90% to <span class="hlt">approximately</span> 60%. Therefore, it was necessary to develop a method for testing this gas for contaminants. An LST test system was designed and built using two existing LSTs, one placed 1 cm above the other. These LSTs detect cosmic muons in place of particles created during the BABAR experiment. The effect of gas contamination was mimicked by reducing the operating voltage of the test system in order to lower the detection efficiency. When contaminated gas was simulated, the coincidence rate and the percent coincidence between the LSTs in the test system dropped off significantly, demonstrating that test system can be used as an indicator of gas purity. In the fall of 2006, the LST test system will be installed in the gas storage area near the BABAR facility for the purpose of testing the gas being sent to the IFR.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21612590','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21612590"><span>Confinement and Lattice Quantum-Electrodynamic Electric <span class="hlt">Flux</span> <span class="hlt">Tubes</span> Simulated with Ultracold Atoms</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zohar, Erez; Reznik, Benni</p> <p>2011-12-30</p> <p>We propose a method for simulating (2+1)D compact lattice quantum-electrodynamics, using ultracold atoms in optical lattices. In our model local Bose-Einstein condensates' (BECs) phases correspond to the electromagnetic vector potential, and the local number operators represent the conjugate electric field. The well-known gauge-invariant Kogut-Susskind Hamiltonian is obtained as an effective low-energy theory. The field is then coupled to external static charges. We show that in the strong coupling limit this gives rise to ''electric <span class="hlt">flux</span> <span class="hlt">tubes</span>'' and to confinement. This can be observed by measuring the local density deviations of the BECs, and is expected to hold even, to some extent, outside the perturbative calculable regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/878071','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/878071"><span>Limited Streamer <span class="hlt">Tubes</span> for the BaBar Instrumented <span class="hlt">Flux</span> Return Upgrade</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lu, C.; /Princeton U.</p> <p>2005-10-11</p> <p>Starting from the very beginning of their operation the efficiency of the RPC chambers in the BaBar Instrumented <span class="hlt">Flux</span> 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 <span class="hlt">Tube</span> (LST) as the replacement of RPC we carried out an R&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&D results, and leave other issues of the IFR system upgrade to the future publications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhRvD..86a4008D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhRvD..86a4008D"><span>X(1835), X(2120), and X(2370) in <span class="hlt">flux</span> <span class="hlt">tube</span> models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deng, Chengrong; Ping, Jialun; Yang, Youchang; Wang, Fan</p> <p>2012-07-01</p> <p>Nonstrange hexaquark state q3q¯3 spectrum is systematically studied by using the Gaussian expansion method in <span class="hlt">flux</span> <span class="hlt">tube</span> models with a six-body confinement potential. All the model parameters are fixed by baryon properties, so the calculation of hexaquark state q3q¯3 is parameter-free. It is found that some ground states of q3q¯3 are stable against disintegrating into a baryon and an anti-baryon. The main components of X(1835) and X(2370), which are observed in the radiative decay of J/ψ by BES collaboration, can be described as compact hexaquark states N8N¯8 and Δ8Δ¯8 with quantum numbers IGJPC=0+0-+, respectively. These bound states should be color confinement resonances with three-dimensional configurations similar to a rugby ball, however, X(2120) can not be accommodated in this model approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SoPh..290.1889H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SoPh..290.1889H"><span>Multiple Scattering of Seismic Waves from Ensembles of Upwardly Lossy Thin <span class="hlt">Flux</span> <span class="hlt">Tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hanson, Chris S.; Cally, Paul S.</p> <p>2015-07-01</p> <p>Our previous semi-analytic treatment of - and -mode multiple scattering from ensembles of thin <span class="hlt">flux</span> <span class="hlt">tubes</span> (Hanson and Cally, Astrophys. J. 781, 125, 2014a; 791, 129, 2014b) is extended by allowing both sausage and kink waves to freely escape at the top of the model using a radiative boundary condition there. As expected, this additional avenue of escape, supplementing downward loss into the deep solar interior, results in substantially greater absorption of incident - and -modes. However, less intuitively, it also yields mildly to substantially smaller phase shifts in waves emerging from the ensemble. This may have implications for the interpretation of seismic data for solar plage regions, and in particular their small measured phase shifts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IAUS..327...86U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IAUS..327...86U"><span>P-mode induced convective collapse in vertical expanding magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Utz, D.; van Doorsselaere, T.; Magyar, N.; Bárta, M.; Campos Rozo, J. I.</p> <p>2017-10-01</p> <p>Small-scale kG strong magnetic field elements in the solar photosphere are often identified as so-called magnetic bright points (MBPs). In principle these MBPs represent the cross-section of a vertical, strong, magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> which is expanding with height in the solar atmosphere. As these magnetic elements represent possible MHD wave guides, a significant interest has been already paid to them from the viewpoint of observations and simulations. In this work we would like to shed more light on a possible scenario for the creation of such strong magnetic field concentrations. The accepted standard scenario involves the convective collapse process. In this ongoing work we will show indications that this convective collapse process may become triggered by sufficiently strong pressure disturbances. However, it is highly unlikely that p-mode waves can be of such a strength.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24929369','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24929369"><span>Asymptotic solution of the diffusion equation in slender impermeable <span class="hlt">tubes</span> of revolution. I. The leading-term <span class="hlt">approximation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Traytak, Sergey D</p> <p>2014-06-14</p> <p>The anisotropic 3D equation describing the pointlike particles diffusion in slender impermeable <span class="hlt">tubes</span> of revolution with cross section smoothly depending on the longitudinal coordinate is the object of our study. We use singular perturbations approach to find the rigorous asymptotic expression for the local particles concentration as an expansion in the ratio of the characteristic transversal and longitudinal diffusion relaxation times. The corresponding leading-term <span class="hlt">approximation</span> is a generalization of well-known Fick-Jacobs <span class="hlt">approximation</span>. This result allowed us to delineate the conditions on temporal and spatial scales under which the Fick-Jacobs <span class="hlt">approximation</span> is valid. A striking analogy between solution of our problem and the method of inner-outer expansions for low Knudsen numbers gas kinetic theory is established. With the aid of this analogy we clarify the physical and mathematical meaning of the obtained results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22420107','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22420107"><span>Asymptotic solution of the diffusion equation in slender impermeable <span class="hlt">tubes</span> of revolution. I. The leading-term <span class="hlt">approximation</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Traytak, Sergey D.</p> <p>2014-06-14</p> <p>The anisotropic 3D equation describing the pointlike particles diffusion in slender impermeable <span class="hlt">tubes</span> of revolution with cross section smoothly depending on the longitudinal coordinate is the object of our study. We use singular perturbations approach to find the rigorous asymptotic expression for the local particles concentration as an expansion in the ratio of the characteristic transversal and longitudinal diffusion relaxation times. The corresponding leading-term <span class="hlt">approximation</span> is a generalization of well-known Fick-Jacobs <span class="hlt">approximation</span>. This result allowed us to delineate the conditions on temporal and spatial scales under which the Fick-Jacobs <span class="hlt">approximation</span> is valid. A striking analogy between solution of our problem and the method of inner-outer expansions for low Knudsen numbers gas kinetic theory is established. With the aid of this analogy we clarify the physical and mathematical meaning of the obtained results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JChPh.140v4102T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JChPh.140v4102T"><span>Asymptotic solution of the diffusion equation in slender impermeable <span class="hlt">tubes</span> of revolution. I. The leading-term <span class="hlt">approximation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Traytak, Sergey D.</p> <p>2014-06-01</p> <p>The anisotropic 3D equation describing the pointlike particles diffusion in slender impermeable <span class="hlt">tubes</span> of revolution with cross section smoothly depending on the longitudinal coordinate is the object of our study. We use singular perturbations approach to find the rigorous asymptotic expression for the local particles concentration as an expansion in the ratio of the characteristic transversal and longitudinal diffusion relaxation times. The corresponding leading-term <span class="hlt">approximation</span> is a generalization of well-known Fick-Jacobs <span class="hlt">approximation</span>. This result allowed us to delineate the conditions on temporal and spatial scales under which the Fick-Jacobs <span class="hlt">approximation</span> is valid. A striking analogy between solution of our problem and the method of inner-outer expansions for low Knudsen numbers gas kinetic theory is established. With the aid of this analogy we clarify the physical and mathematical meaning of the obtained results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJ...813..112T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJ...813..112T"><span>Numerical Study on the Emergence of Kinked <span class="hlt">Flux</span> <span class="hlt">Tube</span> for Understanding of Possible Origin of δ-spot Regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takasao, Shinsuke; Fan, Yuhong; Cheung, Mark C. M.; Shibata, Kazunari</p> <p>2015-11-01</p> <p>We carried out an magnetohydrodynamic simulation where a subsurface twisted kink-unstable <span class="hlt">flux</span> <span class="hlt">tube</span> emerges from the solar interior to the corona. Unlike the previous expectations based on the bodily emergence of a knotted <span class="hlt">tube</span>, we found that the kinked <span class="hlt">tube</span> can spontaneously form a complex quadrupole structure at the photosphere. Due to the development of the kink instability before the emergence, the magnetic twist at the kinked apex of the <span class="hlt">tube</span> is greatly reduced, although the other parts of the <span class="hlt">tube</span> are still strongly twisted. This leads to the formation of a complex quadrupole structure: a pair of the coherent, strongly twisted spots and a narrow complex bipolar pair between it. The quadrupole is formed by the submergence of a portion of emerged magnetic fields. This result is relevant for understanding the origin of the complex multipolar δ-spot regions that have a strong magnetic shear and emerge with polarity orientations not following Hale-Nicholson and Joy Laws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22521922','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22521922"><span>NUMERICAL STUDY ON THE EMERGENCE OF KINKED <span class="hlt">FLUX</span> <span class="hlt">TUBE</span> FOR UNDERSTANDING OF POSSIBLE ORIGIN OF δ-SPOT REGIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Takasao, Shinsuke; Shibata, Kazunari; Fan, Yuhong; Cheung, Mark C. M.</p> <p>2015-11-10</p> <p>We carried out an magnetohydrodynamic simulation where a subsurface twisted kink-unstable <span class="hlt">flux</span> <span class="hlt">tube</span> emerges from the solar interior to the corona. Unlike the previous expectations based on the bodily emergence of a knotted <span class="hlt">tube</span>, we found that the kinked <span class="hlt">tube</span> can spontaneously form a complex quadrupole structure at the photosphere. Due to the development of the kink instability before the emergence, the magnetic twist at the kinked apex of the <span class="hlt">tube</span> is greatly reduced, although the other parts of the <span class="hlt">tube</span> are still strongly twisted. This leads to the formation of a complex quadrupole structure: a pair of the coherent, strongly twisted spots and a narrow complex bipolar pair between it. The quadrupole is formed by the submergence of a portion of emerged magnetic fields. This result is relevant for understanding the origin of the complex multipolar δ-spot regions that have a strong magnetic shear and emerge with polarity orientations not following Hale-Nicholson and Joy Laws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..92c4027D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..92c4027D"><span>Systematic study of Zc+ family from a multiquark color <span class="hlt">flux-tube</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deng, Chengrong; Ping, Jialun; Huang, Hongxia; Wang, Fan</p> <p>2015-08-01</p> <p>Inspired by the present experimental results of charged charmonium-like states Zc+, we present a systematic study of the tetraquark states [c u ][c ¯ d ¯ ] in a color <span class="hlt">flux-tube</span> model with a multibody confinement potential. Our investigation indicates that charged charmonium-like states Zc+(3900 ) or Zc+(3885 ), Zc+(3930 ) , Zc+(4020 ) or Zc+(4025 ), Z1+(4050 ), Z2+(4250 ), and Zc+(4200 ) can be described as a family of tetraquark [c u ][c ¯d ¯] states with the quantum numbers n 2SL+1 J and JP of 1 3S1 and 1+, 2 3S1 and 1+, 1 5S2 and 2+, 1 3P1 and 1-, 1 5D1 and 1+, and 1 3D1 and 1+, respectively. The predicted lowest mass charged tetraquark state [c u ][c ¯ d ¯ ] with 0+ and 1 1S0 lies at 3780 ±10 MeV /c2 in the model. These tetraquark states have compact three-dimensional spatial configurations similar to a rugby ball with higher orbital angular momentum L between the diquark [c u ] and antidiquark [c ¯d ¯] corresponding to a more prolate spatial distribution. The multibody color <span class="hlt">flux</span> <span class="hlt">tube</span>, a collective degree of freedom, plays an important role in the formation of those charged tetraquark states. However, the two heavier charged states Zc+(4430 ) and Zc+(4475 ) cannot be explained as tetraquark states [c u ][c ¯d ¯] in this model approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20657984','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20657984"><span>Peculiarities of Alfven wave propagation along a nonuniform magnetic <span class="hlt">flux</span> <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Erkaev, N.V.; Shaidurov, V.A.; Semenov, V.S.; Langmayr, D.; Biernat, H.K.</p> <p>2005-01-01</p> <p>Within the framework of the assumption of large azimuthal wave numbers, the equations for Alfven and slow magnetosonic waves are obtained using frozen-in material coordinates. These equations are specified for the case of a nonuniform magnetic field with axial symmetry. Assuming a meridional polarization of the magnetic field and velocity perturbations, the effects of Alfven wave propagation are analyzed which are related to geometric characteristics of a nonuniform magnetic field: (a) A finite curvature radius of the magnetic field lines and (b) convergence of magnetic field lines. The interaction between the Alfven and magnetosonic waves is found to be strongly dependent on the curvature radius of the magnetic <span class="hlt">tube</span> and the local plasma {beta} parameter. The electric field amplitude and the length scale of a wave front are found to increase very strongly in the course of the Alfven wave propagation along a converging magnetic <span class="hlt">flux</span> <span class="hlt">tube</span>. Also studied is a temporal decrease of the wave perturbations which is caused by dissipation at the conducting boundary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/111418','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/111418"><span>On the look-up tables for the critical heat <span class="hlt">flux</span> in <span class="hlt">tubes</span> (history and problems)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kirillov, P.L.; Smogalev, I.P.</p> <p>1995-09-01</p> <p>The complication of critical heat <span class="hlt">flux</span> (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 <span class="hlt">flux</span> 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 <span class="hlt">tubes</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSMSM31B..04R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSMSM31B..04R"><span>Particle Energization on <span class="hlt">Flux</span> <span class="hlt">Tubes</span> Threading the Auroral Ionososphere - a Proposed Polar Orbiting Satellite Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rankin, R.; Sydorenko, D.; Watt, C.</p> <p>2009-05-01</p> <p>Observations from the NASA POLAR and FAST missions reveal that Alfven waves are intimately associated with electron and ion particle acceleration in Earth's magnetosphere. Data from POLAR shows intense geomagnetic field-aligned wave Poynting <span class="hlt">flux</span> near and within the plasma sheet tail lobe boundary. The corresponding UVI auroral imaging provides strong, but nevertheless circumstantial evidence that the associated electron acceleration powers auroral emissions above the ionosphere. To explain the data, we present results of modeling that agree with observations of Alfven wave activity, and describe the characteristics of the resulting wave-particle interactions along the entire extent of a magnetic <span class="hlt">flux</span> <span class="hlt">tube</span>. Model results using the Vlasov-Maxwell equations reveal detailed characteristics of the electron distribution functions observed by POLAR, while two-fluid modeling of the resulting ion dynamics is shown to agree with observations of up-flowing ion beams. We argue that missions such as FAST and POLAR reveal the need for more detailed observations at high altitude, on the order of 4-5Re. Such an opportunity is presented by the decision by Canada to launch two Polar Communications Weather (PCW) satellites that sample the relevant region of Geospace within which acceleration by Alfven waves is optimal. We discuss how a well-instrumented PCW mission would be used to demonstrate closure on the nature of Alfven wave-induced particle acceleration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MS%26E..117a2053Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MS%26E..117a2053Y"><span>Rapidly solidified Ag-Cu eutectics: A comparative study using drop-<span class="hlt">tube</span> and melt <span class="hlt">fluxing</span> techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Mullis, A. M.; Cochrane, R. F.</p> <p>2016-03-01</p> <p>A comparative study of rapid solidification of Ag-Cu eutectic alloy processed via melt <span class="hlt">fluxing</span> and drop-<span class="hlt">tube</span> techniques is presented. A computational model is used to estimate the cooling rate and undercooling of the free fall droplets as this cannot be determined directly. SEM micrographs show that both materials consist of lamellar and anomalous eutectic structures. However, below the critical undercooling the morphologies of each are different in respect of the distribution and volume of anomalous eutectic. The anomalous eutectic in <span class="hlt">flux</span>- undercooled samples preferentially forms at cell boundaries around the lamellar eutectic in the cell body. In drop-<span class="hlt">tube</span> processed samples it tends to distribute randomly inside the droplets and at much smaller volume fractions. That the formation of the anomalous eutectic can, at least in part, be suppressed in the drop-<span class="hlt">tube</span> is strongly suggestive that the formation of anomalous eutectic occurs via remelting process, which is suppressed by rapid cooling during solidification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994AN....315..371Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994AN....315..371Y"><span>Darkening of the Sun prior to surface appearance of sunspot <span class="hlt">flux</span> <span class="hlt">tubes</span> and magneto-thermal pulsation of the Sun</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoshimura, H.</p> <p>1994-08-01</p> <p>We found an evidence that the luminosity of the Sun systematically decreased about 20 days before sunspot surface appearance by analyzing time-lag correlation of time derivatives of running mean time profiles of the data ofthe Active Cavity Radiometer Irradiance Monitor (ACRIM) I experiment on board of Solar Maximum Mission (SMM) and of the data of the daily sunspot number. This indicates that sunspot <span class="hlt">flux</span> <span class="hlt">tube</span> cooling and heat transfer blocking by the <span class="hlt">flux</span> <span class="hlt">tubes</span> start to take place in the interior of the solar convection zone well before the sunspot surface appearance. From this finding and our previous finding that the luminosity of the Sun systematically increased and the blocked heat appeared on the surface about 50 days after the sunspot surface appearance, a new view of sunspot formation and dynamics and a new view of the luminosity modulation emerged. (1) Sunspots of a solar cycle are formed from clusters of <span class="hlt">flux</span> <span class="hlt">tubes</span> which can be seen in the running time mean profile of the sunspot number as a peak with duration on the order of 100 to 200 days. (2) Heat flow is blocked by the cluster of sunspot <span class="hlt">flux</span> <span class="hlt">tubes</span> inside the convection zone to decrease the luminosity about 20 days before the surface emergence of the sunspot cluster. (3) The blocked heat appears on the surface about 50 days after the surface emergence of the cluster of sunspot <span class="hlt">flux</span> <span class="hlt">tubes</span> to heat up the surface. This appears as a thermal pulse in the running mean time profile of the ACRIM data in between the peaks of the sunspot running mean time profile. This process of heating the surface makes the temperature gradient less steep and weakens the bouyancy of sunspot <span class="hlt">flux</span> <span class="hlt">tubes</span> below the surface. (4) The radiative cooling of the surface layer by the excess heat release steepens the temperature gradient so that the bouyancy of the sub-surface magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> becomes stronger to cause the next surge of emergence of a cluster of sunspots and other magnetic activities, which creates a peak in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA159548','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA159548"><span>Numerical <span class="hlt">Approximation</span> of the Total Drag of a Body in a <span class="hlt">Tube</span>.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1985-06-25</p> <p>determining the pressure coefficient integral term could probably only be accomplished with an interacting boundary layer approach or a full Navier...separating. Since boundary layer separation is often quite probable , especially near trailing * edges or tail regions, an accurate <span class="hlt">approximation</span> of the drag...Officer Torrance, CA 90505 Naval Underwater Systems Ctr. *Attn: W. W. Haigh Department of the Navy (Copy No. 10) Newport, RI 02840 Attn: D. J. Goodrich</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007EP%26S...59.1219W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007EP%26S...59.1219W"><span>Consistency between the flow at the top of the core and the frozen-<span class="hlt">flux</span> <span class="hlt">approximation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whaler, K. A.; Holme, R.</p> <p>2007-12-01</p> <p>The flow just below the core-mantle boundary is constrained by the radial component of the induction equation. In the Alfvén frozen-<span class="hlt">flux</span> limit, thought to be applicable to the outer core on the decade timescale of interest in geomagnetism, this gives a single equation involving the known radial magnetic field and its secular variation in two unknown flow components, leading to a severe problem of non-uniqueness. Despite this, we have two specific pieces of flow information which can be deduced directly from the frozen-<span class="hlt">flux</span> induction equation: the component of flow perpendicular to null-<span class="hlt">flux</span> curves, contours on which the radial magnetic field vanishes, and the amount of horizontal convergence and divergence at local extrema (maxima, minima and saddle points) of the radial magnetic field. To produce global velocity maps, we make additional assumptions about the nature of the flow and invert the radial induction equation for flow coefficients. However, it is not clear a priori that the flows thus generated are consistent with what we know about them along null-<span class="hlt">flux</span> curves and at local extrema. This paper examines that issue. We look at typical differences between the null-<span class="hlt">flux</span> curve perpendicular flow component, and convergence and divergence values at extrema, deduced directly from the induction equation and those from the inversions, investigate the effect of forcing the inversions to produce the correct null-<span class="hlt">flux</span> curve and extremal values, and characterise the uncertainties on the various quantities contributing. Although the differences between the flow values from the induction equation directly and obtained by inversion seem large, and imposing the direct flow information as side constraints during inversion alters the flows significantly, we also show that these differences are within the likely uncertainties. Thus, we conclude that flows obtained through inversion do not contravene the specific flow information obtained directly from the radial induction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HMT...tmp..315S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HMT...tmp..315S"><span>Prediction of forced convective heat transfer and critical heat <span class="hlt">flux</span> for subcooled water flowing in miniature <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shibahara, Makoto; Fukuda, Katsuya; Liu, Qiusheng; Hata, Koichi</p> <p>2017-09-01</p> <p>The heat transfer characteristics of forced convection for subcooled water in small <span class="hlt">tubes</span> were clarified using the commercial computational fluid dynamic (CFD) code, PHENICS ver. 2013. The analytical model consists of a platinum <span class="hlt">tube</span> (the heated section) and a stainless <span class="hlt">tube</span> (the non-heated section). Since the platinum <span class="hlt">tube</span> was heated by direct current in the authors' previous experiments, a uniform heat <span class="hlt">flux</span> with the exponential function was given as a boundary condition in the numerical simulation. Two inner diameters of the <span class="hlt">tubes</span> were considered: 1.0 and 2.0 mm. The upward flow velocities ranged from 2 to 16 m/s and the inlet temperature ranged from 298 to 343 K. The numerical results showed that the difference between the surface temperature and the bulk temperature was in good agreement with the experimental data at each heat <span class="hlt">flux</span>. The numerical model was extended to the liquid sublayer analysis for the CHF prediction and was evaluated by comparing its results with the experimental data. It was postulated that the CHF occurs when the fluid temperature near the heated wall exceeds the saturated temperature, based on Celata et al.'s superheated layer vapor replenishment (SLVR) model. The suggested prediction method was in good agreement with the experimental data and with other CHF data in literature within ±25%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017439','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017439"><span>High-Energy X-Ray Detection of G359.89-0.08 (SGR A-E): Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> Emission Powered by Cosmic Rays?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Tomsick, John A; Zhang, Will</p> <p>2014-01-01</p> <p>We report the first detection of high-energy X-ray (E (is) greater than 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to <span class="hlt">approximately</span> 50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index gamma <span class="hlt">approximately</span> equals 2.3 confirms a non-thermal emission mechanism. The observed <span class="hlt">flux</span> in the 3-79 keV band is F(sub X) = (2.0 +/- 0.1) × 10(exp -12)erg cm(-2) s(-1) , corresponding to an unabsorbed X-ray luminosity L(sub X) = (2.6+/-0.8)×10(exp 34) erg s(-1) assuming a distance 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 <span class="hlt">flux</span> <span class="hlt">tube</span> which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to (is) <span class="hlt">approximately</span> 100 kyr) with low surface brightness and radii up to (is) <span class="hlt">approximately</span> 30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22521997','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22521997"><span>MAGNETOHYDRODYNAMIC KINK WAVES IN NONUNIFORM SOLAR <span class="hlt">FLUX</span> <span class="hlt">TUBES</span>: PHASE MIXING AND ENERGY CASCADE TO SMALL SCALES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Soler, Roberto; Terradas, Jaume</p> <p>2015-04-10</p> <p>Magnetohydrodynamic (MHD) kink waves are ubiquitously observed in the solar atmosphere. The propagation and damping of these waves may play relevant roles in the transport and dissipation of energy in the solar atmospheric medium. However, in the atmospheric plasma dissipation of transverse MHD wave energy by viscosity or resistivity needs very small spatial scales to be efficient. Here, we theoretically investigate the generation of small scales in nonuniform solar magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> due to phase mixing of MHD kink waves. We go beyond the usual approach based on the existence of a global quasi-mode that is damped in time due to resonant absorption. Instead, we use a modal expansion to express the MHD kink wave as a superposition of Alfvén continuum modes that are phase mixed as time evolves. The comparison of the two techniques evidences that the modal analysis is more physically transparent and describes both the damping of global kink motions and the building up of small scales due to phase mixing. In addition, we discuss that the processes of resonant absorption and phase mixing are closely linked. They represent two aspects of the same underlying physical mechanism: the energy cascade from large scales to small scales due to naturally occurring plasma and/or magnetic field inhomogeneities. This process may provide the necessary scenario for efficient dissipation of transverse MHD wave energy in the solar atmospheric plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950059820&hterms=dissipative&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddissipative','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950059820&hterms=dissipative&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddissipative"><span>Dissipative MHD solutions for resonant Alfven waves in 1-dimensional magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goossens, Marcel; Ruderman, Michail S.; Hollweg, Joseph V.</p> <p>1995-01-01</p> <p>The present paper extends the analysis by Sakurai, Goossens, and Hollweg (1991) on resonant Alfven waves in nonuniform magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span>. It proves that the fundamental conservation law for resonant Alfven waves found in ideal MHD by Sakurai, Goossens, and Hollweg remains valid in dissipative MHD. This guarantees that the jump conditions of Sakurai, Goossens, and Hollweg, that connect the ideal MHD solutions for xi(sub r), and P' across the dissipative layer, are correct. In addition, the present paper replaces the complicated dissipative MHD solutions obtained by Sakurai, Goossens, and Hollweg for xi(sub r), and P' in terms of double integrals of Hankel functions of complex argument of order 1/3 with compact analytical solutions that allow a straight- forward mathematical and physical interpretation. Finally, it presents an analytical dissipative MHD solution for the component of the Lagrangian displacement in the magnetic surfaces perpen- dicular to the magnetic field lines xi(sub perpendicular) which enables us to determine the dominant dynamics of resonant Alfven waves in dissipative MHD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005A%26A...444..961A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005A%26A...444..961A"><span>Current sheet formation in quasi-separatrix layers and hyperbolic <span class="hlt">flux</span> <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aulanier, G.; Pariat, E.; Démoulin, P.</p> <p>2005-12-01</p> <p>In 3D magnetic field configurations, quasi-separatrix layers (QSLs) are defined as volumes in which field lines locally display strong gradients of connectivity. Considering QSLs both as the preferential locations for current sheet development and magnetic reconnection, in general, and as a natural model for solar flares and coronal heating, in particular, has been strongly debated issues over the past decade. In this paper, we perform zero-β resistive MHD simulations of the development of electric currents in smooth magnetic configurations which are, strictly speaking, bipolar though they are formed by four <span class="hlt">flux</span> concentrations, and whose potential fields contain QSLs. The configurations are driven by smooth and large-scale sub-Alfvénic footpoint motions. Extended electric currents form naturally in the configurations, which evolve through a sequence of quasi non-linear force-free equilibria. Narrow current layers also develop. They spontaneously form at small scales all around the QSLs, whatever the footpoint motions are. For long enough motions, the strongest currents develop where the QSLs are the thinnest, namely at the Hyperbolic <span class="hlt">Flux</span> <span class="hlt">Tube</span> (HFT), which generalizes the concept of separator. These currents progressively take the shape of an elongated sheet, whose formation is associated with a gradual steepening of the magnetic field gradients over tens of Alfvén times, due to the different motions applied to the field lines which pass on each side of the HFT. Our model then self-consistently accounts for the long-duration energy storage prior to a flare, followed by a switch-on of reconnection when the currents reach the dissipative scale at the HFT. In configurations whose potential fields contain broader QSLs, when the magnetic field gradients reach the dissipative scale, the currents at the HFT reach higher magnitudes. This implies that major solar flares which are not related to an early large-scale ideal instability, must occur in regions whose</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PASJ...69....5M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PASJ...69....5M"><span>Structural properties of the solar flare-producing coronal current system developed in an emerging magnetic <span class="hlt">flux</span> <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Magara, Tetsuya</p> <p>2017-02-01</p> <p>The activity of a magnetic structure formed in the solar corona depends on a coronal current system developed in the structure, which determines how an electric current flows in the corona. To investigate structural properties of the coronal current system responsible for producing a solar flare, we perform magnetohydrodynamic simulation of an emerging magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> which forms a coronal magnetic structure. Investigation using fractal dimensional analysis and electric current streamlines reveals that the flare-producing coronal current system relies on a specific coronal current structure of two-dimensional spatiality, which has a sub-region where a nearly anti-parallel magnetic field configuration is spontaneously generated. We discuss the role of this locally generated anti-parallel magnetic field configuration in causing the reconnection of a three-dimensional magnetic field, which is a possible mechanism for producing a flare. We also discuss how the twist of a magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> affects structural properties of a coronal current system, showing how much volume current <span class="hlt">flux</span> is carried into the corona by an emerging <span class="hlt">flux</span> <span class="hlt">tube</span>. This gives a way to evaluate the activity of a coronal magnetic structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860049331&hterms=LTE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DLTE','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860049331&hterms=LTE&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DLTE"><span>On magnetohydrodynamic thermal instabilities in magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span>. [in plane parallel stellar atmosphere in LTE and hydrostatic equilibrium</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Massaglia, S.; Ferrari, A.; Bodo, G.; Kalkofen, W.; Rosner, R.</p> <p>1985-01-01</p> <p>The stability of current-driven filamentary modes in magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> embedded in a plane-parallel atmosphere in LTE and in hydrostatic equilibrium is discussed. Within the <span class="hlt">tube</span>, energy transport by radiation only is considered. The dominant contribution to the opacity is due to H- ions and H atoms (in the Paschen continuum). A region in the parameter space of the equilibrium configuration in which the instability is effective is delimited, and the relevance of this process for the formation of structured coronae in late-type stars and accretion disks is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20075635','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20075635"><span><span class="hlt">Approximate</span> techniques for the performance analysis and optimization of two-dimensional plate fins circumscribing circular <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kundu, B.; Das, P.K.</p> <p>2000-04-01</p> <p>Efficiency of noncircular fins circumscribing circular <span class="hlt">tubes</span> is generally determined by one of two <span class="hlt">approximate</span> techniques, the equivalent annulus method or the sector method. In the present work the predictions of these two methods are compared with results obtained from a semianalytical technique for square, hexagonal, and eccentric annular fins. It is observed that the accuracy of the equivalent annulus method reduces with the increase of the two-dimensionality of the fins. However, the sector method guarantees very close agreement with the semianalytical technique over a wide range of parametric variations for all the fins. An improved definition of fin efficiency for the sector method is also put forward to take care of the heat loss from fin tips. Finally, it is shown that the optimum dimensions of the fins determined by the sector method closely match the predictions of the semianalytical technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930034888&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drotation%2Bmagnetic%2Bflux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930034888&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Drotation%2Bmagnetic%2Bflux"><span>Evolution of a magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> in two-dimensional penetrative convection</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jennings, R. L.; Brandenburg, A.; Nordlund, A.; Stein, R. F.</p> <p>1992-01-01</p> <p>Highly supercritical compressible convection is simulated in a two-dimensional domain in which the upper half is unstable to convection while the lower half is stably stratified. This configuration is an idealization of the layers near the base of the solar convection zone. Once the turbulent flow is well developed, a toroidal magnetic field B sub tor is introduced to the stable layer. The field's evolution is governed by an advection-diffusion-type equation, and the Lorentz force does not significantly affect the flow. After many turnover times the field is stratified such that the absolute value of B sub tor/rho is <span class="hlt">approximately</span> constant in the convective layer, where rho is density, while in the stable layer this ratio decreases linearly with depth. Consequently most of the magnetic <span class="hlt">flux</span> is stored in the overshoot layer. The inclusion of rotation leads to travelling waves which transport magnetic <span class="hlt">flux</span> latitudinally in a manner reminiscent of the migrations seen during the solar cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930034888&hterms=Tor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DTor','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930034888&hterms=Tor&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DTor"><span>Evolution of a magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> in two-dimensional penetrative convection</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jennings, R. L.; Brandenburg, A.; Nordlund, A.; Stein, R. F.</p> <p>1992-01-01</p> <p>Highly supercritical compressible convection is simulated in a two-dimensional domain in which the upper half is unstable to convection while the lower half is stably stratified. This configuration is an idealization of the layers near the base of the solar convection zone. Once the turbulent flow is well developed, a toroidal magnetic field B sub tor is introduced to the stable layer. The field's evolution is governed by an advection-diffusion-type equation, and the Lorentz force does not significantly affect the flow. After many turnover times the field is stratified such that the absolute value of B sub tor/rho is <span class="hlt">approximately</span> constant in the convective layer, where rho is density, while in the stable layer this ratio decreases linearly with depth. Consequently most of the magnetic <span class="hlt">flux</span> is stored in the overshoot layer. The inclusion of rotation leads to travelling waves which transport magnetic <span class="hlt">flux</span> latitudinally in a manner reminiscent of the migrations seen during the solar cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034232','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034232"><span>Lava <span class="hlt">tube</span> shatter rings and their correlation with lava <span class="hlt">flux</span> increases at Kīlauea Volcano, Hawai‘i</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Orr, T.R.</p> <p>2011-01-01</p> <p>Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava <span class="hlt">tubes</span>. 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 <span class="hlt">tube</span>, 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 <span class="hlt">flux</span>, and were coincident with lava breakouts from shatter rings constructed over the lava <span class="hlt">tube</span>. The repetitive behavior of the lava <span class="hlt">flux</span> 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 <span class="hlt">tube</span> roof. The locations of shatter rings along the active lava <span class="hlt">tube</span> suggest that they form where there is an abrupt decrease in flow velocity through the <span class="hlt">tube</span>, e.g., large increase in <span class="hlt">tube</span> width, abrupt decrease in <span class="hlt">tube</span> slope, and (or) sudden change in <span class="hlt">tube</span> direction. To conserve volume, this necessitates an abrupt increase in lava stream depth and causes over-pressurization of the <span class="hlt">tube</span>. 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011BVol...73..335O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011BVol...73..335O"><span>Lava <span class="hlt">tube</span> shatter rings and their correlation with lava <span class="hlt">flux</span> increases at Kīlauea Volcano, Hawai`i</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orr, Tim R.</p> <p>2011-04-01</p> <p>Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava <span class="hlt">tubes</span>. 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 <span class="hlt">tube</span>, 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 <span class="hlt">flux</span>, and were coincident with lava breakouts from shatter rings constructed over the lava <span class="hlt">tube</span>. The repetitive behavior of the lava <span class="hlt">flux</span> 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 <span class="hlt">tube</span> roof. The locations of shatter rings along the active lava <span class="hlt">tube</span> suggest that they form where there is an abrupt decrease in flow velocity through the <span class="hlt">tube</span>, e.g., large increase in <span class="hlt">tube</span> width, abrupt decrease in <span class="hlt">tube</span> slope, and (or) sudden change in <span class="hlt">tube</span> direction. To conserve volume, this necessitates an abrupt increase in lava stream depth and causes over-pressurization of the <span class="hlt">tube</span>. 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 fluctuation in lava</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/772124','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/772124"><span>Critical heat <span class="hlt">flux</span> and boiling heat transfer to water in a 3-mm-diameter horizontal <span class="hlt">tube</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yu, W.; Wambsganss, M. W.; Hull, J. R.; France, D. M.</p> <p>2000-12-04</p> <p>Boiling of the coolant in an engine, by design or by circumstance, is limited by the critical heat <span class="hlt">flux</span> phenomenon. As a first step in providing relevant engine design information, this study experimentally addressed both rate of boiling heat transfer and conditions at the critical point of water in a horizontal <span class="hlt">tube</span> of 2.98 mm inside diameter and 0.9144 m heated length. Experiments were performed at system pressure of 203 kPa, mass <span class="hlt">fluxes</span> in range of 50 to 200 kg/m{sup z}s, and inlet temperatures in range of ambient to 80 C. Experimental results and comparisons with predictive correlations are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790057332&hterms=magnetic+lift&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmagnetic%2Blift','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790057332&hterms=magnetic+lift&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmagnetic%2Blift"><span>Sunspots and the physics of magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span>. IV - Aerodynamic lift on a thin cylinder in convective flows</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tsinganos, K. C.</p> <p>1979-01-01</p> <p>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 <span class="hlt">flux</span> <span class="hlt">tubes</span> in the convection beneath the surface of the sun are considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMSH23B1536N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMSH23B1536N"><span>Measurements of TRACE 171A Twisting Coronal Loop Fans about a Twisted Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> Originating From Below the Photosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nightingale, R. W.; Ma, G.; Ji, E.</p> <p>2009-12-01</p> <p>In our previous studies of rotating sunspots about their umbral centers over the past decade, we have been measuring the rotation at the photosphere of the cross sections of large, twisted magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> passing through from below. Many such rotating sunspots have been found and reported in the literature and at earlier meetings [e.g., Brown et al., Sol. Phys. 216, 79, 2003; Yan et al., ApJ 682, L65, 2008; Nightingale et al., Fall AGU Mtg. 2007]. Here we are attempting to measure the rotation of 1 million degree K EUV loops seen in TRACE 171A images emerging from what may be a large 6000 deg K magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> (invisible at EUV), which may be the extension of the associated rotating sunspot up in the corona, for active region 9114 on August 8 - 10, 2000. These nonpotential EUV loops appear to be attached at their other end to nonrotating opposite polarity magnetic <span class="hlt">flux</span> regions and also appear to be flipping around like a twisted jump rope that is attached to a wall at one end. In movies of these twisted coronal loop fans the rotation appears obvious, but is difficult to measure, because of the constant motion and change of intensity of the fans, which tend to obscure each other and the apparent <span class="hlt">tube</span> center. We will show movies over the 3 days of the twisted loop fans, and details and first results of our measurements, which appear to be similar to those previously found for the associated rotating sunspot down at the photosphere. We will discuss how the twisted magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> energizes the corona, carrying energy up from beneath the photosphere. This work was supported by NASA under the TRACE contract NAS5-38099.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HMT...tmp...81S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HMT...tmp...81S"><span>Effects of outlet subcoolings and heat generation rates on transient critical heat <span class="hlt">flux</span> for subcooled flow boling of water in a vertical <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shibahara, M.; Fukuda, K.; Liu, Q. S.; Hata, K.</p> <p>2017-04-01</p> <p>Critical heat <span class="hlt">fluxes</span> (CHFs) for subcooled flow boiling of water in a vertical <span class="hlt">tube</span> due to steady and exponentially heat inputs were measured. The platinum <span class="hlt">tube</span> with an inner diameter of 2.0 mm and a length of 94.8 mm was placed vertically in the experimental water loop. The upward flow velocity was <span class="hlt">approximately</span> 2.5 m/s and the outlet subcooling ranged from 18 to 48 K. The heat generation rate was varied exponentially to investigate the effect of e-folding time on the CHFs. As an experimental result, the CHFs increased with a decrease in the e-folding time. When the e-folding times were longer, the CHFs were almost constant, whereas the CHFs increased for shorter e-folding times. The CHFs were independent on outlet subcoolings at low flow conditions. Moreover, it was considered that the explosive-like CHF occurred when the inner surface temperature of the <span class="hlt">tube</span> exceeded the lower limit of heterogeneous spontaneous nucleation (HSN) temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HMT....53.2999S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HMT....53.2999S"><span>Effects of outlet subcoolings and heat generation rates on transient critical heat <span class="hlt">flux</span> for subcooled flow boling of water in a vertical <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shibahara, M.; Fukuda, K.; Liu, Q. S.; Hata, K.</p> <p>2017-09-01</p> <p>Critical heat <span class="hlt">fluxes</span> (CHFs) for subcooled flow boiling of water in a vertical <span class="hlt">tube</span> due to steady and exponentially heat inputs were measured. The platinum <span class="hlt">tube</span> with an inner diameter of 2.0 mm and a length of 94.8 mm was placed vertically in the experimental water loop. The upward flow velocity was <span class="hlt">approximately</span> 2.5 m/s and the outlet subcooling ranged from 18 to 48 K. The heat generation rate was varied exponentially to investigate the effect of e-folding time on the CHFs. As an experimental result, the CHFs increased with a decrease in the e-folding time. When the e-folding times were longer, the CHFs were almost constant, whereas the CHFs increased for shorter e-folding times. The CHFs were independent on outlet subcoolings at low flow conditions. Moreover, it was considered that the explosive-like CHF occurred when the inner surface temperature of the <span class="hlt">tube</span> exceeded the lower limit of heterogeneous spontaneous nucleation (HSN) temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhRvB..78b4510A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhRvB..78b4510A"><span><span class="hlt">Flux</span> <span class="hlt">tubes</span> and the type-I/type-II transition in a superconductor coupled to a superfluid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alford, Mark G.; Good, Gerald</p> <p>2008-07-01</p> <p>We analyze magnetic-<span class="hlt">flux</span> <span class="hlt">tubes</span> 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 <span class="hlt">flux</span> <span class="hlt">tubes</span> with an arbitrary number of <span class="hlt">flux</span> 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 <span class="hlt">flux</span> <span class="hlt">tube</span>, steps from 1 to infinity. For lower neutron density, the coupling creates spinodal regions around the type-I/type-II boundary, in which metastable <span class="hlt">flux</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21143589','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21143589"><span><span class="hlt">Flux</span> <span class="hlt">tubes</span> and the type-I/type-II transition in a superconductor coupled to a superfluid</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Alford, Mark G.; Good, Gerald</p> <p>2008-07-01</p> <p>We analyze magnetic-<span class="hlt">flux</span> <span class="hlt">tubes</span> 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 <span class="hlt">flux</span> <span class="hlt">tubes</span> with an arbitrary number of <span class="hlt">flux</span> quanta and compare their energies. This allows us to map the type-I/type-II transition in the superconductor, which occurs at the conventional {kappa}{identical_to}{lambda}/{xi}=1/{radical}(2) if the condensates are uncoupled. We find that a density coupling between the condensates raises the critical {kappa} 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 <span class="hlt">flux</span> <span class="hlt">tube</span>, steps from 1 to infinity. For lower neutron density, the coupling creates spinodal regions around the type-I/type-II boundary, in which metastable <span class="hlt">flux</span> configurations are possible. We find that a gradient coupling between the condensates lowers the critical {kappa} 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004A%26A...420..699C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004A%26A...420..699C"><span>Properties of longitudinal <span class="hlt">flux</span> <span class="hlt">tube</span> waves. II. Limiting shock strength behavior</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cuntz, M.</p> <p>2004-06-01</p> <p>We extend our previous work on analytic evaluations of properties of longitudinal <span class="hlt">tube</span> waves to waves propagating in gravitational atmospheres. We derive an expression for the limiting shock strength and discuss the behavior of the shock strength in <span class="hlt">tubes</span> of different geometry. It is found that a height-independent value for the limiting strength is attained for constant cross-section <span class="hlt">tubes</span> and exponential <span class="hlt">tubes</span>, whereas for wine-glass <span class="hlt">tubes</span> the limiting shock strength increases with height due to the increase of the <span class="hlt">tube</span> cross section. The limiting shock strength is well reproduced by time-dependent simulations. The derived limiting shock strength as well as the energy dissipation rate of the waves show significant similarities to acoustic waves. The limiting shock strength allows to estimate the heating potential of waves in the absence of detailed time-dependent computations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/276277','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/276277"><span>Critical heat-<span class="hlt">flux</span> characteristics of R-113 boiling two-phase flow in twisted-tape-inserted <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lee, Sangryoul; Inoue, Akira; Takahashi, Minoru</p> <p>1996-07-01</p> <p>This paper presents experimental data on the critical heat <span class="hlt">flux</span> (CHF) in twisted-tape-inserted <span class="hlt">tubes</span> over a wide quality range of {minus}0.25 to 0.8. The influences of quality, twist ratio, mass velocity, and clearance between the twisted tape and <span class="hlt">tube</span> inner wall on CHF were investigated. In the subcooled region, it was observed, using an infrared thermoviewer, that CHF was initiated locally at the wall near the twisted tape. Consequently, twisted tape insertion with small tape-well clearance decreased CHF to below the value of the empty <span class="hlt">tubes</span> at a low flow rate. This decrease was found to be avoidable by adjusting the clearance. In the net quality region, CHF of the twisted-tape-inserted <span class="hlt">tubes</span> increased with increasing flow rate contrary to the case of the empty <span class="hlt">tubes</span>. However, CHF in the net quality region was also decreased by insertion of twisted tapes with high twist ratio (loosely twisted tapes) at a very low flow rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22518731','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22518731"><span>ERUPTING FILAMENTS WITH LARGE ENCLOSING <span class="hlt">FLUX</span> <span class="hlt">TUBES</span> AS SOURCES OF HIGH-MASS THREE-PART CMEs, AND ERUPTING FILAMENTS IN THE ABSENCE OF ENCLOSING <span class="hlt">FLUX</span> <span class="hlt">TUBES</span> AS SOURCES OF LOW-MASS UNSTRUCTURED CMEs</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hutton, Joe; Morgan, Huw</p> <p>2015-11-01</p> <p>The 3-part appearance of many coronal mass ejections (CMEs) arising from erupting filaments emerges from a large magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> structure, consistent with the form of the erupting filament system. Other CMEs arising from erupting filaments lack a clear 3-part structure and reasons for this have not been researched in detail. This paper aims to further establish the link between CME structure and the structure of the erupting filament system and to investigate whether CMEs which lack a 3-part structure have different eruption characteristics. A survey is made of 221 near-limb filament eruptions observed from 2013 May 03 to 2014 June 30 by Extreme UltraViolet (EUV) imagers and coronagraphs. Ninety-two filament eruptions are associated with 3-part structured CMEs, 41 eruptions are associated with unstructured CMEs. The remaining 88 are categorized as failed eruptions. For 34% of the 3-part CMEs, processing applied to EUV images reveals the erupting front edge is a pre-existing loop structure surrounding the filament, which subsequently erupts with the filament to form the leading bright front edge of the CME. This connection is confirmed by a <span class="hlt">flux</span>-rope density model. Furthermore, the unstructured CMEs have a narrower distribution of mass compared to structured CMEs, with total mass comparable to the mass of 3-part CME cores. This study supports the interpretation of 3-part CME leading fronts as the outer boundaries of a large pre-existing <span class="hlt">flux</span> <span class="hlt">tube</span>. Unstructured (non 3-part) CMEs are a different family to structured CMEs, arising from the eruption of filaments which are compact <span class="hlt">flux</span> <span class="hlt">tubes</span> in the absence of a large system of enclosing closed field.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1060841','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1060841"><span>An <span class="hlt">Approximate</span> Analytic Expression for the <span class="hlt">Flux</span> Density of Scintillation Light at the Photocathode</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Braverman, Joshua B; Harrison, Mark J; Ziock, Klaus-Peter</p> <p>2012-01-01</p> <p>The <span class="hlt">flux</span> density of light exiting scintillator crystals is an important factor affecting the performance of radiation detectors, and is of particular importance for position sensitive instruments. Recent work by T. Woldemichael developed an analytic expression for the shape of the light spot at the bottom of a single crystal [1]. However, the results are of limited utility because there is generally a light pipe and photomultiplier entrance window between the bottom of the crystal and the photocathode. In this study, we expand Woldemichael s theory to include materials each with different indices of refraction and compare the adjusted light spot shape theory to GEANT 4 simulations [2]. Additionally, light reflection losses from index of refraction changes were also taken into account. We found that the simulations closely agree with the adjusted theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1850o0002F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1850o0002F"><span>Heat transfer experiments with a central receiver <span class="hlt">tube</span> subjected to unsteady and non-uniform heat <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernández-Torrijos, María; Marugán-Cruz, Carolina; Sobrino, Celia; Santana, Domingo</p> <p>2017-06-01</p> <p>In this work, a molten salt test loop to study the heat transfer process in external molten salt receivers is described. The experimental installation is formed by a cylindrical molten salt tank, a pump, a flow meter, and an induction heater to generate the heat <span class="hlt">flux</span>, which is applied in a small rectangular region of the <span class="hlt">tube</span> surface. In central tower plants, the external receiver pipe is considered to be under unilateral concentrated solar radiation, because only one side of the pipe receives high heat <span class="hlt">flux</span>. The main advantage of using an induction heater is the control of heating in different areas of the <span class="hlt">tube</span>. In order to measure the effects of a non-homogenous and unsteady heat <span class="hlt">flux</span> on the wall temperature distribution a series of experiments have been carried out. 4 K-type thermocouples have been welded at different axial and azimuthal positions of the pipe to obtain the wall temperature distribution. Different temperature measurements have been made varying the heat <span class="hlt">flux</span> and water velocity to study their effects on the heat transfer process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.815a2024K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.815a2024K"><span><span class="hlt">Approximate</span> method for calculating convective heat <span class="hlt">flux</span> on the surface of bodies of simple geometric shapes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuzenov, V. V.; Ryzhkov, S. V.</p> <p>2017-02-01</p> <p>The paper formulated engineering and physical mathematical model for aerothermodynamics hypersonic flight vehicle (HFV) in laminar and turbulent boundary layers (model designed for an <span class="hlt">approximate</span> estimate of the convective heat flow in the range of speeds M = 6-28, and height H = 20-80 km). 2D versions of calculations of convective heat flows for bodies of simple geometric forms (individual elements of the design HFV) are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApOpt..50.4237Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApOpt..50.4237Y"><span>Hybrid diffusion and two-<span class="hlt">flux</span> <span class="hlt">approximation</span> for multilayered tissue light propagation modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yudovsky, Dmitry; Durkin, Anthony J.</p> <p>2011-07-01</p> <p>Accurate and rapid estimation of fluence, reflectance, and absorbance in multilayered biological media has been essential in many biophotonics applications that aim to diagnose, cure, or model in vivo tissue. The radiative transfer equation (RTE) rigorously models light transfer in absorbing and scattering media. However, analytical solutions to the RTE are limited even in simple homogeneous or plane media. Monte Carlo simulation has been used extensively to solve the RTE. However, Monte Carlo simulation is computationally intensive and may not be practical for applications that demand real-time results. Instead, the diffusion <span class="hlt">approximation</span> has been shown to provide accurate estimates of light transport in strongly scattering tissue. The diffusion <span class="hlt">approximation</span> is a greatly simplified model and produces analytical solutions for the reflectance and absorbance in tissue. However, the diffusion <span class="hlt">approximation</span> breaks down if tissue is strongly absorbing, which is common in the visible part of the spectrum or in applications that involve darkly pigmented skin and/or high local volumes of blood such as port-wine stain therapy or reconstructive flap monitoring. In these cases, a model of light transfer that can accommodate both strongly and weakly absorbing regimes is required. Here we present a model of light transfer through layered biological media that represents skin with two strongly scattering and one strongly absorbing layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=160564','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=160564"><span>Pollen <span class="hlt">tube</span> growth is coupled to the extracellular calcium ion <span class="hlt">flux</span> and the intracellular calcium gradient: effect of BAPTA-type buffers and hypertonic media.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pierson, E S; Miller, D D; Callaham, D A; Shipley, A M; Rivers, B A; Cresti, M; Hepler, P K</p> <p>1994-01-01</p> <p>Lily pollen <span class="hlt">tubes</span> possess a steep, tip-focused intracellular Ca2+ gradient and a tip-directed extracellular Ca2+ influx. Ratiometric ion imaging revealed that the gradient extends from above 3.0 microM at the apex to <span class="hlt">approximately</span> 0.2 microM within 20 microns from the tip, while application of the Ca(2+)-specific vibrating electrode indicated that the extracellular influx measured between 1.4 and 14 pmol cm-2 sec-1. We examined the relationship between these phenomena and their role in <span class="hlt">tube</span> growth by using different 1,2-bis(o-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA)-type buffers and hypertonic media. Injection of active BAPTA-type buffers or application of elevated levels of sucrose reversibly inhibited growth, destroyed tip zonation of organelles, and modified normal patterns of cytoplasmic streaming. Simultaneously, these treatments dissipated both the intracellular tip-focused gradient and the extracellular Ca2+ <span class="hlt">flux</span>. Of the BAPTA-type buffers, 5,5'-dibromo-BAPTA (dissociation constant [Kd] is 1.5 microM) and 4,4'-difluoro-BAPTA (Kd of 1.7 microM) exhibited greater activity than those buffers with either a higher affinity (5,5'-dimethyl-BAPTA, Kd of 0.15 microM; BAPTA, Kd of 0.21 microM; 5,5'-difluoro-BAPTA, Kd of 0.25 microM) or lower affinity (5-methyl, 5'-nitro-BAPTA, Kd of 22 microM) for Ca2+. Our findings provide evidence that growing pollen <span class="hlt">tubes</span> have open Ca2+ channels in their tip and that these channels become inactivated in nongrowing <span class="hlt">tubes</span>. The studies with elevated sucrose support the view that stretching of the apical plasma membrane contributes to the maintenance of the Ca2+ signal. PMID:7866026</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OcMod.116...33B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OcMod.116...33B"><span><span class="hlt">Approximation</span> of wave action <span class="hlt">flux</span> velocity in strongly sheared mean flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Banihashemi, Saeideh; Kirby, James T.; Dong, Zhifei</p> <p>2017-08-01</p> <p>Spectral wave models based on the wave action equation typically use a theoretical framework based on depth uniform current to account for current effects on waves. In the real world, however, currents often have variations over depth. Several recent studies have made use of a depth-weighted current U˜ due to [Skop, R. A., 1987. <span class="hlt">Approximate</span> dispersion relation for wave-current interactions. J. Waterway, Port, Coastal, and Ocean Eng. 113, 187-195.] or [Kirby, J. T., Chen, T., 1989. Surface waves on vertically sheared flows: <span class="hlt">approximate</span> dispersion relations. J. Geophys. Res. 94, 1013-1027.] in order to account for the effect of vertical current shear. Use of the depth-weighted velocity, which is a function of wavenumber (or frequency and direction) has been further simplified in recent applications by only utilizing a weighted current based on the spectral peak wavenumber. These applications do not typically take into account the dependence of U˜ on wave number k, as well as erroneously identifying U˜ as the proper choice for current velocity in the wave action equation. Here, we derive a corrected expression for the current component of the group velocity. We demonstrate its consistency using analytic results for a current with constant vorticity, and numerical results for a measured, strongly-sheared current profile obtained in the Columbia River. The effect of choosing a single value for current velocity based on the peak wave frequency is examined, and we suggest an alternate strategy, involving a Taylor series expansion about the peak frequency, which should significantly extend the range of accuracy of current estimates available to the wave model with minimal additional programming and data transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/953359','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/953359"><span>Nano-cavities observed in a 316SS PWR <span class="hlt">Flux</span> Thimble <span class="hlt">Tube</span> Irradiated to 33 and 70 dpa</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Edwards, Danny J.; Garner, Francis A.; Bruemmer, Stephen M.; Efsing, Pal G.</p> <p>2009-02-28</p> <p>The radiation-induced microstructure of a cold-worked 316SS <span class="hlt">flux</span> thimble <span class="hlt">tube</span> from an operating pressurized water reactor (PWR) was examined. Two irradiated conditions, 33 dpa at 290ºC and 70 dpa at 315ºC were examined by transmission electron microscopy. The original dislocation network had completely disappeared and was replaced by fine dispersions of Frank loops and small nano-cavities at high densities. The latter appear to be bubbles containing high levels of helium and hydrogen. An enhanced distribution of these nano-cavities was found at grain boundaries and may play a role in the increased susceptibility of the irradiated 316SS to intergranular failure of specimens from this <span class="hlt">tube</span> during post-irradiation slow strain rate testing in PWR water conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/153096','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/153096"><span>Symmetric <span class="hlt">flux</span> continuous positive definite <span class="hlt">approximation</span> of the elliptic full tensor pressure equation in local conservative form</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Edwards, M.G.</p> <p>1995-12-31</p> <p>A classical finite volume scheme well known in computational aerodynamics for solving the Transonic full potential equation is imported into reservoir simulation and applied to the full tensor pressure equation. Cell vertex discretization is shown to be a natural framework for <span class="hlt">approximation</span>. With permeability placed at the cell centers and potential at the vertices (cell corner points), of the grid the scheme is <span class="hlt">flux</span> continuous and locally conservative. Analysis is presented which proves that the resulting discrete matrix is symmetric positive definite provided the full permeability tensor is symmetric elliptic. The discrete matrix is also diagonally dominant subject to a sufficient elliptically condition. For a diagonal anisotropic tensor the discrete matrix is always symmetric positive definite and the scheme is up to 4th order accurate. A cell centered version of the scheme is indicated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...843...93C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...843...93C"><span>Magnetic <span class="hlt">Flux</span> Rope Shredding By a Hyperbolic <span class="hlt">Flux</span> <span class="hlt">Tube</span>: The Detrimental Effects of Magnetic Topology on Solar Eruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chintzoglou, Georgios; Vourlidas, Angelos; Savcheva, Antonia; Tassev, Svetlin; Tun Beltran, Samuel; Stenborg, Guillermo</p> <p>2017-07-01</p> <p>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 Lyα (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 <span class="hlt">Flux</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1356893-experimental-design-analysis-irradiation-sic-sic-composite-tubes-under-prototypic-high-heat-flux','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1356893-experimental-design-analysis-irradiation-sic-sic-composite-tubes-under-prototypic-high-heat-flux"><span>Experimental design and analysis for irradiation of SiC/SiC composite <span class="hlt">tubes</span> under a prototypic high heat <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Petrie, Christian M.; Koyanagi, Takaaki; McDuffee, Joel L.; ...</p> <p>2017-05-04</p> <p>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 <span class="hlt">tube</span> outer surface temperature in the range of 300–350 °C under a representative high heat <span class="hlt">flux</span> (~0.66 MW/m2) during one cycle of irradiation in an un-instrumented “rabbit” capsule in the High <span class="hlt">Flux</span> Isotope Reactor. An engineered aluminum foil was developed to absorb the expansionmore » of the cladding <span class="hlt">tubes</span>, 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 <span class="hlt">tubes</span> (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.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JNuM..491...94P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JNuM..491...94P"><span>Experimental design and analysis for irradiation of SiC/SiC composite <span class="hlt">tubes</span> under a prototypic high heat <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrie, Christian M.; Koyanagi, Takaaki; McDuffee, Joel L.; Deck, Christian P.; Katoh, Yutai; Terrani, Kurt A.</p> <p>2017-08-01</p> <p>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 <span class="hlt">tube</span> outer surface temperature in the range of 300-350 °C under a representative high heat <span class="hlt">flux</span> (∼0.66 MW/m2) during one cycle of irradiation in an un-instrumented ;rabbit; capsule in the High <span class="hlt">Flux</span> Isotope Reactor. An engineered aluminum foil was developed to absorb the expansion of the cladding <span class="hlt">tubes</span>, 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 <span class="hlt">tubes</span> (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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCoPh.284..462A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCoPh.284..462A"><span>Control-volume distributed multi-point <span class="hlt">flux</span> <span class="hlt">approximation</span> coupled with a lower-dimensional fracture model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmed, R.; Edwards, M. G.; Lamine, S.; Huisman, B. A. H.; Pal, M.</p> <p>2015-03-01</p> <p>A cell-centered control-volume distributed multi-point <span class="hlt">flux</span> <span class="hlt">approximation</span> (CVD-MPFA) finite-volume formulation is presented for discrete fracture-matrix simulations. The grid is aligned with the fractures and barriers which are then modeled as lower-dimensional interfaces located between the matrix cells in the physical domain. The nD pressure equation is solved in the matrix domain coupled with an (n - 1)D pressure equation solved in the fractures. The CVD-MPFA formulation naturally handles fractures with anisotropic permeabilities on unstructured grids. Matrix-fracture <span class="hlt">fluxes</span> are expressed in terms of matrix and fracture pressures, and must be added to the lower-dimensional flow equation (called the transfer function). An additional transmission condition is used between matrix cells adjacent to low permeable fractures to link the velocity and pressure jump across the fractures. Numerical tests serve to assess the convergence and accuracy of the lower-dimensional fracture model for highly anisotropic fractures having different apertures and permeability tensors. A transport equation for tracer flow is coupled via the Darcy <span class="hlt">flux</span> for single and intersecting fractures. The lower-dimensional approach for intersecting fractures avoids the more restrictive CFL condition corresponding to the equi-dimensional <span class="hlt">approximation</span> with explicit time discretization. Lower-dimensional fracture model results are compared with hybrid-grid and equi-dimensional model results. Fractures and barriers are efficiently modeled by lower-dimensional interfaces which yield comparable results to those of the equi-dimensional model. Highly conductive fractures are modeled as lower-dimensional entities without the use of locally refined grids that are required by the equi-dimensional model, while pressure continuity across fractures is built into the model, without depending on the extra degrees of freedom which must be added locally by the hybrid-grid method. The lower-dimensional fracture</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1021406','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1021406"><span>A Comparison between a Minijet Model and a Glasma <span class="hlt">Flux</span> <span class="hlt">Tube</span> Model for Central Au-Au Collisions at sqrt NN=200 GeV</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Longacre, R.S.</p> <p>2011-05-17</p> <p>In this paper we compare two models with central Au-Au collisions at sqrtsNN=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 <span class="hlt">flux</span> <span class="hlt">tube</span> model which leads to <span class="hlt">flux</span> <span class="hlt">tubes</span> on the surface of a radial expanding fireball driven by interacting <span class="hlt">flux</span> <span class="hlt">tubes</span> near the center of the fireball through plasma instabilities. This internal fireball becomes an opaque hydro fluid which pushes the surface <span class="hlt">flux</span> <span class="hlt">tubes</span> outward. Around ~12 surfaceflux <span class="hlt">tubes</span> 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 pt1 pt2 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994IJHMT..37...69W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994IJHMT..37...69W"><span>A phenomenological model for boiling heat transfer and the critical heat <span class="hlt">flux</span> in <span class="hlt">tubes</span> containing twisted tapes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weisman, J.; Yang, J. Y.; Usman, S.</p> <p>1994-01-01</p> <p>New critical heat <span class="hlt">flux</span> (CHF) and boiling heat transfer data were obtained in the subcooled and low quality regions using refrigerant 113. These data were obtained in a 0.61 cm round <span class="hlt">tube</span> containing a twisted tape having a twist ratio of 6.25. The new CHF data, plus water data from the literature, were compared to a modified version of the CHF predictive model based on bubble crowding and coalescence in the bubbly layer (Weisman and Pei, (1983), Weisman and Illeslamlou, (1988)). Reasonably good predictions were obtained within the range of the model. It was also found that the Yang and Weisman (1991) extension of the CHF model to boiling heat transfer held for swirling flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22348095','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22348095"><span>The behavior of transverse waves in nonuniform solar <span class="hlt">flux</span> <span class="hlt">tubes</span>. II. Implications for coronal loop seismology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Goossens, Marcel</p> <p>2014-02-01</p> <p>The seismology of coronal loops using observations of damped transverse oscillations in combination with results from theoretical models is a tool to indirectly infer physical parameters in the solar atmospheric plasma. Existing seismology schemes based on <span class="hlt">approximations</span> of the period and damping time of kink oscillations are often used beyond their theoretical range of applicability. These <span class="hlt">approximations</span> assume that the variation of density across the loop is confined to a nonuniform layer much thinner than the radius of the loop, but the results of the inversion problem often do not satisfy this preliminary hypothesis. Here, we determine the accuracy of the analytic <span class="hlt">approximations</span> of the period and damping time, and the impact on seismology estimates when largely nonuniform loops are considered. We find that the accuracy of the <span class="hlt">approximations</span> when used beyond their range of applicability is strongly affected by the form of the density profile across the loop, that is observationally unknown and so must be arbitrarily imposed as part of the theoretical model. The error associated with the analytic <span class="hlt">approximations</span> can be larger than 50% even for relatively thin nonuniform layers. This error directly affects the accuracy of <span class="hlt">approximate</span> seismology estimates compared to actual numerical inversions. In addition, assuming different density profiles can produce noncoincident intervals of the seismic variables in inversions of the same event. The ignorance about the true shape of density variation across the loop is an important source of error that may dispute the reliability of parameters seismically inferred assuming an ad hoc density profile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990Ap%26SS.166..289C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990Ap%26SS.166..289C"><span>The kink instability in infinite cylindrical <span class="hlt">flux</span> <span class="hlt">tubes</span> - Eigenvalues for power-law twist profiles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Craig, I. J. D.; Robb, T. D.; Sneyd, A. D.; McClymont, A. N.</p> <p>1990-04-01</p> <p>Simple, accurate methods of calculating ideal MHD instability eigenvalues for infinitely long cylindrical <span class="hlt">tubes</span> with twist function T(r) are developed. The results show that the most rapidly growing and energetic instabilities occur in the Gold-Hoyle v = 0 field, with the instability progressively weakening with increasing v. However, the maximum force eigenvalue is always small, so that even in the Gold-Hoyle case only a small proportion of the available magnetic energy can be released in the linear phase. The results also confirm that the linear pinch is remarkably weak yet relatively resistant to line-tying. It is shown that the weakness of the force eigenvalue implies that the influence of uniform gas pressure on stability is negligible. Implications for the energy-release mechanism in solar flares are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890062607&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drotation%2Bmagnetic%2Bflux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890062607&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drotation%2Bmagnetic%2Bflux"><span>Slow twists of solar magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> and the polar magnetic field of the sun</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hollweg, Joseph V.; Lee, Martin A.</p> <p>1989-01-01</p> <p>The solar wind model of Weber and Davis (1967) is generalized to compute the heliospheric magnetic field resulting from solar rotation or a steady axisymmetric twist including a geometrical expansion which is more rapid than spherical. The calculated increase in the ratio of the toroidal to poloidal field components with heliocentric radial distance r clarifies an expression derived recently by Jokipii and Kota (1989). Magnetic-field components transverse to r do not in general grow to dominate the radial component at large r. The analysis also yields expressions for the Poynting <span class="hlt">flux</span> associated with the steady twists.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/271900','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/271900"><span>Enhancement of critical heat <span class="hlt">flux</span> for subcooled flow boiling of water in <span class="hlt">tubes</span> with a twisted tape and with a helically coiled wire</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kabata, Y.; Nakajima, R.; Shioda, K.</p> <p>1996-08-01</p> <p>This paper reports results of an experimental investigation for critical heat <span class="hlt">flux</span> (CHF) up to 30 MW/m{sup 2} in subcooled flow boiling of water in <span class="hlt">tubes</span> with a twisted tape and with a helically coiled wire. Experiments were carried out using uniformly heated horizontal <span class="hlt">tubes</span> with inner diameters of 8 and 12 mm, and with a heated length of 50 mm. Although the CHF of <span class="hlt">tubes</span> with and without the twisted tape depends on velocity and exit subcooling of water, no observable influence of the <span class="hlt">tube</span> diameter is detected. As for the CHF enhancement ratio of the <span class="hlt">tubes</span> with the tape, it is at least 40% higher than the case without the tape, and increases as the exit water subcooling decreases. In the case of the helically coiled wire, the CHF increases as the wire diameter becomes larger and as the coil pitch smaller. The increase of the CHF by the coil, which is the wire diameter of 1.0 mm and the coil pitch of 12 mm, is higher than that by the twisted tape. The CHF model for the smooth <span class="hlt">tube</span> developed by Celata et al. was applied to the swirl <span class="hlt">tube</span> by modifying for the calculation of the friction factor, and the radial temperature and velocity distribution in the liquid. Prediction using the modified Celata model accounts for almost all available experimental data for the swirl <span class="hlt">tube</span> within {+-}25%. This study is relevant for the development of fusion reactors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14611516','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14611516"><span>Electroweak production of hybrid mesons in a <span class="hlt">flux-tube</span> simulation of lattice QCD.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Close, F E; Dudek, J J</p> <p>2003-10-03</p> <p>We make the first calculation of the electroweak couplings of hybrid mesons to conventional mesons appropriate to photoproduction and to the decays of B or D mesons. E1 amplitudes are found to be large and may contribute in charge exchange gammap-->nH(+) allowing production of (among others) the charged 1(-+) exotic hybrid off a(2) exchange. Axial hybrid meson photoproduction is predicted to be large courtesy of pi exchange, and its strange hybrid counterpart is predicted in B-->psiK(H)(1(+)) with branching ratio B <span class="hlt">approximately</span> 10(-4). Higher multipoles and some implications for hybrid charmonium are briefly discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.469.2313G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.469.2313G"><span>Post-glitch exponential relaxation of radio pulsars and magnetars in terms of vortex creep across <span class="hlt">flux</span> <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gügercinoğlu, Erbil</p> <p>2017-08-01</p> <p>Timing observations of rapidly rotating neutron stars revealed a great number of glitches, observed from both canonical radio pulsars and magnetars. Among them, 76 glitches have shown exponential relaxation(s) with characteristic decay times ranging from several days to a few months, followed by a more gradual recovery. Glitches displaying exponential relaxation with single or multiple decay time constants are analysed in terms of a model based on the interaction of the vortex lines with the toroidal arrangement of <span class="hlt">flux</span> <span class="hlt">tubes</span> in the outer core of the neutron star. Model results agree with the observed time-scales in general. Thus, the glitch phenomenon can be used to deduce valuable information about neutron star structure, in particular on the interior magnetic field configuration which is unaccessible from surface observations. One immediate conclusion is that the magnetar glitch data are best explained with a much cooler core and therefore require that direct Urca-type fast-cooling mechanisms should be effective for magnetars.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.453.2982D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.453.2982D"><span>Self-organized criticality in a two-dimensional cellular automaton model of a magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> with background flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dănilă, B.; Harko, T.; Mocanu, G.</p> <p>2015-11-01</p> <p>We investigate the transition to self-organized criticality in a two-dimensional model of a <span class="hlt">flux</span> <span class="hlt">tube</span> with a background flow. The magnetic induction equation, represented by a partial differential equation with a stochastic source term, is discretized and implemented on a two-dimensional cellular automaton. The energy released by the automaton during one relaxation event is the magnetic energy. As a result of the simulations, we obtain the time evolution of the energy release, of the system control parameter, of the event lifetime distribution and of the event size distribution, respectively, and we establish that a self-organized critical state is indeed reached by the system. Moreover, energetic initial impulses in the magnetohydrodynamic flow can lead to one-dimensional signatures in the magnetic two-dimensional system, once the self-organized critical regime is established. The applications of the model for the study of gamma-ray bursts (GRBs) is briefly considered, and it is shown that some astrophysical parameters of the bursts, like the light curves, the maximum released energy and the number of peaks in the light curve can be reproduced and explained, at least on a qualitative level, by working in a framework in which the systems settles in a self-organized critical state via magnetic reconnection processes in the magnetized GRB fireball.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830045177&hterms=radio+wave+uses&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dradio%2Bwave%2Buses','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830045177&hterms=radio+wave+uses&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dradio%2Bwave%2Buses"><span>Induced mass and wave motions in the lower solar atmosphere. I - Effects of shear motion of <span class="hlt">flux</span> <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, S. T.; Hu, Y. Q.; Nakagawa, Y.; Tandberg-Hanssen, E.</p> <p>1983-01-01</p> <p>Observations indicate that various dynamic solar phenomena lead to enhanced emission of electromagnetic waves from radio to X-ray wavelengths which can be traced to magnetic activity in the photospheric level. A number of previous investigations have ignored the dynamic responses in the solar atmosphere. On the other hand, Nakagawa et al. (1978, 1981) have studied the atmospheric responses in the frame of MHD in the supersonic super-Alfvenic region. Studies of the slowly varying dynamic response (subsonic) have been unsuccessful because of the requirements of high accuracy in the numerical scheme in which a rigorous mathematical treatment of the boundary conditions is necessary. Recently, a numerical MHD model was constructed by using the full implicit continuous eulerian method. The present investigation makes use of a method which is written in a more convenient numerical code. A two-dimensional, time-dependent, nonplanar MHD model is used to investigate the induced mass and wave motions in the lower solar atmosphere due to the shear motion of <span class="hlt">flux</span> <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015HESS...19.2639H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015HESS...19.2639H"><span>Technical Note: <span class="hlt">Approximate</span> solution of transient drawdown for constant-<span class="hlt">flux</span> pumping at a partially penetrating well in a radial two-zone confined aquifer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, C.-S.; Yang, S.-Y.; Yeh, H.-D.</p> <p>2015-06-01</p> <p>An aquifer consisting of a skin zone and a formation zone is considered as a two-zone aquifer. Existing solutions for the problem of constant-<span class="hlt">flux</span> pumping in a two-zone confined aquifer involve laborious calculation. This study develops a new <span class="hlt">approximate</span> solution for the problem based on a mathematical model describing steady-state radial and vertical flows in a two-zone aquifer. Hydraulic parameters in these two zones can be different but are assumed homogeneous in each zone. A partially penetrating well may be treated as the Neumann condition with a known <span class="hlt">flux</span> along the screened part and zero <span class="hlt">flux</span> along the unscreened part. The aquifer domain is finite with an outer circle boundary treated as the Dirichlet condition. The steady-state drawdown solution of the model is derived by the finite Fourier cosine transform. Then, an <span class="hlt">approximate</span> transient solution is developed by replacing the radius of the aquifer domain in the steady-state solution with an analytical expression for a dimensionless time-dependent radius of influence. The <span class="hlt">approximate</span> solution is capable of predicting good temporal drawdown distributions over the whole pumping period except at the early stage. A quantitative criterion for the validity of neglecting the vertical flow due to a partially penetrating well is also provided. Conventional models considering radial flow without the vertical component for the constant-<span class="hlt">flux</span> pumping have good accuracy if satisfying the criterion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4693191','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4693191"><span>Effective Estimation of Dynamic Metabolic <span class="hlt">Fluxes</span> Using 13C Labeling and Piecewise Affine <span class="hlt">Approximation</span>: From Theory to Practical Applicability</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Schumacher, Robin; Wahl, S. Aljoscha</p> <p>2015-01-01</p> <p>The design of microbial production processes relies on rational choices for metabolic engineering of the production host and the process conditions. These require a systematic and quantitative understanding of cellular regulation. Therefore, a novel method for dynamic <span class="hlt">flux</span> identification using quantitative metabolomics and 13C labeling to identify piecewise-affine (PWA) <span class="hlt">flux</span> functions has been described recently. Obtaining <span class="hlt">flux</span> estimates nevertheless still required frequent manual reinitalization to obtain a good reproduction of the experimental data and, moreover, did not optimize on all observables simultaneously (metabolites and isotopomer concentrations). In our contribution we focus on measures to achieve faster and robust dynamic <span class="hlt">flux</span> estimation which leads to a high dimensional parameter estimation problem. Specifically, we address the following challenges within the PWA problem formulation: (1) Fast selection of sufficient domains for the PWA <span class="hlt">flux</span> functions, (2) Control of over-fitting in the concentration space using shape-prescriptive modeling and (3) robust and efficient implementation of the parameter estimation using the hybrid implicit filtering algorithm. With the improvements we significantly speed up the convergence by efficiently exploiting that the optimization problem is partly linear. This allows application to larger-scale metabolic networks and demonstrates that the proposed approach is not purely theoretical, but also applicable in practice. PMID:26690237</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998SoPh..183...45G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998SoPh..183...45G"><span>On Analysis of Dual Spacecraft Stereoscopic Observations to Determine the Three-Dimensional Morphology and Plasma Properties of Solar Coronal <span class="hlt">Flux</span> <span class="hlt">Tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gary, G. Allen; Davis, John M.; Moore, Ronald</p> <p>1998-11-01</p> <p>By using two spacecraft equipped with multi-bandpass X-ray telescopes, it is possible to obtain direct 3-dimensional morphology of coronal structures which is essential for understanding the energetics and dynamics of the solar atmosphere. X-ray observations taken only in orbit about the Earth are inadequate to fully resolve the 3-dimensional nature of the solar corona. These Earth-orbit observations produce 2-dimensional images and an appropriate model must be included to derive the 3-dimensional structures from the line-of-sight information. Stereoscopic observations from space will remove this limitation and are needed if we are to improve our knowledge of the 3-dimensional morphology of the corona. Several important points regarding a stereoscopic mission are investigated and illustrated using model coronal <span class="hlt">flux</span> <span class="hlt">tubes</span> and image-rendering techniques. Synthesized images are formed by integrating the emission from volume elements along the line-of-sight path through a 3-dimensional volume in which a set of model <span class="hlt">flux</span> <span class="hlt">tubes</span> are located. The <span class="hlt">flux</span> <span class="hlt">tubes</span> are defined by (1) a plasma model defining the emissivity for a specific density, temperature, and pressure distribution, and (2) a magnetic field model from which a set of field lines are selected to define the geometry of the <span class="hlt">flux</span> <span class="hlt">tubes</span>. The field lines are used to define the <span class="hlt">flux-tube</span> volume by assuming an initial base radius and conservation of <span class="hlt">flux</span>. An effective instrumental spectral-response function is folded into the integration. Analysis of pairs of these synthesized images with various angular perspectives are used to investigate the effect of angular separation on mission objectives. The resulting images and analysis provide guidelines for developing a stereoscopic mission. Our study produced four important results, namely: (1) An angular separation of ~30 degrees maximizes the scientific return by direct triangulation analysis because of the tradeoff between increased line-of-sight resolution of position</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1100715-gluon-correlations-from-glasma-flux-tube-model-compared-measured-hadron-correlations-transverse-momentum-pt-pt-angular-differences','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1100715-gluon-correlations-from-glasma-flux-tube-model-compared-measured-hadron-correlations-transverse-momentum-pt-pt-angular-differences"><span>Gluon correlations from a glasma <span class="hlt">flux-tube</span> model compared to measured hadron correlations on transverse momentum (pt,pt) and angular differences (ηΔ,φΔ)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Trainor, Thomas A.; Ray, R. L.</p> <p>2011-09-09</p> <p>A glasma <span class="hlt">flux-tube</span> model has been proposed to explain strong elongation on pseudorapidity η of the same-side two-dimensional (2D) peak in minimum-bias angular correlations from √(sNN)=200 GeV Au-Au collisions. The same-side peak or “soft ridge” is said to arise from coupling of <span class="hlt">flux</span> <span class="hlt">tubes</span> to radial flow whereby gluons radiated transversely from <span class="hlt">flux</span> <span class="hlt">tubes</span> are boosted by radial flow to form a narrow structure or ridge on azimuth. In this study we test the theory conjecture by comparing measurements to predictions for particle production, spectra, and correlations from the glasma model and from conventional fragmentation processes. We conclude that themore » glasma model is contradicted by measured hadron yields, spectra, and correlations, whereas a two-component model of hadron production, including minimum-bias parton fragmentation, provides a quantitative description of most features of the data, although η elongation of the same-side 2D peak remains undescribed.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015HESSD..12.2741H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015HESSD..12.2741H"><span>Technical Note: <span class="hlt">Approximate</span> solution of transient drawdown for constant-<span class="hlt">flux</span> pumping at a partially penetrating well in a radial two-zone confined aquifer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, C.-S.; Yang, S.-Y.; Yeh, H.-D.</p> <p>2015-03-01</p> <p>An aquifer consisting of a skin zone and a formation zone is considered as a two-zone aquifer. Existing solutions for the problem of constant-<span class="hlt">flux</span> pumping (CFP) in a two-zone confined aquifer involve laborious calculation. This study develops a new <span class="hlt">approximate</span> solution for the problem based on a mathematical model including two steady-state flow equations with different hydraulic parameters for the skin and formation zones. A partially penetrating well may be treated as the Neumann condition with a known <span class="hlt">flux</span> along the screened part and zero <span class="hlt">flux</span> along the unscreened part. The aquifer domain is finite with an outer circle boundary treated as the Dirichlet condition. The steady-state drawdown solution of the model is derived by the finite Fourier cosine transform. Then, an <span class="hlt">approximate</span> transient solution is developed by replacing the radius of the boundary in the steady-state solution with an analytical expression for a dimensionless time-dependent radius of influence. The <span class="hlt">approximate</span> solution is capable of predicting good temporal drawdown distributions over the whole pumping period except at the early stage. A quantitative criterion for the validity of neglecting the vertical flow component due to a partially penetrating well is also provided. Conventional models considering radial flow without the vertical component for the CFP have good accuracy if satisfying the criterion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26113161','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26113161"><span>Bisphenol A affects germination and <span class="hlt">tube</span> growth in Picea meyeri pollen through modulating Ca2+ <span class="hlt">flux</span> and disturbing actin-dependent vesicular trafficking during cell wall construction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chang, Tongjie; Fan, Chengyu; Man, Yi; Zhou, Junhui; Jing, Yanping</p> <p>2015-09-01</p> <p>Bisphenol A (BPA), a widespread pollutant, is reportedly harmful to humans, animals and plants. However, the effect of BPA on plant pollen <span class="hlt">tube</span> growth, as well as the mechanism involved, remains unclear. Here, we report that BPA significantly inhibited Picea meyeri pollen germination and <span class="hlt">tube</span> elongation in a dose-dependent manner. Transmission electron microscopy showed that BPA was detrimental to organelles such as mitochondria and Golgi apparatus. Non-invasive detection revealed that BPA inhibited extracellular Ca(2+) influx and promoted intracellular Ca(2+) efflux at the pollen <span class="hlt">tube</span> tip, thereby inducing a dissipated Ca(2+) gradient. Fluorescence labeling showed that BPA disorganized actin filaments (AFs), which subsequently led to abnormal vesicle trafficking. Furthermore, BPA reduced the activity of acid phosphatase, a typical exocytosis enzyme. Moreover, Fourier transform infrared (FTIR) analysis and subsequent fluorescence labeling revealed that BPA induced an abnormal deposition of cell wall components, including pectins and callose. Taken together, our results indicate that BPA, a ubiquitous environmental pollutant, disturbs Ca(2+) <span class="hlt">flux</span> in P. meyeri pollen <span class="hlt">tubes</span>, thus disrupting AF organization, resulting in abnormal actin-dependent vesicle trafficking and further affecting the deposition of cell wall components. These findings provide new insight into the mechanism of BPA toxicity in pollen <span class="hlt">tube</span> tip growth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009HMT....45.1351L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009HMT....45.1351L"><span>The relationship between absolute vorticity <span class="hlt">flux</span> along the main flow and convection heat transfer in a <span class="hlt">tube</span> inserting a twisted tape</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Zhi-Min; Sun, Dong-Liang; Wang, Liang-Bi</p> <p>2009-09-01</p> <p>As passive enhancement devices, twisted tape insert has been used for almost a century, the most dominant heat transfer enhancement mechanism of circular <span class="hlt">tube</span> fitted with twisted tape is the secondary flow generated by the tape. There is a parameter to specify the intensity of secondary flow, but this parameter cannot be applied to more general cases. Here cross-averaged absolute vorticity <span class="hlt">flux</span> in the main flow direction is used to specify the intensity of secondary flow produced by twisted tape inserted in a <span class="hlt">tube</span>. The relationship between the intensity of secondary flow and the intensity of laminar convective heat transfer is studied using a numerical method. The results reveal that the cross-averaged absolute vorticity <span class="hlt">flux</span> in the main flow direction can reflect the intensity of secondary flow and a significant relationship between this cross-averaged absolute vorticity <span class="hlt">flux</span> and Nusselt number exists for studied cases. The presented results validate that the cross-averaged absolute vorticity <span class="hlt">flux</span> in the main flow direction is a general specifying of the intensity of secondary flow and can be used in other cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/872520','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/872520"><span>Tapered pulse <span class="hlt">tube</span> for pulse <span class="hlt">tube</span> refrigerators</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Swift, Gregory W.; Olson, Jeffrey R.</p> <p>1999-01-01</p> <p>Thermal insulation of the pulse <span class="hlt">tube</span> in a pulse-<span class="hlt">tube</span> refrigerator is maintained by optimally varying the radius of the pulse <span class="hlt">tube</span> to suppress convective heat loss from mass <span class="hlt">flux</span> streaming in the pulse <span class="hlt">tube</span>. A simple cone with an optimum taper angle will often provide sufficient improvement. Alternatively, the pulse <span class="hlt">tube</span> radius r as a function of axial position x can be shaped with r(x) such that streaming is optimally suppressed at each x.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAP...112b3909Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAP...112b3909Y"><span>The effect of a constraining metal <span class="hlt">tube</span> on <span class="hlt">flux</span> pinning induced stress in a long cylindrical superconductor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Xiaobin; Tu, Shan-Tung</p> <p>2012-07-01</p> <p>The use of an alloy <span class="hlt">tube</span> to impose pressure on a superconducting cylinder during magnetizing reduces pinning-induced tensile stress in high temperature superconductors has been well established. In this paper the natural contact state between the superconducting cylinder and the metal <span class="hlt">tube</span> is modeled. An exact solution is obtained for the isotropic magnetoelastic problem with the superconductor behaving magnetically, and an expression for the contact pressure exerted on the superconductor by the metal <span class="hlt">tube</span> is obtained. This expression explicitly gives the contribution of the ratio of Young's modulus of the superconductor to that of the metal and the ratio of the internal to external radii of the metal <span class="hlt">tube</span>. The stress profile in the superconductor, subjected to the restriction of metal <span class="hlt">tube</span>, with both field cooled activation and pulse field activation is analyzed in terms of the Bean critical-state model. The results show that the metal <span class="hlt">tube</span> can prevent radial expansion of the superconductor and can reduce the maximum tension for field-cooled and pulsed-field activations. These results are important for the selection of materials as well as the optimization of sizes of the alloy <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24816522','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24816522"><span>Reduction-melting combined with a Na₂CO₃ <span class="hlt">flux</span> recycling process for lead recovery from cathode ray <span class="hlt">tube</span> funnel glass.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Okada, Takashi; Yonezawa, Susumu</p> <p>2014-08-01</p> <p>With large quantity of <span class="hlt">flux</span> (Na2CO3), lead can be recovered from the funnel glass of waste cathode-ray <span class="hlt">tubes</span> via reduction-melting at 1000°C. To reduce <span class="hlt">flux</span> cost, a technique to recover added <span class="hlt">flux</span> from the generated oxide phase is also important in order to recycle the <span class="hlt">flux</span> recovered from the reduction-melting process. In this study, the phase separation of sodium and the crystallization of water-soluble sodium silicates were induced after the reduction-melting process to enhance the leachability of sodium in the oxide phase and to extract the sodium from the phase for the recovery of Na2CO3 as <span class="hlt">flux</span>. A reductive atmosphere promoted the phase separation and crystallization, and the leachability of sodium from the oxide phase was enhanced. The optimum temperature and treatment time for increasing the leachability were 700°C and 2h, respectively. After treatment, more than 90% of the sodium in the oxide phase was extracted in water. NaHCO3 can be recovered by carbonization of the solution containing sodium ions using carbon dioxide gas, decomposed to Na2CO3 at 50°C and recycled for use in the reduction-melting process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21978040','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21978040"><span>Improved motion-compensated image reconstruction for PET using sensitivity correction per respiratory gate and an <span class="hlt">approximate</span> <span class="hlt">tube</span>-of-response backprojector.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dikaios, Nikolaos; Fryer, Tim D</p> <p>2011-09-01</p> <p>One limitation of positron emission tomography (PET) imaging of the torso is patient motion. Motion-compensated image reconstruction (MCIR) is one method employed to reduce the deleterious effects of motion. Existing MCIR algorithms use a single sensitivity correction term, which provides inexact normalization for multigate data. Consequently, in this study, the authors derive and examine the performance of an MCIR algorithm with sensitivity correction per gate. In addition, they demonstrate an <span class="hlt">approximate</span> <span class="hlt">tube</span>-of-response (TOR) backprojector. Simulated data from the NCAT phantom with six lesions added were used to compare MCIR algorithms with and without the incorporation of sensitivity correction per gate and TOR backprojection to postreconstruction registration (PRR) and images reconstructed without motion correction. To make the simulations more realistic, intragate motion was included. Deformation fields were determined from NCAT anatomical images using a free-form deformation approach with bending energy regularization. Sensitivity correction per gate and TOR backprojection improved mean lesion contrast-to-noise ratio by 6%-8%, with the maximum increase (21%-23%) found for the smallest lesion. These increases were obtained despite a small increase (3%) in noise as measured by standard deviation in a uniform lung region. Sensitivity correction per gate comes at no extra computational cost, whilst replacing line-of-response backprojection with TOR backprojection increased the overall computation time by ∼20%. In addition, MCIR was found to be superior to PRR, with one factor contributing to this difference being the differential impact of interpolation following deformation. MCIR was also shown to exhibit super-resolution. Replacing a single sensitivity correction term in MCIR with sensitivity correction per gate improves lesion detectability. For a small increase in computational expense, further improvements are achieved using an <span class="hlt">approximate</span> TOR</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007APS..TSF.B4006H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..TSF.B4006H"><span>Simulations of the Cleft Ion Fountain outflows resulting from the passage of Storm Enhanced Density (SED) plasma <span class="hlt">flux</span> <span class="hlt">tubes</span> through the dayside cleft auroral processes region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Horwitz, James; Zeng, Wen</p> <p>2007-10-01</p> <p>Foster et al. [2002] reported elevated ionospheric density regions convected from subauroral plasmaspheric regions toward noon, in association with convection of plasmaspheric tails. These Storm Enhanced Density (SED) regions could supply cleft ion fountain outflows. Here, we will utilize our Dynamic Fluid Kinetic (DyFK) model to simulate the entry of a high-density ``plasmasphere-like'' <span class="hlt">flux</span> <span class="hlt">tube</span> entering the cleft region and subjected to an episode of wave-driven transverse ion heating. It is found that the O^+ ion density at higher altitudes increases and the density at lower altitudes decreases, following this heating episode, indicating increased <span class="hlt">fluxes</span> of O^+ ions from the ionospheric source gain sufficient energy to reach higher altitudes after the effects of transverse wave heating. Foster, J. C., P. J. Erickson, A. J. Coster, J. Goldstein, and F. J. Rich, Ionospheric signatures of plasmaspheric tails, Geophys. Res. Lett., 29(13), 1623, doi:10.1029/2002GL015067, 2002.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCoPh.303..470A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCoPh.303..470A"><span>Three-dimensional control-volume distributed multi-point <span class="hlt">flux</span> <span class="hlt">approximation</span> coupled with a lower-dimensional surface fracture model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmed, Raheel; Edwards, Michael G.; Lamine, Sadok; Huisman, Bastiaan A. H.; Pal, Mayur</p> <p>2015-12-01</p> <p>A novel cell-centred control-volume distributed multi-point <span class="hlt">flux</span> <span class="hlt">approximation</span> (CVD-MPFA) finite-volume formulation is presented for discrete fracture-matrix simulations on unstructured grids in three-dimensions (3D). The grid is aligned with fractures and barriers which are then modelled as lower-dimensional surface interfaces located between the matrix cells in the physical domain. The three-dimensional pressure equation is solved in the matrix domain coupled with a two-dimensional (2D) surface pressure equation solved over fracture networks via a novel surface CVD-MPFA formulation. The CVD-MPFA formulation naturally handles fractures with anisotropic permeabilities on unstructured grids. Matrix-fracture <span class="hlt">fluxes</span> are expressed in terms of matrix and fracture pressures and define the transfer function, which is added to the lower-dimensional flow equation and couples the three-dimensional and surface systems. An additional transmission condition is used between matrix cells adjacent to low permeable fractures to couple the velocity and pressure jump across the fractures. Convergence and accuracy of the lower-dimensional fracture model is assessed for highly anisotropic fractures having a range of apertures and permeability tensors. A transport equation for tracer flow is coupled via the Darcy <span class="hlt">flux</span> for single and intersecting fractures. The lower-dimensional <span class="hlt">approximation</span> for intersecting fractures avoids the more restrictive CFL condition corresponding to the equi-dimensional <span class="hlt">approximation</span> with explicit time discretisation. Lower-dimensional fracture model results are compared with equi-dimensional model results. Fractures and barriers are efficiently modelled by lower-dimensional interfaces which yield comparable results to those of the equi-dimensional model. Pressure continuity is built into the model across highly conductive fractures, leading to reduced local degrees of freedom in the CVD-MPFA <span class="hlt">approximation</span>. The formulation is applied to geologically complex</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...840...20S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...840...20S"><span>Propagation of Torsional Alfvén Waves from the Photosphere to the Corona: Reflection, Transmission, and Heating in Expanding <span class="hlt">Flux</span> <span class="hlt">Tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Ballester, José Luis</p> <p>2017-05-01</p> <p>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 <span class="hlt">flux</span> <span class="hlt">tubes</span> 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 <span class="hlt">flux</span> <span class="hlt">tube</span> increases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA241936','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA241936"><span>Nucleate Pool Boiling Performance of Small High <span class="hlt">Flux</span> and Turbo-B <span class="hlt">Tube</span> Bundles in R-114/Oil Mixtures</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1990-12-01</p> <p>88 APPENDIX C. UNCERTAINTY ANALYSIS ........................... 97 LIST OF REFERENCES...TABLE 3.2 COMPUTER /DATA ACQUISITION ASSIGN;.’,ENT ........... 21 TABLE 5.1 BOILING HEAT TRANSFER COEFFICIENTS AND ENHANCEMENT RATIOS FOR SMOOTH <span class="hlt">TUBE</span>...86 TABLE C.1 UNCERTAINTY ANALYSIS RESULTS .................. 101 vi UST OF FIGURES Figure 2.1 Typical Boiling Curve</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22599892','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22599892"><span>Gradient-driven <span class="hlt">flux-tube</span> simulations of ion temperature gradient turbulence close to the non-linear threshold</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Peeters, A. G.; Rath, F.; Buchholz, R.; Grosshauser, S. R.; Strintzi, D.; Weikl, A.; Camenen, Y.; Candy, J.; Casson, F. J.; Hornsby, W. A.</p> <p>2016-08-15</p> <p>It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat <span class="hlt">fluxes</span> 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 <span class="hlt">flux</span>, 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 <span class="hlt">flux</span> then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat <span class="hlt">flux</span> is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat <span class="hlt">flux</span> is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat <span class="hlt">flux</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PFR.....1...17H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PFR.....1...17H"><span>Thermal Analysis on Mono-Block Type Divertor Based on Subcooled Flow Boiling Critical Heat <span class="hlt">Flux</span> Data against Inlet Subcooling in Short Vertical <span class="hlt">Tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki</p> <p></p> <p>The subcooled flow boiling critical heat <span class="hlt">fluxes</span> (CHFs) and the heat transfer coefficients (HTCs) data for the <span class="hlt">tube</span> length, L, of 49, 99 and 149 mm with 9-mm inner diameter were applied to thermal analysis on the Mono-block type divertor of LHD. Incident CHFs for the divertor with the cooling <span class="hlt">tube</span> diameter, d, of 10 mm and the carbon armor outer diameter, D, of 26 and 33 mm were numerically analyzed based on the measured CHFs and HTCs at the inlet pressure of around 800 kPa. The numerical solutions were also compared with those for the Flat-plate type divertor, which were numerically analyzed for the divertor with the cooling <span class="hlt">tube</span> diameter d=10 mm and the divertor width, w, ranging from 16 to 30 mm. It is confirmed that the ratio of the one-side heating CHF data, qcr,inc, to the uniform heating CHF data, qcr,sub, can be represented as the simple equation based on the numerical solutions. The values of the qcr,inc for L=50, 100 and 150 mm were estimated with various D/d and w/d at higher pressures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/783489','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/783489"><span>High <span class="hlt">flux</span> compact neutron generators</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reijonen, J.; Lou, T.-P.; Tolmachoff, B.; Leung, K.-N.; Verbeke, J.; Vujic, J.</p> <p>2001-06-15</p> <p>Compact high <span class="hlt">flux</span> neutron generators are developed at the Lawrence Berkeley National Laboratory. The neutron production is based on D-D or D-T reaction. The deuterium or tritium ions are produced from plasma using either a 2 MHz or 13.56 MHz radio frequency (RF) discharge. RF-discharge yields high fraction of atomic species in the beam which enables higher neutron output. In the first <span class="hlt">tube</span> design, the ion beam is formed using a multiple hole accelerator column. The beam is accelerated to energy of 80 keV by means of a three-electrode extraction system. The ion beam then impinges on a titanium target where either the 2.4 MeV D-D or 14 MeV D-T neutrons are generated. The MCNP computation code has predicted a neutron <span class="hlt">flux</span> of {<span class="hlt">approximately</span>}10{sup 11} n/s for the D-D reaction at beam intensity of 1.5 A at 150 kV. The neutron <span class="hlt">flux</span> measurements of this <span class="hlt">tube</span> design will be presented. Recently new compact high <span class="hlt">flux</span> <span class="hlt">tubes</span> are being developed which can be used for various applications. These <span class="hlt">tubes</span> also utilize RF-discharge for plasma generation. The design of these <span class="hlt">tubes</span> and the first measurements will be discussed in this presentation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JGR...10614301S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JGR...10614301S"><span>On the accuracy of the independent column <span class="hlt">approximation</span> in calculating the downward <span class="hlt">fluxes</span> in the UVA, UVB, and PAR spectral ranges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scheirer, Ronald; Macke, Andreas</p> <p>2001-07-01</p> <p>In order to investigate the accuracy of simplification in modeling the radiative transfer in those solar spectral regions with major impacts on bio-organisms, i.e., the UVA (0.32-0.4 μm), the UVB (0.28-0.32 μm), and the photosynthetically active radiation (PAR, 0.4-0.7 μm), radiative transfer calculations with varying treatments of cloud geometries (plane-parallel homogeneous (PPHOM), independent column <span class="hlt">approximation</span> (ICA), and three-dimensional (3-D) inhomogeneous) have been performed. The complete sets of atmospheric information for 133 cloud realizations are taken from the three-dimensional nonhydrostatic mesoscale atmospheric model (GESIMA). A Monte Carlo radiative transfer model (GRIMALDI) has been developed that simulates scattering and absorption for arbitrarily three-dimensional distributions of cloud hydrometeors, air molecules, and water vapor. Results are shown for domain-averaged direct and total transmission (and so, implicitly, diffuse transmission) at the ground surface. In the UVA the PPHOM assumption leads to an underestimation in direct (total) downward <span class="hlt">flux</span> by as much as 43 (28) W m-2, which is about 49% (32%) of the incoming irradiation, whereas results based on the ICA are almost identical to the 3-D case, except for convective clouds where the error in the UVA for direct (total) downward <span class="hlt">flux</span> reaches 5 (2) W m-2, or 6% (2%) of the incoming solar irradiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090042328&hterms=tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dtube','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090042328&hterms=tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dtube"><span>The Funnel Geometry of Open <span class="hlt">Flux</span> <span class="hlt">Tubes</span> in the Low Solar Corona Constrained by O VI and Ne VIII Outflow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Byhring, Hanne S.; Esser, Ruth; Lie-Svendsen, Oystein</p> <p>2008-01-01</p> <p>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 <span class="hlt">tube</span> expansion as well as the location of the expansion in the transition region/lower corona.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090042328&hterms=lie&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dlie','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090042328&hterms=lie&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dlie"><span>The Funnel Geometry of Open <span class="hlt">Flux</span> <span class="hlt">Tubes</span> in the Low Solar Corona Constrained by O VI and Ne VIII Outflow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Byhring, Hanne S.; Esser, Ruth; Lie-Svendsen, Oystein</p> <p>2008-01-01</p> <p>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 <span class="hlt">tube</span> expansion as well as the location of the expansion in the transition region/lower corona.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=convection&pg=3&id=EJ844005','ERIC'); return false;" href="http://eric.ed.gov/?q=convection&pg=3&id=EJ844005"><span>The Role of the Velocity Gradient in Laminar Convective Heat Transfer through a <span class="hlt">Tube</span> with a Uniform Wall Heat <span class="hlt">Flux</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia</p> <p>2009-01-01</p> <p>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 <span class="hlt">flux</span>, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=thermal+AND+physics&pg=5&id=EJ844005','ERIC'); return false;" href="https://eric.ed.gov/?q=thermal+AND+physics&pg=5&id=EJ844005"><span>The Role of the Velocity Gradient in Laminar Convective Heat Transfer through a <span class="hlt">Tube</span> with a Uniform Wall Heat <span class="hlt">Flux</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia</p> <p>2009-01-01</p> <p>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 <span class="hlt">flux</span>, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880012333','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880012333"><span>Splitting of inviscid <span class="hlt">fluxes</span> for real gases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liou, Meng-Sing; Vanleer, Bram; Shuen, Jian-Shun</p> <p>1988-01-01</p> <p><span class="hlt">Flux</span>-vector and <span class="hlt">flux</span>-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, <span class="hlt">approximations</span> or 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-<span class="hlt">tube</span> and nozzle problems show their quality and robustness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900038396&hterms=Bram&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DBram','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900038396&hterms=Bram&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DBram"><span>Splitting of inviscid <span class="hlt">fluxes</span> for real gases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liou, Meng-Sing; Van Leer, Bram; Shuen, Jian-Shun</p> <p>1990-01-01</p> <p><span class="hlt">Flux</span>-vector and <span class="hlt">flux</span>-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, <span class="hlt">approximations</span> 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-<span class="hlt">tube</span> and nozzle problems show their quality and robustness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900038396&hterms=gases+reales&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgases%2Breales','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900038396&hterms=gases+reales&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgases%2Breales"><span>Splitting of inviscid <span class="hlt">fluxes</span> for real gases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liou, Meng-Sing; Van Leer, Bram; Shuen, Jian-Shun</p> <p>1990-01-01</p> <p><span class="hlt">Flux</span>-vector and <span class="hlt">flux</span>-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, <span class="hlt">approximations</span> 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-<span class="hlt">tube</span> and nozzle problems show their quality and robustness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012HMT....48.1425C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012HMT....48.1425C"><span>Predicting the critical heat <span class="hlt">flux</span> in concentric-<span class="hlt">tube</span> open thermosiphon: a method based on support vector machine optimized by chaotic particle swarm optimization algorithm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Jiejin</p> <p>2012-08-01</p> <p>This study presents a method based on support vector machine (SVM) optimized by chaotic particle swarm optimization algorithm (CPSO) for the prediction of the critical heat <span class="hlt">flux</span> (CHF) in concentric-<span class="hlt">tube</span> open thermosiphon. In this process, the parameters C, ɛ and δ2 of SVM have been determined by the CPSO. As for a comparision, the traditional back propagation neural network (BPNN), radial basis function neural network (RBFNN), general regression neural network (GRNN) are also used to predict the CHF for the same experimental results under a variety of operating conditions. The MER and RMSE of SVM-CPSO model are about 45% of the BPNN model, about 60% of the RBFNN model, and about 80% of GRNN model. The simulation results demonstrate that the SVM-CPSO method can get better accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20770222','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20770222"><span>Effects of EHD on heat transfer enhancement and pressure drop during two-phase condensation of pure R-134a at high mass <span class="hlt">flux</span> in a horizontal micro-fin <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Laohalertdecha, Suriyan; Wongwises, Somchai</p> <p>2006-07-15</p> <p>Effects of electrohydrodynamic (EHD) on the two-phase heat transfer enhancement and pressure drop of pure R-134a condensing inside a horizontal micro-fin <span class="hlt">tube</span> are experimentally investigated. The test section is a 2.5m long counter flow <span class="hlt">tube-in-tube</span> heat exchanger with refrigerant flowing in the inner <span class="hlt">tube</span> and cooling water flowing in the annulus. The inner <span class="hlt">tube</span> is made from micro-fin horizontal copper <span class="hlt">tubing</span> of 9.52mm outer diameter. The electrode is made from cylindrical stainless steel of 1.47mm diameter. Positive high voltage is supplied to the electrode wire, with the micro-fin <span class="hlt">tube</span> grounded. In the presence of the electrode, a maximum heat transfer enhancement of 1.15 is obtained at a heat <span class="hlt">flux</span> of 10kW/m{sup 2}, mass <span class="hlt">flux</span> of 200kg/m{sup 2}s and saturation temperature of 40{sup o}C, while the application of an EHD voltage of 2.5kV only slightly increases the pressure drop. New correlations of the experimental data based on the data gathered during this work for predicting the condensation heat transfer coefficients are proposed for practical application. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...784....6Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...784....6Z"><span>High-energy X-Ray Detection of G359.89-0.08 (Sgr A-E): Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> Emission Powered by Cosmic Rays?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Tomsick, John A.; Zhang, William W.</p> <p>2014-03-01</p> <p>We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to ~50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed <span class="hlt">flux</span> in the 3-79 keV band is FX = (2.0 ± 0.1) × 10-12 erg cm-2 s-1, corresponding to an unabsorbed X-ray luminosity LX = (2.6 ± 0.8) × 1034 erg s-1 assuming a distance 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 <span class="hlt">flux</span> <span class="hlt">tube</span> which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to ~100 kyr) with low surface brightness and radii up to ~30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22519960','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22519960"><span>COMPARISON OF IMPLICIT SCHEMES TO SOLVE EQUATIONS OF RADIATION HYDRODYNAMICS WITH A <span class="hlt">FLUX</span>-LIMITED DIFFUSION <span class="hlt">APPROXIMATION</span>: NEWTON–RAPHSON, OPERATOR SPLITTING, AND LINEARIZATION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tetsu, Hiroyuki; Nakamoto, Taishi</p> <p>2016-03-15</p> <p>Radiation is an important process of energy transport, a force, and a basis for synthetic observations, so radiation hydrodynamics (RHD) calculations have occupied an important place in astrophysics. However, although the progress in computational technology is remarkable, their high numerical cost is still a persistent problem. In this work, we compare the following schemes used to solve the nonlinear simultaneous equations of an RHD algorithm with the <span class="hlt">flux</span>-limited diffusion <span class="hlt">approximation</span>: the Newton–Raphson (NR) method, operator splitting, and linearization (LIN), from the perspective of the computational cost involved. For operator splitting, in addition to the traditional simple operator splitting (SOS) scheme, we examined the scheme developed by Douglas and Rachford (DROS). We solve three test problems (the thermal relaxation mode, the relaxation and the propagation of linear waves, and radiating shock) using these schemes and then compare their dependence on the time step size. As a result, we find the conditions of the time step size necessary for adopting each scheme. The LIN scheme is superior to other schemes if the ratio of radiation pressure to gas pressure is sufficiently low. On the other hand, DROS can be the most efficient scheme if the ratio is high. Although the NR scheme can be adopted independently of the regime, especially in a problem that involves optically thin regions, the convergence tends to be worse. In all cases, SOS is not practical.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJS..223...14T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJS..223...14T"><span>Comparison of Implicit Schemes to Solve Equations of Radiation Hydrodynamics with a <span class="hlt">Flux</span>-limited Diffusion <span class="hlt">Approximation</span>: Newton--Raphson, Operator Splitting, and Linearization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tetsu, Hiroyuki; Nakamoto, Taishi</p> <p>2016-03-01</p> <p>Radiation is an important process of energy transport, a force, and a basis for synthetic observations, so radiation hydrodynamics (RHD) calculations have occupied an important place in astrophysics. However, although the progress in computational technology is remarkable, their high numerical cost is still a persistent problem. In this work, we compare the following schemes used to solve the nonlinear simultaneous equations of an RHD algorithm with the <span class="hlt">flux</span>-limited diffusion <span class="hlt">approximation</span>: the Newton-Raphson (NR) method, operator splitting, and linearization (LIN), from the perspective of the computational cost involved. For operator splitting, in addition to the traditional simple operator splitting (SOS) scheme, we examined the scheme developed by Douglas & Rachford (DROS). We solve three test problems (the thermal relaxation mode, the relaxation and the propagation of linear waves, and radiating shock) using these schemes and then compare their dependence on the time step size. As a result, we find the conditions of the time step size necessary for adopting each scheme. The LIN scheme is superior to other schemes if the ratio of radiation pressure to gas pressure is sufficiently low. On the other hand, DROS can be the most efficient scheme if the ratio is high. Although the NR scheme can be adopted independently of the regime, especially in a problem that involves optically thin regions, the convergence tends to be worse. In all cases, SOS is not practical.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/413376','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/413376"><span>Monte Carlo simulation of false alarms and detection reliability in magnetic <span class="hlt">flux</span> leakage inspection of steel <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Altschuler, E.; Pignotti, A.; Paiuk, J.</p> <p>1996-09-01</p> <p>The same flaw gives rise to different signals when inspected by the same nondestructive testing (NDT) equipment under closely similar circumstances. A laboratory example involving six identical cracks is shown. This is a consequence of unavoidable fluctuations in the parameters that influence the detection process and is illustrated using a Monte Carlo simulation based on a numerical model of crack detection in steel pipes by magnetic <span class="hlt">flux</span> leakage. The effects of these uncertainties on the fault detection reliability and on the appearance of false alarms are analyzed. The occurrence of Type I errors (lack of detection of unacceptable defects) and Type II errors (false alarms) is studied as a function of the detection threshold, and guidelines for improving detection efficiency are suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B33C0667B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B33C0667B"><span>High-speed Air Temperature Measurements in a Closed-path Cell and Quality of CO2 and H2O <span class="hlt">Fluxes</span> from a Short-<span class="hlt">tube</span> Gas Analyzer.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burba, G. G.; Kathilankal, J. C.; Fratini, G.</p> <p>2015-12-01</p> <p>Gas analyzers traditionally used for eddy covariance method measure gas density. When <span class="hlt">fluxes</span> are calculated, corrections are applied to account for the changes in gas density due to changing temperature and pressure (Ideal Gas Law) and changing water vapor density (Dalton's Law). The new generation of gas analyzers with fast air temperature and pressure measurements in the sampling cell enables on-the-fly calculation of fast dry mole fraction. This significantly simplifies the <span class="hlt">flux</span> processing because the WPL density terms are no longer required, and leads to the reduction in uncertainties associated with latent and sensible heat <span class="hlt">flux</span> inputs into the density terms. Traditional closed-path instruments with long intake <span class="hlt">tubes</span> often can effectively dampen the fast temperature fluctuations in the <span class="hlt">tube</span> before reaching the measurement cell, thus reducing or eliminating the need for temperature correction for density-based <span class="hlt">fluxes</span>. But in instruments with a short-<span class="hlt">tube</span> design, most - but not all - of the temperature fluctuations are attenuated, so calculating unbiased <span class="hlt">fluxes</span> using fast dry mole fraction requires high-speed precise temperature measurements of the air stream inside the cell. Fast pressure and water vapor content of the sampled air should also be measured in the cell and carefully aligned in time with gas density and sample temperature measurements.In this study we examine the impact of fast-response air temperature measurements in the cell on the calculations of carbon dioxide and water vapor <span class="hlt">fluxes</span> at different time scales from three different ecosystems. The fast cell air temperature data is filtered mathematically to obtain slower response cell temperature time series, which is used in the calculation of <span class="hlt">fluxes</span>. This exercise is intended to simulate the use of thicker slower response thermocouples instead of fast response fine wire thermocouples for estimating cell temperature. The directly measured block temperature is also utilized to illustrate the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.C41C0475S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.C41C0475S"><span>Evaluating the numerical <span class="hlt">approximation</span> of the atmospheric latent heat <span class="hlt">flux</span> used by CSIM5 and it's influence on the distribution of sea-ice thickness within the Southern Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stampone, M. D.</p> <p>2009-12-01</p> <p>The sea-ice thickness response produced by the National Center for Atmospheric Research (NCAR) Community Sea Ice Model, Version 5 (CSIM5) to the numerical <span class="hlt">approximation</span> of the latent heat <span class="hlt">flux</span> within the stand-alone ice model is evaluated for ice-covered water south of 55 °S latitude. Previous work indicated that the simulated sea-ice environment produced by both coupled and stand-alone versions of the CSIM5 responded strongly to the value of atmospheric specific humidity due to the parameterized numerical <span class="hlt">approximation</span> of the latent heat <span class="hlt">flux</span> used by CSIM5. The latent heat <span class="hlt">approximation</span> used by CSIM5 results in a greater flow of latent heat energy toward the ice surface in response to high atmospheric moisture. In the case of high atmospheric moisture, CSIM5 produced an erroneously thinner ice pack with a lesser extent, indicated by large (> 50 cm), negative model prediction errors. Conversely, model prediction errors for areas of low atmospheric moisture were large (> 200 cm) and positive, indicating a thicker, more extensive ice pack than observed. To reduce the sensitivity of the simulated sea-ice thickness distribution to atmospheric humidity, the CSIM5 <span class="hlt">approximation</span> of the latent heat <span class="hlt">flux</span> was modified to better represent the variable nature of the exchange of latent heat energy between the atmosphere and ice surface. This modification is a more reasonable <span class="hlt">approximation</span> of the latent heat <span class="hlt">flux</span>, improving the CSIM5 representation of the sea-ice thickness distribution within the Southern Ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22351541','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22351541"><span>High-energy X-ray detection of G359.89–0.08 (SGR A–E): Magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> emission powered by cosmic rays?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhang, Shuo; Hailey, Charles J.; Gotthelf, Eric V.; Mori, Kaya; Nynka, Melania; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Tomsick, John A.; Christensen, Finn E.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.</p> <p>2014-03-20</p> <p>We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89–0.08 (Sgr A–E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to ∼50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed <span class="hlt">flux</span> in the 3-79 keV band is F{sub X} = (2.0 ± 0.1) × 10{sup –12} erg cm{sup –2} s{sup –1}, corresponding to an unabsorbed X-ray luminosity L{sub X} = (2.6 ± 0.8) × 10{sup 34} erg s{sup –1} assuming a distance 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 <span class="hlt">flux</span> <span class="hlt">tube</span> which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to ∼100 kyr) with low surface brightness and radii up to ∼30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMSM31B0453Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMSM31B0453Z"><span>Fluid-kinetic simulations of the passage of Storm Enhanced Density (SED) plasma <span class="hlt">flux</span> <span class="hlt">tubes</span> through the dayside cleft auroral processes region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeng, W.; Horwitz, J. L.</p> <p>2007-12-01</p> <p>Foster et al. [2002] and others have reported on elevated ionospheric density regions being convected from the subauroral plasmaspheric region toward noon, in association with convection of plasmaspheric tails in the dayside magnetosphere. It has been suggested that these so-called Storm Enhanced Density (SED) regions could serve as ionospheric plasma source populations for cleft ion fountain outflows. To investigate this scenario, we have used our Dynamic Fluid Kinetic (DyFK) model to simulate the entry of a high-density "plasmasphere-like" <span class="hlt">flux</span> <span class="hlt">tube</span> entering the cleft region and subjected to an episode of wave-driven transverse ion heating. We find that the O+ ion density at higher altitudes increases and the density at lower altitudes decreases, following this heating episode, indicating increased numbers of O+ ions from the ionospheric source gain sufficient energy to reach higher altitudes after the effects of transverse wave heating. We also find that O+- H+ crossing point in topside ionosphere moves upward as the wave heating continues. Foster, J. C., P. J. Erickson, A. J. Coster, J. Goldstein, and F. J. Rich, Ionospheric signatures of plasmaspheric tails, Geophys. Res. Lett., 29(13), 1623, doi:10.1029/2002GL015067, 2002.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvC..92f4904R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvC..92f4904R"><span>Modeling early stages of relativistic heavy ion collisions: Coupling relativistic transport theory to decaying color-electric <span class="hlt">flux</span> <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruggieri, M.; Puglisi, A.; Oliva, L.; Plumari, S.; Scardina, F.; Greco, V.</p> <p>2015-12-01</p> <p>In this study we model early-time dynamics of relativistic heavy ion collisions by an initial color-electric field which then decays to a plasma by the Schwinger mechanism, coupling the dynamical evolution of the initial color field to the dynamics of the many particles system produced by the decay. The latter is described by relativistic kinetic theory in which we fix the ratio η /s rather than insisting on specific microscopic processes, and the backreaction on the color field is taken into account by solving self-consistently the kinetic and the field equations. We study isotropization and thermalization of the system produced by the field decay for a static box and for a 1 +1 D expanding geometry. We find that regardless of the viscosity of the produced plasma, the initial color-electric field decays within 1 fm/c ; however, in the case where η /s is large, oscillations of the field are effective along all the entire time evolution of the system, which affect the late-time evolution of the ratio between longitudinal and transverse pressure. In the case of small η /s (η /s ≲0.3 ) we find τisotropization≈0.8 fm/c and τthermalization≈1 fm/c , in agreement with the common lore of hydrodynamics. Moreover, we have investigated the effect of turning from the relaxation time <span class="hlt">approximation</span> to the Chapman-Enskog one: We find that this improvement affects mainly the early-time evolution of the physical quantities, the effect being milder in the late-time evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997SPD....28.0233H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997SPD....28.0233H"><span>Chromospheric Heating and the Excitation of Magnetic <span class="hlt">Tube</span> Waves Through p-Mode Buffeting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hindman, Bradley W.</p> <p>1997-05-01</p> <p>The dissipation of magnetic <span class="hlt">tube</span> waves may be the primary source of energy in the thermal balance of the solar chromosphere and corona. In this paper, I compute an upper limit on the energy <span class="hlt">flux</span> of <span class="hlt">tube</span> waves that can be driven into the chromosphere if the waves are excited by buffeting of magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> by p--modes. In addition, I estimate the p--mode line widths which result from this transfer of energy from the modes to the <span class="hlt">flux</span> <span class="hlt">tube</span> waves. To obtain the upper limit, I assume that the solar magnetic field has a fibril structure consisting of a large set of well--separated, identical <span class="hlt">tubes</span>. Each <span class="hlt">tube</span> is axisymmetric, vertical and slender. I <span class="hlt">approximate</span> the solar atmosphere with a truncated isentropic polytrope, chosen such that it's upper surface matches the tau_ {5000}=1 layer of the photospheric model of Maltby (1986). The response of the fibrils is described using the thin <span class="hlt">flux</span> <span class="hlt">tube</span> <span class="hlt">approximation</span>, ignoring multiple scattering between the <span class="hlt">tubes</span>, and assuming that the p--modes force the <span class="hlt">tubes</span> incoherently. The effects of the region above the surface of the polytrope, where a flaring <span class="hlt">flux</span> <span class="hlt">tube</span> is poorly represented by the thin <span class="hlt">flux</span> equations, are simulated through a boundary condition applied at the polytrope's surface. By varying this boundary condition the influence of any upper atmosphere can be reproduced. To compute an upper limit, I chose the boundary condition which optimizes the upward <span class="hlt">flux</span> of waves. I find that the largest <span class="hlt">flux</span> of <span class="hlt">tube</span> waves that can be sent into chromosphere is 29 ergs cm(-2) s(-1) for a fibril field with a 1% filling factor. This <span class="hlt">flux</span> is miniscule when compared to the energy <span class="hlt">flux</span> necessary to heat the chromosphere or corona. Therefore, <span class="hlt">tube</span> waves generated by the buffeting of magnetic fibrils by acoustic waves are inconsequential in the energy balance of the upper atmosphere. Furthermore, using the same boundary conditions, I find that the line width of a p--mode due to the absorption of that mode by the fibrils can be a</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHEP...07..008B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHEP...07..008B"><span>Spectrum of the open QCD <span class="hlt">flux</span> <span class="hlt">tube</span> and its effective string description I: 3d static potential in SU( N = 2 , 3)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandt, Bastian B.</p> <p>2017-07-01</p> <p>We perform a high precision measurement of the static q\\overline{q} potential in three-dimensional SU( N) gauge theory with N = 2 , 3 and compare the results to the potential obtained from the effective string theory. In particular, we show that the exponent of the leading order correction in 1 /R is 4, as predicted, and obtain accurate results for the continuum limits of the string tension and the non-universal boundary coefficient {\\overline{b}}_2 , including an extensive analysis of all types of systematic uncertainties. We find that the magnitude of {\\overline{b}}_2 decreases with increasing N, leading to the possibility of a vanishing {\\overline{b}}_2 in the large N limit. In the standard form of the effective string theory possible massive modes and the presence of a rigidity term are usually not considered, even though they might give a contribution to the energy levels. To investigate the effect of these terms, we perform a second analysis, including these contributions. We find that the associated expression for the potential also provides a good description of the data. The resulting continuum values for {\\overline{b}}_2 are about a factor of 2 smaller than in the standard analysis, due to contaminations from an additional 1 /R 4 term. However, {\\overline{b}}_2 shows a similar decrease in magnitude with increasing N. In the course of this extended analysis we also obtain continuum results for the masses appearing in the additional terms and we find that they are around twice as large as the square root of the string tension in the continuum and compatible between SU(2) and SU(3) gauge theory. In the follow up papers we will extend our investigations to the large N limit and excited states of the open <span class="hlt">flux</span> <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21116054','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21116054"><span>An experimental study of convective heat transfer with microencapsulated phase change material suspension: Laminar flow in a circular <span class="hlt">tube</span> under constant heat <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen, Binjiao; Wang, Xin; Zeng, Ruolang; Zhang, Yinping; Di, Hongfa; Wang, Xichun; Niu, Jianlei; Li, Yi</p> <p>2008-09-15</p> <p>By contrast with the conventional heat transfer fluid (water), the microencapsulated phase change material (MPCM) suspension, with a small temperature difference between storing and releasing heat, is of much larger apparent specific heat and much higher thermal energy storage capacity. It has been suggested to serve as a dual-functional medium for thermal energy transport and/or storage. The heat transfer characteristics of a kind of MPCM suspension, formed by microencapsulating industrial-grade 1-bromohexadecane (C{sub 16}H{sub 33}Br) as phase change material, were experimentally studied for laminar flow in a circular <span class="hlt">tube</span> under constant heat <span class="hlt">flux</span>. A new expression of Ste is put forward in the paper, according to the physical definition of Stefan number. The results in the experiments show: (a) the dimensionless internal wall temperature of the MPCM suspension is lower than pure water, and the decrease can be up to 30% of that of water; (b) the heat transfer enhancement ratio can be 1.42 times of that of water at x{sup +} = 4.2 x 10{sup -2} for 15.8 wt% MPCM suspension, which is not as much as in some references; and (c) the pump consumption of the MPCM suspension system decrease greatly for the larger heat transfer rate compared with water, due to phase change, the decrease can be up to 67.5% of that of water at q = 750 W (15.8 wt%). The kind of MPCM suspension has good application feasibility in practice. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1100715','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1100715"><span>Gluon correlations from a glasma <span class="hlt">flux-tube</span> model compared to measured hadron correlations on transverse momentum (p<sub>t</sub>,p<sub>t</sub>) and angular differences (η<sub>Δ</sub>,φ<sub>Δ</sub>)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Trainor, Thomas A.; Ray, R. L.</p> <p>2011-09-09</p> <p>A glasma <span class="hlt">flux-tube</span> model has been proposed to explain strong elongation on pseudorapidity η of the same-side two-dimensional (2D) peak in minimum-bias angular correlations from √(<sup>s</sup>NN)=200 GeV Au-Au collisions. The same-side peak or “soft ridge” is said to arise from coupling of <span class="hlt">flux</span> <span class="hlt">tubes</span> to radial flow whereby gluons radiated transversely from <span class="hlt">flux</span> <span class="hlt">tubes</span> are boosted by radial flow to form a narrow structure or ridge on azimuth. In this study we test the theory conjecture by comparing measurements to predictions for particle production, spectra, and correlations from the glasma model and from conventional fragmentation processes. We conclude that the glasma model is contradicted by measured hadron yields, spectra, and correlations, whereas a two-component model of hadron production, including minimum-bias parton fragmentation, provides a quantitative description of most features of the data, although η elongation of the same-side 2D peak remains undescribed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010LaPhy..20.1368R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010LaPhy..20.1368R"><span>Unconventional application of the two-<span class="hlt">flux</span> <span class="hlt">approximation</span> for the calculation of the Ambartsumyan-Chandrasekhar function and the angular spectrum of the backward-scattered radiation for a semi-infinite isotropically scattering medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Remizovich, V. S.</p> <p>2010-06-01</p> <p>It is commonly accepted that the Schwarzschild-Schuster two-<span class="hlt">flux</span> <span class="hlt">approximation</span> (1905, 1914) can be employed only for the calculation of the energy characteristics of the radiation field (energy density and energy <span class="hlt">flux</span> density) and cannot be used to characterize the angular distribution of radiation field. However, such an inference is not valid. In several cases, one can calculate the radiation intensity inside matter and the reflected radiation with the aid of this simplest <span class="hlt">approximation</span> in the transport theory. In this work, we use the results of the simplest one-parameter variant of the two-<span class="hlt">flux</span> <span class="hlt">approximation</span> to calculate the angular distribution (reflection function) of the radiation reflected by a semi-infinite isotropically scattering dissipative medium when a relatively broad beam is incident on the medium at an arbitrary angle relative to the surface. We do not employ the invariance principle and demonstrate that the reflection function exhibits the multiplicative property. It can be represented as a product of three functions: the reflection function corresponding to the single scattering and two identical h functions, which have the same physical meaning as the Ambartsumyan-Chandrasekhar function ( H) has. This circumstance allows a relatively easy derivation of simple analytical expressions for the H function, total reflectance, and reflection function. We can easily determine the relative contribution of the true single scattering in the photon backscattering at an arbitrary probability of photon survival Λ. We compare all of the parameters of the backscattered radiation with the data resulting from the calculations using the exact theory of Ambartsumyan, Chandrasekhar, et al., which was developed decades after the two-<span class="hlt">flux</span> <span class="hlt">approximation</span>. Thus, we avoid the application of fine mathematical methods (the Wiener-Hopf method, the Case method of singular functions, etc.) and obtain simple analytical expressions for the parameters of the scattered radiation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22092185','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22092185"><span>SCATTERING OF THE f-MODE BY SMALL MAGNETIC <span class="hlt">FLUX</span> ELEMENTS FROM OBSERVATIONS AND NUMERICAL SIMULATIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Felipe, T.; Braun, D.; Crouch, A.; Birch, A.</p> <p>2012-10-01</p> <p>The scattering of f-modes by magnetic <span class="hlt">tubes</span> is analyzed using three-dimensional numerical simulations. An f-mode wave packet is propagated through a solar atmosphere embedded with three different <span class="hlt">flux</span> <span class="hlt">tube</span> models that differ in radius and total magnetic <span class="hlt">flux</span>. A quiet-Sun simulation without a <span class="hlt">tube</span> present is also performed as a reference. Waves are excited inside the <span class="hlt">flux</span> <span class="hlt">tube</span> and propagate along the field lines, and jacket modes are generated in the surroundings of the <span class="hlt">flux</span> <span class="hlt">tube</span>, carrying 40% as much energy as the <span class="hlt">tube</span> modes. The resulting scattered wave is mainly an f-mode composed of a mixture of m = 0 and m = {+-}1 modes. The amplitude of the scattered wave <span class="hlt">approximately</span> scales with the magnetic <span class="hlt">flux</span>. A small amount of power is scattered into the p{sub 1}-mode. We have evaluated the absorption and phase shift from a Fourier-Hankel decomposition of the photospheric vertical velocities. They are compared with the results obtained from the ensemble average of 3400 small magnetic elements observed in high-resolution MDI Doppler datacubes. The comparison shows that the observed dependence of the phase shift with wavenumber can be matched reasonably well with the simulated <span class="hlt">flux</span> <span class="hlt">tube</span> model. The observed variation of the phase shifts with the azimuthal order m appears to depend on details of the ensemble averaging, including possible motions of the magnetic elements and asymmetrically shaped elements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/866633','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/866633"><span><span class="hlt">Tube</span> support</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Mullinax, Jerry L.</p> <p>1988-01-01</p> <p>A <span class="hlt">tube</span> support for supporting horizontal <span class="hlt">tubes</span> from an inclined vertical support <span class="hlt">tube</span> passing between the horizontal <span class="hlt">tubes</span>. A support button is welded to the vertical support <span class="hlt">tube</span>. Two clamping bars or plates, the lower edges of one bearing on the support button, are removably bolted to the inclined vertical <span class="hlt">tube</span>. The clamping bars provide upper and lower surface support for the horizontal <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..DPPJP1091B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..DPPJP1091B"><span>Infrared Radiometery and Heat <span class="hlt">Flux</span> Calculation for a Helicon Plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berisford, Daniel; Lee, Charles A.; Raja, L. L.; Bengtson, Roger D.</p> <p>2006-10-01</p> <p>Using an infrared camera, we measured the external temperature of a quartz <span class="hlt">tube</span> containing a 1 kW helicon Argon plasma. An Inframetrics model 600 IR camera connected to a computer DAQ system records the temperature evolution of the quartz <span class="hlt">tube</span> surface in the vicinity of the antenna during and after the pulse. Using these measurements, we estimated the heat <span class="hlt">flux</span> profile from the plasma into the quartz <span class="hlt">tube</span> walls. A MATLAB code uses pre- and post- pulse snapshot images from the video to estimate the heat <span class="hlt">flux</span> into the quartz from the plasma. Initial results have shown a broad heating profile with localized power input into the quartz under the helical antenna. We find <span class="hlt">approximately</span> 30% of the total RF power deposited into the <span class="hlt">tube</span> as heat, and heating directly under the antenna accounts for about 30% of this heat input.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21390711','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21390711"><span>Evaporation heat transfer and friction characteristics of R-134a flowing downward in a vertical corrugated <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Aroonrat, Kanit; Wongwises, Somchai</p> <p>2011-01-15</p> <p>Differently from most previous studies, the heat transfer and friction characteristics of the pure refrigerant HFC-134a during evaporation inside a vertical corrugated <span class="hlt">tube</span> are experimentally investigated. The double <span class="hlt">tube</span> test sections are 0.5 m long with refrigerant flowing in the inner <span class="hlt">tube</span> and heating water flowing in the annulus. The inner <span class="hlt">tubes</span> are one smooth <span class="hlt">tube</span> and two corrugated <span class="hlt">tubes</span>, which are constructed from smooth copper <span class="hlt">tube</span> of 8.7 mm inner diameter. The test runs are performed at evaporating temperatures of 10, 15, and 20 C, heat <span class="hlt">fluxes</span> of 20, 25, and 30 kW/m{sup 2}, and mass <span class="hlt">fluxes</span> of 200, 300, and 400 kg/m{sup 2} s. The quality of the refrigerant in the test section is calculated using the temperature and pressure obtained from the experiment. The pressure drop across the test section is measured directly by a differential pressure transducer. The effects of heat <span class="hlt">flux</span>, mass <span class="hlt">flux</span>, and evaporation temperature on the heat transfer coefficient and two-phase friction factor are also discussed. It is found that the percentage increases of the heat transfer coefficient and the two-phase friction factor of the corrugated <span class="hlt">tubes</span> compared with those of the smooth <span class="hlt">tube</span> are <span class="hlt">approximately</span> 0-10% and 70-140%, respectively. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.entnet.org/content/ear-tubes','NIH-MEDLINEPLUS'); return false;" href="http://www.entnet.org/content/ear-tubes"><span>Ear <span class="hlt">Tubes</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... ENTCareers Marketplace Find an ENT Doctor Near You Ear <span class="hlt">Tubes</span> Ear <span class="hlt">Tubes</span> Patient Health Information News media ... and throat specialist) may be considered. What are ear <span class="hlt">tubes</span>? Ear <span class="hlt">tubes</span> are tiny cylinders placed through ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930057641&hterms=patten&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpatten','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930057641&hterms=patten&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpatten"><span>The dynamics of magnetic <span class="hlt">flux</span> rings</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deluca, E. E.; Fisher, G. H.; Patten, B. M.</p> <p>1993-01-01</p> <p>The evolution of magnetic fields in the presence of turbulent convection is examined using results of numerical simulations of closed magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> embedded in a steady 'ABC' flow field, which <span class="hlt">approximate</span> some of the important characteristics of a turbulent convecting flow field. Three different evolutionary scenarios were found: expansion to a steady deformed ring; collapse to a compact fat <span class="hlt">flux</span> ring, separated from the expansion type of behavior by a critical length scale; and, occasionally, evolution toward an advecting, oscillatory state. The work suggests that small-scale flows will not have a strong effect on large-scale, strong fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22375958','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22375958"><span>Contactless diagnostics of biophysical parameters of skin and blood on the basis of <span class="hlt">approximating</span> functions for radiation <span class="hlt">fluxes</span> scattered by skin</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lisenko, S A; Kugeiko, M M</p> <p>2014-03-28</p> <p><span class="hlt">Approximating</span> expressions are derived to calculate spectral and spatial characteristics of diffuse reflection of light from a two-layer medium mimicking human skin. The effectiveness of the use of these expressions in the optical diagnosis of skin biophysical parameters (tissue scattering parameters, concentration of melanin in the epidermis, concentration of total haemoglobin and bilirubin in the tissues of the dermis) and content of haemoglobin derivatives in blood (oxy-, deoxy-, met-, carboxy- and sulfhaemoglobin) is analysed numerically. The methods are proposed to determine in realtime these parameters without contact of the measuring instrument with the patient's body. (biophotonics)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014QuEle..44..252L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014QuEle..44..252L"><span>Contactless diagnostics of biophysical parameters of skin and blood on the basis of <span class="hlt">approximating</span> functions for radiation <span class="hlt">fluxes</span> scattered by skin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lisenko, S. A.; Kugeiko, M. M.</p> <p>2014-03-01</p> <p><span class="hlt">Approximating</span> expressions are derived to calculate spectral and spatial characteristics of diffuse reflection of light from a two-layer medium mimicking human skin. The effectiveness of the use of these expressions in the optical diagnosis of skin biophysical parameters (tissue scattering parameters, concentration of melanin in the epidermis, concentration of total haemoglobin and bilirubin in the tissues of the dermis) and content of haemoglobin derivatives in blood (oxy-, deoxy-, met-, carboxy- and sulfhaemoglobin) is analysed numerically. The methods are proposed to determine in realtime these parameters without contact of the measuring instrument with the patient's body.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSM41E..04P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSM41E..04P"><span>How the Saturnian Magnetosphere Conserves Magnetic <span class="hlt">Flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Powell, R. L.; Wei, H.; Russell, C. T.; Arridge, C. S.; Dougherty, M. K.</p> <p>2012-12-01</p> <p>The magnetospheric dynamics at Saturn are driven by the centrifugal force of near co-rotating water group ions released at a rate of hundreds of kilograms per second by Saturn's moon Enceladus. The plasma is accelerated up to co-rotation speed by the magnetospheric magnetic field coupled to the Saturnian ionosphere. The plasma is lost ultimately through the process of magnetic reconnection in the tail. Conservation of magnetic <span class="hlt">flux</span> requires that plasma-depleted, "empty" <span class="hlt">flux</span> <span class="hlt">tubes</span> return magnetic <span class="hlt">flux</span> to the inner magnetosphere. After completion of the initial inrush of the reconnected and largely emptied <span class="hlt">flux</span> <span class="hlt">tubes</span> inward of the reconnection point, the <span class="hlt">flux</span> <span class="hlt">tubes</span> face the outflowing plasma and must move inward against the flow. Observations of such <span class="hlt">flux</span> <span class="hlt">tubes</span> have been identified in the eight years of Cassini magnetometer data. The occurrence of these <span class="hlt">tubes</span> is observed at all local times indicating slow inward transport of the <span class="hlt">tubes</span> relative to the co-rotation speed. Depleted <span class="hlt">flux</span> <span class="hlt">tubes</span> observed in the equatorial region appear as an enhancement in the magnitude of the magnetic field, whereas the same <span class="hlt">flux</span> <span class="hlt">tubes</span> observed at higher latitudes appear as decreased field strength. The difference in appearance of the low latitude and the high latitude <span class="hlt">tubes</span> is due to the plasma environment just outside the <span class="hlt">tube</span>. Warm low-density plasma fills the inside of the <span class="hlt">flux</span> <span class="hlt">tube</span> at all latitudes. This <span class="hlt">flux</span> <span class="hlt">tube</span> thus will expand in the less dense regions away from the magnetic equator and will be observed as a decrease in the magnitude of the magnetic field from the background. These <span class="hlt">flux</span> <span class="hlt">tubes</span> near the equator, where the plasma density outside of the <span class="hlt">flux</span> <span class="hlt">tube</span> is much greater, will be observed as an enhancement in the magnitude of the magnetic field. Cassini magnetometer and CAPS data are examined to understand the properties of these <span class="hlt">flux</span> <span class="hlt">tubes</span> and their radial and latitudinal evolution throughout the Saturnian magnetospheric environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4333483','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4333483"><span><span class="hlt">TUBE</span> TESTER</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Gittings, H.T. Jr.; Kalbach, J.F.</p> <p>1958-01-14</p> <p>This patent relates to <span class="hlt">tube</span> testing, and in particular describes a <span class="hlt">tube</span> tester for automatic testing of a number of vacuum <span class="hlt">tubes</span> while in service and as frequently as may be desired. In it broadest aspects the <span class="hlt">tube</span> tester compares a particular <span class="hlt">tube</span> with a standard <span class="hlt">tube</span> tarough a difference amplifier. An unbalanced condition in the circuit of the latter produced by excessive deviation of the <span class="hlt">tube</span> in its characteristics from standard actuates a switch mechanism stopping the testing cycle and indicating the defective <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990GMS....58.....R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990GMS....58.....R"><span>Physics of magnetic <span class="hlt">flux</span> ropes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Russell, C. T.; Priest, E. R.; Lee, L. C.</p> <p></p> <p>The present work encompasses papers on the structure, waves, and instabilities of magnetic <span class="hlt">flux</span> ropes (MFRs), photospheric <span class="hlt">flux</span> <span class="hlt">tubes</span> (PFTs), the structure and heating of coronal loops, solar prominences, coronal mass ejections and magnetic clouds, <span class="hlt">flux</span> ropes in planetary ionospheres, the magnetopause, magnetospheric field-aligned currents and <span class="hlt">flux</span> <span class="hlt">tubes</span>, 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 <span class="hlt">flux</span> <span class="hlt">tubes</span>, waves in solar PFTs, twisted <span class="hlt">flux</span> 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 <span class="hlt">flux</span> ropes above the South Pole, substorms and MFR structures, evidence for <span class="hlt">flux</span> ropes in the earth magnetotail, and MFRs in 3D MHD simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6228777','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6228777"><span><span class="hlt">Tube</span> supports</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cannon, K.A.</p> <p>1989-01-10</p> <p>This patent describes an apparatus consisting of parallel <span class="hlt">tubes</span> arranged in the form of a <span class="hlt">tube</span> bundle having a first plurality of parallel <span class="hlt">tube</span> rows with lanes between adjacent rows and a second plurality of parallel <span class="hlt">tube</span> rows with lanes between adjacent rows and support structure for supporting the <span class="hlt">tubes</span>. The support structure consists of at least a first baffle and a second baffle, wherein each baffle comprises an outer ring surrounding the <span class="hlt">tube</span> bundle and at least one slat attached to the outer ring as a chord and extending through the <span class="hlt">tube</span> bundle between adjacent rows in one of the parallel <span class="hlt">tube</span> rows. At least one slat is characterized by corrugations or folds extending along its length for point contact with the <span class="hlt">tubes</span> of the bundle, the slat in the first baffle extending in lanes between the first plurality of parallel <span class="hlt">tube</span> rows, and the slat in the second baffle extending in lanes between the second plurality of parallel <span class="hlt">tube</span> rows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7310673','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7310673"><span>Interaction effects of a lower heated <span class="hlt">tube</span> on pool boiling of R-124 from an upper horizontal <span class="hlt">tube</span>. Master's thesis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yusician, J.E.</p> <p>1993-12-01</p> <p>An investigation of the interaction effects of a lower heated <span class="hlt">tube</span> on pool boiling of pure R-124 from an upper horizontal <span class="hlt">tube</span> was conducted at a saturation temperature of 2.2 deg C. The test <span class="hlt">tubes</span> used were: (1) smooth <span class="hlt">tubes</span> and (2) deformed surface (TURBO-B) enhanced <span class="hlt">tubes</span>. The effects of <span class="hlt">tube</span> spacing/configuration and lower <span class="hlt">tube</span> heat <span class="hlt">flux</span> on the heat transfer performance of the upper <span class="hlt">tube</span> were investigated. For both <span class="hlt">tube</span> arrays, the enhancing effect of bubbles from a lower <span class="hlt">tube</span> was dramatic. This enhancement increased as lower <span class="hlt">tube</span> heat <span class="hlt">flux</span> increased. However, when upper <span class="hlt">tube</span> heat <span class="hlt">fluxes</span> were greater than 20 kW/sq. meters all enhancement disappeared. For a smooth <span class="hlt">tube</span> array in natural convection, the effect of a lower heated <span class="hlt">tube</span> on the heat transfer from an upper <span class="hlt">tube</span> was small. In nucleate boiling, a P/D of 1.8 gave the best upper <span class="hlt">tube</span> heat transfer performance and a vigorously nucleating lower <span class="hlt">tube</span> eliminated upper <span class="hlt">tube</span> hysteresis. With the lower <span class="hlt">tube</span> unheated and an upper <span class="hlt">tube</span> heat <span class="hlt">flux</span> of greater than 3 kW/sq m, the performance using R-124 was generally better than for R-114. With a nucleating lower <span class="hlt">tube</span> (at lO kW/sq. meters), again the performance of R-124 was better, but only for upper <span class="hlt">tube</span> heat <span class="hlt">fluxes</span> of greater than 40 kW/sq. meters. For a TURBO-B <span class="hlt">tube</span> array, a 30 degree offset of the upper <span class="hlt">tube</span> reduced the upper <span class="hlt">tube</span> heat transfer performance (compared to the in-line configurations). This may indicate bubbles depart TURBO-B <span class="hlt">tubes</span> differently than smooth <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...578A..60M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...578A..60M"><span>Energy and energy <span class="hlt">flux</span> in axisymmetric slow and fast waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreels, M. G.; Van Doorsselaere, T.; Grant, S. D. T.; Jess, D. B.; Goossens, M.</p> <p>2015-06-01</p> <p>Aims: We aim to calculate the kinetic, magnetic, thermal, and total energy densities and the <span class="hlt">flux</span> of energy in axisymmetric sausage modes. The resulting equations should contain as few parameters as possible to facilitate applicability for different observations. Methods: The background equilibrium is a one-dimensional cylindrical <span class="hlt">flux</span> <span class="hlt">tube</span> model with a piecewise constant radial density profile. This enables us to use linearised magnetohydrodynamic equations to calculate the energy densities and the <span class="hlt">flux</span> of energy for axisymmetric sausage modes. Results: The equations used to calculate the energy densities and the <span class="hlt">flux</span> of energy in axisymmetric sausage modes depend on the radius of the <span class="hlt">flux</span> <span class="hlt">tube</span>, the equilibrium sound and Alfvén speeds, the density of the plasma, the period and phase speed of the wave, and the radial or longitudinal components of the Lagrangian displacement at the <span class="hlt">flux</span> <span class="hlt">tube</span> boundary. <span class="hlt">Approximate</span> relations for limiting cases of propagating slow and fast sausage modes are also obtained. We also obtained the dispersive first-order correction term to the phase speed for both the fundamental slow body mode under coronal conditions and the slow surface mode under photospheric conditions. Appendix A is available in electronic form at http://www.aanda.org</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010Ge%26Ae..50..749S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010Ge%26Ae..50..749S"><span>Beta electron <span class="hlt">fluxes</span> inside a magnetic plasma cavern: Calculation and comparison with experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stupitskii, E. L.; Smirnov, E. V.; Kulikova, N. A.</p> <p>2010-12-01</p> <p>We study the possibility of electrostatic blanking of beta electrons in the expanding spherical blob of a radioactive plasma in a rarefied ionosphere. From numerical studies on the dynamics of beta electrons departing a cavern, we obtain the form of a function that determines the portion of departing electrons and calculate the <span class="hlt">flux</span> density of beta electrons inside the cavern in relation to the Starfish Prime nuclear blast. We show that the <span class="hlt">flux</span> density of electrons in geomagnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> and inside the cavern depend on a correct allowance for the quantity of beta electrons returning to the cavern. On the basis of a physical analysis, we determine the <span class="hlt">approximate</span> criterion for the return of electrons from a geomagnetic <span class="hlt">flux</span> <span class="hlt">tube</span> to the cavern. We compare calculation results in terms of the <span class="hlt">flux</span> density of beta electrons inside the cavern with the recently published experimental results from operation Starfish Prime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AdWR...28.1003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AdWR...28.1003B"><span>Green Ampt <span class="hlt">approximations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barry, D. A.; Parlange, J.-Y.; Li, L.; Jeng, D.-S.; Crapper, M.</p> <p>2005-10-01</p> <p>The solution to the Green and Ampt infiltration equation is expressible in terms of the Lambert W-1 function. <span class="hlt">Approximations</span> for Green and Ampt infiltration are thus derivable from <span class="hlt">approximations</span> for the W-1 function and vice versa. An infinite family of asymptotic expansions to W-1 is presented. Although these expansions do not converge near the branch point of the W function (corresponds to Green-Ampt infiltration with immediate ponding), a method is presented for <span class="hlt">approximating</span> W-1 that is exact at the branch point and asymptotically, with interpolation between these limits. Some existing and several new simple and compact yet robust <span class="hlt">approximations</span> applicable to Green-Ampt infiltration and <span class="hlt">flux</span> are presented, the most accurate of which has a maximum relative error of 5 × 10 -5%. This error is orders of magnitude lower than any existing analytical <span class="hlt">approximations</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930071260&hterms=Shibata&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DShibata%252C%2BM','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930071260&hterms=Shibata&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DShibata%252C%2BM"><span>Three-dimensional magnetohydrodynamics of the emerging magnetic <span class="hlt">flux</span> in the solar atmosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Matsumoto, R.; Tajima, T.; Shibata, K.; Kaisig, M.</p> <p>1993-01-01</p> <p>The nonlinear evolution of an emerging magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> or sheet in the solar atmosphere is studied through 3D MHD simulations. In the initial state, a horizontal magnetic <span class="hlt">flux</span> sheet or <span class="hlt">tube</span> is assumed to be embedded at the bottom of MHD two isothermal gas layers, which <span class="hlt">approximate</span> the solar photosphere/chromosphere and the corona. The magnetic <span class="hlt">flux</span> sheet or <span class="hlt">tube</span> is unstable against the undular mode of the magnetic buoyancy instability. The magnetic loop rises due to the linear and then later nonlinear instabilities caused by the buoyancy enhanced by precipitating the gas along magnetic field lines. We find by 3D simulation that during the ascendance of loops the bundle of <span class="hlt">flux</span> <span class="hlt">tubes</span> or even the <span class="hlt">flux</span> sheet develops into dense gas filaments pinched between magnetic loops. The interchange modes help produce a fine fiber <span class="hlt">flux</span> structure perpendicular to the magnetic field direction in the linear stage, while the undular modes determine the overall buoyant loop structure. The expansion of such a bundle of magnetic loops follows the self-similar behavior observed in 2D cases studied earlier. Our study finds the threshold <span class="hlt">flux</span> for arch filament system (AFS) formation to be about 0.3 x 10 exp 20 Mx.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016HMT....52.2015U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016HMT....52.2015U"><span>Experimental study of laminar forced convective heat transfer of deionized water based copper (I) oxide nanofluids in a <span class="hlt">tube</span> with constant wall heat <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Umer, Asim; Naveed, Shahid; Ramzan, Naveed</p> <p>2016-10-01</p> <p>Nanofluids, having 1-100 nm size particles in any base fluid are promising fluid for heat transfer intensification due to their enhanced thermal conductivity as compared with the base fluid. The forced convection of nanofluids is the major practical application in heat transfer equipments. In this study, heat transfer enhancements at constant wall heat <span class="hlt">flux</span> under laminar flow conditions were investigated. Nanofluids of different volume fractions (1, 2 and 4 %) of copper (I) oxide nanoparticles in deionized water were prepared using two step technique under mechanical mixing and ultrasonication. The results were investigated by increasing the Reynolds number of the nanofluids at constant heat <span class="hlt">flux</span>. The trends of Nusselt number variation with dimensionless length (X/D) and Reynolds numbers were studied. It was observed that heat transfer coefficient increases with increases particles volume concentration and Reynolds number. The maximum enhancement in heat transfer coefficient of 61 % was observed with 4 % particle volume concentration at Reynolds number (Re ~ 605).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016HMT....52.1683S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016HMT....52.1683S"><span>A correlation to predict the heat <span class="hlt">flux</span> on the air-side of a vapor chamber with overturn-U flattened <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Srimuang, Wasan; Limkaisang, Viroj</p> <p>2016-08-01</p> <p>The heat transfer characteristics of a conventional vapor chamber (CVC) and a loop vapor chamber (LVC) are compared. The vapor chambers consisted of a stainless steel box with different covers. The results indicated that the heat <span class="hlt">flux</span> and convective heat transfer coefficient of the air-side of LVC is higher than CVC. An empirical correlation was developed to predict the convective heat transfer coefficient of the air-side of the LVC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040012679&hterms=turns&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D60%26Ntt%3Dturns','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040012679&hterms=turns&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D60%26Ntt%3Dturns"><span>Eruption of a Multiple-Turn Helical Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gary, G. Allen; Moore, R. L.</p> <p>2003-01-01</p> <p>We present observations and an interpretation of a unique multiple-turn spiral <span class="hlt">flux</span> <span class="hlt">tube</span> eruption from AR10030 on 2002 July 15. The TRACE CIV observations clearly show a <span class="hlt">flux</span> <span class="hlt">tube</span> that is helical and that is erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption starts 25 seconds after the peak of the flare s strongest impulsive spike of microwave gryosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double CME. The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection heats the two-ribbon flare and might or might not produce the helix. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is associated with rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel, and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation. However, the observations are compatible with internal reconnection in a sheared magnetic arcade in the formation and eruption of the helix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040121118&hterms=turns&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D50%26Ntt%3Dturns','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040121118&hterms=turns&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D50%26Ntt%3Dturns"><span>Eruption of a Multiple-Turn Helical Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gary, G. Allen; Moore, R. L.</p> <p>2004-01-01</p> <p>We present observations and an interpretation of a unique multiple-turn spiral <span class="hlt">flux</span> <span class="hlt">tube</span> eruption from active region 10030 on 2002 July 15. The TRACE C IV observations clearly show a <span class="hlt">flux</span> <span class="hlt">tube</span> that is helical and erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption. as determined by a linear backward extrapolation, starts 25 s after the peak of the flare's strongest impulsive spike of microwave gyrosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double coronal mass ejection (CME). The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection releases the helix and heats the two-ribbon flare. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is compatible with the observed rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel. and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040012679&hterms=Double+helix&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DDouble%2Bhelix','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040012679&hterms=Double+helix&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DDouble%2Bhelix"><span>Eruption of a Multiple-Turn Helical Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gary, G. Allen; Moore, R. L.</p> <p>2003-01-01</p> <p>We present observations and an interpretation of a unique multiple-turn spiral <span class="hlt">flux</span> <span class="hlt">tube</span> eruption from AR10030 on 2002 July 15. The TRACE CIV observations clearly show a <span class="hlt">flux</span> <span class="hlt">tube</span> that is helical and that is erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption starts 25 seconds after the peak of the flare s strongest impulsive spike of microwave gryosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double CME. The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection heats the two-ribbon flare and might or might not produce the helix. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is associated with rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel, and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation. However, the observations are compatible with internal reconnection in a sheared magnetic arcade in the formation and eruption of the helix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040121118&hterms=Double+helix&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DDouble%2Bhelix','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040121118&hterms=Double+helix&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DDouble%2Bhelix"><span>Eruption of a Multiple-Turn Helical Magnetic <span class="hlt">Flux</span> <span class="hlt">Tube</span> in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gary, G. Allen; Moore, R. L.</p> <p>2004-01-01</p> <p>We present observations and an interpretation of a unique multiple-turn spiral <span class="hlt">flux</span> <span class="hlt">tube</span> eruption from active region 10030 on 2002 July 15. The TRACE C IV observations clearly show a <span class="hlt">flux</span> <span class="hlt">tube</span> that is helical and erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption. as determined by a linear backward extrapolation, starts 25 s after the peak of the flare's strongest impulsive spike of microwave gyrosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double coronal mass ejection (CME). The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection releases the helix and heats the two-ribbon flare. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is compatible with the observed rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel. and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22391215','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22391215"><span>Eddy current signal comparison for <span class="hlt">tube</span> identification</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Glass, S. W. E-mail: Ratko.Vojvodic@areva.com; Vojvodic, R. E-mail: Ratko.Vojvodic@areva.com</p> <p>2015-03-31</p> <p>Inspection of nuclear power plant steam generator <span class="hlt">tubes</span> is required to justify continued safe plant operation. The steam generators consist of thousands of <span class="hlt">tubes</span> with nominal diameters of 15 to 22mm, <span class="hlt">approximately</span> 1mm wall thickness, and 20 to 30m in length. The <span class="hlt">tubes</span> are inspected by passing an eddy current probe through the <span class="hlt">tubes</span> from <span class="hlt">tube</span> end to <span class="hlt">tube</span> end. It is critical to know exactly which <span class="hlt">tube</span> identification (row and column) is associated with each <span class="hlt">tube</span>'s data. This is controlled by a precision manipulator that provides the <span class="hlt">tube</span> ID to the eddy current system. Historically there have been some instances where the manipulator incorrectly reported the <span class="hlt">tube</span> ID. This can have serious consequences including lack of inspection of a <span class="hlt">tube</span>, or if a pluggable indication is detected, the <span class="hlt">tube</span> is likely to be mis-plugged thereby risking a primary to secondary leak.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650.1506G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650.1506G"><span>Eddy current signal comparison for <span class="hlt">tube</span> identification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Glass, S. W.; Vojvodic, R.</p> <p>2015-03-01</p> <p>Inspection of nuclear power plant steam generator <span class="hlt">tubes</span> is required to justify continued safe plant operation. The steam generators consist of thousands of <span class="hlt">tubes</span> with nominal diameters of 15 to 22mm, <span class="hlt">approximately</span> 1mm wall thickness, and 20 to 30m in length. The <span class="hlt">tubes</span> are inspected by passing an eddy current probe through the <span class="hlt">tubes</span> from <span class="hlt">tube</span> end to <span class="hlt">tube</span> end. It is critical to know exactly which <span class="hlt">tube</span> identification (row and column) is associated with each <span class="hlt">tube</span>'s data. This is controlled by a precision manipulator that provides the <span class="hlt">tube</span> ID to the eddy current system. Historically there have been some instances where the manipulator incorrectly reported the <span class="hlt">tube</span> ID. This can have serious consequences including lack of inspection of a <span class="hlt">tube</span>, or if a pluggable indication is detected, the <span class="hlt">tube</span> is likely to be mis-plugged thereby risking a primary to secondary leak.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://apfed.org/resources/for-patients/for-adults/feeding-tubes/?q=adults_living_with_EGIDs','NIH-MEDLINEPLUS'); return false;" href="http://apfed.org/resources/for-patients/for-adults/feeding-tubes/?q=adults_living_with_EGIDs"><span>Feeding <span class="hlt">Tubes</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... Feeding <span class="hlt">Tubes</span> Health Information Sheet Q & A with Experts Patient Stories Social Security Disability Application Process For Kids ... Feeding <span class="hlt">Tubes</span> Health Information Sheet Q & A with Experts Patient Stories Social Security Disability Application Process For Kids ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6636944','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6636944"><span>Design of a <span class="hlt">flux</span> diverter and containment <span class="hlt">tube</span> with results of tests at ACTF and CNRS. [For testing response of soils to thermal pulse of nuclear detonations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gordon, B.A.; Knasel, T.M.; Sievers, R.; Bomar, S.; Royere, C.; McDonnel, M.D.</p> <p>1980-01-01</p> <p>Obtaining empirical data on the response of soils and changes in the overlying air due to the thermal pulse of nuclear detonations required development of special test apparatus and use of high <span class="hlt">fluxes</span> in a large solar furnace. The development of such apparatus, based on non-imaging optic principles; the influence of solar furnace test series in which the apparatus and instrumentation have been tested for thoroughput, durability, and suitability for meeting the requirements are discussed. Tests were conducted at the Advanced Components Test Facility and the Centre National de la Recherche Scientifique 1 MW solar furnace. These tests resulted in apparatus redesign, and change in procedures and instrumentation in preparation for further testing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4830004C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4830004C"><span>3D Collision of Active Region-Sized Emerging <span class="hlt">Flux</span> <span class="hlt">Tubes</span> in the Solar Convection Zone and its Manifestation in the Photospheric Surface</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chintzoglou, Georgios; Cheung, Mark; Rempel, Matthias D.</p> <p>2017-08-01</p> <p>We present observations obtained with the Solar Dynamics Observatory’s Helioseismic Magnetic Imager (SDO/HMI) of target NOAA Active Regions (AR) 12017 and 12644, which initially were comprised of a simple bipole and later on became quadrupolar via parasitic bipole emergence right next to their leading polarities. Once these ARs became quadrupolar, they spewed multiple Coronal Mass Ejections (CMEs) and a multitude of highly energetic flares (a large number of M class flares). The proximity of the parasitic bipole to one of the two pre-existing sunspots forms a compact polarity inversion line (PIL). This type of quadrupolar ARs are known to be very flare- and CME-productive due to the continuous interaction of newly emerging non-potential <span class="hlt">flux</span> with pre-existing <span class="hlt">flux</span> in the photosphere. We show that well before the emergence of the parasitic bipole, the pre-existing polarity (typically a well-developed sunspot) undergoes interesting precursor dynamic evolution, namely (a) displacement of pre-existing sunspot’s position, (b) progressive and significant oblateness of its initially nearly-circular shape, and (c) opposite polarity enhancement in the divergent moat flow around the sunspot. We employ high-resolution radiative-convective 3D MHD simulations of an emerging parasitic bipole to show that all these activity aspects seen in the photosphere are associated with the collision of a parasitic bipole with the nearby pre-existing polarity below the photospheric surface. Given the rich flare and CME productivity of this class of ARs and the precursor-like dynamic evolution of the pre-existing polarity, this work presents the potential for predicting inclement space weather.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DPS....4750201R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DPS....4750201R"><span>Transport of magnetic <span class="hlt">flux</span> in Saturn’s inner magnetosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Russell, Christopher T.; Lai, H. R.; Wei, H. Y.; Jia, Y. D.; Dougherty, M. K.</p> <p>2015-11-01</p> <p>The dynamics of the Saturnian magnetosphere, which rotates rapidly with an internal plasma source provided by Enceladus, qualitatively resembles those of the jovian magnetosphere powered by Io. The newly added plasma is accelerated to the corotation speed and moves outward together with the magnetic <span class="hlt">flux</span>. In the near tail region, reconnection cuts the magnetic <span class="hlt">flux</span>, reconnects it into plasma-depleted inward moving <span class="hlt">flux</span> <span class="hlt">tubes</span> and outward moving massive plasmoids. The buoyant empty <span class="hlt">tubes</span> then convect inward against the outward flow to conserve the total magnetic <span class="hlt">flux</span> established by the internal dynamo. In both jovian and saturnian magnetospheres, <span class="hlt">flux</span> <span class="hlt">tubes</span> with enhanced field strength relative to their surroundings are detected in the equatorial region. Recent observations show that there are <span class="hlt">flux</span> <span class="hlt">tubes</span> with reduced field strength off the equator in the saturnian magnetosphere. To understand the formation mechanism of both types of <span class="hlt">flux</span> <span class="hlt">tubes</span>, we have surveyed all the available 1-sec magnetic field data from Cassini. The systematic statistical study confirms the different latitudinal distributions of the two types of <span class="hlt">flux</span> <span class="hlt">tubes</span>. In addition, enhanced-field <span class="hlt">flux</span> <span class="hlt">tubes</span> are closer to the planet while reduced-field <span class="hlt">flux</span> <span class="hlt">tubes</span> can be detected at larger distances; both types of <span class="hlt">flux</span> <span class="hlt">tubes</span> become indistinguishable from the background magnetic <span class="hlt">flux</span> inside an L-value of about 4; the local time distribution of both types of <span class="hlt">flux</span> <span class="hlt">tubes</span> are similar and they contain about the same amount of magnetic <span class="hlt">flux</span>. Therefore, the two types of <span class="hlt">flux</span> <span class="hlt">tubes</span> are the same phenomena with different manifestations in different plasma environments. When the surrounding plasma density is high (near the equator and closer to the plasma source region), the <span class="hlt">flux</span> <span class="hlt">tubes</span> are compressed and have enhanced field strength inside; while in the low-plasma density region (off the equator and further from the plasma source region), the <span class="hlt">flux</span> <span class="hlt">tubes</span> expand and have reduced field strength inside.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24891201','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24891201"><span>Tracheostomy <span class="hlt">tubes</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hess, Dean R; Altobelli, Neila P</p> <p>2014-06-01</p> <p>Tracheostomy <span class="hlt">tubes</span> are used to administer positive-pressure ventilation, to provide a patent airway, and to provide access to the lower respiratory tract for airway clearance. They are available in a variety of sizes and styles from several manufacturers. The dimensions of tracheostomy <span class="hlt">tubes</span> are given by their inner diameter, outer diameter, length, and curvature. Differences in dimensions between <span class="hlt">tubes</span> with the same inner diameter from different manufacturers are not commonly appreciated but may have important clinical implications. Tracheostomy <span class="hlt">tubes</span> can be cuffed or uncuffed and may be fenestrated. Some tracheostomy <span class="hlt">tubes</span> are designed with an inner cannula. It is important for clinicians caring for patients with a tracheostomy <span class="hlt">tube</span> to appreciate the nuances of various tracheostomy <span class="hlt">tube</span> designs and to select a <span class="hlt">tube</span> that appropriately fits the patient. The optimal frequency of changing a chronic tracheostomy <span class="hlt">tube</span> is controversial. Specialized teams may be useful in managing patients with a tracheostomy. Speech can be facilitated with a speaking valve in patients with a tracheostomy <span class="hlt">tube</span> who are breathing spontaneously. In mechanically ventilated patients with a tracheostomy, a talking tracheostomy <span class="hlt">tube</span>, a deflated cuff technique with a speaking valve, or a deflated cuff technique without a speaking valve can be used to facilitate speech. Copyright © 2014 by Daedalus Enterprises.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=34165','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=34165"><span><span class="hlt">Approximation</span> algorithms</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Schulz, Andreas S.; Shmoys, David B.; Williamson, David P.</p> <p>1997-01-01</p> <p>Increasing global competition, rapidly changing markets, and greater consumer awareness have altered the way in which corporations do business. To become more efficient, many industries have sought to model some operational aspects by gigantic optimization problems. It is not atypical to encounter models that capture 106 separate “yes” or “no” decisions to be made. Although one could, in principle, try all 2106 possible solutions to find the optimal one, such a method would be impractically slow. Unfortunately, for most of these models, no algorithms are known that find optimal solutions with reasonable computation times. Typically, industry must rely on solutions of unguaranteed quality that are constructed in an ad hoc manner. Fortunately, for some of these models there are good <span class="hlt">approximation</span> algorithms: algorithms that produce solutions quickly that are provably close to optimal. Over the past 6 years, there has been a sequence of major breakthroughs in our understanding of the design of <span class="hlt">approximation</span> algorithms and of limits to obtaining such performance guarantees; this area has been one of the most flourishing areas of discrete mathematics and theoretical computer science. PMID:9370525</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28127145','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28127145"><span>An approach for safe conversion of an oral endotracheal <span class="hlt">tube</span> to a nasal endotracheal <span class="hlt">tube</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hofkamp, Michael; Diao, Zhiying</p> <p>2017-01-01</p> <p>We present an approach for safe management of a patient with an oral endotracheal <span class="hlt">tube</span> who required conversion to a nasal endotracheal <span class="hlt">tube</span>. A 35-year-old man presented for mandibular fracture repair after multiple injuries sustained in a motor vehicle accident. The patient already had an oral endotracheal <span class="hlt">tube</span>, and the surgical team requested a nasal endotracheal <span class="hlt">tube</span> to facilitate surgical exposure and postoperative airway management in anticipation of a wired jaw. A nasal endotracheal <span class="hlt">tube</span> was inserted through the naris and a video laryngoscope was used to visualize the glottis. A tracheal <span class="hlt">tube</span> introducer was inserted through the oral endotracheal <span class="hlt">tube</span>, and the oral endotracheal <span class="hlt">tube</span> was then withdrawn <span class="hlt">approximately</span> 5 cm. The nasal endotracheal <span class="hlt">tube</span> was advanced through the vocal cords alongside the tracheal <span class="hlt">tube</span> introducer. The nasal endotracheal <span class="hlt">tube</span> cuff was then inflated and the tracheal <span class="hlt">tube</span> introducer was withdrawn.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5242126','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5242126"><span>An approach for safe conversion of an oral endotracheal <span class="hlt">tube</span> to a nasal endotracheal <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Diao, Zhiying</p> <p>2017-01-01</p> <p>We present an approach for safe management of a patient with an oral endotracheal <span class="hlt">tube</span> who required conversion to a nasal endotracheal <span class="hlt">tube</span>. A 35-year-old man presented for mandibular fracture repair after multiple injuries sustained in a motor vehicle accident. The patient already had an oral endotracheal <span class="hlt">tube</span>, and the surgical team requested a nasal endotracheal <span class="hlt">tube</span> to facilitate surgical exposure and postoperative airway management in anticipation of a wired jaw. A nasal endotracheal <span class="hlt">tube</span> was inserted through the naris and a video laryngoscope was used to visualize the glottis. A tracheal <span class="hlt">tube</span> introducer was inserted through the oral endotracheal <span class="hlt">tube</span>, and the oral endotracheal <span class="hlt">tube</span> was then withdrawn <span class="hlt">approximately</span> 5 cm. The nasal endotracheal <span class="hlt">tube</span> was advanced through the vocal cords alongside the tracheal <span class="hlt">tube</span> introducer. The nasal endotracheal <span class="hlt">tube</span> cuff was then inflated and the tracheal <span class="hlt">tube</span> introducer was withdrawn. PMID:28127145</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800000052&hterms=evacuated+solar+collector&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Devacuated%2Bsolar%2Bcollector','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800000052&hterms=evacuated+solar+collector&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Devacuated%2Bsolar%2Bcollector"><span>Glycol/water evacuated-<span class="hlt">tube</span> solar collector</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1980-01-01</p> <p>Report describes performance of 8 <span class="hlt">tube</span> and 10 <span class="hlt">tube</span> commercially produced solar collectors. Tests include thermal efficiency, time constant for temperature drop after solar <span class="hlt">flux</span> is cut, change in efficiency with Sun angle, and temperature rise if circulation is stopped.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/002937.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/002937.htm"><span>Feeding <span class="hlt">tube</span> insertion - gastrostomy</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... <span class="hlt">tube</span> insertion; G-<span class="hlt">tube</span> insertion; PEG <span class="hlt">tube</span> insertion; Stomach <span class="hlt">tube</span> insertion; Percutaneous endoscopic gastrostomy <span class="hlt">tube</span> insertion ... and down the esophagus, which leads to the stomach. After the endoscopy <span class="hlt">tube</span> is inserted, the skin ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150007699','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150007699"><span>Simulations of Emerging Magnetic <span class="hlt">Flux</span>. II. The Formation of Unstable Coronal <span class="hlt">Flux</span> Ropes and the Initiation of Coronal Mass Ejections</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leake, James E.; Linton, Mark G.; Antiochos, Spiro K.</p> <p>2014-01-01</p> <p>We present results from three-dimensional magnetohydrodynamic simulations of the emergence of a twisted convection zone <span class="hlt">flux</span> <span class="hlt">tube</span> into a pre-existing coronal dipole field. As in previous simulations, following the partial emergence of the sub-surface <span class="hlt">flux</span> into the corona, a combination of vortical motions and internal magnetic reconnection forms a coronal <span class="hlt">flux</span> rope. Then, in the simulations presented here, external reconnection between the emerging field and the pre-existing dipole coronal field allows further expansion of the coronal <span class="hlt">flux</span> rope into the corona. After sufficient expansion, internal reconnection occurs beneath the coronal <span class="hlt">flux</span> rope axis, and the <span class="hlt">flux</span> rope erupts up to the top boundary of the simulation domain (<span class="hlt">approximately</span> 36 Mm above the surface).We find that the presence of a pre-existing field, orientated in a direction to facilitate reconnection with the emerging field, is vital to the fast rise of the coronal <span class="hlt">flux</span> rope. The simulations shown in this paper are able to self-consistently create many of the surface and coronal signatures used by coronal mass ejection (CME) models. These signatures include surface shearing and rotational motions, quadrupolar geometry above the surface, central sheared arcades reconnecting with oppositely orientated overlying dipole fields, the formation of coronal <span class="hlt">flux</span> ropes underlying potential coronal field, and internal reconnection which resembles the classical flare reconnection scenario. This suggests that proposed mechanisms for the initiation of a CME, such as "magnetic breakout," are operating during the emergence of new active regions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://kidshealth.org/en/parents/g-tube.html','NIH-MEDLINEPLUS'); return false;" href="https://kidshealth.org/en/parents/g-tube.html"><span>Gastrostomy <span class="hlt">Tube</span> (G-<span class="hlt">Tube</span>)</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... warmth at the <span class="hlt">tube</span> site; discharge that's yellow, green, or foul-smelling; fever) excessive bleeding or drainage from the <span class="hlt">tube</span> site severe abdominal pain persistent vomiting or diarrhea trouble passing gas or having a bowel movement pink-red tissue (called granulation tissue) coming out ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12315288','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12315288"><span>Using a nasogastric <span class="hlt">tube</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Candy, C</p> <p>1986-09-01</p> <p>This discussion of the use of a nasogastric <span class="hlt">tube</span> covers the equipment needed, the method, rehydration and feeding, prolonged nasogastric feeding, and stopping nasogastric feeding. A nasogastric <span class="hlt">tube</span> is useful when children are unable to drink safely and in sufficient amounts for any of the following reasons: severe dehydration; if intravenous (IV) therapy is unavailable; low birth weight infants; or the child is drowsy or vomiting. Severely malnourished children may be fed initially in this way if they are too weak or anorexic to eat or drink normally. The following equipment is needed: nasogastric <span class="hlt">tube</span>; lubricating fluid; a syringe; blue litmus paper, if available; adhesive tape; stethoscope if available; and fluid to be given. Explain to the child's parents and the child, if old enough to understand, what will be done; lie infants flat; measure the <span class="hlt">approximate</span> length from the child's nostril to the ear lobe and then to the top of the abdomen with the <span class="hlt">tube</span> and mark the position; clean the nostrils to remove the mucus, and lubricate the tip of the <span class="hlt">tube</span> and gently insert into the nostril; give the child a drink of water if he or she is conscious; continue to pass the <span class="hlt">tube</span> down until the position marked reaches the nostril; use the syringe to suck up some fluid and test with blue litmus paper to check that the <span class="hlt">tube</span> is in the stomach; and inject 5-10 ml of fluid (saline or oral rehydration solution, not milk formula) by syringe if satisfied the <span class="hlt">tube</span> is in the correct position. Where possible, give a continuous drip of fluid. If this is not possible, give frequent small amounts using the syringe as a funnel. If feeding continues for more than 24 hours, clean the nostrils daily with warm water and change the <span class="hlt">tube</span> to the other nostril every few days. Also keep the mouth very clean with a dilute solution of 8% sodium bicarbonate, if available, or citrus fruit juice. To remove the <span class="hlt">tube</span>, remove the adhesive tape, take the <span class="hlt">tube</span> out gently and smoothly, and offer the child a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011SPIE.8013E..0JS','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011SPIE.8013E..0JS"><span>Infrared imaging of LED lighting <span class="hlt">tubes</span> and fluorescent <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siikanen, Sami; Kivi, Sini; Kauppinen, Timo; Juuti, Mikko</p> <p>2011-05-01</p> <p>The low energy efficiency of conventional light sources is mainly caused by generation of waste heat. We used infrared (IR) imaging in order to monitor the heating of both LED <span class="hlt">tube</span> luminaires and ordinary T8 fluorescent <span class="hlt">tubes</span>. The IR images showed clearly how the surface temperatures of the fluorescent <span class="hlt">tube</span> ends quickly rose up to about +50...+70°C, whereas the highest surface temperatures seen on the LED <span class="hlt">tubes</span> were only about +30...+40°C. The IR images demonstrated how the heat produced by the individual LED chips can be efficiently guided to the supporting structure in order to keep the LED emitters cool and hence maintain efficient operation. The consumed electrical power and produced illuminance were also recorded during 24 hour measurements. In order to assess the total luminous efficacy of the luminaires, separate luminous <span class="hlt">flux</span> measurements were made in a large integrating sphere. The currently available LED <span class="hlt">tubes</span> showed efficacies of up to 88 lm/W, whereas a standard "cool white" T8 fluorescent <span class="hlt">tube</span> produced ca. 75 lm/W. Both lamp types gave ca. 110 - 130 lx right below the ceiling-mounted luminaire, but the LED <span class="hlt">tubes</span> consume only 40 - 55% of the electric power compared to fluorescent <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/863285','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/863285"><span>Protective <span class="hlt">tubes</span> for sodium heated water <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Essebaggers, Jan</p> <p>1979-01-01</p> <p>A heat exchanger in which water <span class="hlt">tubes</span> are heated by liquid sodium which minimizes the results of accidental contact between the water and the sodium caused by failure of one or more of the water <span class="hlt">tubes</span>. A cylindrical protective <span class="hlt">tube</span> envelopes each water <span class="hlt">tube</span> and the sodium flows axially in the annular spaces between the protective <span class="hlt">tubes</span> and the water <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22039407','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22039407"><span>SURFACE ALFVEN WAVES IN SOLAR <span class="hlt">FLUX</span> <span class="hlt">TUBES</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Goossens, M.; Andries, J.; Soler, R.; Van Doorsselaere, T.; Arregui, I.; Terradas, J.</p> <p>2012-07-10</p> <p>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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21322747','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21322747"><span>Regular black holes with <span class="hlt">flux</span> <span class="hlt">tube</span> core</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zaslavskii, Oleg B.</p> <p>2009-09-15</p> <p>We consider a class of black holes for which the area of the two-dimensional spatial cross section has a minimum on the horizon with respect to a quasiglobal (Krusckal-like) coordinate. If the horizon is regular, one can generate a tubelike counterpart of such a metric and smoothly glue it to a black hole region. The resulting composite space-time is globally regular, so all potential singularities under the horizon of the original metrics are removed. Such a space-time represents a black hole without an apparent horizon. It is essential that the matter should be nonvacuum in the outer region but vacuumlike in the inner one. As an example we consider the noninteracting mixture of vacuum fluid and matter with a linear equation of state and scalar phantom fields. This approach is extended to distorted metrics, with the requirement of spherical symmetry relaxed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1093228','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1093228"><span>Multiple <span class="hlt">tube</span> premixing device</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Uhm, Jong Ho; Naidu, Balachandar; Ziminksy, Willy Steve; Kraemer, Gilbert Otto; Yilmaz, Ertan; Lacy, Benjamin; Stevenson, Christian; Felling, David</p> <p>2013-08-13</p> <p>The present application provides a premixer for a combustor. The premixer may include a fuel plenum with a number of fuel <span class="hlt">tubes</span> and a burner <span class="hlt">tube</span> with a number of air <span class="hlt">tubes</span>. The fuel <span class="hlt">tubes</span> extend about the air <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1082468','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1082468"><span>Multiple <span class="hlt">tube</span> premixing device</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Uhm, Jong Ho; Varatharajan, Balachandar; Ziminsky, Willy Steve; Kraemer, Gilbert Otto; Yilmaz, Ertan; Lacy, Benjamin; Stevenson, Christian; Felling, David</p> <p>2012-12-11</p> <p>The present application provides a premixer for a combustor. The premixer may include a fuel plenum with a number of fuel <span class="hlt">tubes</span> and a burner <span class="hlt">tube</span> with a number of air <span class="hlt">tubes</span>. The fuel <span class="hlt">tubes</span> extend about the air <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19670000094','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19670000094"><span>Ultrasonics permits brazing complex stainless steel assembly without <span class="hlt">flux</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baker, W. H.</p> <p>1967-01-01</p> <p>Ultrasonic vibration of an assembly of stainless steel instrumentation <span class="hlt">tubes</span> ensures brazing without <span class="hlt">flux</span>. Vibration with an ultrasonic transducer permits the brazing material to flow down each <span class="hlt">tube</span> in contact with a seal plug installed in a pressure vessel wall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA243265','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA243265"><span>Gun <span class="hlt">Tube</span> Heating</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1991-12-01</p> <p>researchers to use ingenious <span class="hlt">approximation</span> techniques (Rapp 1990) and curve fitting to produce a history of <span class="hlt">tube</span> heating during the interior ballistic cycle... Automotive Command U.S. Army Materiel Command ATTN: ASQNC-TAC-DIT (Technical ATTN: AMCAM Information Center) 5001 Eisenhower Avenue Warren, MI 48397-5000...36360 ATTN: ATRC-L, Mr. Cameron Fort Lee, VA 23801-6140 2 Program Manager U.S. Army Tank- Automotive Command 1 Commandant ATTN: AMCPM-ABMS, T. Dean (2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21069902','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21069902"><span>Coaxial helicity injection in open-<span class="hlt">flux</span> low-aspect-ratio toroidal discharges</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Redd, A. J.; Jarboe, T. R.; Nelson, B. A.; O'Neill, R. G.; Smith, R. J.</p> <p>2007-11-15</p> <p>Open-<span class="hlt">flux</span> low-aspect-ratio toroidal discharges generated and sustained by coaxial helicity injection (CHI) in the Helicity Injected Torus device (HIT-II) are described. The discharges in this study are <span class="hlt">flux</span> <span class="hlt">tubes</span> directly connected to the CHI electrodes, with poloidal <span class="hlt">flux</span> less than or equal to the CHI injector <span class="hlt">flux</span>, and no possibility of a significant closed-<span class="hlt">flux</span> plasma core. Theoretically derived scalings for the dependence of CHI injector current on the toroidal field current and magnitude of the injector <span class="hlt">flux</span> are experimentally confirmed, and empirical models are developed for the poloidal magnetic field and toroidal plasma current in open-<span class="hlt">flux</span> discharges. In particular, the toroidal plasma current is independent of the toroidal magnetic field, both theoretically and empirically. Variations in injector <span class="hlt">flux</span> geometry demonstrate that the CHI injector current leaves the electrode surfaces at the <span class="hlt">flux</span> strike points, and that the relative width of the CHI injector determines whether the dominant observed relaxation mechanism is a harmonic mode at the plasma edge or reconnection near the CHI electrodes. In the case of an effective interelectrode distance <span class="hlt">approximately</span> equal to the device minor radius, the ratio of toroidal plasma current to CHI injector current is maximized. Global magnetic equilibrium quantities and local magnetic measurements are consistent with modelling these open-<span class="hlt">flux</span> discharges as thin current sheets connected to the CHI electrodes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhPl...14k2511R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhPl...14k2511R"><span>Coaxial helicity injection in open-<span class="hlt">flux</span> low-aspect-ratio toroidal discharges</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Redd, A. J.; Jarboe, T. R.; Nelson, B. A.; O'Neill, R. G.; Smith, R. J.</p> <p>2007-11-01</p> <p>Open-<span class="hlt">flux</span> low-aspect-ratio toroidal discharges generated and sustained by coaxial helicity injection (CHI) in the Helicity Injected Torus device (HIT-II) are described. The discharges in this study are <span class="hlt">flux</span> <span class="hlt">tubes</span> directly connected to the CHI electrodes, with poloidal <span class="hlt">flux</span> less than or equal to the CHI injector <span class="hlt">flux</span>, and no possibility of a significant closed-<span class="hlt">flux</span> plasma core. Theoretically derived scalings for the dependence of CHI injector current on the toroidal field current and magnitude of the injector <span class="hlt">flux</span> are experimentally confirmed, and empirical models are developed for the poloidal magnetic field and toroidal plasma current in open-<span class="hlt">flux</span> discharges. In particular, the toroidal plasma current is independent of the toroidal magnetic field, both theoretically and empirically. Variations in injector <span class="hlt">flux</span> geometry demonstrate that the CHI injector current leaves the electrode surfaces at the <span class="hlt">flux</span> strike points, and that the relative width of the CHI injector determines whether the dominant observed relaxation mechanism is a harmonic mode at the plasma edge or reconnection near the CHI electrodes. In the case of an effective interelectrode distance <span class="hlt">approximately</span> equal to the device minor radius, the ratio of toroidal plasma current to CHI injector current is maximized. Global magnetic equilibrium quantities and local magnetic measurements are consistent with modelling these open-<span class="hlt">flux</span> discharges as thin current sheets connected to the CHI electrodes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=exercise+AND+skin&pg=3&id=ED251714','ERIC'); return false;" href="http://eric.ed.gov/?q=exercise+AND+skin&pg=3&id=ED251714"><span><span class="hlt">Tube</span> Feedings.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Plummer, Nancy</p> <p></p> <p>This module on <span class="hlt">tube</span> feedings is intended for use in inservice or continuing education programs for persons who work in long-term care. Instructor information, including teaching suggestions and a listing of recommended audiovisual materials and their sources appear first. The module goal and objectives are then provided. A brief discussion follows…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=skin+AND+care&pg=6&id=ED251714','ERIC'); return false;" href="https://eric.ed.gov/?q=skin+AND+care&pg=6&id=ED251714"><span><span class="hlt">Tube</span> Feedings.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Plummer, Nancy</p> <p></p> <p>This module on <span class="hlt">tube</span> feedings is intended for use in inservice or continuing education programs for persons who work in long-term care. Instructor information, including teaching suggestions and a listing of recommended audiovisual materials and their sources appear first. The module goal and objectives are then provided. A brief discussion follows…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998ApJ...492..804E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998ApJ...492..804E"><span>The Physics of Twisted Magnetic <span class="hlt">Tubes</span> Rising in a Stratified Medium: Two-dimensional Results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Emonet, T.; Moreno-Insertis, F.</p> <p>1998-01-01</p> <p>The physics of a twisted magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> rising in a stratified medium is studied using a numerical magnetohydrodynamic (MHD) code. The problem considered is fully compressible (has no Boussinesq <span class="hlt">approximation</span>), includes ohmic resistivity, and is two-dimensional, i.e., there is no variation of the variables in the direction of the <span class="hlt">tube</span> axis. We study a high-plasma β-case with a small ratio of radius to external pressure scale height. The results obtained will therefore be of relevance to understanding the transport of magnetic <span class="hlt">flux</span> across the solar convection zone. We confirm that a sufficient twist of the field lines around the <span class="hlt">tube</span> axis can suppress the conversion of the <span class="hlt">tube</span> into two vortex rolls. For a <span class="hlt">tube</span> with a relative density deficit on the order of 1/β (the classical Parker buoyancy) and a radius smaller than the pressure scale height (R2<<H2p), the minimum amount of twist necessary corresponds to an average pitch angle on the order of sin-1 [(R/Hp)1/2]. The evolution of a <span class="hlt">tube</span> with this degree of twist is studied in detail, including the initial transient phase, the internal torsional oscillations, and the asymptotic, quasi-stationary phase. During the initial phase, the outermost, weakly magnetized layers of the <span class="hlt">tube</span> are torn off its main body and endowed with vorticity. They yield a trailing magnetized wake with two vortex rolls. The fraction of the total magnetic <span class="hlt">flux</span> that is brought to the wake is a function of the initial degree of twist. In the weakly twisted case, most of the initial <span class="hlt">tube</span> is turned into vortex rolls. With a strong initial twist, the <span class="hlt">tube</span> rises with only a small deformation and no substantial loss of magnetic <span class="hlt">flux</span>. The formation of the wake and the loss of <span class="hlt">flux</span> from the main body of the <span class="hlt">tube</span> are basically complete after the initial transient phase. A sharp interface between the <span class="hlt">tube</span> interior and the external flows is formed at the <span class="hlt">tube</span> front and sides; this area has the characteristic features of a magnetic boundary layer. Its</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10529918','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10529918"><span>Mathematical model of gas bubble evolution in a straight <span class="hlt">tube</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Halpern, D; Jiang, Y; Himm, J F</p> <p>1999-10-01</p> <p>Deep sea divers suffer from decompression sickness (DCS) when their rate of ascent to the surface is too rapid. When the ambient pressure drops, inert gas bubbles may form in blood vessels and tissues. The evolution of a gas bubble in a rigid <span class="hlt">tube</span> filled with slowly moving fluid, intended to simulate a bubble in a blood vessel, is studied by solving a coupled system of fluid-flow and gas transport equations. The governing equations for the fluid motion are solved using two techniques: an analytical method appropriate for small nondeformable spherical bubbles, and the boundary element method for deformable bubbles of arbitrary size, given an applied steady flow rate. A steady convection-diffusion equation is then solved numerically to determine the concentration of gas. The bubble volume, or equivalently the gas mass inside the bubble for a constant bubble pressure, is adjusted over time according to the mass <span class="hlt">flux</span> at the bubble surface. Using a quasi-steady <span class="hlt">approximation</span>, the evolution of a gas bubble in a <span class="hlt">tube</span> is obtained. Results show that convection increases the gas pressure gradient at the bubble surface, hence increasing the rate of bubble evolution. Comparing with the result for a single gas bubble in an infinite tissue, the rate of evolution in a <span class="hlt">tube</span> is <span class="hlt">approximately</span> twice as fast. Surface tension is also shown to have a significant effect. These findings may have important implications for our understanding of the mechanisms of inert gas bubbles in the circulation underlying decompression sickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090005212','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090005212"><span>Pulse <span class="hlt">tube</span> cooler having 1/4 wavelength resonator <span class="hlt">tube</span> instead of reservoir</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gedeon, David R. (Inventor)</p> <p>2008-01-01</p> <p>An improved pulse <span class="hlt">tube</span> cooler having a resonator <span class="hlt">tube</span> connected in place of a compliance volume or reservoir. The resonator <span class="hlt">tube</span> has a length substantially equal to an integer multiple of 1/4 wavelength of an acoustic wave in the working gas within the resonator <span class="hlt">tube</span> at its operating frequency, temperature and pressure. Preferably, the resonator <span class="hlt">tube</span> is formed integrally with the inertance <span class="hlt">tube</span> as a single, integral <span class="hlt">tube</span> with a length <span class="hlt">approximately</span> 1/2 of that wavelength. Also preferably, the integral <span class="hlt">tube</span> is spaced outwardly from and coiled around the connection of the regenerator to the pulse <span class="hlt">tube</span> at a cold region of the cooler and the turns of the coil are thermally bonded together to improve heat conduction through the coil.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4329976','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4329976"><span>QUANTIZING <span class="hlt">TUBE</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Jensen, A.S.; Gray, G.W.</p> <p>1958-07-01</p> <p>Beam deflection <span class="hlt">tubes</span> are described for use in switching or pulse amplitude analysis. The salient features of the invention reside in the target arrangement whereby outputs are obtained from a plurality of collector electrodes each correspondlng with a non-overlapping range of amplitudes of the input sigmal. The <span class="hlt">tube</span> is provded with mcans for deflecting the electron beam a1ong a line in accordance with the amplitude of an input signal. The target structure consists of a first dymode positioned in the path of the beam wlth slots spaced a1ong thc deflection line, and a second dymode posltioned behind the first dainode. When the beam strikes the solid portions along the length of the first dymode the excited electrons are multiplied and collected in separate collector electrodes spaced along the beam line. Similarly, the electrons excited when the beam strikes the second dynode are multiplied and collected in separate electrodes spaced along the length of the second dyode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/927860','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/927860"><span>Neutron <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Leung, Ka-Ngo; Lou, Tak Pui; Reijonen, Jani</p> <p>2008-03-11</p> <p>A neutron <span class="hlt">tube</span> or generator is based on a RF driven plasma ion source having a quartz or other chamber surrounded by an external RF antenna. A deuterium or mixed deuterium/tritium (or even just a tritium) plasma is generated in the chamber and D or D/T (or T) ions are extracted from the plasma. A neutron generating target is positioned so that the ion beam is incident thereon and loads the target. Incident ions cause D-D or D-T (or T-T) reactions which generate neutrons. Various embodiments differ primarily in size of the chamber and position and shape of the neutron generating target. Some neutron generators are small enough for implantation in the body. The target may be at the end of a catheter-like drift <span class="hlt">tube</span>. The target may have a tapered or conical surface to increase target surface area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1034165','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1034165"><span>Electron <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Suyama, Motohiro [Hamamatsu, JP; Fukasawa, Atsuhito [Hamamatsu, JP; Arisaka, Katsushi [Los Angeles, CA; Wang, Hanguo [North Hills, CA</p> <p>2011-12-20</p> <p>An electron <span class="hlt">tube</span> 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 <span class="hlt">tube</span> 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.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/002947.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/002947.htm"><span>Chest <span class="hlt">tube</span> insertion</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Chest drainage <span class="hlt">tube</span> insertion; Insertion of <span class="hlt">tube</span> into chest; <span class="hlt">Tube</span> thoracostomy; Pericardial drain ... When your chest <span class="hlt">tube</span> is inserted, you will lie on your side or sit partly upright, with one arm over your head. Sometimes, ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/patientinstructions/000181.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/patientinstructions/000181.htm"><span>Jejunostomy feeding <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Feeding - jejunostomy <span class="hlt">tube</span>; G-J <span class="hlt">tube</span>; J-<span class="hlt">tube</span>; Jejunum <span class="hlt">tube</span> ... Q-tip to clean the skin around the J-<span class="hlt">tube</span> 1 to 3 times a day with ... To flush the J-<span class="hlt">tube</span>, follow the instructions your nurse gave you. You will use the syringe to slowly push warm water into ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/patientinstructions/000182.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/patientinstructions/000182.htm"><span>Nasogastric feeding <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Feeding - nasogastric <span class="hlt">tube</span>; NG <span class="hlt">tube</span>; Bolus feeding; Continuous pump feeding; Gavage <span class="hlt">tube</span> ... If your child has an NG <span class="hlt">tube</span>, try to keep your child from touching or pulling on the <span class="hlt">tube</span>. After your nurse teaches you how to flush the <span class="hlt">tube</span> ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/762826','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/762826"><span>Source Terms for HFIR Beam <span class="hlt">Tube</span> Shielding Analyses, and a Complete Shielding Analysis of the HB-3 <span class="hlt">Tube</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bucholz, J.A.</p> <p>2000-07-01</p> <p>The High <span class="hlt">Flux</span> 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 <span class="hlt">tubes</span>, all of which will be replaced or redesigned. The HB-2 beam <span class="hlt">tube</span> will be enlarged to support more guide <span class="hlt">tubes</span>, while the HB-4 beam <span class="hlt">tube</span> will soon include a cold neutron source.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/777683','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/777683"><span>Neutron and Gamma <span class="hlt">Fluxes</span> and dpa Rates for HFIR Vessel Beltline Region (Present and Upgrade Designs)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blakeman, E.D.</p> <p>2001-01-11</p> <p>The Oak Ridge National Laboratory (ORNL) High <span class="hlt">Flux</span> Isotope Reactor (HFIR) is currently undergoing an upgrading program, a part of which is to increase the diameters of two of the four radiation beam <span class="hlt">tubes</span> (HB-2 and HB-4). This change will cause increased neutron and gamma radiation dose rates at and near locations where the <span class="hlt">tubes</span> penetrate the vessel wall. Consequently, the rate of radiation damage to the reactor vessel wall at those locations will also increase. This report summarizes calculations of the neutron and gamma <span class="hlt">flux</span> (particles/cm{sup 2}/s) and the dpa rate (displacements/atom/s) in iron at critical locations in the vessel wall. The calculated dpa rate values have been recently incorporated into statistical damage evaluation codes used in the assessment of radiation induced embrittlement. Calculations were performed using models based on the discrete ordinates methodology and utilizing ORNL two-dimensional and three-dimensional discrete ordinates codes. Models for present and proposed beam <span class="hlt">tube</span> designs are shown and their results are compared. Results show that for HB-2, the dpa rate in the vessel wall where the <span class="hlt">tube</span> penetrates the vessel will be increased by {<span class="hlt">approximately</span>}10 by the proposed enlargement. For HB-4, a smaller increase of {<span class="hlt">approximately</span>}2.6 is calculated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513889L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513889L"><span>Adiabatic Betatron deceleration of ionospheric charged particles: a new explanation for (i) the rapid outflow of ionospheric O ions, and for (ii) the increase of plasma mass density observed in magnetospheric <span class="hlt">flux</span> <span class="hlt">tubes</span> during main phases of geomagnetic s</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lemaire, Joseph; Pierrard, Viviane; Darrouzet, Fabien</p> <p>2013-04-01</p> <p>Using European arrays of magnetometers and the cross-phase analysis to determine magnetic field line resonance frequencies, it has been found by Kale et al. (2009) that the plasma mass density within plasmaspheric <span class="hlt">flux</span> <span class="hlt">tubes</span> increased rapidly after the SSC of the Hallowe'en 2003 geomagnetic storms. These observations tend to confirm other independent experimental results, suggesting that heavy ion up-flow from the ionosphere is responsible for the observed plasma density increases during main phases of geomagnetic storms. The aim of our contribution is to point out that, during main phases, reversible Betatron effect induced by the increase of the southward Dst-magnetic field component (|Δ Bz|), diminishes slightly the perpendicular kinetic energy (W?) of charged particles spiraling along field lines. Furthermore, due to the conservation of the first adiabatic invariant (μ = Wm/ Bm) the mirror points of all ionospheric ions and electrons are lifted up to higher altitudes i.e. where the mirror point magnetic field (Bm) is slightly smaller. Note that the change of the mirror point altitude is given by: Δ hm = -1/3 (RE + hm) Δ Bm / Bm. It is independent of the ion species and it does not depend of their kinetic energy. The change of kinetic energy is determined by: Δ Wm = Wm Δ Bm / Bm. Both of these equations have been verified numerically by Lemaire et al. (2005; doi: 10.1016/S0273-1177(03)00099-1) using trajectory calculations in a simple time-dependant B-field model: i.e. the Earth's magnetic dipole, plus an increasing southward B-field component: i.e. the Dst magnetic field whose intensity becomes more and more negative during the main phase of magnetic storms. They showed that a variation of Bz (or Dst) by more than - 50 nT significantly increases the mirror point altitudes by more than 100 km which is about equal to scale height of the plasma density in the topside ionosphere where particles are almost collisionless (see Fig. 2 in Lemaire et al., 2005</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6503555','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6503555"><span><span class="hlt">Tube</span> wall temperature monitoring technique</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Granton, R.L.</p> <p>1985-07-01</p> <p>In 1977, Monsanto and Conoco undertook the construction of a new, modern technology ethylene plant at Chocolate Bayou, near Alvin, Texas. This plant included high severity cracking furnaces with potential <span class="hlt">tube</span> wall temperatures considerably higher than any we had previously experienced. Furnace on-stream time between decokes, a factor in the economics of plant operation, was limited by <span class="hlt">tube</span> wall temperature, thus requiring its accurate knowledge. Earlier work with other ethylene furnaces had also demonstrated our lack of knowledge concerning high temperature measurements in a furnace firebox environment. This had to change. An outside consultant was called upon to provide a threeday workshop on radiant <span class="hlt">tube</span> temperature sensing. The workshop consisted of two days of formal training in the theory and practice of temperature measurement and one day of field training. This workshop was conducted at a site away from the plant. <span class="hlt">Approximately</span> 20 engineers (manufacturing and technical groups) attended. The major topics covered by this workshop are as follows: radiant <span class="hlt">tube</span> temperature sensing, radiation situation of radiant <span class="hlt">tubes</span>, g.a. method: sample calculations, noncontact sensors: methods of specifying and purchasing, thermal imager strategies, calibration of noncontact sensors, avoiding problems with noncontact sensors, optical aids to radiant <span class="hlt">tube</span> viewing, <span class="hlt">tube</span> temperature management and its environmental implications, and contact temperature sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1001791','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1001791"><span><span class="hlt">Tube</span>-wave seismic imaging</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Korneev, Valeri A [Lafayette, CA; Bakulin, Andrey [Houston, TX</p> <p>2009-10-13</p> <p>The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded <span class="hlt">approximately</span> 2000 feet above the reservoir. A <span class="hlt">tube</span>-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a <span class="hlt">tube</span>-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The <span class="hlt">tube</span>-wave has been shown to be extremely sensitive to changes in reservoir characteristics. <span class="hlt">Tube</span>-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/988156','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/988156"><span><span class="hlt">Tube</span>-wave seismic imaging</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Korneev, Valeri A [LaFayette, CA</p> <p>2009-05-05</p> <p>The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded <span class="hlt">approximately</span> 2000 feet above the reservoir. A <span class="hlt">tube</span>-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a <span class="hlt">tube</span>-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The <span class="hlt">tube</span>-wave has been shown to be extremely sensitive to changes in reservoir characteristics. <span class="hlt">Tube</span>-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5569781','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5569781"><span>Pool boiling of R-114/oil mixtures from single <span class="hlt">tubes</span> and <span class="hlt">tube</span> bundles. Master's thesis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Murphy, T.J.</p> <p>1987-09-01</p> <p>An apparatus was designed, fabricated, and operated for the testing of horizontal <span class="hlt">tube</span> bundles for boiling of R-114 with various concentrations of oil. Preliminary data were taken on the top <span class="hlt">tube</span> in the bundle, with and without the other <span class="hlt">tubes</span> in operation. Results showed up to a 37% increase in the boiling heat-transfer coefficient as a result of the favorable bundle effect. In a separate single-<span class="hlt">tube</span> apparatus, three enhanced <span class="hlt">tubes</span> were tested at a saturation temperature of 2.2 C with oil mass concentrations of 0, 1, 2, 3, 6 and 10%. The <span class="hlt">tubes</span> were: 1) a finned <span class="hlt">tube</span> with 1024 fins per meter, 2) a finned <span class="hlt">tube</span> with 1575 fins per meter and 3) a Turbo-B <span class="hlt">tube</span>. These <span class="hlt">tubes</span> resulted in enhancement ratios in pure refrigerant of 2.8, 3.8 and 5.2, respectively, at a practical heat <span class="hlt">flux</span> of 30 kW/sq. meter. With 3% oil, these ratios were decreased to 2.6, 3.5 and 5, while with 10% oil, these ratios were further reduced to 2.6, 3.2 and 4.7, respectively. Based on these results, the use of Turbo-B <span class="hlt">tubes</span> is expected to result in significant savings in weight and size of evaporators over the finned <span class="hlt">tubes</span> presently in use on board some naval vessels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/868088','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/868088"><span><span class="hlt">Tube</span> furnace</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Foster, Kenneth G.; Frohwein, Eugene J.; Taylor, Robert W.; Bowen, David W.</p> <p>1991-01-01</p> <p>A vermiculite insulated <span class="hlt">tube</span> furnace is heated by a helically-wound resistance wire positioned within a helical groove on the surface of a ceramic cylinder, that in turn is surroundingly disposed about a doubly slotted stainless steel cylindrical liner. For uniform heating, the pitch of the helix is of shorter length over the two end portions of the ceramic cylinder. The furnace is of large volume, provides uniform temperature, offers an extremely precise programmed heating capability, features very rapid cool-down, and has a modest electrical power requirement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/10160226','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/10160226"><span><span class="hlt">Tube</span> furnace</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Foster, K.G.; Frohwein, E.J.; Taylor, R.W.; Bowen, D.W.</p> <p>1990-12-31</p> <p>A vermiculite insulated <span class="hlt">tube</span> furnace is heated by a helically-wound resistance wire positioned within a helical groove on the surface of a ceramic cylinder, that in turn is surroundingly disposed about a doubly slotted stainless steel cylindrical liner. For uniform heating, the pitch of the helix is of shorter length over the two end portions of the ceramic cylinder. The furnace is of large volume, provides uniform temperature, offers an extremely precise programmed heating capability, features very rapid cool-down, and has a modest electrical power requirement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5096515','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5096515"><span><span class="hlt">Tube</span> furnace</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Foster, K.G.; Frohwein, E.J.; Taylor, R.W.; Bowen, D.W.</p> <p>1990-01-01</p> <p>A vermiculite insulated <span class="hlt">tube</span> furnace is heated by a helically-wound resistance wire positioned within a helical groove on the surface of a ceramic cylinder, that in turn is surroundingly disposed about a doubly slotted stainless steel cylindrical liner. For uniform heating, the pitch of the helix is of shorter length over the two end portions of the ceramic cylinder. The furnace is of large volume, provides uniform temperature, offers an extremely precise programmed heating capability, features very rapid cool-down, and has a modest electrical power requirement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.3410L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.3410L"><span>The Return of Magnetic <span class="hlt">Flux</span> to the Inner Saturnian Magnetosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lai, Hairong; Russell, Christopher T.; Jia, Yingdong; Masters, Adam; Dougherty, Michele K.</p> <p>2017-04-01</p> <p>The addition of plasma to the rotating inner Saturnian magnetosphere drives the circulation of the magnetic <span class="hlt">flux</span>. The magnetic <span class="hlt">flux</span> is loaded with cold plasma originating from Enceladus and its plasma torus. It then convects outward to the tail region, is emptied of plasma during reconnection events, and returns buoyantly to the inner magnetosphere. Returning <span class="hlt">flux</span> <span class="hlt">tubes</span> carry hot and tenuous plasma that serves as a marker of this type of <span class="hlt">flux</span> <span class="hlt">tube</span>. The plasma inside the <span class="hlt">tubes</span> drifts at different rates depending on energy in the curved and inhomogeneous magnetosphere when the <span class="hlt">tubes</span> convect inward. This energy dispersion can be used to track the <span class="hlt">flux</span> <span class="hlt">tube</span>. With data from MAG and CAPS, we model the energy dispersion of the electrons to determine the age and the point of return of the 'empty' <span class="hlt">flux</span> <span class="hlt">tubes</span>. The results show that even the 'fresh' <span class="hlt">flux</span> <span class="hlt">tubes</span> are several hours old when seen and they start to return at 19 Saturn radii, near Titan's orbit. This supports the hypothesis that returning <span class="hlt">flux</span> <span class="hlt">tubes</span> generated by reconnection in the far-tail region are injected directly into the inner magnetosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1004617','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1004617"><span>AUTOMATED WATER LEVEL MEASUREMENTS IN SMALL-DIAMETER AQUIFER <span class="hlt">TUBES</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>PETERSEN SW; EDRINGTON RS; MAHOOD RO; VANMIDDLESWORTH PE</p> <p>2011-01-14</p> <p>Groundwater contaminated with hexavalent chromium, strontium-90, and uranium discharges into the Columbia River along <span class="hlt">approximately</span> 16 km (10 mi) of the shoreline. Various treatment systems have and will continue to be implemented to eliminate the impact of Hanford Site contamination to the river. To optimize the various remediation strategies, it is important to understand interactions between groundwater and the surface water of the Columbia River. An automated system to record water levels in aquifer sampling <span class="hlt">tubes</span> installed in the hyporheic zone was designed and tested to (1) gain a more complete understanding of groundwater/river water interactions based on gaining and losing conditions ofthe Columbia River, (2) record and interpret data for consistent and defensible groundwater/surface water conceptual models that may be used to better predict subsurface contaminant fate and transport, and (3) evaluate the hydrodynamic influence of extraction wells in an expanded pump-and-treat system to optimize the treatment system. A system to measure water levels in small-diameter aquifer <span class="hlt">tubes</span> was designed and tested in the laboratory and field. The system was configured to allow manual measurements to periodically calibrate the instrument and to permit aquifer <span class="hlt">tube</span> sampling without removing the transducer <span class="hlt">tube</span>. Manual measurements were collected with an e-tape designed and fabricated especially for this test. Results indicate that the transducer system accurately records groundwater levels in aquifer <span class="hlt">tubes</span>. These data are being used to refine the conceptual and numeric models to better understand interactions in the hyporheic zone of the Columbia River and the adjacent river water and groundwater, and changes in hydrochemistry relative to groundwater <span class="hlt">flux</span> as river water recharges the aquifer and then drains back out in response to changes in the river level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/871658','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/871658"><span><span class="hlt">Tube-in-tube</span> thermophotovoltaic generator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Ashcroft, John; Campbell, Brian; DePoy, David</p> <p>1998-01-01</p> <p>A thermophotovoltaic device includes at least one thermal radiator <span class="hlt">tube</span>, a cooling <span class="hlt">tube</span> concentrically disposed within each thermal radiator <span class="hlt">tube</span> and an array of thermophotovoltaic cells disposed on the exterior surface of the cooling <span class="hlt">tube</span>. A shell having a first end and a second end surrounds the thermal radiator <span class="hlt">tube</span>. Inner and outer tubesheets, each having an aperture corresponding to each cooling <span class="hlt">tube</span>, are located at each end of the shell. The thermal radiator <span class="hlt">tube</span> extends within the shell between the inner tubesheets. The cooling <span class="hlt">tube</span> extends within the shell through the corresponding apertures of the two inner tubesheets to the corresponding apertures of the two outer tubesheets. A plurality of the thermal radiator <span class="hlt">tubes</span> can be arranged in a staggered or an in-line configuration within the shell.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/672525','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/672525"><span><span class="hlt">Tube-in-tube</span> thermophotovoltaic generator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Ashcroft, J.; Campbell, B.; DePoy, D.</p> <p>1998-06-30</p> <p>A thermophotovoltaic device includes at least one thermal radiator <span class="hlt">tube</span>, a cooling <span class="hlt">tube</span> concentrically disposed within each thermal radiator <span class="hlt">tube</span> and an array of thermophotovoltaic cells disposed on the exterior surface of the cooling <span class="hlt">tube</span>. A shell having a first end and a second end surrounds the thermal radiator <span class="hlt">tube</span>. Inner and outer tubesheets, each having an aperture corresponding to each cooling <span class="hlt">tube</span>, are located at each end of the shell. The thermal radiator <span class="hlt">tube</span> extends within the shell between the inner tubesheets. The cooling <span class="hlt">tube</span> extends within the shell through the corresponding apertures of the two inner tubesheets to the corresponding apertures of the two outer tubesheets. A plurality of the thermal radiator <span class="hlt">tubes</span> can be arranged in a staggered or an in-line configuration within the shell. 8 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ThEng..57..232K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ThEng..57..232K"><span>Generalization of data on critical heat <span class="hlt">fluxes</span> for flow swirled using a tape</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krug, A. F.; Kuzma-Kichta, Yu. A.; Komendantov, A. S.</p> <p>2010-03-01</p> <p>The available data on critical heat <span class="hlt">fluxes</span> for boiling of subcooled and saturated liquid in <span class="hlt">tubes</span> with twisted tape inserts are considered. Experimental data obtained by different researchers are generalized, and an equation for calculating critical heat <span class="hlt">fluxes</span> for both smooth <span class="hlt">tubes</span> and <span class="hlt">tubes</span> with flow swirling by means of a tape is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ArTh...32..103T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ArTh...32..103T"><span>New technique of the local heat <span class="hlt">flux</span> measurement in combustion chambers of steam boilers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taler, Jan; Taler, Dawid; Sobota, Tomasz; Dzierwa, Piotr</p> <p>2011-12-01</p> <p>A new method for measurement of local heat <span class="hlt">flux</span> to water-walls of steam boilers was developed. A <span class="hlt">flux</span> meter <span class="hlt">tube</span> was made from an eccentric <span class="hlt">tube</span> of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall <span class="hlt">tubes</span>, so that the temperature distribution in the heat <span class="hlt">flux</span> meter is not influenced by neighbouring water-wall <span class="hlt">tubes</span>. The thickness of the heat <span class="hlt">flux</span> <span class="hlt">tube</span> wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat <span class="hlt">flux</span> determination. Based on the temperature measurements at selected points inside the heat <span class="hlt">flux</span> meter, the heat <span class="hlt">flux</span> absorbed by the water-wall, heat transfer coefficient on the inner <span class="hlt">tube</span> surface and temperature of the water-steam mixture was determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Series+AND+fourier&pg=3&id=EJ434949','ERIC'); return false;" href="http://eric.ed.gov/?q=Series+AND+fourier&pg=3&id=EJ434949"><span>Interpolation and <span class="hlt">Approximation</span> Theory.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Kaijser, Sten</p> <p>1991-01-01</p> <p>Introduced are the basic ideas of interpolation and <span class="hlt">approximation</span> theory through a combination of theory and exercises written for extramural education at the university level. Topics treated are spline methods, Lagrange interpolation, trigonometric <span class="hlt">approximation</span>, Fourier series, and polynomial <span class="hlt">approximation</span>. (MDH)</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22140276','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22140276"><span>STABILITY AND DYNAMICS OF A <span class="hlt">FLUX</span> ROPE FORMED VIA <span class="hlt">FLUX</span> EMERGENCE INTO THE SOLAR ATMOSPHERE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>An, J. M.; Magara, T. E-mail: magara@khu.ac.kr</p> <p>2013-08-10</p> <p>We study the stability and dynamics of a <span class="hlt">flux</span> rope formed through the emergence of a twisted magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> into the solar atmosphere. A three-dimensional magnetohydrodynamic simulation has been performed to investigate several key factors affecting the dynamics of the <span class="hlt">flux</span> rope. The stability of the <span class="hlt">flux</span> rope is examined by deriving the decay index of the coronal magnetic field surrounding the <span class="hlt">flux</span> rope. We investigate a transition between the quasi-static and dynamic states of the <span class="hlt">flux</span> rope through an analysis of the curvature and scale height of emerging magnetic field. A practical application of this analysis for global eruptions is also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/patientinstructions/000464.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/patientinstructions/000464.htm"><span>Tracheostomy <span class="hlt">tube</span> - eating</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... page: //medlineplus.gov/ency/patientinstructions/000464.htm Tracheostomy <span class="hlt">tube</span> - eating To use the sharing features on this ... you swallow foods or liquids. Eating and Tracheostomy <span class="hlt">Tubes</span> When you get your tracheostomy <span class="hlt">tube</span>, or trach, ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.marchofdimes.org/baby/neural-tube-defects.aspx','NIH-MEDLINEPLUS'); return false;" href="http://www.marchofdimes.org/baby/neural-tube-defects.aspx"><span>Neural <span class="hlt">Tube</span> Defects</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... Birth defects & other health conditions > Neural <span class="hlt">tube</span> defects Neural <span class="hlt">tube</span> defects E-mail to a friend Please ... this page It's been added to your dashboard . Neural <span class="hlt">tube</span> defects (NTDs) are birth defects of the ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7204436','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/7204436"><span>Heat exchanger <span class="hlt">tube</span> mounts</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Wolowodiuk, W.; Anelli, J.; Dawson, B.E.</p> <p>1974-01-01</p> <p>A heat exchanger in which <span class="hlt">tubes</span> are secured to a <span class="hlt">tube</span> sheet by internal bore welding is described. The <span class="hlt">tubes</span> may be moved into place in preparation for welding with comparatively little trouble. A number of segmented <span class="hlt">tube</span> support plates are provided which allow a considerable portion of each of the <span class="hlt">tubes</span> to be moved laterally after the end thereof has been positioned in preparation for internal bore welding to the <span class="hlt">tube</span> sheet. (auth)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790000571&hterms=bending+tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dbending%2Btube','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790000571&hterms=bending+tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dbending%2Btube"><span><span class="hlt">Tube</span>-shape verifier</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, A. N.; Christ, C. R.</p> <p>1980-01-01</p> <p>Inexpensive apparatus checks accuracy of bent <span class="hlt">tubes</span>. Assortment of slotted angles and clamps is bolted down to flat aluminum plate outlining shape of standard <span class="hlt">tube</span> bent to desired configuration. Newly bent <span class="hlt">tubes</span> are then checked against this outline. Because parts are bolted down, <span class="hlt">tubes</span> can be checked very rapidly without disturbing outline. One verifier per <span class="hlt">tube</span>-bending machine can really speed up production in <span class="hlt">tube</span>-bending shop.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22328125','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22328125"><span>Diurnal changes in assimilate concentrations and <span class="hlt">fluxes</span> in the phloem of castor bean (Ricinus communis L.) and tansy (Tanacetum vulgare L.).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kallarackal, Jose; Bauer, Susanne N; Nowak, Heike; Hajirezaei, Mohammad-Reza; Komor, Ewald</p> <p>2012-07-01</p> <p>Reports about diurnal changes of assimilates in phloem sap are controversial. We determined the diurnal changes of sucrose and amino acid concentrations and <span class="hlt">fluxes</span> in exudates from cut aphid stylets on tansy leaves (Tanacetum vulgare), and sucrose, amino acid and K(+) concentrations and <span class="hlt">fluxes</span> in bleeding sap of castor bean pedicel (Ricinus communis). <span class="hlt">Approximately</span> half of the tansy sieve <span class="hlt">tubes</span> exhibited a diurnal cycle of sucrose concentrations and <span class="hlt">fluxes</span> in phloem sap. Data from many tansy plants indicated an increased sucrose <span class="hlt">flux</span> in the phloem during daytime in case of low N-nutrition, not at high N-nutrition. The sucrose concentration in phloem sap of young Ricinus plants changed marginally between day and night, whereas the sucrose <span class="hlt">flux</span> increased 1.5-fold during daytime (but not in old Ricinus plants). The amino acid concentrations and <span class="hlt">fluxes</span> in tansy sieve <span class="hlt">tubes</span> exhibited a similar diurnal cycle as the sucrose concentrations and <span class="hlt">fluxes</span>, including their dependence on N-nutrition. The amino acid <span class="hlt">fluxes</span>, but not the concentrations, in phloem sap of Ricinus were higher at daytime. The sucrose/amino acid ratio showed no diurnal cycle neither in tansy nor in Ricinus. The K(+)-concentrations in phloem sap of Ricinus, but not the K(+) <span class="hlt">fluxes</span>, decreased slightly during daytime and the sucrose/K(+)-ratio increased. In conclusion, a diurnal cycle was observed in sucrose, amino acid and K(+) <span class="hlt">fluxes</span>, but not necessarily in concentrations of these assimilates. Because of the large variations between different sieve <span class="hlt">tubes</span> and different plants, the nutrient delivery to sink tissues is not homeostatic over time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20002469','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20002469"><span>Mist/steam cooling in a 180{degree} <span class="hlt">tube</span> bend</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guo, T.; Wang, T.; Gaddis, J.L.</p> <p>1999-07-01</p> <p>An experimental study on mist/steam cooling in a highly heated, horizontal 180{degree} <span class="hlt">tube</span> bend has been performed. The mist/steam mixture is obtained by blending fine water droplets (3{<span class="hlt">approximately</span>}15 microns) with the saturated steam at 1.5 bar. The test section consists of a thin wall ({<span class="hlt">approximately</span>}0.9 mm), welded, circular, stainless steel 180-degree <span class="hlt">tube</span> (20 mm ID) with a straight section downstream of the curved section, and is heated directly by a DC power supply. The experiment was conducted with steam Reynolds numbers ranging from 10,000 to 35,000, wall superheat up to 300 C, and droplet to steam mass ratio at about 2%. The results show that the heat transfer performance of steam can be significantly improved by adding mist into the main flow. Due to the effect of centrifugal force, the outer wall of the test section always exhibits a higher heat transfer enhancement than the inner wall. The highest enhancement occurs at a location on the outer wall about 45{degree} downstream of the inlet of the test section. Generally, only a small number of droplets can survive the 180{degree} turn and be present in the downstream straight section, as observed by a Phase Doppler Particle Analyzer (PDPA) system. The overall cooling enhancement of the mist/steam flow ranges from 40% to 300%. It increases as the main steam flow increases, but decreases as the wall heat <span class="hlt">flux</span> increases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986GMS....38..172M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986GMS....38..172M"><span>Statistical study of enhanced ion <span class="hlt">fluxes</span> in the outer plasmasphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menietti, J. D.; Burch, J. L.; Williams, R. L.; Gallagher, D. L.; Waite, J. H., Jr.</p> <p></p> <p>Statistical studies of outer plasmaspheric ions in the northern hemisphere have been made utilizing the High Altitude Plasma Instrument (HAPI) on board the Dynamics Explorer-1 satellite. The data were collected during equinox and winter seasons and during a period of solar maximum activity conditions. The data include <span class="hlt">approximately</span> 40 dayside and over 50 nightside plasmaspheric passes covering a range of magnetic activities (0 < Kp < 7). A total of six magnetic storms and recovery periods and a number of quiet times are included in the sampling. The range of magnetic local times on the dayside is from about 6 hours to 12 hours, while the nightside range is from about 18 hours to 23 hours. Our results indicate a clear enhancement in the low energy (5 eV < E < 30 eV) number <span class="hlt">flux</span> during periods of large magnetic activity in both the dayside and nightside outer plasmasphere (the inner plasmasphere was not observed). The dayside plasmaspheric <span class="hlt">fluxes</span> were predominately upward (anti-parallel to B¯) while the nightside plasmaspheric <span class="hlt">fluxes</span> were predominately downward (parallel to B¯). The net number <span class="hlt">fluxes</span> sometimes reached a value of over 108cm sec-1 (assuming H+ as the predominate species). The largest flows up the field line occur in the outer plasmasphere and decrease in the plasma trough. The ion temperatures in the outer plasmasphere were typically lower than those in the plasma trough and auroral regions. Since the largest flows both parallel and anti-parallel to B¯ are observed at periods of high magnetic activity, enhanced outer plasmaspheric <span class="hlt">fluxes</span> may be due to ionospheric ions expanding into depleted plasmaspheric <span class="hlt">flux</span> <span class="hlt">tubes</span>. The nightside <span class="hlt">fluxes</span> may be due to expansion of the ionosphere in the magnetic conjugate hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950059826&hterms=electric+current&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Delectric%2Bcurrent','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950059826&hterms=electric+current&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Delectric%2Bcurrent"><span>Line-of-sight magnetic <span class="hlt">flux</span> imbalances caused by electric currents</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gary, G. Allen; Rabin, Douglas</p> <p>1995-01-01</p> <p>Several physical and observational effects contribute to the significant imbalances of magnetic <span class="hlt">flux</span> that are often observed in active regions. We consider an effect not previously treated: the influence of electric currents in the photosphere. Electric currents can cause a line-of-sight <span class="hlt">flux</span> imbalance because of the directionality of the magnetic field they produce. Currents associated with magnetic <span class="hlt">flux</span> <span class="hlt">tubes</span> produce larger imbalances than do smoothly-varying distributions of <span class="hlt">flux</span> and current. We estimate the magnitude of this effect for current densities, total currents, and magnetic geometry consistent with observations. The expected imbalances lie <span class="hlt">approximately</span> in the range 0-15%, depending on the character of the current-carying fields and the angle from which they are viewed. Observationally, current-induced <span class="hlt">flux</span> imbalances could be indicated by a statistical dependence of the imbalance on angular distance from disk center. A general study of magnetic <span class="hlt">flux</span> balance in active regions is needed to determine the relative importance of other- probably larger- effects such as dilute <span class="hlt">flux</span> (too weak to measure or rendered invisible by radiative transfer effects), merging with weak background fields, and long-range connections between active regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PPCF...59e5002C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PPCF...59e5002C"><span>Collisionality scaling of the electron heat <span class="hlt">flux</span> in ETG turbulence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Colyer, G. J.; Schekochihin, A. A.; Parra, F. I.; Roach, C. M.; Barnes, M. A.; Ghim, Y.-c.; Dorland, W.</p> <p>2017-05-01</p> <p>In electrostatic simulations of MAST plasma at electron-gyroradius scales, using the local <span class="hlt">flux-tube</span> gyrokinetic code GS2 with adiabatic ions, we find that the long-time saturated electron heat <span class="hlt">flux</span> (the level most relevant to energy transport) decreases as the electron collisionality decreases. At early simulation times, the heat <span class="hlt">flux</span> ‘quasi-saturates’ without any strong dependence on collisionality, and with the turbulence dominated by streamer-like radially elongated structures. However, the zonal fluctuation component continues to grow slowly until much later times, eventually leading to a new saturated state dominated by zonal modes and with the heat <span class="hlt">flux</span> proportional to the collision rate, in <span class="hlt">approximate</span> agreement with the experimentally observed collisionality scaling of the energy confinement in MAST. We outline an explanation of this effect based on a model of ETG turbulence dominated by zonal-nonzonal interactions and on an analytically derived scaling of the zonal-mode damping rate with the electron-ion collisionality. Improved energy confinement with decreasing collisionality is favourable towards the performance of future, hotter devices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...826..205T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...826..205T"><span>Relaxation Processes within <span class="hlt">Flux</span> Ropes in Solar Wind</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Telloni, D.; Carbone, V.; Perri, S.; Bruno, R.; Lepreti, F.; Veltri, P.</p> <p>2016-08-01</p> <p><span class="hlt">Flux</span> ropes are localized structures in space plasma whose <span class="hlt">tube</span>-like organized magnetic configuration can be well <span class="hlt">approximated</span> by a force-free field model. Both numerical simulations and simple models suggest that the ideal magnetohydrodynamics (MHD) can relax toward a minimum energy state, where magnetic helicity is conserved, characterized by force-free magnetic fields (Taylor relaxation). In this paper, we evaluate MHD rugged invariants within more than 100 <span class="hlt">flux</span> ropes identified in the solar wind at 1 AU, showing that the magnetic and cross-helicity content carried out by these structures tend to be “attracted” toward a particular subphase in the parameter plane. The final configuration of the MHD rugged invariants in the parameter plane suggests indeed that <span class="hlt">flux</span> ropes represent well-organized structures coming from the dynamical evolution of MHD turbulent cascade. These observational results, along with a simple model based on a truncated set of nonlinear ordinary differential equations for both the velocity and magnetic field Fourier coefficients, thus, support a scenario in which the <span class="hlt">flux</span> ropes naturally come out from the ideal MHD decay to large-scale magnetic field in space plasmas, probably governed by relaxation processes similar to those observed in laboratory plasmas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800000051&hterms=evacuated+solar+collector&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Devacuated%2Bsolar%2Bcollector','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800000051&hterms=evacuated+solar+collector&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Devacuated%2Bsolar%2Bcollector"><span>Evacuated-<span class="hlt">tube</span> solar collector--performance evaluation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1980-01-01</p> <p>Report gives thermal performance test procedures and results for commercially produced, water-filled, 8-<span class="hlt">tube</span> collectors. Tests include efficiency, time constant for temperature drop after solar <span class="hlt">flux</span> is cut, change in efficiency as function of sun angle, and test to see if <span class="hlt">tubes</span> break when filled with hot water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996SPIE.2887..129U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996SPIE.2887..129U"><span>New laser tracheal <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ungemach, Josef; Foth, Hans-Jochen; Hoermann, Karl; Preponis, E.</p> <p>1996-09-01</p> <p>The complication of a laser induced <span class="hlt">tube</span> fire during surgery was first published in 1979. The protection of tracheal <span class="hlt">tubes</span> against ignition is necessary to enable a safe laser surgery of the upper airway. in an experimental study a new compound <span class="hlt">tube</span> was tested: this <span class="hlt">tube</span> had a higher laser resistance than a pure metal <span class="hlt">tube</span>. The damage threshold of this <span class="hlt">tube</span> was tested against the emission of various lasers as CO2. The metal <span class="hlt">tube</span> was damaged within seconds at CO2 laser power densities of 103 W/cm2 whereas the damage threshold of the compound <span class="hlt">tube</span> was 3.106 W/cm2. We compared the compound laser <span class="hlt">tube</span> to the so far used metal <span class="hlt">tube</span> in a prospective clinical trial in our department of ENT in patients undergoing CO2-laser surgery of the upper airway. 66 patients were included into the study: 33 received the compound <span class="hlt">tube</span>, 33 the metal <span class="hlt">tube</span>. During endotracheal intubation the handling of the compound <span class="hlt">tube</span> was better. During laser surgery high airway pressures occured more often with the metal <span class="hlt">tube</span>. Whereas kinking was the problem of the compound <span class="hlt">tubes</span>. Destruction of cuffs occured in both groups but did not cause any complications. No <span class="hlt">tube</span> or cuff fire was noticed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1030739','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1030739"><span>EC <span class="hlt">Tube</span> Fits</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kurita, C.H.; /Fermilab</p> <p>1987-03-03</p> <p>In the design of the EC, the beam <span class="hlt">tube</span>, through which the beam line travels, can be found in the IH <span class="hlt">tube</span> which is centrally located in the IH module. However, also between the beam <span class="hlt">tube</span> and the IH <span class="hlt">tube</span> lie both the vacuum and inner <span class="hlt">tubes</span> of the vacuum and inner vessels. It is the vacuum between these vessels which provides insulation between the ambient beam <span class="hlt">tube</span> and liquid argon in the cryostat. while the vacuum <span class="hlt">tube</span> is supported along its length with the inner <span class="hlt">tube</span> as best as possible, the inner <span class="hlt">tube</span> will only be supported at the ends. The beam <span class="hlt">tube</span> will also be end-supported, but it will be allowed to rest directly on the inner surface of the vacuum <span class="hlt">tube</span>. It is required that the beam <span class="hlt">tube</span> be able to slide in and out of the vacuum <span class="hlt">tube</span> with relative ease in order that the EC's can be moved away from the CC when necessary (repair work, etc.). Although the frequency of such a move is not known, it is hoped to be low, and it would therefore be desirable, for cost reasons, to be able to use stock <span class="hlt">tubing</span> for the vacuum and beam <span class="hlt">tubes</span> instead of using specially machined <span class="hlt">tubing</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8497233','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8497233"><span>Neutron <span class="hlt">fluxes</span> in radiotherapy rooms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Agosteo, S; Foglio Para, A; Maggioni, B</p> <p>1993-01-01</p> <p>The spatial distribution of the neutron <span class="hlt">flux</span>, originated in an electron accelerator therapy room when energies above the threshold of (y,n) and (e,e'n) reactions are employed, is physically due to a direct <span class="hlt">flux</span>, coming from the accelerator head, and to a <span class="hlt">flux</span> diffused from the walls. In this work, the <span class="hlt">flux</span> is described to a high degree of <span class="hlt">approximation</span> by a set of functions whose spatial behavior is univocally determined by the angular distributions of the neutrons emitted from the shield of the accelerator head and diffused from the walls. The analytical results are verified with an extended series of Monte Carlo simulations obtained with the MCNP code.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998JGR...10327465S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998JGR...10327465S"><span>Flow and convective cooling in lava <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sakimoto, S. E. H.; Zuber, M. T.</p> <p>1998-11-01</p> <p><span class="hlt">Tube</span>-fed basaltic lava flows with lengths ranging from 10 to 200 km are inferred to exhibit similar amounts of cooling. To explain the wide range of implied cooling rates, we consider forced convection as a dominant cooling process in lava <span class="hlt">tubes</span> and present solutions that express mean temperature versus distance down the <span class="hlt">tube</span> as a function of flow rate and flow cross section. Our models treat forced convective thermal losses in steady laminar flow through a lava <span class="hlt">tube</span> with constant temperature walls and constant material properties. We explore the effects of different wall temperature and heat <span class="hlt">flux</span> rate boundary conditions for circular <span class="hlt">tube</span> and parallel plate flows over a range of <span class="hlt">tube</span> sizes, plate spacings, eruption temperatures, and volume flow rates. Results show that nonlinear cooling rates over distance are characteristic of constant wall temperature for a piecewise parallel plate/circular <span class="hlt">tube</span> model. This provides the best fit to temperature observations for Hawaiian <span class="hlt">tubes</span>. Such a model may also provide an explanation for the very low (˜10°C) cooling observed in ˜10 km long Hawaii <span class="hlt">tube</span> flows and inferred in longer ˜50 to 150 km <span class="hlt">tube</span>-fed flows in Queensland. The forced convective cooling model may also explain similar flow morphologies for long <span class="hlt">tube</span>-fed basaltic lava flows in a wide variety of locations, since small variations in eruption temperature or flow rate can accommodate the entire range of flow lengths and cooling rates considered. Our results are consistent with previous suggestions that long basaltic flows may be a reflection of low slopes, a particularly steady moderate eruption rate, and well-insulated flow, rather than of high discharge rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830000206&hterms=Bender&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBender','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830000206&hterms=Bender&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBender"><span>Bender/Coiler for <span class="hlt">Tubing</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stoltzfus, J. M.</p> <p>1983-01-01</p> <p>Easy-to-use tool makes coils of <span class="hlt">tubing</span>. <span class="hlt">Tubing</span> to be bend clamped with stop post. Die positioned snugly against <span class="hlt">tubing</span>. Operator turns handle to slide die along <span class="hlt">tubing</span>, pushing <span class="hlt">tubing</span> into spiral groove on mandrel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10165282','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10165282"><span><span class="hlt">Approximate</span> flavor symmetries</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rasin, A.</p> <p>1994-04-01</p> <p>We discuss the idea of <span class="hlt">approximate</span> flavor symmetries. Relations between <span class="hlt">approximate</span> flavor symmetries and natural flavor conservation and democracy models is explored. Implications for neutrino physics are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5700607','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5700607"><span><span class="hlt">Tubing</span> suspension system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Berner, P. C.; Brickman, E. L.</p> <p>1985-12-31</p> <p>A <span class="hlt">tubing</span> suspension system for undersea well production operations employs a nonoriented <span class="hlt">tubing</span> hanger having an inner body for supporting a <span class="hlt">tubing</span> string and a landing collar for supporting the <span class="hlt">tubing</span> hanger on a wellhead casing. The <span class="hlt">tubing</span> hanger includes three co-operating concentric sleeve assemblies which are employed to lock and seal the <span class="hlt">tubing</span> hanger to the wellhead housing. The outer sleeve assembly includes a locking actuator and a dual seal assembly and is separately retrievable from the remainder of the hanger assmebly. A nonorienting hydraulic set running tool is employed to run the <span class="hlt">tubing</span> hanger, set the seals, lock the <span class="hlt">tubing</span> hanger to the wellhead casing, retrieve either the outer sleeve assembly or the entire <span class="hlt">tubing</span> hanger. The running tool includes a hydraulically controlled actuating sleeve which carries a latch dog assembly which locks with the <span class="hlt">tubing</span> hanger.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014sems.book..148N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014sems.book..148N"><span><span class="hlt">Approximation</span> of Laws</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niiniluoto, Ilkka</p> <p>2014-03-01</p> <p><span class="hlt">Approximation</span> of laws is an important theme in the philosophy of science. If we can make sense of the idea that two scientific laws are "close" to each other, then we can also analyze such methodological notions as <span class="hlt">approximate</span> explanation of laws, <span class="hlt">approximate</span> reduction of theories, <span class="hlt">approximate</span> empirical success of theories, and <span class="hlt">approximate</span> truth of laws. Proposals for measuring the distance between quantitative scientific laws were given in Niiniluoto (1982, 1987). In this paper, these definitions are reconsidered as a response to the interesting critical remarks by Liu (1999).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA07055&hterms=subsidence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsubsidence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA07055&hterms=subsidence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsubsidence"><span>Lava <span class="hlt">Tube</span> Collapse Pits</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/> We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava <span class="hlt">tubes</span> on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the <span class="hlt">tube</span> will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava <span class="hlt">tube</span>. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. <p/> These collapse pits are found in the southern hemisphere of Mars. They are likely lava <span class="hlt">tube</span> collapse pits related to flows from Hadriaca Patera. <p/> Image information: VIS instrument. Latitude -36.8, Longitude 89.6 East (270.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to <span class="hlt">approximate</span> spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. <p/> NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA07055&hterms=pit+void&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpit%2Bvoid','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA07055&hterms=pit+void&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpit%2Bvoid"><span>Lava <span class="hlt">Tube</span> Collapse Pits</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p><p/> [figure removed for brevity, see original site] <p/> We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava <span class="hlt">tubes</span> on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the <span class="hlt">tube</span> will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava <span class="hlt">tube</span>. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. <p/> These collapse pits are found in the southern hemisphere of Mars. They are likely lava <span class="hlt">tube</span> collapse pits related to flows from Hadriaca Patera. <p/> Image information: VIS instrument. Latitude -36.8, Longitude 89.6 East (270.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to <span class="hlt">approximate</span> spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. <p/> NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920014749','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920014749"><span>Collapse of composite <span class="hlt">tubes</span> under end moments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stockwell, Alan E.; Cooper, Paul A.</p> <p>1992-01-01</p> <p>Cylindrical <span class="hlt">tubes</span> of moderate wall thickness such as those proposed for the original space station truss, may fail due to the gradual collapse of the <span class="hlt">tube</span> cross section as it distorts under load. Sometimes referred to as the Brazier instability, it is a nonlinear phenomenon. This paper presents an extension of an <span class="hlt">approximate</span> closed form solution of the collapse of isotropic <span class="hlt">tubes</span> subject to end moments developed by Reissner in 1959 to include specially orthotropic material. The closed form solution was verified by an extensive nonlinear finite element analysis of the collapse of long <span class="hlt">tubes</span> under applied end moments for radius to thickness ratios and composite layups in the range proposed for recent space station truss framework designs. The finite element analysis validated the assumption of inextensional deformation of the cylindrical cross section and the <span class="hlt">approximation</span> of the material as specially orthotropic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002APS..DFD.JC012B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002APS..DFD.JC012B"><span>Steady Slug Flow in a Circular <span class="hlt">Tube</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bian, Xiaoqiang; Perlin, Marc; Schultz, William W.</p> <p>2002-11-01</p> <p>The steady motion of a water slug in a circular <span class="hlt">tube</span> is studied. When the contact lines completely stick to the <span class="hlt">tube</span>, the axisymmetric surface modes are solved with a spectral method for originally spherical menisci. The results agree well with a simple 0-degree <span class="hlt">approximation</span> for lowest slosh mode. The effects of slip in natural frequencies are also discussed. The velocity and menisci geometry are measured for slugs moving in a tilted <span class="hlt">tube</span> for dry and pre-wetted inner <span class="hlt">tube</span> surfaces. A custom glass <span class="hlt">tube</span> has a square outer cross section for minimizing optic distortions and measuring velocity and meniscus geometry. Asymptotic methods and numerics solve the menisci sliding on pre-wetted inner surface. These results are qualitatively compared with our experiments and those in NASA TN-515. As expected, near-meniscus behavior plays a big role in the total resistance to the moving slug.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12793728','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12793728"><span>Lunar lava <span class="hlt">tube</span> radiation safety analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Angelis, Giovanni; Wilson, J W; Clowdsley, M S; Nealy, J E; Humes, D H; Clem, J M</p> <p>2002-12-01</p> <p>For many years it has been suggested that lava <span class="hlt">tubes</span> on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava <span class="hlt">tubes</span> has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith layer and rock. The chemical composition has been chosen as typical of the lunar regions where the largest number of lava <span class="hlt">tube</span> candidates are found. Particles have been transported all through the regolith and the rock, and received particles <span class="hlt">flux</span> and doses have been calculated. The radiation safety of lunar lava <span class="hlt">tubes</span> environments has been demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040087656&hterms=chemical+safety&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dchemical%2Bsafety','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040087656&hterms=chemical+safety&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dchemical%2Bsafety"><span>Lunar lava <span class="hlt">tube</span> radiation safety analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>De Angelis, Giovanni; Wilson, J. W.; Clowdsley, M. S.; Nealy, J. E.; Humes, D. H.; Clem, J. M.</p> <p>2002-01-01</p> <p>For many years it has been suggested that lava <span class="hlt">tubes</span> on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava <span class="hlt">tubes</span> has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith layer and rock. The chemical composition has been chosen as typical of the lunar regions where the largest number of lava <span class="hlt">tube</span> candidates are found. Particles have been transported all through the regolith and the rock, and received particles <span class="hlt">flux</span> and doses have been calculated. The radiation safety of lunar lava <span class="hlt">tubes</span> environments has been demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040087656&hterms=lava+rock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlava%2Brock','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040087656&hterms=lava+rock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlava%2Brock"><span>Lunar lava <span class="hlt">tube</span> radiation safety analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>De Angelis, Giovanni; Wilson, J. W.; Clowdsley, M. S.; Nealy, J. E.; Humes, D. H.; Clem, J. M.</p> <p>2002-01-01</p> <p>For many years it has been suggested that lava <span class="hlt">tubes</span> on the Moon could provide an ideal location for a manned lunar base, by providing shelter from various natural hazards, such as cosmic radiation, meteorites, micrometeoroids, and impact crater ejecta, and also providing a natural environmental control, with a nearly constant temperature, unlike that of the lunar surface showing extreme variation in its diurnal cycle. An analysis of radiation safety issues on lunar lava <span class="hlt">tubes</span> has been performed by considering radiation from galactic cosmic rays (GCR) and Solar Particle Events (SPE) interacting with the lunar surface, modeled as a regolith layer and rock. The chemical composition has been chosen as typical of the lunar regions where the largest number of lava <span class="hlt">tube</span> candidates are found. Particles have been transported all through the regolith and the rock, and received particles <span class="hlt">flux</span> and doses have been calculated. The radiation safety of lunar lava <span class="hlt">tubes</span> environments has been demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930091676','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930091676"><span>Torsion Tests of <span class="hlt">Tubes</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stang, Ambrose H; Ramberg, Walter; Back, Goldie</p> <p>1937-01-01</p> <p>This report presents the results of tests of 63 chromium-molybdenum steel <span class="hlt">tubes</span> and 102 17st aluminum-alloy <span class="hlt">tubes</span> of various sizes and lengths made to study the dependence of the torsional strength on both the dimensions of the <span class="hlt">tube</span> and the physical properties of the <span class="hlt">tube</span> material. Three types of failure are found to be important for sizes of <span class="hlt">tubes</span> frequently used in aircraft construction: (1) failure by plastic shear, in which the <span class="hlt">tube</span> material reached its yield strength before the critical torque was reached; (2) failure by elastic two-lobe buckling, which depended only on the elastic properties of the <span class="hlt">tube</span> material and the dimensions of the <span class="hlt">tube</span>; and (3) failure by a combination of (1) and (2) that is, by buckling taking place after some yielding of the <span class="hlt">tube</span> material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMP....58h2202C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMP....58h2202C"><span><span class="hlt">Approximate</span> symmetries of Hamiltonians</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chubb, Christopher T.; Flammia, Steven T.</p> <p>2017-08-01</p> <p>We explore the relationship between <span class="hlt">approximate</span> symmetries of a gapped Hamiltonian and the structure of its ground space. We start by considering <span class="hlt">approximate</span> symmetry operators, defined as unitary operators whose commutators with the Hamiltonian have norms that are sufficiently small. We show that when <span class="hlt">approximate</span> symmetry operators can be restricted to the ground space while <span class="hlt">approximately</span> preserving certain mutual commutation relations. We generalize the Stone-von Neumann theorem to matrices that <span class="hlt">approximately</span> satisfy the canonical (Heisenberg-Weyl-type) commutation relations and use this to show that <span class="hlt">approximate</span> symmetry operators can certify the degeneracy of the ground space even though they only <span class="hlt">approximately</span> form a group. Importantly, the notions of "<span class="hlt">approximate</span>" and "small" are all independent of the dimension of the ambient Hilbert space and depend only on the degeneracy in the ground space. Our analysis additionally holds for any gapped band of sufficiently small width in the excited spectrum of the Hamiltonian, and we discuss applications of these ideas to topological quantum phases of matter and topological quantum error correcting codes. Finally, in our analysis, we also provide an exponential improvement upon bounds concerning the existence of shared <span class="hlt">approximate</span> eigenvectors of <span class="hlt">approximately</span> commuting operators under an added normality constraint, which may be of independent interest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1031762','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1031762"><span>End Calorimeter Warm <span class="hlt">Tube</span> Heater</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Primdahl, K.; /Fermilab</p> <p>1991-08-06</p> <p> corresponding heat <span class="hlt">flux</span>, temperature of the nichrome wire can be estimated. The possibility of frost is of genuine concern, as evidenced by the 250 K minimum temperature for the warm <span class="hlt">tube</span> while heaters are not operating. Noting that steady state operation at 1 Amp (40 volts) allows the nichrome wire to stay below the critical temperature for Kapton, a conservative plan is to allow several days of heater operation, at 1 Amp (40 volts), before roll-back. Warm-up can be accelerated by operating the heaters in excess of 1 Amp, as evidenced by the test where a maximum of 3.2 Amp was supplied. Operating the heaters in excess of 1 Amp must be done with care since a rapid rise in temperature will likely occur once any ice present has been melted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhLB..725..218D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhLB..725..218D"><span>Inflation from <span class="hlt">flux</span> cascades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Amico, Guido; Gobbetti, Roberto; Kleban, Matthew; Schillo, Marjorie L.</p> <p>2013-10-01</p> <p>When electric-type <span class="hlt">flux</span> threads compact extra dimensions, a quantum nucleation event can break a <span class="hlt">flux</span> line and initiate a cascade that unwinds many units of <span class="hlt">flux</span>. Here, we present a novel mechanism for inflation based on this phenomenon. From the 4D point of view, the cascade begins with the formation of a bubble containing an open Friedmann-Robertson-Walker cosmology, but the vacuum energy inside the bubble is initially only slightly reduced, and subsequently decreases gradually throughout the cascade. If the initial <span class="hlt">flux</span> number Q0 ≳ O (100), during the cascade the universe can undergo N ≳ 60 efolds of inflationary expansion with gradually decreasing Hubble constant, producing a nearly scale-invariant spectrum of adiabatic density perturbations with amplitude and tilt consistent with observation, and a potentially observable level of non-Gaussianity and tensor modes. The power spectrum has a small oscillatory component that does not decay away during inflation, with a period set <span class="hlt">approximately</span> by the light-crossing time of the compact dimension(s). Since the ingredients are <span class="hlt">fluxes</span> threading compact dimensions, this mechanism fits naturally into the string landscape, but does not appear to suffer from the eta problem or require fine-tuning (beyond the usual anthropic requirement of small vacuum energy after reheating).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790010868','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790010868"><span>Application of an electron beam facility for heat transfer measurements in capillary <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lunde, A. R.; Kramer, T.</p> <p>1977-01-01</p> <p>A unique method was developed for the determination of heat transfer coefficients for water flowing through capillary <span class="hlt">tubes</span> using a rastered electron beam heater. Heat <span class="hlt">flux</span> levels of 150 and 500 watts/sq cm were provided on the top surface of four square <span class="hlt">tubes</span>. Temperature gradient along the <span class="hlt">tube</span> length and mass flow rates versus pressure drop were measured.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/619430','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/619430"><span>Determination of pollutant diffusion coefficients in naturally formed biofilms using a single <span class="hlt">tube</span> extractive membrane bioreactor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhang, S.F.; Splendiani, A.; Freitas dos Santos, L.M.; Livingston, A.G.</p> <p>1998-07-05</p> <p>A novel technique has been used to determine the effective diffusion coefficients for 1,1,2-trichloroethane (TCE), a nonreacting tracer, in biofilms growing on the external surface of a silicone rubber membrane <span class="hlt">tube</span> during degradation of 1,2-dichloroethane (DCE) by Xanthobacter autotrophicus GJ10 and monochlorobenzene (MCB) by Pseudomonas JS150. Experiments were carried out in a single <span class="hlt">tube</span> extractive membrane bioreactor (STEMB), whose configuration makes it possible to measure the transmembrane <span class="hlt">flux</span> of substrates. A video imaging technique (VIT) was employed for in situ biofilm thickness measurement and recording. Diffusion coefficients of TCE in the biofilms and TCE mass transfer coefficients in the liquid films adjacent to the biofilms were determined simultaneously using a resistances-in-series diffusion model. It was found that the <span class="hlt">flux</span> and overall mass transfer coefficient of TCE decrease with increasing biofilm thickness, showing the importance of biofilm diffusion on the mass transfer process. Similar <span class="hlt">fluxes</span> were observed for the nonreacting tracer (TCE) and the reactive substrates (MCB or DCE), suggesting that membrane-attached biofilm systems can be rate controlled primarily by substrate diffusion. The TCE diffusion coefficient in the JS150 biofilm appeared to be dependent on biofilm thickness, decreasing markedly for biofilm thicknesses of >1 mm. The values of the TCE diffusion coefficients in the JS150 biofilms <1-mm thick are <span class="hlt">approximately</span> twice those in water and fall to around 30% of the water value for biofilms >1-mm thick.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950014974','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950014974"><span>Dual Active Surface Heat <span class="hlt">Flux</span> Gage Probe</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liebert, Curt H.; Kolodziej, Paul</p> <p>1995-01-01</p> <p>A unique plug-type heat <span class="hlt">flux</span> gage probe was tested in the NASA Ames Research Center 2x9 turbulent flow duct facility. The probe was fabricated by welding a miniature dual active surface heat <span class="hlt">flux</span> gage body to the end of a hollow metal cylindrical bolt containing a metal inner <span class="hlt">tube</span>. Cooling air flows through the inner <span class="hlt">tube</span>, impinges onto the back of the gage body and then flows out through the annulus formed between the inner <span class="hlt">tube</span> and the hollow bolt wall. Heat <span class="hlt">flux</span> was generated in the duct facility with a Huels arc heater. The duct had a rectangular cross section and one wall was fabricated from 2.54 centimeter thick thermal insulation rigid surface material mounted onto an aluminum plate. To measure heat <span class="hlt">flux</span>, the probe was inserted through the plate and insulating materials with the from of the gage located flush with the hot gas-side insulation surface. Absorbed heat <span class="hlt">fluxes</span> measured with the probe were compared with absorbed heat <span class="hlt">fluxes</span> measured with six water-cooled reference calorimeters. These calorimeters were located in a water-cooled metal duct wall which was located across from the probe position. Correspondence of transient and steady heat <span class="hlt">fluxes</span> measured with the reference calorimeters and heat <span class="hlt">flux</span> gage probe was generally within a satisfactory plus or minus 10 percent. This good correspondence was achieved even though the much cooler probe caused a large surface temperature disruption of 1000K between the metal gage and the insulation. However, this temperature disruption did not seriously effect the accuracy of the heat <span class="hlt">flux</span> measurement. A current application for dual active surface heat <span class="hlt">flux</span> gages is for transient and steady absorbed heat <span class="hlt">flux</span>, surface temperature and heat transfer coefficient measurements on the surface of an oxidizer turbine inlet deflector operating in a space shuttle test bed engine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995inin.symp....7L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995inin.symp....7L"><span>Dual active surface heat <span class="hlt">flux</span> gage probe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liebert, Curt H.; Kolodziej, Paul</p> <p>1995-02-01</p> <p>A unique plug-type heat <span class="hlt">flux</span> gage probe was tested in the NASA Ames Research Center 2x9 turbulent flow duct facility. The probe was fabricated by welding a miniature dual active surface heat <span class="hlt">flux</span> gage body to the end of a hollow metal cylindrical bolt containing a metal inner <span class="hlt">tube</span>. Cooling air flows through the inner <span class="hlt">tube</span>, impinges onto the back of the gage body and then flows out through the annulus formed between the inner <span class="hlt">tube</span> and the hollow bolt wall. Heat <span class="hlt">flux</span> was generated in the duct facility with a Huels arc heater. The duct had a rectangular cross section and one wall was fabricated from 2.54 centimeter thick thermal insulation rigid surface material mounted onto an aluminum plate. To measure heat <span class="hlt">flux</span>, the probe was inserted through the plate and insulating materials with the from of the gage located flush with the hot gas-side insulation surface. Absorbed heat <span class="hlt">fluxes</span> measured with the probe were compared with absorbed heat <span class="hlt">fluxes</span> measured with six water-cooled reference calorimeters. These calorimeters were located in a water-cooled metal duct wall which was located across from the probe position. Correspondence of transient and steady heat <span class="hlt">fluxes</span> measured with the reference calorimeters and heat <span class="hlt">flux</span> gage probe was generally within a satisfactory plus or minus 10 percent. This good correspondence was achieved even though the much cooler probe caused a large surface temperature disruption of 1000K between the metal gage and the insulation. However, this temperature disruption did not seriously effect the accuracy of the heat <span class="hlt">flux</span> measurement. A current application for dual active surface heat <span class="hlt">flux</span> gages is for transient and steady absorbed heat <span class="hlt">flux</span>, surface temperature and heat transfer coefficient measurements on the surface of an oxidizer turbine inlet deflector operating in a space shuttle test bed engine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6164582','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6164582"><span>New directions in ceramic radiant <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1993-05-20</p> <p>Natural gas-fired ceramic radiant <span class="hlt">tubes</span> (CRTs) made some giant steps forward during the past five years. New heat-resistant ceramic materials developed under GRI contract by companies such as Coors Ceramics and INEX led the way. Then, under GRI sponsorship, Eclipse Combustion and Pyronics both developed ceramic single-ended recuperative radiant (SER) <span class="hlt">tube</span> assemblies suitable for high temperature applications. These ceramic <span class="hlt">tubes</span> were a step up from metallic radiant <span class="hlt">tubes</span> and could tolerate high temperatures and high heat <span class="hlt">fluxes</span>. Further, they offered substantial lifecycle cost and maintenance savings over conventional metal radiant <span class="hlt">tubes</span>. The next generation of CRT developments follows closely on the heels of the first. Responding to today's environmental concerns and tightening emissions restrictions, Eclipse Combustion and Pyronics, under GRI sponsorship, are developing low NO[sub x] SERs that offer all the advantages of their earlier <span class="hlt">tubes</span> plus reduced emissions. INEX and Coors Ceramics, again under GRI sponsorship, are working on ceramic radiant U-<span class="hlt">tubes</span> which, when perfected, can be used in larger furnaces than the SERs. This paper describes these newest developments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1215359','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1215359"><span>Analytical Modeling of a Novel Transverse <span class="hlt">Flux</span> Machine for Direct Drive Wind Turbine Applications: Preprint</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hasan, IIftekhar; Husain, Tausif; Uddin, Md Wasi; Sozer, Yilmaz; Husain; Iqbal; Muljadi, Eduard</p> <p>2015-08-24</p> <p>This paper presents a nonlinear analytical model of a novel double-sided <span class="hlt">flux</span> concentrating Transverse <span class="hlt">Flux</span> Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of <span class="hlt">flux</span> <span class="hlt">tubes</span> to predict the <span class="hlt">flux</span> paths through different parts of the machine including air gaps, permanent magnets, stator, and rotor. The two-dimensional MEC model <span class="hlt">approximates</span> the complex three-dimensional <span class="hlt">flux</span> paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry that makes it a good alternative for evaluating prospective designs of TFM compared to finite element solvers that are numerically intensive and require more computation time. A single-phase, 1-kW, 400-rpm machine is analytically modeled, and its resulting <span class="hlt">flux</span> distribution, no-load EMF, and torque are verified with finite element analysis. The results are found to be in agreement, with less than 5% error, while reducing the computation time by 25 times.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1252172','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1252172"><span>Analytical Modeling of a Novel Transverse <span class="hlt">Flux</span> Machine for Direct Drive Wind Turbine Applications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hasan, IIftekhar; Husain, Tausif; Uddin, Md Wasi; Sozer, Yilmaz; Husain, Iqbal; Muljadi, Eduard</p> <p>2015-09-02</p> <p>This paper presents a nonlinear analytical model of a novel double sided <span class="hlt">flux</span> concentrating Transverse <span class="hlt">Flux</span> Machine (TFM) based on the Magnetic Equivalent Circuit (MEC) model. The analytical model uses a series-parallel combination of <span class="hlt">flux</span> <span class="hlt">tubes</span> to predict the <span class="hlt">flux</span> paths through different parts of the machine including air gaps, permanent magnets (PM), stator, and rotor. The two-dimensional MEC model <span class="hlt">approximates</span> the complex three-dimensional <span class="hlt">flux</span> paths of the TFM and includes the effects of magnetic saturation. The model is capable of adapting to any geometry which makes it a good alternative for evaluating prospective designs of TFM as compared to finite element solvers which are numerically intensive and require more computation time. A single phase, 1 kW, 400 rpm machine is analytically modeled and its resulting <span class="hlt">flux</span> distribution, no-load EMF and torque, verified with Finite Element Analysis (FEA). The results are found to be in agreement with less than 5% error, while reducing the computation time by 25 times.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/125388','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/125388"><span>Characterization of stainless steel 304 <span class="hlt">tubing</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sunwoo, A.J.; Brooks, M.A.; Kervin, J.E.</p> <p>1995-10-16</p> <p>Earlier studies have shown that stainless steel 304 (SS304) containing martensite is susceptible to hydrogen embrittlement. This generated concern regarding the structural integrity of SS304 <span class="hlt">tubing</span> we use in the W87 pit <span class="hlt">tube</span>. During surveillance operations, the pit <span class="hlt">tube</span> undergoes a series of bending and straightening as it goes through a number of surveillance cycles. This motivated the study to characterize austenitic SS304 <span class="hlt">tubing</span> obtained from Rocky Flats. The <span class="hlt">tubes</span> continued to display structural soundness even after numerous repeated bending and straightening cycles. The minimum and maximum number of bends to failure occurred after 13 and 16 cycles, respectively. After 5 bends, both the inner and outer surfaces of the <span class="hlt">tubing</span> showed no microcracks. When the bent <span class="hlt">tubing</span> samples were pressurized and tested using deuterium at 74{degrees}C and at {<span class="hlt">approximately</span>}78{degrees}C, they failed away from the bent area. Thus deuterium embrittlement of the bent SS304 <span class="hlt">tubing</span> should not be a problem. Moreover, to increase our 95% confidence level to 5 bends, we are planning to perform at least four additional bends to failure tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950037427&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Drotation%2Bmagnetic%2Bflux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950037427&hterms=rotation+magnetic+flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Drotation%2Bmagnetic%2Bflux"><span>Dynamics of emerging active region <span class="hlt">flux</span> loops</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fan, Y.; Fisher, G. H.; Mcclymont, A. N.</p> <p>1994-01-01</p> <p>The buoyant rise of a magnetic <span class="hlt">flux</span> loop arising from a single perturbed segment of a toroidal <span class="hlt">flux</span> ring lying slightly beneath the base of the convection zone is studied by way of numerical simulations. We have considered <span class="hlt">flux</span> loop evolution assuming both solid-body rotation, and differential rotation consistent with recent results from helioseismology. Our major results are presented, and we offer some speculations on the decay of active regions, based on the results of our studies. We speculate that as plasma in the <span class="hlt">tube</span> attempts to establish hydrostatic equilibrium along the field lines after the <span class="hlt">flux</span> emergence has taken place, the <span class="hlt">tube</span> field strength at some intermediate depths below the surface becomes sufficiently small at the surface portions of the <span class="hlt">tube</span> (which have cooled and undergone convective collapse) become dynamically disconnected from those portions near the base of the convection zone. The surface proportions of the emerged <span class="hlt">flux</span> <span class="hlt">tubes</span> are then transported by motions near the photosphere, such as supergranular convection and meridional flow.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/231637','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/231637"><span>Fracture analysis of HFIR beam <span class="hlt">tube</span> caused by radiation embrittlement</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chang, S.J.</p> <p>1994-12-31</p> <p>With an attempt to estimate the neutron beam <span class="hlt">tube</span> embrittlement condition for the Oak Ridge High <span class="hlt">Flux</span> Isotope Reactor (HFIR), fracture mechanics calculations are carried out in this paper. The analysis provides some numerical result on how the <span class="hlt">tube</span> 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 <span class="hlt">tube</span> has been subjected to an extended period of irradiation. It is also calculated that buckling strength of the <span class="hlt">tube</span> is increased, not decreased, with irradiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890040236&hterms=Linguistics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DLinguistics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890040236&hterms=Linguistics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DLinguistics"><span><span class="hlt">Approximate</span> spatial reasoning</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dutta, Soumitra</p> <p>1988-01-01</p> <p>A model for <span class="hlt">approximate</span> spatial reasoning using fuzzy logic to represent the uncertainty in the environment is presented. Algorithms are developed which can be used to reason about spatial information expressed in the form of <span class="hlt">approximate</span> linguistic descriptions similar to the kind of spatial information processed by humans. Particular attention is given to static spatial reasoning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890040236&hterms=27601&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D27601','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890040236&hterms=27601&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D27601"><span><span class="hlt">Approximate</span> spatial reasoning</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dutta, Soumitra</p> <p>1988-01-01</p> <p>A model for <span class="hlt">approximate</span> spatial reasoning using fuzzy logic to represent the uncertainty in the environment is presented. Algorithms are developed which can be used to reason about spatial information expressed in the form of <span class="hlt">approximate</span> linguistic descriptions similar to the kind of spatial information processed by humans. Particular attention is given to static spatial reasoning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19710000510','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19710000510"><span>Glass <span class="hlt">tube</span> splitting tool</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Klein, J. A.; Murray, C. D.; Stein, J. A.</p> <p>1971-01-01</p> <p>Tool accurately splits glass <span class="hlt">tubing</span> so cuts are aligned 180 deg apart and reassembled <span class="hlt">tube</span> forms low pressure, gastight enclosure. Device should interest industries using cylindrical closed glass containers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/imagepages/19596.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/imagepages/19596.htm"><span>Eustachian <span class="hlt">tube</span> (image)</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... are more common in children because their eustachian <span class="hlt">tubes</span> are shorter, narrower, and more horizontal than in ... become trapped when the tissue of the eustachian <span class="hlt">tube</span> becomes swollen from colds or allergies. Bacteria trapped ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/neuraltubedefects.html','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/neuraltubedefects.html"><span>Neural <span class="hlt">Tube</span> Defects</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>Neural <span class="hlt">tube</span> defects are birth defects of the brain, spine, or spinal cord. They happen in the first month ... she is pregnant. The two most common neural <span class="hlt">tube</span> defects are spina bifida and anencephaly. In spina ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/patientinstructions/000900.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/patientinstructions/000900.htm"><span>PEG <span class="hlt">tube</span> insertion -- discharge</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... shower or bathe. Keeping the PEG-<span class="hlt">tube</span> in Place If the feeding <span class="hlt">tube</span> comes out, the stoma ... eds. Pfenninger and Fowler's Procedures for Primary Care . 3rd ed. Philadelphia, PA: Elsevier Mosby; 2011:chap 100. ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/007235.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/007235.htm"><span>Feeding <span class="hlt">tube</span> - infants</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... NG - infants Images Feeding <span class="hlt">tube</span> References Kim YS. Nasogastric and nasoenteric <span class="hlt">tube</span> insertion. In: Pfenninger JL, Fowler GC, eds. Pfenninger and Fowler's Procedures for Primary Care . 3rd ed. Philadelphia, PA: Elsevier Mosby; 2011:chap ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://medlineplus.gov/ency/article/001630.htm','NIH-MEDLINEPLUS'); return false;" href="https://medlineplus.gov/ency/article/001630.htm"><span>Eustachian <span class="hlt">tube</span> patency</span></a></p> <p><a target="_blank" href="http://medlineplus.gov/">MedlinePlus</a></p> <p></p> <p></p> <p>... refers to how much the eustachian <span class="hlt">tube</span> is open. The eustachian <span class="hlt">tube</span> runs between the middle ear and the throat. It controls the pressure behind the eardrum and middle ear space. This helps keep the middle ear free of ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5337202','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5337202"><span>A comparison of augmentation techniques during in-<span class="hlt">tube</span> evaporation of R-113</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reid, R.S. ); Pate, M.B. ); Bergles, A.E. )</p> <p>1991-05-01</p> <p>An experimental study was conducted to determine the potential of three techniques for augmenting in-<span class="hlt">tube</span> evaporation of refrigerants: high-fin <span class="hlt">tubes</span>, microfin <span class="hlt">tubes</span>, and twisted tape inserts. Five <span class="hlt">tubes</span> with internal fins and one smooth <span class="hlt">tube</span> with a twisted-tape insert were tested. Additionally, experiments were performed with two reference smooth <span class="hlt">tubes</span> having diameters similar to the maximum inside diameters of the finned <span class="hlt">tubes</span>. All experiments involved evaporating Refrigerant 113 (R-113) by direct electrical heating of the <span class="hlt">tube</span> wall. Local evaporation heat transfer coefficients were measured as a function of quality for a range of mass <span class="hlt">fluxes</span> and heat <span class="hlt">fluxes</span>. Enhancement factors were calculated by forming ratios of the heat transfer coefficient for the augmented <span class="hlt">tube</span> and a smooth <span class="hlt">tube</span> of the same maximum inside diameter. Mass <span class="hlt">fluxes</span>, pressure levels, and qualities were fixed when enhancement factors were calculated. For the internally finned <span class="hlt">tubes</span> the enhancement factors varied from 1.1 to 2.8. An internally finned <span class="hlt">tube</span> having helical spiral angles of 16 deg produced the largest enhancement of heat transfer. The <span class="hlt">tube</span> with the twisted-tape insert typically had an enhancement factor of about 1.5. Pressure gradient ratios and enhancement performance ratios are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6385107','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6385107"><span>Guide <span class="hlt">tube</span> flow diffuser</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Berringer, R.T.; Myron, D.L.</p> <p>1980-11-04</p> <p>A nuclear reactor upper internal guide <span class="hlt">tube</span> has a flow diffuser integral with its bottom end. The guide <span class="hlt">tube</span> provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide <span class="hlt">tube</span> thereby limiting the amount of coolant flow and turbulence within the guide <span class="hlt">tube</span>, thus enhancing the ease of movement of the control rods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1150327','SCIGOV-DOEDE'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1150327"><span>Microhole <span class="hlt">Tubing</span> Bending Report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/dataexplorer">DOE Data Explorer</a></p> <p>Oglesby, Ken</p> <p>2012-01-01</p> <p>A downhole <span class="hlt">tubing</span> bending study was made and is reported herein. IT contains a report and 2 excel spreadsheets to calculate <span class="hlt">tubing</span> bending and to estimate contact points of the <span class="hlt">tubing</span> to the drilled hole wall (creating a new support point).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5790229','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5790229"><span>1992 <span class="hlt">tubing</span> tables</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Not Available</p> <p>1992-01-01</p> <p>This paper is helpful to those designing oil well completions or purchasing <span class="hlt">tubing</span> with proprietary or premium connections. Tables contain specifications and application data for over 100 different <span class="hlt">tubing</span> joints, including those used with fiberglass pipe. The tables this year contain dimensional and performance data for coiled <span class="hlt">tubing</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5885134','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5885134"><span>Evaluation of commercial enhanced <span class="hlt">tubes</span> in pool boiling: Topical report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jung, C.; Bergles, A.E.</p> <p>1989-03-01</p> <p>In support of a study of shellside boiling with enhanced <span class="hlt">tubes</span>, a pool boiling apparatus was developed and used to test single <span class="hlt">tubes</span> with various structured boiling surfaces in R-113. The basic design of the <span class="hlt">tube</span>-bundle test section was carried out and certain critical design features were tested experimentally. Copper <span class="hlt">tubes</span>, 3/4 in. o.d. and 4 in. long, were selected with 1/4 in. diameter cartridge heaters. Four thermocouples were inserted in 3/32 in. diameter, 2 in. long holes. The pool boiling characteristics of a plain <span class="hlt">tube</span> agree well with previous tests. Wolverine Turbo-B <span class="hlt">tubes</span> with small, medium, and large features performed identically for a heat <span class="hlt">flux</span> greater than 20 kW/m/sup 2/. For lower heat <span class="hlt">flux</span>, however, the Turbo-B S was slightly superior. In general, the Wolverine Turbo-B <span class="hlt">tubes</span> had more favorable boiling characteristics than the single Wieland Gewa-T <span class="hlt">tube</span> that was tested. The test procedure is deemed entirely adequate for screening enhanced <span class="hlt">tubes</span> to see which ones should be used in the <span class="hlt">tube</span>-bundle test section. Three different ways of mounting the <span class="hlt">tubes</span> were tested in R-113 at 65/degree/C and 5 bar gage pressure. As all three constructions sealed well, the simplest design is recommended in which a snap ring fixes the <span class="hlt">tube</span> to the wall and an O-ring seals against the pressure. The general design features of the <span class="hlt">tube</span> bundle test chamber are also presented. 14 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10176556','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10176556"><span>Enhanced shell-and-<span class="hlt">tube</span> heat eschangers for the power and process industries. Final report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bergles, A.E.; Jensen, M.K.; Somerscales, E.F.; Curcio, L.A. Jr.; Trewin, R.R.</p> <p>1994-08-01</p> <p>Single-<span class="hlt">tube</span> pool boiling tests were performed with saturated pure refrigerants and binary mixtures of refrigerants. Generally, with pure refrigerants, the High <span class="hlt">Flux</span> surface performed better at the higher heat <span class="hlt">fluxes</span> compared to the Turbo-B <span class="hlt">tube</span>, and both enhanced surfaces performed significantly better than smooth surface. In tests of R-11/R-113 mixtures, the enhanced surfaces had much less degradation in heat transfer coefficient due to mixture effects compared to smooth <span class="hlt">tubes</span>; the largest degradation occurred at a mixture of 25% R-11/75% R-113. Under boiling in saturated aqueous solution of calcium sulfate, with a single <span class="hlt">tube</span>, effects of fouling were more pronounced at the higher heat <span class="hlt">fluxes</span> for all surfaces. Two staggered <span class="hlt">tube</span> bundles were tested with <span class="hlt">tube</span> pitch-diameter ratios of 1.17 and 1.50. For the pure refrigerant, tests on the smooth-<span class="hlt">tube</span> bundle indicated that the effects on the heat transfer coefficient of varying mass <span class="hlt">flux</span>, quality, and <span class="hlt">tube</span>-bundle geometry were small, except at low heat <span class="hlt">fluxes</span>. Neither enhanced surface showed any effect with changing mass <span class="hlt">flux</span> or quality. The binary mixture bundle-boiling tests had results that were very similar to those obtained with the pure refrigerants. When boiling a refrigerant-oil mixture, all three surfaces (smooth, High <span class="hlt">Flux</span>, and Turbo-B) experienced a degradation in its heat transfer coefficient; no surface studied was found to be immune or vulnerable to the presence of oil than another surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM44A..09F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM44A..09F"><span>How Much <span class="hlt">Flux</span> does a <span class="hlt">Flux</span> Transfer Event Transfer?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fear, R. C.; Trenchi, L.; Coxon, J.; Milan, S. E.</p> <p>2016-12-01</p> <p><span class="hlt">Flux</span> transfer events are bursts of reconnection at the dayside magnetopause, which give rise to characteristic signatures that are observed by a range of magnetospheric/ionospheric instrumentation. Spacecraft situated near the magnetopause observe a bipolar variation in the component of the magnetic field normal to the magnetopause (BN); auroral instrumentation (either ground- or space-based) observe poleward moving auroral forms which indicate the convection of newly-opened <span class="hlt">flux</span> into the polar cap, and ionospheric radars similarly observe pulsed ionospheric flows or poleward moving radar auroral forms. One outstanding problem is the fact that there is a fundamental mismatch between the estimates of the <span class="hlt">flux</span> that is opened by each <span class="hlt">flux</span> transfer event - in other words, their overall significance in the Dungey cycle. Spacecraft-based estimates of the <span class="hlt">flux</span> content of individual FTEs correspond to each event transferring <span class="hlt">flux</span> equivalent to <span class="hlt">approximately</span> 1% of the open <span class="hlt">flux</span> in the magnetosphere, whereas studies based on global-scale radar and auroral observations suggest this figure could be more like 10%. In the former case, <span class="hlt">flux</span> transfer events would be a minor detail in the Dungey cycle, but in the latter they could be its main driver. We present observations of a conjunction between <span class="hlt">flux</span> transfer event signatures observed by the Cluster spacecraft, and pulsed ionospheric flows observed by the SuperDARN network on the 8th February 2002. Over the course of an hour, a similar number of FTE signatures were observed by Cluster (at 13 MLT) and the Prince George radar (at 7 MLT). We argue that the reason for the existing mismatch in <span class="hlt">flux</span> estimates is that implicit assumptions about <span class="hlt">flux</span> transfer event structure lead to a major underestimate of the <span class="hlt">flux</span> content based on spacecraft observations. If these assumptions are removed, a much better match is found.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920051839&hterms=bending+tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbending%2Btube','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920051839&hterms=bending+tube&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dbending%2Btube"><span>Collapse of composite <span class="hlt">tubes</span> under end moments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stockwell, Alan E.; Cooper, Paul A.</p> <p>1992-01-01</p> <p>The Reissner (1959) <span class="hlt">approximate</span> closed-form solution of the collapse of isotropic <span class="hlt">tubes</span> subject to end moments is presently extended to encompass specially orthotropic material. This closed-form solution is verified via extensive nonlinear FEM analysis of the collapse of long <span class="hlt">tubes</span> under applied end-moments; the radius/thickness value and composite layup ranges are representative of space-station truss framework designs. The FEM analysis validates the assumption of an inextensional deformation of the cylindrical cross-section, as well as the <span class="hlt">approximation</span> of the material as specially orthotropic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title21-vol8/pdf/CFR-2013-title21-vol8-sec868-5800.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title21-vol8/pdf/CFR-2013-title21-vol8-sec868-5800.pdf"><span>21 CFR 868.5800 - Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a></p> <p></p> <p>2013-04-01</p> <p>... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff. 868.5800 Section... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5800 Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff. (a) Identification. A tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff is a device intended to be placed into...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2014-title21-vol8/pdf/CFR-2014-title21-vol8-sec868-5800.pdf','CFR2014'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2014-title21-vol8/pdf/CFR-2014-title21-vol8-sec868-5800.pdf"><span>21 CFR 868.5800 - Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2014&page.go=Go">Code of Federal Regulations, 2014 CFR</a></p> <p></p> <p>2014-04-01</p> <p>... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff. 868.5800 Section... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5800 Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff. (a) Identification. A tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff is a device intended to be placed into...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol8/pdf/CFR-2012-title21-vol8-sec868-5800.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title21-vol8/pdf/CFR-2012-title21-vol8-sec868-5800.pdf"><span>21 CFR 868.5800 - Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff.</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a></p> <p></p> <p>2012-04-01</p> <p>... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff. 868.5800 Section... (CONTINUED) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Therapeutic Devices § 868.5800 Tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff. (a) Identification. A tracheostomy <span class="hlt">tube</span> and <span class="hlt">tube</span> cuff is a device intended to be placed into...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20843288','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20843288"><span>Two-phase frictional pressure drop of R-134a and R-410A refrigerant-oil mixtures in straight <span class="hlt">tubes</span> and U-type wavy <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chen, Ing Youn; Wu, Yu-Shi; Chang, Yu-Juei; Wang, Chi-Chuan</p> <p>2007-02-15</p> <p>This study presents single-phase and two-phase pressure drop data for R-134a/oil mixture flowing in a wavy <span class="hlt">tube</span> with inner diameter of D=5.07mm and curvature ratio 2R/D=5.18 and R-410A/oil mixture flowing in a wavy <span class="hlt">tube</span> of D=3.25mm and 2R/D=3.91. Both mixtures have oil concentration C=0%, 1%, 3% and 5% for the tests. The ratio of frictional factor between U-bend in wavy <span class="hlt">tube</span> and straight <span class="hlt">tube</span> (f{sub C}/f{sub S}) is about 3.5 for Re<2500 and is <span class="hlt">approximate</span> 2.5 for Re=3500-25,000 for oil and liquid R-134a mixture flowing in the 5.07mm diameter wavy <span class="hlt">tube</span>. The influence of oil concentration on single-phase friction factor is negligible, provided that the properties are based on the mixture of lubricant and refrigerant. The ratio between two-phase pressure gradients of U-bend and straight <span class="hlt">tube</span> is about 2.5-3.5. This ratio is increased with oil concentration and vapor quality. The influence of oil is augmented at a higher mass <span class="hlt">flux</span> for liquid spreading around the periphery at an annular flow pattern. Moreover, the influence of lubricant becomes more evident of a U-bend configuration. This is associated the induced swirled flow motion and an early change of flow pattern from stratified to annular flow pattern. The frictional two-phase multiplier for straight <span class="hlt">tube</span> can be fairly correlated by using the Chisholm correlation for the data having Martinelli parameter X between 0.05 and 1.0. Fridel correlation also shows a good agreement with a mean deviation of 17.6% to all the straight <span class="hlt">tube</span> data. For the two-phase pressure drop in U-bend, the revised Geary correlation agrees very well with the R-134a and R-410A oil-refrigerant data with a mean deviation of 16.4%. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA158265','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA158265"><span>Intrinsic Nilpotent <span class="hlt">Approximation</span>.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1985-06-01</p> <p>RD-A1II58 265 INTRINSIC NILPOTENT <span class="hlt">APPROXIMATION</span>(U) MASSACHUSETTS INST 1/2 OF TECH CAMBRIDGE LAB FOR INFORMATION AND, DECISION UMCLRSSI SYSTEMS C...TYPE OF REPORT & PERIOD COVERED Intrinsic Nilpotent <span class="hlt">Approximation</span> Technical Report 6. PERFORMING ORG. REPORT NUMBER LIDS-R-1482 7. AUTHOR(.) S...certain infinite-dimensional filtered Lie algebras L by (finite-dimensional) graded nilpotent Lie algebras or g . where x E M, (x,,Z) E T*M/O. It</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998AtmRe..49...77V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998AtmRe..49...77V"><span>Anomalous diffraction <span class="hlt">approximation</span> limits</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Videen, Gorden; Chýlek, Petr</p> <p></p> <p>It has been reported in a recent article [Liu, C., Jonas, P.R., Saunders, C.P.R., 1996. Accuracy of the anomalous diffraction <span class="hlt">approximation</span> to light scattering by column-like ice crystals. Atmos. Res., 41, pp. 63-69] that the anomalous diffraction <span class="hlt">approximation</span> (ADA) accuracy does not depend on particle refractive index, but instead is dependent on the particle size parameter. Since this is at odds with previous research, we thought these results warranted further discussion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4282086','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4282086"><span>REACTOR COOLANT <span class="hlt">TUBE</span> SEAL</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Morris, W.J.</p> <p>1958-12-01</p> <p>A plle-flattenlng control element and a fluid seal therefore to permit movement of the element into a liquld contnining region of a neutronlc reactor are described. The device consists of flattened, thin-walled aluminum <span class="hlt">tubing</span> contalnlng a uniform mixture of thermal neutron absorbing material, and a number of soft rubber closures for the process <span class="hlt">tubes</span>, having silts capable of passing the flattened elements therethrough, but effectively sealing the process <span class="hlt">tubes</span> against fluld leaknge by compression of the rubber. The flattened <span class="hlt">tubing</span> is sufficiently flexible to enable it to conform to the configuratlon of the annular spacing surrounding the fuel elements ln the process <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080004743','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080004743"><span>Telescoping <span class="hlt">tube</span> assembly</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sturm, Albert J. (Inventor); Marrinan, Thomas E. (Inventor)</p> <p>1995-01-01</p> <p>An extensible and retractable telescoping <span class="hlt">tube</span> positions test devices that inspect large stationary objects. The <span class="hlt">tube</span> has three dimensional adjustment capabilities and is vertically suspended from a frame. The <span class="hlt">tube</span> sections are independently supported with each section comprising U-shaped housing secured to a thicker support plate. Guide mechanisms preferably mounted only to the thicker plates guide each <span class="hlt">tube</span> section parallel to a reference axis with improved accuracy so that the position of the remote end of the telescoping <span class="hlt">tube</span> is precisely known.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20734260','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20734260"><span>Pollen <span class="hlt">tube</span> development.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Johnson, Mark A; Kost, Benedikt</p> <p>2010-01-01</p> <p>Pollen <span class="hlt">tubes</span> grow rapidly in a strictly polarized manner as they transport male reproductive cells through female flower tissues to bring about fertilization. Vegetative pollen <span class="hlt">tube</span> cells are an excellent model system to investigate processes underlying directional cell expansion. In this chapter, we describe materials and methods required for (1) the identification of novel factors essential for polarized cell growth through the isolation and analysis of Arabidopsis mutants with defects in pollen <span class="hlt">tube</span> growth and (2) the detailed functional characterization of pollen <span class="hlt">tube</span> proteins based on transient transformation and microscopic analysis of cultured tobacco pollen <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890006192&hterms=mathematical+reasoning&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmathematical%2Breasoning','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890006192&hterms=mathematical+reasoning&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmathematical%2Breasoning"><span><span class="hlt">Approximate</span> spatial reasoning</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dutta, Soumitra</p> <p>1988-01-01</p> <p>Much of human reasoning is <span class="hlt">approximate</span> in nature. Formal models of reasoning traditionally try to be precise and reject the fuzziness of concepts in natural use and replace them with non-fuzzy scientific explicata by a process of precisiation. As an alternate to this approach, it has been suggested that rather than regard human reasoning processes as themselves <span class="hlt">approximating</span> to some more refined and exact logical process that can be carried out with mathematical precision, the essence and power of human reasoning is in its capability to grasp and use inexact concepts directly. This view is supported by the widespread fuzziness of simple everyday terms (e.g., near tall) and the complexity of ordinary tasks (e.g., cleaning a room). Spatial reasoning is an area where humans consistently reason <span class="hlt">approximately</span> with demonstrably good results. Consider the case of crossing a traffic intersection. We have only an <span class="hlt">approximate</span> idea of the locations and speeds of various obstacles (e.g., persons and vehicles), but we nevertheless manage to cross such traffic intersections without any harm. The details of our mental processes which enable us to carry out such intricate tasks in such apparently simple manner are not well understood. However, it is that we try to incorporate such <span class="hlt">approximate</span> reasoning techniques in our computer systems. <span class="hlt">Approximate</span> spatial reasoning is very important for intelligent mobile agents (e.g., robots), specially for those operating in uncertain or unknown or dynamic domains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25528318','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25528318"><span><span class="hlt">Approximate</span> kernel competitive learning.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wu, Jian-Sheng; Zheng, Wei-Shi; Lai, Jian-Huang</p> <p>2015-03-01</p> <p>Kernel competitive learning has been successfully used to achieve robust clustering. However, kernel competitive learning (KCL) is not scalable for large scale data processing, because (1) it has to calculate and store the full kernel matrix that is too large to be calculated and kept in the memory and (2) it cannot be computed in parallel. In this paper we develop a framework of <span class="hlt">approximate</span> kernel competitive learning for processing large scale dataset. The proposed framework consists of two parts. First, it derives an <span class="hlt">approximate</span> kernel competitive learning (AKCL), which learns kernel competitive learning in a subspace via sampling. We provide solid theoretical analysis on why the proposed <span class="hlt">approximation</span> modelling would work for kernel competitive learning, and furthermore, we show that the computational complexity of AKCL is largely reduced. Second, we propose a pseudo-parallelled <span class="hlt">approximate</span> kernel competitive learning (PAKCL) based on a set-based kernel competitive learning strategy, which overcomes the obstacle of using parallel programming in kernel competitive learning and significantly accelerates the <span class="hlt">approximate</span> kernel competitive learning for large scale clustering. The empirical evaluation on publicly available datasets shows that the proposed AKCL and PAKCL can perform comparably as KCL, with a large reduction on computational cost. Also, the proposed methods achieve more effective clustering performance in terms of clustering precision against related <span class="hlt">approximate</span> clustering approaches.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910012160','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910012160"><span>Heat <span class="hlt">tube</span> device</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Khattar, Mukesh K. (Inventor)</p> <p>1990-01-01</p> <p>The present invention discloses a heat <span class="hlt">tube</span> device through which a working fluid can be circulated to transfer heat to air in a conventional air conditioning system. The heat <span class="hlt">tube</span> device is disposable about a conventional cooling coil of the air conditioning system and includes a plurality of substantially U-shaped <span class="hlt">tubes</span> connected to a support structure. The support structure includes members for allowing the heat <span class="hlt">tube</span> device to be readily positioned about the cooling coil. An actuatable adjustment device is connected to the U-shaped <span class="hlt">tubes</span> for allowing, upon actuation thereof, for the heat <span class="hlt">tubes</span> to be simultaneously rotated relative to the cooling coil for allowing the heat transfer from the heat <span class="hlt">tube</span> device to air in the air conditioning system to be selectively varied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4971991','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4971991"><span>Intercostal drainage <span class="hlt">tube</span> or intracardiac drainage <span class="hlt">tube</span>?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Anitha, N.; Kamath, S. Ganesh; Khymdeit, Edison; Prabhu, Manjunath</p> <p>2016-01-01</p> <p>Although insertion of chest drain <span class="hlt">tubes</span> is a common medical practice, there are risks associated with this procedure, especially when inexperienced physicians perform it. Wrong insertion of the <span class="hlt">tube</span> 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. PMID:27397467</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27735061','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27735061"><span>Spallation of Small Particles From Peristaltic Pump <span class="hlt">Tube</span> Segments.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Yi; Faria, Monica; Leonard, Edward</p> <p>2017-07-01</p> <p>In most extracorporeal filtration devices such as hemodialysis a peristaltic pump is used to circulate blood. Pump function requires the repeated compression of an elastomeric <span class="hlt">tube</span> from which particles may be shed into the circulatory system, a process called spallation. Earlier studies are likely to have missed the large number of small particles (<2 µm in diameter) that appear. The present study uses more modern equipment that detects and sizes particles down to 0.6 µm. As polyvinyl chloride (PVC) <span class="hlt">tubing</span> is commonly used for this process, a series of studies was conducted on three different types to study its spallation characteristics, along with a co-extruded PVC/polyurethane <span class="hlt">tubing</span> known for its enhanced biocompatibility properties. For all types of PVC <span class="hlt">tubes</span>, the average size of the spallated particles was 0.83 ± 0.03 µm; for the PVC/polyurethane <span class="hlt">tubing</span> the average size of the spallated particles was <span class="hlt">approximately</span> twice that reported for PVC <span class="hlt">tubing</span>. For PVC <span class="hlt">tubes</span> with equal inner diameter, those with less plasticizer released fewer particles; for <span class="hlt">tubes</span> with the same Shore hardness, <span class="hlt">tubes</span> with larger internal diameters released fewer particles. It was also shown that PVC <span class="hlt">tubes</span> operating at a slower flow rate does not reduce the total number of particles released per volume pumped. The total number of particles spallated from the PVC/polyurethane <span class="hlt">tubing</span> was 10 times lower than from the lowest spallating PVC <span class="hlt">tubing</span>. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6302499','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6302499"><span>Inspection of irradiated P-7 fuel <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Peacock, H.B.; Sturcken, E.F.</p> <p>1980-08-20</p> <p>Mark 16 U-A1 alloy production fuel <span class="hlt">tubes</span> and six special U{sub 3}O{sub 8}-A1 powder metallurgy (PM) test assemblies were successfully irradiated in P-7 reactor charge beginning December 1976. A year after irradiation, the outer surfaces were inspected under water in P-Area basin. Inspection showed that a black'' oxide had formed on the bottom {sup {<span class="hlt">approximately</span>}}2/3 and flaked off in some areas for both the production and PM <span class="hlt">tubes</span>. A small cladding defect was also observed on one PM outer <span class="hlt">tube</span> near the bottom. Sections were cut from the <span class="hlt">tubes</span> and metallographically examined in the SRL High Level Caves (HLC). This report gives results of the examinations. 8 refs., 9 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21278853','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21278853"><span>Quasistatic Modeling of Concentric <span class="hlt">Tube</span> Robots with External Loads.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lock, Jesse; Laing, Genevieve; Mahvash, Mohsen; Dupont, Pierre E</p> <p>2010-12-03</p> <p>Concentric <span class="hlt">tube</span> robots are a subset of continuum robots constructed by combining pre-curved elastic <span class="hlt">tubes</span>. As the <span class="hlt">tubes</span> are rotated and translated with respect to each other, their curvatures interact elastically, enabling control of the robot's tip configuration as well as the curvature along its length. This technology is projected to be useful in many types of minimally invasive medical procedures. Because these robots are flexible by design, they deflect considerably when applying forces to the external environment. Thus, in contrast to rigid-link robots, their kinematic and static force models are coupled. This paper derives a multi-<span class="hlt">tube</span> quasistatic model that relates <span class="hlt">tube</span> rotations and translations together with externally applied loads to robot shape and tip configuration. The model can be applied in robot design, procedure planning as well as control. For validation, the multi-<span class="hlt">tube</span> model is compared experimentally to a computationally-efficient single-<span class="hlt">tube</span> <span class="hlt">approximate</span> model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3028209','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3028209"><span>Quasistatic Modeling of Concentric <span class="hlt">Tube</span> Robots with External Loads</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lock, Jesse; Laing, Genevieve; Mahvash, Mohsen; Dupont, Pierre E.</p> <p>2010-01-01</p> <p>Concentric <span class="hlt">tube</span> robots are a subset of continuum robots constructed by combining pre-curved elastic <span class="hlt">tubes</span>. As the <span class="hlt">tubes</span> are rotated and translated with respect to each other, their curvatures interact elastically, enabling control of the robot's tip configuration as well as the curvature along its length. This technology is projected to be useful in many types of minimally invasive medical procedures. Because these robots are flexible by design, they deflect considerably when applying forces to the external environment. Thus, in contrast to rigid-link robots, their kinematic and static force models are coupled. This paper derives a multi-<span class="hlt">tube</span> quasistatic model that relates <span class="hlt">tube</span> rotations and translations together with externally applied loads to robot shape and tip configuration. The model can be applied in robot design, procedure planning as well as control. For validation, the multi-<span class="hlt">tube</span> model is compared experimentally to a computationally-efficient single-<span class="hlt">tube</span> <span class="hlt">approximate</span> model. PMID:21278853</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..91k4511S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..91k4511S"><span>Covariant <span class="hlt">approximation</span> averaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shintani, Eigo; Arthur, Rudy; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph</p> <p>2015-06-01</p> <p>We present a new class of statistical error reduction techniques for Monte Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive <span class="hlt">approximations</span> without introducing any systematic bias in the final result. We introduce a new class of covariant <span class="hlt">approximation</span> averaging techniques, known as all-mode averaging (AMA), in which the <span class="hlt">approximation</span> takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in Nf=2 +1 lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte Carlo calculations over conventional methods for the same cost.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22341971','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22341971"><span>Simulations of emerging magnetic <span class="hlt">flux</span>. I. The formation of stable coronal <span class="hlt">flux</span> ropes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Leake, James E.; Linton, Mark G.; Török, Tibor</p> <p>2013-12-01</p> <p>We present results from three-dimensional visco-resistive magnetohydrodynamic simulations of the emergence of a convection zone magnetic <span class="hlt">flux</span> <span class="hlt">tube</span> into a solar atmosphere containing a pre-existing dipole coronal field, which is orientated to minimize reconnection with the emerging field. We observe that the emergence process is capable of producing a coronal <span class="hlt">flux</span> rope by the transfer of twist from the convection zone, as found in previous simulations. We find that this <span class="hlt">flux</span> rope is stable, with no evidence of a fast rise, and that its ultimate height in the corona is determined by the strength of the pre-existing dipole field. We also find that although the electric currents in the initial convection zone <span class="hlt">flux</span> <span class="hlt">tube</span> are almost perfectly neutralized, the resultant coronal <span class="hlt">flux</span> rope carries a significant net current. These results suggest that <span class="hlt">flux</span> <span class="hlt">tube</span> emergence is capable of creating non-current-neutralized stable <span class="hlt">flux</span> ropes in the corona, tethered by overlying potential fields, a magnetic configuration that is believed to be the source of coronal mass ejections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TRACE..11...89M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TRACE..11...89M"><span>Pulse <span class="hlt">Tube</span> Refrigerator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsubara, Yoichi</p> <p></p> <p>The pulse <span class="hlt">tube</span> refrigerator is one of the regenerative cycle refrigerators such as Stirling cycle or Gifford-McMahon cycle which gives the cooling temperature below 150 K down to liquid helium temperature. In 1963, W. E. Gifford invented a simple refrigeration cycle which is composed of compressor, regenerator and simple <span class="hlt">tube</span> named as pulse <span class="hlt">tube</span> which gives a similar function of the expander in Stirling or Gifford-McMahon cycle. The thermodynamically performance of this pulse <span class="hlt">tube</span> refrigerator is inferior to that of other regenerative cycles. In 1984, however, Mikulin and coworkers made a significant advance in pulse <span class="hlt">tube</span> configuration called as orifice pulse <span class="hlt">tube</span>. After this, several modifications of the pulse <span class="hlt">tube</span> hot end configuration have been developed. With those modifications, the thermodynamic performance of the pulse <span class="hlt">tube</span> refrigerator became the same order to that of Stirling and Gifford-McMahon refrigerator. This article reviews the brief history of the pulse <span class="hlt">tube</span> refrigerator development in the view point of its thermodynamically efficiency. Simplified theories of the energy flow in the pulse <span class="hlt">tube</span> have also been described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2273317C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2273317C"><span><span class="hlt">Approximate</span> Bayesian Computation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cisewski, Jessi</p> <p>2015-08-01</p> <p>Explicitly specifying a likelihood function is becoming increasingly difficult for many problems in astronomy. Astronomers often specify a simpler <span class="hlt">approximate</span> likelihood - leaving out important aspects of a more realistic model. <span class="hlt">Approximate</span> Bayesian computation (ABC) provides a framework for performing inference in cases where the likelihood is not available or intractable. I will introduce ABC and explain how it can be a useful tool for astronomers. In particular, I will focus on the eccentricity distribution for a sample of exoplanets with multiple sub-populations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/672075','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/672075"><span>Multicriteria <span class="hlt">approximation</span> through decomposition</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Burch, C.; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E.</p> <p>1998-06-01</p> <p>The authors propose a general technique called solution decomposition to devise <span class="hlt">approximation</span> algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of their technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic <span class="hlt">approximation</span> algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. Their method yields as corollaries unified solutions to a number of well studied problems and it provides the first <span class="hlt">approximation</span> algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) the authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing; (2) they also show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria <span class="hlt">approximation</span> algorithms for problems including the k-Hurdle and the Network Inhibition problems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/642754','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/642754"><span>Multicriteria <span class="hlt">approximation</span> through decomposition</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Burch, C. |; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E. |</p> <p>1997-12-01</p> <p>The authors propose a general technique called solution decomposition to devise <span class="hlt">approximation</span> algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of the technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic <span class="hlt">approximation</span> algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. The method yields as corollaries unified solutions to a number of well studied problems and it provides the first <span class="hlt">approximation</span> algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) The authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing. (2) They show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria <span class="hlt">approximation</span> algorithms for problems including the k-Hurdle and the Network Inhibition problems.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED051258.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED051258.pdf"><span>On Stochastic <span class="hlt">Approximation</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Wolff, Hans</p> <p></p> <p>This paper deals with a stochastic process for the <span class="hlt">approximation</span> of the root of a regression equation. This process was first suggested by Robbins and Monro. The main result here is a necessary and sufficient condition on the iteration coefficients for convergence of the process (convergence with probability one and convergence in the quadratic…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=visual+AND+basic&pg=3&id=EJ769566','ERIC'); return false;" href="https://eric.ed.gov/?q=visual+AND+basic&pg=3&id=EJ769566"><span><span class="hlt">Approximating</span> Integrals Using Probability</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maruszewski, Richard F., Jr.; Caudle, Kyle A.</p> <p>2005-01-01</p> <p>As part of a discussion on Monte Carlo methods, which outlines how to use probability expectations to <span class="hlt">approximate</span> the value of a definite integral. The purpose of this paper is to elaborate on this technique and then to show several examples using visual basic as a programming tool. It is an interesting method because it combines two branches of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=%22Visual+basic%22&pg=2&id=EJ769566','ERIC'); return false;" href="http://eric.ed.gov/?q=%22Visual+basic%22&pg=2&id=EJ769566"><span><span class="hlt">Approximating</span> Integrals Using Probability</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maruszewski, Richard F., Jr.; Caudle, Kyle A.</p> <p>2005-01-01</p> <p>As part of a discussion on Monte Carlo methods, which outlines how to use probability expectations to <span class="hlt">approximate</span> the value of a definite integral. The purpose of this paper is to elaborate on this technique and then to show several examples using visual basic as a programming tool. It is an interesting method because it combines two branches of…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930008081','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930008081"><span>Lunar Lava <span class="hlt">Tube</span> Sensing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>York, Cheryl Lynn; Walden, Bryce; Billings, Thomas L.; Reeder, P. Douglas</p> <p>1992-01-01</p> <p>Large (greater than 300 m diameter) lava <span class="hlt">tube</span> 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 <span class="hlt">tube</span> 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 <span class="hlt">tube</span> caverns can be incorporated into current precursor lunar mission plans. Some searches can even be done from Earth. Specific recommendations for lunar lava <span class="hlt">tube</span> search and exploration are (1) an Earth-based radar interferometer, (2) an Earth-penetrating radar (EPR) orbiter, (3) kinetic penetrators for lunar lava <span class="hlt">tube</span> confirmation, (4) a 'Moon Bat' hovering rocket vehicle, and (5) the use of other proposed landers and orbiters to help find lunar lava <span class="hlt">tubes</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740026673&hterms=Hawaiian+island+formation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DHawaiian%2Bisland%2Bformation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740026673&hterms=Hawaiian+island+formation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DHawaiian%2Bisland%2Bformation"><span>Kaumana lava <span class="hlt">tube</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greeley, R.</p> <p>1974-01-01</p> <p>The entrance to Kaumana Lava <span class="hlt">Tube</span> is in a picnic ground next to Highway 20 (Kaumana Drive) about 6.5 km southwest of Hilo. The area is passed on the way to the Kona Coast via the Saddle Road and is identified by a Hawaii Visitors Bureau sign. Although it is not the largest lava <span class="hlt">tube</span> in the islands, Kaumana Lava <span class="hlt">Tube</span> is an interesting geological formation, displaying many of the features typical of lava <span class="hlt">tube</span> interiors. It is accessible, relatively easy to walk through, and is in an excellent state of preservation. The <span class="hlt">tube</span> developed in a historic lava flow (1881, from Mauna Loa), and many aspects of lava <span class="hlt">tube</span> activity are observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993SPIE.1997..328I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993SPIE.1997..328I"><span>Critical heat <span class="hlt">flux</span> of subcooled flow boiling with water for high heat <span class="hlt">flux</span> application</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inasaka, Fujio; Nariai, Hideki</p> <p>1993-11-01</p> <p>Subcooled flow boiling in water is thought to be advantageous in removing high heat load of more than 10 MW/m2. Characteristics of the critical heat <span class="hlt">flux</span> (CHF), which determines the upper limit of heat removal, are very important for the design of cooling systems. In this paper, studies on subcooled flow boiling CHF, which have been conducted by the authors, are reported. Experiments were conducted using direct current heating of stainless steel <span class="hlt">tube</span>. For uniform heating conditions, CHF increment in small diameter <span class="hlt">tubes</span> (1 - 3 mm inside diameter) and the CHF characteristics in <span class="hlt">tubes</span> with internal twisted tapes were investigated, and also the existing CHF correlations for ordinary <span class="hlt">tubes</span> (more than 3 mm inside diameter) were evaluated. For peripherally non-uniform heating conditions using the <span class="hlt">tube</span>, whose wall thickness was partly reduced, the CHF for swirl flow was higher than the CHF under uniform heating conditions with an increase of the non-uniformity factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820007424','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820007424"><span>Ruggedized electronographic <span class="hlt">tube</span> development</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nevin, S.</p> <p>1981-01-01</p> <p>Because of their glass components and lack of far ultraviolet sensitivity, currently available Spectracons are not suited for rocket launch. Technology developed for second generation image <span class="hlt">tubes</span> and for magnetically focused image <span class="hlt">tubes</span> can be applied to improve the optical and mechanical properties of these magnetically focused electronographic <span class="hlt">tubes</span> whose 40 kilovolt signal electrons exit a 4-micrometer thick mica window and penetrate a photographic recording emulsion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4770999','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4770999"><span>COAXIAL <span class="hlt">TUBE</span> COUPLING</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Niemoth, H.R.</p> <p>1963-02-26</p> <p>BS>This patent shows a device for quickly coupling coaxial <span class="hlt">tubes</span> in metal-to-metal fashion, so as to be suitable for use in a nuclear reactor. A threaded coliar urges a tapered metal extension on the outer coaxial <span class="hlt">tube</span> into a tapered seat in the device and simultaneously exerts pressure through a coaxial helical spring so that a similar extension on the inner <span class="hlt">tube</span> seats in a similar seat near the other end. (AEC)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/4037526','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/4037526"><span><span class="hlt">TUBE</span> SPLITTING APPARATUS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Frantz, C.E.; Cawley, W.E.</p> <p>1961-05-01</p> <p>A tool is described for cutting a coolant <span class="hlt">tube</span> adapted to contain fuel elements to enable the <span class="hlt">tube</span> to be removed from a graphite moderator mass. The tool splits the <span class="hlt">tube</span> longitudinally into halves and curls the longitudinal edges of the halves inwardly so that they occupy less space and can be moved radially inwardly away from the walls of the hole in the graphite for easy removal from the graphite.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18687961','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18687961"><span>Programming DNA <span class="hlt">tube</span> circumferences.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yin, Peng; Hariadi, Rizal F; Sahu, Sudheer; Choi, Harry M T; Park, Sung Ha; Labean, Thomas H; Reif, John H</p> <p>2008-08-08</p> <p>Synthesizing molecular <span class="hlt">tubes</span> with monodisperse, programmable circumferences is an important goal shared by nanotechnology, materials science, and supermolecular chemistry. We program molecular <span class="hlt">tube</span> circumferences by specifying the complementarity relationships between modular domains in a 42-base single-stranded DNA motif. Single-step annealing results in the self-assembly of long <span class="hlt">tubes</span> displaying monodisperse circumferences of 4, 5, 6, 7, 8, 10, or 20 DNA helices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/233971','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/233971"><span><span class="hlt">Tubing</span> weld cracking test</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lundin, C.D.; Qiao, C.Y.P.</p> <p>1995-12-31</p> <p>A <span class="hlt">tubing</span> weld cracking (TWC) test was developed for applications involving advanced austenitic alloys (such as modified 800H and 310HCbN). Compared to the Finger hot cracking test, the TWC test shows an enhanced ability to evaluate the crack sensitivity of <span class="hlt">tubing</span> materials. The TWC test can evaluate the cracking tendency of base as well as filter materials. Thus, it is a useful tool for <span class="hlt">tubing</span> suppliers, filler metal producers and fabricators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/865270','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/865270"><span>Conduction cooled <span class="hlt">tube</span> supports</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Worley, Arthur C.; Becht, IV, Charles</p> <p>1984-01-01</p> <p>In boilers, process <span class="hlt">tubes</span> are suspended by means of support studs that are in thermal contact with and attached to the metal roof casing of the boiler and the upper bend portions of the process <span class="hlt">tubes</span>. The support studs are sufficiently short that when the boiler is in use, the support studs are cooled by conduction of heat to the process <span class="hlt">tubes</span> and the roof casing thereby maintaining the temperature of the stud so that it does not exceed 1400.degree. F.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800000277&hterms=welder&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwelder','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800000277&hterms=welder&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwelder"><span><span class="hlt">Tube</span>-welder aids</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weaver, J. F.</p> <p>1980-01-01</p> <p>Simple tools assist in setting up and welding <span class="hlt">tubes</span>. Welder aids can be easily made to fit given <span class="hlt">tube</span> diameter. Finished set can be used repeatedly to fix electrode-to-weld gap and mark sleeve and joint positions. Tools are readily made in <span class="hlt">tube</span>-manufacturing plants and pay for themselves in short time in reduced labor costs and quality control: Conventional measurements are too slow for mass production and are prone to errors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25614839','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25614839"><span>Retrograde gastrojejunostomy <span class="hlt">tube</span> migration.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Adesina, Adeleke; Rammohan, Guhan; Jeanmonod, Rebecca</p> <p>2014-01-01</p> <p>Percutaneous enteral feeding <span class="hlt">tubes</span> are placed about 250,000 times each year in the United States. Although they are relatively safe, their placement may be complicated by perforation, infection, bleeding, vomiting, dislodgment, and obstruction. There have been numerous reports of antegrade migration of gastrojejunostomy (G-J) <span class="hlt">tubes</span>. We report a case of G-J <span class="hlt">tube</span> regurgitation following protracted vomiting and discuss the management of this very rare entity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/873003','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/873003"><span>Sapphire <span class="hlt">tube</span> pressure vessel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Outwater, John O.</p> <p>2000-01-01</p> <p>A pressure vessel is provided for observing corrosive fluids at high temperatures and pressures. A transparent Teflon bag contains the corrosive fluid and provides an inert barrier. The Teflon bag is placed within a sapphire <span class="hlt">tube</span>, which forms a pressure boundary. The <span class="hlt">tube</span> is received within a pipe including a viewing window. The combination of the Teflon bag, sapphire <span class="hlt">tube</span> and pipe provides a strong and inert pressure vessel. In an alternative embodiment, tie rods connect together compression fittings at opposite ends of the sapphire <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1345224','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1345224"><span>Fuel nozzle <span class="hlt">tube</span> retention</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Cihlar, David William; Melton, Patrick Benedict</p> <p>2017-02-28</p> <p>A system for retaining a fuel nozzle premix <span class="hlt">tube</span> includes a retention plate and a premix <span class="hlt">tube</span> which extends downstream from an outlet of a premix passage defined along an aft side of a fuel plenum body. The premix <span class="hlt">tube</span> includes an inlet end and a spring support feature which is disposed proximate to the inlet end. The premix <span class="hlt">tube</span> extends through the retention plate. The spring retention feature is disposed between an aft side of the fuel plenum and the retention plate. The system further includes a spring which extends between the spring retention feature and the retention plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20050921','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20050921"><span>Sapphire <span class="hlt">tube</span> pressure vessel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Outwater, J.O.</p> <p>2000-05-23</p> <p>A pressure vessel is provided for observing corrosive fluids at high temperatures and pressures. A transparent Teflon bag contains the corrosive fluid and provides an inert barrier. The Teflon bag is placed within a sapphire <span class="hlt">tube</span>, which forms a pressure boundary. The <span class="hlt">tube</span> is received within a pipe including a viewing window. The combination of the Teflon bag, sapphire <span class="hlt">tube</span> and pipe provides a strong and inert pressure vessel. In an alternative embodiment, tie rods connect together compression fittings at opposite ends of the sapphire <span class="hlt">tube</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/864748','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/864748"><span>Wound <span class="hlt">tube</span> heat exchanger</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Ecker, Amir L.</p> <p>1983-01-01</p> <p>What is disclosed is a wound <span class="hlt">tube</span> heat exchanger in which a plurality of <span class="hlt">tubes</span> having flattened areas are held contiguous adjacent flattened areas of <span class="hlt">tubes</span> by a plurality of windings to give a double walled heat exchanger. The plurality of windings serve as a plurality of effective force vectors holding the conduits contiguous heat conducting walls of another conduit and result in highly efficient heat transfer. The resulting heat exchange bundle is economical and can be coiled into the desired shape. Also disclosed are specific embodiments such as the one in which the <span class="hlt">tubes</span> are expanded against their windings after being coiled to insure highly efficient heat transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100010917','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100010917"><span>Composite Pulse <span class="hlt">Tube</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin, Jerry L.; Cloyd, Jason H.</p> <p>2007-01-01</p> <p>A modification of the design of the pulse <span class="hlt">tube</span> in a pulse-<span class="hlt">tube</span> cryocooler reduces axial thermal conductance while preserving radial thermal conductance. It is desirable to minimize axial thermal conductance in the pulse-<span class="hlt">tube</span> wall to minimize leakage of heat between the warm and cold ends of the pulse <span class="hlt">tube</span>. At the same time, it is desirable to maximize radial thermal conductance at the cold end of the pulse <span class="hlt">tube</span> to ensure adequate thermal contact between (1) a heat exchanger in the form of a stack of copper screens inside the pulse <span class="hlt">tube</span> at the cold end and (2) the remainder of the cold tip, which is the object to which the heat load is applied and from which heat must be removed. The modified design yields a low-heat-leak pulse <span class="hlt">tube</span> that can be easily integrated with a cold tip. A typical pulse <span class="hlt">tube</span> of prior design is either a thin-walled metal <span class="hlt">tube</span> or a metal <span class="hlt">tube</span> with a nonmetallic lining. It is desirable that the outer surface of a pulse <span class="hlt">tube</span> be cylindrical (in contradistinction to tapered) to simplify the design of a regenerator that is also part of the cryocooler. Under some conditions, it is desirable to taper the inner surface of the pulse <span class="hlt">tube</span> to reduce acoustic streaming. The combination of a cylindrical outer surface and a tapered inner surface can lead to unacceptably large axial conduction if the pulse <span class="hlt">tube</span> is made entirely of metal. Making the pulse-<span class="hlt">tube</span> wall of a nonmetallic, lowthermal- conductivity material would not solve the problem because the wall would not afford the needed thermal contact for the stack of screens in the cold end. The modified design calls for fabricating the pulse <span class="hlt">tube</span> in two parts: a longer, nonmetallic part that is tapered on the inside and cylindrical on the outside and a shorter, metallic part that is cylindrical on both the inside and the outside. The nonmetallic part can be made from G-10 fiberglass-reinforced epoxy or other low-thermal-conductivity, cryogenically compatible material. The metallic part must have high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990esdu.reptR.....','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990esdu.reptR....."><span>Boiling inside <span class="hlt">tubes</span>: Post dry-out heat transfer in vertical <span class="hlt">tubes</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p></p> <p>1990-04-01</p> <p>Methods are presented for calculating the heat transfer coefficient in the post dry-out region (that is when the critical heat <span class="hlt">flux</span> is exceeded and the liquid no longer wets the <span class="hlt">tube</span> walls) for upward flow in vertical <span class="hlt">tubes</span>. The methods are restricted to high quality flow (that is when a large proportion of the fluid is vapor) and a test for the applicability of the methods is included. Two different methods are given, one for steam/water flows and one for other fluids. Detailed step-by-step calculation procedures are set out in both cases for the determination of either the wall temperature when the <span class="hlt">tube</span> is subjected to know heat <span class="hlt">flux</span> (for example, when electrically heated) or the heat <span class="hlt">flux</span> when the <span class="hlt">tube</span> is heated to a known temperature, and all four cases are illustrated by worked example calculations. The accuracy of the methods is discussed and for steam/water is stated to be better than 20 percent by comparison of predictions with some 2000 experimental values for which the ranges of the variables are also given. Results in the case of the method for other fluids were about the same, but were tested against 350 experimental points for four fluids. The ranges of the experimental data are again included. A method of taking account of radiation is also provided.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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